These are representative sample records from Science.gov related to your search topic.
For comprehensive and current results, perform a real-time search at Science.gov.
1

Buoyant Force  

NSDL National Science Digital Library

This activity is a lab where students gather data on buoyant force and height of and object being submerged in two different types of fluids. The slope of the buoyant force and height is proportional to the density of the fluid. Students compare the densities of the fluids calculated with the actual densities.

Renae Garski, Bigfork High School, Bigfork, MN, based on an original activity from Science Workshop, p. 115

2

Titan buoyant station  

NASA Technical Reports Server (NTRS)

The proposed mission concept evolves about one or more buoyant stations (balloons and/or airship) operating at varying altitudes in Titan's atmosphere. An orbiter of Titan provides communications link support and accomplishes remote sensing science experiments. The paper describes science objectives and payloads, the reference mission concept and various aspects of mission design analysis.

Friedlander, A. L.

1984-01-01

3

Downward buoyant filtration combustion  

Microsoft Academic Search

We consider heterogeneous combustion in a porous medium subject to gravity-induced buoyant forces. A vertical sample, open to flow at the top and bottom, is ignited at the top. Buoyancy causes the hot gases to leave the sample through the top, thus drawing in fresh cool gas, containing both oxidizer and inert gases, through the bottom. The incoming gas supplies

B. J. Matkowsky; D. A. Schult

1996-01-01

4

Buoyant plume calculations  

SciTech Connect

Smoke from raging fires produced in the aftermath of a major nuclear exchange has been predicted to cause large decreases in surface temperatures. However, the extent of the decrease and even the sign of the temperature change, depend on how the smoke is distributed with altitude. We present a model capable of evaluating the initial distribution of lofted smoke above a massive fire. Calculations are shown for a two-dimensional slab version of the model and a full three-dimensional version. The model has been evaluated by simulating smoke heights for the Hamburg firestorm of 1943 and a smaller scale oil fire which occurred in Long Beach in 1958. Our plume heights for these fires are compared to those predicted by the classical Morton-Taylor-Turner theory for weakly buoyant plumes. We consider the effect of the added buoyancy caused by condensation of water-laden ground level air being carried to high altitude with the convection column as well as the effects of background wind on the calculated smoke plume heights for several fire intensities. We find that the rise height of the plume depends on the assumed background atmospheric conditions as well as the fire intensity. Little smoke is injected into the stratosphere unless the fire is unusually intense, or atmospheric conditions are more unstable than we have assumed. For intense fires significant amounts of water vapor are condensed raising the possibility of early scavenging of smoke particles by precipitation. 26 references, 11 figures.

Penner, J.E.; Haselman, L.C.; Edwards, L.L.

1985-01-01

5

Buoyant station mission comcepts for titan exploration  

NASA Technical Reports Server (NTRS)

An advanced mission to this unique satellite of Saturn appropriate to the turn-of-the-century time period is described. The mission concept evolves about one or more buoyant stations (balloons and/or airship) operating at varying altitudes in Titan's atmosphere. An orbiter of Titan provides communications link support and accomplishes remote sensing science objectives. Use of buoyant stations are favored over a fixed site lander for two reasons: (1) adaptable to several possible surface physical states and topographies; and (2) capable of exploring both the atmosphere and surface with regional and possibly global mobility. Auxiliary payload concepts investigated include tethered packages and sounding rockets deployed from the buoyant station, and haze probes and surface penetrators deployed from the orbiter. The paper describes science objectives and payloads, propulsion system/mass delivery trades, balloon design requirements and deployment/motion characteristics, and communications link geometry and data characteristics.

Friedlander, A. L.

1985-01-01

6

BUOYANT ADVECTION OF GASES IN UNSATURATED SOIL  

PubMed Central

In unsaturated soil, methane and volatile organic compounds can significantly alter the density of soil gas and induce buoyant gas flow. A series of laboratory experiments was conducted in a two-dimensional, homogeneous sand pack with gas permeabilities ranging from 110 to 3,000 darcy. Pure methane gas was injected horizontally into the sand and steady-state methane profiles were measured. Experimental results are in close agreement with a numerical model that represents the advective and diffusive components of methane transport. Comparison of simulations with and without gravitational acceleration permits identification of conditions where buoyancy dominates methane transport. Significant buoyant flow requires a Rayleigh number greater than 10 and an injected gas velocity sufficient to overcome dilution by molecular diffusion near the source. These criteria allow the extension of laboratory results to idealized field conditions for methane as well as denser-than-air vapors produced by volatilizing nonaqueous phase liquids trapped in unsaturated soil. PMID:20396624

Seely, Gregory E.; Falta, Ronald W.; Hunt, James R.

2010-01-01

7

Experimental investigation of a stratified buoyant wake  

E-print Network

for the degree of MASTER OF SCIENCE Approved as to style and content by: Malcolm Andrews (Chair of Committee) Gerald Morrison (Member) Paul Cizmas (Member) Dennis O?Neal (Head of Department) August 2004 Major Subject...: Mechanical Engineering iii ABSTRACT Experimental Investigation of a Stratified Buoyant Wake. (August 2004) Wayne N. Kraft, B.S., Texas A&M University Chair of Advisory Committee: Dr. Malcolm Andrews An existing water channel facility at Texas A...

Kraft, Wayne Neal

2004-11-15

8

Towards Understanding the Mixing Characteristics of Turbulent Buoyant Flows  

NASA Astrophysics Data System (ADS)

This work proposes a new simulation methodology in which variable density turbulent flows can be studied in the context of a mixing layer with or without the presence of gravity. This methodology is developed to probe the nature of non-buoyantly-driven or buoyantly-driven mixing inside a mixing layer. Numerical forcing methods are incorporated into the velocity and scalar fields, extending the length of time over which mixing physics can be studied. The simulation framework is designed to allow for independent variation of four non-dimensional parameters, including the Reynolds, Richardson, Atwood, and Schmidt numbers. The governing equations are integrated in such a way to allow for the relative magnitude of buoyant energy production and non-buoyant energy production to be varied. The computational requirements needed to implement the proposed configuration are presented. Key features of turbulent buoyant flows are reproduced as validation of the proposed methodology. These features include the recovery of isotropic Kolmogorov scales under buoyant and non-buoyant conditions, the recovery of anisotropic one-dimensional energy spectra under buoyant conditions, and the preservation of known statistical distributions in the scalar field, as found in other DNS studies. This simulation method is used to perform a parametric study of turbulent buoyant flows to discern the effects of varying the Reynolds, Richardson, and Atwood numbers on mixing. The effects of the Reynolds and Atwood numbers are isolated by examining two energy dissipation rate conditions under non-buoyant (variable density) and constant density conditions. The effects of Richardson number are isolated by varying the ratio of buoyant energy production to total energy production from zero (non-buoyant) to one (entirely buoyant) under constant Atwood number, Schmidt number, and energy dissipation rate conditions. It is found that the primary differences between non-buoyant and buoyant turbulent flows are contained in the transfer spectrum and longitudinal structure functions, while all other metrics are largely similar. However, the scalar field dynamics are found to be similar whether the velocity field is subjected to buoyancy forces or not. Hence, the mixing dynamics in the scalar field are insensitive to the source of turbulent kinetic energy production (non-buoyant vs. buoyant).

Carroll, Phares L.

9

Pinch-off and formation number of negatively buoyant jets  

NASA Astrophysics Data System (ADS)

Previous investigations of starting buoyant jets are extended towards negative buoyancy to address key issues in the formation processes. A series of large-eddy simulations (LES) is performed to identify whether an optimal vortex can be formed with negative buoyancy and if so what the corresponding formation number would be. The numerical code was previously validated for non-buoyant and positively buoyant jets and is further validated here for negatively buoyant jets using literature data on submerged fountains. Subsequently, jets with a range of negative buoyancies are simulated using source Reynolds numbers of 2000 < Re < 3000. A revised, directional form of Richardson number (Rid) is proposed to accommodate the entire range of buoyancy, with Rid > 0 for positively buoyant jets, Rid = 0 for non-buoyant jets, and Rid < 0 for negatively buoyant jets. Simulations identify two ranges of negative buoyancy. For weakly negatively buoyant starting jets (- 0.05 <˜ Rid < 0), the pinch-off and formation of an optimal starting vortex occur, and the corresponding formation number can be determined using a revised algorithm, catering to negative buoyancy, based on the observed step jump in the vortex ring's circulation. This algorithm suggests a continuation of the declining trend in formation number with declining Rid identified previously for positively buoyant jets. For strongly negatively buoyant jets (Rid < -0.05), the starting vortex falls back onto the stem after the initial roll-up for -2.0 <˜ Rid < -0.05, and the pinch-off process does not exist for Rid <˜ -2.0 with the starting vortex and stem connected at all time. A plot of time-varying vortex circulation and penetration for starting plumes with different Rid unifies our understanding of buoyant vortex dynamics.

Wang, Ruo-Qian; Wing-Keung Law, Adrian; Adams, E. Eric

2011-05-01

10

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

Code of Federal Regulations, 2014 CFR

...false Buoyant apparatus with plastic foam buoyancy. 160.010-5 Section 160.010-5...010-5 Buoyant apparatus with plastic foam buoyancy. (a) Buoyant apparatus with plastic foam buoyancy must have a plastic foam body with...

2014-10-01

11

Generation of available buoyant energy by cloud glaciation  

Microsoft Academic Search

The available buoyant energy (ABE, energy from the environment which becomes available to a parcel for buoyant accelerations) arising from glaciation is computed by integrating upward the differences in temperature between a parcel that undergoes instantaneous and isenthalpic freezing followed by an ice-saturation ascent, and one that experiences only a water-saturation ascent from the same initial cloud base conditions. This

Charles F. Chappell; David R. Smith

1975-01-01

12

Turbulence attenuation by large neutrally buoyant particles  

E-print Network

Turbulence modulation by inertial-range-size, neutrally-buoyant particles is investigated experimentally in a von K\\'arm\\'an flow. Increasing the particle volume fraction $\\Phi_\\mathrm{v}$, maintaining constant impellers Reynolds number attenuates the fluid turbulence. The inertial-range energy transfer rate decreases as $\\propto\\Phi_\\mathrm{v}^{2/3}$, suggesting that only particles located on a surface affect the flow. Small-scale turbulent properties, such as structure functions or acceleration distribution, are unchanged. Finally, measurements hint at the existence of a transition between two different regimes occurring when the average distance between large particles is of the order of the thickness of their boundary layers.

Cisse, Mamadou; Gibert, Mathieu; Bodenschatz, Eberhard; Bec, Jeremie

2015-01-01

13

Simulations of Buoyant Bubbles in Galaxy Clusters  

E-print Network

It is generally argued that most clusters of galaxies host cooling flows in which radiative cooling in the centre causes a slow inflow. However, recent observations by Chandra and XMM conflict with the predicted cooling flow rates. Here we report highly resolved hydrodynamic simulations which show that buoyant bubbles can offset the cooling in the inner regions of clusters and can significantly delay the deposition of cold gas. The subsonic rise of bubbles uplifts colder material from the central regions of the cluster. This colder material appears as bright rims around the bubbles. The bubbles themselves appear as depressions in the X-ray surface brightness as observed in a growing number of clusters.

M. Bruggen

2003-01-17

14

Baroclinic instability of a buoyant coastal current  

NASA Astrophysics Data System (ADS)

Classic models of baroclinic instability, notably the Eady model, depend on the Rossby (or Richardson) number as the sole non-dimensional parameter. Inclusion of a sloping bottom requires an additional parameter, the slope Burger number, Bu = ?Nf-1, where ? is the bottom slope. Numerical simulations of the evolution of instabilities along the edge of a coastally trapped buoyant flow suggest that the slope may help to stabilize the flow when the deformation radius is similar to or larger than the with of the buoyant flow, that is, the flow is stable when the slope Burger number is larger than about 0.3. In unstable cases, Bu < 0.3, baroclinic instabilities in the flow cause the isopycnals to relax, thereby increasing the local Burger number until the critical condition, Bu ? 0.3, is met. At this point the instabilities no longer grow in time, preventing further offshore buoyancy flux by the eddies. This final state corresponds approximately to the case where the slope of the ground is similar to the slope of the mean isopycnal surfaces. The nonlinear, three-dimensional numerical simulations are in basic agreement with one-dimensional linear stability analysis, with a few key exceptions. Notably, numerical simulations suggest that cross-shelf buoyancy fluxes are strongest in within the bottom boundary layer, showing a similar pattern to continental shelf waves in the vertical structure of current and tracer variability. Idealized simulations show a marked similarity to instabilities along the Mississippi/Atchafalaya plume front, as seen in observations and realistic regional models. These eddies have been shown to be important in Lagrangian transport of surface particles, notably oil spill trajectory prediction, and create patchiness in bottom dissolved oxygen distributions during periods of summertime seasonal hypoxia.

Hetland, Robert

2014-05-01

15

46 CFR 160.010-3 - Inflatable buoyant apparatus.  

Code of Federal Regulations, 2014 CFR

...boarding ramp (or boarding ladder, if no ramps are installed), and ready for immediate use; (ii) Knives. Two buoyant safety knives ready for use near the painter attachment; (iii) Bailer. One bailer as described in §...

2014-10-01

16

Behavior of buoyant moist plumes in turbulent atmospheres  

E-print Network

A widely applicable computational model of buoyant moist plumes in turbulent atmospheres has been constructed. To achieve this a one dimensional Planetary Boundary Layer (P.B.L.) model has been developed to account for ...

Hamza, Redouane

1981-01-01

17

Formation number of positively and negatively buoyant vortex rings  

NASA Astrophysics Data System (ADS)

The formation process of both negatively and positively buoyant vortex rings in a piston/cylinder arrangement is investigated numerically with the aim of understanding the effect of buoyancy, characterized by a Richardson number, on the formation number. More specifically, the study focuses on how vorticity is distributed inside the vortex ring and how this vorticity distribution compares with the neutrally buoyant case. It is well known that the kinetic energy of a neutrally buoyant vortex ring, when made dimensionless with its impulse and circulation, has a universal value of End1/3. The limits of validity of this value for moderate Richardson numbers, both in the positively and negatively buoyant cases, are examined.

Rodríguez-Rodríguez, Javier; Marugán-Cruz, Carolina; Martínez-Bazán, Carlos

2010-11-01

18

Using buoyant mass to measure the growth of single cells  

E-print Network

We used a suspended microchannel resonator (SMR) combined with picoliter-scale microfluidic control to measure buoyant mass and determine the 'instantaneous' growth rates of individual cells. The SMR measures mass with ...

Godin, Michel

19

46 CFR 160.010-6 - Capacity of buoyant apparatus.  

Code of Federal Regulations, 2014 CFR

...following methods: (1) Final buoyancy of the buoyant apparatus in Newtons...divided by 145 (divided by 32 if buoyancy is measured in pounds). The divisor must be changed to 180 (40 if buoyancy is measured in pounds) if the...

2014-10-01

20

Shapes of buoyant and nonbuoyant laminar jet diffusion flames  

SciTech Connect

Flame shapes were measured for buoyant and nonbuoyant laminar gas jet diffusion flames burning, methane, ethane, and propane in quiescent air. Test conditions involved burner diameters of 0.19--5.5 mm, ambient pressures of 0.25--2 atm, and fuel flowrates of 0.04--4.6 mg/s. Care was taken to minimize interference from soot emissions and from ignition disturbances. Microgravity conditions were obtained in the 2.2-s drop tower at the NASA Lewis Research Center. Normalized lengths of both buoyant and nonbuoyant flames were proportional to source Reynolds number, but the nonbuoyant flames were 40% longer on average. Normalized widths of the nonbuoyant flames were constant for Re {ge} 100, whereas buoyant flame widths scaled with source Froude number. Several nonbuoyant flame models are evaluated with the present shape data.

Sunderland, P.B. [National Research Council, Cleveland, OH (United States)] [National Research Council, Cleveland, OH (United States); Mendelson, B.J. [Princeton Univ., NJ (United States). Dept. of Mechanical and Aerospace Engineering] [Princeton Univ., NJ (United States). Dept. of Mechanical and Aerospace Engineering; Yuan, Z.G. [National Center for Microgravity Research, Cleveland, OH (United States)] [National Center for Microgravity Research, Cleveland, OH (United States); Urban, D.L. [NASA Lewis Research Center, Cleveland, OH (United States)] [NASA Lewis Research Center, Cleveland, OH (United States)

1999-02-01

21

Mixing by turbulent buoyant jets in slender containers  

NASA Astrophysics Data System (ADS)

A turbulent buoyant jet injected vertically into a slender cylinder containing a stratified fluid is investigated experimentally. The working fluid is water, and salt is used to change its density to obtain either a positively or negatively buoyant jet. The interest is the vertical density distribution in container and its dependence on time and other parameters. For each case (lighter or heavier jet) the experimental data could be collapsed into a ‘universal’ time dependent behavior, when properly non-dimensionalized. A theoretical model is advanced to explain the results. Possible applications include refilling of crude oil into U.S. strategic petroleum reserves caverns.

Voropayev, S. I.; Nath, C.; Fernando, H. J. S.

2012-10-01

22

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

23

Dispersion of buoyant emissions from low level sources in urban areas: water channel modelling  

E-print Network

sources in urban areas: water channel modelling’, Int. J.level sources in urban areas: water channel modelling Sammodelling the dispersion from low level buoyant sources: Dispersion of buoyant emissions from low level sources in urban

Pournazeri, Sam; Schulte, Nico; Tan, Si; Princevac, Marko; Venkatram, Akula

2013-01-01

24

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

25

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

26

Hands-On Experiences with Buoyant-Less Water  

ERIC Educational Resources Information Center

The phenomenon of weightlessness is known to students thanks to videos of amazing things astronauts do in spaceships orbiting the Earth. In this article we propose two hands-on activities which give students opportunities to infer by themselves the absence of buoyant force in a gravity accelerated system. The system is a free-falling or vertically…

Slisko, Josip; Planinsic, Gorazd

2010-01-01

27

Horizontal penetration of inclined thermal buoyant water jets  

SciTech Connect

Submerged buoyant jets occur in the discharge from thermal power plants and in the operation of pumped storage hydroelectric plants. Accurate prediction of the jet trajectory and temperature dilution are necessary if discharge structures are to be designed to meet the appropriate standards. A modified version of the integral Fan-Brooks model has been used to calculate the horizontal penetration of inclined thermal buoyant water jets. The classical densimetric Froude number F{sub 0} is substituted by a Froude number F{sub a} based on the thermal expansion coefficient of water. Using the above model, a new equation is derived which can predict the horizontal penetration of the thermal jet at a given Froude number F{sub a} and discharge angle.

Pantokratoras, A. [Democritus Univ. of Thrace, Xanthi (Greece). School of Engineering] [Democritus Univ. of Thrace, Xanthi (Greece). School of Engineering

1998-05-01

28

Modelling thermal radiation in buoyant turbulent diffusion flames  

Microsoft Academic Search

This work focuses on the numerical modelling of radiative heat transfer in laboratory-scale buoyant turbulent diffusion flames. Spectral gas and soot radiation is modelled by using the Full-Spectrum Correlated-k (FSCK) method. Turbulence-Radiation Interactions (TRI) are taken into account by considering the Optically-Thin Fluctuation Approximation (OTFA), the resulting time-averaged Radiative Transfer Equation (RTE) being solved by the Finite Volume Method (FVM).

J. L. Consalvi; R. Demarco; A. Fuentes

2012-01-01

29

The pinch-off process in a starting buoyant plume  

Microsoft Academic Search

The vortex ring formation process of a starting buoyant plume was studied experimentally using digital particle image thermometry and velocimetry (DPITV). The vortex ring was observed to pinch-off, or become disconnected, from the trailing plume. Pinch-off occurred at non-dimensional times, or formation numbers, between 4.4 and 4.9. The observed pinch-off process is consistent with an explanation based upon the Kelvin–Benjamin

T. S. Pottebaum; M. Gharib

2004-01-01

30

Numerical simulations of buoyant reactive jets with sidewall effects  

Microsoft Academic Search

The near field dynamics of buoyant reactive jets with adjacent sidewalls is investigated by time-dependent three-dimensional\\u000a direct simulations. The physical problem is a fuel jet issuing vertically into an oxidant ambient environment in a corner\\u000a configuration with sidewall boundaries. Simulation results are presented for two cases with different jet nozzle geometries:\\u000a a corner-round reactive jet and a corner-square reactive jet

Heping Zhang; Xi Jiang; Wei Wang; Yun Yang; Liang Xu; Weicheng Fan

2004-01-01

31

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

32

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.

33

Hands-on experiences with buoyant-less water  

NASA Astrophysics Data System (ADS)

The phenomenon of weightlessness is known to students thanks to videos of amazing things astronauts do in spaceships orbiting the Earth. In this article we propose two hands-on activities which give students opportunities to infer by themselves the absence of buoyant force in a gravity accelerated system. The system is a free-falling or vertically tossed bottle filled with water with a small, inflated balloon attached to the bottom by a spring. Practical hints on how to make efficient demonstration experiments are added.

Sliško, Josip; Planinši?, Gorazd

2010-05-01

34

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

35

Pattern formation in a rotating suspension of non-Brownian buoyant particles  

E-print Network

Pattern formation in a rotating suspension of non-Brownian buoyant particles Makrand G. Kalyankar,1 and Technology, Clear Water Bay, Kowloon, Hong Kong Received 1 April 2008; accepted 23 July 2008; published in a horizontal rotating cylinder completely filled with a monodisperse suspension of non-Brownian buoyant

Tong, Penger

36

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

37

Sheathless hydrodynamic positioning of buoyant drops and bubbles inside microchannels  

NASA Astrophysics Data System (ADS)

Particles, bubbles, and drops carried by a fluid in a confined environment such as a pipe can be subjected to hydrodynamic lift forces, i.e., forces that are perpendicular to the direction of the flow. We investigated the positioning effect of lift forces acting on buoyant drops and bubbles suspended in a carrier fluid and flowing in a horizontal microchannel. We report experiments on drops of water in fluorocarbon liquid, and on bubbles of nitrogen in hydrocarbon liquid and silicone oil, inside microchannels with widths on the order of 0.1-1 mm. Despite their buoyancy, drops and bubbles could travel without contacting with the walls of channels; the most important parameters for reaching this flow regime in our experiments were the viscosity and the velocity of the carrier fluid, and the sizes of drops and bubbles. The dependencies of the transverse position of drops and bubbles on these parameters were investigated. At steady state, the trajectories of drops and bubbles approached the center of the channel for drops and bubbles almost as large as the channel, carried by rapidly flowing viscous liquids; among our experiments, these flow conditions were characterized by larger capillary numbers and smaller Reynolds numbers. Analytical models of lift forces developed for the flow of drops much smaller than the width of the channel failed to predict their transverse position, while computational fluid dynamic simulations of the experiments agreed better with the experimental measurements. The degrees of success of these predictions indicate the importance of confinement on generating strong hydrodynamic lift forces. We conclude that, inside microfluidic channels, it is possible to support and position buoyant drops and bubbles simply by flowing a single-stream (i.e., “sheathless”) carrier liquid that has appropriate velocity and hydrodynamic properties.

Stan, Claudiu A.; Guglielmini, Laura; Ellerbee, Audrey K.; Caviezel, Daniel; Stone, Howard A.; Whitesides, George M.

2011-09-01

38

46 CFR 160.010-4 - General requirements for buoyant apparatus.  

Code of Federal Regulations, 2010 CFR

...Each metal part of a buoyant apparatus must be— (1) 410 stainless steel or have salt water and salt air corrosion characteristics equal or superior to 410 stainless steel; and (2) Galvanically compatible with each other metal...

2010-10-01

39

AN EXPERIMENTAL/ANALYTICAL INVESTIGATION OF DEEP SUBMERGED MULTIPLE BUOYANT JETS  

EPA Science Inventory

The results of an experimental and analytical study of deep submerged multiple-port thermal discharges are presented. The experimental results include the measured downstream thermal dilution, width, and centerline trajectory of the buoyant thermal plume from multiple port discha...

40

EVALUATION OF A CONVECTIVE SCALING PARAMETERIZATION FOR ESTIMATING THE DIFFUSION OF A BUOYANT PLUME  

EPA Science Inventory

During limited-mixed convective conditions, high concentrations of air pollutants have been observed at ground-level from buoyant plumes. Routinely-applied Gaussian plume dispersion models have difficulty simulating diffusion for these conditions. However, advances in convective ...

41

Turbulent channel flow of dense suspensions of neutrally buoyant spheres  

NASA Astrophysics Data System (ADS)

Dense particle suspensions are widely encountered in many applications and in environmental flows. While many previous studies investigate their rheological properties in laminar flows, little is known on the behaviour of these suspensions in the turbulent/inertial regime. The present study aims to fill this gap by investigating the turbulent flow of a Newtonian fluid laden with solid neutrally-buoyant spheres at relatively high volume fractions in a plane channel. Direct Numerical Simulation are performed in the range of volume fractions Phi=0-0.2 with an Immersed Boundary Method used to account for the dispersed phase. The results show that the mean velocity profiles are significantly altered by the presence of a solid phase with a decrease of the von Karman constant in the log-law. The overall drag is found to increase with the volume fraction, more than one would expect just considering the increase of the system viscosity due to the presence of the particles. At the highest volume fraction here investigated, Phi=0.2, the velocity fluctuation intensities and the Reynolds shear stress are found to decrease. The analysis of the mean momentum balance shows that the particle-induced stresses govern the dynamics at high Phi and are the main responsible of the overall drag increase. In the dense limit, we therefore find a decrease of the turbulence activity and a growth of the particle induced stress, where the latter dominates for the Reynolds numbers considered here.

Picano, Francesco; Breugem, Wim-Paul; Brandt, Luca

2015-02-01

42

The vertical distribution of buoyant plastics at sea  

NASA Astrophysics Data System (ADS)

Millimeter-sized plastics are numerically abundant and widespread across the world's ocean surface. These buoyant macroscopic particles can be mixed within the upper water column due to turbulent transport. Models indicate that the largest decrease in their concentration occurs within the first few meters of water, where subsurface observations are very scarce. By using a new type of multi-level trawl at 12 sites within the North Atlantic accumulation zone, we measured concentrations and physical properties of plastics from the air-seawater interface to a depth of 5 m, at 0.5 m intervals. Our results show that plastic concentrations drop exponentially with water depth, but decay rates decrease with increasing Beaufort scale. Furthermore, smaller pieces presented lower rise velocities and were more susceptible to vertical transport. This resulted in higher depth decays of plastic mass concentration (mg m-3) than numerical concentration (pieces m-3). Further multi-level sampling of plastics will improve our ability to predict at-sea plastic load, size distribution, drifting pattern, and impact on marine species and habitats.

Reisser, J.; Slat, B.; Noble, K.; du Plessis, K.; Epp, M.; Proietti, M.; de Sonneville, J.; Becker, T.; Pattiaratchi, C.

2014-11-01

43

Residence time of buoyant objects in drowning machines  

PubMed Central

Hydraulic jumps are a common feature of rivers and waterways, where they can be found close to spillways, weirs, rocky ledges, and boulders. People adrift upstream of a hydraulic jump are liable to become trapped in the turbulent roller of the hydraulic jump. For this reason, hydraulic jumps have been termed “drowning machines” and are recognized as a public hazard. We use experiments and theory to show that on average a buoyant object spends a time ?/p trapped in a jump, where ? is the period of a harmonic process inherent in the jump, and p is the probability that the object will escape in any time interval ?. The probability p is governed by the statistical theory of extreme values and depends primarily on the ratio between the density of the object and the density of the fluid. We use our results to draw conclusions that might prove to be useful to public-safety agencies intent on carrying out tests in drowning machines. Our results can also be used to predict the amount of flotsam that accumulates at the toe of a hydraulic jump.

Gioia, Gustavo; Chakraborty, Pinaki; Gary, Stefan F.; Zamalloa, Carlo Zuñiga; Keane, Richard D.

2011-01-01

44

A new Lagrangian method for modelling the buoyant plume rise  

NASA Astrophysics Data System (ADS)

A new method for the buoyant plume rise computation is proposed. Following Alessandrini and Ferrero (Phys A 388:1375-1387, 2009) a scalar transported by the particles and representing the temperature difference between the plume and the environment air is introduced. As a consequence, no more particles than those inside the plume have to be released to simulate the entrainment of the background air temperature. A second scalar, the vertical plume velocity, is assigned to each particle. In this way the entrainment is properly simulated and the plume rise is calculated from the local property of the flow. The model has been tested against data from two laboratory experiments in neutral and stable stratified flows. The comparison shows a good agreement. Then, we tested our new model against literature analytical formulae in a simple uniform neutral atmosphere, considering either the case of a single plume or the one of two plumes from adjacent stacks combining during the rising stage. Finally, a comparison of the model against an atmospheric tracer experiment (Bull Run), characterized by vertically non-homogeneous fields (wind velocity, temperature, velocity standard deviations and time scales), was performed. All the tests confirmed the satisfactory performance of the model.

Alessandrini, Stefano; Ferrero, Enrico; Anfossi, Domenico

2013-10-01

45

Microstructure and rheology of finite inertia neutrally buoyant suspensions  

E-print Network

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.

Hamed Haddadi; Jeffrey F. Morris

2014-03-30

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

Oil-entrapped sterculia gum-alginate buoyant systems of aceclofenac: development and in vitro evaluation.  

PubMed

The current investigation deals with the development and optimization of oil-entrapped sterculia gum-alginate buoyant beads containing aceclofenac by ionotropic emulsion-gelation technique using 3(2) factorial design. The effect of polymer to drug ratio and sodium alginate to sterculia gum ratio on the drug entrapment efficiency (%), and cumulative drug release after 7 h (%) was optimized. The optimized oil-entrapped sterculia gum-alginate buoyant beads containing aceclofenac (F-O) showed drug entrapment efficiency of 90.92±2.34%, cumulative drug release of 41.65±3.97% after 7 h in simulated gastric fluid (pH 1.2), and well buoyancy over 8 h in simulated gastric fluid (pH 1.2) with 5.20 min buoyant lag-time. The in vitro drug release from these buoyant beads followed Korsmeyer-Peppas model (R(2)=0.9866-0.9995) with anomalous (non-Fickian) diffusion drug release mechanism. These new sterculia gum-alginate buoyant beads containing aceclofenac were also characterized using SEM, FTIR, and P-XRD analysis. PMID:23334180

Guru, Pravat Ranjan; Nayak, Amit Kumar; Sahu, Rajendra Kumar

2013-04-01

48

A Lagrangian particle random walk model for simulating a deep-sea hydrothermal plume with both buoyant and non-buoyant features  

NASA Astrophysics Data System (ADS)

This paper presents a computational model of simulating a deep-sea hydrothermal plume based on a Lagrangian particle random walk algorithm. This model achieves the efficient process to calculate a numerical plume developed in a fluid-advected environment with the characteristics such as significant filament intermittency and significant plume meander due to flow variation with both time and location. Especially, this model addresses both non-buoyant and buoyant features of a deep-sea hydrothermal plume in three dimensions, which significantly challenge a strategy for tracing the deep-sea hydrothermal plume and localizing its source. This paper also systematically discusses stochastic initial and boundary conditions that are critical to generate a proper numerical plume. The developed model is a powerful tool to evaluate and optimize strategies for the tracking of a deep-sea hydrothermal plume via an autonomous underwater vehicle (AUV).

Tian, Yu; Li, Wei; Zhang, Ai-qun

2013-04-01

49

Note: Buoyant-force assisted liquid membrane electrochemical etching for nano-tip preparation.  

PubMed

A liquid membrane electrochemical etching process for preparing nano-tips is proposed by the introduction of buoyant force to the lower tip, in which the lower portion of the anodic wire is immersed into a floating layer. A mathematical model of this method is derived. Both calculation and experimental results demonstrate that the introduction of buoyant force can significantly decrease the tip radius. The lubricating oil and deionized water floating layers were tested for the processing of nano-tips. Further, high-aspect-ratio nano-electrodes were prepared by applying a relative vertical movement to the anodic wire. PMID:25554341

Zeng, Yongbin; Wang, Yufeng; Wu, Xiujuan; Xu, Kun; Qu, Ningsong

2014-12-01

50

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

51

Structure and Soot Properties of Non-Buoyant Laminar Round-Jet Diffusion Flames  

NASA Technical Reports Server (NTRS)

The structure and soot properties of nonbuoyant laminar diffusion flames are being studied experimentally and theoretically in order to better understand the soot and thermal radiation emissions from luminous flames. The measurements involve weakly-buoyant flames at low pressure in normal gravity (ng) and nonbuoyant flames at normal pressures in microgravity (micro g). The objectives of the present investigation are to study the differences of soot properties between nonbuoyant and buoyant diffusion flames, and to evaluate predictions based on the laminar flamelet approach.

Mortazavi, Saeed; Sunderland, Peter B.; Jurng, Jongsoo; Faeth, Gerard M.

1993-01-01

52

Note: Buoyant-force assisted liquid membrane electrochemical etching for nano-tip preparation  

NASA Astrophysics Data System (ADS)

A liquid membrane electrochemical etching process for preparing nano-tips is proposed by the introduction of buoyant force to the lower tip, in which the lower portion of the anodic wire is immersed into a floating layer. A mathematical model of this method is derived. Both calculation and experimental results demonstrate that the introduction of buoyant force can significantly decrease the tip radius. The lubricating oil and deionized water floating layers were tested for the processing of nano-tips. Further, high-aspect-ratio nano-electrodes were prepared by applying a relative vertical movement to the anodic wire.

Zeng, Yongbin; Wang, Yufeng; Wu, Xiujuan; Xu, Kun; Qu, Ningsong

2014-12-01

53

Buoyant convection resulting from dissolution and permeability growth in vertical limestone fractures  

NASA Astrophysics Data System (ADS)

Upward flow through vertical fractures in limestone formations under a geothermal gradient favors dissolution and permeability growth. We investigate the transition from conductive and forced convective regimes to instability and buoyant convection as a result of permeability growth. The onset time for instability and roll height at onset depend on the initial aperture and driving pressure. A modified Rayleigh number criterion is proposed, which provides a unified interpretation of the instability across a wide range of initial aperture and driving pressure. Interaction between buoyant convection and aperture alteration leads to narrow upward flow paths supporting dissolution and precipitation in surrounding downward flow regions.

Chaudhuri, A.; Rajaram, H.; Viswanathan, H.; Zyvoloski, G.; Stauffer, P.

2009-02-01

54

An experimental study of gravity-driven thin-film flow with buoyant particles  

NASA Astrophysics Data System (ADS)

Our experimental study involves silicone oil with buoyant foamed glass spheres, flowing under the action of gravity. We perform an extensive parametric study varying the angle of inclination, particle size, density and concentration. In the case of heavy particles, three regimes arise involving settling of particles to the substrate versus settling to the front of the flow. In contrast, only one regime is observed with buoyant particles, however the dynamics depart significantly from that of a clear fluid. We discuss results for front position versus time as well as changes in the fingering instability as a function of experimental parameters.

Rosenthal, Wylie; Latterman, Paul; Hill, Spencer; David, Paul; Mata, Matthew; Mavromoustaki, Aliki; Bertozzi, Andrea

2011-11-01

55

3D Numerical Simulation of Turbulent Buoyant Flow and Heat Transport in a Curved Open Channel  

Technology Transfer Automated Retrieval System (TEKTRAN)

A three-dimensional buoyancy-extended version of kappa-epsilon turbulence model was developed for simulating the turbulent flow and heat transport in a curved open channel. The density- induced buoyant force was included in the model, and the influence of temperature stratification on flow field was...

56

Sensitivity of buoyant plume heights to ambient atmospheric conditions: Implications for volcanic eruption columns  

Microsoft Academic Search

A theoretical model is developed to investigate the sensitivity of buoyant atmospheric plumes to a wide range of ambient atmospheric conditions, including the temperature gradient, the latitude of the source, and the season. The formulation highlights the compressibility of an ideal gas, internal consistency between the governing equations for the conservation of momentum and energy, and the explicit use of

Lori S. Glaze; Stephen M. Baloga

1996-01-01

57

46 CFR 160.010-4 - General requirements for buoyant apparatus.  

Code of Federal Regulations, 2011 CFR

...Each buoyant apparatus must be capable of passing the tests in § 160.010-7. (b) Materials not covered...apparatus must be— (1) 410 stainless steel or have salt water and salt air corrosion characteristics equal or superior to 410...

2011-10-01

58

46 CFR 160.010-4 - General requirements for buoyant apparatus.  

Code of Federal Regulations, 2014 CFR

...Each buoyant apparatus must be capable of passing the tests in § 160.010-7. (b) Materials not covered...apparatus must be— (1) 410 stainless steel or have salt water and salt air corrosion characteristics equal or superior to 410...

2014-10-01

59

46 CFR 160.010-4 - General requirements for buoyant apparatus.  

Code of Federal Regulations, 2013 CFR

...Each buoyant apparatus must be capable of passing the tests in § 160.010-7. (b) Materials not covered...apparatus must be— (1) 410 stainless steel or have salt water and salt air corrosion characteristics equal or superior to 410...

2013-10-01

60

46 CFR 160.010-4 - General requirements for buoyant apparatus.  

Code of Federal Regulations, 2012 CFR

...Each buoyant apparatus must be capable of passing the tests in § 160.010-7. (b) Materials not covered...apparatus must be— (1) 410 stainless steel or have salt water and salt air corrosion characteristics equal or superior to 410...

2012-10-01

61

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

62

The Effect of an Externally Attached Neutrally Buoyant Transmitter on Mortal Injury during Simulated Hydroturbine Passage  

SciTech Connect

On their seaward migration, juvenile salmonids commonly pass hydroelectric dams. Fish passing through hydroturbines experience a rapid decrease in pressure as they pass by the turbine blade and the severity of this decompression can be highly variable. This rapid decrease in pressure can result in injuries such as swim bladder rupture, exophthalmia, and emboli and hemorrhaging in the fins and tissues. However, recent research indicates that the presence of a telemetry tag (acoustic, radio, inductive) implanted inside the coelom of a juvenile salmon increases the likelihood that the fish will be injured or die during turbine passage. Thus, previous research conducted using telemetry tags implanted into the coelom of fish may have been inaccurate. Thus, a new technique is needed to provide unbiased estimates of survival through turbines. This research provides an evaluation of the effectiveness of a neutrally buoyant externally attached acoustic transmitter. Both nontagged fish and fish tagged with a neutrally buoyant external transmitter were exposed to a range of rapid decompressions simulating turbine passage. Juvenile Chinook salmon tagged with a neutrally buoyant externally attached acoustic transmitter did not receive a higher degree of barotrauma than their nontagged counterparts. We suggest that future research include field-based comparisons of survival and behavior among fish tagged with a neutrally buoyant external transmitter and those internally implanted with transmitters.

Brown, Richard S.; Pflugrath, Brett D.; Carlson, Thomas J.; Deng, Zhiqun

2012-02-03

63

BUOYANT PLUME DISPERSAL IN THE CONVECTIVE BOUNDARY LAYER: ANALYSIS OF EXPERIMENTAL DATA AND LAGRANGIAN MODELING  

EPA Science Inventory

The aim of this research program is to improve our knowledge and predictive capability of buoyant plume dispersion in the convective boundary layer (CBL) with emphasis on the mean (C) and root-mean-square (?c) concentration fields. The CBL turbulence leads to large random fluc...

64

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

65

Capturing the Pulsation Frequency of a Buoyant Pool Fire using the Large Eddy Simulation Approach  

Microsoft Academic Search

A numerical model using the large eddy simulation (LES) approach with considerations of turbulence, combustion, soot chemistry and radiation effects is presented and employed to capture the pulsation frequency of a turbulent buoyant pool fire. Numerical results from the present model are validated and compared against the experimental data and predictions from another LES field model–fire dynamic simulator (FDS). Quantitative

A. L. K. Cheung; E. W. M. Lee; R. K. K. Yuen; G. H. Yeoh; S. C. P. Cheung

2007-01-01

66

What is a flux tube? On the magnetic field topology of buoyant flux structures  

E-print Network

in the language of flux tube models (see e.g. Ossendrijver (2003) and references therein). One of the distinctiveWhat is a flux tube? On the magnetic field topology of buoyant flux structures Fausto Cattaneo, visually resembling idealised magnetic flux tubes, are generated self-consistently by numerical simulation

67

Impact of thermally induced buoyant flow on contaminant transport in homogeneous and layered systems  

NASA Astrophysics Data System (ADS)

Electrical resistance heating (ERH) is currently the most widely used thermal remediation technology in the United States (U.S. EPA, In situ thermal treatment site profiles database). Typically, ERH is operated at or above boiling point temperatures to ensure complete volatilization of subsurface contaminants. However, heating sites to these temperatures requires both high power requirements and off-gas collection systems, and therefore high operational costs. As such, operating ERH at lower temperatures to take advantage of buoyancy effects on flow and transport has been proposed as a sustainable alternative. In this study, buoyant flow associated with thermal remediation was investigated using a two dimensional electro-thermal model. The model incorporated electrical current flow associated with resistance heating, energy and mass transport, and density dependent water flow. The model was used to simulate heating for sixteen subsurface scenarios, in which the applied groundwater flux and soil permeability were varied. The effects on contaminant transport were investigated using dimensionless numbers. Consistent with other studies, the model predicted the development of buoyant flow when the ratio between the Rayleigh and thermal Peclet numbers (buoyancy ratio) was greater than 1. Subsequently, the modeled scenarios were grouped into three categories based on the occurrence of buoyant flow and its effect on contaminant transport. The effect of buoyant flow on contaminant transport was largely dependent on the Rayleigh number. The impact of low permeability layers on heat and mass transport was also investigated by simulating layered systems with different electrode placements. In this case, higher temperatures developed in the low permeability layers due to their greater electrical conductivity. In addition, heating under low permeability layers led to stagnation zones and mass accumulation, while heating above the layers led to lower subsurface concentrations. Thus, the model provides insights into ERH design that can be used to optimize this technology.

Krol, M. M.; Johnson, R.; Zhang, D.; Sleep, B. E.

2012-12-01

68

Proper orthogonal decomposition analysis of coherent structures in a transient buoyant jet  

Microsoft Academic Search

The spatial evolution of a circular buoyant jet at moderate Reynolds number (Re = 103) and density ratio (rgr* = 2) has been investigated using large-eddy simulation (LES). The Smagorinsky subgrid-scale model is used for the unresolved small-scale turbulence. Dynamic puffing phenomena is observed and corresponds to the formation of large-scale vortex structures near the plume base with an axisymmetric

X. Zhou; D. L. Hitt

2004-01-01

69

Preparation of amoxicillin intragastric buoyant sustained-release tablets and the dissolution characteristics.  

PubMed

An intragastric buoyant sustained-release tablet (IGB-T) containing 100 mg of amoxicillin (AMX) was prepared to eradicate gastric Helicobacter pylori. A tablet prepared by compressing the mixture of hydroxypropylcellulose-H (HPC-H), citric acid (17.2 mg), sodium hydrogen carbonate (22.8 mg) and AMX was employed as the basic system for preparing IGB-T. The weight and diameter of the tablets were designed to be about 300 mg and 10 mm, respectively. IGB-T containing 5 mg of AMX and HPC-H (255 mg) was buoyant and showed a sustained-release pattern in water. However, when AMX was increased and HPC-H decreased to maintain the tablet weight (300 mg), there was no apparent sustained-release pattern. To prepare IGB-T containing 50 mg of AMX, the surface of the tablet was coated with HPC-H after a tablet was prepared from the mixture of AMX (50 mg), HPC-H (210 mg), citric acid (17.2 mg), and sodium hydrogen carbonate (22.8 mg). This tablet (IGB-T50-Coating) was buoyant and showed a sustained-release pattern in water. However, to complete IGB-T with 100 mg of AMX, it was necessary not only to coat the surface of the tablet but also to use granulated AMX with a particle size of 300-500 microm (IGB-T100-Coating-300-500G). IGB-T100-Coating-300-500G was confirmed to be buoyant for 24 h while maintaining a tablet shape and showed a sustained-release pattern in water and buffer solutions of pH 1.2 and 6.8. PMID:16380190

Tokumura, Tadakazu; Machida, Yoshiharu

2006-02-21

70

Evidence for osmoregulation of cell growth and buoyant density in Escherichia coli  

SciTech Connect

The buoyant density of cells of Escherichia coli B/r NC32 increased with the osmolarity of the growth medium. Growth rate and its variability were also dependent upon the osmolarity of the medium. Maximum growth rates and minimum variability of these rates were obtained in Luria broth by addition of NaCl to a concentration of about 0.23 M. 6 references, 1 figure, 1 table.

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

1984-07-01

71

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

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. PMID:24359319

2013-01-01

74

Numerical simulations of negatively buoyant jets in an immiscible fluid using the Particle Finite Element Method  

NASA Astrophysics Data System (ADS)

In this work we investigate numerically the injection of a negatively buoyant jet into a homogenous immiscible ambient fluid using the Particle Finite Element Method (PFEM), a newly developed tool that combines the flexibility of particle-based methods with the accuracy of the finite element discretization. In order to test the applicability of PFEM to the study of negatively buoyant jets, we have compared the two-dimensional numerical results with experiments investigating the injection of a jet of dyed water through a nozzle in the base of a cylindrical tank containing rapeseed oil. In both simulations and experiments, the fountain inlet flow velocity and nozzle diameter were varied to cover a wide range of Reynolds Re and Froude numbers Fr, such that 0.1 < Fr < 30, reproducing both weak and strong fountains in a laminar regime (8 < Re < 1350). Numerical results, together with the experimental observations, allow us to describe three different fountain behaviors that have not been previously reported. Based on the Re and Fr values for the numerical and experimental simulations, we have built a regime map to define how these values may control the occurrence of each of the observed flow types. Whereas the Fr number itself provides a prediction of the maximum penetration height of the jet, its combination with the Re number provides a prediction of the flow behavior for a specific nozzle diameter and injection velocity. Conclusive remarks concerning the dynamics of negatively buoyant jets may be applied later on to several geological situations, e.g. the flow structure of a fully submerged subaqueous eruptive vent discharging magma or the replenishment of magma chambers in the Earth's crust.

Mier-Torrecilla, Monica; Geyer, Adelina; Phillips, Jeremy C.; Idelsohn, Sergio R.; Oñate, Eugenio

2010-05-01

75

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

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

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,

78

Estimating the neutrally buoyant energy density of a Rankine-cycle/fuel-cell underwater propulsion system  

NASA Astrophysics Data System (ADS)

A unique requirement of underwater vehicles' power/energy systems is that they remain neutrally buoyant over the course of a mission. Previous work published in the Journal of Power Sources reported gross as opposed to neutrally-buoyant energy densities of an integrated solid oxide fuel cell/Rankine-cycle based power system based on the exothermic reaction of aluminum with seawater. This paper corrects this shortcoming by presenting a model for estimating system mass and using it to update the key findings of the original paper in the context of the neutral buoyancy requirement. It also presents an expanded sensitivity analysis to illustrate the influence of various design and modeling assumptions. While energy density is very sensitive to turbine efficiency (sensitivity coefficient in excess of 0.60), it is relatively insensitive to all other major design parameters (sensitivity coefficients < 0.15) like compressor efficiency, inlet water temperature, scaling methodology, etc. The neutral buoyancy requirement introduces a significant (?15%) energy density penalty but overall the system still appears to offer factors of five to eight improvements in energy density (i.e., vehicle range/endurance) over present battery-based technologies.

Waters, Daniel F.; Cadou, Christopher P.

2014-02-01

79

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

80

Buoyant Response of the Tank 241-SY-101 Crust to Transfer and Back-Dilution  

SciTech Connect

The mixer pump installed in Hanford Tank 241-SY-101 (SY-101) in July 1993 has prevented the large buoyant displacement gas release events (BD GRE) it has historically exhibited. But the absence of periodic disruption from GREs and the action of mixing have allowed the crust to grow. The accelerated gas retention has resulted in over 30 inches of waste level growth and the flammable gas volume stored in the crust has become a hazard. To remediate gas retention in the crust and the potential for buoyant displacement gas releases from below the crust, SY-101 will be diluted in the fall of 1999 to dissolve a large fraction of the solids in the tank. The plan is to transfer waste out and back-dilute with water in several steps of about 100,000 gallons each. Back-dilution water may be added at the transfer pump inlet, the base of the mixer pump, and on top of the crust. The mixer pump will continue to be required to prevent formation of a deep nonconnective layer and resumption of BD GREs. Therefore, it is vital to ensure that the transfer and back-dilution processes do not significantly degrade the pump's effectiveness. Part of the strategy to avoid mixer pump degradation is to keep the base of the crust layer well above the pump inlet, which is 236 inches above the tank bottom. The maximum transfer for which an equal back-dilution is possible without sinking the crust is 90 kgal if water is injected at the 96-inch transfer pump inlet and 120 kgal for injection at the 9-inch mixer pump burrowing ring. To keep the crust base above the lowest observed elevation of 295 inches, transfer and back-dilution must be limited to 143 kgal and 80 kgal, respectively, for the 96-inch back-dilution and 175 kgal with a 112 kgal back-dilution using the 9-inch back-dilution elevation. These limits can be avoided by adding water to the top of the crust to dissolve the negatively buoyant layers. If 20 kgal of water is placed on top of the crust and the rest of the back-dilution is placed under the crust, back-dilution becomes limited by crust sinking at a 128 kgal transfer using the 96-inch injection point and at 160 kgal at 9 inches. The crust base remains well above the 295-inch minimum, and crust base elevation does not limit transfer volume. This result shows that top dilution is very beneficial in providing operational flexibility to the transfer and back-dilution process.

CW Stewart

1999-11-08

81

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

82

Further studies on the relationship between platelet buoyant density and platelet age  

SciTech Connect

The relationship between platelet buoyant density and platelet age was investigated in eight human subjects submitted to an autologous chromium labeled platelet survival study. Platelets were isolated after isopycnic centrifugation using eight discontinuous isoosmotic stractan gradients (five subjects), or various continuous and linear isoosmolar gradients (three subjects). A paradoxical radioactivity enrichment of the dense platelets and a premature loss of radioactivity in the light platelets were observed. These results are explained by a shift of the radioactivity distribution curve toward higher densities during the 3-4 days after platelet injection, while the standard deviation of the distribution was conserved throughout the platelet life span. These results suggest that young platelets are heterogeneous and slightly less dense than the total platelet population.

Boneu, B.; Vigoni, F.; Boneu, A.; Caranobe, C.; Sie, P.

1982-01-01

83

Characteristic patterns of buoyant flows in the Block Island Sound: Data analysis and numerical simulation  

NASA Astrophysics Data System (ADS)

The surface coastal circulation in and off the Block Island Sound (BIS) is examined based on one-year HF radar (CODAR) observations, bottom-mounted Acoustic Doppler Current Profiler (ADCP) moorings, and a three-dimensional, primitive-equation model to characterize the buoyant flow patterns and their temporal evolution. The surface flow patterns in BIS are determined from one-year CODAR observations and their temporal evolution is examined. Three analysis methods, visual sorting, Self-Organizing Maps (SOM) and Empirical Orthogonal Functions (EOF), are used and their results are compared. The study shows that the SOM analysis nicely complements the traditional EOF analysis, and both are consistent with the visual sorting. A synoptic description of the surface circulation is presented in terms of three characteristic patterns in spring/summer (April to September) and four characteristic patterns in fall/winter (January to March and October to December). The characteristic flow patterns are mainly determined by the wind and seasonal Long Island Sound (LIS) outflows. In spring and summer, a southwestward coastal mean flow is strong, and the wind is generally insignificant. In fall and winter, on the other hand, the coastal mean flow is weak, and the flow is mostly forced by synoptic storms. The Princeton Ocean Model (POM) is applied to study the three-dimensional barotropic semidiurnal tidal response in the New York Bight (NYB) and Block Island Sound (BIS). The model is driven at the open boundary with specified tidal transports. Model tidal sea levels and current ellipses are verified with the coastal sea levels, historical moored bottom pressure and current meter observations, and moored ADCP observations. The model results generally show very good agreement with the observations. The model results also are used to evaluate the CODAR data quality by comparing the total and radial tidal current ellipses. While the CODAR measurements generally are of high quality, the data at the mouth of Long Island Sound seems less reliable. POM also is used to simulate the coastal buoyant flows for a one-year (2001) period. The external forcing includes the LIS outflows, ambient coastal currents, semidiurnal tides, and local winds. Model results are compared with the CODAR and ADCP observations. The agreement in the low-frequency current fluctuations is very good. Consistent with the data analysis, model results indicate that the wind and seasonal LIS outflows are the dominant factors on coastal buoyant outflows. On the other hand, the model predicts a persistent (mean) headland tidal residual eddy south of Montauk Point, which is not supported by the ADCP and CODAR observations. This suggests that small-scale lateral dissipation which is not explicitly treated in the model may be important. This work represents the first comprehensive model and observation comparisons of the coastal buoyant outflows for an entire seasonal cycle. The success of our study is a major step towards developing a model-observational based coastal observatory system.

Mau, Jenq-Chi

84

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

85

Dispersal of volcaniclasts during deep-sea eruptions: Settling velocities and entrainment in buoyant seawater plumes  

NASA Astrophysics Data System (ADS)

We use tank experiments to measure settling rates of deep-sea volcaniclastic material recovered from the Arctic (85°E Gakkel Ridge) and Pacific (Juan de Fuca Ridge, Loihi seamount) Oceans. We find that clast size and shape exert a strong influence on settling velocity, with velocities of ~ 30 cm/s for large (~ 8 mm), blocky clasts, compared to velocities of ~ 2.5 cm/s for small (< 0.5 mm), sheet-like clasts. We fit our observations to the generalized model of Ferguson and Church (2004) to establish empirical scaling laws for settling velocity, and then use these results to test the hypothesis that entrainment in a buoyant plume of hot seawater is an important dispersal mechanism for volcaniclastic material in the deep-sea (Clague et al., 2009). We superpose the observed settling rates on velocity fields generated with the Morton et al. (1956) model for turbulent plumes in stratified media to estimate the rise height of the clastic material under water column conditions corresponding to the Gakkel and Juan de Fuca (JdFR) Ridges, and then estimate dispersal distances assuming the grains settle to the seafloor while being advected in lateral currents. Dispersal distances in our model are a function plume strength (i.e., buoyancy flux), lateral current speeds, and clast settling velocity. Our model demonstrates that large (30 GW) eruption 'megaplumes' can loft volcaniclastic material more than a kilometer above the seafloor where entrainment in deep-sea currents can advect dominant clast types (~ 1 mm, blocky grains) up to a few hundred meters from a source vent. Small bubble-wall fragments (e.g., limu o Pele) entrained in a megaplume could be advected as far as a few kilometers from a source region. These results indicate that entrainment in buoyant seawater plumes during an eruption may play an important role in clast dispersal, but it is not clear if this mechanism can explain the distribution of volcaniclastic material at the sites on the Gakkel and Juan de Fuca Ridges where our samples were acquired. In order to understand the dispersal of volcaniclastic material in the deep-sea it will be necessary to rigorously characterize existing deposits, and develop models capable of incorporating explosive gas phases into the eruption plume.

Barreyre, Thibaut; Soule, S. Adam; Sohn, Robert A.

2011-08-01

86

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

87

3D Mixing Inside a Neutrally Buoyant Drop Driven by Electrohydrodynamic Flows  

NASA Astrophysics Data System (ADS)

For a neutrally buoyant drop subjected to a uniform electric field, the internal flow is the well-known Taylor circulation. In Phys. Fluids 19 013102 (2007), we theoretically studied three dimensional mixing by periodically switching a uniform electric field through an angle ?. Periodically switching the field is equivalent to periodically changing the symmetry axis of the Taylor circulation. For ?=0.5 ?, there is no chaotic mixing because the common heteroclinic trajectories form the separatrix of the flow. For other switching angles, chaotic advection is generated due to perturbations of the heteroclinic trajectory. Experimental investigations of mixing were carried out using a nearly isopycnic silicone oil/castor oil system. For ?=0.5 ?, our experiments show the existence of symmetry planes. In addition, two blobs of particles are observed to maintain almost invariant shapes for very long time, indicating the absence of chaotic mixing, as predicted by the theory. For other switching angles, experiments show the penetration of symmetry planes by tracer particles. However it is difficult to draw definitive conclusions regarding chaotic mixing because of charge relaxation, long initial transients and drop translation effects.

Xu, Xiumei; Homsy, G. M.

2007-11-01

88

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

89

Reexamination of the Association Between Melting Point, Buoyant Density, and Chemical Base Composition of Deoxyribonucleic Acid  

PubMed Central

The equations currently used for the calculation of the chemical base composition of deoxyribonucleic acid (DNA), expressed as moles per cent guanine plus cytosine (% GC), from either buoyant density (?) or midpoint of thermal denaturation (Tm) were recalculated by using only sets of data on DNA determined with the same strains. All available information from the literature was screened and supplemented by unpublished data. The results were calculated by regression and correlation analysis and treated statistically. From the data on 96 strains of bacteria, it was calculated that% GC = 2.44 (Tm – 69.4). Tm appears to be unaffected by the substitution of cytosine by hydroxymethylcytosine. This equation is also valid for nonbacterial DNA. From the data on 84 strains of bacteria, the relation% GC = 1038.47 (–1.6616) was calculated. The constants in this equation are slightly modified when data on nonbacterial DNA are included. Both correlations differ only slightly from those currently used, but now they lean on a statistically sound basis. As a control, the relation between ? and Tm was calculated from data of 197 strains; it agrees excellently with the above two equations. PMID:5438045

De Ley, J.

1970-01-01

90

Highly vesicular pumice generated by buoyant detachment of magma in subaqueous volcanism  

NASA Astrophysics Data System (ADS)

Many submarine caldera volcanoes are blanketed with deposits of highly vesicular pumice, typically attributed to vigorous explosive activity. However, it is challenging to relate volcanic products to specific eruptive styles in submarine volcanism. Here we document vesicularity and textural characteristics of pumice clasts dredged from the submarine Macauley volcano in the Kermadec arc, southwest Pacific Ocean. We find that clasts show a bimodal distribution, with corresponding differences in vesicle abundances and shapes. Specifically, we find a sharp mode at 91% vesicularity and a broad mode at 65-80%. Subordinate clasts show gradients in vesicularity. We attribute the bimodality to a previously undocumented eruptive style that is neither effusive nor explosive. The eruption rate is insufficient to cause magma to fragment explosively, yet too high to passively feed a lava dome. Instead, the magma foam buoyantly detaches at the vent and rises as discrete magma parcels, or blebs, while continuing to vesiculate internally. The blebs are widely distributed by ocean currents before they disintegrate or become waterlogged. This disintegration creates individual clasts from interior and rim fragments, yielding the bimodal vesicularity characteristics. We conclude that the generation and widespread dispersal of highly vesicular pumice in the marine environment does not require highly explosive activity.

Rotella, Melissa D.; Wilson, Colin J. N.; Barker, Simon J.; Wright, Ian C.

2013-02-01

91

Turbulence Modeling Effects on the Prediction of Equilibrium States of Buoyant Shear Flows  

NASA Technical Reports Server (NTRS)

The effects of turbulence modeling on the prediction of equilibrium states of turbulent buoyant shear flows were investigated. The velocity field models used include a two-equation closure, a Reynolds-stress closure assuming two different pressure-strain models and three different dissipation rate tensor models. As for the thermal field closure models, two different pressure-scrambling models and nine different temperature variance dissipation rate, Epsilon(0) equations were considered. The emphasis of this paper is focused on the effects of the Epsilon(0)-equation, of the dissipation rate models, of the pressure-strain models and of the pressure-scrambling models on the prediction of the approach to equilibrium turbulence. Equilibrium turbulence is defined by the time rate (if change of the scaled Reynolds stress anisotropic tensor and heat flux vector becoming zero. These conditions lead to the equilibrium state parameters. Calculations show that the Epsilon(0)-equation has a significant effect on the prediction of the approach to equilibrium turbulence. For a particular Epsilon(0)-equation, all velocity closure models considered give an equilibrium state if anisotropic dissipation is accounted for in one form or another in the dissipation rate tensor or in the Epsilon(0)-equation. It is further found that the models considered for the pressure-strain tensor and the pressure-scrambling vector have little or no effect on the prediction of the approach to equilibrium turbulence.

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

2001-01-01

92

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

NASA Astrophysics Data System (ADS)

This study focuses on how wave-current and wave-turbulence interactions modify the transport of buoyant particles in the ocean. Here the particles can represent oil droplets, plastic particles, or plankton such as 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, affects the drift of the particles. The energy and momentum fluxes, as well as the Stokes drift, depend on the directional wave spectrum obtained from a wave model. As a first test, the depth and velocity scales from the model are compared with analytical solutions based on a constant eddy viscosity (i.e., classical Ekman theory). Secondly, the model is applied to a case in which we investigate the oil drift after an oil spill off the west 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 oil-drift models. In this case, using wind and wave forcing from the ERA Interim archive it is shown that the wave effects are important for the resultant drift and have the potential to improve drift forecasting.

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

2014-12-01

93

Buoyant flexure and basal crevassing in dynamic mass loss at Helheim Glacier  

NASA Astrophysics Data System (ADS)

Iceberg calving accounts for a significant proportion of annual mass loss from marine-terminating glaciers and may have been a factor in the rapid demise of ancient ice sheets. The largest contributions from the main outlet glaciers of the Greenland ice sheet to sea-level rise over the next two centuries have been projected to be dynamic in origin, that is, driven by glacier flow and calving. However, present physical models remain a coarse approximation of real calving mechanisms because models are poorly constrained by sparse glacier geometry observations. Here we present a record of daily digital elevation models from the calving margin of Greenland’s Helheim Glacier at a high spatial resolution. Our digital elevation models are derived from stereo terrestrial photography taken over the summers of 2010 and 2011. We find that during these two summers dynamic mass loss at Helheim Glacier was dominated by calving events exceeding 1 km3 that were the result of buoyant flexure and the propagation of basal crevasses. We suggest that this buoyancy-driven mechanism for calving may be common elsewhere in Greenland and could be a first-order control on the ice sheet’s future contribution to sea-level rise.

James, Timothy D.; Murray, Tavi; Selmes, Nick; Scharrer, Kilian; O'Leary, Martin

2014-08-01

94

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

95

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

96

Genetic Affinities between Trans-Oceanic Populations of Non-Buoyant Macroalgae in the High Latitudes of the Southern Hemisphere  

PubMed Central

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

97

The Effects of Neutrally Buoyant, Externally Attached Transmitters on Swimming Performance and Predator Avoidance of Juvenile Chinook Salmon  

SciTech Connect

The presence of an externally attached telemetry tag is often associated with the potential for impaired swimming performance (i.e., snags and drag) as well as increased susceptibility to predation, specifically for smaller fish. The effects on swimming performance due to the presence of a neutrally buoyant externally attached acoustic transmitter were examined by comparing critical swimming speeds (Ucrit) for juvenile Chinook salmon tagged with two different neutrally buoyant external transmitters (Type A and B), nontagged individuals, and those surgically implanted with the current JSATS acoustic transmitter. Fish tagged with the Type A and B designs had lower Ucrit when compared to nontagged individuals. However, there was no difference in Ucrit among fish tagged with Type A or B designs compared to those with surgically implanted tags. Further testing was then conducted to determine if predator avoidance ability was affected due to the presence of Type A tags when compared to nontagged fish. No difference was detected in the number of tagged and nontagged fish consumed by rainbow trout throughout the predation trials. The results of this study support the further testing on the efficacy of a neutrally buoyant externally attached telemetry tag for survival studies involving juvenile salmonids passing through hydro turbines.

Janak, Jill M.; Brown, Richard S.; Colotelo, Alison HA; Pflugrath, Brett D.; Stephenson, John R.; Deng, Zhiqun; Carlson, Thomas J.; Seaburg, Adam

2012-08-01

98

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

PubMed

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. PMID:24825997

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

2010-12-01

99

Chemical processes in buoyant hydrothermal plumes on the East Pacific Rise near 21°N  

NASA Astrophysics Data System (ADS)

Hydrothermal plume water containing suspended particles of precipitated black "smoke" has been sampled from three hydrothermal vent fields on the East Pacific Rise near 21°N. The samples were taken within the lower 22 m of the buoyant plumes, directly above 273-350°C black smoker vents, using Go-flo bottles mounted on the submersible Alvin. Based on Li as a conservative tracer of the high-temperature endmember solution, mixing ratios of 10 2 to 10 4 g seawater/g vent water are achieved within the lower 22 m of the plumes. The particle concentrations sampled in the lower 13 m of the plumes are much larger than predicted for these mixing ratios, suggesting that the particles are settling within the lower part of the plume. The major minerals in the smoke are pyrrhotite, Fe-rich sphalerite, pyrite, unidentified Fe - S ± Si and Fe - Si ± S phases, chalcopyrite, amorphous silica, sulfur, Fe-oxyhydroxides (including goethite) and anhydrite. Present in trace quantities are barite, isocubanite, wurtzite, covellite, marcasite(?), and unidentified silicates and Alsilicates. Organic matter is common. The composition of the plume solutions indicates that 35 ± 25% of the hydrothermally injected Fe remains in dissolved form (i.e., < 0.45 ?m) within the lower 22 m of the plume, in spite of a 3- to 9-fold excess of H 2S in the vent solutions. Nearly all of the Mn and Si and most of the Ba also remain in solution. H 2S, by contrast, has been largely (70-100%) removed - by precipitation as Sulfides and sulfur, but mainly by oxidation to dissolved species with intermediate oxidation states. Its early removal implies that 50 ± 30% of the injected Fe will eventually precipitate as primary oxides rather than as Sulfides and that Fe can be fractionated from the other chalcophile metals during sulfide precipitation. Compared with the vent water, the particles are enriched in Cu, Co, Ag, Cd, Al, Zn, Pb, and Ni by factors of 4 to 20 relative to Fe and depleted in Ba, S, Si, and Mn. Scavenging from seawater may play a role in Co and Cu enrichment at the NGS field, and for Ag, Cd, and Ni at all three fields, but is negligible for Pb and Zn. These results indicate that two distinct metalliferous components are delivered to the distal regions of a plume as a result of reactions in the lower part of the buoyant plume: 1) a dissolved component that includes about half the Fe and all of the Mn and will eventually precipitate as oxides, and 2) a particulate component consisting of fine-grained sulfide minerals that are enriched in ore metals by factors of 4 to 20.

Mottl, Michael J.; McConachy, Timothy F.

1990-07-01

100

Three-Dimensional Magnetohydrodynamic Simulations of Buoyant Bubbles in Galaxy Clusters  

NASA Astrophysics Data System (ADS)

We report results of three-dimensional magnetohydrodynamic simulations of the dynamics of buoyant bubbles in magnetized galaxy cluster media. The simulations are three-dimensional extensions of two-dimensional calculations reported by Jones and De Young. Initially, spherical bubbles and briefly inflated spherical bubbles all with radii a few times smaller than the intracluster medium (ICM) scale height were followed as they rose through several ICM scale heights. Such bubbles quickly evolve into a toroidal form that, in the absence of magnetic influences, is stable against fragmentation in our simulations. This ring formation results from (commonly used) initial conditions that cause ICM material below the bubbles to drive upwards through the bubble, creating a vortex ring; that is, hydrostatic bubbles develop into "smoke rings," if they are initially not very much smaller or very much larger than the ICM scale height. Even modest ICM magnetic fields with ? = P gas/P mag lsim 103 can influence the dynamics of the bubbles, provided the fields are not tangled on scales comparable to or smaller than the size of the bubbles. Quasi-uniform, horizontal fields with initial ? ~ 102 bifurcated our bubbles before they rose more than about a scale height of the ICM, and substantially weaker fields produced clear distortions. These behaviors resulted from stretching and amplification of ICM fields trapped in irregularities along the top surface of the young bubbles. On the other hand, tangled magnetic fields with similar, modest strengths are generally less easily amplified by the bubble motions and are thus less influential in bubble evolution. Inclusion of a comparably strong, tangled magnetic field inside the initial bubbles had little effect on our bubble evolution, since those fields were quickly diminished through expansion of the bubble and reconnection of the initial field.

O'Neill, S. M.; De Young, D. S.; Jones, T. W.

2009-04-01

101

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

102

Deformation statistics of sub-Kolmogorov-scale ellipsoidal neutrally buoyant drops in isotropic turbulence  

E-print Network

Small droplets in turbulent flows can undergo highly variable deformations and orientational dynamics. For neutrally buoyant droplets smaller than the Kolmogorov scale, the dominant effects from the surrounding turbulent flow arise through Lagrangian time histories of the velocity gradient tensor. Here we study the evolution of representative droplets using a model that includes rotation and stretching effects from the surrounding fluid, and restoration effects from surface tension including a constant droplet volume constraint, while assuming that the droplets maintain an ellipsoidal shape. The model is combined with Lagrangian time histories of the velocity gradient tensor extracted from DNS of turbulence to obtain simulated droplet evolutions. These are used to characterize the size, shape and orientation statistics of small droplets in turbulence. A critical capillary number, $Ca_c$ is identified associated with unbounded growth of one or two of the droplet's semi-axes. Exploiting analogies with dynamics of polymers in turbulence, the $Ca_c$ number can be predicted based on the large deviation theory for the largest Finite Time Lyapunov exponent. Also, for sub-critical $Ca$ the theory enables predictions of the slope of the power-law tails of droplet size distributions in turbulence. For cases when the viscosities of droplet and outer fluid differ in a way that enables vorticity to decorrelate the shape from the straining directions, the large deviation formalism based on the stretching properties of the velocity gradient tensor loses validity and its predictions fail. Even considering the limitations of the assumed ellipsoidal droplet shape, the results highlight the complex coupling between droplet deformation, orientation and the local fluid velocity gradient tensor to be expected when small viscous drops interact with turbulent flows.

Luca Biferale; Charles Meneveau; Roberto Verzicco

2014-09-02

103

Filament formation and evolution in buoyant coastal waters: Observation and modelling  

NASA Astrophysics Data System (ADS)

This paper presents a detailed analysis of the formation and subsequent evolution of filament-like structures observed in a relatively small area of the mid-Tyrrhenian Sea (Mediterranean Sea). The filament dynamics and potential impact on the cross-shelf exchange budget are investigated based on a combined use of remote sensing imagery, in situ data and numerical modelling. The complexity of these phenomena is shown by focusing on four distinct events that led to cross-shelf transport, each representative of a different dynamic process and a distinct expected impact on the coastal area. A systematic analysis of available observations for the years 1998-2006 underlines the role of the interplay of atmospheric freshwater fluxes, river loads and wind stress variations, which may create favourable conditions for the convergence of shelf waters (particularly at coastal capes) and the subsequent formation of short-lived filaments along the coast. The response of the buoyant coastal waters to periods of wind reversal and fluctuating freshwater discharge rates is examined through idealised Regional Ocean Modeling System (ROMS) simulations. The filaments observed in remote sensing imagery were well reproduced by the numerical exercise, where the filaments appear as organised submesoscale structures that possess high relative vorticity and develop at the river mouths or adjacent capes. In both scenarios, the filaments appear largely determined by (i) the presence of a buoyancy anomaly, (ii) the angle between the wind pulse direction and the coast and (iii) irregularities in the coastal profile. The ensemble of results suggests that the occurrence of such transient, intense structures may contribute considerably to the biological variability and cross-shelf exchange in coastal areas with similar traits.

Iermano, Ilaria; Liguori, Giovanni; Iudicone, Daniele; Buongiorno Nardelli, Bruno; Colella, Simone; Zingone, Adriana; Saggiomo, Vincenzo; Ribera d'Alcalà, Maurizio

2012-11-01

104

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

105

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. PMID:5874533

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

1964-01-01

106

Synthesis of buoyant metal-coated fly ash cenosphere and its excellent catalytic performance in dye degradation.  

PubMed

In this work, Ag(+) and Ag(0) were absorbed onto the surface of 3-mercaptopropyltriethoxysilane modified fly ash cenospheres (FACs) in two Ag activation processes. The activation methods, avoiding traditional surface sensitization by SnCl2, successfully initiated electroless copper particles deposition for the preparation of buoyant Cu-FAC and CuAg-FAC composites. The CuAg-FAC had a much more uniform morphology than the Cu-FAC. The catalytic performance of the Cu-FAC and CuAg-FAC was examined by the reduction of Orange IV azo dye with the presence of NaBH4. 98.4% of Orange IV was rapidly reduced within 25min by the CuAg-FAC, whereas 76.4% of Orange IV was removed by the Cu-FAC. The results reveal that the degradation processes matched well with the pseudo-first-order kinetics model, and rate constants of 0.057 and 0.186min(-1) were obtained for the Cu-FAC and CuAg-FAC, respectively. Moreover, two other dyes of Orange II and Reactive Black 5 were also efficiently reduced by the CuAg-FAC which could be easily recycled and stably reused at least four times. These buoyant metal-coated FAC composites would be very useful in various catalytic reductions. PMID:25585281

Wang, Wei; Zhai, Jianping; Li, Qin

2015-04-15

107

Buoyant magnetic flux ropes in a magnetized stellar envelope: Idealized numerical 2.5-D MHD simulations  

E-print Network

Context: The context of this paper is buoyant toroidal magnetic flux ropes, which is a part of flux tube dynamo theory and the framework of solar-like magnetic activity. Aims: The aim is to investigate how twisted magnetic flux ropes interact with a simple magnetized stellar model envelope--a magnetic "convection zone"--especially to examine how the twisted magnetic field component of a flux rope interacts with a poloidal magnetic field in the convection zone. Method: Both the flux ropes and the atmosphere are modelled as idealized 2.5-dimensional concepts using high resolution numerical magneto-hydrodynamic (MHD) simulations. Results: It is illustrated that twisted toroidal magnetic flux ropes can interact with a poloidal magnetic field in the atmosphere to cause a change in both the buoyant rise dynamics and the flux rope's geometrical shape. The details of these changes depend primarily on the polarity and strength of the atmospheric field relative to the field strength of the flux rope. It is suggested that the effects could be verified observationally.

S. B. F. Dorch

2006-09-22

108

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

109

46 CFR 160.047-3a - Materials-Dee ring and snap hook assemblies and other instruments of closure for buoyant vests.  

Code of Federal Regulations, 2014 CFR

...of closure for buoyant vests must— (1) Be tested for weathering. The Coast Guard will determine which one or more of the...hours; and (2) Within 5 minutes of completion of the weathering test required by paragraph (b)(1) of this...

2014-10-01

110

46 CFR 160.060-3a - Materials-Dee ring and snap hook assemblies and other instruments of closure for buoyant vests.  

Code of Federal Regulations, 2013 CFR

...of closure for buoyant vests must— (1) Be tested for weathering. The Coast Guard will determine which one or more of the...hours; and (2) Within 5 minutes of completion of the weathering test required by paragraph (b)(1) of this...

2013-10-01

111

46 CFR 160.047-3a - Materials-Dee ring and snap hook assemblies and other instruments of closure for buoyant vests.  

Code of Federal Regulations, 2013 CFR

...of closure for buoyant vests must— (1) Be tested for weathering. The Coast Guard will determine which one or more of the...hours; and (2) Within 5 minutes of completion of the weathering test required by paragraph (b)(1) of this...

2013-10-01

112

46 CFR 160.052-3a - Materials-Dee ring and snap hook assemblies and other instruments of closure for buoyant vests.  

Code of Federal Regulations, 2013 CFR

...of closure for buoyant vests must— (1) Be tested for weathering. The Coast Guard will determine which one or more of the...hours; and (2) Within 5 minutes of completion of the weathering test required by paragraph (b)(1) of this...

2013-10-01

113

46 CFR 160.052-3a - Materials-Dee ring and snap hook assemblies and other instruments of closure for buoyant vests.  

Code of Federal Regulations, 2014 CFR

...of closure for buoyant vests must— (1) Be tested for weathering. The Coast Guard will determine which one or more of the...hours; and (2) Within 5 minutes of completion of the weathering test required by paragraph (b)(1) of this...

2014-10-01

114

46 CFR 160.060-3a - Materials-Dee ring and snap hook assemblies and other instruments of closure for buoyant vests.  

Code of Federal Regulations, 2014 CFR

...of closure for buoyant vests must— (1) Be tested for weathering. The Coast Guard will determine which one or more of the...hours; and (2) Within 5 minutes of completion of the weathering test required by paragraph (b)(1) of this...

2014-10-01

115

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

116

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. 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

117

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

118

Physiological considerations in applying laboratory-determined buoyant densities to predictions of bacterial and protozoan transport in groundwater: Results of in-situ and laboratory tests  

USGS Publications Warehouse

Buoyant densities were determined for groundwater bacteria and microflagellates (protozoa) from a sandy aquifer (Cape Cod, MA) using two methods: (1) density-gradient centrifugation (DGC) and (2) Stoke's law approximations using sedimentation rates observed during natural-gradient injection and recovery tests. The dwarf (average cell size, 0.3 ??m), unattached bacteria inhabiting a pristine zone just beneath the water table and a majority (~80%) of the morphologically diverse community of free- living bacteria inhabiting a 5-km-long plume of organically-contaminated groundwater had DGC-determined buoyant densities <1.019 g/cm3 before culturing. In the aquifer, sinking rates for the uncultured 2-??m size class of contaminant plume bacteria were comparable to that of the bromide tracer (1.9 x 10-3 M), also suggesting a low buoyant density. Culturing groundwater bacteria resulted in larger (0.8-1.3 ??m), less neutrally- buoyant (1.043-1.081 g/cm3) cells with potential sedimentation rates up to 64-fold higher than those predicted for the uncultured populations. Although sedimentation generally could be neglected in predicting subsurface transport for the community of free-living groundwater bacteria, it appeared to be important for the cultured isolates, at least until they readapt to aquifer conditions. Culturing-induced alterations in size of the contaminant-plume microflagellates (2-3 ??m) were ameliorated by using a lower nutrient, acidic (pH 5) porous growth medium. Buoyant densities of the cultured microflagellates were low, i.e., 1.024-1.034 g/cm3 (using the DGC assay) and 1.017-1.039 g/cm3 (estimated from in-situ sedimentation rates), suggesting good potential for subsurface transport under favorable conditions.

Harvey, R.W.; Metge, D.W.; Kinner, N.; Mayberry, N.

1997-01-01

119

Changes in pH of seawater in the neighborhood of a buoyant CO{sub 2} droplet in the ocean  

SciTech Connect

Changes in pH around a buoyant CO{sub 2} droplet in the ocean are studied. Based on a convection-diffusion model, mass transfer from the CO{sub 2} droplet into seawater is analyzed. Chemical reactions that occur in the carbonate system are considered assuming local chemical equilibrium. A relationship between pH and the CO{sub 2} concentration (in a total-carbonate sense) is obtained. Based on this relationship, changes in pH around the droplet can be predicted. It is found in this study that the pH distribution around a buoyant CO{sub 2} droplet in the ocean is highly asymmetric; at the front of the droplet, changes in pH are restricted to a thin surface layer, however, a low-pH wake forms at the rear of the droplet and this wake can extend for a distance of several times the droplet radius.

Teng, H.; Yamasaki, Akihiro [National Inst. of Materials and Chemical Research, Tsukuba, Ibaraki (Japan)

1997-12-31

120

Hands-on experiences with buoyant-less water This article has been downloaded from IOPscience. Please scroll down to see the full text article.  

E-print Network

Hands-on experiences with buoyant-less water This article has been downloaded from IOPscience. Please scroll down to see the full text article. 2010 Phys. Educ. 45 292 (http://iopscience.iop.org/0031-9120/45/3/011) Download details: IP Address: 93.103.38.94 The article was downloaded on 05/05/2010 at 17:47 Please note

Planin�iè, Gorazd

121

In-Situ Optical and Acoustical Measurements of the Buoyant Cyanobacterium P. Rubescens: Spatial and Temporal Distribution Patterns  

PubMed Central

Optical (fluorescence) and acoustic in-situ techniques were tested in their ability to measure the spatial and temporal distribution of plankton in freshwater ecosystems with special emphasis on the harmful and buoyant cyanobacterium P. rubescens. Fluorescence was measured with the multi-spectral FluoroProbe (Moldaenke FluoroProbe, MFP) and a Seapoint Chlorophyll Fluorometer (SCF). In-situ measurements of the acoustic backscatter strength (ABS) were conducted with three different acoustic devices covering multiple acoustic frequencies (614 kHz ADCP, 2 MHz ADP, and 6 MHz ADV). The MFP provides a fast and reliable technique to measure fluorescence at different wavelengths in situ, which allows discriminating between P. rubescens and other phytoplankton species. All three acoustic devices are sensitive to P. rubescens even if other scatterers, e.g., zooplankton or suspended sediment, are present in the water column, because P. rubescens containing gas vesicles has a strong density difference and hence acoustic contrast to the ambient water and other scatterers. After calibration, the combination of optical and acoustical measurements not only allows qualitative and quantitative observation of P. rubescens, but also distinction between P. rubescens, other phytoplankton, and zooplankton. As the measuring devices can sample in situ at high rates they enable assessment of plankton distributions at high temporal (minutes) and spatial (decimeters) resolution or covering large temporal (seasonal) and spatial (basin scale) scales. PMID:24303028

Hofmann, Hilmar; Peeters, Frank

2013-01-01

122

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. PMID:24167789

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

2013-01-01

123

Some factors affecting the use of lighter than air systems. [economic and performance estimates for dirigibles and semi-buoyant hybrid vehicles  

NASA Technical Reports Server (NTRS)

The uses of lighter-than-air vehicles are examined in the present day transportation environment. Conventional dirigibles were found to indicate an undesirable economic risk due to their low speeds and to uncertainties concerning their operational use. Semi-buoyant hybrid vehicles are suggested as an alternative which does not have many of the inferior characteristics of conventional dirigibles. Economic and performance estimates for hybrid vehicles indicate that they are competitive with other transportation systems in many applications, and unique in their ability to perform some highly desirable emergency missions.

Havill, C. D.

1974-01-01

124

JBFA - buoyant flight  

NASA Technical Reports Server (NTRS)

A method was developed whereby a balloon was used to carry lumber out of a forest in order to continue lumber production without destroying the natural environment and view of the forest. Emphasis was on the best shape for a logging balloon, development of a balloon logging system suitable for cutting lumber and safety plans, tests on balloon construction and development of netting, and weather of mountainous areas, especially solutions to problems caused by winds.

Ohari, T.

1982-01-01

125

Buoyant despite Downturn  

ERIC Educational Resources Information Center

Even as libraries face the economic downturn, a record-setting number of people attended the American Library Association (ALA) annual conference in Chicago, July 9-15. The tough economy, however, was felt in the number of exhibitors, which declined from the previous record set in 2007 in Washington, DC, and in anecdotal evidence that suggested…

Berry, John N., III; Fialkoff, Francine; Fox, Bette-Lee; Hadro, Josh; Horrocks, Norman; Kuzyk, Raya; Oder, Norman

2009-01-01

126

HGSYSTEM/UF{sub 6} model enhancements for plume rise and dispersion around buildings, lift-off of buoyant plumes, and robustness of numerical solver  

SciTech Connect

The HGSYSTEM/UF{sub 6} model was developed for use in preparing Safety Analysis Reports (SARs) by estimating the consequences of possible accidental releases of UF{sub 6} to the atmosphere at the gaseous diffusion plants (GDPs) located in Portsmouth, Ohio, and Paducah, Kentucky. Although the latter report carries a 1996 date, the work that is described was completed in late 1994. When that report was written, the primary release scenarios of interest were thought to be gas pipeline and liquid tank ruptures over open terrain away from the influence of buildings. However, upon further analysis of possible release scenarios, the developers of the SARs decided it was necessary to also consider accidental releases within buildings. Consequently, during the fall and winter of 1995-96, modules were added to HGSYSTEM/UF{sub 6} to account for flow and dispersion around buildings. The original HGSYSTEM/UF{sub 6} model also contained a preliminary method for accounting for the possible lift-off of ground-based buoyant plumes. An improved model and a new set of wind tunnel data for buoyant plumes trapped in building recirculation cavities have become available that appear to be useful for revising the lift-off algorithm and modifying it for use in recirculation cavities. This improved lift-off model has been incorporated in the updated modules for dispersion around buildings.

Hanna, S.R.; Chang, J.C.

1997-01-01

127

1/12-Scale mixing interface visualization and buoyant particle release tests in support of Tank 241-SY-101 hydrogen mitigation  

SciTech Connect

In support of tank waste safety programs, visualization tests were performed in the 1/12-scale tank facility, using a low-viscosity simulant. The primary objective of the tests was to obtain video records of the transient jet-sludge interaction. The intent is that these videos will provide useful qualitative data for comparison with model predictions. Two tests were initially planned: mixing interface visualization (MIV) and buoyant particle release (BPR). Completion of the buoyant particle release test was set aside in order to complete additional MIV tests. Rheological measurements were made on simulant samples before testing, and the simulant was found to exhibit thixotropic behavior. Shear vane measurements were also made on an in-situ analog of the 1/12-scale tank simulant. Simulant shear strength has been observed to be time dependent. The primary objective of obtaining video records of jet-sludge interaction was satisfied, and the records yielded jet location information which may be of use in completing model comparisons. The modeling effort is not part of this task, but this report also discusses test specific instrumentation, visualization techniques, and shear vane instrumentation which would enable improved characterization of jet-sludge interaction and simulant characteristics.

Eschbach, E.J.; Enderlin, C.W.

1993-10-01

128

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

129

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

130

ANALYSIS OF BUOYANT SURFACE JETS  

EPA Science Inventory

To obtain improved prediction of heated plume characteristics from a surface jet, an integral analysis computer model was modified and a comprehensive set of field and laboratory data available from the literature was gathered, analyzed, and correlated for estimating the magnitud...

131

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

132

Buoyant currents arrested by convective dissolution  

E-print Network

When carbon dioxide (CO[subscript 2]) dissolves into water, the density of water increases. This seemingly insubstantial phenomenon has profound implications for geologic carbon sequestration. Here we show, by means of ...

MacMinn, Christopher W.

133

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

134

A Buoyant Life Investigating Mobile Platform (BLIMP)  

NASA Astrophysics Data System (ADS)

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 mobile aerial vehicle that is a proxy for the exploration approaches and instrument techniques necessary for the next stage of life detection on other planets. We do this by deploying a mobile organic laboratory on Earth to demonstrate the requisite techniques. Terrestrial field trials will provide new insights on the colonization by life of fresh volcanic flows, and the competition between biotic and abiotic processes on a newly cooling piece of the Earth's crust. This paper suggests that such work could be very effectively conducted on Hawaii, where the erupted lava is basaltic, an important crustal component for terrestrial planets. The presence of water is generally agreed to be a prerequisite for planetary habitability but the combination of basalt and water is chemically unstable at the temperatures to which basalt cools after eruption. The subsequent chemical reactions occur because the total energy of the products is lower than that of the precursor materials and on Earth biological processes prosper by harvesting that difference in energy. For life processes to succeed they must out-compete the rate at which abiotic chemistry might accomplish the same tasks. Monitoring the rate at which chemical processes occur is therefore a life-detection approach. Biotic involvement in the rate of weathering of basalts is a test case for this new, generic life detection paradigm. This approach would be applicable to the periglacial zones of Mars, if liquid water were proven to be present there. We show that the use of a 15 meter autonomous blimp to carry various instrument packages (including camera, visible spectrometer, Tunable Diode Laser Spectrometer (TDLS) for gas and gas isotope analysis, gas chromatograph/mass spectrometer (GCMS). These could be calibrated followed by ground-truthing using field experiments in the interior of Meteor Crater in Arizona. This well understood system could then study the extreme environment of the still active volcanic caldera of Kilauea and the adjacent older lava flows. For Mars the blimp is a proxy for a lighter balloon or even a Martian Rover, which could carry a similar suite of instruments and take a similar set of measurements. For Titan, with its dense and high-molecular weight atmosphere calm winds and low gravity, a blimp will be the vehicle of choice. The experiments would be directly relevant. We discuss how a Titan Blimp could search for organic compounds in the post-Cassini exploration of Titan.

Coleman, M.; Jones, J.; Rodgers, D.

135

A buoyant life investigating mobile platform (BLIMP)  

NASA Astrophysics Data System (ADS)

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 mobile aerial vehicle that is a proxy for the exploration approaches and instrument techniques necessary for the next stage of life detection on other planets. We do this by deploying a mobile organic laboratory on Earth to demonstrate the requisite techniques. We show how terrestrial field trials provide new insights on the colonization by life of fresh volcanic flows, and the competition between biotic and abiotic processes on a newly cooling piece of the Earth’s crust. This paper suggests that such work could be very effectively conducted on Hawaii, where the erupted lava is basaltic, an important crustal component for terrestrial planets. The presence of water is generally agreed to be a prerequisite for planetary habitability but the combination of basalt and water is chemically unstable at the temperatures to which basalt cools after eruption. The subsequent chemical reactions occur because the total energy of the products is lower than that of the precursor materials and on Earth biological processes result from organisms harvesting that difference in energy. For life processes to succeed they must out-compete the rate at which abiotic chemistry might accomplish the same tasks. Monitoring the rate at which chemical processes occur is therefore a life-detection approach. Biotic involvement in the rate of weathering of basalts is the test case for this new, generic life detection paradigm. This approach would be applicable to the periglacial zones of Mars, if liquid water were proven to be present there. We show that a 15 m autonomous BLIMP could carry various instrument packages including camera, visible spectrometer, tunable diode laser spectrometer (TDLS) for gas and gas isotope analysis, gas chromatograph/mass spectrometer (GCMS). These could be calibrated followed by ground-truthing using field experiments in the interior of Meteor Crater in Arizona. This well understood system could then study the extreme environment of the still active volcanic caldera of Kilauea and the adjacent older lava flows. For Mars the BLIMP is a proxy for a lighter balloon or even a Martian Rover, which could carry a similar suite of instruments and take a similar set of measurements. For Titan, with its dense and high-molecular weight atmosphere calm winds and low gravity, a BLIMP will be the vehicle of choice. The experiments would be directly relevant. We discuss how a Titan BLIMP could search for organic compounds in the post-Cassini exploration of Titan.

Coleman, Max; Rodgers, David; Jones, Jack

2006-01-01

136

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

137

A modeling of buoyant gas plume migration  

SciTech Connect

This work is motivated by the growing interest in injecting carbon dioxide into deep geological formations as a means of avoiding its atmospheric emissions and consequent global warming. Ideally, the injected greenhouse gas stays in the injection zone for a geologic time, eventually dissolves in the formation brine and remains trapped by mineralization. However, one of the potential problems associated with the geologic method of sequestration is that naturally present or inadvertently created conduits in the cap rock may result in a gas leakage from primary storage. Even in a supercritical state, the carbon dioxide viscosity and density are lower than those of the formation brine. Buoyancy tends to drive the leaked CO{sub 2} plume upward. Theoretical and experimental studies of buoyancy-driven supercritical CO{sub 2} flow, including estimation of time scales associated with plume evolution and migration, are critical for developing technology, monitoring policy, and regulations for safe carbon dioxide geologic sequestration. In this study, we obtain simple estimates of vertical plume propagation velocity taking into account the density and viscosity contrast between CO{sub 2} and brine. We describe buoyancy-driven countercurrent flow of two immiscible phases by a Buckley-Leverett type model. The model predicts that a plume of supercritical carbon dioxide in a homogeneous water-saturated porous medium does not migrate upward like a bubble in bulk water. Rather, it spreads upward until it reaches a seal or until it becomes immobile. A simple formula requiring no complex numerical calculations describes the velocity of plume propagation. This solution is a simplification of a more comprehensive theory of countercurrent plume migration (Silin et al., 2007). In a layered reservoir, the simplified solution predicts a slower plume front propagation relative to a homogeneous formation with the same harmonic mean permeability. In contrast, the model yields much higher plume propagation estimates in a high-permeability conduit like a vertical fracture.

Silin, D.; Patzek, T.; Benson, S.M.

2008-12-01

138

TURBULENCE MODELING APPLIED TO BUOYANT PLUMES  

EPA Science Inventory

A viable computer model was developed that is based on second-order closure of the turbulent correlation equations for predicting the fate of nonchemically reacting contaminants released in the atmospheric boundary layer. The invariant turbulence model discussed in previous repor...

139

Candle Flames in Non-Buoyant Atmospheres  

NASA Technical Reports Server (NTRS)

This paper addresses the behavior of a candle flame in a long-duration, quiescent microgravity environment both on the space Shuttle and the Mir Orbiting Station. On the Shuttle, the flames became dim blue after an initial transient where there was significant yellow (presumably soot) in the flame. The flame lifetimes were typically less than 60 seconds. The safety-mandated candlebox that contained the candle flame inhibited oxygen transport to the flame and thus limited the flame lifetime. The flames on the Mir were similar, except that the yellow luminosity persisted longer into the flame lifetime because of a higher initial oxygen concentration, The Mir flames burned for as long as 45 minutes. The difference in the flame lifetime between the Shuttle and Mir flames was primarily the redesigned candlebox that did not inhibit oxygen transport to the flame. In both environments, the flame intensity and the height-to-width ratio gradually decreased as the ambient oxygen content in the sealed chamber slowly decreased. Both sets of experiments showed spontaneous, axisymmetric flame oscillations just prior to extinction. The paper also presents a numerical model of a candle flame. The formulation is two-dimensional and time-dependent in the gas phase with constant specific heats, thermal conductivity and Lewis number (although different species can have different Lewis numbers), one-step finite-rate kinetics, and gas-phase radiative losses from CO2 and H2O. The treatment of the liquid/wick phase assumes that the, fuel evaporates from a constant diameter sphere connected to an inert cone. The model predicts a steady flame with a shape and size quantitatively similar to the Shuttle and Mir flames. The computation predicts that the flame size will increase slightly with increasing ambient oxygen mole fraction. The model also predicts pre-extinction flame oscillations if the rate of decrease in ambient oxygen is small enough, such as that which would occur for a flame burning in a sealed ambient.

Dietrich, D. L.; Ross, H. D.; Shu, Y.; Chang, P.; Tien, J. S.

2000-01-01

140

Candle Flames in Non-Buoyant Atmospheres  

Microsoft Academic Search

This paper addresses the behavior of a candle flame in a long-duration, quiescent microgravity environment both on the space Shuttle and the Mir Orbiting Station. On the Shuttle, the flames became dim blue after an initial transient where there was significant yellow (presumably soot) in the flame. The flame lifetimes were typically less than 60 seconds. The safety-mandated candlebox that

D. L. DIETRICH; H. D. ROSS; Y. SHU; P. CHANG; J. S. TIEN

2000-01-01

141

Label-free buoyant mass assays with suspended microchannel resonators  

E-print Network

Improved methods are needed for routine, inexpensive monitoring of biomarkers that could facilitate earlier detection and characterization of complex diseases like cancer. Development of new assay formats based on microfluidic, ...

Von Muhlen, Marcio Goldani

2010-01-01

142

Hyperpycnal and buoyant plumes from a sediment-laden river  

Microsoft Academic Search

The interaction of river plumes and sediment transport is examined using a three-dimensional numerical model which couples the hydrodynamics and sediment transport. Only large rivers in midlatitudes are considered so that the effect of Coriolis deflection becomes important. Winds and tides are excluded. In an initially quiescent coastal sea, sediment-freshwater mixture is released from the inner reaches of a river.

Shenn-yu Chao

1998-01-01

143

Buoyant plumes with inertial and chemical reaction-driven forcing  

E-print Network

the plume head has risen to the top of a fluid filled tank leaving only a persistent conduit. Plume. The forced plumes were compositionally buoy- ant and were injected with inertial forcing into a fluid filled tank. The autocatalytic plumes were produced without mechanical forcing by buoyancy that was entirely

Morris, Stephen W.

144

Buoyant Low Stretch Diffusion Flames Beneath Cylindrical PMMA Samples  

NASA Technical Reports Server (NTRS)

A unique new way to study low gravity flames in normal gravity has been developed. To study flame structure and extinction characteristics in low stretch environments, a normal gravity low-stretch diffusion flame is generated using a cylindrical PMMA sample of varying large radii. Burning rates, visible flame thickness, visible flame 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 6-7/ sec, as determined by curvefits to the non-monotonic trends in peak temperatures, solid and gas-phase temperature gradients, and non-dimensional standoff distances. 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, while the magnitude of the losses remains the same. 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.

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

1999-01-01

145

Buoyant plane plumes from heated horizontal confined wires and cylinders  

Microsoft Academic Search

Two-dimensional computations are reported for time-dependent laminar buoyancy-induced flows above a horizontal heated source\\u000a immersed in an air-filled vessel. Two kinds of heated source were considered: a line heat source, modelled as a heat source\\u000a term in the energy equation, and a heat-flux cylinder of small diameter. First, comparisons are presented for the results\\u000a obtained for these two heated sources.

Guy Lauriat; Gilles Desrayaud

1994-01-01

146

Time-dependent buoyant puff model for explosive sources  

SciTech Connect

Several models exist to predict the time dependent behavior of bouyant puffs that result from explosions. This paper presents a new model that is derived from the strong conservative form of the conservation partial differential equations that are integrated over space to yield a coupled system of time dependent nonlinear ordinary differential equations. This model permits the cloud to evolve from an intial spherical shape not an ellipsoidal shape. It ignores the Boussinesq approximation, and treats the turbulence that is generated by the puff itself and the ambient atmospheric tubulence as separate mechanisms in determining the puff history. The puff cloud rise history was found to depend no only on the mass and initial temperature of the explosion, but also upon the stability conditions of the ambient atmosphere. This model was calibrated by comparison with the Roller Coaster experiments.

Kansa, E.J.

1997-01-01

147

Lipid composition of positively buoyant eggs of reef building corals  

NASA Astrophysics Data System (ADS)

Lipid composition of the eggs of three reef building corals, Acropora millepora, A. tenuis and Montipora digitata, were determined. Sixty to 70% of the egg dry weight was lipid, which consisted of wax esters (69.5 81.8%), triacylglycerols (1.1 8.4%) and polar lipids c/mainly phospholipids (11.9 13.2%). Montipora digitata also contained some polar lipids typical of the thylakoid membrane in chloroplasts, probably due to the presence of symbiotic zooxanthellae in the eggs. The wax esters appeared to be the major contributor to positive buoyancy of the eggs, and specific gravity of wax esters in A. millepora was estimated to be 0.92. Among the fatty acids of the wax esters, 34.9 51.3% was hexadecanoic acid (16:0) while the major fatty acids in polar lipids were octadecenoic acid (18:1), hexadecanoic acid (16:0), eicosapentaenoic acid (20:5) and eicosatetraenoic acid (20:4). The wax ester appears to be the main component of the 4.5 6.0 ?m diameter lipid droplets which fill most of the central mass of the coral eggs.

Arai, Iakayuki; Kato, Misako; Heyward, Andrew; Ikeda, Yutaka; Iizuka, Tokio; Maruyama, Tadashi

1993-07-01

148

Second order closure modeling of turbulent buoyant wall plumes  

NASA Technical Reports Server (NTRS)

Non-intrusive measurements of scalar and momentum transport in turbulent wall plumes, using a combined technique of laser Doppler anemometry and laser-induced fluorescence, has shown some interesting features not present in the free jet or plumes. First, buoyancy-generation of turbulence is shown to be important throughout the flow field. Combined with low-Reynolds-number turbulence and near-wall effect, this may raise the anisotropic turbulence structure beyond the prediction of eddy-viscosity models. Second, the transverse scalar fluxes do not correspond only to the mean scalar gradients, as would be expected from gradient-diffusion modeling. Third, higher-order velocity-scalar correlations which describe turbulent transport phenomena could not be predicted using simple turbulence models. A second-order closure simulation of turbulent adiabatic wall plumes, taking into account the recent progress in scalar transport, near-wall effect and buoyancy, is reported in the current study to compare with the non-intrusive measurements. In spite of the small velocity scale of the wall plumes, the results showed that low-Reynolds-number correction is not critically important to predict the adiabatic cases tested and cannot be applied beyond the maximum velocity location. The mean and turbulent velocity profiles are very closely predicted by the second-order closure models. but the scalar field is less satisfactory, with the scalar fluctuation level underpredicted. Strong intermittency of the low-Reynolds-number flow field is suspected of these discrepancies. The trends in second- and third-order velocity-scalar correlations, which describe turbulent transport phenomena, are also predicted in general, with the cross-streamwise correlations better than the streamwise one. Buoyancy terms modeling the pressure-correlation are shown to improve the prediction slightly. The effects of equilibrium time-scale ratio and boundary condition are also discussed.

Zhu, Gang; Lai, Ming-Chia; Shih, Tsan-Hsing

1992-01-01

149

Lipid composition of positively buoyant eggs of reef building corals  

Microsoft Academic Search

Lipid composition of the eggs of three reef building corals, Acropora millepora, A. tenuis and Montipora digitata, were determined. Sixty to 70% of the egg dry weight was lipid, which consisted of wax esters (69.5–81.8%), triacylglycerols (1.1–8.4%) and polar lipids c\\/mainly phospholipids (11.9–13.2%). Montipora digitata also contained some polar lipids typical of the thylakoid membrane in chloroplasts, probably due to

Iakayuki Arai; Misako Kato; Andrew Heyward; Yutaka Ikeda; Tokio Iizuka; Tadashi Maruyama

1993-01-01

150

PIV Measurements in Weakly Buoyant Gas Jet Flames  

NASA Technical Reports Server (NTRS)

Despite numerous experimental investigations, the characterization of microgravity laminar jet diffusion flames remains incomplete. Measurements to date have included shapes, temperatures, soot properties, radiative emissions and compositions, but full-field quantitative measurements of velocity are lacking. Since the differences between normal-gravity and microgravity diffusion flames are fundamentally influenced by changes in velocities, it is imperative that the associated velocity fields be measured in microgravity flames. Velocity measurements in nonbuoyant flames will be helpful both in validating numerical models and in interpreting past microgravity combustion experiments. Pointwise velocity techniques are inadequate for full-field velocity measurements in microgravity facilities. In contrast, Particle Image Velocimetry (PIV) can capture the entire flow field in less than 1% of the time required with Laser Doppler Velocimetry (LDV). Although PIV is a mature diagnostic for normal-gravity flames , restrictions on size, power and data storage complicate these measurements in microgravity. Results from the application of PIV to gas jet flames in normal gravity are presented here. Ethane flames burning at 13, 25 and 50 kPa are considered. These results are presented in more detail in Wernet et al. (2000). The PIV system developed for these measurements recently has been adapted for on-rig use in the NASA Glenn 2.2-second drop tower.

Sunderland, Peter B.; Greenbberg, Paul S.; Urban, David L.; Wernet, Mark P.; Yanis, William

2001-01-01

151

Continents as lithological icebergs: The importance of buoyant lithospheric roots  

USGS Publications Warehouse

An understanding of the formation of new continental crust provides an important guide to locating the oldest terrestrial rocks and minerals. We evaluated the crustal thicknesses of the thinnest stable continental crust and of an unsubductable oceanic plateau and used the resulting data to estimate the amount of mantle melting which produces permanent continental crust. The lithospheric mantle is sufficiently depleted to produce permanent buoyancy (i.e., the crust is unsubductable) at crustal thicknesses greater than 25-27 km. These unsubductable oceanic plateaus and hotspot island chains are important sources of new continental crust. The newest continental crust (e.g., the Ontong Java plateau) has a basaltic composition, not a granitic one. The observed structure and geochemistry of continents are the result of convergent margin magmatism and metamorphism which modify the nascent basaltic crust into a lowermost basaltic layer overlain by a more silicic upper crust. The definition of a continent should imply only that the lithosphere is unsubductable over ??? 0.25 Ga time periods. Therefore, the search for the oldest crustal rocks should include rocks from lower to mid-crustal levels.

Abbott, D.H.; Drury, R.; Mooney, W.D.

1997-01-01

152

Time-dependent buoyant puff model for explosive sources  

SciTech Connect

This paper presents a new model for explosive puff rise histories that is derived from the strong conservative form of the partial differential equations of mass, momenta, and total energy that are integrated over space to yield a coupled system of time dependent nonlinear ordinary differential equations (ODEs). By allowing the dimensions of the puff to evolve laterally and horizontally, the initial rising spherical shaped puff evolves into a rising ellipsoidal shaped mushroom cloud. This model treats the turbulence that is generated by the puff itself and the ambient atmospheric turbulence as separate mechanisms in determining the puff history. The puff rise history was found to depend not only upon the mass and initial temperature of the explosion, but also upon the local stability conditions of the ambient atmosphere through which the puff rises. This model was calibrated by comparison with the Roller Coaster experiments, ranging from unstable to very stable atmospheric conditions; the agreement of the model history curves with these experimental curves was within 10%.

Kansa, E.J.

1997-10-01

153

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

154

Laminar, turbulent, and inertial shear-thickening regimes in channel flow of neutrally buoyant particle suspensions.  

PubMed

The aim of this Letter is to characterize the flow regimes of suspensions of finite-size rigid particles in a viscous fluid at finite inertia. We explore the system behavior as a function of the particle volume fraction and the Reynolds number (the ratio of flow and particle inertia to viscous forces). Unlike single-phase flows, where a clear distinction exists between the laminar and the turbulent states, three different regimes can be identified in the presence of a particulate phase, with smooth transitions between them. At low volume fractions, the flow becomes turbulent when increasing the Reynolds number, transitioning from the laminar regime dominated by viscous forces to the turbulent regime characterized by enhanced momentum transport by turbulent eddies. At larger volume fractions, we identify a new regime characterized by an even larger increase of the wall friction. The wall friction increases with the Reynolds number (inertial effects) while the turbulent transport is weakly affected, as in a state of intense inertial shear thickening. This state may prevent the transition to a fully turbulent regime at arbitrary high speed of the flow. PMID:25554885

Lashgari, Iman; Picano, Francesco; Breugem, Wim-Paul; Brandt, Luca

2014-12-19

155

An osmometer model for changes in the buoyant density of chromaffin granules.  

PubMed Central

We present a model for the structure of isolated bovine adrenal medulla chromaffin granules derived from the dependence of granule density on the osmotic pressure of the suspension medium at 2 degrees C. The granule consists of a flexible, inelastic membrane bounding an osmotically active core. The core consists of a solution space and a separate, nonosmotic phase. Since the granule behaves like a "perfect" osmometer over a wide range of osmolarities, we conclude that (a) within these limits, the core consists of a constant amount of condensed material and a constant number of particles in solution, (b) from the constraints of the osmometer model, the osmolality inside the granule must equal the osmolality outside. Therefore the high concentrations of catecholamines (greater than 0.7 M) and ATP (greater than 0.18 M) measured biochemically cannot be dissolved in the core solution as separate molecules, but must be condensed into larger aggregates. These results are supported by electron micrographic examination of the effect of osmotic pressure changes on granule morphology. Images FIGURE 5 PMID:901901

Morris, S J; Schultens, H A; Schober, R

1977-01-01

156

Sink fast and swim harder! Round-trip cost-of-transport for buoyant divers.  

PubMed

Efficient locomotion between prey resources at depth and oxygen at the surface is crucial for breath-hold divers to maximize time spent in the foraging layer, and thereby net energy intake rates. The body density of divers, which changes with body condition, determines the apparent weight (buoyancy) of divers, which may affect round-trip cost-of-transport (COT) between the surface and depth. We evaluated alternative predictions from external-work and actuator-disc theory of how non-neutral buoyancy affects round-trip COT to depth, and the minimum COT speed for steady-state vertical transit. Not surprisingly, the models predict that one-way COT decreases (increases) when buoyancy aids (hinders) one-way transit. At extreme deviations from neutral buoyancy, gliding at terminal velocity is the minimum COT strategy in the direction aided by buoyancy. In the transit direction hindered by buoyancy, the external-work model predicted that minimum COT speeds would not change at greater deviations from neutral buoyancy, but minimum COT speeds were predicted to increase under the actuator disc model. As previously documented for grey seals, we found that vertical transit rates of 36 elephant seals increased in both directions as body density deviated from neutral buoyancy, indicating that actuator disc theory may more closely predict the power requirements of divers affected by gravity than an external work model. For both models, minor deviations from neutral buoyancy did not affect minimum COT speed or round-trip COT itself. However, at body-density extremes, both models predict that savings in the aided direction do not fully offset the increased COT imposed by the greater thrusting required in the hindered direction. PMID:23014571

Miller, Patrick J O; Biuw, Martin; Watanabe, Yuuki Y; Thompson, Dave; Fedak, Mike A

2012-10-15

157

ESTIMATING SURFACE CONCENTRATIONS FROM AN ELEVATED, BUOYANT PLUME IN A LIMITED-MIXED CONVECTIVE BOUNDARY LAYER  

EPA Science Inventory

In the past decade, recent advances have suggested that convective scaling can be used to parameterize diffusion from a plume in the convective boundary layer (CBL). New methods such as convective scaling need to be explored because the traditionally used Gaussian plume model doe...

158

Preventing Buoyant Displacement Gas Release Events in Hanford Double-Shell Waste Tanks  

SciTech Connect

This report summarizes the predictive methods used to ensure that waste transfer operations in Hanford waste tanks do not create waste configurations that lead to unsafe gas release events. The gas release behavior of the waste in existing double-shell tanks has been well characterized, and the flammable gas safety issues associated with safe storage of waste in the current configuration are being formally resolved. However, waste is also being transferred between double-shell tanks and from single-shell tanks into double-shell tanks by saltwell pumping and sluicing that create new wastes and waste configurations that have not been studied as well. Additionally, planning is underway for various waste transfer scenarios to support waste feed delivery to the proposed vitrification plant. It is critical that such waste transfers do not create waste conditions with the potential for dangerous gas release events.

Meyer, Perry A.; Stewart, Charles W.

2001-01-01

159

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

160

Model-Based Inquiry: A Buoyant Force Module for High School Physics Classes  

ERIC Educational Resources Information Center

Model-Based Inquiry (MBI) is an emergent instructional strategy that is gaining acceptance among science educators. This approach to learning realistically mirrors the work of scientists, who develop and test hypotheses to construct more sophisticated understandings of the natural world. This article details how the authors collaboratively taught…

Neilson, Drew; Campbell, Todd; Allred, Benjamin

2010-01-01

161

Observations of the frontal region of a buoyant river plume using an autonomous underwater vehicle  

NASA Astrophysics Data System (ADS)

characterize the transitional region from the near-field to far-field of a river plume entering coastal waters, we conducted four surveys using an autonomous underwater vehicle (AUV) to target the outflow of the New River Inlet, North Carolina, during maximum ebb tide. The utilization of a mobile sensor to synoptically observe current velocity data in tandem with natural river plume tracers (e.g., colored dissolved organic matter, salinity) was essential in understanding the mechanisms driving the observed circulation and mixing patterns within these waters. We find that this region is regularly impacted by two primary processes: (1) the interaction of an old dredged channel plume with the main discharge and (2) the recirculation of the discharge plume by an eddy that persistently forms between the old channel and main discharge location. Wind-driven processes in the nearshore can enhance the interaction of these two plumes resulting in unstable regions where mixing of the merged plume with the receiving waters is accelerated. We also conduct comparisons between AUV velocity observations from two surveys and their corresponding velocity outputs from a parallelized quasi-3-D model. We conclude that the ability to observe the estuarine outflow transitional region at near-synoptic temporal scales and resolutions discussed in this paper is key in providing the mechanisms driving local circulation which is essential for proper parameterization of high-resolution numerical coastal models.

Rogowski, Peter; Terrill, Eric; Chen, Jialin

2014-11-01

162

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

NASA Astrophysics Data System (ADS)

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 CO2 is controlled by capillary forces and by the inertial force driving CO2 inside the carbonate aquifer. The entrapped/residual brine will be a site for geochemical reactions which could alter the pore network and/or the permeability of the formation. Therefore, the pore-scale understanding of displacement of resident brine by CO2 is critical to evaluate the storage efficiency of carbonate aquifers and to quantify any dissolution or precipitation of minerals (e.g., gypsum, calcite, dolomite). In this project, we have developed a multiphase flow model, based on the lattice Boltzmann equation, that can describe pore-scale displacement of brine by invading CO2. The multiphase flow model is applied to three different pore networks saturated with brine. The amount of brine trapped after invasion of the domain by CO2 is strongly dependent on the pore network. We also examine the effects of CO2 density and viscosity (which depend on formation temperature and pressure) on the amount of entrapped brine. Only by resolving the flow at the pore scale can we predict the residual brine saturation and other parameters which control CO2 sequestration in deep saline aquifers. Future work will focus on coupling the pore-scale multiphase flow model to a chemistry model to predict mineral dissolution and precipitation.

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

2010-12-01

163

Effect of capillary heterogeneity on buoyant plumes: A new local trapping mechanism  

Microsoft Academic Search

CO2 can be immobilized in an aquifer as a residual phase trapped by capillary forces. The “inject low and let rise” strategy of storing CO2 in d eep saline aquifers is one method to maximize residual trapping. The more uniform the saturation front during upward movement of CO2, the greater the amount of CO2 trapped in this form. Previous studies

Ehsan Saadatpoor; Steven L. Bryant; Kamy Sepehrnoori

2009-01-01

164

The effect of wind mixing on the vertical distribution of buoyant plastic debris  

NASA Astrophysics Data System (ADS)

Micro-plastic marine debris is widely distributed in vast regions of the subtropical gyres and has emerged as a major open ocean pollutant. The fate and transport of plastic marine debris is governed by poorly understood geophysical processes, such as ocean mixing within the surface boundary layer. Based on profile observations and a one-dimensional column model, we demonstrate that plastic debris is vertically distributed within the upper water column due to wind-driven mixing. These results suggest that total oceanic plastics concentrations are significantly underestimated by traditional surface measurements, requiring a reinterpretation of existing plastic marine debris data sets. A geophysical approach must be taken in order to properly quantify and manage this form of marine pollution.

Kukulka, T.; Proskurowski, G.; Morét-Ferguson, S.; Meyer, D. W.; Law, K. L.

2012-04-01

165

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

166

The behaviour of buoyant plumes in neutral and stable conditions in canada  

NASA Astrophysics Data System (ADS)

Plume dispersion parameters obtained during six years of research by the Canadian Combustion Research Laboratory (CCRL) have been evaluated and compared to the standard predictive relationships established by Briggs and Pasquill-Gifford. The data correspond to neutral and stable conditions, stability class C to F but excludes any limited-mixing or layered atmosphere studies or situations where topography influences plume spread. In all, ten sources in five geographic regions were studied during Spring, Fall and Winter. It has been shown that the plume rise data can be represented by the Briggs and Moore form of relationship for neutral conditions. The data suggest a proportionality constant of 0.87 and a levelling-off at 15 stack heights when constrained to the 2/3 power law required by the Briggs continuous model. The unconstrained regression yielded a constant of 0.5 and 0.71 power law relationship with downwind distance, between the Briggs and Moore relationships. However, both of the latter significantly overestimate the measured data. In stable conditions the Briggs levelling-off value of 2.9 for the dimensionless plume rise is in good agreement with the findings in this paper, but this occurs at a dimensionless downwind distance of 18.4 rather than 2.4. A slight variation in the maximum plume rise with the bulk Richardson number over the dispersion zone has been noted for stable conditions. The Pasquill-Gifford plume spread curves as modified by Bowne for rural conditions represent a convenient means of comparing the data obtained under corresponding stability and topographic conditions in Canada. The variation of measured horizontal spread parameters, ?y with downwind distance differed significantly from the P/G curves, being wider by at least two stability classes for unstable/neutral, i.e. A/B rather than C/D, and for stable, C rather than E. In the case of very stable F class, the measured ?y values corresponded to A class, six classes wider than expected. The vertical spread parameters, ?z were usually in agreement with P/G curves from 4 to 10 km from the source, closer to the source ?z was greater and farther from the source ?z was less than predicted. It was also found that the bulk Richardson number could be used to classify the plume spread parameters in a similar manner to the P/G stability classes.

Whaley, H.; Lee, G. K.

167

A Numerical Investigation of Cross Wind Effects on a Turbulent Buoyant Diffusion Flame  

Microsoft Academic Search

The behaviour of a turbulent diffusion flame subjected to cross wind conditions is studied numerically using a finite-volume procedure. A k-?-gRNG turbulence model and a ß-probability density function (pdf) are used for the description of the turbulent nonpremixed combustion process. The gas\\/soot radiation model used in the analysis is based on the PI-differential approximation method and coupled with a two-equation

D. MORVAN; B. PORTERIE; J. C. LORAUD; M. LARINI

2001-01-01

168

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...

169

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

170

Periodic large-amplitude thermal oscillations occurring in a buoyant plume  

SciTech Connect

Reactor events such as N-1 loop operation in conjunction with a leaky check valve in the down loop can cause flow to be convected back into the reactor outlet nozzle/piping region and to be back-flushed into the reactor outlet plenum. The preceding results in a temperature difference between pipe inflow and plenum. This temperature difference causes buoyancy forces which if large enough can cause: a pipe backflow and recirculation loop; and a thermal plume in the plenum. Both phenomena are being studied because they can produce undesirable pipe, nozzle and plenum wall thermal distributions, and hence undesirable thermal stresses. This paper discusses some features of the plume.

Oras, J.J.; Kasza, K.E.

1983-01-01

171

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

172

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

Code of Federal Regulations, 2011 CFR

...MIL-P-40619. (c) The external protective covering must be— (1) Fibrous-glass-reinforced plastic, constructed of a polyester resin listed on the current Qualified Products List for MIL-P-21607, or accepted by the Commandant (G-MSE) as...

2011-10-01

173

Buoyant replenishment in silicic magma reservoirs: Experimental approach and implications for magma  

E-print Network

on replenishment of rhyolite magma chambers by rhyolite magma using corn syrup-water solutions. We emphasize small ascent through the mush. Our results have implications for rhyolites bearing crystals with disequilibrium decades to investigate these processes. This study focuses on rhyolite magma replenishing rhyolite

Long, Bernard

174

NMR imaging and hydrodynamic analysis of neutrally buoyant non-Newtonian slurry flows  

SciTech Connect

The flow of solids loaded suspension in cylindrical pipes has been the object of intense experimental and theoretical investigations in recent years. These types of flows are of great interest in chemical engineering because of their important use in many industrial manufacturing processes. Such flows are for example encountered in the manufacture of solid-rocket propellants, advanced ceramics, reinforced polymer composites, in heterogenous catalytic reactors, and in the pipeline transport of liquid-solids suspensions. In most cases, the suspension microstructure and the degree of solids dispersion greatly affect the final performance of the manufactured product. For example, solid propellant pellets need to be extremely-well dispersed in gel matrices for use as rocket engine solid fuels. The homogeneity of pellet dispersion is critical to allow good uniformity of the burn rate, which in turn affects the final mechanical performance of the engine. Today`s manufacturing of such fuels uses continuous flow processes rather than batch processes. Unfortunately, the hydrodynamics of such flow processes is poorly understood and is difficult to assess because it requires the simultaneous measurements of liquid/solids phase velocities and volume fractions. Due to the recent development in pulsed Fourier Transform NMR imaging, NMR imaging is now becoming a powerful technique for the non intrusive investigation of multi-phase flows. This paper reports and exposes a state-of-the-art experimental and theoretical methodology that can be used to study such flows. The hydrodynamic model developed for this study is a two-phase flow shear thinning model with standard constitutive fluid/solids interphase drag and solids compaction stresses. this model shows good agreement with experimental data and the limitations of this model are discussed.

Bouillard, J.X. [Argonne National Lab., IL (United States); Sinton, S.W. [Lockheed Missiles and Space Co., Palo Alto, CA (United States). Research Lab.

1995-02-01

175

Acoustic scattering from a thermally driven buoyant plume revisited John Oeschger  

E-print Network

. Where these variations are such that weak scattering theory can be applied to describe the behavior and L. Goodman, JASA, Acoustic scattering 1 #12;Far-field weak scattering theory is applied to the case condition; this is the Fourier component of the plume variability that produces scattering. Results

Goodman, Louis

176

A fast 3D particle method for simulations of buoyant and reacting flows  

E-print Network

This thesis describes progress in several areas related to three dimensional vortex methods and their application to multiphysics problems. The first is the solution of a generic scalar transport equation by advecting and ...

Schlegel, Fabrice

2007-01-01

177

Laminar, Turbulent, and Inertial Shear-Thickening Regimes in Channel Flow of Neutrally Buoyant Particle Suspensions  

NASA Astrophysics Data System (ADS)

The aim of this Letter is to characterize the flow regimes of suspensions of finite-size rigid particles in a viscous fluid at finite inertia. We explore the system behavior as a function of the particle volume fraction and the Reynolds number (the ratio of flow and particle inertia to viscous forces). Unlike single-phase flows, where a clear distinction exists between the laminar and the turbulent states, three different regimes can be identified in the presence of a particulate phase, with smooth transitions between them. At low volume fractions, the flow becomes turbulent when increasing the Reynolds number, transitioning from the laminar regime dominated by viscous forces to the turbulent regime characterized by enhanced momentum transport by turbulent eddies. At larger volume fractions, we identify a new regime characterized by an even larger increase of the wall friction. The wall friction increases with the Reynolds number (inertial effects) while the turbulent transport is weakly affected, as in a state of intense inertial shear thickening. This state may prevent the transition to a fully turbulent regime at arbitrary high speed of the flow.

Lashgari, Iman; Picano, Francesco; Breugem, Wim-Paul; Brandt, Luca

2014-12-01

178

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

179

A smoothed particle hydrodynamics study on the electrohydrodynamic deformation of a droplet suspended in a neutrally buoyant Newtonian fluid  

NASA Astrophysics Data System (ADS)

In this paper, we have presented a 2D Lagrangian two-phase numerical model to study the deformation of a droplet suspended in a quiescent fluid subjected to the combined effects of viscous, surface tension and electric field forces. The electrostatics phenomena are coupled to hydrodynamics through the solution of a set of Maxwell equations. The relevant Maxwell equations and associated interface conditions are simplified relying on the assumptions of the so-called leaky dielectric model. All governing equations and the pertinent jump and boundary conditions are discretized in space using the incompressible Smoothed Particle Hydrodynamics method with improved interface and boundary treatments. Upon imposing constant electrical potentials to upper and lower horizontal boundaries, the droplet starts acquiring either prolate or oblate shape, and shows rather different flow patterns within itself and in its vicinity depending on the ratios of the electrical permittivities and conductivities of the constituent phases. The effects of the strength of the applied electric field, permittivity, surface tension, and the initial droplet radius on the droplet deformation parameter have been investigated in detail. Numerical results are validated by two highly credential analytical results which have been frequently cited in the literature. The numerically and analytically calculated droplet deformation parameters show good agreement for small oblate and prolate deformations. However, for some higher values of the droplet deformation parameter, numerical results overestimate the droplet deformation parameter. This situation was also reported in literature and is due to the assumption made in both theories, which is that the droplet deformation is rather small, and hence the droplet remains almost circular. Moreover, the flow circulations and their corresponding velocities in the inner and outer fluids are in agreement with theories.

Shadloo, M. S.; Rahmat, A.; Yildiz, M.

2013-09-01

180

Experimental Study of the Propagation of a Hydraulic Fracture Containing a Constant Volume of Buoyant, Viscous Fluid  

NASA Astrophysics Data System (ADS)

We present the results of laboratory experiments whose ultimate aim is to contribute to understanding the propagation of magma-filled fractures in the Earth's lithosphere. The immediate goal is to verify physical models of simpler systems before building in greater complexity. We study the propagation of isothermal, hydraulic fractures, containing differing but constant volumes of fluid, in elastic, brittle solid. The flows are driven by buoyancy of the fluid with respect to the solid and have low Reynolds Numbers. Fluids are Newtonian and the solid hosting the fractures is gelatin with isotropic homogeneous elastic properties. Elastic modulus and fracture toughness vary between experiments. We present a visualization technique enabling us to measure the opening profile of the fissure and hence deduce the profile of elastic pressure during propagation. We highlight two results: First, propagation speed is not constant, but steadily decreases as the fractures lengthen. Numerical calculations of fracture propagation in two dimensions suggest that length should increase like (time)^{1/3}, whereas experimentally we observe a range of exponents from 0.05 to 0.5. Second, fractures eventually stop at some final length despite the fact that the buoyancy pressure based on total fracture length should (using a 2-dimensional argument) be enough to continue fracturing the solid. Our experimental data on the final lengths and widths of fractures can be correlated by a dimensionless parameter constructed from the fluid buoyancy, the released volume, and on the fracture toughness of the solid. These scaling laws suggest that the arrest of fractures in the Earth's lithosphere on these purely mechanical grounds could be a common occurrence. This result implies that for given rock properties and magma reservoir depth, there should be a minimum volume threshold necessary for eruption to occur.

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

2006-12-01

181

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. PMID:23112396

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

2011-01-01

182

Laminar round jet diffusion flame buoyant instabilities: Study on the disappearance of varicose structures at ultra-low Froude number  

SciTech Connect

At very low Froude number, buoyancy instabilities of round laminar jet diffusion flames disappear (except for small tip oscillations referred to as flickering) and those flames look stable and smooth. This study examines the contributions of the different phenomena in the flow dynamics that may explain this effect. It is observed that, at ultra-low Froude/Reynolds numbers, the material influenced by buoyancy is the plume of the flame and not the flame itself (reaction zone) that is short. Therefore, the vorticity creation zone does not profit from the reaction neighbourhood promoting a sharp gradient of density. Expansion and stretch are also important as they push vorticity creation terms more inside the flame and closer to the burner rim compared to moderate Froude flames. In these latter, the vorticity is continuously created around the flame reaction zone, along its developed height and closer to the vertical direction (in average). (author)

Boulanger, Joan [Gas Turbine Laboratory, Institute for Aerospace Research, Ottawa, Ontario (Canada)

2010-04-15

183

THE DYNAMIC EVOLUTION OF TWISTED MAGNETIC FLUX TUBES IN A THREE-DIMENSIONAL CONVECTING FLOW. I. UNIFORMLY BUOYANT HORIZONTAL TUBES  

E-print Network

between downdrafts as possible progenitors of solar active regions. As the initial field strength, adiabatically stratified model solar convection zone. Tubes with 10 times the equipartition field strength fields 1. INTRODUCTION If the magnetic field seen in sunspots and active regions on the solar surface

Abbett, Bill

184

E. J. Plate et al. (eds.), Buoyant Convection in Geophysical Flows, 265-290. 1998 Kluwer Academic Publishers. Printed in the Netherlands.  

E-print Network

Academic Publishers. Printed in the Netherlands. BULK MODELS OF THE ATMOSPHERIC CONVECTIVE BOUNDARY LAYER E historical stages. Most #12;266 extensively, the CBL was studied with the so-called zero-order jump models, the potential temperature within the CBL is presumed to be height constant. Its changes with height

Fedorovich, Evgeni

185

46 CFR 160.049-1 - Incorporation by reference.  

Code of Federal Regulations, 2010 CFR

...EQUIPMENT Specification for a Buoyant Cushion Plastic Foam § 160.049-1 Incorporation by... 160.055—Life Preservers, Unicellular Plastic Foam, Adult and Child. 164.015—Plastic Foam, Unicellular, Buoyant, Sheet and...

2010-10-01

186

46 CFR 160.052-1 - Incorporation by reference.  

Code of Federal Regulations, 2010 CFR

...Specification for a Buoyant Vest, Unicellular Plastic Foam, Adult and Child § 160.052-1... 160.055—Life Preservers, Unicellular Plastic Foam, Adult and Child. 164.015—Plastic Foam, Unicellular, Buoyant Sheet and...

2010-10-01

187

46 CFR 160.052-1 - Incorporation by reference.  

Code of Federal Regulations, 2011 CFR

...Specification for a Buoyant Vest, Unicellular Plastic Foam, Adult and Child § 160.052-1... 160.055—Life Preservers, Unicellular Plastic Foam, Adult and Child. 164.015—Plastic Foam, Unicellular, Buoyant Sheet and...

2011-10-01

188

46 CFR 160.049-1 - Incorporation by reference.  

Code of Federal Regulations, 2011 CFR

...EQUIPMENT Specification for a Buoyant Cushion Plastic Foam § 160.049-1 Incorporation by... 160.055—Life Preservers, Unicellular Plastic Foam, Adult and Child. 164.015—Plastic Foam, Unicellular, Buoyant, Sheet and...

2011-10-01

189

33 CFR 175.23 - Serviceable condition.  

Code of Federal Regulations, 2011 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...

2011-07-01

190

33 CFR 175.23 - Serviceable condition.  

Code of Federal Regulations, 2014 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...

2014-07-01

191

46 CFR 180.15 - Applicability to existing vessels.  

Code of Federal Regulations, 2010 CFR

...liferaft, inflatable buoyant apparatus, life float, and buoyant apparatus on the...of the cognizant Officer in Charge, Marine Inspection, (OCMI) on or after March...Until February 1, 1999, a Federal Communications Commission (FCC) Type Accepted...

2010-10-01

192

46 CFR 117.15 - Applicability to existing vessels.  

Code of Federal Regulations, 2010 CFR

...liferaft, inflatable buoyant apparatus, life float, and buoyant apparatus on the...of the cognizant Officer in Charge, Marine Inspection, (OCMI) on or after March...Until February 1, 1999, a Federal Communications Commission (FCC) Type Accepted...

2010-10-01

193

46 CFR 180.15 - Applicability to existing vessels.  

Code of Federal Regulations, 2011 CFR

...liferaft, inflatable buoyant apparatus, life float, and buoyant apparatus on the...of the cognizant Officer in Charge, Marine Inspection, (OCMI) on or after...Until February 1, 1999, a Federal Communications Commission (FCC) Type Accepted...

2011-10-01

194

46 CFR 117.15 - Applicability to existing vessels.  

Code of Federal Regulations, 2011 CFR

...liferaft, inflatable buoyant apparatus, life float, and buoyant apparatus on the...of the cognizant Officer in Charge, Marine Inspection, (OCMI) on or after March...Until February 1, 1999, a Federal Communications Commission (FCC) Type Accepted...

2011-10-01

195

46 CFR 160.010-2 - Definitions.  

Code of Federal Regulations, 2014 CFR

...Inflatable buoyant apparatus. An inflatable buoyant apparatus is flotation equipment that depends on inflated compartments for buoyancy and is designed to support a specified number of persons completely out of the water. [CGD 79-167, 47 FR 41372,...

2014-10-01

196

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...

197

An acceleration mechanism for loop transients in the outer corona  

Microsoft Academic Search

The heliocentrifugal motion of coronal loop transients is likely driven largely by the buoyant force exerted by the ambient medium. In the outer corona where the solar wind is well formed, the buoyant force results mainly from the rapid outward decrease in the ambient pressure of the solar wind. The contribution from magnetic buoyancy is not so significant as in

Tyan Yeh; Murray Dryer

1981-01-01

198

Double Diffusive Plumes  

Microsoft Academic Search

Sour gas flares attempt to dispose of deadly H2S gas through combustion. What does not burn rises as a buoyant plume. But the gas is heavier than air at room temperature, so as the rising gas cools eventually it becomes negatively buoyant and descends back to the ground. Ultimately, our intent is to predict the concentrations of the gas at

Bruce Sutherland; Brace Lee

2008-01-01

199

SURFACE TENSION In the fall a fisherman's boat is often surrounded by fallen leaves that are lying on the  

E-print Network

and the resulting buoyant force balances its weight, as Section 11.6 discusses. The leaves, however, float leaves that are lying on the water. The boat floats, because it is partially immersed in the water for a different reason. They are not immersed in the water, so the weight of a leaf is not balanced by a buoyant

California at Santa Cruz, University of

200

Growth of the hemispheric dichotomy and the cessation of plate tectonics on Mars  

Microsoft Academic Search

Although Mars is currently not tectonically active, it may have experienced plate tectonics early in its history. The southern hemisphere of Mars possesses a thick crust which probably renders the lithosphere positively buoyant. In this paper we present numerical and scaling arguments which show that if the area of positively buoyant lithosphere grows beyond a critical fraction (?50% for Mars),

A. Lenardic; F. Nimmo; L. Moresi

2004-01-01

201

Shear and Convective Turbulence in a Model of Thermohaline Intrusions  

Microsoft Academic Search

Thermohaline interleaving is an important mechanism for laterally fluxing salt, heat, and nutrients be- tween water masses. Interleaving is driven by a release of potential energy resulting from the differing diffusivities of heat and salt in seawater. The flows are composed of stacked intrusions that flux more buoyant and less buoyant water in opposite directions. In this paper, we investigate

Rachael D. Mueller; William D. Smyth; Barry Ruddick

2007-01-01

202

46 CFR 160.052-5 - Construction-standard vests.  

Code of Federal Regulations, 2014 CFR

...in which are enclosed inserts of buoyant material arranged and distributed so as to provide the flotation characteristics and buoyancy required to hold the wearer in an upright or slightly backward position with head and face out of water. The buoyant...

2014-10-01

203

46 CFR 160.064-3 - Requirements. 1  

Code of Federal Regulations, 2014 CFR

...device to a boat. The arrangement of the buoyancy of devices intended to be worn...resistant or treated for mildew resistance. Buoyancy shall be provided by inherently buoyant...inflation. So long as the minimum required buoyancy is provided by inherently buoyant...

2014-10-01

204

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

205

Intracellular Water Exchange for Measuring the Dry Mass, Water Mass and Changes in Chemical Composition of Living Cells  

E-print Network

We present a method for direct non-optical quantification of dry mass, dry density and water mass of single living cells in suspension. Dry mass and dry density are obtained simultaneously by measuring a cell’s buoyant ...

Cermak, Nathan

206

Experimentally Determining the Molar Mass of Carbon Dioxide Using a Mylar Balloon.  

ERIC Educational Resources Information Center

Describes how to determine the mass of a gas in a flexible, lightweight container and argues that the buoyant force of air needs to be taken into account. Recommends the use of mylar and describes equipment preparation. (DDR)

Jackson, Barbara Albers; Crouse, David J.

1998-01-01

207

77 FR 19937 - Inflatable Personal Flotation Devices  

Federal Register 2010, 2011, 2012, 2013, 2014

...Standard for Safety for Marine Buoyant Devices''; UL 1180, ``UL Standard for Safety...Inflatable Recreational Personal Flotation Devices''; and UL 1191, ``UL Standard for Safety for Components for Personal Flotation Devices.'' The section that...

2012-04-03

208

A Tale of Two Spills: Novel Science and Policy Implications of an Emerging New Oil Spill Model  

E-print Network

The 2010 Deepwater Horizon oil release posed the challenges of two types of spill: a familiar spill characterized by buoyant oil, fouling and killing organisms at the sea surface and eventually grounding on and damaging ...

Adams, E. Eric

209

Sedimentation Of Oil-MIneral Aggregates For Remediation Of Vegetable Oil Spills  

EPA Science Inventory

A response alternative for floating vegetable oil spills based on sedimentation of negatively buoyant oil-mineral aggregrates followed by anaerobic biodegradation in the sediments is under investigation. Sedimentation of floating canola oil by interaction with montmorillonite wa...

210

46 CFR 164.015-3 - Material and workmanship.  

Code of Federal Regulations, 2011 CFR

...SPECIFICATIONS AND APPROVAL MATERIALS Plastic Foam, Unicellular, Buoyant, Sheet and...workmanship. (a) The unicellular plastic foam shall be all new material complying...015-4(a). (b) The unicellular plastic foam shall be produced in sheet stock...

2011-10-01

211

46 CFR 160.052-3 - Materials-standard vests.  

Code of Federal Regulations, 2010 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...

2010-10-01

212

46 CFR 160.049-3 - Materials.  

Code of Federal Regulations, 2011 CFR

...EQUIPMENT Specification for a Buoyant Cushion Plastic Foam § 160.049-3 Materials. (a) General...requirements of subpart 164.019. (b) Unicellular plastic foam. The unicellular plastic foam shall be all new material complying...

2011-10-01

213

46 CFR 160.052-3 - Materials-standard vests.  

Code of Federal Regulations, 2011 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...

2011-10-01

214

46 CFR 164.015-3 - Material and workmanship.  

Code of Federal Regulations, 2010 CFR

...SPECIFICATIONS AND APPROVAL MATERIALS Plastic Foam, Unicellular, Buoyant, Sheet and...workmanship. (a) The unicellular plastic foam shall be all new material complying...015-4(a). (b) The unicellular plastic foam shall be produced in sheet stock...

2010-10-01

215

FLOCCULATION-FLOTATION AIDS FOR TREATMENT OF COMBINED SEWER OVERFLOWS  

EPA Science Inventory

The objectives of this study were to investigate the flocculation/flotation characteristics of combined sewer overflow through laboratory and field testing. The concept involves the introduction of chemicals and buoyant flotation aids into the overflow and the subsequent cofloccu...

216

Bell Pirie Power Corp. (PHL) Energy Island Bell Pirie Ltd. (UK)  

E-print Network

for OTEC Abundant practical resource Buoyant debt and equity market Large market opportunity ­ > GWs OTEC and reasonable tariff per kWh. >>> #12;blue jagged line is daily forecasts black smooth line is monthly averages

217

Experimental study of gravitation effects in the flow of a particle-laden thin film on an inclined plane  

E-print Network

The flow of viscous, particle-laden wetting thin films on an inclined plane is studied experimentally as the particle concentration is increased to the maximum packing limit. The slurry is a non-neutrally buoyant mixture ...

Ward, Thomas

218

46 CFR 160.055-1 - Incorporation by reference.  

Code of Federal Regulations, 2012 CFR

...Model 62, Adult. Sheet 2—Construction and Arrangement, Vinyl Dip Coated, Model 66, Child. Dwg. No. 160.055-IB: Sheet 1—Construction and Arrangement, Cloth Covered, Model 63, Adult. Sheet 2—Buoyant Inserts, Model 63....

2012-10-01

219

46 CFR 160.055-1 - Incorporation by reference.  

Code of Federal Regulations, 2013 CFR

...Model 62, Adult. Sheet 2—Construction and Arrangement, Vinyl Dip Coated, Model 66, Child. Dwg. No. 160.055-IB: Sheet 1—Construction and Arrangement, Cloth Covered, Model 63, Adult. Sheet 2—Buoyant Inserts, Model 63....

2013-10-01

220

46 CFR 160.048-3 - Materials.  

Code of Federal Regulations, 2010 CFR

...for a Buoyant Cushion, Fibrous Glass § 160.048-3 Materials...properly processed. (c) Fibrous glass. The fibrous glass shall comply with the requirements...The welting where used may be any fiber or plastic material suitable...

2010-10-01

221

46 CFR 160.171-1 - Scope.  

Code of Federal Regulations, 2010 CFR

...adult and 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...

2010-10-01

222

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 ...

223

Zoology 112 (2009) 393402 Whole-body lift and ground effect during pectoral fin locomotion in the  

E-print Network

the mechanism of lift generation for near- bottom swimming. A vortex in the wake of the pectoral fins slightly negatively buoyant, but there are both extant and extinct lineages that are heavily armored

Summers, Adam P.

224

Amosphdc Ensirmment Vol. 15, No. IO/l 1, pp. 207%209O, 1981 OoOM981i81/102079-12 SO2.W~O  

E-print Network

-burning wood fires larger than 5 ha were similar in convection column volume after the initial buoyant, ring-vortex reduction and radiation extinction occurred during the first 210s of the fires. 1. INTRODUCi'ION The multi

Clements, Craig

225

46 CFR 160.055-7 - Sampling, tests, and inspections.  

Code of Federal Regulations, 2014 CFR

...with this section and § 160.001-5. (b) Buoyancy test. The buoyancy of the pad inserts from the life preserver shall...submersion must be at least 48 hours. (c) Buoyancy required. The buoyant pad inserts from...

2014-10-01

226

46 CFR 160.053-4 - Inspections and tests.  

Code of Federal Regulations, 2014 CFR

...have on hand the necessary apparatus for conducting buoyancy tests in compliance with this specification...undergoing tests or change in water level. (e) Buoyancy —(1) Buoyancy test method. Remove the buoyant inserts...

2014-10-01

227

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

Code of Federal Regulations, 2014 CFR

...with this section and § 160.001-5. (b) Buoyancy test. The buoyancy of the pad inserts from the life preserver shall...submersion must be at least 48 hours. (c) Buoyancy required. The buoyant pad inserts from...

2014-10-01

228

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

Code of Federal Regulations, 2014 CFR

...with this section and § 160.001-5. (b) Buoyancy test. The buoyancy of the pad inserts from the life preserver shall...submersion must be at least 48 hours. (c) Buoyancy required. The buoyant pad inserts from...

2014-10-01

229

46 CFR 160.056-2 - Construction.  

Code of Federal Regulations, 2014 CFR

...The rescue boat shall be fitted with three thwarts. The middle thwart shall be arranged as the rowing seat. (e) Internal buoyancy. Buoyant material of suitable unicellular plastic foam shall be installed in the rescue boat. This material...

2014-10-01

230

Cell-wall morphology correlated with vertical migration in the non-motile marine dinoflagellate Pyrocystis noctiluca  

Microsoft Academic Search

We report an ultrastructural study of the morphological changes in cells of the marine dinoflagellate Pyrocystis noctiluca Murray, which correlate with its vertical migration pattern. Cells alternate between a large, highly vacuolated, positively\\u000a buoyant, vegetative cyst surrounded by a dinosporin-containing wall and a smaller, more compact, negatively buoyant, cellulose-bounded\\u000a cell. The cyst wall is composed of two layers: a thin

K. S. Seo; L. Fritz

2000-01-01

231

Measurements and implications of vortex motions using two flow-visualization techniques  

NASA Technical Reports Server (NTRS)

The present comparative study of two different, but complementary flow-visualization techniques, which yield different interpretations of vortex-migration distance and lifetime, gives attention to the difficulty of determining vortex evolution and lifetime from flow-visualization measurements. The techniques involved the release of a fluorescent dye and of neutrally buoyant particles in a water-filled towing tank. Vortices are found to migrate farther, and last longer, when visualized with neutrally buoyant particles rather than with dyes.

Delisi, Donald P.; Greene, George C.

1990-01-01

232

Buoyancy Bulls-Eye  

NSDL National Science Digital Library

In this hands-on activity, learners will construct a scuba diver that can float in order to explore how sea creatures stay neutrally buoyant in the ocean and to see what kinds of forces might be influencing their buoyancy. By adding materials such as balloons, rubber bands, toothpicks, pennies, etc. to their figure, they will try to make it neutrally buoyant in a bucket of water. This lesson plan includes discussion questions, key vocabulary, and is standards-based.

California Academy of Sciences

2008-01-01

233

Coupled convective instabilities at crystal-melt interfaces  

Microsoft Academic Search

The stability of the parallel flow between a vertical crystal-melt interface and a vertical wall held at a temperature above the melting point of the crystal is analyzed for Prandtl numbers, P, ranging from 0.01 to 100. Three modes of instability occur: (1) a buoyant mode, (2) a shear mode, and (3) a coupled crystal-melt mode. The buoyant and shear

S. R. Coriell; G. B. McFadden; R. F. Boisvert; M. E. Glicksman; Q. T. Fang

1984-01-01

234

Particle geochemistry in the Rainbow hydrothermal plume, Mid-Atlantic Ridge  

NASA Astrophysics Data System (ADS)

We report the analysis of 18 large volume (500-1500 L) in situ filtered samples of particulate material from the largest hydrothermal plume on the Mid-Atlantic Ridge, overlying the ultramafic-hosted Rainbow hydrothermal field at 36° 14'N. Measured particulate iron concentrations reach 614 nM. High concentrations of particulate Fe oxyhydroxides result from the extremely high Fe concentration (˜24 mM) and Fe/H 2S ratio (˜24) of the vent fluids, and persist to at least 10 km away from the vent site due to the advection of plume material with the ambient along-axis flow. Two of the nine pairs of pump deployments appear to have intercepted the buoyant or otherwise very young portion of the hydrothermal plume. These samples are characterized by anomalously (compared to neutrally buoyant plume samples) high concentrations of Mg, U, and chalcophile elements, and low concentrations of Mn, Ca, V, Y, and the rare earth elements (REE). Within the neutrally buoyant plume, elemental distributions are largely consistent with previously observed behaviors: preferential removal of chalcophile elements, conservative behavior of oxyanions (P, V, and U), and continuous scavenging of Y and the REE. This consistency is particularly significant in light of the underlying differences in fluid chemistry between Rainbow and other studied sites. Chalcophile elements are preferentially removed from the plume in the order Cd>Zn>Co>Cu. Phosphorus/iron and vanadium/iron ratios for the neutrally buoyant plume are consistent with global trends with respect to the concentration of dissolved phosphate in ambient seawater. Comparison of buoyant and neutrally buoyant plume ratios with data from hydrothermal sediments underlying the Rainbow plume (Cave et al., 2002) indicates, however, that while P/Fe ratios are indeed constant V/Fe ratios increase progressively from early stage plume particles to sediments. REE distributions in the buoyant and neutrally buoyant plume appear most consistent with a continuous scavenging process during dispersion through the water column.

Edmonds, Henrietta N.; German, Christopher R.

2004-02-01

235

Feasibility study of modern airships, phase 2. Volume 1: Heavy lift airship vehicle. Book 1: Overall study results  

NASA Technical Reports Server (NTRS)

A Heavy Lift Airship combining buoyant lift derived from a conventional helium-filled non-rigid airship hull with propulsive lift derived from conventional helicopter rotors was investigated. The buoyant lift essentially offsets the empty weight of the vehicle; thus the rotor thrust is available for useful load and to maneuver and control the vehicle. Such a vehicle is capable of providing a quantum increase in current vertical lifting capability. Certain critical deficiencies of past airships are significantly minimized or eliminated.

1976-01-01

236

Scavenging rates of dissolved manganese in a hydrothermal vent plume  

NASA Astrophysics Data System (ADS)

The biogeochemical scavenging of dissolved manganese (Mn) from hydrothermal plumes was investigated using radiotracer ( 54Mn) techniques. The measured scavenging rate constant, k 1, was lowest in the buoyant plume (<0.2 y -1), increasing to ˜2 y -1 in the non-buoyant plume at distances of 20 km from the ridge valley axis. The direct biological contribution to the dissolved Mn scavenging rate (i.e the fraction suppressed by the addition of a metabolic poison) also increased over the same distances, being minor or absent at plume depths in the proximal plume, yet the major component at distal plume stations. These and other data suggest that the capacity for scavenging dissolved Mn onto particles evolves with increasing age of the plume, suggestive of a microbial response to changing conditions within the plume. Estimated maximum scavenging rates of dissolved Mn onto particles ( RDMn = k 1 [DMn])were noted at plume depths for all stations, a function of very high dissolved Mn concentrations in the case of the buoyant plume and proximal non-buoyant plume. RDMn values, integrated over plume depths, ranged from 3.4 to 1.7 mM m -2 y -1 for the non-buoyant plume at on-axis and off-axis stations, respectively. The application of the data to the dispersal of hydrothermal constituents and to plume aging is discussed.

Cowen, James P.; Massoth, Gary J.; Feely, Richard A.

1990-10-01

237

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

238

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

239

Mass and Density Measurements of Live and Dead Gram-Negative and Gram-Positive Bacterial Populations  

PubMed Central

Monitoring cell growth and measuring physical features of food-borne pathogenic bacteria are important for better understanding the conditions under which these organisms survive and proliferate. To address this challenge, buoyant masses of live and dead Escherichia coli O157:H7 and Listeria innocua were measured using Archimedes, a commercially available suspended microchannel resonator (SMR). Cell growth was monitored with Archimedes by observing increased cell concentration and buoyant mass values of live growing bacteria. These growth data were compared to optical density measurements obtained with a Bioscreen system. We observed buoyant mass measurements with Archimedes at cell concentrations between 105 and 108 cells/ml, while growth was not observed with optical density measurements until the concentration was 107 cells/ml. Buoyant mass measurements of live and dead cells with and without exposure to hydrogen peroxide stress were also compared; live cells generally had a larger buoyant mass than dead cells. Additionally, buoyant mass measurements were used to determine cell density and total mass for both live and dead cells. Dead E. coli cells were found to have a larger density and smaller total mass than live E. coli cells. In contrast, density was the same for both live and dead L. innocua cells, while the total mass was greater for live than for dead cells. These results contribute to the ongoing challenge to further develop existing technologies used to observe cell populations at low concentrations and to measure unique physical features of cells that may be useful for developing future diagnostics. PMID:24705320

Craig, Caelli C.; Senecal, Andre G.

2014-01-01

240

Mass and density measurements of live and dead Gram-negative and Gram-positive bacterial populations.  

PubMed

Monitoring cell growth and measuring physical features of food-borne pathogenic bacteria are important for better understanding the conditions under which these organisms survive and proliferate. To address this challenge, buoyant masses of live and dead Escherichia coli O157:H7 and Listeria innocua were measured using Archimedes, a commercially available suspended microchannel resonator (SMR). Cell growth was monitored with Archimedes by observing increased cell concentration and buoyant mass values of live growing bacteria. These growth data were compared to optical density measurements obtained with a Bioscreen system. We observed buoyant mass measurements with Archimedes at cell concentrations between 10(5) and 10(8) cells/ml, while growth was not observed with optical density measurements until the concentration was 10(7) cells/ml. Buoyant mass measurements of live and dead cells with and without exposure to hydrogen peroxide stress were also compared; live cells generally had a larger buoyant mass than dead cells. Additionally, buoyant mass measurements were used to determine cell density and total mass for both live and dead cells. Dead E. coli cells were found to have a larger density and smaller total mass than live E. coli cells. In contrast, density was the same for both live and dead L. innocua cells, while the total mass was greater for live than for dead cells. These results contribute to the ongoing challenge to further develop existing technologies used to observe cell populations at low concentrations and to measure unique physical features of cells that may be useful for developing future diagnostics. PMID:24705320

Lewis, Christina L; Craig, Caelli C; Senecal, Andre G

2014-06-01

241

LTA structures and materials technology  

NASA Technical Reports Server (NTRS)

The state-of-the-art concerning structures and materials technology is reviewed. It is shown that many present materials developments resulting from balloon and aircraft research programs can be applied to new concepts in LTA vehicles. Both buoyant and semi-buoyant vehicles utilize similar approaches to solving structural problems and could involve pressurized non-rigid and unpressurized rigid structures. System designs common to both and vital to structural integrity include much of the past technology as well. Further research is needed in determination of structural loads, especially in future design concepts.

Mayer, N. J.

1975-01-01

242

Falling bodies through sharply stratified fluids: theory and experiments  

NASA Astrophysics Data System (ADS)

The motion of bodies and fluids moving through a stratified background fluid arises naturally in the context of carbon (marine snow) settling in the ocean, as well as less naturally in the context of the DWH Gulf oil spill. The details of the settling rates may affect the ocean contribution to the earth's carbon cycle. We look at phenomena associated with many falling spheres in stratified fluids, as well as behavior of multiphase buoyant plumes penetrating strong stratification. We present careful measurements critical heights for fully miscible jets and companion analytical prediction. In turn, we examine cases involving clouds of sinking particulate and rising buoyant oil emulsions and associated plume trapping behaviors.

McLaughlin, Richard; Camassa, Roberto; Falcon, Claudia; Harenberg, Steve; Mertens, Keith; Reis, Johnny; Schlieper, William; Watson, Bailey; White, Brian

2011-11-01

243

Diapiric Flow at Subduction Zones: A Recipe for Rapid Transport  

NASA Astrophysics Data System (ADS)

Recent geochemical studies of uranium-thorium series disequilibrium in rocks from subduction zones require magmas to be transported through the mantle from just above the subducting slab to the surface in as little as ~30,000 years. We present a series of laboratory experiments that investigate the characteristic time scales and flow patterns of the diapiric upwelling model of subduction zone magmatism. Results indicate that the interaction between buoyantly upwelling diapirs and subduction-induced flow in the mantle creates a network of low-density, low-viscosity conduits through which buoyant flow is rapid, yielding transport times commensurate with those indicated by uranium-thorium studies.

Hall, Paul S.; Kincaid, Chris

2001-06-01

244

Cartesian Divers  

NSDL National Science Digital Library

This activity gives students a hands-on look at the effects of increased water pressure and shows them how submarines work. Using a balloon and plastic water bottle, students create a neutrally buoyant diver. Then they squeeze the bottle to see how increased pressure compresses the balloon, making it heavier and causing it to sink. The activity includes an extension that has students further explore how animals use their swim bladders to dive and rise. Students can find out with a balloon and a bottle of water how a submarine, which is buoyant to start with, becomes heavier and dives down into the water.

245

Repeat Hydrography at the Endeavour Integrated Study Site, 2004 - 2006  

Microsoft Academic Search

Significant differences exist between hydrographic transects made in the summers from 2004 to 2006 at the Endeavour Segment Integrated Study Site on the Juan de Fuca Ridge. Along and across axis sections describe the hydrographic conditions above the segment in three dimensions. The resulting sections allow for rapid evaluation of the characteristics of the neutrally buoyant plume over each of

J. P. Kellogg; R. E. McDuff; R. E. Thomson; F. R. Stahr

2006-01-01

246

Heat Flux From the Endeavour Segment of the Juan de Fuca Ridge  

Microsoft Academic Search

The very essence of a hydrothermal system is transfer of heat by a convecting fluid, yet the flux of heat remains a poorly known quantity. Past studies of heat flux consisted primarily of point measurements of temperature and fluid flow at individual vent sites and inventories of the neutrally buoyant plume above the field. In 2000 the Flow Mow project

W. J. Thompson; R. E. McDuff; F. R. Stahr; D. R. Yoerger; M. Jakuba

2005-01-01

247

Airborne Doppler radar observations of convective plumes and radar `fine-lines' ERAD02-A-00007  

E-print Network

data suggest that these plumes are buoyant and that they contain more water vapor. The detectability measured directly. Ground-based radar and lidar systems have been used to profile the BL Cloud Radar (WCR, http://www.atmos.uwyo.edu/wcr/projects/ihop02/) taken during the International Water

Geerts, Bart

248

Private Security Contractors in the Debate about Darfur: Reflecting and Reinforcing Neo-Liberal Governmentality  

Microsoft Academic Search

This article explores the loud presence of private security contractors in the evolving and buoyant discussion surrounding Darfur. Relying primarily on statements by security contractors and industry lobby organizations, this article suggests that neo-liberal governmentality has bolstered the expert status of security contractors in the discussions surrounding Darfur. Both in Darfur and more widely, neo-liberal governmentality tends to `depoliticize' security

Anna Leander; Rens van Munster

2007-01-01

249

Electrohydrodynamic flow and chaotic mixing inside drops  

Microsoft Academic Search

Electrohyodynamics, proposed by G. I. Taylor (1966), is the study of fluid motion under the influence of electric fields. In this work, we investigate theoretically and experimentally the electrohydrodynamic flow field inside a dielectric liquid drop and its application in driving chaotic mixing. Previous works on the electrohydrodynamic flows are mainly restricted to neutrally buoyant drops. Since settling drops are

Xiumei Xu

2007-01-01

250

Limitations and Functions: Four Examples of Integrating Thermodynamics  

ERIC Educational Resources Information Center

Physics students are usually unaware of the limitations and functions of related principles, and they tend to adopt "hot formulas" inappropriately. This paper introduces four real-life examples for bridging five principles, from fluids to thermodynamics, including (1) buoyant force, (2) thermal expansion, (3) the ideal-gas law, (4) the 1st law,…

Chang, Wheijen

2011-01-01

251

Subduction and slab breakoff controls on Asian indentation tectonics and Himalayan western  

E-print Network

, CNRS, Grenoble, France [1] We test the link between large-scale Asian continent deformations and Indian of the subducting-upper plates system. We find that the subduction of the buoyant continent results in the reduction episodes. Continent subduction and breakoff during India-Asia convergence offer an explanation

252

Magnetic-field effect on thermal convection of a nematic liquid crystal at large Rayleigh  

E-print Network

Magnetic-field effect on thermal convection of a nematic liquid crystal at large Rayleigh numbers-turbulent thermal convection of a nematic liquid crystal heated from below in a cylindrical cell with an aspect conductivity in the thermal boundary layers due to a field-induced director alignment. Key words: buoyant

Ahlers, Guenter

253

Ocean urea fertilization for carbon credits poses high ecological risks  

Microsoft Academic Search

The proposed plan for enrichment of the Sulu Sea, Philippines, a region of rich marine biodiversity, with thousands of tonnes of urea in order to stimulate algal blooms and sequester carbon is flawed for multiple reasons. Urea is preferentially used as a nitrogen source by some cyanobacteria and dinoflagellates, many of which are neutrally or positively buoyant. Biological pumps to

Patricia M. Glibert; Rhodora Azanza; Michele Burford; Ken Furuya; Eva Abal; Adnan Al-Azri; Faiza Al-Yamani; Per Andersen; Donald M. Anderson; John Beardall; G. Mine Berg; Larry Brand; Deborah Bronk; Justin Brookes; JoAnn M. Burkholder; Allan Cembella; William P. Cochlan; Jackie L. Collier; Yves Collos; Robert Diaz; Martina Doblin; Thomas Drennen; Sonya Dyhrman; Yasuwo Fukuyo; Miles Furnas; James Galloway; Edna Granéli; Dao Viet Ha; Gustaaf Hallegraeff; John Harrison; Paul J. Harrison; Cynthia A. Heil; Kirsten Heimann; Robert Howarth; Cécile Jauzein; Austin A. Kana; Todd M. Kana; Hakgyoon Kim; Raphael Kudela; Catherine Legrand; Michael Mallin; Margaret Mulholland; Shauna Murray; Judith O’Neil; Grant Pitcher; Yuzao Qi; Nancy Rabalais; Robin Raine; Sybil Seitzinger; Paulo S. Salomon; Caroline Solomon; Diane K. Stoecker; Gires Usup; Joanne Wilson; Kedong Yin; Mingjiang Zhou; Mingyuan Zhu

2008-01-01

254

nonindigenous freshwater bryozoans  

Microsoft Academic Search

Aim The transport of organisms in ships' ballast tanks is a dominant vector for aquatic invasions worldwide. Until recently, efforts to manage this vector have overlooked the potential transport of invertebrate resting stages in the residual waters and sediments within emptied ballast tanks, i.e. NOBOB ('No Ballast On Board') tanks. The resting stages (statoblasts) of freshwater bryozoans are often buoyant

R. Kipp; S. A. Bailey; H. J. MacIsaac; A. Ricciardi

2010-01-01

255

Mortgage Equity Withdrawal in Australia and Britain: Towards a Wealth-fare State?  

Microsoft Academic Search

Across the decade to 2007, a combination of house price appreciation and relaxed credit constraints gave a boost to consumption through the mechanism of mortgage equity withdrawal (MEW). Arguably, this kept developed economies buoyant, even through periods of recession. This paper uses panel data on British and Australian homeowners to show that, notwithstanding its macro-economic effects, such borrowing has far-reaching

Sharon Parkinson; Beverley A. Searle; Susan J. Smith; Alice Stoakes; Gavin Wood

2009-01-01

256

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

257

Upper mantle structure beneath the Caribbean-South American plate boundary from surface wave tomography  

E-print Network

-slip fault system along the northern coast of Venezuela, illustrating the differences between the South beneath the South American plate. In eastern Venezuela, linear crustal low velocities are associated the buoyant continental South American plate offshore of northeastern Venezuela. The continental lithosphere

Niu, Fenglin

258

Dynamics of sediment subduction, melange formation, and prism accretion  

Microsoft Academic Search

The descending plate and overriding block in a subduction zone are analogous to the guide surface and slide block in a slipper bearing, and subducted sediment is analogous to the lubricant. Subduction is more complex and varied, however, because the overriding block is not rigid, the sediment is buoyant, underplating can occur, and sediment supply can vary widely. A model

Ronald L. Shreve; Mark Cloos

1986-01-01

259

European Journal of Mechanics B/Fluids 28 (2009) 405410 Contents lists available at ScienceDirect  

E-print Network

European Journal of Mechanics B/Fluids 28 (2009) 405­410 Contents lists available at ScienceDirect European Journal of Mechanics B/Fluids www.elsevier.com/locate/ejmflu Steady shape of a miscible bubble Keywords: Bubble Sloping boundary Low Re Gravity currents When a buoyant volume of fluid impinges

Manga, Michael

260

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

261

Applied Ocean Research 15 (1993) 137-154 Gust loading factors for tension leg platforms  

E-print Network

-scale offshore measurements. A modified coherence function for offshore applications is presented based. The response statistics of an offshore platform are predicted in the light of para.metric uncertainties efficient. The tension leg platform (TLP) is a promising concept for deep water drilling. A TLP is a buoyant

Kareem, Ahsan

262

J. Fluid Mech. (2007), vol. 587, pp. 337346. c 2007 Cambridge University Press doi:10.1017/S0022112007007537 Printed in the United Kingdom  

E-print Network

and the sphere gradually slows. A movie is available with the online version of the paper. 1. Introduction Vortex buoyant sphere was free to move in response to the impulse delivered by the vortex ring during ring with a sphere that is free to respond to the vortex ring impulse. This experiment represents

Shashikanth, Banavara N.

263

Vortex interaction with a moving sphere  

Microsoft Academic Search

This paper details the experimental results of the axisymmetric collision of a vortex ring with a sphere. The experiments were conducted in water and a neutrally buoyant sphere was free to move in response to the impulse delivered by the vortex ring during the interaction. Good agreement has been achieved between kinematic data for the sphere speed and acceleration and

J. J. A LLEN; Y. J OUANNE; B. N. S HASHIKANTH

2007-01-01

264

SCOOP--An Improved Submarine Cable Recovery System  

Microsoft Academic Search

For more than twenty years, acoustically controlled, buoyant subsurface arrays have been utilized by research institutions and industry for mooring, location, and retrieval of oceanographic instruments. Submarine telecommunications cable laying and repair operations typically involve location and retrieval of free cable ends left on the seafloor. In deep water areas, conventional methods for cable-end location and recovery included the use

G. Rich; J. Ewald; C. Jeffcoat; R. Weller

1984-01-01

265

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

266

Fireball Ejection from a Molten Hot Spot to Air by Localized Microwaves Vladimir Dikhtyar and Eli Jerby*  

E-print Network

Fireball Ejection from a Molten Hot Spot to Air by Localized Microwaves Vladimir Dikhtyar and Eli; published 30 January 2006) A phenomenon of fireball ejection from hot spots in solid materials (silicon drop evolved from the hot spot is blown up, and forms a stable fireball buoyant in the air

Jerby, Eli

267

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

268

Interleaving intrusions produced by internal waves: a laboratory experiment  

Microsoft Academic Search

A statically stable stratified water column that also contains horizontal property contrasts (either of passive tracer alone or of two dynamically active solutes) is generated and continuously maintained for a long period by releasing two turbulent buoyant plumes of equal buoyancy fluxes into opposite ends of a long channel of water. The bottom outflows from the plumes also continuously excite

Ross W. Griffiths; Ali A. Bidokhti

2008-01-01

269

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

270

JET-SUSPENDED, CALCITE-BALLASTED CYANOBACTERIAL.WATERWARTS IN A tment of Arizona State ,Tempe, USA  

E-print Network

(2002) JET-SUSPENDED, CALCITE-BALLASTED CYANOBACTERIAL.WATERWARTS IN A DESERT Bman D. tment contained orderly arrangements of mineral made up of microcrystallinelow-magnesiumcalcitewith high levels of strontium and sulfur. were 95.9% glycan, 2.8% cells, and 1.3% mineral grains and had a buoyant density of 1

Farmer, Jack D.

271

A simplified model for understanding natural convection driven biomass cooking stoves—Part 1: Setup and baseline validation  

Microsoft Academic Search

It is estimated that half the world's population cooks over an open biomass fire; improved biomass cooking stove programs have the potential to impact indoor air quality, deforestation, climate change, and quality of life on a global scale. The majority of these cooking stoves operate in a natural convection mode (being driven by chimney effect buoyant fluid forces). Simplified theories

Joshua Agenbroad; Morgan DeFoort; Allan Kirkpatrick; Cory Kreutzer

2011-01-01

272

CHARACTERIZATION OF THE DNA OF A NONOCCLUDED BACULOVIRUS, HZ-1V  

EPA Science Inventory

The DNA of the nonoccluded baculovirus (Hz-1V) obtained from the IMC-Hz-1 cell line was characterized by physicochemical and restriction endonuclease techniques. Hz-1V DNA isolated from purified virus had buoyant densities of 1.58 and 1.54 g/ml in CsC1-ethidium bromide density gr...

273

Apparatus for Teaching Physics.  

ERIC Educational Resources Information Center

Describes the following: a device which converts the displacement of a pendulum into an electric signal and is used as a voltage generator of low frequencies; a turn-by-turn transformer demonstration; how to remove the buoyant force on a piece of cork immersed in water; and how to demonstrate Coulomb's Law on the overhead projector. (GA)

Gottlieb, Herbert H., Ed.

1979-01-01

274

The Budgets of Turbulent Kinetic Energy and Temperature Variance in the Atmospheric Surface Layer  

Microsoft Academic Search

Measurements of the shear production, buoyant production, turbulent transport (flux divergence) and dissipation terms in the budget of turbulent kinetic energy, and production and turbulent transport terms in the temperature variance budget are presented. Direct observations of the surface stress and heat flux over a horizontally uniform site enable presentation of the data in terms of surface layer similarity theory.The

J. C. Wyngaard; O. R. Coté

1971-01-01

275

Buoyancy of the continental upper mantle Robyn K. Kelly  

E-print Network

peridotite xenoliths in the Kaapvaal craton give equilibration temperatures and pressures that define kbar. We calculated normative densities for a ``low-temperature'' garnet and spinel peridotite xenolith-temperature peridotites are positively buoyant with respect to the convecting mantle, which is inconsistent

276

46 CFR 160.047-3 - Materials.  

Code of Federal Regulations, 2012 CFR

...meeting the requirements of Federal Specification L-P-375 for Type I or II, class 1, film. (f) Tie tapes and body strap loops. The tie tapes and body strap loops for an adult or child size buoyant vest specified by this subpart must...

2012-10-01

277

46 CFR 160.047-3 - Materials.  

Code of Federal Regulations, 2014 CFR

...meeting the requirements of Federal Specification L-P-375 for Type I or II, class 1, film. (f) Tie tapes and body strap loops. The tie tapes and body strap loops for an adult or child size buoyant vest specified by this subpart must...

2014-10-01

278

46 CFR 160.047-3 - Materials.  

Code of Federal Regulations, 2013 CFR

...meeting the requirements of Federal Specification L-P-375 for Type I or II, class 1, film. (f) Tie tapes and body strap loops. The tie tapes and body strap loops for an adult or child size buoyant vest specified by this subpart must...

2013-10-01

279

46 CFR 160.151-27 - Approval inspections and tests for inflatable liferafts.  

Code of Federal Regulations, 2010 CFR

...first. (2) Mooring-out test (Paragraph 1/5.5). Initial... (3) Loading and seating test (Paragraph 1/5.7). ...determine seating capacity shall wear insulated buoyant immersion suits...lifejackets. (4) Boarding test (Paragraph 1/5.8)....

2010-10-01

280

Flame structure of steady and pulsed sooting inverse jet diffusion flames  

Microsoft Academic Search

In turbulent buoyant fire plumes, local inverse diffusion flames of air injected into gaseous fuel or fuel vapors occur, but little is known about the tendency to form soot and produce thermal radiation in these flame structures. To investigate these phenomena, steady and pulsed normal and inverse jet diffusion flames of methane\\/air and ethylene\\/air have been stabilized on a slot

Timothy C. Williams; Christopher R. Shaddix; Linda Gail Blevins; Robert W. Schefer

2004-01-01

281

Flame structure of steady and pulsed sooting inverse jet diffusion flames  

Microsoft Academic Search

In turbulent buoyant fire plumes, local inverse diffusion flames of air injected into gaseous fuel or fuel vapors occur, but little is known about the tendency to form soot and produce thermal radiation in these flame structures. To investigate these phenomena, steady and pulsed normal and inverse jet diffusion flames of methane\\/air and ethylene\\/air have been stabilized on a slot

Christopher R. Shaddix; Timothy C. Williams; Linda G. Blevins; Robert W. Schefer

2005-01-01

282

Proceedings of the Combustion Institute, Volume 29, 2002/pp. 16631670 CHEMILUMINESCENT OH* AND CH* FLAME STRUCTURE AND  

E-print Network

with inverse diffusion flames of small density difference with their surrounding ambient to study low Grashof* AND CH* FLAME STRUCTURE AND AERODYNAMIC SCALING OF WEAKLY BUOYANT, NEARLY SPHERICAL DIFFUSION FLAMES S. W uncertainty in the flame structure caused by the flow field. For diffusion flames, a suitable configuration

Tse, Stephen D.

283

On the structure and dynamics of stationary and rotating spherical diffusion flames  

Microsoft Academic Search

This dissertation research is concerned with diffusion flames generated by a porous spherical burner. It consists of two parts: the structure and extinction of weakly buoyant, nearly spherical, stationary flames, and the structure and dynamics of these flames in response to rotation of the burner in micro-gravity. In the first part of the investigation, normal-gravity experiments were conducted with nearly

Sean Won S. Yoo

2006-01-01

284

Forward scattering of a pulsed continuous wave signal through laminar and turbulent thermal plumes  

Microsoft Academic Search

The results of an experiment examining the forward propagation of an acoustic signal through a buoyant plume are discussed. Two distinct testing sights were used. One made use of a small fresh water tank in NUWC to provide a controlled plume. The other used a larger salt water tank at Woods Hole Oceanographic Institute (WHOI) to create a more realistic

Stephen G. Bowen

1993-01-01

285

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

Code of Federal Regulations, 2011 CFR

...2011-10-01 2011-10-01 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...

2011-10-01

286

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

Code of Federal Regulations, 2010 CFR

...2010-10-01 2010-10-01 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...

2010-10-01

287

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

288

Role of the Laboratory: Static Equilibrium  

NSDL National Science Digital Library

This activity from the PTRA Manual "The Role of the Laboratory in Teaching Introductory Physics" is a variation of the typical static laboratory activity, and includes a method of measuring buoyant force. See article "Static Equilibrium", by Jim Nelson in the December, 1985 issue of The Science Teacher.

Nelson, Jim; Nelson, Jane

2006-06-18

289

Extrachromosomal genetics of Claviceps purpurea  

Microsoft Academic Search

In order to establish a system for gene cloning in the ergot fungus Claviceps purpurea mitochondrial DNA was purified from two wild strains and four descendants of production strains. A characterization of the mt DNA with respect to buoyant density, molecular weight (45 kb corresponding to acontour lenght of 14 µm) showed no differences. However, considerable differences were detected in

Paul Tudzynski; Andrea DiJvell; Karl Esser

1983-01-01

290

Smelting of foundry iron on magnesia-alumina slags with a charge containing slags from ferroalloys production  

Microsoft Academic Search

Smelting foundry iron in blast furnaces is more difficult than smelting conversion pig iron. Foundry-iron smelting has several distinctive features: significant heating of the hearth; an increase in the buoyant effect of the hearth gases; upward movement of the slag region; a reduction in smelting rate and furnace productivity and an increase in unit coke consumption. The widespread practice of

Zh. E. Sleptsov; V. Ao Shatlov

1998-01-01

291

[Isolation and study of the physicochemical properties of the DNA of the iridescent virus from the mosquito Aedes cantans].  

PubMed

Molecules of DNA of Aedes cantans mosquito iridescent virus were found to be of linear shape, about 150 micron in length. The temperature of melting, sedimentation coefficient, molecular weight, and buoyant density of DNA were determined as well as the content of GC pairs in it. PMID:6613094

Buchatski?, L P; Kuznetsova, M A; Prima, V I

1983-01-01

292

Iridescent virus type 22 DNA  

Microsoft Academic Search

Summary Double stranded DNA extracted from iridescent virus type (IV22) was characterized by its buoyant density in CsCl, thermal denaturation profile and guanine plus cytosine content. The DNA was linear with a molecular weight of 130–143 × 106 determined by reassociation kinetics, contour length measurements and restriction endonuclease analysis.

Jill A. Hibbin; D. C. Kelly

1981-01-01

293

Magma to Microbe: Modeling Hydrothermal Processes at Ocean Spreading Centers  

E-print Network

233 Magma to Microbe: Modeling Hydrothermal Processes at Ocean Spreading Centers Geophysical in the seafloor, reacts with hot rock and magma-derived com- pounds, and then exits the seafloor as hot, buoyant to mixing between #12;234 MIcrOBE MInErAl prOcESSES In SEAflOOr SulfIdES seawater and the hydrothermal

Holden, James F.

294

Technical Notes Simulation of Microgravity Diffusion  

E-print Network

Technical Notes Simulation of Microgravity Diffusion Flames Using Sub-Atmospheric Pressures Natalie DOI: 10.2514/1.J051306 I. Introduction THE subject of combustion in weakly buoyant or microgravity in the reaction process [11]. Flames are also generally wider in microgravity than in normal gravity [12,13]. Some

Gülder, �mer L.

295

Three-dimensional analysis of heat transfer and thermophoretic particle deposition in OVD process  

Microsoft Academic Search

Heat transfer and particle deposition in the OVD process are simply modeled as a buoyant jet flow impinging on a circular target cylinder and numerically analyzed using a finite volume method on the flow, heat transfer and thermophoretic particle deposition over the cylinder. Effects of the three-dimensionality, conjugate heat transfer and longitudinal traversing of the jet on the particle deposition

Ki-Hyuck Hong; Shin-Hyoung Kang

1998-01-01

296

090109-038 1 Abstract Air filled salvage lift bags have been a problem and  

E-print Network

, is filled with air via either an umbilical hose from the surface or a portable compressed air tank brought090109-038 1 Abstract ­ Air filled salvage lift bags have been a problem and danger since valve. I. INTRODUCTION he concept of using buoyant objects such as barrels or bags filled with air

Wood, Stephen L.

297

Underwater vehicles: The minimum time problem Department of Mathematics  

E-print Network

the equations of motion for an ellipsoidal, neutrally buoyant, uniformly distributed vehicle submerged arcs, etc. In [6] we study the 2­singular extremals while their optimality is discussed in [5]. We must contain totally bang arcs as well as u 3 ­singular arcs. The theoretical conjectures are supported

Sussmann, Hector

298

The Earth's Interior How we know what's inside?  

E-print Network

vertically and laterally deformed average chemical composition is similar to andesite density: 2.7 g/cm3 is similar to andesite density: 3.0 g/cm3 Isostasy: The less dense crust "floats" on the less buoyant, denser

Siebel, Wolfgang

299

Lecture Ch. 7 Stability  

E-print Network

of water to condense so cools (relative to environment). Parcel now is colder than environment. Energy be converted into kinetic energy of a rising buoyant parcel. Numerical approximation for CAPE environment: saturated air with some dry air entrained into it (7.27) · Saturated (RH100%) ­ Some liquid water is present

Russell, Lynn

300

JWST331-c23 JWST331-Venditti Printer: Yet to Come May 3, 2013 12:11 246mm189mm UNCORRECTEDPROOFS  

E-print Network

on the decay of turbulent kinetic energy (TKE) and TKE dissipation rate (). This region of frontal mixing is marked on the water surface by upwelling streaks of relatively cool water that extend landward from at Earth's Surface observations of the buoyant gravity current generated by fresh, warm water discharged

Talke, Stefan

301

1 FEBRUARY 2004 281F E D O R O V I C H E T A L . 2004 American Meteorological Society  

E-print Network

-mean turbulence kinetic energy and the energy drain from the CBL top are both negligibly small. The zero from other numerical simulations, water tank experiments, and atmospheric measurements are also at the bottom of the layer (surface heating) or at its top (radiative cooling from clouds), or both. Buoyant

Fedorovich, Evgeni

302

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...

303

The role of chemical boundary layers in regulating the thickness of continental and oceanic thermal boundary layers  

Microsoft Academic Search

An important feature of continents and oceans is that they are underlain by chemically distinct mantle, made intrinsically buoyant and highly viscous by melt depletion and accompanying dehydration, respectively. Of interest here are the influences of these preexisting chemical boundary layers on small-scale convective processes (as opposed to large-scale processes, which govern the drift of continents and the eventual fate

Cin-Ty Aeolus Lee; Adrian Lenardic; Catherine M. Cooper; Fenglin Niu; Alan Levander

2005-01-01

304

Buoyancy control on continent subduction and implications for the dynamics of India-Asia convergence  

Microsoft Academic Search

At some point during their evolution, most trenches encounter continental lithosphere. Because average continental lithosphere is positively buoyant, collision is often the result. However, there is evidence that some continental crust and lithosphere does get subducted. For example, Indian plate kinematic reconstructions show that Meso-Cenozoic subduction consumed a highly heterogeneous lithosphere including small oceanic basins and substantial portions of the

S. Goes; F. A. Capitanio; G. Morra

2007-01-01

305

Frontal observations of the Delaware Coastal Current source region  

Microsoft Academic Search

The Delaware Coastal Current is formed by the outflow of buoyant estuarine water from Delaware Bay. Its source region is concentrated near the Delaware coast at the estuary mouth in a narrow region typically only 4 6 km in width. We used a combination of moored current, temperature, and conductivity records together with CTD profiles, underway surface thermosalinograph records, and

Todd M. Sanders; Richard W. Garvine

1996-01-01

306

Frontal observations of the Delaware Coastal Current source region  

Microsoft Academic Search

The Delaware Coastal Current is formed by the outflow of buoyant estuarine water from Delaware Bay. Its source region is concentrated near the Delaware coast at the estuary mouth in a narrow region typically only 4–6 km in width.We used a combination of moored current, temperature, and conductivity records together with CTD profiles, underway surface thermosalinograph records, and repeated acoustic

Todd M. Sanders; Richard W. Garvine

1996-01-01

307

Modulation of homogeneous turbulence seeded with finite size bubbles or particles  

Microsoft Academic Search

The dynamics of homogeneous, isotropic turbulence seeded with finite sized particles or bubbles is investigated in a series of numerical simulations, using the force-coupling method for the particle phase and low wavenumber forcing of the flow to sustain the turbulence. Results are given on the modulation of the turbulence due to massless bubbles, neutrally buoyant particles and inertial particles of

K. Yeo; S. Dong; E. Climent; M. R. Maxey

2010-01-01

308

Thompson/Ocean 420/Winter 2005 Internal Gravity Waves 1 I. Two-layer internal waves  

E-print Network

Thompson/Ocean 420/Winter 2005 Internal Gravity Waves 1 u1 I. Two-layer internal waves The simplest. The ocean analogy is a wave much like the surface gravity waves we have studied, but which acts-sea interface. For gravity waves, the wave speed, as well as the frequency, is proportional to the buoyant

Thompson, LuAnne

309

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

310

50 CFR 27.33 - Water skiing.  

Code of Federal Regulations, 2011 CFR

...The direction of a tow boat when circling will be counter clockwise. (d) Skiers must wear U.S. Coast Guard approved ski belts, life jackets or buoyant vests. (e) Water skiing is prohibited within 300 feet of harbors, swimming beaches,...

2011-10-01

311

Warm discharges in cold fresh water: 1. Line plumes in a uniform ambient.  

E-print Network

Warm discharges in cold fresh water: 1. Line plumes in a uniform ambient. ANTHONY KAY Department: +44 1509 223969 Email: A.Kay@Lboro.ac.uk 1 #12;Abstract Turbulent buoyant plumes in cold fresh water are obtained for both rising and descending plumes from virtual sources with all possible combinations

312

46 CFR 169.529 - Description of lifeboat equipment.  

Code of Federal Regulations, 2011 CFR

...adequate strength, 10 fathoms in length, and 1 inch in circumference. It must remain buoyant after being submerged for 24 hours...Painters must be of manila rope not less than 23/4 inches in circumference, or equivalent, and of a length not...

2011-10-01

313

46 CFR 169.529 - Description of lifeboat equipment.  

Code of Federal Regulations, 2014 CFR

...adequate strength, 10 fathoms in length, and 1 inch in circumference. It must remain buoyant after being submerged for 24 hours...Painters must be of manila rope not less than 23/4 inches in circumference, or equivalent, and of a length not...

2014-10-01

314

46 CFR 169.529 - Description of lifeboat equipment.  

Code of Federal Regulations, 2013 CFR

...adequate strength, 10 fathoms in length, and 1 inch in circumference. It must remain buoyant after being submerged for 24 hours...Painters must be of manila rope not less than 23/4 inches in circumference, or equivalent, and of a length not...

2013-10-01

315

46 CFR 169.529 - Description of lifeboat equipment.  

Code of Federal Regulations, 2010 CFR

...adequate strength, 10 fathoms in length, and 1 inch in circumference. It must remain buoyant after being submerged for 24 hours...Painters must be of manila rope not less than 23/4 inches in circumference, or equivalent, and of a length not...

2010-10-01

316

46 CFR 169.529 - Description of lifeboat equipment.  

Code of Federal Regulations, 2012 CFR

...adequate strength, 10 fathoms in length, and 1 inch in circumference. It must remain buoyant after being submerged for 24 hours...Painters must be of manila rope not less than 23/4 inches in circumference, or equivalent, and of a length not...

2012-10-01

317

Environ Fluid Mech DOI 10.1007/s10652-007-9023-x  

E-print Network

-scale models for simulations of neutrally buoyant shear-driven atmospheric boundary layer flows William C atmospheric boundary layer (ABL) flows. The popular Smagorinsky closure and an alternative closure based range scaling of spectra. Keywords Atmospheric boundary layer · Large-eddy simulation · Neutral

Basu, Sukanta

318

Parameterization of the Turbulent Energy Budget at the Top of the Daytime Atmospheric Boundary Layer  

Microsoft Academic Search

The budget of turbulent kinetic energy at the base of the inversion which caps the daytime atmospheric boundary layer depends on the lapse rate of potential temperature in the air aloft. The principal gain term in the energy budget is turbulent transport of kinetic energy, the principal loss term is buoyant conversion of kinetic energy into potential energy. The contributions

Otto Zeman; H. Tennekes

1977-01-01

319

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

320

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

321

Penetration of mantle plumes through depleted lithosphere  

Microsoft Academic Search

Laboratory experiments and numerical calculations are used to study how a laminar thermal plume deforms and penetrates a buoyant and viscous layer, which serves as an analog for continental lithosphere. The viscosity contrast between the two liquids and the buoyancy ratio B (the ratio between the intrinsic chemical density contrast and the thermal density contrast due to temperature differences) are

D. Jurine; C. Jaupart; G. Brandeis; P. J. Tackley

2005-01-01

322

Visual Comput (2006) 22: 856864 DOI 10.1007/s00371-006-0071-x O R I G I N A L A R T I C L E  

E-print Network

floating in the fluid by applying a buoyant force to the center of mass of the instantaneous submerged conversion process [11]. Gonzalez et al. [6] combined a polynomial free-form surface repre- sentation resulting from the interplay between a fluid system and a floating rigid body system. If we assume

Terzopoulos, Demetri

323

A three-dimensional numerical simulation of spreading umbrella clouds  

Microsoft Academic Search

During explosive volcanic eruptions, an eruption column buoyantly rises as a turbulent plume, and an umbrella cloud spreads laterally as a gravity current at the neutral buoyancy level. The source conditions of explosive eruptions such as mass discharge rates of magma at vents have been estimated from the field observations (e.g., satellite images) on the height of the eruption columns

Y. J. Suzuki; T. Koyaguchi

2009-01-01

324

Application of the E-? turbulence closure model to separated atmospheric surface-layer flows  

Microsoft Academic Search

Neutrally buoyant atmospheric surface-layer flow over a thin vertical wall has been studied using a turbulence closure scheme designed specifically to address flow problems containing high shears. The turbulent flow model consists of a general solution of the time averaged, steady state, twodimensional Navier-Stokes equations, where the E-? turbulence model has been used to close the system of equations. Model

G. E. Liston; R. L. Brown; J. Dent

1993-01-01

325

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

326

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

327

The University of Maryland Space Systems Laboratory is developing the capability to simulate partial gravity levels  

E-print Network

to simulate partial gravity levels for human operational activities through the use of ballast on body the force of gravity. The human body is close to neutrally buoyant underwater, so adding ballast canABSTRACT The University of Maryland Space Systems Laboratory is developing the capability

Akin, David

328

Seismic implications of mantle wedge plumes  

Microsoft Academic Search

We use a coupled petrological–thermomechanical model to investigate the dynamical effects of metamorphic reactions and melting on the seismic structure of thermal–chemical plumes beneath volcanic arcs. Plume generation is driven by the subduction of buoyant crustal rocks and expulsion of aqueous slab fluids that causes hydration and partial melting of the mantle wedge. The model demonstrates two chemically distinct types

Taras V. Gerya; James A. D. Connolly; David A. Yuen; Weronika Gorczyk; Allison M. Capel

2006-01-01

329

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

330

Physics of the granite sphere fountain Jacco H. Snoeijer1  

E-print Network

forms a prime example of lubrication theory. It is demonstrated how the viscosity and flow rate related cases of levitation by lubrication. I. INTRODUCTION Granite sphere or "kugel" fountains (see Fig under the impression that the sphere was hollow. In reality, however, it is solid and the buoyant force

Snoeijer, Jacco

331

Collective migration Inertial migration Transition to turbulence Particulate flow  

E-print Network

to turbulence Particulate flow in a pipe Rigid spherical particles Neutrally-buoyant particles Particulate flow Collective migration of rigid spherical particles in pipe flow Inertial migration of rigid spherical particles in pipe flow Transition to turbulence in particulate pipe flow Particulate flow IUSTI - CNRS

332

ADVANCES IN SIX-DEGREE-OF-FREEDOM DYNAMICS AND CONTROL OF UNDERWATER VEHICLES  

E-print Network

of a low-speed, fully actuated, neutrally buoyant underwater vehicle and the first reported use of TLSADVANCES IN SIX-DEGREE-OF-FREEDOM DYNAMICS AND CONTROL OF UNDERWATER VEHICLES by Stephen C. Martin #12;Abstract This thesis addresses the topics of (1) high level control of underwater vehicles; (2

Whitcomb, Louis L.

333

Geophysical and Astrophysical Fluid Dynamics Vol. 98, No. 6, December, 2004, pp. 453471  

E-print Network

a vertical conducting wire stretched through the interface, acting as an in situ capacitative level sensor, and relies upon the optical rotation properties of the working liquids. The previous methods returned only advanced. By adding small, neutrally buoyant beads to the working liquid, sophisticated particle tracking

Williams, Paul

334

Disengaged and Disaffected Young People: Surviving the System  

ERIC Educational Resources Information Center

There are counter-narratives of youth as at risk and as buoyant and agentive. The article maps the conceptual terrain concerning resilience, well-being, buoyancy, enjoyment and happiness and selects factors related to the successful navigation of schooling. It analyses data from a subset of a national data set, from 65 young people considered to…

Lumby, Jacky

2012-01-01

335

Expression of Sporophytic Storage Proteins in the Corm of the Quillwort (Isoetes echinospora Dur.)  

Microsoft Academic Search

Parenchyma cells from the corm tissue of the aquatic lycopod lsoefes echinospora Dur. were shown by electron microscopy to be packed with amyloplasts, lipid bodies, and protein bodies. The protein bodies are morphologically similar to those identified in seeds and certain vegetative tissues of higher plants. Globoid- containing protein bodies (1-10 pm) isolated in a sucrose gradient possessed a buoyant

James D. Decamp; David A. Stetler; Augustus E. DeMaggio

1994-01-01

336

Film flow of a suspension of liquid drops Department of Applied Mathematics, Illinois Institute of Technology, 10 West 32nd Street, Chicago,  

E-print Network

buoyant liquid drops down an inclined plane wall is investigated by numerical simulation in the limit near the inclined plane but not near the free surface. © 2002 American Institute of Physics. DOI: 10 of a suspension of liquid drops down an inclined plane, distin- guished from the channel flow

Heller, Barbara

337

Film flow of a suspension of liquid drops Department of Applied Mathematics, Illinois Institute of Technology, 10 West 32nd Street, Chicago,  

E-print Network

buoyant liquid drops down an inclined plane wall is investigated by numerical simulation in the limit near the inclined plane but not near the free surface. © 2002 American Institute of Physics. #DOI: 10 of a suspension of liquid drops down an inclined plane, distin­ guishe

Heller, Barbara

338

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

339

Applicability of an integrated plume rise model for the dispersion from wild-land fires  

NASA Astrophysics Data System (ADS)

We have presented an overview of a mathematical model, BUOYANT, that was originally designed for the evaluation of the dispersion of buoyant plumes originated from major warehouse fires. The model addresses the variations of the cross-plume integrated properties of a buoyant plume in the presence of a vertically varying atmosphere. The model also includes a treatment for a rising buoyant plume interacting with an inversion layer. We have compared the model predictions with the data of two prescribed wild-land fire experiments. For the SCAR-C experiment in Quinault (US) in 1994, the predicted vertical extents of the plume at maximum plume rise were between 500 and 800 m and between 200 and 700 m, using two alternative meteorological data sets. The corresponding observed injection heights of the aerosol particles measured using an airborne lidar (light detection and ranging) ranged from 250 to 600 m. For the prescribed burning experiment in Hyytiälä (Finland) in 2009, the model predictions were compared with plume elevations and diameters, determined based on particulate matter number concentration measurements onboard an aeroplane. However, the agreement between modelled and measured results substantially depends on how the properties of the source term are evaluated, especially regarding the convective heat fluxes from the fire. The results demonstrate that in field experiments on wild-land fires, there are substantial uncertainties in estimating both (i) the source terms for the atmospheric dispersion computations and (ii) the relevant vertical meteorological profiles.

Kukkonen, J.; Nikmo, J.; Sofiev, M.; Riikonen, K.; Petäjä, T.; Virkkula, A.; Levula, J.; Schobesberger, S.; Webber, D. M.

2014-11-01

340

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

341

Distribution and relative abundance of flyingfish (Exocoetidae) in the eastern Caribbean. II. Spawning substrata, eggs and larvae  

Microsoft Academic Search

We investigated the distribution and relative abundance of flyingfish spawning substrata (flotsam), eggs and larvae by neuston tows at 40 stations across a 67 500 square nautical mile (mm2) area of the eastern Caribbean from April 10 to May 6, 1988. Flotsam occurred m only 48% of the tows and in quantities < 1 g nmil tow. Non-buoyant flyingfish eggs

W Hunte; HA Oxenford; R Mahon

1995-01-01

342

Tellus (2006), 58A, 98103 Copyright C Blackwell Munksgaard, 2006 Printed in Singapore. All rights reserved TELLUS  

E-print Network

). The questions then arise: does the temperature increase with decreasing radius at constant height or constant atmosphere in various coordinate systems given the tangential wind speed as a function of radius and height decreasing with height is positively buoyant in terms of density differences compared at constant height

Smith, Roger K.

343

Effects of Non-Uniform Thermal Conduction on Solar Convection-Zone Flux Tubes  

Microsoft Academic Search

The dynamo model of solar magnetic field generation assumes that magnetic flux is retained at the dynamo site for times of the order of the solar-cycle period. However, flux tubes in the solar convection zone are expected to be buoyant, rising to the surface on timescales much shorter than the solar cycle. Since the initial 1955 paper by Parker on

D. D. Lenz; F. Moreno-Insertis

2000-01-01

344

The Impact of Chinese Exports on Global Import Prices &ast  

Microsoft Academic Search

AbstractThis paper evaluates the evidence bearing on the question of whether China's buoyant export growth has led to significant changes in the import prices, and thus inflation performance, of its trading partners. This evidence suggests that the impact of Chinese exports on global import prices has been, while non- negligible, fairly modest. We identify a statistically significant effect of US

Steven B. Kamin; Mario Marazzi; John W. Schindler

2006-01-01

345

Is China \\  

Microsoft Academic Search

In the past few years, observers increasingly have pointed to China as a source of downward pressure on global prices. This paper evaluates the theoretical and empirical evidence bearing on the question of whether China's buoyant export growth has led to significant changes in the inflation performance of its trading partners. This evidence suggests that the impact of Chinese exports

Steven B. Kamin; Mario Marazzi; John W. Schindler

2004-01-01

346

Dynamics of magma ascent in the volcanic conduit  

E-print Network

). If the cause of frag- mentation is the interaction of hot magma with external water, the ensuing eruption or crystal-rich magmas, do not allow bubbles to ascend buoyantly and may also hinder bubble growth. This can is called phreatomagmatic. Eruptions that do not involve external water are called "dry," in which case

Manga, Michael

347

Revisiting Carbon Flux Through the Ocean's Twilight Zone  

Microsoft Academic Search

The oceanic biological pump drives sequestration of carbon dioxide in the deep sea via sinking particles. Rapid biological consumption and remineralization of carbon in the ``twilight zone'' (depths between the euphotic zone and 1000 meters) reduce the efficiency of sequestration. By using neutrally buoyant sediment traps to sample this chronically understudied realm, we measured a transfer efficiency of sinking particulate

Ken O. Buesseler; Carl H. Lamborg; Philip W. Boyd; Phoebe J. Lam; Thomas W. Trull; Robert R. Bidigare; James K. B. Bishop; Karen L. Casciotti; Frank Dehairs; Marc Elskens; Makio Honda; David M. Karl; David A. Siegel; Mary W. Silver; Deborah K. Steinberg; Jim Valdes; Benjamin Van Mooy; Stephanie Wilson

2007-01-01

348

Implications of a plume-fed asthenosphere layer for mantle flow and mid-ocean ridge melting processes  

Microsoft Academic Search

Based on current evidence for a relative low density and low viscosity layer beneath most oceanic lithosphere, we propose the asthenosphere layer to be formed by upwelling mantle plumes. In our scenario the asthenosphere is a hot, thus buoyant and weak layer that is chemically depleted due to melt extraction at the plume locations (hotspots volcanism) and the subsequent melting

J. Hasenclever; J. Phipps Morgan; M. Hort

2005-01-01

349

Temperature inversions in the vicinity of Oak Ridge, Tennessee, as characterized by tethersonde data  

SciTech Connect

Accidental releases of hazardous materials to the atmosphere may result from fires that create a buoyant plume which may rise several hundred meters above the ground. For such buoyant release cases, estimates of ground-level concentrations may be as much as a factor of 100 lower than similar, nonbuoyant releases. For the Oak Ridge Reservation, safety analyses often examine buoyant release accident scenarios and resulting downwind, ground-level consequence estimates. For these analyses, careful consideration of buoyant plume rise is important. Plume rise can be limited by a stable vertical atmospheric temperature profile, commonly called an inversion, where the air temperature increases with height. There is a concern that inversions may interact with the complex terrain on the Oak Ridge Reservation, particularly at the Y-12 Plant, which is located in a relatively shallow but narrow valley, to trap the plume and increase ground-level consequences. The purpose of this paper is to review the available meteorological data that provide information on inversions in the Oak Ridge area.

Blasing, T.J.; Wang, J.C.; Lombardi, D.A.

1998-01-01

350

An automatically profiling temperature sensor for upper ocean measurements  

Microsoft Academic Search

An automatically profiling buoy system has been developed for measuring temperature in the upper 50 meters of the ocean. Temperature and pressure sensors are housed in a profiling unit which is tethered to a support buoy on the surface via a neutrally buoyant electrical cable and air hose. An air bladder within the profiler causes the profiler to cycle between

C. Nelson; R. Chappell

1982-01-01

351

Free fall plasma-arc reactor for synthesis of carbon nanotubes in microgravity  

Microsoft Academic Search

High temperatures inside the plasma of a carbon arc generate strong buoyancy driven convection which has an effect on the growth and morphology of the single-walled carbon nanotubes (SWNTs). To study the effect of buoyancy on the arc process, a miniature carbon arc apparatus was designed and developed to synthesize SWNTs in a microgravity environment substantially free from buoyant convective

J. M. Alford; G. R. Mason; D. A. Feikema

2006-01-01

352

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

353

RESEARCH ARTICLE Caldera resurgence during magma replenishment  

E-print Network

/or erupted into each system; this magma is chemically distinct from rhyolite magma which was resident in each the system, it is able to heat, remobilize, and mingle with residual crystal-rich rhyolite remaining in the shallow mag- ma chamber. Dacite and remobilized rhyolite rise buoyantly to form laccoliths by lifting

354

The Great Plankton Race  

NSDL National Science Digital Library

In this activity, learners are challenged to design a planktonic organism that will neither float like a cork nor sink like a stone. They are given pictures of planktonic organisms and simple materials. The best model of a planktonic organism will sink slowly or be neutrally buoyant. After designing with their teammates, learners test and race their plankton in a simulated ocean.

COSEE Ocean Learning Communities

2012-07-12

355

Chapter 6: Forces in Fluids Did you read chapter 6  

E-print Network

, and pressure acts perpendicular to the surface of submerged objects #12;1/20/2010 4 Archimedes Principle. normal force · b. friction A volume of water in pool Weight Buoyant Force Archimedes Principle An object Demo Floating Objects According to Archimedes Principle, an object will sink until its weight equals

Hart, Gus

356

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

357

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

358

Motion of the Easter hot spot relative to Hawaii and Louisville hot spots  

E-print Network

Motion of the Easter hot spot relative to Hawaii and Louisville hot spots Bernhard Steinberger to the Easter, Hawaii and Louisville hot spots. Computations are performed for a range of different buoyant that a westward motion of the Easter hot spot at several cm per year relative to Hawaii and Louisville hot spots

Steinberger, Bernhard

359

Lateral Migration and Rotational Motion of Elliptic Particles in Planar Poiseuille Flow  

NASA Technical Reports Server (NTRS)

Simulations of elliptic particulate suspensions in the planar Poiseuille flow are performed by using the lattice Boltzmann equation. Effects of the multi-particle on the lateral migration and rotational motion of both neutrally and non-neutrally buoyant elliptic particles are investigated. Low and intermediate total particle volume fraction f(sub a) = 13%, 15%, and 40% are considered in this work.

Qi, Dewei; Luo, Li-Shi; Aravamuthan, Raja; Strieder, William; Bushnell, Dennis M. (Technical Monitor)

2002-01-01

360

ODOR FLUX MEASUREMENTS AT A FACULTATIVE SWINE LAGOON STRATIFIED BY SURFACE AERATION  

Microsoft Academic Search

Odor-related complaints are a major concern of pork producers. Open manure storage and treatment facilities such as uncovered anaerobic treatment lagoons are a major contributor to odor nuisance. Repeatable and valid field measurement techniques are needed for evaluating baseline odor emissions from existing livestock facilities and the effectiveness of odor abatement technologies. A buoyant convective flux chamber (BCFC) for measuring

A. J. Heber; J.-Q. Ni; T. T. Lim

361

46 CFR 160.060-7 - Inspections and tests-standard and nonstandard vests. 1  

Code of Federal Regulations, 2014 CFR

...lot of buoyant vests to be tested for buoyancy in accordance with paragraph (e) of...060-7(b )(4)—Sample for Buoyancy Tests Lot size Number of vests in... 4 (5) If a sample vest fails the buoyancy test, the sample from the next...

2014-10-01

362

46 CFR 160.156-13 - Approval inspections and tests for prototype rescue boats and fast rescue boats.  

Code of Federal Regulations, 2014 CFR

...by weighing as a group or individually. Each person must wear an inherently buoyant SOLAS lifejacket with at least 150 N of buoyancy or a Coast Guard-approved lifejacket approved under approval series 160.155. The operator(s) must demonstrate...

2014-10-01

363

46 CFR 160.002-4 - Construction.  

Code of Federal Regulations, 2014 CFR

...Displacement of pad inserts. The volume of the finished individual heat-sealed buoyant pad inserts shall be such as to provide buoyancy as set forth in the following table when tested in accordance with the method set forth in § 160.002-5(d),...

2014-10-01

364

46 CFR 160.052-7 - Inspections and tests-standard and nonstandard vests. 1  

Code of Federal Regulations, 2014 CFR

...lot of buoyant vests to be tested for buoyancy in accordance with paragraph (e) of...At least one vest from each lot for buoyancy in accordance with procedures contained...section. (6) If a vest fails the buoyancy test, the sample from the next...

2014-10-01

365

46 CFR 160.047-4 - Construction.  

Code of Federal Regulations, 2014 CFR

...distributed so as to provide the proper flotation characteristics and buoyancy required to hold the wearer in an upright backward position...heat-sealed buoyant pad inserts shall be such as to provide buoyancy as set forth in Table 160.047-4(c)(4) when...

2014-10-01

366

Genome Size and Deoxyribonucleic Acid Base Composition of .Thermop lasma acidophilurn  

Microsoft Academic Search

The deoxyribonucleic acid base composition of two strains of Thermoplasrna acidophilum including the type strain 122-1B2 was determined by buoyant den- sity and thermal denaturation temperature. The guanine plus cytosine content of the two strains examined was found by both methods to be about 46%. This re- sult is strikingly at variance with the significantly lower values, about 25%, re-

CLAUS CHRISTIANSEN; E. A. FREUNDT; FINN T. BLACK

1975-01-01

367

Applicability of an integrated plume rise model for the dispersion from wild-land fires  

NASA Astrophysics Data System (ADS)

We have presented an overview of a mathematical model, BUOYANT, that was originally designed for the evaluation of the dispersion of buoyant plumes originated from major warehouse fires. The model addresses the variations of the cross-plume integrated properties of a buoyant plume in the presence of a vertically varying atmosphere. The model also includes a treatment for a rising buoyant plume interacting with an inversion layer. We have compared the model predictions with the data of two prescribed wild-land fire experiments. For the SCAR-C experiment in Quinault (US) in 1994, the predicted vertical extents of the plume at maximum plume rise were between 500-800 m and 200-700 m, using two alternative meteorological datasets. The corresponding observed injection heights of the aerosol particles measured using an airborne LIDAR (LIght Detection And Ranging) ranged from 250 and 600 m. For the prescribed burning experiment in Hyytiälä (Finland) in 2009, the model predictions were compared with plume elevations and diameters, determined based on particulate matter number concentration measurements on board an aeroplane. The agreement of modelled and measured results was good, provided that one assumes the measured maximum convective heat fluxes as input data for the model. The results demonstrate that in field experiments on wild-land fires, there are substantial uncertainties in estimating both (i) the source terms for the atmospheric dispersion computations, and (ii) the relevant vertical meteorological profiles. The results provide more confidence that cross-plume integrated mathematical models, such as the BUOYANT model, can be used to fairly good accuracy for evaluating the dispersion from major wild-land fires.

Kukkonen, J.; Nikmo, J.; Sofiev, M.; Riikonen, K.; Petäjä, T.; Virkkula, A.; Levula, J.; Schobesberger, S.; Webber, D. M.

2014-01-01

368

Mechanism for generating power from wave motion on a body of water  

SciTech Connect

A mechanism for generating power from wave motion on a body of water is described. The mechanism includes a buoyant body which is adapted to float on a body of water and to roll and pitch in response to the wave motion of the water. A gyro-wave energy transducer is mounted on the buoyant body for translating the pendulum-like motions of the buoyant body into rotational motion. The gyro-wave energy transducer includes a gimbal comprised of first and second frames, with the first frame being pivotally mounted to the second frame and the second frame being pivotally mounted to the buoyant body. A gyroscope is mounted to the first frame for rotation about an axis perpendicular to the axes of rotation of the first and second frames. A motor/generator is coupled to the gyroscope for maintaining a controlled rotational velocity for the gyroscope. Transferring members are associated with one of the first and second frames for transferring torque of one of the first and second frames to the gyroscope about an axis that is perpendicular to that of the gyroscope which results in rotation of the other of the first and second frames. An electrical generator is responsive to the relative rotational movement of the first and second frames for generating electrical energy. A storage battery is mounted on the buoyant body for storing and releasing electrical energy and is operatively coupled to the motor/generator and the electrical generator. A control circuit is associated with the generator and the motor/generator unit of the gyroscope and is responsive to the time rate of change of current produced by the generator for controlling the rotational velocity of the gyroscope in order to maintain maximum power output from the electrical generator.

Sachs, G.A.; Sachs, H.K.

1982-09-28

369

Opening and closing slab windows in congested subduction zones  

NASA Astrophysics Data System (ADS)

Subduction zones often try to swallow buoyant material which is embedded in the oceanic lithosphere: plume material or hotspot residues, oceanic plateaux, and fragments of continental material. This often results in the formation of a slab window and it has been shown (Mason et al, 2010; Betts et al, 2012) that this window strongly influences the subsequent evolution of the slab and the advance/retreat rate of the trench. The buoyant material typically pushes the trench into a local state of advance, and the creation of the slab window allows the rest of the trench to retreat as the mantle behind the slab flows in through the window. This situation is inherently unstable: if the buoyancy anomaly is finite in size, then the retreating trench will soon move behind the anomaly and juxtapose negatively buoyant oceanic lithosphere with active subduction. This creates the potential to close the slab window and, in doing so, transfer the buoyant material to the over-riding plate. Models show that this closure of the window initially occurs through a lateral rollback process followed by a catastrophic re-initiation of subduction behind the colliding buoyant anomaly. This rollback leaves a characteristic, tightly rolled remnant in the mantle and significant rotation in the over-riding plate and the newly-docked block. The over-riding plate is thrown into extension perpendicular to the original orientation of the trench. This same situation applies at the late-stages of a closing ocean due to the passive margin geometry and the presence of debris collected from the closing ocean floor and it seems likely that these models can also be applied to the complicated geometry of subduction in such environments. Mason, W. G.; Moresi, L.; Betts, P. G. & Miller, M. S. Three-dimensional numerical models of the influence of a buoyant oceanic plateau on subduction zones Tectonophysics, 2010, 483, 71-79 P. Betts, W. Mason, L. Moresi, The influence of mantle plumes on subduction zone dynamics, Geology, 40, 739-742 (2012)

Moresi, Louis

2013-04-01

370

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

371

Aeromechanical stability analysis of a multirotor vehicle with application to hybrid heavy lift helicopter dynamics  

NASA Technical Reports Server (NTRS)

The Hybrid Heavy Lift Helicopter (HHLH) is a potential candidate vehicle aimed at providing heavy lift capability at low cost. This vehicle consists of a buoyant envelope attached to a supporting structure. Four rotor systems are also attached to the supporting structure. Nonlinear equations of motion capable of modeling the dynamics of this multi-rotor/support frame/vehicle system have been developed and used to study the fundamental aeromechanical stability characteristics of this class of vehicles. The mechanism of coupling between the blades, supporting structure and rigid body modes is identified and the effect of buoyancy ratio (buoyant lift/total weight) on the vehicle dynamics is studied. It is shown that dynamics effects have a major role in the design of such vehicles. The analytical model developed is also useful for studying the aeromechanical stability of single rotor and tandem rotor coupled rotor/fuselage systems.

Venkatesan, C.; Friedmann, P. P.

1984-01-01

372

Investigation of the free flow electrophoretic process. Volume 2: Technical analysis  

NASA Technical Reports Server (NTRS)

The effect of gravity on the free flow electrophoretic process was investigated. The demonstrated effects were then compared with predictions made by mathematical models. Results show that the carrier buffer flow was affected by gravity induced thermal convection and that the movement of the separating particle streams was affected by gravity induced buoyant forces. It was determined that if gravity induced buoyant forces were included in the mathematical models, then effective predictions of electrophoresis chamber separation performance were possible. The results of tests performed using various methods of electrophoresis using supportive media show that the mobility and the ability to separate were essentially independent of concentration, providing promise of being able to perform electrophoresis with higher inlet concentrations in space.

Weiss, R. A.; Lanham, J. W.; Richman, D. W.; Walker, C. D.

1979-01-01

373

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

374

Feedbacks of phytoplankton surface mats on ocean physics  

NASA Astrophysics Data System (ADS)

The effects of phytoplankton on ocean physics through the feedback by light absorption have been investigated repeatedly. In contrast, additional feedback mechanisms involving positively buoyant phytoplankton have been largely ignored. However, extensive surface mats of buoyant cyanobacteria, as they occur regularly in the Baltic Sea in summer, may have significant effects on wind drag and albedo. Using an ecosystem model that is embedded in a water column or an ocean circulation model, we study the relative importance of all three feedback mechanisms. We show that surface floating cyanobacteria substantially alter their environment. The light absorption and wind drag feedbacks, however, are stronger than the albedo feedback. Overall, we find that the increase of sea surface temperatures and cooling subsurface mediated by cyanobacteria also modify ocean circulation patterns. Since the abundance of surface floating cyanobacteria is expected to increase in future, we recommend to include these biological-physical feedback mechanisms in the next generation of ocean climate models.

Hense, Inga; Sonntag, Sebastian

2014-05-01

375

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

376

HYDROGEL TRACER BEADS: THE DEVELOPMENT, MODIFICATION, AND TESTING OF AN INNOVATIVE TRACER FOR BETTER UNDERSTANDING LNAPL TRANSPORT IN KARST AQUIFERS  

SciTech Connect

The goal of this specific research task is to develop proxy tracers that mimic contaminant movement to better understand and predict contaminant fate and transport in karst aquifers. Hydrogel tracer beads are transported as a separate phase than water and can used as a proxy tracer to mimic the transport of non-aqueous phase liquids (NAPL). They can be constructed with different densities, sizes & chemical attributes. This poster describes the creation and optimization of the beads and the field testing of buoyant beads, including sampling, tracer analysis, and quantitative analysis. The buoyant beads are transported ahead of the dissolved solutes, suggesting that light NAPL (LNAPL) transport in karst may occur faster than predicted from traditional tracing techniques. The hydrogel beads were successful in illustrating this enhanced transport.

Amanda Laskoskie, Harry M. Edenborn, and Dorothy J. Vesper

2012-01-01

377

Dissipative inertial transport patterns near coherent Lagrangian eddies in the ocean  

E-print Network

Recent developments in dynamical systems theory have revealed long-lived and coherent Lagrangian (i.e., material) eddies in incompressible, satellite-derived surface ocean velocity fields. Paradoxically, observed drifting buoys and floating matter tend to create dissipative-looking patterns near oceanic eddies, which appear to be inconsistent with the conservative fluid particle patterns created by coherent Lagrangian eddies. Here we show that inclusion of inertial effects (i.e., those produced by the buoyancy and size finiteness of an object) in a rotating two-dimensional incompressible flow context resolves this paradox. Specifically, we obtain that anticyclonic coherent Lagrangian eddies attract (repel) negatively (positively) buoyant finite-size particles, while cyclonic coherent Lagrangian eddies attract (repel) positively (negatively) buoyant finite-size particles. We show how these results explain dissipative-looking satellite-tracked surface drifter and subsurface float trajectories, as well as satellite-derived \\emph{Sargassum} distributions.

F. J. Beron-Vera; M. J. Olascoaga; G. Haller; M. Farazmand; J. Trinanes; Y. Wang

2014-08-27

378

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

379

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

380

Aeromechanical stability analysis of a multirotor vehicle model representing a hybrid heavy lift airship (HHLA)  

NASA Technical Reports Server (NTRS)

Hybrid Heavy Lift Airship (HHLA) is a proposed candidate vehicle aimed at providing heavy lift capability at low cost. This vehicle consists of a buoyant envelope attached to a supporting structure to which four rotor systems, taken from existing helicopters are attached. Nonlinear equations of motion capable of modelling the dynamics of this coupled multi-rotor/support frame/vehicle system have been developed. Using these equations of motion the aeroelastic and aeromechanical stability analysis is performed aimed at identifying potential instabilities which could occur for this type of vehicle. The coupling between various blade, supporting structure and rigid body modes is identified. Furthermore, the effects of changes in buoyancy ratio (Buoyant lift/total weight) on the dynamic characteristics of the vehicle are studied. The dynamic effects found are of considerable importance for the design of such vehicles. The analytical model developed is also useful for studying the aeromechanical stability of single rotor and tandem rotor coupled rotor/fuselage systems.

Venkatesan, C.; Friedmann, P. P.

1984-01-01

381

Three-Dimensional Convection Planforms With Internal Heat Generation  

Microsoft Academic Search

Thermal convection planforms in an infinite Prandtl number, isoviscous fluid layer with basal and internal heating are determined using three-dimensional finite difference calculations. With basal heating only, at Rayleigh number RaT=1.5×105 the planform consists of a weakly time-dependent spoke pattern, with connected networks of equally buoyant up- and down-wellings. With volumetric heat sources the planform is strongly time variable. It

Bryan Travis; Stuart Weinstein; Peter Olson

1990-01-01

382

Three-dimensional convection planforms with internal heat generation  

Microsoft Academic Search

Thermal convection planforms in an infinite Prandtl number, isoviscous fluid layer with basal and internal heating are determined using three-dimensional finite difference calculations. With basal heating only, at Rayleigh number Ra(T) = 150,000, the planform consists of a weakly time-dependent spoke pattern, with connected networks of equally buoyant up- and down-wellings. With volumetric heat sources, the planform is strongly time

Bryan Travis; Stuart Weinstein; Peter Olson

1990-01-01

383

Measurement of velocity and temperature profiles in low-speed, turbulent non-isothermal flows  

NASA Astrophysics Data System (ADS)

A probe was developed utilizing thermocouples as the sensors which, together with associated data reduction and processing equipment, makes it possible to measure velocity and temperature profiles in low-speed, turbulent, nonisothermal flows. The technique presented might be well suited for transient processes where simultaneous measurements are required in multiple locations. The probe was devised in order to measure the velocity and temperature profiles in the jet formed under a ceiling when a buoyant plume from a fire impinges on the ceiling.

Motevalli, V.; Marks, C. H.; McCaffrey, B. J.

1987-11-01

384

Microconvective thermal conductivity in disperse two-phase mixtures as observed in a low velocity couette flow experiment  

Microsoft Academic Search

Eddy transport associated with microscopic flow fields in shearing two-phase flows was investigated. Although such microconvective effects are expected to be present in all disperse two-phase flows, usually they are masked by other collateral mechanisms and could not be studied critically. In the present study, effective thermal conductivities of neutrally buoyant solid-fluid mixtures were measured in a rotating Couette flow

C. W. Sohn; M. M. Chen

1981-01-01

385

Spitzer Observations of Transient, Extended Dust in Two Elliptical Galaxies: New Evidence of Recent Feedback Energy Release in Galactic Cores  

E-print Network

Spitzer observations of extended dust in two optically normal elliptical galaxies provide a new confirmation of buoyant feedback outflow in the hot gas atmospheres around these galaxies. AGN feedback energy is required to prevent wholesale cooling and star formation in these group-centered galaxies. In NGC 5044 we observe interstellar (presumably PAH) emission at 8 microns out to about 5 kpc. Both NGC 5044 and 4636 have extended 70 microns emission from cold dust exceeding that expected from stellar mass loss. The sputtering lifetime of this extended dust in the ~1keV interstellar gas, ~10^7 yrs, establishes the time when the dust first entered the hot gas. Evidently the extended dust originated in dusty disks or clouds, commonly observed in elliptical galaxy cores, that were disrupted, heated and buoyantly transported outward. The surviving central dust in NGC 5044 and 4636 has been disrupted into many small filaments. It is remarkable that the asymmetrically extended 8 micron emission in NGC 5044 is spatially coincident with Halpha+[NII] emission from warm gas. A calculation shows that dust-assisted cooling in buoyant hot gas moving out from the galactic core can cool within a few kpc in about ~10^7 yrs, explaining the optical line emission observed. The X-ray images of both galaxies are disturbed. All timescales for transient activity - restoration of equilibrium and buoyant transport in the hot gas, dynamics of surviving dust fragments, and dust sputtering - are consistent with a central release of feedback energy in both galaxies about 10^7 yrs ago.

Pasquale Temi; Fabrizio Brighenti; William G. Mathews

2007-07-25

386

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

387

Transparent exopolymer particles in a deep-sea hydrothermal system: Guaymas Basin, Gulf of California  

Microsoft Academic Search

This is the first report of transparent exopolymer particle (TEP) concentrations within deep-sea hydrothermal vent systems\\u000a using colorimetric methods, measuring TEP in supernatants of sediments surrounding the vents, in fluids emanating directly\\u000a from hydrothermal vents and in neutrally buoyant hydrothermal plumes. Samples were collected at Guaymas Basin (Gulf of California),\\u000a a sedimented hydrothermal system. TEP concentrations within the hydrothermal fluids

L. Prieto; J. P. Cowen

2007-01-01

388

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

389

Microbial ammonia oxidation and enhanced nitrogen cycling in the Endeavour hydrothermal plume  

NASA Astrophysics Data System (ADS)

Ammonium was injected from the subseafloor hydrothermal system at the Endeavour Segment, Juan de Fuca Ridge, into the deep-sea water column resulting in an NH4+-rich (?177 nM) neutrally buoyant hydrothermal plume. This NH4+ was quickly removed by both autotrophic ammonia oxidation and assimilation. The former accounted for at least 93% of total net NH4+ removal, with its maximum rate in the neutrally buoyant plume (?53 nM d -1) up to 10-fold that in background deep water. Ammonia oxidation in this plume potentially added 26-130 mg NO3-md into the deep-sea water column. This oxidation process was heavily influenced by the presence of organic-rich particles, with which ammonia-oxidizing bacteria (AOB) were often associated (40-68%). AOB contributed up to 10.8% of the total microbial communities within the plume, and might constitute a novel lineage of ?-proteobacterial AOB based on 16S rRNA and amoA phylogenetic analyses. Meanwhile, NH4+ assimilation rates were also substantially enhanced within the neutrally buoyant plume (?26.4 nM d -1) and accounted for at least 47% of total net NH4+ removal rates. The combined NH4+ oxidation and assimilation rates always exceeded total net removal rates, suggesting active in situNH4+regeneration rates of at least an order of magnitude greater than the particulate nitrogen flux from the euphotic zone. Ammonia oxidation is responsible for NH4+ turnover of 0.7-13 days and is probably the predominant in situ organic carbon production process (0.6-13 mg C m -2 d -1) at early stages of Endeavour neutrally buoyant plumes.

Lam, Phyllis; Cowen, James P.; Popp, Brian N.; Jones, Ronald D.

2008-05-01

390

Transatlantic Freshwater Aqueduct  

Microsoft Academic Search

This paper offers a technical and geopolitical reappraisal of a macro-engineering proposal to plumb Earth’s freshwater, siphoning\\u000a some of it from a region of surplus (Amazon River Basin) to a region of shortage (arid northern Africa) via his positively buoyant (subsurface floating) seabed-anchored Transatlantic Freshwater Aqueduct. Two different routes for\\u000a the pipeline, of length 4,317 and 3,745 km, respectively, have been

Viorel Badescu; Dragos Isvoranu; Richard B. Cathcart

2010-01-01

391

Diffusion Mass Transfer in Miscible Oil Recovery: Visual Experiments and Simulation  

Microsoft Academic Search

Co-and counter-current type transfers due to diffusion and -free- convection caused by the buoyant forces between fracture\\u000a and matrix were studied experimentally using 2-D glass-bead models. Mineral oil and kerosene were used as the displaced phase.\\u000a The model saturated with oil was exposed to solvent phase (pentane) under static conditions (no flow in fracture) to mimic\\u000a matrix-fracture interaction during gas

Can Ulas Hatiboglu; Tayfun Babadagli

2008-01-01

392

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

393

A New Test Method for Material Flammability Assessment in Microgravity and Extraterrestrial Environments  

NASA Technical Reports Server (NTRS)

The objective of this research is to modify the well-instrumented standard cone configuration to provide a reproducible bench-scale test environment that simulates the buoyant or ventilation flow that would be generated by or around a burning surface in a spacecraft or extraterrestrial gravity level. We will then develop a standard test method with pass-fail criteria for future use in spacecraft materials flammability screening. (For example, dripping of molten material will be an automatic fail.)

Olson, S. L.; Beeson, H. D.; Haas, J. P.; Baas, J. S.

2004-01-01

394

Microstructural investigations of the yielding behaviour of bidisperse magnetorheological fluids  

Microsoft Academic Search

Particle level simulations were used to investigate the effects of size bidispersity and particle size ratios on the static\\u000a and yielding behaviour of magnetorheological fluids (MRF). The MRF were treated as linearly magnetisable, neutrally buoyant\\u000a particles dispersed in a viscous carrier liquid. In the quiescent mode (static structures), the bidisperse suspensions were\\u000a found to have a higher tendency to form

Charles Ekwebelam; Howard See

2009-01-01

395

Fireball Ejection from a Molten Hot Spot to Air by Localized Microwaves  

Microsoft Academic Search

A phenomenon of fireball ejection from hot spots in solid materials (silicon, germanium, glass, ceramics, basalt, etc.) to the atmosphere is presented. The hot spot is created in the substrate material by the microwave-drill mechanism [Jerby , Science 298, 587 (2002)SCIEAS0036-807510.1126\\/science.1077062]. The vaporized drop evolved from the hot spot is blown up, and forms a stable fireball buoyant in the

Vladimir Dikhtyar; Eli Jerby

2006-01-01

396

Buoyancy: Archimedes Principle  

NSDL National Science Digital Library

This site describes bouyancy (the difference between the upward and downward forces acting on the bottom and the top of an object) and the Archimedes Principle, which states that the buoyant force on a submerged object is equal to the weight of the fluid that is displaced by it. It consists of text descriptions of these principles, using the examples of metal cubes suspended in water and hot air baloons in the atmosphere. Mathematical word problems are included.

397

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

398

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

399

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

400

Characterization of Brucite and Portlandite Reactivity with Wet Supercritical CO2 by In Situ High Pressure XRD  

Microsoft Academic Search

One proposed method of controlling greenhouse gas emissions while still utilizing fossil fuels is long-term geologic storage of CO2. Injected into deep sedimentary or basalt formations, CO2 would reside as a buoyant water-containing (``wet'') supercritical fluid in contact with low permeability seals (caprock), slowly dissolving into formation waters over hundreds of years with some of the dissolved CO2 reacting with

H. T. Schaef; B. P. McGrail; K. M. Rosso

2010-01-01

401

Purification and hemagglutinating properties of egg drop syndrome 1976 virus  

Microsoft Academic Search

Summary We purified three populations of virus particles, F7, F9 and F17, with buoyant densities of 1.34, 1.33 and 1.29 g\\/ml, respectively, in CsCl equilibrium density gradients from cultures of chick embryo liver cells infected with the H-162 strain of the virus of egg drop syndrome 1976. F9 particles were infectious complete virions and most F17 particles were empty particles.

S. Takai; M. Higashihara; M. Matumoto

1984-01-01

402

What happens to minerals as they get squeezed in the mantle?  

NASA Astrophysics Data System (ADS)

The motion of the Earth's mantle is controlled in part by how mantle minerals respond to changes in temperature and pressure. The chemical and physical shifts that minerals undergo as they are heated and squeezed cause some to sink down toward the core and others to rise up toward the surface. This buoyant pressure and gravitational sinking, in turn, affect the convection of the mantle and the large-scale cycling of the Earth.

Schultz, Colin

2014-11-01

403

Interactions between soot and CH ? in a laminar boundary layer type diffusion flame in microgravity  

Microsoft Academic Search

A three-dimensional laminar non-buoyant diffusion flame was studied with the objective of improving the understanding of the soot production. The flame originated from a porous ethylene burner discharging into a laminar boundary layer. Soot volume fractions were measured using Laser-Induced Incandescence (LII), and the spontaneous emission from CH? was determined using chemiluminescence. The main parameter varied was the oxidizer flow.

A. Fuentes; G. Legros; A. Claverie; P. Joulain; J.-P. Vantelon; J. L. Torero

2007-01-01

404

A Numerical Simulation of Residual Circulation in Tampa Bay. Part II: Lagrangian Residence Time  

Microsoft Academic Search

Lagrangian retention and flushing are examined by advecting neutrally buoyant point particles within a circulation field generated\\u000a by a numerical ocean model of Tampa Bay. Large temporal variations in Lagrangian residence time are found under realistic\\u000a changes in boundary conditions. Two 90-day time periods are examined. The first (P1) is characterized by low freshwater inflow\\u000a and weak baroclinic circulation. The

Steven D. Meyers; Mark E. Luther

2008-01-01

405

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

406

Preliminary Characterization of Virus-Like Particles in a Mosquito (Aedes pseudoscutellaris) Cell Line (Mos. 61)  

Microsoft Academic Search

Summary Electron microscopic examination of an Aedes pseudoscutellaris mosquito cell line (Mos. 61) revealed the presence of a large number of virus-like particles (VLP) in the cytoplasm of approximately 10% of the cells. These particles have a diameter of 36 nm, do not contain a lipid envelope, and have a buoyant density of 1.40 g\\/ml in CsCl. VLP contain DNA

Mario Gorziglia; Ligia Botero; Francisco Gil; José Esparza

1980-01-01

407

The role of simulation prior to manufacturing in space  

NASA Technical Reports Server (NTRS)

Prior to manufacturing in space, it is useful to conduct analog experiments where possible so that problems that are apt to be encountered may be identified and planning toward their solution considered. An example is presented involving containerless casting in a near zero gravitational field using paraffin wax as the material cast surrounded by a heated fluid immiscible with the wax that renders it neutrally buoyant.

Shaw, M. C.

1983-01-01

408

Above Water: Buoyancy & Displacement  

NSDL National Science Digital Library

In an investigation called "Shape It!" learners craft tiny boats out of clay, set them afloat on water and then add weight loads to them, in order to explore: how objects stay afloat in water; what the relationship is among surface tension, buoyancy, density and displacement; and how shape, size, and type of material affect an object's ability to remain buoyant. The introductory text discusses how heavy steel ships can float on bodies of water like rivers, bays and oceans.

2013-12-18

409

The ocean-going noni, or Indian Mulberry ( Morinda citrifolia , Rubiaceae) and some of its “colorful” relatives  

Microsoft Academic Search

The genus Morinda embraces about 80 species, mostly of Old World origin.M. citrifolia L. (southern Asia Australia), noted as a source of dye and edible leaves, has buoyant seeds that float for many months and\\u000a commonly appears in the Pacific and also in tropical America where M. royoc L., piña de ratón, is indigenous, inhabits inland\\u000a hammocks and pinelands as

Julia F. Morton

1992-01-01

410

Linear Stability of Return Thermocapillary Flows under Vertical Gravity Modulation  

Microsoft Academic Search

A linear stability analysis of a time-harmonic parallel flow in a slot geometry is presented. A constant temperature gradient applied along the length of a slot with a flat free interface at the top drives a steady thermocapillary return flow. A vertical time-harmonic gravity modulation drives a time-periodic buoyant return flow. The relative strength of the two components is characterized

Vinod Suresh; George Homsy

2000-01-01

411

Stability of return thermocapillary flows under gravity modulation  

Microsoft Academic Search

The effect of gravity modulation on the stability of a time-harmonic parallel flow in a slot geometry is studied. A constant temperature gradient applied along the length of a slot with a flat free interface at the top drives a steady thermocapillary return flow. A vertical time-harmonic gravity modulation drives a time-periodic buoyant return flow. The relative strength of the

V. Suresh; G. M. Homsy

2001-01-01

412

The influence of buoyancy and drag on the dive behaviour of an Arctic seabird, the Thick-billed Murre  

Microsoft Academic Search

We used time-depth recorders to investigate the behaviour of free-ranging Thick-billed Murres (Uria lomvia L., 1758) after attaching positively (n = 9), negatively (n = 10), or neutrally (n = 9) buoyant handicaps and increasing cross- sectional area by 3% (2.8 cm2; n = 8) or 6% (5.6 cm2; n = 6). When buoyancy was altered or drag increased, murres

Kyle H. Elliott; Gail K. Davoren; Anthony J. Gaston

2007-01-01

413

Physical properties of the DNA of bacteriophage SP50  

Microsoft Academic Search

The following properties of the DNA of B. subtilis phage SP50 were established: Molecular weight (in Daltons) 102×106 (sedimentation velocity) 97×106 (viscosity) 97×106 (contour lengths of electron micrographs) Base Composition (in % GC) 41.7 (chemical analysis) 44 (melting point) 44 (buoyant density) No unusual bases were observed. The complementary strands of the DNA can be separated. The phage DNA has

N. Biswal; A. K. Kleinschmidt; H. C. Spatz; T. A. Trautner

1967-01-01

414

Isolation and characterization of a bacteriophage lytic for Desulfovibrio salexigens, a salt-requiring, sulfate-reducing bacterium  

SciTech Connect

A bacteriophage that lysed Desulfovibrio salexigens cells was isolated from marine sediments and preliminarily characterized by electron microscopy and electrophoretic analysis of structural proteins and genomic nucleic acid. The bacteriophage had an icosahedral head and a long flexible tail, and the buoyant density of the bacteriophage particles was 1.468 g/ml in cesium chloride. The particles consisted of a double-stranded DNA molecule about 33 kilobase pairs long and at least 11 structural proteins.

Kamimura, Kazuo; Araki, Michio (Government Industrial Research Institute, Chugoku (Japan))

1989-03-01

415

Jack Hills, evidence of more very old detrital zircons in Western Australia  

Microsoft Academic Search

The age of the Earth's oldest crustal minerals sets a time-limit on the earliest preservation of buoyant solid crust. The oldest mineral ages reported so far are ~4,180 Myr for detrital zircons from quartzites at Mount Narryer1, in the Yilgarn Block, Western Australia. The oldest-known intact rocks, as distinct from individual minerals, are substantially younger; they formed ~3,813-Myr ago2 in

W. Compston; R. T. Pidgeon

1986-01-01

416

Application of the E -? turbulence closure model to separated atmospheric surface-layer flows  

Microsoft Academic Search

Neutrally buoyant atmospheric surface-layer flow over a thin vertical wall has been studied using a turbulence closure scheme designed specifically to address flow problems containing high shears. The turbulent flow model consists of a general solution of the time averaged, steady state, twodimensional Navier-Stokes equations, where theE-e turbulence model has been used to close the system of equations. Model output

G. E. Liston; R. L. Brown; J. Dent

1993-01-01

417

Ultradeep continental roots and their oceanic remnants: A solution to the geochemical “mantle reservoir” problem?  

Microsoft Academic Search

High-resolution global seismic tomography (Vs) models reveal high-velocity domains beneath cratonic crust in Africa that extend to depths of 300–400 km. These high-velocity domains show a distinct contrast with the characteristics of “normal” asthenosphere and are interpreted as depleted, buoyant roots that formed in the Archean and have been metasomatised over time, but have remained attached to the overlying crust. Such

Suzanne Y. O'Reilly; Ming Zhang; William L. Griffin; Graham Begg; Jon Hronsky

2009-01-01

418

Proteus mirabilis Phage 5006M: a Physical Characterization  

Microsoft Academic Search

SUMMARY This report deals with physical characterization of the generalized transducing Proteus rnirabilis phage 5oo6M. The morphology of the phage is presented, the buoyant density was determined (i.49 r g\\/ml) and the G + C content of the phage DNA was found to be 44°\\/\\/o. The phage genome has a length of 14.8 tim and tool. wt. of 3o'7 x

G. H. J. Pretorius; W. F. Coetzee

1979-01-01

419

Flow visualization of film cooling with spanwise injection from a small array of holes and compound-angle injection from a large array  

NASA Technical Reports Server (NTRS)

Film injection from discrete holes in a smooth, flat plate was studied for two configurations: (1) spanwise injection through a four hole staggered array; and (2) compound angle injection through a 49 hole staggered array. The ratio of boundary layer thicknesses to hole diameter and the Reynolds number were typical of gas turbine film cooling applications. Streaklines showing the motion of the injected air were obtained by photographing small, neutrally buoyant, helium-filled soap bubbles that followed the flow field.

Russell, L. M.

1978-01-01

420

STS-45 MS Foale in EMU is lowered into JSC's WETF pool for underwater test  

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) and standing on a platform, is lowered into a 25 ft deep 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. SCUBA-equipped divers (swimmers) assist during the exercise.

1991-01-01

421

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

422

Dynamic Large-Eddy Simulation of Droplet Effects on a Reacting Plume in Countercurrent Configuration  

Microsoft Academic Search

The effects of evaporating droplets on a reacting plume have been investigated using large-eddy simulation (LES) with dynamic subgrid flow models. A countercurrent configuration, in which droplets are discharged downward toward a rising buoyant reacting plume, is used to mimic an idealized small-scale, water-based fire suppression system. Parametric studies have been conducted by varying the initial Stokes number (St0) or

J. Xia; K. H. Luo; H. Zhao

2011-01-01

423

Analysis and Modeling of the Turbulent Diffusion of Turbulent Kinetic Energy in Natural Convection  

Microsoft Academic Search

Buoyant flows often contain regions with unstable and stable thermal stratification from which counter gradient turbulent\\u000a fluxes are resulting, e.g. fluxes of heat or of any turbulence quantity. Basing on investigations in meteorology an improvement\\u000a in the standard gradient-diffusion model for turbulent diffusion of turbulent kinetic energy is discussed. The two closure\\u000a terms of the turbulent diffusion, the velocity-fluctuation triple

Laltu Chandra; Günther Grötzbach

2007-01-01

424

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

425

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

426

SHEAR STRENGTH MEASURING EQUIPMENT EVALUATION AT THE COLD TEST FACILITY  

Microsoft Academic Search

Retrievals under current criteria require that approximately 2,000,000 gallons of double-shell tank (DST) waste storage space not be used to prevent creating new tanks that might be susceptible to buoyant displacement gas release events (BDGRE). New criteria are being evaluated, based on actual sludge properties, to potentially show that sludge wastes do not exhibit the same BDGRE risk. Implementation of

MEACHAM JE

2009-01-01

427

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.

428

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

429

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

430

The Instability and Breakdown of a Round Variable - Jet  

Microsoft Academic Search

A study has been made of the instability and the subsequent breakdown of non-buoyant axisymmetric jets whose mean density is less than that of the ambient fluid. Two kinds of instability are observed in the near-field, depending upon the mean flow parameters. Whenever the ratio of the nozzle fluid density to ambient fluid density is greater than ~0.6, shear layer

David Mccauley Kyle

1991-01-01

431

Evolution of the effective nozzle diameter in the buoyancy free development of turbulent jets with variable density  

Microsoft Academic Search

Decay laws in the initial, non buoyant region of round, turbulent, variable density jets can be derived from dimensional\\u000a similarity considerations. This paper presents the concept of normalized effective diameter. In the case of turbulent jets\\u000a issuing into a coflow air stream (initial density ratio varying from 0.07 to 1), this quantity is experimentally derived from\\u000a measurements of mean density

J. C. Sautet; D. Stepowski

1998-01-01

432

Cartesian Diver  

NSDL National Science Digital Library

Students observe Pascal's law, Archimedes' principle and the ideal gas law as a Cartesian diver moves within a closed system. The Cartesian diver is neutrally buoyant and begins to sink when an external pressure is applied to the closed system. A basic explanation and proof of this process is provided in this activity, and supplementary ideas for more extensive demonstrations and independent group activities are presented.

National Science Foundation GK-12 and Research Experience for Teachers (RET) Programs,

433

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

434

A gender bias in the calcification response to ocean acidification  

Microsoft Academic Search

The effects of nutrients and pCO2 on zooxanthellate and azooxanthellate colonies of the temperate scleractinian coral Astrangia poculata (Ellis and Solander, 1786) were investigated at two different temperatures (16 °C and 24 °C). Corals exposed to elevated pCO2 tended to have lower relative calcification rates, as estimated from changes in buoyant weights. No nutrient effect was observed. At 16 °C,

M. Holcomb; A. L. Cohen; D. C. McCorkle

2011-01-01

435

Long-term effects of nutrient and CO 2 enrichment on the temperate coral Astrangia poculata (Ellis and Solander, 1786)  

Microsoft Academic Search

Zooxanthellate colonies of the scleractinian coral Astrangia poculata were grown under combinations of ambient and elevated nutrients (5µM NO3?, 0.3µM PO4?3, and 2nM Fe+2) and CO2 (?780ppmv) treatments for a period of 6months. Coral calcification rates, estimated from buoyant weights, were not significantly affected by moderately elevated nutrients at ambient CO2 and were negatively affected by elevated CO2 at ambient

Michael Holcomb; Daniel C. McCorkle; Anne L. Cohen

2010-01-01

436

Finite Time Blow Up for a 1D Model of 2D Boussinesq System  

NASA Astrophysics Data System (ADS)

The 2D conservative Boussinesq system describes inviscid, incompressible, buoyant fluid flow in a gravity field. The possibility of finite time blow up for solutions of this system is a classical problem of mathematical hydrodynamics. We consider a 1D model of the 2D Boussinesq system motivated by a particular finite time blow up scenario. We prove that finite time blow up is possible for the solutions to the model system.

Choi, Kyudong; Kiselev, Alexander; Yao, Yao

2014-08-01

437

Effect of Gravity on the Near Field Flow Structure of Helium Jet in Air  

NASA Technical Reports Server (NTRS)

Experiments have shown that a low-density jet injected into a high-density surrounding medium undergoes periodic oscillations in the near field. Although the flow oscillations in these jets at Richardson numbers about unity are attributed to the buoyancy, the direct physical evidence has not been acquired in the experiments. If the instability were indeed caused by buoyancy, the near-field flow structure would undergo drastic changes upon removal of gravity in the microgravity environment. The present study was conducted to investigate this effect by simulating microgravity environment in the 2.2-second drop tower at the NASA Glenn Research Center. The non-intrusive, rainbow schlieren deflectometry technique was used for quantitative measurements of helium concentrations in buoyant and non-buoyant jets. Results in a steady jet show that the radial growth of the jet shear layer in Earth gravity is hindered by the buoyant acceleration. The jet in microgravity was 30 to 70 percent wider than that in Earth gravity. The microgravity jet showed typical growth of a constant density jet shear layer. In case of a self-excited helium jet in Earth gravity, the flow oscillations continued as the jet flow adjusted to microgravity conditions in the drop tower. The flow oscillations were however not present at the end of the drop when steady microgravity conditions were reached.

Agrawal, Ajay K.; Parthasarathy, Ramkumar; Griffin, DeVon

2002-01-01

438

Differential force balances during levitation  

NASA Astrophysics Data System (ADS)

The simplest arithmetic of inertial, buoyant, magnetic and electrokinetic levitation is explored in the context of a model living system with “acceleration-sensitive structures” in which motion, if allowed, produces a biological effect. The simple model is a finite-sized object enclosed within another finite-sized object suspended in an outer fluid (liquid or vapor) medium. The inner object has density and electrical and magnetic properties quantitatively different from those of the outer object and the medium. In inertial levitation (“weightlessness”) inertial accelerations are balanced, and the forces due to them are canceled in accordance with Newton’s third law. In the presence of inertial acceleration (gravity, centrifugal) motionlessness depends on a balance between the levitating force and the inertial force. If the inner and outer objects differ in density one or the other will be subjected to an unbalanced force when one object is levitated by any other force (buoyant, magnetic, electrokinetic). The requirements for motionlessness of the internal object in the presence of a levitating force are equality of density in the case of buoyant levitation, equality of magnetic susceptibility in the case of magnetic levitation, and equality of zeta potential and dielectric constant in the case of electrokinetic levitation. Examples of internal “acceleration-sensitive structures” are cellular organelles and the organs of advanced plants and animals. For these structures fundamental physical data are important in the interpretation of the effects of forces used for levitation.

Todd, Paul

439

Physical and morphological characteristics of eucaryotic ribosomes and lipopolysaccharide complexes.  

PubMed

Lipopolysaccharides (LPS) from Pasteurella multocida or Brucella abortus were complexed with Aspergillus fumigatus ribosomes by mixing and fixation for 3 days in 3.8% formaldehyde. To investigate the nature of their physical association, ribosomes, LPS, and ribosome-LPS complexes were (i) centrifuged in CsCl gradients to determine buoyant densities, (ii) examined by electron microscopy, and (iii) monitored by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Ribosomes were found to bind to LPS from either P. multocida or B. abortus, producing complexes with densities of 1.45 to 1.50 g/ml. The buoyant density of the fixed ribosomes was 1.54 g/ml, and the buoyant densities of the fixed P. multocida and B. abortus LPS were 1.41 and 1.35 g/ml, respectively. Electron microscopy showed that formaldehyde-fixed ribosomes were attached to the LPS. Complexing of ribosomes to LPS may be of importance as a potentiator or carrier for experimental subunit vaccines. PMID:3114145

Phillips, M; Brogden, K A

1987-09-01

440

Device for accurately measuring mass flow of gases  

DOEpatents

A device for measuring mass flow of gases which utilizes a substantially buoyant pressure vessel suspended within a fluid/liquid in an enclosure is disclosed. The pressure vessel is connected to a weighing device for continuously determining weight change of the vessel as a function of the amount of gas within the pressure vessel. In the preferred embodiment, this pressure vessel is formed from inner and outer right circular cylindrical hulls, with a volume between the hulls being vented to the atmosphere external the enclosure. The fluid/liquid, normally in the form of water typically with an added detergent, is contained within an enclosure with the fluid/liquid being at a level such that the pressure vessel is suspended beneath this level but above a bottom of the enclosure. The buoyant pressure vessel can be interconnected with selected valves to an auxiliary pressure vessel so that initial flow can be established to or from the auxiliary pressure vessel prior to flow to or from the buoyant pressure vessel. 5 figs.

Hylton, J.O.; Remenyik, C.J.

1994-08-09

441

Analytical Theory of the Destruction Terms in Dissipation Rate Transport Equations  

NASA Technical Reports Server (NTRS)

Modeled dissipation rate transport equations are often derived by invoking various hypotheses to close correlations in the corresponding exact equations. D. C. Leslie suggested that these models might be derived instead from Kraichnan's wavenumber space integrals for inertial range transport power. This suggestion is applied to the destruction terms in the dissipation rate equations for incompressible turbulence, buoyant turbulence, rotating incompressible turbulence, and rotating buoyant turbulence. Model constants like C(epsilon 2) are expressed as integrals; convergence of these integrals implies the absence of Reynolds number dependence in the corresponding destruction term. The dependence of C(epsilon 2) on rotation rate emerges naturally; sensitization of the modeled dissipation rate equation to rotation is not required. A buoyancy related effect which is absent in the exact transport equation for temperature variance dissipation, but which sometimes improves computational predictions, also arises naturally. Both the presence of this effect and the appropriate time scale in the modeled transport equation depend on whether Bolgiano or Kolmogorov inertial range scaling applies. A simple application of these methods leads to a preliminary, dissipation rate equation for rotating buoyant turbulence.

Rubinstein, Robert; Zhou, Ye

1996-01-01

442

Buoyancy Effects on the Development of the Leading Vortex Ring in a Starting Jet  

NASA Astrophysics Data System (ADS)

The initial development of negatively buoyant jets has been investigated experimental and numerically, more specifically the role played by gravity in the development of the leading vortex ring. A classical piston-cylinder arrangement has been used to produce the negatively buoyant jets. Under the experimental conditions considered in this work, the Froude number, Fr, which compares the jet momentum and the buoyancy flux is the most important parameter characterizing the dynamics of the flow. When the value of this parameter is sufficiently small the initial vortex ring generated at the start of the motion is pushed upwards by the gravity force before it can entrain enough vorticity to acquire a self induced velocity. However when the Froude number exceeds a critical value, Frc ˜ 1, the vortex ring can travel downwards and entrainins vorticity from the trailing jet during a longer time. Total and vortex circulation, as well as the trajectory of the leading vortex have been measured to clarify the effect of gravity on the distribution of vorticity during the initial development of negatively buoyant jets.

Marugan-Cruz, Carolina; Rodriguez-Rodriguez, Javier; Martinez-Bazan, Carlos

2008-11-01

443

Convective Heat Transfer Scaling of Ignition Delay and Burning Rate with Heat Flux and Stretch Rate in the Equivalent Low Stretch Apparatus  

NASA Technical Reports Server (NTRS)

To better evaluate the buoyant contributions to the convective cooling (or heating) inherent in normal-gravity material flammability test methods, we derive a convective heat transfer correlation that can be used to account for the forced convective stretch effects on the net radiant heat flux for both ignition delay time and burning rate. The Equivalent Low Stretch Apparatus (ELSA) uses an inverted cone heater to minimize buoyant effects while at the same time providing a forced stagnation flow on the sample, which ignites and burns as a ceiling fire. Ignition delay and burning rate data is correlated with incident heat flux and convective heat transfer and compared to results from other test methods and fuel geometries using similarity to determine the equivalent stretch rates and thus convective cooling (or heating) rates for those geometries. With this correlation methodology, buoyant effects inherent in normal gravity material flammability test methods can be estimated, to better apply the test results to low stretch environments relevant to spacecraft material selection.

Olson, Sandra

2011-01-01

444

Spreading continents kick-started plate tectonics.  

PubMed

Stresses acting on cold, thick and negatively buoyant oceanic lithosphere are thought to be crucial to the initiation of subduction and the operation of plate tectonics, which characterizes the present-day geodynamics of the Earth. Because the Earth's interior was hotter in the Archaean eon, the oceanic crust may have been thicker, thereby making the oceanic lithosphere more buoyant than at present, and whether subduction and plate tectonics occurred during this time is ambiguous, both in the geological record and in geodynamic models. Here we show that because the oceanic crust was thick and buoyant, early continents may have produced intra-lithospheric gravitational stresses large enough to drive their gravitational spreading, to initiate subduction at their margins and to trigger episodes of subduction. Our model predicts the co-occurrence of deep to progressively shallower mafic volcanics and arc magmatism within continents in a self-consistent geodynamic framework, explaining the enigmatic multimodal volcanism and tectonic record of Archaean cratons. Moreover, our model predicts a petrological stratification and tectonic structure of the sub-continental lithospheric mantle, two predictions that are consistent with xenolith and seismic studies, respectively, and consistent with the existence of a mid-lithospheric seismic discontinuity. The slow gravitational collapse of early continents could have kick-started transient episodes of plate tectonics until, as the Earth's interior cooled and oceanic lithosphere became heavier, plate tectonics became self-sustaining. PMID:25230662

Rey, Patrice F; Coltice, Nicolas; Flament, Nicolas

2014-09-18

445

HGSYSTEMUF6. Model for Simulating Dispersion due to Atmospheric Release of UF6  

SciTech Connect

HGSYSTEMUF6 is a suite of models designed for use in estimating consequences associated with accidental, atmospheric release of Uranium Hexafluoride (UF6) and its reaction products, namely Hydrogen Fluoride (HF), and other non-reactive contaminants which are either negatively, neutrally, or positively buoyant. It is based on HGSYSTEM Version 3.0 of Shell Research LTD., and contains specific algorithms for the treatment of UF6 chemistry and thermodynamics. HGSYSTEMUF6 contains algorithms for the treatment of dense gases, dry and wet deposition, effects due to the presence of buildings (canyon and wake), plume lift-off, and the effects of complex terrain. The models components of the suite include (1) AEROPLUME/RK, used to model near-field dispersion from pressurized two-phase jet releases of UF6 and its reaction products, (2) HEGADAS/UF6 for simulating dense, ground based release of UF6, (3) PGPLUME for simulation of passive, neutrally buoyant plumes (4) UF6Mixer for modeling warm, potentially reactive, ground-level releases of UF6 from buildings, and (5) WAKE, used to model elevated and ground-level releases into building wake cavities of non-reactive plumes that are either neutrally or positively buoyant.

Hanna, G [George Mason University, (United States); Chang, J.C. [Earthtech, Inc., (United States); Zhang, J.X. [BlazeTech Corporation, (United States); Bloom, S.G. [Lockheed Martin Energy Systems, Oak Ridge, TN (United States); Goode, W.D. Jr [Bechtel Jacobs Company, Oak Ridge, TN (United States); Lombardi, D.A. [JBF Associates, (United States); Yambert, M.W. [LMERC, Oak Ridge, TN (United States)

1998-08-01

446

Flux Emergence in a Magnetized Convection Zone  

NASA Astrophysics Data System (ADS)

We study the influence of a dynamo magnetic field on the buoyant rise and emergence of twisted magnetic flux ropes and their influence on the global external magnetic field. We ran three-dimensional MHD numerical simulations using the ASH code (anelastic spherical harmonics) and analyzed the dynamical evolution of such buoyant flux ropes from the bottom of the convection zone until the post-emergence phases. The global nature of this model can only very crudely and inaccurately represent the local dynamics of the buoyant rise of the implanted magnetic structure, but nonetheless allows us to study the influence of global effects, such as self-consistently generated differential rotation and meridional circulation, and of Coriolis forces. Although motivated by the solar context, this model cannot be thought of as a realistic model of the rise of magnetic structures and their emergence in the Sun, where the local dynamics are completely different. The properties of initial phases of the buoyant rise are determined essentially by the flux-rope's properties and the convective flows and consequently are in good agreement with previous studies. However, the effects of the interaction of the background dynamo field become increasingly strong as the flux ropes evolve. During the buoyant rise across the convection zone, the flux-rope's magnetic field strength scales as Bvprop??, with ? <~ 1. An increase of radial velocity, density, and current density is observed to precede flux emergence at all longitudes. The geometry, latitude, and relative orientation of the flux ropes with respect to the background magnetic field influences the resulting rise speeds, zonal flow amplitudes (which develop within the flux ropes), and the corresponding surface signatures. This influences the morphology, duration and amplitude of the surface shearing, and the Poynting flux associated with magnetic flux-rope emergence. The emerged magnetic flux influences the system's global polarity, leading in some cases to a polarity reversal while inhibiting the background dynamo from doing so in others. The emerged magnetic flux is slowly advected poleward while being diffused and assimilated by the background dynamo field.

Pinto, R. F.; Brun, A. S.

2013-07-01

447

Coupled cycling of Fe and organic carbon in submarine hydrothermal systems: Modelling approach  

NASA Astrophysics Data System (ADS)

It has been recently proposed that hydrothermal plumes may be a significant source of dissolved Fe to the oceans. In order to assess this proposal, we investigated the fate of dissolved Fe released from hydrothermal systems to the overlying ocean using an approach that combined modelling and field values. We based our work on a consensus conceptual model developed by members of SCOR-InterRidge Working Group 135. The model was both complex enough to capture the main processes of dissolved Fe released from hydrothermal systems and chemical transformation in the hydrothermal plume, and simple enough to be parameterized with existing field data. It included the following flows: Fe, water and heat in the high temperature vent fluids, in the fluids diffusing around the vent, and in the entrained seawater in the buoyant plume; Fe precipitation in polymetallic sulphides near the vent; transport of Fe in the non-buoyant plume, and both its precipitation in particles onto the sea bottom away from the vent and dissolution into deep-sea waters. In other words, there were three Fe input flows into the buoyant hydrothermal plume (vent-fluids; entrained diffuse flow; entrained seawater) and three Fe output flows (sedimentation from the buoyant plume as polymetallic sulfides; sedimentation from the non-buoyant plume in particulate form; export to the deep ocean in dissolved or nanoparticulate form). The output flows balanced the input flows. We transformed the conceptual model into equations, and parameterized these with field data. To do so, we assumed that all hydrothermal systems, globally, can be represented by the circumstances that prevail at the EPR 9°50'N hydrothermal field, although we knew this assumption not to be accurate. We nevertheless achieved, by following this approach, two important goals, i.e. we could assemble into a coherent framework, for the first time, several discrete data sets acquired independently over decades of field work, and we could obtain model results that were consistent with recent field observations. We used our model to explore scenarios of Fe emissions and transformations under various constraints. The modelling exercises indicated that the provision of significant amounts of dissolved Fe to the oceans by hydrothermal plumes was consistent with realistic model parameters. This supported the proposition that hydrothermal systems play significant roles in the global biogeochemical Fe cycle.

Legendre, Louis; German, Christopher R.; Sander, Sylvia G.; Niquil, Nathalie

2014-05-01

448

FLUX EMERGENCE IN A MAGNETIZED CONVECTION ZONE  

SciTech Connect

We study the influence of a dynamo magnetic field on the buoyant rise and emergence of twisted magnetic flux ropes and their influence on the global external magnetic field. We ran three-dimensional MHD numerical simulations using the ASH code (anelastic spherical harmonics) and analyzed the dynamical evolution of such buoyant flux ropes from the bottom of the convection zone until the post-emergence phases. The global nature of this model can only very crudely and inaccurately represent the local dynamics of the buoyant rise of the implanted magnetic structure, but nonetheless allows us to study the influence of global effects, such as self-consistently generated differential rotation and meridional circulation, and of Coriolis forces. Although motivated by the solar context, this model cannot be thought of as a realistic model of the rise of magnetic structures and their emergence in the Sun, where the local dynamics are completely different. The properties of initial phases of the buoyant rise are determined essentially by the flux-rope's properties and the convective flows and consequently are in good agreement with previous studies. However, the effects of the interaction of the background dynamo field become increasingly strong as the flux ropes evolve. During the buoyant rise across the convection zone, the flux-rope's magnetic field strength scales as B{proportional_to}{rho}{sup {alpha}}, with {alpha} {approx}< 1. An increase of radial velocity, density, and current density is observed to precede flux emergence at all longitudes. The geometry, latitude, and relative orientation of the flux ropes with respect to the background magnetic field influences the resulting rise speeds, zonal flow amplitudes (which develop within the flux ropes), and the corresponding surface signatures. This influences the morphology, duration and amplitude of the surface shearing, and the Poynting flux associated with magnetic flux-rope emergence. The emerged magnetic flux influences the system's global polarity, leading in some cases to a polarity reversal while inhibiting the background dynamo from doing so in others. The emerged magnetic flux is slowly advected poleward while being diffused and assimilated by the background dynamo field.

Pinto, R. F.; Brun, A. S., E-mail: rui.pinto@cea.fr [Laboratoire AIM Paris-Saclay, CEA/Irfu Universite Paris-Diderot CNRS/INSU, F-91191 Gif-sur-Yvette (France)

2013-07-20

449

CO 2 and the eruptibility of picrite and komatiite  

NASA Astrophysics Data System (ADS)

A tholeiitic picrite erupted from the summit region of Kilauea volcano, Hawaii in 1959. Work by Wright, Helz and Schwindinger and Anderson shows that the 1959 magma was a mixture of new, hot, MgO-rich magma that rose through and mixed with cooler stored magma causing crystallization of abundant olivine phenocrysts. CO 2 dissolved in melt inclusions in olivine phenocrysts from the eruption of 1959 reveals that most of the olivines grew at pressures less than 1 kbar (100 MPa). Therefore, the new magma probably was buoyant relative to stored magma at 1 kbar. The MgO-rich magma is characterized by a relatively dense melt and could only be buoyant, if it contained more gas than the stored magma. Compositions of inclusions indicate that the gas was rich in CO 2. Because gas is highly compressible, the mass fraction of CO 2-rich gas that is required for magma buoyancy increases at greater pressures. A critical pressure is that at which gassy, MgO-rich, parental magma has the same density as stored magma. If the parental magma invades stored magma at a sufficiently great pressure, it will be negatively buoyant and its consequent descent will inhibit its eruption. Kilauea's degassing suggests that Kilauean parental basalt may contain about 0.3 wt.% CO 2. Gassy picritic magma (liquid with 15 wt.% MgO + 0.3 bulk wt.% CO 2) is buoyant with respect to degassed tholeiitic basalt (8 wt.% MgO liquid) at pressures less than about 2 kbar. For Kilauea's 1959 picrite the inferred 1 kbar pressure at which new MgO-rich magma invaded stored magma is consistent with its buoyant rise to the surface and eruption. Although the parental magma of Kilauea is considered to have a picritic composition, erupted picrite is uncommon, particularly in Kilauean summit eruptions. Beneath Kilauea's summit a reservoir of intermittent magma storage extends downward to about 10 km corresponding to a pressure of about 2.7 kbar. Ryan has argued that the base of the magma storage reservoir is controlled by the transition region that separates porosity elimination from mineral compression. The rarity of erupted picrite as a lava on Kilauea probably reflects a combination of two factors: (1) parental Kilauean picritic magma probably has a CO 2 content less than about 0.3 wt.%; (2) most parental picritic magma enters the reservoir near its base where the pressure is sufficiently high to result in the bulk density of parental magma being greater than that of stored magma. The new, 1959 picritic magma ascended through an unusual route and probably first encountered stored magma at an unusually shallow level where the new magma was relatively buoyant. Because of the role of porosity, the base of subvolcanic magma storage reservoirs is dependent only on pressure and rock strength. Therefore, the base of reservoirs of stored magma beneath active volcanoes likely occurred between 2 and 3 kbar during ancient as well as modern times. Because gas-free komatiitic magma is relatively dense, it too is expected to be trapped beneath stored magma. Komatiitic magmas containing more than about 0.6 wt.% of CO 2, however, would be buoyant relative to stored, degassed basalt melt even at the base of magma storage reservoirs. The common occurrence of komatiitic lavas in Archaean times may reflect a greater CO 2 content of mantle-derived Archean parental magmas.

Anderson, A. T.

1995-01-01

450

On the influence of eddy aging processes on colliding East Australian Current warm core eddies  

NASA Astrophysics Data System (ADS)

DieCAST, a 4th-order-accurate numerical model of the East Australian Current (EAC), having low total dissipation and numerical dispersion, is used to study the kinematics and dynamics of the collisions and mergings of previously pinched-off EAC anticyclonic eddies. Earlier studies show that eddies which extrude and reside for months to the south of the EAC retroflection region east of Sydney, a) naturally tend to become more barotropic and less buoyant under quasi-geostrophic dynamics with near-surface energy propagating to deeper levels; and b) by having been modified through air-sea exchange in cooler, more southern latitudes (especially after a winter season) are even less buoyant and more nearly barotropic. During merging, less dense surface water from younger eddies arriving from the north has been observed by Cresswell to override the less buoyant water of the older eddies. This process is being theoretically and numerically investigated. The high-resolution model is nested in a Southwest Pacific Ocean regional model that provides realistic upstream conditions for the East Australian Current. In order to address the nature and function of frontal eddies and other small-scale features which form around the edges of the main anticyclones during water-mass transformations, the model uses physically-based surface heat fluxes and E-P. These are derived using a new method that does not damp small-scale surface features by restoring to climatology, while leading to (by construction) the ensemble-mean annual cycle while converging to the observed annual surface cycle climatology as time progresses.

Bowman, M.; Dietrich, D.; Sanderson, B.

2003-04-01

451

Late Pleistocene crustal uplift and gravity anomaly in the eastern part of Kyushu, Japan, and its geophysical implications  

NASA Astrophysics Data System (ADS)

The Miyazaki Plain, eastern part of Kyushu, Japan, is characterized by both significant negative gravity anomalies and aseismic crustal uplifting (˜1 mm/year) in the Late Pleistocene and Holocene. We examine the relationship between these two phenomena, which may provide important constraints on the interaction between the collision and/or subduction of the Kyushu-Palau Ridge and the forearc. We estimate the mass deficiency below 11-km depth by using the gravity anomalies and P-wave velocity structure of the upper crust. The onset of the load accumulation, 0.5-0.4 Ma, is inferred from the movement of the fluvial terraces considering the tephrochronology. The loading history is assumed to be a linear function of time. We evaluate the crustal rebound by assuming a viscoelastic plate deformation with an underplating load existing at 20- or 30-km depth. The predicted crustal movement for models with a lithospheric (crustal) viscosity of 10 23-10 24 Pa s can explain the observed altitudes of the shoreline of the marine terraces formed at the Last Interglacial of about 125 kyr BP and the middle Holocene of 5-6 kyr BP. Although we cannot restrict the origin of the buoyant body, the subduction of the Kyushu-Palau Ridge, remnant arc associated with back-arc opening of the Shikoku Basin, may be related to the buoyancy for the uplifting region examined here. On the other hand, the buoyant body off the Miyazaki Plain probably plays an important role in the interaction between the subducting oceanic slab and the overriding forearc crust. Thus, the observed lateral variation of the interplate coupling on the convergent boundary along the Nankai Trough may be attributed to the existence of the buoyant body.

Nakada, M.; Tahara, M.; Shimizu, H.; Nagaoka, S.; Uehira, K.; Suzuki, S.

2002-07-01

452

Suppression of Soot Formation and Shapes of Laminar Jet Diffusion Flames  

NASA Technical Reports Server (NTRS)

Laminar nonpremixed (diffusion) flames are of interest because they provide model flame systems that are far more tractable for analysis and experiments than practical turbulent flames. In addition, many properties of laminar diffusion flames are directly relevant to turbulent diffusion flames using laminar flamelet concepts. Finally, laminar diffusion flame shapes have been of interest since the classical study of Burke and Schumann because they involve a simple nonintrusive measurement that is convenient for evaluating flame shape predictions. Motivated by these observations, the shapes of round hydrocarbon-fueled laminar jet diffusion flames were considered, emphasizing conditions where effects of buoyancy are small because most practical flames are not buoyant. Earlier studies of shapes of hydrocarbon-fueled nonbuoyant laminar jet diffusion flames considered combustion in still air and have shown that flames at the laminar smoke point are roughly twice as long as corresponding soot-free (blue) flames and have developed simple ways to estimate their shapes. Corresponding studies of hydrocarbon-fueled weakly-buoyant laminar jet diffusion flames in coflowing air have also been reported. These studies were limited to soot-containing flames at laminar smoke point conditions and also developed simple ways to estimate their shapes but the behavior of corresponding soot-free flames has not been addressed. This is unfortunate because ways of selecting flame flow properties to reduce soot concentrations are of great interest; in addition, soot-free flames are fundamentally important because they are much more computationally tractable than corresponding soot-containing flames. Thus, the objectives of the present investigation were to observe the shapes of weakly-buoyant laminar jet diffusion flames at both soot-free and smoke point conditions and to use the results to evaluate simplified flame shape models. The present discussion is brief.

Xu, F.; Dai, Z.; Faeth, G. M.

2001-01-01

453

Free convection in the Matian atmosphere  

NASA Technical Reports Server (NTRS)

The 'free convective' regime for the Martian atmospheric boundary layer (ABL) was investigated. This state occurs when the mean windspeed at the top of the ABL drops below some critical value U(sub c) and positive buoyant forces are present. Such forces can arise either from vertical temperature or water vapor gradients across the atmospheric surface layer. During free convection, buoyant forces drive narrow plumes that ascend to the inversion height with a return circulation consisting of broad slower-moving downdraughts. Horizontal pressure, temperature, windspeed, and water vapor fluctuations resulting form this circulation pattern can be quite large adjacent to the ground (within the surface layer). The local turbulent fluctuations cause non-zero mean surface stresses, sensible heat fluxes, and latent heat fluxes, even when the mean regional windspeed is zero. Although motions above the surface layer are insensitive to the nature of the surface, the sensible and latent heat fluxes are primarily controlled by processes within the interfacial sublayer immediately adjacent to the ground during free convection. Thus the distinction between aerodynamically smooth and rough airflow within the interfacial sublayer is more important than for the more typical situation where the mean regional windspeed is greater than U(sub c). Buoyant forces associated with water vapor gradients are particularly large on Mars at low pressures and high temperatures when the surface relative humidity is 100 percent, enhancing the likelihood of free convection under these conditions. On this basis, Ingersol postulated the evaporative heat losses from an icy surface on Mars at 237 K and current pressures would exceed the available net radiative flux at the surface, thus prohibiting ice from melting at low atmospheric pressures. Schumann has developed equations describing the horizontal fluctuations and mean vertical gradients occurring during free convection. Schumann's model was generalized to include convection driven by water vapor gradients and to include the effects of circulation above both aerodynamically smooth and rough surfaces.

Clow, G. D.; Haberle, R. M.

1990-01-01

454

ON THE IMPACT OF THREE DIMENSIONS IN SIMULATIONS OF NEUTRINO-DRIVEN CORE-COLLAPSE SUPERNOVA EXPLOSIONS  

SciTech Connect

We present one-dimensional (1D), two-dimensional (2D), and three-dimensional (3D) hydrodynamical simulations of core-collapse supernovae including a parameterized neutrino heating and cooling scheme in order to investigate the critical core neutrino luminosity (L{sub crit}) required for explosion. In contrast to some previous works, we find that 3D simulations explode later than 2D simulations, and that L{sub crit} at fixed mass accretion rate is somewhat higher in three dimensions than in two dimensions. We find, however, that in two dimensions L{sub crit} increases as the numerical resolution of the simulation increases. In contrast to some previous works, we argue that the average entropy of the gain region is in fact not a good indicator of explosion but is rather a reflection of the greater mass in the gain region in two dimensions. We compare our simulations to semi-analytic explosion criteria and examine the nature of the convective motions in two dimensions and three dimensions. We discuss the balance between neutrino-driven buoyancy and drag forces. In particular, we show that the drag force will be proportional to a buoyant plume's surface area while the buoyant force is proportional to a plume's volume and, therefore, plumes with greater volume-to-surface-area ratios will rise more quickly. We show that buoyant plumes in two dimensions are inherently larger, with greater volume-to-surface-area ratios, than plumes in three dimensions. In the scenario that the supernova shock expansion is dominated by neutrino-driven buoyancy, this balance between buoyancy and drag forces may explain why 3D simulations explode later than 2D simulations and why L{sub crit} increases with resolution. Finally, we provide a comparison of our results with other calculations in the literature.

Couch, Sean M., E-mail: smc@flash.uchicago.edu [Flash Center for Computational Science, Department of Astronomy and Astrophysics, University of Chicago, Chicago, IL 60637 (United States)

2013-09-20

455

Observations of solitary waves in a viscously deformable pipe  

NASA Astrophysics Data System (ADS)

We have made simple observations of the ascent of a buoyant fluid through a pipe formed in a denser and more viscous fluid that can deform viscously and allow the pipe radius to change. There is no wall between the two fluids, and the Reynolds number is small in both fluids. If the buoyant fluid is supplied at a uniform rate, the system exhibits uniform Poiseuille flow. The response of the system to fluctuations in the rate of supply of the buoyant fluid is to form local maxima in the pipe radius that ascend as solitary waves. Larger-amplitude waves can catch up and collide with smaller waves and, to a good approximation, both waves recover their original form and amplitude after such a collision. Periodic wavetrains are formed when the supply of fluid to the pipe is increased and sustained at a higher rate. These observations gain significance because the system is analogous to that of one-dimensional buoyancy-driven porous flow in a viscous matrix. The experiment may be regarded as a laboratory analogue for studying some aspects of the equations governing porous flow. The observed behaviour is consistent with recent theoretical and computational studies1,2, which have focused on the problem of magma migration in the Earth. The behaviour we observe will, however, arise in other systems governed by the same mechanics. The existence of solitary waves in such systems means that the responses to transient changes in the porosity or the supply of fluid could be long-lived.

Scott, David R.; Stevenson, David J.; Whitehead, John A.

1986-02-01

456

Novel B melatonin-loaded chitosan microcapsules: in vitro characterization and antiapoptosis efficacy for aflatoxin B1-induced apoptosis in rat liver.  

PubMed

The aim of this study was to prepare buoyant (B) melatonin (MT)-loaded chitosan microcapsules having favourable sustained release characteristics (in simulated gastric fluid (SGF), pH 1.2) in comparison with non-buoyant (NB) chitosan particles. The new buoyant microcapsules were prepared by the ionotropic gelation method using sodium lauryl sulfate (NaLS) for coagulation. The microcapsule characteristics were affected by the initial drug and NaLS concentrations, as well as the presence of sodium dioctyl sulfosuccinate (DOS) or pectin with NaLS in the external phase. In general, spherical microcapsules with 36.90-56.23% encapsulation efficiencies, hollow core and satisfactory release properties were produced. The best sustained release profiles (t(50%): 5h) with near zero-order kinetics were observed with the higher theoretical payload microcapsules prepared with both NaLS and DOS in a 1:2 ratio. In vivo studies were also carried out to exploit the protective effect of the MT-loaded NaLS-DOS microcapsules against aflatoxin B1 (AFB1)-induced toxicity (liver apoptosis) in male rats. The results implied that apoptotic rate was significantly reduced when MT or its microcapsules formulation was co-administered with AFB1. The levels of the oxidative stress indices (malondialdehyde (MDA), a lipid peroxidation product and nitric oxide (NO)) in liver tissues were significantly reduced, while the levels of the hepatic antioxidants (glutathione (GSH) and zinc (Zn), as well as the enzyme activities of glutathione reductase (GR), glutathione peroxidase (GSPx) and glutathione-S-transferase (GST)) which act as antiapoptosis were significantly increased as compared to AFB1 group (without MT). MT microcapsules appeared more effective in reduction of apoptotic rate than free MT as indicated by the decline of caspase-3 activities (an apoptotic marker) and confirmed by histopathology. PMID:12818806

El-Gibaly, I; Meki, A M A; Abdel-Ghaffar, S K

2003-07-01

457

Deep-water microbialites of the Mesoproterozoic Dismal Lakes Group: microbial growth, lithification, and implications for coniform stromatolites.  

PubMed

Offshore facies of the Mesoproterozoic Sulky Formation, Dismal Lakes Group, arctic Canada, preserve microbialites with unusual morphology. These microbialites grew in water depths greater than several tens of meters and correlate with high-relief conical stromatolites of the more proximal September Lake reef complex. The gross morphology of these microbial facies consists of ridge-like vertical supports draped by concave-upward, subhorizontal elements, resulting in tent-shaped cuspate microbialites with substantial primary void space. Morphological and petrographic analyses suggest a model wherein penecontemporaneous upward growth of ridge elements and development of subhorizontal draping elements initially resulted in a buoyantly supported, unlithified microbial form. Lithification began via precipitation within organic elements during microbialite growth. Mineralization either stabilized or facilitated collapse of initially neutrally buoyant microbialite forms. Microbial structures and breccias were then further stabilized by precipitation of marine herringbone cement. During late-stage diagenesis, remaining void space was occluded by ferroan dolomite cement. Cuspate microbialites are most similar to those found in offshore facies of Neoarchean carbonate platforms and to unlithified, buoyantly supported microbial mats in modern ice-covered Antarctic lakes. We suggest that such unusual microbialite morphologies are a product of the interaction between motile and non-motile communities under nutrient-limiting conditions, followed by early lithification, which served to preserve the resultant microbial form. The presence of marine herringbone cement, commonly associated with high dissolved inorganic carbon (DIC), low O2 conditions, also suggests growth in association with reducing environments at or near the seafloor or in conjunction with a geochemical interface. Predominance of coniform stromatolite forms in the Proterozoic-across a variety of depositional environments-may thus reflect a combination of heterogeneous nutrient distribution, potentially driven by variable redox conditions, and an elevated carbonate saturation state, which permits preservation of these unusual microbialite forms. PMID:25354129

Bartley, J K; Kah, L C; Frank, T D; Lyons, T W

2015-01-01

458

THE EFFECT OF HEPATIC LIPASE ON CORONARY ARTERY DISEASE IN HUMANS IS INFLUENCED BY THE UNDERLYING LIPOPROTEIN PHENOTYPE  

PubMed Central

Increased or decreased hepatic lipase (HL) activity has been associated with coronary artery disease (CAD). This is consistent with the findings that gene variants that influence HL activity were associated with increased CAD risk in some population studies but not in others. In this review, we will explain the conditions that influence the effects of HL on CAD. Increased HL is associated with smaller and denser LDL (sdLDL) and HDL (HDL3) particles, while decreased HL is associated with larger and more buoyant LDL and HDL particles. The effect of HL activity on CAD risk is dependent on the underlying lipoprotein phenotype or disorder. Central obesity with hypertriglyceridemia (HTG) is associated with high HL activity that leads to the formation of sdLDL that is proatherogenic. In the absence of HTG, where large buoyant cholesteryl ester-enriched LDL is prominent, elevation of HL does not raise the risk for CAD. In HTG patients, drug therapy that decreases HL activity selectively decreases sdLDL particles, an antiatherogenic effect. Drug therapy that raises HDL2 cholesterol has not decreased the risk for CAD. In trials where inhibition of cholesterol ester transfer protein (CETP) or HL occurs, the increase in HDL2 most likely is due to inhibition of catabolism of HDL2 and impairment of reverse cholesterol transport (RCT). In patients with isolated hypercholesterolemia, but with normal triglyceride levels and big-buoyant LDL particles, an increase in HL activity is beneficial; possibly because it increases RCT. Drugs that lower HL activity might decrease the risk for CAD only in hypertriglyceridemic patients with sdLDL by selectively clearing sdLDL particles from plasma, which would override the potentially pro-atherogenic effect on RCT. PMID:21986251

BRUNZELL, JOHN D.; ZAMBON, ALBERTO; DEEB, SAMIR S.

2012-01-01

459

Convection in a two-layer fluid system  

NASA Technical Reports Server (NTRS)

Experimental results are presented, and preliminary computations are performed on a system of two immiscible liquid layers with a temperature gradient applied parallel to the interface. The experiments reflect the combined contribution of buoyancy and surface-tension-induced (Marangoni) convection. It is concluded that buoyancy effects appear to be dominant and mask any surface-tension-induced convection present. Numerical computations show significant modification of pure buoyant convection by surface-tension gradients. The results are of interest in connection with the liquid encapsulation of GaAs melts in a microgravity environment.

Prakash, A.; Peltier, L. J.; Fujita, D.; Koster, J.; Biringen, S.

1991-01-01

460

Flux emergence in a magnetized convection zone  

NASA Astrophysics Data System (ADS)

We study the influence of a dynamo magnetic field on the buoyant rise and emergence of twisted magnetic flux-ropes, and their influence on the global external magnetic field. We ran three-dimensional MHD numerical simulations using the ASH code and analysed the dynamical evolution of such buoyant flux-ropes from the bottom of the convection zone until the post-emergence phases. The actual flux-emergence episode is preceded by a localised increase of radial velocity, density and current density at the top of the convection zone. During the buoyant rise, the flux-rope's magnetic field strength and density scale as B~rho(alpha) , with alpha?sssim 1. The properties of initial phases of the buoyant rise are determined essentially by the flux-rope's properties and the convective flows and are, in consequence, in good agreement with previous studies. However, the effects of the interaction of the background dynamo field become increasingly stronger as the flux-ropes evolve. The threshold for the initial magnetic field amplitude is slightly increased by the presence of the background dynamo field, even if it is on average much weaker than the flux-rope's field. The geometry and relative orientation of the magnetic field in the flux-ropes with respect to that in the background magnetic field influences the resulting rise speeds, zonal flows amplitudes (which develop within the flux-ropes) and surface signatures of magnetic flux emergence. This strongly influences the morphology, duration and amplitude of the surface shearing and Poynting flux associated with magnetic flux-rope emergence, which are key ingredients to the current coronal eruption triggering scenarios. The actual magnetic flux emergence is consistently preceded by strong and localised radial velocity enhancements at the place where the flux rope will emerge. The emerged magnetic flux is in most of the cases studied enough to influence the global surface magnetic field. In some cases, the emergence reinforces the system's global polarity reversal while in some others it inhibits the background dynamo from doing so. The fraction of magnetic flux which remains attached to the flux-rope is slowly spread out in latitude, diffused and assimilated by the background dynamo field.

Pinto, Rui; Brun, Allan Sacha

461

Kinetics of gas-to-liquid and liquid-to-solid transfer of particles in metal-matrix composites  

NASA Technical Reports Server (NTRS)

Analytical models for transfer of particles from gas to liquid and from liquid to solid are introduced. The model for calculation of the pushing/engulfment transition in directionally solidified particulate metal matrix composites, considers process thermodynamics, process kinetics, thermophysical properties and buoyant forces. Based on processing variables (solidification velocity and direction) and on material variables (interface energies, particle size, particle and liquid density, volume fraction of particles and particle/liquid thermal conductivity ratio) four types of behavior were predicted. Also, two numerical models for liquid-to-solid transfer are discussed, as well as the limitations of presently available models.

Stefanescu, D. M.; Rana, F.; Moitra, A.; Kacar, S.

1990-01-01

462

Laboratory and in situ flotation rates of lecithotrophic eggs from the bathyal echinoid Phormosoma placenta  

NASA Astrophysics Data System (ADS)

The large, lecithotrophic eggs of the bathyal echinothuriid echinoid Phormosoma placenta are positively buoyant both in vitro and in situ to depths of at least 608 m. Eggs attain terminal velocity in less than 5 cm. At constant salinity, flotation rate is related linearly to temperature; eggs move more slowly at lower temperatures. This effect is attributed to increased water viscosity at lower temperatures, not differential changes in egg and water density. Based on an average flotation velocity of 0.42 cm s -1, it is predicted that eggs produced at bathyal depths will reach the surface in approximately 2 days.

Young, Craig M.; Cameron, J. Lane

1987-09-01

463

Evidence for extreme mantle fractionation in early Archaean ultramafic rocks from northern Labrador  

NASA Technical Reports Server (NTRS)

Samarium-neodymium isotope data for tectonically interleaved fragments of lithospheric mantle and meta-komatiite from the North Atlantic craton provide the first direct record of mantle differentiation before 3,800 Myr ago. The results confirm the magnitude of light-rare-earth-element depletion in the early mantle, and also its depleted neodymium isotope composition. The mantle fragments were able to retain these ancient geochemical signatures by virtue of having been tectonically incorporated in buoyant felsic crust, thus escaping recycling and homogenization by mantle convection.

Collerson, Kenneth D.; Campbell, Lisa M.; Weaver, Barry L.; Palacz, Zenon A.

1991-01-01

464

Systematic shifts in subducting slab behavior with depth  

NASA Astrophysics Data System (ADS)

When tectonic plates collide, the less buoyant plate will, in some cases, be forced beneath the other. At such subduction zones the sinking tectonic plate, known as a slab, does not follow a simple path from the surface to the deeper mantle. Instead, new research by Fukao and Obayashi suggests that subducting slabs pass through four largely distinct stages as they penetrate toward the core. To systematically catalog the stages of slab subduction, the authors analyzed roughly 10 million observations of the subsurface that were part of a tomographic study that used primary seismic waves to detect the structure of slabs in subduction zones around the Pacific.

Schultz, Colin

2014-01-01

465

A New Methodology for Turbulence Modelers Using DNS Database Analysis  

NASA Technical Reports Server (NTRS)

Many industrial applications in such fields as aeronautical, mechanical, thermal, and environmental engineering involve complex turbulent flows containing global separations and subsequent reattachment zones. Accurate prediction of this phenomena is very important because separations influence the whole fluid flow and may have an even bigger impact on surface heat transfer. In particular, reattaching flows are known to be responsible for large local variations of the local wall heat transfer coefficient as well as modifying the overall heat transfer. For incompressible, non-buoyant situations, the fluid mechanics have to be accurately predicted in order to have a good resolution of the temperature field.

Parneix, S.; Durbin, P.

1996-01-01

466

Microwave generation of stable atmospheric-pressure fireballs in air  

SciTech Connect

The generation of stable buoyant fireballs in a microwave cavity in air at atmospheric pressure without the use of vaporized solids is described. These fireballs have some of the characteristics of ball lightning and resemble those reported by Dikhtyar and Jerby [Phys. Rev. Lett. 96, 045002 (2006)], although of a different color, and do not require the presence of molten or vaporized material. Mechanisms of microwave plasma formation and fluid dynamics can account for the observed behavior of the fireballs, which do not appear to meet the accepted definition of dusty plasmas in this case. Relevance to models of ball lightning and industrial applications are discussed.

Stephan, Karl D. [Department of Engineering and Technology, Texas State University-San Marcos, San Marcos, Texas 78666 (United States) and Process Energetics Laboratory, Dept. of Electrical and Computer Engineering, University of Texas at Austin, Austin, Texas 78758 (United States)

2006-11-15

467

Microwave generation of stable atmospheric-pressure fireballs in air.  

PubMed

The generation of stable buoyant fireballs in a microwave cavity in air at atmospheric pressure without the use of vaporized solids is described. These fireballs have some of the characteristics of ball lightning and resemble those reported by Dikhtyar and Jerby [Phys. Rev. Lett. 96, 045002 (2006)], although of a different color, and do not require the presence of molten or vaporized material. Mechanisms of microwave plasma formation and fluid dynamics can account for the observed behavior of the fireballs, which do not appear to meet the accepted definition of dusty plasmas in this case. Relevance to models of ball lightning and industrial applications are discussed. PMID:17279961

Stephan, Karl D

2006-11-01

468

Illinois PER Interactive Examples: Floating Cylinders  

NSDL National Science Digital Library

This is an interactive homework problem for introductory physics students relating to fluids and buoyant force. It involves two differently shaped cylinders with the same mass density floating in a container of non-moving water. The student must determine the ratio of the height of Cylinder #2 above the water to the height of Cylinder #1 above the water. A user-activated "help" sequence is provided for each step of the problem-solving, from conceptual analysis through quantitative calculation. To promote critical thinking, immediate feedback is received for both correct and incorrect responses. This item is part of a larger collection of interactive homework problems for introductory physics.

Gladding, Gary

2008-09-10

469

Fractional cloudiness in shallow cumulus layers  

NASA Technical Reports Server (NTRS)

Fractional cloudiness influences the planetary boundary layer (PBL) by controlling the cloud-top radiative cooling rate, and regulating the buoyant production and consumption of turbulence kinetic energy. Betts, Hanson, and Albrecht have modeled partly cloudy PBLs by assuming a single family of convective circulations. The same idealized model has been used in observational studies, based on conditional sampling and/or joint distribution functions, by Lenschow, Albrecht, and others. This approach is extended. None of these authors has proposed a method to determine the fractional area covered by rising motion; finding such a method was a key objective of the present study.

Randall, David A.

1990-01-01

470

Three-dimensional imaging of a turbulent jet using shearing interferometry and optical tomography  

Microsoft Academic Search

The 3-D density field of a round, neutrally buoyant turbulent jet is obtained using a finite-fringe, shearing interferometer.\\u000a A He–Ne laser beam (?=632.8?nm) is subdivided into six beams of equal intensity, which intersect a helium–argon jet flowing\\u000a from a vertical nozzle. Two-dimensional projection data of the jet are captured simultaneously from six viewing directions\\u000a distributed over 140°. The desired phase

B. J. Pelliccia-Kraft; D. W. Watt

2000-01-01

471

Helium jet dispersion to atmosphere  

NASA Technical Reports Server (NTRS)

On the event of loss of vacuum guard of superinsulated helium dewar, high rate of heat transfer into the tank occurs. The rapid boiling of liquid helium causes the burst disk to rupture at four atmospheres and consequently the helium passes to the atmosphere through vent lines. The gaseous helium forms a vertical buoyant jet as it exits the vent line into a stagnant environment. Characterization of the gaseous jet is achieved by detailed analysis of the axial and radial dependence of the flow parameters.

Khan, Hasna J.

1986-01-01

472

Extension of the Gabrielli-von Karman limit for fluidborne vehicles  

NASA Astrophysics Data System (ADS)

The overall technical performance of airborne and waterborne vehicles was reviewed in the light of the Karman-Gabrielli work. Specific energy is defined as a further simple measure of vehicle efficiency, like lift-drag ratio and transport efficiency. Specific energy is an energy efficiency equal to the product of transport efficiency and Froude number. In terms of specific energy, the empirical performance data for fluidborne vehicles reveal consistent trends with Froude number for fully-immersed buoyant vehicles, surface ships, and dynamic-lift vehicles.

Jewell, D.

1980-01-01

473

Investigations of flowfields found in typical combustor geometries  

NASA Technical Reports Server (NTRS)

The flowfields of gas turbine combustion chambers were investigated. Six flowfield configurations with sidewall angles alpha = 90 and 45 deg. and swirl vane angles phi = 0, 45 and 70 deg. are characterized. Photography of neutrally-buoyant helium-filled soap bubbles, tufts, and injected smoke helps to characterize the time-mean streamlines, recirculation zones and regions of highly turbulent flow. Five-hole pitot probe pressure measurements allow the determination of time-mean velocities u, v and w. An advanced computer code equipped with a standard two-equation kappa-epsilon turbulence model was used to predict corresponding flow situations and to compare results with the experimental data.

Lilley, D. G.; Mclaughlin, D. K.

1981-01-01

474

Bubbles  

NASA Astrophysics Data System (ADS)

Vanitas vanitatum et omnia vanitas: bubbles are emptiness, non-liquid, a tiny cloud shielding a mathematical singularity. Born from chance, a violent and brief life ending in the union with the (nearly) infinite. But a wealth of phenomena spring forth from this nothingness: underwater noise, sonoluminescence, boiling, and many others. Some recent results on a "blinking bubble" micropump and vapor bubbles in sound fields are outlined. The last section describes Leonardo da Vinci's observation of the non-rectlinear ascent of buoyant bubbles and justifies the name Leonardo's paradox recently attributed to this phenomenon.

Prosperetti, Andrea

2004-06-01

475

A Role for Lipid Shells in Targeting Proteins to Caveolae, Rafts, and Other Lipid Domains  

NSDL National Science Digital Library

The surface membrane of cells is studded with morphologically distinct regions, or domains, like microvilli, cell-cell junctions, and coated pits. Each of these domains is specialized for a particular function, such as nutrient absorption, cell-cell communication, and endocytosis. Lipid domains, which include caveolae and rafts, are one of the least understood membrane domains. These domains are high in cholesterol and sphingolipids, have a light buoyant density, and function in both endocytosis and cell signaling. A major mystery, however, is how resident molecules are targeted to lipid domains. Here, we propose that the molecular address for proteins targeted to lipid domains is a lipid shell.

Richard G. W. Anderson (University of Texas Southwestern Medical Center, University of North Carolina School of Medicine;Department of Cell Biology, Department of Cell and Developmental Biology and Lineberger Comprehensive Cancer Center); Ken Jacobson (University of Texas Southwestern Medical Center, University of North Carolina School of Medicine;Department of Cell Biology, Department of Cell and Developmental Biology and Lineberger Comprehensive Cancer Center)

2008-06-07

476

The influence of cropping systems on inoculum density of Rhizoctonia solani and sheath blight of rice (Oryza sativa)  

E-print Network

is initiated during permanent flood when buoyant sclerotia float to the water surface and produce mycelium to infect tillers at the water line (15). A greater loss in the yield of rice occurs when plants become infected during the vegetative and early... for the second year of the study. The inoculum density was highly correlated to disease incidence. These data suggested that overall for the fields surveyed during 1984 and 1985, that sclerotia of R. salani were responsible for causing sheath blight of rice...

Belmar, Scott Bradley

2012-06-07

477

Existence, uniqueness and regularity of a time-periodic probability density distribution arising in a sedimentation-diffusion problem  

NASA Technical Reports Server (NTRS)

The sedimentation and diffusion of a nonneutrally buoyant Brownian particle in vertical fluid-filled cylinder of finite length which is instantaneously inverted at regular intervals are investigated analytically. A one-dimensional convective-diffusive equation is derived to describe the temporal and spatial evolution of the probability density; a periodicity condition is formulated; the applicability of Fredholm theory is established; and the parameter-space regions are determined within which the existence and uniqueness of solutions are guaranteed. Numerical results for sample problems are presented graphically and briefly characterized.

Nitsche, Ludwig C.; Nitsche, Johannes M.; Brenner, Howard

1988-01-01

478

High order statistics of turbulence Lagrangian acceleration  

NASA Astrophysics Data System (ADS)

It is well known that the Lagrangian acceleration of a fluid element in turbulence is highly intermittent. Therefore it has been a challenge to accurately measure higher order statistics of acceleration. We report measurements of the scaling of acceleration moments with Reynolds number and compare our results with several available theories, including the standard K41, K62 with intermittency correction, and a recent theory advocated by Yakhot and co-workers. We achieved these measurements by optically tracking neutrally buoyant polystyrene microspheres at high spatial and temporal resolution in a nearly homogeneous and isotropic water flow driven by 12 independently controlled propellers in a newly constructed turbulence generator.

Xu, Haitao; Zimmermann, Robert; Bodenschatz, Eberhard

2008-11-01

479

Biophysical Studies on Rhinovirus and Poliovirus  

PubMed Central

An explanation has been sought for the high buoyant density of rhinoviruses, which are classified as acid-sensitive picornaviruses. Heat degradation of purified preparations of rhinovirus type 1B and poliovirus type LSc leads to the extrusion of ribonucleoprotein strands. Contour lengths of these strands were measured by electron microscopy, and the molecular weights of rhinovirus and poliovirus ribonucleic acid (RNA) were determined. Values of 2 × 106 and 4 × 106 daltons were obtained for the molecular weight of poliovirus and rhinovirus RNA, respectively. This additional nucleic acid in the rhinovirion probably accounts for the increased density and may be related to the acid sensitivity of the rhinovirus. Images PMID:4316016

McGregor, Sandy; Mayor, Heather D.

1968-01-01

480

Investigation of Vibrational Control of the Bridgman Crystal Growth Technique  

NASA Technical Reports Server (NTRS)

The objectives are: Conduct a parametric theoretical and numerical investigation of vibro-convective buoyancy-driven flow in differentially heated cylindrical containers. Investigate buoyant vibro-convective transport regimes in Bridgman-type systems with a focus on the use of vibration to suppress, or control, convection in order to achieve transport control during crystal growth. Assess the feasibility of vibro-convective control as a means of offsetting "g-jitter" effects under microgravity conditions, Exchange information with the experimental group at the General Physics Institute (GPI) of the Russian Academy of Science who are undertaking a complementary experimental program.

Fedoseyev, Alexandre I.

1998-01-01

481

Airships for transporting highly volatile commodities  

NASA Technical Reports Server (NTRS)

Large airships may prove feasible as carriers of commodities that move as gases or cryogenic liquids; buoyant gaseous cargo could be ballasted with liquid cargo. Airships are compact in shape, operate in a rarified medium, and hence can be fast and perhaps economic carriers of costly cryogenic tanks. The high-pressure gas pipeline has excessive surface area when carrying hydrogen and excessive fluid density when carrying natural gas, while the cryogenic ocean tanker runs in a dense medium and makes gravity waves. But the airship, despite its fluid dynamic advantages, faces problems of safety, weather, and altitude control.

Sonstegaard, M.

1975-01-01

482

Strain Hardening of Fractal Colloidal Gels  

NASA Astrophysics Data System (ADS)

We report on experiments on the rheology of gels formed by diffusion-limited aggregation of neutrally buoyant colloidal particles. These gels form very weak solids, with the elastic modulus, G'\\(?\\), larger than the loss modulus, G''\\(?\\), and with both G'\\(?\\) and G''\\(?\\) exhibiting only a very weak frequency dependence. Upon small but finite strains ?<0.45 the elastic modulus increases roughly exponentially with ?2. We explain the observed strain hardening with the highly nonlinear elastic response of the rigid backbone of the gel to elongational deformation.

Gisler, T.; Ball, R. C.; Weitz, D. A.

1999-02-01

483

Gravitational Stability of Suspensions of Attractive Colloidal Particles  

NASA Astrophysics Data System (ADS)

Colloidal suspensions are susceptible to gravitationally induced phase separation. This can be mitigated by the formation of a particle network caused by depletion attraction. The effectiveness of this network in supporting the buoyant weight of the suspension can be characterized by its compressional modulus. We measure the compressional modulus for emulsion networks induced by depletion attraction and present a model that quantitatively predicts their gravitational stability. We also determine the relationship between the strength of the depletion attraction and the magnitude of the compressional modulus.

Kim, Chanjoong; Liu, Yaqian; Kühnle, Angelika; Hess, Stephan; Viereck, Sonja; Danner, Thomas; Mahadevan, L.; Weitz, David A.

2007-07-01

484

Leishmania (Viannia) shawi sp. n., a parasite of monkeys, sloths and procyonids in Amazonian Brazil.  

PubMed

Leishmania (Viannia) shawi sp. n., is described from the monkeys Cebus apella and Chiropotes satanus, the sloths Choloepus didactylus and Bradypus tridactylus, the procyonid Nasua nasua, and the phlebotomine sandfly Lutzomyia whitmani, all from primary forest in the State of Pará, north Brazil. L. (V.) shawi is variably distinguished from all other known species within the subgenus Viannia by a combination of biological, biochemical and serological characters, as revealed by studies on morphology, isoenzyme profiles, kDNA buoyant densities and monoclonal antibodies. PMID:2504099

Lainson, R; Braga, R R; De Souza, A A; Pôvoa, M M; Ishikawa, E A; Silveira, F T

1989-01-01

485

Direct numerical simulation of turbulent mixing.  

PubMed

The results of three-dimensional numerical simulations of turbulent flows obtained by various authors are reviewed. The paper considers the turbulent mixing (TM) process caused by the development of the main types of instabilities: those due to gravitation (with either a fixed or an alternating-sign acceleration), shift and shock waves. The problem of a buoyant jet is described as an example of the mixed-type problem. Comparison is made with experimental data on the TM zone width, profiles of density, velocity and turbulent energy and degree of homogeneity. PMID:24146009

Statsenko, V P; Yanilkin, Yu V; Zhmaylo, V A

2013-11-28

486

Properties of Delipidated Hepatitis B Surface Antigen (HBsAg) and Preparation of Its Proteolytic Cleavage Fragments Carrying HBsAg-Specific Antigenic Determinants  

Microsoft Academic Search

Summary Treatment of hepatitis B surface antigen (HBsAg) with either chloroform-methanol (2:1, v\\/v) or 50% l,?,3,3’-tetramethylurea did not affect the morphological integrity of the particles (about 20 nm in diameter), although the major portion of lipids was released as indicated by their increased buoyant density in CsCl (1.27 g\\/cm3 as compared with 1.20 g\\/cm3 for intact HBsAg). The antigenicity and

Robert Neurath; Nathan Strick; Chen Ya Huang

1978-01-01

487

The Interaction of Radio Sources and X-ray-Emitting Gas in Cooling Flows  

E-print Network

Recent observations of the interactions between radio sources and the X-ray-emitting gas in cooling flows in the cores of clusters of galaxies are reviewed. The radio sources inflate bubbles in the X-ray gas, which then rise buoyantly outward in the clusters transporting energy to the intracluster medium (ICM). The bright rims of gas around the radio bubbles are cool, rather than hot, and do not show signs of being strongly shocked. Energy deposited into the ICM over the lifetime of a cluster through several outbursts of a radio source helps to account for at least some of the gas that is missing in cooling flows at low temperatures.

Elizabeth L. Blanton

2004-02-13

488

Hybrid LTA vehicle controllability as affected by buoyancy ratio  

NASA Technical Reports Server (NTRS)

The zero and low speed controllability of heavy lift airships under various wind conditions as affected by the buoyancy ratio are investigated. A series of three hybrid LTA vehicls were examined, each having a dynamic thrust system comprised of four H-34 helicopters, but with buoyant envelopes of different volumes (and hence buoyancies), and with varying percentage of helium inflation and varying useful loads (hence gross weights). Buoyancy ratio, B, was thus examined varying from approximately 0.44 to 1.39. For values of B greater than 1.0, the dynamic thrusters must supply negative thrust (i.e. downward).

Meyers, D. N.; Kubicki, P.; Tarczynski, T.; Fairbanks, A.; Piasecki, F. N.

1979-01-01

489

Genomic environment of variant surface antigen genes of Trypanosoma equiperdum.  

PubMed

Expression of variant antigen genes in Trypanosoma equiperdum is accompanied by the duplication of a silent basic copy gene and the transposition of the copy to an expression site elsewhere in the genome. We have analyzed the genomic locations of both the basic and expression-linked copies of the T. equiperdum gene for variable surface glycoprotein VSG-1. Both copies are situated proximal to termini in both extracted DNA and in chromatin. The regions between the VSG-1 genes and the termini have a very high buoyant density in CsCl and contain an unidentified nucleoside that replaces deoxycytidine. PMID:6308614

Raibaud, A; Gaillard, C; Longacre, S; Hibner, U; Buck, G; Bernardi, G; Eisen, H

1983-07-01

490

Numerical study of three-dimensional mixed convection due to buoyancy and centrifugal force in an oxide melt for Czochralski growth  

NASA Astrophysics Data System (ADS)

Mixed convection due to buoyant and centrifugal forces in the crucible of a Czochralski apparatus has a significant effect on the quality and stability of growing oxide single crystals. Thus, the present investigation is concerned with the time-dependent and three-dimensional simulation of the flow and heat transfer in an oxide melt with a rotating crystal for a fundamental understanding of mixed convection and its effect on the surface waves. Based on an efficient block-structured finite-volume Navier-Stokes solver, quasi-direct numerical simulations (quasi-DNS) were carried out. A cylindrical crucible filled with a high Prandtl number (Pr=10.45) model fluid was considered for different combinations of Rayleigh numbers (Ra=4.0×10 8 and 7.6×10 8) and Reynolds numbers (Re=235-461). It was found that the surface wave pattern is strongly dependent on the structure of the three-dimensional and time-dependent fluid flow in the crucible. For all cases predicted, the waves exhibit regularity and the flow structure is fully symmetric in the vertical midplane as long as the centrifugal force has a significant effect on the flow below the disc. Furthermore, a downward buoyant jet was found to form at the disc center in all cases when the upper flow column due to the centrifugal force becomes restricted to the top. The transient flow development can be characterized by Gr/Re 2. For Gr/Re 2=235 the flow field is always periodic whereas it attains a non-periodic state through a number of quasi-periodic modes for Gr/Re 2 larger than 334. Increasing values of Gr/Re 2 lead to an earlier onset of the non-periodicity. Except during the initial period, the hot fluid is pushed below the disc primarily by the radial buoyant convection. This hot fluid interacts with the cold column of the downward buoyant flow controlling the temperature at the crystal/melt interface. The shape, the rotation rate of the waves, and the transient nature of the flow field were found to be in agreement with experimental observations.

Enger, Sven; Basu, Biswajit; Breuer, Michael; Durst, Franz

2000-10-01

491

Aquatic Invertebrate Development Working Group  

NASA Technical Reports Server (NTRS)

Little definitive evidence exists to show that gravity plays a major role in embyrogenesis of aquatic invertebrates. Two reasons for this may be: (1) few studies have been done that emphasize the role of gravity; and (2) there simply may not be any gravity effect. The buoyant nature of the aquatic environment could have obscured any evolutionary effect of gravity. The small size of most eggs and their apparent lack of orientation suggests reduced gravitational influence. Therefore, it is recommended that the term development, as applied to aquatic invertebrates, be loosely defined to encompass behavioral and morphological parameters for which baseline data already exist.

Meyers, D.

1985-01-01

492

Air-dispersion modeling and the real world  

SciTech Connect

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 rise is added to the height of the source stack, or emission point, to determine the effective stack height, also called the plume centerline height. Second, ground-level concentrations beneath the plume are predicted using the Gaussian dispersion equation.

Beychok, M.T. [Beychok (Milton R.), Irvine, CA (United States)

1996-06-01

493

Paint-Stirrer Submarine  

NSDL National Science Digital Library

In today's fast-paced, technological world, it is a constant struggle for teachers to find new and exciting ways to challenge and engage our students. The Paint-Stirrer Submarine is a unique and challenging laboratory exercise that keeps the students enthralled. They won't even realize they are learning because they will be having too much fun. This inquiry-based, hands-on experience in building a submarine allows the students to learn about buoyancy, buoyant force, Archimedes' principle, and motion in an engaging manner. It will be an experience neither you nor your students will ever forget.

Young, Jocelyn; Hardy, Kevin

2007-02-01

494

Dietary composition modulates brain mass and amyloid beta levels in a mouse model of aggressive Alzheimer's amyloid pathology  

E-print Network

: Cholesterol-dependent gamma-secretase activity in buoyant cholesterol-rich mem- brane microdomains. Neurobiol Dis 2002, 9:11-23. 4. Wang J, Ho L, Qin W, Rocher AB, Seror I, Humala N, Maniar K, Dolios G, Wang R, Hof PR, Pasinetti GM: Caloric restriction... 2007, 282:36275-82. 10. Ho L, Qin W, Pompl PN, Xiang Z, Wang J, Zhao Z, Peng Y, Cambareri G, Rocher A, Mobbs CV, Hof PR, Pasinetti GM: Diet-induced insu- lin resistance promotes amyloidosis in a transgenic mouse model of Alzheimer's disease. FASEB J...

Pedrini, Steve; Thomas, Carlos; Brautigam, Hannah; Schmeidler, James; Ho, Lap; Fraser, Paul; Westaway, David; St George Hyslop, Peter; Martins, Ralph N; Buxbaum, Joseph D; Pasinetti, Giulio M; Dickstein, Dara L; Hof, Patrick R; Ehrlich, Michelle E; Gandy, Sam

2009-10-21

495

Capillary-driven two-dimensional buoyancy in vertical soap films  

NASA Astrophysics Data System (ADS)

The present study aims to investigate the capillary-driven buoyant effects in nearly two-dimensional systems. The case of rising rings in vertical soap films is studied both experimentally and theoretically. Since the pioneering works of Mysels and coworkers, the thickness differences and related two-dimensional densities are considered as the motor leading to two-dimensional buoyancy. We show how this effect can be re-interpreted in terms of the surface tension profiles present at the film interfaces. We propose a model involving surface tension profiles, as well as an adapted expression for the mass of the rising rings, and compare it to experimental data.

Adami, N.; Caps, H.

2014-05-01

496

In-flight cabin smoke control.  

PubMed

Fatal accidents originating from in-flight cabin fires comprise only about 1% of all fatal accidents in the civil jet transport fleet. Nevertheless, the impossibility of escape during flight accentuates the hazards resulting from low visibility and toxic gases. Control of combustion products in an aircraft cabin is affected by several characteristics that make the aircraft cabin environment unique. The aircraft fuselage is pressurized in flight and has an air distribution system which provides ventilation jets from the ceiling level air inlets running along the cabin length. A fixed quantity of ventilation air is metered into the cabin and air discharge is handled primarily by pressure controlling outflow valves in the rear lower part of the fuselage. Earlier airplane flight tests on cabin smoke control used generators producing minimally buoyant smoke products that moved with and served as a telltales for overall cabin ventilation flows. Analytical studies were done with localized smoke production to predict the percent of cabin length that would remain smoke-free during continuous generation. Development of a buoyant smoke generator allowed simulation of a fire plume with controllable simulated temperature and heat release rates. Tests on a Boeing 757, modified to allow smoke venting out through the top of the cabin, showed that the buoyant smoke front moved at 0.46m/s (1.5ft/sec) with and 0.27m/sec (0.9ft/sec) against, the axial ventilation airflow. Flight tests in a modified Boeing 727 showed that a ceiling level counterflow of about 0.55m/sec (1.8ft/sec) was required to arrest the forward movement of buoyant smoke. A design goal of 0.61m/s (2ft/sec) axial cabin flow would require a flow rate of 99m3/min (3500ft3/min) in a furnished Boeing 757. The current maximum fresh air cabin ventilation flow is 78m3/min (2756 ft3/min). Experimental results indicate that buoyancy effects cause smoke movement behaviour that is not predicted by traditional design analyses and flight test methodologies. Augmenting available ventilation for smoke control remains a design and safety challenge. PMID:9016748

Eklund, T I

1996-12-31

497

Simulations of Hot Bubbles in the ICM  

E-print Network

We review the general properties of the intracluster medium (ICM) in clusters that host a cooling flow, and in particular the effects on the ICM of the injection of hot plasma by a powerful active galactic nucleus (AGN). It is observed that, in some cases, the hot plasma produces cavities in the ICM that finally detach and rise, perhaps buoyantly. The gas dynamics induced by the rising bubbles can help explain the absence of a cooled gas component in clusters with a cooling flow. This scenario is explored using numerical simulations.

A. Gardini; P. M. Ricker

2004-09-15

498

Amphibian egg cytoplasm response to altered g-forces and gravity orientation  

NASA Technical Reports Server (NTRS)

Elucidation of dorsal/ventral polarity and primary embryonic axis development in amphibian embryos requires an understanding of cytoplasmic rearrangements in fertile eggs at the biophysical, physiological, and biochemical levels. Evidence is presented that amphibian egg cytoplasmic components are compartmentalized. The effects of altered orientation to the gravitational vector (i.e., egg inversion) and alterations in gravity force ranging from hypergravity (centrifugation) to simulated microgravity (i.e., horizontal clinostat rotation) on cytoplasmic compartment rearrangements are reviewed. The behavior of yolk compartments as well as a newly defined (with monoclonal antibody) nonyolk cytoplasmic compartment, in inverted eggs and in eggs rotated on horizontal clinostats at their buoyant density, is discussed.

Neff, A. W.; Smith, R. C.; Malacinski, G. M.

1986-01-01

499

Active galactic nucleus feedback in clusters of galaxies  

PubMed Central

Observations made during the last ten years with the Chandra X-ray Observatory have shed much light on the cooling gas in the centers of clusters of galaxies and the role of active galactic nucleus (AGN) heating. Cooling of the hot intracluster medium in cluster centers can feed the supermassive black holes found in the nuclei of the dominant cluster galaxies leading to AGN outbursts which can reheat the gas, suppressing cooling and large amounts of star formation. AGN heating can come in the form of shocks, buoyantly rising bubbles that have been inflated by radio lobes, and the dissipation of sound waves. PMID:20351250

Blanton, Elizabeth L.; Clarke, T. E.; Sarazin, Craig L.; Randall, Scott W.; McNamara, Brian R.

2010-01-01

500

Spawning and rearing Atlantic menhaden  

SciTech Connect

Two-year-old Atlantic menhaden (Brevoortia tyrannus) held in the laboratory at ambient temperatures and salinities for more than 1 year, were induced to spawn by injecting first human chorionic gonadotropin and then carp pituitary powder. Spawning took place at temperatures of 16 to 20/sup 0/C in a 2100-L indoor tank modified to recover the buoyant fertilized eggs. Larvae were reared to the juvenile stage on a diet of cultured rotifers (Brachionus plicatilus), sieved wild zooplankton (64 to 500 ..mu..m), brine shrimp (Artemia salina) nauplii, and powdered trout food.

Hettler, W.F.

1981-04-01