Time and force dependence of the rupture of glycoprotein IIb-IIIa-fibrinogen bonds between latex spheres.

PubMed Central

Goldsmith, H L; McIntosh, F A; Shahin, J; Frojmovic, M M

2000-01-01

We studied the shear-induced breakup of doublets of aldehyde/sulfate (A/S) latex spheres covalently linked with purified platelet GPIIb-IIIa receptor, and cross-linked by fibrinogen. Flow cytometry with fluorescein isothiocyanate-fibrinogen showed than an average of 22,500 molecules of active GPIIb-IIIa were captured per sphere, with a mean K(d) = 56 nM for fibrinogen binding. The spheres, suspended in buffered 19% Ficoll 400 containing 120 or 240 pM fibrinogen, were subjected to Couette flow in a counter-rotating cone-plate rheoscope. Doublets, formed by two-body collisions at low shear rate (G = 8 s(-1)) for < or =15 min, were subjected to shear stress from 0.6 to 2.9 Nm(-2), their rotations recorded until they broke up or were lost to view. Although breakup was time dependent, occurring mostly in the first 2 rotations after the onset of shear, the percentage of doublets broken up after 10 rotations were almost independent of normal hydrodynamic force, F(n): at 240 pN, 15.6, 16.0, and 17.0% broke up in the force range 70-150 pN, 150-230 pN, and 230-310 pN. Unexpectedly, at both [fibrinogen], the initial rate of breakup was highest in the lowest force range, and computer simulation using a stochastic model of breakup was unable to simulate the time course of breakup. When pre-sheared at low G for >15 min, no doublets broke up within 10 rotations at 70 < F(n) < 310 pN; it required >3 min shear (>1110 rotations) at F(n) = 210 pN for significant breakup to occur. Other published work has shown that binding of fibrinogen to GPIIb-IIIa immobilized on plane surfaces exhibits an initial fast reversible process with relative low affinity succeeded by transformation of GPIIb-IIIa to a stable high-affinity complex. We postulate that most doublet breakups observed within 10 rotations were from a population of young doublets having low numbers of bonds, by dissociation of the initial receptor complex relatively unresponsive to force. The remaining, older doublets with GPIIb-IIIa in the high-affinity complex were not broken up in the time or range of forces studied. PMID:10692309

Measurement of axial spin observables in the polarized deuteron-polarized proton breakup at 270MeV

NASA Astrophysics Data System (ADS)

Whitaker, Thomas Jenkins

We report the measurement of "axial" spin observables in the dp breakup reaction at 270MeV. These measurements were made using a stored polarized "cooled" deuteron beam and a polarized internal hydrogen target at the Indiana University Cyclotron Facility (IUCF). Given our beam and target spin-alignment directions we were able to measure the axial spin observables Apz , Cy,x - Cx,y, and Czz,z. Axial spin observables are the subset of observables which are antisymmetric under the parity operation and are thus forbidden in reactions where the outgoing momenta are coplanar with the beam momentum. It has been argued that axial observables may be more sensitive to a three-body force than other spin observables. We compare our measurements to theoretical predictions based on the CD-Bonn nucleon-nucleon potential and the TM ' three-nucleon force, using a new method to correctly take into account the experimental constraints. The only previous measurement of Apz for pd breakup was carried out at 9MeV and yielded a result consistent with zero. In contrast, at Tp = 135 MeV, the present experiment reports a sizeable value for Apz , Cy,x - Cx,y, and Czz,z. To our knowledge, this is the first time axial correlation coefficients have been measured in a nuclear reaction. The expected sensitivity of axial observables to the three-nucleon force is not confirmed by our measurement.

Break-up of droplets in a concentrated emulsion flowing through a narrow constriction

NASA Astrophysics Data System (ADS)

Kim, Minkyu; Rosenfeld, Liat; Tang, Sindy; Tang Lab Team

2014-11-01

Droplet microfluidics has enabled a wide range of high throughput screening applications. Compared with other technologies such as robotic screening technology, droplet microfluidics has 1000 times higher throughput, which makes the technology one of the most promising platforms for the ultrahigh throughput screening applications. Few studies have considered the throughput of the droplet interrogation process, however. In this research, we show that the probability of break-up increases with increasing flow rate, entrance angle to the constriction, and size of the drops. Since single drops do not break at the highest flow rate used in the system, break-ups occur primarily from the interactions between highly packed droplets close to each other. Moreover, the probabilistic nature of the break-up process arises from the stochastic variations in the packing configuration. Our results can be used to calculate the maximum throughput of the serial interrogation process. For 40 pL-drops, the highest throughput with less than 1% droplet break-up was measured to be approximately 7,000 drops per second. In addition, the results are useful for understanding the behavior of concentrated emulsions in applications such as mobility control in enhanced oil recovery.

Marine floc strength and breakup response in turbulent flow

NASA Astrophysics Data System (ADS)

Rau, Matthew; Ackleson, Steven; Smith, Geoffrey

2017-11-01

The effect of turbulence on marine floc formation and breakup is studied experimentally using a recirculating breakup facility. Flocs of bentonite clay particles are grown in a large, stirred aggregation tank of salt water (salinity of 10 ppt) before being subjected to fully-developed pipe flow. Pipe flow conditions range from laminar to turbulent with dissipation rates up to 2.1 m2/s3. Particle size distributions are measured through in-situ sampling of the small-angle forward volume scattering function and through microscopic imaging. Floc size is compared before and after exposure to turbulence and found to be a strong function of the dissipation rate of turbulent kinetic energy. Hydrodynamic conditions within the aggregation tank have a large influence on overall floc strength; flocs formed with stirred aggregation resist breakup compared to flocs formed without stirring. Floc shape and structure statistics are quantified through image analysis and the results are discussed in relation to the measured floc breakup response. Finally, the relevance of these findings to quantifying and predicting marine floc dynamics and the eventual fate of particles in the ocean is presented. The authors thank the National Research Council Postdoctoral Program for their support of this work.

Droplet Deformation Prediction With the Droplet Deformation and Breakup Model (DDB)

NASA Technical Reports Server (NTRS)

Vargas, Mario

2012-01-01

The Droplet Deformation and Breakup Model was used to predict deformation of droplets approaching the leading edge stagnation line of an airfoil. The quasi-steady model was solved for each position along the droplet path. A program was developed to solve the non-linear, second order, ordinary differential equation that governs the model. A fourth order Runge-Kutta method was used to solve the equation. Experimental slip velocities from droplet breakup studies were used as input to the model which required slip velocity along the particle path. The center of mass displacement predictions were compared to the experimental measurements from the droplet breakup studies for droplets with radii in the range of 200 to 700 mm approaching the airfoil at 50 and 90 m/sec. The model predictions were good for the displacement of the center of mass for small and medium sized droplets. For larger droplets the model predictions did not agree with the experimental results.

Correcting the beam centroid motion in an induction accelerator and reducing the beam breakup instability

NASA Astrophysics Data System (ADS)

Coleman, J. E.; Ekdahl, C. A.; Moir, D. C.; Sullivan, G. W.; Crawford, M. T.

2014-09-01

Axial beam centroid and beam breakup (BBU) measurements were conducted on an 80 ns FWHM, intense relativistic electron bunch with an injected energy of 3.8 MV and current of 2.9 kA. The intense relativistic electron bunch is accelerated and transported through a nested solenoid and ferrite induction core lattice consisting of 64 elements, exiting the accelerator with a nominal energy of 19.8 MeV. The principal objective of these experiments is to quantify the coupling of the beam centroid motion to the BBU instability and validate the theory of this coupling for the first time. Time resolved centroid measurements indicate a reduction in the BBU amplitude, ⟨ξ⟩, of 19% and a reduction in the BBU growth rate (Γ) of 4% by reducing beam centroid misalignments ˜50% throughout the accelerator. An investigation into the contribution of the misaligned elements is made. An alignment algorithm is presented in addition to a qualitative comparison of experimental and calculated results which include axial beam centroid oscillations, BBU amplitude, and growth with different dipole steering.

Mechanism of Water Droplet Breakup Near the Leading Edge of an Airfoil

NASA Technical Reports Server (NTRS)

Vargas, Mario; Sor, Suthyvann; Magarino, Adelaida, Garcia

2012-01-01

This work presents results of an experimental study on droplet deformation and breakup near the leading edge of an airfoil. The experiment was conducted in the rotating rig test cell at the Instituto Nacional de Tecnica Aeroespacial (INTA) in Madrid, Spain. The airfoil model was placed at the end of the rotating arm and a monosize droplet generator produced droplets that fell from above, perpendicular to the path of the airfoil. The interaction between the droplets and the airfoil was captured with high speed imaging and allowed observation of droplet deformation and breakup as the droplet approached the airfoil near the stagnation line. Image processing software was used to measure the position of the droplet centroid, equivalent diameter, perimeter, area, and the major and minor axes of an ellipse superimposed over the deforming droplet. The horizontal and vertical displacement of each droplet against time was also measured, and the velocity, acceleration, Weber number, Bond number, Reynolds number, and the drag coefficients were calculated along the path of the droplet to the beginning of breakup. Droplet deformation is defined and studied against main parameters. The high speed imaging allowed observation of the actual mechanism of breakup and identification of the sequence of configurations from the initiation of the breakup to the disintegration of the droplet. Results and comparisons are presented for droplets of diameters in the range of 500 to 1800 microns, and airfoil velocities of 70 and 90 m/sec.

Mechanism of Water Droplet Breakup near the Leading Edge of an Airfoil

NASA Technical Reports Server (NTRS)

Vargas, Mario; Sor, Suthyvann; Magarino, Adelaida Garcia

2012-01-01

This work presents results of an experimental study on droplet deformation and breakup near the leading edge of an airfoil. The experiment was conducted in the rotating rig test cell at the Instituto Nacional de T cnica Aeroespacial (INTA) in Madrid, Spain. The airfoil model was placed at the end of the rotating arm and a monosize droplet generator produced droplets that fell from above, perpendicular to the path of the airfoil. The interaction between the droplets and the airfoil was captured with high speed imaging and allowed observation of droplet deformation and breakup as the droplet approached the airfoil near the stagnation line. Image processing software was used to measure the position of the droplet centroid, equivalent diameter, perimeter, area, and the major and minor axes of an ellipse superimposed over the deforming droplet. The horizontal and vertical displacement of each droplet against time was also measured, and the velocity, acceleration, Weber number, Bond number, Reynolds number, and the drag coefficients were calculated along the path of the droplet to the beginning of breakup. Droplet deformation is defined and studied against main parameters. The high speed imaging allowed observation of the actual mechanism of breakup and identification of the sequence of configurations from the initiation of the breakup to the disintegration of the droplet. Results and comparisons are presented for droplets of diameters in the range of 500 to 1800 micrometers, and airfoil velocities of 70 and 90 meters/second.

Controlled fragmentation of multimaterial fibres and films via polymer cold-drawing.

PubMed

Shabahang, Soroush; Tao, Guangming; Kaufman, Joshua J; Qiao, Yangyang; Wei, Lei; Bouchenot, Thomas; Gordon, Ali P; Fink, Yoel; Bai, Yuanli; Hoy, Robert S; Abouraddy, Ayman F

2016-06-23

Polymer cold-drawing is a process in which tensile stress reduces the diameter of a drawn fibre (or thickness of a drawn film) and orients the polymeric chains. Cold-drawing has long been used in industrial applications, including the production of flexible fibres with high tensile strength such as polyester and nylon. However, cold-drawing of a composite structure has been less studied. Here we show that in a multimaterial fibre composed of a brittle core embedded in a ductile polymer cladding, cold-drawing results in a surprising phenomenon: controllable and sequential fragmentation of the core to produce uniformly sized rods along metres of fibre, rather than the expected random or chaotic fragmentation. These embedded structures arise from mechanical-geometric instabilities associated with 'neck' propagation. Embedded, structured multimaterial threads with complex transverse geometry are thus fragmented into a periodic train of rods held stationary in the polymer cladding. These rods can then be easily extracted via selective dissolution of the cladding, or can self-heal by thermal restoration to re-form the brittle thread. Our method is also applicable to composites with flat rather than cylindrical geometries, in which case cold-drawing leads to the break-up of an embedded or coated brittle film into narrow parallel strips that are aligned normally to the drawing axis. A range of materials was explored to establish the universality of this effect, including silicon, germanium, gold, glasses, silk, polystyrene, biodegradable polymers and ice. We observe, and verify through nonlinear finite-element simulations, a linear relationship between the smallest transverse scale and the longitudinal break-up period. These results may lead to the development of dynamical and thermoreversible camouflaging via a nanoscale Venetian-blind effect, and the fabrication of large-area structured surfaces that facilitate high-sensitivity bio-detection.

Controlled fragmentation of multimaterial fibres and films via polymer cold-drawing

NASA Astrophysics Data System (ADS)

Shabahang, Soroush; Tao, Guangming; Kaufman, Joshua J.; Qiao, Yangyang; Wei, Lei; Bouchenot, Thomas; Gordon, Ali P.; Fink, Yoel; Bai, Yuanli; Hoy, Robert S.; Abouraddy, Ayman F.

2016-06-01

Polymer cold-drawing is a process in which tensile stress reduces the diameter of a drawn fibre (or thickness of a drawn film) and orients the polymeric chains. Cold-drawing has long been used in industrial applications, including the production of flexible fibres with high tensile strength such as polyester and nylon. However, cold-drawing of a composite structure has been less studied. Here we show that in a multimaterial fibre composed of a brittle core embedded in a ductile polymer cladding, cold-drawing results in a surprising phenomenon: controllable and sequential fragmentation of the core to produce uniformly sized rods along metres of fibre, rather than the expected random or chaotic fragmentation. These embedded structures arise from mechanical-geometric instabilities associated with ‘neck’ propagation. Embedded, structured multimaterial threads with complex transverse geometry are thus fragmented into a periodic train of rods held stationary in the polymer cladding. These rods can then be easily extracted via selective dissolution of the cladding, or can self-heal by thermal restoration to re-form the brittle thread. Our method is also applicable to composites with flat rather than cylindrical geometries, in which case cold-drawing leads to the break-up of an embedded or coated brittle film into narrow parallel strips that are aligned normally to the drawing axis. A range of materials was explored to establish the universality of this effect, including silicon, germanium, gold, glasses, silk, polystyrene, biodegradable polymers and ice. We observe, and verify through nonlinear finite-element simulations, a linear relationship between the smallest transverse scale and the longitudinal break-up period. These results may lead to the development of dynamical and thermoreversible camouflaging via a nanoscale Venetian-blind effect, and the fabrication of large-area structured surfaces that facilitate high-sensitivity bio-detection.

Influence of surfactant on the drop bag breakup in a continuous air jet stream

NASA Astrophysics Data System (ADS)

Zhao, Hui; Zhang, Wen-Bin; Xu, Jian-Liang; Li, Wei-Feng; Liu, Hai-Feng

2016-05-01

The deformation and breakup of surfactant-laden drops is a common phenomenon in nature and numerous practical applications. We investigate influence of surfactant on the drop bag breakup in a continuous air jet stream. The airflow would induce the advection diffusion of surfactant between interface and bulk of drop. Experiments indicate that the convective motions of deforming drop would induce the non-equilibrium distribution of surfactant, which leads to the change of surface tension. When the surfactant concentration is smaller than critical micelle concentration (CMC), with the increase of surface area of drop, the surface tension of liquid-air interface and the critical Weber number will increase. When the surfactant concentration is bigger than CMC, the micelle can be considered as the source term, which can supply the monomers. So in the presence of surfactant, there would be the significant nonlinear variation on the critical Weber number of bag breakup. We build the dynamic non-monotonic relationship between concentrations of surfactant and critical Weber number theoretically. In the range of parameters studied, the experimental results are consistent with the model estimates.

Tracking the seasonal cycle of coastal sea ice: Community-based observations and satellite remote sensing in service of societal needs

NASA Astrophysics Data System (ADS)

Eicken, Hajo; Lee, Olivia A.; Johnson, Mark A.; Pulsifer, Peter; Danielsen, Finn

2017-04-01

Break-up and freeze-up of coastal sea ice determine the timing and extent of a number of human activities, ranging from ice use by Indigenous hunters to coastal shipping. Yet, while major reductions in the extent of Arctic summer sea ice have been well studied, changes in its seasonal cycle have received less attention. Here, we discuss decadal scale changes and interannual variability in the timing of spring break-up and fall freeze-up, with a focus on coastal communities in Arctic Alaska. Observations of ice conditions by Indigenous sea-ice experts since 2006 indicate significant interannual variability in both the character and timing of freeze-up and break-up in the region. To aid in the archival and sharing of such observations, we have developed a database for community ice observations (eloka-arctic.org/sizonet). Development of this database addressed key questions ranging from community guidance on different levels of data sharing and access to the development of protocols that may lend themselves for implementation in the context of operational programs such as Global Cryosphere Watch. The lessons learned and tools developed through this effort may help foster the emergence of common observation protocols and sharing practices across the Arctic, as explored jointly with the Greenlandic PISUNA initiative and the European INTAROS project. For the Arctic Alaska region, we developed an algorithm to extract the timing of break-up and freeze-up from passive microwave satellite data, drawing on community-based observations. Data from 1979 to 2013 show break-up start arriving earlier by 5-9 days per decade and freeze-up start arriving later by 7-14 days per decade in the Chukchi and Beaufort Seas. The trends towards a shorter ice season observed over the past several decades point towards a substantial change in the winter ice regime by mid-century with incipient overlap of the end of the freeze-up and start of the break-up season as defined by coastal ice users.

Effect of Injector Geometry on Atomization of a Liquid-Liquid Double Swirl Coaxial Injector Using Non-invasive Laser, Optical and X-ray Techniques

NASA Technical Reports Server (NTRS)

Radke, C. R.; Meyer, T. R.

2014-01-01

The spray characteristics of a liquid-liquid double swirl coaxial injector were studied using non-invasive optical, laser, and X-ray diagnostics. A parametric study of injector exit geometry demonstrated that spray breakup time, breakup type and sheet stability could be controlled with exit geometry. Phase Doppler interferometry was used to characterize droplet statistics and non-dimensional droplet parameters over a range of inlet conditions and for various fluids allowing for a study on the role of specific fluid properties in atomization. Further, X-ray radiography allowed for investigation of sheet thickness and breakup length to be quantified for different recess exit diameters and inlet pressures. Finally, computed tomography scans revealed that the spray cone was distinctively non-uniform and comprised of several pockets of increased mass flux.

Effect of Injector Geometry on Atomization of a Liquid-Liquid Double Swirl Coaxial Injector using Non-Invasive Laser, Optical and X-ray Techniques

NASA Technical Reports Server (NTRS)

Radke, C. R.; Meyer, T. R.

2014-01-01

The spray characteristics of a Liquid-Liquid Double Swirl Coaxial Injector were studied using noninvasive Optical, Laser, and X-ray diagnostics. A parametric study of injector exit geometry demonstrated that spray breakup time, breakup type and sheet stability could be controlled with exit geometry. Phase Doppler Particle Analysis characterized droplet statistics and non-dimensional droplet parameters over a range of inlet conditions and for various fluids allowing for a study on the role of specific fluid properties in atomization. Further, x-ray radiographs allowed for investigations of sheet thickness and breakup length to be quantified for different recess exits and inlet pressures. Finally Computed Tomography scans revealed that the spray cone was distinctively non-uniform and comprised of several pockets of increased mass flux.

Wind tunnel investigation of the effect of high relative velocities on the structural integrity of birds

NASA Technical Reports Server (NTRS)

Bresnahan, D. L.

1972-01-01

An experimental investigation was conducted in a supersonic wind tunnel to determine the effect a sudden high velocity headwind had on the physical deformation and structural breakup characteristics of birds. Several sizes of recently killed birds were dropped into the test section at free-stream Mach numbers ranging from 0.2 to 0.8 and photographed with high-speed motion-picture cameras. These conditions simulated flow conditions encountered when birds are ingested into the inlets of high speed aircraft, thereby constituting a safety hazard to the aircraft and its occupants. The investigation shows that, over the range of headwind conditions tested, the birds remained structurally intact and did not suffer any appreciable deformation or structural breakup.

Systematic Study of Three-Nucleon System Dynamics in Deuteron-Proton Breakup Reaction

NASA Astrophysics Data System (ADS)

Kozela, A.; Ciepał, I.; Garbacz, M.; Jamróz, B.; Kłos, B.; Kistryn, St.; Khatri, G.; Kuboś, J.; Kulessa, P.; Liptak, A.; Parol, W.; Rusnok, A.; Sȩkowski, P.; Skwira-Chalot, I.; Stephan, E.; Wilczek, A.; Włoch, B.; Zejma, J.

2017-03-01

We report on preliminary results of the first measurement of elastic scattering of protons from deuterons and proton induced deuteron breakup at proton beam energy of 108 MeV conducted at new Cyclotron Center Bronowice IFJ PAN in Kraków. The experiment is aimed at precise determination of the differential cross section for extensive set of kinematical configurations in a wide range of angular acceptance. In the first data taking run the average statistical per-point accuracy of about 5% has been reached.

Magma-assisted rifting in Ethiopia.

PubMed

Kendall, J-M; Stuart, G W; Ebinger, C J; Bastow, I D; Keir, D

2005-01-13

The rifting of continents and evolution of ocean basins is a fundamental component of plate tectonics, yet the process of continental break-up remains controversial. Plate driving forces have been estimated to be as much as an order of magnitude smaller than those required to rupture thick continental lithosphere. However, Buck has proposed that lithospheric heating by mantle upwelling and related magma production could promote lithospheric rupture at much lower stresses. Such models of mechanical versus magma-assisted extension can be tested, because they predict different temporal and spatial patterns of crustal and upper-mantle structure. Changes in plate deformation produce strain-enhanced crystal alignment and increased melt production within the upper mantle, both of which can cause seismic anisotropy. The Northern Ethiopian Rift is an ideal place to test break-up models because it formed in cratonic lithosphere with minor far-field plate stresses. Here we present evidence of seismic anisotropy in the upper mantle of this rift zone using observations of shear-wave splitting. Our observations, together with recent geological data, indicate a strong component of melt-induced anisotropy with only minor crustal stretching, supporting the magma-assisted rifting model in this area of initially cold, thick continental lithosphere.

Parallel and Perpendicular Alignment of Anisotropic Particles in Free Liquid Microjets and Emerging Microdroplets.

PubMed

Schlenk, Mathias; Hofmann, Eddie; Seibt, Susanne; Rosenfeldt, Sabine; Schrack, Lukas; Drechsler, Markus; Rothkirch, Andre; Ohm, Wiebke; Breu, Josef; Gekle, Stephan; Förster, Stephan

2018-04-24

Liquid microjets play a key role in fiber spinning, inkjet printing, and coating processes. In all of these applications, the liquid jets carry dispersed particles whose spatial and orientational distributions within the jet critically influence the properties of the fabricated structures. Despite its importance, there is currently no knowledge about the orientational distribution of particles within microjets and droplets. Here, we demonstrate a microfluidic device that allows to determine the local particle distribution and orientation by X-ray scattering. Using this methodology, we discovered unexpected changes in the particle orientation upon exiting the nozzle to form a free jet, and upon jet break-up into droplets, causing an unusual biaxial particle orientation. We show how flow and aspect ratio determine the flow orientation of anisotropic particles. Furthermore, we demonstrate that the observed phenomena are a general characteristic of anisotropic particles. Our findings greatly enhance our understanding of particle orientation in free jets and droplets and provide a rationale for controlling particle alignment in liquid jet-based fabrication methodologies.

A Fragment-Cloud Approach for Modeling Atmospheric Breakup of Asteroids with Varied Internal Structures

NASA Astrophysics Data System (ADS)

Wheeler, Lorien; Mathias, Donovan; NASA Engineering Risk Assessment Team, NASA Asteroid Threat Assessment Project

2016-10-01

As an asteroid descends toward Earth, it deposits energy in the atmosphere through aerodynamic drag and ablation. Asteroid impact risk assessments rely on energy deposition estimates to predict blast overpressures and ground damage that may result from an airburst, such as the one that occurred over Chelyabinsk, Russia in 2013. The rates and altitudes at which energy is deposited along the entry trajectory depend upon how the bolide fragments, which in turn depends upon its internal structure and composition. In this work, an analytic asteroid fragmentation model has been developed to model the atmospheric breakup and resulting energy deposition of asteroids with a range of internal structures. The modeling approach combines successive fragmentation of larger independent pieces with aggregate debris clouds released with each fragmentation event. The model can vary the number and masses of fragments produced, the amount of mass released as debris clouds, and the size-strength scaling used to increase the robustness of smaller fragments. The initial asteroid body can be seeded with a distribution of independent fragment sizes amid a remaining debris mass to represent loose rubble pile conglomerations, or can be defined as a monolith with an outer regolith layer. This approach enables the model to represent a range of breakup behaviors and reproduce detailed energy deposition features such as multiple flares due to successive burst events, high-altitude regolith blow-off, or initial disruption of rubble piles followed by more energetic breakup of the constituent boulders. These capabilities provide a means to investigate sensitivities of ground damage to potential variations in asteroid structure.

On the Surface Breakup of a Non-turbulent Round Liquid Jet in Cross-flow

NASA Astrophysics Data System (ADS)

Behzad, Mohsen; Ashgriz, Nasser

2011-11-01

The atomization of a non-turbulent liquid jet injected into a subsonic cross-flow consists of two parts: (1) primary breakup and (2) secondary breakup. Two distinct regimes for the liquid jet primary breakup have been recognized; the so called column breakup and surface breakup. In the column breakup mode, the entire liquid jet undergoes disintegration into large liquid lumps. Quiet differently in the surface breakup regime, liquid fragments with various sizes and shapes are separated from the surface of the jet. Despite many experimental studies the mechanisms of jet surface breakup is not fully understood. Thus this study aims at providing useful observations regarding the underlying physics involving the surface breakup mechanism of a liquid jet in cross-flow, using detailed numerical simulations. The results show that a two-stage mechanism can be responsible for surface breakup. In the first stage, a sheet-like structure extrudes towards the downstream, and in the second stage it disintegrates into ligaments and droplets due to aerodynamic instability.

Middle-high latitude N2O distributions related to the arctic vortex breakup

NASA Astrophysics Data System (ADS)

Zhou, L. B.; Zou, H.; Gao, Y. Q.

2006-03-01

The relationship of N2O distributions with the Arctic vortex breakup is first analyzed with a probability distribution function (PDF) analysis. The N2O concentration shows different distributions between the early and late vortex breakup years. In the early breakup years, the N2O concentration shows low values and large dispersions after the vortex breakup, which is related to the inhomogeneity in the vertical advection in the middle and high latitude lower stratosphere. The horizontal diffusion coefficient (K,,) shows a larger value accordingly. In the late breakup years, the N2O concentration shows high values and more uniform distributions than in the early years after the vortex breakup, with a smaller vertical advection and K,, after the vortex breakup. It is found that the N2O distributions are largely affected by the Arctic vortex breakup time but the dynamically defined vortex breakup time is not the only factor.

Simultaneous all-sky and multi-satellite observations of auroral breakup and magnetic reconnection

NASA Astrophysics Data System (ADS)

Kawashima, T.; Ieda, A.; Machida, S.; Nishimura, Y.; Miura, T.

2017-12-01

A substorm is a large-scale disturbance including auroral breakup in the ionosphere and magnetic reconnection in the magnetotail. Two predominant models of the substorm time history have been proposed: the near-Earth neutral line (NENL) model and the current disruption model. The former is of outside-in type with tailward propagation of the disturbance, whereas the latter is of inside-out type with earthward propagation of the disturbance. To determine such time histories of such substorms using aurora all-sky and magnetotail multi-satellite observations, the National Aeronautics and Space Administration (NASA) is conducting a mission named the "Time History of Events and Macroscale Interactions during Substorms (THEMIS)". The time history of a substorm is expected to be best clarified when satellites are aligned along the tail axis. A substorm occurred under such a satellite distribution on 0743:42 UT February 27, 2009, and we investigated the auroral breakup and fast plasma flows produced by the magnetic reconnection in this substorm. The THEMIS satellites observed that a northward magnetic field variation propagated earthward. Because this earthward propagation is consistent with the NENL model, observation of a substorm onset after the magnetic reconnection was expected. However, the substorm onset was observed in the all-sky images before the magnetic reconnection, as noted in a previous study. In this study, we report that another earthward fast plasma flow occurred before the substorm onset, indicating that another magnetic reconnection occurred before the substorm onset. In addition, we confirm that the above mentioned post-onset magnetic reconnection occurred simultaneously with auroral poleward expansion, within a 1-min period. These results support the NENL model and further suggest that the two-step development of magnetic reconnection is a key component of the substorm time history.

The optical manifestation of dispersive field-aligned bursts in auroral breakup arcs

NASA Astrophysics Data System (ADS)

Dahlgren, H.; Semeter, J. L.; Marshall, R. A.; Zettergren, M.

2013-07-01

High-resolution optical observations of a substorm expansion show dynamic auroral rays with surges of luminosity traveling up the magnetic field lines. Observed in ground-based imagers, this phenomenon has been termed auroral flames, whereas the rocket signatures of the corresponding energy dispersions are more commonly known as field-aligned bursts. In this paper, observations of auroral flames obtained at 50 frames/s with a scientific-grade Complementary Metal Oxide Semiconductor (CMOS) sensor (30° × 30° field of view, 30 m resolution at 120 km) are used to provide insight into the nature of the precipitating electrons similar to high-resolution particle detectors. Thanks to the large field of view and high spatial resolution of this system, it is possible to obtain a first-order estimate of the temporal evolution in altitude of the volume emission rate from a single sensor. The measured volume emission rates are compared with the sum of modeled eigenprofiles obtained for a finite set of electron beams with varying energy provided by the TRANSCAR auroral flux tube model. The energy dispersion signatures within each auroral ray can be analyzed in detail during a fraction of a second. The evolution of energy and flux of the precipitation shows precipitation spanning over a large range of energies, with the characteristic energy dropping from 2.1 keV to 0.87 keV over 0.2 s. Oscillations at 2.4 Hz in the magnetic zenith correspond to the period of the auroral flames, and the acceleration is believed to be due to Alfvenic wave interaction with electrons above the ionosphere.

Surfactant-laden drop jellyfish-breakup mode induced by the Marangoni effect

NASA Astrophysics Data System (ADS)

Zhao, Hui; Zhang, Wen-Bin; Xu, Jian-Liang; Li, Wei-Feng; Liu, Hai-Feng

2017-03-01

Drop breakup is a familiar event in both nature and technology. In this study, we find that the bag breakup mode can be replaced by a new breakup mode: jellyfish breakup, when the surfactant concentration of a surfactant-laden drop is high. This new breakup mode has a morphology resembling a jellyfish with many long tentacles. This is due to the inhomogeneous distribution of surfactant in the process of drop deformation and breakup. The thin film of liquid can remain stable as a result of the Marangoni effect. Finally, we propose that the dimensionless surfactant concentration can serve as a criterion for breakup mechanisms.

Application of the Constrained Admissible Region Multiple Hypothesis Filter to Initial Orbit Determination of a Break-up

NASA Astrophysics Data System (ADS)

Kelecy, Tom; Shoemaker, Michael; Jah, Moriba

2013-08-01

A break-up in Low Earth Orbit (LEO) is simulated for 10 objects having area-to-mass ratios (AMR's) ranging from 0.1-10.0 m2/kg. The Constrained Admissible Region Multiple Hypothesis Filter (CAR-MHF) is applied to determining and characterizing the orbit and atmospheric drag parameters (CdA/m) simultaneously for each of the 10 objects with no a priori orbit or drag information. The results indicate that CAR-MHF shows promise for accurate, unambiguous and autonomous determination of the orbit and drag states.

Asymptotic and near-target direct breakup of 6Li and 7Li

NASA Astrophysics Data System (ADS)

Kalkal, Sunil; Simpson, E. C.; Luong, D. H.; Cook, K. J.; Dasgupta, M.; Hinde, D. J.; Carter, I. P.; Jeung, D. Y.; Mohanto, G.; Palshetkar, C. S.; Prasad, E.; Rafferty, D. C.; Simenel, C.; Vo-Phuoc, K.; Williams, E.; Gasques, L. R.; Gomes, P. R. S.; Linares, R.

2016-04-01

Background: Li,76 and 9Be are weakly bound against breakup into their cluster constituents. Breakup location is important for determining the role of breakup in above-barrier complete fusion suppression. Recent works have pointed out that experimental observables can be used to separate near-target and asymptotic breakup. Purpose: Our purpose is to distinguish near-target and asymptotic direct breakup of Li,76 in reactions with nuclei in different mass regions. Method: Charged particle coincidence measurements are carried out with pulsed Li,76 beams on 58Ni and 64Zn targets at sub-barrier energies and compared with previous measurements using 208Pb and 209Bi targets. A detector array providing a large angular coverage is used, along with time-of-flight information to give definitive particle identification of the direct breakup fragments. Results: In interactions of 6Li with 58Ni and 64Zn, direct breakup occurs only asymptotically far away from the target. However, in interactions with 208Pb and 209Bi, near-target breakup occurs in addition to asymptotic breakup. Direct breakup of 7Li into α -t is not observed in interactions with 58Ni and 64Zn. However, near-target dominated direct breakup was observed in measurements with 208Pb and 209Bi. A modified version of the Monte Carlo classical trajectory model code platypus, which explicitly takes into account lifetimes associated with unbound states, is used to simulate sub-barrier breakup reactions. Conclusions: Near-target breakup in interactions with Li,76 is an important mechanism only for the heavy targets 208Pb and 209Bi. There is insignificant near-target direct breakup of 6Li and no direct breakup of 7Li in reactions with 58Ni and 64Zn. Therefore, direct breakup is unlikely to suppress the above-barrier fusion cross section in reactions of Li,76 with 58Ni and 64Zn nuclei.

Surviving Atmospheric Spacecraft Breakup

NASA Technical Reports Server (NTRS)

Szewczyk, Nathaniel J.; Conley, Catharine A.

2003-01-01

In essence, to survival a spacecraft breakup an animal must not experience a lethal event. Much as with surviving aircraft breakup, dissipation of lethal forces via breakup of the craft around the organism is likely to greatly increase the odds of survival. As spacecraft can travel higher and faster than aircraft, it is often assumed that spacecraft breakup is not a survivable event. Similarly, the belief that aircraft breakup or crashes are not survivable events is still prevalent in the general population. As those of us involved in search and rescue know, it is possible to survive both aircraft breakup and crashes. Here we make the first report of an animal, C. elegans, surviving atmospheric breakup of the spacecraft supporting it and discuss both the lethal events these animals had to escape and the implications implied for search and rescue following spacecraft breakup.

Droplet breakup driven by shear thinning solutions in a microfluidic T-junction

NASA Astrophysics Data System (ADS)

Chiarello, Enrico; Gupta, Anupam; Mistura, Giampaolo; Sbragaglia, Mauro; Pierno, Matteo

2017-12-01

Droplet-based microfluidics turned out to be an efficient and adjustable platform for digital analysis, encapsulation of cells, drug formulation, and polymerase chain reaction. Typically, for most biomedical applications, the handling of complex, non-Newtonian fluids is involved, e.g., synovial and salivary fluids, collagen, and gel scaffolds. In this study, we investigate the problem of droplet formation occurring in a microfluidic T-shaped junction, when the continuous phase is made of shear thinning liquids. At first, we review in detail the breakup process, providing extensive, side-by-side comparisons between Newtonian and non-Newtonian liquids over unexplored ranges of flow conditions and viscous responses. The non-Newtonian liquid carrying the droplets is made of Xanthan solutions, a stiff, rodlike polysaccharide displaying a marked shear thinning rheology. By defining an effective Capillary number, a simple yet effective methodology is used to account for the shear-dependent viscous response occurring at the breakup. The droplet size can be predicted over a wide range of flow conditions simply by knowing the rheology of the bulk continuous phase. Experimental results are complemented with numerical simulations of purely shear thinning fluids using lattice Boltzmann models. The good agreement between the experimental and numerical data confirm the validity of the proposed rescaling with the effective Capillary number.

CONSTRAINTS ON THE PHYSICAL PROPERTIES OF MAIN BELT COMET P/2013 R3 FROM ITS BREAKUP EVENT

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

Hirabayashi, Masatoshi; Sánchez, Diego Paul; Gabriel, Travis

2014-07-01

Jewitt et al. recently reported that main belt comet P/2013 R3 experienced a breakup, probably due to rotational disruption, with its components separating on mutually hyperbolic orbits. We propose a technique for constraining physical properties of the proto-body, especially the initial spin period and cohesive strength, as a function of the body's estimated size and density. The breakup conditions are developed by combining mutual orbit dynamics of the smaller components and the failure condition of the proto-body. Given a proto-body with a bulk density ranging from 1000 kg m{sup –3} to 1500 kg m{sup –3} (a typical range of the bulk density of C-type asteroids),more » we obtain possible values of the cohesive strength (40-210 Pa) and the initial spin state (0.48-1.9 hr). From this result, we conclude that although the proto-body could have been a rubble pile, it was likely spinning beyond its gravitational binding limit and would have needed cohesive strength to hold itself together. Additional observations of P/2013 R3 will enable stronger constraints on this event, and the present technique will be able to give more precise estimates of its internal structure.« less

Negative Emotions and Behaviors are Markers of Breakup Distress

ERIC Educational Resources Information Center

Field, Tiffany; Diego, Miguel; Pelaez, Martha; Deeds, Osvelia; Delgado, Jeanette

2013-01-01

Method: University students who experienced a recent romantic breakup were given several self-report measures and were then divided into high versus low breakup distress groups. Results: The high breakup distress versus the low breakup distress groups had higher scores on negative emotions scales including depression, anxiety and anger and…

Modeling of drop breakup in the bag breakup regime

NASA Astrophysics Data System (ADS)

Wang, C.; Chang, S.; Wu, H.; Xu, J.

2014-04-01

Several analytic models for predicting the drop deformation and breakup have been developed over the last three decades, but modeling drop breakup in the bag-type regime is less reported. In this Letter, a breakup model has been proposed to predict the drop deformation length and breakup time in the bag-type breakup regime in a more accurate manner. In the present model, the drop deformation which is approximately as the displacement of the centre of mass (c. m.) along the axis located at the centre of the drop, and the movement of c. m. is obtained by solving the pressure balance equation. The effects of the drop deformation on the drop external aerodynamic force are considered in this model. Drop breakup occurs when the deformation length reaches the maximum value and the maximum deformation length is a function of Weber number. The performance and applicability of the proposed breakup model are tested against the published experimental data.

Comparative analysis of proton- and neutron-halo breakups

NASA Astrophysics Data System (ADS)

Mukeru, B.

2018-06-01

A detailed analysis of the proton- and neutron-halo breakup cross sections is presented. Larger neutron-halo breakup cross sections than proton-halo breakup cross sections are obtained. This is found to be mainly due to the projectile structure, namely the ground state wave function and the dipole electric response function. It is also found that the continuum–continuum couplings are stronger in the proton-halo breakup than in the neutron-halo breakup. The increase of proton- and neutron-halo ground state separation energy slightly strengthens these couplings in the proton- and neutron-halo total and nuclear breakups, while they are weakened in the proton- and neutron-halo Coulomb breakups. The Coulomb-nuclear interference remains strongly destructive in both proton- and neutron-halo breakups and this is independent of the ground state separation energy. The results also show that the increase of the neutron-halo ground state separation energy decreases significantly the agreement between the proton- and neutron-halo breakup cross sections, both qualitatively and quantitatively. It is obtained that when the proton-halo ground state separation energy is increased by a factor of 4.380, the proton-halo breakup cross section is reduced by a factor of 4.392, indicating a clear proportionality. However, when the neutron-halo ground state separation energy is increased by the same factor, the neutron-halo total breakup cross section is reduced by a factor of 8.522.

Dynamics of associative polymer solutions: Capillary break-up, jetting and rheology

NASA Astrophysics Data System (ADS)

Sharma, Vivek; Serdy, James G.; Threfall-Holmes, Phil; McKinley, Gareth H.

2011-11-01

Associative polymer solutions are used in extensively in the formulations for water-borne paints, food, inks, cosmetics, etc to control the rheology and processing behavior of multi-component dispersions. These complex dispersions are processed and used over a broad range of shear and extensional rates. Furthermore, the commercially relevant formulations use dilute solutions of associative polymers, which have low viscosity and short relaxation times, and hence their non-Newtonian response is not apparent in a conventional rheometer. In this talk, we explore several methods for systematically exploring the linear and nonlinear solution rheology of associative polymer dispersions, including: fractional model description of physical gelation, high frequency oscillatory tests at frequencies up to 10 kHz, microfluidic shear rheometry at deformation rates up to 1000000 /s and the influence of transient extensional rheology in the jet breakup. We show that high deformation rates can be obtained in jetting flows, and the growth and evolution of instability during jetting and break-up of these viscoelastic fluids shows the influence of both elasticity and extensibility.

Cryogenic and Simulated Fuel Jet Breakup in Argon, Helium and Nitrogen Gas Flows

NASA Technical Reports Server (NTRS)

Ingebo, Robert D.

1995-01-01

Two-phase flow atomization of liquid nitrogen jets was experimentally investigated. They were co-axially injected into high-velocity gas flows of helium, nitrogen and argon, respectively, and atomized internally inside a two-fluid fuel nozzle. Cryogenic sprays with relatively high specific surface areas were produced, i.e., ratios of surface area to volume were fairly high. This was indicated by values of reciprocal Sauter mean diameters, RSMD's, as measured with a scattered- light scanning instrument developed at NASA Lewis Research Center. Correlating expressions were derived for the three atomizing gases over a gas temperature range of 111 to 422 K. Also, the correlation was extended to include waterjet breakup data that had been previously obtained in simulating fuel jet breakup in sonic velocity gas flow. The final correlating expression included a new dimensionless molecular-scale acceleration group. It was needed to correlate RSMD data, for LN2 and H2O sprays, with the fluid properties of the liquid jets and atomizing gases used in this investigation.

Transition Theory and Experimental Comparisons on (I) Amplification into Streets and (II) a Strongly Nonlinear Break-up Criterion

NASA Astrophysics Data System (ADS)

Smith, F. T.; Bowles, R. I.

1992-10-01

The two stages I, II are studied by using recent nonlinear theory and then compared with the experiments of Nishioka et al. (1979) on the transition of plane Poiseuille flow. The first stage I starts at low amplitude from warped input, which is deformed through weakly nonlinear interaction into a blow-up in amplitude and phase accompanied by spanwise focusing into streets. This leads into the strongly nonlinear stage II. It holds for a broad range of interactive boundary layers and related flows, to all of which the nonlinear break-up criterion applies. The experimental comparisons on I, II for channel flow overall show encouraging quantitative agreement, supporting recent comparisons (in the boundary-layer setting) of the description of stage I in Stewart & Smith (1992) with the experiments of Klebanoff & Tidstrom (1959) and of the break-up criterion of Smith (1988a) with the computations of Peridier et al. (1991 a, b).

Vibration-Induced Gas-Liquid Interface Breakup

NASA Astrophysics Data System (ADS)

O'Hern, Timothy; Torczynski, John; Romero, Ed; Shelden, Bion

2010-11-01

Gas-liquid interfaces can be forced to break up when subjected to vibrations within critical ranges of frequency and amplitude. This breakup mechanism was examined experimentally using deep layers of silicone oils over a range of viscosity and sinusoidal, primarily axial vibration conditions that can produce dramatic disturbances at the gas-liquid free surface. Although small-amplitude vibrations produce standing Faraday waves, large-amplitude vibrations produce liquid jets into the gas, droplets pinching off from the jets, gas cavities in the liquid from droplet impact, and bubble transport below the interface. Experiments used several different silicone oils over a range of pressures and vibration conditions. Computational simulations exhibiting similar behavior will be included in the presentation. Applications include liquid fuel rockets, inertial sensing devices, moving vehicles, mixing processes, and acoustic excitation. Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the United States Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.

Effect of Eccentricity in Compound Droplets Subject to a Simple Shear Flow

NASA Astrophysics Data System (ADS)

Kim, Sangkyu; Dabiri, Sadegh

2016-11-01

A double emulsion, or a compound droplet, is a system where two liquids are separated by an immiscible third liquid, thereby forming an emulsion inside an emulsion. Compound drops benefit from this separation in applications such food sciences, microfluidics, pharmaceutical engineering, and polymer sciences. While the subjects of double emulsion preparations, deformations, and breakup mechanisms are well-explored, the time-evolution of non-concentric compound drops has received far less analytical or computational scrutiny. In this work, we present computational results using finite volume method with front-tracking approach for initially spherical and non-concentric compound drops in a shear flow. Our findings for low Reynolds number flows show that: 1. The surrounding shear flow to the outer drop induces a rotational velocity field inside it, causing the inner drop to tumble with the flow, 2. the tumbling motion persists in time, and acts to increase the eccentricity of the compound drop, and 3. the hemisection-plane to the outer drop that is aligned with the plane of the simple shear defines an unstable equilibrium for inner drop's center, and the inner drop continuously drifts away from that plane. This work suggests a means of favorably configuring compound drops suitable for breakups, and helps to understand their migration in channel flows.

Breakup of a thin drop under a stagnation point flow

NASA Astrophysics Data System (ADS)

Hooshanginejad, Alireza; Lee, Sungyon; Shelley, Michael

2017-11-01

Recent studies by Hooshanginejad and Lee (2017) have demonstrated complex depinning behaviors of a partially wetting droplet under wind. Motivated by this study, we examine the coupled evolution of a 2D thin drop and external wind, when it is initially held against a fast stagnation point flow. Our drop lubrication model employs the potential flow and Prandtl boundary layer theory for outer flow to compute the internal drop flow corresponding to drop deformations. Furthermore, both the analytical and numerical steady state solutions provide a partial prediction for the drop's final shape and help identify the range of droplet sizes that undergo a breakup for the given flow condition.

Modeling of Turbulence Effects on Liquid Jet Atomization and Breakup

NASA Technical Reports Server (NTRS)

Trinh, Huu P.; Chen, C. P.

2005-01-01

Recent experimental investigations and physical modeling studies have indicated that turbulence behaviors within a liquid jet have considerable effects on the atomization process. This study aims to model the turbulence effect in the atomization process of a cylindrical liquid jet. Two widely used models, the Kelvin-Helmholtz (KH) instability of Reitz (blob model) and the Taylor-Analogy-Breakup (TAB) secondary droplet breakup by O Rourke et al, are further extended to include turbulence effects. In the primary breakup model, the level of the turbulence effect on the liquid breakup depends on the characteristic scales and the initial flow conditions. For the secondary breakup, an additional turbulence force acted on parent drops is modeled and integrated into the TAB governing equation. The drop size formed from this breakup regime is estimated based on the energy balance before and after the breakup occurrence. This paper describes theoretical development of the current models, called "T-blob" and "T-TAB", for primary and secondary breakup respectivety. Several assessment studies are also presented in this paper.

Solar Wind-Magnetosphere Coupling Influences on Pseudo-Breakup Activity

NASA Technical Reports Server (NTRS)

Fillingim, M. O.; Brittnacher, M.; Parks, G. K.; Germany, G. A.; Spann, J. F.

1998-01-01

Pseudo-breakups are brief, localized aurora[ arc brightening, which do not lead to a global expansion, are historically observed during the growth phase of substorms. Previous studies have demonstrated that phenomenologically there is very little difference between substorm onsets and pseudo-breakups except for the degree of localization and the absence of a global expansion phase. A key open question is what physical mechanism prevents a pseudo-breakup form expanding globally. Using Polar Ultraviolet Imager (UVI) images, we identify periods of pseudo-breakup activity. Foe the data analyzed we find that most pseudo-breakups occur near local midnight, between magnetic local times of 21 and 03, at magnetic latitudes near 70 degrees, through this value may change by several degrees. While often discussed in the context of substorm growth phase events, pseudo-breakups are also shown to occur during prolonged relatively inactive periods. These quiet time pseudo-breakups can occur over a period of several hours without the development of a significant substorm for at least an hour after pseudo-breakup activity stops. In an attempt to understand the cause of quiet time pseudo-breakups, we compute the epsilon parameter as a measure of the efficiency of solar wind-magnetosphere coupling. It is noted that quiet time pseudo-breakups occur typically when epsilon is low; less than about 50 GW. We suggest that quiet time pseudo-breakups are driven by relatively small amounts of energy transferred to the magnetosphere by the solar wind insufficient to initiate a substorm expansion onset.

A Numerical Analysis of Droplet Breakup in Asymmetric T-Junctions with Different Outlet Pressure Gradients

NASA Astrophysics Data System (ADS)

Cheng, Way Lee; Han, Arum; Sadr, Reza

2016-11-01

Droplet splitting is the breakup of a parent droplet into two or more daughter droplets of desired sizes. It is done to improve production efficiency and investigational capacity in microfluidic devices. Passive splitting is the breakup of droplets into precise volume ratios at predetermined locations without external power sources. In this study, a 3-D simulation was conducted using the Volume-of-Fluid method to analysis the breakup process of a droplet in asymmetric T-junctions with different outlet arm lengths. The arrangement allows a droplet to be split into two smaller droplets of different sizes, where the volumetric ratio of the daughter droplets depends on the length ratios of the outlet arms. The study identified different breakup regimes such as primary, transition, bubble and non-breakup under different flow conditions and channel configurations. Furthermore, a close analysis to the primary breakup regimes were done to determine the breakup mechanisms at various flow conditions. The analysis show that the breakup mechanisms in asymmetric T-junctions is different than a regular split. A pseudo-phenomenological model for the breakup criteria was presented at the end. The model was an expanded version to a theoretically derived model for the symmetric droplet breakup. The Qatar National Research Fund (a member of the Qatar Founda- tion), under Grant NPRP 5-671-2-278, supported this work.

Drop Breakup in Fixed Bed Flows as Model Stochastic Flow Fields

NASA Technical Reports Server (NTRS)

Shaqfeh, Eric S. G.; Mosler, Alisa B.; Patel, Prateek

1999-01-01

We examine drop breakup in a class of stochastic flow fields as a model for the flow through fixed fiber beds and to elucidate the general mechanisms whereby drops breakup in disordered, Lagrangian unsteady flows. Our study consists of two parallel streams of investigation. First, large scale numerical simulations of drop breakup in a class of anisotropic Gaussian fields will be presented. These fields are generated spectrally and have been shown in a previous publication to be exact representations of the flow in a dilute disordered bed of fibers if close interactions between the fibers and the drops are dynamically unimportant. In these simulations the drop shape is represented by second and third order small deformation theories which have been shown to be excellent for the prediction of drop breakup in steady strong flows. We show via these simulations that the mechanisms of drop breakup in these flows are quite different than in steady flows. The predominant mechanism of breakup appears to be very short lived twist breakups. Moreover, the occurrence of breakup events is poorly predicted by either the strength of the local flow in which the drop finds itself at breakup, or the degree of deformation that the drop achieves prior to breakup. It is suggested that a correlation function of both is necessary to be predictive of breakup events. In the second part of our research experiments are presented where the drop deformation and breakup in PDMS/polyisobutylene emulsions is considered. We consider very dilute emulsions such that coalescence is unimportant. The flows considered are simple shear and the flow through fixed fiber beds. Turbidity, small angle light scattering, dichroism and microscopy are used to interrogate the drop deformation process in both flows. It is demonstrated that breakup at very low capillary numbers occurs in both flows but larger drop deformation occurs in the fixed bed flow. Moreover, it is witnessed that breakup in the bed occurs continuously during flow and apparently with uniform probability through the bed length. The drop deformations witnessed in our experiments are larger than those predicted by the numerical simulations, and future plans to investigate these differences are discussed.

The contemptuous separation: Facial expressions of emotion and breakups in young adulthood

PubMed Central

Heshmati, Saeideh; Sbarra, David A.; Mason, Ashley E.

2017-01-01

The importance of studying specific and expressed emotions after a stressful life event is well known, yet few studies have moved beyond assessing self-reported emotional responses to a romantic breakup. This study examined associations between computer-recognized facial expressions and self-reported breakup-related distress among recently separated college-aged young adults (N = 135; 37 men) on four visits across 9 weeks. Participants’ facial expressions were coded using the Computer Expression Recognition Toolbox while participants spoke about their breakups. Of the seven expressed emotions studied, only Contempt showed a unique association with breakup-related distress over time. At baseline, greater Contempt was associated with less breakup-related distress; however, over time, greater Contempt was associated with greater breakup-related distress. PMID:29249896

The contemptuous separation: Facial expressions of emotion and breakups in young adulthood.

PubMed

Heshmati, Saeideh; Sbarra, David A; Mason, Ashley E

2017-06-01

The importance of studying specific and expressed emotions after a stressful life event is well known, yet few studies have moved beyond assessing self-reported emotional responses to a romantic breakup. This study examined associations between computer-recognized facial expressions and self-reported breakup-related distress among recently separated college-aged young adults ( N = 135; 37 men) on four visits across 9 weeks. Participants' facial expressions were coded using the Computer Expression Recognition Toolbox while participants spoke about their breakups. Of the seven expressed emotions studied, only Contempt showed a unique association with breakup-related distress over time. At baseline, greater Contempt was associated with less breakup-related distress; however, over time, greater Contempt was associated with greater breakup-related distress.

Investigation of the impact of high liquid viscosity on jet atomization in crossflow via high-fidelity simulations

NASA Astrophysics Data System (ADS)

Li, Xiaoyi; Gao, Hui; Soteriou, Marios C.

2017-08-01

Atomization of extremely high viscosity liquid can be of interest for many applications in aerospace, automotive, pharmaceutical, and food industries. While detailed atomization measurements usually face grand challenges, high-fidelity numerical simulations offer the advantage to comprehensively explore the atomization details. In this work, a previously validated high-fidelity first-principle simulation code HiMIST is utilized to simulate high-viscosity liquid jet atomization in crossflow. The code is used to perform a parametric study of the atomization process in a wide range of Ohnesorge numbers (Oh = 0.004-2) and Weber numbers (We = 10-160). Direct comparisons between the present study and previously published low-viscosity jet in crossflow results are performed. The effects of viscous damping and slowing on jet penetration, liquid surface instabilities, ligament formation/breakup, and subsequent droplet formation are investigated. Complex variations in near-field and far-field jet penetrations with increasing Oh at different We are observed and linked with the underlying jet deformation and breakup physics. Transition in breakup regimes and increase in droplet size with increasing Oh are observed, mostly consistent with the literature reports. The detailed simulations elucidate a distinctive edge-ligament-breakup dominated process with long surviving ligaments for the higher Oh cases, as opposed to a two-stage edge-stripping/column-fracture process for the lower Oh counterparts. The trend of decreasing column deflection with increasing We is reversed as Oh increases. A predominantly unimodal droplet size distribution is predicted at higher Oh, in contrast to the bimodal distribution at lower Oh. It has been found that both Rayleigh-Taylor and Kelvin-Helmholtz linear stability theories cannot be easily applied to interpret the distinct edge breakup process and further study of the underlying physics is needed.

Drops moving along and across a filament

NASA Astrophysics Data System (ADS)

Sahu, Rakesh P.; Sinha-Ray, Suman; Yarin, Alexander; Pourdeyhimi, Behnam

2013-11-01

The present work is devoted to the experimental study of oil drop motion both along and across a filament due to the air jet blowing. In case of drop moving along the filament, phenomena such as drop stick-slip motion, shape oscillations, shedding of a tail along the filament, the tail capillary instability and drop recoil motion were observed which were rationalized in the framework of simplified models. Experiments with cross-flow of the surrounding gas relative to the filament with an oil drop on it were conducted, with air velocity in the range of 7.23 to 22.7 m s-1. The Weber number varied from 2 to 40 and the Ohnesorge number varied from 0.07 to 0.8. The lower and upper critical Weber numbers were introduced to distinguish between the beginning of the drop blowing off the filament and the onset of the bag-stamen breakup. The range of the Weber number between these two critical values is filled with three types of vibrational breakup: V1 (a balloon-like drop being blown off), V2 (a drop on a single stamen being blown off), and V3 (a drop on a double stamen being blown off). The Weber number/Ohnesorge number plane was delineated into domains of different breakup regimes. The work is supported by the Nonwovens Cooperative Research Center (NCRC).

Temperature dependence of droplet breakup in 8CB and 5CB liquid crystals.

PubMed

Porter, Daniel; Savage, John R; Cohen, Itai; Spicer, Patrick; Caggioni, Marco

2012-04-01

Droplet breakup of many Newtonian fluids is well described by current experiments, theory, and simulations. Breakup in complex fluids where interactions between mesoscopic structural features can affect the flows remains poorly understood and a burgeoning area of research. Here, we report on our investigations of droplet breakup in thermotropic liquid crystals. We investigate breakup in the smectic, nematic, and isotropic phases of 4-cyano 4-octylbiphenyl (8CB) and the nematic and isotropic phases of 4-cyano 4-pentylbiphenyl (5CB). The experiment consists of varying the ambient temperature to control liquid crystalline phase and imaging breakup using a fast video camera at up to 110000 frames/s. We expand on previous work [John R. Savage et al., Soft Matter 6, 892 (2010)] that shows breakup in the smectic phase is symmetric, producing no satellite droplets, and is well described by a similarity solution for a shear-thinning power-law fluid. We show that in the nematic phase the breakup occurs in two stages. In the first stage, the breakup is symmetric and the power-law exponent for the minimum radius dependence on the time left to breakup is 1.2

Numerical and experimental study of liquid breakup process in solid rocket motor nozzle

NASA Astrophysics Data System (ADS)

Yen, Yi-Hsin

Rocket propulsion is an important travel method for space exploration and national defense, rockets needs to be able to withstand wide range of operation environment and also stable and precise enough to carry sophisticated payload into orbit, those engineering requirement makes rocket becomes one of the state of the art industry. The rocket family have been classified into two major group of liquid and solid rocket based on the fuel phase of liquid or solid state. The solid rocket has the advantages of simple working mechanism, less maintenance and preparing procedure and higher storage safety, those characters of solid rocket make it becomes popular in aerospace industry. Aluminum based propellant is widely used in solid rocket motor (SRM) industry due to its avalibility, combusion performance and economical fuel option, however after aluminum react with oxidant of amonimum perchrate (AP), it will generate liquid phase alumina (Al2O3) as product in high temperature (2,700˜3,000 K) combustion chamber enviornment. The liquid phase alumina particles aggromorate inside combustion chamber into larger particle which becomes major erosion calprit on inner nozzle wall while alumina aggromorates impinge on the nozzle wall surface. The erosion mechanism result nozzle throat material removal, increase the performance optimized throat diameter and reduce nozzle exit to throat area ratio which leads to the reduction of exhaust gas velocity, Mach number and lower the propulsion thrust force. The approach to avoid particle erosion phenomenon taking place in SRM's nozzle is to reduce the alumina particle size inside combustion chamber which could be done by further breakup of the alumina droplet size in SRM's combustion chamber. The study of liquid breakup mechanism is an important means to smaller combustion chamber alumina droplet size and mitigate the erosion tack place on rocket nozzle region. In this study, a straight two phase air-water flow channel experiment is set up for liquid breakup phenomenon observation. The liquid water material in this experiment will play a comparison role as liquid alumina in high temerature enviornment. The method proposed to control the liquid breakup size of liquid droplet is done by the means of changing the liquid properties of surface tension. The surface tenion of liquid plays an inportant role of providing major liquid droplet bounding pressure or Laplace pressure. By reduceing surface tension of liquid leads to lower Laplace pressure of droplet and result in less droplet dynamic stability which could be breakup under external pressure difference. The reduction of surface tension of liquid aluminum could be achieved by adding magnisium and strontium, it is reported that the surface tension reeducation level could reach 10%˜15% when those additive mension above are adding to aluminum. This study of liquid breakup mechanism include two major part, first part is straight two-phase channel experiment and simulation comparison which provide a validation work of CFD simulation performance when compare to experiment. Second part is single droplet breakup experiment, in this experiment the relation of surface tension and liquid breakup behavior is carefully studied. The straight two-phase flow channel experiment setting will enable to us to study the liquid breakup process in macro scale. The quantification method is achieved by analyzing high-speed camera image by MatLab image process code develop in UW-Milwaukee wind tunnel lab which extract data in images and provide information including liquid droplet count and size distribution, wave frequency and time averaging two-phase free boundary. It was found that liquid breakup mechanism proportional to gas-droplet velocity difference square, gas density and liquid droplet size and inverse proportional to liquid surface tension. The single droplet experiment part is provide a close up view of liquid breakup and prove the reduced surface tension will enhance liquid breakup activity. In this study, we could observe the evidence of enhance liquid breakup activity by the reduced surface tension of liquid. Therefor the approach of reducing surface tension of Solid Rocket Motor (SRM) fuel reacting product is a high potential solution to SRM nozzle erosion.

Seismic anisotropy in eastern Africa, mantle flow, and the African superplume

NASA Astrophysics Data System (ADS)

Bagley, Brian; Nyblade, Andrew A.

2013-04-01

New estimates of seismic anisotropy from shear wave splitting measurements in eastern Africa reveal a pattern of seismic anisotropy dominated by a NE alignment of fast polarization directions with local changes around the thick Archean lithosphere of the Tanzania craton. The overall pattern is consistent with mantle flow from the African superplume but not with absolute plate motion, a plume head, or fossil anisotropy in the lithosphere. In combination with tomographic images of the African superplume, this finding suggests that plateau uplift, volcanism, and continental breakup along the Afro-Arabian rift system is strongly influenced by flow from the lower mantle and indicates a connection between lower mantle processes and the tectonic deformation of the Earth's surface.

Hydrological Measurements in Several Streams During Breakup in the National Petroleum Reserve - Alaska

NASA Astrophysics Data System (ADS)

Vas, D. A.; Toniolo, H. A.; Kemnitz, R.; Brailey, D.; Lamb, E. K.

2011-12-01

The National Petroleum Reserve - Alaska (NPR - A) expands from the North side of the Brooks Range to the Arctic Ocean over 23.5 million acres. There is a renewed interest in opening NPR -A for oil and gas exploration and hydrological data is critical to the development of pipelines, roads, and bridges. A set of hydraulic measurements, which includes discharge measurements using Acoustic Doppler Current Profiler (ADCP), water slope, and suspended sediment sampling during breakup were conducted on Otuk Creek, Seabee Creek, Prince Creek, Ikpikpuk River, Judy Creek, Fish Creek, and Ublutuoch River in the NPR - A region. We will present preliminary results, grouped by stream characteristics.

Different modes of continental break-up triggered by a sole mantle plume: a 2D and 3D numerical study

NASA Astrophysics Data System (ADS)

Beniest, Anouk; Koptev, Alexander; Leroy, Sylvie; Burov, Evgueni

2017-04-01

We used 2D and 3D numerical models to investigate the impact of a single mantle plume on continental rifting and breakup processes. We varied the thermo-rheological structure of the continental lithosphere, its geometry and the initial plume position. Based on the results of our 2D experiments, three continental break-up modes can be distinguished: A) 'central' continental break-up, the break-up center is located directly above the original mantle anomaly position, B) 'shifted' break-up, the break-up center is 50 to 200 km displaced from the initial plume location and C) 'distant' break-up, due to convection and/or slab-subduction/delamination, the break-up center is considerably shifted (300 to 800 km) from the primary plume position. Our 3D model, with a laterally homogeneous initial setup also results in continental break-up with the axis of continental break-up hundreds of kilometers shifted from the original plume location. The model results show that the classical, 'central' view of mantle plume induced continental break-up is not the only mode of break-up. When considering a diversity of break-up styles, it is possible to explain a variety of observed geophysical and geological features. For example, the mantle material glued to the base of the lithosphere at shallower depths corresponds geometrically and location-wise to high-velocity/high-density bodies observed on seismic data below the thinned continental lithosphere and the transition zone of the South Atlantic domain. During migration, products of partial melting of the mantle material can move vertically to (shallow) lower crustal levels. They might resemble high density bodies observed at lower crustal levels inside continental crust with similar geometries observed with gravity modelling. Also, topographic variation form in the very early stages of rifting on the first impingement of upwelled plume material. These variations remain visible, as the final position of the spreading center is shifted from the point of impingement and can be interpreted as aborted rifts, observed along passive margins. Our modelling demonstrates that both simple and perfectly symmetric preliminary settings as well as complex initial setups can result in a variety of break-up systems.

Substorm onset: Current sheet avalanche and stop layer

NASA Astrophysics Data System (ADS)

Haerendel, Gerhard

2015-03-01

A new scenario is presented for the onset of a substorm and the nature of the breakup arc. There are two main components, current sheet avalanche and stop layer. The first refers to an earthward flow of plasma and magnetic flux from the central current sheet of the tail, triggered spontaneously or by some unknown interaction with an auroral streamer or a suddenly appearing eastward flow at the end of the growth phase. The second offers a mechanism to stop the flow abruptly at the interface between magnetosphere and tail and extract momentum and energy to be partially processed locally and partially transmitted as Poynting flux toward the ionosphere. The stop layer has a width of the order of the ion inertial length. The different dynamics of the ions entering freely and the magnetized electrons create an electric polarization field which stops the ion flow and drives a Hall current by which flow momentum is transferred to the magnetic field. A simple formalism is used to describe the operation of the process and to enable quantitative conclusions. An important conclusion is that by necessity the stop layer is also highly structured in longitude. This offers a natural explanation for the coarse ray structure of the breakup arc as manifestation of elementary paths of energy and momentum transport. The currents aligned with the rays are balanced between upward and downward directions. While the avalanche is invoked for explaining the spontaneous substorm onset at the inner edge of the tail, the expansion of the breakup arc for many minutes is taken as evidence for a continued formation of new stop layers by arrival of flow bursts from the near-Earth neutral line. This is in line with earlier conclusions about the nature of the breakup arc. Small-scale structure, propagation speed, and energy flux are quantitatively consistent with observations. However, the balanced small-scale currents cannot constitute the substorm current wedge. The source of the latter must be located just earthward of the stop layer in the near-dipolar magnetosphere and be powered by the internal energy of the flow bursts. The stop layer mechanism is in some way the inverse of reconnection, as it converts flow into electromagnetic energy, and may have wide applicability in astrophysical plasmas.

Influence of breakup on elastic and α-production channels in the 6Li+ 116Sn reaction

NASA Astrophysics Data System (ADS)

Patel, D.; Mukherjee, S.; Deshmukh, N.; Lubian, J.; Wang, Jian-Song; Correa, T.; Nayak, B. K.; Yang, Yan-Yun; Ma, Wei-Hu; Biswas, D. C.; Gupta, Y. K.; Santra, S.; Mirgule, E. T.; Danu, L. S.; Singh, N. L.; Saxena, A.

2017-10-01

The effects of breakup reactions on elastic and α-production channels for the 6Li+116Sn system have been investigated at energies below and near the Coulomb barrier. The angular distributions of α-particle production differential cross sections have been obtained at several projectile energies between 22 and 40 MeV. The measured breakup α-particle differential cross sections and elastic scattering angular distributions have been compared with the predictions of continuum-discretized coupled channels (CDCC) calculations. The influence of breakup coupling has also been investigated by extracting dynamic polarization potentials (DPP) from the CDCC calculations. From the predictions of CDCC calculations the relative importance of the nuclear, Coulomb, and total breakup contributions have also been investigated. The nuclear breakup couplings are observed to play an important role in comparison to the Coulomb breakup for the direct breakup mechanisms associated in the reaction of 6Li projectile with 116Sn target nuclei. The influence of strong nuclear breakup coupling exhibits suppression in the Coulomb-nuclear interference peak. The direct breakup cross sections from the CDCC calculations under-predict the measured α-particle differential cross sections at all energies. This suggests that the measured α particles may also have contributions from other possible breakup reaction channels. One of the authors (SM) would like to thank DAE-BRNS for financial assistance through a major research project. This work is supported by National Natural Science Foundation of China (U1432247, 11575256, U1632138, 11605253) and China Postdoctoral Science Foundation (2016M602906)

Antimisting fuel breakup and flammability

NASA Technical Reports Server (NTRS)

Parikh, P.; Fleeter, R.; Sarohia, V.

1983-01-01

The breakup behavior and flammability of antimisting turbine fuels subjected to aerodynamic shear are investigated. Fuels tested were Jet A containing 0.3% FM-9 polymer at various levels of degradation ranging from virgin AMK to neat Jet A. The misting behavior of the fuels was quantified by droplet size distribution measurements. A technique based on high resolution laser photography and digital image processing of photographic records for rapid determination of droplet size distribution was developed. The flammability of flowing droplet-air mixtures was quantified by direct measurements of temperature rise in a flame established in the wake of a continuous ignition source. The temperature rise measurements were correlated with droplet size measurements. The flame anchoring phenomenon associated with the breakup of a liquid fuel in the wake of bluff body was shown to be important in the context of a survivable crash scenario. A pass/fail criterion for flammability testing of antimisting fuels, based on this flame-anchoring phenomenon, was proposed. The role of various ignition sources and their intensity in ignition and post-ignition behavior of antimisting fuels was also investigated.

Investigation and Comparison between New Satellite Impact Test Results and NASA Standard Breakup Model

NASA Technical Reports Server (NTRS)

Sakuraba, K.; Tsuruda, Y.; Hanada, T.; Liou, J.-C.; Akahoshi, Y.

2007-01-01

This paper summarizes two new satellite impact tests conducted in order to investigate on the outcome of low- and hyper-velocity impacts on two identical target satellites. The first experiment was performed at a low velocity of 1.5 km/s using a 40-gram aluminum alloy sphere, whereas the second experiment was performed at a hyper-velocity of 4.4 km/s using a 4-gram aluminum alloy sphere by two-stage light gas gun in Kyushu Institute of Technology. To date, approximately 1,500 fragments from each impact test have been collected for detailed analysis. Each piece was analyzed based on the method used in the NASA Standard Breakup Model 2000 revision. The detailed analysis will conclude: 1) the similarity in mass distribution of fragments between low and hyper-velocity impacts encourages the development of a general-purpose distribution model applicable for a wide impact velocity range, and 2) the difference in area-to-mass ratio distribution between the impact experiments and the NASA standard breakup model suggests to describe the area-to-mass ratio by a bi-normal distribution.

Nuclear structure research at the Triangle Universities Nuclear Laboratory

NASA Astrophysics Data System (ADS)

Mitchell, G. E.

1992-10-01

Studies of fundamental symmetries by the TRIPLE collaboration using the unique capabilities at LAMTF have found unexpected systematics in the parity-violating amplitudes for epithermal-neutron scattering. Tests to lower the present limits on time-reversal-invariance violation in the strong interaction are being made at in experiments on the scattering of polarized fast neutrons from aligned holmium targets. Studies of few-nucleon systems have received increasing emphasis over the past year, involving a broad program for testing the low- to medium-energy internucleon interactions, from the tensor component in n-p scattering and the n-n scattering lengths, through three-nucleon systems and the alpha particle, on up to Be-8. Of particular interest are three-nucleon systems, both in elastic scattering and in three-body breakup. Beam requirements range from production of intense and highly-polarized neutron beams to tensor-polarized beams for measurements at both very low energies (25-80 keV) and at tandem energies for definitive measurements of D-state components of the triton, He-3, and He-4 obtained from transfer reactions. The program in nuclear astrophysics expanded during 1991-1992. Several facets of the nuclear many-body problem and of excitation mechanisms of the nucleus are being elucidated, including measurements and analyses to elucidate the neutron-nucleus elastic-scattering interaction over a wide range of nuclei and energies. Several projects involved developments in electronuclear physics, instrumentation, RF-transition units, and low-temperature bolometric particle detectors.

Fragmentation of cancer cells

NASA Astrophysics Data System (ADS)

Vanapalli, Siva; Kamyabi, Nabiollah

Tumor cells have to travel through blood capillaries to be able to metastasize and colonize in distant organs. Among the numerous cells that are shed by the primary tumor, very few survive in circulation. In vivo studies have shown that tumor cells can undergo breakup at microcapillary junctions affecting their survival. It is currently unclear what hydrodynamic and biomechanical factors contribute to fragmentation and moreover how different are the breakup dynamics of highly and weakly metastatic cells. In this study, we use microfluidics to investigate flow-induced breakup of prostate and breast cancer cells. We observe several different modes of breakup of cancer cells, which have striking similarities with breakup of viscous drops. We quantify the breakup time and find that highly metastatic cancer cells take longer to breakup than lowly metastatic cells suggesting that tumor cells may dynamically modify their deformability to avoid fragmentation. We also identify the role that cytoskeleton and membrane plays in the breakup process. Our study highlights the important role that tumor cell fragmentation plays in cancer metastasis. Cancer Prevention and Research Institute of Texas.

Modelling wave-induced sea ice break-up in the marginal ice zone

NASA Astrophysics Data System (ADS)

Montiel, F.; Squire, V. A.

2017-10-01

A model of ice floe break-up under ocean wave forcing in the marginal ice zone (MIZ) is proposed to investigate how floe size distribution (FSD) evolves under repeated wave break-up events. A three-dimensional linear model of ocean wave scattering by a finite array of compliant circular ice floes is coupled to a flexural failure model, which breaks a floe into two floes provided the two-dimensional stress field satisfies a break-up criterion. A closed-feedback loop algorithm is devised, which (i) solves the wave-scattering problem for a given FSD under time-harmonic plane wave forcing, (ii) computes the stress field in all the floes, (iii) fractures the floes satisfying the break-up criterion, and (iv) generates an updated FSD, initializing the geometry for the next iteration of the loop. The FSD after 50 break-up events is unimodal and near normal, or bimodal, suggesting waves alone do not govern the power law observed in some field studies. Multiple scattering is found to enhance break-up for long waves and thin ice, but to reduce break-up for short waves and thick ice. A break-up front marches forward in the latter regime, as wave-induced fracture weakens the ice cover, allowing waves to travel deeper into the MIZ.

Modelling wave-induced sea ice break-up in the marginal ice zone

PubMed Central

Squire, V. A.

2017-01-01

A model of ice floe break-up under ocean wave forcing in the marginal ice zone (MIZ) is proposed to investigate how floe size distribution (FSD) evolves under repeated wave break-up events. A three-dimensional linear model of ocean wave scattering by a finite array of compliant circular ice floes is coupled to a flexural failure model, which breaks a floe into two floes provided the two-dimensional stress field satisfies a break-up criterion. A closed-feedback loop algorithm is devised, which (i) solves the wave-scattering problem for a given FSD under time-harmonic plane wave forcing, (ii) computes the stress field in all the floes, (iii) fractures the floes satisfying the break-up criterion, and (iv) generates an updated FSD, initializing the geometry for the next iteration of the loop. The FSD after 50 break-up events is unimodal and near normal, or bimodal, suggesting waves alone do not govern the power law observed in some field studies. Multiple scattering is found to enhance break-up for long waves and thin ice, but to reduce break-up for short waves and thick ice. A break-up front marches forward in the latter regime, as wave-induced fracture weakens the ice cover, allowing waves to travel deeper into the MIZ. PMID:29118659

Modelling wave-induced sea ice break-up in the marginal ice zone.

PubMed

Montiel, F; Squire, V A

2017-10-01

A model of ice floe break-up under ocean wave forcing in the marginal ice zone (MIZ) is proposed to investigate how floe size distribution (FSD) evolves under repeated wave break-up events. A three-dimensional linear model of ocean wave scattering by a finite array of compliant circular ice floes is coupled to a flexural failure model, which breaks a floe into two floes provided the two-dimensional stress field satisfies a break-up criterion. A closed-feedback loop algorithm is devised, which (i) solves the wave-scattering problem for a given FSD under time-harmonic plane wave forcing, (ii) computes the stress field in all the floes, (iii) fractures the floes satisfying the break-up criterion, and (iv) generates an updated FSD, initializing the geometry for the next iteration of the loop. The FSD after 50 break-up events is unimodal and near normal, or bimodal, suggesting waves alone do not govern the power law observed in some field studies. Multiple scattering is found to enhance break-up for long waves and thin ice, but to reduce break-up for short waves and thick ice. A break-up front marches forward in the latter regime, as wave-induced fracture weakens the ice cover, allowing waves to travel deeper into the MIZ.

Importance of lifetime effects in breakup and suppression of complete fusion in reactions of weakly bound nuclei

NASA Astrophysics Data System (ADS)

Cook, K. J.; Simpson, E. C.; Luong, D. H.; Kalkal, Sunil; Dasgupta, M.; Hinde, D. J.

2016-06-01

Background: Complete fusion cross sections in collisions of light weakly bound nuclei and high-Z targets show suppression of complete fusion at above-barrier energies. This has been interpreted as resulting from the breakup of the weakly bound nucleus prior to reaching the fusion barrier, reducing the probability of complete charge capture. Below-barrier studies of reactions of 9Be have found that the breakup of 8Be formed by neutron stripping dominates over direct breakup and that transfer-triggered breakup may account for the observed suppression of complete fusion. Purpose: This paper investigates how the above conclusions are affected by lifetimes of the resonant states that are populated prior to breakup. If the mean life of a populated resonance (above the breakup threshold) is much longer than the fusion time scale, then its breakup (decay) cannot suppress complete fusion. For short-lived resonances, the situation is more complex. This work explicitly includes the mean life of the short-lived 2+ resonance in 8Be in classical dynamical model calculations to determine its effect on energy and angular correlations of the breakup fragments and on model predictions of suppression of cross sections for complete fusion at above-barrier energies. Method: Previously performed coincidence measurements of breakup fragments produced in reactions of 9Be with 144Sm, 168Er, 186W, 196Pt, 208Pb, and 209Bi at energies below the barrier have been reanalyzed using an improved efficiency determination of the BALiN detector array. Predictions of breakup observables and of complete and incomplete fusion at energies above the fusion barrier are then made using the classical dynamical simulation code platypus, modified to include the effect of lifetimes of resonant states. Results: The agreement of the breakup observables is much improved when lifetime effects are included explicitly. Sensitivity to subzeptosecond lifetime is observed. The predicted suppression of complete fusion owing to breakup is nearly independent of Z and has an average value of ˜9 % . This is below the experimentally determined fusion suppression, which is typically ˜30 % in these systems. Conclusions: Inclusion of resonance lifetimes is essential to correctly reproduce breakup observables. This results in a larger fraction of nuclei remaining intact at the fusion-barrier radius compared with calculations that do not explicitly include lifetime effects. The more realistic treatment of breakup followed in this work leads to the conclusion that the suppression of complete fusion cannot be fully explained by breakup prior to reaching the fusion barrier. Only one-third of the observed fusion suppression can be attributed to the competing process of breakup. Other mechanisms that can suppress complete fusion must therefore be investigated. One of the possible candidates is cluster transfer that produces the same heavy targetlike nuclei as those formed by incomplete fusion.

Studying the field induced breakup of acoustically levitated drops

NASA Astrophysics Data System (ADS)

Warschat, C.; Riedel, J.

2017-10-01

Coulomb fission of charged droplets (The terms drop and droplet are often used synonymous. Throughout this manuscript, to avoid confusion, the terms drop and droplet will be used for liquid spheres with radii in the millimeter range and the micrometer range, respectively. In our experiments, the first correspond to the parent drop while the latter describes the ejected progeny droplets.) is a well-studied natural phenomenon. Controlled droplet fission is already successfully employed in several technological applications. Still, since the occurring surface rupture relies on the exact understanding and description of the liquid gas boundary, some details are still under debate. Most empirical systematic studies observe falling micrometer droplets passing through the electric field inside a plate capacitor. This approach, although easily applicable and reliable, limits the experimental degrees of freedom regarding the observable time and the maximum size of the drops and can only be performed in consecutive individual observations of different subsequent drops. Here we present a novel setup to study the field induced breakup of acoustically levitated drops. The design does not bear any restrictions towards the temporal window of observation, and allows handling of drops of a tunable radius ranging from 10 μm to several millimeters and a real-time monitoring of one single drop. Our comprehensive study includes a time resolved visual inspection, laser shadowgraphy, laser induced fluorescence imaging, and ambient mass spectrometric interrogation of the nascent Taylor cone. The results shown for a millimeter sized drop, previously inaccessible for Coulomb fission experiments, are mostly comparable with previous results for smaller drops. The major difference is the time scale and the threshold potential of the drop rupture. Both values, however, resemble theoretically extrapolations to the larger radius. The technique allows for a systematic study of breakup behavior of drops of different charge, material, and size.

Atmospheric Energy Deposition Modeling and Inference for Varied Meteoroid Structures

NASA Technical Reports Server (NTRS)

Wheeler, Lorien; Mathias, Donovan; Stokan, Edward; Brown, Peter

2018-01-01

Asteroids populations are highly diverse, ranging from coherent monoliths to loosely-bound rubble piles with a broad range of material and compositional properties. These different structures and properties could significantly affect how an asteroid breaks up and deposits energy in the atmosphere, and how much ground damage may occur from resulting blast waves. We have previously developed a fragment-cloud model (FCM) for assessing the atmospheric breakup and energy deposition of asteroids striking Earth. The approach represents ranges of breakup characteristics by combining progressive fragmentation with releases of variable fractions of debris and larger discrete fragments. In this work, we have extended the FCM to also represent asteroids with varied initial structures, such as rubble piles or fractured bodies. We have used the extended FCM to model the Chelyabinsk, Benesov, Kosice, and Tagish Lake meteors, and have obtained excellent matches to energy deposition profiles derived from their light curves. These matches provide validation for the FCM approach, help guide further model refinements, and enable inferences about pre-entry structure and breakup behavior. Results highlight differences in the amount of small debris vs. discrete fragments in matching the various flare characteristics of each meteor. The Chelyabinsk flares were best represented using relatively high debris fractions, while Kosice and Benesov cases were more notably driven by their discrete fragmentation characteristics, perhaps indicating more cohesive initial structures. Tagish Lake exhibited a combination of these characteristics, with lower-debris fragmentation at high altitudes followed by sudden disintegration into small debris in the lower flares. Results from all cases also suggest that lower ablation coefficients and debris spread rates may be more appropriate for the way in which debris clouds are represented in FCM, offering an avenue for future model refinement.

Post-breakup tectonics in southeast Brazil from thermochronological data and combined inverse-forward thermal history modeling

NASA Astrophysics Data System (ADS)

Cogné, Nathan; Gallagher, Kerry; Cobbold, Peter R.; Riccomini, Claudio; Gautheron, Cecile

2012-11-01

The continental margin of southeast Brazil is elevated. Onshore Tertiary basins and Late Cretaceous/Paleogene intrusions are good evidence for post breakup tectono-magmatic activity. To constrain the impact of post-rift reactivation on the geological history of the area, we carried out a new thermochronological study. Apatite fission track ages range from 60.7 ± 1.9 Ma to 129.3 ± 4.3 Ma, mean track lengths from 11.41 ± 0.23 μm to 14.31 ± 0.24 μm and a subset of the (U-Th)/He ages range from 45.1 ± 1.5 to 122.4 ± 2.5 Ma. Results of inverse thermal history modeling generally support the conclusions from an earlier study for a Late Cretaceous phase of cooling. Around the onshore Taubaté Basin, for a limited number of samples, the first detectable period of cooling occurred during the Early Tertiary. The inferred thermal histories for many samples also imply subsequent reheating followed by Neogene cooling. Given the uncertainty of the inversion results, we did deterministic forward modeling to assess the range of possibilities of this Tertiary part of the thermal history. The evidence for reheating seems to be robust around the Taubaté Basin, but elsewhere the data cannot discriminate between this and a less complex thermal history. However, forward modeling results and geological information support the conclusion that the whole area underwent cooling during the Neogene. The synchronicity of the cooling phases with Andean tectonics and those in NE Brazil leads us to assume a plate-wide compressional stress that reactivated inherited structures. The present-day topographic relief of the margin reflects a contribution from post-breakup reactivation and uplift.

Coherent ρ 0 photoproduction in ultra-peripheral Pb-Pb collisions at $$ \\sqrt{s_{\\mathrm{NN}}}=2.76 $$ TeV

DOE PAGES

Adam, J.; Adamová, D.; Aggarwal, M. M.; ...

2015-09-15

We report the first measurement at the LHC of coherent photoproduction of ρ o mesons in ultra-peripheral Pb-Pb collisions. The invariant mass and transverse momentum distributions for ρ o production are studied in the π +π - decay channel at mid-rapidity. The production cross section in the rapidity range |y| < 0.5 is found to be dσ/dy = 425 ± 10(stat.) -50 + 42 (sys.) mb. Coherent ρ o production is studied with and without requirement of nuclear breakup, and the fractional yields for various breakup scenarios are presented. Lastly, the results are compared with those from lower energies andmore » with model predictions.« less

Nuclear science experiments with a bright neutron source from fusion reactions on the OMEGA Laser System

NASA Astrophysics Data System (ADS)

Forrest, C. J.; Knauer, J. P.; Schroeder, W. U.; Glebov, V. Yu.; Radha, P. B.; Regan, S. P.; Sangster, T. C.; Sickles, M.; Stoeckl, C.; Szczepanski, J.

2018-04-01

Subnanosecond impulses of 1013 to 1014 neutrons, produced in direct-drive laser inertial confinement fusion implosions, have been used to irradiate deuterated targets at the OMEGA Laser System (Boehly et al., 1997). The target compounds include heavy water (D2O) and deuterated benzene (C6D6). Yields and energy spectra of neutrons from D(n,2n)p to study the breakup reaction have been measured at a forward angle of θlab = 3 .5∘ ± 3.5° with a sensitive, high-dynamic-range neutron time-of-flight spectrometer to infer the double-differential breakup cross section d2 σ/dE d Ω for 14-MeV D-T fusion neutrons.

Power Scaling and Seasonal Evolution of Floe Areas in the Arctic East Siberian Sea

NASA Astrophysics Data System (ADS)

Barton, C. C.; Geise, G. R.; Tebbens, S. F.

2016-12-01

The size distribution of floes and its evolution during the Arctic summer season and a model of fragmentation that generates a power law scaling distribution of fragment sizes are the subject of this paper. This topic is of relevance to marine vessels that encounter floes, to the calculation of sea ice albedo, to the determination of Arctic heat exchange which is strongly influenced by ice concentrations and the amount of open water between floes, and to photosynthetic marine organisms which are dependent upon sunlight penetrating the spaces between floes. Floes are 2-3 m thick and initially range in area from one to millions of square meters. The cumulative number versus floe area distribution of seasonal sea floes from six satellite images of the Arctic Ocean during the summer breakup and melting is well fit by two scale-invariant power law scaling regimes for floe areas ranging from 30 m2 to 28,400,000 m2. Scaling exponents, B, for larger floe areas range from -0.6 to -1.0 with an average of -0.8. Scaling exponents, B, for smaller floe areas range from -0.3 to -0.6 with an average of -0.5. The inflection point between the two scaling regimes ranges from 283 x 102 m2 to 4850 x 102 m2 and generally moves from larger to smaller floe areas through the summer melting season. We observe that the two scaling regimes and the inflection between them are established during the initial breakup of sea ice solely by the process of fracture. The distributions of floe size regimes retain their scaling exponents as the floe pack evolves from larger to smaller floe areas from the initial breakup through the summer season, due to grinding, crushing, fracture, and melting. The scaling exponents for floe area distribution are in the same range as those reported in previous studies of Arctic floes and for the single scaling exponents found for crushed and ground geologic materials including streambed gravel, lunar debris, and artificially crushed quartz. A probabilistic fragmentation model that produces a power distribution of particle sizes has been developed and will be presented.

Interactions Forces and the Flow-Induced Coalescence of Drops and Bubbles

NASA Technical Reports Server (NTRS)

Leal, L. Gary; Israelachvili, J.

2004-01-01

In order to accomplish the proposed macroscale experimental goals, we designed and built a pair of miniaturized computer-controlled four-roll mills, similar but much smaller than the 4-roll mill that had been develop earlier in Prof. Leal's group for studies of drop deformation and breakup. This unique experimental facility allows for controlled experiments on the breakup and coalescence of very small drops in the size range of 20-200 micrometers in diameter for a wide variety of flows and under a wide range of flow conditions including time-dependent flows, etc. The small size of this device is necessary for coalescence studies, since coalescence occurs in viscous fluids at capillary numbers that are large enough to be experimentally accessible only for drops that are smaller than approximately 100_m in diameter. Using these miniaturized 4-roll mills, we have obtained the first quantitative data (so far as we are aware) on the flow-induced coalescence process.

Giant phonon anomaly associated with superconducting fluctuations in the pseudogap phase of cuprates

DOE PAGES

Liu, Ye-Hua; Konik, Robert M.; Rice, T. M.; ...

2016-01-20

The pseudogap in underdoped cuprates leads to significant changes in the electronic structure, and was later found to be accompanied by anomalous fluctuations of superconductivity and certain lattice phonons. Here we propose that the Fermi surface breakup due to the pseudogap, leads to a breakup of the pairing order into two weakly coupled sub-band amplitudes, and a concomitant low energy Leggett mode due to phase fluctuations between them. This increases the temperature range of superconducting fluctuations containing an overdamped Leggett mode. In this range inter-sub-band phonons show strong damping due to resonant scattering into an intermediate state with a pairmore » of overdamped Leggett modes. In the ordered state, the Leggett mode develops a finite energy, changing the anomalous phonon damping into an anomaly in the dispersion. Finally, this proposal explains the intrinsic connection between the anomalous pseudogap phase, enhanced superconducting fluctuations and giant anomalies in the phonon spectra.« less

Breaking Up is Hard to do: The Impact of Unmarried Relationship Dissolution on Mental Health and Life Satisfaction

PubMed Central

Rhoades, Galena K.; Kamp Dush, Claire M.; Atkins, David C.; Stanley, Scott M.; Markman, Howard J.

2011-01-01

This study was the first to examine the impact of unmarried relationship break-up on psychological distress and life satisfaction using a within-subjects design. Among unmarried 18 to 35-year olds (N = 1295), 36.5% had one or more break-ups over a 20-month period. Experiencing a break-up was associated with an increase in psychological distress and a decline in life satisfaction (from pre- to post-dissolution). In addition, several characteristics of the relationship or of the break-up were associated with the magnitude of the changes in life satisfaction following a break-up. Specifically, having been cohabiting and having had plans for marriage were associated with larger declines in life satisfaction while having begun to date someone new was associated with smaller declines. Interestingly, having higher relationship quality at the previous wave was associated with smaller declines in life satisfaction following a break-up. No relationship or break-up characteristics were significantly associated with the magnitude of changes in psychological distress after a break-up. Existing theories are used to explain the results. Implications for clinical work and future research on unmarried relationships are also discussed. PMID:21517174

Observations of breakup processes of liquid jets using real-time X-ray radiography

NASA Technical Reports Server (NTRS)

Char, J. M.; Kuo, K. K.; Hsieh, K. C.

1988-01-01

To unravel the liquid-jet breakup process in the nondilute region, a newly developed system of real-time X-ray radiography, an advanced digital image processor, and a high-speed video camera were used. Based upon recorded X-ray images, the inner structure of a liquid jet during breakup was observed. The jet divergence angle, jet breakup length, and fraction distributions along the axial and transverse directions of the liquid jets were determined in the near-injector region. Both wall- and free-jet tests were conducted to study the effect of wall friction on the jet breakup process.

Deformation and breakup of a stretching liquid bridge covered with an insoluble surfactant monolayer

NASA Astrophysics Data System (ADS)

Liao, Ying-Chih; Franses, Elias I.; Basaran, Osman A.

2006-02-01

The breakup of surfactant-laden drops and jets is of technological interest and fundamental scientific importance. Surfactants are routinely used to control the breakup of drops and jets in applications ranging from inkjet printing to crop spraying. Accurate computation of breakup of surfactant-laden drops and jets is often the key to the development of new applications and to providing a rational fundamental understanding of both existing and emerging applications. While highly accurate algorithms for studying the breakup of surfactant-free drops and jets are well documented and much is now known about the dynamics in such situations, little is known by contrast about the closely related problem of interface rupture when surfactant effects cannot be neglected. The deformation and breakup of a stretching liquid bridge of an incompressible Newtonian fluid whose surface is covered with an insoluble surfactant monolayer are analyzed here experimentally and computationally. In the experiments, high-speed visualization is used to capture the transient deformation of a bridge. The dynamic shapes of bridges (captive between two rods of 3.15 mm diameter) are captured and analyzed with a time resolution of 1 ms. The bridge lengths are 3.15 mm initially and about 4-7 mm at breakup, which occurs after stretching for about 0.1-0.2 s, depending on the volume and viscosity of the liquid and the surface density of spread monolayers. The dynamics of a surfactant-covered bridge is governed by the Navier-Stokes and convection-diffusion equations. First, these equations are solved with a three-dimensional, but axisymmetric, or two-dimensional (2D), finite element algorithm using elliptic mesh generation. Second, the governing set of 2D equations is reduced to a set of one-dimensional (1D) equations by means of the slender-jet approximation and the resulting set of 1D equations is solved with a 1D finite element algorithm. The presence of surfactant results not only in the lowering of surface tension and the capillary pressure, but also in surface tension gradients and Marangoni stresses, both of which affect the transient dynamics leading to breakup. In particular, the role of Marangoni stresses in delaying bridge breakup and on formation of satellite droplets is investigated as a function of the initial surface density and surface activity of the surfactant, and surface Peclet number that measures the importance of convection relative to diffusion. The predictions of the 2D algorithm are confirmed to be faithful to the physics by demonstrating that the computed results accord well with the experiments and existing scaling theories. In the pinch-off region, the surfactant is swept out of a thinning neck by strong convection. The calculations thus reveal that the scaling behavior in the presence of surfactant parallels that observed in the absence of surfactant, in accordance with recent reports by others. The 2D computations and the experiments are used in tandem to identify regions in the space of governing parameters where the 1D equations can be used with confidence.

The fix for tough spots

NASA Technical Reports Server (NTRS)

Anders, John B.; Walsh, Michael J.; Bushnell, Dennis M.

1988-01-01

Modern turbulence-control techniques are discussed. Particular atention is given to retrofit techniques such as riblets and large-eddy breakup (LEBU) devices which use passive elements suitable for a variety of existing vehicles with minimum added complexity. Riblets are small flow-aligned grooves in the aircraft skin that damp turbulence and reduce skin friction; the mechanism of riblet drag reduction derives from the enhancement of turbulence-altering, transverse viscous forces by strong spanwise surface geometry gradients. LEBUs are thin plates or ribbons suspended in a turbulent boundary layer to sever or break up the large vortices that form the convoluted outer edge of the layer. Other turbulence-control techniques are discussed, including one that involves the injection of control vortices into the turbulent boundary layer to modify or substitute for large-eddy structures.

Droplet Breakup in Expansion-contraction Microchannels

PubMed Central

Zhu, Pingan; Kong, Tiantian; Lei, Leyan; Tian, Xiaowei; Kang, Zhanxiao; Wang, Liqiu

2016-01-01

We investigate the influences of expansion-contraction microchannels on droplet breakup in capillary microfluidic devices. With variations in channel dimension, local shear stresses at the injection nozzle and focusing orifice vary, significantly impacting flow behavior including droplet breakup locations and breakup modes. We observe transition of droplet breakup location from focusing orifice to injection nozzle, and three distinct types of recently-reported tip-multi-breaking modes. By balancing local shear stresses and interfacial tension effects, we determine the critical condition for breakup location transition, and characterize the tip-multi-breaking mode quantitatively. In addition, we identify the mechanism responsible for the periodic oscillation of inner fluid tip in tip-multi-breaking mode. Our results offer fundamental understanding of two-phase flow behaviors in expansion-contraction microstructures, and would benefit droplet generation, manipulation and design of microfluidic devices. PMID:26899018

Trojan horse particle invariance: The impact on nuclear astrophysics

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

Pizzone, R. G.; La Cognata, M.; Spitaleri, C.

In the current picture of nuclear astrophysics indirect methods and, in particular, the Trojan Horse Method cover a crucial role for the measurement of charged particle induced reactions cross sections of astrophysical interest, in the energy range required by the astrophysical scenarios. To better understand its cornerstones and its applications to physical cases many tests were performed to verify all its properties and the possible future perspectives. The key to the method is the quasi-free break-up and some of its properties will be investigated in the present work. In particular, the Trojan Horse nucleus invariance will be studied and previousmore » studies will be extended to the cases of the binary d(d, p)t and {sup 6}Li(d,α){sup 4}He reactions, which were tested using different quasi-free break-up's, namely {sup 6}Li and {sup 3}He. The astrophysical S(E)-factor were then extracted with the Trojan Horse formalism applied to the two different break-up schemes and compared with direct data as well as with previous indirect investigations. The very good agreement confirms the independence of binary indirect cross section on the chosen spectator particle also for these reactions.« less

Scaling in two-fluid pinch-off

NASA Astrophysics Data System (ADS)

Pommer, Chris; Suryo, Ronald; Subramani, Hariprasad; Harris, Michael; Basaran, Osman

2009-11-01

Two-fluid pinch-off is encountered when drops or bubbles of one fluid are ejected from a nozzle into another fluid or when a compound jet breaks. While the breakup of a drop in a passive environment and that of a passive bubble in a liquid are well understood, the physics of pinch-off when both the inner and outer fluids are dynamically active is inadequately understood. In this talk, the breakup of a compound jet whose core and shell are both incompressible Newtonian fluids is analyzed computationally by a method of lines ALE algorithm which uses finite elements with elliptic mesh generation for spatial discretization and adaptive finite differences for time integration. Pinch-off dynamics are investigated well beyond the limit of experiments set by the wavelength of visible light and that of various algorithms used in the literature. Simulations show that the minimum neck radius r initially scales with time τ before breakup as &αcirc; where α varies over a certain range. However, depending on the values of the governing dimensionless groups, this initial scaling regime may be transitory and, closer to pinch-off, the dynamics may transition to a final asymptotic regime for which r ˜&βcirc;, where β!=α.

Systematic continuum-discretized coupled-channels calculations of total fusion for 6Li with targets 28Si, 59Co, 96Zr, 198Pt, and 209Bi: Effect of resonance states

NASA Astrophysics Data System (ADS)

Gómez Camacho, A.; Wang, Bing; Zhang, H. Q.

2018-05-01

Continuum discretized coupled-channel (CDCC) calculations of total fusion cross sections for reactions induced by the weakly bound nucleus 6Li with targets 28Si, 59Co, 96Zr, 198Pt, and 209Bi at energies around the Coulomb barrier are presented. In the cluster structure frame of 6Li→α +d , short-range absorption potentials are considered for the interactions between the α and d fragments with the targets. The effect of resonance (l =2 , Jπ=3+,2+,1+ ) and nonresonance states of 6Li on fusion is studied by using two approaches: (1) by omitting the resonance states from the full discretized CDCC breakup space and (2) by considering only the resonance subspace. A systematic analysis of the effect on fusion from resonance breakup couplings is carried out from light to heavy mass targets. Among other things, it is found that resonance breakup states produce strong repulsive polarization potentials that lead to fusion suppression. Couplings from nonresonance states give place to weak repulsive potentials at high energies; however, these become attractive for the heavier targets at low energies.

A Three-Year Comparison of Hydrological Measurements in Seven Streams During Breakup in the National Petroleum Reserve - Alaska

NASA Astrophysics Data System (ADS)

Vas, D. A.; Toniolo, H. A.; Kemnitz, R.; Lamb, E.

2012-12-01

National Petroleum Reserve-Alaska (NPR-A) is an extensive 22.8 million acre oil, gas, and coal rich area that extends from the north foothills of the Brooks range all the way to the Arctic Ocean. Due to increasing demand for oil and natural gas the United States Department of Interior, Bureau of Land Management (BLM) is holding annual oil and gas lease sales in the NPR-A region. BLM is also supporting research to aid responsible oil exploration in the NPR-A region. We conducted a set of hydraulic measurements, which includes discharge measurements using Acoustic Doppler Current Profiler (ADCP), water slope, and suspended sediment sampling during breakup, the most important hydrologic event of the year, from 2010 to 2012 on Otuk Creek, Seabee Creek, Prince Creek, Ikpikpuk River, Judy Creek, Fish Creek, and Ublutuoch River in the NPR - A region. The hydraulic data we collected helped us understand how rivers change yearly which is useful for the development of new infrastructure such as pipe lines, bridges, and roads in the NPR-A region. The goal of this work is to present the results of our 2010 to 2012 spring breakup measurements.

Experimental investigation of the breakup of a round liquid jet in a shock-induced crossflow

NASA Astrophysics Data System (ADS)

Olles, Joseph; Guildenbecher, Daniel; Wagner, Justin; Demauro, Edward; Farias, Paul; Grasser, Thomas; Sojka, Paul

2015-11-01

The breakup of a round water jet due to a step change in the convective air velocity following a 1D air-shock was experimentally investigated. Variations of this experiment have been conducted in the past, however here quantitative results on the breakup sizes and trajectories are shown. A shock tube was utilized to create the jet breakup, and the primary shape of the liquid and secondary droplet sizes were recorded optically. Through the use of digital in-line holography (DIH), the sizes, 3D position, and 3C velocities of secondary droplets were measured at kHz rates. Care was taken to ensure that the jet was kept round throughout the shock tube test section (absent of Plateau-Rayleigh instability). While the liquid jet geometry and velocity was kept constant, various gas-phase velocities allowed for the investigation of multiple breakup morphologies, as a function of the crossflow Weber number. The typical breakup regimes are seen; bag, multimode, and sheet-thinning. With high temporal and spatial resolution, interfacial and liquid column instabilities are seen in the jet breakup.

On the numerical treatment of Coulomb forces in scattering problems

NASA Astrophysics Data System (ADS)

Randazzo, J. M.; Ancarani, L. U.; Colavecchia, F. D.; Gasaneo, G.; Frapiccini, A. L.

2012-11-01

We investigate the limiting procedures to obtain Coulomb interactions from short-range potentials. The application of standard techniques used for the two-body case (exponential and sharp cutoff) to the three-body break-up problem is illustrated numerically by considering the Temkin-Poet (TP) model of e-H processes.

Trajectory and Breakup of Cryogenic Jets in Crossflow

NASA Astrophysics Data System (ADS)

Richards, William

This study investigated the breakup processes of subcritical cryogenic jets injected in to subsonic crossflows of heated air. The crossflow speed, temperature, and jet velocity were varied to demonstrate the effect of thermal differences on a jet in crossflow. High speed back-lit photography and Mie scattering were used to examine the primary breakup regimes, trajectory, and breakup points. The breakup regimes show little change from jets in crossflow near thermodynamic equilibrium. Penetration of the jet increased with an increase in crossflow temperature. The breakup points in the streamwise direction followed trends previously observed for conventional jets. While the height of column fracture did not increase with momentum flux ratio as much as would be expected, its dependence matched that of the trajectory correlation. It is hypothesized that the observed differences are due to the development of a sheath of evaporated fluid around the main liquid core of the jet.

Numerical Simulation of Droplet Breakup and Collision in the Solution Precursor Plasma Spraying

NASA Astrophysics Data System (ADS)

Shan, Y.; Coyle, T. W.; Mostaghimi, J.

2007-12-01

Finely structured ceramic coatings can be obtained by solution precursor plasma spraying. The final structure of the coating highly depends on the droplet size and velocity distribution at the injection, the evolution of the spray in the jet, and droplet breakup and collision within the spray. This article describes a 3D model to simulate the transport phenomena and the trajectory and heating of the solution spray in the process. O’Rourke’s droplet collision model is used to take into account the influence of droplet collision. The influence of droplet breakup is also considered by implementing TAB droplet breakup models into the plasma jet model. The effects of droplet collisions and breakup on the droplet size, velocity, and temperature distribution of the solution spray are investigated. The results indicate that droplet breakup and collision play an important role in determining the final particle size and velocity distributions on the substrate.

Tunable Droplet Breakup Dynamics on Micropillared Superhydrophobic Surfaces.

PubMed

Zhang, Rui; Hao, Pengfei; Zhang, Xiwen; Niu, Fenglei; He, Feng

2018-06-22

Functional materials with controllable droplet breakup properties have extensive application prospects in aircraft anti-icing, spraying cooling, surface coating, and so on. Here we show that introducing micropillar arrays with various morphologies to fabricate superhydrophobic surfaces could either facilitate or suppress droplet splitting. The spacing and height of micropillars play an essential role in tuning the splitting patterns. Delayed splashing occurs on dense pillars which support the liquid lamella and provide channels for air to escape. A novel droplet breakup mechanism is found on sparse tall pillars, which rises from the instability of lateral liquid jets and significantly reduces the droplet breakup threshold. The critical Weber number of the rupture of low-viscous liquid is solely determined by the geometric parameters of micropillars and droplets. This work unveils the impact of ordered microstructures on the droplet breakup dynamics and provides a quantitative analysis of the geometric parameters in revising the breakup criteria.

Artificial satellite break-ups. I - Soviet ocean surveillance satellites

NASA Astrophysics Data System (ADS)

Johnson, N. L.

1983-02-01

An analysis of the breakup patterns of eight Soviet Kosmos series ocean surveillance satellites is presented. It is noted that half of the 4700 objects presently detected in earth orbit are shards from destroyed objects. The locations and heading of each Soviet satellite breakup were tracked by the Naval Space Survelliance System. All events in the eastern hemisphere occurred in the ascending phase, while western hemisphere breakups happened in the descending phase. Gabbard (1971) diagrams of altitude vs. period are plotted as a function of a fragment's orbital period. The diagrams have been incorporated into a NASA computer program to backtrack along the fragments' paths to determine the pattern of the breakup. Although objects have been projected to have separated from some of the satellites before breakup, a discussion of the evidence leads to the conclusion that even though the satellites may have exploded no purpose can yet be discerned for the actions.

Numerical Simulation of Liquid Jet Atomization Including Turbulence Effects

NASA Technical Reports Server (NTRS)

Trinh, Huu P.; Chen, C. P.; Balasubramanyam, M. S.

2005-01-01

This paper describes numerical implementation of a newly developed hybrid model, T-blob/T-TAB, into an existing computational fluid dynamics (CFD) program for primary and secondary breakup simulation of liquid jet atomization. This model extend two widely used models, the Kelvin-Helmholtz (KH) instability of Reitz (blob model) and the Taylor-Analogy-Breakup (TAB) secondary droplet breakup by O'Rourke and Amsden to include turbulence effects. In the primary breakup model, the level of the turbulence effect on the liquid breakup depends on the characteristic scales and the initial flow conditions. For the secondary breakup, an additional turbulence force acted on parent drops is modeled and integrated into the TAB governing equation. Several assessment studies are presented and the results indicate that the existing KH and TAB models tend to under-predict the product drop size and spray angle, while the current model provides superior results when compared with the measured data.

Neutron-neutron quasifree scattering in nd breakup at 10 MeV

NASA Astrophysics Data System (ADS)

Malone, R. C.; Crowe, B.; Crowell, A. S.; Cumberbatch, L. C.; Esterline, J. H.; Fallin, B. A.; Friesen, F. Q. L.; Han, Z.; Howell, C. R.; Markoff, D.; Ticehurst, D.; Tornow, W.; Witała, H.

2016-03-01

The neutron-deuteron (nd) breakup reaction provides a rich environment for testing theoretical models of the neutron-neutron (nn) interaction. Current theoretical predictions based on rigorous ab-initio calculations agree well with most experimental data for this system, but there remain a few notable discrepancies. The cross section for nn quasifree (QFS) scattering is one such anomaly. Two recent experiments reported cross sections for this particular nd breakup configuration that exceed theoretical calculations by almost 20% at incident neutron energies of 26 and 25 MeV [1, 2]. The theoretical values can be brought into agreement with these results by increasing the strength of the 1S0 nn potential matrix element by roughly 10%. However, this modification of the nn effective range parameter and/or the 1S0 scattering length causes substantial charge-symmetry breaking in the nucleon-nucleon force and suggests the possibility of a weakly bound di-neutron state [3]. We are conducting new measurements of the cross section for nn QFS in nd breakup. The measurements are performed at incident neutron beam energies below 20 MeV. The neutron beam is produced via the 2H(d, n)3He reaction. The target is a deuterated plastic cylinder. Our measurements utilize time-of-flight techniques with a pulsed neutron beam and detection of the two emitted neutrons in coincidence. A description of our initial measurements at 10 MeV for a single scattering angle will be presented along with preliminary results. Also, plans for measurements at other energies with broad angular coverage will be discussed.

NASA's Ground-Based Observing Campaigns of Rocket Bodies with the UKIRT and NASA ES-MCAT Telescopes

NASA Technical Reports Server (NTRS)

Lederer, Susan M.; Buckalew, Brent A.; Anz-Meador, Phillip; Cowardin, Heather M.; Frith, James M.; Matney, Mark

2017-01-01

Rocket bodies comprise a class of human-made space debris that are at the same time essential for launching every spacecraft from the Earth, but are also a significant source of debris both as intact objects, as well as fragmented debris. Unspent fuel has been long theorized as a potential cause of catastrophic rocket body break-ups. Given typical orbital speeds range from approximately 2-3 kilometers per second at Geosynchronous Orbit (GEO) and up to 15 kilometers per second in low Earth orbit (LEO), collisions with uncatalogued and undetected debris can also cause catastrophic breakups. Understanding break-ups is a necessary step in preventing them, and one key step in that process is to correlate and characterize daughter fragments with their parent bodies. Two very different methods include (1) conducting photometric surveys to correlate an object's motion and orbital elements to the parent body, and (2) characterizing what materials comprise the target to determine whether those materials are consistent with the parent body or like objects. With this in mind, photometric data were taken shortly after the breakup of one rocket body for short-term orbital studies, and a suite of spectral data were taken of rocket bodies that are fully intact to compare with debris, for characterization studies. Targets included Titan Transtage, Briz-M, and Ariane rocket bodies and debris. Spectra of each sub-class of rocket body were very similar within their rocket body type, but differed distinctly from one type to the next, supporting the effectiveness of this approach.

PLATYPUS: A code for reaction dynamics of weakly-bound nuclei at near-barrier energies within a classical dynamical model

NASA Astrophysics Data System (ADS)

Diaz-Torres, Alexis

2011-04-01

A self-contained Fortran-90 program based on a three-dimensional classical dynamical reaction model with stochastic breakup is presented, which is a useful tool for quantifying complete and incomplete fusion, and breakup in reactions induced by weakly-bound two-body projectiles near the Coulomb barrier. The code calculates (i) integrated complete and incomplete fusion cross sections and their angular momentum distribution, (ii) the excitation energy distribution of the primary incomplete-fusion products, (iii) the asymptotic angular distribution of the incomplete-fusion products and the surviving breakup fragments, and (iv) breakup observables, such as angle, kinetic energy and relative energy distributions. Program summaryProgram title: PLATYPUS Catalogue identifier: AEIG_v1_0 Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AEIG_v1_0.html Program obtainable from: CPC Program Library, Queen's University, Belfast, N. Ireland Licensing provisions: Standard CPC licence, http://cpc.cs.qub.ac.uk/licence/licence.html No. of lines in distributed program, including test data, etc.: 332 342 No. of bytes in distributed program, including test data, etc.: 344 124 Distribution format: tar.gz Programming language: Fortran-90 Computer: Any Unix/Linux workstation or PC with a Fortran-90 compiler Operating system: Linux or Unix RAM: 10 MB Classification: 16.9, 17.7, 17.8, 17.11 Nature of problem: The program calculates a wide range of observables in reactions induced by weakly-bound two-body nuclei near the Coulomb barrier. These include integrated complete and incomplete fusion cross sections and their spin distribution, as well as breakup observables (e.g. the angle, kinetic energy, and relative energy distributions of the fragments). Solution method: All the observables are calculated using a three-dimensional classical dynamical model combined with the Monte Carlo sampling of probability-density distributions. See Refs. [1,2] for further details. Restrictions: The program is suited for a weakly-bound two-body projectile colliding with a stable target. The initial orientation of the segment joining the two breakup fragments is considered to be isotropic. Additional comments: Several source routines from Numerical Recipies, and the Mersenne Twister random number generator package are included to enable independent compilation. Running time: About 75 minutes for input provided, using a PC with 1.5 GHz processor.

Direct processes in 54-MeV Li-7 breakup reactions on C-12 and Au-197 targets, and the extraction of astrophysical cross sections

NASA Astrophysics Data System (ADS)

Gazes, S. B.; Mason, J. E.; Roberts, R. B.; Teichmann, S. G.

1992-01-01

Strong direct processes were observed for elastic breakup in 54-MeV Li-7 + C-12, Au-197 reactions. In the case of C-12, the observed Li-7 to alpha + t direct-breakup yield was significantly larger than predicted by a Coulomb-breakup calculation, indicating the importance of the nuclear field. For Au-197, final-state interactions produced a strong distortion in the fragment energy spectra, as well as a modulation of the coincidence efficiency for different detector geometries. Such Coulomb effects are found to severely complicate the extraction of radiative-capture cross sections from direct-breakup data.

Mechanism for Spiral Wave Breakup in Excitable and Oscillatory Media

NASA Astrophysics Data System (ADS)

Yang, Junzhong; Xie, Fagen; Qu, Zhilin; Garfinkel, Alan

2003-10-01

We study spiral wave breakup using a Fitzhugh-Nagumo type system. We find that spiral wave breakup can occur near the core or far from it in both excitable and oscillatory regimes. There is a faraway breakup scenario in both excitable and oscillatory media that depends on long wavelength modulation modes. We observed three distinct scenarios, including one that involves breakup that does not develop into turbulence. However, we find that the mechanisms behind these three scenarios are the same: they are caused by the interaction between the dispersion relation and the asymptotic behavior of the modulation mode. The difference in phenomenology is due to the asymptotic behavior of the modulation mode.

Study of Liquid Breakup Process in Solid Rocket Motors

DTIC Science & Technology

2014-01-01

waves. The breakup level increases with the surrounding gas velocity; more liquid breakup in the nozzle throat reduces the liquid alumina droplet size...process of a liquid film that flows along the wall of a straight channel while a high-speed gas moves over it. We have used an unsteady-flow Reynolds...Averaged Navier-Stokes code (URANS) to investigate the interaction of the liquid film flow with the gas flow, and analyzed the breakup process for

Modeling of Turbulence Effects on Liquid Jet Atomization and Breakup

NASA Technical Reports Server (NTRS)

Trinh, Huu; Chen, C. P.

2004-01-01

Recent experimental investigations and physical modeling studies have indicated that turbulence behaviors within a liquid jet have considerable effects on the atomization process. For certain flow regimes, it has been observed that the liquid jet surface is highly turbulent. This turbulence characteristic plays a key role on the breakup of the liquid jet near to the injector exit. Other experiments also showed that the breakup length of the liquid core is sharply shortened as the liquid jet is changed from the laminar to the turbulent flow conditions. In the numerical and physical modeling arena, most of commonly used atomization models do not include the turbulence effect. Limited attempts have been made in modeling the turbulence phenomena on the liquid jet disintegration. The subject correlation and models treat the turbulence either as an only source or a primary driver in the breakup process. This study aims to model the turbulence effect in the atomization process of a cylindrical liquid jet. In the course of this study, two widely used models, Reitz's primary atomization (blob) and Taylor-Analogy-Break (TAB) secondary droplet breakup by O Rourke et al. are examined. Additional terms are derived and implemented appropriately into these two models to account for the turbulence effect on the atomization process. Since this enhancement effort is based on a framework of the two existing atomization models, it is appropriate to denote the two present models as T-blob and T-TAB for the primary and secondary atomization predictions, respectively. In the primary breakup model, the level of the turbulence effect on the liquid breakup depends on the characteristic time scales and the initial flow conditions. This treatment offers a balance of contributions of individual physical phenomena on the liquid breakup process. For the secondary breakup, an addition turbulence force acted on parent drops is modeled and integrated into the TAB governing equation. The drop size formed from this breakup regime is estimated based on the energy balance before and after the breakup occurrence. The turbulence energy is also considered in this process.

A Fragment-Cloud Model for Breakup of Asteroids with Varied Internal Structures

NASA Technical Reports Server (NTRS)

Wheeler, Lorien; Mathias, Donovan; Stokan, Ed; Brown, Peter

2016-01-01

As an asteroid descends toward Earth, it deposits energy in the atmosphere through aerodynamic drag and ablation. Asteroid impact risk assessments rely on energy deposition estimates to predict blast overpressures and ground damage that may result from an airburst, such as the one that occurred over Chelyabinsk, Russia in 2013. The rates and altitudes at which energy is deposited along the entry trajectory depend upon how the bolide fragments, which in turn depends upon its internal structure and composition. In this work, we have developed an analytic asteroid fragmentation model to assess the atmospheric energy deposition of asteroids with a range of structures and compositions. The modeling approach combines successive fragmentation of larger independent pieces with aggregate debris clouds released with each fragmentation event. The model can vary the number and masses of fragments produced, the amount of mass released as debris clouds, the size-strength scaling used to increase the robustness of smaller fragments, and other parameters. The initial asteroid body can be seeded with a distribution of independent fragment sizes amid a remaining debris mass to represent loose rubble pile conglomerations, can be given an outer regolith later, or can be defined as a coherent or fractured monolith. This approach enables the model to represent a range of breakup behaviors and reproduce detailed energy deposition features such as multiple flares due to successive burst events, high-altitude regolith blow-off, or initial disruption of rubble piles followed by more energetic breakup of the constituent boulders. These capabilities provide a means to investigate sensitivities of ground damage to potential variations in asteroid structure.

Droplet Breakup in Asymmetric T-Junctions at Intermediate to Large Capillary Numbers

NASA Astrophysics Data System (ADS)

Sadr, Reza; Cheng, Way Lee

2017-11-01

Splitting of a parent droplet into multiple daughter droplets of desired sizes is usually desired to enhance production and investigational efficiency in microfluidic devices. This can be done in an active or passive mode depending on whether an external power sources is used or not. In this study, three-dimensional simulations were done using the Volume-of-Fluid (VOF) method to analyze droplet splitting in asymmetric T-junctions with different outlet lengths. The parent droplet is divided into two uneven portions the volumetric ratio of the daughter droplets, in theory, depends on the length ratios of the outlet branches. The study identified various breakup modes such as primary, transition, bubble and non-breakup under various flow conditions and the configuration of the T-junctions. In addition, an analysis with the primary breakup regimes were conducted to study the breakup mechanisms. The results show that the way the droplet splits in an asymmetric T-junction is different than the process in a symmetric T-junction. A model for the asymmetric breakup criteria at intermediate or large Capillary number is presented. The proposed model is an expanded version to a theoretically derived model for the symmetric droplet breakup under similar flow conditions.

Study of Liquid Breakup Process in Solid Rocket Motor Nozzle

DTIC Science & Technology

2016-02-16

liquid film flow with the gas flow. The rate of the wave breakup was characterized by introducing Breakup-length, Ohnesorge Number (Oh) and Weber Number... liquid film that flows along the wall of a strraight test channel while a relatively higher-speed gas moves over it. We have used an unsteady-flow...Reynolds- Averaged Navier-Stokes code (URANS) to investigate the interaction of the liquid film flow with the gas flow. The rate of the wave breakup was

Effect of the breakup context on unwanted pursuit behavior perpetration between former partners.

PubMed

De Smet, Olivia; Buysse, Ann; Brondeel, Ruben

2011-07-01

Former partners comprise the most important subgroup of stalkers. However, contextual factors related to the breakup are hardly examined to explain ex-partner pursuit. In a community sample of 194 separated persons, about one-fifth perpetrated at least one unwanted pursuit behavior in the past 2 weeks. Being female, lowly educated, and socially undesirable raised the number of perpetrated behaviors. Beyond these effects, the number of behaviors increased when the cause of the break was attributed to the ex-partner or external factors and when the ex was appraised as the breakup initiator. Breakup reasons, the ex-partner's lack in meeting family obligations and own infidelity, also related to pursuit behaviors albeit inferior to subjective attributions and appraisals of initiation. Finally, participants who felt more anxious or lonely negative showed more behaviors. The results enlighten that the breakup context gains further attention. Clinical treatment might benefit from fostering cognitive reconstructions and breakup adjustment. © 2011 American Academy of Forensic Sciences.

Stalking perpetrators and psychological maltreatment of partners: anger-jealousy, attachment insecurity, need for control, and break-up context.

PubMed

Davis, K E; Ace, A; Andra, M

2000-01-01

Two studies of the correlates of self-reported courtship persistence, stalking-like behaviors following a relationship break-up, and psychological maltreatment of partners were conducted in samples of male (N = 46 and 93) and female (N = 123 and 110) college students. Approximately 40% (38.5% and 44.6%) engaged in at least one stalking behavior following a break-up. A total of 10.7% (study 1) and 7.6% (study 2) engaged in 6 or more stalking behaviors. Stalking was significantly related to psychological maltreatment of the partner (PMP) prior to the break-up. Being the recipient of the breakup was associated with feelings of anger, jealousy and obsessiveness and with higher levels of courtship persistence, and stalking. A replicated path model showed that anxious attachment and need for control were related to PMP and that need for control had a direct contribution to stalking. For anxious attachment, its connection to stalking was indirect, mediated by the degree of anger-jealousy over the break-up.

Space Shuttle Range Safety Command Destruct System Analysis and Verification. Phase 1. Destruct System Analysis and Verification

DTIC Science & Technology

1981-03-01

overcome the shortcomings of this system. A phase III study develops the breakup model of the Space Shuttle clus’ter at various times into flight. The...2-1 ROCKET MODEL ..................................................... 2-5 COMBUSTION CHAMBER OPERATION ................................... 2-5...2-19 RESULTS .......................................................... 2-22 ROCKET MODEL

Effect of Rheological Properties on Liquid Curtain Coating

NASA Astrophysics Data System (ADS)

Mohammad Karim, Alireza; Suszynski, Wieslaw; Griffith, William; Pujari, Saswati; Carvalho, Marcio; Francis, Lorraine; Dow Chemical Company Collaboration; PUC-Rio Collaboration

2017-11-01

Curtain coating is one of the preferred methods for high-speed precision application of single-layer and multi-layer coatings in technology. However, uniform coatings are only obtained in a certain range of operating parameters, called coating window. The two main physical mechanisms that limit successful curtain coating are liquid curtain breakup and air entrainment. The rheological properties of the liquid play an important role on these mechanisms, but the fundamental understanding of these relations is still not complete. The effect of rate-dependent shear and extensional viscosities on the stability of viscoelastic and shear thinning liquid curtains were explored by high-speed visualization. Aqueous solutions of polyethylene oxide (PEO) and polyethylene glycol (PEG) were used as viscoelastic liquids. Xanthan Gum in water and glycerol solutions with a range of compositions were used as shear thinning liquids. The critical condition was determined by examining flow rate below which curtain broke. In this work, we also analyze relative importance of rate-dependent shear and extensional viscosity on both curtain breakup and air entrainment. We would like to acknowledge the financial support from the Dow Chemical Company.

Image Alignment for Multiple Camera High Dynamic Range Microscopy.

PubMed

Eastwood, Brian S; Childs, Elisabeth C

2012-01-09

This paper investigates the problem of image alignment for multiple camera high dynamic range (HDR) imaging. HDR imaging combines information from images taken with different exposure settings. Combining information from multiple cameras requires an alignment process that is robust to the intensity differences in the images. HDR applications that use a limited number of component images require an alignment technique that is robust to large exposure differences. We evaluate the suitability for HDR alignment of three exposure-robust techniques. We conclude that image alignment based on matching feature descriptors extracted from radiant power images from calibrated cameras yields the most accurate and robust solution. We demonstrate the use of this alignment technique in a high dynamic range video microscope that enables live specimen imaging with a greater level of detail than can be captured with a single camera.

Image Alignment for Multiple Camera High Dynamic Range Microscopy

PubMed Central

Eastwood, Brian S.; Childs, Elisabeth C.

2012-01-01

This paper investigates the problem of image alignment for multiple camera high dynamic range (HDR) imaging. HDR imaging combines information from images taken with different exposure settings. Combining information from multiple cameras requires an alignment process that is robust to the intensity differences in the images. HDR applications that use a limited number of component images require an alignment technique that is robust to large exposure differences. We evaluate the suitability for HDR alignment of three exposure-robust techniques. We conclude that image alignment based on matching feature descriptors extracted from radiant power images from calibrated cameras yields the most accurate and robust solution. We demonstrate the use of this alignment technique in a high dynamic range video microscope that enables live specimen imaging with a greater level of detail than can be captured with a single camera. PMID:22545028

Exploring incomplete fusion fraction in 6,7Li induced nuclear reactions

NASA Astrophysics Data System (ADS)

Parkar, V. V.; Jha, V.; Kailas, S.

2017-11-01

We have included breakup effects explicitly to simultaneously calculate the measured cross-sections of the complete fusion, incomplete fusion, and total fusion for 6,7Li projectiles on various targets using the Continuum Discretized Coupled Channels method. The breakup absorption cross-sections obtained with different choices of short range imaginary potentials are utilized to evaluate the individual α-capture and d/t-capture cross-sections and compare with the measured data. It is interesting to note, while in case of 7Li projectile the cross-sections for triton-ICF/triton-capture is far more dominant than α-ICF/α-capture at all energies, similar behavior is not observed in case of 6Li projectile for the deuteron-ICF/deuteron-capture and α-ICF/α-capture. Both these observations are also corroborated by the experimental data for all the systems studied.

Dissociative electron attachment studies on acetone

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

Prabhudesai, Vaibhav S., E-mail: vaibhav@tifr.res.in; Tadsare, Vishvesh; Ghosh, Sanat

Dissociative electron attachment (DEA) to acetone is studied in terms of the absolute cross section for various fragment channels in the electron energy range of 0–20 eV. H{sup −} is found to be the most dominant fragment followed by O{sup −} and OH{sup −} with only one resonance peak between 8 and 9 eV. The DEA dynamics is studied by measuring the angular distribution and kinetic energy distribution of fragment anions using Velocity Slice Imaging technique. The kinetic energy and angular distribution of H{sup −} and O{sup −} fragments suggest a many body break-up for the lone resonance observed. Themore » ab initio calculations show that electron is captured in the multi-centered anti-bonding molecular orbital which would lead to a many body break-up of the resonance.« less

Nuclear science experiments with a bright neutron source from fusion reactions on the OMEGA Laser System

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

Forrest, C. J.; Knauer, J. P.; Schroeder, W. U.

Subnanosecond impulses of 10 13 to 10 14 neutrons, produced in direct-drive laser inertial confinement fusion implosions, have been used to irradiate deuterated targets at the OMEGA Laser System [T. R. Boehly et al., Opt. Commun. 133, 495 (1997)]. The target compounds include heavy water (D 2O) and deuterated benzene (C 6D 6). Yields and energy spectra of neutrons from D(n,2n)p to study the breakup reaction have been measured at a forward angle of θlab = 3.5 degrees plus/minus 3.5 degrees with a sensitive, high-dynamic-range neutron time-of-flight spectrometer to infer the double-differential breakup cross section d2sigma/dEdomega for 14-MeV D–T fusionmore » neutrons.« less

Beam breakup in an advanced linear induction accelerator

DOE PAGES

Ekdahl, Carl August; Coleman, Joshua Eugene; McCuistian, Brian Trent

2016-07-01

Two linear induction accelerators (LIAs) have been in operation for a number of years at the Los Alamos Dual Axis Radiographic Hydrodynamic Test (DARHT) facility. A new multipulse LIA is being developed. We have computationally investigated the beam breakup (BBU) instability in this advanced LIA. In particular, we have explored the consequences of the choice of beam injector energy and the grouping of LIA cells. We find that within the limited range of options presently under consideration for the LIA architecture, there is little adverse effect on the BBU growth. The computational tool that we used for this investigation wasmore » the beam dynamics code linear accelerator model for DARHT (LAMDA). In conclusion, to confirm that LAMDA was appropriate for this task, we first validated it through comparisons with the experimental BBU data acquired on the DARHT accelerators.« less

Nuclear science experiments with a bright neutron source from fusion reactions on the OMEGA Laser System

DOE PAGES

Forrest, C. J.; Knauer, J. P.; Schroeder, W. U.; ...

2018-01-31

Subnanosecond impulses of 10 13 to 10 14 neutrons, produced in direct-drive laser inertial confinement fusion implosions, have been used to irradiate deuterated targets at the OMEGA Laser System [T. R. Boehly et al., Opt. Commun. 133, 495 (1997)]. The target compounds include heavy water (D 2O) and deuterated benzene (C 6D 6). Yields and energy spectra of neutrons from D(n,2n)p to study the breakup reaction have been measured at a forward angle of θlab = 3.5 degrees plus/minus 3.5 degrees with a sensitive, high-dynamic-range neutron time-of-flight spectrometer to infer the double-differential breakup cross section d2sigma/dEdomega for 14-MeV D–T fusionmore » neutrons.« less

Breakup Effects on University Students' Perceived Academic Performance

ERIC Educational Resources Information Center

Field, Tiffany; Diego, Miguel; Pelaez, Martha; Deeds, Osvelia; Delgado, Jeannette

2012-01-01

The Problem: Problems that might be expected to affect perceived academic performance were studied in a sample of 283 university students. Results: Breakup Distress Scale scores, less time since the breakup and no new relationship contributed to 16% of the variance on perceived academic performance. Variables that were related to academic…

STUDY OP THE 12C(α, γ)16O REACTION BY BREAKUP OF A 16O -BEAM AT 100 MeV/A

NASA Astrophysics Data System (ADS)

Tatischeff, V.; Kiener, J.; Aguer, P.; Angulo-Perez, C.; Bogaert, G.; Coc, A.; Disdier, D.; Ichihara, T.; Kraus, L.; Lefebvre, A.; Linck, I.; Mittig, W.; Motobayashi, T.; Oliveira, F.; Roussel-Chomaz, P.; Stephan, C.; Thibaud, J. P.

We present some preliminary calculations on cross sections for the breakup of 16O around 100 MeV/A with emphasis on the effect of nuclear breakup on the angular distributions. Underlying the results of these calculations, the possibilities and problems of extracting the astrophysical S-factor for the 12C(α, γ)16O reaction at very low energies are discussed. Some considerations on the experimental conditions for a 16O breakup experiment aiming at this astrophysical information, are given.

A comparative study on the breakup of Newtonian and viscoelastic liquid films

NASA Astrophysics Data System (ADS)

Qian, Lijuan; Song, Shaobo; Jiang, Lisha; Li, Xiaolu; Lin, Jianzhong

2018-05-01

The breakup of viscoelastic liquid films are investigated experimentally and analytically. The breakup phenomena of viscoelastic liquid film are recorded by the time resolved high speed camera. Video images reveal the difference behavior of liquid bubble breakup for Newtonian and viscoelastic liquid. For the Newtonian liquid, cylindrical ligaments are stretched into droplets with large distributions of drop size. For the viscoelastic liquid, the pinch-off point is located on the liquid connections to the nozzle and finally the main part of the ligament no longer elongates. Furthermore, a dispersion relation based on the stability analysis is involved to predict the ligament length and drop mean size after breakup for liquid film. The calculated ligament length is validated by the measured drop mean size at higher air-to-liquid mass flow ratio.

Observing Strategies for Focused Orbital Debris Surveys Using the Magellan Telescope

NASA Technical Reports Server (NTRS)

Frith, James; Cowardin, Heather; Buckalew, Brent; Anz-Meador, Phillip; Lederer, Susan; Matney, Mark

2017-01-01

A breakup of the Titan 3C-17 Transtage rocket body was reported to have occurred on June 4th, 2014 at 02:38 UT by the Space Surveillance Network (SSN). Five objects were associated with this breakup and this is the fourth breakup known for this class of object. There are likely many more objects associated with this event that are not within the Space Surveillance Network's ability to detect and have not been catalogued. Several months after the breakup, observing time was obtained on the Magellan Baade 6.5 meter telescope to be used for observations of geosynchronous (GEO) space debris targets. Using the NASA Standard Satellite Breakup Model (SSBM), a simulated debris cloud of the recent Transtage breakup was produced and propagated forward in time. This provided right ascension, declination, and tracking rate predictions for where debris associated with this breakup may be more likely to be found in the sky over Magellan for our observing run. Magellan observations were then optimized using the angles and tracking rates from the model predictions to focus the search for Transtage debris. Data were collected and analysed and preliminary comparisons made between the number of objects detected and the number expected from the model. We present our results here.

Strategic obstacle placement reduces drop breakup probability in concentrated emulsion flowing into a constriction

NASA Astrophysics Data System (ADS)

Khor, Jian Wei; Hua, Yu; Bick, Alison; Tang, Sindy

2017-11-01

In this study, we investigate the effect of an obstacle on the breakup probability of droplets within a concentrated emulsion flowing into a constriction. We introduce a concentrated emulsion as a 2D monolayer through a tapered channel into a narrow constriction. This geometry is commonly used for the serial interrogation of droplet content in droplet microfluidics applications. We found that certain drop-drop interactions near the constriction entrance lead to the breakup of these drops at a high flow rates. Such breakup sets the upper limit for the droplet interrogation throughput. Incidentally, previous findings have shown that strategic placement of a circular post near a narrow exit can reduce the conflict from the interactions among living organisms (humans, ants, and sheep) or a cluster of particles when entering a narrow exit. Inspired by these results, we modify the tapered channel by placing a circular post in a strategic location near the constriction entrance in order to reduce catastrophic drop-drop interactions and to avoid breakup. Preliminary work shows that the circular posts can reduce the breakup fraction of drops by up to 17%. The optimization of the location and size of the obstacle is expected to further reduce the breakup fraction.

The Galactic Center S-stars and the Hypervelocity Stars in the Galactic Halo: Two Faces of the Tidal Breakup of Stellar Binaries by the Central Massive Black Hole?

NASA Astrophysics Data System (ADS)

Zhang, Fupeng; Lu, Youjun; Yu, Qingjuan

2013-05-01

In this paper, we investigate the link between the hypervelocity stars (HVSs) discovered in the Galactic halo and the Galactic center (GC) S-stars, under the hypothesis that they are both the products of the tidal breakup of the same population of stellar binaries by the central massive black hole (MBH). By adopting several hypothetical models for binaries to be injected into the vicinity of the MBH and doing numerical simulations, we realize the tidal breakup processes of the binaries and their follow-up dynamical evolution. We find that many statistical properties of the detected HVSs and GC S-stars could be reproduced under some binary injecting models, and their number ratio can be reproduced if the stellar initial mass function is top-heavy (e.g., with slope ~ - 1.6). The total number of the captured companions is ~50 that have masses in the range ~3-7 M ⊙ and semimajor axes <~ 4000 AU and survive to the present within their main-sequence lifetime. The innermost one is expected to have a semimajor axis ~300-1500 AU and a pericenter distance ~10-200 AU, with a significant probability of being closer to the MBH than S2. Future detection of such a close star would offer an important test to general relativity. The majority of the surviving ejected companions of the GC S-stars are expected to be located at Galactocentric distances <~ 20 kpc, and have heliocentric radial velocities ~ - 500-1500 km s-1 and proper motions up to ~5-20 mas yr-1. Future detection of these HVSs may provide evidence for the tidal breakup formation mechanism of the GC S-stars.

Free-surface liquid jet impingement on rib patterned superhydrophobic surfaces

NASA Astrophysics Data System (ADS)

Maynes, D.; Johnson, M.; Webb, B. W.

2011-05-01

We report experimental results characterizing the dynamics of a liquid jet impinging normally on hydrophilic, hydrophobic, and superhydrophobic surfaces spanning the Weber number (based on the jet velocity and diameter) range from 100 to 1900. The superhydrophobic surfaces are fabricated with both hydrophobically coated silicon and polydimethylsiloxane that exhibit alternating microribs and cavities. For all surfaces a transition from a thin radially moving liquid sheet occurs. This takes the form of the classical hydraulic jump for the hydrophilic surfaces but is markedly different for the hydrophobic and superhydrophobic surfaces, where the transition is significantly influenced by surface tension and a break-up into droplets is observed at high Weber number. For the superhydrophobic surfaces, the transition exhibits an elliptical shape with the major axis being aligned parallel to the ribs, concomitant with the frictional resistance being smaller in the parallel direction than in the transverse direction. However, the total projected area of the ellipse exhibits a nearly linear dependence on the jet Weber number, and was nominally invariant with varying hydrophobicity and relative size of the ribs and cavities. For the hydrophobic and superhydrophobic scenarios, the local Weber number based on the local radial velocity and local depth of the radially moving liquid sheet is observed to be of order unity at the transition location. The results also reveal that for increasing relative size of the cavities, the ratio of the ellipse axis (major-to-minor) increases.

Star of Condor - A strontium critical velocity experiment, Peru, 1983

NASA Technical Reports Server (NTRS)

Wescott, E. M.; Stenbaek-Nielsen, H. C.; Hallinan, T.; Foeppl, H.; Valenzuela, A.

1986-01-01

'Star of Condor' was a critical velocity experiment using Sr vapor produced in a radial shaped charge, which was carried to 571.11 km altitude on a Taurus-Tomahawk rocket launched from Punto Lobos, Peru, and detonated in the plane of the magnetic field lines so that all ranges of pitch angles from parallel to B to perpendicular to B were covered. Sr has a critical velocity of 3.3 km/s, and from observation, 42.5 percent of the neutral Sr gas had a velocity component perpendicular to B exceeding that value. No Sr ion emissions were detected shortly after the burst with usual TV integration times. However, about 10 min after the detonation a faint field-aligned streak was discovered with long TV integration times. The brightness is estimated as 5 R, which, combined with the streak geometry, implies an ion production of 2.4 x 10 to the 19th ions. This is only 0.0036 percent ionization of the Sr vapor. All the ions could easily have been produced by thermal ionization from the original detonation thermal distribution. The breakup of the Sr gas into small bloblike structures may have allowed the high-energy electrons to escape before an ionization cascade could be produced. For whatever reason, the Alfven mechanism proposed for space plasmas in the absence of laboratory walls did not produce an ionization cascade in the experiment.

Multi-dimensional dynamics of stimulated Brillouin scattering in a laser speckle: Ion acoustic wave bowing, breakup, and laser-seeded two-ion-wave decay

DOE PAGES

Albright, B. J.; Yin, L.; Bowers, K. J.; ...

2016-03-04

Two- and three-dimensional particle-in-cell simulations of stimulated Brillouin scattering(SBS) in laser speckle geometry have been analyzed to evaluate the relative importance of competing nonlinear processes in the evolution and saturation of SBS. It is found that ion-trapping-induced wavefront bowing and breakup of ion acoustic waves(IAW) and the associated side-loss of trapped ions dominate electron-trapping-induced IAW wavefront bowing and breakup, as well as the two-ion-wave decay instability over a range of ZT e/T i conditions and incident laser intensities. In the simulations, the latter instability does not govern the nonlinear saturation of SBS; however, evidence of two-ion-wave decay is seen, appearingmore » as a modulation of the ion acoustic wavefronts. This modulation is periodic in the laser polarization plane, anti-symmetric across the speckle axis, and of a wavenumber matching that of the incident laser pulse. Furthermore, a simple analytic model is provided for how spatial “imprinting” from a high frequency inhomogeneity (in this case, the density modulation from the laser) in an unstable system with continuum eigenmodes can selectively amplify modes with wavenumbers that match that of the inhomogeneity.« less

Drag Coefficient of Water Droplets Approaching the Leading Edge of an Airfoil

NASA Technical Reports Server (NTRS)

Vargas, Mario; Sor, Suthyvann; Magarino, Adelaida Garcia

2013-01-01

This work presents results of an experimental study on droplet deformation and breakup near the leading edge of an airfoil. The experiment was conducted in the rotating rig test cell at the Instituto Nacional de Tecnica Aeroespacial (INTA) in Madrid, Spain. An airfoil model was placed at the end of the rotating arm and a monosize droplet generator produced droplets that fell from above, perpendicular to the path of the airfoil. The interaction between the droplets and the airfoil was captured with high speed imaging and allowed observation of droplet deformation and breakup as the droplet approached the airfoil near the stagnation line. Image processing software was used to measure the position of the droplet centroid, equivalent diameter, perimeter, area, and the major and minor axes of an ellipse superimposed over the deforming droplet. The horizontal and vertical displacement of each droplet against time was also measured, and the velocity, acceleration, Weber number, Bond number, Reynolds number, and the drag coefficients were calculated along the path of the droplet to the beginning of breakup. Results are presented and discussed for drag coefficients of droplets with diameters in the range of 300 to 1800 micrometers, and airfoil velocities of 50, 70 and 90 meters/second. The effect of droplet oscillation on the drag coefficient is discussed.

Drop Ejection From an Oscillating Rod

NASA Technical Reports Server (NTRS)

Wilkes, E. D.; Basaran, O. A.

1999-01-01

The dynamics of a drop of a Newtonian liquid that is pendant from or sessile on a solid rod that is forced to undergo time-periodic oscillations along its axis is studied theoretically. The free boundary problem governing the time evolution of the shape of the drop and the flow field inside it is solved by a method of lines using a finite element algorithm incorporating an adaptive mesh. When the forcing amplitude is small, the drop approaches a limit cycle at large times and undergoes steady oscillations thereafter. However, drop breakup is the consequence if the forcing amplitude exceeds a critical value. Over a wide range of amplitudes above this critical value, drop ejection from the rod occurs during the second oscillation period from the commencement of rod motion. Remarkably, the shape of the interface at breakup and the volume of the primary drop formed are insensitive to changes in forcing amplitude. The interface shape at times close to and at breakup is a multi-valued function of distance measured along the rod axis and hence cannot be described by recently popularized one-dimensional approximations. The computations show that drop ejection occurs without the formation of a long neck. Therefore, this method of drop formation holds promise of preventing formation of undesirable satellite droplets.

Micro-scale extensional rheometry using hyperbolic converging/diverging channels and jet breakup

PubMed Central

Keshavarz, Bavand

2016-01-01

Understanding the elongational rheology of dilute polymer solutions plays an important role in many biological and industrial applications ranging from microfluidic lab-on-a-chip diagnostics to phenomena such as fuel atomization and combustion. Making quantitative measurements of the extensional viscosity for dilute viscoelastic fluids is a long-standing challenge and it motivates developments in microfluidic fabrication techniques and high speed/strobe imaging of millifluidic capillary phenomena in order to develop new classes of instruments. In this paper, we study the elongational rheology of a family of dilute polymeric solutions in two devices: first, steady pressure-driven flow through a hyperbolic microfluidic contraction/expansion and, second, the capillary driven breakup of a thin filament formed from a small diameter jet (Dj∼O(100 μm)). The small length scale of the device allows very large deformation rates to be achieved. Our results show that in certain limits of low viscosity and elasticity, jet breakup studies offer significant advantages over the hyperbolic channel measurements despite the more complex implementation. Using our results, together with scaling estimates of the competing viscous, elastic, inertial and capillary timescales that control the dynamics, we construct a dimensionless map or nomogram summarizing the operating space for each instrument. PMID:27375824

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

Eddy, N.; Fellenz, B.; Prieto, P.

The first cryomodule for the beam test facility at the Fermilab New-Muon-Lab building is currently under RF commissioning. Among other diagnostics systems, the transverse position of the helium gas return pipe with the connected 1.3 GHz SRF accelerating cavities is measured along the {approx}15 m long module using a stretched-wire position monitoring system. An overview of the wire position monitor system technology is given, along with preliminary results taken at the initial module cooldown, and during further testing. As the measurement system offers a high resolution, we also discuss options for use as a vibration detector. An electron beam testmore » facility, based on superconducting RF (SRF) TESLA-style cryomodules is currently under construction at the Fermilab New-Muon-Lab (NML) building. The first, so-called type III+, cryomodule (CM-1), equipped with eight 1.3 GHz nine-cell accelerating cavities was recently cooled down to 2 K, and is currently under RF conditioning. The transverse alignment of the cavity string within the cryomodule is crucial for minimizing transverse kick and beam break-up effects, generated by the high-order dipole modes of misaligned accelerating structures. An optimum alignment can only be guaranteed during the assembly of the cavity string, i.e. at room temperatures. The final position of the cavities after cooldown is uncontrollable, and therefore unknown. A wire position monitoring system (WPM) can help to understand the transverse motion of the cavities during cooldown, their final location and the long term position stability after cryo-temperatures are settled, as well as the position reproducibility for several cold-warm cycles. It also may serve as vibration sensor, as the wire acts as a high-Q resonant detector for mechanical vibrations in the low-audio frequency range. The WPM system consists out of a stretched-wire position detection system, provided with help of INFN-Milano and DESY Hamburg, and RF generation and read-out electronics, developed at Fermilab.« less

Dynamics of Debris Motion and the Collision Hazard to Spacecraft Resulting from an Orbital Breakup

DTIC Science & Technology

1988-01-01

Time, Clohessy - Wiltshire and Torus Approximation ....................................... 44 21. J2 Parameters, C1 , C2 , C3, versus Av; 200-nmi...revolving about the same gravitational attracting mass is the Clohessy - Wiltshire equations. In matrix form, the analytical solution is 38 r 42 x I 6(wt...can determine the range of validity of the Clohessy - Wiltshire equations. 3.3 RESULTS The range of validity can be determined by comparing the effects

Long-range dynamic polarization potentials for 11Be projectiles on 64Zn

NASA Astrophysics Data System (ADS)

So, W. Y.; Kim, K. S.; Choi, K. S.; Cheoun, Myung-Ki

2015-07-01

We investigate the effects of the long-range dynamic polarization (LRDP) potential, which consists of the Coulomb dipole excitation (CDE) potential and the long-range nuclear (LRN) potential, for the 11Be projectile on 64Zn. To study these effects, we perform a χ2 analysis of an optical model including the LRDP potential as well as a conventional short-range nuclear (SRN) potential. To take these effects into account, we argue that both the CDE and LRN potentials are essential to explaining the experimental values of PE, which is the ratio of the elastic scattering cross section to the Rutherford cross section. The Coulomb and nuclear parts of the LRDP potential are found to contribute to a strong absorption effect. Strong absorption occurs because the real part of the CDE and LRN potentials lowers the barrier, and the imaginary part of the CDE and LRN potentials removes the flux from the elastic channel in the 11Be+64Zn system. Finally, we extract the total reaction cross section σR including the inelastic, breakup, and fusion cross sections. The contribution of the inelastic scattering by the first excited state at ɛx1 st=0.32 MeV (1 /2-) is found to be relatively large and cannot be ignored. In addition, our results are shown to agree quite well with the experimental breakup reaction cross section by using a fairly large radius parameter.

Elastic Coulomb breakup of 34Na

NASA Astrophysics Data System (ADS)

Singh, G.; Shubhchintak, Chatterjee, R.

2016-08-01

Background: 34Na is conjectured to play an important role in the production of seed nuclei in the alternate r -process paths involving light neutron rich nuclei very near the β -stability line, and as such, it is important to know its ground state properties and structure to calculate rates of the reactions it might be involved in, in the stellar plasma. Found in the region of `island of inversion', its ground state might not be in agreement with normal shell model predictions. Purpose: The aim of this paper is to study the elastic Coulomb breakup of 34Na on 208Pb to give us a core of 33Na with a neutron and in the process we try and investigate the one neutron separation energy and the ground state configuration of 34Na. Method: A fully quantum mechanical Coulomb breakup theory within the architecture of post-form finite range distorted wave Born approximation extended to include the effects of deformation is used to research the elastic Coulomb breakup of 34Na on 208Pb at 100 MeV/u. The triple differential cross section calculated for the breakup is integrated over the desired components to find the total cross-section, momentum, and angular distributions as well as the average momenta, along with the energy-angular distributions. Results: The total one neutron removal cross section is calculated to test the possible ground state configurations of 34Na. The average momentum results along with energy-angular calculations indicate 34Na to have a halo structure. The parallel momentum distributions with narrow full widths at half-maxima signify the same. Conclusion: We have attempted to analyze the possible ground state configurations of 34Na and in congruity with the patterns in the `island of inversion' conclude that even without deformation, 34Na should be a neutron halo with a predominant contribution to its ground state most probably coming from 33Na(3 /2+)⊗ 2 p3 /2ν configuration. We also surmise that it would certainly be useful and rewarding to test our predictions with an experiment to put stricter limits on its ground state configuration and binding energy.

Modelling the breakup of solid aggregates in turbulent flows

NASA Astrophysics Data System (ADS)

B?Bler, Matth?Us U.; Morbidelli, Massimo; Ba?Dyga, Jerzy

The breakup of solid aggregates suspended in a turbulent flow is considered. The aggregates are assumed to be small with respect to the Kolmogorov length scale and the flow is assumed to be homogeneous. Further, it is assumed that breakup is caused by hydrodynamic stresses acting on the aggregates, and breakup is therefore assumed to follow a first-order kinetic where KB(x) is the breakup rate function and x is the aggregate mass. To model KB(x), it is assumed that an aggregate breaks instantaneously when the surrounding flow is violent enough to create a hydrodynamic stress that exceeds a critical value required to break the aggregate. For aggregates smaller than the Kolmogorov length scale the hydrodynamic stress is determined by the viscosity and local energy dissipation rate whose fluctuations are highly intermittent. Hence, the first-order breakup kinetics are governed by the frequency with which the local energy dissipation rate exceeds a critical value (that corresponds to the critical stress). A multifractal model is adopted to describe the statistical properties of the local energy dissipation rate, and a power-law relation is used to relate the critical energy dissipation rate above which breakup occurs to the aggregate mass. The model leads to an expression for KB(x) that is zero below a limiting aggregate mass, and diverges for x . When simulating the breakup process, the former leads to an asymptotic mean aggregate size whose scaling with the mean energy dissipation rate differs by one third from the scaling expected in a non-fluctuating flow.

Breakup of a liquid rivulet falling over an inclined plate: Identification of a critical Weber number

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

Singh, Rajesh K.; Galvin, Janine E.; Whyatt, Greg A.

2017-05-01

We have numerically investigated the breakup of a rivulet falling over a smooth inclined plate using the volume of fluid method. The breakup the rivulet is a complex phenomenon that is dictated by many factors, such as solvent properties, contact angle, inertia, plate inclination, etc. An extensive simulation campaign was conducted wherein these factors were systematically investigated. Regimes for a stable rivulet and an unstable rivulet that leads to the breakup and formation of a droplet are examined in terms of a critical value of the Weber number (Wecr) that delineates these regimes. The effect of plate inclination on themore » breakup of the rivulet shows that the critical Weber number decreases with increased inclination angle () owing to higher liquid velocity. However, the effect is negligible beyond >60. The impact of solvent properties is characterized using the Kapitza number (Ka). Variation of Wecr with Ka shows two trends depending on the Ka value of the solvent. Solvents with lower Ka values, corresponding to high viscosities and/or low surface tensions, show smaller values of the critical Weber number and the variation is linear. While solvents with higher Ka values exhibit higher values of the Wecr and the variation in Wecr is steep. This behavior is more pronounced with increasing contact angle. Higher contact angles promote rivulet breakup so that inertia must be higher to the breakup. A phenomenological scaling for a critical Weber number with the Kapitza number and contact angle is presented that can offer insight into rivulet breakup.« less

24 CFR 982.315 - Family break-up.

Code of Federal Regulations, 2011 CFR

2011-04-01

... 24 Housing and Urban Development 4 2011-04-01 2011-04-01 false Family break-up. 982.315 Section... SECTION 8 TENANT BASED ASSISTANCE: HOUSING CHOICE VOUCHER PROGRAM Leasing a Unit § 982.315 Family break-up. (a)(1) The PHA has discretion to determine which members of an assisted family continue to receive...

24 CFR 982.315 - Family break-up.

Code of Federal Regulations, 2010 CFR

2010-04-01

... 24 Housing and Urban Development 4 2010-04-01 2010-04-01 false Family break-up. 982.315 Section... SECTION 8 TENANT BASED ASSISTANCE: HOUSING CHOICE VOUCHER PROGRAM Leasing a Unit § 982.315 Family break-up. (a) The PHA has discretion to determine which members of an assisted family continue to receive...

Robustness of free and pinned spiral waves against breakup by electrical forcing in excitable chemical media.

PubMed

Phantu, Metinee; Sutthiopad, Malee; Luengviriya, Jiraporn; Müller, Stefan C; Luengviriya, Chaiya

2017-04-01

We present an investigation on the breakup of free and pinned spiral waves under an applied electrical current in the Belousov-Zhabotinsky reaction. Spiral fronts propagating towards the negative electrode are decelerated. A breakup of the spiral waves occurs when some segments of the fronts are stopped by a sufficiently strong electrical current. In the absence of obstacles (i.e., free spiral waves), the critical value of the electrical current for the wave breakup increases with the excitability of the medium. For spiral waves pinned to circular obstacles, the critical electrical current increases with the obstacle diameter. Analysis of spiral dynamics shows that the enhancement of the robustness against the breakup of both free and pinned spiral waves is originated by the increment of wave speed when either the excitability is strengthened or the obstacle size is enlarged. The experimental findings are reproduced by numerical simulations using the Oregonator model. In addition, the simulations reveal that the robustness against the forced breakup increases with the activator level in both cases of free and pinned spiral waves.

Family breakup and adolescents' psychosocial maladjustment: public health implications of family disruptions.

PubMed

Roustit, Christelle; Chaix, Basile; Chauvin, Pierre

2007-10-01

Recent changes in family structure are associated with an increase in psychosocial maladjustment in adolescents. We examined, from a public health intervention perspective, the association between family breakup and psychosocial maladjustment in adolescents and assessed the mediating role of family-functioning variables. We analyzed data from the Social and Health Survey of Children and Adolescents in Quebec, Montreal, Canada, which was conducted in 1999. Sample-weighted logistic regression analyses were performed to determine the risk of internalizing disorders, externalizing disorders, substance abuse, and alcohol consumption in relation to family breakups and family-functioning variables, after adjusting for socioeconomic factors. All 4 of the indicators of psychosocial maladjustment were significantly associated with family breakup. The association between family breakups and internalizing disorders was mediated by parental psychological distress and low paternal emotional support. Independently, the witnessing of interparental violence was also strongly associated with internalizing disorders. For the other 3 outcomes, that is, externalizing disorders, substance abuse, and alcohol consumption, family breakup and family-functioning variables had independent effects. Family-based interventions and social approaches are complementary support modalities for adolescents experiencing family disruptions.

Toward a Physical Characterization of Raindrop Collision Outcome Regimes

NASA Technical Reports Server (NTRS)

Testik, F. Y.; Barros, Ana P.; Bilven, Francis L.

2011-01-01

A comprehensive raindrop collision outcome regime diagram that delineates the physical conditions associated with the outcome regimes (i.e., bounce, coalescence, and different breakup types) of binary raindrop collisions is proposed. The proposed diagram builds on a theoretical regime diagram defined in the phase space of collision Weber numbers We and the drop diameter ratio p by including critical angle of impact considerations. In this study, the theoretical regime diagram is first evaluated against a comprehensive dataset for drop collision experiments representative of raindrop collisions in nature. Subsequently, the theoretical regime diagram is modified to explicitly describe the dominant regimes of raindrop interactions in (We, p) by delineating the physical conditions necessary for the occurrence of distinct types of collision-induced breakup (neck/filament, sheet, disk, and crown breakups) based on critical angle of impact consideration. Crown breakup is a subtype of disk breakup for lower collision kinetic energy that presents distinctive morphology. Finally, the experimental results are analyzed in the context of the comprehensive collision regime diagram, and conditional probabilities that can be used in the parameterization of breakup kernels in stochastic models of raindrop dynamics are provided.

History of satellite break-ups in space

NASA Technical Reports Server (NTRS)

Gabbard, J.

1985-01-01

By 28 June 1961 the 1st Aerospace Control Squadron had cataloged 115 Earth orbiting satellites from data supplied by a rather diverse collection of radar and optical sensors. On 29 June 1961, the Able Star rocket of the 1961 Omicron launch exploded causing a quantum jump in the number of Earth orbiting objects. Since that time there have been 69 Earth orbiting satellites break up in space whose debris remained in orbit long enough for orbital elements to be developed. A list of the 69 breakups is provided. The debris from some of the lower altitude breakups has all decayed. Among the 69 breakups, 44 have cataloged debris remaining in orbit. As of 1 July 1982, the size of the cataloged orbiting population was exactly 4700. Forty-nine percent of these objects are fragments of the forty-four breakups. For each breakup the various orbits of its debris represent a family of orbits that are related in characteristics due to their common impulse launch. A few examples are shown of how the families are oriented in space.

Gas density effect on dropsize of simulated fuel sprays

NASA Technical Reports Server (NTRS)

Ingebo, Robert D.

1989-01-01

Two-phase flow in pneumatic two-fluid fuel nozzles was investigated experimentally to determine the effect of atomizing-gas density and gas mass-flux on liquid-jet breakup in sonic-velocity gas-flow. Dropsize data were obtained for the following atomizing-gases: nitrogen; argon; carbon dioxide; and helium. They were selected to cover a gas molecular-weight range of 4 to 44. Atomizing-gas mass-flux ranged from 6 to 50 g/sq cm-sec and four differently sized two-fluid fuel nozzles were used having orifice diameters that varied from 0.32 to 0.56 cm. The ratio of liquid-jet diameter to SMD, D sub o/D sub 32, was correlated with aerodynamic and liquid-surface forces based on the product of the Weber and Reynolds number, We*Re, and gas-to-liquid density ratio, rho sub g/rho sub l. To correlate spray dropsize with breakup forces produced by using different atomizing-gases, a new molecular-scale dimensionless group was derived. The derived dimensionless group was used to obtain an expression for the ratio of liquid-jet diameter to SMD, D sub o/D sub 32. The mathematical expression of this phenomenon incorporates the product of the Weber and Reynolds number, liquid viscosity, surface tension, acoustic gas velocity, the RMS velocity of gas molecules, the acceleration of gas molecules due to gravity, and gas viscosity. The mathematical expression encompassing these parameters agrees well with the atomization theory for liquid-jet breakup in high velocity gas flow. Also, it was found that at the same gas mass-flux, helium was considerably more effective than nitrogen in producing small droplet sprays with SMD's in the order of 5 micrometers.

Incomplete fusion analysis of the 7Li-induced reaction on 93Nb within 3-6.5 MeV/nucleon

NASA Astrophysics Data System (ADS)

Kumar, Deepak; Maiti, Moumita

2017-10-01

Background: It is understood from the recent experimental studies that prompt/resonant breakup, and transfer followed by breakup in the weakly bound Li,76-induced reactions play a significant role in the complete-incomplete fusion (CF-ICF), suppression/enhancement in the fusion cross section around the Coulomb barrier. Purpose: Investigation of ICF over CF by measuring cross sections of the populated residues, produced via different channels in the 7Li-induced reaction on a natNb target within the 3-6.5 MeV/nucleon energy region. Method: The 7Li beam was allowed to hit the self-supporting 93Nb targets, backed by the aluminium (Al) foil alternately, within 3-6.5 MeV/nucleon energy. Populated residues were identified by offline γ -ray spectrometry. Measured excitation functions of different channels were compared with different equilibrium and pre-equilibrium models. Result: The enhancement in cross sections in the proton (˜20 -30 MeV) and α -emitting channels, which may be ascribed to ICF, was observed in the measured energy range when compared to the Hauser-Feshbach and exciton model calculations using empire, which satisfactorily reproduces the neutron channels, compared to the Weisskopf-Ewing model and hybrid Monte Carlo calculations. The increment of the incomplete fusion fraction was observed with rising projectile energy. Conclusion: Contrary to the alice14, experimental results are well reproduced by the empire throughout the measured energy range. The signature of ICF over CF indicates that the breakup/transfer processes are involved in the weakly bound 7Li-induced reaction on 93Nb slightly above the Coulomb barrier.

Outcomes of Thermal Pulsation Treatment for Dry Eye Syndrome in Patients With Sjogren Disease.

PubMed

Godin, Morgan R; Stinnett, Sandra S; Gupta, Preeya K

2018-04-26

To evaluate the clinical outcomes of thermal pulsation treatment in patients with meibomian gland dysfunction (MGD) and dry eye secondary to Sjogren disease. Twenty-four eyes from 13 patients with previously diagnosed Sjogren disease who presented to our institution with dry eye symptoms and had thermal pulsation treatment were prospectively followed up. Patients underwent comprehensive slit-lamp examination, including MGD grading, gland oil flow, corneal and conjunctival staining scores, and tear break-up time (TBUT). Tear osmolarity was tested before and after treatment. The average patient age was 62.4 years (range, 31-78 yrs); 12 were women and 1 a man. The average meibomian gland oil flow score showed an increase from pretreatment 0.71 to 1.75 at 1 year posttreatment (range 9-15 months) (P = 0.001). The average corneal staining score decreased from a pretreatment grade of 1.04 to a posttreatment grade of 0.36 (P < 0.001). The average conjunctival staining score decreased from a pretreatment grade of 1.5 to a posttreatment grade of 0.48 (P < 0.001). The average tear break-up time improved from 3.8 seconds before treatment to 7.5 seconds after thermal pulsation treatment (P < 0.001). There was no statistically significant change in the tear osmolarity or Ocular Surface Disease Index score. Our findings suggest that MGD is an important contributor to dry eye disease in patients with Sjogren disease and should not be overlooked when considering treatment options. Thermal pulsation is a therapeutic option for patients with Sjogren disease who have MGD and dry eye symptoms. After a single treatment, patients exhibited increased oil flow and tear break-up time with an associated decrease in corneal and conjunctival staining.

11Li Breakup on 208 at energies around the Coulomb barrier.

PubMed

Fernández-García, J P; Cubero, M; Rodríguez-Gallardo, M; Acosta, L; Alcorta, M; Alvarez, M A G; Borge, M J G; Buchmann, L; Diget, C A; Falou, H A; Fulton, B R; Fynbo, H O U; Galaviz, D; Gómez-Camacho, J; Kanungo, R; Lay, J A; Madurga, M; Martel, I; Moro, A M; Mukha, I; Nilsson, T; Sánchez-Benítez, A M; Shotter, A; Tengblad, O; Walden, P

2013-04-05

The inclusive breakup for the (11)Li + (208)Pb reaction at energies around the Coulomb barrier has been measured for the first time. A sizable yield of (9)Li following the (11)Li dissociation has been observed, even at energies well below the Coulomb barrier. Using the first-order semiclassical perturbation theory of Coulomb excitation it is shown that the breakup probability data measured at small angles can be used to extract effective breakup energy as well as the slope of B(E1) distribution close to the threshold. Four-body continuum-discretized coupled-channels calculations, including both nuclear and Coulomb couplings between the target and projectile to all orders, reproduce the measured inclusive breakup cross sections and support the presence of a dipole resonance in the (11)Li continuum at low excitation energy.

Facing a breakup: Electromyographic responses moderate self-concept recovery following a romantic separation

PubMed Central

MASON, ASHLEY E.; LAW, RITA W.; BRYAN, AMANDA E. B.; PORTLEY, ROBERT M.; SBARRA, DAVID A.

2015-01-01

Romantic breakups arouse fundamental questions about the self: Who am I without my partner? This study examined self-concept reorganization and psychological well-being over an 8-week period in the months following a breakup. Multilevel analyses revealed that poorer self-concept recovery preceded poorer well-being and was associated with love for an ex-partner, suggesting that failure to redefine the self contributes to post-breakup distress. Psychophysiological data revealed that greater activity in the corrugator supercilia facial muscle while thinking about an ex-partner predicted poorer self-concept recovery and strengthened the negative association between love for an ex-partner and self-concept recovery. Thus, the interaction between self-report and psychophysiological data provided information about the importance of self-concept recovery to post-breakup adjustment not tapped by either method alone. PMID:26167126

With or Without You? Contextualizing the Impact of Romantic Relationship Breakup on Crime Among Serious Adolescent Offenders.

PubMed

Larson, Matthew; Sweeten, Gary; Piquero, Alex R

2016-01-01

The decline and delay of marriage has prolonged adolescence and the transition to adulthood, and consequently fostered greater romantic relationship fluidity during a stage of the life course that is pivotal for both development and offending. Yet, despite a growing literature of the consequences of romantic relationships breakup, little is known about its connection with crime, especially among youth enmeshed in the criminal justice system. This article addresses this gap by examining the effects of relationship breakup on crime among justice-involved youth-a key policy-relevant group. We refer to data from the Pathways to Desistance Study, a longitudinal study of 1354 (14% female) adjudicated youth from the juvenile and adult court systems in Phoenix and Philadelphia, to assess the nature and complexity of this association. In general, our results support prior evidence of breakup's criminogenic influence. Specifically, they suggest that relationship breakup's effect on crime is particularly acute among this at-risk sample, contingent upon post-breakup relationship transitions, and more pronounced for relationships that involve cohabitation. Our results also extend prior work by demonstrating that breakup is attenuated by changes in psychosocial characteristics and peer associations/exposure. We close with a discussion of our findings, their policy implications, and what they mean for research on relationships and crime among serious adolescent offenders moving forward.

The importance of momentum transfer in collision-induced breakups in low Earth orbit

NASA Technical Reports Server (NTRS)

Reynolds, Robert C.; Lillie, Brian J.

1991-01-01

Although there is adequate information on larger objects in low Earth orbit, specifically those objects larger than about 10 cm in diameter, there is little direct information on objects from this size down to 1 mm. Yet, this is the sized regime where objects acting as projectiles represent the ability to seriously damage or destroy a functioning spacecraft if they collide with it. The observed consequences of known collisional breakups in orbit indicates no significant momentum transfer in the resulting debris cloud. The position taken in this paper is that this is an observational selection effect: what is seen in these events is an explosion-like breakup of the target structure arising from shock waves introduced into the structure by the collision, but one that occurs significantly after the collision processes are completed; the collision cloud, in which there is momentum transfer, consists of small, unobserved fragments. Preliminary computations of the contribution of one known collisional breakup, Solwind at 500 km in 1985, and Cosmos 1275 in 1981, assume no momentum transfer on breakup and indicate that these two events are the dominant contributors to the current millimeter and centimeter population. A different story would emerge if momentum transfer was taken into account. The topics covered include: (1) observation of on-orbit collisional breakups; (2) a model for momentum transfer; and (3) velocity space representation of breakup clouds.

Hard Break-Up of Two-Nucleons and QCD Dynamics of NN Interaction

NASA Astrophysics Data System (ADS)

Sargsian, Misak; Granados, Carlos

2009-05-01

We investigate hard photodisintegration of two nucleons from ^3He nucleus within the framework of hard rescattering model (HRM). In HRM a quark of one nucleon knocked-out by incoming photon rescatters with a quark of the other nucleon leading to the production of two nucleons with high relative momentum. HRM allows to express the amplitude of two-nucleon break-up reaction through the convolution of photon-quark scattering, NN hard scattering amplitude and nuclear spectral function which can be calculated using nonrelativistic ^3He wave function. HRM predicts several specific features for hard break-up reaction. First, the cross section will approximately scale as s-11. Also one predicts comparable or larger cross section for pp break up as compared to that of pn break-up, which is opposite to what is observed in low energy kinematics. Another result is the prediction of different spectator momentum dependencies of pp and pn break-up cross sections. This is due to the fact that same-helicity pp-component is strongly suppressed in the ground state wave function of ^3He. Due to this suppression HRM predicts significantly different asymmetries for the cross section of polarization transfer NN break-up reactions for circularly polarized photons. For the pp break-up this asymmetry is predicted to be zero while for the pn it is close to 23.

Structure and rheology of the lithosphere below southeastern margin of India and Sri Lanka, and its conjugate segment of the east Antarctica: Implications on early breakup history and margin formation

NASA Astrophysics Data System (ADS)

Rao Gangumalla, Srinivasa; Radhakrishna, Munukutla

2014-05-01

The eastern continental margin of India has evolved as a consequence of rifting and breakup between India and east Antarctica during the early Cretaceous. Plate reconstruction models for the breakup of eastern Gondwanaland by many earlier workers have unambiguously placed the southeast margin of Sri Lanka and India together as a conjugate segment with the east Antarctica margin that extends from Gunnerus Ridge in the west to western Enderby basin in the east. In this study, we present results of integrated analysis of gravity, geoid, magnetic and seismic data from these two conjugate portions in order to examine the lithosphere structure and early seafloor spreading, style of breakup, continent-ocean boundary (COB) and rheological characteristics at these margins. The interpreted COB lies at a distance of 55-140 km on the side of southeast margin of Sri Lanka and India, whereas, it lies at a distance of 190-550 km on the side of east Antarctica margin. The seismic profiles and the constrained potential field models across these two segments do not show the existence of seaward dipping reflector sequences or magmatic underplating suggesting that these segments have not encountered major magmatic activity. While, significant crustal thinning/stretching is observed at the east Antarctic margin, the Cauvery offshore had experienced limited stretching with faulted Moho interface. Further, the conspicuous residual geoid low in the Cauvery offshore basin is inferred to be due to a continental crustal block. The modelled Lithosphere-Astenosphere Boundary (LAB) in these two margins is located around 110-120 km depth with slightly thicker lithosphere at the east Antarctica margin. In addition, the interpretation of magnetic anomalies provided structure of the oceanic crust generated through seafloor spreading processes with age and magnetization data constrained from the identified magnetic anomalies in the respective margins. Using the Bouguer coherence method, we computed spatial variations in effective elastic thickness (Te) at these margin segments. The estimated Te values at the Indian margin ranges between 5-8 km in the southeast of Sri Lanka to around 10-12 km in the Cauvery offshore which decrease further north to < 5 km in the Cauvery-Palar basin. Along the east Antarctic margin, the Te values ranges between 5-10 km in the Gunnerus ridge region, 35-40 km in the western Enderby basin which decrease further towards the central Enderby basin up to 20 km. In this study, the above results have been analyzed in terms of early breakup mechanism and subsequent evolution of these two conjugate segments.

Breakup of a liquid rivulet falling over an inclined plate: Identification of a critical Weber number

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

Singh, Rajesh K.; Galvin, Janine E.; Whyatt, Greg A.

Here, we have numerically investigated the breakup of a rivulet falling over a smooth inclined plate using the volume of fluid method. The breakup the rivulet is a complex phenomenon that is dictated by many factors, such as solvent properties, contact angle, inertia, plate inclination, etc. An extensive simulation campaign was conducted wherein these factors were systematically investigated. Regimes for a stable rivulet and an unstable rivulet that leads to the breakup and formation of a droplet are examined in terms of a critical value of the Weber number (We cr) that delineates these regimes. The effect of plate inclinationmore » on the breakup of the rivulet shows that the critical Weber number decreases with increased inclination angle (θ) owing to higher liquid velocity. However, the effect is negligible beyond θ > 60°. The impact of solvent properties is characterized using the Kapitza number (Ka). Variation of We cr with Ka shows two trends depending on the Ka value of the solvent. Solvents with lower Ka values, corresponding to high viscosities and/or low surface tensions, show smaller values of the critical Weber number and the variation is linear. While solvents with higher Ka values exhibit higher values of the We cr and the variation in We cr is steep. This behavior is more pronounced with increasing contact angle. Higher contact angles promote rivulet breakup so that inertia must be higher to the breakup. As a result, a phenomenological scaling for a critical Weber number with the Kapitza number and contact angle is presented that can offer insight into rivulet breakup.« less

Breakup of a liquid rivulet falling over an inclined plate: Identification of a critical Weber number

DOE PAGES

Singh, Rajesh K.; Galvin, Janine E.; Whyatt, Greg A.; ...

2017-05-04

Here, we have numerically investigated the breakup of a rivulet falling over a smooth inclined plate using the volume of fluid method. The breakup the rivulet is a complex phenomenon that is dictated by many factors, such as solvent properties, contact angle, inertia, plate inclination, etc. An extensive simulation campaign was conducted wherein these factors were systematically investigated. Regimes for a stable rivulet and an unstable rivulet that leads to the breakup and formation of a droplet are examined in terms of a critical value of the Weber number (We cr) that delineates these regimes. The effect of plate inclinationmore » on the breakup of the rivulet shows that the critical Weber number decreases with increased inclination angle (θ) owing to higher liquid velocity. However, the effect is negligible beyond θ > 60°. The impact of solvent properties is characterized using the Kapitza number (Ka). Variation of We cr with Ka shows two trends depending on the Ka value of the solvent. Solvents with lower Ka values, corresponding to high viscosities and/or low surface tensions, show smaller values of the critical Weber number and the variation is linear. While solvents with higher Ka values exhibit higher values of the We cr and the variation in We cr is steep. This behavior is more pronounced with increasing contact angle. Higher contact angles promote rivulet breakup so that inertia must be higher to the breakup. As a result, a phenomenological scaling for a critical Weber number with the Kapitza number and contact angle is presented that can offer insight into rivulet breakup.« less

Hard breakup of two nucleons from the He3 nucleus

NASA Astrophysics Data System (ADS)

Sargsian, Misak M.; Granados, Carlos

2009-07-01

We investigate a large angle photodisintegration of two nucleons from the He3 nucleus within the framework of the hard rescattering model (HRM). In the HRM a quark of one nucleon knocked out by an incoming photon rescatters with a quark of the other nucleon leading to the production of two nucleons with large relative momentum. Assuming the dominance of the quark-interchange mechanism in a hard nucleon-nucleon scattering, the HRM allows the expression of the amplitude of a two-nucleon breakup reaction through the convolution of photon-quark scattering, NN hard scattering amplitude, and nuclear spectral function, which can be calculated using a nonrelativistic He3 wave function. The photon-quark scattering amplitude can be explicitly calculated in the high energy regime, whereas for NN scattering one uses the fit of the available experimental data. The HRM predicts several specific features for the hard breakup reaction. First, the cross section will approximately scale as s-11. Second, the s11 weighted cross section will have the shape of energy dependence similar to that of s10 weighted NN elastic scattering cross section. Also one predicts an enhancement of the pp breakup relative to the pn breakup cross section as compared to the results from low energy kinematics. Another result is the prediction of different spectator momentum dependencies of pp and pn breakup cross sections. This is due to the fact that the same-helicity pp-component is strongly suppressed in the ground state wave function of He3. Because of this suppression the HRM predicts significantly different asymmetries for the cross section of polarization transfer NN breakup reactions for circularly polarized photons. For the pp breakup this asymmetry is predicted to be zero while for the pn it is close to (2)/(3).

Romantic Partner Monitoring After Breakups: Attachment, Dependence, Distress, and Post-Dissolution Online Surveillance via Social Networking Sites.

PubMed

Fox, Jesse; Tokunaga, Robert S

2015-09-01

Romantic relationship dissolution can be stressful, and social networking sites make it difficult to separate from a romantic partner online as well as offline. An online survey (N = 431) tested a model synthesizing attachment, investment model variables, and post-dissolution emotional distress as predictors of interpersonal surveillance (i.e., "Facebook stalking") of one's ex-partner on Facebook after a breakup. Results indicated that anxious attachment predicted relational investment but also seeking relationship alternatives; avoidant attachment was negatively related to investment but positively related to seeking alternatives. Investment predicted commitment, whereas seeking alternatives was negatively related to commitment. Commitment predicted emotional distress after the breakup. Distress predicted partner monitoring immediately following the breakup, particularly for those who did not initiate the breakup, as well as current partner monitoring. Given their affordances, social media are discussed as potentially unhealthy enablers for online surveillance after relationship termination.

Capillary break-up, gelation and extensional rheology of hydrophobically modified cellulose ethers

NASA Astrophysics Data System (ADS)

Sharma, Vivek; Haward, Simon; Pessinet, Olivia; Soderlund, Asa; Threlfall-Holmes, Phil; McKinley, Gareth

2012-02-01

Cellulose derivatives containing associating hydrophobic groups along their hydrophilic polysaccharide backbone are used extensively in the formulations for inks, water-borne paints, food, nasal sprays, cosmetics, insecticides, fertilizers and bio-assays to control the rheology and processing behavior of multi-component dispersions. These complex dispersions are processed and used over a broad range of shear and extensional rates. The presence of hydrophobic stickers influences the linear and nonlinear rheology of cellulose ether solutions. In this talk, we systematically contrast the difference in the shear and extensional rheology of a cellulose ether: ethy-hydroxyethyl-cellulose (EHEC) and its hydrophobically-modified analog (HMEHEC) using microfluidic shear rheometry at deformation rates up to 10^6 inverse seconds, cross-slot flow extensional rheometry and capillary break-up during jetting as a rheometric technique. Additionally, we provide a constitutive model based on fractional calculus to describe the physical gelation in HMEHEC solutions.

The influence of cavitation in the breakup of liquid free jets

NASA Astrophysics Data System (ADS)

Bode, Juergen

1991-03-01

The interaction between a diesel injection nozzle flow and the atomizing jet was investigated over a wide range of Reynolds numbers. If the pressure gradient towards the centerline of the injection nozzle, generated by the curved streamlines, becomes too large, cavitation occurs at the inlet corner. The cavitation region grows in length and boundary surface with increasing Reynolds number. The instability of the reentry flow causes unsteady fluctuations of the cavitation which influences the breakup of the liquid jet, whereby liquid films are generated which take off from the jet. Cavitation amplifies the mechanism of the atomization, based on the interaction between the jet and surrounding gas. The influence of the cavitation on the atomization is restricted to the region directly behind the nozzle exit. The injection pressure and the temperature of the gas hardly affect the atomization. The jet angle depends mainly on the density of the surrounding gas.

Relationship between large horizontal electric fields and auroral arc elements

NASA Astrophysics Data System (ADS)

Lanchester, B. S.; Kailá, K.; McCrea, I. W.

1996-03-01

High time resolution optical measurements in the magnetic zenith are compared with European Incoherent Scatter (EISCAT) field-aligned measurements of electron density at 0.2-s resolution and with horizontal electric field measurements made at 278 km with resolution of 9 s. In one event, 20 min after a spectacular auroral breakup, a system of narrow and active arc elements moved southward into the magnetic zenith, where it remained for several minutes. During a 30-s interval of activity in a narrow arc element very close to the radar beam, the electric field vectors at 3-s resolution were found to be extremely large (up to 400 mVm-1) and to point toward the bright optical features in the arc, which moved along its length. It is proposed that the large electric fields are short-lived and are directly associated with the particle precipitation that causes the bright features in auroral arc elements.

Embedded binaries and their dense cores

NASA Astrophysics Data System (ADS)

Sadavoy, Sarah I.; Stahler, Steven W.

2017-08-01

We explore the relationship between young, embedded binaries and their parent cores, using observations within the Perseus Molecular Cloud. We combine recently published Very Large Array observations of young stars with core properties obtained from Submillimetre Common-User Bolometer Array 2 observations at 850 μm. Most embedded binary systems are found towards the centres of their parent cores, although several systems have components closer to the core edge. Wide binaries, defined as those systems with physical separations greater than 500 au, show a tendency to be aligned with the long axes of their parent cores, whereas tight binaries show no preferred orientation. We test a number of simple, evolutionary models to account for the observed populations of Class 0 and I sources, both single and binary. In the model that best explains the observations, all stars form initially as wide binaries. These binaries either break up into separate stars or else shrink into tighter orbits. Under the assumption that both stars remain embedded following binary break-up, we find a total star formation rate of 168 Myr-1. Alternatively, one star may be ejected from the dense core due to binary break-up. This latter assumption results in a star formation rate of 247 Myr-1. Both production rates are in satisfactory agreement with current estimates from other studies of Perseus. Future observations should be able to distinguish between these two possibilities. If our model continues to provide a good fit to other star-forming regions, then the mass fraction of dense cores that becomes stars is double what is currently believed.

Estimation of d- 2 H Breakup Neutron Energy Distributions From d- 3 He

DOE PAGES

Hoop, B.; Grimes, S. M.; Drosg, M.

2017-06-19

A method is described to estimate deuteron-on-deuteron breakup neutron distributions at 0° using deuterium bombardment of 3He. Break-up neutron distributions are modeled with the product of a Fermi-Dirac distribution and a cumulative logistic distribution function. Four measured break-up neutron distributions from 6.15- to 12.0-MeV deuterons on 3He are compared with thirteen measured distributions from 6.83- to 11.03-MeV deuterons on deuterium. Model pararmeters that describe d -3He neutron distributions are used to estimate neutron distributions from 6- to 12-MeV deuterons on deuterium.

Assessment of the Breakup of the Antarctic Polar Vortex in Two New Chemistry-Climate Models

NASA Technical Reports Server (NTRS)

Hurwitz, M. M.; Newman, P. A.; Oman, L. D.; Li, F.; Morgenstern, O.; Braesicke, P.; Pyle, J. A.

2010-01-01

Successful simulation of the breakup of the Antarctic polar vortex depends on the representation of tropospheric stationary waves at Southern Hemisphere middle latitudes. This paper assesses the vortex breakup in two new chemistry-climate models (CCMs). The stratospheric version of the UK Chemistry and Aerosols model is able to reproduce the observed timing of the vortex breakup. Version 2 of the Goddard Earth Observing System (GEOS V2) model is typical of CCMs in that the Antarctic polar vortex breaks up too late; at 10 hPa, the mean transition to easterlies at 60 S is delayed by 12-13 days as compared with the ERA-40 and National Centers for Environmental Prediction reanalyses. The two models' skill in simulating planetary wave driving during the October-November period accounts for differences in their simulation of the vortex breakup, with GEOS V2 unable to simulate the magnitude and tilt of geopotential height anomalies in the troposphere and thus underestimating the wave driving. In the GEOS V2 CCM the delayed breakup of the Antarctic vortex biases polar temperatures and trace gas distributions in the upper stratosphere in November and December.

On the breakup of viscous liquid threads

NASA Technical Reports Server (NTRS)

Papageorgiou, Demetrios T.

1995-01-01

A one-dimensional model evolution equation is used to describe the nonlinear dynamics that can lead to the breakup of a cylindrical thread of Newtonian fluid when capillary forces drive the motion. The model is derived from the Stokes equations by use of rational asymptotic expansions and under a slender jet approximation. The equations are solved numerically and the jet radius is found to vanish after a finite time yielding breakup. The slender jet approximation is valid throughout the evolution leading to pinching. The model admits self-similar pinching solutions which yield symmetric shapes at breakup. These solutions are shown to be the ones selected by the initial boundary value problem, for general initial conditions. Further more, the terminal state of the model equation is shown to be identical to that predicted by a theory which looks for singular pinching solutions directly from the Stokes equations without invoking the slender jet approximation throughout the evolution. It is shown quantitatively, therefore, that the one-dimensional model gives a consistent terminal state with the jet shape being locally symmetric at breakup. The asymptotic expansion scheme is also extended to include unsteady and inerticial forces in the momentum equations to derive an evolution system modelling the breakup of Navier-Stokes jets. The model is employed in extensive simulations to compute breakup times for different initial conditions; satellite drop formation is also supported by the model and the dependence of satellite drop volumes on initial conditions is studied.

Breakup and fusion cross sections of the 6Li nucleus with targets of mass A = 58, 144 and 208

NASA Astrophysics Data System (ADS)

Mukeru, B.; Rampho, G. J.; Lekala, M. L.

2018-04-01

We use the continuum discretized coupled channels method to investigate the effects of continuum-continuum coupling on the breakup and fusion cross sections of the weakly bound 6Li nucleus with the 58Ni, 144Sm and 208Pb nuclear targets. The cross sections were analyzed at incident energies E cm below, close to and above the Coulomb barrier V B. We found that for the medium and heavy targets, the breakup cross sections are enhanced at energies below the Coulomb barrier (E cm/V B ≤ 0.8) owing to these couplings. For the lighter target, relatively small enhancement of the breakup cross sections appear at energies well below the barrier (E cm/V B ≤ 0.6). At energies E cm/V B > 0.8 for medium and heavy targets, and E cm/V B > 0.6 for the light target, the continuum-continuum couplings substantially suppress the breakup cross sections. On the other hand, the fusion cross sections are enhanced at energies E cm/V B < 1.4, E cm/V B < 1.2 and E cm/V B < 0.8 for the light, medium and heavy target, respectively. The enhancement decreases as the target mass increases. Above the indicated respective energies, these couplings suppress the fusion cross sections. We also compared the breakup and fusion cross sections, and found that below the barrier, the breakup cross sections are more dominant regardless of whether continuum-continuum couplings are included.

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

Singh, Rajesh K.; Galvin, Janine E.; Sun, Xin

We have numerically investigated the breakup of a rivulet falling over a smooth inclined plate using the volume of fluid method. The breakup the rivulet is a complex phenomenon that is dictated by many factors, such as solvent properties, contact angle, inertia, plate inclination, etc. An extensive simulation campaign was conducted wherein these factors were systematically investigated. Regimes for a stable rivulet and an unstable rivulet that leads to the breakup and formation of a droplet are examined in terms of a critical value of the Weber number (Wecr) that delineates these regimes. The effect of plate inclination on themore » breakup of the rivulet shows that the critical Weber number decreases with increased inclination angle () owing to higher liquid velocity. However, the effect is negligible beyond >60. The impact of solvent properties is characterized using the Kapitza number (Ka). Variation of Wecr with Ka shows two trends depending on the Ka value of the solvent. Solvents with lower Ka values, corresponding to high viscosities and/or low surface tensions, show smaller values of the critical Weber number and the variation is linear. While solvents with higher Ka values exhibit higher values of the Wecr and the variation in Wecr is steep. This behavior is more pronounced with increasing contact angle. Higher contact angles promote rivulet breakup so that inertia must be higher to the breakup. A phenomenological scaling for a critical Weber number with the Kapitza number and contact angle is presented that can offer insight into rivulet breakup.« less

Measurement of transparency ratios for protons from short-range correlated pairs

NASA Astrophysics Data System (ADS)

Hen, O.; Hakobyan, H.; Shneor, R.; Piasetzky, E.; Weinstein, L. B.; Brooks, W. K.; May-Tal Beck, S.; Gilad, S.; Korover, I.; Beck, A.; Adhikari, K. P.; Aghasyan, M.; Amaryan, M. J.; Anefalos Pereira, S.; Arrington, J. R.; Baghdasaryan, H.; Ball, J.; Battaglieri, M.; Batourine, V.; Bedlinskiy, I.; Biselli, A. S.; Bono, J.; Boiarinov, S.; Briscoe, W. J.; Burkert, V. D.; Carman, D. S.; Celentano, A.; Chandavar, S.; Cole, P. L.; Contalbrigo, M.; Crede, V.; D'Angelo, A.; Dashyan, N.; De Vita, R.; De Sanctis, E.; Deur, A.; Djalali, C.; Dodge, G. E.; Doughty, D.; Dupre, R.; Egiyan, H.; El Alaoui, A.; El Fassi, L.; Eugenio, P.; Fedotov, G.; Fegan, S.; Fleming, J. A.; Gabrielyan, M. Y.; Gevorgyan, N.; Gilfoyle, G. P.; Giovanetti, K. L.; Girod, F. X.; Goetz, J. T.; Gohn, W.; Golovatch, E.; Gothe, R. W.; Griffioen, K. A.; Guo, L.; Hafidi, K.; Harrison, N.; Heddle, D.; Hicks, K.; Holtrop, M.; Hyde, C. E.; Ilieva, Y.; Ireland, D. G.; Ishkhanov, B. S.; Isupov, E. L.; Jo, H. S.; Joo, K.; Keller, D.; Khandaker, M.; Khetarpal, P.; Kim, A.; Klein, F. J.; Koirala, S.; Kubarovsky, A.; Kubarovsky, V.; Kuhn, S. E.; Livingston, K.; Lu, H. Y.; MacGregor, I. J. D.; Martinez, D.; Mayer, M.; McKinnon, B.; Mineeva, T.; Mokeev, V.; Montgomery, R. A.; Moutarde, H.; Munevar, E.; Munoz Camacho, C.; Mustapha, B.; Nadel-Turonski, P.; Nasseripour, R.; Niccolai, S.; Niculescu, G.; Niculescu, I.; Osipenko, M.; Ostrovidov, A. I.; Pappalardo, L. L.; Paremuzyan, R.; Park, K.; Park, S.; Pasyuk, E.; Phelps, E.; Phillips, J. J.; Pisano, S.; Pivnyuk, N.; Pogorelko, O.; Pozdniakov, S.; Price, J. W.; Procureur, S.; Protopopescu, D.; Puckett, A. J. R.; Raue, B. A.; Rimal, D.; Ripani, M.; Ritchie, B. G.; Rosner, G.; Rossi, P.; Sabatié, F.; Saini, M. S.; Schott, D.; Schumacher, R. A.; Seraydaryan, H.; Sharabian, Y. G.; Smith, G. D.; Sober, D. I.; Sokhan, D.; Stepanyan, S. S.; Stepanyan, S.; Strauch, S.; Taiuti, M.; Tang, W.; Taylor, C. E.; Tian, Ye; Tkachenko, S.; Ungaro, M.; Vernarsky, B.; Vlassov, A.; Voskanyan, H.; Voutier, E.; Walford, N. K.; Watts, D. P.; Wood, M. H.; Zachariou, N.; Zana, L.; Zhang, J.; Zheng, X.; Zonta, I.

2013-05-01

Nuclear transparency, Tp (A), is a measure of the average probability for a struck proton to escape the nucleus without significant re-interaction. Previously, nuclear transparencies were extracted for quasi-elastic A (e ,e‧ p) knockout of protons with momentum below the Fermi momentum, where the spectral functions are well known. In this Letter we extract a novel observable, the transparency ratio, Tp (A) /Tp(12 C), for knockout of high-missing-momentum protons from the breakup of short-range correlated pairs (2N-SRC) in Al, Fe and Pb nuclei relative to C. The ratios were measured at momentum transfer Q2 ⩾ 1.5(GeV /c) 2 and xB ⩾ 1.2 where the reaction is expected to be dominated by electron scattering from 2N-SRC. The transparency ratios of the knocked-out protons coming from 2N-SRC breakup are 20-30% lower than those of previous results for low missing momentum. They agree with Glauber calculations and agree with renormalization of the previously published transparencies as proposed by recent theoretical investigations. The new transparencies scale as A - 1 / 3, which is consistent with dominance of scattering from nucleons at the nuclear surface.

Recent Developments in X-Ray Diagnostics for Cryogenic and Optically Dense Coaxial Rocket Sprays

NASA Technical Reports Server (NTRS)

Radke, Christopher D.; Kastengren, Alan L.; Meyer, Terrence R.

2017-01-01

The mixing and atomization of propellants is often characterized by optically dense flow fields and complex breakup dynamics. In the development of propulsion systems, the complexity of relevant physics and the range of spatio-temporal scales often makes computational simulation impractical for full scale injector elements; consequently, continued research into improved systems for experimental flow diagnostics is ongoing. One area of non-invasive flow diagnostics which has seen widespread growth is using synchrotron based x-ray diagostics. Over the past 3 years, a series of water and cryogenic based experiments were performed at the Advanced Photon Source, Argonne National Lab, on a NASA in-house designed swirl co-axial rocket injector, designed for operation using liquid oxygen and liquid methane in support of Project Morpheus. A range of techniques, such as x-ray fluorescence and time-averaged radiography were performed providing qualitative and quantitative mass and phase distributions, and were complemented by investigations using time-resolved radiography and white beam imaging, which provided information on breakup and mixing dynamics. Results of these investigations are presented, and conclusions regarding the viability of x-ray based diagnostics are discussed.

Sensor assembly method using silicon interposer with trenches for three-dimensional binocular range sensors

NASA Astrophysics Data System (ADS)

Nakajima, Kazuhiro; Yamamoto, Yuji; Arima, Yutaka

2018-04-01

To easily assemble a three-dimensional binocular range sensor, we devised an alignment method for two image sensors using a silicon interposer with trenches. The trenches were formed using deep reactive ion etching (RIE) equipment. We produced a three-dimensional (3D) range sensor using the method and experimentally confirmed that sufficient alignment accuracy was realized. It was confirmed that the alignment accuracy of the two image sensors when using the proposed method is more than twice that of the alignment assembly method on a conventional board. In addition, as a result of evaluating the deterioration of the detection performance caused by the alignment accuracy, it was confirmed that the vertical deviation between the corresponding pixels in the two image sensors is substantially proportional to the decrease in detection performance. Therefore, we confirmed that the proposed method can realize more than twice the detection performance of the conventional method. Through these evaluations, the effectiveness of the 3D binocular range sensor aligned by the silicon interposer with the trenches was confirmed.

The Primary Break-up Instabilities in a gas-liquid coaxial atomizer combined with electro-spray

NASA Astrophysics Data System (ADS)

Osuna, Rodrigo; Machicoane, Nathanael; Aliseda, Alberto

2017-11-01

We present an experimental study of a canonical coaxial gas-liquid atomizer, balancing the physics of gas-assisted atomization and electro-sprays. The laminar liquid stream is injected through a long straight metallic pipe at the center of the turbulent gas jet. The liquid needle is used as the anode, while the cathode is formed by a ring located on the streamwise face of the coaxial gas chamber. The gas Reynolds number ranges from 104-106, while keeping the liquid Reynolds number constant at 103. The electrospray voltage applied is varied from 100 to 5000 V and the resulting negative charge transferred to the liquid jet spans from O(10-3 - 10-1) Coulomb per cubic meter. The relative influence of the high speed gas to the liquid electric charge on the primary instability and jet break-up is studied. The effect of the electric field on the atomization process is characterized by high speed visualization at the nozzle exit, complemented with the resulting droplet size distribution in the mid field after break-up has ended. The quantitative visualization captures the fast dynamics of the interface de-stabilization and clearly shows the changes in the liquid stream instabilities caused by the electric field. These instabilities control the liquid droplet sizes and their spatio-temporal distribution in the spray, as measured from light interferometry.

Contribution of three nucleon force investigated in deuteron-proton breakup reaction

NASA Astrophysics Data System (ADS)

Parol, W.; Kozela, A.; Ciepał, I.; Bodek, K.; Jamroz, B.; Kalantar-Nayestanaki, N.; Khatri, G.; Kistryn, St.; Kłos, B.; Kuboś, J.; Kulessa, P.; Magiera, A.; Mazumdar, I.; Messchendorp, J. G.; Rozpędzik, D.; Rusnok, A.; Skwira-Chalot, I.; Stephan, E.; Wilczek, A.; Włoch, B.; Wrońska, A.; Zejma, J.

2016-11-01

The elastic scattering and deuteron breakup data were collected in the experiment performed at KVI (Groningen) with use of unpolarized deuteron beam with energy of 80 MeV per nucleon, impinging on hydrogen target. The procedure applied to determine total integrated luminosity is presented. The result will be used for normalization of the differential cross section for the deuteron-proton breakup reaction.

Monitoring ice break-up on the Mackenzie River using MODIS data

NASA Astrophysics Data System (ADS)

Muhammad, P.; Duguay, C.; Kang, K.-K.

2016-03-01

The aim of this study was to develop an approach for estimating ice break-up dates on the Mackenzie River (MR) using more than a decade of MODIS Level 3 500 m snow products (MOD/MYD10A1), complemented with 250 m Level 1B radiance products (MOD/MYD02QKM) from the Terra and Aqua satellite platforms. The analysis showed break-up began on average between days of year (DOYs) 115 and 125 and ended between DOYs 145 and 155 over 13 ice seasons (2001-2013), resulting in an average melt duration of ca. 30-40 days. Thermal processes were more important in driving ice break-up south of the MR confluence with the Liard River, while dynamically driven break-up was more important north of the Liard. A comparison of the timing of ice disappearance with snow disappearance from surrounding land areas of the MR with MODIS Level 3 snow products showed varying relationships along the river. Ice-off and snow-off timing were in sync north of the MR-Liard River confluence and over sections of the MR before it enters the Mackenzie Delta, but ice disappeared much later than snow on land in regions where thermal ice break-up processes dominated. MODIS observations revealed that channel morphology is a more important control of ice break-up patterns than previously believed with ice runs on the MR strongly influenced by channel morphology (islands and bars, confluences and channel constriction). Ice velocity estimates from feature tracking were able to be made in 2008 and 2010 and yielded 3-4-day average ice velocities of 1.21 and 1.84 m s-1 respectively, which is in agreement with estimates from previous studies. These preliminary results confirm the utility of daily MODIS data for monitoring ice break-up processes along the Mackenzie River. The addition of optical and synthetic aperture radar data from recent and upcoming satellite missions (e.g. Sentinel-1/2/3 and RADARSAT Constellation) would improve the monitoring of ice break-up in narrower sections of the MR.

DebriSat - A Planned Laboratory-Based Satellite Impact Experiment for Breakup Fragment Characterizations

NASA Technical Reports Server (NTRS)

Liou, Jer-Chyi; Clark, S.; Fitz-Coy, N.; Huynh, T.; Opiela, J.; Polk, M.; Roebuck, B.; Rushing, R.; Sorge, M.; Werremeyer, M.

2013-01-01

The goal of the DebriSat project is to characterize fragments generated by a hypervelocity collision involving a modern satellite in low Earth orbit (LEO). The DebriSat project will update and expand upon the information obtained in the 1992 Satellite Orbital Debris Characterization Impact Test (SOCIT), which characterized the breakup of a 1960 s US Navy Transit satellite. There are three phases to this project: the design and fabrication of DebriSat - an engineering model representing a modern, 60-cm/50-kg class LEO satellite; conduction of a laboratory-based hypervelocity impact to catastrophically break up the satellite; and characterization of the properties of breakup fragments down to 2 mm in size. The data obtained, including fragment size, area-to-mass ratio, density, shape, material composition, optical properties, and radar cross-section distributions, will be used to supplement the DoD s and NASA s satellite breakup models to better describe the breakup outcome of a modern satellite.

Interplay of charge clustering and weak binding in reactions of 8Li

NASA Astrophysics Data System (ADS)

Cook, K. J.; Carter, I. P.; Simpson, E. C.; Dasgupta, M.; Hinde, D. J.; Bezzina, L. T.; Kalkal, Sunil; Sengupta, C.; Simenel, C.; Swinton-Bland, B. M. A.; Vo-Phuoc, K.; Williams, E.

2018-02-01

In collisions of light, stable, weakly bound nuclides, complete fusion (capture of all of the projectile charge) has been found to be suppressed by ˜30 % at above-barrier energies. This is thought to be related to their low thresholds for breakup into charged clusters. The observation of fusion suppression in the neutron-rich radioactive nucleus 8Li is therefore puzzling: the lowest breakup threshold yields 7Li+n which cannot contribute to fusion suppression because 7Li retains all the projectile charge. In this work, the full characteristics of 8Li breakup in reactions with 209Bi are presented, including, for the first time, coincidence measurements of breakup into charged clusters. Correlations of cluster fragments show that most breakup occurs too slowly to significantly suppress fusion. However, a large cross section for unaccompanied α particles was found, suggesting that charge clustering, facilitating partial charge capture, rather than weak binding is the crucial factor in fusion suppression, which may therefore persist in exotic nuclides.

Anisotropic piezoresistivity characteristics of aligned carbon nanotube-polymer nanocomposites

NASA Astrophysics Data System (ADS)

Sengezer, Engin C.; Seidel, Gary D.; Bodnar, Robert J.

2017-09-01

Dielectrophoresis under the application of AC electric fields is one of the primary fabrication techniques for obtaining aligned carbon nanotube (CNT)-polymer nanocomposites, and is used here to generate long range alignment of CNTs at the structural level. The degree of alignment of CNTs within this long range architecture is observed via polarized Raman spectroscopy so that its influence on the electrical conductivity and piezoresistive response in both the alignment and transverse to alignment directions can be assessed. Nanocomposite samples consisting of randomly oriented, well dispersed single-wall carbon nanotubes (SWCNTs) and of long range electric field aligned SWCNTs in a photopolymerizable monomer blend (urethane dimethacrylate and 1,6-hexanediol dimethacrylate) are quantitatively and qualitatively evaluated. Piezoresistive sensitivities in form of gauge factors were measured for randomly oriented, well dispersed specimens with 0.03, 0.1 and 0.5 wt% SWCNTs and compared with gauge factors in both the axial and transverse to SWCNT alignment directions for electric field aligned 0.03 wt% specimens under both quasi-static monotonic and cyclic tensile loading. Gauge factors in the axial direction were observed to be on the order of 2, while gauge factors in the transverse direction demonstrated a 5 fold increase with values on the order of 10 for aligned specimens. Based on Raman analysis, it is believed the higher sensitivity of the transverse direction is related to architectural evolution of misaligned bridging structures which connect alignment structures under load due to Poisson’s contraction.

Cellular self-organization by autocatalytic alignment feedback

PubMed Central

Junkin, Michael; Leung, Siu Ling; Whitman, Samantha; Gregorio, Carol C.; Wong, Pak Kin

2011-01-01

Myoblasts aggregate, differentiate and fuse to form skeletal muscle during both embryogenesis and tissue regeneration. For proper muscle function, long-range self-organization of myoblasts is required to create organized muscle architecture globally aligned to neighboring tissue. However, how the cells process geometric information over distances considerably longer than individual cells to self-organize into well-ordered, aligned and multinucleated myofibers remains a central question in developmental biology and regenerative medicine. Using plasma lithography micropatterning to create spatial cues for cell guidance, we show a physical mechanism by which orientation information can propagate for a long distance from a geometric boundary to guide development of muscle tissue. This long-range alignment occurs only in differentiating myoblasts, but not in non-fusing myoblasts perturbed by microfluidic disturbances or other non-fusing cell types. Computational cellular automata analysis of the spatiotemporal evolution of the self-organization process reveals that myogenic fusion in conjunction with rotational inertia functions in a self-reinforcing manner to enhance long-range propagation of alignment information. With this autocatalytic alignment feedback, well-ordered alignment of muscle could reinforce existing orientations and help promote proper arrangement with neighboring tissue and overall organization. Such physical self-enhancement might represent a fundamental mechanism for long-range pattern formation during tissue morphogenesis. PMID:22193956

Novel Techniques for Quantification of Correlation Between Primary Liquid Jet Breakup and Downstream Spray Characteristics

DTIC Science & Technology

2016-05-08

unlimited. 5 1. Introduction Several liquid -fuelled combustion systems, such as liquid propellant rocket engines and gas turbines...AFRL-AFOSR-JP-TR-2016-0084 Novel techniques for quantification of correlation between primary liquid jet breakup and downstream spray characteristics...to 17 Apr 2016 4.  TITLE AND SUBTITLE Novel techniques for quantification of correlation between primary liquid jet breakup and downstream spray

Novel Techniques for Quantification of Correlation Between Primary Liquid Jet Breakup and Downstream Spray Characteristics

DTIC Science & Technology

2016-10-05

unlimited. 5 1. Introduction Several liquid -fuelled combustion systems, such as liquid propellant rocket engines and gas turbines...AFRL-AFOSR-JP-TR-2016-0084 Novel techniques for quantification of correlation between primary liquid jet breakup and downstream spray characteristics...to 17 Apr 2016 4.  TITLE AND SUBTITLE Novel techniques for quantification of correlation between primary liquid jet breakup and downstream spray

Improved Root Normal Size Distributions for Liquid Atomization

DTIC Science & Technology

2015-11-01

Jackson, Primary Breakup of Round Aerated- Liquid Jets in Supersonic Crossflows, Atomization and Sprays, 16(6), 657-672, 2006 H. C. Simmons, The...Breakup in Liquid - Gas Mixing Layers, Atomization and Sprays, 1, 421-440, 1991 P.-K. Wu, L.-K. Tseng, and G. M. Faeth, Primary Breakup in Gas / Liquid ...Improved Root Normal Size Distributions for Liquid Atomization Distribution Statement A. Approved for public release; distribution is unlimited

Galinstan liquid metal breakup and droplet formation in a shock-induced cross-flow

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

Chen, Yi; Wagner, Justin L.; Farias, Paul Abraham

Liquid metal breakup processes are important for understanding a variety of physical phenomena including metal powder formation, thermal spray coatings, fragmentation in explosive detonations and metalized propellant combustion. Since the breakup behaviors of liquid metals are not well studied, we experimentally investigate the roles of higher density and fast elastic surface oxide formation on breakup morphology and droplet characteristics. This work compares the column breakup of water with Galinstan, a room-temperature eutectic liquid metal alloy of gallium, indium and tin. A shock tube is used to generate a step change in convective velocity and back-lit imaging is used to classifymore » morphologies for Weber numbers up to 250. Digital in-line holography (DIH) is then used to quantitatively capture droplet size, velocity and three-dimensional position information. Differences in geometry between canonical spherical drops and the liquid columns utilized in this paper are likely responsible for observations of earlier transition Weber numbers and uni-modal droplet volume distributions. Scaling laws indicate that Galinstan and water share similar droplet size-velocity trends and root-normal volume probability distributions. Furthermore, measurements indicate that Galinstan breakup occurs earlier in non-dimensional time and produces more non-spherical droplets due to fast oxide formation.« less

Practical method to identify orbital anomaly as spacecraft breakup in the geostationary region

NASA Astrophysics Data System (ADS)

Hanada, Toshiya; Uetsuhara, Masahiko; Nakaniwa, Yoshitaka

2012-07-01

Identifying a spacecraft breakup is an essential issue to define the current orbital debris environment. This paper proposes a practical method to identify an orbital anomaly, which appears as a significant discontinuity in the observation data, as a spacecraft breakup. The proposed method is applicable to orbital anomalies in the geostationary region. Long-term orbital evolutions of breakup fragments may conclude that their orbital planes will converge into several corresponding regions in inertial space even if the breakup epoch is not specified. This empirical method combines the aforementioned conclusion with the search strategy developed at Kyushu University, which can identify origins of observed objects as fragments released from a specified spacecraft. This practical method starts with selecting a spacecraft that experienced an orbital anomaly, and formulates a hypothesis to generate fragments from the anomaly. Then, the search strategy is applied to predict the behavior of groups of fragments hypothetically generated. Outcome of this predictive analysis specifies effectively when, where and how we should conduct optical measurements using ground-based telescopes. Objects detected based on the outcome are supposed to be from the anomaly, so that we can confirm the anomaly as a spacecraft breakup to release the detected objects. This paper also demonstrates observation planning for a spacecraft anomaly in the geostationary region.

Galinstan liquid metal breakup and droplet formation in a shock-induced cross-flow

DOE PAGES

Chen, Yi; Wagner, Justin L.; Farias, Paul Abraham; ...

2018-05-22

Liquid metal breakup processes are important for understanding a variety of physical phenomena including metal powder formation, thermal spray coatings, fragmentation in explosive detonations and metalized propellant combustion. Since the breakup behaviors of liquid metals are not well studied, we experimentally investigate the roles of higher density and fast elastic surface oxide formation on breakup morphology and droplet characteristics. This work compares the column breakup of water with Galinstan, a room-temperature eutectic liquid metal alloy of gallium, indium and tin. A shock tube is used to generate a step change in convective velocity and back-lit imaging is used to classifymore » morphologies for Weber numbers up to 250. Digital in-line holography (DIH) is then used to quantitatively capture droplet size, velocity and three-dimensional position information. Differences in geometry between canonical spherical drops and the liquid columns utilized in this paper are likely responsible for observations of earlier transition Weber numbers and uni-modal droplet volume distributions. Scaling laws indicate that Galinstan and water share similar droplet size-velocity trends and root-normal volume probability distributions. Furthermore, measurements indicate that Galinstan breakup occurs earlier in non-dimensional time and produces more non-spherical droplets due to fast oxide formation.« less

Changes in diadenosine polyphosphates during alignment-fit and orthokeratology rigid gas permeable lens wear.

PubMed

Carracedo, Gonzalo; González-Méijome, José Manuel; Pintor, Jesús

2012-07-03

To evaluate the levels of dinucleotides diadenosine tetraphosphate (Ap(4)A) and diadenosine pentaphosphate (Ap(5)A) in tears of patients wearing rigid gas permeable (RGP) contact lenses on a daily wear basis and of patients wearing reverse-geometry RGP lenses overnight for orthokeratology treatment. Twenty-two young volunteers (10 females, 12 males; 23.47 ± 4.49 years) were fitted with an alignment-fit RGP lens (paflufocon B) for a month, and after a 15-day washout period they were fitted with reverse-geometry RGP lenses for corneal reshaping (paflufocon D) for another month. During each period, tears were collected at baseline day 1, 7, 15, and 28. Ap(4)A and Ap(5)A were measured by high-pressure liquid chromatography (HPLC). Additionally, corneal staining, break-up time (BUT), Schirmer test, and dryness symptoms were evaluated. Ap(4)A concentrations increased significantly from baseline during the whole period of daily wear of RGP lenses (P < 0.001); concentration was also significantly higher than in the orthokeratology group, which remained at baseline levels during the study period except at day 1 (P < 0.001) and day 28 (P = 0.041). While BUT and Schirmer remained unchanged in both groups, discomfort and dryness were significantly increased during alignment-fit RGP daily wear but not during the orthokeratology period. Daily wear of RGP lenses increased the levels of Ap(4)A due to mechanical stimulation by blinking of the corneal epithelium, and this is associated with discomfort. Also, orthokeratology did not produce symptoms or signs of ocular dryness, which could be a potential advantage over soft contact lenses in terms of contact lens-induced dryness.

Apparatus for monitoring X-ray beam alignment

DOEpatents

Steinmeyer, Peter A.

1991-10-08

A self-contained, hand-held apparatus is provided for minitoring alignment of an X-ray beam in an instrument employing an X-ray source. The apparatus includes a transducer assembly containing a photoresistor for providing a range of electrical signals responsive to a range of X-ray beam intensities from the X-ray beam being aligned. A circuit, powered by a 7.5 VDC power supply and containing an audio frequency pulse generator whose frequency varies with the resistance of the photoresistor, is provided for generating a range of audible sounds. A portion of the audible range corresponds to low X-ray beam intensity. Another portion of the audible range corresponds to high X-ray beam intensity. The transducer assembly may include an a photoresistor, a thin layer of X-ray fluorescent material, and a filter layer transparent to X-rays but opaque to visible light. X-rays from the beam undergoing alignment penetrate the filter layer and excite the layer of fluorescent material. The light emitted from the fluorescent material alters the resistance of the photoresistor which is in the electrical circuit including the audio pulse generator and a speaker. In employing the apparatus, the X-ray beam is aligned to a complete alignment by adjusting the X-ray beam to produce an audible sound of the maximum frequency.

Apparatus for monitoring X-ray beam alignment

DOEpatents

Steinmeyer, P.A.

1991-10-08

A self-contained, hand-held apparatus is provided for monitoring alignment of an X-ray beam in an instrument employing an X-ray source. The apparatus includes a transducer assembly containing a photoresistor for providing a range of electrical signals responsive to a range of X-ray beam intensities from the X-ray beam being aligned. A circuit, powered by a 7.5 VDC power supply and containing an audio frequency pulse generator whose frequency varies with the resistance of the photoresistor, is provided for generating a range of audible sounds. A portion of the audible range corresponds to low X-ray beam intensity. Another portion of the audible range corresponds to high X-ray beam intensity. The transducer assembly may include an a photoresistor, a thin layer of X-ray fluorescent material, and a filter layer transparent to X-rays but opaque to visible light. X-rays from the beam undergoing alignment penetrate the filter layer and excite the layer of fluorescent material. The light emitted from the fluorescent material alters the resistance of the photoresistor which is in the electrical circuit including the audio pulse generator and a speaker. In employing the apparatus, the X-ray beam is aligned to a complete alignment by adjusting the X-ray beam to produce an audible sound of the maximum frequency. 2 figures.

Numerical models for continental break-up: Implications for the South Atlantic

NASA Astrophysics Data System (ADS)

Beniest, A.; Koptev, A.; Burov, E.

2017-03-01

We propose a mechanism that explains in one unified framework the presence of continental break-up features such as failed rift arms and high-velocity and high-density bodies that occur along the South Atlantic rifted continental margins. We used 2D and 3D numerical models to investigate the impact of thermo-rheological structure of the continental lithosphere and initial plume position on continental rifting and break-up processes. 2D experiments show that break-up can be 1) "central", mantle plume-induced and directly located above the centre of the mantle anomaly, 2) "shifted", mantle plume-induced and 50 to 200 km shifted from the initial plume location or 3) "distant", self-induced due to convection and/or slab-subduction/delamination and 300 to 800 km off-set from the original plume location. With a 3D, perfectly symmetrical and laterally homogeneous setup, the location of continental break-up can be shifted hundreds of kilometres from the initial position of the mantle anomaly. We demonstrate that in case of shifted or distant continental break-up with respect to the original plume location, multiple features can be explained. Its deep-seated source can remain below the continent at one or both sides of the newly-formed ocean. This mantle material, glued underneath the margins at lower crustal levels, resembles the geometry and location of high velocity/high density bodies observed along the South Atlantic conjugate margins. Impingement of vertically up-welled plume material on the base of the lithosphere results in pre-break-up topography variations that are located just above this initial anomaly impingement. This can be interpreted as aborted rift features that are also observed along the rifted margins. When extension continues after continental break-up, high strain rates can relocalize. This relocation has been so far attributed to rift jumps. Most importantly, this study shows that there is not one, single rift mode for plume-induced crustal break-up.

Re-appraisal of the Magma-rich versus Magma-poor Paradigm at Rifted Margins: consequences for breakup processes

NASA Astrophysics Data System (ADS)

Tugend, J.; Gillard, M.; Manatschal, G.; Nirrengarten, M.; Harkin, C. J.; Epin, M. E.; Sauter, D.; Autin, J.; Kusznir, N. J.; McDermott, K.

2017-12-01

Rifted margins are often classified based on their magmatic budget only. Magma-rich margins are commonly considered to have excess decompression melting at lithospheric breakup compared with steady state seafloor spreading while magma-poor margins have suppressed melting. New observations derived from high quality geophysical data sets and drill-hole data have revealed the diversity of rifted margin architecture and variable distribution of magmatism. Recent studies suggest, however, that rifted margins have more complex and polyphase tectono-magmatic evolutions than previously assumed and cannot be characterized based on the observed volume of magma alone. We compare the magmatic budget related to lithospheric breakup along two high-resolution long-offset deep reflection seismic profiles across the SE-Indian (magma-poor) and Uruguayan (magma-rich) rifted margins. Resolving the volume of magmatic additions is difficult. Interpretations are non-unique and several of them appear plausible for each case involving variable magmatic volumes and mechanisms to achieve lithospheric breakup. A supposedly 'magma-poor' rifted margin (SE-India) may show a 'magma-rich' lithospheric breakup whereas a 'magma-rich' rifted margin (Uruguay) does not necessarily show excess magmatism at lithospheric breakup compared with steady-state seafloor spreading. This questions the paradigm that rifted margins can be subdivided in either magma-poor or magma-rich margins. The Uruguayan and other magma-rich rifted margins appear characterized by an early onset of decompression melting relative to crustal breakup. For the converse, where the onset of decompression melting is late compared with the timing of crustal breakup, mantle exhumation can occur (e.g. SE-India). Our work highlights the difficulty in determining a magmatic budget at rifted margins based on seismic reflection data alone, showing the limitations of margin classification based solely on magmatic volumes. The timing of decompression melting onset and melting rates (magmatic processes) relative to crustal thinning (tectonic processes) appear equally, if not more important, than the magmatic budget for unravelling the evolution of rifted margins.

Supercontinent break-up: Causes and consequences

NASA Astrophysics Data System (ADS)

Li, Z. X.

2014-12-01

Supercontinent break-up has most commonly been linked to plume or superplume events, and/or supercontinent thermal insulation, but precise mechanisms are yet to be worked out. Even less know is if and what roles other factors may play. Key factors likely include gravitational force due to the continental superswell driven by both the lower-mantle superplume and continental thermal insulation, mental convention driven by the superplume and individual plumes atop the superplume, assisted by thermal/magmatic weakening of the supercontinent interior (both plume heat and thermal insulation heat). In addition, circum-supercontinent slab downwelling may not only drive the formation of the antipodal superplumes (thus the break-up of the supercontinent), the likely roll-back of the subduction system would also create extension within the supercontinent, facilitating supercontinent break-up. Consequences of supercontinent break-up include long-term sea-level rise, climatic changes due to changes in ocean circulation pattern and carbon cycle, and biodiversification. It has long been demonstrated that the existence of the supercontinent Pangea corresponds to a long-term sea-level drop, whereas the break-up of the supercontinent corresponds to a long-term sea-level rise (170 m higher than it is today). A recent analysis of Neoproterozoic sedimentary facies illustrates that the time of Neoproterozoic supercontinent Rodinia corresponds to a low in the percentage of deep marine facies occurrence, whereas the time of Rodinia break-up corresponds to a significantly higher percentage of deep marine facies occurrence. The long-tern sea-level drop during supercontinent times were likely caused by both plume/superplume dynamic topography and an older mean age of the oceanic crust, whereas long-tern sea-level rise during supercontinent break-up (720-580 Ma for Rodinia and Late Jurassic-Cretaceous for Pangea) likely corresponds to an younger mean age of the oceanic crust, massive plume-induced magmatism in the oceans, and perhaps the effect of continents drifting away from a weakening sub-supercontinent superplume.

Direct microscopic image and measurement of the atomization process of a port fuel injector

NASA Astrophysics Data System (ADS)

Esmail, Mohamed; Kawahara, Nobuyuki; Tomita, Eiji; Sumida, Mamoru

2010-07-01

The main objective of this study is to observe and investigate the phenomena of atomization, i.e. the fuel break-up process very close to the nozzle exit of a practical port fuel injector (PFI). In order to achieve this objective, direct microscopic images of the atomization process were obtained using an ultra-high-speed video camera that could record 102 frames at rates of up to 1 Mfps, coupled with a long-distance microscope and Barlow lens. The experiments were carried out using a PFI in a closed chamber at atmospheric pressure. Time-series images of the spray behaviour were obtained with a high temporal resolution using backlighting. The direct microscopic images of a liquid column break-up were compared with experimental results from laser-induced exciplex fluorescence (LIEF), and the wavelength obtained from the experimental results compared with that predicated from the Kelvin-Helmholtz break-up model. The droplet size diameters from a ligament break-up were compared with results predicated from Weber's analysis. Furthermore, experimental results of the mean droplet diameter from a direct microscopic image were compared with the results obtained from phase Doppler anemometry (PDA) experimental results. Three conclusions were obtained from this study. The atomization processes and detailed characterizations of the break-up of a liquid column were identified; the direct microscopic image results were in good agreement with the results obtained from LIEF, experimental results of the wavelength were in good agreement with those from the Kelvin-Helmholtz break-up model. The break-up process of liquid ligaments into droplets was investigated, and Weber's analysis of the predicated droplet diameter from ligament break-up was found to be applicable only at larger wavelengths. Finally, the direct microscopic image method and PDA method give qualitatively similar trends for droplet size distribution and quantitatively similar values of Sauter mean diameter.

Climate change alters the reproductive phenology and investment of a lacustrine fish, the three-spine stickleback.

PubMed

Hovel, Rachel A; Carlson, Stephanie M; Quinn, Thomas P

2017-06-01

High-latitude lakes are particularly sensitive to the effects of global climate change, demonstrating earlier ice breakup, longer ice-free seasons, and increased water temperatures. Such physical changes have implications for diverse life-history traits in taxa across entire lake food webs. Here, we use a five-decade time series from an Alaskan lake to explore effects of climate change on growth and reproduction of a widely distributed lacustrine fish, the three-spine stickleback (Gasterosteus aculeatus). We used multivariate autoregressive state-space (MARSS) models to describe trends in the mean length for multiple size classes and to explore the influence of physical (date of ice breakup, surface water temperature) and biological (density of con- and heterospecifics) factors. As predicted, mean size of age 1 and older fish at the end of the growing season increased across years with earlier ice breakup and warmer temperatures. In contrast, mean size of age 0 fish decreased over time. Overall, lower fish density and warmer water temperatures were associated with larger size for all cohorts. Earlier ice breakup was associated with larger size for age 1 and older fish but, paradoxically, with smaller size of age 0 fish. To explore this latter result, we used mixing models on age 0 size distributions, which revealed an additional cohort in years with early ice breakup, lowering the mean size of age 0 fish. Moreover, early ice breakup was associated with earlier breeding, evidenced by earlier capture of age 0 fish. Our results suggest that early ice breakup altered both timing and frequency of breeding; three-spine stickleback spawned earlier and more often in response to earlier ice breakup date. While previous studies have shown the influence of changing conditions in northern lakes on breeding timing and growth, this is the first to document increased breeding frequency, highlighting another pathway by which climate change can alter the ecology of northern lakes. © 2016 John Wiley & Sons Ltd.

Breakup Style and Magmatic Underplating West of the Lofoten Islands, Norway, Based on OBS Data.

NASA Astrophysics Data System (ADS)

Breivik, A. J.; Faleide, J. I.; Mjelde, R.; Murai, Y.; Flueh, E. R.

2014-12-01

The breakup of the Northeast Atlantic in the Early Eocene was magma-rich, forming the major part of the North Atlantic Igneous Province (NAIP). This is seen as extrusive and intrusive magmatism in the continental domain, and as a thicker than normal oceanic crust produced the first few million years after continental breakup. The maximum magma productivity and the duration of excess magmatism varies along the margins of Northwest Europe and East Greenland, to some extent as a function of the distance from the Iceland hotspot. The Vøring Plateau off mid-Norway is the northernmost of the margin segments in northwestern Europe with extensive magmatism. North of the plateau, magmatism dies off towards the Lofoten Margin, marking the northern boundary of the NAIP here. In 2003, as part of the Euromargins Program we collected an Ocean Bottom Seismometer (OBS) profile from mainland Norway, across the Lofoten Islands, and out into the deep ocean. Forward velocity modeling using raytracing reveals a continental margin that shows transitional features between magma-rich and magma-poor rifting. On one hand, we detect an up to 2 km thick and 40-50 km wide magmatic underplate of the outer continent, on the other hand, continental thinning is greater and intrusive magmatism less than farther south. Continental breakup also appears to be somewhat delayed compared to breakup on the Vøring Plateau, consistent with increased extension. This indicates that magmatic diking, believed to quickly lead to continental breakup of volcanic margins and thus to reduce continental thinning, played a much lesser role here than at the plateau. Early post-breakup oceanic crust is up to 8 km thick, less than half of that observed farther south. The most likely interpretation of these observations, is that the source for the excess magmatism of the NAIP was not present at the Lofoten Margin during rifting, and that the excess magmatism actually observed was the result of lateral transport from the south around breakup time.

A Genesis breakup and burnup analysis in off-nominal Earth return and atmospheric entry

NASA Technical Reports Server (NTRS)

Salama, Ahmed; Ling, Lisa; McRonald, Angus

2005-01-01

The Genesis project conducted a detailed breakup/burnup analysis before the Earth return to determine if any spacecraft component could survive and reach the ground intact in case of an off-nominal entry. In addition, an independent JPL team was chartered with the responsibility of analyzing several definitive breakup scenarios to verify the official project analysis. This paper presents the analysis and results of this independent team.

Description of Jet Breakup

NASA Technical Reports Server (NTRS)

Papageorgiou, Demetrios T.

1996-01-01

In this article we review recent results on the breakup of cylindrical jets of a Newtonian fluid. Capillary forces provide the main driving mechanism and our interest is in the description of the flow as the jet pinches to form drops. The approach is to describe such topological singularities by constructing local (in time and space) similarity solutions from the governing equations. This is described for breakup according to the Euler, Stokes or Navier-Stokes equations. It is found that slender jet theories can be applied when viscosity is present, but for inviscid jets the local shape of the jet at breakup is most likely of a non-slender geometry. Systems of one-dimensional models of the governing equations are solved numerically in order to illustrate these differences.

History of on-orbit satellite fragmentations

NASA Technical Reports Server (NTRS)

Nauer, David J.

1992-01-01

Since the first serious satellite fragmentation occurred in Jun. 1961, and instantaneously increased the total Earth satellite population by more than 400 percent, the issue of space operations within the finite region of space around the Earth has been the subject of increasing interest and concern. The prolific satellite fragmentations of the 1970's and the marked increase in the number of fragmentations in the 1980's served to widen international research into the characteristics and consequences of such events. Plans for large, manned space stations in the next decade and beyond demand a better understanding of the hazards of the dynamic Earth satellite population. The contribution of satellite fragmentations to the growth of the Earth satellite population is complex and varied. The majority of detectable fragmentation debris have already fallen out of orbit, and the effects of 40 percent of all fragmentations have completely disappeared. In this volume, satellite fragmentations are categorized by their assessed nature and to a lesser degree by their effect on the near-Earth space environment. A satellite breakup is the usually destructive disassociation of an orbital payload, rocket body, or structure, often with a wide range of ejecta velocities. A satellite breakup may be accidental or the result of intentional actions, e.g., due to a propulsion system malfunction or a space weapons test, respectively. An anomalous event is the unplanned separation, usually at low velocity, of one or more detectable objects from a satellite which remains essentially intact. Anomalous events can be caused by material deterioration of items such as thermal blankets, protective shields, or solar panels. As a general rule, a satellite breakup will produce considerably more debris, both trackable and non-trackable, than an anomalous event. From one perspective, satellite breakups may be viewed as a measure of the effects of man's activity on the environment, while anomalous events may be a measure of the environment on man-made objects.

NASA's Orbital Debris Optical and IR Ground-based Observing Program: Utilizing the MCAT, UKIRT, and Magellan Telescopes

NASA Astrophysics Data System (ADS)

Lederer, S.; Cowardin, H.; Buckalew, B.; Frith, J.; Hickson, P.; Pace, L.; Matney, M.; Anz-Meador, P.; Seitzer, P.; Stansbery, E.; Glesne, T.

2016-09-01

Characterizing debris in Earth-orbit has become increasingly important as the growing population of debris poses greater threats to active satellites each year. Currently, the Joint Space Operations is tracking > 23,000 objects ranging in size from 1-meter and larger in Geosychronous orbits (GEO) to 10-cm and larger at low-Earth orbits (LEO). Model estimates suggest that there are hundreds of thousands of pieces of spacecraft debris larger than 10 cm currently in orbit around the Earth. With such a small fraction of the total population being tracked, and new break-ups occurring from LEO to GEO, new assets, techniques, and approaches for characterizing this debris are needed. With this in mind, NASA's Orbital Debris Program Office has actively tasked a suite of telescopes around the world. In 2015, the newly-built 1.3m optical Meter Class Autonomous Telescope (MCAT) came on-line on Ascension Island and is now being commissioned. MCAT is designed to track Earth-orbiting objects above 200km, conduct surveys at GEO, and work with a co-located Raven-class commercial-off-the-shelf system, a 0.4m telescope with a field-of-view similar to MCAT's and research-grade instrumentation designed to complement MCAT. The 3.8m infrared UKIRT telescope on Mauna Kea, Hawaii has been heavily tasked to collect data on individual targets and in survey modes to study both the general GEO population and a break-up event. Data collected include photometry and spectroscopy in the near-Infrared (0.85 - 2.5μm) and the mid-infrared (8-16μm). Finally, the 6.5-m Baade Magellan telescope at Las Campanas Observatory in Chile was used to collect optical photometric survey data in October 2015 of two GEO Titan transtage breakups, focusing on locations of possible debris concentrations as indicated by the NASA standard break-up model.

A stacking ensemble learning framework for annual river ice breakup dates

NASA Astrophysics Data System (ADS)

Sun, Wei; Trevor, Bernard

2018-06-01

River ice breakup dates (BDs) are not merely a proxy indicator of climate variability and change, but a direct concern in the management of local ice-caused flooding. A framework of stacking ensemble learning for annual river ice BDs was developed, which included two-level components: member and combining models. The member models described the relations between BD and their affecting indicators; the combining models linked the predicted BD by each member models with the observed BD. Especially, Bayesian regularization back-propagation artificial neural network (BRANN), and adaptive neuro fuzzy inference systems (ANFIS) were employed as both member and combining models. The candidate combining models also included the simple average methods (SAM). The input variables for member models were selected by a hybrid filter and wrapper method. The performances of these models were examined using the leave-one-out cross validation. As the largest unregulated river in Alberta, Canada with ice jams frequently occurring in the vicinity of Fort McMurray, the Athabasca River at Fort McMurray was selected as the study area. The breakup dates and candidate affecting indicators in 1980-2015 were collected. The results showed that, the BRANN member models generally outperformed the ANFIS member models in terms of better performances and simpler structures. The difference between the R and MI rankings of inputs in the optimal member models may imply that the linear correlation based filter method would be feasible to generate a range of candidate inputs for further screening through other wrapper or embedded IVS methods. The SAM and BRANN combining models generally outperformed all member models. The optimal SAM combining model combined two BRANN member models and improved upon them in terms of average squared errors by 14.6% and 18.1% respectively. In this study, for the first time, the stacking ensemble learning was applied to forecasting of river ice breakup dates, which appeared promising for other river ice forecasting problems.

Tear-Film Evaporation Rate from Simultaneous Ocular-Surface Temperature and Tear-Breakup Area.

PubMed

Dursch, Thomas J; Li, Wing; Taraz, Baseem; Lin, Meng C; Radke, Clayton J

2018-01-01

A corneal heat-transfer model is presented to quantify simultaneous measurements of fluorescein tear-breakup area (TBA) and ocular-surface temperature (OST). By accounting for disruption of the tear-film lipid layer (TFLL), we report evaporation rates through lipid-covered tear. The modified heat-transfer model provides new insights into evaporative dry eye. A quantitative analysis is presented to assess human aqueous tear evaporation rate (TER) through intact TFLLs from simultaneous in vivo measurement of time-dependent infrared OST and fluorescein TBA. We interpret simultaneous OST and TBA measurements using an extended heat-transfer model. We hypothesize that TBAs are ineffectively insulated by the TFLL and therefore exhibit higher TER than does that for a well-insulting TFLL-covered tear. As time proceeds, TBAs increase in number and size, thereby increasing the cornea area-averaged TER and decreasing OST. Tear-breakup areas were assessed from image analysis of fluorescein tear-film-breakup video recordings and are included in the heat-transfer description of OST. Model-predicted OSTs agree well with clinical experiments. Percent reductions in TER of lipid-covered tear range from 50 to 95% of that for pure water, in good agreement with literature. The physical picture of noninsulating or ruptured TFLL spots followed by enhanced evaporation from underlying cooler tear-film ruptures is consistent with the evaporative-driven mechanism for local tear rupture. A quantitative analysis is presented of in vivo TER from simultaneous clinical measurement of transient OST and TBA. The new heat-transfer model accounts for increased TER through expanding TBAs. Tear evaporation rate varies strongly across the cornea because lipid is effectively missing over tear-rupture troughs. The result is local faster evaporation compared with nonruptured, thick lipid-covered tear. Evaporative-driven tear-film ruptures deepen to a thickness where fluorescein quenching commences and local salinity rises to uncomfortable levels. Mitigation of tear-film rupture may therefore reduce dry eye-related symptoms.

History of on-orbit satellite fragmentations

NASA Astrophysics Data System (ADS)

Nauer, David J.

1992-07-01

Since the first serious satellite fragmentation occurred in Jun. 1961, and instantaneously increased the total Earth satellite population by more than 400 percent, the issue of space operations within the finite region of space around the Earth has been the subject of increasing interest and concern. The prolific satellite fragmentations of the 1970's and the marked increase in the number of fragmentations in the 1980's served to widen international research into the characteristics and consequences of such events. Plans for large, manned space stations in the next decade and beyond demand a better understanding of the hazards of the dynamic Earth satellite population. The contribution of satellite fragmentations to the growth of the Earth satellite population is complex and varied. The majority of detectable fragmentation debris have already fallen out of orbit, and the effects of 40 percent of all fragmentations have completely disappeared. In this volume, satellite fragmentations are categorized by their assessed nature and to a lesser degree by their effect on the near-Earth space environment. A satellite breakup is the usually destructive disassociation of an orbital payload, rocket body, or structure, often with a wide range of ejecta velocities. A satellite breakup may be accidental or the result of intentional actions, e.g., due to a propulsion system malfunction or a space weapons test, respectively. An anomalous event is the unplanned separation, usually at low velocity, of one or more detectable objects from a satellite which remains essentially intact. Anomalous events can be caused by material deterioration of items such as thermal blankets, protective shields, or solar panels. As a general rule, a satellite breakup will produce considerably more debris, both trackable and non-trackable, than an anomalous event. From one perspective, satellite breakups may be viewed as a measure of the effects of man's activity on the environment, while anomalous events may be a measure of the environment on man-made objects.

Minimal formulation of the linear spatial analysis of capillary jets: Validity of the two-mode approach

NASA Astrophysics Data System (ADS)

González, H.; Vazquez, P. A.; García, F. J.; Guerrero, J.

2018-04-01

A rigorous and complete formulation of the linear evolution of harmonically stimulated capillary jets should include infinitely many spatial modes to account for arbitrary exit conditions [J. Guerrero et al., J. Fluid Mech. 702, 354 (2012), 10.1017/jfm.2012.182]. However, it is not rare to find works in which only the downstream capillary dominant mode, the sole unstable one, is retained, with amplitude determined by the jet deformation at the exit. This procedure constitutes an oversimplification, unable to handle a flow rate perturbation without jet deformation at the exit (the most usual conditions). In spite of its decaying behavior, the other capillary mode (subdominant) must be included in what can be called a "minimal linear formulation." Deformation and mean axial velocity amplitudes at the jet exit are the two relevant parameters to simultaneously find the amplitudes of both capillary modes. Only once these amplitudes are found, the calculation of the breakup length may be eventually simplified by disregarding the subdominant mode. Simple recipes are provided for predicting the breakup length, which are checked against our own numerical simulations. The agreement is better than in previous attempts in the literature. Besides, the limits of validity of the linear formulation are explored in terms of the exit velocity amplitude, the wave number, the Weber number, and the Ohnesorge number. Including the subdominant mode extends the range of amplitudes for which the linear model gives accurate predictions, the criterion for keeping this mode being that the breakup time must be shorter than a given formula. It has been generally assumed that the shortest intact length happens for the stimulation frequency with the highest growth rate. However, we show that this correlation is not strict because the amplitude of the dominant mode has a role in the breakup process and it depends on the stimulation frequency.

Forecast Tools for Alaska River Ice Breakup Timing and Severity

NASA Astrophysics Data System (ADS)

Moran, E. H.; Lindsey, S.; van Breukelen, C. M.; Thoman, R.

2016-12-01

Spring Breakup on the large interior rivers in Alaska means a time of nervous anticipation for many of the residents in the villages alongside those rivers. On the Yukon and Kuskokwim Rivers the record flood for most villages occurred as a result of ice jams that backed up water and dump truck sized ice floes into the village. Those floods can occur suddenly and can literally wipe out a village. The challenge is that with a limited observation network (3 automated USGS gages along the 1200 miles of the Yukon River flowing through Alaska) and the inherently transient nature of ice jam formation, prediction of the timing and severity of these events has been a tremendous challenge. Staff at the Alaska Pacific River Forecast Center as well as the Alaska Region Climate Program Manager have been developing more quantitative tools to attempt to provide a longer lead time for villages to prepare for potentially devastating flooding. In the past, a very qualitative assessment of the primary drivers of Spring Breakup (snow pack, river ice thickness and forecast spring weather) have led to the successful identification of years when flood severity was likely to be elevated or significantly decreased. These qualitative assessments have also allowed the forecasting of the probability of either a thermal or a dynamic breakup. But there has continued to be a need for an objective tool that can handle weather patterns that border on the tails of the climatic distributions as well as the timing and flood potential from weather patterns that are closer to the median of the distribution. Over the past 8 years there have been a significant number of years with anomalous spring weather patterns including cold springs followed by rapid warmups leading to record flooding from ice jams during spring breakup (2009, 2013), record late breakup (2013), record early breakup (2016), record high snowfall (2012), record snowmelt and aufeis flooding (2015) and record low snowfall (2015). The need for improved tools that can handle these events over the full breadth of the distribution has never been greater. This talk will describe efforts to incorporate climate signals into the spring breakup outlook and show results of some temperature based indices as an indicator of breakup timing.

Bag breakup of low viscosity drops in the presence of a continuous air jet

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

Kulkarni, V., E-mail: vkulkarn@purdue.edu; Sojka, P. E.

This work examines the breakup of a single drop of various low viscosity fluids as it deforms in the presence of continuous horizontal air jet. Such a fragmentation typically occurs after the bulk liquid has disintegrated upon exiting the atomizer and is in the form of an ensemble of drops which undergo further breakup. The drop deformation and its eventual disintegration is important in evaluating the efficacy of a particular industrial process, be it combustion in automobile engines or pesticide spraying in agricultural applications. The interplay between competing influences of surface tension and aerodynamic disruptive forces is represented by themore » Weber number, We, and Ohnesorge number, Oh, and used to describe the breakup morphology. The breakup pattern considered in our study corresponds to that of a bag attached to a toroidal ring which occurs from ∼12 < We < ∼16. We aim to address several issues connected with this breakup process and their dependence on We and Oh which have been hitherto unexplored. The We boundary at which breakup begins is theoretically determined and the expression obtained, We=12(1+2/3Oh{sup 2}), is found to match well with experimental data ([L.-P. Hsiang and G. M. Faeth, Int. J. Multiphase Flow 21(4), 545–560 (1995)] and [R. S. Brodkey, “Formation of drops and bubbles,” in The Phenomena of Fluid Motions (Addison-Wesley, Reading, 1967)]). An exponential growth in the radial extent of the deformed drop and the streamline dimension of the bag is predicted by a theoretical model and confirmed by experimental findings. These quantities are observed to strongly depend on We. However, their dependence on Oh is weak.« less

Deformation and Breakup of Two Fluid Jets

NASA Astrophysics Data System (ADS)

Doshi, Pankaj; Ramkrishna, Doraiswamy; Basaran, Osman

2001-11-01

Two fluid jets consists of an inner liquid core surrounded by an annulus of outer immiscible liquid. The perturbation in the inner and outer interphase could cause capillary instability resulting in large deformation and breakup of the jet into drops. The jet breakup and drop size distribution is largely influenced by the properties of inner and outer fluid phases. Out of the various jet breakup phenomena one with most technological importance is the one in which inner interphase ruptures followed by the outer interphase resulting in the formation of compound drops. The compound drop formation is very useful for the microencapsulation technology, which find use in diverse pharmaceutical and chemical industry applications. In this paper we present a computational analysis of non-linear deformation and breakup of two fluid jets of Newtonian fluids. The analysis involves study of capillary instability driven deformation of a free jet with periodic boundary conditions. Although small amplitude deformation of two fluid jets have previously been studied, large amplitude deformation exhibiting interesting nonlinear dynamics and eventual breakup of the two fluid jets have been beyond the reach of previously used analytical and computational techniques. The computational difficulties result from the facts that (1) the inner and outer interphase can overturn during the motion and (2) pressure and normal stress are discontinuous at the inner interphase. We overcome both of these difficulties by using a new Galerkin/finite element algorithm that relies on a powerful elliptic mesh generation technique. The results to be presented includes jet deformation and breakup time as a function of inner and outer fluid phase properties. The highlight of the results will be prediction of drop size distribution which is of critical importance for microencapsulation technology.

Midlatitude and high-latitude N2O distributions in the Northern Hemisphere in early and late Arctic polar vortex breakup years

NASA Astrophysics Data System (ADS)

Akiyoshi, H.; Zhou, L. B.

2007-09-01

Simulated N2O distributions at midlatitudes and high latitudes in the Northern Hemisphere are analyzed in early and late vortex breakup years with the probability distribution function (PDF) technique. The data are from a Center for Climate System Research/National Institute for Environmental Studies (CCSR/NIES) nudging chemical transport model (CTM) for 24 years from 1979 to 2002. Results show that there is a large difference in midlatitude and high-latitude N2O concentrations on the 600 K isentrope between early and late vortex breakup years. In the early breakup years, the N2O concentration with the maximum area shows low values in the lower stratosphere in the springtime after the vortex breakup. In the late breakup years, the maximum area concentration shows constant high values from the winter to the summer. Our analyses show that the winter and springtime meridional circulation is a main factor for these differences in N2O concentration. In the early breakup years, a larger eddy heat flux causes a stronger winter meridional circulation and a stronger downward advection of low-N2O concentration air at higher altitudes to the lower stratosphere, which leads to the low values of N2O concentration in the lower stratosphere in late winter and early spring. Inside the Arctic vortex, however, the importance of vertical advection is smaller than or comparable to other processes such as horizontal divergence and subgrid-scale motions. These results are consistent with the previous studies on tracer distribution, which showed that not only the vertical advection but also the horizontal eddy transport are important for tracer concentration tendency in the polar vortex.

The Dispersal of East Gondwana from Continental Breakup to the Start of the Cretaceous Quiet Zone

NASA Astrophysics Data System (ADS)

Davis, J. K.; Lawver, L. A.; Norton, I. O.; Gahagan, L.

2014-12-01

Existing plate models for the breakup of Africa and East Gondwana (Australia, East Antarctica, India, Madagascar, the Seychelles, and Sri Lanka) are problematic and require revision. Specific problems include the utilization of dubious Gondwana configurations, improbable plate motion, and/or a failure to satisfy the holistic marine magnetic anomaly data. I present here a new model for the breakup of East Gondwana. This new model begins from a constrained, pre-breakup, Gondwana configuration. Out of this initial "tight-fit" configuration, East Gondwana rifts from West Gondwana (Africa & South America) as a cohesive unit. During this breakup and subsequent seafloor spreading, East Gondwana is devoid of any internal compression or anomalous plate motion. The overall motion of East Gondwana is constrained by seafloor spreading in the coeval Somali Basin and Mozambique/Riiser Larsen Basins. Seafloor spreading in these basins is modeled using existing marine magnetic anomaly interpretations and satellite-derived gravity data. Our model is uniquely able to satisfy the magnetic anomaly observations in both of the aforementioned basins without invoking improbable plate motion or configurations. Additionally, our plate model provides valuable insight into the breakup of India and East Antarctica. In this model, we fix India to Madagascar from breakup to 90 Ma, thus eventual separation between India and East Antarctica is an output, not an input of our model. We suggest that this separation occurred diachronously from ~140 Ma in the east to ~120 Ma in the west. This modeled motion between India and East Antarctica agrees well with geophysical observations from the margin of East Antarctica and our preliminary analysis of margin character and variability.

Bag breakup of low viscosity drops in the presence of a continuous air jet

NASA Astrophysics Data System (ADS)

Kulkarni, V.; Sojka, P. E.

2014-07-01

This work examines the breakup of a single drop of various low viscosity fluids as it deforms in the presence of continuous horizontal air jet. Such a fragmentation typically occurs after the bulk liquid has disintegrated upon exiting the atomizer and is in the form of an ensemble of drops which undergo further breakup. The drop deformation and its eventual disintegration is important in evaluating the efficacy of a particular industrial process, be it combustion in automobile engines or pesticide spraying in agricultural applications. The interplay between competing influences of surface tension and aerodynamic disruptive forces is represented by the Weber number, We, and Ohnesorge number, Oh, and used to describe the breakup morphology. The breakup pattern considered in our study corresponds to that of a bag attached to a toroidal ring which occurs from ˜12 < We < ˜16. We aim to address several issues connected with this breakup process and their dependence on We and Oh which have been hitherto unexplored. The We boundary at which breakup begins is theoretically determined and the expression obtained, We = 12( {1 + 2/3 Oh^2 } ), is found to match well with experimental data {[L.-P. Hsiang and G. M. Faeth, Int. J. Multiphase Flow 21(4), 545-560 (1995)] and [R. S. Brodkey, "Formation of drops and bubbles," in The Phenomena of Fluid Motions (Addison-Wesley, Reading, 1967)]}. An exponential growth in the radial extent of the deformed drop and the streamline dimension of the bag is predicted by a theoretical model and confirmed by experimental findings. These quantities are observed to strongly depend on We. However, their dependence on Oh is weak.

Breakup processes in heavy-ion induced reactions

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

Udagawa, T.; Tamura, T.; Shimoda, T.

1979-11-01

Cross sections for breakup of /sup 20/Ne into /sup 16/O and ..cap alpha.. during scattering from /sup 40/Ca were calculated in terms of the distorted-wave Born approximation. The inclusive /sup 16/O cross section observed in the /sup 40/Ca(/sup 20/Ne,/sup 16/O) reaction was then found to be fitted very well by the sum of this breakup contribution and that of the ..cap alpha..-transfer reaction calculated in our previous work.

Modeling of spray droplets deformation and breakup

NASA Technical Reports Server (NTRS)

Ibrahim, E. A.; Yang, H. Q.; Przekwas, A. J.

1993-01-01

A droplet deformation and breakup (DDB) model is proposed to study shear-type mechanism of spray droplets in pure extentional flows. A numerical solution of the DDB model equation is obtained using a fourth-order Runge-Kutta initial-value solver. The predictions of the DDB model as well as semianalytical and the Taylor analogy models are compared with the experimental data (Krzeczkowski, 1980) for shear breakup, which depict the dimensionless deformation of the drop vs dimensionless time.

When the group practice breaks up: a qualitative study

PubMed Central

2013-01-01

Background Group practices are increasingly common for primary care physicians worldwide. Although breakups are likely to happen frequently within group practices, their process has not been studied to date. The aims of this study were therefore to explore the reasons for breakups of group practices of general practitioners and to describe the associated feelings. Methods We conducted a qualitative study consisting of in-depth interviews of 21 general practitioners and one secretary from past group practices in the Rhône-Alpes region, France, who experienced a breakup. Results When getting started in group practice for the first time, young doctors did not feel ready and supported, and did not necessarily share the same expectations as their partners. The reasons for the breakups involved imbalances within the groups, contrasting working and management styles, and breakdowns in communication. The breakup process often generated long-persistent feelings of suffering and failure for almost every partner who experienced a breakup, particularly for the partner who was leaving. Conclusions Weakening factors exist from the very beginning of a partnership, and problems are likely to increase at every change or event occurring in the group. We provide several recommendations, including fair management, a shared project based on a precise contract, the consultation of third parties as necessary and, in the worst case scenario, leaving the group practice in time. PMID:23642277

Mechanism of Paleo-Mesoproterozoic rifts related to breakup of Columbia supercontinent: A paleostress field modeling

NASA Astrophysics Data System (ADS)

Sun, Shuai; Hou, Guiting; Hari, K. R.; Liu, Shuwen; Guan, Shuwei

2017-06-01

The Paleo-Mesoproterozoic Zhongtiao aulacogen in the North China Craton and Cuddapah basin in the Indian Craton, have both been interpreted as intra-continental rift formed by a mantle plume that led to the breakup of Columbia supercontinent, but the mechanism has not been completely deciphered. In this paper, the mechanism of the Zhongtiao aulacogen and Cuddapah basin related to initial breakup of Columbia has been evaluated with 2D elastic finite element models of the North China Craton and the Indian Craton. The trajectories of the horizontal maximum principal compressive stress of the best-fit model fit well with the trends of dyke swarms in the North China Craton and the Indian Craton. When the other three models generated were compared with the best-fit model, it can be found that a mantle plume beneath the Zhongtiao and Cuddapah areas played the most vital role in developing the Zhongtiao aulacogen, Cuddapah basin and initial breakup of Columbia supercontinent. The boundary subduction forces, including the northern margin of the NCC, the northwest and southwest margins of the Indian Craton are indispensable factors for the rifting and breakup, whereas the mechanical properties have little influence on these modeling results. The initial breakup of Columbia supercontinent might have been resulted from the coupling between a mantle plume upwelling and some plate tectonic forces.

Numerical simulation of the gas-liquid interaction of a liquid jet in supersonic crossflow

NASA Astrophysics Data System (ADS)

Li, Peibo; Wang, Zhenguo; Sun, Mingbo; Wang, Hongbo

2017-05-01

The gas-liquid interaction process of a liquid jet in supersonic crossflow with a Mach number of 1.94 was investigated numerically using the Eulerian-Lagrangian method. The KH (Kelvin-Helmholtz) breakup model was used to calculate the droplet stripping process, and the secondary breakup process was simulated by the competition of RT (Rayleigh-Taylor) breakup model and TAB (Taylor Analogy Breakup) model. A correction of drag coefficient was proposed by considering the compressible effects and the deformation of droplets. The location and velocity models of child droplets after breakup were improved according to droplet deformation. It was found that the calculated spray features, including spray penetration, droplet size distribution and droplet velocity profile agree reasonably well with the experiment. Numerical results revealed that the streamlines of air flow could intersect with the trajectory of droplets and are deflected towards the near-wall region after they enter into spray zone around the central plane. The analysis of gas-liquid relative velocity and droplet deformation suggested that the breakup of droplets mainly occurs around the front region of the spray where gathered a large number of droplets with different sizes. The liquid trailing phenomenon of jet spray which has been discovered by the previous experiment was successfully captured, and a reasonable explanation was given based on the analysis of gas-liquid interaction process.

Design of a self-aligned, wide temperature range (300 mK-300 K) atomic force microscope/magnetic force microscope with 10 nm magnetic force microscope resolution

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

Karcı, Özgür; Department of Nanotechnology and Nanomedicine, Hacettepe University, Beytepe, 06800 Ankara; Dede, Münir

We describe the design of a wide temperature range (300 mK-300 K) atomic force microscope/magnetic force microscope with a self-aligned fibre-cantilever mechanism. An alignment chip with alignment groves and a special mechanical design are used to eliminate tedious and time consuming fibre-cantilever alignment procedure for the entire temperature range. A low noise, Michelson fibre interferometer was integrated into the system for measuring deflection of the cantilever. The spectral noise density of the system was measured to be ~12 fm/√Hz at 4.2 K at 3 mW incident optical power. Abrikosov vortices in BSCCO(2212) single crystal sample and a high density hardmore » disk sample were imaged at 10 nm resolution to demonstrate the performance of the system.« less

Alternans and Spiral Breakup in an Excitable Reaction-Diffusion System: A Simulation Study

PubMed Central

Gani, M. Osman; Ogawa, Toshiyuki

2014-01-01

The determination of the mechanisms of spiral breakup in excitable media is still an open problem for researchers. In the context of cardiac electrophysiological activities, spiral breakup exhibits complex spatiotemporal pattern known as ventricular fibrillation. The latter is the major cause of sudden cardiac deaths all over the world. In this paper, we numerically study the instability of periodic planar traveling wave solution in two dimensions. The emergence of stable spiral pattern is observed in the considered model. This pattern occurs when the heart is malfunctioning (i.e., ventricular tachycardia). We show that the spiral wave breakup is a consequence of the transverse instability of the planar traveling wave solutions. The alternans, that is, the oscillation of pulse widths, is observed in our simulation results. Moreover, we calculate the widths of spiral pulses numerically and observe that the stable spiral pattern bifurcates to an oscillatory wave pattern in a one-parameter family of solutions. The spiral breakup occurs far below the bifurcation when the maximum and the minimum excited states become more distinct, and hence the alternans becomes more pronounced. PMID:27379274

Alternans and Spiral Breakup in an Excitable Reaction-Diffusion System: A Simulation Study.

PubMed

Gani, M Osman; Ogawa, Toshiyuki

2014-01-01

The determination of the mechanisms of spiral breakup in excitable media is still an open problem for researchers. In the context of cardiac electrophysiological activities, spiral breakup exhibits complex spatiotemporal pattern known as ventricular fibrillation. The latter is the major cause of sudden cardiac deaths all over the world. In this paper, we numerically study the instability of periodic planar traveling wave solution in two dimensions. The emergence of stable spiral pattern is observed in the considered model. This pattern occurs when the heart is malfunctioning (i.e., ventricular tachycardia). We show that the spiral wave breakup is a consequence of the transverse instability of the planar traveling wave solutions. The alternans, that is, the oscillation of pulse widths, is observed in our simulation results. Moreover, we calculate the widths of spiral pulses numerically and observe that the stable spiral pattern bifurcates to an oscillatory wave pattern in a one-parameter family of solutions. The spiral breakup occurs far below the bifurcation when the maximum and the minimum excited states become more distinct, and hence the alternans becomes more pronounced.

Breakup phenomena of a coaxial jet in the non-dilute region using real-time X-ray radiography

NASA Astrophysics Data System (ADS)

Cheung, F. B.; Kuo, K. K.; Woodward, R. D.; Garner, K. N.

1990-07-01

An innovative approach to the investigation of liquid jet breakup processes in the near-injector region has been developed to overcome the experimental difficulties associated with optically opaque, dense sprays. Real-time X-ray radiography (RTR) has been employed to observe the inner structure and breakup phenomena of coaxial jets. In the atomizing regime, droplets much smaller than the exit diameter are formed beginning essentially at the injector exit. Through the use of RTR, the instantaneous contour of the liquid core was visualized. Experimental results consist of controlled-exposure digital video images of the liquid jet breakup process. Time-averaged video images have also been recorded for comparison. A digital image processing system is used to analyze the recorded images by creating radiance level distributions of the jet. A rudimentary method for deducing intact-liquid-core length has been suggested. The technique of real-time X-ray radiography has been shown to be a viable approach to the study of the breakup processes of high-speed liquid jets.

Fragmentation dynamics in the droplet bag breakup regime

NASA Astrophysics Data System (ADS)

Kulkarni, Varun; Sojka, Paul

2014-11-01

The closing stages of a droplet bag breakup event is marked by the appearance of several topological changes in the drop shape, followed by its fragmentation owing to hydrodynamics instabilities. In the present work we examine this breakup event, which occurs when a drop enters a continuous jet air stream. The deformed drop before eventual fragmentation is comprised of two main features: a bag and a bounding rim. Our investigation discusses the mechanism of rim/ bag breakup and the ensuing drop size distribution. The role of two possible instabilities, Plateau -Rayleigh and Rayleigh -Taylor, in rim breakup is examined and the dominant role of the Plateau -Rayleigh instability is revealed. In contrast, the Rayleigh -Taylor instability is seen to explain the disintegration of the bag well. The effects of viscosity and air jet velocity are also investigated. The formation of secondary features, such as nodes on the rim and holes on the bag, are also discussed. To conclude, a simple scaling argument based on the characteristic time scales of these instabilities is presented to explain the commonly observed early bursting of the bag, vis-à-vis the rim.

Alignment of gold nanorods by angular photothermal depletion

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

Taylor, Adam B.; Chow, Timothy T. Y.; Chon, James W. M., E-mail: jchon@swin.edu.au

2014-02-24

In this paper, we demonstrate that a high degree of alignment can be imposed upon randomly oriented gold nanorod films by angular photothermal depletion with linearly polarized laser irradiation. The photothermal reshaping of gold nanorods is observed to follow quadratic melting model rather than the threshold melting model, which distorts the angular and spectral hole created on 2D distribution map of nanorods to be an open crater shape. We have accounted these observations to the alignment procedures and demonstrated good agreement between experiment and simulations. The use of multiple laser depletion wavelengths allowed alignment criteria over a large range ofmore » aspect ratios, achieving 80% of the rods in the target angular range. We extend the technique to demonstrate post-alignment in a multilayer of randomly oriented gold nanorod films, with arbitrary control of alignment shown across the layers. Photothermal angular depletion alignment of gold nanorods is a simple, promising post-alignment method for creating future 3D or multilayer plasmonic nanorod based devices and structures.« less

Cooperative breakups induced by drop-to-drop interactions in one-dimensional flows of drops against micro-obstacles.

PubMed

Schmit, Alexandre; Salkin, Louis; Courbin, Laurent; Panizza, Pascal

2015-03-28

Depending on the capillary number at play and the parameters of the flow geometry, a drop may or may not break when colliding with an obstacle in a microdevice. Modeling the flow of one-dimensional trains of monodisperse drops impacting a micro-obstacle, we show numerically that complex dynamics may arise through drop-to-drop hydrodynamic interactions: we observe sequences of breakup events in which the size of the daughter drops created upon breaking mother ones becomes a periodic function of time. We demonstrate the existence of numerous bifurcations between periodic breakup regimes and we establish diagrams mapping the possible breakup dynamics as a function of the governing (physicochemical, hydrodynamic, and geometric) parameters. Microfluidic experiments validate our model as they concur very well with predictions.

Evidence of Middle Jurassic magmatism within the Seychelles microcontinent: Implications for the breakup of Gondwana

NASA Astrophysics Data System (ADS)

Shellnutt, J. G.; Lee, T.-Y.; Chiu, H.-Y.; Lee, Y.-H.; Wong, J.

2015-12-01

The breakup of East and West Gondwana occurred during the Jurassic, but the exact timing is uncertain due to the limited exposure of rocks suitable for radioisotopic dating. Trachytic rocks from Silhouette Island, Seychelles, yielded a range of zircon ages from Paleoproterozoic to Cenozoic. The 206Pb/238U age of the trachyte is 64.9 ± 1.6 Ma (Danian) but the majority of zircons yielded an age of 163.8 ± 1.8 Ma (Callovian) with a small subset yielding an age of 147.7 ± 4.5 Ma (Tithonian). The Hf isotopes of the Callovian (ɛHf(t) = +4.1 to +13.4) and Danian (ɛHf(t) = +1.9 to +7.1) zircons indicate that they were derived from moderately depleted mantle sources whereas the Tithonian zircons (ɛHf(t) = -7.0 to -7.3) were derived from an enriched source. The identification of middle Jurassic zircons indicates that rifting and magmatism were likely contemporaneous during the initial separation of East and West Gondwana.

The Role of Crustal Strength in Controlling Magmatism and Melt Chemistry During Rifting and Breakup

NASA Astrophysics Data System (ADS)

Armitage, John J.; Petersen, Kenni D.; Pérez-Gussinyé, Marta

2018-02-01

The strength of the crust has a strong impact on the evolution of continental extension and breakup. Strong crust may promote focused narrow rifting, while wide rifting might be due to a weaker crustal architecture. The strength of the crust also influences deeper processes within the asthenosphere. To quantitatively test the implications of crustal strength on the evolution of continental rift zones, we developed a 2-D numerical model of lithosphere extension that can predict the rare Earth element (REE) chemistry of erupted lava. We find that a difference in crustal strength leads to a different rate of depletion in light elements relative to heavy elements. By comparing the model predictions to rock samples from the Basin and Range, USA, we can demonstrate that slow extension of a weak continental crust can explain the observed depletion in melt chemistry. The same comparison for the Main Ethiopian Rift suggests that magmatism within this narrow rift zone can be explained by the localization of strain caused by a strong lower crust. We demonstrate that the slow extension of a strong lower crust above a mantle of potential temperature of 1,350 °C can fit the observed REE trends and the upper mantle seismic velocity for the Main Ethiopian Rift. The thermo-mechanical model implies that melt composition could provide quantitative information on the style of breakup and the initial strength of the continental crust.

Experimental study on immiscible jet breakup using refractive index matched oil-water pair

NASA Astrophysics Data System (ADS)

Xue, Xinzhi; Katz, Joseph

2016-11-01

A subsea oil well blowout creates an immiscible crude oil jet. This jet fragments shortly after injection, resulting in generation of a droplet cloud. Detailed understanding of the processes involved is crucial for modeling the fragmentation and for predicting the droplet size distribution. High density of opaque droplets near nozzle limits our ability to visualize and quantify the breakup process. To overcome this challenge, two immiscible fluids: silicone oil and sugar water with the same index of refraction (1.4015) are used as surrogates for crude oil and seawater, respectively. Their ratios of kinematic viscosity (5.64), density (0.83) and interfacial tension are closely matched with those of crude oil and seawater. Distribution of the oil phase is visualized by fluorescent tagging. Both phases are also seeded with particles for simultaneous PIV measurements. The measurements are performed within atomization range of Ohnesorge and Reynolds numbers. Index matching facilitates undistorted view of the phase distribution in illuminated section. Ongoing tests show that the jet surface initially rolls up into Kelvin-Helmholtz rings, followed by development of dispersed phase ligaments further downstream, which then break into droplets. Some of these droplets are re-entrained into the high momentum core, resulting in secondary breakup. As the oil layer and ligaments evolve, they often entrain water, resulting in generation of multiple secondary water droplets encapsulated within the oil droplets. This research is made possible by a Grant from Gulf of Mexico Research Initiative.

Massive collisions in debris disks: possible application to the beta Pic disc

NASA Astrophysics Data System (ADS)

Kral, Q.; Thébault, P.; Augereau, J.-C.; Boccaletti, A.; Charnoz, S.

2014-09-01

The new LIDT-DD code has been used to study massive collisions in debris discs. This new hybrid model is a fully self-consistent code coupling dynamics and collisions to study debris discs (Kral et al. 2013). It models the full complexity of debris discs' physics such as high velocity collisions, radiation-pressure affected orbits, wide range of grains' dynamical behaviour, etc. LIDT-DD can be used on many possible applications. Our first test case concerns the violent breakup of a massive planetesimal such as the ones happening during the late stages of planetary formation or with the biggest bodies in debris belts. We investigate the duration, magnitude and spatial structure of the signature left by such a violent event, as well as its observational detectability. We find that the breakup of a Ceres-sized body creates an asymmetric dust disc that is homogenized, by the coupled action of collisions and dynamics. The luminosity excess in the breakup's aftermath should be detectable by mid-IR photometry, from a 30 pc distance. As for the asymmetric structures, we derive synthetic images for the SPHERE/VLT and MIRI/JWST instruments, showing that they should be clearly visible and resolved from a 10 pc distance. We explain the observational signature of such impacts and give scaling laws to extrapolate our results to different configurations. These first results confirm that our code can be used to study the massive collision scenario to explain some asymmetries in the Beta-Pic disc.

Molecular-dynamics study of propane-hydrate dissociation: Fluctuation-dissipation and non-equilibrium analysis.

PubMed

Ghaani, Mohammad Reza; English, Niall J

2018-03-21

Equilibrium and non-equilibrium molecular-dynamics (MD) simulations have been performed to investigate thermal-driven break-up of planar propane-hydrate interfaces in contact with liquid water over the 260-320 K range. Two types of hydrate-surface water-lattice molecular termination were adopted, at the hydrate edge with water, for comparison: a 001-direct surface cleavage and one with completed cages. Statistically significant differences in melting temperatures and initial break-up rates were observed between both interface types. Dissociation rates were observed to be strongly dependent on temperature, with higher rates at larger over-temperatures vis-à-vis melting. A simple coupled mass and heat transfer model, developed previously, was applied to fit the observed dissociation profiles, and this helps us to identify clearly two distinct hydrate-decomposition régimes; following a highly temperature-dependent break-up phase, a second well-defined stage is essentially independent of temperature, in which the remaining nanoscale, de facto two-dimensional system's lattice framework is intrinsically unstable. Further equilibrium MD-analysis of the two-phase systems at their melting point, with consideration of the relaxation times gleaned from the auto-correlation functions of fluctuations in a number of enclathrated guest molecules, led to statistically significant differences between the two surface-termination cases; a consistent correlation emerged in both cases between the underlying, non-equilibrium, thermal-driven dissociation rates sampled directly from melting with that from an equilibrium-MD fluctuation-dissipation approach.

Molecular-dynamics study of propane-hydrate dissociation: Fluctuation-dissipation and non-equilibrium analysis

NASA Astrophysics Data System (ADS)

Ghaani, Mohammad Reza; English, Niall J.

2018-03-01

Equilibrium and non-equilibrium molecular-dynamics (MD) simulations have been performed to investigate thermal-driven break-up of planar propane-hydrate interfaces in contact with liquid water over the 260-320 K range. Two types of hydrate-surface water-lattice molecular termination were adopted, at the hydrate edge with water, for comparison: a 001-direct surface cleavage and one with completed cages. Statistically significant differences in melting temperatures and initial break-up rates were observed between both interface types. Dissociation rates were observed to be strongly dependent on temperature, with higher rates at larger over-temperatures vis-à-vis melting. A simple coupled mass and heat transfer model, developed previously, was applied to fit the observed dissociation profiles, and this helps us to identify clearly two distinct hydrate-decomposition régimes; following a highly temperature-dependent break-up phase, a second well-defined stage is essentially independent of temperature, in which the remaining nanoscale, de facto two-dimensional system's lattice framework is intrinsically unstable. Further equilibrium MD-analysis of the two-phase systems at their melting point, with consideration of the relaxation times gleaned from the auto-correlation functions of fluctuations in a number of enclathrated guest molecules, led to statistically significant differences between the two surface-termination cases; a consistent correlation emerged in both cases between the underlying, non-equilibrium, thermal-driven dissociation rates sampled directly from melting with that from an equilibrium-MD fluctuation-dissipation approach.

Relationships between Liquid Atomization and Solid Fragmentation

DTIC Science & Technology

2016-03-01

Sallam, C. Aalburg, G.M. Faeth, K.-C. Lin, C.D. Carter, and T.A. Jackson, Primary Breakup of Aerated- Liquid Jets in Supersonic Crossflows, Atomization...Wu, L.-K. Tseng, and G. M. Faeth, Primary Breakup in Gas / Liquid Mixing Layers for Turbulent Liquids , Atomization and Sprays, 295-317, 1992 P.-K...Wu, G. A. Ruff, and G. M. Faeth, Primary Breakup in Liquid - Gas Mixing Layers, Atomization and Sprays, 1, 421-440, 1991 P.-K. Wu and G. M. Faeth

Modeling of Fragmentation of Asteroids

NASA Technical Reports Server (NTRS)

Agrawal, Parul; Prabhu, Dinesh K.; Carlozzi, Alexander; Hart, Kenneth; Bryson, Katie; Sears, Derek

2015-01-01

The objective of this study is to understand fragmentation and fracture of a given asteroid and mechanisms of break-up. The focus of the present work is to develop modeling techniques for stony asteroids in 10m-100m range to answer two questions: 1) What is the role of material makeup of an asteroid in the stress distribution? 2)How is stress distribution altered in the presence of pre-existing defects?

Treating fossils as terminal taxa in divergence time estimation reveals ancient vicariance patterns in the palpimanoid spiders.

PubMed

Wood, Hannah Marie; Matzke, Nicholas J; Gillespie, Rosemary G; Griswold, Charles E

2013-03-01

Incorporation of fossils into biogeographic studies can have a profound effect on the conclusions that result, particularly when fossil ranges are nonoverlapping with extant ranges. This is the case in archaeid spiders, where there are known fossils from the Northern Hemisphere, yet all living members are restricted to the Southern Hemisphere. To better understand the biogeographic patterns of archaeid spiders and their palpimanoid relatives, we estimate a dated phylogeny using a relaxed clock on a combined molecular and morphological data set. Dating information is compared with treating the archaeid fossil taxa as both node calibrations and as noncontemporaneous terminal tips, both with and without additional calibration points. Estimation of ancestral biogeographic ranges is then performed, using likelihood and Bayesian methods to take into account uncertainty in phylogeny and in dating. We find that treating the fossils as terminal tips within a Bayesian framework, as opposed to dating the phylogeny based only on molecular data with the dates coming from node calibrations, removes the subjectivity involved in assigning priors, which has not been possible with previous methods. Our analyses suggest that the diversification of the northern and southern archaeid lineages was congruent with the breakup of Pangaea into Laurasia and Gondwanaland. This analysis provides a rare example, and perhaps the most strongly supported, where a dated phylogeny confirms a biogeographical hypothesis based on vicariance due to the breakup of the ancient continental plates.

Inclusive Breakup Theory of Three-Body Halos

NASA Astrophysics Data System (ADS)

Hussein, Mahir S.; Souza, Lucas A.; Chimanski, Emanuel; Carlson, Brett; Frederico, Tobias

2017-11-01

We present a recently developed theory for the inclusive breakup of three-fragment projectiles within a four-body spectator model [1], for the treatment of the elastic and inclusive non-elastic break up reactions involving weakly bound three-cluster nuclei in A (a; b) X / a = x1 + x2 + b collisions. The four-body theory is an extension of the three-body approaches developed in the 80's by Ichimura, Autern and Vincent (IAV) [2], Udagawa and Tamura (UT) [3] and Hussein and McVoy (HM) [4]. We expect that experimentalists shall be encouraged to search for more information about the x1 + x2 system in the elastic breakup cross section and that also further developments and extensions of the surrogate method will be pursued, based on the inclusive non-elastic breakup part of the b spectrum.

Fluid breakup in carbon nanotubes: An explanation of ultrafast ion transport

NASA Astrophysics Data System (ADS)

Gao, Xiang; Zhao, Tianshou; Li, Zhigang

2017-09-01

Ultrafast ion transport in carbon nanotubes (CNTs) has been experimentally observed, but the underlying mechanism is unknown. In this work, we investigate ion transport in CNTs through molecular dynamics (MD) simulations. It is found that the flow in CNTs undergoes a transition from the passage of a continuous liquid chain to the transport of isolated ion-water clusters as the CNT length or the external electric filed strength is increased. The breakup of the liquid chain in CNTs greatly reduces the resistance caused by the hydrogen bonds of water and significantly enhances the ionic mobility, which explains the two-order-magnitude enhancement of ionic conductance in CNTs reported in the literature. A theoretical criterion for fluid breakup is proposed, which agrees well with MD results. The fluid breakup phenomenon provides new insights into enhancing ion transport in nanoconfinements.

Sikuliqiruq: Ice dynamics of the Meade river - Arctic Alaska, from freezeup to breakup from time-series ground imagery

USGS Publications Warehouse

Beck, R.A.; Rettig, A.J.; Ivenso, C.; Eisner, Wendy R.; Hinkel, Kenneth M.; Jones, Benjamin M.; Arp, C.D.; Grosse, G.; Whiteman, D.

2010-01-01

Ice formation and breakup on Arctic rivers strongly influence river flow, sedimentation, river ecology, winter travel, and subsistence fishing and hunting by Alaskan Natives. We use time-series ground imagery ofthe Meade River to examine the process at high temporal and spatial resolution. Freezeup from complete liquid cover to complete ice cover ofthe Meade River at Atqasuk, Alaska in the fall of 2008 occurred in less than three days between 28 September and 2 October 2008. Breakup in 2009 occurred in less than two hours between 23:47 UTC on 23 May 2009 and 01:27 UTC on 24 May 2009. All times in UTC. Breakup in 2009 and 2010 was ofthe thermal style in contrast to the mechanical style observed in 1966 and is consistent with a warming Arctic. ?? 2010 Taylor & Francis.

Wave packet analysis and break-up length calculations for an accelerating planar liquid jet

NASA Astrophysics Data System (ADS)

Turner, M. R.; Healey, J. J.; Sazhin, S. S.; Piazzesi, R.

2012-02-01

This paper examines the process of transition to turbulence within an accelerating planar liquid jet. By calculating the propagation and spatial evolution of disturbance wave packets generated at a nozzle where the jet emerges, we are able to estimate break-up lengths and break-up times for different magnitudes of acceleration and different liquid to air density ratios. This study uses a basic jet velocity profile that has shear layers in both air and the liquid either side of the fluid interface. The shear layers are constructed as functions of velocity which behave in line with our CFD simulations of injecting diesel jets. The non-dimensional velocity of the jet along the jet centre-line axis is assumed to take the form V (t) = tanh(at), where the parameter a determines the magnitude of the acceleration. We compare the fully unsteady results obtained by solving the unsteady Rayleigh equation to those of a quasi-steady jet to determine when the unsteady effects are significant and whether the jet can be regarded as quasi-steady in typical operating conditions for diesel engines. For a heavy fluid injecting into a lighter fluid (density ratio ρair/ρjet = q < 1), it is found that unsteady effects are mainly significant at early injection times where the jet velocity profile is changing fastest. When the shear layers in the jet thin with time, the unsteady effects cause the growth rate of the wave packet to be smaller than the corresponding quasi-steady jet, whereas for thickening shear layers the unsteady growth rate is larger than that of the quasi-steady jet. For large accelerations (large a), the unsteady effect remains at later times but its effect on the growth rate of the wave packet decreases as the time after injection increases. As the rate of acceleration is reduced, the range of velocity values for which the jet can be considered as quasi-steady increases until eventually the whole jet can be considered quasi-steady. For a homogeneous jet (q = 1), the range of values of a for which the jet can be considered completely quasi-steady increases to larger values of a. Finally, we investigate approximating the wave packet break-up length calculations with a method that follows the most unstable disturbance wave as the jet accelerates. This approach is similar to that used in CFD simulations as it greatly reduces computational time. We investigate whether or not this is a good approximation for the parameter values typically used in diesel engines.

The Transition from Volcanic to Rift Dominated Crustal Breakup - From the Vøring Plateau to the Lofoten Margin, Norway

NASA Astrophysics Data System (ADS)

Breivik, A. J.; Faleide, J. I.; Mjelde, R.; Flueh, E.; Murai, Y.

2017-12-01

The Vøring Plateau was part of the Northeast Atlantic igneous province (NAIP) during early Cenozoic crustal breakup. Crustal breakup at the Vøring Plateau occurred marginal to the deep Cretaceous basins on the shelf, with less extension of the crust. Intrusive magmatism and oceanic crust up to three times normal thickness caused a period of sub-aerial magmatism around breakup time. The transition to the Lofoten Margin is rapid to a deep-water plain. Still, there is some excess magmatism north of this transition, where early oceanic crustal thickness is reduced to half of that of the Vøring Plateau 150 km away. Our estimates of the earliest seafloor spreading rates using new ship-track magnetic profiles on different margin segments offer a clue to what caused this rapid transition. While crustal breakup occurred within the magnetic polarity C24r in other parts of the NAIP, there is a delayed breakup for the Lofoten/Vesterålen margin. Modeling of the earliest seafloor spreading with geomagnetic reversals, indicate a breakup within C24n.3n (anomaly 24b), approximately 1 m.y. later. Both old wide-angle seismic models (from Ocean Bottom Seismometers) off southern Lofoten and a newly published profile farther north show a strongly extended outer margin. Applying early seafloor half-spreading rates ( 30 mm/y) from other NAIP margin segments for 1 m.y. can account for 30 km extra extension, giving a factor of three crustal thinning, and gives a high strain rate of 3.2 ·10-14. Crustal breakup at the magma-poor Iberian Margin occurred at a low strain rate of 4.4·10-15, allowing the ascending mantle to cool, favoring tectonic extension over magmatism. Similar strain rates are found within the main Ethiopian Rift, but there is much magmatism and crustal separation is dominated by dike injection. Mantle tomography models show an exceptionally low seismic velocity below the area interpreted as an unusually hot upper mantle, which will favor magmatism. The transition from the Vøring Plateau to the Lofoten Margin can therefore be explained by the presence/absence of hot mantle plume material under the different segments during rifting. Only after significant extension and close to crustal breakup time did a minor amount of plume material reach the Lofoten/Vesterålen margin to cause some elevated but short-lived excess magmatism there.

Turbulence intensity's effect on liquid jet breakup from long circular pipes

NASA Astrophysics Data System (ADS)

Trettel, Ben; Ezekoye, Ofodike

2017-11-01

Long pipes which produce fully developed flow are frequently used as a nozzle in jet breakup research. We compiled experimental data from over 20 pipe jet studies for many breakup quantities and developed correlations for these quantities based on existing theories and our own theories. Previous experimental studies often had confounding between some variables (e.g., the Reynolds and Weber numbers), neglected important quantities (e.g., the turbulence intensity), or made apples to oranges comparisons (e.g., different nozzles). By independently tracking the Reynolds number, Weber number, density ratio, and turbulence intensity, and focusing only on pipe jets to keep other variables nearly constant, we minimize these issues. Turbulence is a cause of jet breakup, yet there is little quantitative research on this due to the difficulty of turbulence measurements in free surface flows. To avoid those difficulties, we exploited the fact that adjusting the roughness of a long pipe allows one to quantifiably control the turbulence intensity. We correlated turbulence intensity as a function of the friction factor. Data for rough pipes was used to include turbulence intensity in our study. Comparisons were made with theories for the effect of turbulence intensity on breakup.

Droplet breakup dynamics of weakly viscoelastic fluids

NASA Astrophysics Data System (ADS)

Marshall, Kristin; Walker, Travis

2016-11-01

The addition of macromolecules to solvent, even in dilute quantities, can alter a fluid's response in an extensional flow. For low-viscosity fluids, the presence of elasticity may not be apparent when measured using a standard rotational rheometer, yet it may still alter the response of a fluid when undergoing an extensional deformation, especially at small length scales where elastic effects are enhanced. Applications such as microfluidics necessitate investigating the dynamics of fluids with elastic properties that are not pronounced at large length scales. In the present work, a microfluidic cross-slot configuration is used to study the effects of elasticity on droplet breakup. Droplet breakup and the subsequent iterated-stretching - where beads form along a filament connecting two primary droplets - were observed for a variety of material and flow conditions. We present a relationship on the modes of bead formation and how and when these modes will form based on key parameters such as the properties of the outer continuous-phase fluid. The results are vital not only for simulating the droplet breakup of weakly viscoelastic fluids but also for understanding how the droplet breakup event can be used for characterizing the extensional properties of weakly-viscoelastic fluids.

Cretaceous origin of giant rhinoceros beetles (Dynastini; Coleoptera) and correlation of their evolution with the Pangean breakup.

PubMed

Jin, Haofei; Yonezawa, Takahiro; Zhong, Yang; Kishino, Hirohisa; Hasegawa, Masami

2017-03-17

The giant rhinoceros beetles (Dynastini, Scarabaeidae, Coleoptera) are distributed in tropical and temperate regions in Asia, America and Africa. Recent molecular phylogenetic studies have revealed that the giant rhinoceros beetles can be divided into three clades representing Asia, America and Africa. Although a correlation between their evolution and the continental drift during the Pangean breakup was suggested, there is no accurate divergence time estimation among the three clades based on molecular data. Moreover, there is a long chronological gap between the timing of the Pangean breakup (Cretaceous: 110-148 Ma) and the emergence of the oldest fossil record (Oligocene: 33 Ma). In this study, we estimated their divergence times based on molecular data, using several combinations of fossil calibration sets, and obtained robust estimates. The inter-continental divergence events among the clades were estimated to have occurred about 99 Ma (Asian clade and others) and 78 Ma (American clade and African clade), both of which are after the Pangean breakup. These estimates suggest their inter-continental divergences occurred by overseas sweepstakes dispersal, rather than by vicariances of the population caused by the Pangean breakup.

Mechanisms behind overshoots in mean cluster size profiles in aggregation-breakup processes.

PubMed

Sadegh-Vaziri, Ramiar; Ludwig, Kristin; Sundmacher, Kai; Babler, Matthaus U

2018-05-26

Aggregation and breakup of small particles in stirred suspensions often shows an overshoot in the time evolution of the mean cluster size: Starting from a suspension of primary particles the mean cluster size first increases before going through a maximum beyond which a slow relaxation sets in. Such behavior was observed in various systems, including polymeric latices, inorganic colloids, asphaltenes, proteins, and, as shown by independent experiments in this work, in the flocculation of microalgae. This work aims at investigating possible mechanism to explain this phenomenon using detailed population balance modeling that incorporates refined rate models for aggregation and breakup of small particles in turbulence. Four mechanisms are considered: (1) restructuring, (2) decay of aggregate strength, (3) deposition of large clusters, and (4) primary particle aggregation where only aggregation events between clusters and primary particles are permitted. We show that all four mechanisms can lead to an overshoot in the mean size profile, while in contrast, aggregation and breakup alone lead to a monotonic, "S"-shaped size evolution profile. In order to distinguish between the different mechanisms simple protocols based on variations of the shear rate during the aggregation-breakup process are proposed. Copyright © 2018 Elsevier Inc. All rights reserved.

Longing for Ex-Partners out of Fear of Being Single.

PubMed

Spielmann, Stephanie S; MacDonald, Geoff; Joel, Samantha; Impett, Emily A

2016-12-01

This research investigated whether people who fear being single have a more difficult time letting go of ex-partners following a romantic breakup. Data were collected in a cross-sectional study (N = 209, 64% women, M age  = 30 years old) as well as a 1-month daily experience study of individuals who just went through a romantic breakup (N = 117, 44% women, M age  = 27 years old). Findings from both studies revealed that those with stronger fear of being single (Spielmann et al., 2013) reported greater longing for their ex-partners. Pre- to post-breakup analyses revealed that fear of being single increased after a breakup, regardless of who initiated the breakup. Within-day analyses revealed that longing for an ex-partner and attempts to renew the relationship were greater on days with stronger fear of being single. Lagged-day analyses provided support for the conclusion that fear of being single increased longing and renewal attempts over time, but longing and renewal attempts did not influence fear of being single. These findings suggest that fear of being single is a particularly useful construct for understanding the romantic detachment process. © 2015 Wiley Periodicals, Inc.

Dynamics of flexible molecules in thinning fluid filaments

NASA Astrophysics Data System (ADS)

Arratia, Paulo E.; Juarez, Gabriel

2011-11-01

Newtonian liquids that contain small amounts (~ppm) of flexible polymers can exhibit viscoelastic behavior in extensional flows. In this talk, we report the results of experiments on the thinning and breakup of polymeric fluids in a simple microfluidic device. We aim to understand the stretching dynamics of flexible polymers by direct visualization of fluorescent DNA molecules, a model polymer. A Boger fluid, composed of 100 ppm polyacrylamide and 85% w/w glycerol, is seeded with stained lambdaâDNA molecules (<10% v/v) imaged by high speed epifluorescence microscopy. We observe that the strong flow in the thinning fluid threads provide sufficient forces to stretch the DNA molecules away from their equilibrium coiled state. The distribution of stretch lengths, however, is very heterogeneous due to molecular individualism and initial conditions. Once the molecules are stretched to their full length and aligned with the flow, they translate along the fluid thread as rigid rods until the point of pinch off. After pinch off, both the fluid and molecules return to a relaxed state.

Method for protecting chip corners in wet chemical etching of wafers

DOEpatents

Hui, Wing C.

1994-01-01

The present invention is a corner protection mask design that protects chip corners from undercutting during anisotropic etching of wafers. The corner protection masks abut the chip corner point and extend laterally from segments along one or both corner sides of the corner point, forming lateral extensions. The protection mask then extends from the lateral extensions, parallel to the direction of the corner side of the chip and parallel to scribe lines, thus conserving wafer space. Unmasked bomb regions strategically formed in the protection mask facilitate the break-up of the protection mask during etching. Corner protection masks are useful for chip patterns with deep grooves and either large or small chip mask areas. Auxiliary protection masks form nested concentric frames that etch from the center outward are useful for small chip mask patterns. The protection masks also form self-aligning chip mask areas. The present invention is advantageous for etching wafers with thin film windows, microfine and micromechanical structures, and for forming chip structures more elaborate than presently possible.

Method for protecting chip corners in wet chemical etching of wafers

DOEpatents

Hui, W.C.

1994-02-15

The present invention is a corner protection mask design that protects chip corners from undercutting during anisotropic etching of wafers. The corner protection masks abut the chip corner point and extend laterally from segments along one or both corner sides of the corner point, forming lateral extensions. The protection mask then extends from the lateral extensions, parallel to the direction of the corner side of the chip and parallel to scribe lines, thus conserving wafer space. Unmasked bomb regions strategically formed in the protection mask facilitate the break-up of the protection mask during etching. Corner protection masks are useful for chip patterns with deep grooves and either large or small chip mask areas. Auxiliary protection masks form nested concentric frames that etch from the center outward are useful for small chip mask patterns. The protection masks also form self-aligning chip mask areas. The present invention is advantageous for etching wafers with thin film windows, microfine and micromechanical structures, and for forming chip structures more elaborate than presently possible. 63 figures.

Navigated total knee arthroplasty: is it error-free?

PubMed

Chua, Kerk Hsiang Zackary; Chen, Yongsheng; Lingaraj, Krishna

2014-03-01

The aim of this study was to determine whether errors do occur in navigated total knee arthroplasty (TKAs) and to study whether errors in bone resection or implantation contribute to these errors. A series of 20 TKAs was studied using computer navigation. The coronal and sagittal alignments of the femoral and tibial cutting guides, the coronal and sagittal alignments of the final tibial implant and the coronal alignment of the final femoral implant were compared with that of the respective bone resections. To determine the post-implantation mechanical alignment of the limb, the coronal alignment of the femoral and tibial implants was combined. The median deviation between the femoral cutting guide and bone resection was 0° (range -0.5° to +0.5°) in the coronal plane and 1.0° (range -2.0° to +1.0°) in the sagittal plane. The median deviation between the tibial cutting guide and bone resection was 0.5° (range -1.0° to +1.5°) in the coronal plane and 1.0° (range -1.0° to +3.5°) in the sagittal plane. The median deviation between the femoral bone resection and the final implant was 0.25° (range -2.0° to 3.0°) in the coronal plane. The median deviation between the tibial bone resection and the final implant was 0.75° (range -3.0° to +1.5°) in the coronal plane and 1.75° (range -4.0° to +2.0°) in the sagittal plane. The median post-implantation mechanical alignment of the limb was 0.25° (range -3.0° to +2.0°). When navigation is used only to guide the positioning of the cutting jig, errors may arise in the manual, non-navigated steps of the procedure. Our study showed increased cutting errors in the sagittal plane for both the femur and the tibia, and following implantation, the greatest error was seen in the sagittal alignment of the tibial component. Computer navigation should be used not only to guide the positioning of the cutting jig, but also to check the bone resection and implant position during TKA. IV.

Homogeneous alignment of nematic liquid crystals by ion beam etched surfaces

NASA Technical Reports Server (NTRS)

Wintucky, E. G.; Mahmood, R.; Johnson, D. L.

1979-01-01

A wide range of ion beam etch parameters capable of producing uniform homogeneous alignment of nematic liquid crystals on SiO2 films are discussed. The alignment surfaces were generated by obliquely incident (angles of 5 to 25 deg) argon ions with energies in the range of 0.5 to 2.0 KeV, ion current densities of 0.1 to 0.6 mA sq cm and etch times of 1 to 9 min. A smaller range of ion beam parameters (2.0 KeV, 0.2 mA sq cm, 5 to 10 deg and 1 to 5 min.) were also investigated with ZrO2 films and found suitable for homogeneous alignment. Extinction ratios were very high (1000), twist angles were small ( or = 3 deg) and tilt-bias angles very small ( or = 1 deg). Preliminary scanning electron microscopy results indicate a parallel oriented surface structure on the ion beam etched surfaces which may determine alignment.

The NASA Ames Hypervelocity Free Flight Aerodynamic Facility: Experimental Simulation of the Atmospheric Break-Up of Meteors

NASA Technical Reports Server (NTRS)

Wilder, M. C.; Bogdanoff, D. W.

2015-01-01

The Hypervelocity Free Flight Aerodynamic Facility at NASA Ames Research Center provides a potential platform for the experimental simulation of meteor breakup at conditions that closely match full-scale entry condition for select parameters. The poster describes the entry environment simulation capabilities of the Hypervelocity Free Flight Aerodynamic Facility (HFFAF) at NASA Ames Research Center and provides example images of the fragmentation of a hypersonic projectile for which break-up was initiated by mechanical forces (impact with a thin polymer diaphragm).

Spectrophotometry of planetary atmosphere from the X-15 rocket airplane

NASA Technical Reports Server (NTRS)

Murcray, W. B.

1973-01-01

Nike-Apache and Nike-Tomahawk rocket flights using spectrophotometric techniques to investigate auroral activity are reported. The specific objectives were to obtain data relative to typical auroral situations, including quiet pre-breakup auroras, westward traveling surges, breakup auroras, and post-breakup auroras. It was found that excited atoms move considerable distances between excitation and emission owing to the high velocity wind conditions prevailing above 200 km. Based on the results of these observations, recommendations are made for future studies of ionized atmospheric activity at higher altitudes.

Study of breakup and transfer of weakly bound nucleus 6Li to explore the low energy reaction dynamics

NASA Astrophysics Data System (ADS)

Zhang, G. L.; Zhang, G. X.; Hu, S. P.; Zhang, H. Q.; Gomes, P. R. S.; Lubian, J.; Guo, C. L.; Wu, X. G.; Yang, J. C.; Zheng, Y.; Li, C. B.; He, C. Y.; Zhong, J.; Li, G. S.; Yao, Y. J.; Guo, M. F.; Sun, H. B.; Valiente-Dobòn, J. J.; Goasduff, A.; Siciliano, M.; Galtarosa, F.; Francesco, R.; Testov, D.; Mengoni, D.; Bazzacco, D.; John, P. R.; Qu, W. W.; Wang, F.; Zheng, L.; Yu, L.; Chen, Q. M.; Luo, P. W.; Li, H. W.; Wu, Y. H.; Zhou, W. K.; Zhu, B. J.; Li, E. T.; Hao, X.

2017-11-01

Investigation of the breakup and transfer effect of weakly bound nuclei on the fusion process has been an interesting research topic in the past several years. However, owing to the low intensities of the presently available radioactive ion beam (RIB), it is difficult to clearly explore the reaction mechanisms of nuclear systems with unstable nuclei. In comparison with RIB, the beam intensities of stable weakly bound nuclei such as 6,7Li and 9Be, which have significant breakup probability, are orders of magnitude higher. Precise fusion measurements have already been performed with those stable weakly bound nuclei, and the effect of breakup of those nuclei on the fusion process has been extensively studied. Those nuclei indicated large production cross sections for particles other than the α + x breakup. The particles are originated from non-capture breakup (NCBU), incomplete fusion (ICF) and transfer processes. However, the conclusion of reaction dynamics was not clear and has the contradiction. In our previous experiments we have performed 6Li+96Zr and 154Sm at HI-13 Tandem accelerator of China Institute of Atomic Energy (CIAE) by using HPGe array. It is shown that there is a small complete fusion (CF) suppression on medium-mass target nucleus 96Zr different from about 35% suppression on heavier target nucleus 154Sm at near-barrier energies. It seems that the CF suppression factor depends on the charge of target nuclei. We also observed one neutron transfer process. However, the experimental data are scarce for medium-mass target nuclei. In order to have a proper understanding of the influence of breakup and transfer of weakly bound projectiles on the fusion process, we performed the 6Li+89Y experiment with incident energies of 22 MeV and 34 MeV on Galileo array in cooperation with Si-ball EUCLIDES at Legnaro National Laboratory (LNL) in Italy. Using particle-particle and particle-γ coincidences, the different reaction mechanisms can be clearly explored.

Assessment of the consequences of the Fengyun-1C breakup in low Earth orbit

NASA Astrophysics Data System (ADS)

Pardini, Carmen

On 11 January 2007, the 880 kg (958 kg at launch) weather spacecraft Fengyun-1C, launched on 10 May 1999 into a sun-synchronous orbit with a CZ-4B booster from the Taiyuan Satellite Launch Center, was destroyed over central China as a result of the first successful Chinese anti-satellite weapon test. It was carried out with a direct ascent interception with a kinetic energy kill vehicle launched by an SC-19 missile, fired from a mobile ground platform close to the Xichang Satellite Launch Center. While the technical details of the test, probably the third attempt, and the characteristics of the weapon used remain shrouded in secrecy, the intentional breakup of the aging weather spacecraft, fully functional until 2005, produced a huge amount of debris in one of the orbital regimes already most affected by past fragmentation events. At present, the US Space Surveillance Network has identified about 2600 objects, typically larger than 10 cm, but the fragments larger than 1 cm may be more than 100,000. After two decades of substantial international progress in the field of orbital debris mitigation, in order to preserve the low Earth and geosynchronous environments for future space missions, the Fengyun-1C destruction represented a serious turnabout. In fact, it abruptly increased by approximately 20% the number of cataloged debris in orbit. To give a rough idea of the impact of this single event on the circumterrestrial environment, it is sufficient to realize that about 15 years of global space activity - including failures and accidental breakups - had been needed to increase, by a comparable amount, the number of cataloged debris in orbit to the level observed before the Chinese anti-satellite test. The purpose of this presentation is to assess the impact of the debris cloud generated by the Fengyun-1C breakup on the low Earth environment. The anti-satellite test was carried out at an altitude of about 863 km, spreading the cataloged fragments between 200 and 4000 km, with maximum concentration around the breakup height. The environmental impact was particularly significant in all the altitude range between 700 and 1000 km, where the debris density due to past space activities was already at worrisome levels. Considering the inclination, nearly polar, and the height of the target, such a deliberate act of debris generation was therefore one of worst conceivable with current technology and its consequences will unfortunately be felt for many decades.

Energy level alignment at molecule-metal interfaces from an optimally tuned range-separated hybrid functional

DOE PAGES

Liu, Zhen-Fei; Egger, David A.; Refaely-Abramson, Sivan; ...

2017-02-21

The alignment of the frontier orbital energies of an adsorbed molecule with the substrate Fermi level at metal-organic interfaces is a fundamental observable of significant practical importance in nanoscience and beyond. Typical density functional theory calculations, especially those using local and semi-local functionals, often underestimate level alignment leading to inaccurate electronic structure and charge transport properties. Here, we develop a new fully self-consistent predictive scheme to accurately compute level alignment at certain classes of complex heterogeneous molecule-metal interfaces based on optimally tuned range-separated hybrid functionals. Starting from a highly accurate description of the gas-phase electronic structure, our method by constructionmore » captures important nonlocal surface polarization effects via tuning of the long-range screened exchange in a range-separated hybrid in a non-empirical and system-specific manner. We implement this functional in a plane-wave code and apply it to several physisorbed and chemisorbed molecule-metal interface systems. Our results are in quantitative agreement with experiments, the both the level alignment and work function changes. This approach constitutes a new practical scheme for accurate and efficient calculations of the electronic structure of molecule-metal interfaces.« less

Energy level alignment at molecule-metal interfaces from an optimally tuned range-separated hybrid functional

NASA Astrophysics Data System (ADS)

Liu, Zhen-Fei; Egger, David A.; Refaely-Abramson, Sivan; Kronik, Leeor; Neaton, Jeffrey B.

2017-03-01

The alignment of the frontier orbital energies of an adsorbed molecule with the substrate Fermi level at metal-organic interfaces is a fundamental observable of significant practical importance in nanoscience and beyond. Typical density functional theory calculations, especially those using local and semi-local functionals, often underestimate level alignment leading to inaccurate electronic structure and charge transport properties. In this work, we develop a new fully self-consistent predictive scheme to accurately compute level alignment at certain classes of complex heterogeneous molecule-metal interfaces based on optimally tuned range-separated hybrid functionals. Starting from a highly accurate description of the gas-phase electronic structure, our method by construction captures important nonlocal surface polarization effects via tuning of the long-range screened exchange in a range-separated hybrid in a non-empirical and system-specific manner. We implement this functional in a plane-wave code and apply it to several physisorbed and chemisorbed molecule-metal interface systems. Our results are in quantitative agreement with experiments, the both the level alignment and work function changes. Our approach constitutes a new practical scheme for accurate and efficient calculations of the electronic structure of molecule-metal interfaces.

Wave drag reduction with a self-aligning aerodisk on a missile configuration

NASA Astrophysics Data System (ADS)

Schnepf, C.; Wysocki, O.; Schülein, E.

2017-06-01

A self-aligning aerodisk to reduce the wave drag on a pitching missile is numerically investigated. The motion and the Mach number were chosen to match a maneuver flight of an actual missile: pitching frequency f = 7.5 Hz, Mach number M = 2.2, and range of angle of attack 0° < < 21° . The self-alignment was realized with a coupling of the §ow solver with a 6DoF (6 degrees of freedom) tool. In the entire range of angle of attack, the drag could be reduced with the self-aligning aerodisk. A comparison with experimental data showed in parts a quite good agreement in the aerodynamic coe©cients, in the shock structure, and in the alignment of the aerodisk.

Break-ups Before Marriage: The End of 103 Affairs

ERIC Educational Resources Information Center

Hill, Charles T.; And Others

1976-01-01

Factors that predicted breakups before marriage, investigated as part of a two-year study of dating relationships among college students include unequal involvement in the relationship and discrepant age, educational aspirations, intelligence, and physical attractiveness. (Author/AM)

Anomalous Lower Crustal and Surface Features as a Result of Plume-induced Continental Break-up: Inferences from Numerical Models

NASA Astrophysics Data System (ADS)

Beniest, A.; Koptev, A.; Leroy, S. D.

2016-12-01

Anomalous features along the South American and African rifted margins at depth and at the surface have been recognised with gravity and magnetic modelling. They include high velocity/high density bodies at lower crustal level and topography variations that are usually interpreted as aborted rifts. We present fully-coupled lithosphere-scale numerical models that permit us to explain both features in a relatively simple framework of an interaction between rheologically stratified continental lithosphere and an active mantle plume. We used 2D and 3D numerical models to investigate the impact of thermo-rheological structure of the continental lithosphere and initial plume position on continental rifting and breakup processes. Based on the results of our 2D experiments, three main types of continental break-up are revealed: A) mantle plume-induced break-up, directly located above the centre of the mantle anomaly, B) mantle plume-induced break-up, 50 to 250 km displaced from the initial plume location and C) self-induced break-up due to convection and/or slab-subduction/delamination, considerably shifted (300 to 800 km) from the initial plume position. With our 3D, laterally homogenous initial setup, we show that a complex system, with the axis of continental break-up 100's of km's shifted from the original plume location, can arise spontaneously from simple and perfectly symmetric preliminary settings. Our modelling demonstrates that fragments of a laterally migrating plume head become glued to the base of the lithosphere and remain at both sides of the newly-formed oceanic basin after continental break-up. Underplated plume material soldered into lower parts of lithosphere can be interpreted as the high-velocity/high density magmatic bodies at lower crustal levels. In the very early stages of rifting, first impingement of the vertically upwelled mantle plume to the lithospheric base leads to surface topographic variations. Given the shifted position of the final spreading centre with respect to initial plume position, these topographic variations resemble aborted rifts that are observed on passive margins. Lastly, after continuous extension and transition to the spreading state, strain rate relocalizations develop that can be interpreted as ridge jumps that are commonly observed in nature.

Sharing Remote and Local Information for Tracking Spring Breakup in the Mackenzie Delta and Beaufort Sea

NASA Astrophysics Data System (ADS)

Forbes, D. L.; Whalen, D.; Fraser, P.

2015-12-01

The Mackenzie Delta is the second largest on the Arctic Ocean, covering 13 000 km2. The annual flood regime in the delta is dominated by the spring snowmelt freshet and associated ice breakup, as water from the south arrives in the ice-covered delta and spreads over bottomfast and adjacent floating sea ice at the delta front. The complex processes of water-ice interaction, flow partitioning, and overbank flooding to replenish waters in 43 000 delta lakes threaten community, transportation, subsistence, and energy infrastructure in the delta. The annual breakup season is a time of rejuvenation, excitement, and anxiety for delta residents and stakeholders. To track the progress of breakup and meet the need for knowledge dissemination to the local communities, a Mackenzie-Beaufort breakup newsletter has been produced by Natural Resources Canada on a quasi-daily basis during the May-June spring flood season for 10 years, and distributed to an e-mail list that grew to over 300 subscribers. This provides near real-time tracking of water levels and breakup using on-line gauges (Environment Canada), daily MODIS satellite imagery (NASA), Landsat imagery (USGS) and intermittent radar imagery (various sources). In earlier years, information was also supplied from field programs operating in the delta during breakup, but changing priorities and funding have reduced the number of outside researchers present during these critical weeks. Meanwhile the number of local contributors has grown, providing observations and photographs to share with the local, regional and global readership. In this way the newsletter evolved into a two-way communication tool and community portal. The newsletter is a chronicle of each breakup season and a key resource for territorial and municipal managers, subsistence organizations, and emergency response agencies, with routine requests for specific imagery in areas of concern. With the completion of 10 years under the present model, we are exploring alternative approaches to enable more direct involvement in the region. The new model will be supported by the Circumpolar Coastal Communities Observatory Network (CACCON), Future Earth Coasts, and ArcticNet, and co-designed and co-managed with regional users to share timely information on the transformative event of each spring season in the delta.

Cluster Observations of Multiple Dipolarization Fronts

NASA Technical Reports Server (NTRS)

Hwang, Kyoung-Joo; Goldstein, Melvyn L.; Lee, Ensang; Pickett, Jolene S.

2011-01-01

We present Cluster observations of a series of dipolarization fronts (DF 1 to 6) at the central current sheet in Earth's magnetotail. The velocities of fast earthward flow following behind each DF 1-3, are comparable to the Alfven velocity, indicating that the flow bursts might have been generated by bursty reconnection that occurred tailward of the spacecraft. Based on multi-spacecraft timing analysis, DF normals are found to propagate mainly earthward at $160-335$ km/s with a thickness of 900-1500 km, which corresponds to the ion inertial length or gyroradius scale. Each DF is followed by significant fluctuations in the $x$ and $y$ components of the magnetic field whose peaks are found 1-2 minutes after the DF passage. These $(B_{x},B_{y} )$-fluctuations propagate dawnward (mainly) and earthward. Strongly enhanced field-aligned beams are observed coincidently with $(B_{x},B_{y})$ fluctuations, while an enhancement of cross-tail currents is associated with the DFs. From the observed pressure imbalance and flux-tube entropy changes between the two regions separated by the DF, we speculate that interchange instability destabilizes the DFs and causes the deformation of the mid-tail magnetic topology. This process generates significant field-aligned currents, and might power the auroral brightening in the ionosphere. However, this event is neither associated with the main substorm auroral breakup nor the poleward expansion, which might indicate that the observed multiple DFs have been dissipated before they reach the inner plasma sheet boundary.

Cluster Observations of Multiple Dipolarization Fronts

NASA Technical Reports Server (NTRS)

Hwang, K.-J.; Goldstein, M. L.; Lee, E.; Pickett, J. S.

2011-01-01

We present Cluster observations of a series of dipolarization fronts (DF 1 to 6) at the central current sheet in Earth's magnetotail. The velocities of fast earthward flow following behind each DF 1.3 are comparable to the Alfven velocity, indicating that the flow bursts might have been generated by bursty reconnection that occurred tailward of the spacecraft. Based on multispacecraft timing analysis, DF normals are found to propagate mainly earthward at 160.335 km/s with a thickness of 900-1500 km, which corresponds to the ion inertial length or gyroradius scale. Each DF is followed by significant fluctuations in the x and y components of the magnetic field whose peaks are found 1.2 min after the DF passage. These (B(sub x), B(sub y)) fluctuations propagate dawnward (mainly) and earthward. Strongly enhanced field-aligned beams are observed coincidently with (B(sub x), B(sub y)) fluctuations, while an enhancement of cross-tail currents is associated with the DFs. From the observed pressure imbalance and flux tube entropy changes between the two regions separated by the DF, we speculate that interchange instability destabilizes the DFs and causes the deformation of the midtail magnetic topology. This process generates significant field-aligned currents and might power the auroral brightening in the ionosphere. However, this event is associated with neither the main substorm auroral breakup nor the poleward expansion, which might indicate that the observed multiple DFs have been dissipated before they reach the inner plasma sheet boundary.

Breakup fusion theory of nuclear reactions

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

Mastroleo, R.C.

1987-01-01

Continuum spectra of particles emitted in incomplete fusion reactions are one of the major interests in current nuclear reaction studies. Based on an idea of the so-called breakup fusion (BF) reaction, several authors derived closed formulas for the singles cross section of the particles that are emitted. There have been presented, however, two conflicting cross section formulas for the same BF reaction. For convenience, we shall call one of them the IAV (Ichimura, Austern and Vincent) and the other UT (Udagawa and Tamura) cross section formulas. In this work, the formulation of the UT cross section formula (prior-form) is presented,more » and the post-form version of the IAV cross section formula is evaluted for a few {alpha}- and d-induced reactions based on the exact finite range method. It is shown that the values thus calculated are larger by an order of magnitude as compared with the experimental cross sections for the {alpha}-induced reactions, while they are comparable with the experimental cross sections for the d-induced reactions. A possible origin of why such a large cross section is resulted in the case of {alpha}-induced reactions is also discussed. Polarization of the residual compound nucleus produced in breakup fusion reactions are calculated and compared with experiments. It is shown that the polarization is rather sensitive to the deflection angles of the strongly absortive partial waves and to obtain a good fit with the experimental data a l-dependent potential in the incident channel is needed in order to stress the lower partial waves.« less

Drop-on-demand drop formation of polyethylene oxide solutions

NASA Astrophysics Data System (ADS)

Yan, Xuejia; Carr, Wallace W.; Dong, Hongming

2011-10-01

The dynamics of drop-on-demand (DOD) drop formation for solutions containing polyethylene oxide (PEO) have been studied experimentally. Using a piezoelectrical actuated inkjet printhead with the nozzle orifice diameter of 53 μm, experiments were conducted for a series of PEO aqueous solutions with molecular weights ranging from 14 to 1000 kg/mol, polydispersity from 1.02 to 2.5, and concentrations from 0.005 to 10 wt. %. The addition of a small amount of PEO can have a significant effect on the DOD drop formation process, increasing breakup time, decreasing primary drop speed, and decreasing the number of satellite drops in some cases. The effects depend on both molecular weight and concentration. At lower molecular weights (14 and 35 kg/mol), the effect of PEO over the dilute solution regime is insignificant even at concentrations large enough that the solution does not fall in the dilute regime. As PEO molecular weight increased, the effects became significant. For monodispersed PEO solutions, breakup time and primary drop speed closely correlated with effective relaxation time but not for polydispersed PEO. Effective relaxation time depended greatly on molecular weight distribution. Viscosity-average molecular weight, used in calculating effective relaxation time for polydispersed PEO solutions, did not adequately account for high molecular fractions in the molecular weight distribution of the polydispersed PEOs. A mixture rule was developed to calculate the effective relaxation times for aqueous solutions containing mixtures of monodispersed PEO, and breakup times and primary drop speeds correlated well with effective relaxation times. For our experiments, DOD drop formation was limited to Deborah number ≲ 23.

Experimental investigation of 150-KG-scale corium melt jet quenching in water

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

Magallon, D.; Hohmann, H.

This paper compares and discusses the results of two large scale FARO quenching tests known as L-11 and L-14, which involved, respectively, 151 kg of W% 76.7 UO{sub 2} + 19.2 ZrO{sub 2} + 4.1 Zr and 125 kg of W% 80 UO{sub 2} + 20 ZrO{sub 2} melts poured into 600-kg, 2-m-depth water at saturation at 5.0 MPa. The results are further compared with those of two previous tests performed using a pure oxidic melt, respectively 18 and 44 kg of W% 80 UO{sub 2} + 20 ZrO{sub 2} melt quenched in 1-m-depth water at saturation at 5.0 MPa.more » In all the tests, significant breakup and quenching took place during the melt fall through the water. No steam explosion occurred. In the tests performed with a pure oxide UO{sub 2}-ZrO{sub 2} melt, part of the corium (from 1/6 to 1/3) did not breakup and reached the bottom plate still molten whatever the water depth was. Test L-11 data suggest that full oxidation and complete breakup of the melt occurred during the melt fall through the water. A proportion of 64% of the total energy content of the melt was released to the water during this phase ({approximately}1.5 s), against 44% for L-14. The maximum temperature increase of the bottom plate was 330 K (L-14). The mean particle size of the debris ranged between 2.5 and 4.8mm.« less

Role of breakup and direct processes in deuteron-induced reactions at low energies

NASA Astrophysics Data System (ADS)

Avrigeanu, M.; Avrigeanu, V.

2015-08-01

Background: Recent studies of deuteron-induced reactions around the Coulomb barrier B pointed out that numerical calculations for deuteron-induced reactions are beyond current capabilities. The statistical model of nuclear reactions was used in this respect since the compound-nucleus (CN) mechanism was considered to be responsible for most of the total-reaction cross section σR in this energy range. However, specific noncompound processes such as the breakup (BU) and direct reactions (DR) should be also considered for the deuteron-induced reactions, making them different from reactions with other incident particles. Purpose: The unitary and consistent BU and DR consideration in deuteron-induced reactions is proved to yield results at variance with the assumption of negligible noncompound components. Method: The CN fractions of σR obtained by analysis of measured neutron angular distributions in deuteron-induced reactions on 27Al, 56Fe, 63,63Cu, and 89Y target nuclei, around B , are compared with the results of an unitary analysis of every reaction mechanism. The latter values have been supported by the previously established agreement with all available deuteron data for 27Al 54,56,-58,natCu, 63,65,natCu and 93Nb. Results: There is a significant difference between the larger CN contributions obtained from measured neutron angular distributions and calculated results of an unitary analysis of every deuteron-interaction mechanism. The decrease of the latter values is mainly due to the BU component. Conclusions: The above-mentioned differences underline the key role of the breakup and direct reactions that should be considered explicitly in the case of deuteron-induced reactions.

Identification of a Debris Cloud from the Nuclear Powered SNAPSHOT Satellite with Haystack Radar Measurements

NASA Technical Reports Server (NTRS)

Stokely, C.; Stansbery, E.

2006-01-01

Data from the MIT Lincoln Laboratory (MIT/LL) Long Range Imaging Radar (known as the Haystack radar) have been used in the past to examine families of objects from individual satellite breakups or families of orbiting objects that can be isolated in altitude and inclination. This is possible because for some time after a breakup, the debris cloud of particles can remain grouped together in similar orbit planes. This cloud will be visible to the radar, in fixed staring mode, for a short time twice each day, as the orbit plane moves through the field of view. There should be a unique three-dimensional pattern in observation time, range, and range rate which can identify the cloud. Eventually, through slightly differing precession rates of the right ascension of ascending node of the debris cloud, the observation time becomes distributed so that event identification becomes much more difficult. Analyses of the patterns in observation time, range, and range rate have identified good debris candidates released from the polar orbiting SNAPSHOT satellite (International Identifier: 1965-027A). For orbits near 90o inclination, there is essentially no precession of the orbit plane. The SNAPSHOT satellite is a well known nuclear powered satellite launched in 1965 to a near circular 1300 km orbit with an inclination of 90.3o. This satellite began releasing debris in 1979 with new pieces being discovered and cataloged over the years. 51 objects are still being tracked by the United States Space Surveillance Network. An analysis of the Haystack data has identified at least 60 pieces of debris separate from the 51 known tracked debris pieces, where all but 2 of the 60 pieces have a size less than 10cm. The altitude and inclination (derived from range-rate with a circular orbit assumption) are consistent with the SNAPSHOT satellite and its tracked debris cloud.

Material Density Distribution of Small Debris in Earth Orbit

NASA Technical Reports Server (NTRS)

Krisko, P. H.; Xu, Y.-l.; Opiela, J. N.; Hill, N. M.; Matney, M. J.

2008-01-01

Over 200 spacecraft and rocket body breakups in Earth orbit have populated that regime with debris fragments in the sub-micron through meter size range. Though the largest debris fragments can cause significant collisional damage to active (operational) spacecraft, these are few and trackable by radar. Fragments on the order of a millimeter to a centimeter in size are as yet untrackable. But this smaller debris can result in damage to critical spacecraft systems and, under the worst conditions, fragmenting collision events. Ongoing research at the NASA Orbital Debris Program Office on the sources of these small fragments has focused on the material components of spacecraft and rocket bodies and on breakup event morphology. This has led to fragment material density estimates, and also the beginnings of shape categorizations. To date the NASA Standard Breakup Model has not considered specific material density distinctions of small debris. The basis of small debris in that model is the fourth hypervelocity impact event of the Satellite Orbital Debris Characterization Impact Test (SOCIT) series. This test targeted a flight-ready, U.S. Transit navigation satellite with a solid aluminum sphere impactor. Results in this event yield characteristic length (size) and area-to-mass distributions of fragments smaller than 10 cm in the NASA model. Recent re-analysis of the SOCIT4 small fragment dataset highlighted the material-specific characteristics of metals and non-metals. Concurrent analysis of Space Shuttle in-situ impact data showed a high percentage of aluminum debris in shuttle orbit regions. Both analyses led to the definition of three main on-orbit debris material density categories -low density (< 2 g/cc), medium density (2 to 6 g/cc), and high density (> 6 g/cc). This report considers the above studies in an explicit extension of the NASA Standard Breakup Model where separate material densities for debris are generated and these debris fragments are propagated in Earth orbit. The near Earth environment is thus parameterized by debris density percentages within subsections of that environment. This model version is used in the upgraded NASA Orbital Debris Engineering Model (ORDEM).

A four-body model for the breakup of Borromean nucleus 22C

NASA Astrophysics Data System (ADS)

Miyamoto, Tomokazu

A Borromean system is a bound 3-body system where no 2-body subsystems are bound. In nuclear physics, a nucleus that can be modelled as a Borromean system is called a Borromean nucleus; 6 He and 11 Li are good examples of this. Recent research suggests that this Borromean nature should also be exhibited by 22 C, the heaviest-known carbon isotope. In this PhD thesis, a schematic approach is taken to study reactions involving Borromean nuclei. Hyperspherical formalism (HH) and coordinate space Faddeev (CSF) method are used for creating their 3-body bound state wave functions. We formulate the reactions of a Borromean nucleus with a stable target at incident energies ranging from tens of (MeV) to a few hundred (MeV); we adopt a 4-body reaction model to deepen our understanding of the reaction mechanism involving Borromean nuclei. The Glauber-WKB framework is used to describe these reactions, which is well-suited for these incident energies. Introducing Watson-Migdal final state interaction, we calculate the E1 strengths for Borromean nuclei so as to elucidate their breakup mechanism and we explore the possibility of the existence of a soft dipole mode. We also calculate the differential breakup cross sections to see how the post-collision interaction can have an impact on the cross sections. As far as 22 C is concerned, it is found that the reactions are mainly focused on the forward angle region, and the contributions from the higher order terms are not significant. This implies that the non-eikonal trajectories do not play a crucial role in the reaction mechanism. Also, both E1 distributions and breakup cross sections seem to sensitive to the 2n-separation energies of the bound state wave functions, but the E1 distributions and the cross sections to 1- continuum state seem not to be sensitive to the FSIs; cross sections to 0+ and 2+ continuum states seem to be sensitive to the FSIs. Our findings does not support the view that, if an soft dipole mode exists, it is induced by the FSIs.

Effects of earlier sea ice breakup on survival and population size of polar bears in western Hudson Bay

USGS Publications Warehouse

Regehr, E.V.; Lunn, N.J.; Amstrup, Steven C.; Stirling, I.

2007-01-01

Some of the most pronounced ecological responses to climatic warming are expected to occur in polar marine regions, where temperature increases have been the greatest and sea ice provides a sensitive mechanism by which climatic conditions affect sympagic (i.e., with ice) species. Population-level effects of climatic change, however, remain difficult to quantify. We used a flexible extension of Cormack-Jolly-Seber capture-recapture models to estimate population size and survival for polar bears (Ursus maritimus), one of the most ice-dependent of Arctic marine mammals. We analyzed data for polar bears captured from 1984 to 2004 along the western coast of Hudson Bay and in the community of Churchill, Manitoba, Canada. The Western Hudson Bay polar bear population declined from 1,194 (95% CI = 1,020-1,368) in 1987 to 935 (95% CI = 794-1,076) in 2004. Total apparent survival of prime-adult polar bears (5-19 yr) was stable for females (0.93; 95% CI = 0.91-0.94) and males (0.90; 95% CI = 0.88-0.91). Survival of juvenile, subadult, and senescent-adult polar bears was correlated with spring sea ice breakup date, which was variable among years and occurred approximately 3 weeks earlier in 2004 than in 1984. We propose that this correlation provides evidence for a causal association between earlier sea ice breakup (due to climatic warming) and decreased polar bear survival. It may also explain why Churchill, like other communities along the western coast of Hudson Bay, has experienced an increase in human-polar bear interactions in recent years. Earlier sea ice breakup may have resulted in a larger number of nutritionally stressed polar bears, which are encroaching on human habitations in search of supplemental food. Because western Hudson Bay is near the southern limit of the species' range, our findings may foreshadow the demographic responses and management challenges that more northerly polar bear populations will experience if climatic warming in the Arctic continues as projected.

Vortex motion in axisymmetric piston-cylinder configurations

NASA Technical Reports Server (NTRS)

Shih, T. I. P.; Smith, G. E.; Springer, G. S.

1982-01-01

By using the Beam and Warming implicit-factored method of solution of the Navier-Stokes equations, velocities were calculated inside axisymmetric piston cylinder configurations during the intake and compression strokes. Results are presented in graphical form which show the formation, growth and breakup of those vortices which form during the intake stroke by the jet issuing from the valve. It is shown that at bore-to-stroke ratio of less than unity, the vortices may breakup during the intake stroke. It is also shown that vortices which do not breakup during the intake stroke coalesce during the compression stroke.

Deformation pathways and breakup modes in acoustically levitated bicomponent droplets under external heating

NASA Astrophysics Data System (ADS)

Pathak, Binita; Basu, Saptarshi

2016-03-01

Controlled breakup of droplets using heat or acoustics is pivotal in applications such as pharmaceutics, nanoparticle production, and combustion. In the current work we have identified distinct thermal acoustics-induced deformation regimes (ligaments and bubbles) and breakup dynamics in externally heated acoustically levitated bicomponent (benzene-dodecane) droplets with a wide variation in volatility of the two components (benzene is significantly more volatile than dodecane). We showcase the physical mechanism and universal behavior of droplet surface caving in leading to the inception and growth of ligaments. The caving of the top surface is governed by a balance between the acoustic pressure field and the restrictive surface tension of the droplet. The universal collapse of caving profiles for different benzene concentration (<70 % by volume) is shown by using an appropriate time scale obtained from force balance. Continuous caving leads to the formation of a liquid membrane-type structure which undergoes radial extension due to inertia gained during the precursor phase. The membrane subsequently closes at the rim and the kinetic energy leads to ligament formation and growth. Subsequent ligament breakup is primarily Rayleigh-Plateau type. The breakup mode shifts to diffusional entrapment-induced boiling with an increase in concentration of the volatile component (benzene >70 % by volume). The findings are portable to any similar bicomponent systems with differential volatility.

An Analysis of Recent Major Breakups in he Low Earth Orbit Region

NASA Technical Reports Server (NTRS)

Liou, Jer-Chyi; Anz-Meador, P. D.

2010-01-01

Of the 190 known satellite breakups between 1961 and 2006, only one generated more than 500 cataloged fragments. The event was the explosion of the Pegasus Hydrazine Auxiliary Propulsion System in 1996, adding 713 fragments to the U.S. Satellite Catalog. Since the beginning of 2007; however, the near-Earth environment has been subjected to several major breakups, including the Fengyun-1C anti-satellite test and the explosion of Briz-M in 2007, the unusual breakup of Cosmos 2421 in 2008, and the collision between Iridium 33 and Cosmos 2251 in 2009. Combined, these events added more than 5000 large (> or equal 10 cm) fragments to the environment. Detailed analysis of the radar cross section measurements and orbit histories of the fragments from these major events reveals several unusual characteristics in their size and area-to-mass ratio distributions. The characteristics could be related to the material composition of the parent vehicles, the nature of the breakup, and the composition and physical property of the fragments. In addition, the majority of these fragments are expected to remain in orbit for at least decades. Their long-term impact to the environment is analyzed using the NASA orbital debris evolutionary model, LEGEND. Descriptions of these analyses and a summary are included in this paper.

Separable Ernst-Shakin-Thaler expansions of local potentials

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

Bund, G.W.

The boundary condition Ernst-Shakin-Thaler method, introduced previously to generate separable expansions of local potentials of finite range, is applied to the study of the triplet s-wave Malfliet-Tjon potential. The effect of varying the radius where the boundary condition is applied on the T matrix is analyzed. Further, we compare the convergence of the n-d scattering cross sections in the quartet state below the breakup threshold for expansions corresponding to two different boundaries.

Structural alignment sensor. [laser applications and interferometry

NASA Technical Reports Server (NTRS)

Davis, L.; Buholz, N. E.; Gillard, C. W.; Huang, C. C.; Wells, W. M., III

1978-01-01

Comparative Michelson interferometers are discussed as well as the operating range potential of a structural alignment sensor (SAS) which requires only one laser mode. Schematics are presented for the distance measurement logic, the basic SAS system, the SAS optical layout, the coarse measurement signal processor, and the measured range resolution.

Pair aligning improved motility of Quincke rollers.

PubMed

Lu, Shi Qing; Zhang, Bing Yue; Zhang, Zhi Chao; Shi, Yan; Zhang, Tian Hui

2018-06-06

Density-dependent speed is studied in a two-dimensional active colloid in which the colloidal particles are propelled by an external electric field via a Quincke rotation. Above the critcal electric field, dense dynamic clusters form spotaneously, in which the particles are highly aligned in velocity and move much faster than isolated units. Detailed observations on pair collision reveal that the alignment of velocity is induced by the long-ranged hydrodynamic interactions and the improvement of speed in the clusters arises from pair aligning in which two particles are closely paired and rotate synchronically. In the aligning state, the short-range in-plane dipole-dipole attraction enhances the rotation torque and gives rises to a larger rolling speed. The pair aligning becomes difficult and unstable at high electric field where the normal dipole-dipole repulsion becomes dominant. As a consequence, the dependence of speed on density becomes weak increasingly upon the increase of the electric field. This result offers an interpretation for the discrepancy between our and previous observations on Quincke rollers.

Probing the remarkable thermal kinetics of visual rhodopsin with E181Q and S186A mutants

NASA Astrophysics Data System (ADS)

Guo, Ying; Hendrickson, Heidi P.; Videla, Pablo E.; Chen, Ya-Na; Ho, Junming; Sekharan, Sivakumar; Batista, Victor S.; Tully, John C.; Yan, Elsa C. Y.

2017-06-01

We recently reported a very unusual temperature dependence of the rate of thermal reaction of wild type bovine rhodopsin: the Arrhenius plot exhibits a sharp "elbow" at 47 °C and, in the upper temperature range, an unexpectedly large activation energy (114 ± 8 kcal/mol) and an enormous prefactor (1072±5 s-1). In this report, we present new measurements and a theoretical model that establish convincingly that this behavior results from a collective, entropy-driven breakup of the rigid hydrogen bonding networks (HBNs) that hinder the reaction at lower temperatures. For E181Q and S186A, two rhodopsin mutants that disrupt the HBNs near the binding pocket of the 11-cis retinyl chromophore, we observe significant decreases in the activation energy (˜90 kcal/mol) and prefactor (˜1060 s-1), consistent with the conclusion that the reaction rate is enhanced by breakup of the HBN. The results provide insights into the molecular mechanism of dim-light vision and eye diseases caused by inherited mutations in the rhodopsin gene that perturb the HBNs.

Effect of Elasticity on Stability of Viscoelastic Liquid Curtain

NASA Astrophysics Data System (ADS)

Mohammad Karim, Alireza; Suszynski, Wieslaw; Francis, Lorraine; Carvalho, Marcio; University of Minnesota, Twin Cities Collaboration; Pontifícia Universidade Católica do Rio de Janeiro Collaboration; Dow Chemical Company Collaboration

2016-11-01

Curtain coating is one the preferred methods for high-speed precision application of single-layer and multi-layer coatings in industry. Despite the extensive variety of applications of curtain coating, its operation is challenging and uniform coating is only obtained in a certain range of operating parameters, called the coating window. The two main physical mechanisms that limit curtain coating are the breakup of the liquid curtain, below a critical flow rate, and the catastrophic event of air entrainment, which occurs above a certain web speed. The rheological characteristics of the coating liquid play an important role on these mechanisms, but the fundamental understanding of the role of rheology is still not complete. In this work, we analyze the relative importance of shear and extensional viscosity on both curtain breakup and dynamic contact line instability (i.e. air entrainment). Aqueous solutions of polyethylene oxide (PEO) and polyethylene glycol (PEG) of different molecular weights were used as model liquids to obtain fluids with different levels of extensional thickening behavior. We would like to acknowledge the financial support from the Dow Chemical Company.

Visualization of sneeze ejecta: steps of fluid fragmentation leading to respiratory droplets

NASA Astrophysics Data System (ADS)

Scharfman, B. E.; Techet, A. H.; Bush, J. W. M.; Bourouiba, L.

2016-02-01

Coughs and sneezes feature turbulent, multiphase flows that may contain pathogen-bearing droplets of mucosalivary fluid. As such, they can contribute to the spread of numerous infectious diseases, including influenza and SARS. The range of contamination of the droplets is largely determined by their size. However, major uncertainties on the drop size distributions persist. Here, we report direct observation of the physical mechanisms of droplet formation at the exit of the mouth during sneezing. Specifically, we use high-speed imaging to directly examine the fluid fragmentation at the exit of the mouths of healthy subjects. We reveal for the first time that the breakup of the fluid into droplets continues to occur outside of the respiratory tract during violent exhalations. We show that such breakup involves a complex cascade of events from sheets, to bag bursts, to ligaments, which finally break into droplets. Finally, we reveal that the viscoelasticity of the mucosalivary fluid plays an important role in delaying fragmentation by causing the merger of the droplet precursors that form along stretched filaments; thereby affecting the final drop size distribution farther downstream.

DebriSat - A Planned Laboratory-Based Satellite Impact Experiment for Breakup Fragment Characterization

NASA Technical Reports Server (NTRS)

Liou, J.-C.; Fitz-Coy, N.; Werremeyer, M.; Huynh, T.; Voelker, M.; Opiela, J.

2012-01-01

DebriSat is a planned laboratory ]based satellite hypervelocity impact experiment. The goal of the project is to characterize the orbital debris that would be generated by a hypervelocity collision involving a modern satellite in low Earth orbit (LEO). The DebriSat project will update and expand upon the information obtained in the 1992 Satellite Orbital Debris Characterization Impact Test (SOCIT), which characterized the breakup of a 1960 's US Navy Transit satellite. There are three phases to this project: the design and fabrication of an engineering model representing a modern, 50-cm/50-kg class LEO satellite known as DebriSat; conduction of a laboratory-based hypervelocity impact to catastrophically break up the satellite; and characterization of the properties of breakup fragments down to 2 mm in size. The data obtained, including fragment size, area ]to ]mass ratio, density, shape, material composition, optical properties, and radar cross ]section distributions, will be used to supplement the DoD fs and NASA fs satellite breakup models to better describe the breakup outcome of a modern satellite. Updated breakup models will improve mission planning, environmental models, and event response. The DebriSat project is sponsored by the Air Force fs Space and Missile Systems Center and the NASA Orbital Debris Program Office. The design and fabrication of DebriSat is led by University of Florida with subject matter experts f support from The Aerospace Corporation. The major milestones of the project include the complete fabrication of DebriSat by September 2013, the hypervelocity impact of DebriSat at the Air Force fs Arnold Engineering Development Complex in early 2014, and fragment characterization and data analyses in late 2014.

Nanofiber alignment of a small diameter elastic electrospun scaffold

NASA Astrophysics Data System (ADS)

Patel, Jignesh

Cardiovascular disease is the leading cause of death in western countries with coronary heart disease making up 50% of these deaths. As a treatment option, tissue engineered grafts have great potential. Elastic scaffolds that mimic arterial extracellular matrix (ECM) may hold the key to creating viable vascular grafts. Electrospinning is a widely used scaffold fabrication technique to engineer tubular scaffolds. In this study, we investigated how the collector rotation speed altered the nanofiber alignment which may improve mechanical characteristics making the scaffold more suitable for arterial grafts. The scaffold was fabricated from a blend of PCL/Elastin. 2D Fast Fourier Transform (FFT) image processing tool and MatLab were used to quantitatively analyze nanofiber orientation at different collector speeds (13500 to 15500 rpm). Both Image J and MatLab showed graphical peaks indicating predominant fiber orientation angles. A collector speed of 15000 rpm was found to produce the best nanofiber alignment with narrow peaks at 90 and 270 degrees, and a relative amplitude of 200. This indicates a narrow distribution of circumferentially aligned nanofibers. Collector speeds below and above 15000 rpm caused a decrease in fiber alignment with a broader orientation distribution. Uniformity of fiber diameter was also measured. Of 600 measures from the 15000 rpm scaffolds, the fiber diameter range from 500 nm to 899 nm was most prevalent. This diameter range was slightly larger than native ECM which ranges from 50 nm to 500 nm. The second most prevalent diameter range had an average of 404 nm which is within the diameter range of collagen. This study concluded that with proper electrospinning technique and collector speed, it is possible to fabricate highly aligned small diameter elastic scaffolds. Image J 2D FFT results confirmed MatLab findings for the analyses of circumferentially aligned nanofibers. In addition, MatLab analyses simplified the FFT orientation data providing an accurate, user friendly orientation measurement tool.

Explicit demonstration of the role of Marangoni effect in the breakup of nanoscale liquid filaments

NASA Astrophysics Data System (ADS)

Seric, Ivana; Mahady, Kyle; Afkhami, Shahriar; Hartnett, Chris; Fowlkes, Jason; Rack, Philip; Kondic, Lou

2016-11-01

We consider a breakup of bi-metal filaments deposited on a solid substrate. These filaments are exposed to laser irradiation and, while in the liquid phase, evolve by a process resembling breakup of a liquid jet governed by the Rayleigh-Plateau instability. The novel element is that the Marangoni effect, resulting from a different surface tension of the two metals from which the filament is built, is crucial in understanding the instability development. In particular, Marangoni effect may lead to the inversion of the breakup process, producing droplets at the locations where according to the Rayleigh-Plateau theory dry spots would be expected. We present experimental results carried out with Cu-Ni filaments, as well as direct numerical simulations based on a novel algorithm that includes variable surface tension in a Volume-of-Fluid based Navier-Stokes solver. These results suggest the possibility of using Marangoni effect for the purpose of self- and directed-assembly on the nanoscale. Supported by the NSF Grant No. CBET-1604351.

Breakup-related appraisals and the psychological well-being of young adult gay and bisexual men.

PubMed

Ceglarek, Peter; Darbes, Lynae; Stephenson, Rob; Bauermeister, Jose

2017-01-01

Participation in romantic relationships during adolescence and young adulthood provides opportunities to explore one's sexuality, yet may also cause distress once these relationships dissolve. Although researchers have asserted that participation in same-sex relationships may be beneficial for young gay and bisexual men's (YGBM) psychosocial well-being, less is known about YGBM appraisals of breakups after participating in same-sex relationships. We examined the association between self-reported psychological well-being (e.g., symptoms of depression and anxiety; self-esteem, sense of personal competency) and YGBM's negative and positive appraisals of breakups within a sample of single YGBM (N=1,040; ages 18-24) who reported prior serious same-sex relationships. Negative appraisals were associated with lower psychological well-being. Positive appraisals were associated with greater anxiety symptoms, self-esteem and sense of personal competency. Our findings highlight the need to acknowledge how YGBM's differential responses to breakups may be associated with their psychological well-being.

Breakup-related appraisals and the psychological well-being of young adult gay and bisexual men

PubMed Central

Ceglarek, Peter; Darbes, Lynae; Stephenson, Rob; Bauermeister, Jose

2017-01-01

Participation in romantic relationships during adolescence and young adulthood provides opportunities to explore one’s sexuality, yet may also cause distress once these relationships dissolve. Although researchers have asserted that participation in same-sex relationships may be beneficial for young gay and bisexual men’s (YGBM) psychosocial well-being, less is known about YGBM appraisals of breakups after participating in same-sex relationships. We examined the association between self-reported psychological well-being (e.g., symptoms of depression and anxiety; self-esteem, sense of personal competency) and YGBM’s negative and positive appraisals of breakups within a sample of single YGBM (N=1,040; ages 18–24) who reported prior serious same-sex relationships. Negative appraisals were associated with lower psychological well-being. Positive appraisals were associated with greater anxiety symptoms, self-esteem and sense of personal competency. Our findings highlight the need to acknowledge how YGBM’s differential responses to breakups may be associated with their psychological well-being. PMID:28989559

Impinging jets atomization

NASA Technical Reports Server (NTRS)

Ibrahim, E. A.; Przekwas, A. J.

1991-01-01

An analysis of the characteristics of the spray produced by an impinging-jet injector is presented. Predictions of the spray droplet size and distribution are obtained through studying the formation and disintegration of the liquid sheet formed by the impact of two cylindrical jets of the same diameter and momentum. Two breakup regimes of the sheet are considered depending on Weber number, with transition occurring at Weber numbers between 500 and 2000. In the lower Weber number regime, the breakup is due to Taylor cardioidal waves, while at Weber number higher than 2000, the sheet disintegration is by the growth of Kelvin-Helmholtz instability waves. Theoretical expressions to predict the sheet thickness and shape are derived for the low Weber number breakup regime. An existing mathematical analysis of Kelvin-Helmholtz instability of radially moving liquid sheets is adopted in the predictions of resultant drop sizes by sheet breakup at Weber numbers greater than 2000. Comparisons of present theoretical results with experimental measurements and empirical correlations reported in the literature reveal favorable agreement.

Drop deformation and breakup in a partially filled horizontal rotating cylinder

NASA Astrophysics Data System (ADS)

White, Andrew; Pereira, Caroline; Hyacinthe, Hyaquino; Ward, Thomas

2014-11-01

Drop deformation and breakup due to shear flow has been studied extensively in Couette devices as well as in gravity-driven flows. In these cases shear is generated either by the moving wall or the drop's motion. For such flows the drop shape remains unperturbed at low capillary number (Ca), deforms at moderate Ca , and can experience breakup as Ca --> 1 and larger. Here single drops of NaOH(aq) will be placed in a horizontal cylindrical rotating tank partially filled with vegetable oil resulting in 10-2 < Ca <101 . It will be shown that the reactive vegetable oil-NaOH(aq) system, where surfactants are produced in situ by saponification, can yield lower minimum surface tensions and faster adsorption than non-reactive surfactant systems. Oil films between the wall and drop as well as drop shape will be observed as rotation rates and NaOH(aq) concentration are varied. Results will be presented in the context of previous work on bubble and drop shapes and breakup. NSF CBET #1262718.

Instability of nano- and microscale liquid metal filaments: Transition from single droplet collapse to multidroplet breakup

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

Hartnett, Chris A.; Mahady, Kyle; Fowlkes, Jason Davidson

We carry out experimental and numerical studies to investigate the collapse and breakup of finite size, nano- and microscale, liquid metal filaments supported on a substrate. We find the critical dimensions below which filaments do not break up but rather collapse to a single droplet. The transition from collapse to breakup can be described as a competition between two fluid dynamic phenomena: the capillary driven end retraction and the Rayleigh–Plateau type instability mechanism that drives the breakup. We focus on the unique spatial and temporal transition region between these two phenomena using patterned metallic thin film strips and pulsed-laser-induced dewetting.more » The experimental results are compared to an analytical model proposed by Driessen et al. and modified to include substrate interactions. Additionally, we report the results of numerical simulations based on a volume-of-fluid method to provide additional insight and highlight the importance of liquid metal resolidification, which reduces inertial effects.« less

Instability of nano- and microscale liquid metal filaments: Transition from single droplet collapse to multidroplet breakup

DOE PAGES

Hartnett, Chris A.; Mahady, Kyle; Fowlkes, Jason Davidson; ...

2015-11-23

We carry out experimental and numerical studies to investigate the collapse and breakup of finite size, nano- and microscale, liquid metal filaments supported on a substrate. We find the critical dimensions below which filaments do not break up but rather collapse to a single droplet. The transition from collapse to breakup can be described as a competition between two fluid dynamic phenomena: the capillary driven end retraction and the Rayleigh–Plateau type instability mechanism that drives the breakup. We focus on the unique spatial and temporal transition region between these two phenomena using patterned metallic thin film strips and pulsed-laser-induced dewetting.more » The experimental results are compared to an analytical model proposed by Driessen et al. and modified to include substrate interactions. Additionally, we report the results of numerical simulations based on a volume-of-fluid method to provide additional insight and highlight the importance of liquid metal resolidification, which reduces inertial effects.« less

The initiation of segmented buoyancy-driven melting during continental breakup

PubMed Central

Gallacher, Ryan J.; Keir, Derek; Harmon, Nicholas; Stuart, Graham; Leroy, Sylvie; Hammond, James O. S.; Kendall, J-Michael; Ayele, Atalay; Goitom, Berhe; Ogubazghi, Ghebrebrhan; Ahmed, Abdulhakim

2016-01-01

Melting of the mantle during continental breakup leads to magmatic intrusion and volcanism, yet our understanding of the location and dominant mechanisms of melt generation in rifting environments is impeded by a paucity of direct observations of mantle melting. It is unclear when during the rifting process the segmented nature of magma supply typical of seafloor spreading initiates. Here, we use Rayleigh-wave tomography to construct a high-resolution absolute three-dimensional shear-wave velocity model of the upper 250 km beneath the Afar triple junction, imaging the mantle response during progressive continental breakup. Our model suggests melt production is highest and melting depths deepest early during continental breakup. Elevated melt production during continental rifting is likely due to localized thinning and melt focusing when the rift is narrow. In addition, we interpret segmented zones of melt supply beneath the rift, suggesting that buoyancy-driven active upwelling of the mantle initiates early during continental rifting. PMID:27752044

DebriSat: The New Hypervelocity Impact Test for Satellite Breakup Fragment Characterization

NASA Technical Reports Server (NTRS)

Cowardin, Heather

2015-01-01

To replicate a hyper-velocity fragmentation event using modern-day spacecraft materials and construction techniques to better improve the existing DoD and NASA breakup models: DebriSat is intended to be representative of modern LEO satellites. Major design decisions were reviewed and approved by Aerospace subject matter experts from different disciplines. DebriSat includes 7 major subsystems. Attitude determination and control system (ADCS), command and data handling (C&DH), electrical power system (EPS), payload, propulsion, telemetry tracking and command (TT&C), and thermal management. To reduce cost, most components are emulated based on existing design of flight hardware and fabricated with the same materials. center dotA key laboratory-based test, Satellite Orbital debris Characterization Impact Test (SOCIT), supporting the development of the DoD and NASA satellite breakup models was conducted at AEDC in 1992. Breakup models based on SOCIT have supported many applications and matched on-orbit events reasonably well over the years.

Deformation and Breakup of a Stretching Liquid Bridge

NASA Astrophysics Data System (ADS)

Franses, Elias I.; Liao, Ying-Chih; Basaran, Osman

2004-11-01

Surfactants are routinely used to control the breakup of drops and jets in applications as diverse as ink jet printing, crop spraying, and microarraying. While highly accurate algorithms for studying the breakup of surfactant-free drops and jets are well documented and a great deal of information is now available in such situations, little is known about the closely related problem of interface rupture when surfactant effects cannot be neglected. Here we analyze the deformation and breakup of a stretching liquid bridge whose surface is covered with an insoluble surfactant monolayer by means of a two-dimensional (2-d) finite element algorithm using elliptic mesh generation. That the predictions made with the 2-d algorithm are faithful to the physics is confirmed by demonstrating that the computed results accord well with our new high-speed visualization experiments and existing scaling theories. Comparisons are also made to computations made with a one-dimensional (1-d) algorithm based on the slender-jet equations.

High multiplicity α-particle breakup measurements to study α-condensate states

NASA Astrophysics Data System (ADS)

Bishop, J.; Kokalova, Tz; Freer, M.; Assie, M.; Acosta, L.; Bailey, S.; Cardella, G.; Curtis, N.; De Filippo, E.; Dell'Aquila, D.; De Luca, S.; Francalanza, L.; Gnoffo, B.; Lanzalone, G.; Lombardo, I.; Martorana, N.; Norella, S.; Pagano, A.; Pagano, E. V.; Papa, M.; Pirrone, S.; Politi, G.; Rizzo, F.; Russotto, P.; Quattrocchi, L.; Smith, R.; Stefan, I.; Trifirò, A.; Trimarchì, M.; Verde, G.; Vigilante, M.; Wheldon, C.

2017-06-01

An experiment was performed to investigate α-condensate states via high α-particle multiplicity breakup. The nucleus of interest was 28Si therefore to measure multiplicity 7 particle breakup events, a highly granular detector with a high solid angle coverage was required. For this purpose, the CHIMERA and FARCOS detectors at INFN LNS were employed. Particle identification was achieved through ΔE-E energy loss. The α-particle multiplicity was measured at three beam energies to investigate different excitation regimes in 28Si. At a beam energy where the energy is sufficient to provide the 7 α-particles with enough energy to be identified using the ΔE-E method, multiplicity 7 events can be seen. Given these high multiplicity events, the particles can be reconstructed to investigate the breakup of α-condensate states. Analysing the decay paths of these states can elucidate whether the state of interest corresponds to a non-cluster, clustered or condensed state.

Influence of thermal fluctuations on ligament break-up: a fluctuating lattice Boltzmann study

NASA Astrophysics Data System (ADS)

Xue, Xiao; Biferale, Luca; Sbragaglia, Mauro; Toschi, Federico

2017-11-01

Thermal fluctuations are essential ingredients in a nanoscale system, driving Brownian motion of particles and capillary waves at non-ideal interfaces. Here we study the influence of thermal fluctuations on the breakup of liquid ligaments at the nanoscale. We offer quantitative characterization of the effects of thermal fluctuations on the Plateau-Rayleigh mechanism that drives the breakup process of ligaments. Due to thermal fluctuations, the droplet sizes after break-up need to be analyzed in terms of their distribution over an ensemble made of repeated experiments. To this aim, we make use of numerical simulations based on the fluctuating lattice Boltzmann method (FLBM) for multicomponent mixtures. The method allows an accurate and efficient simulation of the fluctuating hydrodynamics equations of a binary mixture, where both stochastic viscous stresses and diffusion fluxes are introduced. This project has received funding from the European Union's Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie Grant Agreement No 642069.

Scroll wave dynamics in a three-dimensional cardiac tissue model: roles of restitution, thickness, and fiber rotation.

PubMed Central

Qu, Z; Kil, J; Xie, F; Garfinkel, A; Weiss, J N

2000-01-01

Scroll wave (vortex) breakup is hypothesized to underlie ventricular fibrillation, the leading cause of sudden cardiac death. We simulated scroll wave behaviors in a three-dimensional cardiac tissue model, using phase I of the Luo-Rudy (LR1) action potential model. The effects of action potential duration (APD) restitution, tissue thickness, filament twist, and fiber rotation were studied. We found that APD restitution is the major determinant of scroll wave behavior and that instabilities arising from APD restitution are the main determinants of scroll wave breakup in this cardiac model. We did not see a "thickness-induced instability" in the LR1 model, but a minimum thickness is required for scroll breakup in the presence of fiber rotation. The major effect of fiber rotation is to maintain twist in a scroll wave, promoting filament bending and thus scroll breakup. In addition, fiber rotation induces curvature in the scroll wave, which weakens conduction and further facilitates wave break. PMID:10827961

On the first ν6 anti-aligned librating asteroid family of Tina

NASA Astrophysics Data System (ADS)

Carruba, V.; Morbidelli, A.

2011-04-01

Asteroid families are groups of bodies identified in the space of proper elements or of frequencies that share a common origin in the collisional break-up of their progenitors. Their dynamical evolution is shaped by the interaction with the local web of mean-motion and secular resonances, and by non-gravitational effects, such as the 'Yarkovsky' and 'Yarkovsky-O'Keefe-Radzievskii-Paddack' (YORP) effects. Thus, obtaining information on their age and original ejection velocity field is generally a difficult task. Recently, two families were found to have a large fraction of members in the non-linear secular resonance z1: the Agnia and Padua families. Conserved quantities of the z1resonance allowed for a more precise determination of their ages and ejection velocity fields. So far, however, no family was known to be in a linear secular resonance, such as the ν6 resonance, although individual asteroids were known to be in ν6 anti-aligned librating states. The ν6 resonance occurs when there is a commensurability between the frequency of precession of the pericentre of an asteroid and that of Saturn. As a consequence, in librating states, the resonant argument oscillates around a stable point. In anti-aligned librating states, the resonant argument oscillates around the stable point at 180°. Here we show that the newly identified Tina family is characterized by having all its members in such a state, making it the only family in the asteroid belt known to be completely embedded in a secular resonance configuration. This rare dynamical configuration limits the maximum eccentricity of Tina members, preventing them from experiencing Martian close encounters and forming a stable island of a new dynamical type. The current dispersion of asteroid resonant elements suggests that the family should be at least 2.5 Myr old, while Monte Carlo simulations including the Yarkovsky and YORP effects suggest that the Tina family should be 170+20-30 Myr old.

Structure and degree of magmatism of North and South Atlantic rifted margins

NASA Astrophysics Data System (ADS)

Faleide, Jan Inge; Breivik, Asbjørn J.; Blaich, Olav A.; Tsikalas, Filippos; Planke, Sverre; Mansour Abdelmalak, Mohamed; Mjelde, Rolf; Myklebust, Reidun

2014-05-01

The structure and evolution of conjugate rifted margins in the South and North Atlantic have been studied mainly based on seismic reflection and refraction profiles, complemented by potential field data and plate reconstructions. All margins exhibit distinct along-margin structural and magmatic changes reflecting both structural inheritance extending back to a complex pre-breakup geological history and the final breakup processes. The sedimentary basins at the conjugate margins developed as a result of multiple phases of rifting, associated with complex time-dependent thermal structure of the lithosphere. A series of conjugate crustal transects reveal tectonomagmatic asymmetry, both along-strike and across the conjugate margin systems. The continent-ocean transitional domain along the magma-dominated margin segments is characterized by a large volume of flood basalts and high-velocity/high-density lower crust emplaced during and after continental breakup. Both the volume and duration of excess magmatism varies. The extrusive and intrusive complexes make it difficult to pin down a COB to be used in plate reconstructions. The continent-ocean transition is usually well defined as a rapid increase of P-wave velocities at mid- to lower crustal levels. The transition is further constrained by comparing the mean P-wave velocity to the thickness of the crystalline crust. By this comparison we can also address the magmatic processes associated with breakup, whether they are convection dominated or temperature dominated. In the NE Atlantic there is a strong correlation between magma productivity and early plate spreading rate, suggesting a common cause. A model for the breakup-related magmatism should be able to explain this correlation, but also the magma production peak at breakup, the along-margin magmatic segmentation, and the active mantle upwelling. It is likely that mantle plumes (Iceland in the NE Atlantic, Tristan da Cunha in the South Atlantic) may have influenced the volume of magmatism but they did not necessarily alter the process of rifted margin formation, implying that parts of the margins may have much in common with more magma-poor margins. Conjugate margin segments from the North and South Atlantic will be compared and discussed with particular focus on the tectonomagmatic processes associated with continental breakup.

Ocean wave generation by collapsing ice shelves

NASA Astrophysics Data System (ADS)

Macayeal, D. R.; Bassis, J. N.; Okal, E. A.; Aster, R. C.; Cathles, L. M.

2008-12-01

The 28-29 February, 2008, break-up of the Wilkins Ice Shelf, Antarctica, exemplifies the now-familiar, yet largely unexplained pattern of explosive ice-shelf break-up. While environmental warming is a likely ultimate cause of explosive break-up, several key aspects of their short-term behavior need to be explained: (1) The abrupt, near-simultaneous onset of iceberg calving across long spans of the ice front margin; (2) High outward drift velocity (about 0.3 m/s) of a leading phalanx of tabular icebergs that originate from the seaward edge of the intact ice shelf prior to break-up; (3) Rapid coverage of the ocean surface in the wake of this leading phalanx by small, capsized and dismembered tabular icebergs; (4) Extremely large gravitational potential energy release rates, e.g., up to 3 × 1010 W; (5) Lack of proximal iceberg-calving triggers that control the timing of break-up onset and that maintain the high break-up calving rates through to the conclusion of the event. Motivated by seismic records obtained from icebergs and the Ross Ice Shelf that show hundreds of micro- tsunamis emanating from near the ice shelf front, we re-examine the basic dynamic features of ice- shelf/ocean-wave interaction and, in particular, examine the possibility that collapsing ice shelves themselves are a source of waves that stimulate the disintegration process. We propose that ice-shelf generated surface-gravity waves associated with initial calving at an arbitrary seed location produce stress perturbations capable of triggering the onset of calving on the entire ice front. Waves generated by parting detachment rifts, iceberg capsize and break-up act next to stimulate an inverted submarine landslide (ice- slide) process, where gravitational potential energy released by upward movement of buoyant ice is radiated as surface gravity waves in the wake of the advancing phalanx of tabular icebergs. We conclude by describing how field research and remote sensing can be used to test the various conjectures about ice- shelf/wave interaction that appear to be at play during ice-shelf disintegration.

Effects of unconventional breakup modes on incomplete fusion of weakly bound nuclei

NASA Astrophysics Data System (ADS)

Diaz-Torres, Alexis; Quraishi, Daanish

2018-02-01

The incomplete fusion dynamics of 6Li+209Bi collisions at energies above the Coulomb barrier is investigated. The classical dynamical model implemented in the platypus code is used to understand and quantify the impact of both 6Li resonance states and transfer-triggered breakup modes (involving short-lived projectile-like nuclei such as 8Be and 5Li) on the formation of incomplete fusion products. Model calculations explain the experimental incomplete-fusion excitation function fairly well, indicating that (i) delayed direct breakup of 6Li reduces the incomplete fusion cross sections and (ii) the neutron-stripping channel practically determines those cross sections.

Drop formation in shear-thickening granular suspensions.

PubMed

Pan, Zhongcheng; Louvet, Nicolas; Hennequin, Yves; Kellay, Hamid; Bonn, Daniel

2015-11-01

We study droplet formation in granular suspensions by systematically varying the volume fractions (φ) and particle diameters (d). For suspensions with water as the suspending liquid, we find three different regimes. For dilute suspensions (φ≤45%), drop formation follows the predictions for inertial breakup and exhibits identical dynamics to that of pure water. The breakup is strongly asymmetrical in this case. Only for more concentrated suspensions (φ>45%) does the presence of particles change the dynamics and two other regimes, a symmetrical inertial regime and a Bagnoldian regime, are uncovered. We construct and discuss a phase diagram that allows us to understand and predict the breakup behavior in granular suspensions.

Preparation of Nanocomposite Plasmonic Films Made from Cellulose Nanocrystals or Mesoporous Silica Decorated with Unidirectionally Aligned Gold Nanorods.

PubMed

Campbell, Michael G; Liu, Qingkun; Sanders, Aric; Evans, Julian S; Smalyukh, Ivan I

2014-04-11

Using liquid crystalline self-assembly of cellulose nanocrystals, we achieve long-range alignment of anisotropic metal nanoparticles in colloidal nanocrystal dispersions that are then used to deposit thin structured films with ordering features highly dependent on the deposition method. These hybrid films are comprised of gold nanorods unidirectionally aligned in a matrix that can be made of ordered cellulose nanocrystals or silica nanostructures obtained by using cellulose-based nanostructures as a replica. The ensuing long-range alignment of gold nanorods in both cellulose-based and nanoporous silica films results in a polarization-sensitive surface plasmon resonance. The demonstrated device-scale bulk nanoparticle alignment may enable engineering of new material properties arising from combining the orientational ordering of host nanostructures and properties of the anisotropic plasmonic metal nanoparticles. Our approach may also allow for scalable fabrication of plasmonic polarizers and nanoporous silica structures with orientationally ordered anisotropic plasmonic nanoinclusions.

The dynamics of continental breakup-related magmatism on the Norwegian volcanic margin

NASA Astrophysics Data System (ADS)

Breivik, A. J.; Faleide, J. I.; Mjelde, R.

2007-12-01

The Vøring margin off mid-Norway was initiated during the earliest Eocene (~54 Ma), and large volumes of magmatic rocks were emplaced during and after continental breakup. In 2003, an ocean bottom seismometer survey was acquired on the Norwegian margin to constrain continental breakup and early seafloor spreading processes. The profile P-wave model described here crosses the northern part of the Vøring Plateau. Maximum igneous crustal thickness was found to be 18 km, decreasing to ~6.5 km over ~6 M.y. after continental breakup. Both the volume and the duration of excess magmatism after breakup is about twice of what is observed off the Møre Margin south of the Jan Mayen Fracture Zone, which offsets the margin segments by ~170 km. A similar reduction in magmatism occurs to the north over an along-margin distance of ~100 km to the Lofoten margin, but without a margin offset. There is a strong correlation between magma productivity and early plate spreading rate, which are highest just after breakup, falling with time. This is seen both at the Møre and the Vøring margin segments, suggesting a common cause. A model for the breakup- related magmatism should be able to (1) explain this correlation, (2) the magma production peak at breakup, and (3) the magmatic segmentation. Proposed end-member hypotheses are elevated upper-mantle temperatures caused by a hot mantle plume, or edge-driven small-scale convection fluxing mantle rocks through the melt zone. Both the average P-wave velocity and the major-element data at the Vøring margin indicate a low degree of melting consistent with convection. However, small scale convection does not easily explain the issues listed above. An elaboration of the mantle plume model by N. Sleep, in which buoyant plume material fills the rift-topography at the base of the lithosphere, can explain these: When the continents break apart, the buoyant plume-material flows up into the rift zone, causing excess magmatism by both elevated temperature and excess flux, and magmatism dies off as this rift-restricted material is spent. The buoyancy of the plume-material also elevates the plate boundaries and enhances plate spreading forces initially. The rapid drop in magma productivity to the north correlates with the northern boundary of the wide and deep Cretaceous Vøring Basin, thus less plume material was accommodated off Lofoten. This model predicts that the magma segmentation will show little variation in the geochemical signature.

Physics of puffing and microexplosion of emulsion fuel droplets

NASA Astrophysics Data System (ADS)

Shinjo, J.; Xia, J.; Ganippa, L. C.; Megaritis, A.

2014-10-01

The physics of water-in-oil emulsion droplet microexplosion/puffing has been investigated using high-fidelity interface-capturing simulation. Varying the dispersed-phase (water) sub-droplet size/location and the initiation location of explosive boiling (bubble formation), the droplet breakup processes have been well revealed. The bubble growth leads to local and partial breakup of the parent oil droplet, i.e., puffing. The water sub-droplet size and location determine the after-puffing dynamics. The boiling surface of the water sub-droplet is unstable and evolves further. Finally, the sub-droplet is wrapped by boiled water vapor and detaches itself from the parent oil droplet. When the water sub-droplet is small, the detachment is quick, and the oil droplet breakup is limited. When it is large and initially located toward the parent droplet center, the droplet breakup is more extensive. For microexplosion triggered by the simultaneous growth of multiple separate bubbles, each explosion is local and independent initially, but their mutual interactions occur at a later stage. The degree of breakup can be larger due to interactions among multiple explosions. These findings suggest that controlling microexplosion/puffing is possible in a fuel spray, if the emulsion-fuel blend and the ambient flow conditions such as heating are properly designed. The current study also gives us an insight into modeling the puffing and microexplosion of emulsion droplets and sprays.

Modeling of Field-Aligned Guided Echoes in the Plasmasphere

NASA Technical Reports Server (NTRS)

Fung, Shing F.; Green, James L.

2004-01-01

The conditions under which high frequency (f>>f(sub uh)) long-range extraordinary-mode discrete field-aligned echoes observed by the Radio Plasma Imager (RPI) on board the Imager for Magnetopause-to-Aurora Global Exploration (IMAGE) satellite in the plasmasphere are investigated by ray tracing modeling. Field-aligned discrete echoes are most commonly observed by RPI in the plasmasphere although they are also observed over the polar cap region. The plasmasphere field-aligned echoes appearing as multiple echo traces at different virtual ranges are attributed to signals reflected successively between conjugate hemispheres that propagate along or nearly along closed geomagnetic field lines. The ray tracing simulations show that field-aligned ducts with as little as 1% density perturbations (depletions) and less than 10 wavelengths wide can guide nearly field-aligned propagating high frequency X mode waves. Effective guidance of wave at a given frequency and wave normal angle (Psi) depends on the cross-field density scale of the duct, such that ducts with stronger density depletions need to be wider in order to maintain the same gradient of refractive index across the magnetic field. While signal guidance by field aligned density gradient without ducting is possible only over the polar region, conjugate field-aligned echoes that have traversed through the equatorial region are most likely guided by ducting.

Sea spray production by bag breakup mode of fragmentation of the air-water interface at strong and hurricane wind

NASA Astrophysics Data System (ADS)

Troitskaya, Yuliya; Kandaurov, Alexander; Ermakova, Olga; Kozlov, Dmitry; Sergeev, Daniil; Zilitinkevich, Sergej

2016-04-01

Sea sprays is a typical element of the marine atmospheric boundary layer (MABL) of large importance for marine meteorology, atmospheric chemistry and climate studies. They are considered as a crucial factor in the development of hurricanes and severe extratropical storms, since they can significantly enhance exchange of mass, heat and momentum between the ocean and the atmosphere. This exchange is directly provided by spume droplets with the sizes from 10 microns to a few millimeters mechanically torn off the crests of a breaking waves and fall down to the ocean due to gravity. The fluxes associated with the spray are determined by the rate of droplet production at the surface quantified by the sea spray generation function (SSGF), defined as the number of spray particles of radius r produced from the unit area of water surface in unit time. However, the mechanism of spume droplets' formation is unknown and empirical estimates of SSGF varied over six orders of magnitude; therefore, the production rate of large sea spray droplets is not adequately described and there are significant uncertainties in estimations of exchange processes in hurricanes. Experimental core of our work comprise laboratory experiments employing high-speed video-filming, which have made it possible to disclose how water surface looks like at extremely strong winds and how exactly droplets are torn off wave crests. We classified events responsible for spume droplet, including bursting of submerged bubbles, generation and breakup of "projections" or liquid filaments (Koa, 1981) and "bag breakup", namely, inflating and consequent blowing of short-lived, sail-like pieces of the water-surface film, "bags". The process is similar to "bag-breakup" mode of fragmentation of liquid droplets and jets in gaseous flows. Basing on statistical analysis of results of these experiments we show that the main mechanism of spray-generation is attributed to "bag-breakup mechanism On the base of general principles of statistical physics (model of a canonical ensemble) we developed statistics of the "bag-breakup" events and constructed sea spray generation function (SSGF) for the mechanism of "bag-breakup". The "bag breakup" SSGF is shown to be in reasonable agreement in magnitude with SSFGs considered as the most reliable source function for spume droplets. The new SSGF is employed for estimate of the new"bag-breakup" mechanism to momentum and energy exchange in marine atmospheric boundary layer at hurricane conditions. This work was supported by the Russian Foundation of Basic Research (14-05-91767, 13-05-12093, 16-05-00839, 14-05-91767, 16-55-52025) and experiment and equipment was supported by Russian Science Foundation (Agreements 14-17-00667 and 15-17-20009 respectively), Yu.Troitskaya, A.Kandaurov and D.Sergeev were partially supported by FP7 collaborative Project No. 612610.

Colour stabilities of three types of orthodontic clear aligners exposed to staining agents

PubMed Central

Liu, Chen-Lu; Sun, Wen-Tian; Liao, Wen; Lu, Wen-Xin; Li, Qi-Wen; Jeong, Yunho; Liu, Jun; Zhao, Zhi-He

2016-01-01

The aim of this study was to evaluate and compare the colour stabilities of three types of orthodontic clear aligners exposed to staining agents in vitro. Sixty clear orthodontic aligners produced by three manufacturers (Invisalign, Angelalign, and Smartee) were immersed in three staining solutions (coffee, black tea, and red wine) and one control solution (distilled water). After 12-h and 7-day immersions, the aligners were washed in an ultrasonic cleaner and measured with a colourimeter. The colour changes (ΔE*) were calculated on the basis of the Commission Internationale de I'Eclairage L*a*b* colour system (CIE L*a*b*), and the results were then converted into National Bureau of Standards (NBS) units. Fourier transformation infrared (FT-IR) spectroscopy and scanning electron microscopy (SEM) were conducted to observe the molecular and morphologic alterations to the aligner surfaces, respectively. The three types of aligners exhibited slight colour changes after 12 h of staining, with the exception of the Invisalign aligners stained with coffee. The Invisalign aligners exhibited significantly higher ΔE* values (ranging from 0.30 to 27.81) than those of the Angelalign and Smartee aligners (ΔE* values ranging from 0.33 to 1.89 and 0.32 to 1.61, respectively, P<0.05). FT-IR analysis confirmed that the polymer-based structure of aligners did not exhibit significant chemical differences before and after the immersions. The SEM results revealed different surface alterations to the three types of aligner materials after the 7-day staining. The three types of aesthetic orthodontic appliances exhibited colour stability after the 12-h immersion, with the exception of the Invisalign aligners stained by coffee. The Invisalign aligners were more prone than the Angelalign and Smartee aligners to pigmentation. Aligner materials may be improved by considering aesthetic colour stability properties. PMID:27660048

Colour stabilities of three types of orthodontic clear aligners exposed to staining agents.

PubMed

Liu, Chen-Lu; Sun, Wen-Tian; Liao, Wen; Lu, Wen-Xin; Li, Qi-Wen; Jeong, Yunho; Liu, Jun; Zhao, Zhi-He

2016-12-16

The aim of this study was to evaluate and compare the colour stabilities of three types of orthodontic clear aligners exposed to staining agents in vitro. Sixty clear orthodontic aligners produced by three manufacturers (Invisalign, Angelalign, and Smartee) were immersed in three staining solutions (coffee, black tea, and red wine) and one control solution (distilled water). After 12-h and 7-day immersions, the aligners were washed in an ultrasonic cleaner and measured with a colourimeter. The colour changes (ΔE*) were calculated on the basis of the Commission Internationale de I'Eclairage L*a*b* colour system (CIE L*a*b*), and the results were then converted into National Bureau of Standards (NBS) units. Fourier transformation infrared (FT-IR) spectroscopy and scanning electron microscopy (SEM) were conducted to observe the molecular and morphologic alterations to the aligner surfaces, respectively. The three types of aligners exhibited slight colour changes after 12 h of staining, with the exception of the Invisalign aligners stained with coffee. The Invisalign aligners exhibited significantly higher ΔE* values (ranging from 0.30 to 27.81) than those of the Angelalign and Smartee aligners (ΔE* values ranging from 0.33 to 1.89 and 0.32 to 1.61, respectively, P<0.05). FT-IR analysis confirmed that the polymer-based structure of aligners did not exhibit significant chemical differences before and after the immersions. The SEM results revealed different surface alterations to the three types of aligner materials after the 7-day staining. The three types of aesthetic orthodontic appliances exhibited colour stability after the 12-h immersion, with the exception of the Invisalign aligners stained by coffee. The Invisalign aligners were more prone than the Angelalign and Smartee aligners to pigmentation. Aligner materials may be improved by considering aesthetic colour stability properties.

Proving and Improving Wave Models in the Arctic Ocean and its MIZ

DTIC Science & Technology

2015-09-30

in the central Arctic Ocean (Hunkins, 1966); in the Antarctic MIZ, Weddell Sea, slightly larger values were reported ranging from 1.6 × 10-2 m2 s-1...unprecedented spatial resolution. Such vast fields of pancake ice have traditionally only been associated with the advancing Antarctic MIZ, and, on a smaller...achieved in an MIZ dominated by large waves. Data on the break-up of a large tabular iceberg by swell, measured in Baffin Bay, were published

Nanojets: Electrification, Energetics, Dynamics, Stability and Breakup

DTIC Science & Technology

2006-12-31

OF: 17. LIMITATION OF 18 . NUMBER 19a. NAME OF RESPONSIBLE PERSON a. REPORT b. ABSTRACT c. THIS PAGE ABSTRACT OF Dr Uzi Landman PAGES SU 19b. TELEPHONE...F(Ei )dE,. = Fm,, (Ero, )F,,h (Er,,b)dEro, dEwbh. (8) 16 where F,.ot( Erot ), and Fvwb(Evib) are the normalized rotational and vibrational Maxwell...corresponding to the concentrated solution, while the jet 18 dimensions are associated with radii in the range between 2.3 and 3.29 nm, with the larger

Blast Mitigation by Water Mist, (3) Mitigation of Confined and Unconfined Blasts

DTIC Science & Technology

2006-07-14

2 (vv)I1 1 j7(T - TJ) (18) In addition to drag, heat transfer, and vaporization, droplet breakup must also be accounted for when large droplets...Mitigation of Confined and Unconfined Blasts Table of Contents 1 . Introduction 2 . Numerical Model and Solution Procedure 2.1 Gas-phase Model 2.2...enclosure at 1 , 2 , 5, and 15 ms after detonation of a 2.12 kg explosive without water mist present. Temperature contour range is from 300 to 2500 K

Breakup of New Orleans Households after Hurricane Katrina

ERIC Educational Resources Information Center

Rendall, Michael S.

2011-01-01

Theory and evidence on disaster-induced population displacement have focused on individual and population-subgroup characteristics. Less is known about impacts on households. I estimate excess incidence of household breakup resulting from Hurricane Katrina by comparing a probability sample of pre-Katrina New Orleans resident adult household heads…

Color Breakup In Sequentially-Scanned LC Displays

NASA Technical Reports Server (NTRS)

Arend, L.; Lubin, J.; Gille, J.; Larimer, J.; Statler, Irving C. (Technical Monitor)

1994-01-01

In sequentially-scanned liquid-crystal displays the chromatic components of color pixels are distributed in time. For such displays eye, head, display, and image-object movements can cause the individual color elements to be visible. We analyze conditions (scan designs, types of eye movement) likely to produce color breakup.

The Breakup

ERIC Educational Resources Information Center

Lum, Lydia

2011-01-01

This article reports on the breakup between Texas Southmost College (TSC) and the upper-division University of Texas at Brownsville (UTB). The split marks the official end of an unusual 20-year partnership between TSC and the University of Texas System that, for the first time, ushered four-year university education into overwhelmingly Latino…

Intense pulsed light treatment for dry eye disease due to meibomian gland dysfunction; a 3-year retrospective study.

PubMed

Toyos, Rolando; McGill, William; Briscoe, Dustin

2015-01-01

The purpose of this study was to determine the clinical benefits of intense-pulsed-light therapy for the treatment of dry-eye disease caused by meibomian gland dysfunction (MGD). MGD is the leading cause of evaporative dry eye disease. It is currently treated with a range of methods that have been shown to be only somewhat effective, leading to the need for advanced treatment options. A retrospective noncomparative interventional case series was conducted with 91 patients presenting with severe dry eye syndrome. Treatment included intense-pulsed-light therapy and gland expression at a single outpatient clinic over a 30-month study. Pre/post tear breakup time data were available for a subset of 78 patients. For all patients, a specially developed technique for the treatment of dry eye syndrome was applied as a series of monthly treatments until there was adequate improvement in dry eye syndrome symptoms by physician judgment, or until patient discontinuation. Primary outcomes included change in tear breakup time, self-reported patient satisfaction, and adverse events. Physician-judged improvement in dry eye tear breakup time was found for 68 of 78 patients (87%) with seven treatment visits and four maintenance visits on average (medians), and 93% of patients reported post-treatment satisfaction with degree of dry eye syndrome symptoms. Adverse events, most typically redness or swelling, were found for 13% of patients. No serious adverse events were found. Although preliminary, study results of intense-pulsed-light therapy treatment for dry eye syndrome caused by meibomian gland dysfunction are promising. A multisite clinical trial with a larger sample, treatment comparison groups, and randomized controlled trials is currently underway.

Mantle exhumation at magma-poor rifted margin: a competition between frictional shear zones and thermally weakened necking domains. Consequences on time of breakup at Galicia/Newfoundland margins.

NASA Astrophysics Data System (ADS)

Theunissen, T.; Huismans, R. S.

2017-12-01

Here we present a new analysis and interpretation of basement topography of the transitional domain from continental to oceanic crust along the conjugate margin sections SCREETCH-1 (Newfoundland) and WE-1/ISE-1 (Galicia Bank). The absence of significant syn-rift magmatism in this area allows using 2-D thermo-mechanical modelling to understand the formation of the distal margin and exhumed mantle. We show that plastic strain weakening of the exhumed mantle is required to explain observations on basement morphology, and detachment faulting. Our models predict that the evolution of detachment faulting within the transitional domain depends on the degree of frictional-plastic strain-weakening and varies from a single unique steady state asymmetric low angle detachment fault for large degree of strain weakening to multiple out-of-sequence forming detachments with or without dip reversal for lower amounts of strain-weakening. The model behaviour is a consequence of the competition between weak frictional-plastic shear zones and the thermally weakened necking domain in the footwall. The forward models reproduce elevations, wavelength of exhumed mantle ridges for a narrow range of rift velocitiesbetween 10 and 15 mm/yr and considering the increasing thermal conductivity of peridotites at shallow depth. This causes an efficient cooling of the footwall that has then enough strength to support high topography. The forward models also predict that the peridotite ridge is the breakaway of a second detachment fault that dates the crustal breakup and that rocks on top of the peridotite ridge have experimented a fast cooling (< 2 Ma). We use predictions from these forward models to discuss time of breakup and the position of the first steady state oceanic ridge at Galicia/Newfounlandconjugate margins.

Predicting and testing continental vertical motion histories since the Paleozoic

NASA Astrophysics Data System (ADS)

Zhang, Nan; Zhong, Shijie; Flowers, Rebecca M.

2012-02-01

Dynamic topography at the Earth's surface caused by mantle convection can affect a range of geophysical and geological observations including bathymetry, sea-level change, continental flooding, sedimentation and erosion. These observations provide important constraints on and test of mantle dynamic models. Based on global mantle convection models coupled with the surface plate motion history, we compute dynamic topography and its history for the last 400 Ma associated with Pangea assembly and breakup, with particular focus on cratonic regions. We propose that burial-unroofing histories of cratons inferred from thermochronology data can be used as a new diagnostic to test dynamic topography and mantle dynamic models. Our models show that there are currently two broad dynamic topography highs in the Pacific and Africa for the present-day Earth that are associated with the broad, warm structures (i.e., superplumes) in the deep mantle, consistent with previous proposals of dynamical support for the Pacific and African superswells. Our models reveal that Pangea assembly and breakup, by affecting subduction and mantle upwelling processes, have significant effects on continental vertical motions. Our models predict that the Slave craton in North America subsides before Pangea assembly at 330 Ma but uplifts significantly from 330 Ma to 240 Ma in response to pre-Pangea subduction and post-assembly mantle warming. The Kaapvaal craton of Africa is predicted to undergo uplift from ~180 Ma to 90 Ma after Pangea breakup, but its dynamic topography remains stable for the last 90 Ma. The predicted histories of elevation change for the Slave and Kaapvaal cratons compare well with the burial-unroofing histories inferred from thermochronology studies, thus supporting our dynamic models including the development of the African superplume mantle structure. The vertical motion histories for other cratons can provide further tests of and constraints on our mantle dynamic models.

Predicting and testing continental vertical motion histories since the Paleozoic

NASA Astrophysics Data System (ADS)

Zhang, N.; Zhong, S.; Flowers, R. M.

2011-12-01

Dynamic topography at the Earth's surface caused by mantle convection can affect a range of geophysical and geological observations including bathymetry, sea-level change, continental flooding, sedimentation and erosion. These observations provide important constraints on and test of mantle dynamic models. Based on global mantle convection models coupled with the surface plate motion history, we compute dynamic topography and its history for the last 400 Ma associated with Pangea assembly and breakup, with particular focus on continental cratonic regions. We propose that burial-unroofing histories of continental cratons inferred from thermochronology data can be used as a new diagnostic to test dynamic topography and mantle dynamic models. Our models show that there are currently two broad dynamic topography highs in the Pacific and Africa for the present-day Earth that are associated with the broad, warm structures (i.e., superplumes) in the deep mantle, consistent with previous proposals of dynamical support for the Pacific and African superswells. Our models reveal that Pangea assembly and breakup, by affecting subduction and mantle upwelling processes, have significant effects on continental vertical motions. Our models predict that the Slave craton in North America subsides before Pangea assembly at 330 Ma but uplifts significantly from 330 Ma to 240 Ma in response to pre-Pangea subduction and post-assembly mantle warming. The Kaapvaal craton of Africa is predicted to undergo uplift from ~180 Ma to 90 Ma after Pangea breakup, but its dynamic topography remains stable for the last 90 Ma. The predicted histories of elevation change for the Slave and Kaapvaal cratons compare well with the burial-unroofing histories inferred from thermochronology studies, thus supporting our dynamic models including the development of the African superplume mantle structure. The vertical motion histories for other cratons can provide further tests and constraints on our mantle dynamic models.

Depression symptoms and stressful life events among college students in Puerto Rico.

PubMed

Reyes-Rodríguez, Mae Lynn; Rivera-Medina, Carmen L; Cámara-Fuentes, Luis; Suárez-Torres, Alba; Bernal, Guillermo

2013-03-05

The transition from adolescence to adulthood is associated with stressful adaptation experiences that may increase symptoms of depression. We explored the prevalence and sex differences of depressive symptoms and suicidal ideation in freshmen Latino college students in Puerto Rico, and identified stressful life events that could contribute to symptoms of depression. Two thousand one hundred sixty-three freshmen college students from the University of Puerto Rico (UPR) public education system were assessed for depression symptoms using the Beck Depression Inventory (BDI) and stressful life events using open questions. Nine percent of the sample reported depression symptoms at a moderate or severe level (BDI>20). Chi square analyses revealed a significantly higher prevalence for three of the stressful life events in females than males: relocation (10.2% females vs. 7.3% males; X(2) (1)=4.13, p=.042), break-up of a significant relationship (25.3% females vs. 17.8% males; X(2) (1)=13.76, p<.001), and illness (11.2% females vs. 7.3% males; X(2) (1)=7.23, p=.007). The model that best explained the variance of BDI scores among females was the presence of suicide risk, relationship break-up, illness, and relocation for college, whereas for males a similar model without the relationship break-up variable resulted in a better fit. Freshmen college students present a broad range of depression symptoms and certain stressful life events are associated with an increased prevalence of depression symptoms. Early detection of depression and tailored prevention programs should be developed to improve both mental health and academic performance among the college population. Published by Elsevier B.V.

Depression symptoms and stressful life events among college students in Puerto Rico

PubMed Central

Reyes-Rodríguez, Mae Lynn; Rivera-Medina, Carmen L.; Cámara-Fuentes, Luis; Suárez-Torres, Alba; Bernal, Guillermo

2012-01-01

Background The transition from adolescence to adulthood is associated with stressful adaptation experiences that may increase symptoms of depression. We explored the prevalence and sex differences of depressive symptoms and suicidal ideation in freshmen Latino college students in Puerto Rico, and identified stressful life events that could contribute to symptoms of depression. Methods Two thousand one hundred sixty-three freshmen college students from the University of Puerto Rico (UPR) public education system were assessed for depression symptoms using the Beck Depression Inventory (BDI) and stressful life events using open questions. Results Nine percent of the sample reported depression symptoms at a moderate or severe level (BDI ≥ 20). Chi square analyses revealed a significantly higher prevalence for three of the stressful life events in females than males: relocation (10.2% females vs. 7.3% males; X2 (1) = 4.13, p=.042), break-up of a significant relationship (25.3% females vs. 17.8% males; X2 (1) = 13.76, p<.001), and illness (11.2% females vs. 7.3% males; X2 (1) = 7.23, p=.007). The model that best explained the variance of BDI scores among females was the presence of suicide risk, relationship break-up, illness, and relocation for college, whereas for males a similar model without the relationship break-up variable resulted in a better fit. Conclusions Freshmen college students present a broad range of depression symptoms and certain stressful life events are associated with an increased prevalence of depression symptoms. Early detection of depression and tailored prevention programs should be developed to improve both mental health and academic performance among the college population. PMID:22939390

Comparison between natural Rain drop size distributions and corresponding models near equilibrium state during warm rain

NASA Astrophysics Data System (ADS)

Barthes, Laurent; Mallet, Cécile

2010-05-01

Keywords: Rain Drop Size Distribution, Breakup, coalescence, disdrometer The study of the vertical evolution of raindrop size distributions (DSDs) during rainfall, from the freezing level isotherm to ground level, is a key to improving our understanding of the microphysics of rain. In numerous domains such as remote sensing, telecommunications, soil erosion, and the study of the rain's efficiency in 'washing' the atmosphere, the DSD plays an important role. Among the different processes affecting the evolution of DSD, breakup and coalescence are two of the most significant. Models of coalescence and breakup lead to equilibrium of the raindrop size distribution (DSD) after a fall through sufficient vertical height. At equilibrium, the DSD no longer evolves, and its shape is unique whatever the rain rate or LWC. This implies that the DSD is known, to within a multiplication constant. These models based on experimental measurements have been developed over the past 40 years. The Low and List (1982a,b) parameterization (hereinafter LL82) and the Greg M. McFarquhar (2004) model are both based on the same laboratory experiments, which lead to an equilibrium drop size distribution (EDSD) with two or three peaks, and an exponential tail with a slope of approximately Λ=65 cm-1. Numerous measurements using disdrometer collected in different climatic areas: Paris, France (Mars to October 2000), Iowa-City (April to October 2002), and Djougou (Benin June to September 2006) corresponding to 537 hours of rain period have shown that for high rain rates, close to a state of equilibrium, this slope lies between Λ=20 - 22 cm-1. This latter value is corroborated by others measurements found in the literature (Hu & Srivastava, 1995). Hu & Srivastava suggested that the Low and List parameterization may overestimate the effects of the breakup process. This hypothesis is in adequation with recent laboratory experiments (A.P. Barros 2008) in which the authors conclude that the number of fragments droplets produced when small drops and large drops collide is overestimate. As new parameterization of LL82 is not possible due to the lack of new sufficient large experimental dataset, we have simply tried in the present study to 'compensate' the problem previously mentioned by replacing the coalescence/breakup model proposed in LL82 by another one in which the breakup process is less dominant. In order to evaluate the relevance of this modification, some of the DSD parameters such as slope, mean volume diameter, and relation between moments are calculated, and comparisons with experimental DSD are made. Simulations at equilibrium lead to a DSD tail with a slope of 23 cm-1 and a mean volume diameter equal to 2.5 mm. These values are in good agreements with experimental data. Similarly, the linear relationship between No* and the rainfall rate is also in good agreement. In the last part, the modified parameterization is then used to study the evolution of an initially gamma-like DSD in a 1D vertical rain shaft. References Barros, A. P., O. P. Prat, P. Shrestha, F. Y. Testik, and L. F. Bliven, 2008. Revisiting Low and List (1982): evaluation of raindrop collision using laboratory observations and modeling. Journal of the Atmospheric Sciences. Vol. 65(9), pp. 2983-2993. Hu, Z., and R. C. Srivastava: 1995: Evolution of raindrop size distribution by coalescence, breakup, and evaporation: Theory and observations. J. Atmos. Sci., 52, 1761-1783. Low, T. B. and R. List, 1982a: Collision, coalescence, and breakup of raindrops. Part I: Experimentally established coalescence efficiencies and fragment size distributions in breakup. J. Atmos. Sci., 39, 1591-1606. ___ 1982b: Collision, coalescence, and breakup of raindrops. Part II: Parameterization of fragment size distributions. J. Atmos. Sci., 39, 1607-1618. McFarquhar, G. M, 2004: A new representation of collision-induced breakup of raindrops and its implications for the shapes of raindrop size distributions, J. Atmos. Sci., 61(7), 777-794.

Constraining dike emplacement conditions from virtual outcrop modelling

NASA Astrophysics Data System (ADS)

Jørgen Kjøll, Hans; Andersen, Torgeir; Tegner, Christian

2017-04-01

In the Late Neoproterozoic, the paleocontinents of Baltica and Laurentia rifted apart and sea-floor spreading into the Ordovician formed the Iapetus Ocean. The Iapetus later closed and the two continents collided forming the Caledonian orogen. Rocks related to the break-up and subsequent opening of the Iapetus, now reside as partly well-preserved tectonic lenses in thrust nappes within the Scandinavian Caledonides. The break-up architecture can be separated in two distinct domains, one hyperextended magma-poor segment in the SW, and one magma-rich part that comprise the Baltoscandian Dike Swarm (BDS), the main subject of this study. The magma-rich segment is exposed from c. Røros in the south, through Sweden and into Northern Norway, a distance of more than 900 kilometers. The magmatism of the BDS has been dated to c. 580-610 Ma and is now interpreted to represent a break-up related large igneous province (LIP). The BDS is generally well exposed in freshly glaciated outcrops and mountain cliffs. It intrudes proximal to distal marine, argillaceous, meta-sandstones and carbonates that locally display well-preserved extensional features, such as normal faults at both high and low angle. Partial melting of host rocks is observed at several localities, indicating relatively high temperatures during dike emplacement. Temperature estimates by previous workers indicate high-T (850°C) conditions during the break-up from the northernmost part of the dike swarm. Emplacement depths have not yet been accurately constrained, although some anomalous high pressure for an extensional environment (≈9Kbar) is indicated in the Corrovarre area. The spectacular exposure of the dike swarm provides the opportunity to evaluate the conditions during emplacement from dike geometries and morphologies. The several hundred meters high vertical cliff walls give excellent opportunities to assess the dike geometries over a range of host lithologies and across several km of stratigraphy (up to 3 km) in the, now tilted, cross-sections. The outcrops and mountain cliffs have been thoroughly photographed using a UAV and helicopter. 3-dimensional digital outcrop models have been prepared and interpreted together with outcrop observations. The new data give new insight into dike emplacement mechanisms, which in turn provide better constraints for the ambient conditions during emplacement of the dikes. Our regional observations support previous interpretations, that the BDS represented the distal parts of a magma-rich passive margin and the ocean-continent transition. Such tectonic domains are rarely exposed and available for direct observation and the study area in the North Scandinavian Caledonides, therefore represents a unique opportunity to better constrain the conditions during continental break-up as well as the infra-crustal dike emplacement mechanisms at divergent plate margins.

Movement of a female polar bear (Ursus maritimus) in the Kara Sea during the summer sea-ice break-up.

PubMed

Rozhnov, V V; Platonov, N G; Naidenko, S V; Mordvintsev, I N; Ivanov, E A

2017-01-01

The polar bear movement trajectory in relation to onset date of the sea-ice break-up was studied in the coastal zone of the Taimyr Peninsula, eastern part of the Kara Sea, using as an example a female polar bear tagged by a radio collar with an Argos satellite transmitter. Analysis of the long-term pattern of ice melting and tracking, by means of satellite telemetry, of the female polar bear who followed the ice-edge outgoing in the north-eastern direction (in summer 2012) suggests that direction of the polar bear movement depends precisely on the direction of the sea-ice cover break-up.

Duplex Tear Film Evaporation Analysis.

PubMed

Stapf, M R; Braun, R J; King-Smith, P E

2017-12-01

Tear film thinning, hyperosmolarity, and breakup can cause irritation and damage to the human eye, and these form an area of active investigation for dry eye syndrome research. Recent research demonstrates that deficiencies in the lipid layer may cause locally increased evaporation, inducing conditions for breakup. In this paper, we explore the conditions for tear film breakup by considering a model for tear film dynamics with two mobile fluid layers, the aqueous and lipid layers. In addition, we include the effects of osmosis, evaporation as modified by the lipid, and the polar portion of the lipid layer. We solve the system numerically for reasonable parameter values and initial conditions and analyze how shifts in these cause changes to the system's dynamics.

The breakup of a main-belt asteroid 450 thousand years ago.

PubMed

Nesvorný, David; Vokrouhlický, David; Bottke, William F

2006-06-09

Collisions in the asteroid belt frequently lead to catastrophic breakups, where more than half of the target's mass is ejected into space. Several dozen large asteroids have been disrupted by impacts over the past several billion years. These impact events have produced groups of fragments with similar orbits called asteroid families. Here we report the discovery of a very young asteroid family around the object 1270 Datura. Our work takes advantage of a method for identification of recent breakups in the asteroid belt using catalogs of osculating (i.e., instantaneous) asteroid orbits. The very young families show up in these catalogs as clusters in a five-dimensional space of osculating orbital elements.

On the breakup of tectonic plates by polar wandering

NASA Technical Reports Server (NTRS)

Liu, H.-S.

1974-01-01

The equations for the stresses in a homogeneous shell of uniform thickness caused by a shift of the axis of rotation are derived. The magnitude of these stresses reaches a maximum value of the order of 10 to the 9th power dyn/sq cm, which is sufficient for explaining a tectonic breakup. In order to deduce the fracture pattern according to which the breakup of tectonic plates can be expected the theory of plastic deformation of shells is applied. The analysis of this pattern gives an explanation of the existing boundary systems of the major tectonic plates as described by Morgan (1968), LePichon (1968) and Isacks et al. (1968).

Automated Registration of Multimodal Optic Disc Images: Clinical Assessment of Alignment Accuracy.

PubMed

Ng, Wai Siene; Legg, Phil; Avadhanam, Venkat; Aye, Kyaw; Evans, Steffan H P; North, Rachel V; Marshall, Andrew D; Rosin, Paul; Morgan, James E

2016-04-01

To determine the accuracy of automated alignment algorithms for the registration of optic disc images obtained by 2 different modalities: fundus photography and scanning laser tomography. Images obtained with the Heidelberg Retina Tomograph II and paired photographic optic disc images of 135 eyes were analyzed. Three state-of-the-art automated registration techniques Regional Mutual Information, rigid Feature Neighbourhood Mutual Information (FNMI), and nonrigid FNMI (NRFNMI) were used to align these image pairs. Alignment of each composite picture was assessed on a 5-point grading scale: "Fail" (no alignment of vessels with no vessel contact), "Weak" (vessels have slight contact), "Good" (vessels with <50% contact), "Very Good" (vessels with >50% contact), and "Excellent" (complete alignment). Custom software generated an image mosaic in which the modalities were interleaved as a series of alternate 5×5-pixel blocks. These were graded independently by 3 clinically experienced observers. A total of 810 image pairs were assessed. All 3 registration techniques achieved a score of "Good" or better in >95% of the image sets. NRFNMI had the highest percentage of "Excellent" (mean: 99.6%; range, 95.2% to 99.6%), followed by Regional Mutual Information (mean: 81.6%; range, 86.3% to 78.5%) and FNMI (mean: 73.1%; range, 85.2% to 54.4%). Automated registration of optic disc images by different modalities is a feasible option for clinical application. All 3 methods provided useful levels of alignment, but the NRFNMI technique consistently outperformed the others and is recommended as a practical approach to the automated registration of multimodal disc images.

Bouncing Back from a Breakup: Attachment, Time Perspective, Mental Health, and Romantic Loss

ERIC Educational Resources Information Center

Gilbert, Steven P.; Sifers, Sarah K.

2011-01-01

Coping with a romantic breakup is a normal developmental task of emerging adulthood. Because of their role in influencing interpersonal relationships and adjustment, attachment history and time perspectives may influence resilience to romantic loss. In an online survey of 1,404 university students ages 18-25 who reported experiencing recent…

Beam Dynamics Simulation Platform and Studies of Beam Breakup in Dielectric Wakefield Structures

NASA Astrophysics Data System (ADS)

Schoessow, P.; Kanareykin, A.; Jing, C.; Kustov, A.; Altmark, A.; Gai, W.

2010-11-01

A particle-Green's function beam dynamics code (BBU-3000) to study beam breakup effects is incorporated into a parallel computing framework based on the Boinc software environment, and supports both task farming on a heterogeneous cluster and local grid computing. User access to the platform is through a web browser.

Neoproterozoic paleogeography of the Tarim Block: An extended or alternative "missing-link" model for Rodinia?

NASA Astrophysics Data System (ADS)

Wen, Bin; Evans, David A. D.; Li, Yong-Xiang

2017-01-01

Recent reconstructions of the Rodinia supercontinent and its breakup incorporate South China as a "missing link" between Australia and Laurentia, and place the Tarim craton adjacent to northwestern Australia on the supercontinent's periphery. However, subsequent kinematic evolution toward Gondwana amalgamation requires complex geometric shuffling between South China and Tarim, which cannot be easily resolved with the stratigraphic records of those blocks. Here we present new paleomagnetic data from early Ediacaran strata of northwest Tarim, and document large-scale rotation at near-constant paleolatitudes during Cryogenian time. The rotation is coeval with Rodinia breakup, and Tarim's paleolatitudes are compatible with its placement between Australia and Laurentia, either by itself as an alternative "missing link" or joined with South China in that role. At the same time, indications of subduction-related magmatism in Tarim's Neoproterozoic record suggest that Rodinia breakup was dynamically linked to subduction retreat along its northern margin. Such a model is akin to early stages of Jurassic fragmentation within southern Gondwana, and implies more complicated subduction-related dynamics of supercontinent breakup than superplume impingement alone.

The Role of the Isospin 3/2 Component in Elastic Neutron-Deuteron Scattering and in the Deuteron Breakup Reaction

NASA Astrophysics Data System (ADS)

Witała, H.; Golak, J.; Skibiński, R.; Topolnicki, K.; Kamada, H.

We discuss the importance of the three-nucleon isospin T = 3/2 component in elastic neutron-deuteron scattering and in the deuteron breakup reaction. The contribution of this amplitude originates from charge-independence breaking of the nucleon-nucleon potential. We study the magnitude of that contribution to the elastic scattering and breakup observables, taking the Av18 nucleon-nucleon potential alone or combined with the Urbana IX three-nucleon force as well as the locally regularized chiral N4LO nucleon-nucleon potential alone or supplemented by the chiral N2LO three-nucleon force. We find that the isospin T = 3/2 component is important for the breakup reaction and the proper treatment of charge-independence breaking in this case requires the inclusion of the 1S 0 state with isospin T = 3/2. For neutron-deuteron elastic scattering the T = 3/2 contributions are insignificant and charge-independence breaking can be accounted for by neglecting T = 3/2 component and using the effective t-matrix generated with the so-called “2/3 ‑ 1/3″ rule.

Transverse injection of a particle-laden liquid jet in supersonic flow: A three-phase flow

NASA Technical Reports Server (NTRS)

Schetz, J. A.; Ogg, J. C.

1980-01-01

The results of a two part study of the behavior of particle laden liquid jets injected into air are presented. Water was used as the liquid carrier and either 1-37 or 13-44 microns diam. spherical glass beads with a specific gravity of 2.8-3.0 as the particles. The observations were mainly photographic. The breakup of jets injected into still air was investigated as a function of particle loading, and the results were compared to the pure liquid jet case. The jets were found to be more stable with particles present. The length to breakup was increased, and the formation of satellite droplets was suppressed. The penetration and breakup of transverse jets in a Mach 3.0 air stream was studied. The general breakup mechanism of wave formation was found to be the same as for the all liquid case. Significant separation of the phases was observed, and the penetration of the liquid phase was reduced compared to all liquid cases at the same value of the jet to free stream momentum flux ratio.

Neutron capture cross section of {sup 14}C of astrophysical interest studied by Coulomb breakup of {sup 15}C

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

Nakamura, T.; Fukuda, N.; Aoi, N.

2009-03-15

The neutron capture reaction on {sup 14}C leading to the {sup 15}C ground state, which plays an important role in various nucleosynthesis processes, has been studied using the Coulomb breakup of {sup 15}C on a Pb target at 68 MeV/nucleon. The breakup cross section has been converted into the energy-dependent neutron capture cross section using the principle of detailed balance. The energy spectrum shows typical p-wave neutron capture characteristics, which is explained by the fact that the ground state of {sup 15}C possesses a strong single-particle s-wave component and a moderate-sized neutron halo structure. The capture cross section for themore » {sup 14}C(n,{gamma}){sup 15}C reaction derived from the present experiment has been found to be consistent with the most recent data, directly measured using a {sup 14}C target. This result assures the validity of the Coulomb breakup method in deriving the neutron capture cross section for neutron-rich nuclei.« less

Liquid-bridge stability and breakup on surfaces with contact-angle hysteresis.

PubMed

Akbari, Amir; Hill, Reghan J

2016-08-10

We study the stability and breakup of liquid bridges with a free contact line on surfaces with contact-angle hysteresis (CAH) under zero-gravity conditions. Non-ideal surfaces exhibit CAH because of surface imperfections, by which the constraints on three-phase contact lines are influenced. Given that interfacial instabilities are constraint-sensitive, understanding how CAH affects the stability and breakup of liquid bridges is crucial for predicting the drop size in contact-drop dispensing. Unlike ideal surfaces on which contact lines are always free irrespective of surface wettability, contact lines may undergo transitions from pinned to free and vice versa during drop deposition on non-ideal surfaces. Here, we experimentally and theoretically examine how stability and breakup are affected by CAH, highlighting cases where stability is lost during a transition from a pinned-pinned (more constrained) to pinned-free (less constrained) interface-rather than a critical state. This provides a practical means of expediting or delaying stability loss. We also demonstrate how the dynamic contact angle can control the contact-line radius following stability loss.

Modeling of Turbulence Effect on Liquid Jet Atomization

NASA Technical Reports Server (NTRS)

Trinh, H. P.

2007-01-01

Recent studies indicate that turbulence behaviors within a liquid jet have considerable effect on the atomization process. Such turbulent flow phenomena are encountered in most practical applications of common liquid spray devices. This research aims to model the effects of turbulence occurring inside a cylindrical liquid jet to its atomization process. The two widely used atomization models Kelvin-Helmholtz (KH) instability of Reitz and the Taylor analogy breakup (TAB) of O'Rourke and Amsden portraying primary liquid jet disintegration and secondary droplet breakup, respectively, are examined. Additional terms are formulated and appropriately implemented into these two models to account for the turbulence effect. Results for the flow conditions examined in this study indicate that the turbulence terms are significant in comparison with other terms in the models. In the primary breakup regime, the turbulent liquid jet tends to break up into large drops while its intact core is slightly shorter than those without turbulence. In contrast, the secondary droplet breakup with the inside liquid turbulence consideration produces smaller drops. Computational results indicate that the proposed models provide predictions that agree reasonably well with available measured data.

Pangea breakup and northward drift of the Indian subcontinent reproduced by a numerical model of mantle convection.

PubMed

Yoshida, Masaki; Hamano, Yozo

2015-02-12

Since around 200 Ma, the most notable event in the process of the breakup of Pangea has been the high speed (up to 20 cm yr(-1)) of the northward drift of the Indian subcontinent. Our numerical simulations of 3-D spherical mantle convection approximately reproduced the process of continental drift from the breakup of Pangea at 200 Ma to the present-day continental distribution. These simulations revealed that a major factor in the northward drift of the Indian subcontinent was the large-scale cold mantle downwelling that developed spontaneously in the North Tethys Ocean, attributed to the overall shape of Pangea. The strong lateral mantle flow caused by the high-temperature anomaly beneath Pangea, due to the thermal insulation effect, enhanced the acceleration of the Indian subcontinent during the early stage of the Pangea breakup. The large-scale hot upwelling plumes from the lower mantle, initially located under Africa, might have contributed to the formation of the large-scale cold mantle downwelling in the North Tethys Ocean.

Pangea breakup and northward drift of the Indian subcontinent reproduced by a numerical model of mantle convection

PubMed Central

Yoshida, Masaki; Hamano, Yozo

2015-01-01

Since around 200 Ma, the most notable event in the process of the breakup of Pangea has been the high speed (up to 20 cm yr−1) of the northward drift of the Indian subcontinent. Our numerical simulations of 3-D spherical mantle convection approximately reproduced the process of continental drift from the breakup of Pangea at 200 Ma to the present-day continental distribution. These simulations revealed that a major factor in the northward drift of the Indian subcontinent was the large-scale cold mantle downwelling that developed spontaneously in the North Tethys Ocean, attributed to the overall shape of Pangea. The strong lateral mantle flow caused by the high-temperature anomaly beneath Pangea, due to the thermal insulation effect, enhanced the acceleration of the Indian subcontinent during the early stage of the Pangea breakup. The large-scale hot upwelling plumes from the lower mantle, initially located under Africa, might have contributed to the formation of the large-scale cold mantle downwelling in the North Tethys Ocean. PMID:25673102

Experimental Study of Three-Nucleon Dynamics in the Dp Breakup Collisions Using the WASA Detector

NASA Astrophysics Data System (ADS)

Kłos, B.; Ciepał, I.; Jamróz, B.; Khatri, G.; Kistryn, S.; Kozela, A.; Magiera, A.; Parol, W.; Skwira-Chalot, I.; Stephan, E.

2017-03-01

Until recently, all calculations of breakup observables were carried out in a non-relativistic regime. The relativistic treatment of the breakup reaction in 3 N system is quite a new achievement. The detailed study of various aspects of few-nucleon system dynamics in medium energy region, with a particular emphasis on investigation of relativistic effects and their interplay with three nucleon force (3NF) becomes feasible with increasing available energy in the three nucleon system. Therefore an experiment to investigate the ^1H(d, pp)n breakup cross section using a deuteron beam of 300, 340, 380 and 400 MeV and the WASA detector has been performed at COSY-Jülich. The almost 4π geometry of the WASA detector gives an unique possibility to study variety of kinematic configurations, which reveal different sensitivity to aspects of dynamics of the three nucleon system. The main steps of the analysis, including energy calibration, PID, normalization and efficiency studies, and their impact on the final accuracy of the result, are discussed.

Facebook Surveillance of Former Romantic Partners: Associations with PostBreakup Recovery and Personal Growth

PubMed Central

2012-01-01

Abstract Previous research has found that continuing offline contact with an ex-romantic partner following a breakup may disrupt emotional recovery. The present study examined whether continuing online contact with an ex-partner through remaining Facebook friends and/or engaging in surveillance of the ex-partner's Facebook page inhibited postbreakup adjustment and growth above and beyond offline contact. Analysis of the data provided by 464 participants revealed that Facebook surveillance was associated with greater current distress over the breakup, more negative feelings, sexual desire, and longing for the ex-partner, and lower personal growth. Participants who remained Facebook friends with the ex-partner, relative to those who did not remain Facebook friends, reported less negative feelings, sexual desire, and longing for the former partner, but lower personal growth. All of these results emerged after controlling for offline contact, personality traits, and characteristics of the former relationship and breakup that tend to predict postbreakup adjustment. Overall, these findings suggest that exposure to an ex-partner through Facebook may obstruct the process of healing and moving on from a past relationship. PMID:22946958

Anatomy of an Asteroid Breakup

NASA Astrophysics Data System (ADS)

Kohler, Susanna

2017-05-01

A team of scientists has observed the breakup of an asteroid as it orbits the Sun. In a new study, they reveal what theyve learned from their ground- and space-based observations of this disintegration.These Hubble images show the fragments of R3 in higher resolution over the span of October 2013 to February 2014. [Jewitt et al. 2017]Observations of DisintegrationActive asteroids are objects that move on asteroid-like orbits while displaying comet-like behavior. The cause of their activity can vary ranging from outgassing as the asteroid heats up in its solar approach, to expelled debris from a collision, to the entire asteroid flying apart because its spinning too fast.Led by David Jewitt (University of California at Los Angeles), a team of scientists has analyzed observations of the disintegrating asteroid P/2013 R3. The observations span two years and were made by a number of telescopes, including Hubble, Keck (in Hawaii), Magellan (in Chile), and the Very Large Telescope (in Chile).A schematic diagram of the different fragments of R3 and how they relate to each other. Black numbers estimate the fragment separation velocities; red numbers estimate the separation date. [Jewitt et al. 2017]Jewitt and collaborators then used these observations and a bit of modeling to understand what asteroid R3 was like originally, what its pieces are doing now, and what caused it to break up.Cause of the BreakupThe team found that P/2013 R3 broke up into at least 13 pieces, the biggest of which was likely no more than 100-200 meters in size. The original asteroid was probably less than 400 m in radius.By measuring the velocities of the fragments in the various observations, Jewitt and collaborators were able to work backward to determine when each piece broke off. They found that the fragmentation process was spread out over the span of roughly 5 months suggesting that the asteroids breakup wasnt impact-related (otherwise the fragmentation would likely have been all at once rather than gradual).Timeline of the destruction of R3. Calendar dates are in black, day-of-year dates are in red. The letters below the timeline indicate observations. [Jewitt et al. 2017]So if it wasnt an impact, what caused the breakup of R3? Tidal stresses are unlikely; the asteroid wasnt close enough to the Sun or a planet to experience strong pulls. Gas pressure from sublimating ice also falls short of being strong enough to have caused the disruption, according to the authors calculations.The authors conclude that the most plausible cause of R3s breakup was rotational instability. If an asteroid is made up of a collection of rocky material loosely gravitationally bound in whats known as a rubble-pile composition, then it tends to fly apart if the asteroid spins faster than once every 2.2 hours. The authors show that torques from radiation or anisotropic sublimation could have driven R3 to spin this quickly on a relatively short timescale.A Dusty EndZodiacal light, caused by scattering by dust in the Zodiacal Cloud. [ESO]Lastly, Jewitt and collaborators examine the debris cloud released by the breakup of R3. They use these observations to estimate how much debris disrupted asteroids likely contribute to the Zodiacal Cloud, the cloud of dust found in our solar system, primarily between the Sun and Jupiter.The authors estimate that the fractional contribution by asteroids like R3 is roughly 4% consistent with models that suggest that asteroid dust is a measurable, but not dominant, contributor to the Zodiacal Cloud. Future sky surveys will allow us to better examine this contribution.CitationDavid Jewitt et al 2017 AJ 153 223. doi:10.3847/1538-3881/aa6a57

Characterization of the 2012-044C BRIZ-M Upper Stage Breakup

NASA Astrophysics Data System (ADS)

Matney, M. J.; Hamilton, J.; Horstman, M.; Papanyan, V.

2013-08-01

On 6 August 2012, Russia launched two commercial satellites aboard a Proton rocket, and attempted to place them in geosynchronous orbit using a Briz-M upper stage (2012-044C, SSN 38746). Unfortunately, the upper stage failed early in its burn and was left stranded in an elliptical orbit with a perigee in low Earth orbit (LEO). Because the stage failed with much of its fuel on board, it was deemed a significant breakup risk. These fears were confirmed when it broke up 16 October, creating a large cloud of debris with perigees below that of the International Space Station. The debris cloud was tracked by the U.S. Space Surveillance Network (SSN), which can reliably detect and track objects down to about 10 cm in size. Because of the unusual geometry of the breakup, there was an opportunity for the NASA Orbital Debris Program Office to use specialized radar assets to characterize the extent of the debris cloud in sizes smaller than the standard debris tracked by the SSN. This paper describes the observation campaign to measure the small particle distributions of this cloud and presents the results of the data analysis. We shall compare the data to the modelled size distribution, number, and shape of the cloud, and what implications this may have for future breakup debris models. We shall conclude the paper with a discussion about how this measurement process can be improved for future breakups.

Characterization of the 2012-044C Briz-M Upper Stage Breakup

NASA Technical Reports Server (NTRS)

Matney, M. J.; Hamilton, J.; Horstman, M.; Papanyan, V.

2013-01-01

On 6 August, 2012, Russia launched two commercial satellites aboard a Proton rocket, and attempted to place them in geosynchronous orbit using a Briz-M upper stage (2012-044C, SSN 38746). Unfortunately, the upper stage failed early in its burn and was left stranded in an elliptical orbit with a perigee in low Earth orbit (LEO). Because the stage failed with much of its fuel on board, it was deemed a significant breakup risk. These fears were confirmed when it broke up 16 October, creating a large cloud of debris with perigees below that of the International Space Station. The debris cloud was tracked by the US Space Surveillance Network (SSN), which can reliably detect and track objects down to about 10 cm in size. Because of the unusual geometry of the breakup, there was an opportunity for NASA Orbital Debris Program Office to use specialized radar assets to characterize the extent of the debris cloud in sizes smaller than the standard debris tracked by the SSN. This paper will describe the observation campaign to measure the small particle distributions of this cloud, and presents the results of the analysis of the data. We shall compare the data to the modelled size distribution, number, and shape of the cloud, and what implications this may have for future breakup debris models. We shall conclude the paper with a discussion how this measurement process can be improved for future breakups.

Numerical simulation of liquid droplet breakup in supersonic flows

NASA Astrophysics Data System (ADS)

Liu, Nan; Wang, Zhenguo; Sun, Mingbo; Wang, Hongbo; Wang, Bing

2018-04-01

A five-equation model based on finite-difference frame was utilized to simulate liquid droplet breakup in supersonic flows. To enhance the interface-capturing quality, an anti-diffusion method was introduced as a correction of volume-fraction after each step of calculation to sharpen the interface. The robustness was guaranteed by the hybrid variable reconstruction in which the second-order and high-order method were respectively employed in discontinuous and continuous flow fields. According to the recent classification of droplet breakup regimes, the simulations lay in the shear induced entrainment regime. Comparing to the momentum of the high-speed air flows, surface tension and viscid force were negligible in both two-dimensional and three-dimensional simulations. The inflow conditions were set as Mach 1.2, 1.5 and 1.8 to reach different dynamic pressure with the liquid to gas density ratio being 1000 initially. According to the results of simulations, the breakup process was divided into three stages which were analyzed in details with the consideration of interactions between gas and liquid. The shear between the high-speed gas flow and the liquid droplet was found to be the sources of surface instabilities on windward, while the instabilities on the leeward side were originated by vortices. Movement of the liquid mass center was studied, and the unsteady acceleration was observed. In addition, the characteristic breakup time was around 1.0 based on the criterion of either droplet thickness or liquid volume fraction.

Characterization of the 2012-044c Briz-M Upper Stage Breakup

NASA Technical Reports Server (NTRS)

Matney, M. J.; Hamilton, Joseph; Papanyan, Valen

2013-01-01

On 6 August, 2012, Russia launched two commercial satellites aboard a Proton rocket, and attempted to place them in geosynchronous orbit using a Briz-M upper stage (2012-044C, SSN 38746). Unfortunately, the upper stage failed early in its burn and was left stranded in an elliptical orbit with a perigee in low Earth orbit (LEO). Because the stage failed with much of its fuel on board, it was deemed a significant breakup risk. These fears were confirmed when it broke up 16 October, creating a large cloud of debris with perigees below that of the International Space Station. The debris cloud was tracked by the US Space Surveillance Network (SSN), which can reliably detect and track objects down to about 10 cm in size. Because of the unusual geometry of the breakup, there was an opportunity for NASA Orbital Debris Program Office to request radar assets to characterize the extent of the debris cloud in sizes smaller than the standard debris tracked by the SSN. This paper will describe the observation campaign to measure the small particle distributions of this cloud, and presents the results of the analysis of the data. We shall compare the data to the modelled size distribution, number, and shape of the cloud, and what implications this may have for future breakup debris models. We shall conclude the paper with a discussion how this measurement process can be improved for future breakups.

High-fidelity modeling and impact footprint prediction for vehicle breakup analysis

NASA Astrophysics Data System (ADS)

Ling, Lisa

For decades, vehicle breakup analysis had been performed for space missions that used nuclear heater or power units in order to assess aerospace nuclear safety for potential launch failures leading to inadvertent atmospheric reentry. Such pre-launch risk analysis is imperative to assess possible environmental impacts, obtain launch approval, and for launch contingency planning. In order to accurately perform a vehicle breakup analysis, the analysis tool should include a trajectory propagation algorithm coupled with thermal and structural analyses and influences. Since such a software tool was not available commercially or in the public domain, a basic analysis tool was developed by Dr. Angus McRonald prior to this study. This legacy software consisted of low-fidelity modeling and had the capability to predict vehicle breakup, but did not predict the surface impact point of the nuclear component. Thus the main thrust of this study was to develop and verify the additional dynamics modeling and capabilities for the analysis tool with the objectives to (1) have the capability to predict impact point and footprint, (2) increase the fidelity in the prediction of vehicle breakup, and (3) reduce the effort and time required to complete an analysis. The new functions developed for predicting the impact point and footprint included 3-degrees-of-freedom trajectory propagation, the generation of non-arbitrary entry conditions, sensitivity analysis, and the calculation of impact footprint. The functions to increase the fidelity in the prediction of vehicle breakup included a panel code to calculate the hypersonic aerodynamic coefficients for an arbitrary-shaped body and the modeling of local winds. The function to reduce the effort and time required to complete an analysis included the calculation of node failure criteria. The derivation and development of these new functions are presented in this dissertation, and examples are given to demonstrate the new capabilities and the improvements made, with comparisons between the results obtained from the upgraded analysis tool and the legacy software wherever applicable.

Impacts des conditions de glace de mer sur la reproduction des eiders a duvet (Somateria mollissima) nichant dans l'Arctique canadien

NASA Astrophysics Data System (ADS)

Jean-Gagnon, Frankie

Environmental and climatic conditions on the breeding site affect the reproduction and dynamics of avian populations. The arctic sea ice is an essential environmental component to many marine species, and the sea ice dynamic can affect seabird reproduction. Our objective was to study the role of sea ice conditions early in the season on breeding decisions of Common eiders nesting at East Bay in the Canadian Arctic. Since eider females forage intensively at river mouths at East Bay during the pre-breeding period, we made the assumption that the timing of ice-breakup at river mouths influences the breeding propensity and the timing of laying through an effect on resources accessibility. Using radar satellite images acquired for the summers 2002 to 2013, we determined the timing of ice-breakup at river mouths and the ice-free conditions in the bay for each year. The timing of ice-breakup in June varied greatly between years and was strongly correlated to the day of ice-free conditions in the bay in July. Our results also demonstrated that a late ice-breakup induces a decrease in breeding propensity and a delay in the laying date in common eiders. However, females in lower body condition were more strongly affected by a late ice-breakup than females in better condition. These results shed light on the critical importance of the timing of resources accessibility for reproductive decisions and success of avian species breeding in the Arctic. Furthermore, the timing of ice-breakup could be used as an environmental cue by eiders to adjust their timing of breeding. Globally, our study allows us to better understand the mechanisms underlying the effects of sea ice conditions on breeding decisions of marine birds. This work could be useful to anticipate the effect of climate change on population dynamics of birds breeding in the Arctic.

Primary atomization of liquid jets issuing from rocket engine coaxial injectors

NASA Astrophysics Data System (ADS)

Woodward, Roger D.

1993-01-01

The investigation of liquid jet breakup and spray development is critical to the understanding of combustion phenomena in liquid-propellant rocket engines. Much work has been done to characterize low-speed liquid jet breakup and dilute sprays, but atomizing jets and dense sprays have yielded few quantitative measurements due to their optical opacity. This work focuses on a characteristic of the primary breakup process of round liquid jets, namely the length of the intact liquid core. The specific application considered is that of shear-coaxial type rocket engine injectors. Real-time x-ray radiography, capable of imaging through the dense two-phase region surrounding the liquid core, has been used to make the measurements. Nitrogen and helium were employed as the fuel simulants while an x-ray absorbing potassium iodide aqueous solution was used as the liquid oxygen (LOX) simulant. The intact-liquid-core length data have been obtained and interpreted to illustrate the effects of chamber pressure (gas density), injected-gas and liquid velocities, and cavitation. The results clearly show that the effect of cavitation must be considered at low chamber pressures since it can be the dominant breakup mechanism. A correlation of intact core length in terms of gas-to-liquid density ratio, liquid jet Reynolds number, and Weber number is suggested. The gas-to-liquid density ratio appears to be the key parameter for aerodynamic shear breakup in this study. A small number of hot-fire, LOX/hydrogen tests were also conducted to attempt intact-LOX-core measurements under realistic conditions in a single-coaxial-element rocket engine. The tests were not successful in terms of measuring the intact core, but instantaneous imaging of LOX jets suggests that LOX jet breakup is qualitatively similar to that of cold-flow, propellant-simulant jets. The liquid oxygen jets survived in the hot-fire environment much longer than expected, and LOX was even visualized exiting the chamber nozzle under some conditions. This may be an effect of the single element configuration.

Aligning flaky FeSiAl particles with a two-dimensional rotating magnetic field to improve microwave-absorbing and shielding properties of composites

NASA Astrophysics Data System (ADS)

Liu, Chang; Cai, Jun; Duan, Yubing; Li, Xinghao; Zhang, Deyuan

2018-07-01

In order to enhance the microwave-absorbing and shielding properties of the composites, the flaky FeSiAl particles embedded in an epoxy polymer were aligned with a two-dimensional rotating magnetic field. The morphologies, electromagnetic (EM) characteristics, and microwave-absorbing and shielding properties of the unaligned and aligned FeSiAl/epoxy composites were investigated. The results showed that after alignment treatment, the flaky FeSiAl particles tend to orient uniformly in the rotating magnetic field, and the permittivity and permeability of the aligned composites were increased in the frequency range of 1-18 GHz compared with that of randomly distributed composites. The calculated microwave-absorbing properties indicated that the peak value of the return loss (RL) of the aligned composites can reach 8.8 dB, compared with 5.8 dB of the unaligned composites of 2.5 mm in thickness (60 wt%); and the bandwidth with RL value more than 6 dB is in a wider frequency range from 1 to 2.8 GHz. And the calculated shielding effectiveness (SE) of the aligned composites is 1.1-3 times higher than that of unaligned one in every thickness, and the maximum SE of the aligned one is 31.8 dB at 18 GHz with a thickness of 2.5 mm.

Diffractive optics for precision alignment of Euclid space telescope optics (Conference Presentation)

NASA Astrophysics Data System (ADS)

Asfour, Jean-Michel; Weidner, Frank; Bodendorf, Christof; Bode, Andreas; Poleshchuk, Alexander G.; Nasyrov, Ruslan K.; Grupp, Frank; Bender, Ralf

2017-09-01

We present a method for precise alignment of lens elements using specific Computer Generated Hologram (CGH) with an integrated Fizeau reference flat surface and a Fizeau interferometer. The method is used for aligning the so called Camera Lens Assembly for ESAs Euclid telescope. Each lens has a corresponding annular area on the diffractive optics, which is used to control the position of each lens. The lenses are subsequently positioned using individual annular rings of the CGH. The overall alignment accuracy is below 1 µm, the alignment sensitivity is in the range of 0.1 µm. The achieved alignment accuracy of the lenses relative to each other is mainly depending on the stability in time of the alignment tower. Error budgets when using computer generated holograms and physical limitations are explained. Calibration measurements of the alignment system and the typically reached alignment accuracies will be shown and discussed.

NASA's Orbital Debris Optical and IR Ground-Based Observing Program Utilizing the MCAT, UKIRT, and Magellan Telescopes

NASA Technical Reports Server (NTRS)

Lederer, Susan; Cowardin, H. M.; Buckalew, B.; Frith, J.; Hickson, P.; Pace, L.; Matney, M.; Anz-Meador, P.; Seitzer, P.; Stansbery, E.;

On the Relativistic Separable Functions for the Breakup Reactions

NASA Astrophysics Data System (ADS)

Bondarenko, Serge G.; Burov, Valery V.; Rogochaya, Elena P.

2018-02-01

In the paper the so-called modified Yamaguchi function for the Bethe-Salpeter equation with a separable kernel is discussed. The type of the functions is defined by the analytic stucture of the hadron current with breakup - the reactions with interacting nucleon-nucleon pair in the final state (electro-, photo-, and nucleon-disintegration of the deuteron).

Type of Writing Task and College Students' Meaning Making Following a Romantic Breakup

ERIC Educational Resources Information Center

Primeau, Joanna E.; Servaty-Seib, Heather L.; Enersen, Donna

2013-01-01

In this study, the authors examined the potential effects of type of writing task (loss/gain vs. general prompt) on the narrative content offered by college students (N = 41) who experienced romantic breakup. Qualitative analyses indicated differences based on type of writing task. Students who received the loss/gain prompt exhibited more…

Rayleigh instability at small length scales.

PubMed

Gopan, Nandu; Sathian, Sarith P

2014-09-01

The Rayleigh instability (also called the Plateau-Rayleigh instability) of a nanosized liquid propane thread is investigated using molecular dynamics (MD). The validity of classical predictions at small length scales is verified by comparing the temporal evolution of liquid thread simulated by MD against classical predictions. Previous works have shown that thermal fluctuations become dominant at small length scales. The role and influence of the stochastic nature of thermal fluctuations in determining the instability at small length scale is also investigated. Thermal fluctuations are seen to dominate and accelerate the breakup process only during the last stages of breakup. The simulations also reveal that the breakup profile of nanoscale threads undergo modification due to reorganization of molecules by the evaporation-condensation process.

Universality of fragment shapes.

PubMed

Domokos, Gábor; Kun, Ferenc; Sipos, András Árpád; Szabó, Tímea

2015-03-16

The shape of fragments generated by the breakup of solids is central to a wide variety of problems ranging from the geomorphic evolution of boulders to the accumulation of space debris orbiting Earth. Although the statistics of the mass of fragments has been found to show a universal scaling behavior, the comprehensive characterization of fragment shapes still remained a fundamental challenge. We performed a thorough experimental study of the problem fragmenting various types of materials by slowly proceeding weathering and by rapid breakup due to explosion and hammering. We demonstrate that the shape of fragments obeys an astonishing universality having the same generic evolution with the fragment size irrespective of materials details and loading conditions. There exists a cutoff size below which fragments have an isotropic shape, however, as the size increases an exponential convergence is obtained to a unique elongated form. We show that a discrete stochastic model of fragmentation reproduces both the size and shape of fragments tuning only a single parameter which strengthens the general validity of the scaling laws. The dependence of the probability of the crack plan orientation on the linear extension of fragments proved to be essential for the shape selection mechanism.

Rotation-induced YORP break-up of small bodies to produce post-main-sequence debris

NASA Astrophysics Data System (ADS)

Veras, D.; Jacobson, S. A.; Gänsicke, B. T.

2017-09-01

We hypothesize that the in situ break-up of small bodies such as asteroids spun to fission during the giant branch phases of stellar evolution provides an important contribution to the debris orbiting and ultimately polluting white dwarfs. The YORP (Yarkovsky-O'Keefe-Radviesvki-Paddock) effect, which arises from radiation pressure, accelerates the spin rate of asymmetric asteroids, which can eventually shear themselves apart. This pressure is maintained and enhanced around dying stars because the outward push of an asteroid due to stellar mass loss is insignificant compared to the resulting stellar luminosity increase. Consequently, giant star radiation will destroy nearly all bodies with radii in the range 100 m-10 km that survive their parent star's main-sequence lifetime within a distance of about 7 au; smaller bodies are spun apart to their strongest, competent components. This estimate is conservative and would increase for highly asymmetric shapes or incorporation of the inward drag due to giant star stellar wind. The resulting debris field, which could extend to thousands of au, may be perturbed by remnant planetary systems to reproduce the observed dusty and gaseous discs which accompany polluted white dwarfs.

Intermediate Energies for Nuclear Astrophysics and the Development of a Position Sensitive Microstrip Detector System

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

Sobotka, Lee G.; Blackmon, J.; Bertulani, C.

2015-12-30

The chemical elements are made at astrophysical sites through a sequence of nuclear reactions often involving unstable nuclei. The overarching aim of this project is to construct a system that allows for the inverse process of nucleosynthesis (i.e. breakup of heavier nuclei into lighter ones) to be studied in high efficiency. The specific problem to be overcome with this grant is inadequate dynamic range and (triggering) threshold to detect the products of the breakup which include both heavy ions (with large energy and large deposited energy in a detector system) and protons (with little energy and deposited energy.) Early onmore » in the grant we provided both TAMU and RIKEN (the site of the eventual experiments) with working systems based on the existing technology. This technology could be used with either an external preamplifier that was to be designed and fabricated by our RIKEN collaborators or upgraded by replacing the existing chip with one we designed. The RIKEN external preamplifier project never can to completion but our revised chip was designed, fabricated, used in a test experiment and performs as required.« less

Period Doubling, Tripling, and Quintupling in the Break-up of a Liquid Jet Driven Transversely to Axis of Motion

NASA Astrophysics Data System (ADS)

Hussein, Salome; Bradley, Stuart; Willmott, Geoff

2017-11-01

The Rayleigh-Plateau instability has been the subject of study for over a century. Many modern technologies now actively take advantage of this phenomenon, from ink-jet printing to fuel injection systems. In pursuit of a precision fluid delivery system, we aimed to design a monodisperse droplet generator. One approach used a piezoelectric element to oscillate the jet transversely to the axis of motion. While at certain frequencies (approx. 1.0kHz) we observed the expected and desired jet breakup behavior, lower frequencies yielded a serpentine profile along the jet, with a node and anti-node, before breaking up. In addition, within a range of driving frequencies, we observed the jet splitting into multiple discrete drop trajectories, intermittently converging back into one in between those instances, then finally entering the region where the RP instability dominated. While initially considered an undesirable aspect of the design, we will demonstrate that these regions are predictable and robust enough to offer a much finer degree of control over spray coverage - as opposed to a binary choice between the pinpoint precision of a monodisperse stream and an imprecise conventional spray. New Zealand Ministry of Business, Innovation, and Employment.

Explaining a Consistent Morning NOx Maximum in the Clean Air Forest Boundary Layer

NASA Astrophysics Data System (ADS)

Shepson, P. B.; Alaghmand, M.; Bertman, S. B.; Carroll, M.; Edburg, S. L.; Jobson, B. T.; Keutsch, F. N.; Lamb, B. K.; Starn, T.; Stevens, P. S.; Wallace, W.; Zhou, X.

2010-12-01

Measurements of nitrogen oxides (NOx) at continental surface sites have frequently revealed the presence of an early morning maximum in the NOx concentration. While this observation has most often been interpreted as the result of downward mixing associated with breakup of the nocturnal inversion, the morning NOx peak often occurs earlier than the NBL breakup. Given the importance of NOx to boundary layer photochemistry near forested environments, it is essential that this phenomenon be well understood. Here we examine a variety of measurements, including NOx measurements at various heights, during the 1998, 2001, 2008, and 2009 (CABINEX) summer intensives of the Program for Research on Oxidants: PHotochemistry, Emissions and Transport (PROPHET), at the University of Michigan Biological Station in Northern Michigan. We will discuss the results, in terms of the extent to which the observations support/refute each of the potential drivers of the morning NOx peak: 1) downward mixing, 2) photochemistry on the various surfaces present, 3) soil emissions, and 4) local and long range transport of anthropogenic NOx, and we will report on our conclusions as to the predominant/likely explanation(s) for this phenomenon.

Universality of fragment shapes

PubMed Central

Domokos, Gábor; Kun, Ferenc; Sipos, András Árpád; Szabó, Tímea

2015-01-01

The shape of fragments generated by the breakup of solids is central to a wide variety of problems ranging from the geomorphic evolution of boulders to the accumulation of space debris orbiting Earth. Although the statistics of the mass of fragments has been found to show a universal scaling behavior, the comprehensive characterization of fragment shapes still remained a fundamental challenge. We performed a thorough experimental study of the problem fragmenting various types of materials by slowly proceeding weathering and by rapid breakup due to explosion and hammering. We demonstrate that the shape of fragments obeys an astonishing universality having the same generic evolution with the fragment size irrespective of materials details and loading conditions. There exists a cutoff size below which fragments have an isotropic shape, however, as the size increases an exponential convergence is obtained to a unique elongated form. We show that a discrete stochastic model of fragmentation reproduces both the size and shape of fragments tuning only a single parameter which strengthens the general validity of the scaling laws. The dependence of the probability of the crack plan orientation on the linear extension of fragments proved to be essential for the shape selection mechanism. PMID:25772300

Vertically aligned carbon nanopillars with size and spacing control for a transparent field emission display.

PubMed

Lee, Seok Woo; Lee, Chang Hwa; Lee, Jung A; Lee, Seung S

2013-01-18

A top-down fabrication method is presented for vertically aligned carbon nanopillars (CNPs) using photolithography and pyrolysis. The modified backside exposure method of photolithography fabricates vertically aligned polymer (SU-8) nanopillars. The pyrolysis process, which transforms the polymer to amorphous carbon, reliably produces vertically aligned CNPs with widths ranging from 100 to 400 nm. The CNPs can be used as a transparent field emission cathode for a transparent display and light emission is observed.

Combined 40Ar/39Ar and Fission-Track study of the Freetown Layered Igneous Complex, Freetown, Sierra Leone, West Africa: Implications for the Initial Break-up of Pangea to form the Central Atlantic Ocean and Insight into the Post-rift Evolution of the Sie

NASA Astrophysics Data System (ADS)

Barrie, Ibrahim; Wijbrans, Jan; Andriessen, Paul; Beunk, Frank; Strasser-King, Victor; Fode, Daniel

2010-05-01

Sierra Leone lies within the south-western part of the West African Craton and comprises two major Archaean structural divisions: a low-grade granite-greenstone terrane characterised by N-S striking structures and a NW-SE striking highly metamorphosed belt of strained rocks that form the coastal margin of the craton. Intruded into the belt is the Freetown Layered Igneous Complex (FLIC), a tholeiitic magamtic body emplaced prior to or during the break-up of Pangea to form the Central Atlantic Ocean and, forming today the high ground of the coastal outline of Sierra Leone which is one of the most distinctive features on the West African coast. The break-up of Pangaea to form the Central Atlantic and its passive margins began in the Early Jurassic. Geo-tectonically, the break-up was particularly characterised by the formation of the Central Atlantic Magmatic Province (CAMP), covering once-contiguous parts of North America, Europe, Africa and South America. The FLIC forming part of the heart of CAMP is the largest single layered igneous intrusive yet known on either side of the Central Atlantic, measuring on surface, 65 x 14 x 7 km. Geophysical investigations indicate that the intrusion extends offshore to a depth of about 20 km. Geologically the Complex is a rhythmically layered elongated ultramafic-mafic lopolith divisible into 4 major zones each comprising repeated sequences of troctolitic, gabbroic and anorthositic rocks. An idealised unit of layering is from base upwards: dunite, troctolite, olivine-gabbro, leuco-gabbro, gabbro-norite and anorthosite cumulates. 40Ar-39Ar age spectra and 40Ar/36Ar versus 39Ar/36Ar isochron plots obtained by stepwise-heating experiments on plagioclases, biotites and amphiboles from troctolites, olivine-gabbros, gabbro-norites and anorthosites of the four zones yield plateau and isochron ages that seem to depict the cooling history of the Complex after emplacement. The biotites and some of the plagioclases and amphiboles give very good plateaus that range from 196.3 ± 3 Ma to 232.1 ± 9 Ma with the best-fit isochron plots showing a range from 193.3± 10 Ma to 234.1 ± 11 Ma. Because these dates represent cooling ages, we interpret them as representing a minimum intrusion-age of the Complex implying that its true emplacement age might be somewhat older than 230 Ma. Given that most established CAMP ages revolve around 200 Ma or younger, we hypothesise that FLIC represents a hitherto unknown pre-CAMP magmatic event that might have thermally triggered the initial break-up of Pangaea to form the Central Atlantic. This view is consistent with field-observations that the Complex is cross-cut by predominantly coast-parallel mafic dykes attributed to the CAMP dyke-swarm. To ascertain the hypothesis, we are currently carrying out U-Pb zircon dating to establish, precisely, the true emplacement age of the Complex. The Fission-track ages vary from 91.7 ± 7 Ma to 114.6 ± 9 Ma. This age range shows that after emplacement and crystallisation, the FLIC underwent an extremely slow cooling for a long period of time. This in turn implies that after the break-up of Pangea to form, in part, the Sierra Leone margin, a late and slow uplift (Erosion/denudation) that took place during the Cretaceous was a very important geological process that characterised the post-rift evolution of the margin. References: Barrie, I.J., P.A.M. Andriessen, F.F. Beunk, J.R. Wijbrans, V.E.H. Strasser-King, D.V.A.Fode. (2006). Tectonothermal Evolution of the Sierra Leone Passive Continental Margin, West Africa: Constraints from Thermochronology. Geochemica et Cosmochemica Acta 70 (18): A36- A36 Suppl. S Aug-Sep 2006. Marzoli, A., P.R. Renne, E.M. Piccirillo, M. Ernesto, G. Bellieni, A De Min. (1999). Extensive 200-Million-Year-Old Continental Flood Basalts of the Central Atlantic Magmatic Province. Science284: 616-618. McHone, J.G. (2000). Non-plume magmatism and rifting during the opening of the central Atlantic Ocean. Tectonophysics, 316: 287-296. Umeji, A.C. (1983). Geochemistry and Mineralogy of the Freetown Layered Basic Igneous Complex of Sierra Leone. Chemical Geology, 39: 17-38. Wells, M.K. (1962). Structure and Petrology of the Freetown Layered Basic Complex of Sierra Leone. Overseas Geol. Mineral. Res. Bull. Suppl., 4, 115 pp. Williams, H.R. (1986). The Archaean Kaila Group of Western Sierra Leone: Geology and Relations with adjacent Granite-Greenstone Terrane. Precambrian Research, 38: 201-213.

Functional Alignment of Metabolic Networks.

PubMed

Mazza, Arnon; Wagner, Allon; Ruppin, Eytan; Sharan, Roded

2016-05-01

Network alignment has become a standard tool in comparative biology, allowing the inference of protein function, interaction, and orthology. However, current alignment techniques are based on topological properties of networks and do not take into account their functional implications. Here we propose, for the first time, an algorithm to align two metabolic networks by taking advantage of their coupled metabolic models. These models allow us to assess the functional implications of genes or reactions, captured by the metabolic fluxes that are altered following their deletion from the network. Such implications may spread far beyond the region of the network where the gene or reaction lies. We apply our algorithm to align metabolic networks from various organisms, ranging from bacteria to humans, showing that our alignment can reveal functional orthology relations that are missed by conventional topological alignments.

Use of implanted gold fiducial markers with MV-CBCT image-guided IMRT for pancreatic tumours.

PubMed

Packard, Matthew; Gayou, Olivier; Gurram, Krishna; Weiss, Brandon; Thakkar, Shyam; Kirichenko, Alexander

2015-08-01

Visualisation of soft tissues such as pancreatic tumours by mega-voltage cone beam CT (MV-CBCT) is frequently difficult and daily localisation is often based on more easily seen adjacent bony anatomy. Fiducial markers implanted into pancreatic tumours serve as surrogates for tumour position and may more accurately represent absolute tumour position. Differences in daily shifts based on alignment to implanted fiducial markers vs. alignment to adjacent bony anatomy were compared. Gold fiducial markers were placed into the pancreatic tumour under endoscopic ultrasound (EUS) guidance in 12 patients. Patients subsequently received image-guided intensity-modulated radiation therapy (IG-IMRT). MV-CBCT was performed prior to each fraction and isocentre shifts were performed based on alignment to the fiducial markers. We retrospectively reviewed archived MV-CBCT datasets and calculated shift differences in the left-right (LR), superior-inferior (SI) and anterior-posterior (AP) axes relative to shifts based on alignment to adjacent bony anatomy. Two hundred forty-three fractions were analysed. The mean absolute difference in isocentre shifts between the fiducial markers and those aligned to bony anatomy was 3.4 mm (range 0-13 mm), 6.3 mm (range 0-21 mm) and 2.6 mm (range 0-12 mm), in LR, SI and AP directions, respectively. The mean three-dimensional vector shift difference between markers vs. bony anatomy alignment was 8.6 mm. These data suggest that fiducial markers used in conjunction with MV-CBCT improve the accuracy of daily target delineation compared with localisation using adjacent bony anatomy and that gold fiducial markers using MV-CBCT alignment are a viable option for target localisation during IG-IMRT. © 2015 The Royal Australian and New Zealand College of Radiologists.

The fractured landscape of RNA-seq alignment: the default in our STARs.

PubMed

Ballouz, Sara; Dobin, Alexander; Gingeras, Thomas R; Gillis, Jesse

2018-06-01

Many tools are available for RNA-seq alignment and expression quantification, with comparative value being hard to establish. Benchmarking assessments often highlight methods' good performance, but are focused on either model data or fail to explain variation in performance. This leaves us to ask, what is the most meaningful way to assess different alignment choices? And importantly, where is there room for progress? In this work, we explore the answers to these two questions by performing an exhaustive assessment of the STAR aligner. We assess STAR's performance across a range of alignment parameters using common metrics, and then on biologically focused tasks. We find technical metrics such as fraction mapping or expression profile correlation to be uninformative, capturing properties unlikely to have any role in biological discovery. Surprisingly, we find that changes in alignment parameters within a wide range have little impact on both technical and biological performance. Yet, when performance finally does break, it happens in difficult regions, such as X-Y paralogs and MHC genes. We believe improved reporting by developers will help establish where results are likely to be robust or fragile, providing a better baseline to establish where methodological progress can still occur.

Heuristics for multiobjective multiple sequence alignment.

PubMed

Abbasi, Maryam; Paquete, Luís; Pereira, Francisco B

2016-07-15

Aligning multiple sequences arises in many tasks in Bioinformatics. However, the alignments produced by the current software packages are highly dependent on the parameters setting, such as the relative importance of opening gaps with respect to the increase of similarity. Choosing only one parameter setting may provide an undesirable bias in further steps of the analysis and give too simplistic interpretations. In this work, we reformulate multiple sequence alignment from a multiobjective point of view. The goal is to generate several sequence alignments that represent a trade-off between maximizing the substitution score and minimizing the number of indels/gaps in the sum-of-pairs score function. This trade-off gives to the practitioner further information about the similarity of the sequences, from which she could analyse and choose the most plausible alignment. We introduce several heuristic approaches, based on local search procedures, that compute a set of sequence alignments, which are representative of the trade-off between the two objectives (substitution score and indels). Several algorithm design options are discussed and analysed, with particular emphasis on the influence of the starting alignment and neighborhood search definitions on the overall performance. A perturbation technique is proposed to improve the local search, which provides a wide range of high-quality alignments. The proposed approach is tested experimentally on a wide range of instances. We performed several experiments with sequences obtained from the benchmark database BAliBASE 3.0. To evaluate the quality of the results, we calculate the hypervolume indicator of the set of score vectors returned by the algorithms. The results obtained allow us to identify reasonably good choices of parameters for our approach. Further, we compared our method in terms of correctly aligned pairs ratio and columns correctly aligned ratio with respect to reference alignments. Experimental results show that our approaches can obtain better results than TCoffee and Clustal Omega in terms of the first ratio.

Dielectric properties of vertically aligned multi-walled carbon nanotubes in the terahertz and mid-infrared range

NASA Astrophysics Data System (ADS)

Thomson, Mark D.; Zouaghi, Wissem; Meng, Fanqi; Wiecha, Matthias M.; Rabia, Kaneez; Heinlein, Thorsten; Hussein, Laith; Babu, Deepu; Yadav, Sandeep; Engstler, Jörg; Schneider, Jörg J.; Nicoloso, Norbert; Rychetský, Ivan; Kužel, Petr; Roskos, Hartmut G.

2018-01-01

We investigate the broadband dielectric properties of vertically aligned, multi-wall carbon nanotubes (VACNT), over both the terahertz (THz) and mid-infrared spectral ranges. The nominally undoped, metallic VACNT samples are probed at normal incidence, i.e. the response is predominantly due to polarisation perpendicular to the CNT axis. A detailed comparison of various conductivity models and previously reported results is presented for the non-Drude behaviour we observe in the conventional THz range (up to 2.5 THz). Extension to the mid-infrared range reveals an absorption peak at \

Drop pattern resulting from the breakup of a bidimensional grid of liquid filaments

NASA Astrophysics Data System (ADS)

Cuellar, Ingrith; Ravazzoli, Pablo D.; Diez, Javier A.; González, Alejandro G.

2017-10-01

A rectangular grid formed by liquid filaments on a partially wetting substrate evolves in a series of breakups leading to arrays of drops with different shapes distributed in a rather regular bidimensional pattern. Our study is focused on the configuration produced when two long parallel filaments of silicone oil, which are placed upon a glass substrate previously coated with a fluorinated solution, are crossed perpendicularly by another pair of long parallel filaments. A remarkable feature of this kind of grids is that there are two qualitatively different types of drops. While one set is formed at the crossing points, the rest are consequence of the breakup of shorter filaments formed between the crossings. Here, we analyze the main geometric features of all types of drops, such as shape of the footprint and contact angle distribution along the drop periphery. The formation of a series of short filaments with similar geometric and physical properties allows us to have simultaneously quasi identical experiments to study the subsequent breakups. We develop a simple hydrodynamic model to predict the number of drops that results from a filament of given initial length and width. This model is able to yield the length intervals corresponding to a small number of drops, and its predictions are successfully compared with the experimental data as well as with numerical simulations of the full Navier-Stokes equation that provide a detailed time evolution of the dewetting motion of the filament till the breakup into drops. Finally, the prediction for finite filaments is contrasted with the existing theories for infinite ones.

Development of continental margins of the Atlantic Ocean and successive breakup of the Pangaea-3 supercontinent

NASA Astrophysics Data System (ADS)

Melankholina, E. N.; Sushchevskaya, N. M.

2017-01-01

Comparative tectonic analysis of passive margins of the Atlantic Ocean has been performed. Tectonotypes of both volcanic and nonvolcanic margins are described, and their comparison with other passive Atlantic margins is given. The structural features of margins, peculiarities of magmatism, its sources and reasons for geochemical enrichment of melts are discussed. The important role of melting of the continental lithosphere in the development of magmatism is demonstrated. Enriched EM I and EM II sources are determined for the lower parts of the volcanic section, and a depleted or poorly enriched source is determined for the upper parts of the volcanic section based on isotope data. The conclusions of the paper relate to tectonic settings of the initial occurrence of magmatism and rifting and breakup during the period of opening of the Mesozoic Ocean. It was found out that breakup and magmatism at proximal margins led only to insignificant structural transformations and reduction of the thickness of the ancient continental crust, while very important magmatic events happened later in the distal zone. New growth of magmatic crust at the stage of continental breakup is determined as a typical feature of distal zones of the margins under study. The relationship of development of margins with the impact of deep plumes as the source of magmatic material or a heat source only is discussed. Progradation of the zone of extension and breakup into the areas of cold lithosphere of the Atlantic and the formation of a single tectonomagmatic system of the ocean are under consideration.

A new method to solve the Nd breakup scattering problem in configuration space

NASA Astrophysics Data System (ADS)

Suslov, Vladimir

2005-11-01

A new computational method for solving the configuration-space Faddeev equations for three nucleon system has been developed. This method is based on the spline-decomposition in the angular variable and a generalization of the Numerov method for the hyperradius. The s-wave calculations of the inelasticity and phase-shift, as well as breakup amplitudes for nd and pd breakup scattering for lab energies 14.1 and 42.0 MeV were performed with the Malfliet -Tjon MT I-III potential. In the case of nd breakup scattering the results are in good agreement with those of the benchmark solution [1],[2]. In the case of pd quartet breakup scattering disagreement for the inelasticities reaches up to 6% as compared with those of the Pisa group [3]. The calculated pd amplitudes fulfill the optical theorem with a good precision. 1. J. L. Friar, B. F. Gibson, G. Berthold, W. Gloeckle, Th. Cornelius, H. Witala, J. Haidenbauer, Y. Koike, G. L. Payne, J. A. Tjon, and W. M. Kloet,: http://link.aip.org/link/?&lcreator=getabs-normal&ldir=FWD&lrel=CITES&fromkey=PRVCAN000069000004044003000001&fromkeyType=CVIPS&fromloc=AIP&toj=PRVCAN&tov=42&top=1838&toloc=APS&tourl=http%3A%2F%2Flink.aps.org%2Fabstract%2FPRC%2Fv42%2FPhys. Rev. C 42, 1838 (1990). 2. Frair J.L, Payne G.L., Gl"ockle W., Hueber D., Witala H.: Phys. Rev. C 51, 2356 (1995) 3. Kievsky A., Viviani M., and Rosati S.: Phys. Rev. C 64, 024002 (2001)

The effect of instrument alignment on peripheral refraction measurements by automated optometer.

PubMed

Ehsaei, Asieh; Chisholm, Catharine M; Mallen, Edward A H; Pacey, Ian E

2011-07-01

Interest in peripheral refraction measurement has grown in recent years in response to the insight it may provide into myopia development. In light of the likely increase in the clinical use of open-field autorefractors for peripheral refraction measurements, the question of instrument alignment and its impact on the accuracy of refraction measurements is raised. The aim of this study was to investigate the accuracy and precision when an open-field device was moved away from alignment with the corneal reflex towards the pupil margins, and to determine the optimum alignment position for peripheral refraction measurements. Autorefractions were performed on the right eyes of 10 healthy participants using the Shin-Nippon NVision-K 5001 autorefractor. At least five measurements were taken with the subject fixating a distance target in the primary position of gaze, and then four peripheral fixation targets located along the horizontal meridian (10° and 20° eccentricities in the nasal and temporal retina). Measurements were taken at seven alignment positions across the pupil for each fixation angle. Refraction was recorded as the spherical and cylindrical power. The central objective refraction achieved under cycloplegia based on the autorefraction result for the whole sample, ranged between -5.62 D and +1.85 D for the value of sphere, with a maximum astigmatism of -1.00 D. Acceptable alignment position range varied with fixation angle but was -1.0 to +1.0 mm in width across the pupil. Peripheral refraction measurements centred on the entrance pupil were as reliable as those centred on the corneal reflex. Our data suggest that for peripheral refraction measurements, there is a range of acceptable positions and operators can be confident of the validity of results obtained if aligned half way between the pupil centre and corneal reflex. The alignment becomes more critical at greater eccentricities. Ophthalmic & Physiological Optics © 2011 The College of Optometrists.

Proposal for the Simultaneous Measurement of the Neutron-Neutron and Neutron-Proton Quasi-Free Scattering Cross Section via the Neutron-Deuteron Breakup Reaction at E n = 19 MeV

NASA Astrophysics Data System (ADS)

Tornow, W.; Howell, C. R.; Crowell, A. S.

2013-12-01

In order to confirm or refute the present discrepancy between data and calculation for the neutron-neutron quasi-free scattering cross section in the neutron-deuteron breakup reaction, we describe a new experimental approach currently being pursued at TUNL.

Orbital Debris Modeling

NASA Technical Reports Server (NTRS)

Liou, J. C.

2012-01-01

Presentation outlne: (1) The NASA Orbital Debris (OD) Engineering Model -- A mathematical model capable of predicting OD impact risks for the ISS and other critical space assets (2) The NASA OD Evolutionary Model -- A physical model capable of predicting future debris environment based on user-specified scenarios (3) The NASA Standard Satellite Breakup Model -- A model describing the outcome of a satellite breakup (explosion or collision)

The Soviet Breakup and U.S. Foreign Policy.

ERIC Educational Resources Information Center

Lynch, Allen

1991-01-01

This issue of a quarterly publication on world affairs explores the historical significance of the disintegration of the Soviet Union and the implication for U.S. foreign policy. With the breakup of the USSR in 1990-91, Russia for the first time this century does not have control over the non-Russian nations of its former empire in Central Asia,…

Spiral waves are stable in discrete element models of two-dimensional homogeneous excitable media

NASA Technical Reports Server (NTRS)

Feldman, A. B.; Chernyak, Y. B.; Cohen, R. J.

1998-01-01

The spontaneous breakup of a single spiral wave of excitation into a turbulent wave pattern has been observed in both discrete element models and continuous reaction-diffusion models of spatially homogeneous 2D excitable media. These results have attracted considerable interest, since spiral breakup is thought to be an important mechanism of transition from the heart rhythm disturbance ventricular tachycardia to the fatal arrhythmia ventricular fibrillation. It is not known whether this process can occur in the absence of disease-induced spatial heterogeneity of the electrical properties of the ventricular tissue. Candidate mechanisms for spiral breakup in uniform 2D media have emerged, but the physical validity of the mechanisms and their applicability to myocardium require further scrutiny. In this letter, we examine the computer simulation results obtained in two discrete element models and show that the instability of each spiral is an artifact resulting from an unphysical dependence of wave speed on wave front curvature in the medium. We conclude that spiral breakup does not occur in these two models at the specified parameter values and that great care must be exercised in the representation of a continuous excitable medium via discrete elements.

Transverse liquid fuel jet breakup, burning, and ignition

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

Li, Hsi-shang

1990-01-01

An analytical/numerical study of the breakup, burning, and ignition of liquid fuels injected transversely into a hot air stream is conducted. The non-reacting liquid jet breakup location is determined by the local sonic point criterion first proposed by Schetz, et al. (1980). Two models, one employing analysis of an elliptical jet cross-section and the other employing a two-dimensional blunt body to represent the transverse jet, have been used for sonic point calculations. An auxiliary criterion based on surface tension stability is used as a separate means of determining the breakup location. For the reacting liquid jet problem, a diffusion flamemore » supported by a one-step chemical reaction within the gaseous boundary layer is solved along the ellipse surface in subsonic crossflow. Typical flame structures and concentration profiles have been calculated for various locations along the jet cross-section as a function of upstream Mach numbers. The integrated reaction rate along the jet cross-section is used to predict ignition position, which is found to be situated near the stagnation point. While a multi-step reaction is needed to represent the ignition process more accurately, the present calculation does yield reasonable predictions concerning ignition along a curved surface.« less

Formation of an Oceanic Transform Fault During Continental Rifting

NASA Astrophysics Data System (ADS)

Illsley-Kemp, F.; Bull, J. M.; Keir, D.; Gerya, T.; Pagli, C.; Gernon, T.; Ayele, A.; Goitom, B.; Hammond, J. O. S.; Kendall, J. M.

2017-12-01

We integrate evidence from surface faults, geodetic measurements, local seismicity, and 3D numerical modelling of the subaerial Afar continental rift to show that an oceanic-style transform fault is forming during the final stages of continental breakup. Transform faults are a fundamental tenet of plate tectonics, connecting offset extensional segments of mid-ocean ridges, and are vital in palaeotectonic reconstructions of passive margins. The current consensus is that transform faults initiate after the onset of seafloor spreading. However this inference has been difficult to test given the lack of observations of transform fault formation. We present the first direct observation of transform fault initiation, and shed unprecedented light on their formation mechanisms. We demonstrate that they originate during late-stage continental rifting, earlier in the rifting cycle than previously thought. Our results have important implications for reconstructing the breakup history of the continents. Palaeotectonic reconstructions that use transform fault terminations as an indicator of the continent-ocean boundary may have placed the continent-ocean boundary landward of its true location. This will have led to an overestimation of the age of continental breakup of between 8-18 Myr. Our results therefore have significant implications for studies that rely on accurate dating of continental breakup events.

Phenomenology of break-up modes in contact free externally heated nanoparticle laden fuel droplets

NASA Astrophysics Data System (ADS)

Pathak, Binita; Basu, Saptarshi

2016-12-01

We study thermally induced atomization modes in contact free (acoustically levitated) nanoparticle laden fuel droplets. The initial droplet size, external heat supplied, and suspended particle concentration (wt. %) in droplets govern the stability criterion which ultimately determines the dominant mode of atomization. Pure fuel droplets exhibit two dominant modes of breakup namely primary and secondary. Primary modes are rather sporadic and normally do not involve shape oscillations. Secondary atomization however leads to severe shape deformations and catastrophic intense breakup of the droplets. The dominance of these modes has been quantified based on the external heat flux, dynamic variation of surface tension, acoustic pressure, and droplet size. Addition of particles alters the regimes of the primary and secondary atomization and introduces bubble induced boiling and bursting. We analyze this new mode of atomization and estimate the time scale of bubble growth up to the point of bursting using energy balance to determine the criterion suitable for parent droplet rupture. All the three different modes of breakup have been well identified in a regime map determined in terms of Weber number and the heat utilization rate which is defined as the energy utilized for transient heating, vaporization, and boiling in droplets.

Shoemaker-Levy 9 and the tidal disruption of comets

NASA Technical Reports Server (NTRS)

Benz, W.; Asphaug, E.

1994-01-01

The break-up of Periodic Comet Shoemaker-Levy 9 into multiple pieces following its grazing encounter with Jupiter in July 1992 can be used to study tidally-induced fracture in comets. This spectacular event allows us not only to set limits on the size, strength and density of Shoemaker-Levy 9 itself, but provides invaluable guidance to numerical modeling of such encounters. In an extensive treatment of tidal breakup which assumed self-gravitating, homogeneous, perfectly elastic bodies, Dobrovolskis derived simple analytical expressions for the tidally-induced surface and central stresses. Both can be cast in such a way that Poisson's ratio is the only material dependent constant entering these expressions. Whether both surface and central failure must be initiated as a criterion for breakup, or either one of them is sufficient, remains a subject of disagreement. To resolve this debate, we model the details of cometary breakup using a three-dimensional Smooth Particle Hydrodynamics (SPH) code modified to simulate fracture in small solid objects. At lower stresses associated with brittle failure, we use a rate-dependent strength based on the nucleation of incipient flaws whose number density is given by a Weibull distribution.

Atomization of a High Speed Jet

NASA Astrophysics Data System (ADS)

Xu, Zhiliang; Samulyak, Roman; Li, Xiaolin; Tzanos, Constantine

2005-11-01

We present a numerical study of the jet breakup and spray formation in a diesel engine by the Front Tracking method. The mechanisms of jet breakup and spray formation of a high speed diesel jet injected through a circular nozzle are the key to design a fuel efficient, nonpolluting diesel engine. Many parameters such as the nuzzle shape, the velocity and the turbulence of the jet and the thermodynamic states of liquid and gas could be contributing causes for jet breakup. We conduct the simulations for the jet breakup within a 2D axis-symmetric geometry. Our goal is to model the spray at a micro-physical level, with the creation of individual droplets. The problem is multiscale. The droplets are a few microns in size. The nozzle is about 0.2 mm in diameter and 1 mm in length. In order to resolve various physical patterns such as vortex, shock waves, vacuum and track droplets and spray, the Burger-Colella adaptive mesh refinement technique is used. We model mixed vapor-liquid region through a heterogeneous model with dynamic vapor bubble insertion. On the liquid/vapor interface, a phase transition problem is solved numerically.

Transmitted light microscopy for visualizing the turbulent primary breakup of a microscale liquid jet

NASA Astrophysics Data System (ADS)

Reddemann, Manuel A.; Mathieu, Florian; Kneer, Reinhold

2013-11-01

Aiming at a maximum spatial resolution and a minimum motion blur, a new simple double-imaging transmitted light microscopy technique is developed in this work enabling a fundamental investigation of primary breakup of a microscale liquid jet. Contrary to conventional far-field visualization techniques, the working distance is minimized to increase the numerical aperture. The resulting images provide information about shapes, length scales and velocities of primary liquid structures. The method is applied to an optically dense spray leaving a 109-μm diesel nozzle at various injection pressures under atmospheric conditions. A phenomenological study on the temporal spray evolution is done with focus on droplet and ligament formation. Different breakup processes are identified and described. It is found that the jet is characterized by long ligaments parallel or angular to the inner jet region. These ligaments result from collapsing films developing at the spray edge. A significant influence of outlet velocity variation on shape and velocity of these ligaments is observed. The experimental results prove that a transmitted light microscopy technique with reduced working distance is an appropriate tool for a better understanding of primary breakup for small-scaled diesel nozzles and a valuable complement to highly complex measurement techniques.

Transverse liquid fuel jet breakup, burning, and ignition. M.S. Thesis

NASA Technical Reports Server (NTRS)

Li, Hsi-Shang

1990-01-01

An analytical study of the breakup, burning, and ignition of liquid fuels injected transversely into a hot air stream is conducted. The non-reacting liquid jet breakup location is determined by the local sonic point criterion. Two models, one employing analysis of an elliptical jet cross-section and the other employing a two-dimensional blunt body to represent the transverse jet, were used for sonic point calculations. An auxiliary criterion based on surface tension stability is used as a separate means of determining the breakup location. For the reacting liquid jet problem, a diffusion flame supported by a one-step chemical reaction within the gaseous boundary layer is solved along the ellipse surface in subsonic cross flow. Typical flame structures and concentration profiles were calculated for various locations along the jet cross-section as a function of upstream Mach numbers. The integration reaction rate along the jet cross-section is used to predict ignition position, which is found to be situated near the stagnation point. While a multi-step reaction is needed to represent the ignition process more accurately, the present calculation does yield reasonable predictions concerning ignition along a curved surface.

Long Range In-Plane Order of Oriented Diblock Copolymer Thin Films by Graphoepitaxy

NASA Astrophysics Data System (ADS)

Fontana, Scott; Dadmun, Mark; Lowndes, Douglas

2003-03-01

Previous work by Russell and coworkers has demonstrated that controlling the interfacial energies and wetting behavior of an asymmetric diblock copolymer enables the control of the orientation of its microphases. In particular the cylindrical phase can be readily aligned perpendicular to a substrate when it is placed on a surface that is neutral to both components of the copolymer. The minor phase, PMMA may then be removed using UV radiation leaving a nanoporous template. In this work, we will report long range, in-plane ordering of the hexagonally packed nanopores that is achieved using graphoepitaxy. The long range ordered and vertically aligned diblock copolymer film can be used to produce arrays of catalytic nickel dots, which grow vertically aligned carbon nano-fibers (VACNF), resulting in a well ordered array of VACNFs.

Three-body effects in the Hoyle-state decay

NASA Astrophysics Data System (ADS)

Refsgaard, J.; Fynbo, H. O. U.; Kirsebom, O. S.; Riisager, K.

2018-04-01

We use a sequential R-matrix model to describe the breakup of the Hoyle state into three α particles via the ground state of 8Be. It is shown that even in a sequential picture, features resembling a direct breakup branch appear in the phase-space distribution of the α particles. We construct a toy model to describe the Coulomb interaction in the three-body final state and its effects on the decay spectrum are investigated. The framework is also used to predict the phase-space distribution of the α particles emitted in a direct breakup of the Hoyle state and the possibility of interference between a direct and sequential branch is discussed. Our numerical results are compared to the current upper limit on the direct decay branch determined in recent experiments.

Viscous Particle Breakup within a Cooling Nuclear Fireball

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

Wilkinson, J. T.; Knight, K. B.; Dai, Z.

2016-10-04

Following the surface detonation of a nuclear weapon, the Earth’s crust and immediate surroundings are drawn into the fireball and form melts. Fallout is formed as these melts incorporate radioactive material from the bomb vapor and cool rapidly. The resultant fallout plume and dispersion of radioactive contamination is a function of several factors including weather patterns and fallout particle shapes and size distributions. Accurate modeling of the size distributions of fallout forms an important data point for dispersion codes that calculate the aerial distribution of fallout. While morphological evidence for aggregation of molten droplets is well documented in fallout glassmore » populations, the breakup of these molten droplets has not been similarly studied. This study documents evidence that quenched fallout populations preserve evidence of molten breakup mechanisms.« less

The Polarized Deuteron Breakup Experiment at COSY

NASA Astrophysics Data System (ADS)

Rathmann, F.; Barsov, S.; Dymov, S.; Kacharava, A.; Khoukaz, A.; Komarov, V.; Kulikov, A.; Kurbatov, A.; Lang, N.; Lehmann, I.; Lorentz, B.; Macharashvili, G.; Mussgiller, A.; Paetz gen. Schieck, H.; Schleichert, R.; Seyfarth, H.; Steffens, E.; Ströher, H.; Uzikov, Yu.; Yaschenko, S.; Zalikhanov, B.

2003-07-01

A study of the deuteron breakup reaction pd → (pp)n with forward emission of a fast proton pair with small excitation energy Epp < 3 MeV has been performed using the ANKE spectrometer at COSY Jülich. The differential cross section of the breakup reaction, averaged up to 8° over the cm polar angle of the total momentum of the pp pairs, has been obtained at six proton beam energies Tp = 0.6, 0.7, 0.8, 0.95, 1.35, and 1.9 GeV. A first measurement of the vector analyzing power Ayp has been carried out, using a polarization normalization obtained with the EDDA detector. In addition, for the first time asymmetries of p⃗d elastic scattering at Tp = 500 MeV have been recorded with the spectator setup at ANKE.

Desktop aligner for fabrication of multilayer microfluidic devices.

PubMed

Li, Xiang; Yu, Zeta Tak For; Geraldo, Dalton; Weng, Shinuo; Alve, Nitesh; Dun, Wu; Kini, Akshay; Patel, Karan; Shu, Roberto; Zhang, Feng; Li, Gang; Jin, Qinghui; Fu, Jianping

2015-07-01

Multilayer assembly is a commonly used technique to construct multilayer polydimethylsiloxane (PDMS)-based microfluidic devices with complex 3D architecture and connectivity for large-scale microfluidic integration. Accurate alignment of structure features on different PDMS layers before their permanent bonding is critical in determining the yield and quality of assembled multilayer microfluidic devices. Herein, we report a custom-built desktop aligner capable of both local and global alignments of PDMS layers covering a broad size range. Two digital microscopes were incorporated into the aligner design to allow accurate global alignment of PDMS structures up to 4 in. in diameter. Both local and global alignment accuracies of the desktop aligner were determined to be about 20 μm cm(-1). To demonstrate its utility for fabrication of integrated multilayer PDMS microfluidic devices, we applied the desktop aligner to achieve accurate alignment of different functional PDMS layers in multilayer microfluidics including an organs-on-chips device as well as a microfluidic device integrated with vertical passages connecting channels located in different PDMS layers. Owing to its convenient operation, high accuracy, low cost, light weight, and portability, the desktop aligner is useful for microfluidic researchers to achieve rapid and accurate alignment for generating multilayer PDMS microfluidic devices.

Desktop aligner for fabrication of multilayer microfluidic devices

PubMed Central

Li, Xiang; Yu, Zeta Tak For; Geraldo, Dalton; Weng, Shinuo; Alve, Nitesh; Dun, Wu; Kini, Akshay; Patel, Karan; Shu, Roberto; Zhang, Feng; Li, Gang; Jin, Qinghui; Fu, Jianping

2015-01-01

Multilayer assembly is a commonly used technique to construct multilayer polydimethylsiloxane (PDMS)-based microfluidic devices with complex 3D architecture and connectivity for large-scale microfluidic integration. Accurate alignment of structure features on different PDMS layers before their permanent bonding is critical in determining the yield and quality of assembled multilayer microfluidic devices. Herein, we report a custom-built desktop aligner capable of both local and global alignments of PDMS layers covering a broad size range. Two digital microscopes were incorporated into the aligner design to allow accurate global alignment of PDMS structures up to 4 in. in diameter. Both local and global alignment accuracies of the desktop aligner were determined to be about 20 μm cm−1. To demonstrate its utility for fabrication of integrated multilayer PDMS microfluidic devices, we applied the desktop aligner to achieve accurate alignment of different functional PDMS layers in multilayer microfluidics including an organs-on-chips device as well as a microfluidic device integrated with vertical passages connecting channels located in different PDMS layers. Owing to its convenient operation, high accuracy, low cost, light weight, and portability, the desktop aligner is useful for microfluidic researchers to achieve rapid and accurate alignment for generating multilayer PDMS microfluidic devices. PMID:26233409

Modeling of field-aligned guided echoes in the plasmasphere

NASA Astrophysics Data System (ADS)

Fung, Shing F.; Green, James L.

2005-01-01

Ray tracing modeling is used to investigate the plasma conditions under which high-frequency (f ≫ fuh) extraordinary mode waves can be guided along geomagnetic field lines. These guided signals have often been observed as long-range discrete echoes in the plasmasphere by the Radio Plasma Imager (RPI) onboard the Imager for Magnetopause-to-Aurora Global Exploration satellite. Field-aligned discrete echoes are most commonly observed by RPI in the plasmasphere, although they are also observed over the polar cap region. The plasmasphere field-aligned echoes appearing as multiple echo traces at different virtual ranges are attributed to signals reflected successively between conjugate hemispheres that propagate along or nearly along closed geomagnetic field lines. The ray tracing simulations show that field-aligned ducts with as little as 1% density perturbations (depletions) and <10 wavelengths wide can guide nearly field-aligned propagating high-frequency X mode waves. Effective guidance of a wave at a given frequency and wave normal angle (Ψ) depends on the cross-field density scale of the duct, such that ducts with stronger density depletions need to be wider in order to maintain the same gradient of refractive index across the magnetic field. While signal guidance by field aligned density gradient without ducting is possible only over the polar region, conjugate field-aligned echoes that have traversed through the equatorial region are most likely guided by ducting.

A continuous process to align electrospun nanofibers into parallel and crossed arrays

NASA Astrophysics Data System (ADS)

Laudenslager, Michael J.; Sigmund, Wolfgang M.

2013-04-01

Electrical, optical, and mechanical properties of nanofibers are strongly affected by their orientation. Electrospinning is a nanofiber processing technique that typically produces nonwoven meshes of randomly oriented fibers. While several alignment techniques exist, they are only able to produce either a very thin layer of aligned fibers or larger quantities of fibers with less control over their alignment and orientation. The technique presented herein fills the gap between these two methods allowing one to produce thick meshes of highly oriented nanofibers. In addition, this technique is not limited to collection of fibers along a single axis. Modifications to the basic setup allow collection of crossed fibers without stopping and repositioning the apparatus. The technique works for a range of fiber sizes. In this study, fiber diameters ranged from 100 nm to 1 micron. This allows a few fibers at a time to rapidly deposit in alternating directions creating an almost woven structure. These aligned nanofibers have the potential to improve the performance of energy storage and thermoelectric devices and hold great promise for directed cell growth applications.

Understanding band alignments in semiconductor heterostructures: Composition dependence and type-I-type-II transition of natural band offsets in nonpolar zinc-blende AlxGa1 -xN /AlyGa1 -yN composites

NASA Astrophysics Data System (ADS)

Landmann, M.; Rauls, E.; Schmidt, W. G.

2017-04-01

The composition dependence of the natural band alignment at nonpolar AlxGa1 -xN /AlyGa1 -yN heterojunctions is investigated via hybrid functional based density functional theory. Accurate band-gap data are provided using Heyd-Scuseria-Ernzerhof (HSE) type hybrid functionals with a composition dependent exact-exchange contribution. The unstrained band alignment between zincblende (zb) AlxGa1 -xN semiconductor alloys is studied within the entire ternary composition range utilizing the Branch-point technique to align the energy levels related to the bulklike direct Γv→Γc and indirect, pseudodirect, respectively, Γv→Xc type transitions in zb-AlxGa1 -xN . While the zb-GaN/AlxGa1 -xN band edges consistently show a type-I alignment, the relative position of fundamental band edges changes to a type-II alignment in the Al-rich composition ranges of zb-AlxGa1 -xN /AlN and zb-AlxGa1 -xN /AlyGa1 -yN systems. The presence of a direct-indirect band-gap transition at xc=0.63 in zb-AlxGa1 -xN semiconductor alloys gives rise to a notably different composition dependence of band discontinuities in the direct and indirect energy-gap ranges. Below the critical direct-indirect Al/Ga-crossover concentration, the band offsets show a close to linear dependence on the alloy composition. In contrast, notable bowing characteristics of all band discontinuities are observed above the critical crossover composition.

Attitude algorithm and initial alignment method for SINS applied in short-range aircraft

NASA Astrophysics Data System (ADS)

Zhang, Rong-Hui; He, Zhao-Cheng; You, Feng; Chen, Bo

2017-07-01

This paper presents an attitude solution algorithm based on the Micro-Electro-Mechanical System and quaternion method. We completed the numerical calculation and engineering practice by adopting fourth-order Runge-Kutta algorithm in the digital signal processor. The state space mathematical model of initial alignment in static base was established, and the initial alignment method based on Kalman filter was proposed. Based on the hardware in the loop simulation platform, the short-range flight simulation test and the actual flight test were carried out. The results show that the error of pitch, yaw and roll angle is fast convergent, and the fitting rate between flight simulation and flight test is more than 85%.

Breakup of the Soviet State and Disintegration of the Renowned Sport System. The Future of Athletics in the Commonwealth of Independent States.

ERIC Educational Resources Information Center

Zibberman, Victor; Andersen, Donald R.

1994-01-01

Two articles examine athletics in the Commonwealth of Independent States (CIS). The first discusses the disintegration of the Soviet sport system following the Soviet Union's breakup. The second examines the future of CIS athletics which, it is claimed, may never again reach the stature achieved by the Soviet Union. (SM)

Linking collisional and accretionary orogens during Rodinia assembly and breakup: Implications for models of supercontinent cycles

NASA Astrophysics Data System (ADS)

Cawood, Peter A.; Strachan, Robin A.; Pisarevsky, Sergei A.; Gladkochub, Dmitry P.; Murphy, J. Brendan

2016-09-01

Periodic assembly and dispersal of continental fragments has been a characteristic of the solid Earth for much of its history. Geodynamic drivers of this cyclic activity are inferred to be either top-down processes related to near surface lithospheric stresses at plate boundaries or bottom-up processes related to mantle convection and, in particular, mantle plumes, or some combination of the two. Analysis of the geological history of Rodinian crustal blocks suggests that internal rifting and breakup of the supercontinent were linked to the initiation of subduction and development of accretionary orogens around its periphery. Thus, breakup was a top-down instigated process. The locus of convergence was initially around north-eastern and northern Laurentia in the early Neoproterozoic before extending to outboard of Amazonia and Africa, including Avalonia-Cadomia, and arcs outboard of Siberia and eastern to northern Baltica in the mid-Neoproterozoic (∼760 Ma). The duration of subduction around the periphery of Rodinia coincides with the interval of lithospheric extension within the supercontinent, including the opening of the proto-Pacific at ca. 760 Ma and the commencement of rifting in east Laurentia. Final development of passive margin successions around Laurentia, Baltica and Siberia was not completed until the late Neoproterozoic to early Paleozoic (ca. 570-530 Ma), which corresponds with the termination of convergent plate interactions that gave rise to Gondwana and the consequent relocation of subduction zones to the periphery of this supercontinent. The temporal link between external subduction and internal extension suggests that breakup was initiated by a top-down process driven by accretionary tectonics along the periphery of the supercontinent. Plume-related magmatism may be present at specific times and in specific places during breakup but is not the prime driving force. Comparison of the Rodinia record of continental assembly and dispersal with that for Nuna, Gondwana and Pangea suggests grouping into two supercycles in which Nuna and Gondwana underwent only partial or no break-up phase prior to their incorporation into Rodinia and Pangea respectively. It was only after this final phase of assembly that the supercontinents then underwent full dispersal.

Extrinsic Factors as Component Positions to Bone and Intrinsic Factors Affecting Postoperative Rotational Limb Alignment in Total Knee Arthroplasty.

PubMed

Mochizuki, Tomoharu; Sato, Takashi; Tanifuji, Osamu; Watanabe, Satoshi; Kobayashi, Koichi; Endo, Naoto

2018-02-13

This study aimed to identify the factors affecting postoperative rotational limb alignment of the tibia relative to the femur. We hypothesized that not only component positions but also several intrinsic factors were associated with postoperative rotational limb alignment. This study included 99 knees (90 women and 9 men) with a mean age of 77 ± 6 years. A three-dimensional (3D) assessment system was applied under weight-bearing conditions to biplanar long-leg radiographs using 3D-to-2D image registration technique. The evaluation parameters were (1) component position; (2) preoperative and postoperative coronal, sagittal, and rotational limb alignment; (3) preoperative bony deformity, including femoral torsion, condylar twist angle, and tibial torsion; and (4) preoperative and postoperative range of motion (ROM). In multiple linear regression analysis using a stepwise procedure, postoperative rotational limb alignment was associated with the following: (1) rotation of the component position (tibia: β = 0.371, P < .0001; femur: β = -0.327, P < .0001), (2) preoperative rotational limb alignment (β = 0.253, P = .001), (3) postoperative flexion angle (β = 0.195, P = .007), and (4) tibial torsion (β = 0.193, P = .010). In addition to component positions, the intrinsic factors, such as preoperative rotational limb alignment, ROM, and tibial torsion, affected postoperative rotational limb alignment. On a premise of correct component positions, the intrinsic factors that can be controlled by surgeons should be taken care. In particular, ROM is necessary to be improved within the possible range to acquire better postoperative rotational limb alignment. Copyright © 2018 Elsevier Inc. All rights reserved.

Towards Long-Range RNA Structure Prediction in Eukaryotic Genes.

PubMed

Pervouchine, Dmitri D

2018-06-15

The ability to form an intramolecular structure plays a fundamental role in eukaryotic RNA biogenesis. Proximate regions in the primary transcripts fold into a local secondary structure, which is then hierarchically assembled into a tertiary structure that is stabilized by RNA-binding proteins and long-range intramolecular base pairings. While the local RNA structure can be predicted reasonably well for short sequences, long-range structure at the scale of eukaryotic genes remains problematic from the computational standpoint. The aim of this review is to list functional examples of long-range RNA structures, to summarize current comparative methods of structure prediction, and to highlight their advances and limitations in the context of long-range RNA structures. Most comparative methods implement the “first-align-then-fold” principle, i.e., they operate on multiple sequence alignments, while functional RNA structures often reside in non-conserved parts of the primary transcripts. The opposite “first-fold-then-align” approach is currently explored to a much lesser extent. Developing novel methods in both directions will improve the performance of comparative RNA structure analysis and help discover novel long-range structures, their higher-order organization, and RNA⁻RNA interactions across the transcriptome.

Simulation of exposure and alignment for nanoimprint lithography

NASA Astrophysics Data System (ADS)

Deng, Yunfei; Neureuther, Andrew R.

2002-07-01

Rigorous electromagnetic simulation with TEMPEST is used to examine the exposure and alignment processes for nano-imprint lithography with attenuating thin-film molds. Parameters in the design of topographical features of the nano-imprint system and material choices of the components are analyzed. The small feature size limits light transmission through the feature. While little can be done with auxiliary structures to attract light into small holes, the use of an absorbing material with a low real part of the refractive index such as silver helps mitigates the problem. Results on complementary alignment marks shows that the small transmission through the metal layer and the vertical separation of two alignment marks create the leakage equivalent to 1 nm misalignment but satisfactory alignment can be obtained by measuring alignment signals over a +/- 30 nm range.

The Fragmented Manihiki Plateau - Key Region for Understanding the Break-up of the "Super" Large Igneous Province Ontong Java Nui

NASA Astrophysics Data System (ADS)

Hochmuth, K.; Gohl, K.; Uenzelmann-Neben, G.; Werner, R.

2014-12-01

The Manihiki Plateau of the western Pacific is one of the world - wide greatest Large Igneous Province (LIP) on oceanic crust. It is assumed that the Manihiki Plateau was emplaced as the centerpiece of the "Super-LIP" Ontong Java Nui by multiple volcanic phases during the Cretaceous Magnetic Quiet Period. The subsequent break-up of Ontong Java Nui led to fragmentation of the Manihiki Plateau into three sub-plateaus, which all exhibit individual relicts of the "Super-LIP" break-up. We examine two deep crustal seismic refraction/wide-angle reflection profiles crossing the two largest sub-plateaus of the Manihiki Plateau, the Western Plateaus and the High Plateau. Modeling of P- and S-wave velocities reveals surprising differences in the crustal structure between the two sub-plateaus. Whereas the High Plateau shows a constant crustal thickness of 20 km, relicts of multiple volcanic phases and break-up features at its margins, the model of the Western Plateaus reveals a crustal thickness decreasing from 17 km to only 9 km. There is only little evidence of secondary phases of volcanic activity. The main upper crustal structure on the Western Plateaus consists of fault systems and sedimentary basins. We infer that the High Plateau experienced phases of strong secondary volcanism, and that tectonic deformation was limited to its edges. The Western Plateaus, on the contrary, were deformed by crustal stretching and underwent only little to no secondary volcanism. This indicates that the two main sub-plateaus of the Manihiki Plateau experienced a different geological history and have played their individual parts in the break-up history of Ontong Java Nui.

Characterization of drop aerodynamic fragmentation in the bag and sheet-thinning regimes by crossed-beam, two-view, digital in-line holography

DOE PAGES

Guildenbecher, Daniel R.; Gao, Jian; Chen, Jun; ...

2017-04-19

When a spherical liquid drop is subjected to a step change in relative gas velocity, aerodynamic forces lead to drop deformation and possible breakup into a number of secondary fragments. In order to investigate this flow, a digital in-line holography (DIH) diagnostic is proposed which enables rapid quantification of spatial statistics with limited experimental repetition. To overcome the high uncertainty in the depth direction experienced in previous applications of DIH, a crossed-beam, two-view configuration is introduced. With appropriate calibration, this diagnostic is shown to provide accurate quantification of fragment sizes, three-dimensional positions and three-component velocities in a large measurement volume.more » We apply these capabilities in order to investigate the aerodynamic breakup of drops at two non-dimensional Weber numbers, We, corresponding to the bag (We = 14) and sheet-thinning (We = 55) regimes. Ensemble average results show the evolution of fragment size and velocity statistics during the course of breakup. Our results indicate that mean fragment sizes increase throughout the course of breakup. For the bag breakup case, the evolution of a multi-mode fragment size probability density is observed. This is attributed to separate fragmentation mechanisms for the bag and rim structures. In contrast, for the sheet-thinning case, the fragment size probability density shows only one distinct peak indicating a single fragmentation mechanism. Compared to previous related investigations of this flow, many orders of magnitude more fragments are measured per condition, resulting in a significant improvement in data fidelity. For this reason, this experimental dataset is likely to provide new opportunities for detailed validation of analytic and computational models of this flow.« less

Do supercontinents introvert or extrovert?: Sm-Nd isotope evidence

NASA Astrophysics Data System (ADS)

Brendan Murphy, J.; Damian Nance, R.

2003-10-01

In recent years, two end-member models for the formation of supercontinents have emerged. In the classical Wilson cycle, oceanic crust generated during supercontinent breakup (the interior ocean) is consumed during subsequent amalgamation so that the supercontinent turns “inside in” (introversion). Alternatively, following supercontinent breakup, the exterior margins of the dispersing continental fragments collide during reassembly so that the supercontinent turns “outside in” (extroversion). These end-member models can be distinguished by comparing the Sm-Nd crust-formation ages of accreted mafic complexes (e.g., ophiolites) in the collisional orogens formed during supercontinent assembly with the breakup age of the previous supercontinent. For supercontinents generated by introversion, these crust-formation ages postdate rifting of the previous supercontinent. For supercontinents generated by extroversion, the oceanic lithosphere consumed during reassembly predates breakup of the previous supercontinent, so that crust-formation ages of accreted mafic complexes are older than the age of rifting. In the Paleozoic Appalachian-Caledonide-Variscan orogen, a key collisional orogen in the assembly of Pangea, crust-formation ages of accretionary mafic complexes postdate the formation of the Iapetus Ocean (i.e., are younger than ca. 0.6 Ga), suggesting supercontinent reassembly by introversion. By contrast, the Neoproterozoic East African and Brasiliano orogens, which formed during the amalgamation of Gondwana, are characterized by mafic complexes with crust-formation ages (ca. 0.75 1.2 Ga) that predate the ca. 750 Ma breakup of Rodinia. Hence, these complexes must have formed from lithosphere in the exterior ocean that surrounded Rodinia, implying that this ocean was consumed during the amalgamation of Gondwana. These data indicate that Pangea and Gondwana were formed by introversion and extroversion, respectively, implying that supercontinents can be assembled by fundamentally distinct geodynamic processes.

Magmatism and deformation during continental breakup

NASA Astrophysics Data System (ADS)

Keir, Derek

2013-04-01

The rifting of continents and the transition to seafloor spreading is characterised by extensional faulting and thinning of the lithosphere, and is sometimes accompanied by voluminous intrusive and extrusive magmatism. In order to understand how these processes develop over time to break continents apart, we have traditionally relied on interpreting the geological record at the numerous fully developed, ancient rifted margins around the world. In these settings, however, it is difficult to discriminate between different mechanisms of extension and magmatism because the continent-ocean transition is typically buried beneath thick layers of volcanic and sedimentary rocks, and the tectonic and volcanic activity that characterised breakup has long-since ceased. Ongoing continental breakup in the African and Arabian rift systems offers a unique opportunity to address these problems because it exposes several sectors of tectonically active rift sector development spanning the transition from embryonic continental rifting in the south to incipient seafloor spreading in the north. Here I synthesise exciting, multidisciplinary observational and modelling studies using geophysical, geodetic, petrological and numerical techniques that uniquely constrain the distribution, time-scales, and interactions between extension and magmatism during the progressive breakup of the African Plate. This new research has identified the previously unrecognised role of rapid and episodic dike emplacement in accommodating a large proportion of extension during continental rifting. We are now beginning to realise that changes in the dominant mechanism for strain over time (faulting, stretching and magma intrusion) impact dramatically on magmatism and rift morphology. The challenge now is to take what we're learned from East Africa and apply it to the rifted margins whose geological record documents breakup during entire Wilson Cycles.

Changes in winter air temperatures near Lake Michigan, 1851-1993, as determined from regional lake-ice records

USGS Publications Warehouse

Assel, R.A.; Robertson, Dale M.

1995-01-01

Records of freezeup and breakup dates for Grand Traverse Bay, Michigan, and Lake Mendota, Wisconsin, are among the longest ice records available near the Great Lakes, beginning in 185 1 and 1855, respectively. The timing of freezeup and breakup results from an integration of meteorological conditions (primarily air temperature) that occur before these events. Changes in the average timing of these ice-events are translated into changes in air temperature by the use of empirical and process-driven models. The timing of freezeup and breakup at the two locations represents an integration of air temperatures over slightly different seasons (months). Records from both locations indicate that the early winter period before about 1890 was - 15°C cooler than the early winter period after that time; the mean temperature has, however, remained relatively constant since about 1890. Changes in breakup dates demonstrate a similar 1.0-1 .5”C increase in late winter and early spring air temperatures about 1890. More recent average breakup dates at both locations have been earlier than during 1890-1940, indicating an additional warming of 1.2”C in March since about 1940 and a warming of 1 . 1°C in January-March since about 1980. Ice records at these sites will continue to provide an early indication of the anticipated climatic warming, not only because of the large response of ice cover to small changes in air temperature but also because these records integrate climatic conditions during the seasons (winter-spring) when most warming is forecast to occur. Future reductions in ice cover may strongly affect the winter ecology of the Great Lakes by reducing the stable environment required by various levels of the food chain. 

Gravitational wave searches for aligned-spin binary neutron stars using nonspinning templates

NASA Astrophysics Data System (ADS)

Cho, Hee-Suk; Lee, Chang-Hwan

2018-01-01

We study gravitational wave searches for merging binary neutron stars (NSs). We use nonspinning template waveforms towards the signals emitted from aligned-spin NS-NS binaries, in which the spins of the NSs are aligned with the orbital angular momentum. We use the TaylorF2 waveform model, which can generate inspiral waveforms emitted from aligned-spin compact binaries. We employ the single effective spin parameter χeff to represent the effect of two component spins (χ1, χ2) on the wave function. For a target system, we choose a binary consisting of the same component masses of 1.4 M ⊙ and consider the spins up to χ i = 0.4. We investigate fitting factors of the nonspinning templates to evaluate their efficiency in gravitational wave searches for the aligned-spin NS-NS binaries. We find that the templates can achieve the fitting factors exceeding 0.97 only for the signals in the range of -0.2 ≲ χeff ≲ 0. Therefore, we demonstrate the necessity of using aligned-spin templates not to lose the signals outside that range. We also show how much the recovered total mass can be biased from the true value depending on the spin of the signal.

Tuning vertical alignment and field emission properties of multi-walled carbon nanotube bundles

NASA Astrophysics Data System (ADS)

Sreekanth, M.; Ghosh, S.; Srivastava, P.

2018-01-01

We report the growth of vertically aligned carbon nanotube bundles on Si substrate by thermal chemical vapor deposition technique. Vertical alignment was achieved without any carrier gas or lithography-assisted deposition. Growth has been carried out at 850 °C for different quantities of solution of xylene and ferrocene ranging from 2.25 to 3.00 ml in steps of 0.25 ml at a fixed concentration of 0.02 gm (ferrocene) per ml. To understand the growth mechanism, deposition was carried out for different concentrations of the solution by changing only the ferrocene quantity, ranging from 0.01 to 0.03 gm/ml. A tunable vertical alignment of multi-walled carbon nanotubes (CNTs) has been achieved by this process and examined by scanning and transmission electron microscopic techniques. Micro-crystalline structural analysis has been done using Raman spectroscopy. A systematic variation in field emission (FE) current density has been observed. The highest FE current density is seen for the film grown with 0.02 gm/ml concentration, which is attributed to the better alignment of CNTs, less structural disorder and less entanglement of CNTs on the surface. The alignment of CNTs has been qualitatively understood on the basis of self-assembled catalytic particles.

Facebook use during relationship termination: uncertainty reduction and surveillance.

PubMed

Tong, Stephanie Tom

2013-11-01

Many studies document how individuals use Facebook to meet partners or develop and maintain relationships. Less is known about information-seeking behaviors during the stages of relationship termination. Relational dissolution is a socially embedded activity, and affordances of social network sites offer many advantages in reducing uncertainty after a breakup. A survey collected responses from 110 individuals who use Facebook to gather information about their romantic ex-partners. Results indicated that after breakup, partners may take advantage of the system's information visibility and the relative invisibility of movement depending on relational factors (initiator role and breakup uncertainty), social factors (perceived network approval of Facebook surveillance), and individual privacy concerns. This investigation addresses questions such as what type of information-seeking foci do individuals employ and how do individuals use Facebook as a form of surveillance? What factors motivate surveillance behavior?

Structure of 10Be and 16C nuclei via break-up reactions studied with the 4π Chimera array

NASA Astrophysics Data System (ADS)

Dell'Aquila, D.; Acosta, L.; Amorini, F.; Andolina, R.; Auditore, L.; Berceanu, I.; Cardella, G.; Chatterjiee, M. B.; De Filippo, E.; Francalanza, L.; Gnoffo, B.; Grzeszczuk, A.; Lanzalone, G.; Lombardo, I.; Martorana, N.; Minniti, T.; Pagano, A.; Pagano, E. V.; Papa, M.; Pirrone, S.; Politi, G.; Pop, A.; Porto, F.; Quattrocchi, L.; Rizzo, F.; Rosato, E.; Russotto, P.; Trifirò, A.; Trimarchi, M.; Verde, G.; Vigilante, M.

2018-01-01

The study of cluster states in neutron-rich Be and C isotopes is a subject of interest in Nuclear Physics. These states should be characterized by high deformation where α-clusters are bounded by valence neutrons. We performed a spectroscopic study of 10Be and 16C isotopes via projectile break-up reactions, by using radioactive beams produced at the INFN-LNS FRIBs facility and the Chimera 4π array. The possible evidence of a new 10Be state at 13.5 MeV excitation energy was found in the 6He+4He disintegration channel. The spectroscopy of 16C was studied via the 6He+10Be break-up channel; in this case we found the indication of a possible new state at about 20.6 MeV.

High Energy Break-Up of Few-Nucleon Systems

NASA Astrophysics Data System (ADS)

Sargsian, Misak

2008-03-01

We discus recent developments in theory of high energy two-body break-up reactions of few-nucleon systems. The characteristics of these reactions are such that the hard two-body quasielastic subprocess can be clearly separated from the accompanying soft subprocesses. We discuss in details the hard rescattering model (HRM) in which hard photodisintegration develops in two stages. At first, photon knocks-out an energetic quark which rescatters subsequently with a quark of the other nucleon. The latter provides a mechanism of sharing the initial high momentum of the photon by the outgoing two nucleons. Within HRM we discuss hard break-up reactions involving 2D and 3He targets. Another development of HRM is the prediction of new helicity selection mechanism for hard two-body reactions, which was apparently confirmed in the recent JLab experiment.

Dissipation dynamics of field-free molecular alignment for symmetric-top molecules: Ethane (C2H6)

NASA Astrophysics Data System (ADS)

Zhang, H.; Billard, F.; Yu, X.; Faucher, O.; Lavorel, B.

2018-03-01

The field-free molecular alignment of symmetric-top molecules, ethane, induced by intense non-resonant linearly polarized femtosecond laser pulses is investigated experimentally in the presence of collisional relaxation. The dissipation dynamics of field-free molecular alignment are measured by the balanced detection of ultrafast molecular birefringence of ethane gas samples at high pressures. By separating the molecular alignment into the permanent alignment and the transient alignment, the decay time-constants of both components are quantified at the same pressure. It is observed that the permanent alignment always decays slower compared to the transient alignment within the measured pressure range. This demonstrates that the propensity of molecules to conserve the orientation of angular momentum during collisions, previously observed for linear species, is also applicable to symmetric-top molecules. The results of this work provide valuable information for further theoretical understanding of collisional relaxation within nonlinear polyatomic molecules, which are expected to present interesting and nontrivial features due to an extra rotational degree of freedom.

SU-E-J-33: Comparison Between Soft Tissue Alignment and Bony Alignment for Pancreatic Cancer Radiotherapy

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

Suh, Y; Crane, C; Krishnan, S

Purpose An IGRT modality for pancreatic cancer treatment with dose escalation at our institution is in-room daily CT imaging. The purpose of this study is to assess the difference between soft tissue alignment and bony alignment for pancreatic tumor localization. Methods Eighteen patients with pancreatic tumors who underwent IMRT treatment with an inspiration breath-hold technique between July 2012 and February 2015 are included in this study. Prior to each treatment, a CT scan was acquired. The CT image guidance started with auto-alignment to either the bony anatomy (vertebral bodies) or fiducials (for the six patients with the stent in/near themore » tumor) and then, when necessary, manual adjustments were made based on soft tissue alignment using clinical software (CT-Assisted Targeting system). The difference between soft tissue alignment and bony/fiducial alignment was evaluated. Results Of all 380 treatments, manual adjustment was made in 225 treatments, ranging from 11% (3 treatments out of 28) to 96% (27 treatments out of 28) per patient. The mean of the difference between soft tissue alignment and bony/fiducial alignment per patient ranged from −3.6 to 0.3 mm, −1.5 to 2.8 mm, and −3.3 to 3.4 mm in the AP, SI, and RL directions, respectively. The maximum difference over all treatments was −9.5, −14.6, and −14.6 mm in the AP, SI, and RL directions, respectively. Conclusion About 60% of the time, manual adjustment based on soft tissue alignment was required. The extent of manual adjustment was usually small but varied significantly from patient to patient. The ultimate goal of the IGRT modality using daily CT imaging is not to fully cover the target but to spare organs-at-risk as much as possible to avoid them moving into higher dose gradients than accepted in the treatment plan. To this end, manual adjustment based on soft tissue alignment is critically important.« less

A Southern Hemisphere origin for campanulid angiosperms, with traces of the break-up of Gondwana

PubMed Central

2013-01-01

Background New powerful biogeographic methods have focused attention on long-standing hypotheses regarding the influence of the break-up of Gondwana on the biogeography of Southern Hemisphere plant groups. Studies to date have often concluded that these groups are too young to have been influenced by these ancient continental movements. Here we examine a much larger and older angiosperm clade, the Campanulidae, and infer its biogeographic history by combining Bayesian divergence time information with a likelihood-based biogeographic model focused on the Gondwanan landmasses. Results Our analyses imply that campanulids likely originated in the middle Albian (~105 Ma), and that a substantial portion of the early evolutionary history of campanulids took place in the Southern Hemisphere, despite their greater species richness in the Northern Hemisphere today. We also discovered several disjunctions that show biogeographic and temporal correspondence with the break-up of Gondwana. Conclusions While it is possible to discern traces of the break-up of Gondwana in clades that are old enough, it will generally be difficult to be confident in continental movement as the prime cause of geographic disjunctions. This follows from the need for the geographic disjunction, the inferred biogeographic scenario, and the dating of the lineage splitting events to be consistent with the causal hypothesis. PMID:23565668

Breakup Behavior of a Capillary Bridge on a Hydrophobic Stripe Separating Two Hydrophilic Stripes

NASA Astrophysics Data System (ADS)

Hartmann, Maximilian; Hardt, Steffen

2017-11-01

The breakup dynamics of a capillary bridge on a hydrophobic area between two liquid filaments occupying two parallel hydrophilic stripes is studied experimentally. In addition calculations with the finite-element software Surface Evolver are performed to obtain the corresponding stable minimal surfaces. Droplets of de-ionized water are placed on substrates with alternating hydrophilic and hydrophobic stripes of different width. Their volume decreases by evaporation. This results in a droplet shaped as the letter ``H'' covering two hydrophilic stripes separated by one hydrophobic stripe. The width of the capillary bridge d(t) on the hydrophobic stripe during the breakup process is observed using a high-speed camera mounted on a bright-field microscope. The results of the experiments and the numerical studies show that the critical width dcrit, indicating the point where the capillary bridge becomes unstable, mainly depends on the width ratio of the hydrophilic and hydrophobic stripes. It is found that the time derivative of d(t) first decreases after dcrit has been reached. The final breakup dynamics then follows a t 2 / 3 scaling. We kindly acknowledge the financial support by the German Research Foundation (DFG) within the Collaborative Research Centre 1194 ``Interaction of Transport and Wetting Processes'', Project A02a.

In Vitro Microfluidic Models of Mucus-Like Obstructions in Small Airways

NASA Astrophysics Data System (ADS)

Mulligan, Molly K.; Grotberg, James B.; Sznitman, Josué

2012-11-01

Liquid plugs can form in the lungs as a result of a host of different diseases, including cystic fibrosis and chronic obstructive pulmonary disease. The existence of such fluid obstructions have been found as far down in the bronchiole tree as the sixteenth generation, where bronchiole openings have diameters on the order of a hundred to a few hundred microns. Understanding the propagation of liquid plugs within the bifurcating branches of bronchiole airways is important because their presence in the lungs, and their rupture and break-up, can cause injury to the epithelial cells lining the airway walls as a result of high wall shear stresses. In particular, liquid plug rupture and break-up frequently occurs at airway bifurcations. Until present, however, experimental studies of liquid plugs have generally been restricted to Newtonian fluids that do not reflect the actual pseudoplastic properties of lung mucus. The present work attempts to uncover the propagation, rupture and break-up of mucus-like liquid plugs in the lower generations of the airway tree using microfluidic models. Our approach allows the dynamics of mucus-like plug break-up to be studied in real-time, in a one-to-one in vitro model, as a function of mucus rheology and bronchial tree geometry.

Production of W/O/W (water-in-oil-in-water) multiple emulsions: droplet breakup and release of water.

PubMed

Schuch, Anna; Deiters, Philipp; Henne, Julius; Köhler, Karsten; Schuchmann, Heike P

2013-07-15

We investigate breakup of W/O/W double emulsion droplets at high viscosity ratios and coalescence of inner water droplets dependent on the dispersed phase content (DPC) of the inner emulsion. The rheological analyses of the inner emulsions confirm the behavior expected from literature - increasing viscosity with increasing DPC and elastic behavior for high DPC. The resulting droplet sizes seem to be influenced only by the viscosity ratio calculated using the viscosity of the inner emulsion. An influence of the elastic properties of the inner emulsions could not be observed. Moreover, breakup of double emulsion droplets seems to follow the same rules as breakup of Newtonian droplets. In the second part of the paper we focus on the release of water from double emulsions by coalescence. A direct correlation between resulting double emulsion droplet sizes and encapsulation efficiency was found for each system. The initial inner dispersed phase content has a big influence on the release rate. This can partly be explained by the influence of the dispersed phase content on collision rate. Moreover, it was found that for high internal phase concentrations inner droplets coalesce with each other. The so formed bigger inner droplets seem to increase the overall release rate. Copyright © 2013 Elsevier Inc. All rights reserved.

Observed mechanism for the breakup of small bundles of cellulose Iα and Iβ in ionic liquids from molecular dynamics simulations.

PubMed

Rabideau, Brooks D; Agarwal, Animesh; Ismail, Ahmed E

2013-04-04

Explicit, all-atom molecular dynamics simulations are used to study the breakup of small bundles of cellulose Iα and Iβ in the ionic liquids [BMIM]Cl, [EMIM]Ac, and [DMIM]DMP. In all cases, significant breakup of the bundles is observed with the initial breakup following a common underlying mechanism. Anions bind strongly to the hydroxyl groups of the exterior strands of the bundle, forming negatively charged complexes. Binding also weakens the intrastrand hydrogen bonds present in the cellulose strands, providing greater strand flexibility. Cations then intercalate between the individual strands, likely due to charge imbalances, providing the bulk to push the individual moieties apart and initiating the separation. The peeling of an individual strand from the main bundle is observed in [EMIM]Ac with an analysis of its hydrogen bonds with other strands showing that the chain detaches glucan by glucan from the main bundle in discrete, rapid events. Further analysis shows that the intrastrand hydrogen bonds of each glucan tend to break for a sustained period of time before the interstrand hydrogen bonds break and strand detachment occurs. Examination of similar nonpeeling strands shows that, without this intrastrand hydrogen bond breakage, the structural rigidity of the individual unit can hinder its peeling despite interstrand hydrogen bond breakage.

Analysis and interpretation of satellite fragmentation data

NASA Technical Reports Server (NTRS)

Tan, Arjun

1987-01-01

The velocity perturbations of the fragments of a satellite can shed valuable information regarding the nature and intensity of the fragmentation. A feasibility study on calculating the velocity perturbations from existing equations was carried out by analyzing 23 major documented fragmentation events. It was found that whereas the calculated values of the radial components of the velocity change were often unusually high, those in the two other orthogonal directions were mostly reasonable. Since the uncertainties in the radial component necessarily translate into uncertainties in the total velocity change, it is suggested that alternative expressions for the radial component of velocity be sought for the purpose of determining the cause of the fragmentation from the total velocity change. The calculated variances in the velocity perturbations in the two directions orthogonal to the radial vector indicate that they have the smallest values for collision induced breakups and the largest values for low-intensity explosion induced breakups. The corresponding variances for high-intensity explosion induced breakups generally have values intermediate between those of the two extreme categories. A three-dimensional plot of the variances in the two orthogonal velocity perturbations and the plane change angle shows a clear separation between the three major types of breakups. This information is used to reclassify a number of satellite fragmentation events of unknown category.

Droplet impact on deep liquid pools: Rayleigh jet to formation of secondary droplets

NASA Astrophysics Data System (ADS)

Castillo-Orozco, Eduardo; Davanlou, Ashkan; Choudhury, Pretam K.; Kumar, Ranganathan

2015-11-01

The impact of droplets on a deep pool has applications in cleaning up oil spills, spray cooling, painting, inkjet printing, and forensic analysis, relying on the changes in properties such as viscosity, interfacial tension, and density. Despite the exhaustive research on different aspects of droplet impact, it is not clear how liquid properties can affect the instabilities leading to Rayleigh jet breakup and number of daughter drops formed after its pinch-off. In this article, through systematic experiments we investigate the droplet impact phenomena by varying viscosity and surface tension of liquids as well as impact speeds. Further, using numerical simulations, we show that Rayleigh-Plateau instability is influenced by these parameters, and capillary time scale is the appropriate scale to normalize the breakup time. Based on Ohnesorge number (Oh) and impact Weber number (We), a regime map for no breakup, Rayleigh jet breakup, and crown splash is suggested. Interestingly, crown splash is observed to occur at all Ohnesorge numbers; however, at high Oh, a large portion of kinetic energy is dissipated, and thus the Rayleigh jet is suppressed regardless of high impact velocity. The normalized required time for the Rayleigh jet to reach its peak varies linearly with the critical height of the jet.

Flocculation kinetics of low-turbidity raw water and the irreversible floc breakup process.

PubMed

Marques, Rodrigo de Oliveira; Ferreira Filho, Sidney Seckler

2017-04-01

The main objective of this study was to propose an improvement to the flocculation kinetics model presented by Argaman and Kaufman, by including a new term that accounts for the irreversible floc breakup process. Both models were fitted to the experimental results obtained with flocculation kinetics assays of low turbidity raw water containing Microcystis aeruginosa cells. Aluminum sulfate and ferric chloride were used as coagulants, and three distinct average velocity gradient (G) values were applied in the flocculation stage (20, 40 and 60 s -1 ). Experimental results suggest that the equilibrium between the aggregation and breakup process, as depicted by Argaman and Kaufman's original model, might not be constant over time, since the residual turbidity increased in various assays (phenomenon that was attributed to the irreversible floc breakup process). In the aluminum sulfate assays, the residual turbidity increase was visible when G = 20 s -1 (dosages of 60 and 80 mg L -1 ). For the ferric chloride assays, the phenomenon was noticed when G = 60 s -1 (dosages of 60 and 80 mg L -1 ). The proposed model presented a better fit to the experimental results, especially at higher coagulant dosages and/or higher values of average velocity gradient (G).

Experimental Observations on the Deformation and Breakup of Water Droplets Near the Leading Edge of an Airfoil

NASA Technical Reports Server (NTRS)

Vargas, Mario; Feo, Alex

2011-01-01

This work presents the results of an experimental study on droplet deformation and breakup near the leading edge of an airfoil. The experiment was conducted in the rotating rig test cell at the Instituto Nacional de Tecnica Aeroespacial (INTA) in Madrid, Spain. An airfoil model placed at the end of the rotating arm was moved at speeds of 50 to 90 m/sec. A monosize droplet generator was employed to produce droplets that were allowed to fall from above, perpendicular to the path of the airfoil at a given location. High speed imaging was employed to observe the interaction between the droplets and the airfoil. The high speed imaging allowed observation of droplet deformation and breakup as the droplet approached the airfoil near the stagnation line. A tracking software program was used to measure from the high speed movies the horizontal and vertical displacement of the droplet against time. The velocity, acceleration, Weber number, Bond number, Reynolds number, and the drag coefficients were calculated along the path of a given droplet from beginning of deformation to breakup and/or hitting the airfoil. Results are presented for droplets with a diameter of 490 micrometers at airfoil speeds of 50, 60, 70, 80 and 90 m/sec

Progressive structure-based alignment of homologous proteins: Adopting sequence comparison strategies.

PubMed

Joseph, Agnel Praveen; Srinivasan, Narayanaswamy; de Brevern, Alexandre G

2012-09-01

Comparison of multiple protein structures has a broad range of applications in the analysis of protein structure, function and evolution. Multiple structure alignment tools (MSTAs) are necessary to obtain a simultaneous comparison of a family of related folds. In this study, we have developed a method for multiple structure comparison largely based on sequence alignment techniques. A widely used Structural Alphabet named Protein Blocks (PBs) was used to transform the information on 3D protein backbone conformation as a 1D sequence string. A progressive alignment strategy similar to CLUSTALW was adopted for multiple PB sequence alignment (mulPBA). Highly similar stretches identified by the pairwise alignments are given higher weights during the alignment. The residue equivalences from PB based alignments are used to obtain a three dimensional fit of the structures followed by an iterative refinement of the structural superposition. Systematic comparisons using benchmark datasets of MSTAs underlines that the alignment quality is better than MULTIPROT, MUSTANG and the alignments in HOMSTRAD, in more than 85% of the cases. Comparison with other rigid-body and flexible MSTAs also indicate that mulPBA alignments are superior to most of the rigid-body MSTAs and highly comparable to the flexible alignment methods. Copyright © 2012 Elsevier Masson SAS. All rights reserved.

Arioc: high-throughput read alignment with GPU-accelerated exploration of the seed-and-extend search space

PubMed Central

Budavari, Tamas; Langmead, Ben; Wheelan, Sarah J.; Salzberg, Steven L.; Szalay, Alexander S.

2015-01-01

When computing alignments of DNA sequences to a large genome, a key element in achieving high processing throughput is to prioritize locations in the genome where high-scoring mappings might be expected. We formulated this task as a series of list-processing operations that can be efficiently performed on graphics processing unit (GPU) hardware.We followed this approach in implementing a read aligner called Arioc that uses GPU-based parallel sort and reduction techniques to identify high-priority locations where potential alignments may be found. We then carried out a read-by-read comparison of Arioc’s reported alignments with the alignments found by several leading read aligners. With simulated reads, Arioc has comparable or better accuracy than the other read aligners we tested. With human sequencing reads, Arioc demonstrates significantly greater throughput than the other aligners we evaluated across a wide range of sensitivity settings. The Arioc software is available at https://github.com/RWilton/Arioc. It is released under a BSD open-source license. PMID:25780763

Major strike-slip faulting along the tectonic boundary between East and West Antarctica: implications for early Gondwana break-up and Jurassic granitic magma emplacement

NASA Astrophysics Data System (ADS)

Jordan, T. A.; Ferraccioli, F.; Anderson, L.; Ross, N.; Corr, H.; Leat, P. T.; Bingham, R.; Rippin, D. M.; Le Brocq, A. M.; Siegert, M. J.

2013-12-01

The fragmentation of the Gondwana supercontinent began with continental rifting between the Weddell Sea region of Antarctica and South Africa during the Jurassic. This initial Jurassic phase of continental rifting is critical for understanding the process that initiated supercontinent breakup and dispersal, including the role of mantle plumes and major intracrustal tectonic structures. However, due to the remote location and blanketing ice sheets, the tectonic and magmatic evolution of the Weddell Sea Sector of Antarctica has remained relatively poorly understood. Our recent aeromagnetic and airborne gravity investigations have revealed the inland extent of the Weddell Sea Rift system beneath the West Antarctic Ice Sheet, and indicate the presence of a major left-lateral strike slip fault system separating the Ellsworth Whitmore block (a possible exotic microcontinent derived from the Natal Embayment, or the Shackleton Range region of East Antarctica) from East Antarctica (Jordan et al., 2013 Tectonophysics). In this study we use GPlates plate-tectonic reconstruction software to start evaluating the influence of strike-slip faulting between East and West Antarctica on Gondwana breakup models. Specifically, we investigate the possibility of poly-phase motion along the fault system and explore scenarios involving more diffuse strike slip faulting extending into the interior of East Antarctica in the hinterland of the Transantarctic Mountains. Our preliminary models suggest that there may be a link between the prominent step in the flank of the later Cretaceous-Cenozoic West Antarctic Rift System (at the southern end of Ellsworth-Whitmore Block) and the earlier Jurassic Weddell Sea rift system. Additionally, we present preliminary joint 3D magnetic and gravity models to investigate the crustal architecture of the proposed strike-slip fault system and assess its influence on the emplacement of voluminous Jurassic granitic magmatism along the boundary of the Ellsworth-Whitmore block.

Spray measurements of aerothermodynamic effect on disintegrating liquid jets

NASA Technical Reports Server (NTRS)

Ingebo, Robert D.

1991-01-01

An experimental investigation was made to determine the effect of atomizing gas mass flux and temperature on liquid jet breakup in sonic velocity gas flow. Characteristic drop size data were obtained by using the following atomizing gases: nitrogen, argon, and helium to breakup water jets in high velocity gas flow. A scattered light scanning instrument developed at Lewis Research Center was used to measure Sauter mean diameter (SMD). The three gases gave a molecular weight range of 4 to 40 and atomizing gas mass flux and temperature were varied from 6 to 50 g/sq cm and 275-400 K, respectively. The ratio of liquid jet diameter to SMD, D(sub 0)/D(sub 32), was correlated with aerodynamic and liquid-surface force ratios, i.e., the product of the Weber and Reynolds number, We Re, the gas to liquid density ratio, rho(sub g)/rho(sub 1) g and also the molecular scale dimensionless group, rho(sub 1)(Vm exp 3)/ mu(sub 1) g, to give the following expression: D(sub 0)/D(sub 32) = 0.90 x 10(exp -8) x (We Re rho sub g/rho sub 1)exp 0.44 x (rho sub 1 Vm exp 3/mu sub 1 g)exp 0.67 where We Re = ((rho sub g)exp 2(D sub 0)exp 2(V sub C)exp3))/ mu sub 1 sigma, mu sub 1 is liquid viscosity, sigma is surface tension, V sub C is the acoustic gas velocity, V sub m is the RMS velocity of gas molecules, and g is the acceleration of gas molecules due to gravity. Good agreement was obtained with atomization theory for liquid-jet breakup in the regime of aerodynamic stripping. Also, due to its low molecular weight and high acoustic velocity, helium was considerably more effective than nitrogen or argon in producing small-droplet sprays with values of D(sub 32) on the order of 5 microns.

Detailed assessment of diesel spray atomization models using visible and X-ray extinction measurements

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

Magnotti, G. M.; Genzale, C. L.

The physical mechanisms characterizing the breakup of a diesel spray into droplets are still unknown. This gap in knowledge has largely been due to the challenges of directly imaging this process or quantitatively measuring the outcomes of spray breakup, such as droplet size. Recent x-ray measurements by Argonne National Laboratory, utilized in this work, provide needed information about the spatial evolution of droplet sizes in selected regions of the spray under a range of injection pressures (50–150 MPa) and ambient densities (7.6–22.8 kg/m3) relevant for diesel operating conditions. Ultra-small angle x-ray scattering (USAXS) measurements performed at the Advanced Photon Sourcemore » are presented, which quantify Sauter mean diameters (SMD) within optically thick regions of the spray that are inaccessible by conventional droplet sizing measurement techniques, namely in the near-nozzle region, along the spray centerline, and within the core of the spray. To quantify droplet sizes along the periphery of the spray, a complementary technique is proposed and introduced, which leverages the ratio of path-integrated x-ray and visible laser extinction (SAMR) measurements to quantify SMD. The SAMR and USAXS measurements are then utilized to evaluate current spray models used for engine computational fluid dynamic (CFD) simulations. We explore the ability of a carefully calibrated spray model, premised on aerodynamic wave growth theory, to capture the experimentally observed trends of SMD throughout the spray. The spray structure is best predicted with an aerodynamic primary and secondary breakup process that is represented with a slower time constant and larger formed droplet size than conventionally recommended for diesel spray models. Additionally, spray model predictions suggest that droplet collisions may not influence the resultant droplet size distribution along the spray centerline in downstream regions of the spray.« less

Long-term patterns of benthic irradiance and kelp production in the central Beaufort sea reveal implications of warming for Arctic inner shelves

NASA Astrophysics Data System (ADS)

Bonsell, Christina; Dunton, Kenneth H.

2018-03-01

This study synthesizes a multidecadal dataset of annual growth of the Arctic endemic kelp Laminaria solidungula and corresponding measurements of in situ benthic irradiance from Stefansson Sound in the central Beaufort Sea. We incorporate long-term data on sea ice concentration (National Sea Ice Data Center) and wind (National Weather Service) to assess how ice extent and summer wind dynamics affect the benthic light environment and annual kelp production. We find evidence of significant changes in sea ice extent in Stefansson Sound, with an extension of the ice-free season by approximately 17 days since 1979. Although kelp elongation at 5-7 m depths varies significantly among sites and years (3.8-49.8 cm yr-1), there is no evidence for increased production with either earlier ice break-up or a longer summer ice-free period. This is explained by very low light transmittance to the benthos during the summer season (mean daily percent surface irradiance ± SD: 1.7 ± 3.6 to 4.5 ± 6.6, depending on depth, with light attenuation values ranging from 0.5 to 0.8 m-1), resulting in minimal potential for kelp production on most days. Additionally, on month-long timescales (35 days) in the ice-free summer, benthic light levels are negatively related to wind speed. The frequent, wind-driven resuspension of sediments following ice break-up significantly reduce light to the seabed, effectively nullifying the benefits of an increased ice-free season on annual kelp growth. Instead, benthic light and primary production may depend substantially on the 1-3 week period surrounding ice break-up when intermediate sea ice concentrations reduce wind-driven sediment resuspension. These results suggest that both benthic and water column primary production along the inner shelf of Arctic marginal seas may decrease, not increase, with reductions in sea ice extent.

Visualisation of diesel injector with neutron imaging

NASA Astrophysics Data System (ADS)

Lehmann, E.; Grünzweig, C.; Jollet, S.; Kaiser, M.; Hansen, H.; Dinkelacker, F.

2015-12-01

The injection process of diesel engines influences the pollutant emissions. The spray formation is significantly influenced by the internal flow of the injector. One of the key parameters here is the generation of cavitation caused by the geometry and the needle lift. In modern diesel engines the injection pressure is established up to 3000 bar. The details of the flow and phase change processes inside the injector are of increasing importance for such injectors. With these experimental measurements the validation of multiphase and cavitation models is possible for the high pressure range. Here, for instance, cavitation effects can occur. Cavitation effects in the injection port area destabilize the emergent fuel jet and improve the jet break-up. The design of the injection system in direct-injection diesel engines is an important challenge, as the jet breakup, the atomization and the mixture formation in the combustion chamber are closely linked. These factors have a direct impact on emissions, fuel consumption and performance of an engine. The shape of the spray at the outlet is determined by the internal flow of the nozzle. Here, geometrical parameters, the injection pressure, the injection duration and the cavitation phenomena play a major role. In this work, the flow dependency in the nozzles are analysed with the Neutron-Imaging. The great advantage of this method is the penetrability of the steel structure while a high contrast to the fuel is given due to the interaction of the neutrons with the hydrogen amount. Compared to other methods (optical with glass structures) we can apply real components under highest pressure conditions. During the steady state phase of the injection various cavitation phenomena are visible in the injector, being influenced by the nozzle geometry and the fuel pressure. Different characteristics of cavitation in the sac and spray hole can be detected, and the spray formation in the primary breakup zone is influenced.

Neurient: An Algorithm for Automatic Tracing of Confluent Neuronal Images to Determine Alignment

PubMed Central

Mitchel, J.A.; Martin, I.S.

2013-01-01

A goal of neural tissue engineering is the development and evaluation of materials that guide neuronal growth and alignment. However, the methods available to quantitatively evaluate the response of neurons to guidance materials are limited and/or expensive, and may require manual tracing to be performed by the researcher. We have developed an open source, automated Matlab-based algorithm, building on previously published methods, to trace and quantify alignment of fluorescent images of neurons in culture. The algorithm is divided into three phases, including computation of a lookup table which contains directional information for each image, location of a set of seed points which may lie along neurite centerlines, and tracing neurites starting with each seed point and indexing into the lookup table. This method was used to obtain quantitative alignment data for complex images of densely cultured neurons. Complete automation of tracing allows for unsupervised processing of large numbers of images. Following image processing with our algorithm, available metrics to quantify neurite alignment include angular histograms, percent of neurite segments in a given direction, and mean neurite angle. The alignment information obtained from traced images can be used to compare the response of neurons to a range of conditions. This tracing algorithm is freely available to the scientific community under the name Neurient, and its implementation in Matlab allows a wide range of researchers to use a standardized, open source method to quantitatively evaluate the alignment of dense neuronal cultures. PMID:23384629

A Toolbox of Metrology-Based Techniques for Optical System Alignment

NASA Technical Reports Server (NTRS)

Coulter, Phillip; Ohl, Raymond G.; Blake, Peter N.; Bos, Brent J.; Casto, Gordon V.; Eichhorn, William L.; Gum, Jeffrey S.; Hadjimichael, Theodore J.; Hagopian, John G.; Hayden, Joseph E.;

A Toolbox of Metrology-Based Techniques for Optical System Alignment

NASA Technical Reports Server (NTRS)

Coulter, Phillip; Ohl, Raymond G.; Blake, Peter N.; Bos, Brent J.; Eichhorn, William L.; Gum, Jeffrey S.; Hadjimichael, Theodore J.; Hagopian, John G.; Hayden, Joseph E.; Hetherington, Samuel E.;

Effects of alignment layer thickness on the pretilt angle of liquid crystals

NASA Astrophysics Data System (ADS)

Son, Jong-Ho; Zin, Wang-Cheol

2010-12-01

Mixture solutions of vertical- and planar-aligning polyimide precursors were coated on bare glass. The concentrations of the solutions were varied to control the thicknesses of the films. The resulting blend films were baked to induce imidization and then rubbed. The thicknesses (t) of the blend film and of the pure vertical-alignment film affected their surface energies; the pretilt angle can be fully controlled in the range 5.5°≤Θ0≤87° by adjusting t. The surface energy of pure planar-alignment layers was independent of t.

Relationship problems and extradyadic romantic and sexual activity in a web-sample of Norwegian men and women.

PubMed

Træen, Bente; Thuen, Frode

2013-04-01

The purpose of this paper is to describe the prevalence of self-reported types of extradyadic romantic and sexual activity among adult Norwegians and to explore the role of infidelity in breaking up a permanent relationship. The results are based on 1,001 web interviews with persons ranging in age from 18 to 67 years. The majority of respondents reported having engaged in some kind of extradyadic romantic and/or sexual activity. Forty-five percent of the women and 39% of the men claimed they had experienced a previous breakup from a marriage or cohabiting relationship. Among those aged 50 years or older, the most important reasons for breaking up a previous relationship were infidelity (38%) and lost love (38%). More men (44%) than women (33%) reported infidelity. Respondents younger than 50 years were more motivated by boredom. Among respondents below the age of 50 years, the most frequently reported reasons for considering termination of a present relationship were quarreling (37%), poor sex life (29%), and "other" reasons (25%). Accordingly, infidelity was not identified as an essential factor for considering a breakup from the present relationship. © 2012 The Authors. Scandinavian Journal of Psychology © 2012 The Scandinavian Psychological Associations.

Cambrian palaeomagnetic data confirm a Natal Embayment location for the Ellsworth-Whitmore Mountains, Antarctica, in Gondwana reconstructions

NASA Astrophysics Data System (ADS)

Randall, Darren E.; Mac Niocaill, Conall

2004-04-01

The Ellsworth-Whitmore Mountains (EWM) are one of five terranes that form West Antarctica. Constraining the positions of these terranes in pre-break up Gondwana is crucial to understanding the history of the palaeo-Pacific Gondwana margin. We report the results of a detailed palaeomagnetic investigation of the EWM, which comprises some 150 sites in six formations, ranging in age from Cambrian to Permian. Five of the studied units yield only viscous remnant magnetizations of recent age, or unstable natural remanent magnetizations. The remaining unit, the mid-late Cambrian Frazier Ridge Formation, yielded stable magnetizations at 16 of 35 sites. This component passes a fold test at the 95 per cent confidence level, indicating that it pre-dates Permian deformation, and we argue that it is of primary origin. The resulting palaeopole (9°N 293°E A95= 5.1°) is in good agreement with two previously published palaeopoles from similarly aged rocks in the EWM. Collectively these data indicate that the EWM were located in the Natal Embayment prior to Gondwana break-up, and underwent 90° of anticlockwise rotation during break-up. All three studies, however, yield inclinations that are slightly too shallow when compared with coeval Gondwana reference poles.

Strong and highly variable push of ocean waves on Southern Ocean sea ice.

PubMed

Stopa, Justin E; Sutherland, Peter; Ardhuin, Fabrice

2018-06-05

Sea ice in the Southern Ocean has expanded over most of the past 20 y, but the decline in sea ice since 2016 has taken experts by surprise. This recent evolution highlights the poor performance of numerical models for predicting extent and thickness, which is due to our poor understanding of ice dynamics. Ocean waves are known to play an important role in ice break-up and formation. In addition, as ocean waves decay, they cause a stress that pushes the ice in the direction of wave propagation. This wave stress could not previously be quantified due to insufficient observations at large scales. Sentinel-1 synthetic aperture radars (SARs) provide high-resolution imagery from which wave height is measured year round encompassing Antarctica since 2014. Our estimates give an average wave stress that is comparable to the average wind stress acting over 50 km of sea ice. We further reveal highly variable half-decay distances ranging from 400 m to 700 km, and wave stresses from 0.01 to 1 Pa. We expect that this variability is related to ice properties and possibly different floe sizes and ice thicknesses. A strong feedback of waves on sea ice, via break-up and rafting, may be the cause of highly variable sea-ice properties.

Relationship of Corneal Pain Sensitivity With Dry Eye Symptoms in Dry Eye With Short Tear Break-Up Time.

PubMed

Kaido, Minako; Kawashima, Motoko; Ishida, Reiko; Tsubota, Kazuo

2016-03-01

The purpose of this prospective comparative study was to investigate corneal sensitivity in subjects with unstable tear film, with and without dry eye (DE) symptoms. Forty-one eyes of 41 volunteers (mean age: 45.1 ± 9.4 years; age range, 23-57 years), with normal tear function and ocular surface except for tear stability, were studied. The eyes were divided into two groups depending on the presence or absence of DE symptoms: 21 eyes with DE symptoms (symptomatic group); and 20 eyes without DE symptoms (asymptomatic group). Three types of corneal sensitivity values were measured using a Cochet-Bonnet esthesiometer: the sensitivity for perception of touch (S-touch), the sensitivity for blinking (S-blink), and the sensitivity for pain (S-pain). Mean S-blink and S-pain were significantly higher in the symptomatic group than in the asymptomatic group (P < 0.05), whereas there was no significant difference in mean S-touch between these groups (P > 0.05). Corneal sensitivity for blinking and pain evoked by increased stimuli was higher in the symptomatic group (subjects with short break-up time DE) compared with subjects who have no DE symptoms despite decreased tear stability. The presence of both tear instability and hyperesthesia, rather than tear instability alone, may contribute to DE pathogenesis.

Ultrahigh throughput microfluidic platform for in-air production of microscale droplets

NASA Astrophysics Data System (ADS)

Tirandazi, Pooyan; Healy, John; Hidrovo, Carlos H.

2017-11-01

In-air droplet formation inside microfluidic networks is an alternative technique to the conventional in-liquid systems for creating uniform, microscale droplets. Recent works have highlighted and quantified the use of a gaseous continuous phase for controlled generation of droplets in the Dripping regime in planar structures. Here we demonstrate a new class of non-planar droplet-based systems which rely on controlled breakup of a liquid microjet within a high speed flow of air inside a confined microfluidic flow-focusing PDMS channel. We investigate the physics of confined gas-liquid flows and the effect of geometry on the behavior of a liquid water jet in a gaseous flow. Droplet breakup in the Jetting regime is studied both numerically and experimentally and the results are compared. We show droplet production capability at rates higher than 100 KHz with droplets ranging from 15-30 μm in diameter and a polydispersity index of less than 15%. This work represents an important investigation into the Jetting regime in confined microchannels. The ability to control jet behavior, generation rate, and droplet size in gas-liquid microflows will further expand the potential applications of this system for high throughput operations in material synthesis and biochemical analysis. We acknowledge funding support from NSF CAREER Award Grant CBET-1522841.

Effect of yield curves and porous crush on hydrocode simulations of asteroid airburst

NASA Astrophysics Data System (ADS)

Robertson, D. K.; Mathias, D. L.

2017-03-01

Simulations of asteroid airburst are being conducted to obtain best estimates of damage areas and assess sensitivity to variables for asteroid characterization and mitigation efforts. The simulations presented here employed the ALE3D hydrocode to examine the breakup and energy deposition of asteroids entering the Earth's atmosphere, using the Chelyabinsk meteor as a test case. This paper examines the effect of increasingly complex material models on the energy deposition profile. Modeling the meteor as a rock having a single strength can reproduce airburst altitude and energy deposition reasonably well but is not representative of real rock masses (large bodies of material). Accounting for a yield curve that includes different tensile, shear, and compressive strengths shows that shear strength determines the burst altitude. Including yield curves and compaction of porous spaces in the material changes the detailed mechanics of the breakup but only has a limited effect on the burst altitude and energy deposition. Strong asteroids fail and create peak energy deposition close to the altitude at which ram dynamic pressure equals the material strength. Weak asteroids, even though they structurally fail at high altitude, require the increased pressure at lower altitude to disrupt and disperse the rubble. As a result, a wide range of weaker asteroid strengths produce peak energy deposition at a similar altitude.

Post-main-sequence debris from rotation-induced YORP break-up of small bodies

NASA Astrophysics Data System (ADS)

Veras, Dimitri; Jacobson, Seth A.; Gänsicke, Boris T.

2014-12-01

Although discs of dust and gas have been observed orbiting white dwarfs, the origin of this circumstellar matter is uncertain. We hypothesize that the in situ break-up of small bodies such as asteroids spun to fission during the giant branch phases of stellar evolution provides an important contribution to this debris. The YORP (Yarkovsky-O'Keefe-Radviesvki-Paddock) effect, which arises from radiation pressure, accelerates the spin rate of asymmetric asteroids, which can eventually shear themselves apart. This pressure is maintained and enhanced around dying stars because the outward push of an asteroid due to stellar mass loss is insignificant compared to the resulting stellar luminosity increase. Consequently, giant star radiation will destroy nearly all bodies with radii in the range 100 m-10 km that survive their parent star's main-sequence lifetime within a distance of about 7 au; smaller bodies are spun apart to their strongest, competent components. This estimate is conservative and would increase for highly asymmetric shapes or incorporation of the inward drag due to giant star stellar wind. The resulting debris field, which could extend to thousands of au, may be perturbed by remnant planetary systems to reproduce the observed dusty and gaseous discs which accompany polluted white dwarfs.

Angular momentum transfer in primordial discs and the rotation of the first stars

NASA Astrophysics Data System (ADS)

Hirano, Shingo; Bromm, Volker

2018-05-01

We investigate the rotation velocity of the first stars by modelling the angular momentum transfer in the primordial accretion disc. Assessing the impact of magnetic braking, we consider the transition in angular momentum transport mode at the Alfvén radius, from the dynamically dominated free-fall accretion to the magnetically dominated solid-body one. The accreting protostar at the centre of the primordial star-forming cloud rotates with close to breakup speed in the case without magnetic fields. Considering a physically motivated model for small-scale turbulent dynamo amplification, we find that stellar rotation speed quickly declines if a large fraction of the initial turbulent energy is converted to magnetic energy (≳ 0.14). Alternatively, if the dynamo process were inefficient, for amplification due to flux freezing, stars would become slow rotators if the pre-galactic magnetic field strength is above a critical value, ≃10-8.2 G, evaluated at a scale of nH = 1 cm-3, which is significantly higher than plausible cosmological seed values (˜10-15 G). Because of the rapid decline of the stellar rotational speed over a narrow range in model parameters, the first stars encounter a bimodal fate: rapid rotation at almost the breakup level, or the near absence of any rotation.

Phylogenetic evidence that both ancient vicariance and dispersal have contributed to the biogeographic patterns of anchialine cave shrimps.

PubMed

Jurado-Rivera, José A; Pons, Joan; Alvarez, Fernando; Botello, Alejandro; Humphreys, William F; Page, Timothy J; Iliffe, Thomas M; Willassen, Endre; Meland, Kenneth; Juan, Carlos; Jaume, Damià

2017-06-06

Cave shrimps from the genera Typhlatya, Stygiocaris and Typhlopatsa (Atyidae) are restricted to specialised coastal subterranean habitats or nearby freshwaters and have a highly disconnected distribution (Eastern Pacific, Caribbean, Atlantic, Mediterranean, Madagascar, Australia). The combination of a wide distribution and a limited dispersal potential suggests a large-scale process has generated this geographic pattern. Tectonic plates that fragment ancestral ranges (vicariance) has often been assumed to cause this process, with the biota as passive passengers on continental blocks. The ancestors of these cave shrimps are believed to have inhabited the ancient Tethys Sea, with three particular geological events hypothesised to have led to their isolation and divergence; (1) the opening of the Atlantic Ocean, (2) the breakup of Gondwana, and (3) the closure of the Tethys Seaway. We test the relative contribution of vicariance and dispersal in the evolutionary history of this group using mitochondrial genomes to reconstruct phylogenetic and biogeographic scenarios with fossil-based calibrations. Given that the Australia/Madagascar shrimp divergence postdates the Gondwanan breakup, our results suggest both vicariance (the Atlantic opening) and dispersal. The Tethys closure appears not to have been influential, however we hypothesise that changing marine currents had an important early influence on their biogeography.

Lattice Boltzmann modeling of contact angle and its hysteresis in two-phase flow with large viscosity difference.

PubMed

Liu, Haihu; Ju, Yaping; Wang, Ningning; Xi, Guang; Zhang, Yonghao

2015-09-01

Contact angle hysteresis is an important physical phenomenon omnipresent in nature and various industrial processes, but its effects are not considered in many existing multiphase flow simulations due to modeling complexity. In this work, a multiphase lattice Boltzmann method (LBM) is developed to simulate the contact-line dynamics with consideration of the contact angle hysteresis for a broad range of kinematic viscosity ratios. In this method, the immiscible two-phase flow is described by a color-fluid model, in which the multiple-relaxation-time collision operator is adopted to increase numerical stability and suppress unphysical spurious currents at the contact line. The contact angle hysteresis is introduced using the strategy proposed by Ding and Spelt [Ding and Spelt, J. Fluid Mech. 599, 341 (2008)JFLSA70022-112010.1017/S0022112008000190], and the geometrical wetting boundary condition is enforced to obtain the desired contact angle. This method is first validated by simulations of static contact angle and dynamic capillary intrusion process on ideal (smooth) surfaces. It is then used to simulate the dynamic behavior of a droplet on a nonideal (inhomogeneous) surface subject to a simple shear flow. When the droplet remains pinned on the surface due to hysteresis, the steady interface shapes of the droplet quantitatively agree well with the previous numerical results. Four typical motion modes of contact points, as observed in a recent study, are qualitatively reproduced with varying advancing and receding contact angles. The viscosity ratio is found to have a notable impact on the droplet deformation, breakup, and hysteresis behavior. Finally, this method is extended to simulate the droplet breakup in a microfluidic T junction, with one half of the wall surface ideal and the other half nonideal. Due to the contact angle hysteresis, the droplet asymmetrically breaks up into two daughter droplets with the smaller one in the nonideal branch channel, and the behavior of daughter droplets is significantly different in both branch channels. Also, it is found that the contact angle hysteresis is strengthened with decreasing the viscosity ratio, leading to an earlier droplet breakup and a decrease in the maximum length that the droplet can reach before the breakup. These simulation results manifest that the present multiphase LBM can be a useful substitute to Ba et al. [Phys. Rev. E 88, 043306 (2013)PLEEE81539-375510.1103/PhysRevE.88.043306] for modeling the contact angle hysteresis, and it can be easily implemented with higher computational efficiency.

Experimental constraints on the deformation and breakup of injected magma

NASA Astrophysics Data System (ADS)

Hodge, Kirsten F.; Carazzo, Guillaume; Jellinek, A. Mark

2012-04-01

The injection, breakup and stirring of dikes entering convecting silicic magma chambers can govern how they grow and differentiate, as well as influence their potential for eruption at the surface. Enclaves observed in plutons may preserve a record of this process and, thus, identifying and understanding the physical processes underlying their formation is a crucial issue in volcanology. We use laboratory experiments and scaling theory to investigate the mechanical and rheological conditions leading to the deformation and breakup of analog crystal-rich dikes injected as discrete plumes that descend into an underlying imposed shear flow. To scale the experiments and map the results across a wide range of natural conditions we define the ratio S of the timescale for the growth of a gravitational Rayleigh-Taylor (R-T) instability of the sheared, injected material to the timescale for settling through the fluid layer and the ratio Y of the timescales for shearing and lateral disaggregation of the particle-fluid mixture (yielding). At low S (< 3) and high Y (> 40), descending plumes are stretched and tilted before undergoing R-T instability, forming drips with a wavelength that is comparable to the initial diameter of the injection. At low Y (< 40) and S values that increase from ∼ 3 as Y → 0, an injection yields in tension before a R-T instability can grow, forming discrete particle-fluid blobs that are much smaller than the initial injection diameter and separated by thin filaments of the original mixture. At high S (> 3) and high Y (> 40), injections remain intact as they settle through the layer and pond at the floor. Applied to magma chambers, our results do not support the production of a continuum of enclave sizes. Indeed, from scaling analyses we expect the two breakup regimes to form distinct size populations: Whereas enclaves formed in the R-T regime will be comparable to the injection size, those formed in the tension regime will be much smaller. We show that enclave size distributions observed in the field can potentially be used to infer the Y - S conditions for the magma chamber at the time of injection. In addition, these observations can constrain aspects of the styles of flow, stirring, and mixing within the magma chamber, as well as the rheological contrast between the injected and host magma at the time of enclave formation. Our work shows that the contrast in composition between the injected and host magmas will have a strong effect on the mingling structures that are likely to be generated.

Breakup magmatism style on the North Atlantic Igneous Province: insight from Mid-Norwegian volcanic margin

NASA Astrophysics Data System (ADS)

Mansour Abdelmalak, Mohamed; Faleide, Jan Inge; Planke, Sverre; Theissen-Krah, Sonja; Zastrozhnov, Dmitrii; Breivik, Asbjørn Johan; Gernigon, Laurent; Myklebust, Reidun

2014-05-01

The distribution of breakup-related igneous rocks on rifted margins provide important constraints on the magmatic processes during continental extension and lithosphere separation which lead to a better understanding of the melt supply from the upper mantle and the relationship between tectonic setting and volcanism. The results can lead to a better understanding of the processes forming volcanic margins and thermal evolution of associated prospective basins. We present a revised mapping of the breakup-related igneous rocks in the NE Atlantic area, which are mainly based on the Mid-Norwegian (case example) margin. We divided the breakup related igneous rocks into (1) extrusive complexes, (2) shallow intrusive complexes (sills/dykes) and (3) deep intrusive complexes (Lower Crustal Body: LCB). The extrusive complex has been mapped using the seismic volcanostratigraphic method. Several distinct volcanic seismic facies units have been identified. The top basalt reflection is easily identified because of the high impedance contrast between the sedimentary and volcanic rocks resulting in a major reflector. The basal sequence boundary is frequently difficult to identify but it lies usually over the intruded sedimentary basin. Then the base is usually picked above the shallow sill intrusions identified on seismic profile. The mapping of the top and the base of the basaltic sequences allows us to determine the basalt thickness and estimate the volume of the magma production on the Mid- Norwegian margin. The thicker part of the basalt corresponds to the seaward dipping reflector (SDR). The magma feeder system, mainly formed by dyke and sill intrusions, represents the shallow intrusive complex. Deeper interconnected high-velocity sills are also mappable in the margin. Interconnected sill complexes can define continuous magma network >10 km in vertical ascent. The large-scale sill complexes, in addition to dyke swarm intrusions, represent a mode of vertical long-range magma transport through the upper crust. The deep intrusive complex represents the Lower Crustal Body (LCB) which is observed along the margin and characterized by high P-wave velocity bodies (Vp> 7km/s). On the Vøring margin a strong amplitude dome-shaped reflection (the so-called T-Reflection) has been identified and interpreted as the top LCB. In the sedimentary part of the margin, sill intrusions are the major feeder system and seem to be connected with LCB. In the volcanic part of the margin, dykes represent the main feeder system and lie above the thicker part of the LCB.

Global biogeography since Pangaea.

PubMed

McIntyre, Sarah R N; Lineweaver, Charles H; Groves, Colin P; Chopra, Aditya

2017-06-14

The break-up of the supercontinent Pangaea around 180 Ma has left its imprint on the global distribution of species and resulted in vicariance-driven speciation. Here, we test the idea that the molecular clock dates, for the divergences of species whose geographical ranges were divided, should agree with the palaeomagnetic dates for the continental separations. Our analysis of recently available phylogenetic divergence dates of 42 pairs of vertebrate taxa, selected for their reduced ability to disperse, demonstrates that the divergence dates in phylogenetic trees of continent-bound terrestrial and freshwater vertebrates are consistent with the palaeomagnetic dates of continental separation. © 2017 The Author(s).

Atomizing-gas temperature effect on cryogenic spray dropsize

NASA Technical Reports Server (NTRS)

Ingebo, Robert D.

1993-01-01

Correlating expressions for two-phase flow breakup of liquid nitrogen, LN2, jets in sonic velocity nitrogen gasflows were obtained for an atomizing-gas temperature range of 111 to 442 K. The correlations were based on characteristic dropsize measurements obtained with a scattered-light scanner. The effect of droplet vaporization on the measurements of the volume-median dropsize was calculated by using previously determined heat and momentum transfer expressions for droplets evaporating in high-velocity gasflow. Finally, the dropsize of the originally unvaporized spray was calculated, normalized with respect to jet diameter and correlated with atomizing-gas flowrate and temperature.

Reverse freeze casting: a new method for fabricating highly porous titanium scaffolds with aligned large pores.

PubMed

Yook, Se-Won; Jung, Hyun-Do; Park, Chang-Hoon; Shin, Kwan-Ha; Koh, Young-Hag; Estrin, Yuri; Kim, Hyoun-Ee

2012-07-01

Highly porous titanium with aligned large pores up to 500 μm in size, which is suitable for scaffold applications, was successfully fabricated using the reverse freeze casting method. In this process we have newly developed, the Ti powders migrated spontaneously along the pre-aligned camphene boundaries at a temperature of 45.5°C and formed a titanium-camphene mixture with an aligned structure; this was followed by freeze drying and sintering. As the casting time increased from 24 to 48 h, the initial columnar structures turned into lamellar structures, with the porosity decreasing from 69 to 51%. This reduction in porosity caused the compressive yield strength to increase from 121 to 302 MPa, with an elastic modulus of the samples being in the range of 2-5 GPa. In addition, it was demonstrated that reverse freeze casting can also be successfully applied to various other raw powders, suggesting that the method developed in this work opens up new avenues for the production of a range of porous metallic and ceramic scaffolds with highly aligned pores. Copyright © 2012 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Controlling band alignments by artificial interface dipoles at perovskite heterointerfaces

DOE PAGES

Yajima, Takeaki; Hikita, Yasuyuki; Minohara, Makoto; ...

2015-04-07

The concept ‘the interface is the device' is embodied in a wide variety of interfacial electronic phenomena and associated applications in oxide materials, ranging from catalysts and clean energy systems to emerging multifunctional devices. Many device properties are defined by the band alignment, which is often influenced by interface dipoles. On the other hand, the ability to purposefully create and control interface dipoles is a relatively unexplored degree of freedom for perovskite oxides, which should be particularly effective for such ionic materials. Here we demonstrate tuning the band alignment in perovskite metal-semiconductor heterojunctions over a broad range of 1.7 eV.more » This is achieved by the insertion of positive or negative charges at the interface, and the resultant dipole formed by the induced screening charge. This approach can be broadly used in applications where decoupling the band alignment from the constituent work functions and electron affinities can enhance device functionality.« less

Shape-dependent dispersion and alignment of nonaggregating plasmonic gold nanoparticles in lyotropic and thermotropic liquid crystals.

PubMed

Liu, Qingkun; Tang, Jianwei; Zhang, Yuan; Martinez, Angel; Wang, Shaowei; He, Sailing; White, Timothy J; Smalyukh, Ivan I

2014-05-01

We use both lyotropic liquid crystals composed of prolate micelles and thermotropic liquid crystals made of rod-like molecules to uniformly disperse and unidirectionally align relatively large gold nanorods and other complex-shaped nanoparticles at high concentrations. We show that some of these ensuing self-assembled orientationally ordered soft matter systems exhibit polarization-dependent plasmonic properties with strongly pronounced molar extinction exceeding that previously achieved in self-assembled composites. The long-range unidirectional alignment of gold nanorods is mediated mainly by anisotropic surface anchoring interactions at the surfaces of gold nanoparticles. Polarization-sensitive absorption, scattering, and extinction are used to characterize orientations of nanorods and other nanoparticles. The experimentally measured unique optical properties of these composites, which stem from the collective plasmonic effect of the gold nanorods with long-range order in a liquid crystal matrix, are reproduced in computer simulations. A simple phenomenological model based on anisotropic surface interaction explains the alignment of gold nanorods dispersed in liquid crystals and the physical underpinnings behind our observations.

Hydrodynamic and aerodynamic breakup of liquid sheets

NASA Technical Reports Server (NTRS)

Ingebo, R.

1982-01-01

The effect of hydrodynamic, aerodynamic and liquid surface forces on the mean drop diameter of water sprays that are produced by the breakup of nonswirling and swirling water sheets in quiescent air and in airflows similar to those encountered in gas turbine combustors is investigated. The mean drop diameter is used to characterize fuel sprays and it is a very important factor in determining the performance and exhaust emissions of gas turbine combustors.

Peregrine soliton generation and breakup in standard telecommunications fiber.

PubMed

Hammani, Kamal; Kibler, Bertrand; Finot, Christophe; Morin, Philippe; Fatome, Julien; Dudley, John M; Millot, Guy

2011-01-15

We present experimental and numerical results showing the generation and breakup of the Peregrine soliton in standard telecommunications fiber. The impact of nonideal initial conditions is studied through direct cutback measurements of the longitudinal evolution of the emerging soliton dynamics and is shown to be associated with the splitting of the Peregrine soliton into two subpulses, with each subpulse itself exhibiting Peregrine soliton characteristics. Experimental results are in good agreement with simulations.

Manufacturing Technology for Shipbuilding. Shipbuilding Technology Transfer

DTIC Science & Technology

1983-01-01

to fit those social and traditional parts of our organization that could not or should not be changed at this time. 1) New functions had to be absorbed... traditional mechanical design and design incorporating zone outfitting. - SCOPE OF THE JOB The scope of the engineering required for any job is put into...from the traditional development methodology as follows: - The breakup of the composite area follows the unit breakups rather than the traditional

Microfluidic breakups of confined droplets against a linear obstacle: The importance of the viscosity contrast

NASA Astrophysics Data System (ADS)

Salkin, Louis; Courbin, Laurent; Panizza, Pascal

2012-09-01

Combining experiments and theory, we investigate the break-up dynamics of deformable objects, such as drops and bubbles, against a linear micro-obstacle. Our experiments bring the role of the viscosity contrast Δη between dispersed and continuous phases to light: the evolution of the critical capillary number to break a drop as a function of its size is either nonmonotonic (Δη>0) or monotonic (Δη≤0). In the case of positive viscosity contrasts, experiments and modeling reveal the existence of an unexpected critical object size for which the critical capillary number for breakup is minimum. Using simple physical arguments, we derive a model that well describes observations, provides diagrams mapping the four hydrodynamic regimes identified experimentally, and demonstrates that the critical size originating from confinement solely depends on geometrical parameters of the obstacle.

Analysis of Fuel Injection and Atomization of a Hybrid Air-Blast Atomizer.

NASA Astrophysics Data System (ADS)

Ma, Peter; Esclape, Lucas; Buschhagen, Timo; Naik, Sameer; Gore, Jay; Lucht, Robert; Ihme, Matthias

2015-11-01

Fuel injection and atomization are of direct importance to the design of injector systems in aviation gas turbine engines. Primary and secondary breakup processes have significant influence on the drop-size distribution, fuel deposition, and flame stabilization, thereby directly affecting fuel conversion, combustion stability, and emission formation. The lack of predictive modeling capabilities for the reliable characterization of primary and secondary breakup mechanisms is still one of the main issues in improving injector systems. In this study, an unstructured Volume-of-Fluid method was used in conjunction with a Lagrangian-spray framework to conduct high-fidelity simulations of the breakup and atomization processes in a realistic gas turbine hybrid air blast atomizer. Results for injection with JP-8 aviation fuel are presented and compared to available experimental data. Financial support through the FAA National Jet Fuel Combustion Program is gratefully acknowledged.

Influence of electron beam irradiation on the microrheology of incompatible polymer blends: Thread break-up and coalescence

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

van Gisbergen, J.G.M.; Meijer, H.E.H.

1991-01-01

The microrheology of polymer blends as influenced by crosslinks induced in the dispersed phase via electron beam irradiation, is systematically investigated for the model system polystyrene/low density polyethylene (PS/LDPE). Both break-up of threads and coalescence of particles are delayed to a large extent, but are not inhibited completely and occur faster than would be expected for a nonirradiated material with a comparable viscosity. Small amplitude, dynamic rheological measurements indicated that in the irradiated materials a yield stress could exist. In contrast, direct microrheological measurements showed that this yield stress, which would prevent both break-up and coalescence, could not be realizedmore » by EB irradiation. Apparently, the direct study of the microrheology of a blend system is important for the prediction of the development of its morphology and it is not possible to rely only on rheological data obtained via other methods.« less

Characterization of Orbital Debris Via Hyper-Velocity Ground-Based Tests

NASA Technical Reports Server (NTRS)

Cowardin, Heather

2015-01-01

To replicate a hyper-velocity fragmentation event using modern-day spacecraft materials and construction techniques to better improve the existing DoD and NASA breakup models. DebriSat is intended to be representative of modern LEO satellites.Major design decisions were reviewed and approved by Aerospace subject matter experts from different disciplines. DebriSat includes 7 major subsystems. Attitude determination and control system (ADCS), command and data handling (C&DH), electrical power system (EPS), payload, propulsion, telemetry tracking and command (TT&C), and thermal management. To reduce cost, most components are emulated based on existing design of flight hardware and fabricated with the same materials. A key laboratory-based test, Satellite Orbital debris Characterization Impact Test (SOCIT), supporting the development of the DoD and NASA satellite breakup models was conducted at AEDC in 1992 .Breakup models based on SOCIT have supported many applications and matched on-orbit events reasonably well over the years.

Droplet size in flow: Theoretical model and application to polymer blends

NASA Astrophysics Data System (ADS)

Fortelný, Ivan; Jůza, Josef

2017-05-01

The paper is focused on prediction of the average droplet radius, R, in flowing polymer blends where the droplet size is determined by dynamic equilibrium between the droplet breakup and coalescence. Expressions for the droplet breakup frequency in systems with low and high contents of the dispersed phase are derived using available theoretical and experimental results for model blends. Dependences of the coalescence probability, Pc, on system parameters, following from recent theories, is considered and approximate equation for Pc in a system with a low polydispersity in the droplet size is proposed. Equations for R in systems with low and high contents of the dispersed phase are derived. Combination of these equations predicts realistic dependence of R on the volume fraction of dispersed droplets, φ. Theoretical prediction of the ratio of R to the critical droplet radius at breakup agrees fairly well with experimental values for steadily mixed polymer blends.

Theory and simulation of the dynamics, deformation, and breakup of a chain of superparamagnetic beads under a rotating magnetic field

NASA Astrophysics Data System (ADS)

Vázquez-Quesada, A.; Franke, T.; Ellero, M.

2017-03-01

In this work, an analytical model for the behavior of superparamagnetic chains under the effect of a rotating magnetic field is presented. It is postulated that the relevant mechanisms for describing the shape and breakup of the chains into smaller fragments are the induced dipole-dipole magnetic force on the external beads, their translational and rotational drag forces, and the tangential lubrication between particles. Under this assumption, the characteristic S-shape of the chain can be qualitatively understood. Furthermore, based on a straight chain approximation, a novel analytical expression for the critical frequency for the chain breakup is obtained. In order to validate the model, the analytical expressions are compared with full three-dimensional smoothed particle hydrodynamics simulations of magnetic beads showing excellent agreement. Comparison with previous theoretical results and experimental data is also reported.

Plate break-up geometry in SE-Afar

NASA Astrophysics Data System (ADS)

Geoffroy, Laurent; Le Gall, Bernard; Daoud, Mohamed

2014-05-01

New structural data acquired in Djibouti strongly support the view of a magma-rich to magma-poor pair of conjugate margins developed in SE Afar since at least 9 Ma. Our model is illustrated by a crustal-scale transect that emphasizes the role of a two-stage extensional detachment fault system, with opposing senses of motion through time. The geometry and kinematics of this detachment fault pattern are mainly documented from lavas and fault dip data extracted from remote sensing imagery (Landsat ETM+, and corresponding DEM), further calibrated by field observations. Although expressed by opposite fault geometries, the two successive extensional events evidenced here are part of a two-stage continental extensional tear-system associated with the ongoing propagation of the Aden-Tadjoura oceanic axis to the NW. A flip-flop evolution of detachment faults accommodating lithosphere divergence has recently been proposed for the development of the Indian Ocean and continental margins (Sauter et al., 2013). However, the SE Afar evolution further suggests a radical and sudden change in lithosphere behavior during extension, from a long-term and widespread magmatic stage to a syn-sedimentary break-up stage where mantle melting concentrates along the future oceanic axis. Of special interest is the fact that a late and rapid stage of non-magmatic extension led to break-up, whose geometry triggered the location of the break-up axis and earliest oceanic accretion. New structural data acquired in Djibouti strongly support the view of a magma-rich to magma-poor pair of conjugate margins developed in SE Afar since at least 9 Ma. Our model is illustrated by a crustal-scale transect that emphasizes the role of a two-stage extensional detachment fault system, with opposing senses of motion through time. The geometry and kinematics of this detachment fault pattern are mainly documented from lavas and fault dip data extracted from remote sensing imagery (Landsat ETM+, and corresponding DEM), further calibrated by field observations. Although expressed by opposite fault geometries, the two successive extensional events evidenced here are part of a two-stage continental extensional tear-system associated with the ongoing propagation of the Aden-Tadjoura oceanic axis to the NW. A flip-flop evolution of detachment faults accommodating lithosphere divergence has recently been proposed for the development of the Indian Ocean and continental margins (Sauter et al., 2013). However, the SE Afar evolution further suggests a radical and sudden change in lithosphere behavior during extension, from a long-term and widespread magmatic stage to a syn-sedimentary break-up stage where mantle melting concentrates along the future oceanic axis. Of special interest is the fact that a late and rapid stage of non-magmatic extension led to break-up, whose geometry triggered the location of the break-up axis and earliest oceanic accretion.

Plasma Entry from Tail into the Dipolar Magnetosphere During Substorms

NASA Astrophysics Data System (ADS)

Haerendel, Gerhard

Plasma entering the dipolar magnetosphere from the tail has to overcome the obstacle presented by the conductivity enhancements caused by the poleward arc(s). While the arcs move poleward, the plasma proceeds equatorward as testified by the existence of a westward electric field. The arcs break into smaller-scale structures and loops with a tendency of eastward growth and expansion, although the basic driving force is directed earthward/equatorward. The likely reason is that the arc-related conductivity enhancements act as flow barriers and convert normal into shear stresses. The energy derived from the release of the shear stresses and dissipated in the arcs lowers the entropy content of the flux tubes and enables their earthward progression. In addition, poleward jumps of the breakup arcs are quite common. They result from refreshments of the generator plasma by the sequential arrival of flow bursts from the near-Earth neutral line. Once inside the oval, the plasma continues to move equatorward as manifested through north-south aligned auroral forms. Owing to the existence of an inner border of the oval, marked by the Region 2 currents, all flows are eventually diverted sunward.

Investigation of large α production in reactions involving weakly bound 7Li

NASA Astrophysics Data System (ADS)

Pandit, S. K.; Shrivastava, A.; Mahata, K.; Parkar, V. V.; Palit, R.; Keeley, N.; Rout, P. C.; Kumar, A.; Ramachandran, K.; Bhattacharyya, S.; Nanal, V.; Palshetkar, C. S.; Nag, T. N.; Gupta, Shilpi; Biswas, S.; Saha, S.; Sethi, J.; Singh, P.; Chatterjee, A.; Kailas, S.

2017-10-01

The origin of the large α -particle production cross sections in systems involving weakly bound 7Li projectiles has been investigated by measuring the cross sections of all possible fragment-capture as well as complete fusion using the particle-γ coincidence, in-beam, and off-beam γ -ray counting techniques for the 7Li+93Nb system at near Coulomb barrier energies. Almost all of the inclusive α -particle yield has been accounted for. While the t -capture mechanism is found to be dominant (˜70 % ), compound nuclear evaporation and breakup processes contribute ˜15 % each to the inclusive α -particle production in the measured energy range. Systematic behavior of the t capture and inclusive α cross sections for reactions involving 7Li over a wide mass range is also reported.

Measurement of Neutron Reaction Cross Sections between 8 and 14 MeV

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

Mannhart, Wolf; Schmidt, Dankwart

2005-05-24

Cross-section measurements were performed with special emphasis on access to the 'blind spot' in the neutron energy range from 10 to 13 MeV. The use of a conventional D(d,n) neutron source in combination with TOF measurements of the D(d,np) break-up component allows the precise determination of monoenergetic cross-section data in this range. The procedure is demonstrated with the measurement of the cross sections of 64Zn(n,p)64Cu, 64Zn(n,2n)63Zn, 63Cu(n,2n)62Cu, and 65Cu(n,2n)64Cu. With all reaction products being strong positron emitters, the radioactivity-counting process has been optimised for a perfect registration of the associated annihilation radiation.

Measurement of Neutron Reaction Cross Sections between 8 and 14 MeV

NASA Astrophysics Data System (ADS)

Mannhart, Wolf; Schmidt, Dankwart

2005-05-01

Cross-section measurements were performed with special emphasis on access to the "blind spot" in the neutron energy range from 10 to 13 MeV. The use of a conventional D(d,n) neutron source in combination with TOF measurements of the D(d,np) break-up component allows the precise determination of monoenergetic cross-section data in this range. The procedure is demonstrated with the measurement of the cross sections of 64Zn(n,p)64Cu, 64Zn(n,2n)63Zn, 63Cu(n,2n)62Cu, and 65Cu(n,2n)64Cu. With all reaction products being strong positron emitters, the radioactivity-counting process has been optimised for a perfect registration of the associated annihilation radiation.

Time sequence analysis of flickering auroras. I - Application of Fourier analysis. [in atmosphere

NASA Technical Reports Server (NTRS)

Berkey, F. T.; Silevitch, M. B.; Parsons, N. R.

1980-01-01

Using a technique that enables one to digitize the brightness of auroral displays from individual fields of a video signal, we have analyzed the frequency content of flickering aurora. Through the application of Fourier analysis to our data, we have found that flickering aurora contains a wide range of enhanced frequencies, although the dominant frequency enhancement generally occurs in the range 6-12 Hz. Each incidence of flickering that we observed was associated with increased radio wave absorption. Furthermore, we have found that flickering occurs in bright auroral surges, the occurrence of which is not limited to the 'breakup' phase of auroral substorms. Our results are interpreted in terms of a recently proposed theory of fluctuating double layers that accounts for a number of the observational features.

Outcomes of long retrograde intramedullary nailing for periprosthetic supracondylar femoral fractures following total knee arthroplasty.

PubMed

Lee, Sung-San; Lim, Seung-Jae; Moon, Young-Wan; Seo, Jai-Gon

2014-01-01

The treatment of periprosthetic supracondylar femoral fractures following total knee arthroplasty (TKA) is challenging because of osteopenia and the limited bone available for distal fixation. The purpose of this study was to report the outcomes of periprosthetic supracondylar femoral fractures treated with long retrograde intramedullary nailing. We conducted a retrospective review of 25 patients who were treated with a long retrograde intramedullary nail for periprosthetic supracondylar femoral fractures following TKA. Clinical evaluation included range of motion of knee, Knee Society Score (KSS), Western Ontario and McMaster Universities Arthritis (WOMAC) score, and radiologic evaluation including time to union, coronal and sagittal alignment of femoral component, lower limb alignment, and implant loosening. The mean duration of follow-up after the fracture repair was 39 months (range 12-47). All 25 fractures were united with a mean time of 12 weeks (range 8-20). At the last follow-up, the mean knee flexion was 111° (range 60°-130°), the mean KSS was 81.5 (range 50-100), and the mean WOMAC score was 30.2 (range 5-55). Four (16%) of the 25 patients developed malalignment according to Rorabeck and Taylor criteria, but all patients had a knee flexion of more than 90°. Coronal and sagittal alignments of femoral component and lower limb alignment did not differ significantly between before and after the fracture repair. Complications included the loosening or breakage of distal interlocking screws in three patients. No deep infection or prosthesis loosening was detected at the last follow-up. Surgical treatment of periprosthetic supracondylar femoral fractures following TKA with long retrograde intramedullary nailing resulted in high union rates and encouraging functional outcomes.

Self-Alignment MEMS IMU Method Based on the Rotation Modulation Technique on a Swing Base

PubMed Central

Chen, Zhiyong; Yang, Haotian; Wang, Chengbin; Lin, Zhihui; Guo, Meifeng

2018-01-01

The micro-electro-mechanical-system (MEMS) inertial measurement unit (IMU) has been widely used in the field of inertial navigation due to its small size, low cost, and light weight, but aligning MEMS IMUs remains a challenge for researchers. MEMS IMUs have been conventionally aligned on a static base, requiring other sensors, such as magnetometers or satellites, to provide auxiliary information, which limits its application range to some extent. Therefore, improving the alignment accuracy of MEMS IMU as much as possible under swing conditions is of considerable value. This paper proposes an alignment method based on the rotation modulation technique (RMT), which is completely self-aligned, unlike the existing alignment techniques. The effect of the inertial sensor errors is mitigated by rotating the IMU. Then, inertial frame-based alignment using the rotation modulation technique (RMT-IFBA) achieved coarse alignment on the swing base. The strong tracking filter (STF) further improved the alignment accuracy. The performance of the proposed method was validated with a physical experiment, and the results of the alignment showed that the standard deviations of pitch, roll, and heading angle were 0.0140°, 0.0097°, and 0.91°, respectively, which verified the practicality and efficacy of the proposed method for the self-alignment of the MEMS IMU on a swing base. PMID:29649150

Score distributions of gapped multiple sequence alignments down to the low-probability tail

NASA Astrophysics Data System (ADS)

Fieth, Pascal; Hartmann, Alexander K.

2016-08-01

Assessing the significance of alignment scores of optimally aligned DNA or amino acid sequences can be achieved via the knowledge of the score distribution of random sequences. But this requires obtaining the distribution in the biologically relevant high-scoring region, where the probabilities are exponentially small. For gapless local alignments of infinitely long sequences this distribution is known analytically to follow a Gumbel distribution. Distributions for gapped local alignments and global alignments of finite lengths can only be obtained numerically. To obtain result for the small-probability region, specific statistical mechanics-based rare-event algorithms can be applied. In previous studies, this was achieved for pairwise alignments. They showed that, contrary to results from previous simple sampling studies, strong deviations from the Gumbel distribution occur in case of finite sequence lengths. Here we extend the studies to multiple sequence alignments with gaps, which are much more relevant for practical applications in molecular biology. We study the distributions of scores over a large range of the support, reaching probabilities as small as 10-160, for global and local (sum-of-pair scores) multiple alignments. We find that even after suitable rescaling, eliminating the sequence-length dependence, the distributions for multiple alignment differ from the pairwise alignment case. Furthermore, we also show that the previously discussed Gaussian correction to the Gumbel distribution needs to be refined, also for the case of pairwise alignments.

Macroscopic Ensembles of Aligned Carbon Nanotubes in Bubble Imprints Studied by Polarized Raman Microscopy

DOE PAGES

Ushiba, Shota; Hoyt, Jordan; Masui, Kyoko; ...

2014-01-01

We study the alignment of single-wall carbon nanotubes (SWCNTs) in bubble imprints through polarized Raman microscopy. A hemispherical bubble containing SWCNTs is pressed against a glass substrate, resulting in an imprint of the bubble membrane with a coffee ring on the substrate. We find that macroscopic ensembles of aligned SWCNTs are obtained in the imprints, in which there are three patterns of orientations: (i) azimuthal alignment on the coffee ring, (ii) radial alignment at the edge of the membrane, and (iii) random orientation at the center of the membrane. We also find that the alignment of SWCNTs in the imprintsmore » can be manipulated by spinning bubbles. The orientation of SWCNTs on the coffee ring is directed radially, which is orthogonal to the case of unspun bubbles. This approach enables one to align SWCNTs in large quantities and in a short time, potentially opening up a wide range of CNT-based electronic and optical applications.« less

A Probabilistic Model of Local Sequence Alignment That Simplifies Statistical Significance Estimation

PubMed Central

Eddy, Sean R.

2008-01-01

Sequence database searches require accurate estimation of the statistical significance of scores. Optimal local sequence alignment scores follow Gumbel distributions, but determining an important parameter of the distribution (λ) requires time-consuming computational simulation. Moreover, optimal alignment scores are less powerful than probabilistic scores that integrate over alignment uncertainty (“Forward” scores), but the expected distribution of Forward scores remains unknown. Here, I conjecture that both expected score distributions have simple, predictable forms when full probabilistic modeling methods are used. For a probabilistic model of local sequence alignment, optimal alignment bit scores (“Viterbi” scores) are Gumbel-distributed with constant λ = log 2, and the high scoring tail of Forward scores is exponential with the same constant λ. Simulation studies support these conjectures over a wide range of profile/sequence comparisons, using 9,318 profile-hidden Markov models from the Pfam database. This enables efficient and accurate determination of expectation values (E-values) for both Viterbi and Forward scores for probabilistic local alignments. PMID:18516236

Evaluation of the Safety and Tolerability of Conjunctival Ring for Posterior Segment of the Eye.

PubMed

Kinoshita, Satoshi; Ohguchi, Takeshi; Noda, Kousuke; Murata, Miyuki; Yasueda, Shin-Ichi; Obata, Haruka; Matsunaga, Toru; Fukushima, Tsutomu; Kanda, Atsuhiro; Ishida, Susumu

2017-08-01

To evaluate the safety and tolerability of conjunctival rings (CRs), a novel device for drug delivery to the posterior segment of the eye. In animal studies, CRs containing 5% dexamethasone sodium phosphate (DSP) or vehicle solution were placed on the right and left eyes of C57BL/6J mice, respectively. Contact lenses (CLs) containing vehicle solution were used as a control. Twenty-four hours after placement of the CRs, corneal fluorescein staining was graded based on the McDonald-Shadduck scoring system, ranging from 0 to 4. In humans, CRs containing vehicle solution were placed on the right eye of healthy volunteers for 9 hours. The corneal curvature, corneal thickness, intraocular pressure, visual acuity, tear production (Schirmer I test), tear film break-up time and fluorescein staining scores of the cornea (scores ranging from 0 to 3) and conjunctiva (scores ranging from 0 to 6) were assessed before and after wearing the CRs. The release characteristics of DSP from CRs were also evaluated. In animal experiments, corneal fluorescein staining scores were 1 or less in all the groups, and there was no significant difference between the CR group and the CL group. In the preclinical safety evaluation of CR for humans, ophthalmic examination revealed that CR caused no significant changes in all the parameters investigated including corneal curvature (p = 0.77), corneal thickness (p = 0.96), intraocular pressure (p = 0.59), visual acuity (p = 0.14), Schirmer I test results (p = 0.76), tear film break-up time (p = 0.68), corneal fluorescein staining scores (p = 0.64), and conjunctival fluorescein staining scores (p = 0.52). The DSP release from CRs occurs within a few hours, which is similar to the drug-release property of medicated CL, as reported previously. The current data showed the safety and tolerability of CR as a drug delivery device for the treatment of posterior segment diseases.

Image-based quantification of fiber alignment within electrospun tissue engineering scaffolds is related to mechanical anisotropy.

PubMed

Fee, Timothy; Downs, Crawford; Eberhardt, Alan; Zhou, Yong; Berry, Joel

2016-07-01

It is well documented that electrospun tissue engineering scaffolds can be fabricated with variable degrees of fiber alignment to produce scaffolds with anisotropic mechanical properties. Several attempts have been made to quantify the degree of fiber alignment within an electrospun scaffold using image-based methods. However, these methods are limited by the inability to produce a quantitative measure of alignment that can be used to make comparisons across publications. Therefore, we have developed a new approach to quantifying the alignment present within a scaffold from scanning electron microscopic (SEM) images. The alignment is determined by using the Sobel approximation of the image gradient to determine the distribution of gradient angles with an image. This data was fit to a Von Mises distribution to find the dispersion parameter κ, which was used as a quantitative measure of fiber alignment. We fabricated four groups of electrospun polycaprolactone (PCL) + Gelatin scaffolds with alignments ranging from κ = 1.9 (aligned) to κ = 0.25 (random) and tested our alignment quantification method on these scaffolds. It was found that our alignment quantification method could distinguish between scaffolds of different alignments more accurately than two other published methods. Additionally, the alignment parameter κ was found to be a good predictor the mechanical anisotropy of our electrospun scaffolds. The ability to quantify fiber alignment within and make direct comparisons of scaffold fiber alignment across publications can reduce ambiguity between published results where cells are cultured on "highly aligned" fibrous scaffolds. This could have important implications for characterizing mechanics and cellular behavior on aligned tissue engineering scaffolds. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 104A: 1680-1686, 2016. © 2016 Wiley Periodicals, Inc.

An Accurate Scalable Template-based Alignment Algorithm

PubMed Central

Gardner, David P.; Xu, Weijia; Miranker, Daniel P.; Ozer, Stuart; Cannone, Jamie J.; Gutell, Robin R.

2013-01-01

The rapid determination of nucleic acid sequences is increasing the number of sequences that are available. Inherent in a template or seed alignment is the culmination of structural and functional constraints that are selecting those mutations that are viable during the evolution of the RNA. While we might not understand these structural and functional, template-based alignment programs utilize the patterns of sequence conservation to encapsulate the characteristics of viable RNA sequences that are aligned properly. We have developed a program that utilizes the different dimensions of information in rCAD, a large RNA informatics resource, to establish a profile for each position in an alignment. The most significant include sequence identity and column composition in different phylogenetic taxa. We have compared our methods with a maximum of eight alternative alignment methods on different sets of 16S and 23S rRNA sequences with sequence percent identities ranging from 50% to 100%. The results showed that CRWAlign outperformed the other alignment methods in both speed and accuracy. A web-based alignment server is available at http://www.rna.ccbb.utexas.edu/SAE/2F/CRWAlign. PMID:24772376

X-ray microprobe of orbital alignment in strong-field ionized atoms.

PubMed

Young, L; Arms, D A; Dufresne, E M; Dunford, R W; Ederer, D L; Höhr, C; Kanter, E P; Krässig, B; Landahl, E C; Peterson, E R; Rudati, J; Santra, R; Southworth, S H

2006-08-25

We have developed a synchrotron-based, time-resolved x-ray microprobe to investigate optical strong-field processes at intermediate intensities (10(14) - 10(15) W/cm2). This quantum-state specific probe has enabled the direct observation of orbital alignment in the residual ion produced by strong-field ionization of krypton atoms via resonant, polarized x-ray absorption. We found strong alignment to persist for a period long compared to the spin-orbit coupling time scale (6.2 fs). The observed degree of alignment can be explained by models that incorporate spin-orbit coupling. The methodology is applicable to a wide range of problems.

Growth of vertically aligned carbon nanotubes on silicon and quartz substrate by spray pyrolysis of a natural precursor: Turpentine oil

NASA Astrophysics Data System (ADS)

Afre, Rakesh A.; Soga, T.; Jimbo, T.; Kumar, Mukul; Ando, Y.; Sharon, M.

2005-10-01

Vertically aligned carbon nanotubes (VACNTs) were grown by spray pyrolysis of turpentine oil and ferrocene mixture at 700 °C. Using this simple method, we report the successful growth of vertically aligned nanotubes of 300 μm length and diameter in the range of 50-100 nm on Si(1 0 0) substrate. The ferrocene act as an in situ Fe catalyst precursor and forming the nanosize iron particles for formation of VACNTs on Si and quartz substrates. Morphological differences between aligned carbon nanotubes grown on different substrates are studied and discussed by SEM, TEM and Raman spectroscopy characterizations.

Parental alignments and rejection: an empirical study of alienation in children of divorce.

PubMed

Johnston, Janet R

2003-01-01

This study of family relationships after divorce examined the frequency and extent of child-parent alignments and correlates of children's rejection of a parent, these being basic components of the controversial idea of "parental alienation syndrome." The sample consisted of 215 children from the family courts and general community two to three years after parental separation. The findings indicate that children's attitudes toward their parents range from positive to negative, with relatively few being extremely aligned or rejecting. Rejection of a parent has multiple determinants, with both the aligned and rejected parents contributing to the problem, in addition to vulnerabilities within children themselves.

MetAlign: interface-driven, versatile metabolomics tool for hyphenated full-scan mass spectrometry data preprocessing.

PubMed

Lommen, Arjen

2009-04-15

Hyphenated full-scan MS technology creates large amounts of data. A versatile easy to handle automation tool aiding in the data analysis is very important in handling such a data stream. MetAlign softwareas described in this manuscripthandles a broad range of accurate mass and nominal mass GC/MS and LC/MS data. It is capable of automatic format conversions, accurate mass calculations, baseline corrections, peak-picking, saturation and mass-peak artifact filtering, as well as alignment of up to 1000 data sets. A 100 to 1000-fold data reduction is achieved. MetAlign software output is compatible with most multivariate statistics programs.

Ballistic Imaging of Liquid Breakup Processes in Dense Sprays

DTIC Science & Technology

2009-06-24

spray breakup in its entirety. Gas-phase flowfield dynamics can be captured via particle image velocimetry (PIV) and/or laser Doppler velocimetry... Coherent Legend Ti:Sapphire regenerative amplifier, seeded with a Spectra-Physics Tsunami Ti:Sapphire mode-locked laser generating 40 fs, 2.5 mJ pulses...scattering turbid media. Laser Phys. Lett., 3(9):464–7, 2006. [44] B. Kaldvee, A. Ehn, J. Bood, and M. Aldén. Development of a picosecond- LIDAR system

Breakup of Pack Ice, Antarctic Ice Shelf

NASA Technical Reports Server (NTRS)

1991-01-01

Breakup of Pack Ice along the periphery of the Antarctic Ice Shelf (53.5S, 3.0E) produced this mosaic of ice floes off the Antarctic Ice Shelf. Strong offshore winds, probably associated with strong katabatic downdrafts from the interior of the continent, are seen peeling off the edges of the ice shelf into long filamets of sea ice, icebergs, bergy bits and growlers to flow northward into the South Atlantic Ocean. 53.5S, 3.0E

Low-altitude acceleration of auroral electrons during breakup observed by a mother-daughter rocket

NASA Technical Reports Server (NTRS)

Johnstone, A. D.; Davis, T. N.

1974-01-01

By the use of a mother-daughter rocket combination and ground-based observations with television, time and space variations are resolved in particle measurements in breakup aurora. The spectral variations measured during a temporal variation in the aurora can be explained by a nearly uniform acceleration of all the electrons such as would be caused by an electric potential drop along the magnetic field lines. Many other explanations can be eliminated.

A combined Eulerian-volume of fraction-Lagrangian method for atomization simulation

NASA Technical Reports Server (NTRS)

Seung, S. P.; Chen, C. P.; Ziebarth, John P.

1994-01-01

The tracking of free surfaces between liquid and gas phases and analysis of the interfacial phenomena between the two during the atomization and breakup process of a liquid fuel jet is modeled. Numerical modeling of liquid-jet atomization requires the resolution of different conservation equations. Detailed formulation and validation are presented for the confined dam broken problem, the water surface problem, the single droplet problem, a jet breakup problem, and the liquid column instability problem.

Large-eddy simulation of cavitating nozzle flow and primary jet break-up

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

Örley, F., E-mail: felix.oerley@aer.mw.tum.de; Trummler, T.; Mihatsch, M. S.

We employ a barotropic two-phase/two-fluid model to study the primary break-up of cavitating liquid jets emanating from a rectangular nozzle, which resembles a high aspect-ratio slot flow. All components (i.e., gas, liquid, and vapor) are represented by a homogeneous mixture approach. The cavitating fluid model is based on a thermodynamic-equilibrium assumption. Compressibility of all phases enables full resolution of collapse-induced pressure wave dynamics. The thermodynamic model is embedded into an implicit large-eddy simulation (LES) environment. The considered configuration follows the general setup of a reference experiment and is a generic reproduction of a scaled-up fuel injector or control valve asmore » found in an automotive engine. Due to the experimental conditions, it operates, however, at significantly lower pressures. LES results are compared to the experimental reference for validation. Three different operating points are studied, which differ in terms of the development of cavitation regions and the jet break-up characteristics. Observed differences between experimental and numerical data in some of the investigated cases can be caused by uncertainties in meeting nominal parameters by the experiment. The investigation reveals that three main mechanisms promote primary jet break-up: collapse-induced turbulent fluctuations near the outlet, entrainment of free gas into the nozzle, and collapse events inside the jet near the liquid-gas interface.« less

Time-Resolved Imaging Study of Jetting Dynamics during Laser Printing of Viscoelastic Alginate Solutions.

PubMed

Zhang, Zhengyi; Xiong, Ruitong; Mei, Renwei; Huang, Yong; Chrisey, Douglas B

2015-06-16

Matrix-assisted pulsed-laser evaporation direct-write (MAPLE DW) has been successfully implemented as a promising laser printing technology for various fabrication applications, in particular, three-dimensional bioprinting. Since most bioinks used in bioprinting are viscoelastic, it is of importance to understand the jetting dynamics during the laser printing of viscoelastic fluids in order to control and optimize the laser printing performance. In this study, MAPLE DW was implemented to study the jetting dynamics during the laser printing of representative viscoelastic alginate bioinks and evaluate the effects of operating conditions (e.g., laser fluence) and material properties (e.g., alginate concentration) on the jet formation performance. Through a time-resolved imaging approach, it is found that when the laser fluence increases or the alginate concentration decreases, the jetting behavior changes from no material transferring to well-defined jetting to well-defined jetting with an initial bulgy shape to jetting with a bulgy shape to pluming/splashing. For the desirable well-defined jetting regimes, as the laser fluence increases, the jet velocity and breakup length increase while the breakup time and primary droplet size decrease. As the alginate concentration increases, the jet velocity and breakup length decrease while the breakup time and primary droplet size increase. In addition, Ohnesorge, elasto-capillary, and Weber number based phase diagrams are presented to better appreciate the dependence of jetting regimes on the laser fluence and alginate concentration.

Using Sound To Study the Effect of Frothers on the Breakaway of Air Bubbles at an Underwater Capillary.

PubMed

Chu, Pengbo; Pax, Randolph; Li, Ronghao; Langlois, Ray; Finch, James A

2017-04-04

Frothers, a class of surfactants, are widely employed in froth flotation to aid the generation of small bubbles. Their action is commonly explained by their ability to hinder coalescence. There are occasional references suggesting that the frother may also play a role in the initial breakup of the injected air mass. This work investigates the possible effect of the frother on breakup by monitoring air bubbles produced quasi-statically at an underwater capillary. Under this condition, breakup is isolated from coalescence and an impact of frothers on the detached bubble can be ascribed to an impact on breakup. The breakaway process was monitored by an acoustic technique along with high-speed cinematography. The results showed that the presence of frothers did influence the breakaway process and that the acoustic technique was able to detect the impact. It was demonstrated that the acoustic frequency and acoustic damping ratio depend upon the frother type and concentration and that they are associated with a liquid jet, which initially excites the bubble and then decays to form a surface wave. The addition of the frother did not influence the formation of the jet but did increase its decay rate, hence, dampening the surface wave. It is postulated that the action of the frother is related to an effect on the magnitude of surface tension gradients.

Evaporation of oil-water emulsion drops when heated at high temperature

NASA Astrophysics Data System (ADS)

Strizhak, P. A.; Piskunov, M. V.; Kuznetsov, G. V.; Voytkov, I. S.

2017-10-01

An experimental study on conditions and main characteristics for high-temperature (more than 700 K) evaporation of oil-water drops is presented. The high-temperature water purification from impurities can be the main practical application of research results. Thus, the heating of drops is implemented by the two typical schemes: on a massive substrate (the heating conditions are similar to those achieved in a heating chamber) and in a flow of the heated air. In the latter case, the heating conditions correspond to those attained while moving water drops with impurities in a counter high-temperature gaseous flow in the process of water purification. Evaporation time as function of heating temperature is presented. The influence of oil product concentration in an emulsion drop on evaporation characteristics is discussed. The conditions for intensive flash boiling of an emulsion drop and its explosive breakup with formation of the fine droplets cloud are pointed out. Heat fluxes required for intensive flash boiling and explosive breakup of a drop with further formation of the fine aerosol are determined in the boundary layer of a drop. The fundamental differences between flash boiling and explosive breakup of an emulsion drop when heated on a substrate and in a flow of the heated air are described. The main prospects for the development of the high-temperature water purification technology are detailed taking into account the fast emulsion drop breakup investigated in the paper.

Unstable bidimensional grids of liquid filaments: Drop pattern after breakups

NASA Astrophysics Data System (ADS)

Diez, Javier; Cuellar, Ingrith; Ravazzoli, Pablo; Gonzalez, Alejandro

2017-11-01

A rectangular grid formed by liquid filaments on a partially wetting substrate evolves in a series of breakups leading to arrays of drops with different shapes distributed in a rather regular bidimensional pattern. Our study is focused on the configuration produced when two long parallel filaments of silicone oil, which are placed upon a glass substrate previously coated with a fluorinated solution, are crossed perpendicularly by another pair of long parallel filaments. A remarkable feature of this kind of grids is that there are two qualitatively different types of drops. While one set is formed at the crossing points, the rest are consequence of the breakup of shorter filaments formed between the crossings. Here, we analyze the main geometric features of all types of drops, such as shape of the footprint and contact angle distribution along the drop periphery. The formation of a series of short filaments with similar geometric and physical properties allows us to have simultaneously quasi identical experiments to study the subsequent breakups. We develop a simple hydrodynamic model to predict the number of drops that results from a filament of given initial length and width. This model is able to yield the length intervals corresponding to a small number of drops. We acknowledge support from CONICET-Argentina (Grant PIP 844/2012) and ANPCyT-Argentina (Grant PICT 931/2012).

Hard breakup of the deuteron into two Δ -isobars

NASA Astrophysics Data System (ADS)

Granados, Carlos; Sargsian, Misak

2011-04-01

Photodisintegration of the deuteron into two Δ-isobars at large center of mass angles is studied within the QCD hard rescattering model (HRM). According to the HRM, the reaction proceeds in three main steps: the photon knocks the quark from one of the nucleons in the deuteron; the struck quark rescatters off a quark from the other nucleon sharing the high energy of the photon; then the energetic quarks recombine into two outgoing baryons emerging at large transverse momenta. Within the HRM, the cross section is expressed through the amplitude of pn --> ΔΔ scattering which we evaluated based on the quark-interchange model of hard hadronic scattering. We predict that the cross section of the deuteron breakup to Δ++Δ- is 4-5 times larger than that of the breakup to the Δ+Δ0 channel. Also, the angular distributions for these two channels are markedly different. These can be compared with the predictions based on the assumption that two hard Δ-isobars are the result of the disintegration of initial ΔΔ components of the deuteron wave function. In this case, the angular distributions and cross sections of the breakup in both Δ++Δ- and Δ+Δ0 channels are expected to be similar. This work was supported by U.S. Department of Energy Grant under contract DE-FG02-01ER41172, and by the FIU DEA program.

Hard breakup of the deuteron into two Δ isobars

NASA Astrophysics Data System (ADS)

Granados, Carlos G.; Sargsian, Misak M.

2011-05-01

We study high-energy photodisintegration of the deuteron into two Δ isobars at large center of mass angles within the QCD hard rescattering model (HRM). According to the HRM, the process develops in three main steps: the photon knocks a quark from one of the nucleons in the deuteron; the struck quark rescatters off a quark from the other nucleon sharing the high energy of the photon; then the energetic quarks recombine into two outgoing baryons which have large transverse momenta. Within the HRM, the cross section is expressed through the amplitude of pn→ΔΔ scattering which we evaluated based on the quark-interchange model of hard hadronic scattering. Calculations show that the angular distribution and the strength of the photodisintegration is mainly determined by the properties of the pn→ΔΔ scattering. We predict that the cross section of the deuteron breakup to Δ++Δ- is 4-5 times larger than that of the breakup to the Δ+Δ0 channel. Also, the angular distributions for these two channels are markedly different. These can be compared with the predictions based on the assumption that two hard Δ isobars are the result of the disintegration of the preexisting ΔΔ components of the deuteron wave function. In this case, one expects the angular distributions and cross sections of the breakup in both Δ++Δ- and Δ+Δ0 channels to be similar.

Stability analysis applied to the early stages of viscous drop breakup by a high-speed gas stream

NASA Astrophysics Data System (ADS)

Padrino, Juan C.; Longmire, Ellen K.

2013-11-01

The instability of a liquid drop suddenly exposed to a high-speed gas stream behind a shock wave is studied by considering the gas-liquid motion at the drop interface. The discontinuous velocity profile given by the uniform, parallel flow of an inviscid, compressible gas over a viscous liquid is considered, and drop acceleration is included. Our analysis considers compressibility effects not only in the base flow, but also in the equations of motion for the perturbations. Recently published high-resolution images of the process of drop breakup by a passing shock have provided experimental evidence supporting the idea that a critical gas dynamic pressure can be found above which drop piercing by the growth of acceleration-driven instabilities gives way to drop breakup by liquid entrainment resulting from the gas shearing action. For a set of experimental runs from the literature, results show that, for shock Mach numbers >= 2, a band of rapidly growing waves forms in the region well upstream of the drop's equator at the location where the base flow passes from subsonic to supersonic, in agreement with experimental images. Also, the maximum growth rate can be used to predict the transition of the breakup mode from Rayleigh-Taylor piercing to shear-induced entrainment. The authors acknowledge support of the NSF (DMS-0908561).

Four-body extension of the continuum-discretized coupled-channels method

NASA Astrophysics Data System (ADS)

Descouvemont, P.

2018-06-01

I develop an extension of the continuum-discretized coupled-channels (CDCC) method to reactions where both nuclei present a low breakup threshold. This leads to a four-body model, where the only inputs are the interactions describing the colliding nuclei, and the four optical potentials between the fragments. Once these potentials are chosen, the model does not contain any additional parameter. First I briefly discuss the general formalism, and emphasize the need for dealing with large coupled-channel systems. The method is tested with existing benchmarks on 4 α bound states with the Ali-Bodmer potential. Then I apply the four-body CDCC to the 11Be+d system, where I consider the 10Be(0+,2+)+n configuration for 11Be. I show that breakup channels are crucial to reproduce the elastic cross section, but that core excitation plays a weak role. The 7Li+d system is investigated with an α +t cluster model for 7Li. I show that breakup channels significantly improve the agreement with the experimental cross section, but an additional imaginary term, simulating missing transfer channels, is necessary. The full CDCC results can be interpreted by equivalent potentials. For both systems, the real part is weakly affected by breakup channels, but the imaginary part is strongly modified. I suggest that the present wave functions could be used in future DWBA calculations.

The sagittal stem alignment and the stem version clearly influence the impingement-free range of motion in total hip arthroplasty: a computer model-based analysis.

PubMed

Müller, Michael; Duda, Georg; Perka, Carsten; Tohtz, Stephan

2016-03-01

The component alignment in total hip arthroplasty influences the impingement-free range of motion (ROM). While substantiated data is available for the cup positioning, little is known about the stem alignment. Especially stem rotation and the sagittal alignment influence the position of the cone in relation to the edge of the socket and thus the impingement-free functioning. Hence, the question arises as to what influence do these parameters have on the impingement-free ROM? With the help of a computer model the influence of the sagittal stem alignment and rotation on the impingement-free ROM were investigated. The computer model was based on the CT dataset of a patient with a non-cemented THA. In the model the stem version was set at 10°/0°/-10° and the sagittal alignment at 5°/0°/-5°, which resulted in nine alternative stem positions. For each position, the maximum impingement-free ROM was investigated. Both stem version and sagittal stem alignment have a relevant influence on the impingement-free ROM. In particular, flexion and extension as well as internal and external rotation capability present evident differences. In the position intervals of 10° sagittal stem alignment and 20° stem version a difference was found of about 80° in the flexion and 50° in the extension capability. Likewise, differences were evidenced of up to 72° in the internal and up to 36° in the external rotation. The sagittal stem alignment and the stem torsion have a relevant influence on the impingement-free ROM. To clarify the causes of an impingement or accompanying problems, both parameters should be examined and, if possible, a combined assessment of these factors should be made.

The Role of Transforms in Gulf of Mexico Opening

NASA Astrophysics Data System (ADS)

Lundin, E.; Doré, A. G.

2017-12-01

The curious pie-shaped Gulf of Mexico (GoM) may be considered a high-angle back-arc basin to the Pacific Ocean. Opening was strongly facilitated by transforms, including a terminal transform on its Pacific side. GoM also formed synchronously with the nearby Central Atlantic when Gondwanaland pulled away from Laurasia in the Jurassic. Notably, GoM's oceanic crust never connected with that of the Atlantic, and the isolated nature of this small ocean led to periodically confined conditions that influenced the petroleum system. Of particular importance are the deposition of Callovian age salt and Tithonian age source rocks. The central part of GoM is generally accepted as underlain by oceanic crust, but the position of the continent-ocean boundaries (COB) is debated, as well as the nature of intervening crust. We favor an interpretation of the COBs marked by the regional scale, large-amplitude Houston, Florida, and Campeche magnetic anomalies, in turn probably reflecting seaward dipping reflectors of magma-rich margins. GoM's unusual shape may indirectly represent utilization of pre-existing transforms during the break-up of Pangea. Transforms represent long, linear weaknesses where the crust and lithosphere is already broken. Transforms seem to have governed the break-up of several oceanic segments in the North Atlantic and Arctic. The Suwanne suture of the Rheic Ocean is a pronounced magnetic anomaly that crosses Georgia-Florida and becomes aligned with the Houston magnetic anomaly, which here is interpreted as the northern COB to GoM. The Suwanne suture is oriented at high angle to the rest of the Rheic suture along the Appalachians and probably experienced lateral motion during the transpressional closure of the Rheic Ocean. This transform arguably represents a weak element in the Ouachita-Marathon orogen that allowed the Yucatan microcontinent to easily be plucked from the North American margin during the dispersal of Pangea, forming the GoM in the process. This opening mode is analogous to that of the pie-shaped Iceland Basin and the Jan Mayen microcontinent in the Northeast Atlantic.

Normal-Faulting in Madagascar: Another Round of Continental Rifting?

NASA Astrophysics Data System (ADS)

Wysession, M. E.; Pratt, M. J.; Tsiriandrimanana, R.; Andriampenomanana Ny Ony, F. S. T.; Nyblade, A.; Durrheim, R. J.; Tilmann, F. J.; Rumpker, G.; Rambolamanana, G.; Aleqabi, G. I.; Shore, P.

2017-12-01

Analyses of seismicity and seismic structure within Madagascar suggest the current occurrence of crustal extension, which may be related to continental rifting associated with a diffuse boundary between the Somalia and Lwandle tectonic plates. Madagascar has participated in two major rifting events as part of the break-up of Gondwana: the break-away of Greater India (Madagascar, India, the Seychelles) away from mainland Africa during the Jurassic and the break-away of India from Madagascar during the Cretaceous. Seismic activity and the structures obtained from it, using data from the 2-year (2011-2013) MACOMO project, suggest that this break-up may not be finished, and that continental rifts may be developing again. There are fairly high levels of intraplate seismicity within Madagascar: over 800 events located during the 22 months of the deployment. For comparison, a 2-year deployment of seismometers within the upper Midwest of the U.S. yielded just 12 intraplate earthquakes. While the Madagascar seismicity occurs across the island, it is strongly concentrated in the central region, where Cenozoic volcanism has occurred through the Holocene, and earthquakes align along N-S-trending lineations associated with N-S-trending pull-apart graben structures. The thickness of the crust is still >40 km in this region, but it is underlain by a large low-velocity structure within the lithosphere and asthenosphere that is observed in our studies of surface-wave, body-wave, and Pn-phase tomography. Normal faulting is not observed everywhere on the island, however; seismicity in the north is largely strike-slip, and seismicity in the south appears to be largely reverse faulting. Several studies have suggested that the diffuse boundary between the Somalia and Lwandle plates runs roughly E-W across Madagascar. Extensional faulting seems to predominate only within central Madagascar, likely associated with the current volcanic activity, which also appears to be associated with the delamination of the northern half of Madagascar's subcrustal lithosphere. If so, it may be that the volcanism, seismicity, and extension are all occurring syntectonically, and that we may be witnessing the development of another continental rift involving Madagascar.

Beam/seam alignment control for electron beam welding

DOEpatents

Burkhardt, Jr., James H.; Henry, J. James; Davenport, Clyde M.

1980-01-01

This invention relates to a dynamic beam/seam alignment control system for electron beam welds utilizing video apparatus. The system includes automatic control of workpiece illumination, near infrared illumination of the workpiece to limit the range of illumination and camera sensitivity adjustment, curve fitting of seam position data to obtain an accurate measure of beam/seam alignment, and automatic beam detection and calculation of the threshold beam level from the peak beam level of the preceding video line to locate the beam or seam edges.

Scalable alignment and transfer of nanowires in a Spinning Langmuir Film.

PubMed

Zhu, Ren; Lai, Yicong; Nguyen, Vu; Yang, Rusen

2014-10-21

Many nanomaterial-based integrated nanosystems require the assembly of nanowires and nanotubes into ordered arrays. A generic alignment method should be simple and fast for the proof-of-concept study by a researcher, and low-cost and scalable for mass production in industries. Here we have developed a novel Spinning-Langmuir-Film technique to fulfill both requirements. We used surfactant-enhanced shear flow to align inorganic and organic nanowires, which could be easily transferred to other substrates and ready for device fabrication in less than 20 minutes. The aligned nanowire areal density can be controlled in a wide range from 16/mm(-2) to 258/mm(-2), through the compression of the film. The surface surfactant layer significantly influences the quality of alignment and has been investigated in detail.

Engineering survey planning for the alignment of a particle accelerator: part I. Proposition of an assessment method

NASA Astrophysics Data System (ADS)

Junqueira Leão, Rodrigo; Raffaelo Baldo, Crhistian; Collucci da Costa Reis, Maria Luisa; Alves Trabanco, Jorge Luiz

2018-03-01

The performance of particle accelerators depends highly on the relative alignment between their components. The position and orientation of the magnetic lenses that form the trajectory of the charged beam is kept to micrometric tolerances in a range of hundreds of meters of the length of the machines. Therefore, the alignment problem is fundamentally of a dimensional metrology nature. There is no common way of expressing these tolerances in terms of terminology and alignment concept. The alignment needs for a certain machine is normally given in terms of deviations between the position of any magnet in the accelerator and the fitted line that relates the actual position of the magnets’ assembly. Root mean square errors and standard deviations are normally used interchangeably and measurement uncertainty is often neglected. Although some solutions have been employed successfully in several accelerators, there is no off-the-shelf solution to perform the alignment. Also, each alignment campaign makes use of different measuring instruments to achieve the desired results, which makes the alignment process a complex measurement chain. This paper explores these issues by reviewing the tolerances specified for the alignment of particle accelerators, and proposes a metric to assess the quality of the alignment. The metric has the advantage of fully integrating the measurement uncertainty in the process.

CDCC calculations of fusion of 6Li with targets 144Sm and 154Sm: effect of resonance states

NASA Astrophysics Data System (ADS)

Gómez Camacho, A.; Lubian, J.; Zhang, H. Q.; Zhou, Shan-Gui

2017-12-01

Continuum Discretized Coupled-Channel (CDCC) model calculations of total, complete and incomplete fusion cross sections for reactions of the weakly bound 6Li with 144,154Sm targets at energies around the Coulomb barrier are presented. In the cluster structure frame of 6Li→α+d, short-range absorption potentials are considered for the interactions between the ground state of the projectile 6Li and α-d fragments with the target. In order to separately calculate complete and incomplete fusion and to reduce double-counting, the corresponding absorption potentials are chosen to be of different range. Couplings to low-lying excited states 2+, 3- of 144Sm and 2+, 4+ of 154Sm are included. So, the effect on total fusion from the excited states of the target is investigated. Similarly, the effect on fusion due to couplings to resonance breakup states of 6Li, namely, l=2, J π =3+,2+,1+ is also calculated. The latter effect is determined by using two approaches, (a) by considering only resonance state couplings and (b) by omitting these states from the full discretized energy space. Among other things, it is found that both resonance and non-resonance continuum breakup couplings produce fusion suppression at all the energies considered. A. Gómez Camacho from CONACYT, México, J. Lubian from CNPq, FAPERJ, Pronex, Brazil. S.G.Z was partly supported by the NSF of China (11120101005, 11275248, 11525524, 11621131001, 11647601, 11711540016), 973 Program of China (2013CB834400) and the Key Research Program of Frontier Sciences of CAS. H.Q.Z. from NSF China (11375266)

Postrift history of the eastern central Atlantic passive margin: Insights from the Saharan region of South Morocco

NASA Astrophysics Data System (ADS)

Leprêtre, Rémi; Missenard, Yves; Barbarand, Jocelyn; Gautheron, Cécile; Saddiqi, Omar; Pinna-Jamme, Rosella

2015-06-01

The passive margin of South Morocco is a low-elevated passive margin. It constitutes one of the oldest margins of the Atlantic Ocean, with an Early Jurassic breakup, and little geological data are available concerning its postrift reactivation so far. We investigated the postrift thermal history of the onshore part of the margin with low-temperature thermochronology on apatite crystals. Fission track and (U-Th-Sm)/He ages we obtained are significantly younger than the breakup ( 190 Ma). Fission track ages range from 107 ± 8 to 175 ± 16 Ma, with mean track lengths from 10.7 ± 0.3 to 12.5 ± 0.2 µm. (U-Th-Sm)/He ages range from 14 ± 1 to 185 ± 15 Ma. Using inverse modeling of low-temperature thermochronological data, we demonstrate that the South Moroccan continental margin underwent a complex postrift history with at least two burial and exhumation phases. The first exhumation event occurred during Late Jurassic/Early Cretaceous, and we attribute this to mantle dynamics rather than to intrinsic rifting-related processes such as flexural rebound. The second event, from Late Cretaceous to early Paleogene, might record the onset of Africa/Europe convergence. We show a remarkably common behavior of the whole Moroccan passive margin during its early postrift evolution. The present-day differences result from a segmentation of the margin domains due to the Africa/Europe convergence. Finally we propose that varying retained strengths during rifting and also the specific crustal/lithospheric geometry of stretching explain the difference between the topographical expressions on the continental African margin compared to its American counterpart.

Realizing one-dimensional quantum and high-frequency transport features in aligned single-walled carbon nanotube ropes

NASA Astrophysics Data System (ADS)

Ncube, Siphephile; Chimowa, George; Chiguvare, Zivayi; Bhattacharyya, Somnath

2014-07-01

The superiority of the electronic transport properties of single-walled carbon nanotube (SWNT) ropes over SWNT mats is verified from low temperature and frequency-dependent transport. The overall change of resistance versus in nanotube mats shows that 3D variable range hopping is the dominant conduction mechanism within the 2-300 K range. The magneto-resistance (MR) is found to be predominantly negative with a parabolic nature, which can also be described by the hopping model. Although the positive upturn of the MR at low temperatures establishes the contribution from quantum interference, the inherent quantum transport in individual tubes is suppressed at elevated temperatures. Therefore, to minimize multi-channel effects from inter-tube interactions and other defects, two-terminal devices were fabricated from aligned SWNT (extracted from a mat) for low temperature transport as well as high-frequency measurements. In contrast to the mat, the aligned ropes exhibit step-like features in the differential conductance within the 80-300 K temperature range. The effects of plasmon propagation, unique to one dimension, were identified in electronic transport as a non-universal power-law dependence of the differential conductance on temperature and source-drain voltage. The complex impedance showed high power transmission capabilities up to 65 GHz as well as oscillations in the frequency range up to 30 GHz. The measurements suggest that aligned SWNT ropes have a realistic potential for high-speed device applications.

A Lithospheric Origin for the Elk Creek Carbonatite Complex, SE Nebraska?

NASA Astrophysics Data System (ADS)

Farmer, G. L.

2015-12-01

The Elk Creek carbonatite complex in southeastern Nebraska is part of a widespread Cambrian-Ordovician alkali igneous event that affected much of North America during and after the break-up of the Rodinian supercontinent. We conducted whole rock and mineral Nd, Sr, Pb and Hf isotopic analyses of drill cores obtained from this complex in order to assess the source regions of the parental carbonatite magma. Low precision laser ablation U-Pb age determinations from individual zircon grains separated from carbonate-rich "syenites" range from 480 +/- 20 Ma to 540+/- 14 Ma. Whole rock Nd, Sr and Pb isotopic compositions all plot on Cambrian (~550 Ma) isochrons, implying that the carbonatites crystallized from melts with homogeneous radiogenic isotopic compositions. Initial ɛNd and ɛHf are well defined at ~+2 and ~0, respectively, while initial 87Sr/86Sr values are more variable and range from 0.7028 to 0.7058. The contemporaneously emplaced State Line kimberlites in the Front Range of north central Colorado share the same Nd and Sr isotopic compositions imply that sources of these rocks were similar and geographically widespread. Overall, the isotopic compositions are those expected from "Group 1" alkaline igneous rocks, usually interpreted as derivates from the sublithospheric mantle. Cretaceous-Tertiary alkaline rocks in North America generally belong to "Group 1" and may have originated in this fashion (Genet et al., 2014, Earth Planet. Sci. Lett.). An alternative possibility is that the Cambrian-Ordovician carbonatites and kimberlites were derived from underlying, carbonated portions of the lithospheric mantle that formed after the original stabilization of the latter in the Paleoproterozoic. Nd and Hf depleted mantle model ages for the Elk Creek and State Line alkaline rocks range from ~0.8 Ga to ~1.1 Ga and allow the possibility that both sets of intrusive rocks represent melting of mantle metasomatized either during or after the assembly of Rodinia. Widespread thinning and heating of the metasomatized mantle during the subsequent breakup of Rodinia could have led to the widespread kimberlite and carbonatite magmatism observed in North America during the Cambrian.

Advanced Multi-phase Flow CFD Model Development for Solid Rocket Motor Flowfield Analysis

NASA Technical Reports Server (NTRS)

Liaw, Paul; Chen, Yen-Sen

1995-01-01

A Navier-Stokes code, finite difference Navier-Stokes (FDNS), is used to analyze the complicated internal flowfield of the SRM (solid rocket motor) to explore the impacts due to the effects of chemical reaction, particle dynamics, and slag accumulation on the solid rocket motor (SRM). The particulate multi-phase flowfield with chemical reaction, particle evaporation, combustion, breakup, and agglomeration models are included in present study to obtain a better understanding of the SRM design. Finite rate chemistry model is applied to simulate the chemical reaction effects. Hermsen correlation model is used for the combustion simulation. The evaporation model introduced by Spalding is utilized to include the heat transfer from the particulate phase to the gase phase due to the evaporation of the particles. A correlation of the minimum particle size for breakup expressed in terms of the Al/Al2O3 surface tension and shear force was employed to simulate the breakup of particles. It is assumed that the breakup occurs when the Weber number exceeds 6. A simple L agglomeration model is used to investigate the particle agglomeration. However, due to the large computer memory requirements for the agglomeration model, only 2D cases are tested with the agglomeration model. The VOF (Volume of Fluid) method is employed to simulate the slag buildup in the aft-end cavity of the redesigned solid rocket motor (RSRM). Monte Carlo method is employed to calculate the turbulent dispersion effect of the particles. The flowfield analysis obtained using the FDNS code in the present research with finite rate chemical reaction, particle evaporation, combustion, breakup, agglomeration, and VOG models will provide a design guide for the potential improvement of the SRM including the use of materials and the shape of nozzle geometry such that a better performance of the SRM can be achieved. The simulation of the slag buildup in the aft-end cavity can assist the designer to improve the design of the RSRM geometry.

Central Atlantic Break-up: A competition between CAMP Hotspot and thinning rate.

NASA Astrophysics Data System (ADS)

Sapin, F.; Maurin, T.

2017-12-01

The break-up of the Central Atlantic is known to have ended at about 190Myrs while the CAMP (Central Atlantic Magmatic Province) was still active. Several seismic lines, acquired recently in the deep offshore Senegal and Mauritanian domain, provide detailed images of continent-ocean transition and the oceanic crust architecture. Their interpretation is the opportunity to describe the progressive interaction between the hot spot activity, the architecture and timing of break up and the oceanic crust production. In the North, seismic data and gravity/magnetic inversions suggest an extremely thinned continental crust with possible mantle exhumation. In the South, the continental crust is thick and the transition to oceanic crust is sharp. In addition, three oceanic crust facies were described along the margin in an extremely slow spreading ridge setting ( 0.8cm/yr during the first 20Myrs): facies (1) with a poorly imaged Moho and a strongly faulted thin oceanic crust or exhumed mantle; facies (2) with an extensively faulted 6km thick oceanic crust; facies (3) with abnormally thick (9km) oceanic crust marked by SDR-type reflections. They are diachronous from North to South and the two first one disappear southwards and (facies 3) being younger toward the North. Only a single very thick oceanic crust (12-14km) remains in front of the Guinea Plateau. We concluded that, in the South, the break-up had been forced through a thick or thickened continental crust due to the remnant activity of the CAMP Hotspot. In the North, the magmatic pulse arrived far after the break-up during the spreading and the thinning of the continental crust could lead to hyper extension. This evolution emphasizes that the architecture, and thus processes leading to the break-up can vary a lot considering the influence of thermal vertical forces (mantle dynamics/hotspot/magmatism) and mechanical horizontal forces (plate movement/faulting/spreading), both of them being necessary for a rift to succeed.

Runaway electrons and magnetic island confinement

DOE PAGES

Boozer, Allen H.

2016-08-19

The breakup of magnetic surfaces is a central feature of ITER planning for the avoidance of damage due to runaway electrons. Rapid thermal quenches, which lead to large accelerating voltages, are thought to be due to magnetic surface breakup. Impurity injection to avoid and to mitigate both halo and runaway electron currents utilizes massive gas injection or shattered pellets. The actual deposition is away from the plasma center, and the breakup of magnetic surfaces is thought to spread the effects of the impurities across the plasma cross section. The breakup of magnetic surfaces would prevent runaway electrons from reaching relativisticmore » energies were it not for the persistence of non-intercepting flux tubes. These are tubes of magnetic field lines that do not intercept the walls. In simulations and in magnetic field models, non-intercepting flux tubes are found to persist near the magnetic axis and in the cores of magnetic islands even when a large scale magnetic surface breakup occurs. As long as a few magnetic surfaces reform before all of the non-intercepting flux tubes dissipate, energetic electrons confined and accelerated in these flux tubes can serve as the seed electrons for a transfer of the overall plasma current from thermal to relativistic carriers. The acceleration of electrons is particularly strong because of the sudden changes in the poloidal flux that naturally occur in a rapid magnetic relaxation. Furthermore, the physics of magnetic islands as non-intercepting flux tubes is studied. Expressions are derived for (1) the size of islands required to confine energetic runaway electrons, (2) the accelerating electric field in an island, (3) the increase or reduction in the size of an island by the runaway electron current, (4) the approximate magnitude of the runaway current in an island, and (5) the time scale for the evolution of an island.« less

Evaporation-driven instability of the precorneal tear film.

PubMed

Peng, Cheng-Chun; Cerretani, Colin; Braun, Richard J; Radke, C J

2014-04-01

Tear-film instability is widely believed to be a signature of eye health. When an interblink is prolonged, randomly distributed ruptures occur in the tear film. "Black spots" and/or "black streaks" appear in 15 to 40 s for normal individuals. For people who suffer from dry eye, tear-film breakup time (BUT) is typically less than a few seconds. To date, however, there is no satisfactory quantitative explanation for the origin of tear rupture. Recently, it was proposed that tear-film breakup is related to locally high evaporative thinning. A spatial variation in the thickness of the tear-film lipid layer (TFLL) may lead to locally elevated evaporation and subsequent tear-film breakup. We examine the local-evaporation-driven tear-film-rupture hypothesis in a one-dimensional (1-D) model for the evolution of a thin aqueous tear film overriding the cornea subject to locally elevated evaporation at its anterior surface and osmotic water influx at its posterior surface. Evaporation rate depends on mass transfer both through the coating lipid layer and through ambient air. We establish that evaporation-driven tear-film breakup can occur under normal conditions but only for higher aqueous evaporation rates. Predicted roles of environmental conditions, such as wind speed and relative humidity, on tear-film stability agree with clinical observations. More importantly, locally elevated evaporation leads to hyperosmolar spots in the tear film and, hence, vulnerability to epithelial irritation. In addition to evaporation rate, tear-film instability depends on the strength of healing flow from the neighboring region outside the breakup region, which is determined by the surface tension at the tear-film surface and by the repulsive thin-film disjoining pressure. This study provides a physically consistent and quantitative explanation for the formation of black streaks and spots in the human tear film during an interblink. Copyright © 2013 Elsevier B.V. All rights reserved.

Runaway electrons and magnetic island confinement

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

Boozer, Allen H., E-mail: ahb17@columbia.edu

The breakup of magnetic surfaces is a central feature of ITER planning for the avoidance of damage due to runaway electrons. Rapid thermal quenches, which lead to large accelerating voltages, are thought to be due to magnetic surface breakup. Impurity injection to avoid and to mitigate both halo and runaway electron currents utilizes massive gas injection or shattered pellets. The actual deposition is away from the plasma center, and the breakup of magnetic surfaces is thought to spread the effects of the impurities across the plasma cross section. The breakup of magnetic surfaces would prevent runaway electrons from reaching relativisticmore » energies were it not for the persistence of non-intercepting flux tubes. These are tubes of magnetic field lines that do not intercept the walls. In simulations and in magnetic field models, non-intercepting flux tubes are found to persist near the magnetic axis and in the cores of magnetic islands even when a large scale magnetic surface breakup occurs. As long as a few magnetic surfaces reform before all of the non-intercepting flux tubes dissipate, energetic electrons confined and accelerated in these flux tubes can serve as the seed electrons for a transfer of the overall plasma current from thermal to relativistic carriers. The acceleration of electrons is particularly strong because of the sudden changes in the poloidal flux that naturally occur in a rapid magnetic relaxation. The physics of magnetic islands as non-intercepting flux tubes is studied. Expressions are derived for (1) the size of islands required to confine energetic runaway electrons, (2) the accelerating electric field in an island, (3) the increase or reduction in the size of an island by the runaway electron current, (4) the approximate magnitude of the runaway current in an island, and (5) the time scale for the evolution of an island.« less

Runaway electrons and magnetic island confinement

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

Boozer, Allen H.

The breakup of magnetic surfaces is a central feature of ITER planning for the avoidance of damage due to runaway electrons. Rapid thermal quenches, which lead to large accelerating voltages, are thought to be due to magnetic surface breakup. Impurity injection to avoid and to mitigate both halo and runaway electron currents utilizes massive gas injection or shattered pellets. The actual deposition is away from the plasma center, and the breakup of magnetic surfaces is thought to spread the effects of the impurities across the plasma cross section. The breakup of magnetic surfaces would prevent runaway electrons from reaching relativisticmore » energies were it not for the persistence of non-intercepting flux tubes. These are tubes of magnetic field lines that do not intercept the walls. In simulations and in magnetic field models, non-intercepting flux tubes are found to persist near the magnetic axis and in the cores of magnetic islands even when a large scale magnetic surface breakup occurs. As long as a few magnetic surfaces reform before all of the non-intercepting flux tubes dissipate, energetic electrons confined and accelerated in these flux tubes can serve as the seed electrons for a transfer of the overall plasma current from thermal to relativistic carriers. The acceleration of electrons is particularly strong because of the sudden changes in the poloidal flux that naturally occur in a rapid magnetic relaxation. Furthermore, the physics of magnetic islands as non-intercepting flux tubes is studied. Expressions are derived for (1) the size of islands required to confine energetic runaway electrons, (2) the accelerating electric field in an island, (3) the increase or reduction in the size of an island by the runaway electron current, (4) the approximate magnitude of the runaway current in an island, and (5) the time scale for the evolution of an island.« less

A new tectono-magmatic model for the Lofoten/Vesterålen Margin at the outer limit of the Iceland Plume influence

NASA Astrophysics Data System (ADS)

Breivik, Asbjørn Johan; Faleide, Jan Inge; Mjelde, Rolf; Flueh, Ernst R.; Murai, Yoshio

2017-10-01

The Early Eocene continental breakup was magma-rich and formed part of the North Atlantic Igneous Province. Extrusive and intrusive magmatism was abundant on the continental side, and a thick oceanic crust was produced up to a few m.y. after breakup. However, the extensive magmatism at the Vøring Plateau off mid-Norway died down rapidly northeastwards towards the Lofoten/Vesterålen Margin. In 2003 an Ocean Bottom Seismometer profile was collected from mainland Norway, across Lofoten, and into the deep ocean. Forward/inverse velocity modeling by raytracing reveals a continental margin transitional between magma-rich and magma-poor rifting. For the first time a distinct lower-crustal body typical for volcanic margins has been identified at this outer margin segment, up to 3.5 km thick and ∼50 km wide. On the other hand, expected extrusive magmatism could not be clearly identified here. Strong reflections earlier interpreted as the top of extensive lavas may at least partly represent high-velocity sediments derived from the shelf, and/or fault surfaces. Early post-breakup oceanic crust is moderately thickened (∼8 km), but is reduced to 6 km after 1 m.y. The adjacent continental crystalline crust is extended down to a minimum of 4.5 km thickness. Early plate spreading rates derived from the Norway Basin and the northern Vøring Plateau were used to calculate synthetic magnetic seafloor anomalies, and compared to our ship magnetic profile. It appears that continental breakup took place at ∼53.1 Ma, ∼1 m.y. later than on the Vøring Plateau, consistent with late strong crustal extension. The low interaction between extension and magmatism indicates that mantle plume material was not present at the Lofoten Margin during initial rifting, and that the observed excess magmatism was created by late lateral transport from a nearby pool of plume material into the lithospheric rift zone at breakup time.

Magma-poor vs. magma-rich continental rifting and breakup in the Labrador Sea

NASA Astrophysics Data System (ADS)

Gouiza, M.; Paton, D.

2017-12-01

Magma-poor and magma-rich rifted margins show distinct structural and stratigraphic geometries during the rift to breakup period. In magma-poor margins, crustal stretching is accommodated mainly by brittle faulting and the formation of wide rift basins shaped by numerous graben and half-graben structures. Continental breakup and oceanic crust accretion are often preceded by a localised phase of (hyper-) extension where the upper mantle is embrittled, serpentinized, and exhumed to the surface. In magma-rich margins, the rift basin is narrow and extension is accompanied by a large magmatic supply. Continental breakup and oceanic crust accretion is preceded by the emplacement of a thick volcanic crust juxtaposing and underplating a moderately thinned continental crust. Both magma-poor and magma-rich rifting occur in response to lithospheric extension but the driving forces and processes are believed to be different. In the former extension is assumed to be driven by plate boundary forces, while in the latter extension is supposed to be controlled by sublithospheric mantle dynamics. However, this view fails in explaining observations from many Atlantic conjugate margins where magma-poor and magma-rich segments alternate in a relatively abrupt fashion. This is the case of the Labrador margin where the northern segment shows major magmatic supply during most of the syn-rift phase which culminate in the emplacement of a thick volcanic crust in the transitional domain along with high density bodies underplating the thinned continental crust; while the southern segment is characterized mainly by brittle extension, mantle seprentinization and exhumation prior to continental breakup. In this work, we use seismic and potential field data to describe the crustal and structural architectures of the Labrador margin, and investigate the tectonic and mechanical processes of rifting that may have controlled the magmatic supply in the different segments of the margin.

An analysis of the 2016 Hitomi breakup event

NASA Astrophysics Data System (ADS)

Flegel, Sven; Bennett, James; Lachut, Michael; Möckel, Marek; Smith, Craig

2017-04-01

The breakup of Hitomi (ASTRO-H) on 26 March 2016 is analysed. Debris from the fragmentation is used to estimate the time of the event by propagating backwards and estimating the close approach with the parent object. Based on this method, the breakup event is predicted to have occurred at approximately 01:42 UTC on 26 March 2016. The Gaussian variation of parameters equations based on the instantaneous orbits at the predicted time of the event are solved to gain additional insight into the on-orbit position of Hitomi at the time of the event and to test an alternate approach of determining the event epoch and location. A conjunction analysis is carried out between Hitomi and all catalogued objects which were in orbit around the estimated time of the anomaly. Several debris objects have close approaches with Hitomi; however, there is no evidence to support the breakup was caused by a catalogued object. Debris from both of the largest fragmentation events—the Iridium 33-Cosmos 2251 conjunction in 2009 and the intentional destruction of Fengyun 1C in 2007—is involved in close approaches with Hitomi indicating the persistent threat these events have caused in subsequent space missions. To quantify the magnitude of a potential conjunction, the fragmentation resulting from a collision with the debris is modelled using the EVOLVE-4 breakup model. The debris characteristics are estimated from two-line element data. This analysis is indicative of the threat to space assets that mission planners face due to the growing debris population. The impact of the actual event to the environment is investigated based on the debris associated with Hitomi which is currently contained in the United States Strategic Command's catalogue. A look at the active missions in the orbital vicinity of Hitomi reveals that the Hubble Space Telescope is among the spacecraft which may be immediately affected by the new debris.[Figure not available: see fulltext.

SINGLE BUNCH BEAM BREAKUP - A GENERAL SOLUTION.

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

WANG,J.M.; MANE,S.R.; TOWNE,N.

2000-06-26

Caporaso, Barletta and Neil (CBN) found in a solution to the problem of the single-bunch beam breakup in a linac[1]. However, their method applies only to the case of a beam traveling in a strongly betatron-focused linac under the influence of the resistive wall impedance. We suggest in this paper a method for dealing with the same problem. Our methods is more general; it applies to the same problem under any impedance, and it applies to a linac with or without external betatron focusing.