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1

Sipuleucel-T: APC 8015, APC-8015, prostate cancer vaccine--Dendreon.  

PubMed

Sipuleucel-T [APC 8015, Provenge] is an autologous, dendritic cell-based vaccine under development with Dendreon Corporation for the treatment of androgen-independent and androgen-dependent prostate cancer. It was generated using the company's active immunotherapy platform to stimulate a patient's own immune system to specifically target and destroy cancer cells, while leaving healthy cells unharmed. This approach could provide patients with a meaningful survival benefit and an improved tolerability profile over existing anticancer therapies. Sipuleucel-T selectively targets the prostate-specific antigen (PSA) known as prostatic acid phosphatase (PAP) that is expressed in approximately 95% of prostate cancers. It is produced by ex vivo exposure of dendritic cell precursors to PA 2024, a recombinant fusion protein composed of the PAP target fused to granulocyte-macrophage colony-stimulating factor (GM-CSF) and incorporated into Dendreon's proprietary Antigen Delivery Cassette. Patients are typically administered three intravenous (IV)-infusions of the vaccine over a 1-month period as a complete course of therapy. It is undergoing late-stage clinical evaluation among patients with early and advanced prostate cancer. In November 2003, Kirin Brewery returned to Dendreon the full rights to Sipuleucel-T for Asia. In exchange, Dendreon licensed patent rights relating to the use of certain HLA-DR antibodies to Kirin for $US20 million. This amended agreement enables Dendreon to complete ongoing discussions for a worldwide marketing and sales partnership for Sipuleucel-T. Similarly, Kirin is able to develop its HLA-DR monoclonal antibodies free of potential infringement claims arising from Dendreon's patent rights to HLA-DR. The licensing agreement relates to patent rights owned by Dendreon relating to monoclonal antibodies against the HLA-DR antigen. In addition, Dendreon retains rights to develop and commercialise its two existing HLA-DR monoclonal antibodies, DN 1921 and DN 1924, as well as other HLA-DR antibodies not being developed by Kirin. Previously, in May 1999, Dendreon and Kirin established a collaboration for the development of dendritic cell-based immunotherapeutics for cancer, including Sipuleucel-T. Under the agreement, Kirin would provide financial support for Dendreon's research on dendritic cells focused on developing immunotherapies for cancers most prevalent in Asia. Dendreon would retain US rights to products arising from the collaboration while Kirin would hold the rights to such immuno-therapeutics in Asia and Oceania. In August 2005, Dendreon signed an agreement to lease a commercial manufacturing facility in Hanover, New Jersey, USA. The company intends to develop the facility to meet anticipated clinical and commercial demands of Sipuleucel-T as well as other active immunotherapy product candidates. Dendreon and Diosynth Biotechnology (Akzo Nobel) have an agreement for the commercial production of the PA 2024 antigen component of Sipuleucel-T. In November 2003, Dendreon announced that Diosynth successfully manufactured PA 2024 on a commercial scale. In October 2001, Dendreon announced that Gambro Healthcare Inc. would provide a network of centres for cell collection to support commercial production and clinical development of various Dendreon vaccines, including Sipuleucel-T. Dendreon has outsourced its cell processing operations in Mountain View, California, USA to Progenitor Cell Therapy under an amended agreement signed in August 2002. This agreement is an expansion of an existing agreement, under which Progenitor provided Dendreon with cell-processing services through its facility in Hackensack, New Jersey, USA. The pivotal, two-stage, phase III trial (D9902 study) has been initiated at clinical sites in the US. The first stage of the trial (D9902A study) is a double-blind, placebo-controlled phase III trial designed to evaluate Sipuleucel-T in men with asymptomatic, metastatic, androgen-independent prostate cancer. The trial was originally designed to be the companion study to a previously completed

2006-01-01

2

Serpentine Buoyant Cable Antenna.  

National Technical Information Service (NTIS)

The present invention relates to an improved buoyant cable antenna system. The system includes a buoyant cable transmission line segment and an antenna segment formed from a flexible memory structure comprised of at least one segment of coiled compression...

E. M. Gerhard

2006-01-01

3

Instability of buoyant diffusion flames  

NASA Astrophysics Data System (ADS)

Buoyant jet diffusion flames are known to exhibit large scale vortical flow structures strongly interacting with flame structures. In the present work, the formation and evolution of coherent flow structures is studied in a methane/ air coflow arrangement. This is accomplished by utilizing visualization techniques (planar laser induced hydroxyl fluorescence and Mie-scattering) and Laser Doppler Velocimetry. A striking repeatability and correlation of evolving coherent structures of the air co-flow and the reaction zone is observed. In the transitional region, flow and flame structures oscillate at very pure frequencies ranging from 10 15 Hz. A local absolutely unstable velocity profile close to the burner rim seems to be responsible. Self-excited axisymmetric wavelike structures propagate up- and downstream of this location. We study the influence of the exit velocities and the type of coflowing oxidizer (air or oxygen) on the location of transition to periodic flow structures and related frequencies. Conditional averages of image and velocity data are employed to describe the evolution of coherent flow structures and their interaction with flame structures.

Lingens, A.; Reeker, M.; Schreiber, M.

1996-02-01

4

Strain Gage Instrumentation of a Buoyant Cable.  

National Technical Information Service (NTIS)

The strain gage instrumentation of a buoyant cable used for submarine ELF receiving antennas is presented. Techniques were developed to bond the strain gage reliably to the polyethylene cable jacket and to seal the jacket using an injection molding proces...

O. G. Nackoney

1972-01-01

5

Wind influence on a coastal buoyant outflow  

NASA Astrophysics Data System (ADS)

This paper investigates the interplay between river discharge and winds in forcing coastal buoyant outflows. During light winds a plume influenced by the Earth's rotation will flow down shelf (in the direction of Kelvin wave propagation) as a slender buoyancy-driven coastal current. Downwelling favorable winds augment this down-shelf flow, narrow the plume, and mix the water column. Upwelling favorable winds drive currents that counter the buoyancy-driven flow, spread plume waters offshore, and rapidly mix buoyant waters. Two criteria are developed to assess the wind influence on a buoyant outflow. The wind strength index (Ws) determines whether a plume's along-shelf flow is in a wind-driven or buoyancy-driven state. Ws is the ratio of the wind-driven and buoyancy-driven along-shelf velocities. Wind influence on across-shelf plume structure is rated with a timescale (ttilt) for the isopycnal tilting caused by wind-driven Ekman circulation. These criteria are used to characterize wind influence on the Delaware Coastal Current and can be applied to other coastal buoyant outflows. The Delaware buoyant outflow is simulated for springtime high-river discharge conditions. Simulation results and Ws values reveal that the coastal current is buoyancy-driven most of the time (?Ws? < 1 on average). Wind events, however, overwhelm the buoyancy-driven flow (?Ws? > 1) several times during the high-discharge period. Strong upwelling events reverse the buoyant outflow; they constitute an important mechanism for transporting fresh water up shelf. Across-shelf plume structure is more sensitive to wind influence than the along-shelf flow. Values of ttilt indicate that moderate or strong winds persisting throughout a day can modify plume width significantly. Plume widening during upwelling events is accompanied by mixing that can erase the buoyant outflow.

Whitney, Michael M.; Garvine, Richard W.

2005-03-01

6

Numerical Simulation of Buoyant Convection in Vented Enclosures.  

National Technical Information Service (NTIS)

The buoyant convection in a two-dimensional enclosure with openings is solved using a primitive variable explicit finite difference technique. A non-Boussinesq acoustically-filtered formulation is used which models inviscid buoyantly driven flows in a str...

J. A. Schutt M. R. Baer

1987-01-01

7

Radiation from Buoyant Turbulent Diffusion Flames  

Microsoft Academic Search

The relationship between the radiant fraction, X R, of the total heat release rate from buoyant turbulent diffusion flames and a fuel's laminar flame smoke point is refined and extended to include: additional hydrocarbon fuels, fuel dilution with nitrogen and a range of oxygen\\/nitrogen ambient environments. Correlation of the data allows one to predict X R in terms of the:

L. Orloff; J. DE RIS; M. A. DELICHATSIOS

1992-01-01

8

EXPERIMENTS ON BUOYANT PLUME DISPERSION IN A LABORATORY CONVENTION TANK  

EPA Science Inventory

Buoyant plume dispersion in the convective boundary layer (CBL) is investigated experimentally in a laboratory convection tank. The focus is on highly-buoyant plumes that loft near the CBL capping inversion and resist downward mixing. Highly- buoyant plumes are those with dimen...

9

Analytical model for a vertical buoyant jet  

SciTech Connect

An analytical model for a round and two-dimensional turbulent buoyant jet which is discharged vertically into a stagnant ambient is developed. The buoyant jet is considered to have three separate zone models which are matched to form a complete solution. The velocity field is determined for the entire jet and plume regions by the use of an eddy viscosity which varies along the axis of the jet. The centerline decay of buoyancy is determined throughout and the results are compared to existing numerical codes. The model is applied to the disposal of carbon dioxide enriched seawater. The results can be used to provide design information for minimizing or maximizing the dilution of a discharge by the receiving environment.

Lee, D.W.

1980-10-01

10

Two-link swimming using buoyant orientation  

NASA Astrophysics Data System (ADS)

The scallop theorem posits that a two-link system immersed in a fluid at low Reynolds number cannot achieve any net translation via cyclic changes in its hinge angle. Here, we propose an approach to ``breaking'' this theorem, based on a static separation between the centers of mass and buoyancy in a net neutrally buoyant system. This separation gives the system a natural equilibrium orientation, allowing it to passively reorient without changing shape.

Burton, L. J.; Hatton, R. L.; Choset, H.; Hosoi, A. E.

2010-09-01

11

FORMATION OF NEGATIVE BUOYANT VORTEX RINGS AT AN ORIFICE OPENING  

Microsoft Academic Search

Negative buoyant vortex rings are generated at an orifice opening of variable diameter using a piston- cylinder apparatus and ejected vertically into ambient atmosphere. Ring formation is investigated using a Background-Oriented Schlieren (BOS) method. Under the present conditions, negative buoyant rings may exhibit a leading vortex ring with \\

J. Sznitman; T. Rösgen

12

46 CFR 160.010-5 - Buoyant apparatus with plastic foam buoyancy.  

Code of Federal Regulations, 2013 CFR

...2013-10-01 false Buoyant apparatus with plastic foam buoyancy. 160.010-5 Section...160.010-5 Buoyant apparatus with plastic foam buoyancy. (a) Buoyant apparatus with plastic foam buoyancy must have a plastic...

2013-10-01

13

Bulge Formation of a Buoyant River Outflow  

NASA Astrophysics Data System (ADS)

Observations taken during the Lagrangian Transport and Transformation Experiment (LaTTE) in 2005 indicated that the Hudson's river outflow formed a bulge of recirculating fluid that limits the volume of fresh water that is advected away in a coastal current. Focusing on an event that began with downwelling winds we made estimates of the fresh-water flux in the coastal current and the fresh water inventory of the bulge. The coastal current was characterized by a surface advected plume in thermal wind balance. However, the freshwater transport in the coastal current was less than 1/2 of the total freshwater outflow. The bulge extended 30 km from the coast and 40 km in the along-shore direction and was evident in ocean color imagery. Recirculation in the bulge region was also apparent in daily averaged surface current radar data, but this flow pattern was obscured in the hourly data by tidal and wind-forcing even in the diurnal band. Nevertheless, many aspects of the Hudson's outflow are consistent with recent laboratory experiments and numerical simulations of buoyant discharges. The growing bulge transports the river's outflow to the head of the Hudson shelf valley where it crosses the 50 m isobath. Previous work in this region indicates that frontal features reside along this isobath. We observed fresh water being transported along this isobath and is suggestive of a rapid cross-shelf transport pathway for fresh water. Both the bulge formation and cross-shelf transport have significant biogeochemical implications.

Chant, Robert J.; Glenn, Scott M.; Hunter, Elias; Kohut, Josh; Chen, Robert F.; Houghton, Robert W.; Bosch, Jen; Schofield, Oscar

2008-01-01

14

The case for accretion of the tectosphere by buoyant subduction  

SciTech Connect

The term tectosphere, which formerly applied to all continental lithosphere, more recently is restricted to the seismically fast, cold (meaning that diamond is stable), and thick ({ge}200-400 km) continental lithosphere. This paper tests three hypotheses for the origin of the tectosphere. Continental collision cannot explain the low metamorphic grade of crust that predates the tectosphere. Halfspace cooling and buoyant underplating can both fit the diamond age data, although underplating by buoyant subduction is the favored model. Thermal models provide a further test. If halfspace cooling formed the tectosphere, diamonds from 150 km depth will be at least 200 m.y. younger than diamonds from 190 km. If buoyant subduction formed the tectosphere, diamonds from 150 km depth will be the same age or older than diamonds from 190 km.

Abbott, D. (Columbia Univ., Palisades, NY (United States))

1991-04-01

15

On the near field behavior of inclined negatively buoyant jets  

NASA Astrophysics Data System (ADS)

We have performed an experimental campaign in the laboratory on the near field behavior of inclined negatively buoyant jets, issuing from a circular sharp-edged orifice, in order to investigate the symmetry properties of this phenomenon. The velocity measurements were obtained via a non intrusive image analysis technique, namely Feature Tracking Velocimetry. We present here both first and second order statistics, showing that the asymmetry of inclined negatively buoyant jets cannot be considered only a far field feature of this phenomenon, as it arises very close to the release point.

Besalduch, L. A.; Badas, M. G.; Ferrari, S.; Querzoli, G.

2014-03-01

16

On the structure of a laminar buoyant jet released horizontally  

Microsoft Academic Search

The flow generated by the injection of negatively buoyant fluid in water at rest was investigated by means of both the laser induced fluorescence (LIF) visualization and the particle tracking velocimetry. Statistics on series of LIF images acquired during the same experiment have been evaluated to give quantitative information about the localization of the structures. Such a phenomenon is controlled

G. Querzoli; A. Cenedese

2005-01-01

17

Buoyant density constancy during the cell cycle of Escherichia coli  

SciTech Connect

Cell buoyant densities were determined in exponentially growing cultures of Escherichia coli B/r NC32 and E. coli K-12 PAT84 by equilibrium centrifugation in Percoll gradients. Distributions within density bands were measured as viable cells or total numbers of cells. At all growth rates, buoyant densities had narrow normal distributions with essentially the same value for the coefficient of variation, 0.15%. When the density distributions were determined in Ficoll gradients, they were more than twice as broad, but this increased variability was associated with the binding of Ficoll to the bacteria. Mean cell volumes and cell lengths were independent of cell densities in Percoll bands, within experimental errors, both in slowly and in rapidly growing cultures. Buoyant densities of cells separated by size, and therefore by age, in sucrose gradients also were observed to be independent of age. The results make unlikely any stepwise change in mean buoyant density of 0.1% or more during the cycle. These results also make it unlikely that signaling functions for cell division or for other cell cycle events are provided by density variations. 10 references, 3 figures, 3 tables.

Kubitschek, H.E.; Baldwin, W.W.; Graetzer, R.

1983-09-01

18

Vertical turbulent buoyant jets: A review of experimental data  

Microsoft Academic Search

Experimental data on vertical turbulent buoyant jets issuing into calm neutral or stably stratified environments are reviewed critically. Both plane and axisymmetric jets are included, and the whole Froude number range from the pure jet to the pure plume is covered. Similarity and scaling laws are introduced and the experimental data are interpreted according to these laws. Measurements of the

C. J. Chen; W. Rodi

1980-01-01

19

On a simulator of a buoyant antenna - satellite wireless channel  

Microsoft Academic Search

A model of fading in a buoyant antenna array satellite link is suggested. A random number of active elements is modelled by changes in the Nakagami factor m in a system of randomly switched stochastic differential equations. Analytical solutions are given for the case of slow and fast changes.

Serguei Primak; Jeff Weaver; Valeri Kontorovich

2003-01-01

20

APPLICATION OF BUOYANT MASS TRANSFER MEDIA TO HAZARDOUS MATERIAL SPILLS  

EPA Science Inventory

A prototype system was designed and developed to slurry buoyant activated carbon into a static body of water. The process was developed to remove spilled soluable hazardous compounds from a watercourse. In a simulated spill, up to 98% removal of Diazinon, an organophosphorus pest...

21

Buoyant surface jet analysis of the Yukon River  

Microsoft Academic Search

Thermal infrared satellite imagery of the discharge from the Yukon River obtained on 5 July 1985 was compared with hydraulic theory for the dilution of buoyant surface jets. In a crossflow, the theory predicts that the plume will follow an x trajectory where x is distance alongshore, and that the plume temperature will decay according to x due to mixing

J. P. Gosink

1988-01-01

22

Mixing enhancement in axisymmetric turbulent isothermal and buoyant jets  

Microsoft Academic Search

Measurements of the velocity and concentration in axisymmetric, turbulent, isothermal and buoyant jets have been performed with laser-Doppler velocimetry and planar and point laser-induced fluorescence to quantify the mixing enhancement achieved by periodic forcing when the jet exit has a fully-developed turbulent pipe flow, a situation less well-studied than the case of laminar initial conditions. It was found that forcing

E. Mastorakos; M. Shibasaki; K. Hishida

1996-01-01

23

Quantitative computational infrared imaging of buoyant diffusion flames  

NASA Astrophysics Data System (ADS)

Studies of infrared radiation from turbulent buoyant diffusion flames impinging on structural elements have applications to the development of fire models. A numerical and experimental study of radiation from buoyant diffusion flames with and without impingement on a flat plate is reported. Quantitative images of the radiation intensity from the flames are acquired using a high speed infrared camera. Large eddy simulations are performed using fire dynamics simulator (FDS version 6). The species concentrations and temperature from the simulations are used in conjunction with a narrow-band radiation model (RADCAL) to solve the radiative transfer equation. The computed infrared radiation intensities rendered in the form of images and compared with the measurements. The measured and computed radiation intensities reveal necking and bulging with a characteristic frequency of 7.1 Hz which is in agreement with previous empirical correlations. The results demonstrate the effects of stagnation point boundary layer on the upstream buoyant shear layer. The coupling between these two shear layers presents a model problem for sub-grid scale modeling necessary for future large eddy simulations.

Newale, Ashish S.

24

Do finite-size neutrally buoyant particles cluster?  

NASA Astrophysics Data System (ADS)

The turbulent mixing of small and heavy particles presents a striking feature known as preferential concentration or clustering. We investigate here the preferential concentration of particles that are neutrally buoyant but with a diameter significantly larger than the dissipation scale ? of the carrier flow (4.4?-17?). Such particles are known to not behave as flow tracers (Qureshi et al 2007 Phys. Rev. Lett. 99 184502) but it remains an open question whether they do cluster or not. For this purpose, we produce homogeneous and isotropic turbulence in a closed water flow, and seed the flow with neutrally buoyant particles spanning a range of Stokes numbers from 1.6 to 24.2 depending on the rotation frequency. The spatial structuration of these inclusions is then investigated by Voronoï tesselation analysis, as proposed recently by Monchaux et al (2010 Phys. Fluids 22 103304), from images of the particle concentration field taken in a laser sheet at the center of the flow. No matter what the rotation frequency and the Reynolds and Stokes numbers are, the particles are found to not cluster. Finite-size neutrally buoyant particles are therefore not inertial. We also conclude that the Stokes number per se is an insufficient indicator of the clustering trend in particles-laden flows.

Fiabane, L.; Volk, R.; Pinton, J.-F.; Monchaux, R.; Cartellier, A.; Bourgoin, M.

2013-07-01

25

Performance characteristics of a buoyant quad-rotor research aircraft  

NASA Technical Reports Server (NTRS)

Performance characteristics of a buoyant, quadrotor research aircraft, which represents a hybrid airship concept for heavy lift application, are described. Ceiling altitude and endurance for hovering at typical power levels, including partial power failure, are predicted. Climb performance at various altitude and gross weight conditions have been examined. Forward flight performance of this vehicle is illustrated in terms of typical performance parameters such as maximum speed, maximum range, and endurance, over the full range of its payload capability. Optimum payload weights have been identified which result in maximum range at sea level density altitude and constant endurance at various altitudes, both during hover and cruise flights.

Nagabhushan, B. L.; Jacobs, P. P.; Belknap, C. E.; Euler, D. A.

1982-01-01

26

Dynamics of finite size neutrally buoyant particles in isotropic turbulence  

NASA Astrophysics Data System (ADS)

The dynamics of neutrally buoyant particles suspended in a turbulent flow is investigated experimentally, with particles having diameters larger than the Kolmogorov length scale. To that purpose, a turbulence generator have been constructed and the resulting flow characterized. The fluid was then seeded with polystyrene particles of diameter about 1 mm and their velocity measured separately and simultaneously with the surrounding fluid. Comparison of the velocities statistics between the two phases shows no appreciable discrepancy. However, simultaneous velocity measurement shows that particles may move in different direction from the underlying flow.

Elhimer, M.; Jean, A.; Praud, O.; Bazile, R.; Marchal, M.; Couteau, G.

2011-12-01

27

A large eddy simulation of buoyant and non-buoyant plume dispersion in the atmospheric boundary layer  

NASA Astrophysics Data System (ADS)

The dispersion of contaminants in the convective atmospheric boundary layer is calculated with the aid of a large eddy model. Our initial condition is a model simulation of the quasi-stationary convective boundary layer in a horizontal calculation domain of 5 × 5 km. At t = 0 we introduce in this boundary layer an instantaneous line source of contaminants. Subsequently, we calculate the evolution of the line source by integrating the conservation equation of the contaminant simultaneously with the other governing equations of our large eddy model. We consider both a source of passive material with release heights of zs/ h = 0.04 and 0.49 and also a source of buoyant material with a dimensionless buoyancy parameter F ? = 0.024 and with release heights of zg/ h = 0.16 and 0.49. The buoyant line source is constructed by increasing, at t = 0, the temperature within the source with respect to the mean ambient temperature. When we interpret our instantaneous line-source results in terms of a continuous point source, we may compare our data with the well-established laboratory results of Willis and Deardorff ( Q. Jl R. Met. Soc. 102, 427-445, 1976a; Atmospheric Environment15, 109-117,1981; 17, 2933-2447, 1983). The agreement with these experimental data is good for the case of the passive source but not as clear for the buoyant source. In the latter case the effects of plume rise are clearly noticeable in our calculation results but they do not seem to obey the standard plume-rise equations.

Nieuwstadt, F. T. M.; de Valk, J. P. J. M. M.

28

Phytoplankton productivity in a turbid buoyant coastal plume  

NASA Astrophysics Data System (ADS)

The complex dynamics associated with coastal buoyant plumes make it difficult to document the interactions between light availability, phytoplankton carbon fixation, and biomass accumulation. Using real-time data, provided by satellites and high frequency radar, we adaptively sampled a low salinity parcel of water that was exported from the Hudson river estuary in April 2005. The water was characterized by high nutrients and high chlorophyll concentrations. The majority of the low salinity water was re-circulated within a nearshore surface feature for 5 days during which nitrate concentrations dropped 7-fold, the maximum quantum yield for photosynthesis dropped 10-fold, and primary productivity rates decreased 5-fold. Associated with the decline in nitrate was an increase in phytoplankton biomass. The phytoplankton combined with the Colored Dissolved Organic Matter (CDOM) and non-algal particles attenuated the light so the 1% light level ranged between 3 and 10 m depending on the age of the plume water. As the plume was 10-15 m thick, the majority of the phytoplankton were light-limited. Vertical mixing within the plume was high as indicated by the dispersion of injected of rhodamine dye. The mixing within the buoyant plume was more rapid than phytoplankton photoacclimation processes. Mixing rates within the plume was the critical factor determining overall productivity rates within the turbid plume.

Schofield, Oscar; Moline, Mark; Cahill, Brownyn; Frazer, Thomas; Kahl, Alex; Oliver, Matthew; Reinfelder, John; Glenn, Scott; Chant, Robert

29

Phytoplankton productivity in a turbid buoyant coastal plume  

NASA Astrophysics Data System (ADS)

The complex dynamics associated with coastal buoyant plumes make it difficult to document the interactions between light availability, phytoplankton carbon fixation, and biomass accumulation. Using real-time data, provided by satellites and high frequency radar, we adaptively sampled a low salinity parcel of water that was exported from the Hudson river estuary in April 2005. The water was characterized by high nutrients and high chlorophyll concentrations. The majority of the low salinity water was re-circulated within a nearshore surface feature for 5 days during which nitrate concentrations dropped 7-fold, the maximum quantum yield for photosynthesis dropped 10-fold, and primary productivity rates decreased 5-fold. Associated with the decline in nitrate was an increase in phytoplankton biomass. The phytoplankton combined with the Colored Dissolved Organic Matter (CDOM) and non-algal particles attenuated the light so the 1% light level ranged between 3 and 10m depending on the age of the plume water. As the plume was 10-15m thick, the majority of the phytoplankton were light-limited. Vertical mixing within the plume was high as indicated by the dispersion of injected of rhodamine dye. The mixing within the buoyant plume was more rapid than phytoplankton photoacclimation processes. Mixing rates within the plume was the critical factor determining overall productivity rates within the turbid plume.

Schofield, Oscar; Moline, Mark; Cahill, Brownyn; Frazer, Thomas; Kahl, Alex; Oliver, Matthew; Reinfelder, John; Glenn, Scott; Chant, Robert

2013-07-01

30

Neutrally buoyant tracer in gas cleaning equipment: a case study  

NASA Astrophysics Data System (ADS)

A generic problem when studying the gas flow in gas cleaning equipment is that any conventional tracer, whether solid particles or liquid droplets, is separated out in accordance with the purpose of the equipment. This makes it impossible, for instance, to visualize the core of the vortex in centrifugal gas cleaning equipment. This paper explores the use of a neutrally buoyant tracer. The tracer is soap bubbles filled with helium. The smaller density of the helium relative to the surrounding air is precisely compensated by the mass of the bubble film to create a neutrally buoyant tracer. The method is used to study the flow in a swirl-tube gas-solid separator, highlighting flow features that cannot be shown with, for instance, LDA. Results are shown as controlled exposure time photographs, where pathlines of the tracer show the flow pattern. The results are further clarified by high-time-resolution pressure measurements at the walls. The work shows that the vortex core can be directly visualized using this technique. The vortex core is observed to, under some conditions, bend to—and spin around—the wall of the separator. Under other conditions, the vortex core coincides with the separator axis, and extends to the bottom of the hopper under the swirl tube. Also the flow in the downstream tubing is studied. The possibilities for obtaining quantitative data for the gas velocity field are discussed, and a promising method for doing this is identified.

Peng, Weiming; Hoffmann, Alex C.; Dries, Huub W. A.; Regelink, Michiel; Foo, Kee-Khoon

2005-12-01

31

Formation of parallel meteor trail pairs as associated with their buoyant rise  

Microsoft Academic Search

In this paper we present numerical computations designed to demonstrate effects associated with the buoyant rise of the hot persistent meteor trails produced by large Leonid meteors. We show that, for a horizontally oriented cylinder of hot air, it is an inherent feature of the buoyant acceleration process that the rising cylinder divides into a pair of counter-rotating linear vortices.

John Zinn; Jack Drummond

2007-01-01

32

Buoyant convection in an enclosure under time-periodic magnetizing force  

Microsoft Academic Search

A numerical study is made of buoyant convection of air in an enclosure under constant gravity and time-periodic magnetizing force. Buoyant convection occurs when the two vertical sidewalls are maintained at different temperatures and the horizontal walls are thermally insulated. To this basic layout, electric coils are located at the left and right sides of the cavity for case 1.

Dong Gu Kang; Jae Min Hyun

2007-01-01

33

Buoyant surface jet analysis of the Yukon River  

NASA Technical Reports Server (NTRS)

Thermal infrared satellite imagery of the discharge from the Yukon River obtained on July 5, 1985 was compared with hydraulic theory for the dilution of buoyant surface jets. In a crossflow, the theory predicts that the plume will follow an x exp 1/3 trajectory where x is distance alongshore, and that the plume temperature will decay according to x exp - 1/6 due to mixing with the receiving water. Measurements of the Yukon River discharge indicate very good agreement with the predicted trajectory, and less, but acceptable, agreement with the predicted dilution. Large scale thermal fronts are also observable in the thermal imagery; the fronts may be associated with excursions of the plume due to tidal currents.

Gosink, J. P.

1988-01-01

34

Predicting Buoyant Shear Flows Using Anisotropic Dissipation Rate Models  

NASA Technical Reports Server (NTRS)

This paper examines the modeling of two-dimensional homogeneous stratified turbulent shear flows using the Reynolds-stress and Reynolds-heat-flux equations. Several closure models have been investigated-, the emphasis is placed on assessing the effect of modeling the dissipation rate tensor in the Reynolds-stress equation. Three different approaches are considered: one is an isotropic approach while the other two are anisotropic approaches. The isotropic approach is based on Kolmogorov's hypothesis and a dissipation rate equation modified to account for vortex stretching. One of the anisotropic approaches is based on an algebraic representation of the dissipation rate tensor, while another relies on solving a modeled transport equation for this tensor. In addition, within the former anisotropic approach, two different algebraic representations are examined one is a function of the Reynolds-stress anisotropy tensor, and the other is a function of' the mean velocity gradients. The performance of these closure models is evaluated against experimental and direct numerical simulation data of pure shear flows. pure buoyant flows and buoyant shear flows. Calculations have been carried out over a range of Richardson numbers (Ri) and two different Prandtl numbers (Pr); thus the effect of Pr on the development of counter-gradient heat flux in a stratified shear flow can be assessed. At low Ri, the isotropic model performs well in the predictions of stratified shear flows; however, its performance deteriorates as Ri increases. At high Ri, the transport equation model for the dissipation rate tensor gives the best result. Furthermore, the results also lend credence to the algebraic dissipation rate model based on the Reynolds stress anisotropy tensor. Finally, it is found that Pr has an effect on the development of counter-gradient heat flux. The calculations show that, under the action of shear, counter-gradient heat flux does not occur even at Ri = 1 in an air flow.

So, R. M. C.; Zhao, C. Y.; Gatski, T. B.

1999-01-01

35

Sampling and analysis of particles from buoyant hydrothermal plumes  

NASA Astrophysics Data System (ADS)

The objective of our studies has been to identify the chemical processes that occur in the buoyant part of hydrothermal plumes and to evaluate their role in determining the ultimate fate of the hydrothermal input to the oceans. Our first such effort is described by Mottl and McConachy [1990]. Because the buoyant plume is a small feature that contains very large physical and chemical gradients, we have sampled it from manned submersibles. We have used two different samplers, both manufactured by General Oceanics in Miami: the Go-Flo bottle and the Chopstick sampler. Four Go-Flo bottles of 1.7 L capacity can readily be mounted on most submersibles, vertically and in a forward position in sight of the pilot's viewport and video cameras, without interfering with other operations on a dive. On Alvin they have typically been mounted on the outside starboard edge of the basket. On Turtle they were mounted on the outside edge of the port manipulator. We chose Go-Flo rather than Niskin bottles because the latter are prone to spillage when the rods attached to the end caps are bumped against an object such as the seafloor, as often happens on a submersible dive. Go-Flo bottles are also more easily rigged for pressure filtration than are Niskins. The main disadvantage of Go-Flo bottles vs. Niskins for this application is the internal silicone rubber ring that holds the ball valves in place on each end of the Go-Flo. This ring tends to trap large particles that are then difficult to dislodge and collect. The rings are also difficult to clean between dives.

Mottl, Michael J.

36

Trace Metals and Nutrients in the Hudson River Buoyant Plume  

NASA Astrophysics Data System (ADS)

In order to determine the spatial distribution and biological impacts of contaminant metals and nutrients associated with the Hudson River buoyant plume, the transport and transformations of mercury, other trace metals, and major nutrients are being measured as part of the LaGrangian Transport and Transformation Experiment (LaTTE). Beginning in the spring of 2004, a series of dye patch experiments will be carried out that will include continuous underway chemical and biological sampling within the well-sampled framework of an operational ocean observatory. During the first experiment in May 2004, surface water samples for dissolved and suspended particle concentrations of mercury, monomethylmercury, and bioactive and non-essential trace metals were collected using a trace metal clean, underway sampling system. A semi-continuous (5 min resolution) record of dissolved gaseous mercury (elemental mercury) in surface waters revealed diurnal patterns of mercury reduction and volatilization. The results of this project will improve predictions of contaminant movements and ecosystem impacts within the Middle Atlantic Bight.

Wright, D. D.; Reinfelder, J. R.; Chant, R. J.; Glenn, S. M.; Schofield, O.; Wilkin, J. L.; Houghton, R. W.; Chen, R. F.; Moline, M. A.; Frazier, T. K.

2004-12-01

37

Channelization of buoyant nonwetting fluids in saturated porous media  

NASA Astrophysics Data System (ADS)

We study the development of capillary instabilities during the invasion of a buoyant nonwetting phase in a saturated porous media. Capillary instabilities are generally attributed to heterogeneities in the porous medium resulting in the existence of fluid pathways opposing different resistance to the flow ("passive control"). We use a simple macroscale theoretical model based on the postulate that the nonwetting fluid will be distributed in the porous medium to minimize the resistance to transport. This theoretical argument is used to show that after their formation, some capillary instabilities can grow at the expense of others. The competitive growth between capillary channels arises because of pore-scale fluid interactions that occur even in a porous medium offering identical pathways at the pore scale. The evolution of the pore volume fraction of nonwetting fluid in capillary fingers is therefore dynamically controlled by fluctuations in the nonwetting phase saturation and its effect on the relative permeability ("active control"). The theoretical model predicts (1) the growth of heterogeneities in nonwetting fluid saturation among competing capillary channels if the second derivative of the invading phase relative permeability with respect to its saturation is positive, and (2) that the amplitude of the perturbation in nonwetting fluid content between competing fingers increases with the interfacial tension. We use a pore-scale multiphase flow numerical model to test the validity of the postulate for optimal transport of nonwetting fluids and the two ensuing predictions. We observe that the numerical calculations are in excellent agreement with the theoretical predictions.

Huber, C.; Parmigiani, Andrea; Latt, Jonas; Dufek, J.

2013-10-01

38

Microstructure and rheology of finite inertia neutrally buoyant suspensions  

NASA Astrophysics Data System (ADS)

The microstructure and rheological properties of suspensions of neutrally buoyant hard spherical particles in Newtonian fluid under conditions of finite inertia are studied using the lattice-Boltzmann method (LBM), which is based on a discrete Boltzmann model for the fluid and Newtonian dynamics for the particles. The suspensions are subjected to simple-shear flow and the properties are studied as a function of Reynolds number and volume fraction, $\\phi$. The inertia is characterized by the particle-scale shear flow Reynolds number $Re = \\frac{\\rho \\dot{\\gamma}a^{2}}{\\mu}$, where $a$ is the particle radius, $\\dot{\\gamma}$ is the shear rate and $\\rho$ and $\\mu$ are the density and viscosity of the fluid, respectively. The influences of inertia and of the volume fraction are studied for $0.005\\leqslant Re \\leqslant 5$ and $0.1\\leqslant \\phi \\leqslant 0.35$. The flow-induced microstructure is studied using the pair distribution function $g(\\boldsymbol{r})$. Different stress mechanisms, including those due to surface tractions (stresslet), acceleration, and the Reynolds stress due to velocity fluctuations are computed and their influence on the first and second normal stress differences, the particle pressure and the viscosity of the suspensions are detailed. The probability density functions of particle force and torque are also presented.

Haddadi, Hamed; Morris, Jeffrey F.

2014-06-01

39

Constancy of cell buoyant density for cultured murine cells  

SciTech Connect

The relationship between cell cycle and cell density was determined for three different lines of mouse cells by equilbrium centrifugation of suspension cultures. The mean cell densities of the three lines differed significantly, with values of 1.0622, 1.0678, 1.0540 gm/ml for 70Z/3, S 107, and ABE 8, respectively. However the density distributions within each of the three lines were indistinguishable, with an average coefficient of variation about 5% of the mean reduced density. Quantitative DNA analysis of the cells separated by density showed that the proportion of cells in G1, S, and G2 + M phase of the cell cycle changed very little or not at all with cell density. In addition, cells separated by size using velocity sedimentation had the same means and distributions of densities. These results indicate that there is little or no changes in cell density as the cells traverse the life cycle and that buoyant density appears to be a constant property of a cell type. 12 references, 4 figures, 2 tables.

Loken, M.R.; Kubitschek, H.E.

1984-01-01

40

Fluid Modeling Simulation of Stack-Tip Downwash for Neutrally Buoyant Plumes.  

National Technical Information Service (NTIS)

Downwash of neutrally buoyant effluent on the immediate lee side of a circular stack was modeled using a wind-tunnel simulation. Both subcritical and supercritical turbulent flows were simulated, where the criticality refers to Reynolds numbers below and ...

W. H. Snyder R. E. Lawson

1991-01-01

41

46 CFR 131.865 - Inflatable liferafts and inflatable buoyant apparatus.  

Code of Federal Regulations, 2013 CFR

...Inflatable liferafts and inflatable buoyant apparatus. 131.865 Section 131.865 Shipping COAST GUARD, DEPARTMENT OF HOMELAND...Markings for Fire Equipment and Emergency Equipment § 131.865 Inflatable liferafts and inflatable...

2013-10-01

42

A change in a single gene of Salmonella typhimurium can dramatically change its buoyant density.  

PubMed Central

The growth rates and buoyant densities of a Salmonella typhimurium mutant, TL126 (proB74A+), with enhanced osmotolerance caused by proline overproduction were measured and compared with the growth rates and buoyant densities of an isogenic (wild-type) strain, TL128 (proB+ A+), with normal control of proline production. Growth rates were determined in a rich medium (Luria broth) with added NaCl to produce various osmotic strengths ranging from 300 to 2,000 mosM. At low concentrations of NaCl, there was little variation in doubling times between the two strains. However, as the osmotic strength of the medium approached and exceeded 1,300 mosM, the doubling times of TL126 (osmotolerant) were 1.5 to 2 times faster than those of TL128 (wild type), confirming the osmotolerance of TL126. Buoyant densities were determined by equilibrium sedimentation in a Percoll gradient of osmotic strength equal to that of the growth medium. The osmolarity of the Percoll gradient was adjusted by the addition of NaCl. At low osmolarities (300 to 500 mosM), the buoyant density of TL126 (osmotolerant) was slightly but consistently lower than that of TL128 (wild type). As the osmotic strength was increased, the buoyant density of TL126 (osmotolerant) increased in proportion to the osmotic strength. In contrast, the buoyant density of strain TL128 (wild type) did not increase as much. At high osmolarities (1,600 to 2,000 mosM), the buoyant density of TL126 (osmotolerant) was consistently higher than that of TL128 (wild type). These results suggest that the intracellular accumulation of proline by TL126, the osmotolerant strain, increases both the growth rates and buoyant densities at osmolarities of 1,300 mosM and above.

Baldwin, W W; Kirkish, M A; Koch, A L

1994-01-01

43

Physical and Numerical Modeling of Buoyant Groundwater Plumes  

NASA Astrophysics Data System (ADS)

In coastal states, the injection of treated wastewater into deep saline aquifers offers a disposal alternative to ocean outfalls and discharge directly into local waterways. The density of treated wastewater is similar to that of freshwater but is often much lower than the ambient density of deep aquifers. This significant density contrast can cause upward buoyant movement of the wastewater plume during and after injection. Since some wastewater treatment plants inject more than 100 MGD of this treated wastewater, it is of the utmost importance to be able to not only determine the fate and transport rates of the plume, but to be able to best determine locations for monitoring wells for early detection of possible problems. In this study, both physical and numerical modeling were undertaken to investigate and understand buoyant plume behavior and transport. Physical models using a 2D cross-sectional Plexiglas tank filled with glass beads were carried out under different ambient density scenarios. The experiments consisted of injection of a freshwater pulse-source bubble into a fully saline tank. The injection occurred in an initially static system with no ambient flow. In the scenarios, the freshwater plume migrated vertically upward until reaching the top of the tank. Fingers developed because of the heterogeneity of the density dependent flow field. The vertical velocities and transport patterns of these plumes were compared to one another to investigate variances due to different ambient water densities. Using the finite-difference numerical code SEAWAT to simulate variable density flow, the experiments were numerically modeled and compared with the physical model results. Due to the sensitivity of this problem to numerical resolution, results from three different grids were compared to determine a reasonable compromise between computer runtimes and numerical accuracy. Furthermore, a comparison of advection solvers was undertaken to identify the best solver to use for this specific problem. This involved a comparison between finite- difference, total variation diminishing and mixed Eulerian-Langrangian methods. From these scenarios, the Method of Characteristics (MOC) advection solver with the fine resolution grid (0.1 cm x 0.1 cm x 2.7 cm cells) resulted in a simulation that was in good agreement with the physical experiments. This model was determined to be the base-case problem for further sensitivity analysis. To further verify both the physical and numerical model, SUTRA_MS was also used for comparison. Dimensionless analysis of the flow and transport governing equations was undertaken to determine important physical problem parameters. From these derived dimensionless numbers, it was hypothesized that density, hydraulic conductivity and dispersivity should all play important roles in this problem. A parameter sensitivity analysis was performed using the numerical model base-case. The parameters investigated were hydraulic conductivity, ambient groundwater density, longitudinal dispersivity and injection volume. It was determined that the problem was most sensitive to ambient density, hydraulic conductivity and dispersivity changes as hypothesized, with all three affecting both vertical mass transfer rates, plume fingering and mixing between the fresh and saline waters. The sensitivity to injection volume was not seen to be an important parameter, except for the obvious effect of change in size of the plume.

Brakefield, L. K.; Abarca, E.; Langevin, C. D.; Clement, T. P.

2007-12-01

44

Buoyant subduction on Venus: Implications for subduction around coronae  

NASA Astrophysics Data System (ADS)

Potentially low lithospheric densities, caused by high Venus surface and perhaps mantle temperatures, could inhibit the development of negative buoyancy-driven subduction and a global system of plate tectonics/crustal recycling on that planet. No evidence for a global plate tectonic system was found so far, however, specific features strongly resembling terrestrial subduction zones in planform and topographic cross-section were described, including trenches around large coronae and chasmata in eastern Aphrodite Terra. The cause for the absence, or an altered expression, of plate tectonics on Venus remains to be found. Slab buoyancy may play a role in this difference, with higher lithospheric temperatures and a tendency toward positive buoyancy acting to oppose the descent of slabs and favoring under thrusting instead. The effect of slab buoyancy on subduction was explored and the conditions which would lead to under thrusting versus those allowing the formation of trenches and self-perpetuating subduction were defined. Applying a finite element code to assess the effects of buoyant forces on slabs subducting into a viscous mantle, it was found that mantle flow induced by horizontal motion of the convergent lithosphere greatly influences subduction angle, while buoyancy forces produce a lesser effect. Induced mantle flow tends to decrease subduction angle to near an under thrusting position when the subducting lithosphere converges on a stationary overriding lithosphere. When the overriding lithosphere is in motion, as in the case of an expanding corona, subduction angles are expected to increase. An initial stage involved estimating the changes in slab buoyancy due to slab healing and pressurization over the course of subduction. Modeling a slab, descending at a fixed angle and heated by conduction, radioactivity, and the heat released in phase changes, slab material density changes due to changing temperature, phase, and pressure were derived.

Burt, J. D.; Head, J. W.

1993-03-01

45

Buoyant subduction on Venus: Implications for subduction around coronae  

NASA Technical Reports Server (NTRS)

Potentially low lithospheric densities, caused by high Venus surface and perhaps mantle temperatures, could inhibit the development of negative buoyancy-driven subduction and a global system of plate tectonics/crustal recycling on that planet. No evidence for a global plate tectonic system was found so far, however, specific features strongly resembling terrestrial subduction zones in planform and topographic cross-section were described, including trenches around large coronae and chasmata in eastern Aphrodite Terra. The cause for the absence, or an altered expression, of plate tectonics on Venus remains to be found. Slab buoyancy may play a role in this difference, with higher lithospheric temperatures and a tendency toward positive buoyancy acting to oppose the descent of slabs and favoring under thrusting instead. The effect of slab buoyancy on subduction was explored and the conditions which would lead to under thrusting versus those allowing the formation of trenches and self-perpetuating subduction were defined. Applying a finite element code to assess the effects of buoyant forces on slabs subducting into a viscous mantle, it was found that mantle flow induced by horizontal motion of the convergent lithosphere greatly influences subduction angle, while buoyancy forces produce a lesser effect. Induced mantle flow tends to decrease subduction angle to near an under thrusting position when the subducting lithosphere converges on a stationary overriding lithosphere. When the overriding lithosphere is in motion, as in the case of an expanding corona, subduction angles are expected to increase. An initial stage involved estimating the changes in slab buoyancy due to slab healing and pressurization over the course of subduction. Modeling a slab, descending at a fixed angle and heated by conduction, radioactivity, and the heat released in phase changes, slab material density changes due to changing temperature, phase, and pressure were derived.

Burt, J. D.; Head, J. W.

1993-01-01

46

Wave induced transport and mixing of buoyant particles  

NASA Astrophysics Data System (ADS)

The modeling of wave-current and wave-turbulence interactions have received much attention during recent years. Both the breaking of surface waves and the inclusion of the Stokes shear production have been shown to increase the upper ocean turbulence. Furthermore the Coriolis force acting on the Stokes drift redistributes the momentum in the upper ocean, leading to a deflection of the currents. An important application affected by these processes that still needs to be studied is the mixing and drift of particles. Using an ocean column model, modified to take surface wave effects into account, we investigate how the increased mixing by wave breaking and Stokes shear production as well as the stronger veering by the Coriolis-Stokes force effects the drift of suspended particles. Here the suspended particles are buoyant tracers that can represent oil droplets or plankton, for example fish eggs and larvae. The energy and momentum fluxes as well as the Stokes drift depend on the directional wave spectrum that can be obtained from a wave model or from observations. Comparing with classical Ekman theory some physical effects on the system are studied, and as a realistic test case we use the model to study the oil drift after an offshore oil spill that took place outside the western coast of Norway in 2007. During this accident the average net drift of oil was observed to be approximately 0.1% of the wind speed at an angle of about 90-120 degrees to the right, far slower and more deflected away from the wind direction than predicted by both numerical and empirical models. With wind and wave forcing from ECMWF reanalysis data, it is shown that the wave effects are important for the resultant drift in this case, and has the potential to improve drift forecasting.

Drivdal, Magnus; Broström, Göran; Christensen, Kai H.

2014-05-01

47

Surface Buoyant Plumes from Melting Icebergs in the Labrador Sea  

NASA Astrophysics Data System (ADS)

Canada's Department of Fisheries and Oceans (DFO) conducts annual surveys in the Labrador Sea along the repeat hydrography line AR7W. Since 2012, these shipboard surveys have been supplemented by underway CTD and optical measurements in the upper 200 m layer conducted with the towed undulating platform Moving Vessel Profiler (MVP). The MVP hydrographic data reveal rich variability of the upper layer salinity field on different spatial scales. The occupation of the AR7W line in May 2013 was followed by the experiment aimed at resolving the imprint of melting drifting icebergs on the upper layer thermohaline characteristics in the Labrador Sea. Here we present observations around two icebergs: the first iceberg drifted in relatively warm water of Atlantic origin (~2.5-3.1°C) off Greenland, while the second iceberg was on the Labrador shelf in cold water below 0°C. Both icebergs had a lengthscale of O(100 m). In both cases surface buoyant plumes fed by melt water and attached to the iceberg were observed. The plumes were evident in the anomalous thermohaline characteristics of the seawater. Their density anomalies were sufficiently strong to produce visible frontal structures, which imply a development of the intrinsic dynamics associated with a plume. The first plume formed over a time interval of ~10 hr, while the second plume formed over several days and extended for more than 1 km (tenfold the iceberg's size). Strong vertical displacements of the pycnocline were observed near the second iceberg. They are interpreted as the internal wave wake. This interpretation is based on the temporal scale of these oscillations (local buoyancy frequency), as well as on the spatial orientation of these waves with respect to the iceberg drift relative to the pycnocline. The observed internal waves partially overlapped with the plume and affected its structure. The saline seawater splashing by swell contributed to the surface melting of the icebergs. Scaling analysis of the observed plume suggests that it could be in the "rotational" dynamic regime with recirculating anticyclonic flow. In this case the melt water is trapped in the plume and affects the iceberg's thermodynamics and the rate of melt. These effects are likely to be more pronounced near bigger icebergs or ice islands, and will be a focus of our future observational campaign.

Yankovsky, Alexander; Yashayaev, Igor

2014-05-01

48

Experiments On Buoyant Plume Dispersion In A Laboratory Convection Tank  

NASA Astrophysics Data System (ADS)

Plume dispersion in the convective boundary layer (CBL) is investigated experimentally in a laboratory convection tank. The focusis on highly-buoyant plumes that loft near or become trapped in the CBL capping inversion and resistdownward mixing. Such plumes are defined by dimensionless buoyancy fluxes F* 0.1, where F* = Fb/(U w* 2 zi), Fb is the stack buoyancy flux,U is the mean wind speed, w* is the convective velocity scale, and zi is the CBL depth. The aim is to obtain statistically-reliable mean (C) and root-mean-square (rms, c) concentration fields as a function of F* and the dimensionless distance X = w*x/(U zi), where x is the distance downstream of the source.

The experiments reveal the following mainresults: (1) For 3 X 4and F* 0.1, the crosswind-integrated concentration (CWIC) fields exhibit distinctly uniform profiles below zi with a CWIC maximum aloft, in contrast to the nonuniform profiles obtained earlier by Willis and Deardorff. (2) The lateral dispersion (y) variation with X is consistent with Taylor's theory for * 0.1 and a buoyancy-enhanced dispersion, y/zi F* 1/3X2/3, forF* = 0.2 and 0.4. (3) The entrapment, the plume fraction above zi, has a mean (E) that follows a systematic variationwith X and F*, and a variability (e/E) that is broad ( 0.3 to 2) near the source but subsides to 0.25 far downstream. (4) Vertical profiles of the concentration fluctuation intensity (c/C) are uniform for z < zi and X > 1.5, but exhibit significant increases: (a) at the surface and close to the source (X 1.5), and(b) in the entrainment zone. (5) The cumulative distribution functions (CDFs) of the scaled concentration fluctuations (c/c) separate into mixed-layer and entrainment-layer CDFs for X 2, with the mixed-layer group collapsing to a single distribution independent of z.

Weil, Jeffrey C.; Snyder, William H.; Lawson, Robert E.; et al.

49

A chemical model of the buoyant and neutrally buoyant plume above the TAG vent field, 26 degrees N, Mid-Atlantic Ridge  

NASA Astrophysics Data System (ADS)

The kinetics of iron particle formation in the neutrally buoyant plume above the TAG vent field (26 degrees N, Mid-Atlantic Ridge) have been calculated from submersible-collected CTD data within the initial 150 m of plume rise. Results show that particles form by a two-stage process: about half the iron in the high temperature vent fluid is removed as sulfides within a few seconds of venting and the remainder is removed by Fe 2+ oxidation. The pseudo-first-order rate constant for the second process has been calculated ( k1 = 0.329min -1, similar to literature values for seawater) and gives a halflife time for Fe 2+ in solution of 2.1 minutes. The kinetics of iron particle formation have been used in a conceptual model of the chemistry of the TAG plume. The average dilution at which iron oxyhydroxide particles form, E¯ Fe, is ˜ 570 from which element/Fe ratios of particles at the top of the buoyant plume have been predicted. Oxyanion/Fe ratios can be chiefly accounted for by coprecipitation for Cr (71%), V (67%), As (45%) and P (42%) but Mo (0.1%) and U (0.02%) show anomalously low coprecipitation. Th/Fe and REE/Fe ratios are greater than can be accounted for by coprecipitation, demonstrating that scavenging occurs in the buoyant plume for these elements. 98% of the Th uptake and 15-75% of the REE uptake is by scavenging. Scavenging rate constants are 3.1 * 10 -6 (nmol/kg) -1 s -1 for Th and 1.4-33* 10 -8 (nmol/kg) -1 s -1 for the REE. A scavenging model has been fitted to trace metal data previously reported for neutrally buoyant hydrothermal plume particulate samples collected above the TAG vent field. The model is based on the assumption that there is a characteristic t1/2 for the dilution of the neutrally buoyant plume and this value has been calculated, by comparing 228Th and 230Th with 234Th isotope data, as fourty-one days (? p = 0.0170 day -1). Scavenging rate constants are 2* 10 -9 (nmol/kg) -1 s -1 for Th and 3.5-16*10 -11 (nmol/kg) -1 s -1 for the REE. This shows preferential removal of the intermediate REE from sea water, a pattern which has also been found in those TAG sediments formed from neutrally buoyant plume fallout. Chalcophile elements (Cu, Zn, Co, Pb, Sn) all appear to undergo release from plume particles at the same rate ( t1/2 ? 42days) suggesting alteration or removal of a common substrate. Model ages for particles above the TAG vent field are <50 days within 500 m of the vent field and 50-100 days at greater distances or below the height of the neutral plume. Quantitative removal of vent fluid derived REE, with the possible exception of Eu, during buoyant plume rise means that hydrothermal activity has no direct impact on the seawater chemistry of the REE. If coprecipitation and scavenging within the TAG hydrothermal plume are typical, such processes during plume rise (the buoyant plume) and dispersion (the neutrally buoyant plume) play a significant role in the removal of reactive trace metals and oxyanions from seawater, at rates of the same order as those of river input to the oceans.

Rudnicki, M. D.; Elderfield, H.

1993-07-01

50

Experiments versus modeling of buoyant drying of porous media  

NASA Astrophysics Data System (ADS)

Experiments versus modeling of buoyant drying of porous media D. Salin and A.G. Yiotis, Laboratoire FAST, Univ Pierre & Marie Curie, Univ. Paris-Sud, CNRS, Orsay 91405, France and E.S. Tajer and Y.C. Yortsos, Mork Family Department of Chemical Engineering and Materials Science, University of Southern California, Los Angeles, CA 90089-1450 A series of isothermal drying experiments in packed glass beads saturated with volatile hydrocarbons (hexane or pentane) are conducted. The transparent glass cells containing the packing allow for the visual monitoring of the phase distribution patterns below the surface, including the formation of liquid films, as the gaseous phase invades the pore space, and for the control of the thickness of the diffusive mass boundary layer over the packing. We demonstrate the existence of an early Constant Rate Period, CRP, that lasts as long as the films saturate the surface of the packing, and of a subsequent Falling Rate Period, FRP, that begins practically after the detachment of the film tips from the external surface. During the CRP, the process is controlled by diffusion within the stagnant gaseous phase in the upper part of the cells, yielding a Stefan tube problem solution. During the FRP, the process is controlled by diffusion within the packing, with a drying rate inversely proportional to the observed position of the film tips in the cell. The critical residual liquid saturation that marks the transition between these two regimes is found to be a function of the average bead size in our packs and the incline of the cells with respect to the flat vertical, with larger beads and angles closer to the vertical position leading to earlier film detachment times and higher critical saturations. We developed a model for the drying of porous media in the presence of gravity. It incorporated effects of corner film flow, internal and external mass transfer and the effect of gravity. Analytical results were derived when gravity opposes drying and hence leads to a stable percolation drying front. We are thus able to obtain results for the drying rates, the critical saturation and the extent of the film region with respect to the various dimensionless numbers that describe the process; the Bond (Bo)number, a film-based Capillary (Ca) number and the dimensionless extent of the mass boundary layer (Sh). The experimental results agree very well with the theory, provided that the latter is generalized to account for the effects of corner roundness in the film region which were neglected in our analytical approach. The agreement is achieved for a specific value of the roundness of the films, which is found to be constant and equal to 0.2 for various conditions, and verify the theoretical dependence on Ca, Bo and Sh numbers.

Salin, D.; Yiotis, A.; Tajer, E.; Yortsos, Y. C.

2012-12-01

51

Preliminary study of ground handling characteristics of Buoyant Quad Rotor (BQR) vehicles  

NASA Technical Reports Server (NTRS)

A preliminary investigation of mooring concepts appropriate for heavy lift buoyant quad rotor (BQR) vehicles was performed. A review of the evolution of ground handling systems and procedures for all airship types is presented to ensure that appropriate consideration is given to past experiences. Two buoyant quad rotor designs are identified and described. An analysis of wind loads on a moored airship and the effects of these loads on vehicle design is provided. Four mooring concepts are assessed with respect to the airship design, wind loads and mooring site considerations. Basing requirements and applicability of expeditionary mooring at various operational scenarios are addressed.

Browning, R. G. E.

1980-01-01

52

The Buoyant Filter Bioreactor: a high-rate anaerobic reactor for complex wastewater—process dynamics with dairy effluent  

Microsoft Academic Search

A novel high-rate anaerobic reactor, called “Buoyant Filter Bioreactor” (BFBR), has been developed for treating lipid-rich complex wastewater. The BFBR is able to decouple the biomass and insoluble COD retention time from the hydraulic retention time by means of a granular filter bed made of buoyant polystyrene beads. Filter clogging is prevented by an automatic backwash driven by biogas release,

Ajit Haridas; S. Suresh; K. R. Chitra; V. B. Manilal

2005-01-01

53

Approximate Analysis of the Formation of a Buoyant Solid Sphere in a Supercooled Melt.  

National Technical Information Service (NTIS)

A mathematical model is presented for the idealized formation and development of a buoyant sphere solidifying in an infinite pool of supercooled liquid. The solid and liquid are of the same pure material and the solid is less dense than the liquid. Initia...

A. D. Solomon D. G. Wilson V. Alexiades

1986-01-01

54

The Sedimentation of Buoyant Microcystis Colonies Caused by Precipitation with an Iron-Containing Colloid  

Microsoft Academic Search

Colonies of Microcystis aeruginosa have dominated the phytoplankton in Lund tube C, a limnetic enclosure in Blelham Tarn, English Lake District, during the summer and autumn in recent years. Following holomixis in autumn the previously buoyant colonies sedimented from the water column onto the bottom mud. In all samples gas vesicles, which provided the colonies with buoyancy, were present in

R. L. Oliver; R. H. Thomas; C. S. Reynolds; A. E. Walsby

1985-01-01

55

Interaction of a Buoyant Turbulent Planar Jet with a Co-Flowing Wind.  

National Technical Information Service (NTIS)

The classic theory of buoyant motion of a free planar heated jet in still air is extended to account for environmental winds from the same direction as the jet, that is, co-flowing winds. The model is applicable for wind and jet velocities up to 100 m/sec...

M. M. Klein B. A. Kunkel

1975-01-01

56

Interaction of a Buoyant Turbulent Round Jet with a Co-Flowing Wind.  

National Technical Information Service (NTIS)

A broad effort is being conducted to develop an operational Warm Fog Dispersal System (WFDS) using ground-based heat sources. In order to determine the optimum heat and thrust for the combustors in the WFDS, investigations have been made of the buoyant mo...

M. M. Klein B. A. Kunkel

1975-01-01

57

A study of a buoyant axisymmetric jet in a small co-flow  

Microsoft Academic Search

This paper deals with measurements of and an integral model for a buoyant axisymmetric jet in a very small co-flow. The integral model is based on the insights gained from the measurements presented here and other recent experiments, which suggest that the turbulent flow is simply advected and the entrainment is that normal for a jet or plume in a

M. J. Davidson; S. Gaskin; I. R. Wood

2002-01-01

58

Applying a Predict-Observe-Explain Sequence in Teaching of Buoyant Force  

ERIC Educational Resources Information Center

An active learning sequence based on the predict-observe-explain teaching strategy is applied to a lesson on buoyant force. The results obtained clearly justify the use of this teaching method and suggest devising a series of activities to enable more effective removal of students' commonly held alternative conceptions regarding floating and…

Radovanovic, Jelena; Slisko, Josip

2013-01-01

59

Unsteady analysis of the six DOF motion of a buoyantly rising submarine  

Microsoft Academic Search

The roll instability observed in buoyantly rising small to medium sized submarines is analyzed in this work using a computational fluid dynamics (CFD) RANS solver coupled to the six degree of freedom (DOF) solid body equations of motion for the submarine. The theoretical framework and the numerical implementation, in particular the fluid–rigid-body interaction methodology, are outlined in detail in conjunction

Mark C. Bettle; Andrew G. Gerber; George D. Watt

2009-01-01

60

Buoyant plumes from solute gradients generated by non-motile Escherichia coli.  

PubMed

The effect of hydrodynamic mixing in bacterial populations due to bacterial chemotaxis is a well-described phenomenon known as bioconvection. Here we report the observation of buoyant plumes that result in hydrodynamic mixing, but in contrast to bioconvection the plumes form in the absence of bacterial motility. We propose that the buoyant flow originates from solute gradients created by bacterial metabolism, similar to solute-induced buoyant flow around growing protein crystals. In our experiments, metabolically-active non-motile Escherichia coli were layered along the bottom of flat-bottomed containers. The E. coli consumed glucose in the medium creating a lighter fluid beneath a heavier fluid. The situation is an example of Rayleigh-Taylor instability, in which a lighter fluid pushes on a heavier one. We developed a numerical model to study the effect of E. coli nutrient consumption and by-product excretion on extracellular solute gradients. The model solutions showed reduced-density fluid along the bottom of the fluid domain leading to buoyant plumes, which were qualitatively similar to the experimental plumes. We also used scaling analyses to study the dependence of plume formation on container size and cell size, and to investigate the effect of reduced gravity, such as the microgravity conditions encountered during spaceflight. PMID:19075355

Benoit, M R; Brown, R B; Todd, P; Nelson, E S; Klaus, D M

2008-01-01

61

Development of external and neutrally buoyant acoustic transmitters for juvenile salmon turbine passage evaluation  

Microsoft Academic Search

Fish can sustain injury or mortality when they pass through hydroelectric facilities. To develop a method to monitor the passage and survival of juvenile salmonids without bias through turbines within the Federal Columbia River Power System, we developed and fabricated two designs of neutrally buoyant transmitters: Type A (sutured to the dorsal musculature of the fish anterior to the dorsal

Z. Daniel Deng; Jayson J. Martinez; Alison H. Colotelo; Tylor K. Abel; Andrea P. LeBarge; Richard S. Brown; Brett D. Pflugrath; Robert P. Mueller; Thomas J. Carlson; Adam G. Seaburg; Robert L. Johnson; Martin L. Ahmann

62

Nonlinear adjustment of a localized layer of buoyant, uniform potential vorticity fluid against a vertical wall  

Microsoft Academic Search

The nonlinear evolution of a localized layer of buoyant, uniform potential vorticity fluid with depth H, width w0 and length L released adjacent to a wall in a rotating system is studied using reduced-gravity shallow-water theory and numerical modeling. In the interior, far from the two ends of the layer, the initial adjustment gives, after ignoring inertia–gravity waves, a geostrophic

Karl R. Helfrich

2006-01-01

63

A buoyant plume adjacent to a headland-Observations of the Elwha River plume  

USGS Publications Warehouse

Small rivers commonly discharge into coastal settings with topographic complexities - such as headlands and islands - but these settings are underrepresented in river plume studies compared to more simplified, straight coasts. The Elwha River provides a unique opportunity to study the effects of coastal topography on a buoyant plume, because it discharges into the Strait of Juan de Fuca on the western side of its deltaic headland. Here we show that this headland induces flow separation and transient eddies in the tidally dominated currents (O(100. cm/s)), consistent with other headlands in oscillatory flow. These flow conditions are observed to strongly influence the buoyant river plume, as predicted by the "small-scale" or "narrow" dynamical classification using Garvine's (1995) system. Because of the transient eddies and the location of the river mouth on the headland, flow immediately offshore of the river mouth is directed eastward twice as frequently as it is westward. This results in a buoyant plume that is much more frequently "bent over" toward the east than the west. During bent over plume conditions, the plume was attached to the eastern shoreline while having a distinct, cuspate front along its westernmost boundary. The location of the front was found to be related to the magnitude and direction of local flow during the preceding O(1. h), and increases in alongshore flow resulted in deeper freshwater mixing, stronger baroclinic anomalies, and stronger hugging of the coast. During bent over plume conditions, we observed significant convergence of river plume water toward the frontal boundary within 1. km of the river mouth. These results show how coastal topography can strongly influence buoyant plume behavior, and they should assist with understanding of initial coastal sediment dispersal pathways from the Elwha River during a pending dam removal project. ?? 2010.

Warrick, J. A.; Stevens, A. W.

2011-01-01

64

The early melting of closed duplex DNA: analysis by banding in buoyant neutral rubidium trichloroacetate.  

PubMed Central

Aqueous RbTCA permits the buoyant banding of both native and denatured DNA at room temperature and neutral pH. A unique property of this solvent is the bouyant resolution of closed circular, underwound DNA (I) from the corresponding nicked (II) species. Conditions are reported here in which PM-2 DNA I is physically resolved from native PM-2 DNA II, the buoyant separation being 1.27 mq/ml in 3.3 M RbTCA at 25 degrees C. The separation between nicked and closed DNAs increases with temperature up to 35.5 degrees C, at which PM-2 DNA II cooperatively melts and subsequently pellets. The isothermal buoyant density of a cloed DNA increases linearly as the linking number (Lk) of the closed DNA decreases. The early melting of closed DNA may be monitored with high precision by buoyant banding in RbTCA, it being possible to detect the disruption of as few as 40 base pairs in PM-2 DNA (10,000 base pairs). The constraint that the linking number be conserved in closed DNA requires that a change in duplex winding be accompanied by a compensating change in supercoiling. We estimate the linking number deficiency of PM-2 DNA I to be 0.094 turns per decibase pair. This result permits the estimation of the EtdBr unwinding angle, phi, by comparison with alternative determinations of the linking number deficiency which depend upom the value of phi. The result obtained here is that phi = 27.7 degrees +/- 0.5 degrees and is approximately independent of temperature over the range 15 degrees-35 degrees.

Burke, R L; Bauer, W R

1980-01-01

65

Onshore propagation of a buoyant ocean front observed using a shore-based marine radar  

Microsoft Academic Search

An analysis is presented of a 2-h-long time series of X-band marine radar images, collected at Duck, North Carolina (USA), that captured the evolution of a buoyant ocean front as it propagated onshore, following a period of upwelling-favorable winds. In plan view, the front exhibits a scallop-shaped structure similar to that previously observed along strongly convergent fronts. This alongshore structure

G. O. Marmorino; A. L. Cooper; R. P. Mied; G. J. Lindemann; D. B. Trizna; D. L. Porter

2004-01-01

66

BUOYANT MAGNETIC LOOPS IN A GLOBAL DYNAMO SIMULATION OF A YOUNG SUN  

SciTech Connect

The current dynamo paradigm for the Sun and Sun-like stars places the generation site for strong toroidal magnetic structures deep in the solar interior. Sunspots and starspots on Sun-like stars are believed to arise when sections of these magnetic structures become buoyantly unstable and rise from the deep interior to the photosphere. Here, we present the first three-dimensional global magnetohydrodynamic (MHD) simulation in which turbulent convection, stratification, and rotation combine to yield a dynamo that self-consistently generates buoyant magnetic loops. We simulate stellar convection and dynamo action in a spherical shell with solar stratification, but rotating three times faster than the current solar rate. Strong wreaths of toroidal magnetic field are realized by dynamo action in the convection zone. By turning to a dynamic Smagorinsky model for subgrid-scale turbulence, we here attain considerably reduced diffusion in our simulation. This permits the regions of strongest magnetic field in these wreaths to rise toward the top of the convection zone via a combination of magnetic buoyancy instabilities and advection by convective giant cells. Such a global simulation yielding buoyant loops represents a significant step forward in combining numerical models of dynamo action and flux emergence.

Nelson, Nicholas J.; Toomre, Juri [JILA and Department of Astrophysical and Planetary Sciences, University of Colorado, Boulder, CO 80309-0440 (United States); Brown, Benjamin P. [Department of Astronomy and Center for Magnetic Self-Organization (CSMO) in Laboratory and Astrophysical Plasmas, University of Wisconsin, Madison, WI 53706-1582 (United States); Brun, Allan Sacha [Laboratoire AIM Paris-Saclay, CEA/Irfu Universite Paris-Diderot CNRS/INSU, 91191 Gif-sur-Yvette (France); Miesch, Mark S. [High Altitude Observatory, NCAR, Boulder, CO 80307-3000 (United States)

2011-10-01

67

Buoyant force and sinking conditions of a hydrophobic thin rod floating on water  

NASA Astrophysics Data System (ADS)

Owing to the superhydrophobicity of their legs, such creatures as water striders and fisher spiders can stand effortlessly, walk and jump quickly on water. Directed toward understanding their superior repellency ability, we consider hydrophobic thin rods of several representative cross sections pressing a water surface. First, the shape function of the meniscus surrounding a circular rod is solved analytically, and thereby the maximal buoyant force is derived as a function of the Young’s contact angle and the rod radius. Then we discuss the critical conditions for a rod to sink into water, including the maximal volume condition and the meniscus-contact condition. Furthermore, we study the sinking conditions and the maximal buoyant forces of hydrophobic long rods with elliptical, triangular, or hexagonal cross-section shapes. The theoretical solutions are quantitatively consistent with existing experimental and numerical results. Finally, the optimized structures of water strider legs are analyzed to elucidate why they can achieve a very big buoyant force on water.

Liu, Jian-Lin; Feng, Xi-Qiao; Wang, Gang-Feng

2007-12-01

68

The response of buoyant laminar diffusion flames to low-frequency forcing  

SciTech Connect

Buoyant jet diffusion flames are frequently used to investigate phenomena associated with flares or fires, such as the formation and emission of soot, polycyclic aromatic hydrocarbons (PAH), and carbon monoxide (CO). To systematically investigate the influence of transient vortex-flame interactions on these processes, laminar jet flames may be periodically forced. Previous work has demonstrated that forcing the fuel stream at a (low) frequency close to the natural buoyant instability frequency will trigger the production of vortices on the air side of the high-temperature reaction zone, coupling the overall flame response to the forcing frequency. In the work reported here, measurements in methane/air and ethylene/air slot flames show that over a substantial range of forcing frequencies and amplitudes, the dominant, air-side vortex production is locked at precisely one-half the excitation frequency of the fuel stream. This phenomenon is examined in detail through the utilization of several laser diagnostic techniques, yielding measurements of both the frequency response of the flames and phase-locked images of the internal flame structure. Under some conditions the subharmonic response of the flame leads to transient separation of the PAH and soot layers from the surrounding high-temperature flame zone, potentially affecting the soot formation and radiation processes. This data should provide useful information for comparison with detailed modeling aimed to improve the understanding of the complex nature of the buoyant instability in jet flames. (author)

Williams, Timothy C.; Shaddix, Christopher R.; Schefer, Robert W. [Combustion Research Facility, Sandia National Laboratories, Livermore, CA 94550 (United States); Desgroux, Pascale [Physicochimie des Processus de Combustion et de l'Atmosphere, Universite des Sciences et Technologies de Lille, Villeneuve d'Ascq Cedex (France)

2007-12-15

69

Influence of Buoyant Convection on the Stability of Enclosed Laminar Flames  

NASA Technical Reports Server (NTRS)

Enclosed diffusion flames are commonly found in practical combustion systems, such as the power-plant combustor, gas turbine combustor, and jet engine after-burner. In these systems, fuel is injected into a duct with a co-flowing or cross-flowing air stream. In combustors, this flame is anchored at the burner (i.e., fuel jet inlet) unless adverse conditions cause the flame to lift off or blow out. Investigations of burner stability study the lift off, reattachment, and blow out of the flame. There have been numerous studies of flame stability. Relatively few studies have investigated the stability of flames with an oxidizer co-flow, compared with the number of studies on (nearly) free jet diffusion flames. The air flow around the fuel jet can significantly alter the lift off, reattachment and blow out of the jet diffusion flame. In normal gravity, however, the effects of the air flow on flame stability are often complicated by the presence of buoyant convection. A comparison of normal-gravity and microgravity flames can provide clear indication of the influence of forced and buoyant flows on the flame stability. The overall goal of the Enclosed Laminar Flames (ELF) research, described at the following URL site: http://zeta.lerc.nasa.gov/expr/elf.htm, is to improve our understanding of the effects of buoyant convection on the structure and stability of co-flow diffusion flames.

Brooker, John E.; Jia, Kezhong; Stocker, Dennis P.; Chen. Lea-Der

1999-01-01

70

Buoyant plume dispersion in a coastal environment: evolving plume structure and dynamics  

NASA Astrophysics Data System (ADS)

A field program has been devised to study the dispersion of a buoyant plume formed by the discharge of treated wastewater from the Whites Point outfall into the coastal ocean off the Palos Verdes peninsula off southern California. The program combines high resolution towed surveys of physical and bio-optical variables with continuous time series observations of current velocity. The observations show that after discharge the wastewater forms a submerged buoyant plume of relatively fresh, turbid effluent. Identification of the plume within the water column is complicated by the ambient thermohaline and particle fields which can exhibit natural variability comparable to that introduced by the plume. We present a simple method based on threshold criteria of three measured variables to identify effluent-containing waters under general conditions. The complexity of the effluent field is found to depend strongly on the temporal variability of currents over a period of several hours preceding the observation time and on the ambient density structure. Measurements of small-scale turbulent mixing activity show that high mixing rates occur over the diffusers due to buoyant convection in the rising plume. We use the distribution of turbulent activity to separate the actively mixing region in the rising plume from the passive effluent layer away from the diffusers. In background waters, turbulent patches are occasionally found with horizontal extents of about 1.5 km and vertical extents of about 5 m. Effective eddy diffusivities within these patches are of order Kz ˜ 10 -4 m 2 s -1.

Wu, Yicun; Washburn, Libe; Jones, Burton H.

1994-08-01

71

Onshore propagation of a buoyant ocean front observed using a shore-based marine radar  

NASA Astrophysics Data System (ADS)

An analysis is presented of a 2-h-long time series of X-band marine radar images, collected at Duck, North Carolina (USA), that captured the evolution of a buoyant ocean front as it propagated onshore, following a period of upwelling-favorable winds. In plan view, the front exhibits a scallop-shaped structure similar to that previously observed along strongly convergent fronts. This alongshore structure consists of broad frontal crests (a few hundred meters in length) alternating with sharply angled troughs, or frontal cusps. The evolution of these frontal shapes is explored using a reduced-gravity model (Cooper et al., J. Geophys. Res.-Oceans 106 (2001) 16887) that allows for nonlinear self-interaction of a propagating front. A model simulation shows cusps that develop quickly from initially broad troughs and that point toward the buoyant water, features resembling the observations. However, the simulation also shows a continuous oscillation of frontal shapes, while the observed front reaches a quasi-steady plan form. We attribute this difference in behavior to the gradual shoaling of the observed front as it steadily advances, ultimately reaching water depths of less than 2 m, which is comparable to the thickness of the buoyant layer. As a consequence of the shoaling, we suggest the cusps become sites of enhanced mixing, where water inshore of the front is also accelerated seaward.

Marmorino, G. O.; Cooper, A. L.; Mied, R. P.; Lindemann, G. J.; Trizna, D. B.; Porter, D. L.

2004-06-01

72

Early-stage hypogene karstification in a mountain hydrologic system: A coupled thermohydrochemical model incorporating buoyant convection  

NASA Astrophysics Data System (ADS)

The early stage of hypogene karstification is investigated using a coupled thermohydrochemical model of a mountain hydrologic system, in which water enters along a water table and descends to significant depth (˜1 km) before ascending through a central high-permeability fracture. The model incorporates reactive alteration driven by dissolution/precipitation of limestone in a carbonic acid system, due to both temperature- and pressure-dependent solubility, and kinetics. Simulations were carried out for homogeneous and heterogeneous initial fracture aperture fields, using the FEHM (Finite Element Heat and Mass Transfer) code. Initially, retrograde solubility is the dominant mechanism of fracture aperture growth. As the fracture transmissivity increases, a critical Rayleigh number value is exceeded at some stage. Buoyant convection is then initiated and controls the evolution of the system thereafter. For an initially homogeneous fracture aperture field, deep well-organized buoyant convection rolls form. For initially heterogeneous aperture fields, preferential flow suppresses large buoyant convection rolls, although a large number of smaller rolls form. Even after the onset of buoyant convection, dissolution in the fracture is sustained along upward flow paths by retrograde solubility and by additional "mixing corrosion" effects closer to the surface. Aperture growth patterns in the fracture are very different from those observed in simulations of epigenic karst systems, and retain imprints of both buoyant convection and preferential flow. Both retrograde solubility and buoyant convection contribute to these differences. The paper demonstrates the potential value of coupled models as tools for understanding the evolution and behavior of hypogene karst systems.

Chaudhuri, A.; Rajaram, H.; Viswanathan, H.

2013-09-01

73

An improved genetic system for bioengineering buoyant gas vesicle nanoparticles from Haloarchaea  

PubMed Central

Background Gas vesicles are hollow, buoyant organelles bounded by a thin and extremely stable protein membrane. They are coded by a cluster of gvp genes in the halophilic archaeon, Halobacterium sp. NRC-1. Using an expression vector containing the entire gvp gene cluster, gas vesicle nanoparticles (GVNPs) have been successfully bioengineered for antigen display by constructing gene fusions between the gvpC gene and coding sequences from bacterial and viral pathogens. Results To improve and streamline the genetic system for bioengineering of GVNPs, we first constructed a strain of Halobacterium sp. NRC-1 deleted solely for the gvpC gene. The deleted strain contained smaller, more spindle-shaped nanoparticles observable by transmission electron microscopy, confirming a shape-determining role for GvpC in gas vesicle biogenesis. Next, we constructed expression plasmids containing N-terminal coding portions or the complete gvpC gene. After introducing the expression plasmids into the Halobacterium sp. NRC-1 ?gvpC strain, GvpC protein and variants were localized to the GVNPs by Western blotting analysis and their effects on increasing the size and shape of nanoparticles established by electron microscopy. Finally, a synthetic gene coding for Gaussia princeps luciferase was fused to the gvpC gene fragments on expression plasmids, resulting in an enzymatically active GvpC-luciferase fusion protein bound to the buoyant nanoparticles from Halobacterium. Conclusion GvpC protein and its N-terminal fragments expressed from plasmid constructs complemented a Halobacterium sp. NRC-1 ?gvpC strain and bound to buoyant GVNPs. Fusion of the luciferase reporter gene from Gaussia princeps to the gvpC gene derivatives in expression plasmids produced GVNPs with enzymatically active luciferase bound. These results establish a significantly improved genetic system for displaying foreign proteins on Halobacterium gas vesicles and extend the bioengineering potential of these novel nanoparticles to catalytically active enzymes.

2013-01-01

74

Effects of vent overpressure on buoyant eruption columns: Implications for plume stability  

NASA Astrophysics Data System (ADS)

Volcanic plumes resulting from explosive volcanic eruptions present a variety of hazards depending on their behavior. Buoyant plumes heat and entrain enough of the surrounding air to rise high into the atmosphere, disrupting air traffic and causing regional ash fall. Alternatively, collapsed plumes produce dangerous fast-moving lateral flows of hot ash and gas. The transition between these behaviors and the nature of each hazard is dependent on the fluid dynamics of the volcanic plume, which is largely determined by the conditions at the vent. Most treatments of volcanic plumes for hazard assessment assume that the eruptive fluid exits the vent at pressures equal to atmospheric pressure or that pressure equalizes quickly with little effect on the flow. Here we show that vent pressures greater than atmospheric lead to rapid expansion of the plume and the development of standing shock waves that change the behavior of the entire eruption column. We simulate two volcanic plumes with the same heat flow (J s - 1) at the vent; one exits the vent at atmospheric pressure (pressure-balanced) and the other at four times atmospheric pressure (overpressured). The two simulated plumes have the same radius after the initial rapid decompression of the overpressured case. These plumes show drastically different behavior due to the presence of standing shock waves in the overpressured case despite having the same heat flow at the vent and the same area available for entrainment of ambient air. Both simulated plumes exhibit buoyant rise but the overpressured plume collapses with a regular periodicity. These simulations suggest that the dynamics of a steady-state overpressured vent may result in plumes that oscillate between buoyant rise and collapse, providing a mechanism for the deposition of intraplinian pyroclastic flows.

Ogden, Darcy E.; Glatzmaier, Gary A.; Wohletz, Kenneth H.

2008-04-01

75

Buoyant Boats  

NSDL National Science Digital Library

Students conduct a simple experiment to see how the water level changes in a beaker when a lump of clay sinks in the water and when the same lump of clay is shaped into a bowl that floats in the water. They notice that the floating clay displaces more water than the sinking clay does, perhaps a surprising result. Then they determine the mass of water that is displaced when the clay floats in the water. A comparison of this mass to the mass of the clay itself reveals that they are approximately the same.

Engineering K-Phd Program

76

Buoyant Bubbles  

NSDL National Science Digital Library

What keeps bubbles and other things, like airplanes, floating or flying in the air? In this activity, learners blow bubbles and wave 3x5 cards above, below and on different sides of the bubbles to keep them afloat as long as possible. The Did You Know section explains the Bernoulli principle: how waving cards above the bubbles helps keep them afloat because faster moving air exerts less pressure to push the bubbles down. The activity can be extended by having learners wave their bubbles through an obstacle course they design themselves.

Science, Lawrence H.

2009-01-01

77

Approximate analysis of the formation of a buoyant solid sphere in a supercooled melt  

NASA Astrophysics Data System (ADS)

A mathematical model is presented for the idealized formation and development of a buoyant sphere solidifying in an infinite pool of supercooled liquid. The solid and liquid are of the same pure material and the solid is less dense than the liquid. Initially the liquid is at a uniform temperature that is below its equilibrium freezing temperature, T/sub cr/, but above the so called hypercooled temperature, T/sub cr/ - H/c/sub L/. Here H and c/sub L/ are the latent heat of solidification and the specific heat of the liquid, respectively. An approximate solution is derived based on the Megerlin approximation method.

Solomon, A. D.; Wilson, D. G.; Alexiades, V.

1986-03-01

78

Large Eddy Simulation of a Forced Round Turbulent Buoyant Plume in Neutral Surroundings  

NASA Technical Reports Server (NTRS)

Buoyant flows play an important role in various technological and environmental issues. For example, dispersal of pollutants, smoke, or volcano exhaust in the atmosphere, vertical motion of air, formation of clouds and other weather systems, and flows in cooling towers and fires are all determined primarily by buoyancy effects. The buoyancy force in such flows can originate from either a heat source or due to different densities between a fluid and its surroundings. Whatever the cause, the flow can be understood by studying the effects of the tight coupling between the thermal and the velocity fields since density differences can be characterized as temperature differences.

Basu, A. J.; Mansour, N. N.; Koga, Dennis (Technical Monitor)

1999-01-01

79

Dynamic stability of a buoyant quad-rotor aircraft. [for airlifting payloads externally on a sling  

NASA Technical Reports Server (NTRS)

Stability characteristics of a buoyant quad-rotor aircraft (BQRA) in hover and forward flight are examined by considering linear, state-variable, and nonlinear flight simulation models of such a configuration. The effects of carrying a sling load on the vehicle dynamics is predicted by considering a coupled model of the two bodies. Inherent stability characteristics of the vehicle are analyzed and compared with those of a helicopter and an airship in free flight. Typical operational conditions that could lead to vehicle instability are described in the flight envelope of interest.

Nagabhushan, B. L.; Tomlinson, N. P.

1982-01-01

80

Numerical Computation of Low-Speed Concurrent Flow Flame Spread in Mixed Buoyant and Forced Flow  

NASA Technical Reports Server (NTRS)

The effect of low-speed mixed convection (forced plus buoyant) on concurrent flow flame spread over a thin solid is examined. Computations are carried out using an existing model. Results indicate that seemingly small levels of gravity can significantly alter flame spread rates. Starting with a purely forced flow condition, as gravity is added, the entrainment due to buoyancy lengthens the flame and increases the spread rate significantly. Buoyancy has an influence on the extinction limits. At low speed, the presence of a small gravity level widens the flammability limit.

Ferkul, Paul V.; Tien, James S.

1993-01-01

81

Simultaneous Measurement of Temperature and Velocity in Turbulent Buoyant Plume by Combined LIF and PIV Technique  

SciTech Connect

An experimental technique for simultaneous measurement of temperature and velocity in a thermal flow is described. This technique is based on the two-color laser-induced fluorescence technique combined with the particle image velocimetry. Illumination is provided from Nd: YAG laser and the fluorescent dyes are chosen as Rhodamine B and Fluorescent Sodium, which combination allows the accurate velocity measurement in a wide range of flow velocity and high temperature sensitivity in temperature measurement. The measurement of temperature and velocity in turbulent buoyant plume is carried out by this method, and the structure of the plume is studied in connection with the entrainment of surrounding fluid at the interface. (authors)

Yoshie Watanabe; Yuji Hashizume; Nobuyuki Fujisawa [Niigata University, Niigata City 950-2181 (Japan)

2006-07-01

82

Potentially buoyant releases at TMI-1 (Three Mile Island Unit 1): Source term and steam properties  

SciTech Connect

The Emergency Dose Calculation Model for Three Mile Island-Unit 1 (TMI-1) was recently revised to take into account the guidance of NUREG/CR-3354: Potentially Buoyant Releases at Boiling and Pressurized Water Reactors. This guidance was applied to the modeling of radioactive steam releases from the main steam relief valves and atmospheric dump valves at TMI-1. This paper presents an overview of the modeling of the steam release, starting with the calculation of steam flow rate at the valve inlet and ending with the ejection of the steam into the atmosphere.

Ballangee, D.W.

1989-01-01

83

Buoyant convection of low Prandtl number melts in horizontal boat configuration  

NASA Astrophysics Data System (ADS)

Results of experimental investigations and numerical simulations of buoyant convection in metal and semiconductor melt layers with an applied horizontal temperature gradient are presented. Stability diagrams characterize the transition from steady to unsteady convection in terms of Grashof number, aspect ratio and Prandtl number. Periodic temperature oscillations of the melt are analysed and the oscillatory convection mechanism is discussed by numerical results. In order to grow striation-free crystals by means of the horizontal Bridgman method, the necessary conditions can be concluded by the results obtained.

Kuhl, R.; Wilke, H.

84

Specific association between bacteria and buoyant Microcystis colonies compared with other bulk bacterial communities in the eutrophic Lake Taihu, China.  

PubMed

The diversity of buoyant Microcystis colony-associated, settling particle-associated and free-living freshwater bacteria in the eutrophic Lake Taihu in China was compared by the polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) of 16S rRNA genes and by clone library analysis. The cluster analysis of DGGE profiles revealed that the buoyant Microcystis colony associates collected in summer and winter were clustered together and were distinct from settling particle-associated and free-living bacteria. In contrast, the bacterial communities of the latter two populations collected in summer were clustered together and varied from those collected in winter. The diversity indices of the Microcystis-associated bacterial population were significantly lower than those of the other two bulk bacterial communities (P?buoyant Microcystis-associated bacteria were distinct from the other communities and that they were dominated by Alphaproteobacteria, Betaproteobacteria and Gammaproteobacteria. Proteobacteria, Bacteroidetes and Actinobacteria were prevalent in all three habitats. Other bacterial taxa such as Planctomycetes, Verrucomicrobia, Gemmatimonadetes and Acidobacteria were associated with settling particles and with the water column. Buoyant Microcystis colonies, settling particles and the water column in the eutrophic lake are thus inhabited by different bacterial flora. In addition, specific bacterial communities are associated with buoyant Microcystis colonies. PMID:23760939

Shi, Limei; Cai, Yuanfeng; Kong, Fanxiang; Yu, Yang

2012-12-01

85

Beauty of Lotus is More than Skin Deep: Highly Buoyant Superhydrophobic Films.  

PubMed

We develop highly buoyant superhydrophobic films that mimic the three-dimensional structure of lotus leaves. The high buoyancy of these structure stems from mechanically robust bubbles that significantly reduce the density of the superhydrophobic films. These highly buoyant superhydrophobic films stay afloat on water surface while carrying a load that is more than 200 times their own weight. In addition to imparting high buoyancy, the incorporation of robust hydrophilic bubbles enables the formation of free-standing structures that mimic the water-collection properties of Namib Desert beetle. We believe the incorporation of robust bubbles is a general method that opens up numerous possibilities in imparting high buoyancy to different structures that needs to stay afloat on water surfaces and can potentially be used for the fabrication of lightweight materials. (Image on the upper left reproduced with permission from Yong , J. ; Yang , Q. ; Chen , F. ; Zhang , D. ; Du , G. ; Si , J. ; Yun , F. ; Hou , X. A Bioinspired Planar Superhydrophobic Microboat . [Formula: see text] 2014 , 24 , 035006 . Copyright 2014 IOP Publishing.). PMID:24801001

Choi, Yuri; Brugarolas, Teresa; Kang, Sung-Min; Park, Bum Jun; Kim, Byeong-Su; Lee, Chang-Soo; Lee, Daeyeon

2014-05-28

86

Detection of a buoyant coastal wastewater discharge using airborne hyperspectral and infrared imagery  

NASA Astrophysics Data System (ADS)

Municipal wastewater discharged into the ocean through a submerged pipe, or outfall, can rise buoyantly to the sea surface, resulting in a near-field mixing zone and, in the presence of an ambient ocean current, an extended surface plume. In this paper, data from a CASI (Compact Airborne Spectrographic Imager) and an airborne infrared (IR) camera are shown to detect a municipal wastewater discharge off the southeast coast of Florida, U.S.A., through its elevated levels of chromophoric dissolved organic matter plus detrital material (CDOM) and cooler sea surface temperatures. CDOM levels within a ~15-m-diameter surface 'boil' are found to be about twice those in the ambient shelf water, and surface temperatures near the boil are lower by ~0.4°C, comparable to the vertical temperature difference across the ambient water column. The CASI and IR imagery show a nearly identically shaped buoyant plume, consistent with a fully surfacing discharge, but the IR data more accurately delineate the area of most rapid dilution as compared with previous in-situ measurements. The imagery also allows identification of ambient oceanographic processes that affect dispersion and transport in the far field. This includes an alongshore front, which limits offshore dispersion of the discharge, and shoreward-propagating nonlinear internal waves, which may be responsible for an enhanced onshore transport of the discharge.

Marmorino, George O.; Smith, Geoffrey B.; Miller, W. D.; Bowles, Jeffrey H.

2010-01-01

87

Characterization of buoyant fluorescent particles for field observations of water flows.  

PubMed

In this paper, the feasibility of off-the-shelf buoyant fluorescent microspheres as particle tracers in turbid water flows is investigated. Microspheres' fluorescence intensity is experimentally measured and detected in placid aqueous suspensions of increasing concentrations of clay to simulate typical conditions occurring in natural drainage networks. Experiments are conducted in a broad range of clay concentrations and particle immersion depths by using photoconductive cells and image-based sensing technologies. Results obtained with both methodologies exhibit comparable trends and show that the considered particles are fairly detectable in critically turbid water flows. Further information on performance and integration of the studied microspheres in low-cost measurement instrumentation for field observations is obtained through experiments conducted in a custom built miniature water channel. This experimental characterization provides a first assessment of the feasibility of commercially available buoyant fluorescent beads in the analysis of high turbidity surface water flows. The proposed technology may serve as a minimally invasive sensing system for hazardous events, such as pollutant diffusion in natural streams and flash flooding due to extreme rainfall. PMID:22163540

Tauro, Flavia; Aureli, Matteo; Porfiri, Maurizio; Grimaldi, Salvatore

2010-01-01

88

Formulation and in vitro evaluation of buoyant controlled release lercanidipine lipospheres.  

PubMed

The aim of this study was to prepare and evaluate buoyant lipospheres containing lercanidipine hydrochloride. The lipospheres were prepared by modified melt dispersion technique using hydrophobic matrix of cetostearyl alcohol (CSA). The influence of formulation factors (stirring speed, lipid:drug ratio, lipid:surfactant polymer composition) on particle size, encapsulation efficiency and in-vitro release characteristics of lipospheres were investigated. The yields of all prepared formulation and encapsulation efficiencies were high for formulations which contain high lipid amount. The mean particle size significantly decreased (p < 0.001) by increasing the lipid:surfactant polymer and stirring speed (p < 0.001) of the system. Reduction in encapsulation efficiency (p < 0.001) and drug content (p < 0.001) was observed with increasing stirring speed and percentage of poloxamer 407 in formulation. Although lercanidipine hydrochloride release from Cetostearyl alcohol lipospheres were very slow and incomplete for all formulations f1-f6 ( approximately 65% drug released in 12 h) and was increased (approximately 85% drug released in 12 h) in lipospheres formulations f7-f12, containing Poloxamer 407. Percentage of buoyant lercanidipine lipospheres of CSA (96-100% buoyancy up to 12 h) decreases (p < 0.001) with increasing percentage of poloxamer 407 and achieved the release profile suitable for peroral administration. PMID:19839799

Pandit, Sachin S; Patil, Arun T

2009-11-01

89

Characterization of Buoyant Fluorescent Particles for Field Observations of Water Flows  

PubMed Central

In this paper, the feasibility of off-the-shelf buoyant fluorescent microspheres as particle tracers in turbid water flows is investigated. Microspheres’ fluorescence intensity is experimentally measured and detected in placid aqueous suspensions of increasing concentrations of clay to simulate typical conditions occurring in natural drainage networks. Experiments are conducted in a broad range of clay concentrations and particle immersion depths by using photoconductive cells and image-based sensing technologies. Results obtained with both methodologies exhibit comparable trends and show that the considered particles are fairly detectable in critically turbid water flows. Further information on performance and integration of the studied microspheres in low-cost measurement instrumentation for field observations is obtained through experiments conducted in a custom built miniature water channel. This experimental characterization provides a first assessment of the feasibility of commercially available buoyant fluorescent beads in the analysis of high turbidity surface water flows. The proposed technology may serve as a minimally invasive sensing system for hazardous events, such as pollutant diffusion in natural streams and flash flooding due to extreme rainfall.

Tauro, Flavia; Aureli, Matteo; Porfiri, Maurizio; Grimaldi, Salvatore

2010-01-01

90

A two-color optical method for determining layer thickness in two interacting buoyant plumes  

NASA Astrophysics Data System (ADS)

We describe a technique for measuring the layer thickness of two interacting buoyant rotating gravity currents. The technique can be used generally to differentiate between water masses in experiments with multiple sources and is used here to simulate the dynamics of two adjacent coastal river plumes. The plumes are generated using two identical fresh water inlets, with blue and red dye indicating upstream and downstream river flows, respectively. Two parameters, normalized intensity and color ratio, are measured with a 3-CCD color video camera and used to develop a two-dimensional (intensity-color ratio) calibration map for layer thickness. The calibration is used successfully to determine the depth field for the combined two-plume system and to differentiate between the two plumes. This technique is applied to compute the volumetric growth of a large eddy near the freshwater source and the transport rate of buoyant fluid away from the source in the coastal current. The validation tests show good agreement between the calculated plume volume and the input fresh water volume.

Yuan, Yeping; Avener, Margaret E.; Horner-Devine, Alexander R.

2011-05-01

91

Generating buoyant magnetic flux ropes in solar-like convective dynamos  

NASA Astrophysics Data System (ADS)

Our Sun exhibits strong convective dynamo action which results in magnetic flux bundles emerging through the stellar surface as magnetic spots. Global-scale dynamo action is believed to generate large-scale magnetic structures in the deep solar interior through the interplay of convection, rotation and shear. Portions of these large-scale magnetic structures are then believed to rise through the convective layer, forming magnetic loops which then pierce the photosphere as sunspot pairs. Previous global simulations of three-dimensional magnetohydrodynamic convection in rotating spherical shells have demonstrated mechanisms whereby large-scale magnetic wreaths can be generated in the bulk of the convection zone. Our recent simulations have achieved sufficiently high levels of turbulence to permit portions of these wreaths to become magnetically buoyant and rise through the simulated convective layer through a combination of magnetic buoyancy and advection by convective giant cells. These buoyant magnetic loops are created in the bulk of the convective layer as strong Lorentz force feedback in the cores of the magnetic wreaths dampen small-scale convective motions, permitting the amplification of local magnetic energies to over 100 times the local kinetic energy. While the magnetic wreaths are largely generated the shearing of axisymmetric poloidal magnetic fields by axisymmetric rotational shear (the ?-effect), the loops are amplified to their peak field strengths before beginning to rise by non-axisymmetric processes. This further extends and enhances a new paradigm for the generation of emergent magnetic flux bundles, which we term turbulence-enabled magnetic buoyancy.

Nelson, N. J.; Miesch, M. S.

2014-06-01

92

Similarity theory of the buoyantly interactive planetary boundary layer with entrainment  

NASA Technical Reports Server (NTRS)

A similarity model is developed for the vertical profiles of turbulent flow variables in an entraining turbulent boundary layer of arbitrary buoyant stability. In the general formulation the vertical profiles, internal rotation of the velocity vector, discontinuities or jumps at a capping inversion and bulk aerodynamic coefficients of the boundary layer are given by solutions to a system of ordinary differential equations in the similarity variable. To close the system, a formulation for buoyantly interactive eddy diffusivity in the boundary layer is introduced which recovers Monin-Obukhov similarity near the surface and incorporates a hypothesis accounting for the observed variation of mixing length throughout the boundary layer. The model is tested in simplified versions which depend only on roughness, surface buoyancy, and Coriolis effects by comparison with planetary-boundary-layer wind- and temperature-profile observations, measurements of flat-plate boundary layers in a thermally stratified wind tunnel and observations of profiles of terms in the turbulent kinetic-energy budget of convective planetary boundary layers. On balance, the simplified model reproduced the trend of these various observations and experiments reasonably well, suggesting that the full similarity formulation be pursued further.

Hoffert, M. I.; Sud, Y. C.

1976-01-01

93

Buoyant density of platelets stored at room temperature as platelet concentrates  

SciTech Connect

Separation of platelets by buoyant density centrifugation was periodically performed on platelet concentrates stored up to 96 hr at room temperature. By 72 hr, platelets were much lighter, depending on pH, platelet concentration, and volume of the bag. The mean proportion of platelets in the light fraction (fraction 1) shifted from 4.3% when the concentrate was fresh to 52.2% at 72 hr and 53.6% at 96 hr. The majority of platelets had densities that ranged from 1.034 to 1.088 gm/ml after storage, whereas densities ranged from 1.054 to 1.088 gm/ml in fresh cells. With storage, the light cells became larger than when they were fresh and were mostly balloon-shaped; the heavy cells became smaller but retained their normal shape. Regression analysis showed that density distribution was highly correlated to pH. Most of the changes occurred after 12 hr; those changes that occurred during the initial 12 hr were not related to pH of the platelet concentrate. The changes were related to storage conditions and may reflect injury to the cells. The use of buoyant density separation may be a useful tool to study storage mechanisms and provide a means of separating cells modified by storage stress.

Bolin, R.B.; Cheney, B.A.; Simpliciano, O.A.; Smith, D.J.

1981-09-01

94

Video Image Analysis of Turbulent Buoyant Jets Using a Novel Laboratory Apparatus  

NASA Astrophysics Data System (ADS)

Turbulent buoyant jets play an important role in the transport of heat and mass in a variety of environmental settings on Earth. Naturally occurring examples include the discharges from high-temperature seafloor hydrothermal vents and from some types of subaerial volcanic eruptions. Anthropogenic examples include flows from industrial smokestacks and the flow from the damaged well after the Deepwater Horizon oil leak of 2010. Motivated by a desire to find non-invasive methods for measuring the volumetric flow rates of turbulent buoyant jets, we have constructed a laboratory apparatus that can generate these types of flows with easily adjustable nozzle velocities and fluid densities. The jet fluid comprises a variable mixture of nitrogen and carbon dioxide gas, which can be injected at any angle with respect to the vertical into the quiescent surrounding air. To make the flow visible we seed the jet fluid with a water fog generated by an array of piezoelectric diaphragms oscillating at ultrasonic frequencies. The system can generate jets that have initial densities ranging from approximately 2-48% greater than the ambient air. We obtain independent estimates of the volumetric flow rates using well-calibrated rotameters, and collect video image sequences for analysis at frame rates up to 120 frames per second using a machine vision camera. We are using this apparatus to investigate several outstanding problems related to the physics of these flows and their analysis using video imagery. First, we are working to better constrain several theoretical parameters that describe the trajectory of these flows when their initial velocities are not parallel to the buoyancy force. The ultimate goal of this effort is to develop well-calibrated methods for establishing volumetric flow rates using trajectory analysis. Second, we are working to refine optical plume velocimetry (OPV), a non-invasive technique for estimating flow rates using temporal cross-correlation of image sequence data. Third, we are working to develop a computational algorithm that can quickly and automatically identify turbulent buoyant jets within video imagery so that autonomous instruments or vehicles can locate and investigate these flows in remote environments without human intervention.

Crone, T. J.; Colgan, R. E.; Ferencevych, P. G.

2012-12-01

95

Laminar Smoke Point Based Subgrid Soot Radiation Modeling Applied to LES of Buoyant Turbulent Diffusion Flames  

NASA Astrophysics Data System (ADS)

Large eddy simulations (LES) of gaseous buoyant turbulent flames have been conducted with the application of a flamelet based soot-radiation model. The subgrid model applies a turbulent eddy description of soot formation, oxidation and radiation and is based on the laminar smoke point concept. Two parameters, a local turbulent strain rate and prior enthalpy loss/gain fraction influence the soot formation and radiation. Radiation heat transfer is simulated by solving the finite volume discretized form of the radiative transfer equation (RTE) with the subgrid soot-radiation model implemented. The radiant heating of surfaces in close proximity of the flames is computed and predicted heat fluxes and surface temperatures are compared against experimental data. Fire growth in a rack storage arrangement is simulated with the application of a pyrolysis model. Computed heat release rate (HRR) is compared against experimental data.

Chatterjee, Prateep; de Ris, John L.; Wang, Yi; Krishnamoorthy, Niveditha; Dorofeev, Sergey B.

2012-06-01

96

Inertial migration of neutrally buoyant particles in a square duct: An investigation of multiple equilibrium positions  

NASA Astrophysics Data System (ADS)

Inertial migration of neutrally buoyant particles in a square duct has been investigated by numerical simulation in the range of Reynolds numbers from 100 to 1000. Particles migrate to one of a small number of equilibrium positions in the cross-sectional plane, located near a corner or at the center of an edge. In dilute suspensions, trains of particles are formed along the axis of the flow, near the planar equilibrium positions of single particles. At high Reynolds numbers (Re>=750), we observe particles in an inner region near the center of the duct. We present numerical evidence that closely spaced pairs of particles can migrate to the center at high Reynolds number.

Chun, B.; Ladd, A. J. C.

2006-03-01

97

Wind and tidal forcing of a buoyant plume, Mobile Bay, Alabama  

USGS Publications Warehouse

AVHRR satellite imagery and in situ observations were combined to study the motion of a buoyant plume at the mouth of Mobile Bay, Alabama. The plume extended up to 30 km from shore, with a thickness of about 1 m. The inner plume, which was 3-8 m thick, moved between the Bay and inner shelf in response to tidal forcing. The tidal prism could be identified through the movement of plume waters between satellite images. The plume responded rapidly to alongshore wind, with sections of the plume moving at speeds of more than 70 cm s-1, about 11% of the wind speed. The plume moved predominantly in the direction of the wind with a weak Ekman drift. The enhanced speed of the plume relative to normal surface drift is probably due to the strong stratification in the plume, which limits the transfer of momentum into the underlying ambient waters. ?? 1993.

Stumpf, R. P.; Gelfenbaum, G.; Pennock, J. R.

1993-01-01

98

Remote Under-Ice Roving in Alaska with the Buoyant Rover for Under-Ice Exploration  

NASA Astrophysics Data System (ADS)

The Buoyant Rover for Under-Ice Exploration (BRUIE) is two-wheeled robot capable of roving in two-dimensional space in the under-ice environment. The rover has positive buoyancy, allowing it to stick to the ice underside and operate using similar control principles as those used for traditional above-ground rovers. Recently added capability allows the rover to operate without a tether, communicating with a nearby above-ice ground station, which can relay data to a remote command center for remote operation. Additional upgrades include a dissolved methane sensor and improved capability for escape from entrapment in soft ice pockets. The system has been tested in thermokarst lakes near Barrow, Alaska, and data from onboard video and methane sensors gives scientific insight to the formation and distribution of trapped methane pockets in the lake ice. Here we present the updated design and preliminary data from deployments in the fall seasons of 2012 and 2013.

Berisford, D. F.; Leichty, J.; Klesh, A.; Hand, K. P.

2013-12-01

99

An up-scaled, buoyant invasion percolation model for use in delineating subsurface DNAPL location  

SciTech Connect

We introduce an up-scaled, buoyant invasion percolation model (UIP) for application to non-wetting, dense, non-aqueous phase liquid (DNAPL) migration at the geologic formation scale within the saturated zone of an aquifer. The UEP model incorporates a gravitational potential to model the displacement of fluids of different densities and can be used for either LNAPLs (lighter than water) or DNAPLs (denser than water). We demonstrate model behavior in a simulated braided stream deposit. Simulations show the influence of textural changes across layers and gravity forces in controlling DNAPL migration. While our results are encouraging, the application of this up-scaled percolation model requires a series of tests both in the laboratory and in the field before judgment of sufficient validity for its intended purpose is achieved.

Glass, R.J.; Webb, E.K.; Conrad, S.H.

1995-06-01

100

On the structure of a laminar buoyant jet released horizontally Sur la structure d'un jet flottant laminaire horizontal  

Microsoft Academic Search

The flow generated by the injection of negatively buoyant fluid in water at rest was investigated by means of both the laser induced fluorescence (LIF) visualization and the particle tracking velocimetry. Statistics on series of LIF images acquired during the same experiment have been evaluated to give quantitative information about the localization of the structures. Such a phenomenon is controlled

G. QUERZOLI; Piazza d'Armi; A. CENEDESE

2005-01-01

101

A comparison of the quantity and composition of material caught in a neutrally buoyant versus surface-tethered sediment trap  

Microsoft Academic Search

The flux and composition of material caught using two different upper ocean sediment trap designs was compared at the Bermuda Atlantic Time-series Study site (BATS). The standard surface-tethered trap array at BATS was compared to a newly designed neutrally buoyant sediment trap (NBST). Both traps used identical cylindrical collection tubes. Of particular concern was the effect of horizontal flow on

Ken O. Buesseler; Deborah K. Steinberg; Anthony F. Michaels; Rodney J. Johnson; John E. Andrews; James R. Valdes; James F. Price

2000-01-01

102

The relative importance of local retention and inter-reef dispersal of neutrally buoyant material on coral reefs  

Microsoft Academic Search

Reef-scale, eddy-resolving numerical models are applied to discriminate between local trapping of neutrally buoyant passive material coming from a natal reef versus trapping of this material on reefs downstream. A hydrodynamic model is coupled with a Lagrangian (nongridded) dispersal simulation to map the movement of material such as passive larvae within and between natural reefs. To simplify the interpretation, a

Kerry P. Black

1993-01-01

103

Nonlinear equation of state effects and the momentum-dilution trade-off in a turbulent buoyant jet  

Microsoft Academic Search

This paper presents the results of an investigation aimed at determining the effects of using a nonlinear equation of state (instead of a linearized one) in a mathematical model of an axisymmetric turbulent buoyant jet in a neutrally stratified ambient. It also seeks to establish criteria to determine whether a linear or nonlinear equation of state should be used in

T. C. Ponce

1987-01-01

104

Flow-Field Characteristics of High-Temperature Annular Buoyant Jets and Their Development Laws Influenced by Ventilation System  

PubMed Central

The flow-field characteristics of high-temperature annular buoyant jets as well as the development laws influenced by ventilation system were studied using numerical methods to eliminate the pollutants effectively in this paper. The development laws of high-temperature annular buoyant jets were analyzed and compared with previous studies, including radial velocity distribution, axial velocity and temperature decay, reattachment position, cross-section diameter, volumetric flow rate, and velocity field characteristics with different pressures at the exhaust hood inlet. The results showed that when the ratio of outer diameter to inner diameter of the annulus was smaller than 5/2, the flow-field characteristics had significant difference compared to circular buoyant jets with the same outer diameter. For similar diameter ratios, reattachment in this paper occurred further downstream in contrast to previous study. Besides, the development laws of volumetric flow rate and cross-section diameter were given with different initial parameters. In addition, through analyzing air distribution characteristics under the coupling effect of high-temperature annular buoyant jets and ventilation system, it could be found that the position where maximum axial velocity occurred was changing gradually when the pressure at the exhaust hood inlet changed from 0?Pa to ?5?Pa.

Liu, Jiaping; Wang, Hai; Liu, Qiuhan

2013-01-01

105

Buoyant replenishment in silicic magma reservoirs: Experimental approach and implications for magma dynamics, crystal mush remobilization, and eruption  

Microsoft Academic Search

We present new experiments on replenishment of rhyolite magma chambers by rhyolite magma using corn syrup-water solutions. We emphasize small density contrasts and show that buoyancy is the key controlling factor for whether injections will rise to the top (if buoyant) or pond at the base (if denser). During emplacement, we observe little or no mixing of the injected liquid

Guillaume Girard; John Stix

2009-01-01

106

Stability of buoyant convection in a layer submitted to acoustic streaming  

NASA Astrophysics Data System (ADS)

The linear stability of the flows induced in a fluid layer by buoyant convection (due to an applied horizontal temperature gradient) and by acoustic streaming (due to an applied horizontal ultrasound beam) is studied. The vertical profiles of the basic flows are determined analytically, and the eigenvalue problem resulting from the temporal stability analysis is solved by a spectral Tau Chebyshev method. Pure acoustic streaming flows are found to be sensitive to a shear instability developing in the plane of the flow (two-dimensional instability), and the thresholds for this oscillatory instability depend on the normalized width Hb of the ultrasound beam with a minimum for Hb=0.32 . Acoustic streaming also affects the stability of the buoyant convection. For a centered beam, effects of stabilization are obtained at small Prandtl number Pr for large beam widths Hb (two-dimensional shear instability) and for moderate Pr (three-dimensional oscillatory instability), but destabilization is also effective at small Pr for small beam widths Hb and at large Pr with a spectacular decrease of the thresholds of the three-dimensional steady instability. An adequate decentring of the ultrasound beam can enhance the stabilization. Insight into the stabilizing and destabilizing mechanisms is gained from the analysis of the fluctuating energy budget associated with the disturbances at threshold. The modifications affecting the two-dimensional shear instability thresholds are strongly connected to modifications of the velocity fluctuations when acoustic streaming is applied. Concerning the three-dimensional steady instability, the spectacular decrease of the thresholds is explained by the extension of the zone with inverse stratification in the lower half of the layer.

Dridi, W.; Henry, D.; Ben Hadid, H.

2010-05-01

107

The spatial distribution and speciation of iron in buoyant hydrothermal plumes of the Mid-Cayman Rise  

NASA Astrophysics Data System (ADS)

Biogeochemical cycling of elements, such as iron and sulfur, at mid-ocean ridge spreading centers may modulate hydrothermal fluxes to the ocean. To better understand the nature and scale of these processes, the geochemical gradients in buoyant plumes were examined at the Mid-Cayman Rise, a short (~110 km) ultra-slow spreading center in the Caribbean Sea that hosts the deepest known high temperature venting. Changes in particulate iron and sulfur speciation were measured in the first 40-50 m of buoyant plumes at two vent fields, Von Damm (2,300m) and Piccard (5,000m). These data will be used to identify products of precipitation reactions and define particulate energy sources available for microbial metabolism. A series of samples were collected by in situ filtration at 0.5 m and 50 m above the Beebe Vents, Piccard hydrothermal field and at 1 m, 8 m, and 40 m above the central spire of the Von Damm vent field using the ROV Jason and CTD-casts. Samples were packaged under dinitrogen and frozen shipboard to preserve oxidation-reduction sensitive species for microprobe Fe 1s and S 1s X-ray absorption near edge structure (XANES) spectroscopy (Advanced Light Source, Lawrence Berkeley National Laboratory, beamline 10.3.2). The Von Damm vent is characterized by shimmering vent fluids with dilute particulates in the buoyant plume. Within the particulate phase, the Von Damm buoyant plume was comprised of 38 mol % Fe-sulfides, 40 mol % Fe(II), and 21 mol % Fe(III) at 1 m. At 8 m it is comprised of 32 mol % Fe-sulfides, 7 % Fe(II), and 59 mol % Fe(III). When the plume reaches 40 m, it is 6 mol % Fe-sulfides, 8 mol % Fe(II), 72 mol % Fe(III), and 14 mol % Fe(0). The Beebe vents are characterized by very dense particle formation in their buoyant plumes. The Beebe vent plume sampled comprised 65 mol % sulfides, 3 % mol Fe(II) & 32 mol % Fe(III)¬¬¬¬ at 0.5 m. As the plume reached 50 m above the vent, the fluids were 43 mol % sulfide and 56 mol % Fe(III). Both buoyant plume samples were dominated by reduced iron species that rapidly become more oxidized as they reacted with deep-sea water entrained into the plume. The next steps for this study are to quantify iron and sulfur species in the plumes, and identify the microbial communities that are closely associated with particulate iron and sulfur using fluorescent in situ hybridization (FISH).

Cron, B. R.; Toner, B. M.; Bennett, S. A.; German, C. R.; Dick, G.; Breier, J. A.

2012-12-01

108

Melting due to Buoyant Migration of Water in the Hot Mantle Wedge Above a Subducting Plate  

NASA Astrophysics Data System (ADS)

Water-bearing magma generated at convergent plate boundaries is thought to be due to the release of water carried to depth by the subducting crust and mantle. The objective of our study is to create models of the buoyant upward migration of water-rich fluids from the slab, through the hot mantle wedge, and consequent mantle melting. Fluid in the models is assumed to migrate buoyantly along mineral grain edges with a prescribed melt fraction-grain size-permeability relationship (e.g. Wark et al., 2003). Pressure gradients in the solid mantle flow should be important to melt migration only if the mantle viscosity exceeds about 1018 Pa-s. The model results thus far neglect the effect of solid deformation on melt permeability, including the possible effects of the dependence of grain size on stress and the anisotropic permeability created by solid deformation (e.g. Kohlstedt and Zimmerman, 1996). The volume of melt generated by the interaction of water with the mantle is parameterized using results from MELTS (Ghiorso and Sack, 1995). The volume of water released from the slab between depths of 80 to 150 km is derived from the estimates of Schmidt and Poli (1998). The models consider a range of slab velocities and grain sizes using solid flow and temperature distributions from an earlier model with temperature-dependent viscosity (Kelemen et al., 2003). Melt distribution in the wedge is strongly dependent on both grain size and slab velocity. For a grain size of 2 mm at slab velocities of 2-6 cm/yr, fluid rises from the slab to generate melt. At higher plate velocities or smaller grain sizes, water released from the slab is carried downward into the deeper mantle, in which case melting is not triggered. As a consequence, melt flux at the top of the mantle wedge also varies significantly with convergence rate. At slow to intermediate rates, calculated melt fluxes are comparable to values observed in island arcs. Thus, in the absence of other effects, significant differences in volcanic flux between fast and slow convergence rates would be expected. In appropriate nondimensional form, the ratio of slab velocity to the square of the grain size controls the distribution of fluids in the wedge. In nature, the absence of such a strong convergence rate dependence on magmatic flux might indicate that grain size in the mantle wedge varies with plate velocity. Thus, future work should consider the effect of variable grain size on melt permeability. Accounting for hydrous mineral stability limits may also introduce a convergence rate and plate age dependence to predicted volcanic flux.

Rilling, J. L.; Cagnioncle, A. M.; Elkins-Tanton, L. T.; Parmentier, E. M.

2003-12-01

109

Evolution of localized blobs of swirling or buoyant fluid with and without an ambient magnetic field  

SciTech Connect

We investigate the evolution of localized blobs of swirling or buoyant fluid in an infinite, inviscid, electrically conducting fluid. We consider the three cases of a strong imposed magnetic field, a weak imposed magnetic field, and no magnetic field. For a swirling blob in the absence of a magnetic field, we find, in line with others, that the blob bursts radially outward under the action of the centrifugal force, forming a thin annular vortex sheet. A simple model of this process predicts that the vortex sheet thins exponentially fast and that it moves radially outward with constant velocity. These predictions are verified by high-resolution numerical simulations. When an intense magnetic field is applied, this phenomenon is suppressed, with the energy and angular momentum of the blob now diffusing axially along the magnetic field lines, converting the blob into a columnar structure. For modest or weak magnetic fields, there are elements of both types of behavior, with the radial bursting dominating over axial diffusion for weak fields. However, even when the magnetic field is very weak, the flow structure is quite distinct to that of the nonmagnetic case. In particular, a small but finite magnetic field places a lower bound on the thickness of the annular vortex sheet and produces an annulus of counter-rotating fluid that surrounds the vortex core. The behavior of the buoyant blob is similar. In the absence of a magnetic field, it rapidly develops the mushroomlike shape of a thermal, with a thin vortex sheet at the top and sides of the mushroom. Again, a simple model of this process predicts that the vortex sheet at the top of the thermal thins exponentially fast and rises with constant velocity. These predictions are consistent with earlier numerical simulations. Curiously, however, it is shown that the net vertical momentum associated with the blob increases linearly in time, despite the fact that the vertical velocity at the front of the thermal is constant. As with the swirling blob, an imposed magnetic field inhibits the formation of a vortex sheet. A strong magnetic field completely suppresses the phenomenon, replacing it with an axial diffusion of momentum, while a weak magnetic field allows the sheet to form, but places a lower bound on its thickness. The magnetic field does not, however, change the net vertical momentum of the blob, which always increases linearly with time.

Davidson, P. A. [Department of Engineering, University of Cambridge, Cambridge, CB2 1PZ (United Kingdom); Sreenivasan, Binod [School of Earth and Environment, University of Leeds, Leeds, LS2 9JT (United Kingdom); Aspden, A. J. [Department of Applied Mathematics and Theoretical Physics, University of Cambridge, Cambridge, CB3 0WA (United Kingdom)

2007-02-15

110

Simultaneous velocity and passive scalar concentration measurements in low Reynolds number neutrally buoyant turbulent round jets  

NASA Astrophysics Data System (ADS)

Velocity and scalar concentration characteristics of low Reynolds number ( Re) neutrally buoyant turbulent round jets were studied using coupled particle image velocimetry and laser induced fluorescence. Experiments were conducted on a jet with a fully developed pipe exit profile at Re = 1,500 and Re = 4,000. Measurements were made in the far field (60 < x/ D < 80). Results show that the centerline velocity decay constant increases with Re and the virtual origin is located far from the jet exit. The Re does not have such an influence on the scalar concentration decay constant and scalar field virtual origin. Centerline turbulent intensities show evidence of becoming self-similar past x/ D ? 75 but the same is not observed in the scalar fluctuations. The latter are strongly influenced by the Re, increasing as entrainment of ambient flow on the jet axis increases as the flow approaches laminar conditions. Scalar fluxes showed a marked Re dependence as well. Results were used to estimate the turbulent Schmidt number which decreases as the Re decreases.

Zarruk, G. A.; Cowen, E. A.

2008-06-01

111

Buoyant-thermocapillary instabilities in extended liquid layers subjected to a horizontal temperature gradient  

NASA Astrophysics Data System (ADS)

We report experiments on buoyant-thermocapillary instabilities in differentially heated liquid layers. The results are obtained for a fluid of Prandtl number 10 in a rectangular geometry with different aspect ratios. Depending on the height of liquid and on the aspect ratios, the two-dimensional basic flow destabilizes into oblique traveling waves or longitudinal stationary rolls, respectively, for small and large fluid heights. Temperature measurements and space-time recordings reveal the waves to correspond to the hydrothermal waves predicted by the linear stability analysis of Smith and Davis [J. Fluid Mech. 132, 119 (1983)]. Moreover, the transition between traveling and stationary modes agrees with the work by Mercier and Normand [Phys. Fluids 8, 1433 (1996)] even if the exact characteristics of longitudinal rolls differ from theoretical predictions. A discussion about the relevant nondimensional parameters is included. In the stability domain of the waves, two types of sources have been evidenced. For larger heights, the source is a line and generally evolves towards one end of the container leaving a single wave whereas for smaller heights, the source looks like a point and emits a circular wave which becomes almost planar farther from the source in both directions.

Burguete, J.; Mukolobwiez, N.; Daviaud, F.; Garnier, N.; Chiffaudel, A.

2001-10-01

112

Experimental Studies for the characterization of the mixing processes in negative buoyant jets  

NASA Astrophysics Data System (ADS)

A negatively buoyant jet (NBJ) corresponds to the physical phenomenon that develops when a fluid is discharged upwards into a lighter environment or downwards into a heavier receptor fluid. In a NBJ the flow is initially driven mostly by the momentum, so it basically behaves as a simple jet released withthe same angle, while far from the outlet the buoyancy prevails, bending the jet axis down and making it similar to a plume. The coexistence in the same phenomenon of both the characteristics of simple jets and plumes makes the NBJs a phenomenon still not entirely explained but, considering also the numerous practical applications, very interesting to study. Here some of the experimental results are presented. The laboratory experiment were obtained on a model simulating a typical sea discharge of brine from desalination plants: a pipe laid down on the sea bottom, with orifices on its lateral wall, releasing brine (heavier than the sea water) with a certain angle to the horizontal, in order to increase the jet path before sinking to the seafloor. A non-intrusive image analysis technique, namely Feature Tracking Velocimetry, is applied to measure velocity fields, with the aim at understanding the influence of some non-dimensional parameters driving the phenomenon (e.g. Reynolds number, release angle) on the structure of the NBJ and of the turbulence.

Besalduch, L. A.; Badas, M. G.; Ferrari, S.; Querzoli, G.

2013-04-01

113

Near Surface Vapor Bubble Layers in Buoyant Low Stretch Burning of Polymethylmethacrylate  

NASA Technical Reports Server (NTRS)

Large-scale buoyant low stretch stagnation point diffusion flames over solid fuel (polymethylmethacrylate) were studied for a range of aerodynamic stretch rates of 2-12/ sec which are of the same order as spacecraft ventilation-induced stretch in a microgravity environment. An extensive layer of polymer material above the glass transition temperature is observed. Unique phenomena associated with this extensive glass layer included substantial swelling of the burning surface, in-depth bubble formation, and migration and/or elongation of the bubbles normal to the hot surface. The bubble layer acted to insulate the polymer surface by reducing the effective conductivity of the solid. The reduced in-depth conduction stabilized the flame for longer than expected from theory neglecting the bubble layer. While buoyancy acts to move the bubbles deeper into the molten polymer, thermocapillary forces and surface regression both act to bring the bubbles to the burning surface. Bubble layers may thus be very important in low gravity (low stretch) burning of materials. As bubbles reached the burning surface, monomer fuel vapors jetted from the surface, enhancing burning by entraining ambient air flow. Popping of these bubbles at the surface can expel burning droplets of the molten material, which may increase the fire propagation hazards at low stretch rates.

Olson, Sandra L.; Tien, J. S.

1999-01-01

114

Experiments in vision-based control of a neutrally buoyant free-flyer  

NASA Astrophysics Data System (ADS)

The Laboratory for Space Teleoperation and Robotics is developing a neutrally-buoyant robot for research into the automatic and teleoperated (remote human) control of unmanned robotic vehicles for use in space. The goal of this project is to develop a remote robot with maneuverability and dexterity comparable to that of a space-suited astronaut with a manned maneuvering unit, able to assume many of the tasks currently planned for astronauts during extravehicular activity (EVA). Such a robot would be able to spare the great expense and hazards associated with human EVA, and make possible much less expensive scientific and industrialization exploitation of orbit. Both autonomous and teleoperated control experiments will require the vehicle to be able to automatically control its position and orientation. The laboratory is developing vision-based vehicle navigation system that works by tracking features in video images from cameras mounted on the vehicle and trained at a special target fixed in the environment. The methods are adaptable to a variety of video-based tracking systems, and are based on a linearized vision model, receiving as inputs image feature coordinates at each time step This paper includes a description of the underwater vehicle and the vision system.

Alexander, Harold L.; Eberly, Kurt; Weigl, Harald J.

1992-02-01

115

Numerical simulation of 2D buoyant jets in ice-covered and temperature-stratified water  

NASA Astrophysics Data System (ADS)

A two-dimensional (2D) unsteady simulation model is applied to the problem of a submerged warm water discharge into a stratified lake or reservoir with an ice cover. Numerical simulations and analyses are conducted to gain insight into large-scale convective recirculation and flow processes in a cold waterbody induced by a buoyant jet. Jet behaviors under various discharge temperatures are captured by directly modeling flow and thermal fields. Flow structures and processes are described by the simulated spatial and temporal distributions of velocity and temperature in various regions: deflection, recirculation, attachment, and impingement. Some peculiar hydrothermal and dynamic features, e.g. reversal of buoyancy due to the dilution of a warm jet by entraining cold ambient water, are identified and examined. Simulation results show that buoyancy is the most important factor controlling jet behavior and mixing processes. The inflow boundary is treated as a liquid wall from which the jet is offset. Similarity and difference in effects of boundaries perpendicular and parallel to flow, and of buoyancy on jet attachment and impingement, are discussed. Symmetric flow configuration is used to de-emphasize the Coanda effect caused by offset.

Gu, Ruochuan

116

Wave induced mixing and transport of buoyant particles: application to the Statfjord A oil spill  

NASA Astrophysics Data System (ADS)

The modelling of wave-current and wave-turbulence interactions have received much attention in recent years. In this study the focus is on how these wave effects modify the transport of particles in the ocean. Here the particles are buoyant tracers that can represent oil droplets, plastic particles or plankton, for example fish eggs and larvae. Using the General Ocean Turbulence Model (GOTM), modified to take surface wave effects into account, we investigate how the increased mixing by wave breaking and Stokes shear production as well as the stronger veering by the Coriolis-Stokes force affect the drift of the particles. The energy and momentum fluxes as well as the Stokes drift depend on the directional wave spectrum that can be obtained from a wave model or from observations. As a first test the depth and velocity scales from the model are compared with analytical solutions based on a constant eddy viscosity (e.g. classical Ekman theory). Secondly the model is applied to a case where we investigate the oil drift after an offshore oil spill outside the western coast of Norway in 2007. During this accident the average net drift of oil was observed to be both slower and more deflected away from the wind direction than predicted by empirical models. With wind and wave forcing from the ERA Interim archive, it is shown that the wave effects are important for the resultant drift in this case, and has the potential to improve drift forecasting.

Drivdal, M.; Broström, G.; Christensen, K. H.

2014-05-01

117

Buoyant instabilities in downward flow in a symmetrically heated vertical channel  

SciTech Connect

This study of the downward flow of nitrogen in a tall, partially heated vertical channel (upstream isothermal at T{sub in}*, heated region isothermal at T{sub s}* downstream adiabatic) shows the strong effects of buoyancy even for small temperature differences. Time-dependent oscillations including periodic flow reversals occur along the channel walls. Although the flow and heat transfer are asymmetric, the temperature and axial component of velocity show symmetric reflections at two times that are half a period apart and the lateral component of velocity shows antisymmetric reflections at the two times. There is strong interaction between the downward flow in the central region of the channel and the upward flow along the heated channel walls. At the top of the heated region, the upward buoyant flow turns toward the center of the channel and is incorporated into the downward flow. Along the channel centerline there are nonmonotonic variations of the axial component of velocity and temperature and a large lateral component of velocity that reverses direction periodically. Results are presented for Re = 219.7 and Gr/Re{sup 2} = 1.83, 8.0, and 13.7. The heat transfer and the frequency of the oscillations increases and the flow and temperature fields become more complex as Gr/Re{sup 2} increases. The results have applications to fiber drying, food processing, crystal growth, solar energy collection, cooling of electronic circuits, ventilation, etc.

Evans, G. [Sandia National Lab., Livermore, CA (United States); Greif, R. [Univ. of California, Berkeley, CA (United States)

1996-07-01

118

Large deforming buoyant embolus passing through a stenotic common carotid artery: a computational simulation.  

PubMed

Arterial embolism is responsible for the death of lots of people who suffers from heart diseases. The major risk of embolism in upper limbs is that the ruptured particles are brought into the brain, thus stimulating neurological symptoms or causing the stroke. We presented a computational model using fluid-structure interactions (FSI) to investigate the physical motion of a blood clot inside the human common carotid artery. We simulated transportation of a buoyant embolus in an unsteady flow within a finite length tube having stenosis. Effects of stenosis severity and embolus size on arterial hemodynamics were investigated. To fulfill realistic nonlinear property of a blood clot, a rubber/foam model was used. The arbitrary Lagrangian-Eulerian formulation (ALE) and adaptive mesh method were used inside fluid domain to capture the large structural interfacial movements. The problem was solved by simultaneous solution of the fluid and the structure equations. Stress distribution and deformation of the clot were analyzed and hence, the regions of the embolus prone to lysis were localized. The maximum magnitude of arterial wall shear stress during embolism occurred at a short distance proximal to the throat of the stenosis. Through embolism, arterial maximum wall shear stress is more sensitive to stenosis severity than the embolus size whereas role of embolus size is more significant than the effect of stenosis severity on spatial and temporal gradients of wall shear stress downstream of the stenosis and on probability of clot lysis due to clot stresses while passing through the stenosis. PMID:22365500

Vahidi, Bahman; Fatouraee, Nasser

2012-04-30

119

Lagrangian particle modelling of buoyant point sources: Plume rise and entrapment under convective conditions  

NASA Astrophysics Data System (ADS)

This paper describes several aspects of a Lagrangian particle model capable of simulating dispersion from buoyant point sources. The equations of Briggs (American Meteorological Society, 1975) are used to calculate the plume final rise heights, and a skewed homogeneous turbulence parameterization is used within the convective boundary layer. The homogeneous assumption enables an order of magnitude greater time step to be used than is normally the case, and was shown to have minimal effect on hourly averaged ground level concentrations by Hurley and Physick ( Atmospheric Environment25A, 1313-1325, 1991; 27A, 619-624, 1993). By including statistics from both ambient and source-induced (plume) turbulence in the probability density function (pdf) of the Langevin equation, we are able to apply this equation to particles in the plume as it rises from the stack to the final rise height. The model is used here to simulate various plume rise and entrapment laboratory experiments of Willis and Deardorff ( Atmospheric Environment17, 2435-2447, 1983; 21, 1725-1735, 1987) under convective conditions with a capping stable atmosphere. The simulations show that the model can reproduce the results of the laboratory experiments when a 15% enhancement to the entrainment parameter in the mean plume rise equations is used. Justification for this modification can be related to neglect of the effect of ambient turbulence upon entrainment in the plume rise equations, which in free convective turbulence may be significant.

Hurley, Peter; Physick, William

120

Effects of subducting buoyant oceanic ridges on subduction zones: Area of influence and rotational effects  

NASA Astrophysics Data System (ADS)

The subduction of buoyant oceanic ridges into subduction zones is typically manifested by doming of arc rocks, shallowing of the trench, and diffuse or shallowly-dipping Benioff zones. Two important questions include: 1) what distance inboard of the overriding plate are effects observed; and 2) what is the degree that colliding ridges can induce large-scale rotations of forearc terranes and consequent "back-arc opening" behind rotated forearc blocks. I describe regional effects from five relatively narrow ridges actively entering subduction zones: 1) Carnegie; 2) Cocos; 3) Emperor seamount chain; 4) Louisville, and 5) D'Entrecasteaux. GPS from all areas shows a characteristic outward flow pattern in map view indicative of the strong landward push on the ridge along radial thrust systems within the overriding plate. This area of influence can extend 100s of kms. The pattern of outward flow from GPS vectors is consistent with the of bathymetry, gravity and earthquakes show some of these ridges act as strong indentors that push into the arc along strike-slip systems at their edges. In other cases likely related to thinner crust, no strong disruption of the outer forearc high or forearc basin is observed and adjacent to subducting ridges. Rotating forearc blocks are most expressed by examples where the direction of subduction is highly oblique and the least rotational effects are expressed where the direction of subduction is orthogonal. Wider ridges also appear to have fewer rotational effects.

Mann, W. P.

2012-12-01

121

Isolation of Rare Tumor Cells from Blood Cells with Buoyant Immuno-Microbubbles  

PubMed Central

Circulating tumor cells (CTCs) are exfoliated at various stages of cancer, and could provide invaluable information for the diagnosis and prognosis of cancers. There is an urgent need for the development of cost-efficient and scalable technologies for rare CTC enrichment from blood. Here we report a novel method for isolation of rare tumor cells from excess of blood cells using gas-filled buoyant immuno-microbubbles (MBs). MBs were prepared by emulsification of perfluorocarbon gas in phospholipids and decorated with anti-epithelial cell adhesion molecule (EpCAM) antibody. EpCAM-targeted MBs efficiently (85%) and rapidly (within 15 minutes) bound to various epithelial tumor cells suspended in cell medium. EpCAM-targeted MBs efficiently (88%) isolated frequent tumor cells that were spiked at 100,000 cells/ml into plasma-depleted blood. Anti-EpCAM MBs efficiently (>77%) isolated rare mouse breast 4T1, human prostate PC-3 and pancreatic cancer BxPC-3 cells spiked into 1, 3 and 7 ml (respectively) of plasma-depleted blood. Using EpCAM targeted MBs CTCs from metastatic cancer patients were isolated, suggesting that this technique could be developed into a valuable clinical tool for isolation, enumeration and analysis of rare cells.

Shi, Guixin; Cui, Wenjin; Benchimol, Michael; Liu, Yu-Tsueng; Mattrey, Robert F.; Mukthavaram, Rajesh; Kesari, Santosh; Esener, Sadik C.; Simberg, Dmitri

2013-01-01

122

PLIF and PIV measurements of the self-preserving structure of steady round buoyant turbulent plumes in crossflow  

Microsoft Academic Search

Measurements of the mean concentration of source fluid and mean velocity fields were obtained for the first time in the self-preserving region of steady round buoyant turbulent plumes in uniform crossflows using Planar-Laser-Induced-Fluorescence (PLIF) and Particle-Image-Velocimetry (PIV), respectively. The experiments involved salt water sources injected into water\\/ethanol crossflows within a water channel. Matching the index of refraction of the source

F. J. Diez; L. P. Bernal; G. M. Faeth

2005-01-01

123

Experiments on the distribution of concentration due to buoyant gas low flow rate release in an enclosure  

Microsoft Academic Search

Experiments on buoyant gas dispersion in an enclosure have been conducted in a facility of the typical size of a private garage. Helium is used as a model gas for hydrogen. For release flow rate of the order of 0.1Nl\\/min to 10Nl\\/min, the dispersion is studied in a tightly sealed configuration of the enclosure and for two vertical positions of

B. Cariteau; J. Brinster; I. Tkatschenko

2011-01-01

124

On the response of a turbulent coastal buoyant current to wind events: the case of the Western Adriatic Current  

Microsoft Academic Search

This numerical study focuses on the response of the Western Adriatic Current to wind forcing. The turbulent buoyant surface\\u000a current is induced by the Po river outflow in the Adriatic Sea. Idealized and realistic wind conditions are considered by\\u000a retaining the complex geomorphology of the middle Adriatic basin. In the absence of wind, the Adriatic Promontories force\\u000a the current to

Marcello G. Magaldi; Tamay M. Özgökmen; Annalisa Griffa; Michel Rixen

2010-01-01

125

Migration of Buoyant Mono and Bi-disperse Suspensions in Low Reynolds Number Pressure-Driven Pipe Flow  

Microsoft Academic Search

Suspensions of neutrally buoyant particles in low Reynolds number, pressure-driven flows migrate from regions of high to low shear. When the particle density does not match that of the suspending fluid, buoyancy forces as quantified by a dimensionless buoyancy number determines the particle distribution. We use single-frequency electrical impedance tomography (EIT) to measure the particle distribution in pressure-driven pipe flow

Jay Norman; Hebri Nayak; Roger Bonnecaze

2004-01-01

126

Potentially buoyant releases at TMI-1 (Three Mile Island Unit 1): Plume rise and off-site doses  

SciTech Connect

The Emergency Dose Calculation Model for Three Mile Island Unit 1 (TMI-1) was recently revised to take into account the guidance of NUREG/CR-3354: Potentially Buoyant Releases at Boiling and Pressurized Water Reactors. The guidance provided was applied to the modeling of radioactive steam releases from the main steam relief valves and atmospheric dump valves at TMI-1. This paper presents an overview of the modeling of the plume rise and its impact on off-site doses.

Heck, W.J.

1989-01-01

127

Genetic affinities between trans-oceanic populations of non-buoyant macroalgae in the high latitudes of the Southern Hemisphere.  

PubMed

Marine biologists and biogeographers have long been puzzled by apparently non-dispersive coastal taxa that nonetheless have extensive transoceanic distributions. We here carried out a broad-scale phylogeographic study to test whether two widespread Southern Hemisphere species of non-buoyant littoral macroalgae are capable of long-distance dispersal. Samples were collected from along the coasts of southern Chile, New Zealand and several subAntarctic islands, with the focus on high latitude populations in the path of the Antarctic Circumpolar Current or West Wind Drift. We targeted two widespread littoral macroalgal species: the brown alga Adenocystisutricularis (Ectocarpales, Heterokontophyta) and the red alga Bostrychiaintricata (Ceramiales, Rhodophyta). Phylogenetic analyses were performed using partial mitochondrial (COI), chloroplast (rbcL) and ribosomal nuclear (LSU / 28S) DNA sequence data. Numerous deeply-divergent clades were resolved across all markers in each of the target species, but close phylogenetic relationships - even shared haplotypes - were observed among some populations separated by large oceanic distances. Despite not being particularly buoyant, both Adenocystisutricularis and Bostrychiaintricata thus show genetic signatures of recent dispersal across vast oceanic distances, presumably by attachment to floating substrata such as wood or buoyant macroalgae. PMID:23894421

Fraser, Ceridwen I; Zuccarello, Giuseppe C; Spencer, Hamish G; Salvatore, Laura C; Garcia, Gabriella R; Waters, Jonathan M

2013-01-01

128

Design and evaluation of hydrophobic coated buoyant core as floating drug delivery system for sustained release of cisapride  

PubMed Central

An inert hydrophobic buoyant coated–core was developed as floating drug delivery system (FDDS) for sustained release of cisapride using direct compression technology. Core contained low density, porous ethyl cellulose, which was coated with an impermeable, insoluble hydrophobic coating polymer such as rosin. It was further seal coated with low viscosity hydroxypropyl methyl cellulose (HPMC E15) to minimize moisture permeation and better adhesion with an outer drug layer. It was found that stable buoyant core was sufficient to float the tablet more than 8 h without the aid of sodium bicarbonate and citric acid. Sustained release of cisapride was achieved with HPMC K4M in the outer drug layer. The floating lag time required for these novel FDDS was found to be zero, however it is likely that the porosity or density of the core is critical for floatability of these tablets. The in vitro release pattern of these tablets in simulated gastric fluid showed the constant and controlled release for prolonged time. It can be concluded that the hydrophobic coated buoyant core could be used as FDDS for gastroretentive delivery system of cisapride or other suitable drugs.

Jacob, Shery; Nair, Anroop B; Patil, Pandurang N

2010-01-01

129

Conduit diameter and buoyant rising speed of mantle plumes: Implications for the motion of hot spots and shape of plume conduits  

Microsoft Academic Search

Mantle plumes are expected to be affected by large-scale flow in the Earth's mantle related to plate motions, subducted slabs, and possibly large-scale upwellings. Motion of plume conduits will depend on both large-scale flow and buoyant rising speed of the conduit through the mantle. Here we present a model of depth-dependent plume conduit temperature, viscosity, radius, and buoyant rising speed

B. Steinberger; M. Antretter

2006-01-01

130

Toward the Understanding and Optimization of Chimneys for Buoyantly Driven Biomass Stoves  

NASA Astrophysics Data System (ADS)

The vast majority of indoor combustion devices in the developed world make use of stacks (flues, vents, chimneys, smokestacks) to channel flue gases out of the operator space. In the developing world, where indoor air pollution kills several million people every year, the use of chimneys with biomass cooking and heating stoves has been met with limited success and a high level of controversy. Due to a lack of theoretical understanding, design criteria, poorly executed installation practices, and/or insufficient maintenance routines, many chimney stoves have exhibited inadequate indoor emissions reductions in addition to low thermal efficiencies. This work aims (a) shed light on the physical phenomenon of the "stack effect" as it pertains to dynamic, non-adiabatic, buoyancy-driven stoves (b) apply new understanding toward the optimization of two types of biomass chimney stoves: plancha or griddle type stoves popular in Central America and two-pot stoves common in South America. A numerical heat and fluid flow model was developed that takes into account the highly-coupled variables and dynamic nature of such systems. With a comprehensive physical model, parameter studies were conducted to determine how several field-relevant variables influence the performance of stack-outfitted systems. These parameters include, but are not limited to: power/wood consumption rate, chimney geometry, stove geometry, material properties, heat transfer, and ambient conditions. An instrumented experimental chimney was built to monitor relationships between air flow, differential pressure, gas temperatures, emissions, and thermal efficiency. The draft provided by chimneys was found to have a strong influence over the bulk air-to-fuel ratio of buoyantly-driven cookstoves, greatly affecting the stove's overall performance by affecting gas temperatures, emissions, and efficiency. Armed with new information from the modeling and experimental work, two new stoves were designed and optimized to have significant reductions in fuel use and emissions.

Prapas, Jason

131

Northern Monterey Bay upwelling shadow front: Observations of a coastally and surface-trapped buoyant plume  

USGS Publications Warehouse

During the upwelling season in central California, northwesterly winds along the coast produce a strong upwelling jet that originates at Point A??o Nuevo and flows southward across the mouth of Monterey Bay. A convergent front with a mean temperature change of 3.77 ?? 0.29??C develops between the warm interior waters and the cold offshore upwelling jet. To examine the forcing mechanisms driving the location and movement of the upwelling shadow front and its effects on biological communities in northern Monterey Bay, oceanographic conditions were monitored using cross-shelf mooring arrays, drifters, and hydrographic surveys along a 20 km stretch of coast extending northwestward from Santa Cruz, California, during the upwelling season of 2007 (May-September). The alongshore location of the upwelling shadow front at the northern edge of the bay was driven by: regional wind forcing, through an alongshore pressure gradient; buoyancy forces due to the temperature change across the front; and local wind forcing (the diurnal sea breeze). The upwelling shadow front behaved as a surface-trapped buoyant current, which is superimposed on a poleward barotropic current, moving up and down the coast up to several kilometers each day. We surmise that the front is advected poleward by a preexisting northward barotropic current of 0.10 m s-1 that arises due to an alongshore pressure gradient caused by focused upwelling at Point A??o Nuevo. The frontal circulation (onshore surface currents) breaks the typical two-dimensional wind-driven, cross-shelf circulation (offshore surface currents) and introduces another way for water, and the material it contains (e.g., pollutants, larvae), to go across the shelf toward shore.Copyright 2009 by the American Geophysical Union.

Woodson, C. B.; Washburn, L.; Barth, J. A.; Hoover, D. J.; Kirincich, A. R.; McManus, M. A.; Ryan, J. P.; Tyburczy, J.

2009-01-01

132

The Behavior of Passive and Buoyant Plumes in a Convective Boundary Layer, as Simulated with a Large-Eddy Model.  

NASA Astrophysics Data System (ADS)

With a large-eddy model the large-scale flow structure of the convective boundary layer is simulated in a box of (5 × 5 × 2) km. The calculation is run till the turbulence has reached a quasi-steady state. At that time we introduce a line-source of contaminants and the calculation is continued with an additional equation for the concentration. We consider both passive and buoyant sources. The latter are simulated by increasing the temperature of the line-source with respect to the ambient temperature. We present data for two dimensionless release heights: zs/h = 0.15 and zs/h = 0.48.For a passive source our results agree well with the results of Willis and Deardorff and the results of the CONDORS experiments.With respect to a buoyant source we found that the influence of buoyancy on the plume parameters can be described in terms of the dimensionless buoyancy parameter F(; this conclusion is based on runs for F( = 0.01 and F( = 0.02. The simulations for buoyant plumes are compared with the laboratory experiments of Willis and Deardorff and with the field experiments of Carras and Williams. Only with the latter data did we obtain reasonable agreement. In this comparison we paid special attention to a correction for the initial momentum in the field data and to a correction for the initial dimensions of the line-source in the simulation data.The large-eddy results allow us to distinguish between plume motion caused by convective turbulence and that caused by the plume buoyancy. We found that the plume motion caused by buoyancy does not obey Briggs' 2/3 law, but is more in agreement with a plume rise formula proposed by Nieuwstadt and de Valk which is based on the assumption that the plume grows due to large scale convective turbulence.

van Haren, L.; Nieuwstadt, F. T. M.

1989-09-01

133

The motion of a single and multiple neutrally buoyant elliptical cylinders in plane Poiseuille flow  

NASA Astrophysics Data System (ADS)

In this article, we investigate the motion of neutrally buoyant elliptical cylinders in plane Poiseuille flow of a Newtonian fluid. The method of distributed Lagrange multiplier/fictitious domain was used to solve the Navier-Stokes equations as well as for the motion of elliptical cylinders. The motion of a single elliptical cylinder is shown to be dependent on the channel Reynolds number Re, the particle size ratio K = a*/H*, and the aspect ratio A = a*/b* of the cylinder, where H* is the half height of the channel, a* and b* are the lengths of the semi-major axis and semi-minor axis of the cylinder, respectively. It is found that there is a critical Reynolds number, Rec ~ 3, which distinguishes the lateral migration of a single elliptical cylinder below and above it. As Re is increased, the equilibrium position of the elliptical cylinder shifts towards the wall when Re <= Rec or shifts closer to the central axis when Re >= Rec. Moreover, there are interesting correlations between the center-of-mass trajectories and the orientation dynamics, which depend on the ranges of K and Re. The motion of multiple elliptical cylinders is also affected by the total solid area fraction ?T, which is defined to be the proportion of the area occupied by the cylinders in the domain of computation. For a few elliptical cylinders (the number of cylinders ND = 16 and the corresponding ?T = 3.77%), the cylinders may scatter into several groups at lower Re (<= 100), and each group fluctuates about an averaged position. At the higher Re (= 1000), the cylinders may converge to an equilibrium position on each side of the channel center. For a larger number of cylinders (ND = 36, 54, 72, 108, and the corresponding ?T = 8.48%-25.45%), we observed a significant rheological behavior in the velocity profiles. In addition, there exists a particle-free layer next to each wall, and the thickness of the particle-free layers is increased as A (or K) or Re is increased.

Chen, Shih-Di; Pan, Tsorng-Whay; Chang, Chien-Cheng

2012-10-01

134

Internal circulation in a buoyant two-fluid Newtonian sphere: implications for composed magmatic diapirs  

NASA Astrophysics Data System (ADS)

Igneous plutons frequently show chemical zoning. The most commonly documented zoning is with the lighter, more silicic, rocks in the centre of the body and the denser, more basic, rocks in the external zone (normal zoning). Less commonly, some plutons show reverse zoning so that the more basic rocks occupy the centre. Widespread evidence shows that zoning in many plutons is the result of interaction between basic and silicic melts. This work studies, by means of finite difference numerical models, pluton zoning which is due to internal circulation in diapirs comprising two magmas of different composition. Diapirs are modelled here as buoyant isothermal spheres composed of two Newtonian fluids rising through a Newtonian ambient fluid. Ratios of viscosities and densities of the two fluids were varied and the results demonstrated two different styles of internal circulation in rising spheres. The first style, termed "coupled circulation", is characterised by continuous overturning of both the fluids in a single cell, evolving through both normal and reverse compositional zoning. The overturns stir the fluids and enhance both magma mingling and mixing. Coupled circulation develops in spheres comprising fluids of similar densities and viscosities. As these properties become increasingly different the internal circulation tends to decouple. "Decoupled circulation", is characterised by circulation of the fluids in two separate cells. Decoupling stops the overturns between the two magmas so that the diapir preserves a reverse zoning throughout its rise, with the denser fluid occupying the central zone. There is less possibility of magma mingling in diapirs undergoing decoupled circulation. Thus, pairs of magmas of similar properties, such as andesite and rhyolite, are most likely to develop coupled circulation leading to both normal and reverse zoning in diapirs; whereas magmas of very different properties, such as basalt and rhyolite, are most likely to decouple resulting in reverse zonation. The models indicate that reverse zoning would be the most common internal pluton geometry if zoning were controlled by internal circulation alone. Model diapirs which rise along channels of warm, low viscosity wall-rock (hot Stokes' models) or low viscosity shear zones show an increased tendency towards coupled circulation and more intense mechanical stirring of the magmas.

Weinberg, Roberto Ferrez

1992-05-01

135

Vortex-induced vibrations of a neutrally buoyant circular cylinder near a plane wall  

NASA Astrophysics Data System (ADS)

This paper presents an experimental study of the motions, drag force and vortex shedding patterns of an elastically mounted circular cylinder, which is held at various heights above a plane wall and is subject to vortex-induced vibration (VIV) in the transverse direction. The cylinder is neutrally buoyant with a mass ratio m=1.0 and has a low damping ratio ?=0.0173. Effects of the gap ratio (S/D) ranged from 0.05 to 2.5 and the free-stream velocity (U) ranged from 0.15 to 0.65m/s (corresponding to 3000?Re?13 000, and 1.53?U?6.62) are examined. The flow around the cylinder has been measured using particle image velocimetry (PIV), in conjunction with direct measurements of the dynamic drag force on the cylinder using a piezoelectric load cell. Results of the vibrating cylinder under unbounded (or free-standing) condition, as well as those of a near-wall stationary cylinder at the same gap ratios, are also provided. For the free-standing cylinder, the transition from the initial branch to the upper branch is characterized by a switch of vortex pattern from the classical 2S mode to the newly-discovered 2PO mode by Morse and Williamson (2009). The nearby wall not only affects the amplitude and frequency of vibration, but also leads to non-linearities in the cylinder response as evidenced by the presence of super-harmonics in the drag force spectrum. In contrast to the case of a stationary cylinder that vortex shedding is suppressed below a critical gap ratio (S/D?0.3), the elastically mounted cylinder always vibrates even at the smallest gap ratio S/D=0.05. Due to the proximity of the plane wall, the vortices shed from the vibrating cylinder that would otherwise be in a double-sided vortex street pattern (either 2S or 2PO mode) under free-standing condition are arranged into a single-sided pattern.

Wang, X. K.; Hao, Z.; Tan, S. K.

2013-05-01

136

Base composition of deoxyribonucleic acid of sulfate-reducing bacteria deduced from buoyant density measurements in cesium chloride.  

PubMed

Saunders, Grady F. (University of Illinois, Urbana), L. Leon Campbell, and John R. Postgate. Base composition of deoxyribonucleic acid of sulfate-reducing bacteria deduced from buoyant density measurements in cesium chloride. J. Bacteriol. 87:1073-1078. 1964.-The base composition of the deoxyribonucleic acid (DNA) of sulfate-reducing bacteria was calculated from buoyant density measurements in CsCl. The sporulating sulfate-reducing bacteria fell into two groups: Desulfovibrio orientis with a DNA base composition of 42% guanine plus cytosine (G + C), and Clostridium nigrificans with a DNA base composition of 45% G + C. The mesophilic relative of C. nigrificans had a DNA base composition of 46% G + C. Thirty strains of nonsporulating sulfate-reducing bacteria called D. desulfuricans were studied. They fell into three groups as judged by DNA base composition: group I (11 strains), 60 to 62% G + C; group II (13 strains), 54 to 56% G + C; and group III (6 strains), 46 to 47% G + C. These data underline the need for a taxonomic revision of this group of microorganisms. PMID:5874533

Saunders, G F; Campbell, L L; Postgate, J R

1964-05-01

137

BASE COMPOSITION OF DEOXYRIBONUCLEIC ACID OF SULFATE-REDUCING BACTERIA DEDUCED FROM BUOYANT DENSITY MEASUREMENTS IN CESIUM CHLORIDE  

PubMed Central

Saunders, Grady F. (University of Illinois, Urbana), L. Leon Campbell, and John R. Postgate. Base composition of deoxyribonucleic acid of sulfate-reducing bacteria deduced from buoyant density measurements in cesium chloride. J. Bacteriol. 87:1073–1078. 1964.—The base composition of the deoxyribonucleic acid (DNA) of sulfate-reducing bacteria was calculated from buoyant density measurements in CsCl. The sporulating sulfate-reducing bacteria fell into two groups: Desulfovibrio orientis with a DNA base composition of 42% guanine plus cytosine (G + C), and Clostridium nigrificans with a DNA base composition of 45% G + C. The mesophilic relative of C. nigrificans had a DNA base composition of 46% G + C. Thirty strains of nonsporulating sulfate-reducing bacteria called D. desulfuricans were studied. They fell into three groups as judged by DNA base composition: group I (11 strains), 60 to 62% G + C; group II (13 strains), 54 to 56% G + C; and group III (6 strains), 46 to 47% G + C. These data underline the need for a taxonomic revision of this group of microorganisms.

Saunders, Grady F.; Campbell, L. Leon; Postgate, John R.

1964-01-01

138

Use of a Force Sensor in Archimedes' Principle Experiment, Determination of Buoyant Force and Acceleration Due To Gravity  

NASA Astrophysics Data System (ADS)

In introductory physics, students verify Archimedes' principle by immersing an object in water in a container, with a side-spout to collect the displaced water, resulting in a large uncertainty, due to surface tension. A modified procedure was introduced, in which a plastic bucket is suspended from a force sensor, and an object hangs underneath the bucket. The object is immersed in water in a glass beaker (without any side spout), and the weight loss is measured with a computer-controlled force sensor. Instead of collecting the water displaced by the object, tap water was added to the bucket to compensate for the weight loss, and the Archimedes' principle was verified within less than a percent. With this apparatus, buoyant force was easily studied as a function of volume of displaced water; as well as a function of density of saline solution. By graphing buoyant force as a function of volume (or density of liquid), value of g was obtained from slope. Apparatus and sources of error will be discussed.

Singh Aurora, Tarlok

2013-04-01

139

Is the 'Fast Halo' around Hawaii as imaged in the PLUME experiment direct evidence for buoyant plume-fed asthenosphere?  

NASA Astrophysics Data System (ADS)

An intriguing spatial pattern of variations in shear-wave arrival times has been mapped in the PLUME ocean bottom experiment (Wolfe et al., 2009) around Hawaii. The pattern consists of a halo of fast travel times surrounding a disk of slow arrivals from waves traveling up though the plume. We think it is directly sensing the pattern of dynamic uplift of the base of a buoyant asthenosphere - the buoyancy of the plume conduit lifting a 'rim' of the cooler, denser mantle that the plume rises through. The PLUME analysis inverted for lateral shear velocity variations beneath the lithosphere, after removing the assumed 1-D model velocity structure IASP91. They found that a slow plume-conduit extends to at least 1200 km below the Hawaiian hotspot. In this inversion the slow plume conduit is — quite surprisingly - surrounded by a fast wavespeed halo. A fast halo is impossible to explain as a thermal halo around the plume; this should lead to a slow wavespeed halo, not a fast one. Plume-related shearwave anisotropy also cannot simply explain this pattern — simple vertical strain around the plume conduit would result in an anisotropic slow shear-wavespeed halo, not a fast one. (Note the PLUME experiment’s uniform ‘fast-halo’ structure from 50-400km is likely to have strong vertical streaking in the seismic image; Pacific Plate-driven shear across a low-viscosity asthenosphere would be expected to disrupt and distort any cold sheet of vertical downwelling structure between 50-400km depths so that it would no longer be vertical as it is in the 2009 PLUME image with its extremely poor vertical depth control.) If the asthenosphere is plume-fed, hence more buoyant than underlying mantle, then there can be a simple explanation for this pattern. The anomaly would be due to faster traveltimes resulting from dynamic relief at the asthenosphere-mesosphere interface; uplift of the denser mesosphere by the buoyancy of the rising plume increases the distance a wave travels through faster mantle and reduces the distance though the slower asthenosphere. With this interpretation, the inference of a radially symmetric ~40-70 km high-~250 km-radius ‘bump’ of uplift of the base of buoyant plume-fed asthenosphere (PFA) can be directly estimated from PLUME results and the measured ~6-10% reduction in shear velocity between the PFA and underlying mantle. The inferred dynamic relief at the base of the PFA due to buoyancy within the underlying plume conduit is strikingly similar to the relief we find in recent axisymmetric 2D and Cartesian 3-D numerical experiments that explore the dynamics of mantle convection with a PFA. The width and height of the bump scale directly with the total buoyancy anomaly in the upper ~500km of the plume conduit, we discuss numerical experiments that quantify this relationship, show that it is, to first order, independent of the viscosity of material in the plume conduit or asthenosphere, and which also quantify the ~400km-radius geoid anomaly produced by these subasthenospheric mantle density anomalies. This effect can only happen if the asthenosphere is more buoyant than underlying mantle — and is therefore direct evidence that a buoyant plume-fed asthenosphere exists around Hawaii.

Morgan, J. P.; Shi, C.; Hasenclever, J.

2010-12-01

140

Rates of photocatalytic oxidation of crude oil on salt water on buoyant, cenosphere-attached titanium dioxide  

SciTech Connect

The rate of TiO[sub 2]-photocatalyzed oxidation of crude oils spilled on aqueous 0.5 M NaCA was determined by measuring the rate of O[sub 2] uptake. The photocatalyst was attached to 100-[mu]m-diameter fly-ash-derived buoyant cenospheres. Partial hydrophobic coating of the cenospheres assured their retention at the air-oil interface. The rate depended on the near-UV (broad band, 365-nm peak) irradiance below 25W m[sup [minus]2], but varied only mildly with irradiance in the 25-45 W m[sup [minus]2] range. It increased upon wave motion imitating agitation of the liquid, and upon increase of the cenosphere:oil mass ratio. It varied only mildly for different crudes. From the measured rates, cleanup times as short as 5-10 days were estimated.

Nair, M.; Luo, Zhenghao; Heller, A. (Univ. of Texas, Austin, TX (United States))

1993-10-01

141

A study of a buoyant axisymmetric jet in a small co-flow Etude d'un jet flottant axisymétrique dans un co-courant faible  

Microsoft Academic Search

This paper deals with measurements of and an integral model for a buoyant axisymmetric jet in a very small co-flow. The integral model is based on the insights gained from the measurements presented here and other recent experiments, which suggest that the turbulent flow is simply advected and the entrainment is that normal for a jet or plume in a

M. J. DAVIDSON; S. GASKIN; I. R. WOOD

2002-01-01

142

The Buoyant Filter Bioreactor: a high-rate anaerobic reactor for complex wastewater--process dynamics with dairy effluent.  

PubMed

A novel high-rate anaerobic reactor, called "Buoyant Filter Bioreactor" (BFBR), has been developed for treating lipid-rich complex wastewater. The BFBR is able to decouple the biomass and insoluble COD retention time from the hydraulic retention time by means of a granular filter bed made of buoyant polystyrene beads. Filter clogging is prevented by an automatic backwash driven by biogas release, which fluidizes the granular filter bed in a downward direction. During filter backwash, the solids captured in the filter are reintroduced into the reaction zone of the reactor. The reaction zone is provided with a mixing system, which is independent of the hydraulic retention time. The performance of a laboratory-scale BFBR was studied for the treatment of dairy effluent, chosen as a model complex wastewater. The dairy effluent was not pre-treated for fat removal. The BFBR was operated over 400 d and showed greater than 85% COD removal at 10 kg COD/(m3/d). The COD conversion to methane in the BFBR was essentially complete. The BFBR performance improved with age, and with feed containing 3200 mg COD/l, the treated effluent had 120 mg COD/l and no turbidity. The hold-up of degradable biosolids, including scum, inside the BFBR was estimated using starvation tests. When load is increased, scum accumulates inside the BFBR and then decays after undergoing change from hydrophobic to hydrophilic. This is explained as the accumulation of fat solids, its conversion to insoluble long chain fatty acids and its further solubilization and degradation. PMID:15766954

Haridas, Ajit; Suresh, S; Chitra, K R; Manilal, V B

2005-03-01

143

A Field Evaluation of an External and Neutrally Buoyant Acoustic Transmitter for Juvenile Salmon: Implications for Estimating Hydroturbine Passage Survival  

PubMed Central

Turbine-passed fish are exposed to rapid decreases in pressure which can cause barotrauma. The presence of an implanted telemetry tag increases the likelihood of injury or death from exposure to pressure changes, thus potentially biasing studies evaluating survival of turbine-passed fish. Therefore, a neutrally buoyant externally attached tag was developed to eliminate this bias in turbine passage studies. This new tag was designed not to add excess mass in water or take up space in the coelom, having an effective tag burden of zero with the goal of reducing pressure related biases to turbine survival studies. To determine if this new tag affects fish performance or susceptibility to predation, it was evaluated in the field relative to internally implanted acoustic transmitters (JSATS; Juvenile Salmon Acoustic Telemetry System) used widely for survival studies of juvenile salmonids. Survival and travel time through the study reach was compared between fish with either tag type in an area of high predation in the Snake and Columbia rivers, Washington. An additional group of fish affixed with neutrally-buoyant dummy external tags were implanted with passive integrated transponder (PIT) tags and recovered further downstream to assess external tag retention and injury. There were no significant differences in survival to the first detection site, 12 river kilometers (rkm) downstream of release. Travel times were also similar between groups. Conversely, externally-tagged fish had reduced survival (or elevated tag loss) to the second detection site, 65 rkm downstream. In addition, the retention study revealed that tag loss was first observed in fish recaptured approximately 9 days after release. Results suggest that this new tag may be viable for short term (<8 days) single-dam turbine-passage studies and under these situations, may alleviate the turbine passage-related bias encountered when using internal tags, however further research is needed to confirm this.

Brown, Richard S.; Deng, Z. Daniel; Cook, Katrina V.; Pflugrath, Brett D.; Li, Xinya; Fu, Tao; Martinez, Jayson J.; Li, Huidong; Trumbo, Bradly A.; Ahmann, Martin L.; Seaburg, Adam G.

2013-01-01

144

Oscillating motions of neutrally buoyant particle and red blood cell in Poiseuille flow in a narrow channel  

NASA Astrophysics Data System (ADS)

Two motions of oscillation and vacillating breathing (swing) of red blood cell with a stiffened membrane have been observed in bounded Poiseuille flows [L. Shi, T.-W. Pan, and R. Glowinski, "Deformation of a single blood cell in bounded Poiseuille flows," Phys. Rev. E 85, 16307 (2012)]. To understand such motions, we have compared them with the oscillating motion of a neutrally buoyant particle of the same shape in Poiseuille flow in a narrow channel since a suspended cell is actually a neutrally buoyant entity. In a narrow channel, the particle can be held in the central region for a while with its mass center moving up and down if it is placed at the centerline initially. Its inclination angle oscillates at the beginning; but its range of oscillation keeps increasing and at the end the particle tumbles when the particle migrates away from the centerline due to the inertia effect. When the particle mass center is restricted to move only on the channel centerline, the inclination angle has been locked to a fixed angle without oscillation. Since the mass center of a deformable cell always migrates toward the channel central region in Poiseuille flow, its inclination angle behaves similar to the aforementioned oscillating motion of the particle as long as the cell keeps the long body shape and moves up and down. But when the up-and-down oscillation of the cell mass center damps out, the oscillating motion of the inclination angle also damps out and the cell inclination angle also approaches to a fixed angle.

Shi, Lingling; Yu, Yao; Pan, Tsorng-Whay; Glowinski, Roland

2014-04-01

145

Buoyant replenishment in silicic magma reservoirs: Experimental approach and implications for magma dynamics, crystal mush remobilization, and eruption  

NASA Astrophysics Data System (ADS)

We present new experiments on replenishment of rhyolite magma chambers by rhyolite magma using corn syrup-water solutions. We emphasize small density contrasts and show that buoyancy is the key controlling factor for whether injections will rise to the top (if buoyant) or pond at the base (if denser). During emplacement, we observe little or no mixing of the injected liquid with the reservoir liquid, as predicted by the fact that our injections have low Reynolds numbers (<10, typically). At later stages, the low-buoyancy (?1 kg m-3) injected liquid, which has accumulated at the top of the reservoir, undergoes mixing with the reservoir liquid, which may originate by the gravitational destabilization of a thin layer of denser resident liquid trapped above the injected liquid layer. The presence of a basal crystal mush, modeled by acrylic beads in a corn syrup-water solution matrix is also considered. Slightly buoyant injections entrain a small fraction of mush particles to the top of the overlying liquid layer. Entrainment efficiency increases dramatically for high-buoyancy injections. We hypothesize that the injected liquid can entrain a maximum quantity of mush particles, which corresponds to the amount required for the injected liquid/mush particle suspension to attain neutral buoyancy in the resident liquid. Hence for silicic systems, a replenishing melt can entrain up to 12.5% crystals during its ascent through the mush. Our results have implications for rhyolites bearing crystals with disequilibrium features, as they may represent mush crystals remobilized by a replenishing silicic magma.

Girard, Guillaume; Stix, John

2009-08-01

146

A field evaluation of an external and neutrally buoyant acoustic transmitter for juvenile salmon: implications for estimating hydroturbine passage survival.  

PubMed

Turbine-passed fish are exposed to rapid decreases in pressure which can cause barotrauma. The presence of an implanted telemetry tag increases the likelihood of injury or death from exposure to pressure changes, thus potentially biasing studies evaluating survival of turbine-passed fish. Therefore, a neutrally buoyant externally attached tag was developed to eliminate this bias in turbine passage studies. This new tag was designed not to add excess mass in water or take up space in the coelom, having an effective tag burden of zero with the goal of reducing pressure related biases to turbine survival studies. To determine if this new tag affects fish performance or susceptibility to predation, it was evaluated in the field relative to internally implanted acoustic transmitters (JSATS; Juvenile Salmon Acoustic Telemetry System) used widely for survival studies of juvenile salmonids. Survival and travel time through the study reach was compared between fish with either tag type in an area of high predation in the Snake and Columbia rivers, Washington. An additional group of fish affixed with neutrally-buoyant dummy external tags were implanted with passive integrated transponder (PIT) tags and recovered further downstream to assess external tag retention and injury. There were no significant differences in survival to the first detection site, 12 river kilometers (rkm) downstream of release. Travel times were also similar between groups. Conversely, externally-tagged fish had reduced survival (or elevated tag loss) to the second detection site, 65 rkm downstream. In addition, the retention study revealed that tag loss was first observed in fish recaptured approximately 9 days after release. Results suggest that this new tag may be viable for short term (<8 days) single-dam turbine-passage studies and under these situations, may alleviate the turbine passage-related bias encountered when using internal tags, however further research is needed to confirm this. PMID:24204947

Brown, Richard S; Deng, Z Daniel; Cook, Katrina V; Pflugrath, Brett D; Li, Xinya; Fu, Tao; Martinez, Jayson J; Li, Huidong; Trumbo, Bradly A; Ahmann, Martin L; Seaburg, Adam G

2013-01-01

147

Microgravity Experiments and Numerical Modeling of Rotating Buoyant Convection in a Spherical Shell with Latitudinal Thermal Gradients  

NASA Technical Reports Server (NTRS)

The results of numerical model calculations are compared with space laboratory experiments for rotating, thermally driven flow in a hemispherical shell, and various flow regimes are described. A spherically symmetric body force, analogous to gravity, is imposed in the radial direction through the use of a dielectric fluid and an electrostatic potential difference across the gap. The spherical boundaries are maintained at constant temperature profiles (with the pole and the inner sphere being the warmer surfaces), and the equatorial wall is an insulator. Typical parameter combinations result in highly nonlinear, but laminar, flow. For weak enough buoyant forcing, the flow is axisymmetric. It consists of a single meridional cell, rising in warm latitudes (in this case, near the pole) and sinking in cool latitudes, with prograde flow in the equatorial region and near the inner hemisphere for other latitudes, and retrograde motion elsewhere. For fast rotation, the first transition due to the instability of this simple flow is also axisymmetric, consisting of rings of convection in the polar region, which propagate poleward. The first nonaxisymmetric convection occurs at Rayleigh numbers which increase with rotation rate. The form of the convection near the transition also depends upon the rate of rotation. Selected flow patterns near the transition as well as those beyond it are studied numerically. For those cases where there exist laboratory experiments with which to compare, the numerical and experimental results agree very well.

Leslie, Fred W.; Miller, Timothy L.

1998-01-01

148

Modeling possible spreadings of a buoyant surface plume with lagrangian and eulerian approaches at different resolutions using flow syntheses from 1992-2007 - a Gulf of Mexico study  

Microsoft Academic Search

We present results from an ensemble of BP oil spill simulations. The oil spill slick is modeled as a buoyant surface plume that is transported by ocean currents modulated, in some experiments, by surface winds. Ocean currents are taken from ECCO2 project (see http:\\/\\/ecco2.org ) observationally constrained state estimates spanning 1992-2007. In this work we (i) explore the role of

R. Tulloch; C. N. Hill; O. Jahn

2010-01-01

149

PA-IgG on platelet subpopulations of different buoyant densities: high levels on the low density population is an artifact.  

PubMed

We isolated subpopulations of normal blood platelets from platelet rich plasma (PRP) and, in parallel, from platelet rich saline (PRS) on the basis of their buoyant densities. The MPV, being smallest in the lightest subpopulation, correlated significantly with platelet buoyant density (P < 0.002). In agreement with previous reports, we showed that the least dense platelet subpopulation, separated from PRP, had a high level of PA-IgG (3,486 mol/plt). This value was significantly greater (P < 0.02) than PA-IgG in the lightest subpopulation separated from PRS (693 mol/plt). We believe that the procedure of separating platelets from PRP artificially increased PA-IgG in the least dense subpopulation. Our data showed that when subpopulations were prepared from PRS, PA-IgG correlated with platelet buoyant density (P < 0.002), and that the subpopulation with the highest density had the highest level of PA-IgG. PMID:7977304

Rososhansky, S; Szymanski, I O

1994-12-01

150

Ethyl cellulose and hydroxypropyl methyl cellulose buoyant microspheres of metoprolol succinate: Influence of pH modifiers  

PubMed Central

Introduction: Incorporation of pH modifier has been the usual strategy employed to enhance the dissolution of weakly basic drug from floating microspheres. Microspheres prepared using a combination of both ethyl cellulose (EC) and hydroxypropyl methylcellulose (HPMC) which shows highest release were utilize to investigate the effect of fumaric acid (FA), citric acid (CA), ascorbic acid (AA) and tartaric acid (TA) (all 5-20% w/w) incorporation on metoprolol succinate (MS) release. Materials and Methods: EC, HPMC alone or in combination were used to prepare microspheres that floated in simulated gastric fluid and evaluated for a percent yield, drug entrapment, percent buoyancy and drug release. The higher drug release in combination (MS:HPMC:EC, 1:1:2) was selected for the evaluation of influence of pH modifiers on MS release. CA (5-20% w/w), AA (5-20% w/w), FA (5-20% w/w) and TA (5-20% w/w) were added and evaluated for drug release. Present investigation is directed to develop floating drug delivery system of MS by solvent evaporation technique. Results: The microspheres of MS:HPMC:EC (1:1:2) exhibited the highest entrapment (74.36 ± 2.18). The best percentage yield was obtained at MS:HPMC (1:1) (83.96 ± 1.50) and combination of MS:HPMC:EC (1:1:2) (79.23 ± 1.63). Conclusion: MS release from the prepared microspheres was influenced by changing MS-polymer, MS-polymer-polymer ratio and pH modifier. Although significant increment in MS release was observed with CA (20% w/w), TA (20% w/w) and AA (20% w/w), addition of 20% w/w FA demonstrated more pronounced and significant increase in drug entrapment as well as release from MS:HPMC:EC (1:1:2) buoyant microspheres.

Raut, Neha S; Somvanshi, Sachin; Jumde, Amol B; Khandelwal, Harsha M; Umekar, Milind J; Kotagale, Nandkishor Ramdas

2013-01-01

151

Time resolved measurements of vortex-induced vibrations of a positively buoyant tethered sphere in uniform water flow  

NASA Astrophysics Data System (ADS)

Vortex-induced vibrations (VIV) of a positively buoyant (light) tethered sphere in uniform flow as well as its wake characteristics were measured in a closed loop water channel. Experiments were performed at free stream velocities ranging between 0.048 and 0.22 m/s, corresponding to sphere Reynolds numbers ranging from ReD=430 to 1925. The measurements were done using high-speed sphere tracking as well as time resolved particle image velocimetry in a horizontal plane located at the sphere's center. Until the Hopf bifurcation, the sphere remained stationary and the wake was characterized by a train of hairpin vortices exhibiting near-symmetry in the vertical plane similar to stationary sphere visualization results. For our limited parameter range, the amplitude response of two different data sets (same sphere and free stream velocity but different water viscosity) collapsed better when plotted versus ReD than when plotted versus the reduced velocity, U*. The amplitude response beyond the first bifurcation displayed continuously increasing rms amplitudes in agreement with the sphere's small mass parameter (

Eshbal, L.; Krakovich, A.; van Hout, R.

2012-11-01

152

Glasgow University's Buoyant Scheme.  

ERIC Educational Resources Information Center

LearningWorks, an employee development program for University of Glasgow staff, grants training allowances to pay for learning on their own time. In the first year, 43% of eligible employees participated in a wide range of accessible learning opportunities. (SK)

Maclachlan, Kathy

1998-01-01

153

Near-field mixing of a vertical buoyant jet in a shallow crossflow: Implications on adsorption and flocculation  

NASA Astrophysics Data System (ADS)

The behaviour and movement of pulpmill pollutants discharged into the Northern Fraser River is of significant concern due to their potential impact on this valuable aquatic ecosystem. The shallow receiving water can influence the mixing and subsequent dilution of these discharges. The association of contaminants with suspended sediment, either by direct adsorption or flocculation of contaminated solids discharged with the effluent (biosolids), also affects pollutant fate. This study examined the effects of a shallow crossflow in the near field mixing of a vertical buoyant jet, specifically dilution and trajectory. Physical mixing experiments were carried out in a shallow ambient current over a range of conditions similar to those seen in the Fraser River, specifically peak and low flow conditions. The dilution and trajectory results were then compared to those predicted by CORMIX1. The mechanism of association of contaminants with suspended sediment under these near field conditions was also investigated. A jet classification scheme was developed based on the behaviour of the jets in the shallow crossflow. Jets were classified to be Bottom, Intermediate or Surface Jets. Bottom Jets were influenced primarily by interaction of the jet with the bottom boundary layer, resulting in significantly higher levels of dilution and possible bottom attachment. The mixing of Intermediate Jets was more complicated due to interaction with both the top and bottom boundaries: the free surface inhibited mixing while interactions with the boundary layer enhanced mixing. Surface Jets were drastically affected by the free surface, with a reduction in dilution due to impingement on the free surface. The CORMIX1 model was found to be unsuitable for predicting the dilution in this application since it does not consider the effects of either the free surface or the bottom boundary layer on jet mixing. Adsorption was found to play a limited role in the near field region. Of greater importance, is the potential for flocculation of biosolids with suspended sediment. The most important parameter in predicting where the conditions for this increased flocculation will occur was the ratio of the number of biosolid, particles to the number of suspended sediment particles.

Gomm, Leslie Sharon

1999-10-01

154

Modeling possible spreadings of a buoyant surface plume with lagrangian and eulerian approaches at different resolutions using flow syntheses from 1992-2007 - a Gulf of Mexico study  

NASA Astrophysics Data System (ADS)

We present results from an ensemble of BP oil spill simulations. The oil spill slick is modeled as a buoyant surface plume that is transported by ocean currents modulated, in some experiments, by surface winds. Ocean currents are taken from ECCO2 project (see http://ecco2.org ) observationally constrained state estimates spanning 1992-2007. In this work we (i) explore the role of increased resolution of ocean eddies, (ii) compare inferences from particle based, lagrangian, approaches with eulerian, field based, approaches and (ii) examine the impact of differential response of oil particles and water to normal and extreme, hurricane derived, wind stress. We focus on three main questions. Is the simulated response to an oil spill markedly different for different years, depending on ocean circulation and wind forcing? Does the simulated response depend heavily on resolution and are lagrangian and eulerian estimates comparable? We start from two regional configurations of the MIT General Circulation Model (MITgcm - see http://mitgcm.org ) at 16km and 4km resolutions respectively, both covering the Gulf of Mexico and western North Atlantic regions. The simulations are driven at open boundaries with momentum and hydrographic fields from ECCO2 observationally constrained global circulation estimates. The time dependent surface flow fields from these simulations are used to transport a dye that can optionally decay over time (approximating biological breakdown) and to transport lagrangian particles. Using these experiments we examine the robustness of conclusions regarding the fate of a buoyant slick, injected at a single point. In conclusion we discuss how future drilling operations could use similar approaches to better anticipate outcomes of accidents both in this region and elsewhere.

Tulloch, R.; Hill, C. N.; Jahn, O.

2010-12-01

155

The dynamics of buoyant jets in a linearly stratified ambient cross-flow: Implications for the interaction between volcanic plumes and wind  

NASA Astrophysics Data System (ADS)

Volcanic plumes produced by explosive eruptions commonly interact with atmospheric wind causing plume bending and a reduction of its maximum rise height. It is well known that the maximum height reached by a buoyant plume rising in a cross-flow with uniform velocity is controlled by the plume buoyancy flux at the source, the strength of the initial environmental density stratification, the wind velocity and the efficiency of turbulent entrainment. Although numerous studies have been carried out to understand the effects of variations of environmental and source conditions on the plume maximum height, turbulent entrainment has not been taken into account with the same level of detailed analysis. Here, we present new laboratory experiments aimed at better understanding the contribution of the turbulent entrainment to determining the plume maximum height. The experiments consist in injecting downward fresh water in a tank containing an aqueous NaCl solution with linear density stratification. The jet source is towed at a constant speed through the stationary fluid in order to produce a cross-flow. According to the range of source and environmental conditions, the buoyant jet is distorted or bent-over and its maximum rise height is reduced up to a factor of 2 when wind speed is high. We quantify the efficiency of turbulent entrainment due to wind in our experiments and we show that the dynamical regime strongly depends on the ratio of the horizontal wind speed and the vertical plume velocity, and on the Richardson number defined at the source. Our results provide a robust framework to characterize the entrainment coefficient due to wind in a 1D model of turbulent jet rising in a linearly stratified ambient cross-flow, and hence can be used for the assessment of the impact of atmospheric winds on the dynamics of explosive volcanic plumes.

Carazzo, Guillaume; Girault, Frédéric; Aubry, Thomas; Bouquerel, Hélène; Kaminski, Édouard

2014-05-01

156

Experimental study of reaction between perovskite and molten iron to 146 GPa and implications for chemically-distinct buoyant layer at the top of the core  

NASA Astrophysics Data System (ADS)

Partitioning of oxygen and silicon between molten iron and (Mg,Fe)SiO3 perovskite was investigated to 146 GPa and 3500 K by a combination of laser-heated diamond-anvil cell and analytical transmission electron microscope (TEM). The chemical compositions of co-existing quenched molten iron and perovskite were determined quantitatively with energy-dispersive X-ray spectrometry (EDS) and electron energy loss spectroscopy (EELS) for oxygen content. The results demonstrate that the quenched liquid iron in contact with perovskite contained substantial amounts of oxygen and silicon at such high pressure and temperature. Owing to the pretty high solubilities of oxygen and silicon into the molten iron, the chemical reaction at the core-mantle boundary (CMB) possibly results in the formation of chemically distinct layers both at the mantle side and the core side. Here we calculated the chemical equilibrium between perovskite, ferropericlase, and molten iron at the P-T conditions of the CMB, based on these experimental results and previous data on partitioning of oxygen between molten iron and ferropericlase to 134 GPa [Ozawa et al., 2008 GRL]. Note that perovskite is a predominant phase instead of post-perovskite above 3500 K at the CMB pressure. We found that molten iron should include oxygen and silicon much more than required to account for the core density deficit (less than 10%) when co-existing with both perovskite and ferropericlase at the CMB. These results suggest that the very bottom of the mantle may consist of either one of iron-depleted perovskite or ferropericlase. Alternatively, it is also possible that the bulk outer core liquid is not in direct contact with the mantle. The extensive dissolutions of oxygen and silicon from the mantle may form chemically-distinct buoyant layer at the top of the core. Indeed, seismological observations of a small P-wave velocity reduction in the topmost core have been repeatedly reported, suggesting the presence of such buoyant liquid layer. Such layer physically separates the mantle from the bulk outer core liquid, hindering the chemical reaction between them.

Hirose, K.; Ozawa, H.

2008-12-01

157

Spontaneous outgrowth of Epstein-Barr virus-positive B-cell lines from circulating human B cells of different buoyant densities.  

PubMed

Epstein-Barr virus (EBV) has potent cell-growth-transforming activity for human B lymphocytes in vitro, yet appears to persist in the circulating B-cell pool of virus carriers in vivo as a largely asymptomatic (i.e., non-growth-transforming) infection. The true nature of this infection, and the identity of the cells involved, remain to be determined. Studies of Lewin et al. (1987) have suggested (i) that the frequency of virus-infected cells in the circulating B-cell pool differs in different buoyant density fractions, being most abundant in the low-density population, and (ii) that rare virus-infected cells with the capacity for direct in vitro outgrowth to EBV-transformed cell lines are segregated within the high-density population. We have repeated this work using B-cell fractions from a much larger panel of asymptomatic virus carriers and find (i) that the incidence of virus-infected B cells is not significantly different between high- and low-density fractions, and (ii) that virus-infected cells from both fractions give rise to EBV-transformed cell lines in culture predominantly through a 2-step mechanism of virus replication and secondary infection rather than by direct outgrowth. PMID:1850387

Yao, Q Y; Czarnecka, H; Rickinson, A B

1991-05-10

158

Numerical studies of the effects of large neutrally buoyant particles on the flow instability and transition to turbulence in pipe flow  

NASA Astrophysics Data System (ADS)

The effects of large neutrally buoyant particles on the flow instability and turbulence transition in pipe flow are investigated with the fictitious domain method. The periodic boundary condition is introduced in the streamwise direction. The work comprises two parts. In the first part, the pressure gradient is kept constant, and the purpose is to study the particle-induced flow instability. In our previous study [X. Shao, Z. Yu, and B. Sun, Phys. Fluids 20, 103307 (2008)], it was observed that a particle of a/R = 0.1 (a and R being the radii of the particle and the tube, respectively) induced the flow structure characterized by two pairs of weak and stable streamwise vortices at the Reynolds number of 1000. In the present study, our results show that the flow structure loses stability at the Reynolds number of 1500. However, it is interesting that the system eventually reaches a stable state: the particle spirals forward along the tube wall, accompanied by a stable flow structure for the case of one single particle in the computational domain. In the second part of the present study, the flow flux is kept constant, and the purpose is to examine the effects of particles on the critical Reynolds number based on the mean velocity. Our results show that large particles trigger the turbulence transition at low particle volume fractions, but delay the transition as the particle volume fraction exceeds a critical value, in agreement with the previous experimental observation [J.-P. Matas, J. F. Morris, and É. Guazzelli, Phys. Rev. Lett. 90, 014501 (2003)].

Yu, Zhaosheng; Wu, Tenghu; Shao, Xueming; Lin, Jianzhong

2013-04-01

159

Hypertriglyceridemia during late pregnancy is associated with the formation of small dense low-density lipoproteins and the presence of large buoyant high-density lipoproteins.  

PubMed

Late pregnancy is a unique metabolic state where there are transient increases in the concentrations of plasma triglyceride (TG), cholesterol, and apolipoprotein (apo) B. Despite the hypertriglyceridemic environment, we recently reported that there is an unusual shift in high-density lipoprotein (HDL) subclass distribution from smaller HDL subclasses to the largest, most buoyant HDL2b subclass. In the present investigation, we determined whether the subclasses of low-density lipoprotein (LDL) also change during this transient hyperlipidemic state and whether such changes were associated with plasma TG and apolipoprotein concentrations. Thirty-six Hispanic subjects at 35 to 36 weeks' gestation and at 6 weeks' postpartum were studied. At 35 to 36 weeks of gestation, plasma concentrations of TG, cholesterol, and apo B were increased (218 +/- 62, 234 +/- 48, and 130 +/- 35 mg/dL, respectively) over levels at 6 weeks' postpartum (112 +/- 69, 197 +/- 36, and 97 +/- 25 mg/dL respectively). However, lipoprotein(a) [Lp(a)] concentrations were not changed during pregnancy compared with postpartum. LDL subclass patterns (A, B, or I) were determined by nondenaturing polyacrylamide gradient gel electrophoresis in our group of 36 pregnant women. During late pregnancy, 97% of subjects were categorized as LDL subclass patterns B or I, indicating that small, dense LDL particles predominated. This predominance of small, dense LDL was associated with plasma TG concentration, where there was a significant inverse relationship (r = -.45, P < .01) between the LDL peak particle diameter and plasma TG concentration. In an apparent anomaly, there were significant increases in the concentrations of HDL cholesterol (HDL-C) and HDL2 mass, even though small, dense LDL particles predominated.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:8052144

Silliman, K; Shore, V; Forte, T M

1994-08-01

160

Petrochronological and structural arguments for upper plate thickening and relamination of the lower plate buoyant material in the Variscan Bohemian Massif  

NASA Astrophysics Data System (ADS)

Recent tectonic models for the Variscan evolution of the Bohemian Massif emphasize the role of Rayleigh-Taylor instability for the 355-340 Ma evolution of the Moldanubian domain. This model is based on the presence of weak, low-density felsic material tectonically underplating a high-density mafic layer and its subsequent gravity-driven overturn. However, earlier phases of the Variscan orogeny concerning the emplacement of felsic low-density material to the base of the upper plate are so far poorly documented. We contribute to this problem by deciphering of polyphase early-Variscan (~375 Ma) deformation and metamorphism close to the main Variscan suture. Detailed structural, pseudosection and microstructural analyses combined with LASS monazite dating were carried out in metapelites along the western margin of the upper plate represented by the Teplá Crystalline Complex (TCC). This region is represented by a ~25 km wide deformation zone with E-W metamorphic gradients associated with two distinct early-Variscan events (~380-375 and ~375-370 Ma). The first compressional event produced a vertical NNE-SSW trending fabric and a continuous and prograde Barrovian metamorphic sequence ranging from biotite to kyanite zones at a field geotherm of 20 to 25 °C/km. Subsequently, a gently SE dipping normal shear-zone associated with retrogression develops along the base of the TCC. This sub-horizontal fabric shows normal metamorphic zonation ranging from sillimanite, biotite to chlorite zones and indicates vertical shortening related to unroofing of high pressure metabasites of the underlying Mariánské-Lázn? Complex. The first metamorphic fabric is interpreted to result from early thickening of the upper plate during continental underthrusting of Saxothuringian continent (380 to 375 Ma) while the second deformation and metamorphism (~370 Ma) reflects vertical shortening produced by buoyant uplift of accreted Saxothuringian felsic crust. This event is the unique yet indirect testimony of relamination mechanisms governing further evolution of the orogenic lower crust in the Bohemian massif.

Pe?estý, Vít; Holder, Robert; Lexa, Ondrej; Racek, Martin; Je?ábek, Petr

2014-05-01

161

A new time series of particle export from neutrally buoyant sediments traps at the Bermuda Atlantic Time-series Study site  

NASA Astrophysics Data System (ADS)

Neutrally buoyant sediment traps (NBSTs) were deployed concurrently with particle interceptor traps (PITs) on monthly cruises of the Bermuda Atlantic Time-series Study (BATS) from June 2007 to July 2010. In most months, particulate organic carbon flux measured by the two sediment trap systems agreed within the range of variability for two separate NBSTs. In three periods of this study however, the PITs collected more than three times the amount of particulate organic carbon (POC) than the NBSTs. One of these periods coincided with two instances when the mixed layer was deeper than the trap deployment depth, which may lead to biased collection. One of the anomalous periods occurred during summer months, for which we were unable to find existing evidence of biogeochemical changes that would lead to such increases in POC flux. The third anomalous period occurred when the POC flux measured by the NBSTs was near zero. We hypothesize that the PITs may have a positive bias at low fluxes relative to the NBSTs. Zooplankton swimmers accounted for 49±20% of the total measured carbon flux over the three year period and swimmer removal by screening of samples through a 350 ?m mesh was established as an effective method for this site. Process blank corrections based on sample-identical blanks were important for determining mass and carbon flux from both the NBSTs and the PITs. This new record of particle export from NBSTs suggests that the observed carbon imbalance in this region of the ocean (Michaels et al., 1994) is not due to undersampling by the PITs and that export ratios may be even lower than previously thought.

Owens, S. A.; Buesseler, K. O.; Lamborg, C. H.; Valdes, J.; Lomas, M. W.; Johnson, R. J.; Steinberg, D. K.; Siegel, D. A.

2013-02-01

162

On the suitability of gelatin as a laboratory-scale analogue for host rock to study the propagation of buoyant liquid-filled fractures in geophysical applications, notably magmatic dikes  

NASA Astrophysics Data System (ADS)

Experimental modelling of the propagation of magma-filled fractures or dikes has relied heavily on the use of gelatin as a host solid because of several convenient properties, notably its low elastic shear modulus, as well as the properties of transparency and photo-elasticity. The first of these properties notably allows gelatin to deform under its own weight at laboratory scale. Quite a wide range of fluids have been used in order to study the propagation of cracks filled particularly with (positively or negatively) buoyant fluid, the case of buoyant cracks being believed particularly important for geologic applications. Fluids that have been used include air, various oils, alkanes, and mercury as well as some aqueous solutions, which raises the question of the action of surface energy between hydrophobic fluids and hydrophilic gelatin. One important discrepancy between experimental results and theory is that many experimental cracks filled with a constant volume of buoyant fluid have been observed to propagate at constant velocity whereas theory predicts that they should lengthen proportional to time^(1/3). Physical analysis and numerical calculations on this problem indeed suggest that it may be explained qualitatively by a surface energy effect, however, numerical values for the physical parameters involved indicate that the velocity predicted for viscous flow driven by surface energy between gelatin and different fluids is not that at which the fractures propagate. We review the experimental literature, and show that existing physical models for fissure propagation do not give a very satisfactory quantitative explanation of the fissure velocities observed. One source of discrepancy may be that theories are most commonly limited to 2-dimensional treatments whereas experimental fractures are naturally 3-dimensional. We also revisit the question of whether host solid fracture processes or rheologic variations, which have generally been thought to be unimportant in determining the velocity of fissures in the geologic context, may also be a source of discrepancy in the experimental data.

Tait, S.; Taisne, B.; Craster, R.; Bhat, H.

2012-12-01

163

The influence of buoyant forces and volume fraction of particles on the particle pushing/entrapment transition during directional solidification of Al/SiC and Al/graphite composites  

NASA Technical Reports Server (NTRS)

Directional solidification experiments in a Bridgman-type furnace were used to study particle behavior at the liquid/solid interface in aluminum metal matrix composites. Graphite or silicon-carbide particles were first dispersed in aluminum-base alloys via a mechanically stirred vortex. Then, 100-mm-diameter and 120-mm-long samples were cast in steel dies and used for directional solidification. The processing variables controlled were the direction and velocity of solidification and the temperature gradient at the interface. The material variables monitored were the interface energy, the liquid/particle density difference, the particle/liquid thermal conductivity ratio, and the volume fraction of particles. These properties were changed by selecting combinations of particles (graphite or silicon carbide) and alloys (Al-Cu, Al-Mg, Al-Ni). A model which consideres process thermodynamics, process kinetics (including the role of buoyant forces), and thermophysical properties was developed. Based on solidification direction and velocity, and on materials properties, four types of behavior were predicted. Sessile drop experiments were also used to determine some of the interface energies required in calculation with the proposed model. Experimental results compared favorably with model predictions.

Stefanescu, Doru M.; Moitra, Avijit; Kacar, A. Sedat; Dhindaw, Brij K.

1990-01-01

164

A Buoyant Life Investigating Mobile Platform (BLIMP)  

Microsoft Academic Search

The Search for Life in new environments, e.g. Mars\\/Titan, will be scientifically challenging and have great engineering difficulties. In this paper we discuss an approach to field-testing methods relevant to three scientific thrusts in the detection of life and pre-biotic organic compounds on other worlds. We describe how this can be accomplished through a series of field trials using a

M. Coleman; J. Jones; D. Rodgers

2004-01-01

165

A buoyant life investigating mobile platform (BLIMP)  

Microsoft Academic Search

The search for life in new environments, e.g., Mars\\/Titan, will be scientifically challenging and have great engineering difficulties. In this paper the authors discuss an approach to field-testing methods relevant to three scientific thrusts in the detection of life and pre-biotic organics on other worlds. We describe how this can be accomplished through a series of field trials using a

Max Coleman; David Rodgers; Jack Jones

2006-01-01

166

Buoyant Test Vehicle Polymer Ejection Nose Assembly.  

National Technical Information Service (NTIS)

An underwater vehicle has a generally cylindrically portion with boundary layer polymer fluid storage and a pressurizing source provided therein, and a nose portion secured to the cylindrical portion and capable of being reconfigured for ejecting the poly...

W. H. Nedderman R. Meunier

1996-01-01

167

Buoyant Rover for Under-Ice Exploration  

NASA Astrophysics Data System (ADS)

We have designed, constructed and tested a prototype robotic mobility platform for exploring the underside of ice sheets in frozen lake or ocean environments. The ice-water interface often provides some of the most interesting and dynamic chemistry in partially frozen systems, as dissolved impurities are rejected from the advancing freezing front. Higher concentrations of microorganisms can be found in this region, and the topography of the ice underside can help reveal the history of its formation. Furthermore, in lake environments ice cover can serve to trap gases released from biological and geological processes in the subsurface. The rover uses a two-wheeled design with a flexible dragging tail, enabling it to fit into a 10-inch diameter ice borehole. The sealed air-filled cylindrical body, along with closed-cell foam inside of cone-shaped wheels, provides buoyancy force to enable roving along the underside of the ice. The prototype contains two cameras that stream live video via a tethered connection to a ground station and uses semi-autonomous control via a PC. Preliminary testing of the prototype in a cold lab and in northern Alaskan thermokarst lakes demonstrates the utility and simplicity of this type of robotic platform for exploring the ice-water interface. This technology has potential future use in landed missions to icy ocean worlds in the solar system.

Berisford, D. F.; Leichty, J. M.; Klesh, A. T.; Matthews, J. B.; Hand, K. P.

2012-12-01

168

JBFA-Buoyant Flight, Special Edition  

NASA Technical Reports Server (NTRS)

Progress in the project to traverse the Pacific Ocean by manned balloon is summarized. The development of a hybrid lighter than aircraft combining the buoyancy of a gas bag with the vertical lift off capabilities of the helicopter is also addressed.

Wada, C.; Terada, K.; Ishii, C.; Nagamatsu, K.; Makino, M.; Ichiyoshi, S.

1982-01-01

169

Buoyant pulsating exchanging flow through a vent  

SciTech Connect

Buoyancy-driven bidirectional pulsating exchange flow through a vent in a horizontal partition is studied experimentally using a brine/water system. The associated transient and pulsating exchange flows were studied by densimetric measurements, flow visualization, and laser Doppler velocimetry (LDV) measurements for three different vent length-to-diameter ratios: 0.106, 0.0376, and 0.008. A time scale, based on the rate of decay of the density difference between the two compartments, is developed that collapses all experimental data regarding the decay of density in the top compartment into one curve. Flow visualization was used to understand the flow features contributing to the pulsating flow and to provide a quantitative measure of the major pulsation frequency. Interfacial instability between brine and water at the vent was found to contribute to the pulsation. The pulsation frequencies and their decay were determined from the power spectrum of LDV measurements. For the small length-to-diameter ratios (0.008 and 0.0376) there are two different frequencies that decay at different rates, suggesting multiple flow processes that contribute to flow pulsations. 17 refs., 7 figs., 2 tabs.

Conover, T.A.; Kumar, R.; Kapat, J.S. [Clemson Univ., SC (United States)

1995-08-01

170

Science NetLinks: Buoyant Boats  

NSDL National Science Digital Library

This lessson plan for grades 3-5 has students design and construct boats to test their buoyancy. The lesson is designed to help students understand both buoyancy and Archimedes Principle. Included is a printable student activity for testing and comparing the buoyancy of boats. This is part of a larger collection of lessons, all of which are aligned with specific AAAS Benchmarks for Scientific Literacy.

Science, American A.

2008-08-15

171

46 CFR 160.010-3 - Inflatable buoyant apparatus.  

Code of Federal Regulations, 2010 CFR

...outfit. One set of sealing clamps or plugs as described in § 160.151-21(y)(1); (ix) Pump or bellows. One pump or bellows as described in § 160.151-21(z); and (x) Sea anchor. One sea anchor as described in §...

2010-10-01

172

46 CFR 160.010-3 - Inflatable buoyant apparatus.  

Code of Federal Regulations, 2010 CFR

...outfit. One set of sealing clamps or plugs as described in § 160.151-21(y)(1); (ix) Pump or bellows. One pump or bellows as described in § 160.151-21(z); and (x) Sea anchor. One sea anchor as described in §...

2009-10-01

173

OPTICAL DENSITY VISUALIZATION AND RECONSTRUCTION OF NEGATIVE BUOYANT VORTEX RINGS  

Microsoft Academic Search

A non-invasive optical measurement technique is implemented to study the formation of negative buoy- ant vortex rings generated at the orifice opening of a piston- cylinder apparatus. Qualitative visualiza- tions of the generated CO2-loaded rings are obtained using a Background-Oriented Schlieren (BOS) technique, and two-dimensional quantitative optical density visualizations are extracted using a PIV al- gorithm. An inverse Abel transform

Josué Sznitman; Thomas Rösgen

174

Civil markets for buoyant heavy-lift vehicles  

NASA Technical Reports Server (NTRS)

Worldwide civil markets for heavy lift airships were investigated. Substantial potential market demand was identified for payloads of from 13 to 800 tons. The largest markets appear to be in applications to relieve port congestion, construction of power generating plants, and, most notably, logging. Because of significant uncertainties both in vehicle and market characteristics, further analysis will be necessary to verify the identified market potential of heavy lift airship concepts.

Mettam, P. J.; Hansen, D.; Ardema, M. D.

1981-01-01

175

Countering Solutal Buoyant Convection with High Magnetic Fields  

NASA Technical Reports Server (NTRS)

An important component in biotechnology, particularly in the area of protein engineering and rational drug design is the knowledge of the precise three-dimensional molecular structure of proteins. The quality of structural information obtained from X-ray diffraction methods is directly dependent on the degree of perfection of the protein crystals. As a consequence, the growth of high quality macromolecular crystals for diffraction analyses has been the central focus for biochemist, biologists, and bioengineers. Macromolecular crystals are obtained from solutions that contain the crystallizing species in equilibrium with higher aggregates, ions, precipitant, other possible phases of the protein, foreign particles, the walls of the container, and a likely host of other impurities. By changing transport modes in general, i.e., reduction of convection and sedimentation, as is achieved in microgravity, we have been able to dramatically effect the movement and distribution of macromolecules in the fluid, and thus their transport, formation of crystal nuclei, and adsorption to the crystal surface. While a limited number of high quality crystals from space flights have been obtained, as the recent National Research Council (NRC) review of the NASA microgravity crystallization program pointed out, the scientific approach and research in crystallization of proteins has been mainly empirical yielding inconclusive results. We postulate that we can reduce convection in ground-based experiments and we can understand the different aspects of convection control through the use of strong magnetic fields and field gradients. We postulate that limited convection in a magnetic field will provide the environment for the growth of high quality crystals. The approach exploits the variation of fluid magnetic susceptibility with concentration for this purpose and the convective damping is realized by appropriately positioning the crystal growth cell so that the magnetic susceptibility force counteracts terrestrial gravity. The general objective is to test the hypothesis of convective control using a strong magnetic field and magnetic field gradient and to understand the nature of the various forces that come into play. Specifically we aim to delineate causative factors and to quantify them through experiments, analysis and numerical modeling. The paper will report on the current status of the investigation and discuss results from the experimental and modeling efforts.

Ramachandran, N.; Leslie, F. W.

2002-01-01

176

Water Temperature Effects on Horizontal Buoyant Submerged Jets.  

National Technical Information Service (NTIS)

Pumped storage power generation to meet peak demands for electricity is now in use in approximately twenty-two locations in the United States and approximately twenty-eight other sites are either planned or under construction. In general, a reservoir can ...

J. B. Riester R. A. Bajura S. H. Schwartz

1977-01-01

177

Solutions for turbulent buoyant plumes rising from circular sources  

NASA Astrophysics Data System (ADS)

Analytical solutions are developed for turbulent plumes rising from circular sources of positive buoyancy in a quiescent environment of uniform density. From governing equations written in a form which encompasses both the Boussinesq and non-Boussinesq cases, we derive analytical expressions for all plume variables (radius, velocity, and density deficit) in terms of a single quantity ?, called the plume function. For given source conditions, we then show that ? (and, subsequently, all plume variables) can be evaluated at any height from two integral functions which are defined for lazy and forced plumes. For a practical use, these integral functions are given in tables. Moreover, exact values and locations of the maximum velocity and the plume neck are determined.

Michaux, G.; Vauquelin, O.

2008-06-01

178

Buoyant zones, great earthquakes, and unstable boundaries of subduction  

Microsoft Academic Search

The distribution of large shallow earthquakes along subduction boundaries does not agree with the distribution pattern that might be predicted from a simple model of plate tectonics. That is, along extensive sections of some island ares, large shocks occurred infrequently or not at all during recorded history. Most of these zones of long-term quiescence are nearly coterminous with segments of

John Kelleher; William McCann

1976-01-01

179

Buoyant Subduction on Venus: Implications for Subduction around Coronae.  

National Technical Information Service (NTIS)

Potentially low lithospheric densities, caused by high Venus surface and perhaps mantle temperatures, could inhibit the development of negative buoyancy-driven subduction and a global system of plate tectonics/crustal recycling on that planet. No evidence...

J. D. Burt J. W. Head

1993-01-01

180

Asymptotic and Numerical Methods for Rapidly Rotating Buoyant Flow  

NASA Astrophysics Data System (ADS)

This thesis documents three investigations carried out in pursuance of a doctoral degree in applied mathematics at the University of Colorado (Boulder). The first investigation concerns the properties of rotating Rayleigh-Benard convection -- thermal convection in a rotating infinite plane layer between two constant-temperature boundaries. It is noted that in certain parameter regimes convective Taylor columns appear which dominate the dynamics, and a semi-analytical model of these is presented. Investigation of the columns and of various other properties of the flow is ongoing. The second investigation concerns the interactions between planetary-scale and mesoscale dynamics in the oceans. Using multiple-scale asymptotics the possible connections between planetary geostrophic and quasigeostrophic dynamics are investigated, and three different systems of coupled equations are derived. Possible use of these equations in conjunction with the method of superparameterization, and extension of the asymptotic methods to the interactions between mesoscale and submesoscale dynamics is ongoing. The third investigation concerns the linear stability properties of semi-implicit methods for the numerical integration of ordinary differential equations, focusing in particular on the linear stability of IMEX (Implicit-Explicit) methods and exponential integrators applied to systems of ordinary differential equations arising in the numerical solution of spatially discretized nonlinear partial differential equations containing both dispersive and dissipative linear terms. While these investigations may seem unrelated at first glance, some reflection shows that they are in fact closely linked. The investigation of rotating convection makes use of single-space, multiple-time-scale asymptotics to deal with dynamics strongly constrained by rotation. Although the context of thermal convection in an infinite layer seems somewhat removed from large-scale ocean dynamics, the asymptotic methods generalize directly to the second investigation which simply adds large spatial scales -- the transition from convectively unstable to convectively stable dynamics does not change the mathematical framework. The rotating Navier-Stokes equations in the Boussinesq approximation and the equations derived from them asymptotically in the investigation of rotating convection include dispersive and dissipative linear terms that are stiff, i.e. that hinder numerical solution by explicit methods. A variety of methods which purport to alleviate this difficulty have been derived, and have been tested on and applied largely to problems with purely dissipative linear terms. But it was heretofore unfortunately quite difficult to judge and compare how effectively these methods achieve their goal when the stiff linear term is both dissipative and dispersive. The third investigation therefore introduces a visual, analytical method for comparing the linear stability properties of the various methods (the linear stability properties being a proxy for their ability to alleviate stiffness) and supports the results of this analysis by comprehensive numerical experiments.

Grooms, Ian G.

181

A PDF DISPERSION MODEL FOR BUOYANT PLUMES IN THE CONVECTIVE BOUNDARY LAYER (R823419)  

EPA Science Inventory

The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Concl...

182

Combustion in Turbulent Jets and Buoyant Plumes. Annual Report December 1983 - December 1984.  

National Technical Information Service (NTIS)

Results are reported from an ongoing investigation of the entrainment and mixing mechanisms in momentum-dominated turbulent jets, buoyancy-dominated turbulent plumes, and flows which undergo a transition between these two regimes. This investigation also ...

P. E. Dimotakis, J. E. Broadwell, E. E. Zukoski

1985-01-01

183

Buoyant Turbulent Jets with Off-Source Heating. Part I: ILES Simulations  

NASA Astrophysics Data System (ADS)

Bhat and Narasimha (JFM 1996) presented an investigation of a novel laboratory experiment analogous to latent heat release during cloud formation. An acidic jet was injected into a deionized ambient, and electrodes were used to selectively heat the conducting jet fluid. We use high-resolution three-dimensional implicit LES simulations to investigate the experiment numerically. The ILES approach uses non-oscillatory finite-volume schemes to capture the inviscid cascade of kinetic energy through the inertial range, while the inherent numerical dissipation acts as an implicit sub-grid model. We first consider the implications of using the ILES approach for turbulent jets and plumes, and then examine the complex interaction between momentum, buoyancy and (acid) concentration for a turbulent jet with off-source heating. The simulations provide valuable insight into the flow structure, and motivate a reinterpretation of the experimental data.

Aspden, Andrew; Nikiforakis, Nikos; Dalziel, Stuart

2008-11-01

184

The Tilting Instability with Buoyant Forcing in a Two-Dimensional Viscous Fluid  

Microsoft Academic Search

The tilting instability is an instability of a two-dimensional fluid that transforms convective motion into shear flow. As a generalization of previous analytical work on the tilting instability in an ideal fluid, the authors investigate the instability with thermal buoyancy included as a source supporting convection against viscous dissipation. The results show two distinct instabilities: for large Rayleigh numbers, the

Guennadi I. Soloviev; Vitali D. Shapiro; Richard C. J. Somerville; Boris Shkoller

1996-01-01

185

Displacement forces on a neutral current detector from a buoyant and flexible cable under tension  

SciTech Connect

As a means for maintaining order in the 112 NCD readout cables, it is proposed to put the cables under tension in such a way that they lie as straight as possible and rest along the top surface of the acrylic D{sub 2}O vessel. However, one aim is to avoid using top anchor points to secure the NCDs in the D{sub 2}O vessel, but rather to just let the counter`s inherent buoyancy maintain the necessary vertical orientation. As a result, applying a tension to the readout cable may pull the counters too far off of vertical. Whether or not the counter is pulled too far off of vertical depends in large part on the characteristics of the cable, i.e. modulus of elasticity and initial radius of curvature. Given that the applied tension in equilibrium is just equal to the restoring force on the counter when pulled off of vertical by some arbitrarily small amount, and given that the final radius of curvature of the readout cable is 6 meters (the radius of the D{sub 2}O vessel), what then must the modulus of elasticity be for a given initial radius of curvature of the cable? This assumes that the cable will be wrapped around a spool or somehow coiled for shipment. This also assumes that upon delivery of the cables, some effort can be made to straighten them out somewhat. For this approximation, the buoyancy of the cables is assumed to be negligible. The small length of cable that does not rest against the inner surface of the D{sub 2}O vessel is also neglected.

Walston, S.

1994-05-01

186

Buoyant Density Heterogeneity in Spores of Bacillus subtilis: Biochemical and Physiological Basis  

PubMed Central

The biochemical and physiological basis of density heterogeneity in Renografin of Bacillus subtilis W23 spores was determined by analysis of metals, macromolecules, and dipicolinic acid in the two density classes of the population. Germination rate and heat resistance were measured in both density classes. Atomic absorption spectrophotometry revealed that heavy spores (density = 1.335 g/ml) have 30% more calcium than light spores (density = 1.290 g/ml). Other metals found in greater amounts in heavy spores were manganese and potassium. However, light spores had more sodium than heavy spores. The amounts of carbohydrates, nucleic acids, and proteins were the same in both types of spores, but light spores contained more lipids, whereas heavy spores had 30% more dipicolinic acid than light spores. Calcium and lipid were excluded as causes of the heterogeneity in density in that alteration of their contents in spores did not detectably affect the density of these spores. Spores of two densities were genetically similar. Furthermore, light density spores arose earlier during sporulation than heavy spores as determined by releasing refractile forespores at various times during sporulation. We concluded that light spores represent an incomplete stage in development because they became heavy when reinoculated into spent sporulation medium. This must involve the additional accretion or synthesis of dipicolinic acid.

Dean, D. H.; Douthit, H. A.

1974-01-01

187

Pore-Scale Modeling of Reactive-Multiphase-Buoyant Flow for Carbon Capture and Storage  

Microsoft Academic Search

Physical and geochemical processes at multiple scales are yet to be understood for the storage of carbon dioxide (CO2) in aquifers and the concomitant mitigation of CO2 concentration in the atmosphere. In deep saline aquifers, the pores in the potential aquifers for CO2 storage are initially filled with saline water (brine). The entrapment of brine in pores after injection of

S. Anwar; J. A. Cunningham; M. Trotz; M. W. Thomas; M. Stewart

2010-01-01

188

Influence of Buoyant Convection on the Stability of Enclosed Laminar Flames  

NASA Technical Reports Server (NTRS)

An investigation of the stability limits of Enclosed Laminar Flames (ELF) was conducted in the Middeck Glovebox (MGBX) facility on the STS-87 Space Shuttle mission (November to December 1997). The primary objective of the ELF glovebox investigation is to determine the effect of buoyancy on the stability of round, laminar, gas-jet diffusion flames in a co-flow air duct. Comparison tests were conducted in normal gravity to allow isolation and identification of the influence of buoyancy. The results were used to map the lift-off and blow-out stability limits as a function of the fuel and air velocities for the two buoyancy conditions. Approximately 50 tests were conducted during the Space Shuttle mission, using a 50/50 mixture (volume basis) of methane and nitrogen as the fuel. The experimental results verified the hypothesis that substantially greater velocities are required to destabilize the flame in microgravity. The increase in air velocity required to induce lift off in microgravity (compared to normal gravity) was nearly equal to the increase required to induce blow out. Furthermore, the air velocity increase was relatively independent of the fuel flow, except at low fuel flows. At high fuel flows, it was found that the microgravity flames tend to immediately blow out after lift off. This is in agreement with the free-jet theory which suggests that stable lifted flames are not possible for fuels with a Schmidt number of 0.5

Brooker, John E.; Jia, Kezhong; Stocker, Dennis P.; Chen, Lea-Der

1999-01-01

189

An EOF analysis of HF Doppler radar current measurements of the Chesapeake Bay buoyant outflow  

Microsoft Academic Search

Surface currents measured by HF Doppler radar as part of a study of the Chesapeake Bay outflow plume are examined using a 'real-vector' empirical orthogonal function (EOF) analysis (Kaihatu et al., 1998). Based on about 23 days of nearly continuous data, the analysis shows that the first three EOF modes, judged to be the only significant modes, account for 76%

G. O. Marmorino; L. K. Shay; B. K. Haus; R. A. Handler; H. C. Graber; M. P. Horne

1999-01-01

190

An EOF analysis of HF Doppler radar current measurements of the Chesapeake Bay buoyant outflow  

Microsoft Academic Search

Surface currents measured by HF Doppler radar as part of a study of the Chesapeake Bay outflow plume are examined using a ‘real-vector’ empirical orthogonal function (EOF) analysis (Kaihatu et al., 1998). Based on about 23 days of nearly continuous data, the analysis shows that the first three EOF modes, judged to be the only significant modes, account for 76%

G. O. Marmorino; L. K. Shay; B. K. Haus; R. A. Handler; H. C. Graber; M. P. Horne

1999-01-01

191

Changes in Buoyant Density Relationships of Two Cell Types of 'Coxiella burneti' Phase I.  

National Technical Information Service (NTIS)

Coxiella burneti phase I, purified from a formalin-inactivated yolk-sac vaccine, was separated into two bands of morphologically distinct cell types when subjected to sucrose gradient centrifugation. Recycling of the less dense, rod-shaped cells in unbuff...

R. F. Wachter G. P. Briggs J. D. Gangemi C. E. Pedersen

1975-01-01

192

Buoyant production and consumption of turbulence kinetic energy in cloud-topped mixed layers  

NASA Technical Reports Server (NTRS)

It is pointed out that studies of the entraining planetary boundary layer (PBL) have generally emphasized the role of buoyancy fluxes in driving entrainment. The buoyancy flux is proportional to the rate of conversion of the potential energy of the mean flow into the kinetic energy of the turbulence. It is not unusual for conversion to proceed in both directions simultaneously. This occurs, for instance, in both clear and cloudy convective mixed layers which are capped by inversions. A partitioning of the net conversion into positive parts, generating turbulence kinetic energy (TKE), and negative parts (TKE-consuming), would make it possible to include the positive part in the gross production rate, and closure would be achieved. Three different approaches to partitioning have been proposed. The present investigation is concerned with a comparison of the three partitioning theories. Particular attention is given to the cloud-topped mixed layer because in this case the differences between two partitioning approaches are most apparent.

Randall, D. A.

1984-01-01

193

A particle sedimentation model of buoyant jets: observations of hydrothermal plumes  

NASA Astrophysics Data System (ADS)

Existing transport and sediment deposition models rarely use measured (rather than predicted) flow velocity and particle concentration data. We are developing a sediment deposition model using observed velocities and concentrations in order to model the deposition and transport of hydrothermal plume particles and biologic material. Our prior work developing acoustic imaging techniques to measure the static and dynamic properties of seafloor hydrothermal plumes provides the necessary input to the preliminary model. The general approach is to assume exponential settling of particles from the margins of the plume. Exponential settling states that the rate of decrease in the mass concentration C of sediment suspended in a layer of thickness h is given by dm/dt = -vCA/h, where v is the terminal velocity, C is the mass concentration of particles of given diameter, A is the basal area of the volume through which the settling occurs, and h is the thickness of the layer. Assuming the total thickness h is the height of the plume, the vertically integrated sedimented mass becomes: ?zdm/dz = ?z(vCA/w)/?z(1/w), where ?z(1/w) is the rise time over the region of interest and w is the local vertical velocity in a volume element. In this study, we calculate the terminal velocity (based on the estimated Reynolds number) and net force on the particles of a given size everywhere within the plume and its surroundings based on local velocity in gridded volume elements. In each volume element where the net force is negative (positive is upwards), the loss of sediment from the volume element is calculated. The loss of sediment is then summed vertically to determine the sediment mass deposited on the seafloor. The results for five particle sizes were then combined using three different assumed size distributions. This methodology is applied both to acoustic observations and to the output of an integral (time averaged) model of plume dynamics. Preliminary tests, using the predicted velocity and concentration from a integral model, produced the expected sedimentation maps, where larger grain sizes fall out near the vent, mean grain size decreases away from the vent and transport into the upper plume layers is greatest for the smallest particles. We also applied the sedimentation model to acoustic observations of hydrothermal plumes at Grotto Vent, on the Endeavour Segment of the Juan de Fuca Ridge. Acoustic backscatter data was used to infer particle concentration (as a function of assumed particle size); Doppler shifts in the same acoustic backscatter data were used to infer vertical velocity. The sedimentation model results showed decreasing mean particle size away from the vent. The mass sedimentation patterns are sensitive to the total mass available, which, as inferred from the volume backscattering strength, is also a function of particle size. Bending of the plume in local currents shifts the locus of sedimentation away from the vent, especially for smaller particle sizes. Future efforts will refine the basic settling model and incorporate predictions of the transport of biological material.

Bemis, K. G.; Silver, D.; Rona, P.; Cowen, J.

2005-12-01

194

Practical dispersion modelling for buoyant elevated sources in a tropical region  

NASA Astrophysics Data System (ADS)

The worst-case meteorological scenarios for the air pollution impact of coal-fired power stations located in tropical Australia are usually those of convective or seabreeze states. Under such conditions maximum hourly ground-level concentrations occur within 5 km of typical elevated sources and are potentially important unless either low sulphur coal is burnt (the usual situation for Australian coals) or restrictions are placed upon neighbouring land use. In such conditions even slightly complex surrounding terrain can cause major changes in surface and lower-level wind and turbulence characteristics, although the resultant effects on ground-level concentrations are probably relatively small. The monitoring data bases of an inland and a coastal power station in tropical Queensland give similar qualitative results to recent EPRI studies. Concurrent detailed meteorological measurements show that convective scaling techniques order both data sets in a satisfactory manner. The convective dispersion model of Spillane (1985, CSIRO internal report) has also shown more predictive skill than conventional approaches and emphasizes the importance of gathering vertical velocity statistics for most sites. Some of the forthcoming developments in related Australian dispersion work are outlined.

Best, P. R.; Stümer, L. J.

195

Buoyant low stretch stagnation point diffusion flames over a solid fuel  

NASA Astrophysics Data System (ADS)

Many diffusion flames in microgravity are subject to very low stretch. To study flame structure and extinction characteristics of these unusual flames, a normal gravity low-stretch diffusion flame is generated using a cylindrical PMMA sample of varying large radii. Solid-phase conductive heat loss was also varied by modifying the back surface boundary conditions on the samples. Burning rates, flame thickness and standoff distance, temperature profiles in the solid and gas, and radiative loss from the system were measured. A transition from the blowoff side of the flammability map to the quenching side of the flammability map is observed at approximately 7-8 secsp{-1}, as determined by the non-monotonic trends in peak temperatures, solid and gas-phase temperature gradients, and non-dimensional standoff distances. A unique local extinction flamelet phenomena and associated pre-extinction oscillations are observed at very low stretch. An ultimate quenching extinction limit is found at low stretch with sufficiently high induced heat losses. A surface energy balance reveals that the fraction of heat transfer from the flame that is lost to in-depth conduction and surface radiation increases with decreasing stretch until quenching extinction is observed. This is primarily due to decreased heat transfer from the flame. Applications of this work include fire safety in spacecraft where low velocity flows from spacecraft ventilation equipment or small cooling fans for electronic hardware can impinge upon flammable surface materials and create low stretch environments. Knowledge of the characteristics of these potential fires is vital to prompt detection and proper response to such events.

Olson, Sandra L.

196

Evaluation of the Split-H approach to modeling non-buoyant releases from vent stacks  

SciTech Connect

Position C.2.b of Regulatory Guide 1.111 describes an approach to modeling the diffusion of effluents from roof top vents and short stacks using an elevated plume model under some conditions and using a ground-level source building wake model under other conditions. The approach is sometimes called a Split-H model. This report presents the results of an evaluation of the technical basis for and utility of the concept behind the Split-H model, outlines the devlopment of an upgraded model with those estimated using the Regulatory Guide Split-H model and a ground-level building wake model, and discusses alternatives to the Regulatory Guide position that the NRC may wish to consider. Concentration comparisons are made using model results for meteorological data from 18 nuclear power plant sites.

Ramsdell, J.V.

1983-04-01

197

Engine cooling system air venting arrangement with buoyant air purge valve  

Microsoft Academic Search

An air vent arrangement is described for the cooling system of an automotive type engine having a radiator with a coolant inlet. The engine has coolant passages communicating with the radiator through an outlet essentially horizontally disposed, tubing connecting the radiator inlet and coolant outlet, and a thermostat in the outlet horizontally movable to open and closed positions. A horizontally

Schnizlein

1987-01-01

198

Evidence that platelet buoyant density, but not size, correlates with platelet age in man  

SciTech Connect

Following infusion of 51Cr-labeled autologous platelets into normal subjects, high-density (HD) and low-density (LD) platelet cohorts were isolated by prolonged centrifugation in isosmotic arabino-galactan (Stractan). Specific radio-activity of LD platelets declined rapidly post-infusion (T1/2 . 1.5 days), but specific radioactivity of HD platelets remained constant or increased over a 3--4-day period and gradually declined for 6--7 days thereafter. These differences were exaggerated when platelet cohorts enriched in LD or HD cells by slow centrifugation in high-density albumin were labeled and transfused. Mean survival of a platelet cohort enriched with HD cells was significantly (P less than 0.02) shorter (7.73 days) than that of a cohort enriched with LD cells (9.33) days). In normal subjects treated with aspirin, capacity for thromboxane synthesis was regained more rapidly (P less than 0.05) in LD than in HD platelets. HD and LD platelets differed only slightly in mean volume (HD platelets . 7.57 mu3, LD platelets . 6.87 mu3, 0.05 less than P less than 0.01). We believe the most logical interpretation of these findings is that under normal conditions in man, newly formed platelets are less dense on the average than total platelets and become more dense as they age in the circulation. Thus, specific radioactivity of LD platelets declines rapidly as these platelets move into a more dense compartment and are replaced by newly formed, unlabelled cells; specific radioactivity of HD platelets remains constant or increases as labelled platelets enter this compartment in numbers equal to or greater than the number leaving it at the end of their life span. The similarity in mean volumes of LD and HD platelets suggests that platelet size is unrelated to platelet age under normal conditions.

Mezzano, D.; Hwang, K.; Catalano, P.; Aster, R.H.

1981-01-01

199

Spatiotemporal chaos in the dynamics of buoyantly and diffusively unstable chemical fronts.  

PubMed

Nonlinear dynamics resulting from the interplay between diffusive and buoyancy-driven Rayleigh-Taylor (RT) instabilities of autocatalytic traveling fronts are analyzed numerically for various values of the relevant parameters. These are the Rayleigh numbers of the reactant A and autocatalytic product B solutions as well as the ratio D=D(B)/D(A) between the diffusion coefficients of the two key chemical species. The interplay between the coarsening dynamics characteristic of the RT instability and the constant short wavelength modulation of the diffusive instability can lead in some regimes to complex dynamics dominated by irregular succession of birth and death of fingers. By using spectral entropy measurements, we characterize the transition between order and spatial disorder in this system. The analysis of the power spectrum and autocorrelation function, moreover, identifies similarities between the various spatial patterns. The contribution of the diffusive instability to the complex dynamics is discussed. PMID:22463010

Baroni, M P M A; Guéron, E; De Wit, A

2012-03-01

200

Comparison of fish catches with buoyant pop nets and seines in vegetated and nonvegetated habitats  

USGS Publications Warehouse

Two models of pop nets were developed to sample fish in shallow riverine waters, one for use in vegetated areas and the other for nonvegetated areas. Both nets have a mechanical release mechanism that can be tripped from the water surface. Replicated field tests were conducted to compare pop-net catches with bag-seine collections every 2 weeks from May through mid-October. Overall, total catch per effort did not vary significantly (P 2) was smaller than the area swept by the average seine haul (70-140 m2). The pop net effectively sampled fish in shallow nonvegetated habitats and was useful in heavily vegetated areas where seining or electroshocking was difficult.

Dewey, M. R.; Holland-Bartels, L. E.; Zigler, S. J.

1989-01-01

201

Long-Lived, Maneuverable, Semi-Buoyant Platform for Venus Upper Atmosphere Exploration  

NASA Astrophysics Data System (ADS)

This presentation discusses the continued development of the Northrop Grumman/L’GARDE team’s long-lived, maneuverable platform to explore the Venus upper atmosphere. It focuses on the overall mission architecture and concept of operations.

Lee, G.; Sokol, D.; Polidan, R.; Bolisay, L.; Barnes, N.

2014-06-01

202

A buoyant tornado-probe concept incorporating an inverted lifting device. [and balloon combination  

NASA Technical Reports Server (NTRS)

Addition of an inverted lifting device to a simple balloon probe is shown to make possible low-altitude entry to tornado cores with easier launch conditions than for the simple balloon probe. Balloon-lifter combinations are particularly suitable for penetration of tornadoes with average to strong circulation, but tornadoes of less than average circulation which are inaccessible to simple balloon probes become accessible. The increased launch radius which is needed for access to tornadoes over a wide range of circulation results in entry times of about 3 minutes. For a simple balloon probe the uninflated balloon must be first dropped on, or near, the track of the tornado from a safe distance. The increase in typical launch radius from about 0.75 kilometer to slightly over 1.0 kilometer with a balloon-lifter combination suggests that a direct air launch may be feasible.

Grant, F. C.

1973-01-01

203

A new concept: the use of neutrally-buoyant microemulsions for DNAPL remediation  

Microsoft Academic Search

Even in the absence of mobilization of dense nonaqueous phase liquid (DNAPL), the microemulsion that forms when the surfactant solubilizes a dense contaminant such as trichloroethylene will be more dense than water and tends to migrate downward. This paper addresses the issue of migration with a new concept: surfactant enhanced aquifer remediation at neutral buoyancy. Laboratory results of surfactant remediation

K. Kostarelos; G. A Pope; B. A Rouse; G. M Shook

1998-01-01

204

72 FR 48717 - Self-Regulatory Organizations; NYSE Arca, Inc.; Notice of Filing of Proposed Rule Change Relating...  

Federal Register 2010, 2011, 2012, 2013

...22 additional classes are: SPDR S&P 500 (SPY), Apple Inc. (AAPL), Altria Group (MO), Dendreon Corp. (DNDN), Amgen Inc. (AMGN), Yahoo! Inc. (YHOO), Qualcomm Inc. (QCOM), General Motors (GM), Energy Select Sector SPDR...

2007-08-24

205

72 FR 56396 - Self-Regulatory Organizations; American Stock Exchange LLC; Order Granting Accelerated Approval...  

Federal Register 2010, 2011, 2012, 2013

...options classes to the Pilot: SPDRs (SPY); Apple, Inc. (AAPL); Altria Group Inc. (MO); Dendreon Corp. (DNDN); Amgen Inc. (AMGN); Yahoo! Inc. (YHOO); QUALCOMM Inc. (QCOM); General Motors Corporation (GM); Energy Select...

2007-10-03

206

72 FR 56429 - Self-Regulatory Organizations; Philadelphia Stock Exchange, Inc.; Order Granting Approval to a...  

Federal Register 2010, 2011, 2012, 2013

...options classes to the Pilot: SPDRs (SPY); Apple, Inc. (AAPL); Altria Group Inc. (MO); Dendreon Corp. (DNDN); Amgen Inc. (AMGN); Yahoo! Inc. (YHOO); QUALCOMM Inc. (QCOM); General Motors Corporation (GM); Energy Select...

2007-10-03

207

72 FR 46691 - Self-Regulatory Organizations; Boston Stock Exchange, Inc.; Notice of Filing of Proposed Rule...  

Federal Register 2010, 2011, 2012, 2013

...classes would be as follows: SPDRs (SPY); Apple, Inc. (AAPL); Altria Group Inc. (MO); Dendreon Corp. (DNDN); Amgen Inc. (AMGN); Yahoo! Inc. (YHOO); QUALCOMM Inc. (QCOM); General Motors Corporation (GM); Energy Select...

2007-08-21

208

73 FR 18013 - Self-Regulatory Organizations; Boston Stock Exchange, Inc.; Notice of Filing and Immediate...  

Federal Register 2010, 2011, 2012, 2013

...September 28, 2007: SPY (SPDRs), AAPL (Apple, Inc.), MO (Altria Group Inc.), DNDN (Dendreon Corp.), AMGN (Amgen Inc.), YHOO (Yahoo! Inc.), QCOM (QUALCOMM Inc.), GM (General Motors Corporation), XLE (Energy Select...

2008-04-02

209

74 FR 14829 - Self-Regulatory Organizations; The NASDAQ Stock Market LLC; Notice of Filing and Immediate...  

Federal Register 2010, 2011, 2012, 2013

...options classes were added: SPDRs (SPY); Apple, Inc. (AAPL); Altria Group Inc. (MO); Dendreon Corp. (DNDN); Amgen Inc. (AMGN); Yahoo! Inc. (YHOO); QUALCOMM Inc. (QCOM); General Motors Corporation (GM); Energy Select...

2009-04-01

210

72 FR 56403 - Self-Regulatory Organizations; Chicago Board Options Exchange, Incorporated; Order Granting...  

Federal Register 2010, 2011, 2012, 2013

...options classes to the Pilot: SPDRs (SPY); Apple, Inc. (AAPL); Altria Group Inc. (MO); Dendreon Corp. (DNDN); Amgen Inc. (AMGN); Yahoo! Inc. (YHOO); QUALCOMM Inc. (QCOM); General Motors Corporation (GM); Energy Select...

2007-10-03

211

72 FR 56400 - Self-Regulatory Organizations; Boston Stock Exchange, Inc.; Order Granting Approval to a Proposed...  

Federal Register 2010, 2011, 2012, 2013

...options classes to the Pilot: SPDRs (SPY); Apple, Inc. (AAPL); Altria Group Inc. (MO); Dendreon Corp. (DNDN); Amgen Inc. (AMGN); Yahoo! Inc. (YHOO); QUALCOMM Inc. (QCOM); General Motors Corporation (GM); Energy Select...

2007-10-03

212

72 FR 56412 - Self-Regulatory Organizations; International Securities Exchange, LLC; Order Granting Accelerated...  

Federal Register 2010, 2011, 2012, 2013

...options classes to the Pilot: SPDRs (SPY); Apple, Inc. (AAPL); Altria Group Inc. (MO); Dendreon Corp. (DNDN); Amgen Inc. (AMGN); Yahoo! Inc. (YHOO); QUALCOMM Inc. (QCOM); General Motors Corporation (GM); Energy Select...

2007-10-03

213

The effect of neutrally buoyant finite-size particles on channel flows in the laminar-turbulent transition regime  

NASA Astrophysics Data System (ADS)

The presence of finite-size particles in a channel flow close to the laminar-turbulent transition is simulated with the Force Coupling Method which allows two-way coupling with the flow dynamics. Spherical particles with channel height-to-particle diameter ratio of 16 are initially randomly seeded in a fluctuating flow above the critical Reynolds number corresponding to single phase flow relaminarization. When steady-state is reached, the particle volume fraction is homogeneously distributed in the channel cross-section (? ? 5%) except in the near-wall region where it is larger due to inertia-driven migration. Turbulence statistics (intensity of velocity fluctuations, small-scale vortical structures, wall shear stress) calculated in the fully coupled two-phase flow simulations are compared to single-phase flow data in the transition regime. It is observed that particles increase the transverse r.m.s. flow velocity fluctuations and they break down the flow coherent structures into smaller, more numerous and sustained eddies, preventing the flow to relaminarize at the single-phase critical Reynolds number. When the Reynolds number is further decreased and the suspension flow becomes laminar, the wall friction coefficient recovers the evolution of the laminar single-phase law provided that the suspension viscosity is used in the Reynolds number definition. The residual velocity fluctuations in the suspension correspond to a regime of particulate shear-induced agitation.

Loisel, Vincent; Abbas, Micheline; Masbernat, Olivier; Climent, Eric

2013-12-01

214

A General Computational Approach for Magnetohydrodynamic Flows Using the CFX Code: Buoyant Flow Through a Vertical Square Channel  

SciTech Connect

The buoyancy-driven magnetoconvection in the cross section of an infinitely long vertical square duct is investigated numerically using the CFX code package. The implementation of a magnetohydrodynamic (MHD) problem in CFX is discussed, with particular reference to the Lorentz forces and the electric potential boundary conditions for arbitrary electrical conductivity of the walls. The method proposed is general and applies to arbitrary geometries with an arbitrary orientation of the magnetic field. Results for fully developed flow under various thermal boundary conditions are compared with asymptotic analytical solutions. The comparison shows that the asymptotic analysis is confirmed for highly conducting walls as high velocity jets occur at the side walls. For weakly conducting walls, the side layers become more conducting than the side walls, and strong electric currents flow within these layers parallel to the magnetic field. As a consequence, the velocity jets are suppressed, and the core solution is only corrected by the viscous forces near the wall. The implementation of MHD in CFX is achieved.

Di Piazza, Ivan; Buehler, Leo

2000-09-15

215

Investigation of a co-flowing buoyant jet - Experiments on the effect of Reynolds number and Richardson number  

NASA Technical Reports Server (NTRS)

The behavior of a vertical jet of helium issuing into a co-flow of air at a fixed exit velocity ratio of 2 was investigated experimentally over a wide range of governing parameters with emphasis on flow structure and the scaling properties of the natural frequency of the jet. The experiments were conducted in a variable-pressure facility, which made it possible to vary the Reynolds number and the Richardson number independently. At all the experimental conditions studied, the flow exhibits a strong self-excited periodicity. A buoyancy Strouhal number is defined and used to correlate frequency data from the approximately seventy different Reynolds and Richardson numbers studied. The buoyancy Strouhal number is found to be nearly independent of Reynolds number and Richardson number for Richardson numbers greater than one.

Subbarao, E. R.; Cantwell, B. J.

1992-01-01

216

Investigation of a co-flowing buoyant jet - Experiments on the effect of Reynolds number and Richardson number  

Microsoft Academic Search

The behavior of a vertical jet of helium issuing into a co-flow of air at a fixed exit velocity ratio of 2 was investigated experimentally over a wide range of governing parameters with emphasis on flow structure and the scaling properties of the natural frequency of the jet. The experiments were conducted in a variable-pressure facility, which made it possible

E. R. Subbarao; B. J. Cantwell

1992-01-01

217

Investigation of a co-flowing buoyant jet - Experiments on the effect of Reynolds number and Richardson number  

NASA Astrophysics Data System (ADS)

The behavior of a vertical jet of helium issuing into a co-flow of air at a fixed exit velocity ratio of 2 was investigated experimentally over a wide range of governing parameters with emphasis on flow structure and the scaling properties of the natural frequency of the jet. The experiments were conducted in a variable-pressure facility, which made it possible to vary the Reynolds number and the Richardson number independently. At all the experimental conditions studied, the flow exhibits a strong self-excited periodicity. A buoyancy Strouhal number is defined and used to correlate frequency data from the approximately seventy different Reynolds and Richardson numbers studied. The buoyancy Strouhal number is found to be nearly independent of Reynolds number and Richardson number for Richardson numbers greater than one.

Subbarao, E. R.; Cantwell, B. J.

1992-12-01

218

The effects of Reynolds number and Richardson number on the structure of a vertical co-flowing buoyant jet  

Microsoft Academic Search

The behavior of a vertical jet of helium issuing into a coflow of air at a fixed exit velocity ratio of 2.0 has been studied for various Reynolds numbers and Richardson numbers. It is found that the transition to turbulence is very sudden and that the point of transition moves closer to the jet exit as either the Reynolds number

E. R. Subbarao

1989-01-01

219

A Semi-Analytic Model of a Buoyant Flame Bubble Propagation During the Deflagration Phase of a Type Ia Supernova  

NASA Astrophysics Data System (ADS)

Type Ia supernovae are astronomical events in which a white dwarf, the cold remnant of a star that has exhausted its hydrogen fuel, detonates and briefly produces an explosion brighter than most galaxies. Many researchers think that they could occur as the white dwarf approaches a critical mass of 1.4 solar masses by accreting matter from a companion main sequence star, a scenario that is referred to as the single-degenerate channel. Assuming such a progenitor, we construct a semi-analytic model of the propagation of a flame bubble ignited at a single off-center point within the white dwarf. The bubble then rises under the influences of buoyancy and drag, burning the surrounding fuel material in a process called deflagration. We contrast the behavior of the deflagration phase in the presence of a physically high Reynolds number regime with the low Reynolds number regimes inherent to three-dimensional simulations, which are a consequence of numerical viscosity. Our work may help validate three-dimensional deflagration results over a range of initial conditions.

Jumper, Kevin; Fisher, Robert

2012-03-01

220

Numerical study of wall effects on buoyant gas-bubble rise in a liquid-filled finite cylinder  

PubMed Central

The wall effects on the axisymmetric rise and deformation of an initially spherical gas bubble released from rest in a liquid-filled, finite circular cylinder are numerically investigated. The bulk and gas phases are considered incompressible and immiscible. The bubble motion and deformation are characterized by the Morton number (Mo), Eötvös number (Eo), Reynolds number (Re), Weber number (We), density ratio, viscosity ratio, the ratios of the cylinder height and the cylinder radius to the diameter of the initially spherical bubble (H* = H/d0, R* = R/d0). Bubble rise in liquids described by Eo and Mo combinations ranging from (1,0.01) to (277.5,0.092), as appropriate to various terminal state Reynolds numbers (ReT) and shapes have been studied. The range of terminal state Reynolds numbers includes 0.02 < ReT < 70. Bubble shapes at terminal states vary from spherical to intermediate spherical-cap–skirted. The numerical procedure employs a front tracking finite difference method coupled with a level contour reconstruction of the front. This procedure ensures a smooth distribution of the front points and conserves the bubble volume. For the wide range of Eo and Mo examined, bubble motion in cylinders of height H* = 8 and R* ? 3, is noted to correspond to the rise in an infinite medium, both in terms of Reynolds number and shape at terminal state. In a thin cylindrical vessel (small R*), the motion of the bubble is retarded due to increased total drag and the bubble achieves terminal conditions within a short distance from release. The wake effects on bubble rise are reduced, and elongated bubbles may occur at appropriate conditions. For a fixed volume of the bubble, increasing the cylinder radius may result in the formation of well-defined rear recirculatory wakes that are associated with lateral bulging and skirt formation. The paper includes figures of bubble shape regimes for various values of R*, Eo, Mo, and ReT. Our predictions agree with existing results reported in the literature.

Mukundakrishnan, Karthik; Quan, Shaoping; Eckmann, David M.; Ayyaswamy, Portonovo S.

2009-01-01

221

Buoyant thermocapillary flow with nonuniform supra-heating. I - Liquid-phase behavior. II - Two-phase behavior  

SciTech Connect

The present computational study of transient heat transfer and fluid flow in a circular pool of n-decane which is undergoing central radiative heating from above gives attention to the volumetric absorption of the radiation incident on the pool surface. The first part of this study notes that buoyancy influences the number and recirculation rates of the subsurface vortices by stabilizing hot subsurface fluid above the colder core fluid; this affects the liquid surface temperature profile and in turn governs the velocity profile that is due to thermocapillarity. In the second part, the effects of gas-liquid phase coupling, variable density and thermophysical properties, and vaporization are considered. 49 refs.

Schiller, D.N.; Sirignano, W.A. (California, University, Irvine (United States))

1992-03-01

222

Is the 'Fast Halo' around Hawaii as imaged in the PLUME experiment direct evidence for buoyant plume-fed asthenosphere?  

Microsoft Academic Search

An intriguing spatial pattern of variations in shear-wave arrival times has been mapped in the PLUME ocean bottom experiment (Wolfe et al., 2009) around Hawaii. The pattern consists of a halo of fast travel times surrounding a disk of slow arrivals from waves traveling up though the plume. We think it is directly sensing the pattern of dynamic uplift of

J. P. Morgan; C. Shi; J. Hasenclever

2010-01-01

223

Ranitidine Hydrochloride-loaded Ethyl Cellulose and Eudragit RS 100 Buoyant Microspheres: Effect of pH Modifiers  

PubMed Central

A floating type of dosage form of ranitidine hydrochloride in the form of microspheres capable of floating on simulated gastric fluid was prepared by solvent evaporation technique. Microspheres prepared with ethyl cellulose, Eudragit® RS100 alone or in combination were evaluated for percent yield, drug entrapment, percent buoyancy and drug release and the results demonstrated satisfactory performance. Microspheres exhibited ranitidine hydrochloride release influenced by changing ranitidine hydrochloride-polymer and ranitidine hydrochloride-polymer-polymer ratio. Incorporation of a pH modifier has been the usual strategy employed to enhance the dissolution rate of weakly basic drug from floating microspheres. Further citric acid, fumaric acid, tartaric acid were employed as pH modifiers. Microspheres prepared with ethyl cellulose, Eudragit® RS100 and their combination that showed highest release were utilized to study the effect of pH modifiers on ranitidine hydrochloride release from microspheres which is mainly affected due to modulation of microenvironmental pH. In vitro release of ranitidine hydrochloride from microspheres into simulated gastric fluid at 37° showed no significant burst effect. However the amount of release increased with time and significantly enhanced by pH modifiers. 15% w/w concentration of fumaric acid provide significant drug release from ranitidine hydrochloride microspheres prepared with ranitidine hydrochloride:ethyl cellulose (1:3), ranitidine hydrochloride:Eudragit® RS100 (1:2) and ranitidine hydrochloride:ethyl cellulose:Eudragit® RS100 (1:2:1) whereas citric acid, tartaric acid showed significant cumulative release at 20% w/w. In all this study suggest that ethyl celluose, Eudragit® RS100 alone or in combination with added pH modifiers can be useful in floating microspheres which can be proved beneficial to enhance the bioavailability of ranitidine hydrochloride.

Kotagale, N. R.; Parkhe, A. P.; Jumde, A. B.; Khandelwal, H. M.; Umekar, M. J.

2011-01-01

224

72 FR 47096 - Self-Regulatory Organizations; Chicago Board Options Exchange, Incorporated; Notice of Filing of...  

Federal Register 2010, 2011, 2012, 2013

...Group, Inc. (MO/MO) Financial Select Sector SPDR (XLF/XLF) Dendreon Corp. (DNDN/UKO) AT&T, Inc. (T/T) Amgen Inc. (AMGN/AMQ) Citigroup, Inc. (C/C) Yahoo! Inc. (YHOO/YHQ) Amazon.com Inc. (AMZN/ZQN) Qualcomm...

2007-08-22

225

Photocatalytic oxidation of aqueous trichloroethylene using dye sensitized buoyant photocatalyst monitored via micro-headspace solid-phase microextration gas chromatography\\/electron capture detection and mass spectrometry  

Microsoft Academic Search

Trichloroethylene (TCE), a useful industrial agent which unfortunately exhibits carcinogenic properties, has become an extremely prevalent environmental contaminant. As such, new rapid, sensitive, and cost effective detection methods are needed for the identification of potential point sources of contamination. A new analytic micro-headspace method is described, utilizing solid phase micro-extraction (SPME) fibers and routine gas chromatography\\/electron capture detection (GC\\/ECD) for

Matt V. Alexander; Jeffrey J. Rosentreter

2008-01-01

226

46 CFR 160.049-4 - Construction and workmanship.  

Code of Federal Regulations, 2013 CFR

... LIFESAVING EQUIPMENT Specification for a Buoyant Cushion Plastic Foam § 160.049-4 Construction and workmanship. ...covers buoyant cushions of the box type filled with unicellular plastic foam buoyant material. Such cushions consist...

2013-10-01

227

33 CFR 175.23 - Serviceable condition.  

Code of Federal Regulations, 2013 CFR

...that has become hardened, non-resilient, permanently compressed, waterlogged, oil-soaked, or which shows evidence of fungus or mildew; or (3) Loss of buoyant material or buoyant material that is not securely held in position. (c) In...

2013-07-01

228

46 CFR 160.049-7 - Procedure for approval.  

Code of Federal Regulations, 2013 CFR

... LIFESAVING EQUIPMENT Specification for a Buoyant Cushion Plastic Foam § 160.049-7 Procedure for approval. (a) Group...granted separately to each manufacturer for each unicellular plastic foam buoyant cushion he proposes to manufacture which...

2013-10-01

229

46 CFR 160.049-6 - Marking.  

Code of Federal Regulations, 2010 CFR

... Specification for a Buoyant Cushion Plastic Foam § 160.049-6 Marking. ...following information clearly marked in waterproof lettering: (1) In letters that...buoyant cushions shall be sufficiently waterproof so that after 72 hours...

2009-10-01

230

46 CFR 160.049-6 - Marking.  

Code of Federal Regulations, 2010 CFR

... Specification for a Buoyant Cushion Plastic Foam § 160.049-6 Marking. ...following information clearly marked in waterproof lettering: (1) In letters that...buoyant cushions shall be sufficiently waterproof so that after 72 hours...

2010-10-01

231

46 CFR 160.052-8 - Marking.  

Code of Federal Regulations, 2010 CFR

...Buoyant Vest, Unicellular Plastic Foam, Adult and Child ...information clearly marked in waterproof lettering that can be read... (Lot No.) (b) Waterproof marking. Marking for buoyant vests shall be sufficiently waterproof so that after 72 hours...

2010-10-01

232

46 CFR 160.052-8 - Marking.  

Code of Federal Regulations, 2010 CFR

...Buoyant Vest, Unicellular Plastic Foam, Adult and Child ...information clearly marked in waterproof lettering that can be read... (Lot No.) (b) Waterproof marking. Marking for buoyant vests shall be sufficiently waterproof so that after 72 hours...

2009-10-01

233

CONSEQUENCES OF NON-LINEAR DENSITY EFFECTS ON BUOYANCY AND PLUME BEHAVIOR  

EPA Science Inventory

Aquatic plumes, as turbulent streams, grow by entraining ambient water. Buoyant plumes rise and dense ones sink, but, non-linear kinetic effects can reverse the buoyant force in mid-phenomenon. The class of nascent-density plumes begin as buoyant, upwardly accelerating plumes tha...

234

Development of floating rafts after the rewetting of cut-over bogs: the importance of peat quality  

Microsoft Academic Search

The usual method of restoring cut-over bogs is to rewet the peat surface, but this often leads to the remaining peat layers being deeply inundated. For Sphagnum-dominated vegetation to develop at deeply inundated locations, it is important for floating rafts of buoyant residual peat to develop. In this study, the chemical and physical characteristics of buoyant and inundated peat collected

Hilde B. M. Tomassen; Alfons J. P. Smolders; Leon P. M. Lamers; Jan G. M. Roelofs

2005-01-01

235

Lighter-Than-Air System Enhanced with Kinetic Lift.  

National Technical Information Service (NTIS)

A hybrid airship system is proposed in which the buoyant lift is enhanced with kinetic lift. The airship would consist of twin hulls in which the buoyant gas is contained. The twin hulls would be connected in parallel by a wing having an airfoil contour. ...

M. L. Spearman

2002-01-01

236

46 CFR 160.047-4 - Construction.  

Code of Federal Regulations, 2013 CFR

...glass-filled pads for Models AF-1, CFM-1, and CFS-1. The buoyant pad inserts for Models AF-1, CFM-1, and CFS-1 buoyant vests shall be filled with...minimum) Model CFM-1 (minimum) Model CFS-1 (minimum) Ounces Ounces...

2013-10-01

237

46 CFR 160.062-3 - Materials, construction, workmanship, and performance requirements.  

Code of Federal Regulations, 2010 CFR

...160.062-1(b). (b) Buoyant load capacity. A hydraulic release working in conjunction with its spring-tensioned gripe must demonstrate that it can release buoyant loads between the limits of 200 pounds and 3,750 pounds and within the...

2010-10-01

238

46 CFR 160.062-3 - Materials, construction, workmanship, and performance requirements.  

Code of Federal Regulations, 2010 CFR

...160.062-1(b). (b) Buoyant load capacity. A hydraulic release working in conjunction with its spring-tensioned gripe must demonstrate that it can release buoyant loads between the limits of 200 pounds and 3,750 pounds and within the...

2009-10-01

239

Ocean wave energy converter  

Microsoft Academic Search

A device for converting the energy of ocean waves into electricity, comprises a buoyant body that floats on the surface of the water and rises and falls with the waves. Fixedly secured to the buoyant body at a depth in the region of still water not affected by the waves, is a bucket wheel or bucket chain which will accordingly

1982-01-01

240

The gas content and buoyancy of strombolian ash plumes  

Microsoft Academic Search

Plinian plumes erupt with a bulk density greater than that of air, and depend upon air entrainment during their gas-thrust phase to become buoyant; if entrainment is insufficient, the column collapses into a potentially deadly pyroclastic flow. This study shows that strombolian ash plumes can be erupted in an initially buoyant state due to their extremely high initial gas content,

Matthew Patrick

2007-01-01

241

Parametric study of modern airship productivity  

NASA Technical Reports Server (NTRS)

A method for estimating the specific productivity of both hybrid and fully buoyant airships is developed. Various methods of estimating structural weight of deltoid hybrids are discussed and a derived weight estimating relationship is presented. Specific productivity is used as a figure of merit in a parametric study of fully buoyant ellipsoidal and deltoid hybrid semi-buoyant vehicles. The sensitivity of results as a function of assumptions is also determined. No airship configurations were found to have superior specific productivity to transport airplanes.

Ardema, M. D.; Flaig, K.

1980-01-01

242

46 CFR 25.25-13 - Personal flotation device lights.  

Code of Federal Regulations, 2013 CFR

...UNINSPECTED VESSELS REQUIREMENTS Life Preservers and Other Lifesaving...with § 25.25-5(e), each life preserver, each marine buoyant device intended to be...shoulder area of the immersion suit, life preserver, or other personal...

2013-10-01

243

46 CFR 25.25-15 - Retroreflective material for personal flotation devices.  

Code of Federal Regulations, 2013 CFR

...HOMELAND SECURITY UNINSPECTED VESSELS REQUIREMENTS Life Preservers and Other Lifesaving Equipment § 25...material for personal flotation devices. (a) Each life preserver, each marine buoyant device intended to be worn, and each...

2013-10-01

244

Effects of the pressure perturbation field in numerical models of unidirectionally sheared thunderstorm convection - Two versus three dimensions  

NASA Technical Reports Server (NTRS)

The physical roles of 'buoyant' and 'dynamic' pressure components, and the distinction between buoyant and hydrostatic pressure perturbations, are aspects of the pressure perturbation field in strongly sheared convective storms studied by means of two- and three-dimensional anelastic numerical modeling experiments with common environmental profiles. The pressure analysis clarifies the differences between two- and three-dimensional storms. In the main updraft, strong midlevel thermal buoyancy is partly opposed by a downward-perturbed vertical pressure gradient force. This, however, occurs to a much greater extent in two dimensions than in three, contributing to smaller net upward accelerations. While the buoyant and hydrostatic fields are intimately related to the total buoyancy distribution, the buoyant pressure perturbation is smoother and of lower amplitude than its hydrostatic counterpart. For the model experiments, this distinction is far greater in three dimensions than in two, in association with the smaller scale of the active convection in three dimensions.

Schlesinger, R. E.

1984-01-01

245

46 CFR 160.064-2 - Types and models.  

Code of Federal Regulations, 2013 CFR

...2013-10-01 false Types and models. 160.064-2 Section...CONTINUED) EQUIPMENT, CONSTRUCTION, AND MATERIALS: SPECIFICATIONS...160.064-2 Types and models. (a) Types. Water...intended to be thrown. (b) Models. Water safety buoyant...

2013-10-01

246

Summer Study Program in Geophysical Fluid Dynamics-The Influence of Convection on Large-Scale Circulations-1988.  

National Technical Information Service (NTIS)

Contents: Review of Dry Convection; Other Buoyant Plumes and Thermals; Global Convection; Moist Thermodynamics; Non Precipitating Cloud; Taxonomy of Precipitating Clouds; The Dynamics of precipitating Convection; Tropical Cyclones: Observations and Energe...

G. R. Flierl P. J. Goulart

1989-01-01

247

46 CFR 160.010-10 - Independent laboratory.  

Code of Federal Regulations, 2010 CFR

... false Independent laboratory. 160.010-10...EQUIPMENT Buoyant Apparatus for Merchant Vessels...010-10 Independent laboratory. (a) The approval...conducted by an independent laboratory accepted by the...

2009-10-01

248

46 CFR 160.010-10 - Independent laboratory.  

Code of Federal Regulations, 2010 CFR

... false Independent laboratory. 160.010-10...EQUIPMENT Buoyant Apparatus for Merchant Vessels...010-10 Independent laboratory. (a) The approval...conducted by an independent laboratory accepted by the...

2010-10-01

249

50 CFR 27.33 - Water skiing.  

Code of Federal Regulations, 2013 CFR

...Guard approved ski belts, life jackets or buoyant vests. (e) Water skiing is prohibited within 300 feet of harbors, swimming beaches, and mooring areas, and within 100 feet of any designated swimming...

2013-10-01

250

46 CFR 160.052-3 - Materials-standard vests.  

Code of Federal Regulations, 2013 CFR

...Specification for a Buoyant Vest, Unicellular Plastic Foam, Adult and Child § 160.052-3 Materials...in the finished product. (b) Unicellular plastic foam. The unicellular plastic foam shall be all new material complying...

2013-10-01

251

46 CFR 164.015-5 - Procedure for acceptance.  

Code of Federal Regulations, 2013 CFR

...SPECIFICATIONS AND APPROVAL MATERIALS Plastic Foam, Unicellular, Buoyant, Sheet and...Procedure for acceptance. (a) Unicellular plastic foam is not subject to formal approval...manufacturer. (c) Acceptance of unicellular plastic foam prior to being incorporated...

2013-10-01

252

User's Guide for the CALPUFF Dispersion Model.  

National Technical Information Service (NTIS)

This report describes the CALPUFF dispersion model and associated processing programs. The CALPUFF model described in this report reflect improvements to the model including (1) new modules to treat buoyant rise and dispersion from area sources (such as f...

1995-01-01

253

46 CFR 169.556 - Work vests.  

Code of Federal Regulations, 2013 CFR

...2013-10-01 2013-10-01 false Work vests. 169.556 Section 169.556 Shipping COAST GUARD, DEPARTMENT OF HOMELAND...Firefighting Equipment Additional Lifesaving Equipment § 169.556 Work vests. (a) Buoyant work...

2013-10-01

254

46 CFR 160.064-4 - Marking.  

Code of Federal Regulations, 2013 CFR

...buoyant device must have the following information clearly marked in waterproof lettering: (1) For devices to be worn: (Type II or Type III) Personal Flotation Device. Inspected and tested in accordance with U.S. Coast Guard...

2013-10-01

255

46 CFR 164.015-3 - Material and workmanship.  

Code of Federal Regulations, 2010 CFR

...2009-10-01 false Material and workmanship. 164.015-3 Section 164.015-3 Shipping COAST GUARD, DEPARTMENT OF HOMELAND...Unicellular, Buoyant, Sheet and Molded Shape § 164.015-3 Material and workmanship. (a) The...

2009-10-01

256

46 CFR 164.015-4 - Inspections and tests.  

Code of Federal Regulations, 2010 CFR

...2009-10-01 false Inspections and tests. 164.015-4 Section 164.015-4 Shipping COAST GUARD, DEPARTMENT OF HOMELAND...Unicellular, Buoyant, Sheet and Molded Shape § 164.015-4 Inspections and tests. (a)...

2009-10-01

257

46 CFR 164.015-3 - Material and workmanship.  

Code of Federal Regulations, 2010 CFR

...2010-10-01 false Material and workmanship. 164.015-3 Section 164.015-3 Shipping COAST GUARD, DEPARTMENT OF HOMELAND...Unicellular, Buoyant, Sheet and Molded Shape § 164.015-3 Material and workmanship. (a) The...

2010-10-01

258

46 CFR 160.171-1 - Scope.  

Code of Federal Regulations, 2013 CFR

...child insulated, buoyant immersion suits that are designed to prevent shock upon entering cold water and lessen the effect of hypothermia (extreme body heat loss due to immersion in cold water). Immersion suits approved under this subpart will meet the...

2013-10-01

259

Exploration of the North Atlantic Current and Its Recirculation in the Newfoundland Basin Using SOFAR Floats.  

National Technical Information Service (NTIS)

Trajectories and time series of velocity, temperature, and pressure are presented for 13 neutrally-buoyant, acoustically tracked (SOFAR) floats that were launched in May and June, 1986 in the Newfoundland Basin by the Woods Hole Oceanographic Institution ...

W. B. Owens M. E. Zemanovic

1990-01-01

260

46 CFR 164.013-4 - Samples submitted for acceptance.  

Code of Federal Regulations, 2013 CFR

...AND MATERIALS: SPECIFICATIONS AND APPROVAL MATERIALS Foam, Unicellular Polyethylene (Buoyant, Slab, Slitted Trigonal Pattern) § 164.013-4 Samples submitted for acceptance. Application samples. A product sample submitted for...

2013-10-01

261

46 CFR 164.013-1 - Scope.  

Code of Federal Regulations, 2013 CFR

...AND MATERIALS: SPECIFICATIONS AND APPROVAL MATERIALS Foam, Unicellular Polyethylene (Buoyant, Slab, Slitted Trigonal Pattern) § 164.013-1 Scope. (a) This subpart contains performance requirements, acceptance tests, and...

2013-10-01

262

46 CFR 164.013-7 - Marking.  

Code of Federal Regulations, 2013 CFR

...AND MATERIALS: SPECIFICATIONS AND APPROVAL MATERIALS Foam, Unicellular Polyethylene (Buoyant, Slab, Slitted Trigonal Pattern) § 164.013-7 Marking. (a) General. The manufacturer must ensure that each shipping label, and each...

2013-10-01

263

46 CFR 164.013-3 - Material properties and workmanship.  

Code of Federal Regulations, 2013 CFR

...AND MATERIALS: SPECIFICATIONS AND APPROVAL MATERIALS Foam, Unicellular Polyethylene (Buoyant, Slab, Slitted Trigonal Pattern) § 164.013-3 Material properties and workmanship. (a) General. The unicellular polyethylene foam...

2013-10-01

264

46 CFR 164.013-5 - Acceptance tests.  

Code of Federal Regulations, 2013 CFR

...AND MATERIALS: SPECIFICATIONS AND APPROVAL MATERIALS Foam, Unicellular Polyethylene (Buoyant, Slab, Slitted Trigonal Pattern) § 164.013-5 Acceptance tests. Manufacturers shall ensure that the performance and identification tests...

2013-10-01

265

46 CFR 164.013-2 - Incorporation by reference.  

Code of Federal Regulations, 2013 CFR

...AND MATERIALS: SPECIFICATIONS AND APPROVAL MATERIALS Foam, Unicellular Polyethylene (Buoyant, Slab, Slitted Trigonal Pattern) § 164.013-2 Incorporation by reference. (a) Certain materials are incorporated by reference into...

2013-10-01

266

46 CFR 160.060-1 - Incorporation by reference.  

Code of Federal Regulations, 2013 CFR

...Polyethylene (Buoyant, Slab, Slitted Trigonal Pattern) (b) Plans. The following plans...160.060-1: Sheet 1âCutting Pattern and General Arrangement, Model AY. Sheet 2âCutting Pattern and General Arrangement, Model CYM....

2013-10-01

267

46 CFR 164.013-6 - Production tests, inspections, and marking.  

Code of Federal Regulations, 2013 CFR

...AND MATERIALS: SPECIFICATIONS AND APPROVAL MATERIALS Foam, Unicellular Polyethylene (Buoyant, Slab, Slitted Trigonal Pattern) § 164.013-6 Production tests, inspections, and marking. Manufacturers shall provide in-plant quality...

2013-10-01

268

46 CFR 160.010-2 - Definitions.  

Code of Federal Regulations, 2013 CFR

...the Commandant (CG-ENG-4), Attn: Lifesaving and Fire Safety Division, U.S. Coast Guard Stop 7509, 2703 Martin Luther King Jr. Avenue SE., Washington, DC 20593-7509. Peripheral-body. Peripheral body is buoyant...

2013-10-01

269

Mechanism for Deep-Ocean-Instrumentation Quiet, Remote Release.  

National Technical Information Service (NTIS)

Deep-ocean instruments, after completion of their mission, need a releasable link to separate them from their anchors. The Naval Research Laboratory has developed a quiet, remotely controllable release which upon command frees the buoyantly supported inst...

G. O. Thomas H. E. Barnes

1976-01-01

270

Biochemical and Biophysical Characterization of Calicivirus Isolates from Pinnipeds.  

National Technical Information Service (NTIS)

Two virus isolates from California sea lions and one from an Alaskan fur seal, classified as caliciviruses based on their relationship to vesicular exanthema of swine virus, were examined for biochemical and biophysical properties. They all had a buoyant ...

F. L. Schaffer M. E. Soergel

1973-01-01

271

Buoyancy and Archimedes Principle  

NSDL National Science Digital Library

Summary Buoyancy is based on Archimedes' Principle which states that the buoyant force acting upward on an object completely or partially immersed in a fluid equals the weight of the fluid displaced by the ...

272

Characterization of the Double-stranded RNA Isolated from Cowpea Mosaic Virus-infected Vigna Leaves  

Microsoft Academic Search

SUMMARY A standard procedure for the isolation of virus specific double-stranded RNA from cowpea mosaic virus-infected Vigna leaves is described. The double stranded RNA is characterized by its buoyant density in caesium sulphate and its melting temperature (Tin). The buoyant density and the Tm are compared with those of other double-stranded RNA's on basis of their guanine + cytosine content.

L. J. L. D. van Griensven; A. van Kammen; G. Rezelman

1973-01-01

273

Spreading and convective dissolution of carbon dioxide in vertically confined, horizontal aquifers  

NASA Astrophysics Data System (ADS)

Injection of carbon dioxide (CO2) into saline aquifers is a promising tool for reducing anthropogenic CO2 emissions. At reservoir conditions, the injected CO2 is buoyant relative to the ambient groundwater. The buoyant plume of CO2 rises toward the top of the aquifer and spreads laterally as a gravity current, presenting the risk of leakage into shallower formations via a fracture or fault. In contrast, the mixture that forms as the CO2 dissolves into the ambient water is denser than the water and sinks, driving a convective process that enhances CO2dissolution and promotes stable long-term storage. Motivated by this problem, we study convective dissolution from a buoyant gravity current as it spreads along the top of a vertically confined, horizontal aquifer. We conduct laboratory experiments with analog fluids (water and a mixture of methanol and ethylene glycol) and compare the experimental results with simple theoretical models. Since the aquifer has a finite thickness, dissolved buoyant fluid accumulates along the bottom of the aquifer, and this mixture spreads laterally as a dense gravity current. When dissolved buoyant fluid accumulates slowly, our experiments show that the spreading of the buoyant current is characterized by a parabola-like advance and retreat of its leading edge. When dissolved buoyant fluid accumulates quickly, the retreat of the leading edge slows as further dissolution is controlled by the slumping of the dense gravity current. We show that simple theoretical models predict this behavior in both limits, where the accumulation of dissolved buoyant fluid is either negligible or dominant. Finally, we apply one of these models to a plume of CO2 in a saline aquifer. We show that the accumulation of dissolved CO2 in the water can increase the maximum extent of the CO2 plume by several fold and the lifetime of the CO2 plume by several orders of magnitude.

MacMinn, Christopher W.; Neufeld, Jerome A.; Hesse, Marc A.; Huppert, Herbert E.

2012-11-01

274

Capillary Pinning of Immiscible Gravity Currents in Porous Media  

NASA Astrophysics Data System (ADS)

Gravity currents in porous media have attracted much interest recently in the context of geological carbon dioxide (CO2) storage, where supercritical CO2 is injected underground into deep saline aquifers. Capillary effects can be very important in the spreading and migration of the buoyant CO2 after injection because the typical pore size is very small (~10-100 um), but the impact of capillarity on these flows is not well understood. Here, we study the impact of capillarity on a finite-release gravity current of a buoyant non-wetting fluid. Via simple, table-top experiments, we show that capillary pressure hysteresis causes pinning of a portion of the initial interface, which ultimately stops the spreading of the buoyant current at a finite distance. In addition, capillarity causes blunting at the leading edge of the draining buoyant current. We demonstrate through micromodel experiments that the height of the nose of the current is controlled by the pore geometry as well as the balance between capillarity and gravity. Our analysis suggests that capillary pinning and capillary blunting exert a fundamental control on the interface evolution of immiscible finite-release gravity currents in the context of CO2 sequestration in deep saline aquifers.apillary pressure hysteresis leads to pinning of a portion of the initial interface as the buoyant fluid (air; left) spreads over the denser fluid (glycerol-water; right), here in a flow cell packed with glass beads (1.25 mm diameter). Capillary entry pressure causes blunting at the leading edge of the draining buoyant current. Capillary pinning is responsible for ultimately arresting the migration of the buoyant current, while the combined effects of pinning and blunting creates a rectangular shaped buoyant current in this experiment.

Zhao, B.; MacMinn, C. W.; Szulczewski, M.; Huppert, H. E.; Juanes, R.

2012-12-01

275

Update: Immunological Strategies for Prostate Cancer  

PubMed Central

Prostate cancer is the second most common cause of cancer-related death in US men. Along with initial therapy using surgery, radiotherapy, or cryotherapy, hormonal therapy is the mainstay of treatment. For men with advanced (metastatic) disease, docetaxel-based chemotherapy is US Food and Drug Administration (FDA)-approved, and provides a significant survival advantage. This relative paucity of treatment options drives an ongoing quest for additional treatment modalities; among these is immunotherapy. The concept that prostate cancer is a malignancy that can be targeted by the immune system may seem counterintuitive; certainly kidney cancer and melanoma are more traditionally thought of as immune responsive cancers. However, prostate cancer arises in a relatively unique organ and may express a number of proteins (antigens) against which an immune response can be generated. More importantly, several of these agents have now demonstrated a significant survival benefit in randomized controlled clinical trials, and one agent in particular (Sipuleucel-T, Dendreon Corporation, Seattle, WA) could be FDA-approved in 2010. This update summarizes recent clinical developments in the field of prostate cancer immunotherapy, with a focus on dendritic cell vaccines, virus-based vaccines, DNA-based vaccines, and cell-based vaccines. In addition, the notion of agents that target immune checkpoints is introduced. Enthusiasm for prostate cancer immunotherapy is founded upon its potential to mediate targeted, specific, tumor cell destruction without significant systemic toxicity; however, this has yet to be fully realized in the clinical arena.

Antonarakis, Emmanuel S.

2014-01-01

276

A Lighter-Than-Air System Enhanced with Kinetic Lift  

NASA Technical Reports Server (NTRS)

A hybrid airship system is proposed in which the buoyant lift is enhanced with kinetic lift. The airship would consist of twin hulls in which the buoyant gas is contained. The twin hulls would be connected in parallel by a wing having an airfoil contour. In forward flight, the wing would provide kinetic lift that would add to the buoyant lift. The added lift would permit a greater payload/altitude combination than that which could be supported by the buoyant lift alone. The buoyant lift is a function of the volume of gas and the flight altitude. The kinetic lift is a function of the airfoil section, wing area, and the speed and altitude of flight. Accordingly there are a number of factors that can be manipulated to arrive at a particular design. Particular designs could vary from small, lightweight systems to very large, heavy-load systems. It will be the purpose of this paper to examine the sensitivity of such a design to the several variables. In addition, possible uses made achievable by such a hybrid system will be suggested.

Spearman, M. Leroy

2002-01-01

277

Distribution and composition of hydrothermal plume particles from the ASHES vent field at Axial Volcano, Juan de Fuca Ridge. [Axial Seamount Hydrothermal Emission Study  

SciTech Connect

In 1986 and 1987, buoyant and neutrally buoyant hydrothermal plume particles from the ASHES vent field within Axial Volcano were sampled to study their variations in composition with height above the seafloor. Individual mineral phases were identified using standard X ray diffraction procedures. Elemental composition and particle morphologies were determined by X ray fluorescence spectrometry and scanning electron microscopy/X ray energy spectrometry techniques. The vent particles were primarily composed of sphalerite, anhydrite, pyrite, pyrrhotite, chalcopyrite, barite, hydrous iron oxides, and amorphous silica. Grain size analyses of buoyant plume particles showed rapid particle growth in the first few centimeters above the vent orifice, followed by differential sedimentation of the larger sulfide and sulfate minerals out of the buoyant plume. The neutrally buoyant plume consisted of a lower plume, which was highly enriched in Fe, S, Zn, and Cu, and an upper plume, which was highly enriched in Fe and Mn. The upper plume was enriched in Fe and Mn oxyhydroxide particles, and the lower plume was enriched in suspended sulfide particles in addition to the Fe and Mn oxyhydroxide particles. The chemical data for the water column particles indicate that chemical scavenging and differential sedimentation processes are major factors controlling the composition of the dispersing hydrothermal particles. Short-term sediment trap experiments indicate that the fallout from the ASHES vent field is not as large as some of the other vent fields on the Juan de Fuca Ridge.

Feely, R.A.; Geiselman, T.L.; Baker, E.T.; Massoth, G.J. (NOAA, Seattle, WA (United States)); Hammond, S.R. (NOAA, Newport, OR (United States))

1990-08-10

278

Feasibility of modern airships - Design definition and performance of selected concepts  

NASA Technical Reports Server (NTRS)

Three promising modern airship system concepts and their associated missions were studied: (1) a heavy-lift airship, employing a nonrigid hull and a significant amount of rotor lift, used for short-range transporting and positioning of heavy military and civil payloads; (2) a VTOL (vertical take-off and landing), metal-clad, partially buoyant airship used as a short-haul commercial transport; (3) a fully-buoyant airship used for long-endurance Navy missions. The heavy-lift airship concept offers a dramatic increase in vertical lift capability over existing systems at significantly lower costs per ton-mile. The VTOL airship transport concept appears to be economically competititve with other VTOL aircraft concepts but can attain significantly lower noise levels. The fully-buoyant airship concept can provide an airborne platform with long endurance that satisfies many Navy mission requirements.

Huston, R. R.; Ardema, M. D.

1977-01-01

279

Feasibility study of modern airships. Phase 2: Executive summary  

NASA Technical Reports Server (NTRS)

A feasibility study of modern airships has been completed. Three promising modern airship systems' concepts and their associated missions were studied; (1) a heavy-lift airship, employing a non-rigid hull and a significant amount of rotor lift, used for short-range transport and positioning of heavy military and civil payloads, (2) a VTOL (vertical take-off and landing), metalclad, partially buoyant airship used as a short-haul commercial transport; and (3) a class of fully-buoyant airships used for long-endurance Navy missions. The heavy-lift airship concept offers a substantial increase in vertical lift capability over existing systems and is projected to have lower total operating costs per ton-mile. The VTOL airship transport concept appears to be economically competitive with other VTOL aircraft concepts but can attain significantly lower noise levels. The fully-buoyant airship concept can provide an airborne platform with long endurance that satisfies many Navy mission requirements.

1977-01-01

280

Preliminary estimates of operating costs for lighter than air transports  

NASA Technical Reports Server (NTRS)

A preliminary set of operating cost relationships are presented for airship transports. The starting point for the development of the relationships is the direct operating cost formulae and the indirect operating cost categories commonly used for estimating costs of heavier than air commercial transports. Modifications are made to the relationships to account for the unique features of airships. To illustrate the cost estimating method, the operating costs of selected airship cargo transports are computed. Conventional fully buoyant and hybrid semi-buoyant systems are investigated for a variety of speeds, payloads, ranges, and altitudes. Comparisons are made with aircraft transports for a range of cargo densities.

Smith, C. L.; Ardema, M. D.

1975-01-01

281

Preliminary estimates of operating costs for lighter than air transports  

NASA Technical Reports Server (NTRS)

Presented is a preliminary set of operating cost relationships for airship transports. The starting point for the development of the relationships is the direct operating cost formulae and the indirect operating cost categories commonly used for estimating costs of heavier than air commercial transports. Modifications are made to the relationships to account for the unique features of airships. To illustrate the cost estimating method, the operating costs of selected airship cargo transports are computed. Conventional fully buoyant and hybrid semi-buoyant systems are investigated for a variety of speeds, payloads, ranges, and altitudes. Comparisons are made with aircraft transports for a range of cargo densities.

Smith, C. L.; Ardema, M. D.

1975-01-01

282

Investigations on Soot Formation in Heptane Jet Diffusion Flames by Optical Techniques  

Microsoft Academic Search

Two-dimensional optical measurements were performed for the investigation of soot formation of n-heptane laminar gas-jet diffusion\\u000a flames under buoyant and non-buoyant conditions utilizing the Bremen Drop Tower. Techniques employed were laser-induced incandescence\\u000a for the determination of soot concentration and primary particle sizes and two-color emission pyrometry with a three-point\\u000a Abel inversion for the measurement of temperature fields. In line with

Jörg Reimann; Stephan-André Kuhlmann; Stefan Will

2010-01-01

283

The water entry of decelerating spheres  

NASA Astrophysics Data System (ADS)

We present the results of a combined experimental and theoretical investigation of the vertical impact of low-density spheres on a water surface. Particular attention is given to characterizing the sphere dynamics and the influence of its deceleration on the shape of the resulting air cavity. A theoretical model is developed that yields simple expressions for the pinch-off time and depth. Theoretical predictions compare favorably with our experimental observations, and allow us to rationalize the form of water-entry cavities resulting from the impact of buoyant and nearly buoyant spheres.

Aristoff, Jeffrey; Truscott, Tadd; Techet, Alexandra; Bush, John

2009-11-01

284

The water entry of decelerating spheres  

NASA Astrophysics Data System (ADS)

We present the results of a combined experimental and theoretical investigation of the vertical impact of low-density spheres on a water surface. Particular attention is given to characterizing the sphere dynamics and the influence of its deceleration on the shape of the resulting air cavity. A theoretical model is developed which yields simple expressions for the pinch-off time and depth, as well as the volume of air entrained by the sphere. Theoretical predictions compare favorably with our experimental observations, and allow us to rationalize the form of water-entry cavities resulting from the impact of buoyant and nearly buoyant spheres.

Aristoff, Jeffrey M.; Truscott, Tadd T.; Techet, Alexandra H.; Bush, John W. M.

2010-03-01

285

Technology update: Tethered aerostat structural design and material developments  

NASA Technical Reports Server (NTRS)

Requirements exist for an extremely stable, high performance, all-weather tethered aerostat system. This requirement has been satisfied by a 250,000 cubic foot captive buoyant vehicle as demonstrated by over a year of successful field operations. This achievement required significant advancements in several technology areas including composite materials design, aerostatics and aerodynamics, structural design, electro-mechanical design, vehicle fabrication and mooring operations. This paper specifically addresses the materials and structural design aspects of pressurized buoyant vehicles as related to the general class of Lighter Than Air vehicles.

Witherow, R. G.

1975-01-01

286

Technical manual: hood system capture of process fugitive particulate emissions. Final report, September 1983-September 1985  

SciTech Connect

The manual provides to regulatory officials--charged with the responsibility of reviewing hood systems for capture of process fugitive emissions--with a reference guide on the design and evaluation of hood systems. Engineering analyses of the most-important hood types are presented. In particular, consideration is given to design methods for local and remote capture of buoyant sources, and enclosures for buoyant and inertial sources. A unique collection of case studies of actual or representative hood systems has been included to provide insight into the evaluation of existing systems or the design of a planned system.

Kashdan, E.R.; Coy, D.W.; Spivey, J.J.; Cesta, T.; Goodfellow, H.D.

1986-04-01

287

Target-strength studies on Atlantic cod (Gadus morhua) in Newfoundland waters  

Microsoft Academic Search

(standardized to cod) was 1.5 dB higher at night when cod were up to 140 m oV bottom. Night-time TS did not diVer from theex situTS-daytime TS was significantly lower by 1.5 dB. Our findings are consistent with cod being neutrally buoyant oV bottom (night) and negatively buoyant nearer bottom in the day-time. Pooled neutrally buoyantin situandex situTS (38 kHz)

G. A. Rose; D. R. Porter

1996-01-01

288

Translational Approaches towards Cancer Gene Therapy: Hurdles and Hopes  

PubMed Central

Introduction Of the cancer gene therapy approaches, gene silencing, suicide/apoptosis inducing gene therapy, immunogene therapy and targeted gene therapy are deemed to sub-stantially control the biological consequences of genomic changes in cancerous cells. Thus, a large number of clinical trials have been conducted against various malignancies. In this review, we will discuss recent translational progresses of gene and cell therapy of cancer. Methods Essential information on gene therapy of cancer were reviewed and discussed towards their clinical translations. Results Gene transfer has been rigorously studied in vitro and in vivo, in which some of these gene therapy endeavours have been carried on towards translational investigations and clinical applications. About 65% of gene therapy trials are related to cancer therapy. Some of these trials have been combined with cell therapy to produce personalized medicines such as Sipuleucel-T (Provenge®, marketed by Dendreon, USA) for the treatment of asymptomatic/minimally symptomatic metastatic hormone-refractory prostate cancer. Conclusion Translational approach links two diverse boundaries of basic and clinical researches. For successful translation of geno-medicines into clinical applications, it is essential 1) to have the guidelines and standard operating procedures for development and application of the genomedicines specific to clinically relevant biomarker(s); 2) to conduct necessary animal experimental studies to show the “proof of concept” for the proposed genomedicines; 3) to perform an initial clinical investigation; and 4) to initiate extensive clinical trials to address all necessary requirements. In short, translational researches need to be refined to accelerate the geno-medicine development and clinical applications.

Barar, Jaleh; Omidi, Yadollah

2012-01-01

289

Flow Visualization Studies in the Novacor Left Ventricular Assist System CRADA PC91-002, Final Report  

SciTech Connect

This paper discusses a series of experiments to visualize and measure flow fields in the Novacor left ventricular assist system (LVAS). The experiments utilize a multiple exposure, optical imaging technique called fluorescent image tracking velocimetry (FITV) to hack the motion of small, neutrally-buoyant particles in a flowing fluid.

Borovetz, H.S.; Shaffer, F.; Schaub, R.; Lund, L.; Woodard, J.

1999-01-01

290

METHODOLOGY & CALCULATIONS FOR THE ASSIGNMENT OF WASTE FOR THE LARGE UNDERGROUND WASTE STORAGE TANKS AT HANFORD SITE [SEC 1 & 2  

SciTech Connect

This document categorizes each of the large waste storage tanks into one of several categories based on each tank's waste and characteristics. These waste group assignments reflect a tank's propensity to retain a significant volume of flammable gases and the potential of the waste to release retained gas by a buoyant displacement event.

BARKER, S.A.; HEDENGREN, D.C.

2004-07-28

291

Direct numerical simulations of three-dimensional bubbly flows  

Microsoft Academic Search

Direct numerical simulations of the motion of many buoyant bubbles are presented. The Navier-Stokes equation is solved by a front tracking\\/finite difference method that allows a fully deformable interface. The evolution of 91 nearly spherical bubbles at a void fraction of 6% is followed as the bubbles rise over 100 bubble diameters. While the individual bubble velocities fluctuate, the average

Bernard Bunner; Grétar Tryggvason

1999-01-01

292

Direct numerical simulations of bubbly flows Part 2. Moderate Reynolds number arrays  

Microsoft Academic Search

Direct numerical simulations of the motion of two- and three-dimensional finite Reynolds number buoyant bubbles in a periodic domain are presented. The full Navier Stokes equations are solved by a finite difference\\/front tracking method that allows a fully deformable interface between the bubbles and the ambient fluid and the inclusion of surface tension. The rise Reynolds numbers are around 20

Asghar Esmaeeli; Grétar Tryggvason

1999-01-01

293

Direct numerical simulations of bubbly flows. Part 1. Low Reynolds number arrays  

Microsoft Academic Search

Direct numerical simulations of the motion of two- and three-dimensional buoyant bubbles in periodic domains are presented. The full Navier Stokes equations are solved by a finite difference\\/front tracking method that allows a fully deformable interface between the bubbles and the ambient fluid and the inclusion of surface tension. The governing parameters are selected such that the average rise Reynolds

Asghar Esmaeeli; Grétar Tryggvason

1998-01-01

294

Shape Oscillations of Bubbles in Water Driven by Modulated Ultrasonic Radiation Pressure and Applications to Interfacial Dynamics  

Microsoft Academic Search

Acoustic levitation techniques were used for static and dynamic studies of single air bubbles in aqueous solutions. Bubble sizes ranged from 0.3 to 6 mm in radius. The static position of a bubble, determined by the balance between the buoyant and acoustic forces, agrees well with existing theory. Measured bubble aspect ratios are a nonmonotonic increasing function of bubble size

Thomas James Asaki

1995-01-01

295

Explosive Volcanic Eruptions from Linear Vents on Earth, Venus and Mars: Comparisons with Circular Vent Eruptions  

NASA Technical Reports Server (NTRS)

Conditions required to support buoyant convective plumes are investigated for explosive volcanic eruptions from circular and linear vents on Earth, Venus, and Mars. Vent geometry (linear versus circular) plays a significant role in the ability of an explosive eruption to sustain a buoyant plume. On Earth, linear and circular vent eruptions are both capable of driving buoyant plumes to equivalent maximum rise heights, however, linear vent plumes are more sensitive to vent size. For analogous mass eruption rates, linear vent plumes surpass circular vent plumes in entrainment efficiency approximately when L(sub o) > 3r(sub o) owing to the larger entrainment area relative to the control volume. Relative to circular vents, linear vents on Venus favor column collapse and the formation of pyroclastic flows because the range of conditions required to establish and sustain buoyancy is narrow. When buoyancy can be sustained, however, maximum plume heights exceed those from circular vents. For current atmospheric conditions on Mars, linear vent eruptions are capable of injecting volcanic material slightly higher than analogous circular vent eruptions. However, both geometries are more likely to produce pyroclastic fountains, as opposed to convective plumes, owing to the low density atmosphere. Due to the atmospheric density profile and water content on Earth, explosive eruptions enjoy favorable conditions for producing sustained buoyant columns, while pyroclastic flows would be relatively more prevalent on Venus and Mars. These results have implications for the injection and dispersal of particulates into the planetary atmosphere and the ability to interpret the geologic record of planetary volcanism.

Glaze, Lori S.; Baloga, Stephen M.; Wimert, Jesse

2010-01-01

296

Venus Atmospheric Maneuverable Platform (VAMP)  

NASA Astrophysics Data System (ADS)

VAMP is a long lived, semi-buoyant, atmospheric “rover” that deploys in orbit, enters the Venus atmosphere and flies in the Venus atmosphere between 55 and 70 km for up to one year as a platform to address VEXAG goals I.A, I.B, and I.C.

Polidan, R.; Lee, G.; Sokol, D.; Griffin, K.; Bolisay, L.

2014-05-01

297

Habitat fragmentation and modifications affecting distribution of the Rio Grande silvery minnow  

Microsoft Academic Search

The life history of the Rio Grande silvery minnow begins as semi-buoyant pelagic eggs that drift in the current for several days. The combination of diversion and flood control dams have modified channel morphology and divided the river into distinct reaches. These factors have contributed to the decline of the silvery minnow in the last 5-10% of its former range.

Michael D. Porter; Tamara M. Massong

298

Multi-gradient drilling method and system  

DOEpatents

A multi-gradient system for drilling a well bore from a surface location into a seabed includes an injector for injecting buoyant substantially incompressible articles into a column of drilling fluid associated with the well bore. Preferably, the substantially incompressible articles comprises hollow substantially spherical bodies.

Maurer, William C. (Houston, TX); Medley, Jr., George H. (Spring, TX); McDonald, William J. (Houston, TX)

2003-01-01

299

46 CFR 160.005-5 - Sampling, tests, and inspections.  

Code of Federal Regulations, 2013 CFR

...CONTINUED) EQUIPMENT, CONSTRUCTION, AND MATERIALS: SPECIFICATIONS...and Child (Jacket Type), Models 52 and 56 § 160.005-5...The buoyant pad inserts from Model 3 adult life preservers shall...fresh water, and the pads from Model 5 child life preservers...

2013-10-01

300

46 CFR 160.002-5 - Sampling, tests, and inspections.  

Code of Federal Regulations, 2013 CFR

...CONTINUED) EQUIPMENT, CONSTRUCTION, AND MATERIALS: SPECIFICATIONS...and Child (Jacket Type), Models 3 and 5 § 160.002-5...The buoyant pad inserts from Model 3 adult life preservers shall...fresh water, and the pads from Model 5 child life preservers...

2013-10-01

301

Resilience in Families with Children and Adult Members with Intellectual Disabilities: Tracing Elements of a Psycho-Social Model  

ERIC Educational Resources Information Center

Aim: This paper seeks to illumine how families with children and adult members with intellectual disabilities manage to manifest a buoyant and durable capacity over time. It is therefore concerned centrally with the idea of resilience. Method: Drawing from diverse theoretical literatures from child development and protection and gerontology, the…

Grant, Gordon; Ramcharan, Paul; Flynn, Margaret

2007-01-01

302

Plumes with non-monotonic mixing behaviour  

Microsoft Academic Search

We develop a model for the behaviour of continuous releases (plumes) of fluid which, upon mixing with the ambient fluid, undergo a non-monotonic change in density. This model serves as an analogue for the behaviour of volcanic eruption clouds and hydrothermal plumes. If, at the source, the plume is initially actually a negatively buoyant jet, but has the potential on

Colm-Cille P. Caulfield; Andrew W. Woods

1995-01-01

303

High-Aspect-Ratio Rotating Cell-Culture Vessel  

NASA Technical Reports Server (NTRS)

Cylindrical rotating cell-culture vessel with thin culture-medium layer of large surface area provides exchange of nutrients and products of metabolism with minimal agitation. Rotation causes averaging of buoyant forces otherwise separating components of different densities. Vessel enables growth of cells in homogeneous distribution with little agitation and little shear stress.

Wolf, David A.; Sams, Clarence; Schwarz, Ray P.

1992-01-01

304

Photoassisted oxidation of oil films on water. Final performance report, January 1, 1990March 31, 1993  

Microsoft Academic Search

The objective of the project has been the development of a technology for cleaning up oil spills on water through their photocatalytic oxidation. The photocatalyst used was titanium dioxide. Nanocrytalline TiOâ, of anatase or anatase\\/rutile phase, was bound to hollow ceramic microspheres of sufficiently low density to be buoyant on water. In the presence of these, under sunlight, oil films

Heller

1994-01-01

305

REDUCTION IN FUME EMISSION FROM A SLAG FUMER CHARGE PORT USING CFD MODELLING  

Microsoft Academic Search

Fume and hygiene hoods are widely used to prevent fugitive emissions from charge port, tap holes and many other openings in mineral processing and smelting vessels. The highly buoyant nature of the fume combined with often complex geometries make the design of these hoods difficult with traditional engineering tools. A computational fluid dynamics (CFD) model has been used to predict

Peter WITT; Chris SOLNORDAL; Louis MITTONI; Stephen FINN; John PLUTA

2003-01-01

306

Reducing Fume Emission from Smelting Vessels Using Combined Cfd and Engineering Modelling  

Microsoft Academic Search

Capture of fugitive emissions from charge ports, tap holes and many other openings in mineral processing and smelting vessels poses a significant environmental and hygiene problem. While fume and hygiene hoods are often used the highly buoyant nature of the fume combined with complex geometries makes their design with traditional engineering tools difficult. A computational fluid dynamics (CFD) model has

PJ Witt; CB Solnordal; A Manzoori; S Finn; J Pluta; H Namavari; E Niknejad; M Davari

307

Remote acoustic imaging of the plume from a submarine spring in an arctic fjord.  

PubMed

Acoustic backscatter observations at 200 kilohertz were made of the buoyant plume from a submarine spring at a depth of 47 meters in Cambridge Fiord, Baffin Island. Vertical velocities of up to 37 centimeters per second are inferred from the ascent rates of discrete scattering structures in the plume. PMID:17782423

Hay, A E

1984-09-14

308

Constraining mantle density structure using geological evidence of surface uplift rates: The case of the African Superplume  

Microsoft Academic Search

We explore the hypothesis that southern Africa is actively being uplifted by a large-scale, positively buoyant structure within the mid-lower mantle. Using a new formulation in which dynamic topography and uplift rate are jointly used, we place constraints on mantle density and viscosity. The solution of the momentum equation is coupled with the advection of the density field to solve

Michael Gurnis; Jerry X. Mitrovica; Jeroen Ritsema; Hendrik-Jan van Heijst

2000-01-01

309

46 CFR 164.015-3 - Material and workmanship.  

Code of Federal Regulations, 2013 CFR

...APPROVAL MATERIALS Plastic Foam, Unicellular, Buoyant, Sheet...a) The unicellular plastic foam shall be all new material...164.015-4 shall yield property values within the limits shown...b) The unicellular plastic foam shall be produced in sheet...

2013-10-01

310

Morphological characterization of chicken anaemia agent (CAA)  

Microsoft Academic Search

Summary Chicken anaemia agent (CAA) was characterized as a virion with 25nm in diameter, with a buoyant density in CsCl of 1.36–1.37 g\\/cm3, and containing a circular, single-stranded DNA genome. The virus is composed of 32 hollow morphological units representing a regular T=3 icosahedron.

H. Gelderblom; S. Kling; R. Lurz; I. Tischer; V. v. Bülow

1989-01-01

311

Oceanic transport of calcified eggs: taphonomic and biogeographic implications  

Microsoft Academic Search

Estimates of the temporal and spatial resolution of fossil egg assemblages are required to constrain the inferences that can logically be drawn during assemblage analysis. Consequently, understanding egg transport mechanisms is required before conclusions are developed. Bird eggs are buoyant during part of development and can float from near shore nests during high tides, storm surges, or flooding. Complete and

Thomas Evans

2012-01-01

312

Lattice Boltzmann algorithm for surface tension with greatly reduced microcurrents  

Microsoft Academic Search

We present an algorithm for inserting an interface between the immiscible phases of a multicomponent lattice Boltzmann fluid which is based solely upon the appropriate continuum physics: stress boundary conditions and continuity of velocity. Results are presented for the algorithm when applied to static, neutrally buoyant drops. It is shown that the present algorithm gives a significant reduction in the

S. V. Lishchuk; C. M. Care; I. Halliday

2003-01-01

313

Intralineage diversity of archaebacterial ribosomes: A dichotomy of ribosome features separates sulfur-dependent archaebacteria and methanococcaceae from other archaebacterial taxa  

Microsoft Academic Search

Summary The aggregate masses and relative protein contents of eubacterial and archaebacterial ribosomes have been estimated from the buoyant densities of the ribosomal subunits and the anhydrous weights of the rRNA species. In contrast to the situation in eubacteria, archaebacterial ribosomes fall into two size classes that differ only in the relative abundances of their protein moieties. One class comprises

Angela Teichner; Paola Londei; Piero Cammarano

1986-01-01

314

46 CFR 26.30-1 - Approved unicellular plastic foam work vests.  

Code of Federal Regulations, 2013 CFR

...2013-10-01 2013-10-01 false Approved unicellular plastic foam work vests. 26.30-1 Section 26.30-1 Shipping...OPERATIONS Work Vest § 26.30-1 Approved unicellular plastic foam work vests. (a) Buoyant work vests carried under...

2013-10-01

315

The evolution of a racing snail  

Microsoft Academic Search

Modern cephalopods evolved from slow?moving low metabolic rate shelled ancestors. Rapid efficient jet propulsion depends on a large ejectable mass, impossible while the mantle cavity was enclosed in a shell. The shell was progressively reduced, became internal and finally lost the capacity to provide buoyancy. The streamlined non?buoyant squid were fast but costs of transport soared. Inevitably, there were changes

M. J. Wells

1995-01-01

316

Building the Holocene clinothem in the Gulf of Papua: An ocean circulation study  

Microsoft Academic Search

This paper investigates the role that tidal and wind-driven flows and buoyant river plumes play in the development of the Holocene clinothem in the Gulf of Papua. Time series data from bottom tripods and a mooring were obtained at four locations near the mouth of the Fly River during portions of 2003 and 2004. Flows in the Gulf of Papua

Rudy Slingerland; Robert W. Selover; Andrea S. Ogston; Timothy R. Keen; Neal W. Driscoll; John D. Milliman

2008-01-01

317

Optimising the design of fume extraction hoods using a combination of engineering and CFD modelling  

Microsoft Academic Search

Fume and hygiene hoods are widely used to prevent fugitive emissions from charge ports, tap holes and many other openings in mineral processing and smelting vessels. The highly buoyant nature of the fume combined with often complex geometries make the design of these hoods difficult with traditional engineering tools. However, by combining the traditional engineering approach with computational fluid dynamics

P. J. Witt; C. B. Solnordal; L. J. Mittoni; S. Finn; J. Pluta

2006-01-01

318

Convectively Generated Gravity Waves and Their Effect on the Cloud Environment  

Microsoft Academic Search

This study uses a two-dimensional cloud-resolving model to examine how convectively generated gravity waves modify the environment of an isolated convective cloud. The model is initialized with an idealized sounding, and the cloud is initiated by adding a locally buoyant perturbation. The modeled convection generates a spectrum of gravity waves with vertical wavelengths that are harmonics of the depth of

Michael J. Reeder

2001-01-01

319

Impact of fjord dynamics and glacial runoff on the circulation near Helheim Glacier  

Microsoft Academic Search

Submarine melting is an important contributor to the mass balance of tidewater glaciers in Greenland, and has been suggested as a trigger for their widespread acceleration. Our understanding of this process is limited, however. It generally relies on the simplified model of subglacial discharge in a homogeneous ocean, where the melting circulation consists of an entraining, buoyant plume at the

Fiammetta Straneo; Ruth G. Curry; David A. Sutherland; Gordon S. Hamilton; Claudia Cenedese; Kjetil Våge; Leigh A. Stearns

2011-01-01

320

Buoyancy characteristics of the bloater (Coregonus hoyi) in relation to patterns of vertical migration and acoustic backscattering  

USGS Publications Warehouse

Acoustic studies in Lake Michigan found that bloaters (Coregonus hoyi) were less reflective per size than the other major pelagic species. This difference in in situ acoustic backscattering could indicate that the deep-water bloaters have compressed swimbladders for much of their vertical range with related implications on buoyancy. To test this hypothesis, the buoyancy characteristics of bloaters were determined with fish placed in a cage that was lowered to bottom and monitored with an underwater camera. We found bloaters were positively buoyant near surface, neutrally buoyant at intermediate strata, and negatively buoyant near bottom. This pattern was consistent for the range of depths bloaters occur. The depth of neutral buoyancy (near the 50-n strata) corresponds with the maximum extent of vertical migration for bloaters observed in acoustic surveys. Fish below this depth would be negatively buoyant which supports our contention that bloaters deeper in the water column have compressed swimbladders. Understanding the buoyancy characteristics of pelagic fishes will help to predict the effects of vertical migration on target strength measurement and confirms the use of acoustics as a tool to identify and quantify the ecological phenomenon of vertical migration.

Fleischer, Guy W.; TeWinkel, Leslie M.

1998-01-01

321

46 CFR 160.062-4 - Inspections and tests.  

Code of Federal Regulations, 2010 CFR

...Submergence test. A hydraulic release shall be tested by applying buoyant loads of its designed capacity to its spring-tensioned gripe as required under § 160.062-3(b) while the device is submerged in water or in a water-filled pressure testing...

2009-10-01

322

46 CFR 160.062-4 - Inspections and tests.  

Code of Federal Regulations, 2010 CFR

...Submergence test. A hydraulic release shall be tested by applying buoyant loads of its designed capacity to its spring-tensioned gripe as required under § 160.062-3(b) while the device is submerged in water or in a water-filled pressure testing...

2010-10-01

323

Wind Tunnel, Field and Numerical Investigations of Plume Downwash and Dispersion at AN Arctic Industrial Site  

Microsoft Academic Search

This study was designed to investigate the influence of the arctic atmospheric boundary layer and the complex flow pattern generated by building clusters on dispersion from a buoyant source. This was accomplished by analyzing data from wind tunnel, field, and numerical dispersion experiments for flow around a specific Prudhoe Bay, Alaska oil-gathering center. The results were used to describe plume

Alex Brian Guenther

1989-01-01

324

Wind tunnel, field, and numerical investigations of plume downwash and dispersion at an arctic industrial site  

Microsoft Academic Search

The influence of the arctic atmospheric boundary layer and the complex flow pattern generated by building clusters is investigated on dispersion from a buoyant source. This was accomplished by analyzing data from wind tunnel, field, and numerical dispersion experiments for flow around a specific Prudhoe Bay, Alaska oil-gathering center. The results were used to describe plume downwash and the arctic

Alex Brian Guenther

1989-01-01

325

The formation and chemistry of low degree hydrous partial melt on top of the transition zone  

Microsoft Academic Search

There is some geophysical evidence for the presence of silicate melt on top of the 410 km seismic discontinuity. It has also been argued that the difference in the water storage capacity of upper mantle versus transition zone minerals may cause dehydration melting as material up-wells across the 410. Studies have proposed that hydrous partial melts may be neutrally buoyant

Daniel J. Frost; Mainak Mookherjee

2010-01-01

326

Pipe laying apparatus and method  

Microsoft Academic Search

Apparatus and method are described for laying a pipeline on the bottom of an ocean wherein a wheel-like, buoyant body is adapted to carry a single, continuous length of pipe in the form of horizontal convolutions from a first site at which the pipe is wrapped on the body to a second site where the convolutions are moved into vertical

F. S. Ellers; N. R. Wallace

1981-01-01

327

FLUID MODELING SIMULATION OF STACK-TIP DOWNWASH  

EPA Science Inventory

Downwash of neutrally buoyant effluent on the immediate lee side of a circular stack was modeled using a wind tunnel simulation. oth subcritical and supercritical turbulent flows were simulated, where the criticality refers to Reynolds numbers below and above the critical Reynold...

328

Simulated Transport and Retention of Pelagic Fish Eggs during an Irrigation Release in the Pecos River, New Mexico  

Microsoft Academic Search

The Pecos River between Sumner Dam and Brantley Reservoir (320 km), New Mexico, contains populations of several pelagic-spawning cyprinid fish species, including the federally threatened Pecos bluntnose shiner (Notropis simus pecosensis). Females of this reproductive guild release semi-buoyant eggs that are fertilized and drift, incubate, and hatch on increased flows associated with spring runoff, summer rainstorms, or irrigation releases from

C. Nicolas. Medley; Jon W. Kehmeier; Orrin B. Myers; Richard A. Valdez

2007-01-01

329

Are marine plastic particles transport vectors for organic pollutants to the Arctic?  

Microsoft Academic Search

Plastic litter accounts for 50–80% of waste items stranded on beaches, floating on the ocean surface and lodged in the seabed. Organic pollutants can be absorbed onto plastic particles from sea water, attached to their surfaces or included in the plastic matrix as additives. Such chemicals may be transported to remote regions by buoyant plastics and ocean currents. We have

Christiane Zarfl; Michael Matthies

2010-01-01

330

Operational use of air-pollution models at the space and missile ranges. Final report  

Microsoft Academic Search

The Space Shuttle exhaust ground and cloud results from the exhaust plume from the Space Shuttle Main Engines and the Solid Rocket Boosters initially impinging on the launch complex and flame trench. The initial ground cloud is formed from high-temperature combustion products and vaporized flame trench water. The exhaust cloud rises to an altitude at which buoyant equilibrium with the

B. F. Boyd; C. R. Bowman

1986-01-01

331

The Development of Thermister Chain Buoys for Use in Ice Infested Waters  

Microsoft Academic Search

The use of temperature profiles gathered in near real time can greatly increase the accuracy and timeliness of forecasts such as the prediction of freeze-up. This paper describes the development of ARGOS based thermistor chain buoys to operate in the Gulf of St. Lawrence up to an beyond the appearance of ice. The buoys employ a slack, buoyant mooring system

G. Fowler; G. Budgen

1987-01-01

332

46 CFR 199.640 - Alternatives for cargo vessels in a specified service.  

Code of Federal Regulations, 2010 CFR

...requirement for the liferaft to float free under § 199.290(b...accommodate the total number of people on board. The lifefloat launching...buoyant apparatus or lifefloat to float without contacting any other... (C) The strength of the float-free link and the...

2010-10-01

333

Occurrence and distribution of microplastics in marine sediments along the Belgian coast  

Microsoft Academic Search

Plastic debris is known to undergo fragmentation at sea, which leads to the formation of microscopic particles of plastic; the so called ‘microplastics’. Due to their buoyant and persistent properties, these microplastics have the potential to become widely dispersed in the marine environment through hydrodynamic processes and ocean currents. In this study, the occurrence and distribution of microplastics was investigated

Michiel Claessens; Steven De Meester; Lieve Van Landuyt; Karen De Clerck; Colin R. Janssen

2011-01-01

334

Role of overloading of the vacular apparatus in changes in liver cell lysosomes in acute toxic hepatitis  

Microsoft Academic Search

The physicochemical properties of the liver lysosomes were investigated in rats after administration of a single dose of the lysosomotropic agent Triton WR 1339 to intact rats and to rats with acute toxic hapatitis. Administration of the detergent to intact animals was followed by a decrease in the buoyant density of the particles, solubilization of the lysosomal enzymes, and reduced

T. A. Korolenko

1979-01-01

335

Collection of Reprints.  

National Technical Information Service (NTIS)

A simple model of a neutrally buoyant, steady-state benthic boundary layer is used to examine the relationships between the dimensions of secondary roll vortices in the boundary layer and the spacing of a system of bottom furrows located offshore of the M...

C. E. Adams D. B. Prior J. M. Coleman H. H. Roberts S. P. Murray

1984-01-01

336

46 CFR 160.060-2 - Type and model.  

Code of Federal Regulations, 2013 CFR

...2013-10-01 2013-10-01 false Type and model. 160.060-2 Section 160.060-2...and Child § 160.060-2 Type and model. Each buoyant vest specified in this subpart is a: (a) Standard: (1) Model AY, adult (for persons weighing...

2013-10-01

337

Autonomous Soaring for Improved Endurance of a Small Uninhabited Air Vehicle.  

National Technical Information Service (NTIS)

A relatively unexplored method to improve the endurance of an autonomous aircraft is to use buoyant plumes of air found in the lower atmosphere called thermals or updrafts. Glider pilots and birds commonly use updrafts to improve range, endurance, or cros...

M. J. Allen

2005-01-01

338

Tagging of Arctic Icebergs.  

National Technical Information Service (NTIS)

An air-deployable iceberg tagging system has been developed for use from a C-130 aircraft. The system consists of a steel dart with a trailing buoyant line which can be attached to a floating instrument package. The system allows for considerable melting ...

R. Q. Robe T. S. Ellis

1978-01-01

339

Problem-Based Test: Replication of Mitochondrial DNA during the Cell Cycle  

ERIC Educational Resources Information Center

Terms to be familiar with before you start to solve the test: cell cycle, generation time, S-phase, cell culture synchronization, isotopic pulse-chase labeling, density labeling, equilibrium density-gradient centrifugation, buoyant density, rate-zonal centrifugation, nucleoside, nucleotide, kinase enzymes, polymerization of nucleic acids,…

Setalo, Gyorgy, Jr.

2013-01-01

340

Repetitive DNA sequences in Drosophila  

Microsoft Academic Search

The satellite DNAs of Drosophila melanogaster and D. virilis have been examined by isopycnic centrifugation, thermal denaturation, and in situ molecular hybridization. The satellites melt over a narrow temperature range, reassociate rapidly after denaturation, and separate into strands of differing buoyant density in alkaline CsCl. In D. virilis and D. melanogaster the satellites constitute respectively 41% and 8% of the

Joseph G. Gall; Edward H. Cohen; Mary Lake Polan

1971-01-01

341

Plasmid heterogeneity in various strains of Bacillus megaterium  

Microsoft Academic Search

Seven different strains of Bacillusmegaterium, obtained from strain collections, were investigated for the presence of plasmids. 6 of these contained up to four plasmids which although having identical buoyant density, could be attributed to at least 8 different size classes with contour lengths ranging from 0.63 to 8 µm. With one exception, an identity of these do not appear to

Ulf Stahl; Karl Esser

1983-01-01

342

Feasibility study of modern airships, phase 2. Volume 2: Airport feeder vehicle  

NASA Technical Reports Server (NTRS)

The Airport Feeder vehicle is a VTOL, semi-buoyant ellipsoidal airship capable of transporting passengers or cargo to major CTOL hub terminals from suburban and downtown depots. Six tasks were reviewed: (1) vehicle design definition, (2) operational procedures analysis, (3) cost analysis, (4) comparison with alternate transportation modes, (5) mission/vehicle feasibility assessment, and (6) technology assessment.

1976-01-01

343

RAFOS Floats in the SYNOP Experiment: 1988-1990.  

National Technical Information Service (NTIS)

RAFOS floats are neutrally buoyant isopycnal drifters which are tracked acoustically by ranging to as many as five sound sources that have been moored at the depth of the permanent sound channel south of the Gulf Stream along a line between 73 deg W and 5...

H. T. Rossby S. Anderson-Fontana

1991-01-01

344

Reduction of Selenite and Detoxification of Elemental Selenium by the Phototrophic Bacterium Rhodospirillum rubrum  

PubMed Central

The effect of selenite on growth kinetics, the ability of cultures to reduce selenite, and the mechanism of detoxification of selenium were investigated by using Rhodospirillum rubrum. Anoxic photosynthetic cultures were able to completely reduce as much as 1.5 mM selenite, whereas in aerobic cultures a 0.5 mM selenite concentration was only reduced to about 0.375 mM. The presence of selenite in the culture medium strongly affected cell division. In the presence of a selenite concentration of 1.5 mM cultures reached final cell densities that were only about 15% of the control final cell density. The cell density remained nearly constant during the stationary phase for all of the selenite concentrations tested, showing that the cells were not severely damaged by the presence of selenite or elemental selenium. Particles containing elemental selenium were observed in the cytoplasm, which led to an increase in the buoyant density of the cells. Interestingly, the change in the buoyant density was reversed after selenite reduction was complete; the buoyant density of the cells returned to the buoyant density of the control cells. This demonstrated that R. rubrum expels elemental selenium across the plasma membrane and the cell wall. Accordingly, electron-dense particles were more numerous in the cells during the reduction phase than after the reduction phase.

Kessi, J.; Ramuz, M.; Wehrli, E.; Spycher, M.; Bachofen, R.

1999-01-01

345

The development of a hybrid advanced composite-syntactic foam structural component for use in undersea vehicles  

Microsoft Academic Search

This paper presents the progress of an ongoing program to develop a lightweight, highly buoyant structural member for open-frame, remotely operated vehicles (ROVs). The structural component is fabricated from advanced composite materials and syntactic foam. This unique hybrid member is intended for, but not limited to, underwater vehicles. The paper demonstrates that composite materials and syntactic foams can offer great

John B. Hinves; Craig D. Douglas

1993-01-01

346

Superfluid Turblence Properties of Thermal Counter Flow Jet Measured with Piv  

Microsoft Academic Search

The particle image velocimetry (PIV) technique was applied to the measurement of superfluid turbulence properties of the thermal counterflow jet in He II. Neutrally buoyant hydrogen-deuterium micro solid particles were used as tracers for PIV. For the sake of comparison, A He II co-flow jet driven by a bellows pump was also measured with PIV. The velocity profile and the

N. Yokota; M. Murakami; M. Maeda; T. Takakoshi

2010-01-01

347

Transient wind-driven upwelling in a submarine canyon: A process-oriented modeling study  

Microsoft Academic Search

A hydrodynamic model is employed to study flow near a submarine canyon during conditions of upwelling-favorable coastal winds. Findings reveal that up-canyon flow is the rapid geostrophic adjustment to barotropic pressure gradients establishing across the canyon. Stratification leads to the formation of a cyclonic eddy within the canyon, trapping neutrally buoyant matter, and limits the upwelling depth only when a

Jochen Kämpf

2006-01-01

348

Ocean wave electric generators  

Microsoft Academic Search

This patent describes an apparatus for generating electricity from ocean waves. It consists of: 1.) a hollow buoyant duck positioned in the path of waves including a core about the center axis of which the duck rotates, a lower chamber portion having liquid therein and an upper chamber portion having air therein. The air is alternately compressed and expanded by

1986-01-01

349

Hydrothermal Processes  

Microsoft Academic Search

What is Hydrothermal Circulation?Hydrothermal circulation occurs when seawater percolates downward through fractured ocean crust along the volcanic mid-ocean ridge (MOR) system. The seawater is first heated and then undergoes chemical modification through reaction with the host rock as it continues downward, reaching maximum temperatures that can exceed 400 °C. At these temperatures the fluids become extremely buoyant and rise rapidly

C. R. German; K. L. von Damm

2003-01-01

350

Fluid-particle interaction in solid-liquid two-phase grid turbulence  

Microsoft Academic Search

The interaction between solid spheres and a fluid in the nearly isotropic flow field downstream of a grid was studied experimentally. Also neutrally buoyant plastic particles and heavier glass particles of the size of 600 to 710 microns and of concentrations of 0.2 to 1.5 percent were considered. Velocity measurements of both phases were conducted with a laser Doppler velocimeter.

Stefan Georg Schreck

1988-01-01

351

ESA MS Nicollier is lowered into JSC's WETF pool for underwater simulation  

NASA Technical Reports Server (NTRS)

European Space Agency (ESA) Mission Specialist (MS) Claude Nicollier, fully suited in an extravehicular mobility unit (EMU) and standing on a platform, is lowered into JSC's Weightless Environment Training Facility (WETF) Bldg 29 pool for an underwater extravehicular activity (EVA) simulation and familiarization session. Nicollier's EMU is weighted to facilitate a neutrally buoyant condition. He is assisted by two SCUBA-equipped divers.

1987-01-01

352

Development of a Mixed Layer Float.  

National Technical Information Service (NTIS)

The purpose of this grant was to finish development of a new type of neutrally buoyant float designed to accurately follow the three dimensional motion of water parcels in the ocean mixed layer. This work was joint with David Farmer, of the Institute of O...

E. A. D'Asaro

1993-01-01

353

IN SITU TREATMENT OF HAZARDOUS MATERIAL SPILLS IN FLOWING STREAMS  

EPA Science Inventory

Two methods of applying activated carbon adsorption treatment to flowing streams were evaluated under comparable conditions. The first involved subsurface introduction of buoyant carbon into the water column followed by the floating of the carbon to the surface and subsequent rem...

354

Floating Head Cup  

NSDL National Science Digital Library

In this activity, learners watch a figure "magically" float up through the air. Learners use 2 straws, a cup, rubber band, pipe cleaner, and piece of buoyant material to make a simple model of novel Chinese art pieces, which are typically made out of ceramics. Use this activity to demonstrate the relationship between density and buoyancy.

Workshop, Watsonville E.

2011-01-01

355

The Effective Mass of a Ball in the Air  

ERIC Educational Resources Information Center

The air surrounding a projectile affects the projectile's motion in three very different ways: the drag force, the buoyant force, and the added mass. The added mass is an increase in the projectile's inertia from the motion of the air around it. Here we experimentally measure the added mass of a spherical projectile in air. The results agree well…

Messer, J.; Pantaleone, J.

2010-01-01

356

A Mixture Suitable for an Aerostat.  

National Technical Information Service (NTIS)

A balloon filled with a gas mixture of ammonia and n-hexane will stay at a constant altitude due to condensation at altitude of the n-hexane. Since both components are liquid below about 50 meters in the ocean and together with the load are buoyant, the a...

R. M. Dunlap

1978-01-01

357

Experimental studies of protozoan response to intense magnetic fields and forces  

Microsoft Academic Search

Intense static magnetic fields of up to 31 Tesla were used as a novel tool to manipulate the swimming mechanics of unicellular organisms. It is shown that homogenous magnetic fields alter the swimming trajectories of the single cell protozoan Paramecium caudatum, by aligning them parallel to the applied field. Immobile neutrally buoyant paramecia also oriented in magnetic fields with similar

Karine Guevorkian

2006-01-01

358

The modelling of buoyancy driven flow in bubble columns  

Microsoft Academic Search

Using the analogy between lateral convection of heat and the two-phase flow in bubble columns, alternative turbulence modelling methods were analysed. The k–? turbulence and Reynolds stress models were used to predict the buoyant motion of fluids where a density difference arises due to the introduction of heat or a discrete phase. A large height to width aspect ratio cavity

G. M Cartland Glover; S. C Generalis

2004-01-01

359

The Recent Growth Performance of US Firms in the Industrial Design Sector: An Exploratory Study  

Microsoft Academic Search

This paper assesses the competitive factors associated with company growth in the US industrial design sector. This small but technologically advanced sector delivers critical innovation inputs to firms that produce durable goods. Evidence from a survey of 85 US design companies suggests that competitive success hinges upon service diversity. Specifically, the most commercially buoyant companies have diversified their service offerings

Vida Vanchan; Alan MacPherson

2008-01-01

360

Pancreatic hormone expression in the murine thymus: localization in dendritic cells and macrophages.  

PubMed

The expression of preproinsulin (ppIns), proglucagon, prosomatostatin, and propancreatic polypeptide was investigated in thymic extracts, thymic cells, and thymic cell lines from C57BL/6 mice by RT-PCR. The expression of pancreatic hormones was similar in thymic extracts taken from neonatal and 2-, 4-, and 8-week-old animals, but was decreased in 20-week-old animals. Pancreatic hormone expression was not observed in mouse liver, salivary gland, or spleen. Analysis of thymic cell populations revealed a 10- to 20-fold enrichment in expression of all hormones in low buoyant density cells. No expression was detected in high buoyant density cells (predominantly thymocytes) or in thymic epithelial cell lines, primary cultures of epithelial cells, or peripheral macrophages. In addition, immunoreactive insulin, measured by specific RIA, was detectable in the low buoyant density population, but not in high buoyant density cells. The enriched cell population was depleted of contaminating lymphocytes and sorted based on reactivity to the cell surface markers F4/80 (macrophage) or N418 (dendritic cells). Cells gated for N418 demonstrated expression for ppIns, but not the other pancreatic hormones. Conversely, expression for proglucagon, prosomatostatin, and propancreatic polypeptide, but not ppIns, was detected in F4/80-gated cells. Our data indicate that pancreatic endocrine hormones are differentially expressed by dendritic cells and macrophages in a normal mice. PMID:9564851

Throsby, M; Homo-Delarche, F; Chevenne, D; Goya, R; Dardenne, M; Pleau, J M

1998-05-01

361

Air-dispersion modeling and the real world  

Microsoft Academic Search

Use of computerized programs to model stack-gas dispersion mathematically has grown immensely in the last 15 years. In most dispersion models, determining ground-level pollutant concentrations beneath an elevated, buoyant plume of dispersing stack gas involves two major steps. First, the height to which the plume rises at a given downward distance from the plume source is calculated. The calculated plume

Beychok

1996-01-01

362

METHODOLOGY & CALCULATIONS FOR THE ASSIGNMENT OF WASTE FOR THE LARGE UNDERGROUND WASTE STORAGE TANKS AT HANFORD SITE [SEC 1 & 2  

SciTech Connect

This document categorizes each of the large waste storage tanks into one of several categories based on each tank's waste and characteristics. These waste group assignments reflect a tank's propensity to retain a significant volume of flammable gases and the potential of the waste to release retained gas by a buoyant displacement event.

BARKER, S.A.; HEDENGREN, D.C.

2003-10-14

363

METHODOLOGY & CALCULATIONS FOR THE ASSIGNMENT OF WASTE FOR THE LARGE UNDERGROUND WASTE STORAGE TANKS AT HANFORD SITE [SEC 1 & 2  

SciTech Connect

This document categorizes each of the large waste storage tanks into one of several categories based on each tank's waste and characteristics. These waste group assignments reflect a tank's propensity to retain a significant volume of flammable gases and the potential of the waste to release retained gas by a buoyant displacement event.

BARKER, S.A.; HENDENGREN, D.C.

2004-10-27

364

Methodology and calculations for the assignment of waste groups for the large underground waste storage tanks at the Hanford site [SEC 1 & 2  

SciTech Connect

This document categories each of the large waste storage tanks into one of several categories based on each tank's waste and characteristics. These waste group assignments reflect a tank's propensity to retain a significant volume of flammable gases and the potential of the waste to release retained gas by a buoyant displacement gas release event.

BARKER, S.A.; HEDENGREN, D.C.

2003-03-24

365

Dynamic modeling of the airship using analytical aerodynamic model  

Microsoft Academic Search

Buoyant vehicle concept provides the attractive solution to the many adverse problems. Basic objective is to operate the vehicle with a sufficient level of autonomy under extreme range of atmospheric conditions. In order to achieve these goals, a guidance and control system is needed which controls the airship attitude in the air. The accurate control system first requires an accurate

Zahir Ashraf; M. A. Choudhry

2009-01-01

366

Titan Airship Explorer  

Microsoft Academic Search

Saturn's moon Titan is considered to be one of the prime locations for understanding the origins of life due to its rich environment of organic chemicals. A unique combination of dense atmosphere (more than four times that of the Earth), low gravity (one-sixth of that on the Earth) and small temperature variations makes Titan well-suited for studies with buoyant robotic

Jeffery L. Hall; Viktor V. Kerzhanovich; J. A. Jones; J. A. Cutts; A. A. Yavrouian; A. Colozza; R. D. Lorenz

2002-01-01

367

Basalt Reactivity Variability with Reservoir Depth in Supercritical CO2 and Aqueous Phases  

Microsoft Academic Search

Long term storage of CO in geologic formations is currently considered the most attractive option to reduce greenhouse gas emissions while continuing to utilize fossil fuels for energy production. Injected CO is expected to reside as a buoyant water-saturated supercritical fluid in contact with reservoir rock, the caprock system, and related formation waters. As was reported for the first time

Herbert T. Schaef; B. Peter McGrail; Antionette T. Owen

2011-01-01

368

Coal energy conversion with carbon sequestration via combustion in supercritical saline aquifer water  

Microsoft Academic Search

The standard idea for deep saline aquifer sequestration is to separate carbon dioxide from a process stream, compress it, and inject it underground. However, since carbon dioxide is less dense than water, even at the high pressures found in aquifers, it is buoyant and will move towards the surface unless trapped by an impermeable seal. Also, significant energy expenditure is

J. R. Heberle; C. F. Edwards

2009-01-01

369

NEW DEVELOPMENT IN DISPERSION EXPERIMENTS AND MODELS FOR THE CONVECTIVE BOUNDARY LAYER  

EPA Science Inventory

We present recent experiments and modeling studies of dispersion in the convective boundary layer (CBL) with focus on highly-buoyant plumes that "loft" near the CBL top and resist downward mixing. Such plumes have been a significant problem in earlier dispersion models; they a...

370

49 CFR 214.107 - Working over or adjacent to water.  

Code of Federal Regulations, 2013 CFR

(a) Bridge workers working over or adjacent to water with a depth of four feet or more, or where the danger of drowning exists, shall be provided and shall use life vests or buoyant work vests in compliance with U.S. Coast Guard requirements in 46 CFR 160.047, 160.052, and...

2013-10-01

371

Groundwater and nutrient discharge through karstic coastal springs (Castelló, Spain)  

Microsoft Academic Search

Discharge of groundwater and associated chemical compounds into coastal karstic regions, which are abundant in the Mediterranean basin, is envisaged to be significant. In this study, we evaluate the groundwater discharge and its nutrient load to the open karstic site of Badum (Castelló, East Spain). Salinity profiles evidenced that groundwater discharge from coastal brackish springs causes a buoyant fresher layer,

E. Garcia-Solsona; J. Garcia-Orellana; P. Masqué; V. Rodellas; M. Mejías; B. Ballesteros; J. A. Domínguez

2010-01-01

372

Continental tectonics in the aftermath of plate tectonics  

Microsoft Academic Search

It is shown that the basic tenet of plate tectonics, rigid-body movements of large plates of lithosphere, fails to apply to continental interiors. There, buoyant continental crust can detach from the underlying mantle to form mountain ranges and broad zones of diffuse tectonic activity. The role of crustal blocks and of the detachment of crustal fragments in this process is

Peter Molnar

1988-01-01

373

Type 1193 Mini Wave-Track Buoy  

Microsoft Academic Search

TheType 1193 Mini WAVE-TRACK Buoy provides a convenient, s mall sized t ethered buoy to measure wave heave from a ship or platform. The buoyant tether cable provides a communication I ink from the buoy to a processing computer. The buoy is an orbital following buoy using an accelerometer suspension with a natural period of .35 seconds. A unique resonant

Edward C. Brainard; David Shonting

1989-01-01

374

RELATING ERROR BOUNDS FOR MAXIMUM CONCENTRATION ESTIMATES TO DIFFUSION METEOROLOGY UNCERTAINTY (JOURNAL VERSION)  

EPA Science Inventory

The paper relates the magnitude of the error bounds of data, used as inputs to a Gaussian dispersion model, to the magnitude of the error bounds of the model output. The research addresses the uncertainty in estimating the maximum concentrations from elevated buoyant sources duri...

375

The Birth of TCJ: Father's Curiosity Launched Paul Boyer on His Journey into Indian Country  

ERIC Educational Resources Information Center

From its inception in 1988, the "Tribal College Journal" (TCJ) has been a family affair. Paul Boyer, the buoyant founder of the TCJ who published, produced, and edited the magazine until 1995, says the magazine sprouted not from an idealistic plan but from a combination of his own youthful enthusiasm; the support and guidance of his late father,…

Hernandez, Juan Avila

2009-01-01

376

Evidence for a Rayleigh-Taylor type instability and upwelling of depleted density regions during equatorial spread F  

Microsoft Academic Search

Recent rocket probe, barium cloud and radar measurements conducted during equatorial spread F conditions are interpreted in terms of a Rayleigh-Taylor gravitational instability operating on the bottomside of the F peak. The persistent theoretical problems associated with strong radar echoes typically observed in patch-like structures at high altitudes are explained in terms of regions of depleted plasma density which buoyantly

M. C. Kelley; G. Haerendel; H. Kappler; A. Valenzuela; B. B. Balsley; D. A. Carter; W. L. Ecklund; C. W. Carlson; B. Haeusler; R. Torbert

1976-01-01

377

Planetary spacecraft for the 1980's  

Microsoft Academic Search

The design of spacecraft to accomplish the objectives of planetary exploration during the next decade is considered, with emphasis on development of Viking, Mariner, and Pioneer types. Projects include development of a Mars lander\\/rover, Phobos\\/Deimos lander, and the design of a Venus buoyant station. The use of 'gravity assistance' to reduce propulsion expenditure in the investigation of Jupiter is described.

R. C. Parkinson

1975-01-01

378

Location and extent of Tertiary structures in Cook Inlet Basin, Alaska, and mantle dynamics that focus deformation and subsidence  

USGS Publications Warehouse

Subduction of the buoyant Yakutat microplate likely caused deformation to be focused preferentially in upper Cook Inlet. The upper Cook Inlet region has both the highest degree of shortening and the deepest part of the Neogene basin. This forearc region has a long-wavelength magnetic high, a large isostatic gravity low, high conductivity in the lower mantle, low p-wave velocity (Vp), and a high p-wave to shear-wave velocity ratio (Vp/Vs). These data suggest that fluids in the mantle wedge caused serpentinization of mafic rocks, which may, at least in part, contribute to the long-wavelength magnetic anomaly. This area lies adjacent to the subducting and buoyant Yakutat microplate slab. We suggest the buoyant Yakutat slab acts much like a squeegee to focus mantle-wedge fluid flow at the margins of the buoyant slab. Such lateral flow is consistent with observed shear-wave splitting directions. The additional fluid in the adjacent mantle wedge reduces the wedge viscosity and allows greater corner flow. This results in focused subsidence, deformation, and gravity anomalies in the forearc region.

Haeussler, Peter J.; Saltus, Richard W.

2011-01-01

379

Initiation of Subduction Beneath the Pamirs: Results from Flexural and Gravity Modeling in the Tien Shan, Central Asia  

Microsoft Academic Search

Subduction is conventionally thought of as the underthrusting of dense, negatively buoyant oceanic crust beneath continental crust. However, in a small number of areas around the world, evidence suggests that continental crust has or is being subducted. The Pamir-Hindu Kush region is one area in which there is geophysical evidence for continental subduction occurring today. It is one of the

E. M. Chetwin; M. K. McNutt; Y. Jin

2001-01-01

380

Buoyancy Regulation by Hatchery and Wild Coho Salmon during the Transition from Freshwater to Marine Environments  

Microsoft Academic Search

One aspect of diadromy that has received little attention is buoyancy regulation in fish moving between freshwater and marine environments. Because of density differences between the two water types, fish must alter their whole-fish density (WFD) or they will become positively (float) or negatively (sink) buoyant as they change environments. This idea was first suggested over 80 year ago but

Laurie A. Weitkamp

2008-01-01

381

Ocean Disposal of CO2: Conditions for Producing Sinking CO2 Hydrate  

Microsoft Academic Search

Carbon dioxide sequestration at intermediate ocean depths in the form of a sinking CO2 stream has been shown to be technically feasible. Buoyancy characteristics of CO2 hydrate particles obtained from a coflow reactor operating under conditions that produce negatively buoyant CO2 hydrate composite particles were studied. Using a simplified process model, the limiting ratios of CO2 to water to produce

Jorge Gabitto; David Riestenberg; Sangyong Lee; Liyuan Liang; Costas Tsouris

2004-01-01

382

Investigation of soot formation and temperature field in laminar diffusion flames of LPG–air mixture  

Microsoft Academic Search

Soot formation and burnout were studied at atmospheric pressure in co-flowing, axisymmetric, buoyant laminar diffusion flames and double flames of liquefied petroleum gases (LPG)–air mixtures. In diffusion flames, two different fuel flow rates were examined. In double flames, three different primary air flow rates were examined. A soot sampling probe and a thermocouple were used to measure the local soot

Haroun A. K. Shahad; Yassar K. A. Mohammed

2000-01-01

383

Density gradient characterization of disrupted and untreated eastern encephalitis virus  

Microsoft Academic Search

Summary Preparations of eastern encephalitis virus were disrupted by treatment with sodium deoxycholate. Tween 80 and ether, and sodium lauryl sulfate. The effect of these treatments on the viral specific activities of eastern encephalitis virus were studied. Untreated and disrupted preparations of eastern encephalitis virus were physically characterized by buoyant density centrifugation in cesium chloride density gradients and by rate

N. Karabatsos

1973-01-01

384

Thermal erosion of felsic ground by the laminar flow of a basaltic lava, with application to the Cave Basalt, Mount St. Helens, Washington  

Microsoft Academic Search

The thermal erosion of cold felsic ground by the steady laminar flow of a hot basaltic lava is examined theoretically and experimentally. Initially, a chill layer is grown and then remelted at the base of the lava flow. A steady thermal erosion velocity is then established, which is limited by the buoyant instability of the melted ground or by the

Ross C. Kerr

2009-01-01

385

How Stable Is Stable?  

ERIC Educational Resources Information Center

Provides a problem where students are asked to find the point at which a soda can floating in some liquid changes its equilibrium between stable and unstable as the soda is removed from the can. Requires use of Newton's first law, center of mass, Archimedes' principle, stable and unstable equilibrium, and buoyant force position. (MVL)

Baehr, Marie

1994-01-01

386

The Phoenix Autonomous Underwater Vehicle  

Microsoft Academic Search

The Phoenix autonomous underwater collaboration with other scientists interested in either vehicle (AUV) is a robot for student research in r obot or virtual world. Repeated validation of shallow-water sensing and control (Figure 1). Phoenix simulation extensions through real-world testing is neutrally buoyant at 387 pounds (176 kg) with a hull remains essential. Details are provided on process length of

Don Brutzman; Tony Healey; Dave Marco; Bob McGhee

1997-01-01

387

Radiative Cooling and Heating and Thermal Conduction in M87  

NASA Astrophysics Data System (ADS)

The crisis of the standard cooling flow model brought about by Chandra and XMM-Newton observations of galaxy clusters has led to the development of several models that explore different heating processes in order to assess whether they can quench the cooling flow. Among the most appealing mechanisms are thermal conduction and heating through buoyant gas deposited in the intracluster medium (ICM) by active galactic nuclei (AGNs). We combine Virgo/M87 observations of three satellites (Chandra, XMM-Newton, and BeppoSAX) to inspect the dynamics of the ICM in the center of the cluster. Using the spectral deprojection technique, we derive the physical quantities describing the ICM and determine the extra heating needed to balance the cooling flow, assuming that thermal conduction operates at a fixed fraction of the Spitzer value. We assume that the extra heating is due to buoyant gas, and we fit the data using the model developed by Ruszkowski and Begelman. We derive a scale radius for the model of ~5 kpc, which is comparable with the M87 AGN jet extension, and a required luminosity of the AGN of afew×1042ergss-1, which is comparable to the observed AGN luminosity. We discuss a scenario in which the buoyant bubbles are filled with relativistic particles and magnetic field, which are responsible for the radio emission in M87. The AGN is supposed to be intermittent and to inject populations of buoyant bubbles through a succession of outbursts. We also study the X-ray-cool component detected in the radio lobes and suggest that it is structured in blobs that are tied to the radio buoyant bubbles.

Ghizzardi, Simona; Molendi, Silvano; Pizzolato, Fabio; De Grandi, Sabrina

2004-07-01

388

Rethinking Recycling in Arcs  

NASA Astrophysics Data System (ADS)

Hacker et al EPSL 2011 and Behn et al Nature Geosci 2011 investigated pathways for return of buoyant, subducted material to arc crust. These include (1) diapirs rising into the hot mantle wedge, with extensive melts adding a component to arc magmas, (2) flow of material back up a relatively cold "subduction channel", adding solids to the lower crust and small-degree partial melts to the upper crust, (3) flow from the forearc along the base of arc crust, and (4) imbrication of forearc material into arc crust. These processes add felsic, incompatible-element-rich components to arc crust. The flux of incompatible elements such as Th in arc lavas, thought to be mainly recycled from subducted sediments, is > sediment subduction flux. There are large uncertainties: arc crustal growth rates are imprecise; young, primitive arc lavas may not be representative of magmatic flux into arc crust; sediment subduction flux may have varied. Nevertheless, this result is found for all arcs examined, using recently published growth rates. Perhaps arc growth rates that include subduction erosion are systematically overestimated. Instead or in addition, maybe significant Th comes from material other than sediments. Here, we consider the implications of pathways 1-4 for arc growth rates and incompatible element enrichment, in the context of subduction erosion and arc-arc collision. Subducting arc lithologies can become separated, with only felsic components returned to arc crust. Buoyant lithologies are mobile in viscous instabilities at > 700-800°C. Whereas thin layers such as sediments may become mobile all at once, instabilities may periodically strip the hottest parts from the top of thick buoyant layers, replacing them with hot mantle. In arc-arc collision, the top of a subducting plate starts at about 0°C on the seafloor, so heating is slow. In subduction erosion, forearc material in the subducting package can be > 200°C before erosion so buoyant lithologies reach 700-800°C faster, and in larger volumes at a given time. Subduction erosion rarely, if ever, transports significant amounts of buoyant material deep into the convecting mantle. Because buoyant material can remain part of the crust, it may often be a mistake to add all of the eroded material to the observed arc volume to derive crustal growth rates. Buoyancy instabilities during subduction erosion or arc-arc collision will accumulate felsic arc crust. For example, > 50% of Aleutian arc lavas and exposed plutons are more buoyant than mantle peridotite at 700-800°C, 3-4 GPa. The buoyant material has an average of 60-62 wt% SiO2, molar Mg/(Mg+Fe) 0.4-0.5, and trace elements identical to bulk continental crust, though western Aleutian lavas have the most depleted Sr, Nd and Pb isotope ratios of all arc lavas worldwide. In general, density sorting of arc lithologies, and subsequent partial melting as buoyant rocks rise through the mantle wedge or along a subduction channel, could lead to a kind of double and triple distillation. Incompatible elements such as Th would be enriched in arc crust, retaining correlations with isotopic indicators of a recycled sediment component, while Th-poor, dense, mafic lavas and lower crustal cumulates return to the convecting mantle.

Kelemen, P.; Behn, M. D.; Jagoutz, O.

2012-12-01

389

Specific binding of sup 125 I-rErythropoietin to Friend polycythemia virus-transformed erythroleukemia cells purified by centrifugal elutriation  

SciTech Connect

We have used countercurrent centrifugal elutriation (CCE) to determine the distribution of cells with respect to cell volume and buoyant density for an erythroleukemia cell line (JG6) transformed by the polycythemia strain of Friend virus (FV-P), and to determine the effect of inducing the cells to differentiate with dimethylsulfoxide (DMSO) on this distribution. CCE made it possible to obtain suspensions of modal JG6 populations virtually free of dead cells and uniform with respect to volume and buoyant density. These modal populations were assayed for specific binding of erythropoietin (Epo). Between 500 and 550 Epo receptors per cell were detected. These belonged to a single class having a dissociation constant of 0.36 nM. DMSO induction of differentiation of the JG6 cells had no effect on the number of Epo receptors expressed.

Correa, P.N.; Bard, V.; Axelrad, A.A. (Univ. of Toronto (Canada))

1990-01-01

390

A hybrid airship concept for Naval missions  

NASA Technical Reports Server (NTRS)

A preliminary analysis of a hybrid semibuoyant delta-planform airship was performed using a computer synthesis program. The delta-planform hull shape was studied parametrically to determine the effects on vehicle performance for two Navy antisubmarine missions. The effects of buoyancy ratio, design speed, and altitude were also studied. The results suggest that long-range mission vehicles require a near buoyant or fully buoyant design and that there is no special advantage to the use of a lifting-body hull shape. For shorter-range missions, hybrid vehicles may have merit, and optimum vehicle buoyancy varies depending on whether a minimum-weight or minimum-fuel-consumption design is desired. As compared with conventionally shaped airships, the benefits, if any, from a lifting-body configuration will be limited to missions requiring relatively higher flight speeds.

Harper, M.

1976-01-01

391

Mosquito mass rearing technology: a cold-water vortex device for continuous unattended separation of Anopheles arabiensis pupae from larvae.  

PubMed

In mass rearing of anopheline mosquitoes, pupae are usually separated from larvae on a daily basis to prevent unwanted adult emergence from trays. Depending on the device and species, 2 physical characteristics have most often been used for separation: buoyant density and size. In this report, we describe a system for continuous separation of Anopheles arabiensis larvae from pupae based on the natural difference in buoyant density and behavior between the 2 stages. We determined that temperatures 4-15 degrees C caused neither mortality nor reduction in likelihood of pupation or emergence. Separation improved as temperatures decreased down to 4 degrees C. We devised and demonstrated a 15 degrees C water vortex separator that we anticipate can process approximately 1 million larvae and pupae per hour with a < 0.3% pupal contamination rate and which operates unattended. PMID:22017086

Balestrino, Fabrizio; Gilles, Jérémie R L; Soliban, Sharon M; Nirschl, Anton; Benedict, Quentin E; Benedict, Mark Q

2011-09-01

392

Weighing single cells in two fluids: measuring mass, volume and density  

NASA Astrophysics Data System (ADS)

The Suspended Microchannel Resonator (SMR) is a highly sensitive cantilever-based mass sensor shown to be capable of weighing the buoyant mass of living single cells. We have engineered SMR-based microfluidic systems to achieve consecutive weighing of single cells in two different fluids, with controlled exposure times. By choosing fluids of two different densities, the paired buoyant mass measurements are used to characterize single-cell volume, mass and density. With density precision of 0.001 g.cm-3, we explore the application of our techniques to samples ranging from bacterial to mammalian cells and show that cellular density is a tightly regulated biological property within populations, up to 100-fold more so than the other size parameters.

Feijó Delgado, Francisco; Grover, William; Cermak, Nathan; Bryan, Andrea; Manalis, Scott

2012-02-01

393

Pore-throat sizes in sandstones, siltstones, and shales: Reply  

USGS Publications Warehouse

In his discussion of my article (Nelson, 2009), W. K. Camp takes issue with the concept that buoyancy is not the dominant force in forming and maintaining the distribution of gas in tight-gas accumulations (Camp, 2011). I will restrict my response to the issues he raised regarding buoyant versus nonbuoyant drive and to a few comments regarding water saturation and production. I claim that the pressure generated in petroleum source rocks (Pg), instead of the buoyancy pressure (Pb), provides the energy to charge most tight sandstones with gas. The arguments are fourfold: (1) buoyant columns of sufficient height seldom exist in low-permeability sand-shale sequences, (2) tight-gas systems display a pressure profile that declines instead of increases upward, (3) gas is pervasive in overpressured systems, and (4) source rocks can generate pore pressures sufficiently high to charge tight sandstones.

Nelson, Philip H.

2011-01-01

394

The geochemistry of deepwater particulate matter over the hydrothermal field at 9°d50' N (the East Pacific Rise)  

NASA Astrophysics Data System (ADS)

The results of geochemical studies of particulate matter in the water mass over the hydrothermal field at 9°50' N on the East Pacific Rise are presented. The particulate matter was tested in background waters, in the buoyant plume, and in the near-bottom waters. The contents of Si, Al, P, Corg, Fe, Mn, Cu, Zn, Ni, Co, As, Cr, Cd, Pb, Ag, and Hg were determined. No definite correlations were found between the ele-ments in the background waters. Many of the chemical elements correlated with Fe and associated with its oxyhydroxides in the buoyant plume. In the near-bottom waters, microelements are associated with Fe, Zn, and Cu (probably, to their sulfides formed under fluid mixing with seawater). The matter precipitated in a sed-imentation trap was similar to the near-bottom particulate matter in the elemental composition.

Lukashin, V. N.; Demina, L. L.; Gordeev, V. V.; Gordeev, V. Yu.

2012-04-01

395

Combining a rotating magnetic field and crystal rotation in the floating-zone process with a needle-eye induction coil  

NASA Astrophysics Data System (ADS)

This paper presents numerical solutions for the steady, axisymmetric melt motions in a simplified model of the floating-zone process with a needle-eye induction coil. With only buoyant and thermocapillary convections, there are two meridional circulations, and the stronger, outer circulation involves an undesirable radially inward flow near the crystal-melt interface. Adding crystal rotation alone can only decrease the magnitudes of the meridional circulations. Adding a rotating magnetic field alone has the undesirable effect of increasing the magnitude and extent of the radially inward flow near the crystal-melt interface. Combining a rotating magnetic field in one azimuthal direction with crystal rotation in the opposite azimuthal direction overwhelms the buoyant and thermocapillary convections and produces the desired radially outward flow over the entire crystal-melt interface. The magnitude of this radially outward flow is easily controlled by changing either the angular velocity of the crystal rotation or the strength of the rotating magnetic field.

Ma, N.; Walker, J. S.; Lüdge, A.; Riemann, H.

2001-08-01

396

Lithospheric processes  

SciTech Connect

The authors used geophysical, geochemical, and numerical modeling to study selected problems related to Earth's lithosphere. We interpreted seismic waves to better characterize the thickness and properties of the crust and lithosphere. In the southwestern US and Tien Shari, crust of high elevation is dynamically supported above buoyant mantle. In California, mineral fabric in the mantle correlate with regional strain history. Although plumes of buoyant mantle may explain surface deformation and magmatism, our geochemical work does not support this mechanism for Iberia. Generation and ascent of magmas remains puzzling. Our work in Hawaii constrains the residence of magma beneath Hualalai to be a few hundred to about 1000 years. In the crust, heat drives fluid and mass transport. Numerical modeling yielded robust and accurate predictions of these processes. This work is important fundamental science, and applies to mitigation of volcanic and earthquake hazards, Test Ban Treaties, nuclear waste storage, environmental remediation, and hydrothermal energy.

Baldridge, W. [and others

2000-12-01

397

Feasibility study of modern airships, phase 1. Volume 2: Parametric analysis (task 3). [lift, weight (mass)  

NASA Technical Reports Server (NTRS)

Various types of lighter-than-air vehicles from fully buoyant to semibuoyant hybrids were examined. Geometries were optimized for gross lifting capabilities for ellipsoidal airships, modified delta planform lifting bodies, and a short-haul, heavy-lift vehicle concept. It is indicated that: (1) neutrally buoyant airships employing a conservative update of materials and propulsion technology provide significant improvements in productivity; (2) propulsive lift for VTOL and aerodynamic lift for cruise significantly improve the productivity of low to medium gross weight ellipsoidal airships; and (3) the short-haul, heavy-lift vehicle, consisting of a simple combination of an ellipsoidal airship hull and existing helicopter componentry, provides significant potential for low-cost, near-term applications for ultra-heavy lift missions.

Lancaster, J. W.

1975-01-01

398

Large Prandtl number finite-amplitude thermal convection with Maxwell viscoelasticity. [earth mantle rheological model  

NASA Technical Reports Server (NTRS)

It has long been known that the earth behaves viscoelastically. Viscoelasticity may be of importance in two aspects of mantle convection, including time-dependent behavior and local storage of recoverable work. The present investigation makes use of thermal convection in a box as a prototype of mantle flow. It is demonstrated that recoverable work can be important to the local mechanical energy balance in the descending lithosphere. It is shown that, even when assuming large viscoelastic parameters, an inherent time-dependence of viscoelastic convection appears only in local exchanges of mechanical energy. There is no strong exchange between buoyant potential energy and recoverable strain energy in the Rayleigh number range investigated. The investigation is mainly concerned with viscoelastic effects occurring on a buoyant time scale. It is found that viscoelastic effects have a negligible influence on the long term thermal energetics of mantle convection.

Ivins, E. R.; Unti, T. W. J.; Phillips, R. J.

1982-01-01

399

Rivers as a source of marine litter - A study from the SE Pacific.  

PubMed

Composition and abundance of persistent buoyant litter (plastics, polystyrene and manufactured wood) were investigated at riversides and on adjacent coastal beaches of four rivers flowing into the SE Pacific Ocean. Persistent buoyant litter made up the main share of litter at riversides (36-82%) and on coastal beaches near the river mouths (67-86%). The characteristic litter composition of each river is attributable to human influences along its course. Riverine litter items were deposited to both sides of the river mouths on coastal beaches, and their abundance generally declined with distance from the river mouth. However, maximum litter accumulations were often found on beaches north of the river mouth, suggesting a long-term influence of the prevailing equatorward low-level jet along the Chilean coast. The results confirm that riverine transport has an important impact on litter abundances on coastal beaches. PMID:24726186

Rech, S; Macaya-Caquilpán, V; Pantoja, J F; Rivadeneira, M M; Jofre Madariaga, D; Thiel, M

2014-05-15

400

Measurements of single spherical particle trajectories with lateral migration in a slit with one porous wall under laminar flow conditions  

NASA Astrophysics Data System (ADS)

Lateral migration of spherical, neutrally buoyant particles moving in Poiseuille flow was measured in a slit with a porous membrane at one wall. Neutrally buoyant particles with diameters of 226 ?m were injected into 22% glycerol-water solution flowing vertically in a slit channel (1.6 × 50 × 152 mm). The particles were illuminated with a strobe at 25 flashes/sec and photographed with a 4 × 5 camera under dark field conditions. Measured particle trajectories are compared with theoretically predicted trajectories based on Altena and Belfort's (1984) model. The theoretical trajectories are within the limits of error in the measured trajectories. By confirming the Altena and Belfort (1984) model within the range of experimental conditions tested here, inertial interactions should be included when modeling membrane fouling of dilute suspensions (Belfort et al. 1982).

Otis, J. R.; Altena, F. W.; Mahar, J. T.; Belfort, G.

1986-01-01

401

Biomimetic mechanics behaviors of the strider leg vertically pressing water  

NASA Astrophysics Data System (ADS)

Water striders capture the amazing feature to walk on water surface, and this phenomenon triggered extensive investigations in the past decades. We model the strider leg as a fiber vertically pressing into water surface and explore some striking mechanics behaviors in this process. First, the meniscus morphology is exactly solved by a numerical scheme. Based upon this solution, a non-dimensional parameter is defined in order to properly characterize the "capillary effect" of the objects with different volumes. The discussion of the buoyant force shows that the apparent contact angle has little impact on the variation of the water-supporting force. Besides this, there is no need for the strider leg to pierce into water, for the pinning of the triple contact line ensures a bigger buoyant force. In addition, the radius of the leg should be in an appropriate range to support the body weight. These analyses may cast light on how to design new-typed miniature aquatic devices.

Liu, Jianlin; Sun, Jing; Mei, Yue

2014-06-01

402

Floating microspheres: to prolong the gastric retention time in stomach.  

PubMed

A gastroretentive drug delivery system with prolong retention time in the stomach have great practical importance for drugs with an absorption window in the upper small intestine. Floating drug delivery system are expected to remain buoyant in the gastric content for prolong duration of time thus enhance the bioavailability of drugs. There are several gastroretentive drug delivery systems, which are floating microspheres, granules, tablets, powder, pills, laminated films and capsules. Floating microspheres are gaining special attention because of their wide applicability in the targeting of drug to stomach. Floating microspheres have several advantages, that they remain buoyant in the stomach and distributed uniformly to avoid the vagaries of gastric emptying and release the drug for prolong period of time. PMID:22023206

Bhadouriya, Priyanka; Kumar, Manish; Pathak, Kamla

2012-05-01

403

Sedimentation equilibrium and the generalized Archimedes' principle  

NASA Astrophysics Data System (ADS)

The buoyancy concept is critically re-examined for applications to dispersions of nano-particles, such as colloids, proteins, or macromolecules. It is shown that when the size of the buoyant particle is not too different (say, at most a factor of ten) from the size of the dispersed particles, new intriguing phenomena emerge, leading to the violation of the Archimedes' principle. The resulting buoyancy force depends not only on the volume of the particle and on the mass density of the dispersion, but also on the relative size of the particles, on their geometry, and on the interactions between the buoyant particle and the fluid. Explicit expressions for such a generalized Archimedes' principle are obtained and the results are tested against targeted experiments in colloidal dispersions.

Parola, Alberto; Buzzaccaro, Stefano; Secchi, Eleonora; Piazza, Roberto

2013-03-01

404

Sedimentation equilibrium and the generalized Archimedes' principle.  

PubMed

The buoyancy concept is critically re-examined for applications to dispersions of nano-particles, such as colloids, proteins, or macromolecules. It is shown that when the size of the buoyant particle is not too different (say, at most a factor of ten) from the size of the dispersed particles, new intriguing phenomena emerge, leading to the violation of the Archimedes' principle. The resulting buoyancy force depends not only on the volume of the particle and on the mass density of the dispersion, but also on the relative size of the particles, on their geometry, and on the interactions between the buoyant particle and the fluid. Explicit expressions for such a generalized Archimedes' principle are obtained and the results are tested against targeted experiments in colloidal dispersions. PMID:23534662

Parola, Alberto; Buzzaccaro, Stefano; Secchi, Eleonora; Piazza, Roberto

2013-03-21

405

Basalt Reactivity in the Presence of H2O-Saturated Supercritical CO2 Containing Gaseous Sulfur Compounds  

Microsoft Academic Search

Future impacts of climate change may be minimized by capture of emissions, primarily CO2 from fossil-fueled electric generating stations and subsequent sequestration in deep geologic formations. Injection of dry liquid CO2 into porous geologic reservoirs for long term storage is expected to eventually form a buoyant water-saturated bubble of supercritical fluid. Depending on purification processes and underground injection control regulations,

H. T. Schaef; P. McGrail; A. T. Owen

2009-01-01

406

Three-Dimensional Numerical Simulation of Plume Downwash with a k-  

Microsoft Academic Search

Plume downwash at a large oil-gathering facility in the Prudhoe Bay, Alaska oil-field reservation was simulated in a series of numerical experiments. The purpose of this study was to investigate the potential of the numerical model as a means of assessing the impact of pollutants emitted from buoyant sources influenced by complex aerodynamic wakes. The model is a three-dimensional, Cartesian

Alex Guenther; Brian Lamb; David Stock

1990-01-01

407

Effect of bubble deformation on the properties of bubbly flows  

Microsoft Academic Search

Direct numerical simulations of the motion of 27 three-dimensional deformable buoyant bubbles in periodic domains are presented. The full Navier Stokes equations are solved by a parallelized finite-difference\\/front-tracking method that allows a deformable interface between the bubbles and the suspending fluid and the inclusion of surface tension. The Eötvös number is taken as equal to 5, so that the bubbles

Bernard Bunner; Grétar Tryggvason

2003-01-01

408

Dynamics of homogeneous bubbly flows Part 1. Rise velocity and microstructure of the bubbles  

Microsoft Academic Search

Direct numerical simulations of the motion of up to 216 three-dimensional buoyant bubbles in periodic domains are presented. The full Navier Stokes equations are solved by a parallelized finite-difference\\/front-tracking method that allows a deformable interface between the bubbles and the suspending fluid and the inclusion of surface tension. The governing parameters are selected such that the average rise Reynolds number

Bernard Bunner; Grétar Tryggvason

2002-01-01

409

Observations at the tidal plume front of a high-volume river outflow  

Microsoft Academic Search

We present shipboard observations of very strong convergence, vertical velocities and mixing, and near-bed impacts associated with the leading-edge front of the tidally-pulsed Columbia River plume. With upwelling-favorable winds and riverflow of 4900 m3s?1, the plume propagates as a buoyant gravity current with a rotary, bore-like vertical frontal circulation and downwelling as strong as 0.35 m s?1. In waters as

Philip M. Orton; David A. Jay

2005-01-01

410

Volatile Transport by Volcanic Plumes on Earth, Venus and Mars  

NASA Technical Reports Server (NTRS)

Explosive volcanic eruptions can produce sustained, buoyant columns of ash and gas in the atmosphere (Fig. 1). Large flood basalt eruptions may also include significant explosive phases that generate eruption columns. Such eruptions can transport volcanic volatiles to great heights in the atmosphere. Volcanic eruption columns can also redistribute chemical species within the atmosphere by entraining ambient atmosphere at low altitudes and releasing those species at much higher altitudes.

Glaze, Lori S.; Self, Stephen; Baloga, Steve; Stofan, Ellen R.

2012-01-01

411

Haloarchaeal Megaplasmids  

Microsoft Academic Search

\\u000a Many salt-loving archaea, or haloarchaea, commonly harbor one or more megaplasmids in their genomes. The haloarchaeal model\\u000a organism, Halobacterium sp. NRC-1, contains two related replicons, pNRC100 (191 kb in size) and pNRC200 (365 kb), both of which code for buoyant\\u000a gas vesicles as well as other genes that are important or essential for the host. Two other haloarchaea, Haloarcula marismortui

Shiladitya DasSarma; Melinda Capes; Priya DasSarma

412

Toxic metals removal from waste waters by upflow filtration with floating filter medium. I. The case of zinc  

Microsoft Academic Search

The effectiveness of upflow filtration to remove zinc ions was studied in the present paper. Zinc ions were precipitated by employing either the conventional hydroxide route or the carbonate-enhanced route (addition of NaOH plus Na2CO3). Upflow column filtration with synthetic buoyant filter media was used for the subsequent solid–liquid separation of toxic metal precipitates. The experiments were conducted in semi-batch

A. I. Zouboulis; N. K. Lazaridis; A. Grohmann

2002-01-01

413

Purification, characterization and serological detection of virus-like particles associated with banana bunchy top disease in Australia  

Microsoft Academic Search

Isometric virus-like particles, 18 nm in diameter, have been isolated from banana (Musa spp.) affected by bunchy top disease in Australia. Banana bunchy top disease-associated virus-like particles (BBTV) banded as a single component with buoyant density of 1-28 to 1.29 g\\/ml in Cs2SO4 and sedimented at about 46S in isokinetic sucrose density gradients. The A260\\/.42S 0 of purified preparations was

John E. Thomas; Ralf G. Dietzgen

1991-01-01

414

Characterization, pathogenicity and neutralization studies of a nervous necrosis virus isolated from grouper, Epinephelus tauvina, in Singapore  

Microsoft Academic Search

A virus isolated from diseased marine fish, Grouper, Epinephelus tauvina, was cultured in sea bass (SB) cell line, characterized and its pathogenicity and neutralization studies were carried out. This isolated virus is an icosahedral virus with a mean diameter of 28–30 nm and has buoyant density of 1.30–1.35 g\\/ml. It replicates exclusively in the cytoplasm and forms paracrystalline array and

A Hegde; C. L Chen; Q. W Qin; T. J Lam; Y. M Sin

2002-01-01

415

Localization of a highly active pool of type II phosphatidylinositol 4-kinase in a p97/valosin-containing-protein-rich fraction of the endoplasmic reticulum.  

PubMed Central

Different phosphoinositides are synthesized in cell membranes in order to perform a variety of functions. One of the most abundant of these lipids is phosphatidylinositol (PI) 4-phosphate (PI4P), which is formed in human eukaryotes by type II and type III phosphatidylinositol 4-kinase (PI4K II and III) activities. PI4K II activity occurs in many different subcellular membranes, although no detailed analysis of the distribution of this activity has been reported. Using density gradient ultracentrifugation, we have previously found that in A431 cells the predominant PI4K activity arises from a type II alpha enzyme that is localized to a buoyant membrane fraction of unknown origin [Waugh, Lawson, Tan and Hsuan (1998) J. Biol. Chem. 273, 17115-17121]. We show here that these buoyant membranes contain an activated form of PI4K II alpha that can be separated from the bulk of the PI4K II alpha protein in A431 and COS-7 cells. Proteomic analysis revealed that the buoyant membrane fraction contains numerous endoplasmic reticulum (ER)-marker proteins, although it was separated from the bulk of the ER, ER-Golgi intermediate compartment, transitional ER, Golgi and other major subcellular membranes. Furthermore, the majority of the cytoplasmic valosin-containing protein (VCP), an AAA+ATPase implicated in various ER, transitional ER, Golgi and nuclear functions, was almost completely localized to the same buoyant membrane fraction. Co-localization of VCP and PI4K activity was confirmed by co-immunoprecipitation. These results suggest the previously unsuspected existence of an ER-related domain in which the bulk of the cellular PI4P synthesis and VCP are localized.

Waugh, Mark G; Minogue, Shane; Anderson, J Simon; Balinger, Adam; Blumenkrantz, Deena; Calnan, Denis P; Cramer, Rainer; Hsuan, J Justin

2003-01-01

416

Quantitative particle microscopy in self-metered fluids.  

PubMed

We describe a simple device that volumetrically samples poured liquids and draws buoyant? materials into a single field of view for quantitative particle microscopy. Our approach relies on the formation of axisymmetric menisci and computational models of the static fluid developed using surface evolver showed close agreement with experiment. The apparatus was evaluated by counting pollen and demonstrated utility for the field analysis of microparticles. PMID:23517459

White, L V; Cooke, I R; Wakes, S J; Sowerby, S J

2013-06-01

417

The Equation of State and Petrogenesis of Komatiite  

Microsoft Academic Search

1. The equation of state of a molten komatiite was determined from 5 to 36 GPa via shock wave compression from 1550^circC and 0 bar. Shock velocity, U_{rm S}, and particle velocity, U_{rm P}, in km\\/s follow the relationship U _{rm S} = 3.13(+\\/- 0.03) + 1.47(+\\/-0.03) U _{rm P}. Olivine (Fo_{rm 94} ) and clinopyroxene will be neutrally buoyant

Gregory Hale Miller

1990-01-01

418

Thermal Effects on the "Ice-Cube Puzzle"  

ERIC Educational Resources Information Center

When an ice cube floating on water in a container melts, it is said in some textbooks that the water level does not change. However, as pointed out by Lan in a recent work, when the buoyant force from a less dense fluid resting above the waterline is taken into account, one should expect a detectable "increase" in the volume of water. Here in this…

Lima, F. M. S.; Monteiro, F. F.

2012-01-01

419

New multi-scale models on mesoscales and squall lines  

Microsoft Academic Search

Squall lines are coherent turbulent traveling waves on scales of order 100 km in\\u000athe atmosphere that emerge in a few hours from the interaction of strong vertical shear and moist\\u000adeep convection on scales of order 10 km. They are canonical coherent structures in the tropics and\\u000amiddle latitudes reflecting upscale conversion of energy from moist buoyant sources to

Andrew J. Majda; Yulong Xing

2010-01-01

420

Measurements of Lagrangian Atmospheric Dispersion Statistics over Open Water  

Microsoft Academic Search

Atmospheric dispersion statistics in the Lagrangian frame have been evaluated over open water by using a double-theodolite system to track neutrally buoyant balloons released a few kilometers off-shore during onshore winds. Analysis of the trajectories recorded in various atmospheric stabilities finds Lagrangian integral time scales corresponding to Pasquill stability categories C, D and E equal, respectively, to 9.0, 7.3 and

C. M. Sheih; P. Frenzen; R. L. Hart

1980-01-01

421

Measurements of Lagrangian atmospheric dispersion statistics over open water  

Microsoft Academic Search

Atmospheric dispersion statistics in the Lagrangian frame have been evaluated over open water by using a double-theodolite system to track neutrally buoyant balloons released a few kilometers offshore during onshore winds. Analysis of the trajectories recorded in various atmospheric stabilities finds Lagrangian integral time scales corresponding to Pasquill stability categories C, D and E equal, respectively, to 9.0, 7.3 and

C. M. Sheih; P. Frenzen; R. L. Hart

1980-01-01

422

Driving bubbles out of glass  

NASA Technical Reports Server (NTRS)

Surface tension gradient in melt forces gas bubbles to surface, increasing glass strength and transparency. Conventional chemical and buoyant fining are extremely slow in viscous glasses, but tension gradient method moves 250 um bubbles as rapidly as 30 um/s. Heat required for high temperature part of melt is furnished by stationary electrical or natural-gas heater; induction and laser heating are also possible. Method has many applications in industry processes.

Mattox, D. M.

1981-01-01

423

STS-26 mission specialists participate in EVA simulation in JSC's WETF  

NASA Technical Reports Server (NTRS)

STS-26 Discovery, Orbiter Vehicle (OV) 103, mission specialists George D. Nelson (left) and John M. Lounge, wearing extravehicular mobility units (EMUs), participate in a contingency extravehicular activity (EVA) simulation in JSC's Weightless Environment Training Facility (WETF) Bldg 29. Nelson, neutrally buoyant (floating), watches as Lounge, assisted by SCUBA divers, enters payload bay (PLB) mockup through airlock hatch. Photograph was taken by Keith Meyers of the NEW YORK TIMES.

1988-01-01

424

2D Numerical Models of Ridge-Trench Collision: Implications for Slab Detachment Beneath Baja California  

Microsoft Academic Search

The approach of a buoyant spreading ridge to a subduction zone is a scenario that may lead to detachment of a subducted slab. Previous work has called upon the detachment process as a possible explanation for observed ridge abandonment and slab-window related magmatism in Baja CA\\/western Mexico, but such a scenario has not previously been tested using fully-dynamic numerical models.

E. R. Burkett; M. I. Billen

2008-01-01

425

Initiation of Subduction Zones as a Consequence of Lateral Compositional Buoyancy Contrast within the Lithosphere: a Petrological Perspective  

Microsoft Academic Search

Tonga and Mariana fore-arc peridotites, inferred to represent their respective sub-arc mantle lithospheres, are compositionally highly depleted (low Fe\\/Mg) and thus physically buoyant relative to abyssal peridotites representing normal oceanic litho- sphere (high Fe\\/Mg) formed at ocean ridges. The observation that the depletion of these fore-arc lithospheres is unrelated to, and pre-dates, the inception of present-day western Pacific subduction zones

YAOLING NIU; JULIAN A. PEARCE

2003-01-01

426

The history and decay of a Mediterranean salt lens  

Microsoft Academic Search

Subsurface coherent vortices called Meddies1 are formed by the outflow of salty water from the Mediterranean Sea1,2 into the North Atlantic. In October 1984 we began a study to observe the life history and large-scale changes of a Meddy by identifying a specific Meddy, and carefully mapping it and seeding it with Sofar floats3. (These neutrally buoyant floats are tracked

Laurence Armi; Dave Hebert; Neil Oakey; James Price; Philip L. Richardson; Thomas Rossby; Barry Ruddick

1988-01-01

427

Photoassisted oxidation of oil films on water. Final performance report, January 1, 1990--March 31, 1993  

SciTech Connect

The objective of the project has been the development of a technology for cleaning up oil spills on water through their photocatalytic oxidation. The photocatalyst used was titanium dioxide. Nanocrytalline TiO{sub 2}, of anatase or anatase/rutile phase, was bound to hollow ceramic microspheres of sufficiently low density to be buoyant on water. In the presence of these, under sunlight, oil films were photocatalytically oxidized by dissolved oxygen.

Heller, A.

1994-04-19

428

Co-localization of atmospheric H 2 oxidation activity and high affinity H 2-oxidizing bacteria in non-axenic soil and sterile soil amended with Streptomyces sp. PCB7  

Microsoft Academic Search

Two complementary experimental approaches were utilized to examine the extent to which free soil hydrogenases and H2-oxidizing bacteria contribute to the soil uptake of atmospheric H2. First, high affinity hydrogenase activity and H2-oxidizing bacteria were fractionated in non-axenic soil and axenic soil colonized with the high affinity H2-oxidizing bacterium Streptomyces sp. PCB7. Non-axenic soil was fractionated by buoyant density centrifugation.

Philippe Constant; Soumitra Paul Chowdhury; Laura Hesse; Ralf Conrad

2011-01-01

429

A comparison of clay colloid and artificial microsphere transport in natural discrete fractures  

Microsoft Academic Search

Transport of monodispersed buoyant 1-?m latex microspheres, dense 1.34-?m montmorillonite particles, Li+ and Br? was investigated in a naturally fractured chalk core with an average equivalent hydraulic aperture of 183 ?m. Studied parameters were: tracer arrival time, C\\/C0 values, mass recovery, size distribution and the impact of initial concentration. Breakthrough time of both colloidal tracers was faster than that of

Ori Zvikelsky; Noam Weisbrod; Avraham Dody

2008-01-01

430

Antioxidative Activity of HDL Particle Subspecies Is Impaired in Hyperalphalipoproteinemia: Relevance of Enzymatic and Physicochemical Properties  

Microsoft Academic Search

Objective—Hyperalphalipoproteinemia (HALP) is characterized by elevated plasma levels of high-density lipoprotein (HDL) particles with altered composition, metabolism, and function. The impact of such modification on antioxidative activities of HDL subfractions is indeterminate. Methods and Results—Gradient fractionation revealed that buoyant HDL2b and 2a and small dense HDL3b and 3c levels were elevated up to 2.0-fold in HALP subjects (n9; mean plasma

Anatol Kontush; Eliana Cotta de Faria; Sandrine Chantepie; M. John Chapman

2009-01-01

431

The mid-depth circulation of the subpolar North Atlantic Ocean as measured by subsurface floats  

Microsoft Academic Search

The multi-year mean, mid-depth circulation of the subpolar North Atlantic Ocean was estimated from direct velocity measurements obtained over a 7.5-year period by 211 neutrally-buoyant, profiling, subsurface floats. We present a statistical analysis of these drift velocity data, and describe the features of the circulation from 400–1500m depth as measured by the floats. The time-lagged auto-covariances of velocity indicate a

Kara L. Lavender; W. Brechner Owens; Russ E. Davis

2005-01-01

432

Advanced Numerical Modeling of Turbulent Atmospheric Flows  

NASA Astrophysics Data System (ADS)

The present chapter introduces the method of computational simulation to predict and study turbulent atmospheric flows. This includes a description of the fundamental approach to computational simulation and the practical implementation using the technique of large-eddy simulation. In addition, selected contributions from IPA scientists to computational model development and various examples for applications are given. These examples include homogeneous turbulence, convective boundary layers, heated forest canopy, buoyant thermals, and large-scale flows with baroclinic wave instability.

Kühnlein, Christian; Dörnbrack, Andreas; Gerz, Thomas

433

Drag-Based `Hovering' in Ducks: The Hydrodynamics and Energetic Cost of Bottom Feeding  

Microsoft Academic Search

Diving ducks use their webbed feet to provide the propulsive force that moves them underwater. To hold position near the bottom while feeding, ducks paddle constantly to resist the buoyant force of the body. Using video sequences from two orthogonal cameras we reconstructed the 3-dimensional motion of the feet through water and estimated the forces involved with a quasi-steady blade-element

Gal Ribak; John G. Swallow; David R. Jones; Yan Ropert-Coudert

2010-01-01

434

THERMAL ENVIRONMENT OF OUTDOOR UNITS OF VRV SYSTEM IN HIGH RISE BUILDING  

Microsoft Academic Search

Variable Refrigerant Volume(VRV) air-conditioning system is more liable to meet thermal environment problem than other systems such as split-type air-or window-type air-conditioner because its capacity of outdoor unit is much higher. When used in high-rise building, hot air dissipated by the outdoor units will induce buoyant airflow and increase the working temperature of units at high floor when these heat

Gang Wang; Yafeng Hu; Songtao Hu

435

Buoyancy-driven propagation of an isolated fluid-filled crack in rock: implication for fluid transport in metamorphism  

Microsoft Academic Search

A new model for upward transport of buoyant fluid released during metamorphism is proposed. The model is fluid transport by buoyancy-driven propagation of isolated fluid-filled cracks. The mechanical behavior of a two-dimensional, isolated, vertical, and fluid-filled crack in impermeable rock is investigated using linear fractire mechanics and fluid dynamics. The results show that steady-state crack propagation which causes long-distance transport

Yoshito Nakashima

1993-01-01

436

Isolation and Characterization of an Equine Adenovirus  

PubMed Central

A viral agent was isolated from lung tissue obtained upon necropsy of an Arabian foal which had exhibited clinical signs of pneumonia. The virus is 75 nm in diameter, cubic in symmetry, and resistant to chloroform and low pH (3.0). It contains deoxyribonucleic acid and has a buoyant density of 1.31 g/cm3 in cesium chloride. These findings indicate that the virus is a member of the adenovirus group. Images

Ardans, Alexander A.; Pritchett, Randall F.; Zee, Yuan Chung

1973-01-01

437

Three-dimensional miscible displacement simulations in homogeneous porous media with gravity override  

Microsoft Academic Search

High-accuracy three-dimensional numerical simulations of miscible displacements with gravity override in homogeneous porous media are carried out for the quarter five-spot configuration. Special emphasis is placed on describing the influence of viscous and gravitational effects on the overall displacement dynamics in terms of the vorticity variable. Even for neutrally buoyant displacements, three-dimensional effects are seen to change the character of

A. Riaz; E. Meiburg

2003-01-01

438

The influence of the interfacial heat release on nonlinear convective oscillations in two-layer systems  

NASA Astrophysics Data System (ADS)

Nonlinear convective regimes developed under the joint action of buoyant and thermocapillary effects in the silicone oil 2cSt-water system in the presence of an interfacial heat release are investigated. Transitions between the flows with different symmetry properties are studied. It is shown that the presence of the interfacial heat release can change the sequence of bifurcations and lead to the appearance of specific oscillatory regimes in the system.

Simanovskii, Ilya B.

2013-07-01

439

Sensing-based risk mitigation control of hydrogen dispersion and accumulation in a partially open space with low-height openings by forced ventilation  

Microsoft Academic Search

This paper presents the real-time sensing-based risk-mitigation control of hydrogen dispersion and accumulation in a partially open space with low-height openings by forced ventilation. In the partially open space we previously considered (Matsuura et al., Int J Hydrogen Energy, 35(10), p. 4776–4786 (2010)), a hydrogen buoyant plume is subjected to cross flows during forced ventilation, and hydrogen travels over a long

Kazuo Matsuura; Masami Nakano; Jun Ishimoto

440

A Three-Dimensional Hydro-Environmental Model of Dublin Bay  

Microsoft Academic Search

In this study, the impact of Escherichia coli emissions from a sewage treatment plant on the bathing water quality of Dublin Bay (Ireland) is assessed using a three-dimensional\\u000a hydro-environmental model. Before being discharged, the effluent from the plant is mixed with cooling water from a thermal–electrical\\u000a power generation plant, creating a warm buoyant sewage plume that can be 7–9°C higher

Zeinab Bedri; Michael Bruen; Aodh Dowley; Bartholomew Masterson

441

PROPERTIES OF THE COLONY STIMULATING FACTOR IN LEUKAEMIC AND NORMAL MOUSE SERUM§  

Microsoft Academic Search

The factor in normal and leukaemic mouse serum responsible for the stimulation of bone marrow colony growth in vitro has been characterised. It is a heat labile, non-dialysable molecule which migrates electrophoretically in the ?-globulin-post-albumin region, is resistant to treatment with ether, RNA-ase and DNA-ase, has a buoyant density of approximately 1·34 and a sedimentation coefficient of between 4·5 and

ER Stanley; WA Robinson; GL Ada

1968-01-01

442

Motions of alloying additions in the CAS steelmaking operations  

Microsoft Academic Search

Water model studies in a pilot scale ladle (D = 1.12 m andL = 0.93 m) were carried out to investigate the subsurface motion of both buoyant and sinking additions during the CAS (com-position\\u000a adjustment by sealed argon bubbling systems) alloy addition procedure in steelmaking. This technique involves placing a refractory\\u000a baffle around a rising gas\\/liquid plume within a stirred

D. Mazumdar; R. I. L. Guthrie

1993-01-01

443

Melting, dehydration, and the geochemistry of off-axis plume-ridge interaction  

Microsoft Academic Search

We present results from a series of two-dimensional numerical experiments in which synthetic melt compositions are calculated for a system in which a thermally buoyant, off-axis mantle plume interacts with a nearby ridge axis. Spatial gradients in synthetic melt properties are compared to observed spatial gradients in geochemistry from the Easter–Salas y Gomez system in an effort to constrain the

Paul S. Hall; Chris Kincaid; R. F. Viso

2004-01-01

444

The influence of the horizontal component of the temperature gradient on nonlinear convective oscillations in two-layer systems  

NASA Astrophysics Data System (ADS)

The influence of the horizontal component of the temperature gradient on nonlinear oscillatory convective regimes, developed under the joint action of buoyant and thermocapillary effects in the 47 v2 silicone oil-water system, is investigated. Cavities with different lengths have been considered. Transitions between oscillatory flow regimes with different symmetry properties and steady flows have been studied. It is shown that under the action of the horizontal component of the temperature gradient, specific asymmetric oscillatory flow develops in the system.

Simanovskii, Ilya B.; Viviani, Antonio; Dubois, Frank; Legros, Jean-Claude

2012-10-01

445

Pressure-driven flow of a suspension: Buoyancy effects  

Microsoft Academic Search

Dynamic simulation of pressure-driven flow of a non-neutrally buoyant suspension has been performed by Stokesian Dynamics. Channel flow at zero Reynolds number of a monodisperse non-Brownian suspension of spheres in a monolayer was studied for a range of three parameters: bulk particle area fraction ?Ab dimensionless gravitational parameter B = (U0\\/?u?(Ha)2, and dimensionless channel width Ha. Here, U0 is the

J. F. Morris; J. F. Brady

1998-01-01

446

Experimental investigation of a confined heated sodium jet in a co-flow  

NASA Astrophysics Data System (ADS)

Low-Prandtl-number convection is investigated in vertical axisymmetric turbulent buoyant sodium jets discharging into a slowly moving ambient. Measurements of mean velocity, mean temperature and temperature fluctuations are performed simultaneously using a miniature permanent-magnet flowmeter probe. By varying the ratio of momentum to buoyancy flux, or the densimetric Froude number, different intensities of buoyancy are obtained giving a range of conditions encompassing forced-convection jets, buoyant jets and plumes. In line with the classical properties of jets the radial velocity and temperature profiles can be described by the Gaussian function, independent of the flow regime, at all axial measuring positions. The axial decay of the centreline mean velocity for sodium is the same as for fluids of higher Prandtl number, governed by power laws with indices of [minus sign]1 for forced convection, [minus sign]2/3 for the transitional buoyant region and [minus sign]1/3 for plume flow. In contrast, the centreline mean temperatures for sodium plumes decrease with a power of [minus sign]1 compared with the [minus sign]5/3 decay for fluids of higher Prandtl number. The different behaviour in sodium is due to the dominance of molecular diffusion in heat transport, while momentum transport is dictated by turbulent diffusion, which gives a similarity solution for forced-convection jets but not for buoyant jets or plumes. The radial profiles of the temperature r.m.s. values can be described by an axisymmetric curve with two maxima, independent of the flow regime, at all axial measuring positions and the two maxima are more pronounced than in conventional fluids. The temperature fluctuations are analysed to give statistical parameters such as minimum and maximum values, skewness, flatness, probability density functions and spectral distribution. The spectral distributions display both a convective subrange and the conductive subrange predicted for fluids of low Prandtl number. Integral length scales of the temperature fluctuations are evaluated and found to be significantly smaller than turbulent velocity scales.

Knebel, J. U.; Krebs, L.; Müller, U.; Axcell, B. P.

1998-08-01

447

Chemical analysis of cell wall regeneration and reversion of protoplasts from Schizophyllum commune  

Microsoft Academic Search

In the presence of MgSO4 as osmotic stabilizer, nucleated protoplasts of Schizophyllum commune developed a large vacuole and could be isolated on the basis of their low buoyant density. All these protoplasts were capable of wall regeneration and about 50 percent reverted to the hyphal mode of growth in liquid medium. The kinetics of the formation of three main cell-wall

O. M. H. Vries; J. G. H. Wessels

1975-01-01

448

Antibodies to heterogeneous nuclear ribonucleoproteins in sera from patients with rheumatic autoimmune diseases  

Microsoft Academic Search

Ribonucleoprotein (RNP) particles sedimenting at 40 S in sucrose gradients were prepared from calf thymus nuclei. They were identified as heterogeneous nuclear RNP (hnRNP) on the basis of size, electron microscopic examination, buoyant density, and protein electrophoretic patterns. Sera from patients with systemic lupus erythematosus, rheumatoid arthritis, and mixed connective tissue disease were found to interact with hnRNP by counter-immunoelectrophoresis

Moncef Zouali; André Eyquem

1984-01-01

449

Velocity of a freely rising gas bubble in a soda-lime silicate glass melt  

NASA Technical Reports Server (NTRS)

A comparison is conducted between measured velocities for the buoyant rise of single bubbles of varying size and composition, in a soda-lime silicate glass melt, with the steady state velocities predicted by the Stokes and Hadamard-Rybczynski formulas. In all cases, the data are noted to fit the Hadamard-Rybczynski expression for steady state rise speed considerably better than the Stokes formula.

Hornyak, E. J.; Weinberg, M. C.

1984-01-01

450

STS-45 MS Foale in EMU prepares for underwater exercises in JSC's WETF pool  

NASA Technical Reports Server (NTRS)

STS-45 Atlantis, Orbiter Vehicle (OV) 104, Mission Specialist (MS) C. Michael Foale, fully suited in an extravehicular mobility unit (EMU), stands on a platform which will lower him into the nearby pool for an underwater simulation of contingency extravehicular activity (EVA) procedures. The pool is located in JSC's Weightless Environment Training Facility (WETF) Bldg 29. Weights are added around Foale's ankles so he will be neutrally buoyant during the simulation.

1991-01-01

451

ESA MS Nicollier, in EMU, is ready for JSC WETF underwater simulation  

NASA Technical Reports Server (NTRS)

European Space Agency (ESA) Mission Specialist (MS) Claude Nicollier, fully suited in an extravehicular mobility unit (EMU), is ready for an underwater extravehicular activity (EVA) simulation and familiarization session in JSC's Weightless Environment Training Facility (WETF) Bldg 29 pool. The platform Nicollier is standing on is being lowered into the 25 ft deep pool. The weights around Nicollier's ankles were added to make him neutrally buoyant.

1987-01-01

452

Stability of a bottom-heavy underwater vehicle  

Microsoft Academic Search

We study stability of underwater vehicle dynamics for a six-degree-of-freedom vehicle modeled as a neutrally buoyant, submerged rigid body in an ideal fluid. We consider the case in which the center of gravity and the center of buoyancy of the vehicle are noncoincident such that gravity introduces an orientation-dependent moment. Noting that Kirchhoff's equations of motion for a submerged rigid

Naomi Ehrich Leonard

1997-01-01

453

Modelling stellar activity cycles using deep-seated dynamos and surface flux transport  

NASA Astrophysics Data System (ADS)

We investigate the relations between tachocline-based dynamos and the surface flux transport mechanisms in stars with outer convection zones. Using our combined models of flux generation and transport, we demonstrate the importance of the buoyant rise of magnetic flux, which physically determines the emergence latitudes and tilt angles of bipolar magnetic regions. The combined effects of the dynamo strength, flux rise, and surface transport lead to various cyclic and non-cyclic time series of total unsigned surface magnetic flux.

I??k, Emre; Schmitt, Dieter; Schüssler, Manfred

2013-07-01

454

A hydrodynamic model of locomotion in the Basilisk Lizard  

Microsoft Academic Search

ORGANISMS with a body mass of more than one gram and which live at the air-water interface generally support their weight with their buoyant bodies. The maximum swimming speed these animals can attain is limited by wave-making resistance1-3. For high-speed progression across a body of water, shore birds and basilisk lizards (Basiliscus basiliscus) support their bodies above the water surface

J. W. Glasheen; T. A. McMahon

1996-01-01

455

Vertical and lateral splitting of a hydrothermal plume at Steinahóll, Reykjanes Ridge, Iceland  

Microsoft Academic Search

The generation of multiple, neutrally-buoyant intrusions by a single, bubble-rich plume [Asaeda and Imberger, J. Fluid Mech. 249 (1993) 35-57] and plume bifurcation [Ernst et al., Bull. Volcanol. 56 (1994) 159-169 Lavelle, J. Geophys. Res. 102 (1997) 3405-3420], are predicted from theory and experiments but have yet to be documented for hydrothermal plumes. In contrast, bifurcation of volcanic plumes (which

G. G. J. Ernst; R. R. Cave; C. R. German; M. R. Palmer; R. S. J. Sparks

2000-01-01

456

Vertical and lateral splitting of a hydrothermal plume at Steinahóll, Reykjanes Ridge, Iceland  

Microsoft Academic Search

The generation of multiple, neutrally-buoyant intrusions by a single, bubble-rich plume [Asaeda and Imberger, J. Fluid Mech. 249 (1993) 35–57] and plume bifurcation [Ernst et al., Bull. Volcanol. 56 (1994) 159–169; Lavelle, J. Geophys. Res. 102 (1997) 3405–3420], are predicted from theory and experiments but have yet to be documented for hydrothermal plumes. In contrast, bifurcation of volcanic plumes (which

G. G. J. Ernst; R. R. Cave; C. R. German; M. R. Palmer; R. S. J. Sparks

2000-01-01

457

The dynamics of xenolith assimilation  

Microsoft Academic Search

Xenolith assimilation has been simulated with experiments involving melting wax spheres into hot water and aqueous solutions\\u000a and characterised by a theoretical analysis. Both the cases of neutrally buoyant stationary spheres and spheres sinking through\\u000a the hot host fluid are examined. Melt generated on a sphere's surface flows (compositional convection) in two regimes; as\\u000a a sheet over one hemisphere and

Paul McLeod; R. Stephen J. Sparks

1998-01-01

458

Particle-phase distributions of pressure-driven flows of bidisperse suspensions  

Microsoft Academic Search

The phase distribution of a bimodal distribution of negatively buoyant particles in a low-Reynolds-number pressure-driven flow of a suspension in a horizontal pipe is measured using multi-frequency electrical impedance tomography (EIT). Suspensions of heavy silver-coated particles and slightly heavy PMMA particles exhibit different effective conductivities depending on the frequency of an applied electrical current. This difference allows the separate imaging

JAY T. N ORMAN; O. O GUNTADE; ROGER T. B ONNECAZE

2008-01-01

459

Localization of glyoxylate-cycle marker enzymes in peroxisomes of senescent leaves and green cotyledons  

Microsoft Academic Search

Crude particulate homogenates from leaves of barley (Hordeum vulgare L.), rice (Oryza sativa L.), leaf-beet (Beta vulgaris var.cicla L.) and pumpkin (Cucurbita pepo L.) cotyledons were separated on sucrose density gradients. The peroxisomal fractions appeared at a buoyant density of 1.25 g·cm-3 and contained most of the activities of catalase (EC 1.11.1.6), and hydroxypyruvate reductase (EC 1.1.1.81) on the gradients.

Luigi De Bellis; Piero Picciarelli; Laura Pistelli; Amedeo Alpi

1990-01-01

460

Localization of glyoxylate-cycle marker enzymes in peroxisomes of senescent leaves and green cotyledons  

Microsoft Academic Search

Crude particulate homogenates from leaves of barley (Hordeum vulgare L.), rice (Oryza sativa L.), leaf-beet (Beta vulgaris var. cicla L.) and pumpkin (Cucurbita pepo L.) cotyledons were separated on sucrose density gradients. The peroxisomal fractions appeared at a buoyant density of 1.25 g·cm-3 and contained most of the activities of catalase (EC 1.11.1.6), and hydroxypyruvate reductase (EC 1.1.1.81) on the

Luigi De Bellis; Piero Picciarelli; Laura Pistelli; Amedeo Alpi

1990-01-01

461

Transport processes during sterilization of vertical and 5 degree horizontal dead-legs  

Microsoft Academic Search

Experimental temperature profiles and biological kill data from dead-ended tubes of various diameters and lengths commonly used in biotechnology applications were compared to those predicted by a finite element model for steam-in-place (SIP) sterilization at 122°C. Diameter was shown experimentally and numerically to have a significant effect with larger diameter tubes exhibiting greater buoyant driven convective flow and more rapid

J. H. Young; W. C. Lasher; R. P. Gaber

1995-01-01

462

Laminar Flow in the Ocean Ekman Layer  

NASA Astrophysics Data System (ADS)

INTRODUCTION THE EFFECT OF A STABLE DENSITY GRADIENT THE FATAL FLAW FLOW VISUALIZATION THE DISCOVERY OF LAMINAR FLOW FINE STRUCTURE WAVE-INDUCED SHEAR INSTABILITY BILLOW TURBULENCE REVERSE TRANSITION REVISED PARADIGM ONE-DIMENSIONAL MODELLING OF THE UPPER OCEAN DIURNAL VARIATION BUOYANT CONVECTION BILLOW TURBULENCE IN THE DIURNAL THERMOCLINE CONSEQUENCES FOR THE EKMAN CURRENT PROFILE SOLAR RADIATION APPLICATIONS Slippery Seas of Acapulco Pollution Afternoon Effect in Sonar Patchiness Fisheries Climate DISCUSSION CONCLUSION REFERENCES

Woods, J. T. H.

463

Basalt Reactivity Variability with Reservoir Depth in Supercritical CO 2 and Aqueous Phases  

Microsoft Academic Search

Long term storage of CO2 in geologic formations is currently considered the most attractive option to reduce greenhouse gas emissions while continuing to utilize fossil fuels for energy production. Injected CO2 is expected to reside as a buoyant water-saturated supercritical fluid in contact with reservoir rock, the caprock system, and related formation waters. As reported by McGrail et al., experiments

H. T. Schaef; B. P. McGrail; A. T. Owen

2011-01-01

464

A Virus Associated with SR-Spirochetes of Drosophila nebulosa*  

PubMed Central

A virus is associated with a strain of transovarially-transmitted SR-spirochetes, NSR, of Drosophila. This virus, designated spv-1, is able to infect and to multiply in another strain of SR-spirochetes, WSR, thereby eliminating the SR condition from the host flies. Spv-1 contains DNA, has a buoyant density of 1.480 in CsCl, and is spherical in shape, measuring 50-60 nm in diameter. Images

Oishi, K.; Poulson, D. F.

1970-01-01

465

Float trajectories in the deep western boundary current and deep equatorial jets of the tropical Atlantic  

Microsoft Academic Search

Fourteen neutrally buoyant SOFAR floats at a nominal depth of 1800m were tracked acoustically for 3.7yr in the vicinity of the western boundary and the equator of the Atlantic Ocean. The trajectories revealed a swift, narrow, southward-flowing deep western boundary current (DWBC) extending from 7N across the equator. Two floats crossed the equator in the DWBC and went to 10S.

Philip L. Richardson; David M. Fratantoni

1999-01-01

466

Bubble nucleation, growth and coalescence during the 1997 Vulcanian explosions of Soufrière Hills Volcano, Montserrat  

Microsoft Academic Search

Soufrière Hills Volcano had two periods of repetitive Vulcanian activity in 1997, during which 88 explosions occurred. Each explosion discharged the contents of the upper 0.5-2 km of the conduit, two thirds as pyroclastic flows and the rest as fallout from 3-15-km-high buoyant plumes: frothy pumices from a deep, gas-rich zone, lava and breadcrust bombs from a degassed lava plug,

T. H. Druitt; T. Giachetti; A. Burgisser; L. Arbaret

2009-01-01

467

Quantitative models of the fallout and dispersal of tephra from volcanic eruption columns  

Microsoft Academic Search

A theoretical model of clast fallout from convective eruption columns has been developed which quantifies how the maximum clast size dispersal is determined by column height and wind strength. An eruption column consists of a buoyant convecting region which rises to a heightHB where the column density equals that of the atmosphere. AboveHB the column rises further to a heightHT

S. Carey; R. S. J. Sparks

1986-01-01

468

Adequacy of wind ventilation in upgraded shelters. Final report Oct 78-May 80  

SciTech Connect

Experimental and analytical investigations were conducted for the purpose of evaluating the adequacy of natural ventilation in upgraded shelters. A unique low-speed wind tunnel which uses photographic measurement techniques for flow tracing of neutrally buoyant bubbles through openings was utilized to conduct scaled model tests of three shelter models to determine the ventilation air throughput CFM as a function of wind speed, relative wind approach angle and opening pattern.

Henninger, R.H.; Tsal, R.J.; Krishnakumar, C.K.

1980-05-01

469

Surface-pressure variations on a triangular prism by porous fences in a simulated atmospheric boundary layer  

Microsoft Academic Search

Surface-pressure variations on a two-dimensional triangular prism model behind porous wind fences were investigated experimentally at Reynolds number of Re = 2.1 × 105. This is a basic study to evaluate the effectiveness of porous fence to abate wind-blown dusts from triangular-shaped coal piles in an open storage yard. The neutrally buoyant atmospheric boundary layer was generated in the wind

Sang-Joon Lee; Cheol-Woo Park

1998-01-01

470

Case for periodic, colossal jokulhlaups from Pleistocene glacial Lake Missoula.  

USGS Publications Warehouse

Lake Missoula (2500 km3) remained sealed as long as any segment of the glacial dam remained grounded; when the lake rose to a critical level c.600 m in depth, the glacier bed at the seal became buoyant, initiating underflow from the lake. Subglacial tunnels then grew exponentially, leading to catastrophic discharge. Calculations of the water budget for the lake basin (including input from the Cordilleran ice sheet) suggest that the lake filled every three to seven decades. -from Author

Waitt, Jr, R. B.

1985-01-01

471

Modeling wastewater discharge at the planning stage of a marine outfall system  

Microsoft Academic Search

The possibility of marine discharge of a negatively buoyant industrial waste was evaluated by a modeling study using Killworth\\u000a 3-D, which is the first version of the Modular Ocean Model (MOM). The Model was run with the recorded wind direction and speed\\u000a on the cruise dates and the circulation patterns for surface and subsurface were found to be similar with

Esin Esen; Erdem Sayin; Orhan Uslu; Canan Eronat

472

Continental tectonics in the aftermath of plate tectonics  

NASA Technical Reports Server (NTRS)

It is shown that the basic tenet of plate tectonics, rigid-body movements of large plates of lithosphere, fails to apply to continental interiors. There, buoyant continental crust can detach from the underlying mantle to form mountain ranges and broad zones of diffuse tectonic activity. The role of crustal blocks and of the detachment of crustal fragments in this process is discussed. Future areas of investigation are addressed.

Molnar, Peter

1988-01-01

473

Cell-Surface Heparan Sulfate: An Intercalated Membrane Proteoglycan  

Microsoft Academic Search

Two pools of heparan sulfate proteoglycans have been selectively solubilized from rat liver plasma membranes by successive incubations with heparin and detergent. The two populations of proteoglycans have similar polyanionic properties as indicated by identical elution positions on ion-exchange chromatography on DEAE-Sephacel but differ in buoyant density in CsCl when analyzed by density gradient centrifugation in the presence of 4

Lena Kjellen; Inger Pettersson; Magnus Hook

1981-01-01

474

Complexity of Gas Vesicle Biogenesis in Halobacterium sp. Strain NRC1: Identification of Five New Proteins  

Microsoft Academic Search

The genome of Halobacterium sp. strain NRC-1 contains a large gene cluster, gvpMLKJIHGFEDACNO, that is both necessary and sufficient for the production of buoyant gas-filled vesicles. Due to the resistance of gas vesicles to solubilization, only the major gas vesicle protein GvpA and a single minor protein, GvpC, were previously detected. Here, we used immunoblotting analysis to probe for the

Hem Dutt Shukla; Shiladitya DasSarma

2004-01-01

475

Nanoscale Controls on CO2-water-rock Interactions in Saline Reservoirs  

Microsoft Academic Search

It is becoming increasingly widely recognized that geologic sequestration of CO2, when combined with economical means of capture, may be one of the most effective approaches to reducing net CO2 emissions to the atmosphere over the next century. Injection of CO2 into saline geologic formations involves forcing a buoyant, low-viscosity fluid into a more dense, higher viscosity fluid. The difference

J. Deyoreo; D. J. Depaolo

2009-01-01

476

Rayleigh-Taylor Turbulence is Nothing Like Kolmogorov Turbulence in the Self-Similar Regime  

SciTech Connect

An increasing number of numerical simulations and experiments describing the turbulent spectrum of Rayleigh-Taylor (RT) mixing layers came to light over the past few years. Results reported in recent studies allow to rule out a Kolmogorov-like turbulence as a mechanism acting on a self-similar RT turbulent mixing layer. A different mechanism is presented, which complies with both numerical and experimental results and relates RT flow to other buoyant flows.

Poujade, Olivier [Commissariat a l'Energie Atomique, BP12, Bruyeres-le-Cha circumflex tel, 91168 (France)

2006-11-03

477

Evidence for a Rayleigh-Taylor type instability and upwelling of depleted density regions during equatorial spread F  

NASA Technical Reports Server (NTRS)

Recent rocket probe, barium cloud and radar measurements conducted during equatorial spread F conditions are interpreted in terms of a Rayleigh-Taylor gravitational instability operating on the bottomside of the F peak. The persistent theoretical problems associated with strong radar echoes typically observed in patch-like structures at high altitudes are explained in terms of regions of depleted plasma density which buoyantly rise against the gravitational field.

Kelley, M. C.; Haerendel, G.; Kappler, H.; Valenzuela, A.; Balsley, B. B.; Carter, D. A.; Ecklund, W. L.; Carlson, C. W.; Haeusler, B.; Torbert, R.

1976-01-01

478

Captive Water Current Power System  

SciTech Connect

Current energy is converted into shaft power in two stages; First, buoyant power units with stationary hydrofoil wings reach faster than the current speed by sweeping out a captive path. Second, turbines at said power units convert the fast relative local current into shaft power. Power units sweeping along the water surface, using cycloidal turbine methods, as well as power units sweeping on a submerged path, using axial flow turbine methods, are described.

Wuenscher, H. F.; Wuenscher, H. A.

1984-01-31

479

The drifting, rotating deep-ocean shearmeter  

Microsoft Academic Search

The shearmeter is a new member of the family of neutrally-buoyant subsurface Lagrangian floats (Swallow floats). It is a 10-m spar buoy with anemometer-type vanes rigidly mounted at each end, designed so that opposed horizontal flow at the ends due to shear causes the entire instrument to rotate. The vanes must provide torque at very low flow speed, so design

Timothy F. Duda; Douglas C. Webb

1997-01-01

480

Plate tectonics on Venus  

NASA Technical Reports Server (NTRS)

The high surface temperature of Venus implies a permanently buoyant lithosphere and a thick basaltic crust. Terrestrial-style tectonics with deep subduction and crustal recycling is not possible. Overthickened basaltic crust partially melts instead of converting to eclogite. Because mantle magmas do not have convenient access to the surface the Ar-40 abundance in the atmosphere should be low. Venus may provide an analog to Archean tectonics on the earth.

Anderson, D. L.

1981-01-01

481

Biochemical and Biophysical Characterization of Calicivirus Isolates from Pinnipeds  

Microsoft Academic Search

Summary Two virus isolates from California sea lions and one from an Alaskan fur seal, classified as caliciviruses based on their relationship to vesicular exanthema of swine virus, were examined for biochemical and biophysical properties. They all had a buoyant density of 1.37 g\\/ml in CsCl; one showed some heterogeneity in CsCl. The sedimentation rate in 5–20% sucrose was 183S

Frederick L. Schaffer; Marjorie E. Soergel

1973-01-01

482

Restriction endonuclease analysis of plastid DNA from tomato, potato and some of their somatic hybrids  

Microsoft Academic Search

The buoyant density and endonuclease restriction patterns of potato (Solanum tuberosum L.) and tomato (Lycopersicon esculentum) ptDNA were examined and compared with those of their somatic hybrids. The plastids from these plants, both of which belong to the family of Solanaceae, contain a single DNA species whose density of 1.697 gcm-3 and size of approximately 156 kbp are similar to

Barbara Schiller; R. G. Herrmann; G. Melchers

1982-01-01