Science.gov

Sample records for air entrainment behavior

  1. Air entrainment in hairy surfaces

    NASA Astrophysics Data System (ADS)

    Nasto, Alice; Regli, Marianne; Brun, P.-T.; Alvarado, José; Clanet, Christophe; Hosoi, A. E.

    2016-07-01

    Motivated by diving semiaquatic mammals, we investigate the mechanism of dynamic air entrainment in hairy surfaces submerged in liquid. Hairy surfaces are cast out of polydimethylsiloxane elastomer and plunged into a fluid bath at different velocities. Experimentally, we find that the amount of air entrained is greater than what is expected for smooth surfaces. Theoretically, we show that the hairy surface can be considered as a porous medium and we describe the air entrainment via a competition between the hydrostatic forcing and the viscous resistance in the pores. A phase diagram that includes data from our experiments and biological data from diving semiaquatic mammals is included to place the model system in a biological context and predict the regime for which the animal is protected by a plastron of air.

  2. Entrainment of Air into Vertical Jets in a Crosswind

    NASA Astrophysics Data System (ADS)

    Roberts, K. K.; Solovitz, S.; Freedland, G.; Camp, E.; Cal, R. B.; Mastin, L. G.

    2015-12-01

    During volcanic eruptions, ash concentration must be determined for aviation safety, but the limiting threshold is difficult to distinguish visually. Computational models are typically used to predict ash concentrations, using inputs such as plume height, eruptive duration, and wind speeds. The models also depend on empirical parameters, such as the entrainment of atmospheric air as a ratio of the air inflow speed and the jet speed. Entrainment of atmospheric air plays a critical role in the behavior of volcanic plumes in the atmosphere, impacting the mass flow rate, buoyancy, and particle concentration of the plume. This process is more complex in a crosswind, leading to greater uncertainty in the model results. To address these issues, a laboratory-scale study has been conducted to improve the entrainment models. Observations of a vertical, unconfined jet are performed using Particle Image Velocimetry, while varying jet density using different compressed gases and Reynolds number. To test the effects of a crosswind on plume entrainment rates, these are then compared with similar jet experiments in a wind tunnel. A series of jet geometries, jet speeds and tunnel speeds are considered. The measured velocities are used to determine the entrainment response, which can be used to determine ash concentration over time as atmospheric air is entrained into the plume. We also quantify the mean and the fluctuations in flow velocity.

  3. Clouds and entrainment. [cumulus convective turbulence in clear air

    NASA Technical Reports Server (NTRS)

    Randall, D. A.

    1982-01-01

    The concept of entrainment is discussed, and the knowledge that has been acquired about entraining turbulence in clear air is surveyed. Attention is then given to observations and models of stratocumulus entrainment, which show some of the ways in which cloudiness modifies the entrainment process. Entraining cumuli are also considered, with some of the differences between cumulus entrainment and stratocumulus entrainment noted. Emphasis is placed on the dynamical aspects of entrainment; its effects on droplet spectra and other microphysical aspects are mentioned only briefly.

  4. Measurement of air entrainment in plasma jets

    SciTech Connect

    Fincke, J.R.; Rodriquez, R.; Pentecost, C.G.

    1990-01-01

    The concentration and temperature of air entrained into argon and helium plasma jets has been measured using coherent anti-Stokes Raman spectroscopy (CARS). The argon plasma flow field is characterized by a short region of well behaved laminar flow near the nozzle exit followed by an abrupt transition to turbulence. Once the transition of turbulence occurs, air is rapidly mixed into the jet core. The location of the transition region is determined by the rapid cooling of the jet and the resulting increase in Reynolds number. In contrast, the helium plasma flow field never exceeds a Reynolds number of 200 and remains laminar. The entrainment process in this case is controlled by molecular diffusion rather than turbulent mixing. 9 refs., 5 figs., 1 tab.

  5. Measurement of air entrainment in plasma jets

    NASA Astrophysics Data System (ADS)

    Fincke, J. R.; Rodriquez, R.; Pentecost, C. G.

    The concentration and temperature of air entrained into argon and helium plasma jets has been measured using coherent anti-Stokes Raman spectroscopy (CARS). The argon plasma flow field is characterized by a short region of well behaved laminar flow near the nozzle exit followed by an abrupt transition to turbulence. Once the transition of turbulence occurs, air is rapidly mixed into the jet core. The location of the transition region is determined by the rapid cooling of the jet and the resulting increase in Reynolds number. In contrast, the helium plasma flow field never exceeds a Reynolds number of 200 and remains laminar. The entrainment process in this case is controlled by molecular diffusion rather than turbulent mixing.

  6. Dispersal and air entrainment in unconfined dilute pyroclastic density currents

    NASA Astrophysics Data System (ADS)

    Andrews, Benjamin J.

    2014-09-01

    Unconfined scaled laboratory experiments show that 3D structures control the behavior of dilute pyroclastic density currents (PDCs) during and after liftoff. Experiments comprise heated and ambient temperature 20 μm talc powder turbulently suspended in air to form density currents within an unobstructed 8.5 × 6 × 2.6-m chamber. Comparisons of Richardson, thermal Richardson, Froude, Stokes, and settling numbers and buoyant thermal to kinetic energy densities show good agreement between experimental currents and dilute PDCs. The experimental Reynolds numbers are lower than those of PDCs, but the experiments are fully turbulent; thus, the large-scale dynamics are similar between the two systems. High-frequency, simultaneous observation in three orthogonal planes shows that the currents behave very differently than previous 2D (i.e., confined) currents. Specifically, whereas ambient temperature currents show radial dispersal patterns, buoyancy reversal, and liftoff of heated currents focuses dispersal along narrow axes beneath the rising plumes. The aspect ratios, defined as the current length divided by a characteristic width, are typically 2.5-3.5 in heated currents and 1.5-2.5 in ambient temperature currents, reflecting differences in dispersal between the two types of currents. Mechanisms of air entrainment differ greatly between the two currents: entrainment occurs primarily behind the heads and through the upper margins of ambient temperature currents, but heated currents entrain air through their lateral margins. That lateral entrainment is much more efficient than the vertical entrainment, >0.5 compared to ˜0.1, where entrainment is defined as the ratio of cross-stream to streamwise velocity. These experiments suggest that generation of coignimbrite plumes should focus PDCs along narrow transport axes, resulting in elongate rather than radial deposits.

  7. Characteristics of air entrainment during dynamic wetting failure along a planar substrate

    NASA Astrophysics Data System (ADS)

    Kumar, Satish; Vandre, Eric; Carvalho, Marcio

    2014-11-01

    We report results of experiments characterizing the onset of air entrainment during dynamic wetting failure along a planar substrate (J. Fluid Mech. 747, 119 (2014)). Using high-speed video, dynamic contact line (DCL) behavior is recorded as a tape substrate is drawn through a bath of a glycerol/water solution. Air entrainment is identified by triangular air films that elongate from the DCL above a critical substrate speed. Meniscus confinement between the substrate and a stationary plate delays air entrainment to higher speeds for a wide range of liquid viscosities. Liquid pressurization moves the meniscus near a sharp corner, changing its shape and further postponing air entrainment. Meniscus shapes recorded near the DCL demonstrate that smaller entrained air films appear in the more viscous solutions. Regardless of size, air films become unstable to thickness perturbations and ultimately rupture, leading to entrainment of air bubbles. Recorded critical speeds and air-film sizes compare well to predictions from a hydrodynamic model for dynamic wetting failure, indicating that strong air stresses near the DCL trigger the onset of air entrainment. The results suggest strategies for postponing air entrainment, which often limits the maximum speed of industrial coating processes.

  8. Entrainment Rate in Shallow Cumuli: Dependence on Entrained Dry Air Sources and Probability Density Functions

    NASA Astrophysics Data System (ADS)

    Lu, C.; Liu, Y.; Niu, S.; Vogelmann, A. M.

    2012-12-01

    In situ aircraft cumulus observations from the RACORO field campaign are used to estimate entrainment rate for individual clouds using a recently developed mixing fraction approach. The entrainment rate is computed based on the observed state of the cloud core and the state of the air that is laterally mixed into the cloud at its edge. The computed entrainment rate decreases when the air is entrained from increasing distance from the cloud core edge; this is because the air farther away from cloud edge is drier than the neighboring air that is within the humid shells around cumulus clouds. Probability density functions of entrainment rate are well fitted by lognormal distributions at different heights above cloud base for different dry air sources (i.e., different source distances from the cloud core edge). Such lognormal distribution functions are appropriate for inclusion into future entrainment rate parameterization in large scale models. To the authors' knowledge, this is the first time that probability density functions of entrainment rate have been obtained in shallow cumulus clouds based on in situ observations. The reason for the wide spread of entrainment rate is that the observed clouds are affected by entrainment mixing processes to different extents, which is verified by the relationships between the entrainment rate and cloud microphysics/dynamics. The entrainment rate is negatively correlated with liquid water content and cloud droplet number concentration due to the dilution and evaporation in entrainment mixing processes. The entrainment rate is positively correlated with relative dispersion (i.e., ratio of standard deviation to mean value) of liquid water content and droplet size distributions, consistent with the theoretical expectation that entrainment mixing processes are responsible for microphysics fluctuations and spectral broadening. The entrainment rate is negatively correlated with vertical velocity and dissipation rate because entrainment

  9. Dry Air Entrainment into Hurricane Earl

    NASA Technical Reports Server (NTRS)

    Guillory, Anthony R.; Jedlovec, Gary J.; Atkinson, Robert J.; Hood, Robbie E.; LaFontaine, Frank J.

    2000-01-01

    Hurricane Earl formed in the Gulf of Mexico in September 1998. It quickly was upgraded from a tropical disturbance to tropical storm status and then to a hurricane. Earl possessed hybrid (tropical and extratropical) characteristics throughout its lifetime. The system maintained and erratic track, which led to wide variability in the operational track forecasts. It eventually made landfall on the Florida panhandle on 2 September and raced northeastward. During August and September 1998, NASA conducted the third Convection and Moisture Experiment (CAMEX-3). The experiment was focused on studying hurricanes with an emphasis toward developing a better understanding of their intensification and motion. Earl provides a unique opportunity to utilize high spatial and temporal resolution data collected from the DC-8 and high altitude ER-2 NASA platforms, which flew over Earl as it made landfall. These data can also be put into broader view provided by other instruments from the Geosychronous Operational Environmental Satellites (GOES) and the Tropical Rainfall Measuring Mission (TRMM) satellites. Hurricane Earl was affected by entrainment of dry air from the northwest. Hurricane Isis was intensifying and approaching the Mexican Pacific coast with its associated outflow potentially affecting the inflow into Earl as the storm neared Florida. In addition, a longwave synoptic trough circulation was present over the eastern U.S. Either or both of these could be responsible for the dry air into the system. This paper will focus on identifying the source of the dry by using upper-level wind and moisture fields derived from the GOES 6.7 um water vapor imagery. We will attempt to relate the large-scale observations to those from the NASA aircraft. An infrared instrument onboard the ER-2 also has a similar wavelength and may be able to confirm some of the GOES findings. In addition, a microwave radiometer with 4 channels focused on measuring precipitation and its associated ice

  10. Diurnally entrained anticipatory behavior in archaea.

    PubMed

    Whitehead, Kenia; Pan, Min; Masumura, Ken-ichi; Bonneau, Richard; Baliga, Nitin S

    2009-01-01

    By sensing changes in one or few environmental factors biological systems can anticipate future changes in multiple factors over a wide range of time scales (daily to seasonal). This anticipatory behavior is important to the fitness of diverse species, and in context of the diurnal cycle it is overall typical of eukaryotes and some photoautotrophic bacteria but is yet to be observed in archaea. Here, we report the first observation of light-dark (LD)-entrained diurnal oscillatory transcription in up to 12% of all genes of a halophilic archaeon Halobacterium salinarum NRC-1. Significantly, the diurnally entrained transcription was observed under constant darkness after removal of the LD stimulus (free-running rhythms). The memory of diurnal entrainment was also associated with the synchronization of oxic and anoxic physiologies to the LD cycle. Our results suggest that under nutrient limited conditions halophilic archaea take advantage of the causal influence of sunlight (via temperature) on O(2) diffusivity in a closed hypersaline environment to streamline their physiology and operate oxically during nighttime and anoxically during daytime. PMID:19424498

  11. Maximal Air Bubble Entrainment at Liquid-Drop Impact

    NASA Astrophysics Data System (ADS)

    Bouwhuis, Wilco; van der Veen, Roeland C. A.; Tran, Tuan; Keij, Diederik L.; Winkels, Koen G.; Peters, Ivo R.; van der Meer, Devaraj; Sun, Chao; Snoeijer, Jacco H.; Lohse, Detlef

    2012-12-01

    At impact of a liquid drop on a solid surface, an air bubble can be entrapped. Here, we show that two competing effects minimize the (relative) size of this entrained air bubble: for large drop impact velocity and large droplets, the inertia of the liquid flattens the entrained bubble, whereas for small impact velocity and small droplets, capillary forces minimize the entrained bubble. However, we demonstrate experimentally, theoretically, and numerically that in between there is an optimum, leading to maximal air bubble entrapment. For a 1.8 mm diameter ethanol droplet, this optimum is achieved at an impact velocity of 0.25m/s. Our results have a strong bearing on various applications in printing technology, microelectronics, immersion lithography, diagnostics, or agriculture.

  12. What's All the Talc About? Air Entrainment in Dilute Pyroclastic Density Currents

    NASA Astrophysics Data System (ADS)

    Marshall, B. J.; Andrews, B. J.; Fauria, K.

    2015-12-01

    A quantitative understanding of air entrainment is critical to predicting the behaviors of dilute Pyroclastic Density Currents (PDCs), including runout distance, liftoff, and mass fractionation into co-PDC plumes. We performed experiments in an 8.5x6x2.6 meter tank using 20 micron talc powder over a range of conditions to describe air entrainment as a function of temperature, duration and mass flux. The experiments are reproducible and are scaled with respect to the densimetric and thermal Richardson numbers (Ri and RiT), Froude number, thermal to kinetic energy density ratio (TEb/KE), Stokes number, and Settling number, such that they are dynamically similar to natural dilute PDCs. Experiments are illuminated with a swept laser sheet and imaged at 1000 Hz to create 3D reconstructions of the currents, with ~1-2 cm resolution, at up to 1.5 Hz. An array of 30 high-frequency thermocouples record the precise temperature in the currents at 3 Hz. Bulk entrainment rates are calculated based on measured current volumes, surface areas, temperatures and velocities. Entrainment rates vary from ~0-0.9 and do not show simple variation with TEb/KE, Ri, or RiT. Entrainment does, however, increase with decreasing eruption duration and increasing mass flux. Our results suggest that current heads entrain air more efficiently than current bodies (>0.5 compared to ~0.1). Because shorter duration currents have proportionally larger heads, their bulk entrainment rates are controlled by those heads, whereas longer duration currents are dominated by their bodies. Our experiments demonstrate that air entrainment, which exerts a fundamental control on PDC runout and liftoff, varies spatially and temporally within PDCs.

  13. Effect of fast freeze-thaw cycles on mechanical properties of ordinary-air-entrained concrete.

    PubMed

    Shang, Huai-shuai; Cao, Wei-qun; Wang, Bin

    2014-01-01

    Freezing-thawing resistance is a very significant characteristic for concrete in severe environment (such as cold region with the lowest temperature below 0°C). In this study, ordinary-air-entrained (O-A-E) concrete was produced in a laboratory environment; the compressive strength, cubic compressive strength of C50, C40, C30, C25, and C20 ordinary-air-entrained concrete, tensile strength, and cleavage strength of C30 ordinary-air-entrained concrete were measured after fast freeze-thaw cycles. The effects of fast freeze-thaw cycles on the mechanical properties (compressive strength and cleavage strength) of ordinary-air-entrained concrete materials are investigated on the basis of the experimental results. And the concise mathematical formula between mechanical behavior and number of fast freeze-thaw cycles was established. The experiment results can be used as a reference in design, maintenance, and life prediction of ordinary-air-entrained concrete structure (such as dam, offshore platform, etc.) in cold regions. PMID:24895671

  14. Effect of Fast Freeze-Thaw Cycles on Mechanical Properties of Ordinary-Air-Entrained Concrete

    PubMed Central

    Shang, Huai-shuai; Cao, Wei-qun; Wang, Bin

    2014-01-01

    Freezing-thawing resistance is a very significant characteristic for concrete in severe environment (such as cold region with the lowest temperature below 0°C). In this study, ordinary-air-entrained (O-A-E) concrete was produced in a laboratory environment; the compressive strength, cubic compressive strength of C50, C40, C30, C25, and C20 ordinary-air-entrained concrete, tensile strength, and cleavage strength of C30 ordinary-air-entrained concrete were measured after fast freeze-thaw cycles. The effects of fast freeze-thaw cycles on the mechanical properties (compressive strength and cleavage strength) of ordinary-air-entrained concrete materials are investigated on the basis of the experimental results. And the concise mathematical formula between mechanical behavior and number of fast freeze-thaw cycles was established. The experiment results can be used as a reference in design, maintenance, and life prediction of ordinary-air-entrained concrete structure (such as dam, offshore platform, etc.) in cold regions. PMID:24895671

  15. Universal mechanism for air entrainment during liquid impact

    NASA Astrophysics Data System (ADS)

    Hendrix, Maurice H. W.; Bouwhuis, Wilco; van der Meer, Devaraj; Lohse, Detlef; Snoeijer, Jacco H.

    2016-02-01

    When a mm-sized liquid drop approaches a deep liquid pool, both the interface of the drop and the pool deform before the drop touches the pool. The build up of air pressure prior to coalescence is responsible for this deformation. Due to this deformation, air can be entrained at the bottom of the drop during the impact. We quantify the amount of entrained air numerically, using the Boundary Integral Method (BIM) for potential flow for the drop and the pool, coupled to viscous lubrication theory for the air film that has to be squeezed out during impact. We compare our results to various experimental data and find excellent agreement for the amount of air that is entrapped during impact onto a pool. Next, the impact of a rigid sphere onto a pool is numerically investigated and the air that is entrapped in this case also matches with available experimental data. In both cases of drop and sphere impact onto a pool the numerical air bubble volume V_b is found to be in agreement with the theoretical scaling V_b/V_{drop/sphere} ~ St^{-4/3}, where St is the Stokes number. This is the same scaling that has been found for drop impact onto a solid surface in previous research. This implies a universal mechanism for air entrainment for these different impact scenarios, which has been suggested in recent experimental work, but is now further elucidated with numerical results.

  16. Entrainment.

    ERIC Educational Resources Information Center

    Carrier, Romance F.

    1978-01-01

    Presents a literature review including: (1) theoretical studies concerned with the development of methdology to determine the significance of entrainment effects to whale populations and ecosystems; and (2) site and laboratory studies. A list of 107 references drawn from the 1976 and 1977 literature is also presented. (HM)

  17. Freeze-Thaw Durability of Air-Entrained Concrete

    PubMed Central

    Shang, Huai-Shuai; Yi, Ting-Hua

    2013-01-01

    One of the most damaging actions affecting concrete is the abrupt temperature change (freeze-thaw cycles). The types of deterioration of concrete structures by cyclic freeze-thaw can be largely classified into surface scaling (characterized by the weight loss) and internal crack growth (characterized by the loss of dynamic modulus of elasticity). The present study explored the durability of concrete made with air-entraining agent subjected to 0, 100, 200, 300, and 400 cycles of freeze-thaw. The experimental study of C20, C25, C30, C40, and C50 air-entrained concrete specimens was completed according to “the test method of long-term and durability on ordinary concrete” GB/T 50082-2009. The dynamic modulus of elasticity and weight loss of specimens were measured after different cycles of freeze-thaw. The influence of freeze-thaw cycles on the relative dynamic modulus of elasticity and weight loss was analyzed. The findings showed that the dynamic modulus of elasticity and weight decreased as the freeze-thaw cycles were repeated. They revealed that the C30, C40, and C50 air-entrained concrete was still durable after 300 cycles of freeze-thaw according to the experimental results. PMID:23576906

  18. Freeze-thaw durability of air-entrained concrete.

    PubMed

    Shang, Huai-Shuai; Yi, Ting-Hua

    2013-01-01

    One of the most damaging actions affecting concrete is the abrupt temperature change (freeze-thaw cycles). The types of deterioration of concrete structures by cyclic freeze-thaw can be largely classified into surface scaling (characterized by the weight loss) and internal crack growth (characterized by the loss of dynamic modulus of elasticity). The present study explored the durability of concrete made with air-entraining agent subjected to 0, 100, 200, 300, and 400 cycles of freeze-thaw. The experimental study of C20, C25, C30, C40, and C50 air-entrained concrete specimens was completed according to "the test method of long-term and durability on ordinary concrete" GB/T 50082-2009. The dynamic modulus of elasticity and weight loss of specimens were measured after different cycles of freeze-thaw. The influence of freeze-thaw cycles on the relative dynamic modulus of elasticity and weight loss was analyzed. The findings showed that the dynamic modulus of elasticity and weight decreased as the freeze-thaw cycles were repeated. They revealed that the C30, C40, and C50 air-entrained concrete was still durable after 300 cycles of freeze-thaw according to the experimental results. PMID:23576906

  19. Entrained neural oscillations in multiple frequency bands comodulate behavior

    PubMed Central

    Henry, Molly J.; Herrmann, Björn

    2014-01-01

    Our sensory environment is teeming with complex rhythmic structure, to which neural oscillations can become synchronized. Neural synchronization to environmental rhythms (entrainment) is hypothesized to shape human perception, as rhythmic structure acts to temporally organize cortical excitability. In the current human electroencephalography study, we investigated how behavior is influenced by neural oscillatory dynamics when the rhythmic fluctuations in the sensory environment take on a naturalistic degree of complexity. Listeners detected near-threshold gaps in auditory stimuli that were simultaneously modulated in frequency (frequency modulation, 3.1 Hz) and amplitude (amplitude modulation, 5.075 Hz); modulation rates and types were chosen to mimic the complex rhythmic structure of natural speech. Neural oscillations were entrained by both the frequency modulation and amplitude modulation in the stimulation. Critically, listeners’ target-detection accuracy depended on the specific phase–phase relationship between entrained neural oscillations in both the 3.1-Hz and 5.075-Hz frequency bands, with the best performance occurring when the respective troughs in both neural oscillations coincided. Neural-phase effects were specific to the frequency bands entrained by the rhythmic stimulation. Moreover, the degree of behavioral comodulation by neural phase in both frequency bands exceeded the degree of behavioral modulation by either frequency band alone. Our results elucidate how fluctuating excitability, within and across multiple entrained frequency bands, shapes the effective neural processing of environmental stimuli. More generally, the frequency-specific nature of behavioral comodulation effects suggests that environmental rhythms act to reduce the complexity of high-dimensional neural states. PMID:25267634

  20. Freeze-thaw durability of microwave cured air-entrained concrete

    SciTech Connect

    Pheeraphan, T.; Leung, C.K.Y.

    1997-03-01

    The strength development of concrete can be greatly accelerated by curing with microwave energy. Microwave curing can therefore be beneficial to construction operations such as concrete precasting and repair. To provide freeze-thaw durability for infrastructure applications, air entrainment has to be introduced. In this investigation, the freeze-thaw resistance of microwave cured air-entrained concrete is measured, and compared to that of air-entrained concrete under normal curing. Their compressive strength at 14 days and air-void characteristics are also measured and compared. The test results indicate that microwave curing can impair the freeze-thaw durability of high w/c concrete but not for low w/c concrete. Also, under microwave curing, the decrease in strength due to air entrainment becomes more significant. Based on these observations, it is recommended that for microwave cured air-entrained concrete, a low w/c ratio should be employed.

  1. Entrainment of Upper Level Dry Air into Hurricane Earl

    NASA Technical Reports Server (NTRS)

    Guillory, Anthony R.; Jedlovee, Gary J.; Hood, Robbie E.; Atkinson, Robert J.; LaFontaine, Frank J.

    2000-01-01

    Hurricane Earl developed from a tropical wave that moved into the Gulf of Mexico, which triggered abundant convection. On 1 Sept. 1998, the wave was upgraded directly to a tropical storm. Earl reached hurricane status the next morning. The system moved erratically as it interacted with an upper level short wave trough rotating around a long wave trough to the northeast. The storm made landfall near 0600 UTC on 3 September near Panama City, FL. During August and September 1998, NASA conducted the Third Convection and Moisture Experiment (CAMEX-3). It focused on studying the intensity, track, and impacts at landfall of hurricanes. On the afternoon of 2 September 1998, the NASA ER2 high-altitude aircraft flying at 65,000 feet in tandem with the NASA DC-8 flying at 35,000 feet flew over and through, respectively, the eastern rainbands of Earl near the Florida Panhandle as the storm neared landfall in the region. Two approaches to studying Earl are undertaken here: first, an examination of the source and height of the dry air region using GOES-8 water vapor data and, second, a look into the impact of the dry air entrainment on the system using aircraft remote sensing data.

  2. The influence of clean air entrainment on the droplet effective radius of warm maritime convective clouds

    SciTech Connect

    Pontikis, C.A.; Hicks, E.M.

    1993-09-01

    The influence of clear air entrainment on the droplet effective radius of cloudy air parcels is investigated theoretically and experimentally by using data collected in 16 warm maritime tropical cumuli during the Joint Hawaii Warm Rain Project (1985). The theoretical study consists of calculations of the droplet spectrum, droplet effective radius, and liquid water content performed by an entraining cloud parcel model for different entrainment-mixing scenarios. The numerical simulation results are interpreted by means of an analytic equation of the droplet effective radius expressed as a function of both the liquid water content and the droplet concentration. In the experiment study, the behavior of the effective radius is examined at all scales as a function of the liquid water content, used as a dilution degree indicator. At a given cloud level, in the abscence of secondary droplet activation, the effective radius of the droplet spectrum of small-scale parcels (10-Hz data) is roughly independent of the liquid water content and appears unaffected by entrainment. In contrast, if secondary droplet activation occurs in diluted ascending cloud parcels, a wide range of effective radius values is observed for a given liquid water content as a result of the induced variation of the droplet concentration. Further, mean cloud pass effective radii increase with increasing mean pass liquid water contents and mean pass height above cloud base. The results limit the validity of the classical cloud effective radius parameterizations used in the radiative transfer calculations in climate models and some suggestions to improve these parameterizations are presented.

  3. Entrainment of Upper Level Dry Air Into Hurricane Earl

    NASA Technical Reports Server (NTRS)

    Guillory, Anthony R.; Jedlovec, Gary J.; Hood, Robbie E.; Atkinson, Robert J.; LaFontaine, Frank J.

    1999-01-01

    Hurricane Earl formed in the Gulf of Mexico in September 1998. It quickly was upgraded from a tropical disturbance to tropical storm status and then to a hurricane. Earl possessed hybrid (tropical and extratropical) characteristics throughout its lifetime. The system maintained and erratic track, which led to wide variability in the operational track forecasts. It eventually made landfall on the Florida panhandle on 2 September and raced northeastward. During August and September 1998, NASA conducted the third Convection and Moisture Experiment (CAMEX-3). The experiment was focused on studying hurricanes with an emphasis toward developing a better understanding of their intensification and motion. Earl provides a unique opportunity to utilize high spatial and temporal resolution data collected from the DC-8 and high altitude ER-2 NASA platforms, which flew over Earl as it made landfall. These data can also be put into broader view provided by other instruments from the Geosynchronous Operational Environmental Satellites (GOES) and the Tropical Rainfall Measuring Mission (TRMM) satellites. Hurricane Earl was affected by entrainment of dry air from the northwest. Hurricane Isis was intensifying and approaching the Mexican Pacific coast with its associated outflow potentially affecting the inflow into Earl as the storm neared Florida. In addition, a longwave synoptic trough circulation was present over the eastern U.S. Either or both of these could be responsible for the dry air into the system. This paper will focus on identifying the source of the dry by using upper-level wind and moisture fields derived from the GOES 6.7 um water vapor imagery. We will attempt to relate the large-scale observations to those from the NASA aircraft. An infrared instrument onboard the ER-2 also has a similar wavelength and may be able to confirm some of the GOES findings. In addition, a microwave radiometer with 4 channels focused on measuring precipitation and its associated ice

  4. On the relationship between air entrainment, internal flows and closure mechanism in a ventilated supercavity

    NASA Astrophysics Data System (ADS)

    Karn, Ashish; Arndt, Roger; Hong, Jiarong

    2015-11-01

    An understanding of underlying physics behind ventilation demand is critical for the operation of underwater vehicles based on ventilated supercavitation for a number of reasons viz. gas entrainment requirements for cavity formation and sustenance. The prior studies on the ventilation demand have reported that the gas entrainment requirement to form a supercavity is substantially larger than that needed to sustain it. This phenomenon, known as ventilation hysteresis, is particularly important from the viewpoint of reduction in gas requirements. However, little physical insights into this phenomenon has yet been provided. In this study, systematic investigations are conducted into ventilation hysteresis with respect to the formation and collapse behaviors of ventilated supercavities. It is suggested that the supercavity formation process is driven by bubble coalescence, whereas its collapse is related to the pressure difference across the supercavity interface at its rear portion. Further, we examine the relationship between ventilation hysteresis, supercavity closures and air entrainment requirements for supercavity formation and sustenance under steady and unsteady flow conditions. These observations are directly related to the internal flows inside the supercavity.

  5. Quantification of hood effectiveness and entrained subsurface air in a Seattle Hospital

    SciTech Connect

    Dietz, R.N.; Goodrich, R.W.

    1994-05-01

    An underground 3-story wing of a hospital having problems with sewer air odors was tested with perfluorocarbon tracer (PFI) technology to quantify the performance of the mechanical ventilation system and determine the extent of sewer air entrainment and chemical hood effectiveness.

  6. High temperature air-blown woody biomass gasification model for the estimation of an entrained down-flow gasifier.

    PubMed

    Kobayashi, Nobusuke; Tanaka, Miku; Piao, Guilin; Kobayashi, Jun; Hatano, Shigenobu; Itaya, Yoshinori; Mori, Shigekatsu

    2009-01-01

    A high temperature air-blown gasification model for woody biomass is developed based on an air-blown gasification experiment. A high temperature air-blown gasification experiment on woody biomass in an entrained down-flow gasifier is carried out, and then the simple gasification model is developed based on the experimental results. In the experiment, air-blown gasification is conducted to demonstrate the behavior of this process. Pulverized wood is used as the gasification fuel, which is injected directly into the entrained down-flow gasifier by the pulverized wood banner. The pulverized wood is sieved through 60 mesh and supplied at rates of 19 and 27kg/h. The oxygen-carbon molar ratio (O/C) is employed as the operational condition instead of the air ratio. The maximum temperature achievable is over 1400K when the O/C is from 1.26 to 1.84. The results show that the gas composition is followed by the CO-shift reaction equilibrium. Therefore, the air-blown gasification model is developed based on the CO-shift reaction equilibrium. The simple gasification model agrees well with the experimental results. From calculations in large-scale units, the cold gas is able to achieve 80% efficiency in the air-blown gasification, when the woody biomass feedrate is over 1000kg/h and input air temperature is 700K. PMID:18653324

  7. Coherent anti-Stokes Raman spectroscopic measurement of air entrainment in argon plasma jets

    SciTech Connect

    Fincke, J.R.; Rodriquez, R.; Pentecost, C.G.

    1990-01-01

    The concentration and temperature of air entrained into an argon plasma jet has been measured using coherent anti-Stokes Raman spectroscopy (CARS). The flow field is characterized by a short region of well behaved laminar flow near the nozzle exit followed by an abrupt transition to turbulence. Once the transition to turbulence occurs, air is rapidly entrained into the jet core. The location of the transition region is thought to be driven by the rapid cooling of the jet and the resulting increase in Reynolds number. 8 refs., 6 figs.

  8. Coherent anti-Stokes Raman spectroscopic measurement of air entrainment in argon plasma jets

    NASA Astrophysics Data System (ADS)

    Fincke, J. R.; Rodriquez, R.; Pentecost, C. G.

    The concentration and temperature of air entrained into an argon plasma jet has been measured using coherent anti-Stokes Raman spectroscopy (CARS). The flow field is characterized by a short region of well behaved laminar flow near the nozzle exit followed by an abrupt transition to turbulence. Once the transition to turbulence occurs, air is rapidly entrained into the jet core. The location of the transition region is thought to be driven by the rapid cooling of the jet and the resulting increase in Reynolds number.

  9. Air Entrainment and Thermal Evolution of Pyroclastic Density Currents at Tungurahua, Ecuador

    NASA Astrophysics Data System (ADS)

    Benage, M. C.; Dufek, J.; Mothes, P. A.

    2015-12-01

    The entrainment of air into pyroclastic density currents (PDCs) impacts the thermal profile and evolution of the current. However, the associated hazards and opaqueness of PDCs make it difficult to discern internal dynamics and entrainment through direct observations. In this work, we use a three-dimensional multiphase Eulerian-Eulerian-Lagrangian (EEL) model, deposit descriptions, and pyroclast field data, such as paleomagnetic and rind thickness, to study the entrainment efficiency and thus the thermal history of PDCs down the Juive Grande quebrada during the August 16-17th 2006 eruption of Tungurahua volcano. We conclude that 1) the efficient entrainment of ambient air cools the nose and upper portion of the PDCs by 30-60% of the original temperature, 2) PDCs with an initial temperature of 727 °C are on average more efficient at entraining ambient air than PDCs with an initial temperature of 327 °C, 3) the channelized PDCs develop a particle concentration gradient with a concentrated bed load region and suspended load region that leads to a large vertical temperature gradient, and 4) observations and pyroclast temperatures and textures suggest that the PDCs had temperatures greater than 327 °C in the bed load region while the upper, exterior portion of the currents cooled down to temperatures less than 100 °C. By combining field data and numerical models, the structure and dynamics of a PDC can be deduced for these relatively common small volume PDCs.

  10. MEASUREMENT OF AIR ENTRAINMENT AND DUST EMISSION DURING SHELLED CORN RECEIVING OPERATIONS WITH SIMULATED HOPPER BOTTOM GRAIN TRAILERS

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Dust emissions from grain elevator operations can be a safety and health risk, and a nuisance. Dust emission and air entrainment data are needed for designing adequate and effective control methods. This study measured the dust emitted and air entrained during corn receiving operations at an eleva...

  11. A Subgrid Model for Predicting Air Entrainment Rates in Bubbly Flows

    NASA Astrophysics Data System (ADS)

    Ma, Jingsen; Oberai, Assad A.; Drew, Donald E.; Lahey, Richard T., Jr.; Moraga, Francisco J.

    2008-11-01

    In this talk we present a fairly simple subgrid air entrainment model that accurately predicts the rate of air entrainment, which is critical in simulating multiphase (air/water) flows. The derivation of this model begins by assuming that a thin sheet of air is carried into the water by the inertia of the liquid at the free surface. A momentum balance on the entrained gas layer results in an expression for the entrained volumetric gas flow rate, in terms of the local liquid velocity, gas viscosity etc., which are readily available from a multiphase RANS-type simulation. This model has been validated against extensive experimental data on both plunging jets and hydraulic jumps over a wide range of liquid velocities. It was implemented in a two-fluid computational fluid dynamics code (CFDShipM) to be used to predict the void fraction distribution underneath a plunging liquid jet at different depths and jet velocities. The results were found to match the experimental observations very well. The application of this model to more challenging problems, including hydraulic jumps and full-scale ship simulations, is currently underway.

  12. Foam and Entrained Air Management: A Practical Perspective

    NASA Astrophysics Data System (ADS)

    Mirza, Sal; Hoekstra, Philip M.

    Paper machines and the papermaking process have undergone remarkable changes in terms of chemistry applications and design parameters. These trends increase the likelihood that the stock will foam and generate turbulence, thus allowing air to be drawn in. For example, higher machine speeds and gap former technology cause more air to be present in the white water, which could ultimately lead to foam problems if not managed correctly.

  13. Experimental study of near-field air entrainment by subsonic volcanic jets

    USGS Publications Warehouse

    Solovitz, S.A.; Mastin, L.G.

    2009-01-01

    The flow structure in the developing region of a turbulent jet has been examined using particle image velocimetry methods, considering the flow at steady state conditions. The velocity fields were integrated to determine the ratio of the entrained air speed to the jet speed, which was approximately 0.03 for a range of Mach numbers up to 0.89 and. Reynolds numbers up to 217,000. This range of experimental Mach and Reynolds numbers is higher than previously considered for high-accuracy entrainment measures, particularly in the near-vent region. The entrainment values are below those commonly used for geophysical analyses of volcanic plumes, suggesting that existing 1-D models are likely to understate the tendency for column collapse. Copyright 2009 by the American Geophysical Union.

  14. Individual Differences in Rhythmic Cortical Entrainment Correlate with Predictive Behavior in Sensorimotor Synchronization.

    PubMed

    Nozaradan, Sylvie; Peretz, Isabelle; Keller, Peter E

    2016-01-01

    The current study aims at characterizing the mechanisms that allow humans to entrain the mind and body to incoming rhythmic sensory inputs in real time. We addressed this unresolved issue by examining the relationship between covert neural processes and overt behavior in the context of musical rhythm. We measured temporal prediction abilities, sensorimotor synchronization accuracy and neural entrainment to auditory rhythms as captured using an EEG frequency-tagging approach. Importantly, movement synchronization accuracy with a rhythmic beat could be explained by the amplitude of neural activity selectively locked with the beat period when listening to the rhythmic inputs. Furthermore, stronger endogenous neural entrainment at the beat frequency was associated with superior temporal prediction abilities. Together, these results reveal a direct link between cortical and behavioral measures of rhythmic entrainment, thus providing evidence that frequency-tagged brain activity has functional relevance for beat perception and synchronization. PMID:26847160

  15. Individual Differences in Rhythmic Cortical Entrainment Correlate with Predictive Behavior in Sensorimotor Synchronization

    PubMed Central

    Nozaradan, Sylvie; Peretz, Isabelle; Keller, Peter E.

    2016-01-01

    The current study aims at characterizing the mechanisms that allow humans to entrain the mind and body to incoming rhythmic sensory inputs in real time. We addressed this unresolved issue by examining the relationship between covert neural processes and overt behavior in the context of musical rhythm. We measured temporal prediction abilities, sensorimotor synchronization accuracy and neural entrainment to auditory rhythms as captured using an EEG frequency-tagging approach. Importantly, movement synchronization accuracy with a rhythmic beat could be explained by the amplitude of neural activity selectively locked with the beat period when listening to the rhythmic inputs. Furthermore, stronger endogenous neural entrainment at the beat frequency was associated with superior temporal prediction abilities. Together, these results reveal a direct link between cortical and behavioral measures of rhythmic entrainment, thus providing evidence that frequency-tagged brain activity has functional relevance for beat perception and synchronization. PMID:26847160

  16. Large Field of View PIV Measurements of Air Entrainment by SLS SMAT Water Sound Suppression System

    NASA Astrophysics Data System (ADS)

    Stegmeir, Matthew; Pothos, Stamatios; Bissell, Dan

    2015-11-01

    Water-based sound suppressions systems have been used to reduce the acoustic impact of space vehicle launches. Water flows at a high rate during launch in order to suppress Engine Generated Acoustics and other potentially damaging sources of noise. For the Space Shuttle, peak flow rates exceeded 900,000 gallons per minute. Such large water flow rates have the potential to induce substantial entrainment of the surrounding air, affecting the launch conditions and generating airflow around the launch vehicle. Validation testing is necessary to quantify this impact for future space launch systems. In this study, PIV measurements were performed to map the flow field above the SMAT sub-scale launch vehicle scaled launch stand. Air entrainment effects generated by a water-based sound suppression system were studied. Mean and fluctuating fluid velocities were mapped up to 1m above the test stand deck and compared to simulation results. Measurements performed with NASA MSFC.

  17. Material Properties Governing Co-Current Flame Spread: The Effect of Air Entrainment

    NASA Technical Reports Server (NTRS)

    Coutin, Mickael; Rangwala, Ali S.; Torero, Jose L.; Buckley, Steven G.

    2003-01-01

    A study on the effects of lateral air entrainment on an upward spreading flame has been conducted. The fuel is a flat PMMA plate of constant length and thickness but variable width. Video images and surface temperatures have allowed establishing the progression of the pyrolyis front and on the flame stand-off distance. These measurements have been incorporated into a theoretical formulation to establish characteristic mass transfer numbers ("B" numbers). The mass transfer number is deemed as a material related parameter that could be used to assess the potential of a material to sustain co-current flame spread. The experimental results show that the theoretical formulation fails to describe heat exchange between the flame and the surface. The discrepancies seem to be associated to lateral air entrainment that lifts the flame off the surface and leads to an over estimation of the local mass transfer number. Particle Image Velocimetry (PIV) measurements are in the process of being acquired. These measurements are intended to provide insight on the effect of air entrainment on the flame stand-off distance. A brief description of the methodology to be followed is presented here.

  18. Using Neutron Radiography to Quantify Water Transport and the Degree of Saturation in Entrained Air Cement Based Mortar

    NASA Astrophysics Data System (ADS)

    Lucero, Catherine L.; Bentz, Dale P.; Hussey, Daniel S.; Jacobson, David L.; Weiss, W. Jason

    Air entrainment is commonly added to concrete to help in reducing the potential for freeze thaw damage. It is hypothesized that the entrained air voids remain unsaturated or partially saturated long after the smaller pores fill with water. Small gel and capillary pores in the cement matrix fill quickly on exposure to water, but larger pores (entrapped and entrained air voids) require longer times or other methods to achieve saturation. As such, it is important to quantitatively determine the water content and degree of saturation in air entrained cementitious materials. In order to further investigate properties of cement-based mortar, a model based on Beer's Law has been developed to interpret neutron radiographs. This model is a powerful tool for analyzing images acquired from neutron radiography. A mortar with a known volume of aggregate, water to cement ratio and degree of hydration can be imaged and the degree of saturation can be estimated.

  19. Pyrrhotite Oxidation as an Indicator of Air Entrainment into Eruption Columns

    NASA Astrophysics Data System (ADS)

    Matsumoto, K.; Nakamura, M.

    2015-12-01

    Fragmented magmas in eruption columns obtain buoyancy by entrainment and heating of cold air. Theoretically, the proportion of the entrained air and temperature change of the magma fragments can be calculated through rigorous fluid dynamics, but these factors have not been evaluated from natural pyroclasts. In this study, we developed a new method for quantifying the degree of air entrainment based on pyrrhotite (Po) oxidation reactions, whose time scale corresponds to the typical duration of (sub-) Plinian eruptions (i.e., tens of seconds to a few hours). We examined pumice clasts and lava flows from the 1914-15 eruption of Sakurajima. During this event, various types of eruption were observed: Plinian eruptions with intermittent generation of clastogenic lava flow, followed by voluminous effusive lava flow. The products of Po oxidation consisted of magnetite (Mt), hematite (Hm), and their composites. The occurrence of Po and the oxides were systematically correlated with the types of eruption. In Plinian pumices, unreacted Po ± porous Mt-Hm composite reaction rims were dominant, whereas in the clastogenic lava, porous Hm occurred predominantly with scarce unreacted Po and porous Mt. In the effusive lava, a variety of Po, Mt, and Hm assemblage was observed, but Po did not coexist with Hm-rims. The porous Mt crystals in the pumice clasts were found to be Ti-free, whereas those in the effusive lava had Ti-enriched rims. These correlations were explained by considering two factors: the achieved fO2, which was controlled by the extent of fragmentation (i.e., surface area exposed to air), and duration of the maintenance of a high-T and high-fO2 condition. This study has demonstrated that the cooling timescale of pumice clasts in eruption columns can be estimated through the rate of Po oxidation reactions Po→Mt and Mt→Hm. Lavas of clastogenic origin may also be recognized from the reaction.

  20. Turbulent hydraulic jumps: Effect of Weber number and Reynolds number on air entrainment and micro-bubble generation

    NASA Astrophysics Data System (ADS)

    Mortazavi, Milad; Mani, Ali

    2015-11-01

    Air entrainment in breaking waves is a ubiquitous and complex phenomenon. It is the main source of air transfer from atmosphere to the oceans. Furthermore, air entrainment due to ship-induced waves contributes to bubbly flows in ship wakes and also affect their performance. In this study, we consider a turbulent hydraulic jump as a canonical setting to investigate air entrainment due to turbulence-wave interactions. The flow has an inlet Froude number of 2.0, while three different Weber numbers (We = 1820, 729, 292), and two different Reynolds numbers (Re = 11000, 5500) based on the inlet height and inlet velocity are investigated. Air entrainment is shown to be very sensitive to the We number, while Re number has a minor effect. Wave breaking and interface collisions are significantly reduced in the low Weber number cases. As a result, micro-bubble generation is significantly reduced with decreasing Weber number. Vortex shedding events are observed to emerge at the toe of the jump in all of the cases. For high Weber number regimes, shedding of vortices is accompanied by engulfment of air pockets into the jump in a periodic manner, while for lower Webber number regimes such events are significantly suppressed. Reynolds number is shown to have a negligible effect on the air entrainment, wave breaking and micro-bubble generation, contrary to the previous assumptions in other studies. Supported by ONR.

  1. Investigation of air-entraining admixture dosage in fly ash concrete

    SciTech Connect

    Ley, M.T.; Harris, N.J.; Folliard, K.J.; Hover, K.C.

    2008-09-15

    The amount of air-entraining admixture (AEA) needed to achieve a target air content in fresh concrete can vary significantly with differences in the fly ash used in the concrete. The work presented in this paper evaluates the ability to predict the AEA dosage on the basis of tests on the fly ash alone. All results were compared with the dosage of AEA required to produce an air content of 6% in fresh concrete. Fly ash was sampled from six separate sources. For four of these sources, samples were obtained both before and after the introduction of 'low-NOx burners'. Lack of definitive data about the coal itself or the specifics of the burning processes prevents the ability to draw specific conclusions about the impact of low-NOx burners on AEA demand. Nevertheless, the data suggest that modification of the burning process to meet environmental quality standards may affect the fly ash-AEA interaction.

  2. Simulation study on factors influencing the entrainment behavior of liquid steel as bubbles pass through the steel/slag interface

    NASA Astrophysics Data System (ADS)

    Li, Xiang; Bao, Yan-ping; Wang, Min; Lin, Lu

    2016-05-01

    In this study, a water/silicone oil interface was used to simulate the steel/slag interface in a converter. A high-speed camera was used to record the entrainment process of droplets when air bubbles were passed through the water/silicone oil interface. Motion parameters of the bubbles and droplets were obtained using particle kinematic analysis software, and the entrainment rate of the droplets was calculated. It was found that the entrainment rate decreased from 29.5% to 0 when the viscosity of the silicone oil was increased from 60 mPa·s to 820 mPa·s in the case of bubbles with a 5 mm equivalent diameter passing through the water/silicone oil interface. The results indicate that increasing the viscosity of the silicone oil is conducive to reducing the entrainment rate. The entrainment rate increased from 0 to 136.3% in the case of silicone oil with a viscosity of 60 mPa·s when the equivalent diameter of the bubbles was increased from 3 mm to 7 mm. We therefore conclude that small bubbles are also conductive to reducing the entrainment rate. The force analysis results for the water column indicate that the entrainment rate of droplets is affected by the velocity of the bubble passing through the water/silicone oil interface and that the entrainment rate decreases with the bubble velocity.

  3. The effect of water temperature on air entrainment, bubble plumes, and surface foam in a laboratory breaking-wave analog

    NASA Astrophysics Data System (ADS)

    Callaghan, A. H.; Stokes, M. D.; Deane, G. B.

    2014-11-01

    Air-entraining breaking waves form oceanic whitecaps and play a key role in climate regulation through air-sea bubble-mediated gas transfer, and sea spray aerosol production. The effect of varying sea surface temperature on air entrainment, subsurface bubble plume dynamics, and surface foam evolution intrinsic to oceanic whitecaps has not been well studied. By using a breaking wave analog in the laboratory over a range of water temperatures (Tw = 5°C to Tw = 30°C) and different source waters, we have examined changes in air entrainment, subsurface bubble plumes, and surface foam evolution over the course of a breaking event. For filtered seawater, air entrainment was estimated to increase by 6% between Tw = 6°C and Tw = 30°C, driven by increases of about 43% in the measured surface roughness of the plunging water sheet. After active air entrainment, the rate of loss of air through bubble degassing was more rapid at colder water temperatures within the first 0.5 s of plume evolution. Thereafter, the trend reversed and bubbles degassed more quickly in warmer water. The largest observed temperature-dependent differences in subsurface bubble distributions occurred at radii greater than about 700 μm. Temperature-dependent trends observed in the subsurface bubble plume were mirrored in the temporal evolution of the surface whitecap foam area demonstrating the intrinsic link between surface whitecap foam and the subsurface bubble plume. Differences in foam and plume characteristics due to different water sources were greater than the temperature dependencies for the filtered seawater examined.

  4. Keeping warm with fur in cold water: entrainment of air in hairy surfaces

    NASA Astrophysics Data System (ADS)

    Nasto, Alice; Regli, Marianne; Brun, Pierre-Thomas; Clanet, Christophe; Hosoi, Anette

    2015-11-01

    Instead of relying on a thick layer of body fat for insulation as many aquatic mammals do, fur seals and otters trap air in their dense fur for insulation in cold water. Using a combination of model experiments and theory, we rationalize this mechanism of air trapping underwater for thermoregulation. For the model experiments, hairy surfaces are fabricated using laser cut molds and casting samples with PDMS. Modeling the hairy texture as a network of capillary tubes, the imbibition speed of water into the hairs is obtained through a balance of hydrostatic pressure and viscous stress. In this scenario, the bending of the hairs and capillary forces are negligible. The maximum diving depth that can be achieved before the hairs are wetted to the roots is predicted from a comparison of the diving speed and imbibition speed. The amount of air that is entrained in hairy surfaces is greater than what is expected for classic Landau-Levich-Derjaguin plate plunging. A phase diagram with the parameters from experiments and biological data allows a comparison of the model system and animals.

  5. The effect of low-NO{sub x} combustion on residual carbon in fly ash and its adsorption capacity for air entrainment admixtures in concrete

    SciTech Connect

    Pedersen, K.H.; Jensen, A.D.; Dam-Johansen, K.

    2010-02-15

    Fly ash from pulverized coal combustion contains residual carbon that can adsorb the air-entraining admixtures (AEAs) added to control the air entrainment in concrete. This is a problem that has increased by the implementation of low-NO{sub x} combustion technologies. In this work, pulverized fuel has been combusted in an entrained flow reactor to test the impact of changes in operating conditions and fuel type on the AEA adsorption of ash and NO{sub x} formation. Increased oxidizing conditions, obtained by improved fuel-air mixing or higher excess air, decreased the AEA requirements of the produced ash by up to a factor of 25. This was due to a lower carbon content in the ash and a lower specific AEA adsorptivity of the carbon. The latter was suggested to be caused by changes in the adsorption properties of the unburned char and a decreased formation of soot, which was found to have a large AEA adsorption capacity based on measurements on a carbon black. The NO{sub x} formation increased by up to three times with more oxidizing conditions and thus, there was a trade-off between the AEA requirements of the ash and NO{sub x} formation. The type of fuel had high impact on the AEA adsorption behavior of the ash. Ashes produced from a Columbian and a Polish coal showed similar AEA requirements, but the specific AEA adsorptivity of the carbon in the Columbian coal ash was up to six times higher. The AEA requirements of a South African coal ash was unaffected by the applied operating conditions and showed up to 12 times higher AEA adsorption compared to the two other coal ashes. This may be caused by larger particles formed by agglomeration of the primary coal particles in the feeding phase or during the combustion process, which gave rise to increased formation of soot. (author)

  6. ENTRAINMENT MODELS

    EPA Science Inventory

    This presentation presented information on entrainment models. Entrainment models use entrainment hypotheses to express the continuity equation. The advantage is that plume boundaries are known. A major disadvantage is that the problems that can be solved are rather simple. The ...

  7. Entrainment Heat Flux Computed with Lidar and Wavelet Technique in Buenos Aires During Last Chaitén Volcano Eruption

    NASA Astrophysics Data System (ADS)

    Pawelko, Ezequiel Eduardo; Salvador, Jacobo Omar; Ristori, Pablo Roberto; Pallotta, Juan Vicente; Otero, Lidia Ana; Quel, Eduardo Jaime

    2016-06-01

    At Lidar Division of CEILAP (CITEDEF-CONICET) a multiwavelength Raman-Rayleigh lidar optimized to measure the atmospheric boundary layer is being operated. This instrument is used for monitoring important aerosol intrusion events in Buenos Aires, such as the arrival of volcanic ashes from the Chaitén volcano eruption on May 2008. That was the first monitoring of volcanic ash with lidar in Argentina. In this event several volcanic ash plumes with high aerosol optical thickness were detected in the free atmosphere, affecting the visibility, surface radiation and therefore, the ABL evolution. In this work, the impact of ashes in entrainment flux ratio is studied. This parameter is obtained from the atmospheric boundary layer height and entrainment zone thickness using algorithms based on covariance wavelet transform.

  8. Two-phase numerical study of the flow field formed in water pump sump: influence of air entrainment

    NASA Astrophysics Data System (ADS)

    Bayeul-Lainé, A. C.; Simonet, S.; Bois, G.; Issa, A.

    2012-11-01

    In a pump sump it is imperative that the amount of non-homogenous flow and entrained air be kept to a minimum. Free air-core vortex occurring at a water-intake pipe is an important problem encountered in hydraulic engineering. These vortices reduce pump performances, may have large effects on the operating conditions and lead to increase plant operating costs.This work is an extended study starting from 2006 in LML and published by ISSA and al. in 2008, 2009 and 2010. Several cases of sump configuration have been numerically investigated using two specific commercial codes and based on the initial geometry proposed by Constantinescu and Patel. Fluent and Star CCM+ codes are used in the previous studies. The results, obtained with a structured mesh, were strongly dependant on main geometrical sump configuration such as the suction pipe position, the submergence of the suction pipe on one hand and the turbulence model on the other hand. Part of the results showed a good agreement with experimental investigations already published. Experiments, conducted in order to select best positions of the suction pipe of a water-intake sump, gave qualitative results concerning flow disturbances in the pump-intake related to sump geometries and position of the pump intake. The purpose of this paper is to reproduce the flow pattern of experiments and to confirm the geometrical parameter that influences the flow structure in such a pump. The numerical model solves the Reynolds averaged Navier-Stokes (RANS) equations and VOF multiphase model. STAR CCM+ with an adapted mesh configuration using hexahedral mesh with prism layer near walls was used. Attempts have been made to calculate two phase unsteady flow for stronger mass flow rates and stronger submergence with low water level in order to be able to capture air entrainment. The results allow the knowledge of some limits of numerical models, of mass flow rates and of submergences for air entrainment. In the validation of this

  9. Global and local oscillatory entrainment of visual behavior across retinotopic space.

    PubMed

    Sokoliuk, Rodika; VanRullen, Rufin

    2016-01-01

    Ongoing brain oscillations (7-10 Hz) modulate visual perception; in particular, their precise phase can predict target perception. Here, we employ this phase-dependence of perception in a psychophysical experiment to track spatial properties of entrained oscillations of visual perception across the visual field. Is this entrainment local, or a more global phenomenon? If the latter, does oscillatory phase synchronize over space, or vary with increasing distance from the oscillatory source? We presented a disc stimulus in the upper left quadrant, oscillating in luminance at different frequencies (individual alpha frequency (IAF), 5 Hz, and 15 Hz) to entrain an oscillation with specific frequency and spatial origin. Observers fixated centrally, while flash stimuli at perceptual threshold appeared at different positions and times with respect to the oscillating stimulus. IAF and 5 Hz luminance oscillations modulated detection performance at all tested positions, whereas at 15 Hz, the effect was weaker and less consistent. Furthermore, for IAF and 5 Hz entrainment, preferred phases for target detection differed significantly between spatial locations, suggesting "local" entrainment of detection performance next to the oscillatory source, whereas more distant target locations shared a "global" effect with a significantly different phase. This unexpected global component of entrainment is tentatively attributed to widespread connectivity from thalamic nuclei such as the pulvinar. PMID:27126642

  10. Global and local oscillatory entrainment of visual behavior across retinotopic space

    PubMed Central

    Sokoliuk, Rodika; VanRullen, Rufin

    2016-01-01

    Ongoing brain oscillations (7–10 Hz) modulate visual perception; in particular, their precise phase can predict target perception. Here, we employ this phase-dependence of perception in a psychophysical experiment to track spatial properties of entrained oscillations of visual perception across the visual field. Is this entrainment local, or a more global phenomenon? If the latter, does oscillatory phase synchronize over space, or vary with increasing distance from the oscillatory source? We presented a disc stimulus in the upper left quadrant, oscillating in luminance at different frequencies (individual alpha frequency (IAF), 5 Hz, and 15 Hz) to entrain an oscillation with specific frequency and spatial origin. Observers fixated centrally, while flash stimuli at perceptual threshold appeared at different positions and times with respect to the oscillating stimulus. IAF and 5 Hz luminance oscillations modulated detection performance at all tested positions, whereas at 15 Hz, the effect was weaker and less consistent. Furthermore, for IAF and 5 Hz entrainment, preferred phases for target detection differed significantly between spatial locations, suggesting “local” entrainment of detection performance next to the oscillatory source, whereas more distant target locations shared a “global” effect with a significantly different phase. This unexpected global component of entrainment is tentatively attributed to widespread connectivity from thalamic nuclei such as the pulvinar. PMID:27126642

  11. Effect of Coal Properties and Operation Conditions on Flow Behavior of Coal Slag in Entrained Flow Gasifiers: A Brief Review

    SciTech Connect

    Wang,Ping; Massoudi, Mehrdad

    2011-01-01

    Integrated gasification combined cycle (IGCC) is a potentially promising clean technology with an inherent advantage of low emissions, since the process removes contaminants before combustion instead of from flue gas after combustion, as in a conventional coal steam plant. In addition, IGCC has potential for cost-effective carbon dioxide capture. Availability and high capital costs are the main challenges to making IGCC technology more competitive and fully commercial. Experiences from demonstrated IGCC plants show that, in the gasification system, low availability is largely due to slag buildup in the gasifier and fouling in the syngas cooler downstream of the gasification system. In the entrained flow gasifiers used in IGCC plants, the majority of mineral matter transforms to liquid slag on the wall of the gasifier and flows out the bottom. However, a small fraction of the mineral matter (as fly ash) is entrained with the raw syngas out of the gasifier to downstream processing. This molten/sticky fly ash could cause fouling of the syngas cooler. Therefore, it is preferable to minimize the quantity of fly ash and maximize slag. In addition, the hot raw syngas is cooled to convert any entrained molten fly slag to hardened solid fly ash prior to entering the syngas cooler. To improve gasification availability through better design and operation of the gasification process, better understanding of slag behavior and characteristics of the slagging process are needed. Slagging behavior is affected by char/ash properties, gas compositions in the gasifier, the gasifier wall structure, fluid dynamics, and plant operating conditions (mainly temperature and oxygen/carbon ratio). The viscosity of the slag is used to characterize the behavior of the slag flow and is the dominating factor to determine the probability that ash particles will stick. Slag viscosity strongly depends on the temperature and chemical composition of the slag. Because coal has varying ash content and

  12. Physical and computational studies of slag behavior in an entrained flow gasifier

    NASA Astrophysics Data System (ADS)

    Pummill, Randy

    This work details an investigation of how to modify slag flow so as to maintain a clear line of sight across the reaction section of an entrained-flow coal gasifier. Physical and computational models were developed to study methods of diverting the molten slag that flows vertically down the walls of the reactor. The physical models employed silicone oil of varying viscosity. The computational models were developed using the Fluent software package. Based on the insight gained from the results of the models, two devices were created and tested in a pilot scale gasifier located at the University of Utah. The first method of slag diversion studied employed a gas jet to impact the slag film and cause it to flow around a sight port in the gasifier wall. By studying the film and jet interactions, it was discovered that the resulting behavior of such a system can be described by a dimensionless ratio of the kinetic energy of the jet and the surface energy of the film. The development of the dimensionless number, called a Lotte number in this work, is presented in detail. Generally, viscous films will be broken by a jet when the Lotte number is greater than 5 and will reclose when the Lotte number falls below a value of 1.5. The second slag diversion method studied used a round alumina tube protruding horizontally into the reaction section to break up the film. As the film impacts the tube, it progresses horizontally along the length of the tube before resuming the downward flow. The models helped to establish how far the tube should protrude into the reactor in order to successfully break up the slag flow. Slag diversion devices were constructed and installed on a pilot scale gasifier. The jet diversion method was found to require an unreasonably large amount of purge gas to be successful and the metal jet suffered from the high temperature of the reactor despite the cooling effect of the gas. The tube diversion method worked very well for a series of experiments. However

  13. Twilight and photoperiod affect behavioral entrainment in the house mouse (Mus musculus).

    PubMed

    Comas, M; Hut, R A

    2009-10-01

    The effect of twilight transitions on entrainment of C57BL/6JOlaHsd mice (Mus musculus) was studied using light-dark cycles of different photoperiods (6, 12, and 18 h) and twilight transitions of different durations (0, 1, and 2 h). Phase angle differences of the onset, center of gravity, and offset of activity, activity duration (alpha), as well as free-running period (tau) in continuous darkness were analyzed. The main finding was that for all conditions the onset of activity was close to dusk or lights-off except for the short photoperiod with 2 h of twilight where activity onset was on average 5.3 (SEM 1.07) h after lights-off. This finding contrasts with the results of Boulos and Macchi for Syrian hamsters where a 5.9-h earlier activity onset was observed when similar photoperiod and twilight conditions are compared with a rectangular LD cycle. The authors suggest the opposite effects of 2 h of twilight in the 2 species may be related to their different free-running periods under DD conditions following entrainment to short photoperiod with 2-h twilight conditions. Since the authors observed larger variation in phase angle of entrainment in longer twilight conditions, twilight does not necessarily form a stronger zeitgeber. PMID:19755585

  14. Stratocumulus cloud deepening through entrainment

    NASA Technical Reports Server (NTRS)

    Randall, D. A.

    1984-01-01

    Under a substantial range of realistic conditions, stratocumulus cloud top entrainment is noted to either deepen an existing cloud layer or produce clouds in an unsaturated mixed layer, though the entrained air is warmer and drier than the mixed-layer air. These results, which apply irrespective of entrainment rate-determining mechanism, imply that the cloud top entrainment instability discussed by Randall (1980) and Deardorff (1980) does not necessarily destroy a layer cloud. Examples are given which include soundings, marine layer data, and simulation results produced by the UCLA general circulation model.

  15. Size distribution of oceanic air bubbles entrained in sea-water by wave-breaking

    NASA Technical Reports Server (NTRS)

    Resch, F.; Avellan, F.

    1982-01-01

    The size of oceanic air bubbles produced by whitecaps and wave-breaking is determined. The production of liquid aerosols at the sea surface is predicted. These liquid aerosols are at the origin of most of the particulate materials exchanged between the ocean and the atmosphere. A prototype was designed and built using an optical technique based on the principle of light scattering at an angle of ninety degrees from the incident light beam. The output voltage is a direct function of the bubble diameter. Calibration of the probe was carried out within a range of 300 microns to 1.2 mm. Bubbles produced by wave-breaking in a large air-sea interaction simulating facility. Experimental results are given in the form of size spectrum.

  16. Differences in gasification behaviors and related properties between entrained gasifier fly ash and coal char

    SciTech Connect

    Jing Gu; Shiyong Wu; Youqing Wu; Ye Li; Jinsheng Gao

    2008-11-15

    In the study, two fly ash samples from Texaco gasifiers were compared to coal char and the physical and chemical properties and reactivity of samples were investigated by scanning electron microscopy (SEM), SEM-energy-dispersive spectrometry (EDS), X-ray diffraction (XRD), N{sub 2} and CO{sub 2} adsorption method, and isothermal thermogravimetric analysis. The main results were obtained. The carbon content of gasified fly ashes exhibited 31-37%, which was less than the carbon content of 58-59% in the feed coal. The fly ashes exhibited higher Brunauer-Emmett-Teller (BET) surface area, richer meso- and micropores, more disordered carbon crystalline structure, and better CO{sub 2} gasification reactivity than coal char. Ashes in fly ashes occurred to agglomerate into larger spherical grains, while those in coal char do not agglomerate. The minerals in fly ashes, especial alkali and alkaline-earth metals, had a catalytic effect on gasification reactivity of fly ash carbon. In the low-temperature range, the gasification process of fly ashes is mainly in chemical control, while in the high-temperature range, it is mainly in gas diffusion control, which was similar to coal char. In addition, the carbon in fly ashes was partially gasified and activated by water vapor and exhibited higher BET surface area and better gasification activity. Consequently, the fact that these carbons in fly ashes from entrained flow gasifiers are reclaimed and reused will be considered to be feasible. 15 refs., 7 figs., 5 tabs.

  17. Duration and mutual entrainment of changes in parenting practices engendered by behavioral parent training targeting recently separated mothers.

    PubMed

    Reed, Andrea; Snyder, James; Staats, Sarah; Forgatch, Marion S; Degarmo, David S; Patterson, Gerald R; Low, Sabina; Sinclair, Ryan; Schmidt, Nicole

    2013-06-01

    Parent management training (PMT) has beneficial effects on child and parent adjustment that last for 5 to 10 years. Short-term changes in parenting practices have been shown to mediate these effects, but the manner in which changes in specific components of parenting are sequenced and become reciprocally reinforcing (or mutually entrained) to engender and sustain the cascade of long-term beneficial effects resulting from PMT has received modest empirical attention. Long-term changes in parenting resulting from the Oregon model of PMT (PMTO) over a 2-year period were examined using data from the Oregon Divorce Study-II in which 238 recently separated mothers and their 6- to 10-year-old sons were randomly assigned to PMTO or a no treatment control (NTC) group. Multiple indicators of observed parenting practices were used to define constructs for positive parenting, monitoring and discipline at baseline, and at 6-, 12-, 18- and 30-months postbaseline. PMTO relative to NTC resulted in increased positive parenting and prevented deterioration in discipline and monitoring over the 30-month period. There were reliable sequential, transactional relationships among parenting practices; positive parenting supported better subsequent monitoring, and positive parenting and better monitoring supported subsequent effective discipline. Small improvements in parenting resulting from PMTO and small deteriorations in parenting in the NTC group may be sustained and amplified by mutually entrained relationships among parenting practices. These data about the change processes engendered by PMTO may provide information needed to enhance the power, effectiveness, and efficiency of behavioral parent training interventions. PMID:23750517

  18. Airborne & SAR Synergy Reveals the 3D Structure of Air Bubble Entrainment in Internal Waves and Frontal Zones

    NASA Astrophysics Data System (ADS)

    da Silva, J. C. B.; Magalhaes, J. M.; Batista, M.; Gostiaux, L.; Gerkema, T.; New, A. L.

    2013-03-01

    Internal waves are now recognised as an important mixing mechanism in the ocean. Mixing at the base of the mixed layer and in the seasonal thermocline affects the properties of those water masses which define the exchange of heat and freshwater between the atmosphere and ocean. The breaking of Internal Solitary Waves (ISWs) contributes significantly to turbulent mixing in the near-surface layers, through the continual triggering of instabilities as they propagate and shoal towards the coast or shallow topography. Here we report some results of the EU funded project A.NEW (Airborne observations of Nonlinear Evolution of internal Waves generated by internal tidal beams). The airborne capabilities to observe small scale structure of breaking internal waves in the near-shore zone has been demonstrated in recent studies (e.g. Marmorino et al., 2008). In particular, sea surface thermal signatures of shoaling ISWs have revealed the turbulent character of these structures in the form of surface “boil” features. On the other hand, some in situ measurements of internal waves and theoretical work suggest subsurface entrainment of air bubbles in the convergence zones of ISWs (Serebryany and Galybin, 2009; Grimshaw et al., 2010). We conducted airborne remote sensing observations in the coastal zone off the west Iberian Peninsula (off Lisbon, Portugal) using high resolution imaging sensors: LiDAR (Light Detection And Ranging), hyperspectral cameras (Eagle and Hawk) and thermal infrared imaging (TABI-320). These measurements were planned based on previous SAR observations in the region, which included also near-real time SAR overpasses (ESA project AOPT-2423 and TerraSAR-X project OCE-0056). The airborne measurements were conducted from board the NERC (Natural Environmental Research Centre) Do 228 aircraft in the summer of 2010. The TABI-320 thermal airborne broadband imager can distinguish temperature differences as small as one-twentieth of a degree and operates in the

  19. Oscillators entrained by food and the emergence of anticipatory timing behaviors

    PubMed Central

    SILVER, Rae; BALSAM, Peter

    2011-01-01

    Circadian rhythms are adjusted to the external environment by the light–dark cycle via the suprachiasmatic nucleus, and to the internal environment of the body by multiple cues that derive from feeding/fasting. These cues determine the timing of sleep/wake cycles and all the activities associated with these states. We suggest that numerous sources of temporal information, including hormonal cues such as corticoids, insulin, and ghrelin, as well as conditioned learned responses determined by the temporal relationships between photic and feeding/fasting signals, can determine the timing of regularly recurring circadian responses. We further propose that these temporal signals can act additively to modulate the pattern of daily activity. Based on such reasoning, we describe the rationale and methodology for separating the influences of these diverse sources of temporal information. The evidence indicates that there are individual differences in sensitivity to internal and external signals that vary over circadian time, time since the previous meal, time until the next meal, or with duration of food deprivation. All of these cues are integrated in sites and circuits modulating physiology and behavior. Individuals detect changes in internal and external signals, interpret those changes as “hunger,” and adjust their physiological responses and activity levels accordingly. PMID:21544255

  20. Electrode Evaporation Effects on Air Arc Behavior

    NASA Astrophysics Data System (ADS)

    Li, Xingwen; Chen, Degui; Li, Rui; Wu, Yi; Niu, Chunping

    2008-06-01

    A numerical study of the effects of copper and silver vapours on the air arc behavior is performed. The commercial software FLUENT is adapted and modified to develop a two-dimensional magneto-hydrodynamic (MHD) models of arc with the thermodynamic properties and transport coefficients, net emission coefficient for the radiation model of 99% ai-1% Cu, 99% air-1% Ag, and pure air, respectively. The simulation result demonstrates that vaporization of the electrode material may cool the arc center region and reduce the arc velocity. The effects of Ag vapour are stronger compared to those of Cu vapour.

  1. The development and testing of an air/steam blown entrained flow gasifier fuelled with cotton waste and sawdust

    SciTech Connect

    Joseph, S.; Denniss, T.; Lipscombe, R.

    1996-12-31

    Australia produces approximately 50 million tonnes of biomass residue per year. Much of this residue is either burnt in the fields, at factory sites or disposed of in land fill. A recent study, sponsored by the Energy Research and Development Corporation (ERDC), has concluded that there is a potential to generate at least 2000MW of electricity per year from this waste. Research carried out in 1990 by Biomass Energy Services and Technology Pty (BEST) indicated that gasification power generating equipment with electrical outputs of 1-5 MW and installed capital costs of US$1200 per kW could be viable at present electricity prices. At that time equipment was not commercially available at the target price and thus an R & D programme was undertaken to develop gasification equipment suitable for Australian conditions. Following a detailed literature search and design study it appeared that an entrained flow (vortex) gasifier could handle the range of fuels available and could be produced at a price that would ensure its commercial viability. In this paper the design will be outlined and the mathematic modeling of the flow and the results of the tests undertaken will be presented. An outline of the demonstration program to be undertaken next year at a cotton gin will be given, along with the preliminary economic analysis that has been carried out.

  2. ENTRAINMENT BY LIGAMENT-CONTROLLED EFFERVESCENT ATOMIZER-PRODUCED SPRAYS

    EPA Science Inventory

    Entrainment of ambient air into sprays produced by a new type of effervescent atomizer is reported. Entrainment data were obtained using a device similar to that described by Ricou & Spalding (1961). Entrainment data were analyzed using the model of Bush & Sojka (1994), in concer...

  3. Timescales of massive human entrainment.

    PubMed

    Fusaroli, Riccardo; Perlman, Marcus; Mislove, Alan; Paxton, Alexandra; Matlock, Teenie; Dale, Rick

    2015-01-01

    The past two decades have seen an upsurge of interest in the collective behaviors of complex systems composed of many agents entrained to each other and to external events. In this paper, we extend the concept of entrainment to the dynamics of human collective attention. We conducted a detailed investigation of the unfolding of human entrainment--as expressed by the content and patterns of hundreds of thousands of messages on Twitter--during the 2012 US presidential debates. By time-locking these data sources, we quantify the impact of the unfolding debate on human attention at three time scales. We show that collective social behavior covaries second-by-second to the interactional dynamics of the debates: A candidate speaking induces rapid increases in mentions of his name on social media and decreases in mentions of the other candidate. Moreover, interruptions by an interlocutor increase the attention received. We also highlight a distinct time scale for the impact of salient content during the debates: Across well-known remarks in each debate, mentions in social media start within 5-10 seconds after it occurs; peak at approximately one minute; and slowly decay in a consistent fashion across well-known events during the debates. Finally, we show that public attention after an initial burst slowly decays through the course of the debates. Thus we demonstrate that large-scale human entrainment may hold across a number of distinct scales, in an exquisitely time-locked fashion. The methods and results pave the way for careful study of the dynamics and mechanisms of large-scale human entrainment. PMID:25880357

  4. Timescales of Massive Human Entrainment

    PubMed Central

    Fusaroli, Riccardo; Perlman, Marcus; Mislove, Alan; Paxton, Alexandra; Matlock, Teenie; Dale, Rick

    2015-01-01

    The past two decades have seen an upsurge of interest in the collective behaviors of complex systems composed of many agents entrained to each other and to external events. In this paper, we extend the concept of entrainment to the dynamics of human collective attention. We conducted a detailed investigation of the unfolding of human entrainment—as expressed by the content and patterns of hundreds of thousands of messages on Twitter—during the 2012 US presidential debates. By time-locking these data sources, we quantify the impact of the unfolding debate on human attention at three time scales. We show that collective social behavior covaries second-by-second to the interactional dynamics of the debates: A candidate speaking induces rapid increases in mentions of his name on social media and decreases in mentions of the other candidate. Moreover, interruptions by an interlocutor increase the attention received. We also highlight a distinct time scale for the impact of salient content during the debates: Across well-known remarks in each debate, mentions in social media start within 5–10 seconds after it occurs; peak at approximately one minute; and slowly decay in a consistent fashion across well-known events during the debates. Finally, we show that public attention after an initial burst slowly decays through the course of the debates. Thus we demonstrate that large-scale human entrainment may hold across a number of distinct scales, in an exquisitely time-locked fashion. The methods and results pave the way for careful study of the dynamics and mechanisms of large-scale human entrainment. PMID:25880357

  5. Aerosol entrainment from a sparged non-Newtonian slurry.

    PubMed

    Fritz, Brad G

    2006-08-01

    Previous bench-scale experiments have provided data necessary for the development of empirical models that describe aerosol entrainment from bubble bursting. However, previous work has not been extended to non-Newtonian liquid slurries. Design of a waste treatment plant on the Hanford Site in Washington required an evaluation of the applicability of these models outside of their intended range. For this evaluation, aerosol measurements were conducted above an air-sparged mixing tank filled with simulated waste slurry possessing Bingham plastic rheological properties. Three aerosol-size fractions were measured at three sampling heights and for three different sparging rates. The measured entrainment was compared with entrainment models. One model developed based on bench-scale air-water experiments agreed well with measured entrainment. Another model did not agree well with the measured entrainment. It appeared that the source of discrepancy between measured and modeled entrainment stemmed from application beyond the range of data used to develop the model. A possible separation in entrainment coefficients between air-water and steam-water systems was identified. A third entrainment model was adapted to match experimental conditions and fit a posteri to the experimental data, resulting in a modified version that resulted in estimated entrainment rates similar to the first model. PMID:16933643

  6. A Behavioral Intervention to Reduce Child Exposure to Indoor Air Pollution: Identifying Possible Target Behaviors

    ERIC Educational Resources Information Center

    Barnes, Brendon R.; Mathee, Angela; Shafritz, Lonna B.; Krieger, Laurie; Zimicki, Susan

    2004-01-01

    Indoor air pollution has been causally linked to acute lower respiratory infections in children younger than 5. The aim of this study was to identify target behaviors for a behavioral intervention to reduce child exposure to indoor air pollution by attempting to answer two research questions: Which behaviors are protective of child respiratory…

  7. Increasing jet entrainment, mixing and spreading

    DOEpatents

    Farrington, Robert B.

    1994-01-01

    A free jet of air is disturbed at a frequency that substantially matches natural turbulences in the free jet to increase the entrainment, mixing, and spreading of air by the free jet, for example in a room or other enclosure. The disturbances are created by pulsing the flow of air that creates the free jet at the desired frequency. Such pulsing of the flow of air can be accomplished by sequentially occluding and opening a duct that confines and directs the flow of air, such as by rotating a disk on an axis transverse to the flow of air in the duct.

  8. Increasing jet entrainment, mixing and spreading

    DOEpatents

    Farrington, R.B.

    1994-08-16

    A free jet of air is disturbed at a frequency that substantially matches natural turbulences in the free jet to increase the entrainment, mixing, and spreading of air by the free jet, for example in a room or other enclosure. The disturbances are created by pulsing the flow of air that creates the free jet at the desired frequency. Such pulsing of the flow of air can be accomplished by sequentially occluding and opening a duct that confines and directs the flow of air, such as by rotating a disk on an axis transverse to the flow of air in the duct. 11 figs.

  9. Coupling governs entrainment range of circadian clocks

    PubMed Central

    Abraham, Ute; Granada, Adrián E; Westermark, Pål O; Heine, Markus; Kramer, Achim; Herzel, Hanspeter

    2010-01-01

    Circadian clocks are endogenous oscillators driving daily rhythms in physiology and behavior. Synchronization of these timers to environmental light–dark cycles (‘entrainment') is crucial for an organism's fitness. Little is known about which oscillator qualities determine entrainment, i.e., entrainment range, phase and amplitude. In a systematic theoretical and experimental study, we uncovered these qualities for circadian oscillators in the suprachiasmatic nucleus (SCN—the master clock in mammals) and the lung (a peripheral clock): (i) the ratio between stimulus (zeitgeber) strength and oscillator amplitude and (ii) the rigidity of the oscillatory system (relaxation rate upon perturbation) determine entrainment properties. Coupling among oscillators affects both qualities resulting in increased amplitude and rigidity. These principles explain our experimental findings that lung clocks entrain to extreme zeitgeber cycles, whereas SCN clocks do not. We confirmed our theoretical predictions by showing that pharmacological inhibition of coupling in the SCN leads to larger ranges of entrainment. These differences between master and the peripheral clocks suggest that coupling-induced rigidity in the SCN filters environmental noise to create a robust circadian system. PMID:21119632

  10. An observational study of entrainment rate in deep convection

    SciTech Connect

    Guo, Xiaohao; Lu, Chunsong; Zhao, Tianliang; Zhang, Guang Jun; Liu, Yangang

    2015-09-22

    This study estimates entrainment rate and investigates its relationships with cloud properties in 156 deep convective clouds based on in-situ aircraft observations during the TOGA-COARE (Tropical Ocean Global Atmosphere Coupled Ocean Atmosphere Response Experiment) field campaign over the western Pacific. To the authors’ knowledge, this is the first study on the probability density function of entrainment rate, the relationships between entrainment rate and cloud microphysics, and the effects of dry air sources on the calculated entrainment rate in deep convection from an observational perspective. Results show that the probability density function of entrainment rate can be well fitted by lognormal, gamma or Weibull distribution, with coefficients of determination being 0.82, 0.85 and 0.80, respectively. Entrainment tends to reduce temperature, water vapor content and moist static energy in cloud due to evaporative cooling and dilution. Inspection of the relationships between entrainment rate and microphysical properties reveals a negative correlation between volume-mean radius and entrainment rate, suggesting the potential dominance of homogeneous mechanism in the clouds examined. The entrainment rate and environmental water vapor content show similar tendencies of variation with the distance of the assumed environmental air to the cloud edges. Their variation tendencies are non-monotonic due to the relatively short distance between adjacent clouds.

  11. An observational study of entrainment rate in deep convection

    DOE PAGESBeta

    Guo, Xiaohao; Lu, Chunsong; Zhao, Tianliang; Zhang, Guang Jun; Liu, Yangang

    2015-09-22

    This study estimates entrainment rate and investigates its relationships with cloud properties in 156 deep convective clouds based on in-situ aircraft observations during the TOGA-COARE (Tropical Ocean Global Atmosphere Coupled Ocean Atmosphere Response Experiment) field campaign over the western Pacific. To the authors’ knowledge, this is the first study on the probability density function of entrainment rate, the relationships between entrainment rate and cloud microphysics, and the effects of dry air sources on the calculated entrainment rate in deep convection from an observational perspective. Results show that the probability density function of entrainment rate can be well fitted by lognormal,more » gamma or Weibull distribution, with coefficients of determination being 0.82, 0.85 and 0.80, respectively. Entrainment tends to reduce temperature, water vapor content and moist static energy in cloud due to evaporative cooling and dilution. Inspection of the relationships between entrainment rate and microphysical properties reveals a negative correlation between volume-mean radius and entrainment rate, suggesting the potential dominance of homogeneous mechanism in the clouds examined. The entrainment rate and environmental water vapor content show similar tendencies of variation with the distance of the assumed environmental air to the cloud edges. Their variation tendencies are non-monotonic due to the relatively short distance between adjacent clouds.« less

  12. Entrainment and Interfacial Stability in Capillary - Heat Pipes

    NASA Astrophysics Data System (ADS)

    Kim, Bong Hun

    Entrainment phenomena in capillary-driven heat pipes were studied and both analytical and experimental approaches were utilized to identify and better understand the parameters that govern the entrainment of liquid in operating heat pipes. Two experimental investigations, i.e., an aerodynamic simulation and a heat pipe experiment, were conducted using an air-water test channel and a high power heat pipe, respectively. The air-water experiment was used to study the effects of the vapor velocity and wick dimensions on the entrainment phenomenon in heat pipes. The heat pipe experiment was designed to verify the existence of the various modes of entrainment and measure the corresponding entrainment limits. From the comparison of critical velocities obtained in these two experiments, the effectiveness of previous aerodynamic simulations (Ishii and Grolmes, 1975; Matveev et al., 1977) was examined. For both experiments, entrainment was detected by various methods and classified into representative types according to the relative position of the liquid interface to the wick structure and operating conditions. Results of the two experiments were compared with those obtained from previous investigations presented by Cotter (1967), Tien and Chung (1979) and Prenger and Kemme (1981), etc. In addition, the entrainment limit data were theoretically verified using a computer model designed to predict the maximum performance for the given operating conditions. Finally, the entrainment phenomena observed in both the air-water and steam-water experiments were examined from a physical perspective using hydrodynamic instability theories (Kelvin, 1871; Jeffreys, 1926; Miles, 1960).

  13. The ecology of entrainment: Foundations of coordinated rhythmic movement

    PubMed Central

    Phillips-Silver, Jessica; Aktipis, C. Athena; Bryant, Gregory A.

    2011-01-01

    Entrainment has been studied in a variety of contexts including music perception, dance, verbal communication and motor coordination more generally. Here we seek to provide a unifying framework that incorporates the key aspects of entrainment as it has been studied in these varying domains. We propose that there are a number of types of entrainment that build upon pre-existing adaptations that allow organisms to perceive stimuli as rhythmic, to produce periodic stimuli, and to integrate the two using sensory feedback. We suggest that social entrainment is a special case of spatiotemporal coordination where the rhythmic signal originates from another individual. We use this framework to understand the function and evolutionary basis for coordinated rhythmic movement and to explore questions about the nature of entrainment in music and dance. The framework of entrainment presented here has a number of implications for the vocal learning hypothesis and other proposals for the evolution of coordinated rhythmic behavior across an array of species. PMID:21776183

  14. Rhythm as a Coordinating Device: Entrainment with Disordered Speech

    ERIC Educational Resources Information Center

    Borrie, Stephanie A.; Liss, Julie M.

    2014-01-01

    Purpose: The rhythmic entrainment (coordination) of behavior during human interaction is a powerful phenomenon, considered essential for successful communication, supporting social and emotional connection, and facilitating sense-making and information exchange. Disruption in entrainment likely occurs in conversations involving those with speech…

  15. The Impact of Rhythmic Entrainment on a Person with Autism.

    ERIC Educational Resources Information Center

    Orr, Tracy Jo; Myles, Brenda Smith; Carlson, Judith K.

    1998-01-01

    A study investigated the impact of rhythmic entrainment on an 11-year-old girl with autism who engaged in head jerking and screaming. Rhythmic entrainment intervention was more effective when she exhibited behavior that resulted from a moderate level of stress and less effective when stressors were more severe. (CR)

  16. Physiology of circadian entrainment.

    PubMed

    Golombek, Diego A; Rosenstein, Ruth E

    2010-07-01

    Mammalian circadian rhythms are controlled by endogenous biological oscillators, including a master clock located in the hypothalamic suprachiasmatic nuclei (SCN). Since the period of this oscillation is of approximately 24 h, to keep synchrony with the environment, circadian rhythms need to be entrained daily by means of Zeitgeber ("time giver") signals, such as the light-dark cycle. Recent advances in the neurophysiology and molecular biology of circadian rhythmicity allow a better understanding of synchronization. In this review we cover several aspects of the mechanisms for photic entrainment of mammalian circadian rhythms, including retinal sensitivity to light by means of novel photopigments as well as circadian variations in the retina that contribute to the regulation of retinal physiology. Downstream from the retina, we examine retinohypothalamic communication through neurotransmitter (glutamate, aspartate, pituitary adenylate cyclase-activating polypeptide) interaction with SCN receptors and the resulting signal transduction pathways in suprachiasmatic neurons, as well as putative neuron-glia interactions. Finally, we describe and analyze clock gene expression and its importance in entrainment mechanisms, as well as circadian disorders or retinal diseases related to entrainment deficits, including experimental and clinical treatments. PMID:20664079

  17. DEVELOPMENT OF SUPERIOR ENTRAINMENT SEPARATORS

    EPA Science Inventory

    An experimental and theoretical program was carried out to develop an improved design for entrainment separators for scrubbers. The problems of separation efficiency, suspended solids deposition and plugging of the entrainment separator were of primary concern. A pilot scale entr...

  18. Holes and Entrainment in Stratocumulus.

    NASA Astrophysics Data System (ADS)

    Gerber, H.; Frick, G.; Malinowski, S. P.; Brenguier, J.-L.; Burnet, F.

    2005-02-01

    Aircraft flights through stratocumulus clouds (Sc) during the Dynamics and Chemistry of Marine Stratocumulus II (DYCOMS-II) study off the California coast found narrow in-cloud regions with less liquid water content (LWC) and cooler temperatures than average background values. The regions are named cloud holes and are assumed to be a result of water evaporated by the entrainment of dryer air from above the Sc. While such features have been noted previously, this study provided a unique opportunity to investigate in much greater detail the nature of the holes, as well as their relationship to the entrainment rate, because high-speed temperature and LWC probes with maximum spatial resolution of 10 cm were flown together for the first time. Nine long-duration flights were made through mostly unbroken Sc for which conditional sampling was used to identify the location and size of the holes. The holes are concentrated near cloud top, their average width near cloud top is about 5 m, their relative length distribution is nearly constant for all flights, and they can penetrate hundreds of meters deep into the Sc before being lost by mixing. Entrainment velocities at cloud top are estimated from measurements of fluxes of reduced LWC and vapor mixing ratios in holes, the fraction of cloud area covered by holes, and the total water jump between cloud top and the free atmosphere. Rates as large as 10 mm s-1 are found for nocturnal flights, and these rates are about 3 times larger than for daytime flight segments. The rates correlate best with the size of the buoyancy jump above the Sc; the present conditional-sampling approach for measuring the rates gives larger rates than the "flux jump" rates determined by others for the same flights by a factor of about 2. The stability criterion for all Sc predicts thinning and breakup of the Sc, which does not occur. The minimal amount of cloud-top evaporative cooling caused by entrainment contributes little to the top-down convection

  19. Food entrainment: major and recent findings

    PubMed Central

    Carneiro, Breno T. S.; Araujo, John F.

    2012-01-01

    Mammals exhibit daily anticipatory activity to cycles of food availability. Studies on such food anticipatory activity (FAA) have been conducted mainly in nocturnal rodents. They have identified FAA as the behavioral output of a food entrained oscillator (FEO), separate of the known light entrained oscillator (LEO) located in the suprachiasmatic nucleus (SCN) of hypothalamus. Here we briefly review the main characteristics of FAA. Also, we present results on four topics of food anticipation: (1) possible input signals to FEO, (2) FEO substrate, (3) the importance of canonical clock genes for FAA, and (4) potential practical applications of scheduled feeding. This mini review is intended to introduce the subject of food entrainment to those unfamiliar with it but also present them with relevant new findings on the issue. PMID:23205007

  20. Entrainment and mixing mechanism in monsoon clouds

    NASA Astrophysics Data System (ADS)

    Bera, Sudarsan; Prabhakaran, Thara; Pandithurai, Govindan; Brenguier, Jean-Louis

    2015-04-01

    Entrainment and consequent mixing impacts the cloud microphysical parameters and droplet size distribution (DSD) significantly which are very important for cloud radiative properties and the mechanism for first rain drop formation. The entrainment and mixing mechanisms are investigated in this study using in situ observations in warm cumulus clouds over monsoon region. Entrainment is discussed in the framework of the homogeneous and inhomogeneous mixing concepts and their effects on cloud droplet size distribution, number concentration, liquid water content and mean radius are described. The degree of homogeneity increases with droplet number concentration and adiabatic fraction, indicating homogeneous type mixing in the cloud core where dilution is less. Inhomogeneous mixing is found to be a dominating process at cloud edges where dilution is significant. Cloud droplet size distribution (DSD) is found to shift towards lower sizes during a homogeneous mixing event in the cloud core whereas spectral width of DSD decreases due to inhomogeneous mixing at cloud edges. Droplet size spectra suggests that largest droplets are mainly formed in the less diluted cloud core while diluted cloud edges have relatively smaller droplets, so that raindrop formation occurs mainly in the core of the cloud. The origin of the entrained parcels in deep cumulus clouds is investigated using conservative thermodynamical parameters. The entrained parcels originate from a level close to the observation level or slightly below through lateral edges. Cloud edges are significantly diluted due to entrainment of sub-saturated environmental air which can penetrate several hundred meters inside the cloud before it gets mixed completely with the cloud mass. Less diluted parcels inside the cloud core originates from a level much below the cloud base height. Penetrating downdraft from cloud top is seldom observed at the observation level and strong downdrafts may be attributed to in-cloud oscillation

  1. Mesler entrainment in alcohols

    NASA Astrophysics Data System (ADS)

    Saylor, J. R.; Sundberg, R. K.

    2012-11-01

    When a drop impacts a flat surface of the same liquid at an intermediate velocity, the impact can result in the formation of a very large number of very small bubbles. At lower velocities, drops bounce or float, and at larger velocities a single bubble forms, or there is a splash. The formation of large numbers of small bubbles during intermediate velocity impacts is termed Mesler entrainment and its controlling mechanism is poorly understood. Existing research has shown that Mesler entrainment is highly irreproducible when water is the working fluid, and very reproducible when silicone oil is the working fluid. Whether this is because water is problematic, or silicone oil is uniquely well-suited, is unclear. To answer this question, experiments were conducted using three different alcohols. The results of these experiments were very reproducible for all alcohols tested, suggesting that there is something unique about water which accounts for its lack of reproducibility. The data from these experiments were also used to develop a dimensionless group that quantifies the conditions under which Mesler entrainment occurs. This dimensionless group is used to provide insight into the mechanism of this unique method of bubble formation.

  2. Defining the Entrainment Zone in Stratocumulus-topped Boundary Layers

    NASA Astrophysics Data System (ADS)

    Wang, Q.; Zhou, M.; Kalogiros, J. A.; Lenschow, D. H.; Dai, C.; Wang, S.

    2010-12-01

    The presence of an entrainment zone near the top of the stratocumulus-topped boundary layers has been identified by many early studies. However, the definition of the entrainment zone was rather vague. We have examined the fine vertical variations of cloud liquid water content, wind, temperature and humidity near the stratocumulus top and developed a new method to identify the entrainment zone objectively. Aircraft measurements from various field projects in stratocumulus-topped boundary layers are used, taking advantage of the fast sampling capability of many of the aircraft sensors. Because of the inhomogeneous mixing of two air masses with distinctively different thermodynamic properties, the magnitude of temperature perturbations within the entrainment zone is significantly larger than those above or below. This characteristics is used to define the upper and lower boundaries of the entrainment zone using a wavelet spectra analyses. The definition of the entrainment zone is further evaluated by the presence of a linear mixing line through mixing line analyses. Various other interfaces at the cloud top are also examined, including the cloud interface, temperature interface (inversion), and moisture interface. The heights of these interfaces are examined relative to the height of the entrainment zone. This study also systematically revealed the presence of turbulence above the local cloud top and/or above the entrainment zone. Wind shear near the cloud top is one possible source that generated local turbulence. Other potential sources of turbulence will also be discussed.

  3. Physiology and behavior of dogs during air transport

    PubMed Central

    Bergeron, Renée; Scott, Shannon L.; Émond, Jean-Pierre; Mercier, Florent; Cook, Nigel J.; Schaefer, Al L.

    2002-01-01

    Twenty-four beagles were used to measure physiological and behavioral reactions to air transport. Each of 3 groups of 4 sedated (with 0.5 mg/kg body weight of acepromazine maleate) and 4 non-sedated (control) dogs was flown on a separate flight between Montreal, Quebec, and Toronto, Ontario, after being transported by road from Quebec City to Montreal. Saliva and blood samples were taken before ground and air transport and after air transport. The heart rate was monitored during the whole experiment except during ground transport, and behavior was monitored by video during air transport. Sedation did not affect any of the variables measured. The mean plasma cortisol concentration was significantly higher (P < 0.05) after ground transport than at baseline (225.3 vs 134.5 nmol/L); the mean salivary cortisol concentration was significantly higher (P < 0.05) after both ground and air transport than at baseline (16.2 and 14.8, respectively, vs 12.6 nmol/L). The mean neutrophil count was significantly higher (P < 0.05) after both ground and air transport than at baseline (80.6 and 81.4, respectively, vs 69.5 per 100 white blood cells), whereas the mean lymphocyte count was significantly lower (P < 0.05) (13.2 and 13.7, respectively, vs 22.4 per 100 white blood cells). Loading and unloading procedures caused the largest increase in heart rate. On average, the dogs spent more than 50% of the time lying down, and they remained inactive for approximately 75% of the time, except during take-off. These results suggest that transportation is stressful for dogs and that sedation with acepromazine, at the dosage and timing used, does not affect the physiological and behavioral stress responses of dogs to air transport. PMID:12146895

  4. The role of entrainment by falling raindrops in microbursts

    NASA Technical Reports Server (NTRS)

    Krueger, Steven K.

    1988-01-01

    The numerical model of Krueger et al. (1986) for dry microburst simulations is used to study the role of entrainment by falling raindrops. Two series of numerical simulations were conducted: a control series, and a series with the raindrop fall speed set to zero so that the rain moved with the air instead of falling through it. The results show that entrainment due to falling raindrops helps microbursts with large raindrop mixing ratios to form in stable stratifications. It is found that entrainment appears to contribute to the small spatial and temporal scales that characterize microburst outflows.

  5. Aerosol entrainment from a sparged non-Newtonian slurry

    SciTech Connect

    Fritz, Brad G.

    2006-08-01

    Aerosol measurements were conducted above a half-scale air sparged mixing tank filled with simulated waste slurry. Three aerosol size fractions were measured at three sampling heights at three different sparging rates using a filter based ambient air sampling technique. Aerosol concentrations in the head space above the closed tank demonstrated a wide range, varying between 97 ?g m-3 for PM2.5 and 5650 ?g m-3 for TSP. The variation in concentrations was a function of sampling heights, size fraction and sparging rate. Measured aerosol entrainment coefficients showed good agreement with existing entrainment models. The models evaluated generally over predicted the entrainment, but were within a factor of two of the measured entrainment. This indicates that the range of applicability of the models may be extendable to include sparged slurries with Bingham plastic rheological properties.

  6. Behavior of Water Jet Accompanied with Air Suction

    NASA Astrophysics Data System (ADS)

    Kawakami, Hironobu; Ishido, Tsutomu; Ihara, Akio

    In order to atomize a liquid, the authors have investigated the behavior of air-water jets. In a series of experiments, we have discovered a strange phenomenon that the water jet accompanied with air suction from the free surface has made a periodic radial splash of water drop. The purpose of the present paper is to clear out the origin of this phenomenon and the behavior of water jet accompanied with air suction. The behavior of water jet has been photographed by a digital camera aided with a flashlight and high-speed video camera. Those experiments enable us to find the origin of a periodic radial splash due to a formation of single air bubble at the flow separation region inside the nozzle and due to explosive expansion of the bubble after injected in the free space. In order to analyze the radial splash of water, we have conducted the equation of spherical liquid membrane. The numerical results obtained have been compared with the experimental results and good agreement has been obtained in radial expansion velocity.

  7. Entrainment region phenomena for a large plane shear layer

    NASA Technical Reports Server (NTRS)

    Ali, S. K.; Klewicki, C. L.; Disimile, P. J.; Lawson, I.; Foss, J. F.

    1985-01-01

    The subatmospheric test section of the present free shear layer facility allows the entrainment air to be introduced with a negligible disturbance level. The very low frequency oscillations, which are prominently observed in the entrainment stream and which are present throughout the shear layer, are attributed to an inherent instability in the transition from a boundary layer to a free shear layer state. The basic features of the disturbance field are documented herein.

  8. High-Resolution Entrainment in Stratocumulus During the POST Campaign

    NASA Astrophysics Data System (ADS)

    Gerber, H. E.

    2012-12-01

    In July and August of 2008 an NSF-supported field campaign called POST (Physics of Stratocumulus Top) was conducted off the California coast using the fully-instrumented Twin Otter aircraft from the Naval Post Graduate School. POST provided the first opportunity to closely co-locate on an aircraft high-rate and time synchronized microphysics (PVM; LWC and effective radius) and thermodynamics (UFT; Ultra-Fast Temperature) probes and a gust probe to produce measurements of entrainment fluxes and features over entrainment scales thought to be important in warm stratocumulus (Sc). This combination of probes permitted investigating the properties of individual entrained parcels Seventeen flights were conducted during POST in a quasi-Lagrangian fashion in largely unbroken stratocumulus. The horizontal fight path was adjusted to follow the mean air velocity in the Sc. The vertical flight path concentrated on flying between 100-m above and below the cloud-top interface; and some additional profiles were flown to various higher and lower levels where flux runs were made. This presentation describes the analysis of this unique and excellent data set including the following: The data permitted testing Lilly's classical theory for the entrainment velocity where its application requires strong jumps of temperature and moisture across the inversion located above cloud top, a linear flux of the entrained scalar below cloud top, and entrained parcels that descend. All flights showed Sc with wind shear and mixing at cloud top with some strong enough to dissipate the Sc. The relationship between shear and entrainment velocity is described. The pdf of the horizontal size of entrainment parcels vs entrainment flux is established for all flights to help in choosing grid-sizes for modeling. High -resolution in-cloud temperature and LWC measurements in entrained parcels reveal the relative importance of radiative cooling vs cooling by liquid water evaporation in causing buoyancy reversal

  9. Cortical entrainment to music and its modulation by expertise

    PubMed Central

    Doelling, Keith B.; Poeppel, David

    2015-01-01

    Recent studies establish that cortical oscillations track naturalistic speech in a remarkably faithful way. Here, we test whether such neural activity, particularly low-frequency (<8 Hz; delta–theta) oscillations, similarly entrain to music and whether experience modifies such a cortical phenomenon. Music of varying tempi was used to test entrainment at different rates. In three magnetoencephalography experiments, we recorded from nonmusicians, as well as musicians with varying years of experience. Recordings from nonmusicians demonstrate cortical entrainment that tracks musical stimuli over a typical range of tempi, but not at tempi below 1 note per second. Importantly, the observed entrainment correlates with performance on a concurrent pitch-related behavioral task. In contrast, the data from musicians show that entrainment is enhanced by years of musical training, at all presented tempi. This suggests a bidirectional relationship between behavior and cortical entrainment, a phenomenon that has not previously been reported. Additional analyses focus on responses in the beta range (∼15–30 Hz)—often linked to delta activity in the context of temporal predictions. Our findings provide evidence that the role of beta in temporal predictions scales to the complex hierarchical rhythms in natural music and enhances processing of musical content. This study builds on important findings on brainstem plasticity and represents a compelling demonstration that cortical neural entrainment is tightly coupled to both musical training and task performance, further supporting a role for cortical oscillatory activity in music perception and cognition. PMID:26504238

  10. Cortical entrainment to music and its modulation by expertise.

    PubMed

    Doelling, Keith B; Poeppel, David

    2015-11-10

    Recent studies establish that cortical oscillations track naturalistic speech in a remarkably faithful way. Here, we test whether such neural activity, particularly low-frequency (<8 Hz; delta-theta) oscillations, similarly entrain to music and whether experience modifies such a cortical phenomenon. Music of varying tempi was used to test entrainment at different rates. In three magnetoencephalography experiments, we recorded from nonmusicians, as well as musicians with varying years of experience. Recordings from nonmusicians demonstrate cortical entrainment that tracks musical stimuli over a typical range of tempi, but not at tempi below 1 note per second. Importantly, the observed entrainment correlates with performance on a concurrent pitch-related behavioral task. In contrast, the data from musicians show that entrainment is enhanced by years of musical training, at all presented tempi. This suggests a bidirectional relationship between behavior and cortical entrainment, a phenomenon that has not previously been reported. Additional analyses focus on responses in the beta range (∼15-30 Hz)-often linked to delta activity in the context of temporal predictions. Our findings provide evidence that the role of beta in temporal predictions scales to the complex hierarchical rhythms in natural music and enhances processing of musical content. This study builds on important findings on brainstem plasticity and represents a compelling demonstration that cortical neural entrainment is tightly coupled to both musical training and task performance, further supporting a role for cortical oscillatory activity in music perception and cognition. PMID:26504238

  11. A Quantitative Investigation of Entrainment and Detrainment in Numerically Simulated Convective Clouds. Pt. 2; Simulations of Cumulonimbus Clouds

    NASA Technical Reports Server (NTRS)

    Cohen, Charles

    1998-01-01

    Deep cumulonimbus clouds are simulated using a model that makes accurate diagnoses of entrainment and detrainment rates and of the properties of entrained and detrained air. Clouds generated by a variety of initial thermodynamic soundings are compared. In the simulations, updraft entrainment rates are large near and above cloud base, through the entire depth of the conditionally unstable layer. Stronger updrafts in a more unstable environment are better able to entrain relatively undisturbed environmental air, while weaker updrafts can entrain only air that has been modified by the clouds. When the maximum buoyancy is large, the updraft includes parcels with a wide range of buoyancies, while weaker clouds are more horizontally uniform. Strong downdrafts originate from levels at which updrafts detrain, and their mass flux depends on the mass flux of the updraft. The magnitude of mixing between cloud and environment, not the entrainment rate, varies inversely with the cloud radius. How much of the mixed air is entrained depends on the buoyancy.

  12. Collaborative tactical behaviors for autonomous ground and air vehicles

    NASA Astrophysics Data System (ADS)

    Albus, James; Barbera, Anthony; Scott, Harry; Balakirsky, Stephen

    2005-05-01

    Tactical behaviors for autonomous ground and air vehicles are an area of high interest to the Army. They are critical for the inclusion of robots in the Future Combat System (FCS). Tactical behaviors can be defined at multiple levels: at the Company, Platoon, Section, and Vehicle echelons. They are currently being defined by the Army for the FCS Unit of Action. At all of these echelons, unmanned ground vehicles, unmanned air vehicles, and unattended ground sensors must collaborate with each other and with manned systems. Research being conducted at the National Institute of Standards and Technology (NIST) and sponsored by the Army Research Lab is focused on defining the Four Dimensional Real-time Controls System (4D/RCS) reference model architecture for intelligent systems and developing a software engineering methodology for system design, integration, test and evaluation. This methodology generates detailed design requirements for perception, knowledge representation, decision making, and behavior generation processes that enable complex military tactics to be planned and executed by unmanned ground and air vehicles working in collaboration with manned systems.

  13. Fluid Dynamics of Pressurized, Entrained Coal Gasifiers

    SciTech Connect

    1997-12-31

    Pressurized, entrained gasification is a promising new technology for the clean and efficient combustion of coal. Its principle is to operate a coal gasifier at a high inlet gas velocity to increase the inflow of reactants, and at an elevated pressure to raise the overall efficiency of the process. Unfortunately, because of the extraordinary difficulties involved in performing measurements in hot, pressurized, high-velocity pilot plants, its fluid dynamics are largely unknown. Thus the designer cannot predict with certainty crucial phenomena like erosion, heat transfer and solid capture. In this context, we are conducting a study of the fluid dynamics of Pressurized Entrained Coal Gasifiers (PECGs). The idea is to simulate the flows in generic industrial PECGs using dimensional similitude. To this end, we employ a unique entrained gas-solid flow facility with the flexibility to recycle -rather than discard- gases other than air. By matching five dimensionless parameters, suspensions in mixtures of helium, carbon dioxide and sulfur hexafluoride simulate the effects of pressure and scale-up on the fluid dynamics of PECGS. Because it operates under cold, atmospheric conditions, the laboratory facility is ideal for detailed measurements. These activities are conducted with Air Products & Chemicals, Inc., which is a member of a consortium that includes Foster Wheeler and Deutsche Babcock Energie- und Umwelttechnik AG.

  14. Investigations of cumulus entrainment rates through remotely-sensed observations

    NASA Astrophysics Data System (ADS)

    Wagner, T. J.; Turner, D. D.; Berg, L. K.

    2010-12-01

    The entrainment of environmental air into cumulus impacts the radiative, microphysical, and thermodynamic characteristics of the cloud, and by extension, the environment. A need for a robust method to observe entrainment rate without the use of in situ observations has lead to the development of an algorithm to retrieve entrainment rate remotely. Thermodynamic profiles are obtained from the suite of ground-based instruments located at the Southern Great Plains (SGP) site of the United States Department of Energy's Atmospheric Radiation Measurement (ARM) Climate Research Facility. These profiles are used as inputs into the Entrainment Mixing Parcel Model (EMPM), which treats entrainment as a series of discrete mixing events. Output from EMPM is used to calculate quantities that can be observed from the surface, including effective radius and liquid water path. The entrainment rate is adjusted iteratively using Gauss-Newton optimal estimation until convergence with observations is reached. This algorithm currently retrieves the entrainment rate of individual cumulus clouds and shows good agreement with aircraft-based observations.

  15. Universal bursty behavior in the air transportation system.

    PubMed

    Ito, Hidetaka; Nishinari, Katsuhiro

    2015-12-01

    Social activities display bursty behavior characterized by heavy-tailed interevent time distributions. We examine the bursty behavior of airplanes' arrivals in hub airports. The analysis indicates that the air transportation system universally follows a power-law interarrival time distribution with an exponent α=2.5 and an exponential cutoff. Moreover, we investigate the mechanism of this bursty behavior by introducing a simple model to describe it. In addition, we compare the extent of the hub-and-spoke structure and the burstiness of various airline networks in the system. Remarkably, the results suggest that the hub-and-spoke network of the system and the carriers' strategy to facilitate transit are the origins of this universality. PMID:26764752

  16. Universal bursty behavior in the air transportation system

    NASA Astrophysics Data System (ADS)

    Ito, Hidetaka; Nishinari, Katsuhiro

    2015-12-01

    Social activities display bursty behavior characterized by heavy-tailed interevent time distributions. We examine the bursty behavior of airplanes' arrivals in hub airports. The analysis indicates that the air transportation system universally follows a power-law interarrival time distribution with an exponent α =2.5 and an exponential cutoff. Moreover, we investigate the mechanism of this bursty behavior by introducing a simple model to describe it. In addition, we compare the extent of the hub-and-spoke structure and the burstiness of various airline networks in the system. Remarkably, the results suggest that the hub-and-spoke network of the system and the carriers' strategy to facilitate transit are the origins of this universality.

  17. Lidar measurements of the atmospheric entrainment zone and the potential temperature jump across the top of the mixed layer

    NASA Technical Reports Server (NTRS)

    Boers, R.; Eloranta, E. W.

    1986-01-01

    Lidar data of the atmospheric entrainment zone from six days of clear air convection obtained in central Illinois during July 1979 are presented. A new method to measure the potential temperature jump across the entrainment zone based on only one temperature sounding and continuous lidar measurements of the mixed layer height is developed. An almost linear dependence is found between the normalized entrainment rate and the normalized thickness of the entrainment zone.

  18. Power plant intake entrainment analysis

    SciTech Connect

    Edinger, J.E.; Kolluru, V.S.

    2000-04-01

    Power plant condenser cooling water intake entrainment of fish eggs and larvae is becoming an issue in evaluating environmental impacts around the plants. Methods are required to evaluate intake entrainment on different types of water bodies. Presented in this paper is a derivation of the basic relationships for evaluating entrainment from the standing crop of fish eggs and larvae for different regions of a water body, and evaluating the rate of entrainment from the standing crop. These relationships are coupled with a 3D hydrodynamic and transport model that provides the currents and flows required to complete the entrainment evaluation. Case examples are presented for a simple river system, and for the more complex Delaware River Estuary with multiple intakes. Example evaluations are made for individual intakes, and for the cumulative impacts of multiple intakes.

  19. The entraining moist boundary layer

    NASA Technical Reports Server (NTRS)

    Randall, D. A.

    1978-01-01

    A unified theory of entrainment into the planetary boundary layer is presented. It is assumed that the rates of buoyant and shear production of turbulence kinetic energy can be determined in terms of the entrainment mass flux. An expression is derived from the conservation law for turbulence kinetic energy, which, with the introduction of an empirical parameter, can be used together with a second relation between turbulence kinetic energy and the turbulence velocity scale to obtain the mass entrainment flux. The theory provides descriptions of storage-limited entrainment, buoyancy-limited entrainment into a clear mixed layer, and shallowing. It has been incorporated into a simulation of Day 33 of the Wangara experiment using a simple mixed layer model.

  20. A Wavelet Analysis Approach for Categorizing Air Traffic Behavior

    NASA Technical Reports Server (NTRS)

    Drew, Michael; Sheth, Kapil

    2015-01-01

    In this paper two frequency domain techniques are applied to air traffic analysis. The Continuous Wavelet Transform (CWT), like the Fourier Transform, is shown to identify changes in historical traffic patterns caused by Traffic Management Initiatives (TMIs) and weather with the added benefit of detecting when in time those changes take place. Next, with the expectation that it could detect anomalies in the network and indicate the extent to which they affect traffic flows, the Spectral Graph Wavelet Transform (SGWT) is applied to a center based graph model of air traffic. When applied to simulations based on historical flight plans, it identified the traffic flows between centers that have the greatest impact on either neighboring flows, or flows between centers many centers away. Like the CWT, however, it can be difficult to interpret SGWT results and relate them to simulations where major TMIs are implemented, and more research may be warranted in this area. These frequency analysis techniques can detect off-nominal air traffic behavior, but due to the nature of air traffic time series data, so far they prove difficult to apply in a way that provides significant insight or specific identification of traffic patterns.

  1. The Macroscopic Entrainment Processes of Simulated Cumulus Ensemble. Part II: Testing the Entraining-Plume Model.

    NASA Astrophysics Data System (ADS)

    Lin, Chichung; Arakawa, Akio

    1997-04-01

    According to Part I of this paper, it seems that ignoring the contribution from descendent cloud air in a cloud model for cumulus parameterization (CMCP), such as the spectral cumulus ensemble model in the Arakawa-Schubert parameterization, is an acceptable simplification for tropical deep convection. Since each subensemble in the spectral cumulus ensemble model is formally analogous to an entraining plume, the latter is examined using the simulated data from a cloud-resolving model (CRM). The authors first follow the analysis procedure of Warner. With the data from a nonprecipitating experiment, the authors show that the entraining-plume model cannot simultaneously predict the mean liquid water profile and cloud top height of the clouds simulated by the CRM. However, the mean properties of active elements of clouds, which are characterized by strong updrafts, can be described by an entraining plume of similar top height.With the data from a precipitating experiment, the authors examine the spectral cumulus ensemble model using the Paluch diagram. It is found that the spectral cumulus ensemble model appears adequate if different types of clouds in the spectrum are interpreted as subcloud elements with different entrainment characteristics. The resolved internal structure of clouds can thus be viewed as a manifestation of a cloud spectrum. To further investigate whether the fractional rate of entrainment is an appropriate parameter for characterizing cloud types in the spectral cumulus ensemble model, the authors stratify the simulated saturated updrafts (subcloud elements) into different types according to their eventual heights and calculate the cloud mass flux and mean moist static energy for each type. Entrainment characteristics are then inferred through the cloud mass flux and in-cloud moist static energy. It is found that different types of subcloud elements have distinguishable thermodynamic properties and entrainment characteristics. However, for each cloud

  2. Sensory Entrainment Mechanisms in Auditory Perception: Neural Synchronization Cortico-Striatal Activation

    PubMed Central

    Sameiro-Barbosa, Catia M.; Geiser, Eveline

    2016-01-01

    The auditory system displays modulations in sensitivity that can align with the temporal structure of the acoustic environment. This sensory entrainment can facilitate sensory perception and is particularly relevant for audition. Systems neuroscience is slowly uncovering the neural mechanisms underlying the behaviorally observed sensory entrainment effects in the human sensory system. The present article summarizes the prominent behavioral effects of sensory entrainment and reviews our current understanding of the neural basis of sensory entrainment, such as synchronized neural oscillations, and potentially, neural activation in the cortico-striatal system. PMID:27559306

  3. Sensory Entrainment Mechanisms in Auditory Perception: Neural Synchronization Cortico-Striatal Activation.

    PubMed

    Sameiro-Barbosa, Catia M; Geiser, Eveline

    2016-01-01

    The auditory system displays modulations in sensitivity that can align with the temporal structure of the acoustic environment. This sensory entrainment can facilitate sensory perception and is particularly relevant for audition. Systems neuroscience is slowly uncovering the neural mechanisms underlying the behaviorally observed sensory entrainment effects in the human sensory system. The present article summarizes the prominent behavioral effects of sensory entrainment and reviews our current understanding of the neural basis of sensory entrainment, such as synchronized neural oscillations, and potentially, neural activation in the cortico-striatal system. PMID:27559306

  4. Mechanistic modeling and correlations for pool-entrainment phenomenon

    SciTech Connect

    Kataoka, I.; Ishii, M.

    1983-04-01

    Entrainment from a liquid pool with boiling or bubbling is of considerable practical importance in safety evaluation of nuclear reactor under off-normal transients or accidents such as loss-of-coolant and loss-of-flow accidents. Droplets which are suspended from a free surface are partly carried away by streaming gas and partly returned back to free surface by the gravity. A correlation is developed for the pool entrainment amount based on simple mechanistic modeling and a number of data. This analysis reveals that there exist three regions of entrainment in the axial direction from a pool surface. In the first region (near surface region), entrainment is independent of height and gas velocity. In the second region (momentum controlled region), the amount of entrainment decreases with increasing height from the free surface and increases with increasing gas velocity. In the third region (deposition controlled region), the entrainment increases with increasing height due to deposition of droplets. The present correlation agrees well with a large number of experimental data over a wide range of pressure for air-water and steam-water systems.

  5. Investigating the Sensitivity of Model Intraseasonal Variability to Minimum Entrainment

    NASA Astrophysics Data System (ADS)

    Hannah, W. M.; Maloney, E. D.

    2008-12-01

    Previous studies have shown that using a Relaxed Arakawa-Schubert (RAS) convective parameterization with appropriate convective triggers and assumptions about rain re-evaporation produces realistic intraseasonal variability. RAS represents convection with an ensemble of clouds detraining at different heights, each with different entrainment rate, the highest clouds having the lowest entrainment rates. If tropospheric temperature gradients are weak and boundary layer moist static energy is relatively constant, then by limiting the minimum entrainment rate deep convection is suppressed in the presence of dry tropospheric air. This allows moist static energy to accumulate and be discharged during strong intraseasonal convective events, which is consistent with the discharge/recharge paradigm. This study will examine the sensitivity of intra-seasonal variability to changes in minimum entrainment rate in the NCAR-CAM3 with the RAS scheme. Simulations using several minimum entrainment rate thresholds will be investigated. A frequency-wavenumber analysis will show the improvement of the MJO signal as minimum entrainment rate is increased. The spatial and vertical structure of MJO-like disturbances will be examined, including an analysis of the time evolution of vertical humidity distribution for each simulation. Simulated results will be compared to observed MJO events in NCEP-1 reanalysis and CMAP precipitation.

  6. Entrainment across density interfaces

    NASA Astrophysics Data System (ADS)

    Sanchez, M. A.; Carrillo, A.; Mahjoub, O. B.

    2010-05-01

    The structure of non-homogeneous turbulence affected by stratification and rotation is investigated both by means of laboratory and numerical experiments. The experiments investigate zero mean flow across a stably stratified density interface and are used to quantify the entrainment, the mixing efficiency and different types of dominant instability and the topological aspects of the turbulent cascades detected both horizontally and vertically [1,2]. Grid turbulence in a rotating stratified two layer system is measured with PIV as well as with sonic velocimetry. Observations of the horizontal and vertical velocity energy spectra as well as the structure functions are used to estimate local mixedness, entrainment and intermittency [3,4]. The method of estimation of the average eddy diffusivity from the time series images of a sharp density interface marked by fluoresceine also take anisotropy into account. but on the long run, horizontal ( and 2D type flow such as [5]) flow directions will average out so using a single integral length scale defined in Sanchez and Redondo(1998) varying in height will be enough together with the internal frequency. The method of calculating vertical fluxes in time allows to estimate different intermittency parameters as a function of local instability e.g. Kelvin/Helmholtz, Rayleigh-Taylor or Holbmoe[6-8]. Different concentration interfaces show different fractal dimensions, that are also a power function of the local Richardson number, this may be due to different levels of intermittency and thus different spectra, which are not necessarily inertial nor in equilibrium [8,9]. [1] Sanchez M.A. and Redondo J.M.Observations from Grid Stirred Turbulence. Applied Scientific Research 59, 191-204. 1998. [2] Redondo, J.M. and Cantalapiedra I.R. Mixing in Horizontally Heterogeneous Flows . Jour. Flow Turbulence and Combustion. 51, 217-222. 1993. [3] Castilla R, Redondo J.M., Gamez P.J., Babiano A. Coherent vortices and Lagrangian Dynamics in 2D

  7. Disordered speech disrupts conversational entrainment: a study of acoustic-prosodic entrainment and communicative success in populations with communication challenges

    PubMed Central

    Borrie, Stephanie A.; Lubold, Nichola; Pon-Barry, Heather

    2015-01-01

    Conversational entrainment, a pervasive communication phenomenon in which dialogue partners adapt their behaviors to align more closely with one another, is considered essential for successful spoken interaction. While well-established in other disciplines, this phenomenon has received limited attention in the field of speech pathology and the study of communication breakdowns in clinical populations. The current study examined acoustic-prosodic entrainment, as well as a measure of communicative success, in three distinctly different dialogue groups: (i) healthy native vs. healthy native speakers (Control), (ii) healthy native vs. foreign-accented speakers (Accented), and (iii) healthy native vs. dysarthric speakers (Disordered). Dialogue group comparisons revealed significant differences in how the groups entrain on particular acoustic–prosodic features, including pitch, intensity, and jitter. Most notably, the Disordered dialogues were characterized by significantly less acoustic-prosodic entrainment than the Control dialogues. Further, a positive relationship between entrainment indices and communicative success was identified. These results suggest that the study of conversational entrainment in speech pathology will have essential implications for both scientific theory and clinical application in this domain. PMID:26321996

  8. Disordered speech disrupts conversational entrainment: a study of acoustic-prosodic entrainment and communicative success in populations with communication challenges.

    PubMed

    Borrie, Stephanie A; Lubold, Nichola; Pon-Barry, Heather

    2015-01-01

    Conversational entrainment, a pervasive communication phenomenon in which dialogue partners adapt their behaviors to align more closely with one another, is considered essential for successful spoken interaction. While well-established in other disciplines, this phenomenon has received limited attention in the field of speech pathology and the study of communication breakdowns in clinical populations. The current study examined acoustic-prosodic entrainment, as well as a measure of communicative success, in three distinctly different dialogue groups: (i) healthy native vs. healthy native speakers (Control), (ii) healthy native vs. foreign-accented speakers (Accented), and (iii) healthy native vs. dysarthric speakers (Disordered). Dialogue group comparisons revealed significant differences in how the groups entrain on particular acoustic-prosodic features, including pitch, intensity, and jitter. Most notably, the Disordered dialogues were characterized by significantly less acoustic-prosodic entrainment than the Control dialogues. Further, a positive relationship between entrainment indices and communicative success was identified. These results suggest that the study of conversational entrainment in speech pathology will have essential implications for both scientific theory and clinical application in this domain. PMID:26321996

  9. A Balanced Diet Is Necessary for Proper Entrainment Signals of the Mouse Liver Clock

    PubMed Central

    Hirao, Akiko; Tahara, Yu; Kimura, Ichiro; Shibata, Shigenobu

    2009-01-01

    Background The peripheral circadian clock in mice is entrained not only by light-dark cycles but also by daily restricted feeding schedules. Behavioral and cell culture experiments suggest an increase in glucose level as a factor in such feeding-induced entrainment. For application of feeding-induced entrainment in humans, nutrient content and dietary variations should be considered. Principal Finding To elucidate the food composition necessary for dietary entrainment, we examined whether complete or partial substitution of dietary nutrients affected phase shifts in liver clocks of mice. Compared with fasting mice or ad libitum fed mice, the liver bioluminescence rhythm advanced by 3–4 h on the middle day in Per2::luciferase knock-in mice that were administered a standard mouse diet, i.e. AIN-93M formula [0.6–0.85 g/10 g mouse BW] (composition: 14% casein, 47% cornstarch, 15% gelatinized cornstarch, 10% sugar, 4% soybean oil, and 10% other [fiber, vitamins, minerals, etc.]), for 2 days. When each nutrient was tested alone (100% nutrient), an insignificant weak phase advance was found to be induced by cornstarch and soybean oil, but almost no phase advance was induced by gelatinized cornstarch, high-amylose cornstarch, glucose, sucrose, or casein. A combination of glucose and casein without oil, vitamin, or fiber caused a significant phase advance. When cornstarch in AIN-93M was substituted with glucose, sucrose, fructose, polydextrose, high-amylose cornstarch, or gelatinized cornstarch, the amplitude of phase advance paralleled the increase in blood glucose concentration. Conclusions Our results strongly suggest the following: (1) balanced diets containing carbohydrates/sugars and proteins are good for restricted feeding-induced entrainment of the peripheral circadian clock and (2) a balanced diet that increases blood glucose, but not by sugar alone, is suitable for entrainment. These findings may assist in the development of dietary recommendations for on

  10. Dry air entrainment into convective clouds

    NASA Technical Reports Server (NTRS)

    Telford, J. W.

    1977-01-01

    A systematic approach to the study of atmospheric turbulent motion is discussed in terms of weather modification. The background of cloud physics, and the mixing process are described. A zero-g study is proposed to enable the basic experimental data to be collected so that theory may be developed to generalize results for practical applications.

  11. Estimation of convective entrainment properties from a cloud-resolving model simulation during TWP-ICE

    NASA Astrophysics Data System (ADS)

    Zhang, Guang J.; Wu, Xiaoqing; Zeng, Xiping; Mitovski, Toni

    2015-12-01

    The fractional entrainment rate in convective clouds is an important parameter in current convective parameterization schemes of climate models. In this paper, it is estimated using a 1-km-resolution cloud-resolving model (CRM) simulation of convective clouds from TWP-ICE (the Tropical Warm Pool-International Cloud Experiment). The clouds are divided into different types, characterized by cloud-top heights. The entrainment rates and moist static energy that is entrained or detrained are determined by analyzing the budget of moist static energy for each cloud type. Results show that the entrained air is a mixture of approximately equal amount of cloud air and environmental air, and the detrained air is a mixture of ~80 % of cloud air and 20 % of the air with saturation moist static energy at the environmental temperature. After taking into account the difference in moist static energy between the entrained air and the mean environment, the estimated fractional entrainment rate is much larger than those used in current convective parameterization schemes. High-resolution (100 m) large-eddy simulation of TWP-ICE convection was also analyzed to support the CRM results. It is shown that the characteristics of entrainment rates estimated using both the high-resolution data and CRM-resolution coarse-grained data are similar. For each cloud category, the entrainment rate is high near cloud base and top, but low in the middle of clouds. The entrainment rates are best fitted to the inverse of in-cloud vertical velocity by a second order polynomial.

  12. Analysis and numerical simulation of a laboratory analog of radiatively induced cloud-top entrainment.

    SciTech Connect

    Kerstein, Alan R.; Sayler, Bentley J.; Wunsch, Scott Edward; Schmidt, Heiko; Nedelec, Renaud

    2010-11-01

    Numerical simulations using the One-Dimensional-Turbulence model are compared to water-tank measurements [B. J. Sayler and R. E. Breidenthal, J. Geophys. Res. 103 (D8), 8827 (1998)] emulating convection and entrainment in stratiform clouds driven by cloud-top cooling. Measured dependences of the entrainment rate on Richardson number, molecular transport coefficients, and other experimental parameters are reproduced. Additional parameter variations suggest more complicated dependences of the entrainment rate than previously anticipated. A simple algebraic model indicates the ways in which laboratory and cloud entrainment behaviors might be similar and different.

  13. An observational study of stratocumulus entrainment and thermodynamics

    NASA Technical Reports Server (NTRS)

    Kawa, S. R.; Pearson, R., Jr.

    1989-01-01

    The stratocumulus (SC) entrainment and thermodynamics are studied using data from the Dynamics and Chemistry of Marine Stratocumulus (DYCOMS) experiment. The rate of entrainment of air from the free troposphere into the cloud-topped PBL is estimated using a technique based on the measurement of ozone flux and mean distribution. The average measured value of entrainment rate was found to be 3.0 mm/s with a range of 1.0 to 5.0 mm/s for cloudy cases. Thermodynamic budgets are constructed for eight DYCOMS cases. It was found that the divergence of the solar radiative flux is an important component of the boundary-layer energetics during midday, the factor which must be accounted for in mixed-layer models. The net longwave radiative flux profiles show good agreement with theoretical models, but an unambiguous partitioning of the flux divergence between inversion and mixed layers could not be established.

  14. Entrainment in High-Velocity, High Temperature Plasma Jets Part I: Experimental Results

    SciTech Connect

    Fincke, J.R.; Crawford, D.M.; Snyder, S.C.; Swank, W.D.; Haggard, D.C.; Williamson, R.L.

    2002-03-27

    The development of a high-velocity, high-temperature argon plasma jet issuing into air has been investigated. In particular the entrainment of the surrounding air, its effect on the temperature and velocity profiles and the subsequent mixing and dissociation of oxygen has been examined in detail. The total concentration of oxygen and the velocity and temperature profiles in the jet were obtained from an enthalpy probe. High-resolution Thomson scattering provided an independent measure of plasma velocity and temperature, validating enthalpy probe measurements and providing non-intrusive measurements near the nozzle exit. The concentration of atomic oxygen was obtained from two-photon Laser Induced Fluorescence (LIF). Molecular oxygen concentration and temperature was obtained from Coherent Anti-Stokes Raman Spectroscopy (CARS). It was found that both the incompleteness of mixing at the molecular scale and the rate of oxygen dissociation and recombination effects jet behavior.

  15. Laminar Plunging Jets - Interfacial Rupture and Inception of Entrainment

    NASA Astrophysics Data System (ADS)

    Kishore, Aravind

    Interfacial rupture and entrainment are commonly observed, e.g., air bubbles within a container being filled with water from a faucet. The example involves a liquid jet (density, rho, and viscosity, η) plunging into a receiving pool of liquid. Below a critical liquid-jet velocity, the interface develops a cusp-like shape within the receiving pool. The cusp becomes sharper with increasing liquid-jet velocity, and at a critical velocity ( Vc), the interface between the liquid and the surrounding fluid (density, rho0, and viscosity, η0) ruptures. Interfacial tension (sigma) can no longer preserve the integrity of the interface between the two immiscible fluids, and the plunging jet drags/entrains surrounding fluid into the receiving pool. Subsequently, the entrained fluid breaks up into bubbles within the receiving pool. The focus of this dissertation is the numerical prediction of the critical entrainment inception velocities for laminar plunging jets using the Volume-Of-Fluid (VOF) method, a Computational Fluid Dynamics (CFD) method to simulate multi-fluid flows. Canonical to bottle-filling operations in the industry is the plunging-jet configuration -- the liquid jet issues from a nozzle and plunges into a container filled with liquid. Simulations of this configuration require capturing flow phenomena over a large range of length scales (4 orders of magnitude). Results show severe under-prediction of critical entrainment velocities when the maximum resolution is insufficient to capture the sharpening, and eventual rupture, of the interfacial cusp. Higher resolutions resulted in computational meshes with prohibitively large number of cells, and a drastic reduction in time-step values. Experimental results in the literature suggest at least a 100-fold increase in the smallest length scale when the entrained fluid is a liquid instead of air. This narrows the range of length scales in the problem. We exploit the experimental correlation between critical capillary

  16. Investigation of the Entrainment Phenomenon Using a Scaling Approach

    NASA Astrophysics Data System (ADS)

    Kishore, Aravind; Ghia, Urmila

    2014-11-01

    Air entrainment is a commonly observed phenomenon; we see it when filling a glass with water from a faucet, in the frothing of the ocean surface, in white water rapids, etc. The focus of our work is the numerical simulation of the entrainment phenomenon associated with laminar plunging jets. With increasing jet velocity, the interfacial cusp formed between the jet and the liquid pool becomes sharper. At a critical jet velocity, entrainment inception occurs, i.e., the interfacial cusp breaks, the interface ruptures, and air is pulled into the liquid pool. We conduct two-fluid simulations using the Volume-Of-Fluid (VOF) methodology. The large range of length scales in the flow presents a major computational challenge. We postulate an approach based on scaling of the underlying physics and this helps alleviate the constraints that the physics poses on the numerical method. The approach is validated using a simple flow configuration - a cylinder rotating at an interface between two fluids. Our simulations capture the sharpening of the interfacial cusp, and the sudden rupture of the interface. The predicted critical entrainment velocities are within 1% of experimental data, thereby providing confidence in the approach. This work was supported by the UC Simulation Center at the University of Cincinnati.

  17. The Stochastic Parcel Model: A deterministic parameterization of stochastically entraining convection

    NASA Astrophysics Data System (ADS)

    Romps, David M.

    2016-03-01

    Convective entrainment is a process that is poorly represented in existing convective parameterizations. By many estimates, convective entrainment is the leading source of error in global climate models. As a potential remedy, an Eulerian implementation of the Stochastic Parcel Model (SPM) is presented here as a convective parameterization that treats entrainment in a physically realistic and computationally efficient way. Drawing on evidence that convecting clouds comprise air parcels subject to Poisson-process entrainment events, the SPM calculates the deterministic limit of an infinite number of such parcels. For computational efficiency, the SPM groups parcels at each height by their purity, which is a measure of their total entrainment up to that height. This reduces the calculation of convective fluxes to a sequence of matrix multiplications. The SPM is implemented in a single-column model and compared with a large-eddy simulation of deep convection.

  18. Entrainment by the jet in HH 47

    NASA Technical Reports Server (NTRS)

    Raymond, John C.; Morse, Jon A.; Hartigan, P.; Curiel, S.; Heathcote, Steve

    1994-01-01

    Fabry-Perot images of the HH 47 optical jet show that the velocity decreases from the center toward the edges which is interpreted as evidence for entrainment. Those images can be used to investigate the rate of entrainment required to account for the observed luminosity. Entrainment along the jet can account for only small fractions of the jet mass and the molecular outflow seen in CO. We compare the density, excitation, and velocity structure of the jet with the predictions of viscous entrainment models and models of entrainment by expulsion of jet material by internal shocks, and find that either type of model can explain the general features.

  19. Entrainment in electrohydrodynamic heat pipes

    NASA Technical Reports Server (NTRS)

    Jones, T. B.; Perry, M. P.

    1972-01-01

    A theoretical analysis for predicting the onset of the Kelvin-Helmholtz instability is reported. The model for the analysis is described, and the derived stability criterion are given. It is concluded that surface tension plays a role in the entrainment limit of electro hydrodynamic heat pipes. The surface of the liquid in an EHD flow structure is open, with no restriction placed on the wavenumbers of perturbations.

  20. The neurochemical basis of photic entrainment of the circadian pacemaker

    NASA Technical Reports Server (NTRS)

    Rea, Michael A.; Buckley, Becky; Lutton, Lewis M.

    1992-01-01

    Circadian rhythmicity in mammals is controlled by the action of a light-entrainable hypothalamus, in association with two cell clusters known as the supra chiasmatic nuclei (SCN). In the absence of temporal environmental clues, this pacemaker continues to measure time by an endogenous mechanism (clock), driving biochemical, physiological, and behavioral rhythms that reflect the natural period of the pacemaker oscillation. This endogenous period usually differs slightly from 24 hours (i.e., circadian). When mammals are maintained under a 24 hour light-dark (LD) cycle, the pacemaker becomes entrained such that the period of the pacemaker oscillation matches that of the LD cycle. Potentially entraining photic information is conveyed to the SCN via a direct retinal projection, the retinohypothalamic tract (RHT). RHT neurotransmission is thought to be mediated by the release of excitatory amino acids (EAA) in the SCN. In support of this hypothesis, recent experiments using nocturnal rodents have shown that EAA antagonists block the effects of light on pacemaker-driven behavioral rhythms, and attenuate light induced gene expression in SCN cells. An understanding of the neurochemical basis of the photic entrainment process would facilitate the development of pharmacological strategies for maintaining synchrony among shift workers in environments, such as the Space Station, which provide unreliable or conflicting temporal photic clues.

  1. A viscous-inviscid interaction model of jet entrainment

    NASA Technical Reports Server (NTRS)

    Wilmoth, R. G.; Dash, S. M.

    1981-01-01

    A viscous-inviscid interaction model for predicting jet entrainment effects on axisymmetric, nozzle afterbodies at subsonic speeds is presented. The model is based on a displacement thickness correction to the inviscid jet boundary that accounts for mixing-induced streamline deflections in the inviscid region. The displacement correction is shown to be related to the local mass entrainment rate and, for thin mixing layers, the model is shown to be analogous to displacement models used in conventional boundary-layer interaction theory. A method is presented for computing the entrainment rate by an overlaid mixing layer model that accounts for the nonsimilar behavior and pressure gradients occurring in the near field region. An iterative scheme for coupling the model to analyses for the external inviscid flow, the external boundary layer, and the inviscid jet exhaust is also given. Results are presented that illustrate the qualitative behavior of the entrainment interaction under various flow conditions and that demonstrate the validity of the model by comparisons with experiment.

  2. Scale dependence of entrainment-mixing mechanisms in cumulus clouds

    DOE PAGESBeta

    Lu, Chunsong; Liu, Yangang; Niu, Shengjie; Endo, Satoshi

    2014-12-17

    This work empirically examines the dependence of entrainment-mixing mechanisms on the averaging scale in cumulus clouds using in situ aircraft observations during the Routine Atmospheric Radiation Measurement Aerial Facility Clouds with Low Optical Water Depths Optical Radiative Observations (RACORO) field campaign. A new measure of homogeneous mixing degree is defined that can encompass all types of mixing mechanisms. Analysis of the dependence of the homogenous mixing degree on the averaging scale shows that, on average, the homogenous mixing degree decreases with increasing averaging scales, suggesting that apparent mixing mechanisms gradually approach from homogeneous mixing to extreme inhomogeneous mixing with increasingmore » scales. The scale dependence can be well quantified by an exponential function, providing first attempt at developing a scale-dependent parameterization for the entrainment-mixing mechanism. The influences of three factors on the scale dependence are further examined: droplet-free filament properties (size and fraction), microphysical properties (mean volume radius and liquid water content of cloud droplet size distributions adjacent to droplet-free filaments), and relative humidity of entrained dry air. It is found that the decreasing rate of homogeneous mixing degree with increasing averaging scales becomes larger with larger droplet-free filament size and fraction, larger mean volume radius and liquid water content, or higher relative humidity. The results underscore the necessity and possibility of considering averaging scale in representation of entrainment-mixing processes in atmospheric models.« less

  3. Scale dependence of entrainment-mixing mechanisms in cumulus clouds

    SciTech Connect

    Lu, Chunsong; Liu, Yangang; Niu, Shengjie; Endo, Satoshi

    2014-12-17

    This work empirically examines the dependence of entrainment-mixing mechanisms on the averaging scale in cumulus clouds using in situ aircraft observations during the Routine Atmospheric Radiation Measurement Aerial Facility Clouds with Low Optical Water Depths Optical Radiative Observations (RACORO) field campaign. A new measure of homogeneous mixing degree is defined that can encompass all types of mixing mechanisms. Analysis of the dependence of the homogenous mixing degree on the averaging scale shows that, on average, the homogenous mixing degree decreases with increasing averaging scales, suggesting that apparent mixing mechanisms gradually approach from homogeneous mixing to extreme inhomogeneous mixing with increasing scales. The scale dependence can be well quantified by an exponential function, providing first attempt at developing a scale-dependent parameterization for the entrainment-mixing mechanism. The influences of three factors on the scale dependence are further examined: droplet-free filament properties (size and fraction), microphysical properties (mean volume radius and liquid water content of cloud droplet size distributions adjacent to droplet-free filaments), and relative humidity of entrained dry air. It is found that the decreasing rate of homogeneous mixing degree with increasing averaging scales becomes larger with larger droplet-free filament size and fraction, larger mean volume radius and liquid water content, or higher relative humidity. The results underscore the necessity and possibility of considering averaging scale in representation of entrainment-mixing processes in atmospheric models.

  4. The Role of High-Level Processes for Oscillatory Phase Entrainment to Speech Sound

    PubMed Central

    Zoefel, Benedikt; VanRullen, Rufin

    2015-01-01

    Constantly bombarded with input, the brain has the need to filter out relevant information while ignoring the irrelevant rest. A powerful tool may be represented by neural oscillations which entrain their high-excitability phase to important input while their low-excitability phase attenuates irrelevant information. Indeed, the alignment between brain oscillations and speech improves intelligibility and helps dissociating speakers during a “cocktail party”. Although well-investigated, the contribution of low- and high-level processes to phase entrainment to speech sound has only recently begun to be understood. Here, we review those findings, and concentrate on three main results: (1) Phase entrainment to speech sound is modulated by attention or predictions, likely supported by top-down signals and indicating higher-level processes involved in the brain’s adjustment to speech. (2) As phase entrainment to speech can be observed without systematic fluctuations in sound amplitude or spectral content, it does not only reflect a passive steady-state “ringing” of the cochlea, but entails a higher-level process. (3) The role of intelligibility for phase entrainment is debated. Recent results suggest that intelligibility modulates the behavioral consequences of entrainment, rather than directly affecting the strength of entrainment in auditory regions. We conclude that phase entrainment to speech reflects a sophisticated mechanism: several high-level processes interact to optimally align neural oscillations with predicted events of high relevance, even when they are hidden in a continuous stream of background noise. PMID:26696863

  5. The Role of High-Level Processes for Oscillatory Phase Entrainment to Speech Sound.

    PubMed

    Zoefel, Benedikt; VanRullen, Rufin

    2015-01-01

    Constantly bombarded with input, the brain has the need to filter out relevant information while ignoring the irrelevant rest. A powerful tool may be represented by neural oscillations which entrain their high-excitability phase to important input while their low-excitability phase attenuates irrelevant information. Indeed, the alignment between brain oscillations and speech improves intelligibility and helps dissociating speakers during a "cocktail party". Although well-investigated, the contribution of low- and high-level processes to phase entrainment to speech sound has only recently begun to be understood. Here, we review those findings, and concentrate on three main results: (1) Phase entrainment to speech sound is modulated by attention or predictions, likely supported by top-down signals and indicating higher-level processes involved in the brain's adjustment to speech. (2) As phase entrainment to speech can be observed without systematic fluctuations in sound amplitude or spectral content, it does not only reflect a passive steady-state "ringing" of the cochlea, but entails a higher-level process. (3) The role of intelligibility for phase entrainment is debated. Recent results suggest that intelligibility modulates the behavioral consequences of entrainment, rather than directly affecting the strength of entrainment in auditory regions. We conclude that phase entrainment to speech reflects a sophisticated mechanism: several high-level processes interact to optimally align neural oscillations with predicted events of high relevance, even when they are hidden in a continuous stream of background noise. PMID:26696863

  6. Skip the trip: air travelers' behavioral responses to pandemic influenza.

    PubMed

    Fenichel, Eli P; Kuminoff, Nicolai V; Chowell, Gerardo

    2013-01-01

    Theory suggests that human behavior has implications for disease spread. We examine the hypothesis that individuals engage in voluntary defensive behavior during an epidemic. We estimate the number of passengers missing previously purchased flights as a function of concern for swine flu or A/H1N1 influenza using 1.7 million detailed flight records, Google Trends, and the World Health Organization's FluNet data. We estimate that concern over "swine flu," as measured by Google Trends, accounted for 0.34% of missed flights during the epidemic. The Google Trends data correlates strongly with media attention, but poorly (at times negatively) with reported cases in FluNet. Passengers show no response to reported cases. Passengers skipping their purchased trips forwent at least $50 M in travel related benefits. Responding to actual cases would have cut this estimate in half. Thus, people appear to respond to an epidemic by voluntarily engaging in self-protection behavior, but this behavior may not be responsive to objective measures of risk. Clearer risk communication could substantially reduce epidemic costs. People undertaking costly risk reduction behavior, for example, forgoing nonrefundable flights, suggests they may also make less costly behavior adjustments to avoid infection. Accounting for defensive behaviors may be important for forecasting epidemics, but linking behavior with epidemics likely requires consideration of risk communication. PMID:23526970

  7. Skip the Trip: Air Travelers' Behavioral Responses to Pandemic Influenza

    PubMed Central

    Fenichel, Eli P.; Kuminoff, Nicolai V.; Chowell, Gerardo

    2013-01-01

    Theory suggests that human behavior has implications for disease spread. We examine the hypothesis that individuals engage in voluntary defensive behavior during an epidemic. We estimate the number of passengers missing previously purchased flights as a function of concern for swine flu or A/H1N1 influenza using 1.7 million detailed flight records, Google Trends, and the World Health Organization's FluNet data. We estimate that concern over “swine flu,” as measured by Google Trends, accounted for 0.34% of missed flights during the epidemic. The Google Trends data correlates strongly with media attention, but poorly (at times negatively) with reported cases in FluNet. Passengers show no response to reported cases. Passengers skipping their purchased trips forwent at least $50 M in travel related benefits. Responding to actual cases would have cut this estimate in half. Thus, people appear to respond to an epidemic by voluntarily engaging in self-protection behavior, but this behavior may not be responsive to objective measures of risk. Clearer risk communication could substantially reduce epidemic costs. People undertaking costly risk reduction behavior, for example, forgoing nonrefundable flights, suggests they may also make less costly behavior adjustments to avoid infection. Accounting for defensive behaviors may be important for forecasting epidemics, but linking behavior with epidemics likely requires consideration of risk communication. PMID:23526970

  8. Testing Selected Behaviors to Reduce Indoor Air Pollution Exposure in Young Children

    ERIC Educational Resources Information Center

    Barnes, B. R.; Mathee, A.; Krieger, L.; Shafritz, L.; Favin, M.; Sherburne, L.

    2004-01-01

    Indoor air pollution is responsible for the deaths and illness of millions of young children in developing countries. This study investigated the acceptability (willingness to try) and feasibility (ability to perform) of four indoor air pollution reduction behaviors (improve stove maintenance practices, child location practices, ventilation…

  9. Crustal entrainment and pulsar glitches.

    PubMed

    Chamel, N

    2013-01-01

    Large pulsar frequency glitches are generally interpreted as sudden transfers of angular momentum between the neutron superfluid permeating the inner crust and the rest of the star. Despite the absence of viscous drag, the neutron superfluid is strongly coupled to the crust due to nondissipative entrainment effects. These effects are shown to severely limit the maximum amount of angular momentum that can possibly be transferred during glitches. In particular, it is found that the glitches observed in the Vela pulsar require an additional reservoir of angular momentum. PMID:23383772

  10. A method for retrieving the cumulus entrainment rate from ground based observations

    NASA Astrophysics Data System (ADS)

    Wagner, Timothy J.

    2011-12-01

    The entrainment of drier environmental air into cumulus clouds affects the impact that these clouds have on the environment by modifying their radiative, microphysical, and thermodynamic characteristics. Entrainment is a difficult parameter to observe directly, and heretofore has been obtained from occasional aircraft penetrations. To increase the number of cumulus entrainment rate observations under a wide range of atmospheric conditions, an algorithm for retrieving the cumulus entrainment rate from ground-based remote sensing observations has been developed. This algorithm, called the Entrainment Rate In Cumulus Algorithm (ERICA), uses the suite of instruments at the Southern Great Plains (SGP) site of the United States Department of Energy's Atmospheric Radiation Measurement (ARM) Climate Research Facility as inputs into a Gauss-Newton optimal estimation scheme. The forward model in this algorithm is the Explicit Mixing Parcel Model (EMPM), a cloud parcel model that treats entrainment as a series of discrete mixing events. Output from EMPM is used to calculate quantities that can be observed from the surface, including effective radius and liquid water path. The entrainment rate in EMPM is adjusted iteratively until the modeled output converges to the observations. Sensitivity testing and error and information content analysis show that ERICA is a robust method for obtaining accurate estimates of entrainment rate without the drawbacks of aircraft observations. Results from a three-month trial of ERICA show significant variability of the entrainment rate of clouds in a single day and from one day to the next. The mean value from this analysis corresponds well with prior knowledge of the entrainment rate.

  11. The effect of simulated evaporative cooling on thermal entrainment

    NASA Astrophysics Data System (ADS)

    Zhang, Qing; Cotel, Aline

    1998-11-01

    The effect of simulated evaporative cooling on the entrainment of a thermal impinging on a stratified interface is investigated experimentally. Evaporative cooling in atmospheric clouds results in buoyancy reversal, where the mixed fluid is denser than either parent parcel. This is realized in the laboratory by using a mixture of ethyl alcohol and ethylene glycohol in aqueous solution. A thermal is formed by releasing a small volume of buoyant fluid from the bottom of a lucite tank. It rises first through a relatively dense lower layer and then impinges on a thin stratified interface, above which is a relatively light layer. The entrainment of upper layer across the interface is measured optically. The entrainment rate is found to obey a Ri-3/2 power law for values of the buoyancy reversal parameter, D*, between 0 and 0.5. The entrainment rate is independent of D* for a certain range of Ri. This is consistent with the behavior of the buoyancy-reversing thermal in an unstratified environment observed by Johari.

  12. Optimal entrainment of heterogeneous noisy neurons

    PubMed Central

    Wilson, Dan; Holt, Abbey B.; Netoff, Theoden I.; Moehlis, Jeff

    2015-01-01

    We develop a methodology to design a stimulus optimized to entrain nonlinear, noisy limit cycle oscillators with uncertain properties. Conditions are derived which guarantee that the stimulus will entrain the oscillators despite these uncertainties. Using these conditions, we develop an energy optimal control strategy to design an efficient entraining stimulus and apply it to numerical models of noisy phase oscillators and to in vitro hippocampal neurons. In both instances, the optimal stimuli outperform other similar but suboptimal entraining stimuli. Because this control strategy explicitly accounts for both noise and inherent uncertainty of model parameters, it could have experimental relevance to neural circuits where robust spike timing plays an important role. PMID:26074762

  13. Partial entrainment of gravel bars during floods

    USGS Publications Warehouse

    Konrad, C.P.; Booth, D.B.; Burges, S.J.; Montgomery, D.R.

    2002-01-01

    Spatial patterns of bed material entrainment by floods were documented at seven gravel bars using arrays of metal washers (bed tags) placed in the streambed. The observed patterns were used to test a general stochastic model that bed material entrainment is a spatially independent, random process where the probability of entrainment is uniform over a gravel bar and a function of the peak dimensionless shear stress ??*0 of the flood. The fraction of tags missing from a gravel bar during a flood, or partial entrainment, had an approximately normal distribution with respect to ??*0 with a mean value (50% of the tags entrained) of 0.085 and standard deviation of 0.022 (root-mean-square error of 0.09). Variation in partial entrainment for a given ??*0 demonstrated the effects of flow conditioning on bed strength, with lower values of partial entrainment after intermediate magnitude floods (0.065 < ??*0 < 0.08) than after higher magnitude floods. Although the probability of bed material entrainment was approximately uniform over a gravel bar during individual floods and independent from flood to flood, regions of preferential stability and instability emerged at some bars over the course of a wet season. Deviations from spatially uniform and independent bed material entrainment were most pronounced for reaches with varied flow and in consecutive floods with small to intermediate magnitudes.

  14. I. Mixing in doorway flows. II. Entrainment in fire plumes

    NASA Astrophysics Data System (ADS)

    Lim, Christopher S.

    The motion of hot combustion products through a burning structure plays a dominant role in fixing the spread of the fire and the spread of toxic gases. The first part of this report is concerned with the effect of door geometry on the rate of turbulent mixing between the hot and cold layers near a doorway. The second part of the report deals with the entrainment rates in the near field of a buoyant diffusion methane flame.In the study of the motion of the hot combustion products near a doorway, the gas in the burning room is assumed to be divided into two homogeneous layers--the ceiling layer which contains the hot combustion products and the floor layer which contains the denser fresh air. Temperature and carbon dioxide measurements are taken from a half-scale room which uses a pump and furnace to simulate the entrainment and heating of the fresh air by the fire plume. The mass transfer rates are calculated from these measurements and are found to be a function of a Richardson number that uses the interface height measured from the floor as the characteristic length and the average inflow velocity of fresh air as the characteristic velocity. This form for Ri(0) is derived from an analysis based on Taylor's entrainment hypothesis. For a given fire size, i.e., for a given mass flow of fresh air into the room, the effect of reducing the door area is to reduce the value of Ri(0), and hence increase the mixing rate in the room. The door height is found to be a much stronger influence on the mixing rate and interface height than the door width.The entrainment rates of fresh air in the near field of a buoyant diffusion methane flame whose flames extend well above the interface between the hot gas layer and the fresh air layer are measured for several interface heights. In the experiments, the ceiling layer-fire plume interaction is simulated by placing a large steel hood over an axisymmetric burner. The hood may be raised or lowered to change the interface height. The

  15. Quantifying entrainment in pyroclastic density currents from the Tungurahua eruption, Ecuador: Integrating field proxies with numerical simulations

    NASA Astrophysics Data System (ADS)

    Benage, M. C.; Dufek, J.; Mothes, P. A.

    2016-07-01

    The entrainment of air into pyroclastic density currents (PDCs) impacts the dynamics and thermal history of these highly mobile currents. However, direct measurement of entrainment in PDCs is hampered due to hazardous conditions and opaqueness of these flows. We combine three-dimensional multiphase Eulerian-Eulerian-Lagrangian calculations with proxies of thermal conditions preserved in deposits to quantify air entrainment in PDCs at Tungurahua volcano, Ecuador. We conclude that small-volume PDCs develop a particle concentration gradient that results in disparate thermal characteristics for the concentrated bed load (>600 to ~800 K) and the overlying dilute suspended load (~300-600 K). The dilute suspended load has effective entrainment coefficients 2-3 times larger than the bed load. This investigation reveals a dichotomy in entrainment and thermal history between two regions in the current and provides a mechanism to interpret the depositional thermal characteristics of small-volume but frequently occurring PDCs.

  16. Entrainment instability and vertical motion as causes of stratocumulus breakup

    NASA Technical Reports Server (NTRS)

    Weaver, C. J.; Pearson, R., Jr.

    1990-01-01

    Entrainment instability is thought to be a cause of stratocumulus breakup. At the interface between the cloud and the overlying air, mixtures may form which are negatively buoyant because of cloud droplet evaporation. Quantities devised to predict breakup are obtained from aircraft observations and are tested against cloud observations from satellite. Often, the parameters indicate that breakup should occur but the clouds remain, sometimes for several days. One possible explanation for breakup is vertical motion from passing synoptic cyclones. Several cases suggest that breakup is associated with the downward vertical motion from the cold air advected behind an eastward moving cyclone.

  17. Time-Specific Fear Acts as a Non-Photic Entraining Stimulus of Circadian Rhythms in Rats.

    PubMed

    Pellman, Blake A; Kim, Earnest; Reilly, Melissa; Kashima, James; Motch, Oleksiy; de la Iglesia, Horacio O; Kim, Jeansok J

    2015-01-01

    Virtually all animals have endogenous clock mechanisms that "entrain" to the light-dark (LD) cycle and synchronize psychophysiological functions to optimal times for exploring resources and avoiding dangers in the environment. Such circadian rhythms are vital to human mental health, but it is unknown whether circadian rhythms "entrained" to the LD cycle can be overridden by entrainment to daily recurring threats. We show that unsignaled nocturnal footshock caused rats living in an "ethological" apparatus to switch their natural foraging behavior from the dark to the light phase and that this switch was maintained as a free-running circadian rhythm upon removal of light cues and footshocks. Furthermore, this fear-entrained circadian behavior was dependent on an intact amygdala and suprachiasmatic nucleus. Thus, time-specific fear can act as a non-photic entraining stimulus for the circadian system, and limbic centers encoding aversive information are likely part of the circadian oscillator network that temporally organizes behavior. PMID:26468624

  18. Air

    MedlinePlus

    ... do to protect yourself from dirty air . Indoor air pollution and outdoor air pollution Air can be polluted indoors and it can ... this chart to see what things cause indoor air pollution and what things cause outdoor air pollution! Indoor ...

  19. Numerical Analysis on Air Ingress Behavior in GTHTR300H

    SciTech Connect

    Tetsuaki Takeda; Xing Yan; Kazuhiko Kunitomi

    2006-07-01

    Japan Atomic Energy Agency (JAEA) has been developing the analytical code for the safety characteristics of the HTGR and carrying out design study of the gas turbine high temperature reactor of 300 MWe nominal-capacity for hydrogen production, the GTHTR300H (Gas Turbine High Temperature Reactor 300 for Hydrogen). The objective of this study is to clarify safety characteristics of the GTHTR300H for the pipe rupture accident. A numerical analysis of heat and mass transfer fluid flow with multi-component gas mixture has been performed to obtain the variation of the density of the gas mixture, and the onset time of natural circulation of air. From the results obtained in this analysis, it was found that the duration time of the air ingress by molecular diffusion would increase due to the existence of the recuperator in the GTHTR300H system. (authors)

  20. The entrainment rate for a row of turbulent jets. M.S. Thesis Final Report

    NASA Technical Reports Server (NTRS)

    Gordon, Eliott B.; Greber, Isaac

    1990-01-01

    Entrainment rates for a row of isothermal circular air jets issuing into a quiescent environment are found by integrating velocity distributions measured by a linearized hot-wire anemometer. Jet spacing to jet diameter ratios of 2.5, 5, 10, and 20 are studied at jet Reynold's numbers ranging from 5110 to 12070. Velocity distributions are determined at regular downstream intervals at axial distances equal to 16.4 to 164 jet diameters from the jet source. The entrainment rates for the four spacing configurations vary monotonically with increasing spacing/diameter between the limiting case of the slot jet entrainment rate (where the jet spacing to diameter ratio is zero) and the circular jet entrainment rate (in which the spacing to diameter ratio is infinity).

  1. Neurobiological foundations of neurologic music therapy: rhythmic entrainment and the motor system

    PubMed Central

    Thaut, Michael H.; McIntosh, Gerald C.; Hoemberg, Volker

    2015-01-01

    Entrainment is defined by a temporal locking process in which one system’s motion or signal frequency entrains the frequency of another system. This process is a universal phenomenon that can be observed in physical (e.g., pendulum clocks) and biological systems (e.g., fire flies). However, entrainment can also be observed between human sensory and motor systems. The function of rhythmic entrainment in rehabilitative training and learning was established for the first time by Thaut and colleagues in several research studies in the early 1990s. It was shown that the inherent periodicity of auditory rhythmic patterns could entrain movement patterns in patients with movement disorders (see for a review: Thaut et al., 1999). Physiological, kinematic, and behavioral movement analysis showed very quickly that entrainment cues not only changed the timing of movement but also improved spatial and force parameters. Mathematical models have shown that anticipatory rhythmic templates as critical time constraints can result in the complete specification of the dynamics of a movement over the entire movement cycle, thereby optimizing motor planning and execution. Furthermore, temporal rhythmic entrainment has been successfully extended into applications in cognitive rehabilitation and speech and language rehabilitation, and thus become one of the major neurological mechanisms linking music and rhythm to brain rehabilitation. These findings provided a scientific basis for the development of neurologic music therapy. PMID:25774137

  2. Marching along to an Offbeat Drum: Entrainment of Synthetic Gene Oscillators by a Noisy Stimulus.

    PubMed

    Butzin, Nicholas C; Hochendoner, Philip; Ogle, Curtis T; Hill, Paul; Mather, William H

    2016-02-19

    Modulation of biological oscillations by stimuli lies at the root of many phenomena, including maintenance of circadian rhythms, propagation of neural signals, and somitogenesis. While it is well established that regular periodic modulation can entrain an oscillator, an aperiodic (noisy) modulation can also robustly entrain oscillations. This latter scenario may describe, for instance, the effect of irregular weather patterns on circadian rhythms, or why irregular neural stimuli can still reliably transmit information. A synthetic gene oscillator approach has already proven to be useful in understanding the entrainment of biological oscillators by periodic signaling, mimicking the entrainment of a number of noisy oscillating systems. We similarly seek to use synthetic biology as a platform to understand how aperiodic signals can strongly correlate the behavior of cells. This study should lead to a deeper understanding of how fluctuations in our environment and even within our body may promote substantial synchrony among our cells. Specifically, we investigate experimentally and theoretically the entrainment of a synthetic gene oscillator in E. coli by a noisy stimulus. This phenomenon was experimentally studied and verified by a combination of microfluidics and microscopy using the real synthetic circuit. Stochastic simulation of an associated model further supports that the synthetic gene oscillator can be strongly entrained by aperiodic signals, especially telegraph noise. Finally, widespread applicability of aperiodic entrainment beyond the synthetic gene oscillator is supported by results derived from both a model for a natural oscillator in D. discoideum and a model for predator-prey oscillations. PMID:26524465

  3. Neurobiological foundations of neurologic music therapy: rhythmic entrainment and the motor system.

    PubMed

    Thaut, Michael H; McIntosh, Gerald C; Hoemberg, Volker

    2014-01-01

    Entrainment is defined by a temporal locking process in which one system's motion or signal frequency entrains the frequency of another system. This process is a universal phenomenon that can be observed in physical (e.g., pendulum clocks) and biological systems (e.g., fire flies). However, entrainment can also be observed between human sensory and motor systems. The function of rhythmic entrainment in rehabilitative training and learning was established for the first time by Thaut and colleagues in several research studies in the early 1990s. It was shown that the inherent periodicity of auditory rhythmic patterns could entrain movement patterns in patients with movement disorders (see for a review: Thaut et al., 1999). Physiological, kinematic, and behavioral movement analysis showed very quickly that entrainment cues not only changed the timing of movement but also improved spatial and force parameters. Mathematical models have shown that anticipatory rhythmic templates as critical time constraints can result in the complete specification of the dynamics of a movement over the entire movement cycle, thereby optimizing motor planning and execution. Furthermore, temporal rhythmic entrainment has been successfully extended into applications in cognitive rehabilitation and speech and language rehabilitation, and thus become one of the major neurological mechanisms linking music and rhythm to brain rehabilitation. These findings provided a scientific basis for the development of neurologic music therapy. PMID:25774137

  4. Results and code prediction comparisons of lithium-air reaction and aerosol behavior tests

    SciTech Connect

    Jeppson, D.W.

    1986-03-01

    The Hanford Engineering Development Laboratory (HEDL) Fusion Safety Support Studies include evaluation of potential safety and environmental concerns associated with the use of liquid lithium as a breeder and coolant for fusion reactors. Potential mechanisms for volatilization and transport of radioactive metallic species associated with breeder materials are of particular interest. Liquid lithium pool-air reaction and aerosol behavior tests were conducted with lithium masses up to 100 kg within the 850-m/sup 3/ containment vessel in the Containment Systems Test Facility. Lithium-air reaction rates, aerosol generation rates, aerosol behavior and characterization, as well as containment atmosphere temperature and pressure responses were determined. Pool-air reaction and aerosol behavior test results were compared with computer code calculations for reaction rates, containment atmosphere response, and aerosol behavior. The volatility of potentially radioactive metallic species from a lithium pool-air reaction was measured. The response of various aerosol detectors to the aerosol generated was determined. Liquid lithium spray tests in air and in nitrogen atmospheres were conducted with lithium temperatures of about 427/sup 0/ and 650/sup 0/C. Lithium reaction rates, containment atmosphere response, and aerosol generation and characterization were determined for these spray tests.

  5. Numerical characterization of the hydrodynamics and thermal behavior of air flow in flexible air distribution system

    NASA Astrophysics Data System (ADS)

    Gharehdaghi, Samad; Moujaes, Samir

    2013-10-01

    Flexible duct air distribution systems are used in a large percentage of residential and small commercial buildings in the United States . Very few empirical or predictive data are available though to help provide the HVAC design engineer with reliable information . Moreover, because of the ducts flexibility, the shapes of these ducts offer a different set of operating fluid flow and thermal conditions from traditional smooth metal ducts. Hence, both the flow field and heat transfer through this kind of ducts are much more complex and merit to be analyzed from a numerical predictive approach. The aim of this research paper is to compute some of the hydrodynamic and heat transfer characteristics of the air flow inside these ducts over a range of Re numbers commonly used in the flow conditions of these air distribution systems. The information resulting from this CFD simulation, where a κ-ɛ turbulent model is used to predict the flow conditions, provide pressure drop and average convective heat transfer coefficients that exist in these ducts and was compared to previously found data. Circulation zones in the depressions of these ducts are found to exist which are suspected of influencing the pressured drop and heat transfer coefficients as compared to smooth ducts. The results show that fully developed conditions exist much earlier with regard to the inlet for both hydrodynamic and thermal entrance regions than what would be expected in smooth ducts under the same turbulent conditions.

  6. Temperature compensation and entrainment in circadian rhythms

    NASA Astrophysics Data System (ADS)

    Bodenstein, C.; Heiland, I.; Schuster, S.

    2012-06-01

    To anticipate daily variations in the environment and coordinate biological activities into a daily cycle many organisms possess a circadian clock. In the absence of external time cues the circadian rhythm persists with a period of approximately 24 h. The clock phase can be shifted by single pulses of light, darkness, chemicals, or temperature and this allows entrainment of the clock to exactly 24 h by cycles of these zeitgebers. On the other hand, the period of the circadian rhythm is kept relatively constant within a physiological range of constant temperatures, which means that the oscillator is temperature compensated. The mechanisms behind temperature compensation and temperature entrainment are not fully understood, neither biochemically nor mathematically. Here, we theoretically investigate the interplay of temperature compensation and entrainment in general oscillatory systems. We first give an analytical treatment for small temperature shifts and derive that every temperature-compensated oscillator is entrainable to external small-amplitude temperature cycles. Temperature compensation ensures that this entrainment region is always centered at the endogenous period regardless of possible seasonal temperature differences. Moreover, for small temperature cycles the entrainment region of the oscillator is potentially larger for rectangular pulses. For large temperature shifts we numerically analyze different circadian clock models proposed in the literature with respect to these properties. We observe that for such large temperature shifts sinusoidal or gradual temperature cycles allow a larger entrainment region than rectangular cycles.

  7. Rhythmic TMS Causes Local Entrainment of Natural Oscillatory Signatures

    PubMed Central

    Thut, Gregor; Veniero, Domenica; Romei, Vincenzo; Miniussi, Carlo; Schyns, Philippe; Gross, Joachim

    2011-01-01

    Summary Background Neuronal elements underlying perception, cognition, and action exhibit distinct oscillatory phenomena, measured in humans by electro- or magnetoencephalography (EEG/MEG). So far, the correlative or causal nature of the link between brain oscillations and functions has remained elusive. A compelling demonstration of causality would primarily generate oscillatory signatures that are known to correlate with particular cognitive functions and then assess the behavioral consequences. Here, we provide the first direct evidence for causal entrainment of brain oscillations by transcranial magnetic stimulation (TMS) using concurrent EEG. Results We used rhythmic TMS bursts to directly interact with an MEG-identified parietal α-oscillator, activated by attention and linked to perception. With TMS bursts tuned to its preferred α-frequency (α-TMS), we confirmed the three main predictions of entrainment of a natural oscillator: (1) that α-oscillations are induced during α-TMS (reproducing an oscillatory signature of the stimulated parietal cortex), (2) that there is progressive enhancement of this α-activity (synchronizing the targeted, α-generator to the α-TMS train), and (3) that this depends on the pre-TMS phase of the background α-rhythm (entrainment of natural, ongoing α-oscillations). Control conditions testing different TMS burst profiles and TMS-EEG in a phantom head confirmed specificity of α-boosting to the case of synchronization between TMS train and neural oscillator. Conclusions The periodic electromagnetic force that is generated during rhythmic TMS can cause local entrainment of natural brain oscillations, emulating oscillatory signatures activated by cognitive tasks. This reveals a new mechanism of online TMS action on brain activity and can account for frequency-specific behavioral TMS effects at the level of biologically relevant rhythms. PMID:21723129

  8. Entrainment ranges of forced phase oscillators.

    PubMed

    Previte, Joseph P; Sheils, Natalie; Hoffman, Kathleen A; Kiemel, Tim; Tytell, Eric D

    2011-04-01

    In the vertebrate spinal cord, a neural circuit called the central pattern generator produces the basic locomotory rhythm. Short and long distance intersegmental connections serve to maintain coordination along the length of the body. As a way of examining the influence of such connections, we consider a model of a chain of coupled phase oscillators in which one oscillator receives a periodic forcing stimulus. For a certain range of forcing frequencies, the chain will match the stimulus frequency, a phenomenon called entrainment. Motivated by recent experiments in lampreys, we derive analytical expressions for the range of forcing frequencies that entrain the chain, and how that range depends on the forcing location. For short intersegmental connections, in which an oscillator is connected only to its nearest neighbors, we describe two ways in which entrainment is lost: internally, in which oscillators within the chain no longer oscillate at the same frequency; and externally, in which the the chain no longer has the same frequency as the forcing. By analyzing chains in which every oscillator is connected to every other oscillator (i.e., all-to-all connections), we show that the presence of connections with lengths greater than one do not necessarily change the entrainment ranges based on the nearest-neighbor model. We derive a criterion for the ratio of connection strengths under which the connections of length greater than one do not change the entrainment ranges produced in the nearest-neighbor model, provided entrainment is lost externally. However, when this criterion holds, the range of entrained frequencies is a monotonic function of forcing location, unlike experimental results, in which entrainment ranges are larger near the middle of the chain than at the ends. Numerically, we show that similar non-monotonic entrainment ranges are possible if the ratio criterion does not hold, suggesting that in the lamprey central pattern generator, intersegmental

  9. Laboratory experiments on stability and entrainment of oceanic stratocumulus. Part 1: Instability experiment

    NASA Technical Reports Server (NTRS)

    Shy, Shenqyang S.

    1990-01-01

    The existence and persistence of marine stratocumulus play a significant role in the overall energy budget of the earth. Their stability and entrainment process are important in global climate studies, as well as for local weather forecasting. The purposes of the experimental simulations are to study this process and to address this paradox. The effects of buoyancy reversal is investigated, followed by two types of experiments. An instability experiment involves the behavior of a fully turbulent wake near the inversion generated by a sliding plate. Due to buoyancy reversal, the heavy, mixed fluid starts to sink, turning the potential energy created by the mixing process into kinetic energy, thereby increasing the entrainment rate. An entrainment experiment, using a vertically oscillating grid driven by a controllable speed motor, produces many eddy-induced entrainments at a surface region on scales much less than the depth of the layer.

  10. A Quantitative Investigation of Entrainment and Detrainment in Numerically Simulated Convective Clouds. Pt. 1; Model Development

    NASA Technical Reports Server (NTRS)

    Cohen, Charles

    1998-01-01

    A method is developed which uses numerical tracers to make accurate diagnoses of entraimnent and detrainment rates and of the properties of the entrained and detrained air in numerically simulated clouds. The numerical advection scheme is modified to make it nondispersive, as required by the use of the tracers. Tests of the new method are made, and an appropriate definition of clouds is selected. Distributions of mixing fractions in the model consistently show maximums at the end points, for nearly undilute environmental air or nearly undilute cloud air, with a uniform distribution between. The cumulonimbus clouds simulated here entrain air that had been substantially changed by the clouds, and detrained air that is not necessarily representative of the cloud air at the same level.

  11. Particle-size distributions and their effect on entrainment in turbulent buoyant plumes

    NASA Astrophysics Data System (ADS)

    Jessop, D.; Jellinek, M.

    2014-12-01

    Explosive volcanic eruptions produce turbulent, buoyant jets that contain entrained particles. In these flows, turbulent entrainment of ambient air controls the ultimate rise height and spread of the jet. Volcanic jets are a natural example of these dilute particle-gas systems and the particles they contain can strongly control the dynamics of the bulk flow through the coupling between themselves and the surrounding fluid. The metric for the type of particle-fluid coupling is the Stokes number, St, which measures the timescale for the particles inertia against the timescale for the flow field, typically the overturn time of an eddy. We show that particles that are critically coupled to the flow (St=O(1)) change the turbulent structure of the flow by eddy stretching leading to energy cascades which are anisotropic in the horizontal and vertical directions. Crucially, flows laden with such particles carry considerably more energy in the stream-wise direction than particle-free flows which leads to a decrease in entrainment. This behaviour suggests that turbulent entrainment can effectively be shut down under critical St, giving rise to collapsing fountains whereas particle-free flows under the same source conditions would produce buoyant plumes. Changes in entrainment rates in volcanic jets are also manifested in readily observable features such as the rise height. We may therefore infer entrainment rates and their evolution over the course of an eruption from the maximum height and neutral buoyancy level.

  12. Rhythm as a Coordinating Device: Entrainment With Disordered Speech

    PubMed Central

    Borrie, Stephanie A.; Liss, Julie M.

    2014-01-01

    Purpose The rhythmic entrainment (coordination) of behavior during human interaction is a powerful phenomenon, considered essential for successful communication, supporting social and emotional connection, and facilitating sense-making and information exchange. Disruption in entrainment likely occurs in conversations involving those with speech and language impairment, but its contribution to communication disorders has not been defined. As a first step to exploring this phenomenon in clinical populations, the present investigation examined the influence of disordered speech on the speech production properties of healthy interactants. Method Twenty-nine neurologically healthy interactants participated in a quasi-conversational paradigm, in which they read sentences (response) in response to hearing prerecorded sentences (exposure) from speakers with dysarthria (n = 4) and healthy controls (n = 4). Recordings of read sentences prior to the task were also collected (habitual). Results Findings revealed that interactants modified their speaking rate and pitch variation to align more closely with the disordered speech. Production shifts in these rhythmic properties, however, remained significantly different from corresponding properties in dysarthric speech. Conclusion Entrainment offers a new avenue for exploring speech and language impairment, addressing a communication process not currently explained by existing frameworks. This article offers direction for advancing this line of inquiry. PMID:24686410

  13. Robust Entrainment of Circadian Oscillators Requires Specific Phase Response Curves

    PubMed Central

    Pfeuty, Benjamin; Thommen, Quentin; Lefranc, Marc

    2011-01-01

    The circadian clocks keeping time in many living organisms rely on self-sustained biochemical oscillations entrained by external cues, such as light, to the 24-h cycle induced by Earth's rotation. However, environmental cues are unreliable due to the variability of habitats, weather conditions, or cue-sensing mechanisms among individuals. A tempting hypothesis is that circadian clocks have evolved so as to be robust to fluctuations in the signal that entrains them. To support this hypothesis, we analyze the synchronization behavior of weakly and periodically forced oscillators in terms of their phase response curve (PRC), which measures phase changes induced by a perturbation applied at different times of the cycle. We establish a general relationship between the robustness of key entrainment properties, such as stability and oscillator phase, on the one hand, and the shape of the PRC as characterized by a specific curvature or the existence of a dead zone, on the other hand. The criteria obtained are applied to computational models of circadian clocks and account for the disparate robustness properties of various forcing schemes. Finally, the analysis of PRCs measured experimentally in several organisms strongly suggests a case of convergent evolution toward an optimal strategy for maintaining a clock that is accurate and robust to environmental fluctuations. PMID:21641300

  14. Velocity response curves demonstrate the complexity of modeling entrainable clocks.

    PubMed

    Taylor, Stephanie R; Cheever, Allyson; Harmon, Sarah M

    2014-12-21

    Circadian clocks are biological oscillators that regulate daily behaviors in organisms across the kingdoms of life. Their rhythms are generated by complex systems, generally involving interlocked regulatory feedback loops. These rhythms are entrained by the daily light/dark cycle, ensuring that the internal clock time is coordinated with the environment. Mathematical models play an important role in understanding how the components work together to function as a clock which can be entrained by light. For a clock to entrain, it must be possible for it to be sped up or slowed down at appropriate times. To understand how biophysical processes affect the speed of the clock, one can compute velocity response curves (VRCs). Here, in a case study involving the fruit fly clock, we demonstrate that VRC analysis provides insight into a clock׳s response to light. We also show that biochemical mechanisms and parameters together determine a model׳s ability to respond realistically to light. The implication is that, if one is developing a model and its current form has an unrealistic response to light, then one must reexamine one׳s model structure, because searching for better parameter values is unlikely to lead to a realistic response to light. PMID:25193284

  15. Washing of the AN-107 entrained solids

    SciTech Connect

    GJ Lumetta; FV Hoopes

    2000-03-31

    This report describes the results of a test conducted by Battelle to assess the effects of inhibited water washing on the composition of the entrained solids in the diluted AN-107 low-activity waste (LAW) sample. The objective of this work was to gather data on the solubility of the AN-107 entrained solids in 0.01 M NaOH, so that BNFL can evaluate whether these solids require caustic leaching.

  16. Informational Constraints on Spontaneous Visuomotor Entrainment

    PubMed Central

    Varlet, Manuel; Bucci, Colleen; Richardson, Michael J.; Schmidt, R. C.

    2015-01-01

    Past research has revealed that an individual's rhythmic limb movements become spontaneously entrained to an environmental rhythm if visual information about the rhythm is available and its frequency is near that of the individual's movements. Research has also demonstrated that if the eyes track an environmental stimulus, the spontaneous entrainment to the rhythm is strengthened. One hypothesis explaining this enhancement of spontaneous entrainment is that the limb movements and eye movements are linked through a neuromuscular coupling or synergy. Another is that eye-tracking facilitates the pick up of important coordinating information. Experiment 1 investigated the first hypothesis by evaluating whether any rhythmic movement of the eyes would facilitate spontaneous entrainment. Experiment 2 and 3 (respectively) explored whether eye-tracking strengthens spontaneous entrainment by allowing the pickup of trajectory direction change information or allowing an increase in the amount of information to be picked-up. Results suggest that the eye-tracking enhancement of spontaneous entrainment is a consequence of increasing the amount of information available to be picked-up. PMID:25866944

  17. Tuning the phase of circadian entrainment

    PubMed Central

    Bordyugov, Grigory; Abraham, Ute; Granada, Adrian; Rose, Pia; Imkeller, Katharina; Kramer, Achim; Herzel, Hanspeter

    2015-01-01

    The circadian clock coordinates daily physiological, metabolic and behavioural rhythms. These endogenous oscillations are synchronized with external cues (‘zeitgebers’), such as daily light and temperature cycles. When the circadian clock is entrained by a zeitgeber, the phase difference ψ between the phase of a clock-controlled rhythm and the phase of the zeitgeber is of fundamental importance for the fitness of the organism. The phase of entrainment ψ depends on the mismatch between the intrinsic period τ and the zeitgeber period T and on the ratio of the zeitgeber strength to oscillator amplitude. Motivated by the intriguing complexity of empirical data and by our own experiments on temperature entrainment of mouse suprachiasmatic nucleus (SCN) slices, we present a theory on how clock and zeitgeber properties determine the phase of entrainment. The wide applicability of the theory is demonstrated using mathematical models of different complexity as well as by experimental data. Predictions of the theory are confirmed by published data on Neurospora crassa strains for different period mismatches τ − T and varying photoperiods. We apply a novel regression technique to analyse entrainment of SCN slices by temperature cycles. We find that mathematical models can explain not only the stable asymptotic phase of entrainment, but also transient phase dynamics. Our theory provides the potential to explore seasonal variations of circadian rhythms, jet lag and shift work in forthcoming studies. PMID:26136227

  18. Tuning the phase of circadian entrainment.

    PubMed

    Bordyugov, Grigory; Abraham, Ute; Granada, Adrian; Rose, Pia; Imkeller, Katharina; Kramer, Achim; Herzel, Hanspeter

    2015-07-01

    The circadian clock coordinates daily physiological, metabolic and behavioural rhythms. These endogenous oscillations are synchronized with external cues ('zeitgebers'), such as daily light and temperature cycles. When the circadian clock is entrained by a zeitgeber, the phase difference ψ between the phase of a clock-controlled rhythm and the phase of the zeitgeber is of fundamental importance for the fitness of the organism. The phase of entrainment ψ depends on the mismatch between the intrinsic period τ and the zeitgeber period T and on the ratio of the zeitgeber strength to oscillator amplitude. Motivated by the intriguing complexity of empirical data and by our own experiments on temperature entrainment of mouse suprachiasmatic nucleus (SCN) slices, we present a theory on how clock and zeitgeber properties determine the phase of entrainment. The wide applicability of the theory is demonstrated using mathematical models of different complexity as well as by experimental data. Predictions of the theory are confirmed by published data on Neurospora crassa strains for different period mismatches τ - T and varying photoperiods. We apply a novel regression technique to analyse entrainment of SCN slices by temperature cycles. We find that mathematical models can explain not only the stable asymptotic phase of entrainment, but also transient phase dynamics. Our theory provides the potential to explore seasonal variations of circadian rhythms, jet lag and shift work in forthcoming studies. PMID:26136227

  19. Oxytocin Mediates Entrainment of Sensory Stimuli to Social Cues of Opposing Valence

    PubMed Central

    Choe, Han Kyoung; Reed, Michael Douglas; Benavidez, Nora; Montgomery, Daniel; Soares, Natalie; Yim, Yeong Shin; Choi, Gloria B.

    2015-01-01

    Meaningful social interactions modify behavioral responses to sensory stimuli. The neural mechanisms underlying the entrainment of neutral sensory stimuli to salient social cues to produce social learning remains unknown. We used odor-driven behavioral paradigms to ask if oxytocin, a neuropeptide implicated in various social behaviors, plays a crucial role in the formation of learned associations between odor and socially significant cues. Through genetic, optogenetic and pharmacological manipulations, we show that oxytocin receptor signaling is crucial for entrainment of odor to social cues, but is dispensable for entrainment to non-social cues. Furthermore, we demonstrate that oxytocin directly impacts the piriform, the olfactory sensory cortex, to mediate social learning. Lastly, we provide evidence that oxytocin plays a role in both appetitive and aversive social learning. These results suggest that oxytocin conveys saliency of social stimuli to sensory representations in the piriform cortex during odor-driven social learning. PMID:26139372

  20. Droplet entrainment correlation for high pressure annular two-phase flow

    SciTech Connect

    Lopez de Betodano, M.A.; Jan, Cheng-Shiun; Beus, S.G.

    1996-01-01

    The amount of entrainment in annular flow is essential to predict the point of dryout. Most of the entrainment correlations available in the literature are obtained from air-water low pressure data. However many important industrial applications involve high pressure annular flows. There are very few correlations applicable in this range and they are solely based on empirical data fits. Comparing the low pressure entrainment data of Cousins and Hewitt (1968) and the high pressure data of Keeys et. al. (1970) and Wurtz (1978) with existing correlations, the agreement at high pressure is generally poor, except for the empirical correlation of Nigmatulin and Krushenok (1989) which depends on a Weber number that includes the droplet concentration. We propose a new semi-mechanistic entrainment correlation for fully developed annular flow conditions: E = (0.9642)/(1 + (3836/We{sub C})). It is developed based on the droplet continuity equation and the entrainment rate model of Dallman et. al. (1979). This model is then modified to introduce a Weber number that includes the droplet concentration, We{sub C}. This Weber number is shown to scale the available high and low pressure air-water and steam-water data better than the other definitions. Because the new correlation is based on a model of entrainment rate it may be used as a starting point in the development of a correlation for this process applicable to high pressure water-steam annular flows. A correlation is suggested pending validation with high pressure entrainment rate data. 12 refs., 11 figs.

  1. Applying the Theory of Planned Behavior to Explore the Relation between Smoke-Free Air Laws and Quitting Intentions

    ERIC Educational Resources Information Center

    Macy, Jonathan T.; Middlestadt, Susan E.; Seo, Dong-Chul; Kolbe, Lloyd J.; Jay, Stephen J.

    2012-01-01

    Smoke-free air policies have been shown to reduce smoking, but the mechanism of behavior change is not well understood. The authors used structural equation modeling to conduct a theory of planned behavior analysis with data from 395 smokers living in seven Texas cities, three with a comprehensive smoke-free air law and four without a…

  2. Ventilation patterns of the songbird lung/air sac system during different behaviors

    PubMed Central

    Mackelprang, Rebecca; Goller, Franz

    2013-01-01

    SUMMARY Unidirectional, continuous airflow through the avian lung is achieved through an elaborate air sac system with a sequential, posterior to anterior ventilation pattern. This classical model was established through various approaches spanning passively ventilated systems to mass spectrometry analysis of tracer gas flow into various air sacs during spontaneous breathing in restrained ducks. Information on flow patterns in other bird taxa is missing, and these techniques do not permit direct tests of whether the basic flow pattern can change during different behaviors. Here we use thermistors implanted into various locations of the respiratory system to detect small pulses of tracer gas (helium) to reconstruct airflow patterns in quietly breathing and behaving (calling, wing flapping) songbirds (zebra finch and yellow-headed blackbird). The results illustrate that the basic pattern of airflow in these two species is largely consistent with the model. However, two notable differences emerged. First, some tracer gas arrived in the anterior set of air sacs during the inspiration during which it was inhaled, suggesting a more rapid throughput through the lung than previously assumed. Second, differences in ventilation between the two anterior air sacs emerged during calling and wing flapping, indicating that adjustments in the flow pattern occur during dynamic behaviors. It is unclear whether this modulation in ventilation pattern is passive or active. This technique for studying ventilation patterns during dynamic behaviors proves useful for establishing detailed timing of airflow and modulation of ventilation in the avian respiratory system. PMID:23788706

  3. Searching for Roots of Entrainment and Joint Action in Early Musical Interactions

    PubMed Central

    Phillips-Silver, Jessica; Keller, Peter E.

    2012-01-01

    When people play music and dance together, they engage in forms of musical joint action that are often characterized by a shared sense of rhythmic timing and affective state (i.e., temporal and affective entrainment). In order to understand the origins of musical joint action, we propose a model in which entrainment is linked to dual mechanisms (motor resonance and action simulation), which in turn support musical behavior (imitation and complementary joint action). To illustrate this model, we consider two generic forms of joint musical behavior: chorusing and turn-taking. We explore how these common behaviors can be founded on entrainment capacities established early in human development, specifically during musical interactions between infants and their caregivers. If the roots of entrainment are found in early musical interactions which are practiced from childhood into adulthood, then we propose that the rehearsal of advanced musical ensemble skills can be considered to be a refined, mimetic form of temporal and affective entrainment whose evolution begins in infancy. PMID:22375113

  4. Entrainment, Drizzle, and Cloud Albedo

    NASA Technical Reports Server (NTRS)

    Ackerman, A. S.; Kirkpatrick, J. P.; Stevens, D. E.; Toon, O. B.

    2004-01-01

    Increased aerosol and hence droplet concentrations in polluted clouds are expected to inhibit precipitation and thereby increase cloud water, leading to more reflective clouds that partially offset global warming. Yet polluted clouds are not generally observed to hold more water. Much of the uncertainty regarding the indirect aerosol effect stems from inadequate understanding of such changes in cloud water. Detailed simulations show that the relative humidity of air overlying stratocumulus is a leading factor determining whether cloud water increases or decreases when precipitation is suppressed. When the overlying air is dry, cloud water can decrease as droplet concentrations increase.

  5. Attraction and social coordination: mutual entrainment of vocal activity rhythms.

    PubMed

    McGarva, Andrew R; Warner, Rebecca M

    2003-05-01

    To investigate factors that affect the mutual entrainment of vocal activity rhythms, female general psychology students paired according to attitude similarity questionnaires engaged in 40-minute introductory conversations. Fourier analyses performed on speakers' on-off vocal activity demonstrated periodic oscillations in talkativeness. Although some dyads coordinated their vocal activity rhythms, speech accommodation was not predicted by attitude similarity or attraction and did not affect ratings of conversation quality. These rhythms of dialogue appear resistant to change, their behavioral momentum rooted perhaps in an underlying chronobiology. PMID:12845943

  6. Flow Transformation in Pyroclastic Density Currents: Entrainment and Granular Dynamics during the 2006 eruption of Tungurahua

    NASA Astrophysics Data System (ADS)

    Dufek, J.; Benage, M. C.; Geist, D.; Harpp, K. S.

    2013-12-01

    have conducted high resolution simulations in concert with detailed measurements of these flows from both up flow and down flow from the transformation to document the process of dense to dilute flow transition. The field characterization includes mapping of the flows, grain size analysis, documenting flow direction indicators, comminution rounding, thermal proxies for air entrainment, and bed form documentation. We used a three-dimensional, multiphase (Eulerian-Eulerian-Lagrangian, EEL) modeling approach to describe size sorting, concentration gradients, and stresses in these evolving flows using the topography of the near Chambo River crossing (Dufek and Bergantz, 2007a; Dufek and Bertgantz, 2007b). The numerical models reveal extensive entrainment in the surge-generating phase of the flow, and secondary plume generation as fine ash in transported by hot gases higher into the atmosphere. Granular waves develop in the confined channels of the dense flow resulting bed shear stress perturbations. These granular instabilities and entrainment result in pulsing conditions in the surge, accounting for much of the unsteady behavior that results in fluctuations in grain size and bed form in the surge deposits.

  7. Observational estimates of detrainment and entrainment in non-precipitating shallow cumulus

    NASA Astrophysics Data System (ADS)

    Norgren, M. S.; Small, J. D.; Jonsson, H. H.; Chuang, P. Y.

    2014-08-01

    Vertical transport associated with cumulus clouds is important to the redistribution of gases, particles and energy, with subsequent consequences for many aspects of the climate system. Previous studies have suggested that detrainment from clouds can be comparable to the updraft mass flux, and thus represents an important contribution to vertical transport. In this study, we describe a new method to deduce the amounts of gross detrainment and entrainment experienced by non-precipitating cumulus clouds using aircraft observations. The method utilizes equations for three conserved variables: cloud mass, total water and moist static energy. Optimizing these three equations leads to estimates of the mass fractions of adiabatic mixed-layer air, entrained air and detrained air that the sampled cloud has experienced. The method is applied to six flights of the CIRPAS Twin Otter during the Gulf of Mexico Atmospheric Composition and Climate Study (GoMACCS) which took place in the Houston, Texas region during the summer of 2006 during which 176 small, non-precipitating cumulus were sampled. Our analysis suggests that, on average, these clouds were comprised of 30 to 70% mixed-layer air, with entrained air comprising most of the remainder. The mass fraction of detrained air was less than 2% for a majority of the clouds, although 15% of them did exhibit detrained air fractions larger than 10%. Entrained and detrained air mass fractions both increased with altitude, and the largest detrainment events were almost all associated with air that was at their level of neutral buoyancy, findings that are consistent with previous studies.

  8. Nonphotic entrainment of the human circadian pacemaker

    NASA Technical Reports Server (NTRS)

    Klerman, E. B.; Rimmer, D. W.; Dijk, D. J.; Kronauer, R. E.; Rizzo, J. F. 3rd; Czeisler, C. A.

    1998-01-01

    In organisms as diverse as single-celled algae and humans, light is the primary stimulus mediating entrainment of the circadian biological clock. Reports that some totally blind individuals appear entrained to the 24-h day have suggested that nonphotic stimuli may also be effective circadian synchronizers in humans, although the nonphotic stimuli are probably comparatively weak synchronizers, because the circadian rhythms of many totally blind individuals "free run" even when they maintain a 24-h activity-rest schedule. To investigate entrainment by nonphotic synchronizers, we studied the endogenous circadian melatonin and core body temperature rhythms of 15 totally blind subjects who lacked conscious light perception and exhibited no suppression of plasma melatonin in response to ocular bright-light exposure. Nine of these fifteen blind individuals were able to maintain synchronization to the 24-h day, albeit often at an atypical phase angle of entrainment. Nonphotic stimuli also synchronized the endogenous circadian rhythms of a totally blind individual to a non-24-h schedule while living in constant near darkness. We conclude that nonphotic stimuli can entrain the human circadian pacemaker in some individuals lacking ocular circadian photoreception.

  9. On dust entrainment in photoevaporative winds

    NASA Astrophysics Data System (ADS)

    Hutchison, Mark A.; Price, Daniel J.; Laibe, Guillaume; Maddison, Sarah T.

    2016-09-01

    We investigate dust entrainment by photoevaporative winds in protoplanetary discs using dusty smoothed particle hydrodynamics. We use unequal-mass particles to resolve more than five orders of magnitude in disc/outflow density and a one-fluid formulation to efficiently simulate an equivalent magnitude range in drag stopping time. We find that only micron-sized dust grains and smaller can be entrained in extreme-UV radiation-driven winds. The maximum grain size is set by dust settling in the disc rather than aerodynamic drag in the wind. More generally, there is a linear relationship between the base flow density and the maximum entrainable grain size in the wind. A pileup of micron-sized dust grains can occur in the upper atmosphere at critical radii in the disc as grains decouple from the low-density wind. Entrainment is a strong function of location in the disc, resulting in a size sorting of grains in the outflow - the largest grain being carried out between 10 and 20 au. The peak dust density for each grain size occurs at the inner edge of its own entrainment region.

  10. Entrainment and the cranial rhythmic impulse.

    PubMed

    McPartland, J M; Mein, E A

    1997-01-01

    Entrainment is the integration or harmonization of oscillators. All organisms pulsate with myriad electrical and mechanical rhythms. Many of these rhythms emanate from synchronized pulsating cells (eg, pacemaker cells, cortical neurons). The cranial rhythmic impulse is an oscillation recognized by many bodywork practitioners, but the functional origin of this impulse remains uncertain. We propose that the cranial rhythmic impulse is the palpable perception of entrainment, a harmonic frequency that incorporates the rhythms of multiple biological oscillators. It is derived primarily from signals between the sympathetic and parasympathetic nervous systems. Entrainment also arises between organisms. The harmonizing of coupled oscillators into a single, dominant frequency is called frequency-selective entrainment. We propose that this phenomenon is the modus operandi of practitioners who use the cranial rhythmic impulse in craniosacral treatment. Dominant entrainment is enhanced by "centering," a technique practiced by many healers, for example, practitioners of Chinese, Tibetan, and Ayurvedic medicine. We explore the connections between centering, the cranial rhythmic impulse, and craniosacral treatment. PMID:8997803

  11. [Temporal behavior of light emission of dielectric barrier discharges in air at atmospheric pressure].

    PubMed

    Yin, Zeng-qian; Dong, Li-fang; Han, Li; Li, Xue-chen; Chai, Zhi-fang

    2002-12-01

    The experimental setup of dielectric barrier discharge was designed which is propitious to optical measurement. Temporal behavior of light emission of dielectric barrier discharges (filamentary model) in air at atmospheric pressure was measured by using optical method. Temporal behavior of dielectric barrier discharges was obtained. The experimental results show that the discharge burst in each half cycle of applied voltage consists of a series of discharge pulses, the duration of each discharge pulse is about 30-50 ns, and the interval of the neighboring discharge pulses is about a few hundred ns. The result is of great importance to the application of dielectric barrier discharges. PMID:12914154

  12. Air oxidation behavior of fuel for the High Temperature Engineering Test Reactor (HTTR)

    NASA Astrophysics Data System (ADS)

    Kikuchi, Hironobu; Hayashi, Kimio; Fukuda, Kousaku

    1992-08-01

    The oxidation behavior of the HTTR fuel was studied with respect to the scenario of an air ingress accident which had been assessed in the HTTR safety analysis. The coated fuel particles were heated under a sufficient air flow in the temperature range of 900-1400 C for maximum duration of 600 h (at 1300 C). Failure fractions of the SiC coating layer after the heat treatments remained within the fraction at the fuel production. And the failure behavior of the SiC layer did not depend on such heating conditions as the temperature and the duration in the present experiment. It was confirmed by scanning electron microscopy (SEM), X-ray diffraction, and laser Raman spectroscopy that a thin oxide film was formed on the SiC layer by the heat treatments.

  13. An Integrated Framework for Modeling Air Carrier Behavior, Policy, and Impacts in the U.S. Air Transportation System

    NASA Technical Reports Server (NTRS)

    Horio, Brant M.; Kumar, Vivek; DeCicco, Anthony H.; Hasan, Shahab; Stouffer, Virginia L.; Smith, Jeremy C.; Guerreiro, Nelson M.

    2015-01-01

    The implementation of the Next Generation Air Transportation System (NextGen) in the United States is an ongoing challenge for policymakers due to the complexity of the air transportation system (ATS) with its broad array of stakeholders and dynamic interdependencies between them. The successful implementation of NextGen has a hard dependency on the active participation of U.S. commercial airlines. To assist policymakers in identifying potential policy designs that facilitate the implementation of NextGen, the National Aeronautics and Space Administration (NASA) and LMI developed a research framework called the Air Transportation System Evolutionary Simulation (ATS-EVOS). This framework integrates large empirical data sets with multiple specialized models to simulate the evolution of the airline response to potential future policies and explore consequential impacts on ATS performance and market dynamics. In the ATS-EVOS configuration presented here, we leverage the Transportation Systems Analysis Model (TSAM), the Airline Evolutionary Simulation (AIRLINE-EVOS), the Airspace Concept Evaluation System (ACES), and the Aviation Environmental Design Tool (AEDT), all of which enable this research to comprehensively represent the complex facets of the ATS and its participants. We validated this baseline configuration of ATS-EVOS against Airline Origin and Destination Survey (DB1B) data and subject matter expert opinion, and we verified the ATS-EVOS framework and agent behavior logic through scenario-based experiments that explored potential implementations of a carbon tax, congestion pricing policy, and the dynamics for equipage of new technology by airlines. These experiments demonstrated ATS-EVOS's capabilities in responding to a wide range of potential NextGen-related policies and utility for decision makers to gain insights for effective policy design.

  14. Flowmeter for gas-entrained solids flow

    DOEpatents

    Porges, Karl G.

    1990-01-01

    An apparatus and method for the measurement of solids feedrate in a gas-entrained solids flow conveyance system. The apparatus and method of the present invention include a vertical duct connecting a source of solids to the gas-entrained flow conveyance system, a control valve positioned in the vertical duct, and a capacitive densitometer positioned along the duct at a location a known distance below the control valved so that the solid feedrate, Q, of the gas entrained flow can be determined by Q=S.rho..phi.V.sub.S where S is the cross sectional area of the duct, .rho. is the density of the solid, .phi. is the solid volume fraction determined by the capacitive densitometer, and v.sub.S is the local solid velocity which can be inferred from the konown distance of the capacitive densitometer below the control valve.

  15. Resonant entrainment of a confined pulsed jet

    NASA Technical Reports Server (NTRS)

    Parikh, P. G.; Moffat, R. J.

    1982-01-01

    This paper reports the discovery of a new resonant entrainment phenomenon associated with a confined, pulsed jet flow. It was found that a confined jet, when pulsed at an organ-pipe resonant frequency of the confinement tube, experiences greatly enhanced entrainment and mixing near the exit end of the confinement tube compared to a steady confined jet. The mixing and entrainment rates for the resonantly pulsed confined jet approach, and in some cases slightly exceed, those for an unconfined pulsed jet. Both visual and quantitative evidence of this phenomenon is presented. The new effect should be of considerable interest in ejector and combustor design, both of which benefit from any enhancement in mixing between a primary and a secondary flow

  16. Word-by-word entrainment of speech rhythm during joint story building

    PubMed Central

    Himberg, Tommi; Hirvenkari, Lotta; Mandel, Anne; Hari, Riitta

    2015-01-01

    Movements and behavior synchronize during social interaction at many levels, often unintentionally. During smooth conversation, for example, participants adapt to each others' speech rates. Here we aimed to find out to which extent speakers adapt their turn-taking rhythms during a story-building game. Nine sex-matched dyads of adults (12 males, 6 females) created two 5-min stories by contributing to them alternatingly one word at a time. The participants were located in different rooms, with audio connection during one story and audiovisual during the other. They were free to select the topic of the story. Although the participants received no instructions regarding the timing of the story building, their word rhythms were highly entrained (øverlineR = 0.70, p < 0.001) even though the rhythms as such were unstable (øverlineR = 0.14 for pooled data). Such high entrainment in the absence of steady word rhythm occurred in every individual story, independently of whether the subjects were connected via audio-only or audiovisual link. The observed entrainment was of similar strength as typical entrainment in finger-tapping tasks where participants are specifically instructed to synchronize their behavior. Thus, speech seems to spontaneously induce strong entrainment between the conversation partners, likely reflecting automatic alignment of their semantic and syntactic processes. PMID:26124735

  17. Observational estimates of detrainment and entrainment in non-precipitating shallow cumulus

    NASA Astrophysics Data System (ADS)

    Norgren, M. S.; Small, J. D.; Jonsson, H. H.; Chuang, P. Y.

    2016-01-01

    Vertical transport associated with cumulus clouds is important to the redistribution of gases, particles, and energy, with subsequent consequences for many aspects of the climate system. Previous studies have suggested that detrainment from clouds can be comparable to the updraft mass flux, and thus represents an important contribution to vertical transport. In this study, we describe a new method to deduce the amounts of gross detrainment and entrainment experienced by non-precipitating cumulus clouds using aircraft observations. The method utilizes equations for three conserved variables: cloud mass, total water, and moist static energy. Optimizing these three equations leads to estimates of the mass fractions of adiabatic mixed-layer air, entrained air and detrained air that the sampled cloud has experienced. The method is applied to six flights of the CIRPAS Twin Otter during the Gulf of Mexico Atmospheric Composition and Climate Study (GoMACCS) which took place in the Houston, Texas region during the summer of 2006 during which 176 small, non-precipitating cumuli were sampled. Using our novel method, we find that, on average, these clouds were comprised of 30 to 70 % mixed-layer air, with entrained air comprising most of the remainder. The mass fraction of detrained air was usually very small, less than 2 %, although values larger than 10 % were found in 15 % of clouds. Entrained and detrained air mass fractions both increased with altitude, consistent with some previous observational studies. The largest detrainment events were almost all associated with air that was at their level of neutral buoyancy, which has been hypothesized in previous modeling studies. This new method could be readily used with data from other previous aircraft campaigns to expand our understanding of detrainment for a variety of cloud systems.

  18. Ozone conservation and entrainment in cumulus congestus

    NASA Technical Reports Server (NTRS)

    Pearson, R., Jr.; Weaver, C. J.

    1989-01-01

    This study demonstrates that ozone mixing ratio is conserved during moist convection and can be used as a tracer for cloud entrainment studies. The approach is to apply mixing line analysis to pairs of liquid water potential temperature, total water mixing ratio, O3 and pseudo-equivalent potential temperature derived from aircraft penetrations of growing cumulus congestus. Conclusions about entrainment from the mixing diagrams employing O3 agree with those using thermodynamic quantities. Any disagreement uncovered deficiencies in the water substance measurement technique.

  19. Lidar observations of mixed layer dynamics - Tests of parameterized entrainment models of mixed layer growth rate

    NASA Technical Reports Server (NTRS)

    Boers, R.; Eloranta, E. W.; Coulter, R. L.

    1984-01-01

    Ground based lidar measurements of the atmospheric mixed layer depth, the entrainment zone depth and the wind speed and wind direction were used to test various parameterized entrainment models of mixed layer growth rate. Six case studies under clear air convective conditions over flat terrain in central Illinois are presented. It is shown that surface heating alone accounts for a major portion of the rise of the mixed layer on all days. A new set of entrainment model constants was determined which optimized height predictions for the dataset. Under convective conditions, the shape of the mixed layer height prediction curves closely resembled the observed shapes. Under conditions when significant wind shear was present, the shape of the height prediction curve departed from the data suggesting deficiencies in the parameterization of shear production. Development of small cumulus clouds on top of the layer is shown to affect mixed layer depths in the afternoon growth phase.

  20. Study on Droplet Entrainment of High-Viscosity Falling Liquid Film

    NASA Astrophysics Data System (ADS)

    Inumaru, Jun; Ohtaka, Maromu; Watanabe, Hiroaki

    An experimental study of counter-current annular two-phase flow of high-viscosity liquid and air in a large diameter pipe was carried out to investigate the inception criterion for entrainment of molten slag droplet in an entrained flow coal gasifier. Liquid film thickness was measured using a high-speed camera for 4 types of liquid with various viscosities and surface tensions. It was clearly shown that the measured average wave amplitude had a good correlation with the gas Reynolds number, and that the predicted critical gas velocity for droplet inception using new formula of wave amplitude had a good agreement with the experimental results under the condition of very low fluid Reynolds number( Ref ≤10). The critical Weber number Wec =1.73 was obtained as inception criterion of droplet entrainment.

  1. Modeling Atmospheric Entrainment and Transport of Impact Ejecta

    NASA Astrophysics Data System (ADS)

    Barnouin-Jha, Olivier Serge

    1998-10-01

    Many mechanisms have been proposed to explain the origin of fluidized ejecta morphologies observed at craters formed by an asteroid or comet colliding with a planetary surface. The predominant mechanisms include: the incorporation of water or volatiles into a subsequently fluidized ejecta flow resembling a mudslide; the incorporation of air and volatiles into a debris cloud of primary and secondary ejecta that slides along the target surface; the formation of an ejecta ''sturzstrom' following the gravitational collapse of an ejecta curtain that has been decelerated and steepened by impinging atmosphere; and, the formation of strong atmospheric winds generated by an advancing ejecta curtain that entrain and deposit ejecta. Laboratory experiments show that this last mechanism produces fluidized ejecta facies with contiguous ramparts and lobate flows that are remarkably similar to features seen on Mars, Venus and the Earth. In order to quantitatively assess the importance of such winds at planetary scales, this thesis combines a variety of analytical, numerical and empirical techniques to investigate the interactions between an advancing ejecta curtain and an atmosphere. The physical models developed describe the entrainment capacity and initial transport of ejecta by these winds, as well as some of the factors controlling ejecta deposition. The ultimate objective of this study is to model most aspects of ejecta entrainment, transport and deposition. In combination with observations of fluidized ejecta facies, such models should provide new insight into the target and atmospheric conditions present during crater formation. Such information may improve our understanding of past climatic and surface conditions on planets such as Mars.

  2. Relationships of Entrainment Rate with Dynamical and Thermodynamic Properties in Shallow Convection

    NASA Astrophysics Data System (ADS)

    Lu, C.; Liu, Y.; Zhang, G. J.; Wu, X.; Endo, S.; Cao, L.; Li, Y.; Guo, X.

    2015-12-01

    This work examines the relationships of entrainment rate to vertical velocity, buoyancy, turbulent dissipation rate by applying stepwise principal component regression to observational data from shallow cumulus clouds collected during the Routine AAF [Atmospheric Radiation Measurement (ARM) Aerial Facility] Clouds with Low Optical Water Depths (CLOWD) Optical Radiative Observations (RACORO) field campaign over the ARM Southern Great Plains (SGP) site near Lamont, Oklahoma. The cumulus clouds during the RACORO campaign simulated using a large eddy simulation (LES) model are also examined with the same approach. The analysis shows that combination of multiple variables can better represent entrainment rate in both the observations and LES than the single-variable fitting equations and the three commonly used parameterizations. A new parameterization is thus presented that relates entrainment rate to vertical velocity, buoyancy and dissipation rate; the effects of treating clouds as ensembles and humid shells surrounding cumulus clouds on the new parameterization are discussed. Physical mechanisms underlying the relationships of entrainment rate to vertical velocity, buoyancy and dissipation rate are also explored. Furthermore, the effects of relative humidity in the entrained dry air on the above relationships are discussed; a possible physical mechanism for the effects is explored.

  3. Inclined gravity currents filling basins: The influence of Reynolds number on entrainment into gravity currents

    NASA Astrophysics Data System (ADS)

    Hogg, Charlie A. R.; Dalziel, Stuart B.; Huppert, Herbert E.; Imberger, Jörg

    2015-09-01

    In many important natural and industrial systems, gravity currents of dense fluid feed basins. Examples include lakes fed by dense rivers and auditoria supplied with cooled air by ventilation systems. As we will show, the entrainment into such buoyancy driven currents can be influenced by viscous forces. Little work, however, has examined this viscous influence and how entrainment varies with the Reynolds number, Re. Using the idea of an entrainment coefficient, E, we derive a mathematical expression for the rise of the front at the top of the dense fluid ponding in a basin, where the horizontal cross-sectional area of the basin varies linearly with depth. We compare this expression to experiments on gravity currents with source Reynolds numbers, Res, covering the broad range 100 < Res < 1500. The form of the observed frontal rises was well approximated by our theory. By fitting the observed frontal rises to the theoretical form with E as the free parameter, we find a linear trend for E(Res) over the range 350 < Res < 1100, which is in the transition to turbulent flow. In the experiments, the entrainment coefficient, E, varied from 4 × 10-5 to 7 × 10-2. These observations show that viscous damping can be a dominant influence on gravity current entrainment in the laboratory and in geophysical flows in this transitional regime.

  4. Impact of reduced near-field entrainment of overpressured volcanic jets on plume development

    NASA Astrophysics Data System (ADS)

    Saffaraval, Farhad; Solovitz, Stephen A.; Ogden, Darcy E.; Mastin, Larry G.

    2012-05-01

    Volcanic plumes are often studied using one-dimensional analytical models, which use an empirical entrainment ratio to close the equations. Although this ratio is typically treated as constant, its value near the vent is significantly reduced due to flow development and overpressured conditions. To improve the accuracy of these models, a series of experiments was performed using particle image velocimetry, a high-accuracy, full-field velocity measurement technique. Experiments considered a high-speed jet with Reynolds numbers up to 467,000 and exit pressures up to 2.93 times atmospheric. Exit gas densities were also varied from 0.18 to 1.4 times that of air. The measured velocity was integrated to determine entrainment directly. For jets with exit pressures near atmospheric, entrainment was approximately 30% less than the fully developed level at 20 diameters from the exit. At pressures nearly three times that of the atmosphere, entrainment was 60% less. These results were introduced into Plumeria, a one-dimensional plume model, to examine the impact of reduced entrainment. The maximum column height was only slightly modified, but the critical radius for collapse was significantly reduced, decreasing by nearly a factor of two at moderate eruptive pressures.

  5. A numerical study of jet entrainment effects on the subsonic flow over nozzle afterbodies

    NASA Technical Reports Server (NTRS)

    Wilmoth, R. G.; Dash, S. M.; Pergament, H. S.

    1979-01-01

    A viscous-inviscid interaction model has been developed which accounts for jet entrainment effects in the prediction of the subsonic flow over nozzle afterbodies. The jet entrainment model is based on the concept of a weakly interacting shear layer in which the local streamline deflections due to entrainment are accounted for by a displacement-thickness type correction to the inviscid plume boundary. The entire flowfield is solved in an iterative manner to account for the effects on the inviscid external flow of the turbulent boundary layer, turbulent mixing and chemical reactions in the shear layer, and the inviscid jet exhaust flow. The individual components of the computational model are described and numerical results are presented which illustrate the interactive effects of entrainment on the overall flow structure. The validity of the interactive model is assessed by comparisons with data obtained from flowfield measurements on cold-air jet exhausts. Numerical results and experimental data are also given which show the entrainment effects on nozzle boattail drag under various jet exhaust and freestream flow conditions.

  6. Impact of reduced near-field entrainment of overpressured volcanic jets on plume development

    USGS Publications Warehouse

    Saffaraval, Farhad; Solovitz, Stephen A.; Ogden, Darcy E.; Mastin, Larry G.

    2012-01-01

    Volcanic plumes are often studied using one-dimensional analytical models, which use an empirical entrainment ratio to close the equations. Although this ratio is typically treated as constant, its value near the vent is significantly reduced due to flow development and overpressured conditions. To improve the accuracy of these models, a series of experiments was performed using particle image velocimetry, a high-accuracy, full-field velocity measurement technique. Experiments considered a high-speed jet with Reynolds numbers up to 467,000 and exit pressures up to 2.93 times atmospheric. Exit gas densities were also varied from 0.18 to 1.4 times that of air. The measured velocity was integrated to determine entrainment directly. For jets with exit pressures near atmospheric, entrainment was approximately 30% less than the fully developed level at 20 diameters from the exit. At pressures nearly three times that of the atmosphere, entrainment was 60% less. These results were introduced into Plumeria, a one-dimensional plume model, to examine the impact of reduced entrainment. The maximum column height was only slightly modified, but the critical radius for collapse was significantly reduced, decreasing by nearly a factor of two at moderate eruptive pressures.

  7. Thermodynamic model of a thermal storage air conditioning system with dynamic behavior

    SciTech Connect

    Fleming, E; Wen, SY; Shi, L; da Silva, AK

    2013-12-01

    A thermodynamic model was developed to predict transient behavior of a thermal storage system, using phase change materials (PCMs), for a novel electric vehicle climate conditioning application. The main objectives of the paper are to consider the system's dynamic behavior, such as a dynamic air flow rate into the vehicle's cabin, and to characterize the transient heat transfer process between the thermal storage unit and the vehicle's cabin, while still maintaining accurate solution to the complex phase change heat transfer. The system studied consists of a heat transfer fluid circulating between either of the on-board hot and cold thermal storage units, which we refer to as thermal batteries, and a liquid-air heat exchanger that provides heat exchange with the incoming air to the vehicle cabin. Each thermal battery is a shell-and-tube configuration where a heat transfer fluid flows through parallel tubes, which are surrounded by PCM within a larger shell. The system model incorporates computationally inexpensive semianalytic solution to the conjugated laminar forced convection and phase change problem within the battery and accounts for airside heat exchange using the Number of Transfer Units (NTUs) method for the liquid-air heat exchanger. Using this approach, we are able to obtain an accurate solution to the complex heat transfer problem within the battery while also incorporating the impact of the airside heat transfer on the overall system performance. The implemented model was benchmarked against a numerical study for a melting process and against full system experimental data for solidification using paraffin wax as the PCM. Through modeling, we demonstrate the importance of capturing the airside heat exchange impact on system performance, and we investigate system response to dynamic operating conditions, e.g., air recirculation. (C) 2013 Elsevier Ltd. All rights reserved.

  8. Liquid Droplet Detachment and Entrainment in Microscale Flows

    NASA Astrophysics Data System (ADS)

    Hidrovo, Carlos

    2005-11-01

    In this talk we will present a first order study of liquid water detachment and entrainment into air flows in hydrophobic microchannels. Silicon based microstructures consisting of 23 mm long U-shaped channels of different geometry were used for this purpose. The structures are treated with a Molecular Vapor Deposition (MVD) process that renders them hydrophobic. Liquid water is injected through a side slot located 2/3 of the way downstream from the air channel inlet. The water entering the air channel beads up into slugs or droplets that grow in size at this injection location until they fill and flood the channel or are carried away by the air flow. The slugs/droplets dimensions at detachment are correlated against superficial gas velocity and proper dimensionless parameters are postulated and examined to compare hydrodynamic forces against surface tension. It is found that slug/droplet detachment is dominated by two main forces: pressure gradient drag, arising from confinement of a viscous flow in the channel, and inertial drag, arising from the stagnation of the air due to obstruction by the slugs/droplets. A detachment regime map is postulated based on the relative importance of these forces under different flow conditions.

  9. Laminar Entrained Flow Reactor (Fact Sheet)

    SciTech Connect

    Not Available

    2014-02-01

    The Laminar Entrained Flow Reactor (LEFR) is a modular, lab scale, single-user reactor for the study of catalytic fast pyrolysis (CFP). This system can be employed to study a variety of reactor conditions for both in situ and ex situ CFP.

  10. LIQUID ENTRAINMENT FROM A MOBILE BED SCRUBBER

    EPA Science Inventory

    The paper gives results of the measurement of liquid entrainment rate and drop size distribution in the exhaust gas stream from a mobile bed scrubber. The pilot plant scrubber was 46 cm square and was packed with 3.8 cm diameter hollow polyethylene spheres to a static depth of 25...

  11. Washing of the AW-101 entrained solids

    SciTech Connect

    GJ Lumetta

    2000-03-31

    BNFL Inc. (BNFL) is under contract with the US Department of Energy, River Protection Project (DOE-RPP) to design, construct, and operate facilities for treating wastes stored in the single-shell and double-shell tanks at the Hanford Site, Richland, Washington. The DOE-BNFL RPP contract identifies two feeds to the waste treatment plant: (1) primarily liquid low-activity waste (LAW) consisting of less than 2 wt% entrained solids and (2) high-level waste (HLW) consisting of 10 to 200 g/L solids slurry. This report describes the results of a test conducted by Battelle to assess the effects of inhibited water washing on the composition of the entrained solids in the diluted AW-101 low-activity waste (LAW) sample. The objective of this work was to gather data on the solubility of the AW-101 entrained solids in 0.01 M NaOH, so that BNFL can evaluate whether these solids require caustic leaching. The work was conducted according to test plan BNFL-TP-29953-9, Rev. 0, LAW Entrained Solids Water Wash and Caustic Leach Testing. The test went according to plan, with no deviations from the test plan. Based on the results of the 0.01 M NaOH washing, a decision was made by BNFL to not proceed with the caustic leaching test. The composition of the washed solids was such that caustic leaching would not result in significant reduction in the immobilized HLW volume.

  12. Attentional entrainment and perceived event duration

    PubMed Central

    McAuley, J. Devin; Fromboluti, Elisa Kim

    2014-01-01

    This study considered the contribution of dynamic attending theory (DAT) and attentional entrainment to systematic distortions in perceived event duration. Three experiments were conducted using an auditory oddball paradigm, in which listeners judged the duration of a deviant (oddball) stimulus embedded within a series of identical (standard) stimuli. To test for a role of attentional entrainment in perceived oddball duration, oddballs were presented at either temporally expected (on time) or unexpectedly early or late time points relative to extrapolation of the context rhythm. Consistent with involvement of attentional entrainment in perceived duration, duration judgements about the oddball were least distorted when the oddball occurred on time with respect to the entrained rhythm, whereas durations of early and late oddballs were perceived to be shorter and longer, respectively. This pattern of results was independent of the absolute time interval preceding the oddball. Moreover, as expected, an irregularly timed sequence context weakened observed differences between oddballs with on-time and late onsets. Combined with other recent work on the role of temporal preparation in duration distortions, the present findings allot at least a portion of the oddball effect to increased attention to events that are more expected, rather than on their unexpected nature per se. PMID:25385779

  13. Cloud top entrainment instability and cloud top distributions

    NASA Technical Reports Server (NTRS)

    Boers, Reinout; Spinhirne, James D.

    1990-01-01

    Classical cloud-top entrainment instability condition formulation is discussed. A saturation point diagram is used to investigate the details of mixing in cases where the cloud-top entrainment instability criterion is satisfied.

  14. Problems with the process partitioning theory of stratocumulus entrainment

    NASA Technical Reports Server (NTRS)

    Randall, D. A.

    1984-01-01

    Three different approaches to partitioning were proposed. Ball (1960), Lilly (1968), and Deardorff et al. (1969, 1974) considered the sign of the net buoyancy flux at each level. If the net flux is positive, it is counted as TKE producing; otherwise, it is counted as TKE consuming. This approach can be called Eulerian partitioning. The second approach can be called process partitioning. It is assumed that the various processes acting in concert each produce and consume the same energy as if they acted independently (Manins and Turner, 1978). The total rates of TKE production and consumption are obtained by summing the effects of all the forcing processes. The third approach is Lagrangian partitioning. Each air parcel is considered as either producing or consuming TKE, according to the sign of the product of its density and vertical velocity anomalies. Stage and Businger (1981a,b) have applied process partitioning to the cloud topped mixed layer. One of the most important processes influencing entrainment into such a layer is cloud top radiative cooling. The production and consumption due to entrainment and radiative cooling are thus closely related. Model results are sensitive to the choice of formulation.

  15. Speech Entrainment Compensates for Broca's Area Damage

    PubMed Central

    Fridriksson, Julius; Basilakos, Alexandra; Hickok, Gregory; Bonilha, Leonardo; Rorden, Chris

    2015-01-01

    Speech entrainment (SE), the online mimicking of an audiovisual speech model, has been shown to increase speech fluency in patients with Broca's aphasia. However, not all individuals with aphasia benefit from SE. The purpose of this study was to identify patterns of cortical damage that predict a positive response SE's fluency-inducing effects. Forty-four chronic patients with left hemisphere stroke (15 female) were included in this study. Participants completed two tasks: 1) spontaneous speech production, and 2) audiovisual SE. Number of different words per minute was calculated as a speech output measure for each task, with the difference between SE and spontaneous speech conditions yielding a measure of fluency improvement. Voxel-wise lesion-symptom mapping (VLSM) was used to relate the number of different words per minute for spontaneous speech, SE, and SE-related improvement to patterns of brain damage in order to predict lesion locations associated with the fluency-inducing response to speech entrainment. Individuals with Broca's aphasia demonstrated a significant increase in different words per minute during speech entrainment versus spontaneous speech. A similar pattern of improvement was not seen in patients with other types of aphasia. VLSM analysis revealed damage to the inferior frontal gyrus predicted this response. Results suggest that SE exerts its fluency-inducing effects by providing a surrogate target for speech production via internal monitoring processes. Clinically, these results add further support for the use of speech entrainment to improve speech production and may help select patients for speech entrainment treatment. PMID:25989443

  16. Prenatal Exposure to Air Pollution, Maternal Psychological Distress, and Child Behavior

    PubMed Central

    Wang, Shuang; Rauh, Virginia; Zhou, Hui; Stigter, Laura; Camann, David; Jedrychowski, Wieslaw; Mroz, Elzbieta; Majewska, Renata

    2013-01-01

    BACKGROUND: Airborne polycyclic aromatic hydrocarbons (PAHs) are pollutants generated by combustion of fossil fuel and other organic material. Both prenatal PAH exposure and maternal psychological distress during pregnancy have each been associated with neurodevelopmental problems in children. The goal was to evaluate potential interactions between prenatal exposure to airborne PAHs and maternal psychological distress during pregnancy on subsequent behavioral problems in children. METHODS: In a longitudinal birth cohort study, 248 children of nonsmoking white women in the coal-burning region of Krakow, Poland, were followed from in utero until age 9. Prenatal PAH exposure was measured by personal air monitoring during pregnancy, maternal demoralization during pregnancy by the Psychiatric Epidemiology Research Instrument–Demoralization, and child behavior by the Child Behavior Checklist. RESULTS: Significant interactions between maternal demoralization and PAH exposure (high versus low) were identified for symptoms of anxious/depressed, withdrawn/depressed, social problems, aggressive behavior, internalizing problems, and externalizing problems. The effects of demoralization on syndromes of anxious/depressed, withdrawn/depressed, rule-breaking, aggressive behavior, and the composite internalizing and externalizing scores were seen only in conjunction with high PAH exposure. Fewer significant effects with weaker effect sizes were observed in the low-PAH-exposure group. CONCLUSIONS: Maternal demoralization during pregnancy appears to have a greater effect on child neurobehavioral development among children who experienced high prenatal PAH exposure. The results provide the first evidence of an interaction between prenatal exposure to maternal demoralization and air pollution on child neurobehavioral development, indicating the need for a multifaceted approach to the prevention of developmental problems in children. PMID:24101766

  17. Entrainment and motor emulation approaches to joint action: Alternatives or complementary approaches?

    PubMed Central

    Colling, Lincoln J.; Williamson, Kellie

    2014-01-01

    Joint actions, such as music and dance, rely crucially on the ability of two, or more, agents to align their actions with great temporal precision. Within the literature that seeks to explain how this action alignment is possible, two broad approaches have appeared. The first, what we term the entrainment approach, has sought to explain these alignment phenomena in terms of the behavioral dynamics of the system of two agents. The second, what we term the emulator approach, has sought to explain these alignment phenomena in terms of mechanisms, such as forward and inverse models, that are implemented in the brain. They have often been pitched as alternative explanations of the same phenomena; however, we argue that this view is mistaken, because, as we show, these two approaches are engaged in distinct, and not mutually exclusive, explanatory tasks. While the entrainment approach seeks to uncover the general laws that govern behavior the emulator approach seeks to uncover mechanisms. We argue that is possible to do both and that the entrainment approach must pay greater attention to the mechanisms that support the behavioral dynamics of interest. In short, the entrainment approach must be transformed into a neuroentrainment approach by adopting a mechanistic view of explanation and by seeking mechanisms that are implemented in the brain. PMID:25309403

  18. Air Oxidation Behavior of Two Ti-Base Alloys Synthesized by HIP

    NASA Astrophysics Data System (ADS)

    Liu, S.; Guo, Q. Q.; Liu, L. L.; Xu, L.; Liu, Y. Y.

    2016-04-01

    The oxidation behavior of Ti-5Al-2.5Sn and Ti-6Al-4V produced by hot isostatic pressing (HIP) has been studied at 650-850°C in air for 24 h. The oxidation kinetics of both alloys followed the parabolic law with good approximation, except for Ti-5Al-2.5Sn oxidized at 850°C. Multi-layered scales formed on both alloys at 750°C and 850°C. Ternary additions of Sn and V accounted for the different morphology of the scales formed on these two alloys. In addition, the oxidation behavior of HIP alloys is compared with that of the corresponding cast alloys and the scaling mechanism is discussed.

  19. Impacts of winds on volcanic plumes - Do crossflows challenge the Morton, Turner and Taylor entrainment assumptions?

    NASA Astrophysics Data System (ADS)

    Aubry, T. J.; Jellinek, M.; Carazzo, G.

    2014-12-01

    Volcanic plumes rising into Earth's atmosphere are influenced strongly by tropospheric and stratospheric winds. In the absence of wind effects, Morton, Taylor and Turner (MTT, 1956) used a similarity theory to show that the maximum height for these flows is governed mostly by the atmospheric stratification and the buoyancy flux at the vent. Crucially, in developing this theory MTT introduced the "entrainment hypothesis" in which the rate of entrainment of atmospheric air by the large eddies forming at the edge of the plume is proportional to some bulk velocity. In the presence of wind a key question is whether the additional stirring deforms eddies sufficiently to alter their mixing properties. In particular, under what conditions will wind effects enhance or reduce entrainment? Can these effects be captured in a modified form of the MTT similarity theory or is a new theory required? We use an extensive set of experiments on wind-forced turbulent plumes in order to overcome the restricted dynamical conditions explored in previous experimental studies. We introduce a new regime parameter allowing to quantitatively separate three distinct plume regimes. Remarkably, we show that for reasonable conditions on Earth, the major effects of wind can still be captured by a modified scaling law derived from the self-similar theory of MTT, with an entrainment rate including the contributions of wind. However, analysis of the turbulence motions in our experiments shows that even weak winds introduce large asymmetries in the structure of entraining eddies. Our successful application of a mean entrainment rate at the plume edge and a modified MTT similarity theory is, thus, surprising. Does this apparent contradiction simply reveal the way turbulent instabilities driven by wind manifest themselves?

  20. Applying the theory of planned behavior to explore the relation between smoke-free air laws and quitting intentions.

    PubMed

    Macy, Jonathan T; Middlestadt, Susan E; Seo, Dong-Chul; Kolbe, Lloyd J; Jay, Stephen J

    2012-02-01

    Smoke-free air policies have been shown to reduce smoking, but the mechanism of behavior change is not well understood. The authors used structural equation modeling to conduct a theory of planned behavior analysis with data from 395 smokers living in seven Texas cities, three with a comprehensive smoke-free air law and four without a comprehensive law. Agreement with regulating smoking in public places was significantly associated with attitudes and perceived normative pressure about quitting. Nicotine dependence was significantly associated with attitudes and perceived behavioral control. There was also a direct effect of nicotine dependence on intention to take measures to quit smoking. Smoke-free air laws appear to influence quitting intentions through the formation of positive attitudes about regulating smoking in public places and the perception of normative pressure to take measures to quit. Implications for smoke-free air policy campaigns and challenges in evaluating their effectiveness are discussed. PMID:21518919

  1. AW-101 entrained solids - Solubility versus temperature

    SciTech Connect

    GJ Lumetta; RC Lettau; GF Piepel

    2000-03-31

    This report describes the results of a test conducted by Battelle to assess the solubility of the solids entrained in the diluted AW-101 low-activity waste (LAW) sample. BNFL requested Battelle to dilute the AW-1-1 sample using de-ionized water to mimic expected plant operating conditions. BNFL further requested Battelle to assess the solubility of the solids present in the diluted AW-101 sample versus temperature conditions of 30, 40, and 50 C. BNFL requested these tests to assess the composition of the LAW supernatant and solids versus expected plant-operating conditions. The work was conducted according to test plan BNFL-TP-29953-7, Rev. 0, Determination of the Solubility of LAW Entrained Solids. The test went according to plan, with no deviations from the test plan.

  2. Exploring Entrainment Patterns of Human Emotion in Social Media.

    PubMed

    He, Saike; Zheng, Xiaolong; Zeng, Daniel; Luo, Chuan; Zhang, Zhu

    2016-01-01

    Emotion entrainment, which is generally defined as the synchronous convergence of human emotions, performs many important social functions. However, what the specific mechanisms of emotion entrainment are beyond in-person interactions, and how human emotions evolve under different entrainment patterns in large-scale social communities, are still unknown. In this paper, we aim to examine the massive emotion entrainment patterns and understand the underlying mechanisms in the context of social media. As modeling emotion dynamics on a large scale is often challenging, we elaborate a pragmatic framework to characterize and quantify the entrainment phenomenon. By applying this framework on the datasets from two large-scale social media platforms, we find that the emotions of online users entrain through social networks. We further uncover that online users often form their relations via dual entrainment, while maintain it through single entrainment. Remarkably, the emotions of online users are more convergent in nonreciprocal entrainment. Building on these findings, we develop an entrainment augmented model for emotion prediction. Experimental results suggest that entrainment patterns inform emotion proximity in dyads, and encoding their associations promotes emotion prediction. This work can further help us to understand the underlying dynamic process of large-scale online interactions and make more reasonable decisions regarding emergency situations, epidemic diseases, and political campaigns in cyberspace. PMID:26953692

  3. Alignment strategies for the entrainment of music and movement rhythms.

    PubMed

    Moens, Bart; Leman, Marc

    2015-03-01

    Theories of entrainment assume that spontaneous entrainment emerges from dynamic laws that operate via mediators on interactions, whereby entrainment is facilitated if certain conditions are fulfilled. In this study, we show that mediators can be built that affect the entrainment of human locomotion to music. More specifically, we built D-Jogger, a music player that functions as a mediator between music and locomotion rhythms. The D-Jogger makes it possible to manipulate the timing differences between salient moments of the rhythms (beats and footfalls) through the manipulation of the musical period and phase, which affect the condition in which entrainment functions. We conducted several experiments to explore different strategies for manipulating the entrainment of locomotion and music. The results of these experiments showed that spontaneous entrainment can be manipulated, thereby suggesting different strategies on how to embark. The findings furthermore suggest a distinction among different modalities of entrainment: finding the beat (the most difficult part of entrainment), keeping the beat (easier, as a temporal scheme has been established), and being in phase (no entrainment is needed because the music is always adapted to the human rhythm). This study points to a new avenue of research on entrainment and opens new perspectives for the neuroscience of music. PMID:25773621

  4. Auditory-motor entrainment in vocal mimicking species

    PubMed Central

    2010-01-01

    We have recently found robust evidence of motor entrainment to auditory stimuli in multiple species of non-human animal, all of which were capable of vocal mimicry. In contrast, the ability remained markedly absent in many closely related species incapable of vocal mimicry. This suggests that vocal mimicry may be a necessary precondition for entrainment. However, within the vocal mimicking species, entrainment appeared non-randomly, suggesting that other components besides vocal mimicry play a role in the capacity and tendency to entrain. Here we discuss potential additional factors involved in entrainment. New survey data show that both male and female parrots are able to entrain, and that the entrainment capacity appears throughout the lifespan. We suggest routes for future study of entrainment, including both developmental studies in species known to entrain and further work to detect entrainment in species not well represented in our dataset. These studies may shed light on additional factors necessary for entrainment in addition to vocal mimicry. PMID:20714417

  5. Exploring Entrainment Patterns of Human Emotion in Social Media

    PubMed Central

    Luo, Chuan; Zhang, Zhu

    2016-01-01

    Emotion entrainment, which is generally defined as the synchronous convergence of human emotions, performs many important social functions. However, what the specific mechanisms of emotion entrainment are beyond in-person interactions, and how human emotions evolve under different entrainment patterns in large-scale social communities, are still unknown. In this paper, we aim to examine the massive emotion entrainment patterns and understand the underlying mechanisms in the context of social media. As modeling emotion dynamics on a large scale is often challenging, we elaborate a pragmatic framework to characterize and quantify the entrainment phenomenon. By applying this framework on the datasets from two large-scale social media platforms, we find that the emotions of online users entrain through social networks. We further uncover that online users often form their relations via dual entrainment, while maintain it through single entrainment. Remarkably, the emotions of online users are more convergent in nonreciprocal entrainment. Building on these findings, we develop an entrainment augmented model for emotion prediction. Experimental results suggest that entrainment patterns inform emotion proximity in dyads, and encoding their associations promotes emotion prediction. This work can further help us to understand the underlying dynamic process of large-scale online interactions and make more reasonable decisions regarding emergency situations, epidemic diseases, and political campaigns in cyberspace. PMID:26953692

  6. Novel electrochemical behavior of zinc anodes in zinc/air batteries in the presence of additives

    NASA Astrophysics Data System (ADS)

    Lee, Chang Woo; Sathiyanarayanan, K.; Eom, Seung Wook; Kim, Hyun Soo; Yun, Mun Soo

    In our continued efforts to find an electrically rechargeable zn/air secondary battery, we report the unique behavior of a zinc oxide anode in the presence of additives such as phosphoric acid, tartaric acid, succinic acid and citric acid. These additives were added to the electrolyte, which is an 8.5 M KOH solution containing 25 g of ZnO and 3000 ppm of polyethylene glycol in 1 l of water. In zn/air systems there are two main problems namely the hydrogen overpotential and dendrite formation during recharging. Investigations have studied in detail both of the problems in order to overcome them. The results obtained in presence of additives are compared with the behavior of the electrolyte 8.5 M KOH in the absence of additives. It has been concluded that the hydrogen overpotential is raised enormously while dendrite formation is reduced to some extent. Out of the four acids studied, the order of increase in hydrogen overpotential is: tartaric acid > succinic acid > phosphoric acid > citric acid. The prevention of dendrite formation follows the order: citric acid > succinic acid > tartaric acid > phosphoric acid.

  7. Rod Driven Frequency Entrainment and Resonance Phenomena.

    PubMed

    Salchow, Christina; Strohmeier, Daniel; Klee, Sascha; Jannek, Dunja; Schiecke, Karin; Witte, Herbert; Nehorai, Arye; Haueisen, Jens

    2016-01-01

    A controversy exists on photic driving in the human visual cortex evoked by intermittent photic stimulation. Frequency entrainment and resonance phenomena are reported for frequencies higher than 12 Hz in some studies while missing in others. We hypothesized that this might be due to different experimental conditions, since both high and low intensity light stimulation were used. However, most studies do not report radiometric measurements, which makes it impossible to categorize the stimulation according to photopic, mesopic, and scotopic vision. Low intensity light stimulation might lead to scotopic vision, where rod perception dominates. In this study, we investigated photic driving for rod-dominated visual input under scotopic conditions. Twelve healthy volunteers were stimulated with low intensity light flashes at 20 stimulation frequencies, leading to rod activation only. The frequencies were multiples of the individual alpha frequency (α) of each volunteer in the range from 0.40 to 2.30(∗)α. Three hundred and six-channel whole head magnetoencephalography recordings were analyzed in time, frequency, and spatiotemporal domains with the Topographic Matching Pursuit algorithm. We found resonance phenomena and frequency entrainment for stimulations at or close to the individual alpha frequency (0.90-1.10(∗)α) and half of the alpha frequency (0.40-0.55(∗)α). No signs of resonance and frequency entrainment phenomena were revealed around 2.00(∗)α. Instead, on-responses at the beginning and off-responses at the end of each stimulation train were observed for the first time in a photic driving experiment at frequencies of 1.30-2.30(∗)α, indicating that the flicker fusion threshold was reached. All results, the resonance and entrainment as well as the fusion effects, provide evidence for rod-dominated photic driving in the visual cortex. PMID:27588002

  8. Rod Driven Frequency Entrainment and Resonance Phenomena

    PubMed Central

    Salchow, Christina; Strohmeier, Daniel; Klee, Sascha; Jannek, Dunja; Schiecke, Karin; Witte, Herbert; Nehorai, Arye; Haueisen, Jens

    2016-01-01

    A controversy exists on photic driving in the human visual cortex evoked by intermittent photic stimulation. Frequency entrainment and resonance phenomena are reported for frequencies higher than 12 Hz in some studies while missing in others. We hypothesized that this might be due to different experimental conditions, since both high and low intensity light stimulation were used. However, most studies do not report radiometric measurements, which makes it impossible to categorize the stimulation according to photopic, mesopic, and scotopic vision. Low intensity light stimulation might lead to scotopic vision, where rod perception dominates. In this study, we investigated photic driving for rod-dominated visual input under scotopic conditions. Twelve healthy volunteers were stimulated with low intensity light flashes at 20 stimulation frequencies, leading to rod activation only. The frequencies were multiples of the individual alpha frequency (α) of each volunteer in the range from 0.40 to 2.30∗α. Three hundred and six-channel whole head magnetoencephalography recordings were analyzed in time, frequency, and spatiotemporal domains with the Topographic Matching Pursuit algorithm. We found resonance phenomena and frequency entrainment for stimulations at or close to the individual alpha frequency (0.90–1.10∗α) and half of the alpha frequency (0.40–0.55∗α). No signs of resonance and frequency entrainment phenomena were revealed around 2.00∗α. Instead, on-responses at the beginning and off-responses at the end of each stimulation train were observed for the first time in a photic driving experiment at frequencies of 1.30–2.30∗α, indicating that the flicker fusion threshold was reached. All results, the resonance and entrainment as well as the fusion effects, provide evidence for rod-dominated photic driving in the visual cortex. PMID:27588002

  9. Air-floating towing behaviors of multi-bucket foundation platform

    NASA Astrophysics Data System (ADS)

    Le, Cong-huan; Ding, Hong-yan; Zhang, Pu-yang

    2013-10-01

    Air-floating towing behaviors of multi-bucket foundation platform (MBFP) are investigated with the 1/20-scale model tests and hydrodynamic software MOSES. MOSES numerical model was validated by test results, and MOSES prototype model of MBFP can eliminate scale effect of model. The influences of towing factors of towing speed, water depth, freeboard, and wave direction on air-floating towing stability of MBFP were analyzed by model tests and validated MOSES prototype model. It is shown that the reduction of towing speed can effectively decrease the towing force and surge acceleration to improve towing stability. Water depth is another factor in towing stability. Obvious shallow water effect will appear in shallow water with small water depth-draft ratio and it will disappear gradually and air-floating towing becomes more stable with the increase of water depth. Accelerations of surge, sway and heave are small and they have modest changes when freeboard increases from 0.5 to 2 m. For MBFP, the freeboard is not suggested to be larger than 2 m in following wave. Wave direction has large influence on the towing stability, the surge acceleration and towing force are sensitive to the variation of wave direction, the surge acceleration and towing force in following wave (0°) and counter wave (180°) are much larger than that in transverse sea (90° and 270°).

  10. Thermal Behavior of Fe2O3/Al Thermite Mixtures in Air and Vacuum Environments

    SciTech Connect

    Duraes, L.; Santos, R.; Correia, A.; Campos, J.; Portugal, A.

    2006-07-28

    In this work, the thermal behavior of Fe2O3/Al thermite mixtures, in air and vacuum, is studied. The individual reactants and three mixtures - stoichiometric and over aluminized - are tested, by Simultaneous Thermal Analysis (STA) and heating microscopy, with a heating rate of 10 deg. C/min. The STA results show that the presence of O2 from air, or from residual air in vacuum, influenced the reaction scheme. The Al oxidation by this oxygen was extensive, making the thermite reaction with Fe2O3 unviable. There was also evidence of significant conversion of the Fe2O3 into Fe3O4, supporting the previous conclusion. So, the STA curves for the three mixtures were similar and displayed features of the individual reactants' curves. The heating microscopy images confirmed the STA conclusions, with one exception: the thermal explosion of the Al sample close to 550 deg. C. The absence of this phenomenon in STA results was explained by the limited amount of material used in each sample.

  11. Agent Based Modeling of Air Carrier Behavior for Evaluation of Technology Equipage and Adoption

    NASA Technical Reports Server (NTRS)

    Horio, Brant M.; DeCicco, Anthony H.; Stouffer, Virginia L.; Hasan, Shahab; Rosenbaum, Rebecca L.; Smith, Jeremy C.

    2014-01-01

    As part of ongoing research, the National Aeronautics and Space Administration (NASA) and LMI developed a research framework to assist policymakers in identifying impacts on the U.S. air transportation system (ATS) of potential policies and technology related to the implementation of the Next Generation Air Transportation System (NextGen). This framework, called the Air Transportation System Evolutionary Simulation (ATS-EVOS), integrates multiple models into a single process flow to best simulate responses by U.S. commercial airlines and other ATS stakeholders to NextGen-related policies, and in turn, how those responses impact the ATS. Development of this framework required NASA and LMI to create an agent-based model of airline and passenger behavior. This Airline Evolutionary Simulation (AIRLINE-EVOS) models airline decisions about tactical airfare and schedule adjustments, and strategic decisions related to fleet assignments, market prices, and equipage. AIRLINE-EVOS models its own heterogeneous population of passenger agents that interact with airlines; this interaction allows the model to simulate the cycle of action-reaction as airlines compete with each other and engage passengers. We validated a baseline configuration of AIRLINE-EVOS against Airline Origin and Destination Survey (DB1B) data and subject matter expert opinion, and we verified the ATS-EVOS framework and agent behavior logic through scenario-based experiments. These experiments demonstrated AIRLINE-EVOS's capabilities in responding to an input price shock in fuel prices, and to equipage challenges in a series of analyses based on potential incentive policies for best equipped best served, optimal-wind routing, and traffic management initiative exemption concepts..

  12. Entrainment due to a thermal impinging on a stratified interface with and without buoyancy reversal

    NASA Astrophysics Data System (ADS)

    Zhang, Qing; Cotel, Aline

    2000-06-01

    The aim of the present paper is to understand the interaction between a rising thermal and an inversion in the atmosphere and to quantify the turbulent entrainment rate due to a thermal impingement on a stratified interface. This problem was simulated in the laboratory using a water tank. The thermal is created by releasing a small volume of buoyant fluid into a stratified environment composed of two layers of different densities. A thin interface separates the lower layer from the lighter upper layer. The entrainment of upper layer fluid into the thermal is investigated using a passive dye flow visualization technique. The entrainment rate is found to obey a Ri-3/2 power law, as predicted by Cotel and Breidenthal [1997]. The effect of simulated evaporative cooling on the entrainment of a thermal impinging on a stratified interface is also investigated experimentally. Evaporative cooling in atmospheric clouds is simulated in the laboratory using alcohol-water mixtures, so that the mixed fluid is denser than either parent parcel. This is realized in the laboratory by releasing a mixture of ethyl alcohol and ethylene glycol in an aqueous solution. It rises first through a relatively dense lower layer fluid and then impinges on a thin stratified interface, above which is a layer of relatively light fluid. The entrainment rate for values of the buoyancy reversal parameter D* between 0 and 0.5 was found to obey a Ri-3/2 power law. The entrainment rate is independent of D* between 0 and 0.5 for a range of Richardson numbers Ri from 3 to 25. This is consistent with the behavior of the buoyancy-reversing thermal in an unstratified environment observed by Johari [1992].

  13. Decreased Hering-Breuer input-output entrainment in a mouse model of Rett syndrome.

    PubMed

    Dhingra, Rishi R; Zhu, Yenan; Jacono, Frank J; Katz, David M; Galán, Roberto F; Dick, Thomas E

    2013-01-01

    Rett syndrome, a severe X-linked neurodevelopmental disorder caused by mutations in the gene encoding methyl-CpG-binding protein 2 (Mecp2), is associated with a highly irregular respiratory pattern including severe upper-airway dysfunction. Recent work suggests that hyperexcitability of the Hering-Breuer reflex (HBR) pathway contributes to respiratory dysrhythmia in Mecp2 mutant mice. To assess how enhanced HBR input impacts respiratory entrainment by sensory afferents in closed-loop in vivo-like conditions, we investigated the input (vagal stimulus trains) - output (phrenic bursting) entrainment via the HBR in wild-type and MeCP2-deficient mice. Using the in situ perfused brainstem preparation, which maintains an intact pontomedullary axis capable of generating an in vivo-like respiratory rhythm in the absence of the HBR, we mimicked the HBR feedback input by stimulating the vagus nerve (at threshold current, 0.5 ms pulse duration, 75 Hz pulse frequency, 100 ms train duration) at an inter-burst frequency matching that of the intrinsic oscillation of the inspiratory motor output of each preparation. Using this approach, we observed significant input-output entrainment in wild-type mice as measured by the maximum of the cross-correlation function, the peak of the instantaneous relative phase distribution, and the mutual information of the instantaneous phases. This entrainment was associated with a reduction in inspiratory duration during feedback stimulation. In contrast, the strength of input-output entrainment was significantly weaker in Mecp2 (-/+) mice. However, Mecp2 (-/+) mice also had a reduced inspiratory duration during stimulation, indicating that reflex behavior in the HBR pathway was intact. Together, these observations suggest that the respiratory network compensates for enhanced sensitivity of HBR inputs by reducing HBR input-output entrainment. PMID:23565077

  14. Endogenous Delta/Theta Sound-Brain Phase Entrainment Accelerates the Buildup of Auditory Streaming.

    PubMed

    Riecke, Lars; Sack, Alexander T; Schroeder, Charles E

    2015-12-21

    In many natural listening situations, meaningful sounds (e.g., speech) fluctuate in slow rhythms among other sounds. When a slow rhythmic auditory stream is selectively attended, endogenous delta (1‒4 Hz) oscillations in auditory cortex may shift their timing so that higher-excitability neuronal phases become aligned with salient events in that stream [1, 2]. As a consequence of this stream-brain phase entrainment [3], these events are processed and perceived more readily than temporally non-overlapping events [4-11], essentially enhancing the neural segregation between the attended stream and temporally noncoherent streams [12]. Stream-brain phase entrainment is robust to acoustic interference [13-20] provided that target stream-evoked rhythmic activity can be segregated from noncoherent activity evoked by other sounds [21], a process that usually builds up over time [22-27]. However, it has remained unclear whether stream-brain phase entrainment functionally contributes to this buildup of rhythmic streams or whether it is merely an epiphenomenon of it. Here, we addressed this issue directly by experimentally manipulating endogenous stream-brain phase entrainment in human auditory cortex with non-invasive transcranial alternating current stimulation (TACS) [28-30]. We assessed the consequences of these manipulations on the perceptual buildup of the target stream (the time required to recognize its presence in a noisy background), using behavioral measures in 20 healthy listeners performing a naturalistic listening task. Experimentally induced cyclic 4-Hz variations in stream-brain phase entrainment reliably caused a cyclic 4-Hz pattern in perceptual buildup time. Our findings demonstrate that strong endogenous delta/theta stream-brain phase entrainment accelerates the perceptual emergence of task-relevant rhythmic streams in noisy environments. PMID:26628008

  15. Foaming and Antifoaming and Gas Entrainment in Radioactive Waste Preteatment and Immobilization Processes

    SciTech Connect

    Wasan, Darsh T.; Nikolov, Alex

    2005-06-01

    The objectives of this research effort are to develop a fundamental understanding of the physico-chemical mechanisms that produce foaming and air entrainment in the DOE High Level (HLW) and Low Activity (LAW) radioactive waste separation and immobilization processes, and to develop and test advanced antifoam/defoaming/rheology modifier agents. Antifoams/rheology modifiers developed from this research will be tested using non-radioactive simulants of the radioactive wastes obtained from Hanford and the Savannah River Site (SRS).

  16. The influence of entrainment-induced variability of cloud microphysics on the chemical composition of cloudwater

    NASA Astrophysics Data System (ADS)

    Walcek, Chris J.; Brankov, Elvira

    We propose a mechanism by which condensed water within clouds becomes chemically heterogeneous due to the turbulent nature of entrainment of noncloudy air into a rising cloudy parcel. We hypothesize that the observed small-scale variability of cloud microphysics, temperature and vertical velocity results from the formation of turbulent-scale sub-regions composed of varying proportions of undiluted cloudy air mixed with dry, cloud-free air above cloud base. Cloudy regions that are exposed to a higher degree of entrainment will contain lower condensed water contents, lower temperatures, lower droplet number concentrations at smaller sizes, and lower vertical velocities as a result of entrainment-induced dilution and evaporation. Greater entrainment will also increase concentrations of sulfate, nitrate and ammonium in cloudwater, and will lead to a size-dependent chemical composition of cloudwater across the range of entrainment mixtures. We find significant discrepancies between calculated SO 2 oxidation rates that account for turbulent-scale variability, relative to simpler calculations that ignore turbulent-induced variability. The more exact description of a cloud composed of a heterogeneous mix of parcels yields higher sulfur oxidation rates and lower dissolved concentrations of highly soluble sulfate, nitrate and ammonia. Most current measurements and models of cloudwater chemical composition cannot resolve the fine structure of entrainment-induced fluctuations in cloud microphysics, and therefore implicitly "average out" small-scale fluctuations of momentum, heat, buoyancy and water substance within the measurement volume or numerical grid. This averaging can lead to erroneous interpretations of measurements, and may yield biased calculations of SO 2 oxidation within clouds. Using measured concentrations of pertinent air quality concentrations in conjunction with a relatively simple regional-scale atmospheric chemistry model, we find that during most of the

  17. Ethanol consumption in mice: relationships with circadian period and entrainment

    PubMed Central

    Trujillo, Jennifer L.; Do, David T.; Grahame, Nicholas J.; Roberts, Amanda J.; Gorman, Michael R.

    2011-01-01

    A functional connection between the circadian timing system and alcohol consumption is suggested by multiple lines of converging evidence. Ethanol consumption perturbs physiological rhythms in hormone secretion, sleep and body temperature, and conversely, genetic and environmental perturbations of the circadian system can alter alcohol intake. A fundamental property of the circadian pacemaker, the endogenous period of its cycle under free-running conditions, was previously shown to differ between selectively bred High- (HAP) and Low- (LAP) Alcohol Preferring replicate 1 mice. To test whether there is a causal relationship between circadian period and ethanol intake, we induced experimental, rather than genetic, variations in free-running period. Male inbred C57Bl/6J mice and replicate 2 male and female HAP2 and LAP2 mice were entrained to light:dark cycles of 26 h or 22 h or remained in a standard 24 h cycle. Upon discontinuation of the light:dark cycle, experimental animals exhibited longer and shorter free-running periods, respectively. Despite robust effects on circadian period and clear circadian rhythms in drinking, these manipulations failed to alter the daily ethanol intake of the inbred strain or selected lines. Likewise, driving the circadian system at long and short periods produced no change in alcohol intake. In contrast with replicate 1 HAP and LAP lines, there was no difference in free-running period between ethanol naïve HAP2 and LAP2 mice. HAP2 mice, however, were significantly more active than LAP2 mice as measured by general home-cage movement and wheel running, a motivated behavior implicating a selection effect on reward systems. Despite a marked circadian regulation of drinking behavior, the free-running and entrained period of the circadian clock does not determine daily ethanol intake. PMID:20880659

  18. Ethanol consumption in mice: relationships with circadian period and entrainment.

    PubMed

    Trujillo, Jennifer L; Do, David T; Grahame, Nicholas J; Roberts, Amanda J; Gorman, Michael R

    2011-03-01

    A functional connection between the circadian timing system and alcohol consumption is suggested by multiple lines of converging evidence. Ethanol consumption perturbs physiological rhythms in hormone secretion, sleep, and body temperature; and conversely, genetic and environmental perturbations of the circadian system can alter alcohol intake. A fundamental property of the circadian pacemaker, the endogenous period of its cycle under free-running conditions, was previously shown to differ between selectively bred high- (HAP) and low- (LAP) alcohol preferring replicate 1 mice. To test whether there is a causal relationship between circadian period and ethanol intake, we induced experimental, rather than genetic, variations in free-running period. Male inbred C57Bl/6J mice and replicate 2 male and female HAP2 and LAP2 mice were entrained to light:dark cycles of 26 or 22 h or remained in a standard 24 h cycle. On discontinuation of the light:dark cycle, experimental animals exhibited longer and shorter free-running periods, respectively. Despite robust effects on circadian period and clear circadian rhythms in drinking, these manipulations failed to alter the daily ethanol intake of the inbred strain or selected lines. Likewise, driving the circadian system at long and short periods produced no change in alcohol intake. In contrast with replicate 1 HAP and LAP lines, there was no difference in free-running period between ethanol naïve HAP2 and LAP2 mice. HAP2 mice, however, were significantly more active than LAP2 mice as measured by general home-cage movement and wheel running, a motivated behavior implicating a selection effect on reward systems. Despite a marked circadian regulation of drinking behavior, the free-running and entrained period of the circadian clock does not determine daily ethanol intake. PMID:20880659

  19. Entrained liquid fraction calculation in adiabatic disperse-annular flows at low rate in film

    NASA Astrophysics Data System (ADS)

    Yagov, V. V.; Minko, M. V.

    2016-04-01

    In this work, we continue our study [1] and extend further an approach to low reduced pressures. An approximate model of droplets entrainment from the laminar film surface and an equation for calculating entrainment intensity are proposed. To carry out direct verification of this equation using experimental data is extremely difficult because the integral effect—liquid flow rate in a film at a dynamic equilibrium between entrainment and deposition—is usually measured in the experiments. The balance between flows of droplets entrainment and deposition corresponds to the dynamic equilibrium because of turbulent diffusion. The transcendental equation, which was obtained on the basis of this balance, contains one unknown numerical factor and allows one to calculate the liquid rate. Comparing calculation results with the experimental data for the water-air and water-helium flows at low reduced pressures (less than 0.03) has shown their good agreement at the universal value of a numerical constant, if an additional dimensionless parameter, a fourth root of vaporliquid densities ratio, is introduced. The criterion that determines the boundary of using methods of this work and that of [1] in calculations and that reflects effect of pressure and state of film surface on distribution of the liquid in the annular flow is proposed; the numerical value of this criterion has been determined.

  20. Viscous-inviscid calculations of jet entrainment effects on the subsonic flow over nozzle afterbodies

    NASA Technical Reports Server (NTRS)

    Wilmoth, R. G.

    1980-01-01

    A viscous-inviscid interaction model was developed to account for jet entrainment effects in the prediction of the subsonic flow over nozzle afterbodies. The model is based on the concept of a weakly interacting shear layer in which the local streamline deflections due to entrainment are accounted for by a displacement-thickness type of correction to the inviscid plume boundary. The entire flow field is solved in an iterative manner to account for the effects on the inviscid external flow of the turbulent boundary layer, turbulent mixing and chemical reactions in the shear layer, and the inviscid jet exhaust flow. The components of the computational model are described, and numerical results are presented to illustrate the interactive effects of entrainment on the overall flow structure. The validity of the model is assessed by comparisons with data obtained form flow-field measurements on cold-air jet exhausts. Numerical results and experimental data are also given to show the entrainment effects on nozzle boattail drag under various jet exhaust and free-stream flow conditions.

  1. Entrainment and detrainment required to explain updraft properties and work dissipation

    NASA Astrophysics Data System (ADS)

    Michaud, L. M.

    1998-05-01

    A one-dimensional thermodynamic entrainment-detrainment model is used to determine updraft virtual temperature excess, updraft velocity, other updraft properties from sounding data. The model correctly predicts most updraft properties explains how work of buoyancy is dissipated. The unique feature of the model is that fractional entrainment detrainment are both functions of the virtual temperature excess of the updraft independent of updraft mass or diameter. The updraft temperature composition are rigorously determined before updraft velocity is considered. The entrainment detrainment functions allow the flows in out of the updraft to vary in a physically realistic way are used from the base of the sounding to cloud top. The model limits the growth of cumulus under conditions of dry air aloft. The model shows that entrainment inhibits deep convection. The model predicts higher intensity for continental than for oceanic updrafts. High humidity at the bottom of the atmosphere decreases the intensity of the updrafts because it lowers the condensation level, the level at which evaporative cooling comes into play. High humidity aloft increases the intensity of the updrafts because it reduced evaporative cooling.

  2. Liquid entrainment at an upward oriented vertical branch line from a horizontal pipe

    NASA Astrophysics Data System (ADS)

    Welter, Kent Byron

    Under simulated accident conditions, tees in the primary coolant loop of a Pressurized Water Reactor (PWR) can deviate from their original design purpose and become separators that effectively remove core heat sink capacity. This method of primary coolant removal is a phenomenological subset of phase separation known as liquid entrainment, whereby liquid is forced from its original path by the inertia of the gas. A comprehensive literature review revealed common deficiencies in previous studies. The Westinghouse AP600 advanced reactor design was chosen to assess the validity of entrainment models. Following a systematic scaling analysis of the prototypic design a model separate effects test was proposed and constructed at Oregon State University. Just under 100 tests were run to fill the deficiencies found in the literature review. New data from the Air-water Test Loop for Advanced Thermal-hydraulic Studies (ATLATS) could not be predicted by published correlations. A new theoretical model for predicting liquid entrainment onset and steady state entrainment was developed. Comparison with all available data shows a marked improvement for predicting the mass flow rate out the vertical branch.

  3. Computational Study of the Hydrodynamic Behavior during Air Discharge through a Sparger Submerged in the Condensation Pool

    SciTech Connect

    Ahn, Hyung-Joon; Bang, Young-Seok; Kim, In-Goo; Kim, Hho-Jung; Lee, Byeong-Eun; Kwon, Soon-Bum

    2002-07-01

    The In-containment Refueling Water Storage Tank (IRWST) has the function of heat sink when steam is released from the pressurizer. The hydrodynamic behaviors occurring at the sparger are very complex because of the wide variety of operating conditions and the complex geometry. Hydrodynamic behavior when air is discharged through a sparger in a condensation pool is investigated using CFD techniques in the present study. The effect of pressure acting on the sparger header during both water and air discharge through the sparger is studied. In addition, pressure oscillation occurring during air discharge through the sparger is studied for a better understanding of mechanisms of air discharge and a better design of the IRWST, including sparger. (authors)

  4. Experimental study on the flame behaviors of premixed methane/air mixture in horizontal rectangular ducts

    NASA Astrophysics Data System (ADS)

    Chen, Dongliang; Sun, Jinhua; Chen, Sining; Liu, Yi; Chu, Guanquan

    2007-01-01

    In order to explore the flame propagation characteristics and tulip flame formation mechanism of premixed methane/air mixture in horizontal rectangular ducts, the techniques of Schlieren and high-speed video camera are used to study the flame behaviors of the premixed gases in a closed duct and opened one respectively, and the propagation characteristics in both cases and the formation mechanism of the tulip flame are analyzed. The results show that, the propagation flame in a closed duct is prior to form a tulip flame structure than that in an opened duct, and the tulip flame structure formation in a closed duct is related to the flame propagation velocity decrease. The sharp decrease of the flame propagation velocity is one of the reasons to the tulip flame formation, and the decrease of the flame propagation velocity is due to the decrease of the burned product flow velocity mainly.

  5. Entrainment in oscillatory zero-mean flow

    NASA Astrophysics Data System (ADS)

    Medina, P.; Sanchez, M. A.

    2009-04-01

    The dynamical processes associated with the stably stratified atmospheric boundary layer or in the ocean thermocline are less well understood than those of its convective counterparts. This is due to its complexity, and the fact that buoyancy reduces entrainment across density interfaces. We present results on a series of laboratory experiments where a sharp density interface generated by either salt concentration or heat, advances due to grid stirred turbulence. We parametrize the level of buoyancy at the density interface by a local Richardson number defined in terms of the density difference across the interface, which may be due to a temperature or salinity jump. L is the integral lengthscale and u' is the r.m.s. velocity scale. So Ri = C L/u 2. The laboratory experiments were designed to compare the entrainment produced by zero-mean turbulence in heat or salt density interfaces. In the experiment we used a small perspex box of 15 by 10 cm in base, a small mesh grid (M= 0.8 cm ) driven by a motor. So as to generate the density interface by disolving salt in the bottom layer of the water column or by heating the top layer, we added the top light layer, which had a density difference carefully set up by means of a sponge float. The grid was set to oscillate with fixed frequency and stroke at the begining of the experiment and the velocity of advance of the interface Ve was measured by looking at a Shadowgraph or by video recording. The turbulent parameters are derived from previous measurements as a function of the distance between the grid center and the interface z as: l = 0.1 z and the turbulent velocity údecays inversely proportinal to the distance z. There are several mechanisms that produce mixing across the density interface. And there is a dependence of the Prandtl number on the Entrainment law. The entrainment is a power function of the local Richardson number, and the value of the empirical exponent n(Ri,Pr) is compared with previous results. The

  6. AN-107 entrained solids - Solubility versus temperature

    SciTech Connect

    GJ Lumetta; RC Lettau

    2000-03-31

    This report describes the results of a test conducted by Battelle to assess the solubility of the solids entrained in the diluted AN-107 low-activity waste (LAW) sample. BNFL requested Battelle to dilute the AN-107 sample using sodium hydroxide and de-ionized water to mimic expected plant operating conditions. BNFL further requested Battelle to assess the solubility of the solids present in the diluted AN-107 sample versus temperature conditions of 30, 40, and 50 C. BNFL requested these tests to assess the composition of the LAW supernatant and solids versus expected plant-operating conditions.

  7. Entrainment and mixing in thrust augmenting ejectors

    NASA Technical Reports Server (NTRS)

    Bernal, L.; Sarohia, V.

    1983-01-01

    An experimental investigation of two-dimensional thrust augmenting ejector flows has been conducted. Measurements of the shroud surface pressure distribution, mean velocity, turbulent intensities and Reynolds stresses were made in two shroud geometries at various primary nozzle pressure ratios. The effects of shroud geometry and primary nozzle pressure ratio on the shroud surface pressure distribution, mean flow field and turbulent field were determined. From these measurements the evolution of mixing within the shroud of the primary flow and entrained fluid was obtained. The relationship between the mean flow field, the turbulent field and the shroud surface pressure distribution is discussed.

  8. On-line ultrasonic gas entrainment monitor

    DOEpatents

    Day, Clifford K.; Pedersen, Herbert N.

    1978-01-01

    Apparatus employing ultrasonic energy for detecting and measuring the quantity of gas bubbles present in liquids being transported through pipes. An ultrasonic transducer is positioned along the longitudinal axis of a fluid duct, oriented to transmit acoustic energy radially of the duct around the circumference of the enclosure walls. The back-reflected energy is received centrally of the duct and interpreted as a measure of gas entrainment. One specific embodiment employs a conical reflector to direct the transmitted acoustic energy radially of the duct and redirect the reflected energy back to the transducer for reception. A modified embodiment employs a cylindrical ultrasonic transducer for this purpose.

  9. Thermal Gradient Behavior of TBCs Subjected to a Laser Gradient Test Rig: Simulating an Air-to-Air Combat Flight

    NASA Astrophysics Data System (ADS)

    Lima, Rogerio S.; Marple, Basil R.; Marcoux, P.

    2016-01-01

    A computer-controlled laser test rig (using a CO2 laser) offers an interesting alternative to traditional flame-based thermal gradient rigs in evaluating thermal barrier coatings (TBCs). The temperature gradient between the top and back surfaces of a TBC system can be controlled based on the laser power and a forced air back-face cooling system, enabling the temperature history of complete aircraft missions to be simulated. An air plasma spray-deposited TBC was tested and, based on experimental data available in the literature, the temperature gradients across the TBC system (ZrO2-Y2O3 YSZ top coat/CoNiCrAlY bond coat/Inconel 625 substrate) and their respective frequencies during air-to-air combat missions of fighter jets were replicated. The missions included (i) idle/taxi on the runway, (ii) take-off and climbing, (iii) cruise trajectory to rendezvous zone, (iv) air-to-air combat maneuvering, (v) cruise trajectory back to runway, and (vi) idle/taxi after landing. The results show that the TBC thermal gradient experimental data in turbine engines can be replicated in the laser gradient rig, leading to an important tool to better engineer TBCs.

  10. An Ultrasonic and Air Pressure Sensing System for Detection of Behavior before Getting out of Bed Aided by Fuzzy Theory

    NASA Astrophysics Data System (ADS)

    Yamaguchi, Hayato; Nakajima, Hiroshi; Taniguchi, Kazuhiko; Kobashi, Syoji; Hata, Yutaka

    This paper proposes a sensing system for a behavior detection system using an ultrasonic oscillosensor and an air pressure sensor. The ultrasonic oscillosensor sensor has a cylindrical tank filled with water. It detects the vibration of the target object from the signal reflected from the water surface. This sensor can detect a biological vibration by setting to the bottom bed frame. The air pressure sensor consists of a polypropylene sheet and an air pressure sensor, and detects the pressure information by setting under the bed's mattress. An increase (decrease) in the load placed on the bed is detected by the increase (decrease) in the pressure of the air held in the tube attached to the sheet. We propose a behavior detection system using both sensors, complementally. The system recognizes three states (nobody in bed, keeping quiet in bed, moving in bed) using both sensors, and we detect the behavior before getting out of bed by recognized these states. Fuzzy logic plays a primary role in the system. As the fundamental experiment, we applied the system to five healthy volunteers, the system successfully recognized three states, and detected the behavior before getting out of bed. As the clinical experiment, we applied the system to four elderly patients with dementia, the system exactly detected the behavior before getting out of the bed with enough time for medical care support.

  11. Entrainment range of nonidentical circadian oscillators by a light-dark cycle

    NASA Astrophysics Data System (ADS)

    Gu, Changgui; Xu, Jinshan; Liu, Zonghua; Rohling, Jos H. T.

    2013-08-01

    The suprachiasmatic nucleus (SCN) is a principal circadian clock in mammals, which controls physiological and behavioral daily rhythms. The SCN has two main features: Maintaining a rhythmic cycle of approximately 24 h in the absence of a light-dark cycle (free-running period) and the ability to entrain to external light-dark cycles. Both free-running period and range of entrainment vary from one species to another. To understand this phenomenon, we investigated the diversity of a free-running period by the distribution of coupling strengths in our previous work [Phys. Rev. EPLEEE81539-375510.1103/PhysRevE.80.030904 80, 030904(R) (2009)]. In this paper we numerically found that the dispersion of intrinsic periods among SCN neurons influence the entrainment range of the SCN, but has little influence on the free-running periods under constant darkness. This indicates that the dispersion of coupling strengths determines the diversity in free-running periods, while the dispersion of intrinsic periods determines the diversity in the entrainment range. A theoretical analysis based on two coupled neurons is presented to explain the results of numerical simulations.

  12. The CRTC1-SIK1 Pathway Regulates Entrainment of the Circadian Clock

    PubMed Central

    Jagannath, Aarti; Butler, Rachel; Godinho, Sofia I.H.; Couch, Yvonne; Brown, Laurence A.; Vasudevan, Sridhar R.; Flanagan, Kevin C.; Anthony, Daniel; Churchill, Grant C.; Wood, Matthew J.A.; Steiner, Guido; Ebeling, Martin; Hossbach, Markus; Wettstein, Joseph G.; Duffield, Giles E.; Gatti, Silvia; Hankins, Mark W.; Foster, Russell G.; Peirson, Stuart N.

    2013-01-01

    Summary Retinal photoreceptors entrain the circadian system to the solar day. This photic resetting involves cAMP response element binding protein (CREB)-mediated upregulation of Per genes within individual cells of the suprachiasmatic nuclei (SCN). Our detailed understanding of this pathway is poor, and it remains unclear why entrainment to a new time zone takes several days. By analyzing the light-regulated transcriptome of the SCN, we have identified a key role for salt inducible kinase 1 (SIK1) and CREB-regulated transcription coactivator 1 (CRTC1) in clock re-setting. An entrainment stimulus causes CRTC1 to coactivate CREB, inducing the expression of Per1 and Sik1. SIK1 then inhibits further shifts of the clock by phosphorylation and deactivation of CRTC1. Knockdown of Sik1 within the SCN results in increased behavioral phase shifts and rapid re-entrainment following experimental jet lag. Thus SIK1 provides negative feedback, acting to suppress the effects of light on the clock. This pathway provides a potential target for the regulation of circadian rhythms. PMID:23993098

  13. A Simple State-Determined Model Reproduces Entrainment and Phase-Locking of Human Walking

    PubMed Central

    Ahn, Jooeun; Hogan, Neville

    2012-01-01

    Theoretical studies and robotic experiments have shown that asymptotically stable periodic walking may emerge from nonlinear limit-cycle oscillators in the neuro-mechanical periphery. We recently reported entrainment of human gait to periodic mechanical perturbations with two essential features: 1) entrainment occurred only when the perturbation period was close to the original (preferred) walking period, and 2) entrainment was always accompanied by phase locking so that the perturbation occurred at the end of the double-stance phase. In this study, we show that a highly-simplified state-determined walking model can reproduce several salient nonlinear limit-cycle behaviors of human walking: 1) periodic gait that is 2) asymptotically stable; 3) entrainment to periodic mechanical perturbations only when the perturbation period is close to the model's unperturbed period; and 4) phase-locking to locate the perturbation at the end of double stance. Importantly, this model requires neither supra-spinal control nor an intrinsic self-sustaining neural oscillator such as a rhythmic central pattern generator. Our results suggest that several prominent limit-cycle features of human walking may stem from simple afferent feedback processes without significant involvement of supra-spinal control or a self-sustaining oscillatory neural network. PMID:23152761

  14. Oxidation Behavior of Mo-Si-B Alloys in Wet Air

    SciTech Connect

    M. Kramer; A. Thom; O. Degirmen; V. Behrani; M. Akinc

    2002-04-22

    Multiphase composite alloys based on the Mo-Si-B system are candidate materials for ultra-high temperature applications. In non load-bearing uses such as thermal barrier coatings or heat exchangers in fossil fuel burners, these materials may be ideally suited. The present work investigated the effect of water vapor on the oxidation behavior of Mo-Si-B phase assemblages. Three alloys were studied: Alloy 1 = Mo{sub 5}Si{sub 3}B{sub x} (T1)- MoSi{sub 2}- MoB, Alloy 2 = T1- Mo{sub 5}SiB{sub 2} (T2)- Mo{sub 3}Si, and Alloy 3 = Mo- T2- Mo{sub 3}Si. Tests were conducted at 1000 and 1100C in controlled atmospheres of dry air and wet air nominally containing 18, 55, and 150 Torr H{sub 2}O. The initial mass loss of each alloy was approximately independent of the test temperature and moisture content of the atmosphere. The magnitude of these initial losses varied according to the Mo content of the alloys. All alloys formed a continuous, external silica scale that protected against further mass change after volatilization of the initially formed MoO{sub 3}. All alloys experienced a small steady state mass change, but the calculated rates cannot be quantitatively compared due to statistical uncertainty in the individual mass measurements. Of particular interest is that Alloy 3, which contains a significant volume fraction of Mo metal, formed a protective scale. All alloys formed varying amounts of subscale Mo and MoO{sub 2}. This implies that oxygen transport through the external silica scale has been significantly reduced. For all alloys, water vapor accelerated the growth of a multiphase interlayer at the silica scale/unoxidized alloy interface. This interlayer is likely composed of fine Mo and MoO{sub 2} that is dispersed within a thin silica matrix. Alloy 3 was particularly sensitive to water accelerated growth of this interlayer. At 1100 C, the scale thickness after 300 hours increased from about 20 mm in dry air to nearly 100 mm in wet air.

  15. Conditions for super-adiabatic droplet growth after entrainment mixing

    NASA Astrophysics Data System (ADS)

    Yang, Fan; Shaw, Raymond; Xue, Huiwen

    2016-07-01

    Cloud droplet response to entrainment and mixing between a cloud and its environment is considered, accounting for subsequent droplet growth during adiabatic ascent following a mixing event. The vertical profile for liquid water mixing ratio after a mixing event is derived analytically, allowing the reduction to be predicted from the mixing fraction and from the temperature and humidity for both the cloud and environment. It is derived for the limit of homogeneous mixing. The expression leads to a critical height above the mixing level: at the critical height the cloud droplet radius is the same for both mixed and unmixed parcels, and the critical height is independent of the updraft velocity and mixing fraction. Cloud droplets in a mixed parcel are larger than in an unmixed parcel above the critical height, which we refer to as the "super-adiabatic" growth region. Analytical results are confirmed with a bin microphysics cloud model. Using the model, we explore the effects of updraft velocity, aerosol source in the environmental air, and polydisperse cloud droplets. Results show that the mixed parcel is more likely to reach the super-adiabatic growth region when the environmental air is humid and clean. It is also confirmed that the analytical predictions are matched by the volume-mean cloud droplet radius for polydisperse size distributions. The findings have implications for the origin of large cloud droplets that may contribute to onset of collision-coalescence in warm clouds.

  16. Conditions for super-adiabatic droplet growth after entrainment mixing

    DOE PAGESBeta

    Yang, Fan; Shaw, Raymond; Xue, Huiwen

    2016-07-29

    Cloud droplet response to entrainment and mixing between a cloud and its environment is considered, accounting for subsequent droplet growth during adiabatic ascent following a mixing event. The vertical profile for liquid water mixing ratio after a mixing event is derived analytically, allowing the reduction to be predicted from the mixing fraction and from the temperature and humidity for both the cloud and environment. It is derived for the limit of homogeneous mixing. The expression leads to a critical height above the mixing level: at the critical height the cloud droplet radius is the same for both mixed and unmixedmore » parcels, and the critical height is independent of the updraft velocity and mixing fraction. Cloud droplets in a mixed parcel are larger than in an unmixed parcel above the critical height, which we refer to as the “super-adiabatic” growth region. Analytical results are confirmed with a bin microphysics cloud model. Using the model, we explore the effects of updraft velocity, aerosol source in the environmental air, and polydisperse cloud droplets. Results show that the mixed parcel is more likely to reach the super-adiabatic growth region when the environmental air is humid and clean. It is also confirmed that the analytical predictions are matched by the volume-mean cloud droplet radius for polydisperse size distributions. The findings have implications for the origin of large cloud droplets that may contribute to onset of collision–coalescence in warm clouds.« less

  17. Entrainment of Vertical Jets in Turbulent Cross Flow

    NASA Astrophysics Data System (ADS)

    Freedland, Graham; Roberts, Karen; Mastin, Larry; Solovitz, Stephen; Cal, Raul

    2015-11-01

    Volcanic eruptions produce high concentrations of ash that produce clouds in the atmosphere that are hazardous for private and commercial aviation. Without accurate models to predict ash concentrations, air traffic is unable to safely navigate ash clouds downwind of an eruption as critical concentrations are difficult to identify visually. Current models rely on inputs such as plume height, eruptive dissipation and cross-flow wind speeds as well as empirical parameters such as the entrainment ratio between the cross-flow and the plume velocity. A wind tunnel experiment has been designed to investigate these models by injecting air orthogonally into a cross-flow. The ratio of the cross-flow and jet velocities is varied to simulate a weak plume and flow response is measured using particle image velocimetry. Grids upstream of the plume create different turbulence intensities, which, combined with different jet geometries, allow us to study the flow field, mean and second order moments and thereby obtain information to accurately model volcanic ash concentrations in the atmosphere.

  18. Entrainment, Drizzle, and the Indirect Effect in Stratiform Clouds

    NASA Technical Reports Server (NTRS)

    Ackerman, Andrew

    2005-01-01

    Activation of some fraction of increased concentrations of sub-micron soluble aerosol particles lead to enhanced cloud droplet concentrations and hence smaller droplets, increasing their total cross sectional area and thus reflecting solar radiation more efficiently (the Twomey, or first indirect, effect). However, because of competition during condensational growth, droplet distributions tend to broaden as numbers increase, reducing the sensitivity of cloud albedo to droplet concentration on the order of 10%. Also, smaller droplets less effectively produce drizzle through collisions and coalescence, and it is widely expected (and found in large-scale models) that decreased precipitation leads to clouds with more cloud water on average (the so-called cloud lifetime, or second indirect, effect). Much of the uncertainty regarding the overall indirect aerosol effect stems from inadequate understanding of such changes in cloud water. Detailed simulations based on FIRE-I, ASTEX, and DYCOMS-II conditions show that suppression of precipitation from increased droplet concentrations leads to increased cloud water only when sufficient precipitation reaches the surface, a condition favored when the overlying air is-humid or droplet concentrations are very low. Otherwise, aerosol induced suppression of precipitation enhances entrainment of overlying dry air, thereby reducing cloud water and diminishing the indirect climate forcing.

  19. A neuropeptide speeds circadian entrainment by reducing intercellular synchrony

    PubMed Central

    An, Sungwon; Harang, Rich; Meeker, Kirsten; Granados-Fuentes, Daniel; Tsai, Connie A.; Mazuski, Cristina; Kim, Jihee; Doyle, Francis J.; Petzold, Linda R.; Herzog, Erik D.

    2013-01-01

    Shift work or transmeridian travel can desynchronize the body's circadian rhythms from local light–dark cycles. The mammalian suprachiasmatic nucleus (SCN) generates and entrains daily rhythms in physiology and behavior. Paradoxically, we found that vasoactive intestinal polypeptide (VIP), a neuropeptide implicated in synchrony among SCN cells, can also desynchronize them. The degree and duration of desynchronization among SCN neurons depended on both the phase and the dose of VIP. A model of the SCN consisting of coupled stochastic cells predicted both the phase- and the dose-dependent response to VIP and that the transient phase desynchronization, or “phase tumbling”, could arise from intrinsic, stochastic noise in small populations of key molecules (notably, Period mRNA near its daily minimum). The model also predicted that phase tumbling following brief VIP treatment would accelerate entrainment to shifted environmental cycles. We tested this using a prepulse of VIP during the day before a shift in either a light cycle in vivo or a temperature cycle in vitro. Although VIP during the day does not shift circadian rhythms, the VIP pretreatment approximately halved the time required for mice to reentrain to an 8-h shifted light schedule and for SCN cultures to reentrain to a 10-h shifted temperature cycle. We conclude that VIP below 100 nM synchronizes SCN cells and above 100 nM reduces synchrony in the SCN. We show that exploiting these mechanisms that transiently reduce cellular synchrony before a large shift in the schedule of daily environmental cues has the potential to reduce jet lag. PMID:24167276

  20. The effect of entrainment on starting vortices

    NASA Astrophysics Data System (ADS)

    Rosi, Giuseppe; Rival, David

    2015-11-01

    Recent work shows that vortex detachment behind accelerating plates coincides with when streamlines enclosing the starting vortex (SV) form a full saddle. In the case of a linearly accelerating plate, it can be shown that vorticity-containing mass, and thus the SV's development scale with only dimensionless towed distance, while the SV's circulation scales with the acceleration rate. This results in shear-layer instabilities whose structure is Reynold-number independent, but whose strength scale with Reynolds number. It is hypothesized that the increased strength of the instabilities promotes entrainment, which causes the formation of the full saddle and thereby detachment to occur at an earlier dimensionless towed distance. To test this hypothesis, a circular plate is linearly accelerated from rest to pinch-off with chord-based Reynolds numbers of 103, 104, and 105 at the midpoint of the motion. Planar PIV data is acquired, from which FTLE and enstrophy fields are calculated. Vortex detachment is identified from the dynamics of the FTLE saddles, while the enstrophy fields are used to calculate both the vorticity-containing mass entering from the shear layer and the mass entrained from the quiescent surroundings.

  1. Stochastic entrainment of a stochastic oscillator.

    PubMed

    Wang, Guanyu; Peskin, Charles S

    2015-11-01

    In this work, we consider a stochastic oscillator described by a discrete-state continuous-time Markov chain, in which the states are arranged in a circle, and there is a constant probability per unit time of jumping from one state to the next in a specified direction around the circle. At each of a sequence of equally spaced times, the oscillator has a specified probability of being reset to a particular state. The focus of this work is the entrainment of the oscillator by this periodic but stochastic stimulus. We consider a distinguished limit, in which (i) the number of states of the oscillator approaches infinity, as does the probability per unit time of jumping from one state to the next, so that the natural mean period of the oscillator remains constant, (ii) the resetting probability approaches zero, and (iii) the period of the resetting signal approaches a multiple, by a ratio of small integers, of the natural mean period of the oscillator. In this distinguished limit, we use analytic and numerical methods to study the extent to which entrainment occurs. PMID:26651734

  2. Observing of entrainment using small UAS

    NASA Astrophysics Data System (ADS)

    Martin, S.; Bange, J.; Beyrich, F.

    2012-04-01

    Entrainment processes between the atmospheric boundary layer and the free atmosphere are important concerning vertical exchange of momentum, energy, water vapor, trace gases and aerosol. The transition zone between the convectively mixed boundary layer and the stably stratified free atmosphere is called the entrainment zone (EZ). The EZ restrains the domain of turbulence by a temperature inversion and acts as a lid to pollutants. Measurement flights of the mini meteorological aerial vehicle (M2AV) of the Technische Universität Braunschweig were performed in spring 2011 to determine the capability of the unmanned aerial system (UAS) to measure the structure of the EZ. The campaign took place at the Meteorological Observatory Lindenberg / Richard-Aßmann-Observatory of the German Meteorological Service, which is located close to Berlin. Besides the M2AV flights, standard observations were performed by a 12 m and 99 m tower, a sodar, ceilometer and radiosondes. A tethered balloon with measurement units at six different levels was operated especially for this campaign. The measurements of these systems were used to determine the inversion layer and to capture its diurnal cycle. The talk will be focused on vertical profiles of the M2AV up to the free atmosphere, detailed analysis of spatial series of w'θ' at different altitudes and on vertical profiles of normalized variances of the vertical wind component and the potential temperature.

  3. Intrinsic near-24-h pacemaker period determines limits of circadian entrainment to a weak synchronizer in humans.

    PubMed

    Wright, K P; Hughes, R J; Kronauer, R E; Dijk, D J; Czeisler, C A

    2001-11-20

    Endogenous circadian clocks are robust regulators of physiology and behavior. Synchronization or entrainment of biological clocks to environmental time is adaptive and important for physiological homeostasis and for the proper timing of species-specific behaviors. We studied subjects in the laboratory for up to 55 days each to determine the ability to entrain the human clock to a weak circadian synchronizing stimulus [scheduled activity-rest cycle in very dim (approximately 1.5 lux in the angle of gaze) light-dark cycle] at three approximately 24-h periods: 23.5, 24.0, and 24.6 h. These studies allowed us to test two competing hypotheses as to whether the period of the human circadian pacemaker is near to or much longer than 24 h. We report here that imposition of a sleep-wake schedule with exposure to the equivalent of candle light during wakefulness and darkness during sleep is usually sufficient to maintain circadian entrainment to the 24-h day but not to a 23.5- or 24.6-h day. Our results demonstrate functionally that, in normally entrained sighted adults, the average intrinsic circadian period of the human biological clock is very close to 24 h. Either exposure to very dim light and/or the scheduled sleep-wake cycle itself can entrain this near-24-h intrinsic period of the human circadian pacemaker to the 24-h day. PMID:11717461

  4. Intrinsic near-24-h pacemaker period determines limits of circadian entrainment to a weak synchronizer in humans

    NASA Technical Reports Server (NTRS)

    Wright, K. P. Jr; Hughes, R. J.; Kronauer, R. E.; Dijk, D. J.; Czeisler, C. A.

    2001-01-01

    Endogenous circadian clocks are robust regulators of physiology and behavior. Synchronization or entrainment of biological clocks to environmental time is adaptive and important for physiological homeostasis and for the proper timing of species-specific behaviors. We studied subjects in the laboratory for up to 55 days each to determine the ability to entrain the human clock to a weak circadian synchronizing stimulus [scheduled activity-rest cycle in very dim (approximately 1.5 lux in the angle of gaze) light-dark cycle] at three approximately 24-h periods: 23.5, 24.0, and 24.6 h. These studies allowed us to test two competing hypotheses as to whether the period of the human circadian pacemaker is near to or much longer than 24 h. We report here that imposition of a sleep-wake schedule with exposure to the equivalent of candle light during wakefulness and darkness during sleep is usually sufficient to maintain circadian entrainment to the 24-h day but not to a 23.5- or 24.6-h day. Our results demonstrate functionally that, in normally entrained sighted adults, the average intrinsic circadian period of the human biological clock is very close to 24 h. Either exposure to very dim light and/or the scheduled sleep-wake cycle itself can entrain this near-24-h intrinsic period of the human circadian pacemaker to the 24-h day.

  5. Distinct visual pathways mediate Drosophila larval light avoidance and circadian clock entrainment.

    PubMed

    Keene, Alex C; Mazzoni, Esteban O; Zhen, Jamie; Younger, Meg A; Yamaguchi, Satoko; Blau, Justin; Desplan, Claude; Sprecher, Simon G

    2011-04-27

    Visual organs perceive environmental stimuli required for rapid initiation of behaviors and can also entrain the circadian clock. The larval eye of Drosophila is capable of both functions. Each eye contains only 12 photoreceptors (PRs), which can be subdivided into two subtypes. Four PRs express blue-sensitive rhodopsin5 (rh5) and eight express green-sensitive rhodopsin6 (rh6). We found that either PR-subtype is sufficient to entrain the molecular clock by light, while only the Rh5-PR subtype is essential for light avoidance. Acetylcholine released from PRs confers both functions. Both subtypes of larval PRs innervate the main circadian pacemaker neurons of the larva, the neuropeptide PDF (pigment-dispersing factor)-expressing lateral neurons (LNs), providing sensory input to control circadian rhythms. However, we show that PDF-expressing LNs are dispensable for light avoidance, and a distinct set of three clock neurons is required. Thus we have identified distinct sensory and central circuitry regulating light avoidance behavior and clock entrainment. Our findings provide insights into the coding of sensory information for distinct behavioral functions and the underlying molecular and neuronal circuitry. PMID:21525293

  6. Structure of the Entrainment Zone Capping the Convective Atmospheric Boundary Layer.

    NASA Astrophysics Data System (ADS)

    Sullivan, Peter P.; Moeng, Chin-Hoh; Stevens, Bjorn; Lenschow, Donald H.; Mayor, Shane D.

    1998-10-01

    The authors use large-eddy simulation (LES) to investigate entrainment and structure of the inversion layer of a clear convectively driven planetary boundary layer (PBL) over a range of bulk Richardson numbers, Ri. The LES code uses a nested grid technique to achieve fine resolution in all three directions in the inversion layer.Extensive flow visualization is used to examine the structure of the inversion layer and to illustrate the temporal and spatial interaction of a thermal plume and the overlying inversion. It is found that coherent structures in the convective PBL, that is, thermal plumes, are primary instigators of entrainment in the Ri range 13.6 Ri 43.8. At Ri = 13.6, strong horizontal and downward velocities are generated near the inversion layer because of the plume-interface interaction. This leads to folding of the interface and hence entrainment of warm inversion air at the plume's edge. At Ri = 34.5, the inversion's strong stability prevents folding of the interface but strong horizontal and downward motions near the plume's edge pull down pockets of warm air below the nominal inversion height. These pockets of warm air are then scoured off by turbulent motions and entrained into the PBL. The structure of the inversion interface from LES is in good visual agreement with lidar measurements in the PBL obtained during the Lidars in Flat Terrain field experiment.A quadrant analysis of the buoyancy flux shows that net entrainment flux (or average minimum buoyancy flux min) is identified with quadrant IV + < 0 motions, that is, warm air moving downward. Plumes generate both large negative quadrant II + < 0 and positive quadrant III > 0 buoyancy fluxes that tend to cancel.The maximum vertical gradient in potential temperature at every (x, y) grid point is used to define a local PBL height, zi(x, y). A statistical analysis of zi shows that skewness of zi depends on the inversion strength. Spectra of zi exhibit a sensitivity to grid resolution. The

  7. Prediction of nearfield jet entrainment by an interactive mixing/afterburning model

    NASA Technical Reports Server (NTRS)

    Dash, S. M.; Pergament, H. S.; Wilmoth, R. G.

    1978-01-01

    The development of a computational model (BOAT) for calculating nearfield jet entrainment, and its application to the prediction of nozzle boattail pressures, is discussed. BOAT accounts for the detailed turbulence and thermochemical processes occurring in the nearfield shear layers of jet engine (and rocket) exhaust plumes while interfacing with the inviscid exhaust and external flowfield regions in an overlaid, interactive manner. The ability of the model to analyze simple free shear flows is assessed by detailed comparisons with fundamental laboratory data. The overlaid methodology and the entrainment correction employed to yield the effective plume boundary conditions are assessed via application of BOAT in conjunction with the codes comprising the NASA/LRC patched viscous/inviscid model for determining nozzle boattail drag for subsonic/transonic external flows. Comparisons between the predictions and data on underexpanded laboratory cold air jets are presented.

  8. Entrainment rates at the tops of laboratory analogs of cumulus and stratocumulus clouds

    NASA Astrophysics Data System (ADS)

    Górska, Anna; Malinowski, Szymon P.; Fugal, Jacob

    2015-04-01

    We investigate entrainment at tops of laboratory analogs of convective clouds: cumulus and stratocumulus. Cloudy saturated moist air (T ~22 °C) containing droplets of diameters of ~3-10 μm, is introduced into a laboratory cloud chamber of dimensions of 1.0×1.0×1.8 through an opening in the bottom wall. Initialy cloudy air fills ~60 cm thick layer at the bottom. Mixing between the cloud and unsaturated air above (T ~22 °C, RH ~35 %) results in evaporative cooling triggering convection which, in turn, leads to formation of a well mixed layer capperd with a temperature inversion. The temperature jump is about 2 °C within ~30 cm deep layer. Then updrafts are forced through a 30cm high tube extending from the bottom of the chamber. "Strong' updrafts which penetrate the whole inversion layer mimic overshooting cumulus clouds while "weak' updrafts diverging under the inversion simulate stratocumulus clouds. We use a laser sheet technique to image two-dimensional cross sections through the clouds. A specially developed mutiscale Particle Image Velicimetry (PIV) algorithm allows to retrieve 2D velocity fields. Suitable image processing allows to determine cloud-clear air interface in the images. Extracting velocities of cloudy (ui) and environmental (ua) air on both sides of the interface allows us calculate entrainment / detrainment rates: E = -ρa(ua - ui) - entrainment rate D = ρa(ua - ui) - detrainment rate. On the poster we will present fine structures of entraimnet/dertaiment process and discuss similarities and differences in both investigated types of clouds.

  9. Modeling of neutral entrainment in an FRC thruster

    SciTech Connect

    Brackbill, Jeremiah; Gimelshein, Natalia; Gimelshein, Sergey; Cambier, Jean-Luc; Ketsdever, Andrew

    2012-11-27

    Neutral entrainment in a field reversed configuration thruster is modeled numerically with an implicit PIC code extended to include thermal and chemical interactions between plasma and neutral particles. The contribution of charge exchange and electron impact ionization reactions is analyzed, and the sensitivity of the entrainment efficiency to the plasmoid translation velocity and neutral density is evaluated.

  10. Can cloud-top entrainment promote cloud growth?

    NASA Technical Reports Server (NTRS)

    Randall, D. A.

    1984-01-01

    The primary significance of Cloud Deepening through Entrainment (CDE) is that it can prevent the cloud top entrainment instability from destroying a cloud deck. Without suppressing the instability, CDE transforms it from a cloud destroyer to a cloud builder. The analysis does not depend on an entrainment hypothesis. Moreover, it is not restricted to PBL stratocumulus sheets. Stratiform clouds in the free atmosphere can be subject to CDE we need only reinterpret Ps as the pressure at the base of an elevated turbulent mixed layer. Modest departures from well mixedness will alter the results quantitatively but not qualitatively. Processes other than entrainment, such as surface evaporation, radiative cooling, and advection will often work with CDE to build a cloud layer; but of course they can also oppose CDE by reducing the relative humidity. If we make the weak assumption that the deepening of a cloud layer favors an increase in the cloud top entrainment rate (without specifying any particular functional relationship) we are led to speculate that CDE can cause runaway cloud growth, even in the absence of cloud top entrainment instability. through CDE entrainment leads to a deeper cloud, which leads to stronger entrainment.

  11. No Time To Kill: Entrainment and Accelerating Courseware Development.

    ERIC Educational Resources Information Center

    Millington, Paula Crnkovich

    This paper examines the concept of time in multimedia, World Wide Web-based courseware development. The biological concept of entrainment (the alignment of rhythms within and between systems) to accelerate courseware development is explored. The discussion begins with the foundational concepts of entrainment from biological systems and social…

  12. Volcanic jets, plumes, and collapsing fountains: evidence from large-scale experiments, with particular emphasis on the entrainment rate

    NASA Astrophysics Data System (ADS)

    Dellino, P.; Dioguardi, F.; Mele, D.; D'Addabbo, M.; Zimanowski, B.; Büttner, R.; Doronzo, D. M.; Sonder, I.; Sulpizio, R.; Dürig, T.; La Volpe, L.

    2014-06-01

    The source conditions of volcanic plumes and collapsing fountains are investigated by means of large-scale experiments. In the experiments, gas-particle jets issuing from a cylindrical conduit are forced into the atmosphere at different mass flow rates. Dense jets (high particle volumetric concentration, e.g., C 0 > 0.01) generate collapsing fountains, whose height scales with the squared exit velocity. This is consistent with Bernoulli's equation, which is a good approximation if air entrainment is negligible. In this case, kinetic energy is transformed into potential energy without any significant loss by friction with the atmosphere. The dense collapsing fountain, on hitting the ground, generates an intense shear flow similar to a pyroclastic density current. Dilute hot jets (low particle volumetric concentration, e.g., C 0 < 0.01) dissipate their initial kinetic energy at much smaller heights than those predicted by Bernoulli's equation. This is an indication that part of the total mechanical energy is lost by friction with the atmosphere. Significant air entrainment results in this case, leading to the formation of a buoyant column (plume) from which particles settle similarly to pyroclastic fallout. The direct measurement of entrainment coefficient in the experiments suggests that dense collapsing fountains form only when air entrainment is not significant. This is a consequence of the large density difference between the jet and the atmosphere. Cold dilute experiments result in an entrainment coefficient of about 0.06, which is typical of pure jets of fluid dynamics. Hot dilute experiments result in an entrainment coefficient of about 0.11, which is typical of thermally buoyant plumes. The entrainment coefficients obtained by experiments were used as input data in numerical simulations of fountains and plumes. A numerical model was used to solve the classic top-hat system of governing equations, which averages the field variables (e.g., column velocity and

  13. The Reaction Behavior of AlN Powder in Wet Air Between 1573 K and 1773 K

    NASA Astrophysics Data System (ADS)

    Wang, Enhui; Liu, Yanxiang; Chen, Junhong; Chou, Kuo-Chih; Hou, Xinmei

    2016-02-01

    The reaction behavior of aluminium nitride (AlN) powder at the temperature range of 1573 K to 1773 K in wet air was investigated using thermo-gravimetric analysis, x-ray diffraction and scanning electron microscopy. The results show that the reaction behavior of AlN powder in wet air depends on temperature and water content. Initially, weight increases quickly due to oxidation. Once the oxide product Al2O3 is formed, the volatile reaction caused by Al2O3 and H2O occurs simultaneously. Because of the appearance of cracks caused by the phase transformation of Al2O3, the reaction behavior is controlled both by oxidation and volatile reaction at a later stage. This phenomenon becomes more obvious with increasing water content. Based on the experimental result, the reaction kinetics is in reasonable agreement with the real physical picture model.

  14. Fluvial entrainment of low density peat blocks (block carbon)

    NASA Astrophysics Data System (ADS)

    Warburton, Jeff

    2014-05-01

    In many fluvial environments low density materials are transported in significant quantities and these form an important part of the stream load and /or have a distinct impact on sedimentation in these environments. However, there are significant gaps in understanding of how these materials are entrained and transported by streams and rivers. Eroding upland peatland environments in particular, frequently have fluvial systems in which large eroded peat blocks, often exceeding 1 m in length; form an important component of the stream material flux. Transport of this material is significant in determining rates of erosion but also has important impacts in terms of damage to infrastructure and carbon loss. This paper describes a field experiment designed to establish for the first time the conditions under which large peat blocks (c. > 0.1 m b axis) are initially entrained from a rough gravel bed. The field site is Trout Beck, in the North Pennines, Northern England which is an upland wandering river channel with occasional lateral and mid channel bars. Mean low flow stage is typically 0.2 m but during flood can rapidly rise, in one to two hours, to over 1.5 m. To study peat block entrainment a bespoke data acquisition system consisting of two pressure transducers, four release triggers and time lapse camera was set up. The pressure transducers provided a record of local depth and the release triggers were embedded in peat blocks to record initial motion and arranged on the rough stream bed. The time lapse camera provided verification of timing of block entrainment (during daylight hours) and also provided information on the mechanism of initial movement. Peat blocks were cut from a local source and were equidimensional, ranging in size from 0.1 to 0.7 m. The derived entrainment function is related to a critical depth of entrainment. Results demonstrate that peat blocks are entrained when the local depth approximates the height of the peat block. Blocks frequently shift

  15. Scalar entrainment in the mixing layer

    NASA Technical Reports Server (NTRS)

    Sandham, N. D.; Mungal, M. G.; Broadwell, J. E.; Reynolds, W. C.

    1988-01-01

    New definitions of entrainment and mixing based on the passive scalar field in the plane mixing layer are proposed. The definitions distinguish clearly between three fluid states: (1) unmixed fluid, (2) fluid engulfed in the mixing layer, trapped between two scalar contours, and (3) mixed fluid. The difference betwen (2) and (3) is the amount of fluid which has been engulfed during the pairing process, but has not yet mixed. Trends are identified from direct numerical simulations and extensions to high Reynolds number mixing layers are made in terms of the Broadwell-Breidenthal mixing model. In the limit of high Peclet number (Pe = ReSc) it is speculated that engulfed fluid rises in steps associated with pairings, introducing unmixed fluid into the large scale structures, where it is eventually mixed at the Kolmogorov scale. From this viewpoint, pairing is a prerequisite for mixing in the turbulent plane mixing layer.

  16. The behavior of high-purity, low-density air plasma sprayed thermal barrier coatings

    SciTech Connect

    Helminiak, Yanar NM

    2009-12-01

    Research on the behavior of high-purity, low-density (85%) air plasma sprayed (APS) thermal barrier coatings (TBC) with NiCoCrAlY bond coats deposited by argon-shrouded plasma spraying is described. The microstructure of the APS topcoats is one variable in this study intended to maximize the coating thicknesses that can be applied without spallation and to minimize the thermal conduction through the YSZ layer. The specimens were evaluated using cyclic oxidation tests and important properties of the TBCs, such as resistance to sintering and phase transformation, were determined. The high purity resulted in top coats which are highly resistant to sintering and transformation from the metastable tetragonal phase to the equilibrium mixture of monoclinic and cubic phases. The porous topcoat microstructure also resulted in significant durability during thermal cycling. The actual failure mechanisms of the APS coatings were found to depend on topcoat thickness, CTE of the superalloy substrate and the nature of the thermal exposure.

  17. Oxidation Behavior and Mechanism of Pentlandite at 973 K (700 °C) in Air

    NASA Astrophysics Data System (ADS)

    Zhu, Huihui; Chen, Jun; Deng, Jinxia; Yu, Ranbo; Xing, Xianran

    2012-06-01

    The oxidation behavior of synthetic pentlandite at 973 K (700 °C) under isothermal conditions was investigated. The pentlandite sample (Ni,Fe)9S8 was synthesized from pure components and oxidized at 973 K (700 °C) in air in a muffle furnace. The phase identification and components analysis of the oxidation products were performed by using the Rietveld quantitative analysis method based on the powder X-ray diffraction (XRD) profiles and scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy (SEM-EDX). The magnetic hysteresis loops were determined by a vibrating sample magnetometer. Fe2O3, Ni x Fe3- x O4, and NiO were dominant oxidation products, and their weight fractions changed in different ways along with the oxidation time. The nickel-rich phase and sulfur-rich phase were observed as intermediate phases in unreacted cores during oxidation, which led to the formation of gaps and holes. The oxidation reaction rate was rapid in the first 2 hours, and then it slowed down sharply.

  18. Experimental Behavior of Pentaborane-Air Combustion Products During Expansion in a Convergent Divergent Nozzle

    NASA Technical Reports Server (NTRS)

    Branstetter, J. R.; Setze, P. C.

    1958-01-01

    In order to evaluate the post combustion behavior of boric oxide, pentaborane-air mixtures, burned to completion at a combustor pressure of 3 atmospheres, were expanded through a 7.1-inch-long convergent-divergent nozzle having a 4-inch-diameter throat and an exit-to-throat area ratio of 1.68. The experimentally determined thrust performance was in good agreement with the ideal equilibrium performance at stagnation temperatures of 3300 deg R and lower. The boric oxide vapor at the combustor exit required about 400 F deg supercooling before any condensed phase was observed. For a given thrust, fuel consumption was as much as 20 percent greater than predicted from vapor-pressure data for combustor outlet temperatures i n the vicinity of 3600 deg R. A similar result could be expected in full-scale engines, since the test combustor provided an unusually long dwell time and a highly turbulent environment. During the expansion process, the vapor (when present) did not condense to the extent predicted for an equilibrium expansion process. Moreover, condensation was observed only i n the form of small, abrupt phase changes i n the subsonic flow near the throat. Friction, due to liquid boric oxide films on the nozzle surfaces, was negligible when the surface temperature was above 800 F.

  19. The surface cracking behavior in air plasma sprayed thermal barrier coating system incorporating interface roughness effect

    NASA Astrophysics Data System (ADS)

    Zhang, W. X.; Fan, X. L.; Wang, T. J.

    2011-11-01

    The objective of this work is to understand the effect of interface roughness on the strain energy release rate and surface cracking behavior in air plasma sprayed thermal barrier coating system. This is achieved by a parameter investigation of the interfacial shapes, in which the extended finite element method (XFEM) and periodic boundary condition are used. Predictions for the stress field and driving force of multiple surface cracks in the film/substrate system are presented. It is seen that the interface roughness has significant effects on the strain energy release rate, the interfacial stress distribution, and the crack propagation patterns. One can see the completely different distributions of stress and strain energy release rate in the regions of convex and concave asperities of the substrate. Variation of the interface asperity is responsible for the oscillatory characteristics of strain energy release rate, which can cause the local arrest of surface cracks. It is concluded that artificially created rough interface can enhance the durability of film/substrate system with multiple cracks.

  20. Exposure to Prescription Drugs Labeled for Risk of Adverse Effects of Suicidal Behavior or Ideation among 100 Air Force Personnel Who Died by Suicide, 2006-2009

    ERIC Educational Resources Information Center

    Lavigne, Jill E.; McCarthy, Michael; Chapman, Richard; Petrilla, Allison; Knox, Kerry L.

    2012-01-01

    Prescription drugs for many indications are labeled with warnings for potential risk of suicidal ideation or behavior. Exposures to prescription drugs labeled for adverse effects of suicidal behavior or ideation among 100 Air Force personnel who died by suicide between 2006 and 2009 are described. Air Force registry data were linked to…

  1. Ground-Based Remote Retrievals of Cumulus Entrainment Rates

    SciTech Connect

    Wagner, Timothy J.; Turner, David D.; Berg, Larry K.; Krueger, Steven K.

    2013-07-26

    While fractional entrainment rates for cumulus clouds have typically been derived from airborne observations, this limits the size and scope of available data sets. To increase the number of continental cumulus entrainment rate observations available for study, an algorithm for retrieving them from ground-based remote sensing observations has been developed. This algorithm, called the Entrainment Rate In Cumulus Algorithm (ERICA), uses the suite of instruments at the Southern Great Plains (SGP) site of the United States Department of Energy's Atmospheric Radiation Measurement (ARM) Climate Research Facility as inputs into a Gauss-Newton optimal estimation scheme, in which an assumed guess of the entrainment rate is iteratively adjusted through intercomparison of modeled liquid water path and cloud droplet effective radius to their observed counterparts. The forward model in this algorithm is the Explicit Mixing Parcel Model (EMPM), a cloud parcel model that treats entrainment as a series of discrete entrainment events. A quantified value for measurement uncertainty is also returned as part of the retrieval. Sensitivity testing and information content analysis demonstrate the robust nature of this method for retrieving accurate observations of the entrainment rate without the drawbacks of airborne sampling. Results from a test of ERICA on three months of shallow cumulus cloud events show significant variability of the entrainment rate of clouds in a single day and from one day to the next. The mean value of 1.06 km-¹ for the entrainment rate in this dataset corresponds well with prior observations and simulations of the entrainment rate in cumulus clouds.

  2. Percentage entrainment of constituent loads in urban runoff, south Florida

    USGS Publications Warehouse

    Miller, R.A.

    1985-01-01

    Runoff quantity and quality data from four urban basins in south Florida were analyzed to determine the entrainment of total nitrogen, total phosphorus, total carbon, chemical oxygen demand, suspended solids, and total lead within the stormwater runoff. Land use of the homogeneously developed basins are residential (single family), highway, commercial, and apartment (multifamily). A computational procedure was used to calculate, for all storms that had water-quality data, the percentage of constituent load entrainment in specified depths of runoff. The plot of percentage of constituent load entrained as a function of runoff is termed the percentage-entrainment curve. Percentage-entrainment curves were developed for three different source areas of basin runoff: (1) the hydraulically effective impervious area, (2) the contributing area, and (3) the drainage area. With basin runoff expressed in inches over the contributing area, the depth of runoff required to remove 90 percent of the constituent load ranged from about 0.4 inch to about 1.4 inches; and to remove 80 percent, from about 0.3 to 0.9 inch. Analysis of variance, using depth of runoff from the contributing area as the response variable, showed that the factor 'basin' is statistically significant, but that the factor 'constituent' is not statistically significant in the forming of the percentage-entrainment curve. Evidently the sewerage design, whether elongated or concise in plan dictates the shape of the percentage-entrainment curve. The percentage-entrainment curves for all constituents were averaged for each basin and plotted against basin runoff for three source areas of runoff-the hydraulically effective impervious area, the contributing area, and the drainage area. The relative positions of the three curves are directly related to the relative sizes of the three source areas considered. One general percentage-entrainment curve based on runoff from the contributing area was formed by averaging across

  3. Characteristics of rice husk gasification in an entrained flow reactor.

    PubMed

    Zhao, Yijun; Sun, Shaozeng; Tian, Hongming; Qian, Juan; Su, Fengming; Ling, Feng

    2009-12-01

    Experiments were performed in an entrained flow reactor to better understand the characteristics of biomass gasification. Rice husk was used in this study. Effects of the gasification temperature (700, 800, 900 and 1000 degrees C) and the equivalence ratio in the range of 0.22-0.34 on the biomass gasification and the axial gas distribution in the reactor were studied. The results showed that reactions of CnHm were less important in the gasification process except cracking reactions which occurred at higher temperature. In the oxidization zone, reactions between char and oxygen had a more prevailing role. The optimal gasification temperature of the rice husk could be above 900 degrees C, and the optimal value of ER was 0.25. The gasification process was finished in 1.42 s when the gasification temperature was above 800 degrees C. A first order kinetic model was developed for describing rice husk air gasification characteristics and the relevant kinetic parameters were determined. PMID:19589673

  4. Tropical deep convection, entrainment, and dilution during the dynamo field campaign

    NASA Astrophysics Data System (ADS)

    Hannah, Walter

    more humid environment is better explained by a reduction of buoyancy dilution. An additional sensitivity experiment shows that entrainment and dilution are enhanced when convection is organized by the presence of vertical wind shear. The enhanced dilution is associated with entrainment of drier air on average. (Abstract shortened by UMI.).

  5. Laboratory Experiments on Convective Entrainment Using a Saline Water Tank

    NASA Astrophysics Data System (ADS)

    Jonker, Harmen J. J.; Jiménez, Maria A.

    2014-06-01

    Entrainment fluxes in a shear-free convective boundary layer have been measured with a saline water tank set-up. The experiments were targeted towards measuring the entrainment behaviour for medium to high Richardson numbers and use a two-layer design, i.e. two stacked non-stratified (neutral) layers with different densities. With laser induced fluorescence (LIF), the entrainment flux of a fluorescent dye is measured for bulk Richardson numbers in the range 30-260. It is proposed that a carefully chosen combination of top-down and bottom-up processes improves the accuracy of LIF-based entrainment observations. The observed entrainment fluxes are about an order of magnitude lower than reported for thermal water tanks: the derived buoyancy entrainment ratio, , is found to be , which is to be compared with for a thermal convection tank (Deardorff et al., J Fluid Mech 100:41-64, 1980). An extensive discussion is devoted to the influence of the Reynolds and Prandtl numbers in laboratory experiments on entrainment.

  6. Numerical Investigation of Entrainment of Turbulent Dense Currents

    NASA Astrophysics Data System (ADS)

    Bhaganaagar, Kiran; Nayamatulla, Manjure

    2016-04-01

    Entrainment in dense overflows has fundamental importance for understanding the transport of densest water in the ocean. Estimation of entrainment is extremely challenging and to-date we do not have a fundamental framework that parameterizes entrainment. A highly accurate direct numerical simulation and large eddy simulation solvers have been developed to simulate dense currents over range of smooth- and rough-surfaces. Simulations have been performed for both lock-exchange currents and constant flux currents. A mathematical framework has been developed to estimate entrainment of 2-D and 3-D dense currents. Entrainment has been calculated from first-principles as the relative change in the volume of the dense current in time with respect to the buoyancy forcing that drives the dense current. A combination of threshold method, wherein the height of current is evaluated as height corresponding to the specified threshold value and sorting method, wherein, the mixed fluid is sorted into bins ranging from dense fluid at the bottom to ambient fluid at the top has been used to evaluate the interface between the dense and ambient fluid. Entrainment is sensitive to the method of evaluation of the interface height. Finally, we obtained the dependency of entrainment parameter on non-dimensional parameters. Analysis has demonstrated lock-exchange currents have less mixing and entrainment for same Reynolds number and Froude's number than constant flux currents. The differences exist due to differences in nature of Kelvin-Helmholtz instabilities and lobe-cleft currents. Rough-bottom surfaces introduces additional dynamics of the dense currents. The spacing between the roughness elements has demonstrated to be important metric in entrainment parameters for lock-exchange currents. Densely spaced (D-type) currents travel slower as roughness causes hindrance on density current propagation due to enhanced drag and produces additional eddies and instabilities compared to sparsely

  7. Direct numerical simulation of sediment entrainment in turbulent channel flow

    NASA Astrophysics Data System (ADS)

    Ji, C.; Munjiza, A.; Avital, E.; Ma, J.; Williams, J. J. R.

    2013-05-01

    In this paper, the entrainment and movement of coarse particles on the bed of an open channel is numerically investigated. Rather than model the sediment transport using a concentration concept, this study treats the sediment as individual particles and investigates the interaction between turbulent coherent structures and particle entrainment. The applied methodology is a combination of the direct numerical simulation of turbulent flow, the combined finite-discrete element modeling of particle motion and collision, and the immersed boundary method for the fluid-solid interaction. In this study, flow over a water-worked rough-bed consisting of 2-3 layers of densely packed spheres is adopted and the Shields function is 0.065 which is just above the entrainment threshold to give a bed-load regime. Numerical results for turbulent flow, sediment entrainment statistics, hydrodynamic forces acting on the particles, and the interaction between turbulence coherent structures and particle entrainment are presented. It is shown that the presence of entrained particles significantly modifies the mean velocity and turbulence quantity profiles in the vicinity of a rough-bed and that the instantaneous lift force can be larger than a particle's submerged weight in a narrow region above the effective bed location, although the mean lift force is always smaller than the submerged weight. This, from a hydrodynamic point of view, presents strong evidence for a close cause-and-effect relationship between coherent structures and sediment entrainment. Furthermore, instantaneous numerical results on particle entrainment and the surrounding turbulent flow are reported which show a strong correlation between sediment entrainment and sweep events and the underlying mechanisms are discussed.

  8. On the maximum grain size entrained by photoevaporative winds

    NASA Astrophysics Data System (ADS)

    Hutchison, Mark A.; Laibe, Guillaume; Maddison, Sarah T.

    2016-09-01

    We model the behaviour of dust grains entrained by photoevaporation-driven winds from protoplanetary discs assuming a non-rotating, plane-parallel disc. We obtain an analytic expression for the maximum entrainable grain size in extreme-UV radiation-driven winds, which we demonstrate to be proportional to the mass loss rate of the disc. When compared with our hydrodynamic simulations, the model reproduces almost all of the wind properties for the gas and dust. In typical turbulent discs, the entrained grain sizes in the wind are smaller than the theoretical maximum everywhere but the inner disc due to dust settling.

  9. Survival and behavior of Chinese mystery snails (Bellamya chinensis) in response to simulated water body drawdowns and extended air exposure

    USGS Publications Warehouse

    Unstad, Kody M.; Uden, Daniel R.; Allen, Craig R.; Chaine, Noelle M.; Haak, Danielle M.; Kill, Robert A.; Pope, Kevin L.; Stephen, Bruce J.; Wong, Alec

    2013-01-01

    Nonnative invasive mollusks degrade aquatic ecosystems and induce economic losses worldwide. Extended air exposure through water body drawdown is one management action used for control. In North America, the Chinese mystery snail (Bellamya chinensis) is an invasive aquatic snail with an expanding range, but eradication methods for this species are not well documented. We assessed the ability of B. chinensis to survive different durations of air exposure, and observed behavioral responses prior to, during, and following desiccation events. Individual B. chinensis specimens survived air exposure in a laboratory setting for > 9 weeks, and survivorship was greater among adults than juveniles. Several B. chinensis specimens responded to desiccation by sealing their opercula and/or burrowing in mud substrate. Our results indicate that drawdowns alone may not be an effective means of eliminating B. chinensis. This study lays the groundwork for future management research that may determine the effectiveness of drawdowns when combined with factors such as extreme temperatures, predation, or molluscicides.

  10. Scaling in the Transition from Selective Withdrawal to Viscous Entrainment

    NASA Astrophysics Data System (ADS)

    Pommer, Chris; Harris, Michael; Basaran, Osman

    2011-11-01

    In selective withdrawal, fluid is withdrawn through a tube that has its tip suspended a distance S above a flat interface separating two fluids. When the withdrawal rate Q is low, the interface forms a steady-state hump and only the upper fluid is withdrawn. When Q is increased (or S decreased), the interface undergoes a topological transition so that the lower fluid is entrained with the upper one, forming a steady-state spout. Here, this discontinuous transition is analyzed computationally when both fluids are incompressible and Newtonian. The numerical method employed is an implicit method of lines ALE algorithm which uses finite elements with elliptic mesh generation. The new approach neither starts with a priori idealizations, as has been the case with previous computations, nor is limited to length scales above that set by the wavelength of visible light as in any experimental study. In particular, it is shown that the critical withdrawal rate at which the aforementioned transition occurs scales with the nozzle separation raised to some power n. A study of the effect of the physical parameters of the system on the scaling behavior is also presented.

  11. Organic Entrainment and Preservation in Volcanic Glasses

    NASA Technical Reports Server (NTRS)

    Wilhelm, Mary Beth; Ojha, Lujendra; Brunner, Anna E.; Dufek, Josef D.; Wray, James Joseph

    2014-01-01

    Unaltered pyroclastic deposits have previously been deemed to have "low" potential for the formation, concentration and preservation of organic material on the Martian surface. Yet volcanic glasses that have solidified very quickly after an eruption may be good candidates for containment and preservation of refractory organic material that existed in a biologic system pre-eruption due to their impermeability and ability to attenuate UV radiation. Analysis using NanoSIMS of volcanic glass could then be performed to both deduce carbon isotope ratios that indicate biologic origin and confirm entrainment during eruption. Terrestrial contamination is one of the biggest barriers to definitive Martian organic identification in soil and rock samples. While there is a greater potential to concentrate organics in sedimentary strata, volcanic glasses may better encapsulate and preserve organics over long time scales, and are widespread on Mars. If volcanic glass from many sites on Earth could be shown to contain biologically derived organics from the original environment, there could be significant implications for the search for biomarkers in ancient Martian environments.

  12. The Huygens entrainment phenomenon and thermoacoustic engines

    PubMed

    Spoor; Swift

    2000-08-01

    The earliest known reference to the mode-locking, or entrainment, of two maintained oscillators is Christiaan Huygens' description of two pendulum clocks "falling into synchrony" when hung on the same wall. We describe an analogous phenomenon in acoustics-the mode-locking of two thermoacoustic engines which have their cases rigidly welded together, but which are otherwise uncoupled. This "mass-coupling" might compete with acoustic coupling when the latter is used to enforce antiphase mode-locking in such engines, for vibration cancellation. A simple theory relating the phase difference between the engines in the locked state to the corresponding ratio of their pressure amplitudes is in excellent agreement with theory and numerical simulations. The theory's prediction relating the phase difference to the engines' natural frequency difference is qualitatively confirmed by experiment, despite larger experimental uncertainties. The mass coupling is relatively weak compared to the aforementioned acoustic coupling, and in general occurs in antiphase, so we conclude that mass coupling will not interfere with vibration cancellation by acoustic coupling in most circumstances. PMID:10955624

  13. Speech entrainment compensates for Broca's area damage.

    PubMed

    Fridriksson, Julius; Basilakos, Alexandra; Hickok, Gregory; Bonilha, Leonardo; Rorden, Chris

    2015-08-01

    Speech entrainment (SE), the online mimicking of an audiovisual speech model, has been shown to increase speech fluency in patients with Broca's aphasia. However, not all individuals with aphasia benefit from SE. The purpose of this study was to identify patterns of cortical damage that predict a positive response SE's fluency-inducing effects. Forty-four chronic patients with left hemisphere stroke (15 female) were included in this study. Participants completed two tasks: 1) spontaneous speech production, and 2) audiovisual SE. Number of different words per minute was calculated as a speech output measure for each task, with the difference between SE and spontaneous speech conditions yielding a measure of fluency improvement. Voxel-wise lesion-symptom mapping (VLSM) was used to relate the number of different words per minute for spontaneous speech, SE, and SE-related improvement to patterns of brain damage in order to predict lesion locations associated with the fluency-inducing response to SE. Individuals with Broca's aphasia demonstrated a significant increase in different words per minute during SE versus spontaneous speech. A similar pattern of improvement was not seen in patients with other types of aphasia. VLSM analysis revealed damage to the inferior frontal gyrus predicted this response. Results suggest that SE exerts its fluency-inducing effects by providing a surrogate target for speech production via internal monitoring processes. Clinically, these results add further support for the use of SE to improve speech production and may help select patients for SE treatment. PMID:25989443

  14. Music and emotions: from enchantment to entrainment.

    PubMed

    Vuilleumier, Patrik; Trost, Wiebke

    2015-03-01

    Producing and perceiving music engage a wide range of sensorimotor, cognitive, and emotional processes. Emotions are a central feature of the enjoyment of music, with a large variety of affective states consistently reported by people while listening to music. However, besides joy or sadness, music often elicits feelings of wonder, nostalgia, or tenderness, which do not correspond to emotion categories typically studied in neuroscience and whose neural substrates remain largely unknown. Here we review the similarities and differences in the neural substrates underlying these "complex" music-evoked emotions relative to other more "basic" emotional experiences. We suggest that these emotions emerge through a combination of activation in emotional and motivational brain systems (e.g., including reward pathways) that confer its valence to music, with activation in several other areas outside emotional systems, including motor, attention, or memory-related regions. We then discuss the neural substrates underlying the entrainment of cognitive and motor processes by music and their relation to affective experience. These effects have important implications for the potential therapeutic use of music in neurological or psychiatric diseases, particularly those associated with motor, attention, or affective disturbances. PMID:25773637

  15. Granular motions near the threshold of entrainment

    NASA Astrophysics Data System (ADS)

    Valyrakis, Manousos; Alexakis, athanasios-Theodosios

    2016-04-01

    Our society is continuously impacted by significant weather events many times resulting in catastrophes that interrupt our normal way of life. In the context of climate change and increasing urbanisation these "extreme" hydrologic events are intensified both in magnitude and frequency, inducing costs of the order of billions of pounds. The vast majority of such costs and impacts (even more to developed societies) are due to water related catastrophes such as the geomorphic action of flowing water (including scouring of critical infrastructure, bed and bank destabilisation) and flooding. New tools and radically novel concepts are in need, to enable our society becoming more resilient. This presentation, emphasises the utility of inertial sensors in gaining new insights on the interaction of flow hydrodynamics with the granular surface at the particle scale and for near threshold flow conditions. In particular, new designs of the "smart-sphere" device are discussed with focus on the purpose specific sets of flume experiments, designed to identify the exact response of the particle resting at the bed surface for various below, near and above threshold flow conditions. New sets of measurements are presented for particle entrainment from a Lagrangian viewpoint. Further to finding direct application in addressing real world challenges in the water sector, it is shown that such novel sensor systems can also help the research community (both experimentalists and computational modellers) gain a better insight on the underlying processes governing granular dynamics.

  16. Controlled electrochemical etching of nanoporous Si anodes and its discharge behavior in alkaline Si-air batteries.

    PubMed

    Park, Dong-Won; Kim, Soeun; Ocon, Joey D; Abrenica, Graniel Harne A; Lee, Jae Kwang; Lee, Jaeyoung

    2015-02-11

    We report the fabrication of nanoporous silicon (nPSi) electrodes via electrochemical etching to form a porous Si layer with controllable thickness and pore size. Varying the etching time and ethanolic HF concentration results in different surface morphologies, with various degrees of electrolyte access depending on the pore characteristics. Optimizing the etching condition leads to well-developed nPSi electrodes, which have thick porous layers and smaller pore diameter and exhibit improved discharge behavior as anodes in alkaline Si-air cells in contrast to flat Si anode. Although electrochemical etching is effective in improving the interfacial characteristics of Si in terms of high surface area, we observed that mild anodization occurs and produces an oxide overlayer. We then show that this oxide layer in nPSi anodes can be effectively removed to produce an nPSi anode with good discharge behavior in an actual alkaline Si-air cell. In the future, the combination of high surface area nPSi anodes with nonaqueous electrolytes (e.g., room-temperature ionic liquid electrolyte) to minimize the strong passivation behavior and self-discharge in Si could lead to Si-air cells with a stable voltage profile and high anode utilization. PMID:25594400

  17. High cycle fatigue behavior of implant Ti-6Al-4V in air and simulated body fluid.

    PubMed

    Liu, Yong-jie; Cui, Shi-ming; He, Chao; Li, Jiu-kai; Wang, Qing-yuan

    2014-01-01

    Ti-6Al-4V implants that function as artificial joints are usually subjected to long-term cyclic loading. To study long-term fatigue behaviors of implant Ti-6Al-4V in vitro and in vivo conditions exceeding 107 cycles, constant stress amplitude fatigue experiments were carried out at ultrasonic frequency (20 kHz) with two different surface conditions (ground and polished) in ambient air and in a simulated body fluid. The initiation mechanisms of fatigue cracks were investigated with scanning electron microscopy. Improvement of fatigue strength is pronounced for polished specimens below 106 cycles in ambient air since fatigue cracks are initiated from surfaces of specimens. While the cycles exceed 106, surface conditions have no effect on fatigue behaviors because the defects located within the specimens become favorable sites for crack initiation. The endurance limit at 108 cycles of polished Ti-6Al-4V specimens decreases by 7% if it is cycled in simulated body fluid instead of ambient air. Fracture surfaces show that fatigue failure is initiated from surfaces in simulated body fluid. Surface improvement has a beneficial effect on fatigue behaviors of Ti-6Al-4V at high stress amplitudes. The fatigue properties of Ti-6Al-4V deteriorate and the mean endurance limits decrease significantly in simulated body fluid. PMID:24211906

  18. A comparative efficacy study of photic driving brainwave entrainment technology with a novel form of more direct entrainment

    NASA Astrophysics Data System (ADS)

    Knowles, Richard Thomas

    This exploratory study compared the efficacy of a novel brainwave electromagnetic (EM) entrainment technology against a more conventional technology utilizing the photic-driving technique. Both experimental conditions were also compared with a 7-minute control session that took place immediately before each stimulation session. The Schumann Resonance (SR) frequency was selected as the delivery signal and was chosen because of previous findings suggesting that entrainment to this frequency can often produce transpersonal if not paranormal, experiences in the entrainee, which sometimes resemble remote viewing or out-of-body experiences. A pilot study determined which of two novel entrainment modalities (a copper coil or a 16-solenoid headset) worked most effectively for use with the rest of the study. In the main study, an artificial SR signal at 7.8Hz was delivered during the photic-driving sessions, but a recording of the real-time SR was used to deliver the entrainment signal during sessions devoted to the electromagnetic entrainment modality. Sixteen participants were recruited from the local area, and EEG recordings were acquired via a 32-channel Deymed electroencephalography system. Comparative analyses were performed between the control and experimental portions of each session to assess for efficacy of the novel entrainment modality used, and, in the main study, between the electromagnetic and photic-driving sessions, to assess for differential entrainment efficacy between these groups. A follow-up study was additionally performed primarily to determine whether responders could replicate their entrainment effect from the main study. Results showed that EM entrainment appeared to be possible but is not nearly as robust or reliable as photic driving. Additionally, no profound transpersonal or paranormal experiences were elicited during the course of the study, and, when asked, participants were not able to determine with any degree of success, when the

  19. Estimating rates of debris flow entrainment from ground vibrations

    NASA Astrophysics Data System (ADS)

    Kean, J. W.; Coe, J. A.; Coviello, V.; Smith, J. B.; McCoy, S. W.; Arattano, M.

    2015-08-01

    Debris flows generate seismic waves as they travel downslope and can become more dangerous as they entrain sediment along their path. We present field observations that show a systematic relation between the magnitude of seismic waves and the amount of erodible sediment beneath the flow. Specifically, we observe that a debris flow traveling along a channel filled initially with sediment 0.34 m thick generates about 2 orders of magnitude less spectral power than a similar-sized flow over the same channel without sediment fill. We adapt a model from fluvial seismology to explain this observation and then invert it to estimate the level of bed sediment (and rate of entrainment) beneath a passing series of surges. Our estimates compare favorably with previous direct measurements of entrainment rates at the site, suggesting the approach may be a new indirect way to obtain rare field constraints needed to test models of debris flow entrainment.

  20. Entrainment of a Synthetic Oscillator through Queueing Coupling

    NASA Astrophysics Data System (ADS)

    Hochendoner, Philip; Mather, William; Butzin, Nicholas; Ogle, Curtis

    2014-03-01

    Many biological systems naturally exhibit (often noisy) oscillatory patterns that are capable of being entrained by external stimuli, though the mechanism of entrainment is typically obscured by the complexity of native networks. A synthetic biology approach, where genetic programs are wired ``by hand,'' has proven useful in this regard. In the present study, we use a synthetic oscillator in Escherichia coli to demonstrate a novel and potentially widespread mechanism for biological entrainment: competition of proteins for degradation by common pathway, i.e. a entrainment by a bottleneck. To faithfully represent the discrete and stochastic nature of this bottleneck, we leverage results from a recent biological queueing theory, where in particular, the queueing theoretic concept of workload is discovered to simplify the analysis. NSF Award 1330180.

  1. How coupling determines the entrainment of circadian clocks

    NASA Astrophysics Data System (ADS)

    Bordyugov, G.; Granada, A. E.; Herzel, H.

    2011-08-01

    Autonomous circadian clocks drive daily rhythms in physiology and behaviour. A network of coupled neurons, the suprachiasmatic nucleus (SCN), serves as a robust self-sustained circadian pacemaker. Synchronization of this timer to the environmental light-dark cycle is crucial for an organism's fitness. In a recent theoretical and experimental study it was shown that coupling governs the entrainment range of circadian clocks. We apply the theory of coupled oscillators to analyse how diffusive and mean-field coupling affects the entrainment range of interacting cells. Mean-field coupling leads to amplitude expansion of weak oscillators and, as a result, reduces the entrainment range. We also show that coupling determines the rigidity of the synchronized SCN network, i.e. the relaxation rates upon perturbation. Our simulations and analytical calculations using generic oscillator models help to elucidate how coupling determines the entrainment of the SCN. Our theoretical framework helps to interpret experimental data.

  2. Small-scale processes and entrainment in a stratocumulus marine boundary layer

    SciTech Connect

    Stevens, D.E.; Bell, J.B.; Almgren, A.S.; Beckner, V.E.; Rendleman, C.A.

    2000-02-15

    Numerical studies of boundary layer meteorology are increasingly reliant on large eddy simulation (LES) models, but few detailed validation studies of these types of models have been done. In this paper, the authors investigate the behavior of an LES model for simulation of a marine boundary layer. Specifically, the authors focus on the mechanisms that control numerical predictions of entrainment into the tops of marine stratus in a moist generalization of the 1995 Global Energy and Water Cycle Experiment Cloud System Studies model intercomparison. For the computational study the authors present a sequence of simulations of varying resolution, from a typical resolution (50 m horizontal and 25 m vertical mesh size) to a fine resolution (8 m horizontal and 4 m vertical mesh size). The authors also explore variations in the model such as different subgrid models and modifications of the advection scheme. It was found that the thickness of the inversion, the depth of entraining eddies, and the shape of vertical velocity spectra were determined mainly by the mesh spacing used. However, the entrainment rate was found to have a distinct dependence on the amount of combined numerical and subgrid-scale mixing. This indicates that the use of large eddy simulation to study mixing in stratocumulus boundary layers needs to account for both sources of mixing.

  3. Entrainment Ranges for Chains of Forced Neural and Phase Oscillators.

    PubMed

    Massarelli, Nicole; Clapp, Geoffrey; Hoffman, Kathleen; Kiemel, Tim

    2016-12-01

    Sensory input to the lamprey central pattern generator (CPG) for locomotion is known to have a significant role in modulating lamprey swimming. Lamprey CPGs are known to have the ability to entrain to a bending stimulus, that is, in the presence of a rhythmic signal, the CPG will change its frequency to match the stimulus frequency. Bending experiments in which the lamprey spinal cord has been removed and mechanically bent back and forth at a single point have been used to determine the range of frequencies that can entrain the CPG rhythm. First, we model the lamprey locomotor CPG as a chain of neural oscillators with three classes of neurons and sinusoidal forcing representing edge cell input. We derive a phase model using the connections described in the neural model. This results in a simpler model yet maintains some properties of the neural model. For both the neural model and the derived phase model, entrainment ranges are computed for forcing at different points along the chain while varying both intersegmental coupling strength and the coupling strength between the forcer and chain. Entrainment ranges for chains with nonuniform intersegmental coupling asymmetry are larger when forcing is applied to the middle of the chain than when it is applied to either end, a result that is qualitatively similar to the experimental results. In the limit of weak coupling in the chain, the entrainment results of the neural model approach the entrainment results for the derived phase model. Both biological experiments and the robustness of non-monotonic entrainment ranges as a function of the forcing position across different classes of CPG models with nonuniform asymmetric coupling suggest that a specific property of the intersegmental coupling of the CPG is key to entrainment. PMID:27091694

  4. A parameterization of the depth of the entrainment zone

    NASA Technical Reports Server (NTRS)

    Boers, Reinout

    1989-01-01

    A theory of the parameterization of the entrainment zone depth has been developed based on conservation of energy. This theory suggests that the normalized entrainment zone depth is proportional to the inverse square root of the Richardson number. A comparison of this theory with atmospheric observations indicates excellent agreement. It does not adequately predict the laboratory data, although it improves on parcel theory, which is based on a momentum balance.

  5. Differential Entrainment of Neuroelectric Delta Oscillations in Developmental Dyslexia

    PubMed Central

    Soltész, Fruzsina; Szűcs, Denes; Leong, Victoria; White, Sonia; Goswami, Usha

    2013-01-01

    Oscillatory entrainment to the speech signal is important for language processing, but has not yet been studied in developmental disorders of language. Developmental dyslexia, a difficulty in acquiring efficient reading skills linked to difficulties with phonology (the sound structure of language), has been associated with behavioural entrainment deficits. It has been proposed that the phonological ‘deficit’ that characterises dyslexia across languages is related to impaired auditory entrainment to speech at lower frequencies via neuroelectric oscillations (<10 Hz, ‘temporal sampling theory’). Impaired entrainment to temporal modulations at lower frequencies would affect the recovery of the prosodic and syllabic structure of speech. Here we investigated event-related oscillatory EEG activity and contingent negative variation (CNV) to auditory rhythmic tone streams delivered at frequencies within the delta band (2 Hz, 1.5 Hz), relevant to sampling stressed syllables in speech. Given prior behavioural entrainment findings at these rates, we predicted functionally atypical entrainment of delta oscillations in dyslexia. Participants performed a rhythmic expectancy task, detecting occasional white noise targets interspersed with tones occurring regularly at rates of 2 Hz or 1.5 Hz. Both groups showed significant entrainment of delta oscillations to the rhythmic stimulus stream, however the strength of inter-trial delta phase coherence (ITC, ‘phase locking’) and the CNV were both significantly weaker in dyslexics, suggestive of weaker entrainment and less preparatory brain activity. Both ITC strength and CNV amplitude were significantly related to individual differences in language processing and reading. Additionally, the instantaneous phase of prestimulus delta oscillation predicted behavioural responding (response time) for control participants only. PMID:24204644

  6. Entrainment and detrainment in a simple cumulus cloud model

    NASA Technical Reports Server (NTRS)

    Randall, D. A.; Huffman, G. J.

    1982-01-01

    A cumulus cloud model, analogous to the mixed-layer models of the planetary boundary layer and the upper ocean, is developed using a single, unitary entrainment process in which the motion of the cloud boundary relative to the mean flow is permitted, produced, and controlled by turbulent processes. An alternate theory to the mixing-length theory of Asai and Kasahara (1967) is proposed which completely removes the strong scale-dependence of the Asai-Kasahara model. The model reintroduces scale-dependence by introducing including the pe5turbation pressure term of the equation of vertical motion. It is shown that the model predicts deeper clouds than the Asai-Kasahara model for a given sounding, due to the entrainment assumption and the effects of the perturbation pressure. Lateral entrainment dominates cloud-top entrainment, although finite-difference errors increase the cloud-top entrainment rate from zero to a positive value in actual situations. The fractional entrainment rate for updrafts is determined to vary only slightly with height and to decrease only slowly as the cloud radius increases, while the fractional detrainment rate for updrafts increases with height.

  7. Stress and physiological, behavioral and performance patterns of children under varied air ion levels

    NASA Astrophysics Data System (ADS)

    Fornof, K. T.; Gilbert, G. O.

    1988-12-01

    The possibility that individual differences in reactivity to stressors are a major factor underlying discordant results reported for air ion studies prompted an investigation of response patterns in school children under both normal indoor air ion levels and moderately increased negative air ion levels (4000±500/cm3). It was hypothesized that the impact of stressors is reduced with high negative air ionization, and that resultant changes in stress effects would be differentially exhibited according to the children's normal degree of stimulus reactivity. A counter-balanced, replicative, withinssubject design was selected, and the subjects were 12 environmentally sensitive, 1st 4th grade school children. In addition to monitoring stress effects on activity level, attention span, concentration to task and conceptual performance, measures were also made of urinary 5-hydroxyindole acetic acid levels and skin resistance response (SRR) to determine if changes extended to the physiological state. The cold water test was used to add physical stress and enable calculations of Lacey's autonomic lability scores (ALS) as indicators of individual reactivity. The results show main effects for air ions on both physiological parameters, with 48% less change in %SRR ( P<0.01) and 46% less change in urinary 5-HIAA levels ( P<0.055) during negative air ions, indicating increased stress tolerance. Strong interactive effects for ALS x air ion condition appeared, with high and low ALS children reacting oppositely to negative air ions in measures of skin resistance level ( P<0.01), wrist activity ( P<0.01) and digit span backwards ( P<0.004). Thus individual differences in autonomic reactivity and the presence or absence of stressors appear as critical elements for internal validity, and in preventing consequent skewed results from obscuring progress in air ion research.

  8. Mammalian target of rapamycin signaling modulates photic entrainment of the suprachiasmatic circadian clock

    PubMed Central

    Cao, Ruifeng; Li, Aiqing; Cho, Hee-yeon; Lee, Boyoung; Obrietan, Karl

    2010-01-01

    Inducible gene expression appears to be an essential event that couples light to entrainment of the master mammalian circadian clock located in the suprachiasmatic nucleus (SCN) of the hypothalamus. Recently, we reported that light triggers phase-dependent activation of the mammalian target of rapamycin (mTOR) signaling pathway, a major regulator of protein synthesis, in the SCN, thus raising the possibility that mTOR-evoked mRNA translation contributes to clock entrainment. Here, we employed a combination of cellular, molecular and behavioral assays to address this question. To this end, we show that the in vivo infusion of the mTOR inhibitor rapamycin led to a significant attenuation of the phase-delaying effect of early night light. Conversely, disruption of mTOR during the late night augmented the phase-advancing effect of light. To assess the role of mTOR signaling within the context of molecular entrainment, the effects of rapamycin on light-induced expression of PERIOD1 and PERIOD2 were examined. At both the early and late night time points, abrogation of mTOR signaling led to a significant attenuation of light-evoked PERIOD protein expression. Our results also reveal that light-induced mTOR activation leads to translation of mRNAs with a 5′-terminal oligopyrimidine tract such as eukaryotic elongation factor 1 A (eEF1A) and the immediate early gene JunB. Together, these data indicate that the mTOR pathway functions as potent and selective regulator of light-evoked protein translation and SCN clock entrainment. PMID:20445056

  9. Entrapped air bubbles in piezo-driven inkjet printing: Their effect on the droplet velocity

    NASA Astrophysics Data System (ADS)

    de Jong, Jos; Jeurissen, Roger; Borel, Huub; van den Berg, Marc; Wijshoff, Herman; Reinten, Hans; Versluis, Michel; Prosperetti, Andrea; Lohse, Detlef

    2006-12-01

    Air bubbles entrapped in the ink channel are a major problem in piezo-driven inkjet printing. They grow by rectified diffusion and eventually counteract the pressure buildup at the nozzle, leading to a breakdown of the jetting process. Experimental results on the droplet velocity udrop as a function of the equilibrium radius R0 of the entrained bubble are presented. Surprisingly, udrop(R0) shows a pronounced maximum around R0=17μm before it sharply drops to zero around R0=19μm. A simple one-dimensional model is introduced to describe this counterintuitive behavior which turns out to be a resonance effect of the entrained bubble.

  10. Laboratory experiments on stability and entrainment of oceanic stratocumulus. Part 2: Entrainment experiment

    NASA Technical Reports Server (NTRS)

    Shy, Shenqyang S.

    1990-01-01

    A stratified interface is stable to the buoyancy reversal instability for surprisingly large values of D (buoyancy reversal parameter). A new instability mechanism is proposed, which considers the mixing process at the interface. For the type of density curves studied here, under strong perturbations, the mixed parcel must have a buoyancy reversal comparable to the initial stratification before the interface is unstable. This is in accord with a simple model of the interface mixing process, as well as aircraft observations of long-live marine stratocumulus clouds. These clouds' remarkable longevity in the face of finite D indicates that they can be stable (Hanson, 1984; Albrecht et al., 1985; Siems et al., 1989). It is suggested that buoyancy reversal as well as the disturbance must be large for Cloudtop Entrainment Stability. The effect of buoyancy reversal (evaporative cooling) does not always enhance the entrainment rate over that in the inert case, but it may be negligible if Ri (Richardson number) is large (Ri is larger than 50) and D is small (D is smaller than 0.5). This work may shed some light on the fundamental mechanism of the breakup process of the subtropical stratocumulus clouds into tradewind cumulus. These results may also be related to the instability in the Weddell Sea off of Antarctica.

  11. Self-consistent models of basal entrainment in snow avalanches (Invited)

    NASA Astrophysics Data System (ADS)

    Issler, D.; Jóhannesson, T.

    2013-12-01

    Observations indicate that the highest erosion rates in snow avalanches usually occur at the very front of the flow. Despite lower erosion rates, basal entrainment may give a similar contribution to the mass balance due to the extended area over which it occurs. For physical reasons, the erosion rate must be determined uniquely by the properties of the snow-cover and the dynamic characteristics of the flow. However, current entrainment models typically contain adjustable parameters whose relation to the snow-cover and flow characteristics remains elusive. In order to shed some light on this question, the dynamics of basal erosion and entrainment is studied in a simplified setting, assuming perfectly brittle behavior of the snow cover: It breaks instantaneously when the shear stress exceeds its shear strength, but no work is expended thereby. A consequence of this assumption is that the shear stress at the top of the snow cover remains locked at this value whenever erosion occurs. Many current avalanche flow models explixcitly or implicitly assume that all shear is concentrated at the interface. It is shown how this assumption together with the brittleness assumption stated above implies a simple explicit formula for the erosion rate as a function of the flow velocity, normal stress at the interface, and shear strength of the snow cover. The velocity dependence of the erosion rate is determined by the form of the assumed friction law. There are no adjustable parameters, yet the model gives erosion rates consistent with observations if the Voellmy friction law is assumed. For flows with non-uniform velocity profile, a quasi-stationary flow configuration is studied, in which the flow height is artificially held constant by skimming off material from the avalanche surface at the same rate as it is entrained from the snow cover. Assuming a value for the erosion rate, the resulting ODE can be solved explicitly for Binghamian fluids and numerically for non

  12. Tensile behavior of Inconel alloy X-750 in air and vacuum at elevated temperatures

    SciTech Connect

    Taplin, D.M.R.; Mukherjee, A.K.; Pandey, M.C.

    1984-09-01

    The hot tensile properties of Inconel alloy X-750 have been investigated experimentally at 700 C in air and vacuum at strain rates varying from 10 to the -7th to 1.2 x 10 to the -6th per s. The strength and ductile characteristics of the specimens tested in vacuum are found to be better than those tested in air. In air, a ductility minimum is observed at 625 C, whereas in vacuum, significant improvements in creep ductility are observed at 575 and 625 C, with the ductility minimum shifting from 625 to 700 C. It is shown that the creep ductility of the specimens tested in air is largely determined by the following two competing processes: (1) deformation-assisted oxygen diffusion and (2) grain boundary migration. 20 references.

  13. Traffic-Related Air Pollution, Noise at School, and Behavioral Problems in Barcelona Schoolchildren: A Cross-Sectional Study

    PubMed Central

    Forns, Joan; Dadvand, Payam; Foraster, Maria; Alvarez-Pedrerol, Mar; Rivas, Ioar; López-Vicente, Mònica; Suades-Gonzalez, Elisabet; Garcia-Esteban, Raquel; Esnaola, Mikel; Cirach, Marta; Grellier, James; Basagaña, Xavier; Querol, Xavier; Guxens, Mònica; Nieuwenhuijsen, Mark J.; Sunyer, Jordi

    2015-01-01

    Background: The available evidence of the effects of air pollution and noise on behavioral development is limited, and it overlooks exposure at schools, where children spend a considerable amount of time. Objective: We aimed to investigate the associations of exposure to traffic-related air pollutants (TRAPs) and noise at school on behavioral development of schoolchildren. Methods: We evaluated children 7–11 years of age in Barcelona (Catalonia, Spain) during 2012–2013 within the BREATHE project. Indoor and outdoor concentrations of elemental carbon (EC), black carbon (BC), and nitrogen dioxide (NO2) were measured at schools in two separate 1-week campaigns. In one campaign we also measured noise levels inside classrooms. Parents filled out the strengths and difficulties questionnaire (SDQ) to assess child behavioral development, while teachers completed the attention deficit/hyperactivity disorder criteria of the DSM-IV (ADHD-DSM-IV) list to assess specific ADHD symptomatology. Negative binomial mixed-effects models were used to estimate associations between the exposures and behavioral development scores. Results: Interquartile range (IQR) increases in indoor and outdoor EC, BC, and NO2 concentrations were positively associated with SDQ total difficulties scores (suggesting more frequent behavioral problems) in adjusted multivariate models, whereas noise was significantly associated with ADHD-DSM-IV scores. Conclusion: In our study population of 7- to 11-year-old children residing in Barcelona, exposure to TRAPs at school was associated with increased behavioral problems in schoolchildren. Noise exposure at school was associated with more ADHD symptoms. Citation: Forns J, Dadvand P, Foraster M, Alvarez-Pedrerol M, Rivas I, López-Vicente M, Suades-Gonzalez E, Garcia-Esteban R, Esnaola M, Cirach M, Grellier J, Basagaña X, Querol X, Guxens M, Nieuwenhuijsen MJ, Sunyer J. 2016. Traffic-related air pollution, noise at school, and behavioral problems in Barcelona

  14. The behavior of NaOH at the air-water interface, a computational study

    SciTech Connect

    Wick, Collin D.; Dang, Liem X.

    2010-07-14

    Molecular dynamics simulations with a polarizable multi-state empirical valence bond model were carried out to investigate NaOH dissociation and pairing in water bulk and at the air-water interface. It was found that NaOH readily dissociates in the bulk, and the effect of the air-water interface on NaOH dissociation is fairly minor. Also, NaOH complexes were found to be strongly repelled from the air-water interface, which is consistent with surface tension measurements. At the same time, a very strong preference for the hydroxide anion to be oriented towards the air was found that persisted a few angstroms towards the liquid from the Gibbs dividing surface of the air-water interface. This was due to a preference for the hydroxide anion to have its hydrogen pointing towards the air, and the fact that the sodium ion was more likely to be found near the hydroxide oxygen than hydrogen. As a consequence, the simulation results show that surfaces of NaOH solutions should be negatively charged, in agreement with experimental observations, but also that the hydroxide has little surface affinity. This provides the possibility that the surface of water can be devoid of hydroxide anions, but still have a strong negative charge. This work was supported by the US Department of Energy Basic Energy Sciences' Chemical Sciences, Geosciences & Biosciences Division. Pacific Northwest National Laboratory is operated by Battelle for the US Department of Energy.

  15. Turning Off Entrainment: The Role of Particle Size Distributions and Vent GeometryIn The Collapse of Volcanic Jets

    NASA Astrophysics Data System (ADS)

    Jessop, D.; Jellinek, M.; Roche, O.

    2014-12-01

    Volcanic jets can undergo gravitational collapse to produce pyroclastic density currents (PDCs), or loft material several tens of kilometres and spread out as an ash cloud. The key ingredient that determines which of these two phenomena will occur is the turbulent entrainment of atmospheric air, which adds buoyancy to the jet. Classical models of eruption columns assume that the rate of entrainment is fixed and ~10% of the upflow rate of the jet. In particular, the efficiency of entrainment is assumed to be independent of the vent shape as well as the physical properties of the pyroclastic mixture. However, we show that the presence of particles of certain particle-size distributions (PSDs) in the jet can have a significant effect on the entrainment rate owing to their buoyancy and inertia. As a consequence, the conditions for collapse as previously identified must be revisited. In particular, there is a possibility for an eruption to produce both a buoyant column and a collapsing fountain. Using scaled analogue experiments, we test the likelyhood of collapse and the production of pyroclastic flows according to the source geometry and particle-size distributions.

  16. Human activity under high pressure: A case study on fluctuation scaling of air traffic controller's communication behaviors

    NASA Astrophysics Data System (ADS)

    Wang, Yanjun; Zhang, Qiqian; Zhu, Chenping; Hu, Minghua; Duong, Vu

    2016-01-01

    Recent human dynamics research has unmasked astonishing statistical characteristics such as scaling behaviors in human daily activities. However, less is known about the general mechanism that governs the task-specific activities. In particular, whether scaling law exists in human activities under high pressure remains an open question. In air traffic management system, safety is the most important factor to be concerned by air traffic controllers who always work under high pressure, which provides a unique platform to study human activity. Here we extend fluctuation scaling method to study air traffic controller's communication activity by investigating two empirical communication datasets. Taken the number of controlled flights as the size-like parameter, we show that the relationships between the average communication activity and its standard deviation in both datasets can be well described by Taylor's power law, with scaling exponent α ≈ 0.77 ± 0.01 for the real operational data and α ≈ 0.54 ± 0.01 for the real-time training data. The difference between the exponents suggests that human dynamics under pressure is more likely dominated by the exogenous force. Our findings may lead to further understanding of human behavior.

  17. Final Report - "Foaming and Antifoaming and Gas Entrainment in Radioactive Waste Pretreatment and Immobilization Processes"

    SciTech Connect

    Wasan, Darsh T.

    2007-10-09

    The Savannah River Site (SRS) and Hanford site are in the process of stabilizing millions of gallons of radioactive waste slurries remaining from production of nuclear materials for the Department of Energy (DOE). The Defense Waste Processing Facility (DWPF) at SRS is currently vitrifying the waste in borosilicate glass, while the facilities at the Hanford site are in the construction phase. Both processes utilize slurry-fed joule-heated melters to vitrify the waste slurries. The DWPF has experienced difficulty during operations. The cause of the operational problems has been attributed to foaming, gas entrainment and the rheological properties of the process slurries. The rheological properties of the waste slurries limit the total solids content that can be processed by the remote equipment during the pretreatment and meter feed processes. Highly viscous material can lead to air entrainment during agitation and difficulties with pump operations. Excessive foaming in waste evaporators can cause carryover of radionuclides and non-radioactive waste to the condensate system. Experimental and theoretical investigations of the surface phenomena, suspension rheology and bubble generation of interactions that lead to foaming and air entrainment problems in the DOE High Level and Low Activity Radioactive Waste separation and immobilization processes were pursued under this project. The first major task accomplished in the grant proposal involved development of a theoretical model of the phenomenon of foaming in a three-phase gas-liquid-solid slurry system. This work was presented in a recently completed Ph.D. thesis (9). The second major task involved the investigation of the inter-particle interaction and microstructure formation in a model slurry by the batch sedimentation method. Both experiments and modeling studies were carried out. The results were presented in a recently completed Ph.D. thesis. The third task involved the use of laser confocal microscopy to study

  18. VORTEX CREEP AGAINST TOROIDAL FLUX LINES, CRUSTAL ENTRAINMENT, AND PULSAR GLITCHES

    SciTech Connect

    Gügercinoğlu, Erbil; Alpar, M. Ali E-mail: alpar@sabanciuniv.edu

    2014-06-10

    A region of toroidally oriented quantized flux lines must exist in the proton superconductor in the core of the neutron star. This region will be a site of vortex pinning and creep. Entrainment of the neutron superfluid with the crustal lattice leads to a requirement of superfluid moment of inertia associated with vortex creep in excess of the available crustal moment of inertia. This will bring about constraints on the equation of state. The toroidal flux region provides the moment of inertia necessary to complement the crust superfluid with postglitch relaxation behavior fitting the observations.

  19. Flame deformation and entrainment associated with an isothermal transverse fuel jet

    NASA Technical Reports Server (NTRS)

    Jenkins, D. W.; Karagozian, A. R.

    1992-01-01

    This paper describes an analytical model of an incompressible, isothermal reacting jet in crossflow. The model represents the flow in the jet cross-section by a counter rotating vortex pair, a flow structure that has been observed to dominate the jet behavior. The reaction surface surrounding the fuel jet is represented as a composite of strained diffusion flames that are stretched and deformed by the vortex pair flow. The results shed new light on the interaction between the vortex pair circulation and flame structure evolution and their relation to the concept of entrainment.

  20. Surge Across the Chambo: Entrainment, topographical influences, and flow transformation of pyroclastic density currents using a combined field and multiphase modeling approach

    NASA Astrophysics Data System (ADS)

    Benage, M. C.; Dufek, J.; Geist, D.; Harpp, K. S.

    2011-12-01

    simulations in concert with detailed measurements of these flows from both up flow and down flow from the transformation to document the process of dense to dilute flow transition. The field characterization includes mapping of the flows, grain size analysis, documenting flow direction indicators, comminution rounding, thermal proxies for air entrainment, and bed form documentation. We used a three-dimensional, multiphase (Eulerian-Eulerian-Lagrangian, EEL) modeling approach to describe size sorting, concentration gradients, and stresses in these evolving flows using the topography of the near Chambo River crossing (Dufek and Bergantz, 2007). The numerical models reveal extensive entrainment in the surge-generating phase of the flow, and secondary plume generation as fine ash in transported by hot gases higher into the atmosphere. Granular waves develop in the confined channels of the dense flow resulting bed shear stress perturbations. These granular instabilities and entrainment result in pulsing conditions in the surge, accounting for much of the unsteady behavior that results in fluctuations in grain size and bed form in the surge deposits.

  1. Brain wave synchronization and entrainment to periodic acoustic stimuli.

    PubMed

    Will, Udo; Berg, Eric

    2007-08-31

    As known, different brainwave frequencies show synchronies related to different perceptual, motor or cognitive states. Brainwaves have also been shown to synchronize with external stimuli with repetition rates of ca. 10-40 Hz. However, not much is known about responses to periodic auditory stimuli with periodicities found in human rhythmic behavior (i.e. 0.5-5 Hz). In an EEG study we compared responses to periodic stimulations (drum sounds and clicks with repetition rates of 1-8 Hz), silence, and random noise. Here we report inter-trial coherence measures taken at the Cz-electrode that show a significant increase in brainwave synchronization following periodic stimulation. Specifically, we found (1) a tonic synchronization response in the delta range with a maximum response at 2 Hz, (2) a phasic response covering the theta range, and (3) an augmented phase synchronization throughout the beta/gamma range (13-44 Hz) produced through increased activity in the lower gamma range and modulated by the stimulus periodicity. Periodic auditory stimulation produces a mixture of evoked and induced, rate-specific and rate-independent increases in stimulus related brainwave synchronization that are likely to affect various cognitive functions. The synchronization responses in the delta range may form part of the neurophysiological processes underlying time coupling between rhythmic sensory input and motor output; the tonic 2 Hz maximum corresponds to the optimal tempo identified in listening, tapping synchronization, and event-interval discrimination experiments. In addition, synchronization effects in the beta and gamma range may contribute to the reported influences of rhythmic entrainment on cognitive functions involved in learning and memory tasks. PMID:17709189

  2. Understanding viral partitioning in two-phase aqueous nonionic micellar systems: 2. Effect of entrained micelle-poor domains.

    PubMed

    Kamei, Daniel T; King, Jonathan A; Wang, Daniel I C; Blankschtein, Daniel

    2002-04-20

    Unlike the partitioning behavior of hydrophilic, water-soluble proteins, the partitioning behavior of viruses in the two-phase aqueous nonionic n-decyl tetra(ethylene oxide) (C10E4) micellar system cannot be fully explained using the excluded-volume theory developed recently by our group. A central assumption underlying the excluded-volume theory--that macroscopic phase separation equilibrium is attained--was therefore challenged experimentally and theoretically. Photographs of the two-phase aqueous C10E4 micellar system were taken for different volume ratios to demonstrate that the entrainment of micelle-poor (virus-rich) domains in the macroscopic, top, micelle-rich phase decreases with a decrease in the volume ratio. Partitioning experiments were then conducted with the model virus bacteriophage P22 and the model protein cytochrome c at different operating temperatures for different volume ratios. For bacteriophage P22, the measured viral partition coefficient at each temperature decreased by about an order of magnitude when the volume ratio was decreased from 10 to 0.1, which clearly indicated that entrainment is an important factor influencing viral partitioning. For cytochrome c, the measured protein partition coefficient did not change, which demonstrated that this entrainment effect negligibly influences protein partitioning. A new theoretical description of partitioning was also developed that combines the excluded-volume theory with this entrainment effect. In this theory, one fitted parameter--the volume fraction of entrained micelle-poor domains in the macroscopic, top, micelle-rich phase--is used to account for the entrainment. To fit this parameter, only a single partitioning experiment is required for a given volume ratio, irrespectively of the partitioning solute. The new theoretical description of partitioning yielded very good quantitative predictions of the viral partition coefficients. Accordingly, it can be concluded that the primary mechanisms

  3. On the entrainment dynamics of inergodic, non-stationary flows

    NASA Astrophysics Data System (ADS)

    Rosi, Giuseppe; Rival, David

    2014-11-01

    Entrainment is typically studied through the conditional averaging along the turbulent non-turbulent interface (TNTI) of ergodic flows. However, this method is unsuitable for inergodic, non-stationary flows, as the TNTI is non-similar at different points in space and time. To understand how a TNTI's mean time dependence effects entrainment, the current study investigates the transport of irrotational fluid into a vortex forming behind an accelerating plate. The plate accelerates to a final velocity within a full-, half- and quarter-chord tow. Phase-averaged, planar, particle tracking velocimetry data is acquired and the forward finite-time Lyapunov exponent and vorticity fields are used to identify the TNTI. The TNTI is then represented by a contour, which is used to approximate the entrainment rate and investigate the transport mechanisms across the TNTI. Early results show that increasing acceleration suppresses vortex growth and entrainment. We hypothesize that shear-layer structure is integral to entrainment by altering the feeding rate of rotational fluid and the TNTI's convexity. The hypothesis is tested by altering plate-edge geometry and by varying the final chord-based Reynolds number from 5000 to 20 000. Natural Sciences and Engineering Council of Canada.

  4. Simulating entrainment and particle fluxes in stratified estuaries

    SciTech Connect

    Jensen, A.; Jirka, G.; Lion, L.W.; Brunk, B.

    1999-04-01

    Settling and entrainment are the dominant processes governing noncohesive particle concentration throughout the water column of salt-wedge estuaries. Determination of the relative contribution of these transport processes is complicated by vertical gradients in turbulence and fluid density. A differential-turbulence column (DTC) was designed to simulate a vertical section of a natural water column. With satisfactory characterization of turbulence dissipation and saltwater entrainment, the DTC facilitates controlled studies of suspended particles under estuarine conditions. The vertical decay of turbulence in the DTC was found to obey standard scaling law relations when the characteristic length scale for turbulence in the apparatus was incorporated. The entrainment rate of a density interface also followed established grid-stirred turbulence scaling laws. These relations were used to model the change in concentration of noncohesive particles above a density interface. Model simulations and experimental data from the DTC were consistent over the range of conditions encountered in natural salt-wedge estuaries. Results suggest that when the ratio of entrainment rate to particle settling velocity is small, sedimentation is the dominant transport process, while entrainment becomes significant as the ratio increases.

  5. Vasoactive intestinal polypeptide requires parallel changes in adenylate cyclase and phospholipase C to entrain circadian rhythms to a predictable phase

    PubMed Central

    An, Sungwon; Irwin, Robert P.; Allen, Charles N.; Tsai, Connie

    2011-01-01

    Circadian oscillations in the suprachiasmatic nucleus (SCN) depend on transcriptional repression by Period (PER)1 and PER2 proteins within single cells and on vasoactive intestinal polypeptide (VIP) signaling between cells. Because VIP is released by SCN neurons in a circadian pattern, and, after photic stimulation, it has been suggested to play a role in the synchronization to environmental light cycles. It is not known, however, if or how VIP entrains circadian gene expression or behavior. Here, we tested candidate signaling pathways required for VIP-mediated entrainment of SCN rhythms. We found that single applications of VIP reset PER2 rhythms in a time- and dose-dependent manner that differed from light. Unlike VIP-mediated signaling in other cell types, simultaneous antagonism of adenylate cyclase and phospholipase C activities was required to block the VIP-induced phase shifts of SCN rhythms. Consistent with this, VIP rapidly increased intracellular cAMP in most SCN neurons. Critically, daily VIP treatment entrained PER2 rhythms to a predicted phase angle within several days, depending on the concentration of VIP and the interval between VIP applications. We conclude that VIP entrains circadian timing among SCN neurons through rapid and parallel changes in adenylate cyclase and phospholipase C activities. PMID:21389307

  6. Transport, Evolution and Entrainment of Asian Dust/Pollution into the Pacific Marine Boundary

    NASA Astrophysics Data System (ADS)

    Clarke, A. D.; McNaughton, C. S.; Kapustin, V.; Vetter, O.; Dibb, J. E.; Anderson, B. E.; Browell, E. V.; Carmichael, G.; Landing, B.

    2007-05-01

    Various airborne and ship based studies over the past several years have allowed us to measure Asian dust and pollution aerosol from near its source to locations up to 10,000km downwind where it was entrained into the marine boundary layer (MBL). Dust was found to accumulate up to half of the soluble species such as sulfate and nitrate during passage through pollution regions in Asia before being lofted into the free troposphere near Japan. At times, transport in the free troposphere included regions of subsidence in high pressure regions that brought these "rivers" of dust and pollution down to the top of the MBL. Shipboard measurements and lidar data indicated both clear air entrainment and convective activity, associated with the passage of low pressure systems, facilitated dust transport through the inversion. High temperature volatilization of particles in the MBL up to 900C was used to remove most sulfates, nitrates, carbon and sea-salt to leave only dust measured and sized by an optical particle counter. These shipboard data and concurrent chemical measurements revealed the relation between entrainment of pollution and dust into the MBL associated with passage of high pressure systems. Subsequent passage of low pressure systems also revealed scavenging and removal of aerosol through precipitation to the ocean surface. This process appears to be a common removal pathway for dust over the Pacific and a mechanism for supplying the ocean surface with soluble iron and aluminum to the ocean surface. Measurements in the free troposphere and MBL also captured various aspects of these processes. Airborne missions flown north of Hawaii during the NASA PEM-Tropics and IMPEX missions characterized the vertical structure of subsiding dust and pollution. In-flight mapping of the dust/pollution layers and structure using the NASA Langley DIAL LIDAR show a sloping, subsiding Asian air-mass entraining into the marine boundary layer (MBL). In-situ measurements of the aerosol

  7. Evaluation of a soil fixative to retard particle entrainment: A laboratory study

    NASA Astrophysics Data System (ADS)

    Biermann, A.; Sawyer, S.; Cappabianca, R.

    1991-12-01

    We evaluated the effectiveness of liquid spray treatments to reduce particle entrainment and migration from soil surfaces. To simulate particle entrainment from a solid surface, we performed controlled experiments in a laboratory wind tunnel using artificially prepared soil surfaces. The experimental testing included three soil treatments, three soil types, and four wind speeds. The soil treatments were a spray application of a 4 percent water-based flour formulation, a spray application of water only, and no spray treatment. The water-only spray and no spray conditions served as controls for evaluating the treatment with the flour formulation. We also investigated the effect of aging the soil surfaces under hot and dry conditions. In addition, we evaluated a quantitative assessment of the treatment's effectiveness to retard particle movement from the soil surface for both respirable particles from 0.3- to 8.0-microns-in. diameter and larger nonrespirable particles. We varied wind velocities from 2 to 16 m/s. In the wind-tunnel testing, we used three soils--54 percent clay, 72 percent silt, and 78 percent sand. Preparation of the soil surfaces simulated the behavior of an unpacked soil whose surface is exposed to a gust of wind. Spray applications of the treatments to the soil surfaces were typically 8 - 15 mg/sq cm. For wind velocities less than or equal to 22 mph, both treatments were effective in preventing entrainment of respirable particles. Based on aerosol concentration measurements, the effectiveness of the treatments averaged 98 percent over all conditions and soil types (i.e., 50 times less entrainment than for untreated soil surfaces). At the highest wind-velocity condition, 35 mph, the flour-formulation treatment was significantly more effective than the water-only treatment. In general, aerosol results paralleled the surface collection measurements, which indicate the movement of particles too large to be considered respirable. Soil surface treated

  8. Four of the six Drosophila rhodopsin-expressing photoreceptors can mediate circadian entrainment in low light.

    PubMed

    Saint-Charles, Alexandra; Michard-Vanhée, Christine; Alejevski, Faredin; Chélot, Elisabeth; Boivin, Antoine; Rouyer, François

    2016-10-01

    Light is the major stimulus for the synchronization of circadian clocks with day-night cycles. The light-driven entrainment of the clock that controls rest-activity rhythms in Drosophila relies on different photoreceptive molecules. Cryptochrome (CRY) is expressed in most brain clock neurons, whereas six different rhodopsins (RH) are present in the light-sensing organs. The compound eye includes outer photoreceptors that express RH1 and inner photoreceptors that each express one of the four rhodopsins RH3-RH6. RH6 is also expressed in the extraretinal Hofbauer-Buchner eyelet, whereas RH2 is only found in the ocelli. In low light, the synchronization of behavioral rhythms relies on either CRY or the canonical rhodopsin phototransduction pathway, which requires the phospholipase C-β encoded by norpA (no receptor potential A). We used norpA(P24) cry(02) double mutants that are circadianly blind in low light and restored NORPA function in each of the six types of photoreceptors, defined as expressing a particular rhodopsin. We first show that the NORPA pathway is less efficient than CRY for synchronizing rest-activity rhythms with delayed light-dark cycles but is important for proper phasing, whereas the two light-sensing pathways can mediate efficient adjustments to phase advances. Four of the six rhodopsin-expressing photoreceptors can mediate circadian entrainment, and all are more efficient for advancing than for delaying the behavioral clock. In contrast, neither RH5-expressing retinal photoreceptors nor RH2-expressing ocellar photoreceptors are sufficient to mediate synchronization through the NORPA pathway. Our results thus reveal different contributions of rhodopsin-expressing photoreceptors and suggest the existence of several circuits for rhodopsin-dependent circadian entrainment. J. Comp. Neurol. 524:2828-2844, 2016. © 2016 Wiley Periodicals, Inc. PMID:26972685

  9. Circadian entrainment by light and host in the Chagas disease vector, Triatoma infestans.

    PubMed

    Valentinuzzi, Verónica Sandra; Amelotti, Ivana; Gorla, David Eladio; Catalá, Silvia Susana; Ralph, Martin Roland

    2014-03-01

    Triatoma infestans (Reduviidae: Triatominae, "kissing bug") is the main insect vector of Trypanosoma cruzi, the causative agent of Chagas disease, a chronic trypanosomiasis infecting 10 million people world-wide. This hematophagous bug feeds on diurnal and nocturnal species during each host's quiescent time. As the hosts are also its major predators, kissing bugs are subjected to dual selective pressures from a single source. Therefore, synchronization of feeding with the host's behavior is critical to the insects' survival. We show that nonphotic signals linked to the host eclipse the role of light and dark as the primary circadian zeitgeber for these bugs, although light still strongly inhibits locomotor behavior directly. In nature, this combination provides the insect with great flexibility in organizing physiology and behavior: anticipating a quiescent host or avoiding its potential predation while remaining directly responsive to immediate environmental conditions. Manipulation of nonphotic entrainment could be a useful chronobiotic tool in the control of Chagas disease. PMID:24156522

  10. Aeolian Induced Erosion and Particle Entrainment

    NASA Technical Reports Server (NTRS)

    Saint, Brandon

    2007-01-01

    The Granular Physics Department at The Kennedy Space Center is addressing the problem of erosion on the lunar surface. The early stages of research required an instrument that would produce erosion at a specific rate with a specific sample variation. This paper focuses on the development and experimental procedures to measure and record erosion rates. This was done with the construction of an open air wind tunnel, and examining the relationship between airflow and particle motion.

  11. Potent social synchronization can override photic entrainment of circadian rhythms

    PubMed Central

    Fuchikawa, Taro; Eban-Rothschild, Ada; Nagari, Moshe; Shemesh, Yair; Bloch, Guy

    2016-01-01

    Circadian rhythms in behaviour and physiology are important for animal health and survival. Studies with individually isolated animals in the laboratory have consistently emphasized the dominant role of light for the entrainment of circadian rhythms to relevant environmental cycles. Although in nature interactions with conspecifics are functionally significant, social signals are typically not considered important time-givers for the animal circadian clock. Our results challenge this view. By studying honeybees in an ecologically relevant context and using a massive data set, we demonstrate that social entrainment can be potent, may act without direct contact with other individuals and does not rely on gating the exposure to light. We show for the first time that social time cues stably entrain the clock, even in animals experiencing conflicting photic and social environmental cycles. These findings add to the growing appreciation for the importance of studying circadian rhythms in ecologically relevant contexts. PMID:27210069

  12. Potent social synchronization can override photic entrainment of circadian rhythms.

    PubMed

    Fuchikawa, Taro; Eban-Rothschild, Ada; Nagari, Moshe; Shemesh, Yair; Bloch, Guy

    2016-01-01

    Circadian rhythms in behaviour and physiology are important for animal health and survival. Studies with individually isolated animals in the laboratory have consistently emphasized the dominant role of light for the entrainment of circadian rhythms to relevant environmental cycles. Although in nature interactions with conspecifics are functionally significant, social signals are typically not considered important time-givers for the animal circadian clock. Our results challenge this view. By studying honeybees in an ecologically relevant context and using a massive data set, we demonstrate that social entrainment can be potent, may act without direct contact with other individuals and does not rely on gating the exposure to light. We show for the first time that social time cues stably entrain the clock, even in animals experiencing conflicting photic and social environmental cycles. These findings add to the growing appreciation for the importance of studying circadian rhythms in ecologically relevant contexts. PMID:27210069

  13. Heavy Impurity Entrainment in the Parallel Flows of CSDX

    NASA Astrophysics Data System (ADS)

    Gosselin, Jordan; Thakur, Saikat; Tynan, George

    2014-10-01

    The lifetime of the plasma facing components (PFCs) in a tokamak, governed primarily by material erosion and redeposition, has been identified as a crucial research topic. While some work has been done that shows evidence of the entrainment of impurities in linear machines and in tokamaks, detailed controlled studies of entrainment in plasma flows are harder to come by. Recently, experiments in CSDX have shown increasing parallel ion velocity positively correlated with increasing magnetic field. In an effort to study the effects of the background flow on impurity transport, a laser blow off apparatus was installed on the Controlled Shear Decorelation eXperiment (a 3m long linear helicon source operated plasma machine). Results are shown for parallel entrainment of Bismuth impurities in a relatively light background Ar plasma (5.2 mass ratio).

  14. On robustness of phase resetting to cell division under entrainment.

    PubMed

    Ahmed, Hafiz; Ushirobira, Rosane; Efimov, Denis

    2015-12-21

    The problem of phase synchronization for a population of genetic oscillators (circadian clocks, synthetic oscillators, etc.) is considered in this paper, taking into account a cell division process and a common entrainment input in the population. The proposed analysis approach is based on the Phase Response Curve (PRC) model of an oscillator (the first order reduced model obtained for the linearized system and inputs with infinitesimal amplitude). The occurrence of cell division introduces state resetting in the model, placing it in the class of hybrid systems. It is shown that without common entraining input in all oscillators, the cell division acts as a disturbance causing phase drift, while the presence of entrainment guarantees boundedness of synchronization phase errors in the population. The performance of the obtained solutions is demonstrated via computer experiments for two different models of circadian/genetic oscillators (Neurospora׳s circadian oscillation model and the repressilator). PMID:26463679

  15. Saturation point representation of cloud-top entrainment instability

    NASA Technical Reports Server (NTRS)

    Boers, Reinout

    1991-01-01

    Cloud-top entrainment instability was investigated using a mixing line analysis. Mixing time scales are closely related to the actual size of the parcel, so that local instabilities are largely dependent on the scales of mixing near the cloud top. Given a fixed transport velocity, variation over a small range of parcel length scales (parcel mixing velocities) turns an energy-producing mixing process into an energy-consuming mixing process. It is suggested that a single criterion for cloud-top entrainment instability will not be found due to the role of at least three factors operating more or less independently; the stability of the mixing line, the entrainment speed, and the strength of the internal boundary-layer circulation.

  16. Entrainment into a stratocumulus layer with distributed radiative cooling

    NASA Technical Reports Server (NTRS)

    Randall, D. A.

    1980-01-01

    It is shown that the radiative cooling of a cloud layer strongly influences the turbulent flux profiles and the entrainment rate, and that the radiative cooling should be modeled as acting inside the turbulent layer. Numerical experiments demonstrate that a cloud-topped mixed-layer model, similar to that of Lilly (1968), is quite sensitive to delta (p) sub R, the depth of the radiatively cooled layer near cloud top. As delta (p) sub R increases, the model's sensitivity to the entrainment assumption is markedly heightened; for large delta (p) sub R the cloud top and cloud base rise as the entrainment parameter k is increased, while for small delta (p) sub R an increase in k has almost no effect. The model is most sensitive to delta (p) sub R for the cold-water, strong-divergence regime of greatest interest.

  17. Entrainment and Control of Bacterial Populations: An in Silico Study over a Spatially Extended Agent Based Model.

    PubMed

    Mina, Petros; Tsaneva-Atanasova, Krasimira; Bernardo, Mario di

    2016-07-15

    We extend a spatially explicit agent based model (ABM) developed previously to investigate entrainment and control of the emergent behavior of a population of synchronized oscillating cells in a microfluidic chamber. Unlike most of the work in models of control of cellular systems which focus on temporal changes, we model individual cells with spatial dependencies which may contribute to certain behavioral responses. We use the model to investigate the response of both open loop and closed loop strategies, such as proportional control (P-control), proportional-integral control (PI-control) and proportional-integral-derivative control (PID-control), to heterogeinities and growth in the cell population, variations of the control parameters and spatial effects such as diffusion in the spatially explicit setting of a microfluidic chamber setup. We show that, as expected from the theory of phase locking in dynamical systems, open loop control can only entrain the cell population in a subset of forcing periods, with a wide variety of dynamical behaviors obtained outside these regions of entrainment. Closed-loop control is shown instead to guarantee entrainment in a much wider region of control parameter space although presenting limitations when the population size increases over a certain threshold. In silico tracking experiments are also performed to validate the ability of classical control approaches to achieve other reference behaviors such as a desired constant output or a linearly varying one. All simulations are carried out in BSim, an advanced agent-based simulator of microbial population which is here extended ad hoc to include the effects of control strategies acting onto the population. PMID:27110835

  18. Numerical Analysis on Air Ingress Behavior in GTHTR300-Cogeneration System

    NASA Astrophysics Data System (ADS)

    Takeda, Tetsuaki; Yan, Xing; Kunitomi, Kazuhiko

    The objective of this study is to clarify safety characteristics of a High Temperature Gas-Cooled Reactor (HTGR) for the pipe rupture accident. Japan Atomic Energy Agency (JAEA) has been developing the analytical code for the safety characteristics of the HTGR and carrying out design study of the gas turbine high temperature reactor of 300MWe nominal-capacity for hydrogen production, the GTHTR300C (Gas Turbine High Temperature Reactor 300 for Cogeneration). A numerical analysis of heat and mass transfer fluid flow with multi-component gas mixture has been performed to obtain the variation of the density of the gas mixture, and the onset time of natural circulation of air. From the results obtained in this analysis, it was found that the duration time of the air ingress by molecular diffusion would increase due to the existence of the recuperator in the GTHTR300C system.

  19. Using Historical Data to Automatically Identify Air-Traffic Control Behavior

    NASA Technical Reports Server (NTRS)

    Lauderdale, Todd A.; Wu, Yuefeng; Tretto, Celeste

    2014-01-01

    This project seeks to develop statistical-based machine learning models to characterize the types of errors present when using current systems to predict future aircraft states. These models will be data-driven - based on large quantities of historical data. Once these models are developed, they will be used to infer situations in the historical data where an air-traffic controller intervened on an aircraft's route, even when there is no direct recording of this action.

  20. The oxidation behavior of a model molybdenum/tungsten-containing alloy in air alone and in air with trace levels of NaCl(g)

    NASA Technical Reports Server (NTRS)

    Smeggil, J. G.; Bornstein, N. S.

    1983-01-01

    Thermogravimetric, metallographic, and X-ray studies of a model alloy, Ni-(17 a/o)Al-(10 a/o)Mo+W, oxidized in dry air at 600-1200 C and in air with 10 ppm NaCl gas at 900 C, are reported. The alloy was melted under Ar and pretreated in flowing H2 for 24 h at 1300 C. Polished 1.3 x 1.3 x 0.2-cm specimens were washed and degreased prior to oxidation in a quartz tube within a furnace for up to 120 hr. The oxidation activation energy of the alloy is determined to be about 30 kcal/mole. The specimens oxidized at 900 C and hotter exhibited oxidized and nitrided phases covered by complex NiMoO4, NiWO4, and NiAl2O4 scales and a porous, nonprotective outer layer of NiO. The oxidation behavior is found to be determined by the formation and growth of the scale, especially the (Mo,W)O2 component. Al2O3 scale layers were not formed, and further runs with pure O2 or Ar-(20 percent)O2 ruled out an explanation of this phenomenon based on aluminum nitride formation. The oxidation was accelerated by the addition of NaCl gas, a finding attributed to the reaction of NaCl with external locally protective Al2O3 scales and with the internal(Mo, W)O2 layers.

  1. Evidence for Little Shallow Entrainment in Starting Mantle Plumes

    NASA Astrophysics Data System (ADS)

    Lohmann, F. C.; Phipps Morgan, J.; Hort, M.

    2005-12-01

    Basalts from intraplate or hotspot ocean islands show distinct geochemical signatures. Their diversity in composition is generally believed to result from the upwelling plume entraining shallow mantle material during ascent, while potentially also entraining other deep regions of the mantle. Here we present results from analogue laboratory experiments and numerical modelling that there is evidence for little shallow entrainment into ascending mantle plumes, i.e. most of the plume signature is inherited from the source. We conducted laboratory experiments using glucose syrup contaminated with glass beads to visualize fluid flow and origin. The plume is initiated by heating from below or by injecting hot, uncontaminated syrup. Particle movement is captured by a CCD camera. In our numerical experiments we solve the Stokes equations for a viscous fluid at infinite Prandtl number with passive tracer particles being used to track fluid flow and entrainment rates, simulating laboratory as well as mantle conditions. In both analogue experiments and numerical models we observe the classical plume structure being embedded in a `sheath' of material from the plume source region that retains little of the original temperature anomaly of the plume source. Yet, this sheath ascends in the `slipstream' of the plume at speeds close to the ascent speed of the plume head, and effectively prevents the entrainment of surrounding material into the plume head or plume tail. We find that the source region is most effectively sampled by an ascending plume and that compositional variations in the source region are preserved during plume ascent. The plume center and plume sheath combined are composed of up to 85% source material. However, there is also evidence of significant entrainment of up to 30% of surrounding material into the outer layers of the plume sheath. Entrainment rates are found to be influenced by mantle composition and structure, with the radial viscosity profile of the

  2. Fluctuations of a receding contact line near the entrainment transition

    NASA Astrophysics Data System (ADS)

    Bico, Jose; Delon, Giles; Fermigier, Marc

    2004-11-01

    We study experimentally the fluctuations of a contact line receding on a plane solid substrate. The contact line is perturbed by localized defects and we follow the relaxation of perturbations induced by these defects, as a function of the mean contact line speed and wavelengths characteristic of the perturbations. We compare our results with theoretical predictions by Golestanian and Raphael showing a divergence of the relaxation time at the entrainment transition (when the receding velocity exceeds a critical value, the liquid is entrained by the solid).

  3. Observing Entrainment Processes Using a Small Unmanned Aerial Vehicle: A Feasibility Study

    NASA Astrophysics Data System (ADS)

    Martin, Sabrina; Beyrich, Frank; Bange, Jens

    2014-03-01

    Measurement flights with the meteorological mini aerial vehicle (MAV) were performed in spring 2011 to assess the capability of an unmanned aerial vehicle (UAV) to measure the structure of the transition zone between the convective boundary layer and the stably stratified free atmosphere. The campaign took place at the Meteorological Observatory Lindenberg/Richard-Aßmann-Observatory of the German Meteorological Service. Besides the MAV flights, observations were made from a 12-m and a 99-m tower, a sodar, two ceilometers, radiosondes, and a tethered balloon with sensor packages at six different levels. MAV measurements were intentionally combined with remote sensing systems. The height range of the entrainment zone as well as its diurnal cycle were provided by the remote sensing instruments. The UAV provided the high-resolution in situ data of temperature and wind for the study of turbulent processes. It is shown that the MAV is able to maintain constant altitude with very small deviations—a pre-requisite to study processes inside the often quite thin entrainment zone and that MAV high-resolution wind and temperature measurements allow for very detailed studies of the fine structure of the atmosphere and thus for the identification of quite local and/or short-duration processes such as overshooting thermals or downward intrusions of warm air. Spatial series measured by the MAV during horizontal flights show turbulent exchange of heat in short turbulent bursts at heights close to and within the entrainment zone. Scaled vertical profiles of vertical velocity, potential temperature variance, and sensible heat flux confirm the general shape found by previous measurements and numerical studies.

  4. Entrainment of radio frequency chaff by wind as a function of surface aerodynamic roughness.

    PubMed

    Gillies, John A; Nickling, William G

    2003-02-01

    Radio frequency (RF) chaff (approximately 2-cm x 25-microm diameter aluminum-coated glass silicate cylinders) released by military aircraft during testing and training activities has the potential to become entrained by wind upon settling to the Earth's surface. Once entrained from the surface there is the potential for RF chaff to be abraded and produce PM10 and PM2.5, which are regulated pollutants and pose health concerns. A series of portable wind tunnel tests were carried out to examine the propensity of RF chaff to become entrained by wind by defining the relationship between the threshold friction velocity of RF chaff (u(*t RF chaff)) and aerodynamic roughness (z(o)) of surfaces onto which it may deposit. The test surfaces were of varying roughness including types near the Naval Air Station (NAS), Fallon, NV, where RF chaff is released. The u(*t) of this fibrous material ranged from 0.14 m/sec for a smooth playa to 0.82 m/sec for a rough crusted playa surface with larger cobble-sized (approximately 6-26-cm diameter) rocks rising above the surface. The u(*t RF chaff) is dependent on the z(o) of the surface onto which it falls as well as the physical characteristics of the roughness. The wind regime of Fallon would allow for chaff suspension events to occur should it settle on typical surfaces in the area. However, the wind climatology of this area makes the probability of such events relatively low. PMID:12617294

  5. Artificial Neural Networks: A New Approach for Predicting Application Behavior. AIR 2001 Annual Forum Paper.

    ERIC Educational Resources Information Center

    Gonzalez, Julie M. Byers; DesJardins, Stephen L.

    This paper examines how predictive modeling can be used to study application behavior. A relatively new technique, artificial neural networks (ANNs), was applied to help predict which students were likely to get into a large Research I university. Data were obtained from a university in Iowa. Two cohorts were used, each containing approximately…

  6. Volume entrained in the wake of a disk intruding into an oil-water interface

    NASA Astrophysics Data System (ADS)

    Peters, Ivo R.; Madonia, Matteo; Lohse, Detlef; van der Meer, Devaraj

    2016-07-01

    An object moving through a plane interface into a fluid deforms the interface in such a way that fluid from one side of the interface is entrained into the other side, a phenomenon known as Darwin's drift. We investigate this phenomenon experimentally using a disk which is started exactly at the interface of two immiscible fluids, namely, oil and water. First, we observe that due to the density difference between the two fluids the deformation of the interface is influenced by gravity and show that there exists a time window of universal behavior. Second, we show by comparing with boundary integral simulations that, even though the deformation is universal, our results cannot be fully explained by potential flow solutions. We attribute this difference to the starting vortex, which is created in the wake of the disk. Besides contributing significantly to entrainment directly, the vortex also influences the interface deformation due to Darwin's drift. Universal behavior is preserved, however, because the size and strength of the vortex shows the same universality as the potential flow solution.

  7. Thermophysical behavior of St. Peter sandstone: application to compressed air energy storage in an aquifer

    SciTech Connect

    Erikson, R.L.

    1983-12-01

    The long-term stability of a sandstone reservoir is of primary importance to the success of compressed air energy storage (CAES) in aquifers. The purpose of this study was to: develop experimental techniques for the operation of the CAES Porous Media Flow Loop (PMFL), an apparatus designed to study the stability of porous media in subsurface geologic environments, conduct experiments in the PMFL designed to determine the effects of temperature, stress, and humidity on the stability of candidate CAES reservoir materials, provide support for the CAES field demonstration project in Pittsfield, Illinois, by characterizing the thermophysical stability of Pittsfield reservoir sandstone under simulated field conditions.

  8. Distortion Behavior of a Heavy Hydro Turbine Blade Casting During Forced Air Cooling in Normalizing Treatment Process

    NASA Astrophysics Data System (ADS)

    Yu, Hai-Liang; Kang, Jin-Wu; Wang, Tian-Jiao; Ma, Ji-Yu; Hu, Yong-Yi; Huang, Tian-You; Wang, Shi-Bin; Wu, Ying; Zhang, Cheng-Chun; Dai, Yan-Tao; Li, Peng

    2012-01-01

    Distortion behavior of blade castings in heat treatment process determines their geometrical accuracy, and improper control of it may result in additional repair, shape righting, or even rejection. This article presents a novel approach for discovering the distortion behavior of heavy blade castings during heat treatment process in production. Real-time measurements of distortion and temperature field of a heavy hydro turbine blade casting weighted 17 ton during forced air cooling in normalizing treatment process were carried out by using deformation measurement instruments and an infrared thermal imaging camera. The distortion processes of the typical locations of blade and the temperature field of the blade were obtained. One corner on the blade outlet edge side exhibits variation of distortion with two peaks and a valley. The range reaches 97 mm and the final distortion value is 76 mm. The maximum temperature difference on blade surface reaches 460 °C after 80 min of cooling. Influences of thermal stress and phase transformation stress on the distortion of the blade were elucidated and discussed. The results are of great significance for the understanding and control of the distortion behavior of hydro turbine blades in heat treatment.

  9. Experimental study of the behavior of two laser produced plasmas in air

    SciTech Connect

    Yang, Zefeng; Wei, Wenfu; Han, Jiaxun; Wu, Jian Li, Xingwen; Jia, Shenli

    2015-07-15

    The interactions among two laser ablated Al plasmas and their shock wave fronts (SWFs) induced by double laser pulses in air were studied experimentally. The evolution processes, including the expansion and interaction of the two plasmas and their shocks, were investigated by laser shadowgraphs, schlieren images, and interferograms. Remarkably, the distribution of the compressed air and the laser plasmas during the colliding process was clearly obtained using the Mach-Zehnder interferometer. From the refractive index profiles, typical plasmas density and gas density behind the shock front were estimated as ∼5.2 × 10{sup 18 }cm{sup −3} and ∼2.4 × 10{sup 20 }cm{sup −3}. A stagnation layer formed by the collision of gas behind the shock front is observed. The SWFs propagated, collided, and reflected with a higher velocity than plasmas. The results indicated that the slower plasma collided at middle, leading to the formation of the soft stagnation.

  10. Knowing the enemy: ant behavior and control in a pediatric hospital of Buenos Aires.

    PubMed

    Josens, Roxana; Sola, Francisco J; Marchisio, Nahuel; Di Renzo, María Agostina; Giacometti, Alina

    2014-01-01

    Ant control is difficult in systems even where a variety of control strategies and compounds are allowed; in sensitive places such as hospitals, where there are often restrictions on the methods and toxicants to be applied, the challenge is even greater. Here we report the methods and results of how we faced this challenge of controlling ants in a pediatric hospital using baits. Our strategy was based on identifying the species present and analyzing their behavior. On the one hand, we evaluated outdoors in the green areas of the hospital, the relative abundance of ant genera, their food preferences and the behavioral dominances. On the other hand, control treatments were performed using separately two boron compounds added to sucrose solution which was not highly concentrated to avoid constrains due to the viscosity. Most of the species in the food preference test accepted sugary food; only one species was recorded to visit it less than the protein foods. This result was consistent with the efficacy of control treatments by sugary baits within the rooms. For species that showed good acceptance of sugar solutions in the preference test outdoors, sugar bait control indoors was 100& effective. Conversely, for the only species that foraged significantly less on sugar food, the bait treatment was ineffective. This work reveals the importance of considering the behavior and feeding preferences of the species to be controlled by toxic baits. PMID:24855592

  11. Vasoactive intestinal polypeptide entrains circadian rhythms in astrocytes.

    PubMed

    Marpegan, Luciano; Krall, Thomas J; Herzog, Erik D

    2009-04-01

    Many mammalian cell types show daily rhythms in gene expression driven by a circadian pacemaker. For example, cultured astrocytes display circadian rhythms in Period1 and Period2 expression. It is not known, however, how or which intercellular factors synchronize and sustain rhythmicity in astrocytes. Because astrocytes are highly sensitive to vasoactive intestinal polypeptide (VIP), a neuropeptide released by neurons and important for the coordination of daily cycling, the authors hypothesized that VIP entrains circadian rhythms in astrocytes. They used astrocyte cultures derived from knock-in mice containing a bioluminescent reporter of PERIOD2 (PER2) protein, to assess the effects of VIP on the rhythmic properties of astrocytes. VIP induced a dose-dependent increase in the peak-to-trough amplitude of the ensemble rhythms of PER2 expression with maximal effects near 100 nM VIP and threshold values between 0.1 and 1 nM. VIP also induced dose- and phase-dependent shifts in PER2 rhythms and daily VIP administration entrained bioluminescence rhythms of astrocytes to a predicted phase angle. This is the first demonstration that a neuropeptide can entrain glial cells to a phase predicted by a phase-response curve. The authors conclude that VIP potently entrains astrocytes in vitro and is a candidate for coordinating daily rhythms among glia in the brain. PMID:19346450

  12. Vasoactive intestinal polypeptide entrains circadian rhythms in astrocytes

    PubMed Central

    Marpegan, Luciano; Krall, Thomas J.; Herzog, Erik D.

    2009-01-01

    Many mammalian cell types show daily rhythms in gene expression driven by a circadian pacemaker. For example, cultured astrocytes display circadian rhythms in Period1 and Period2 expression. It is not known, however, how or which intercellular factors synchronize and sustain rhythmicity in astrocytes. Because astrocytes are highly sensitive to vasoactive intestinal polypeptide (VIP), a neuropeptide released by neurons and important for the coordination of daily cycling, we hypothesized that VIP entrains circadian rhythms in astrocytes. We used astrocyte cultures derived from knock-in mice containing a bioluminescent reporter of PERIOD2 (PER2) protein, to assess the effects of VIP on the rhythmic properties of astrocytes. VIP induced a dose-dependent increase in the peak-to-trough amplitude of the ensemble rhythms of PER2 expression with maximal effects near 100nM VIP and threshold values between 0.1 and 1 nM. VIP also induced dose- and phase-dependent shifts in PER2 rhythms and daily VIP administration entrained bioluminescence rhythms of astrocytes to a predicted phase angle. This is the first demonstration that a neuropeptide can entrain glial cells to a phase predicted by a phase response curve. We conclude that VIP potently entrains astrocytes in vitro and is a candidate for coordinating daily rhythms among glia in the brain. PMID:19346450

  13. Queueing-Based Synchronization and Entrainment for Synthetic Gene Oscillators

    NASA Astrophysics Data System (ADS)

    Mather, William; Butzin, Nicholas; Hochendoner, Philip; Ogle, Curtis

    Synthetic gene oscillators have been a major focus of synthetic biology research since the beginning of the field 15 years ago. They have proven to be useful both for biotechnological applications as well as a testing ground to significantly develop our understanding of the design principles behind synthetic and native gene oscillators. In particular, the principles governing synchronization and entrainment of biological oscillators have been explored using a synthetic biology approach. Our work combines experimental and theoretical approaches to specifically investigate how a bottleneck for protein degradation, which is present in most if not all existing synthetic oscillators, can be leveraged to robustly synchronize and entrain biological oscillators. We use both the terminology and mathematical tools of queueing theory to intuitively explain the role of this bottleneck in both synchronization and entrainment, which extends prior work demonstrating the usefulness of queueing theory in synthetic and native gene circuits. We conclude with an investigation of how synchronization and entrainment may be sensitive to the presence of multiple proteolytic pathways in a cell that couple weakly through crosstalk. This work was supported by NSF Grant #1330180.

  14. EFFECTS OF CONTINUOUS CHLORINATION ON ENTRAINED ESTUARINE PLANKTON

    EPA Science Inventory

    The effects of continuous chlorination on entrained plankton are investigated in tests using running sea water and adenosine triphosphate (ATP) as an indicator of biomass. Effects were measured by bioluminescence with the use of luciferin-luciferase reagents from firefly lanterns...

  15. Lexical Entrainment and Lexical Differentiation in Reference Phrase Choice

    ERIC Educational Resources Information Center

    Van Der Wege, Mija M.

    2009-01-01

    Speakers reuse prior references to objects when choosing reference phrases, a phenomenon known as lexical entrainment. One explanation is that speakers want to maintain a set of previously established referential precedents. Speakers may also contrast any new referents against this previously established set, thereby avoiding applying the same…

  16. Cumulus clouds - Early aircraft observations and entrainment hypotheses

    NASA Technical Reports Server (NTRS)

    Simpson, J.

    1983-01-01

    The history of cumulus research in the decade following World War II is reviewed in the perspective of the new ideas and advances made during the subsequent generation. Emphasis is placed upon pioneering aircraft measurements, evidence for entrainment, the early model attempts and their attendant controversies.

  17. A vortex entrainment model applied to slender delta wings

    NASA Technical Reports Server (NTRS)

    Coe, P. L., Jr.

    1974-01-01

    A mathematical model of the vortex flow over a slender sharp-edged delta wing is proposed, and is shown to provide good agreement with the experiment. Although the technique requires experimental data in the form of the vortex core locations, it does account for the previously ignored mass entrainment of the vortex core.

  18. Suppression of competing speech through entrainment of cortical oscillations.

    PubMed

    Horton, Cort; D'Zmura, Michael; Srinivasan, Ramesh

    2013-06-01

    People are highly skilled at attending to one speaker in the presence of competitors, but the neural mechanisms supporting this remain unclear. Recent studies have argued that the auditory system enhances the gain of a speech stream relative to competitors by entraining (or "phase-locking") to the rhythmic structure in its acoustic envelope, thus ensuring that syllables arrive during periods of high neuronal excitability. We hypothesized that such a mechanism could also suppress a competing speech stream by ensuring that syllables arrive during periods of low neuronal excitability. To test this, we analyzed high-density EEG recorded from human adults while they attended to one of two competing, naturalistic speech streams. By calculating the cross-correlation between the EEG channels and the speech envelopes, we found evidence of entrainment to the attended speech's acoustic envelope as well as weaker yet significant entrainment to the unattended speech's envelope. An independent component analysis (ICA) decomposition of the data revealed sources in the posterior temporal cortices that displayed robust correlations to both the attended and unattended envelopes. Critically, in these components the signs of the correlations when attended were opposite those when unattended, consistent with the hypothesized entrainment-based suppressive mechanism. PMID:23515789

  19. Airborne observation of mixing across the entrainment zone during PARADE 2011

    NASA Astrophysics Data System (ADS)

    Berkes, F.; Hoor, P.; Bozem, H.; Kunkel, D.; Sprenger, M.; Henne, S.

    2015-10-01

    This study presents the analysis of the structure and air mass characteristics of the lower atmosphere during the field campaign PARADE (PArticles and RAdicals: Diel observations of the impact of urban and biogenic Emissions) on Mount Kleiner Feldberg in southwestern Germany during late summer 2011. We analysed measurements of meteorological variables (temperature, moisture, pressure, wind speed and direction) from radio soundings and of chemical tracers (carbon dioxide, ozone) from aircraft measurements. We focus on the thermodynamic and dynamic properties, that control the chemical distribution of atmospheric constituents in the boundary layer. We show that the evolution of tracer profiles of CO2 and O3 indicate mixing across the inversion layer (or entrainment zone). This finding is supported by the analysis of tracer-tracer correlations which are indicative for mixing and the relation of tracer profiles in relation to the evolution of the boundary layer height deduced from radio soundings. The study shows the relevance of entrainment processes for the lower troposphere in general and specifically that the tracer-tracer correlation method can be used to identify mixing and irreversible exchange processes across the inversion layer.

  20. Saltation thresholds and entrainment of fine particles at Earth and Martian pressures

    NASA Technical Reports Server (NTRS)

    Leach, Rodman; Greeley, Ronald; Pollack, James

    1989-01-01

    An open circuit wind tunnel designed to operate in a large vacuum chamber was built at NASA-Ames to investigate saltation threshold, flux, deflation rates, and other aeolian phenomena on the planet Mars. The vacuum chamber will operate at pressures as low as 4 mbar, and the tunnel operates at windspeeds as high as 150 m/sec. Either air or CO2 can be used as a working fluid. It was found that, to a first order approximation, the same dynamic pressure was required at Martian pressure to entrain or saltate particles as was required on Earth, although wind and particle speed are considerably higher at Martian pressure. A 2nd wind tunnel, designed to operate aboard the NASA KC-135 0-g aircraft to obtain information on the effect of gravity on saltation threshold and the interparticle force at 0-g, is also described and test data presented. Some of the experiments are summarized and various aspects of low pressure aeolian entrainment for particles 12 to 100 micron in diameter are discussed, some of them unique to low pressure testing and some common in Earth pressure particle transport testing. The facility, the modes of operation, and the materials used are described.

  1. Airborne observation of mixing across the entrainment zone during PARADE 2011

    NASA Astrophysics Data System (ADS)

    Berkes, Florian; Hoor, Peter; Bozem, Heiko; Kunkel, Daniel; Sprenger, Michael; Henne, Stephan

    2016-05-01

    This study presents the analysis of the structure and air mass characteristics of the lower atmosphere during the field campaign PARADE (PArticles and RAdicals: Diel observations of the impact of urban and biogenic Emissions) on Mount Kleiner Feldberg in southwestern Germany during late summer 2011. We analysed measurements of meteorological variables (temperature, moisture, pressure, wind speed and direction) from radio soundings and of chemical tracers (carbon dioxide, ozone) from aircraft measurements. We focus on the thermodynamic and dynamic properties that control the chemical distribution of atmospheric constituents in the boundary layer. We show that the evolution of tracer profiles of CO2 and O3 indicate mixing across the inversion layer (or entrainment zone). This finding is supported by the analysis of tracer-tracer correlations which are indicative for mixing and the relation of tracer profiles in relation to the evolution of the boundary layer height deduced from radio soundings. The study shows the relevance of entrainment processes for the lower troposphere in general and specifically that the tracer-tracer correlation method can be used to identify mixing and irreversible exchange processes across the inversion layer.

  2. Effect of electrical current on the tribological behavior of the Cu-WS2-G composites in air and vacuum

    NASA Astrophysics Data System (ADS)

    Qian, Gang; Feng, Yi; Li, Bin; Huang, Shiyin; Liu, Hongjuan; Ding, Kewang

    2013-03-01

    As the traditional graphite-based composites cannot meet the requirement of rapid developing modern industry, novel sliding electrical contact materials with high self-lubricating performance in multiple environments are eagerly required. Herein a copper-based composite with WS2 and graphite as solid lubricant are fabricated by powder metallurgy hot-pressed method. The friction and wear behaviors of the composites with and without current are investigated under the condition with sliding velocity of 10 m/s and normal load of 2.5 N/cm2 in both air and vacuum. Morphologies of the worn surfaces are observed by optical microscope and compositions of the lubricating films are analyzed by XPS. Surface profile curves and roughness of the worn surfaces are obtained by 2205 surface profiler. The results of wear tests show that the friction coefficient and wear volume loss of the composites with current are greater than that without current in both air and vacuum due to the adverse effects of electrical current which damaged the lubricating film partially and roughed the worn surfaces. XPS results demonstrate that the lubricating film formed in air is composed of oxides of Cu, WS2, elemental S and graphite, while the lubricating film formed in vacuum is composed of Cu, WS2 and graphite. Because of the synergetic lubricating action of oxides of Cu, WS2 and graphite, the composites show low friction coefficient and wear volume loss in air condition. Owing to the fact that graphite loses its lubricity which makes WS2 become the only lubricant, severe adhesive and abrasive wear occur and result in a high value of wear rate in vacuum condition. The formation of the lubricating film on the contact interface between the brush and ring is one of the factors which can greatly affect the wear performance of the brushes. The low contact voltage drop of the composites in vacuum condition is attributed to the high content of Cu in the surface film. This study fabricated a kind of new

  3. Zinc air refuelable battery: alternative zinc fuel morphologies and cell behavior

    SciTech Connect

    Cooper, J.F.; Krueger, R.

    1997-01-01

    Multicell zinc/air batteries have been tested previously in the laboratory and as part of the propulsion system of an electric bus; cut zinc wire was used as the anode material. This battery is refueled by a hydraulic transport of 0.5-1 mm zinc particles into hoppers above each cell. We report an investigation concerning alternative zinc fuel morphologies, and energy losses associated with refueling and with overnight or prolonged standby. Three types of fuel pellets were fabricated, tested and compared with results for cut wire: spheres produced in a fluidized bed electrolysis cell; elongated particles produced by gas-atomization; and pellets produced by chopping 1 mm porous plates made of compacted zinc fines. Relative sizes of the particles and cell gap dimensions are critical. All three types transported within the cell 1553 and showed acceptable discharge characteristics, but a fluidized bed approach appears especially attractive for owner/user recovery operations.

  4. Altered Entrainment to the Day/Night Cycle Attenuates the Daily Rise in Circulating Corticosterone in the Mouse

    PubMed Central

    Sollars, Patricia J.; Weiser, Michael J.; Kudwa, Andrea E.; Bramley, Jayne R.; Ogilvie, Malcolm D.; Spencer, Robert L.; Handa, Robert J.; Pickard, Gary E.

    2014-01-01

    The suprachiasmatic nucleus (SCN) is a circadian oscillator entrained to the day/night cycle via input from the retina. Serotonin (5-HT) afferents to the SCN modulate retinal signals via activation of 5-HT1B receptors, decreasing responsiveness to light. Consequently, 5-HT1B receptor knockout (KO) mice entrain to the day/night cycle with delayed activity onsets. Since circulating corticosterone levels exhibit a robust daily rhythm peaking around activity onset, we asked whether delayed entrainment of activity onsets affects rhythmic corticosterone secretion. Wheel-running activity and plasma corticosterone were monitored in mice housed under several different lighting regimens. Both duration of the light∶dark cycle (T cycle) and the duration of light within that cycle was altered. 5-HT1B KO mice that entrained to a 9.5L:13.5D (short day in a T = 23 h) cycle with activity onsets delayed more than 4 h after light offset exhibited a corticosterone rhythm in phase with activity rhythms but reduced 50% in amplitude compared to animals that initiated daily activity <4 h after light offset. Wild type mice in 8L:14D (short day in a T = 22 h) conditions with highly delayed activity onsets also exhibited a 50% reduction in peak plasma corticosterone levels. Exogenous adrenocorticotropin (ACTH) stimulation in animals exhibiting highly delayed entrainment suggested that the endogenous rhythm of adrenal responsiveness to ACTH remained aligned with SCN-driven behavioral activity. Circadian clock gene expression in the adrenal cortex of these same animals suggested that the adrenal circadian clock was also aligned with SCN-driven behavior. Under T cycles <24 h, altered circadian entrainment to short day (winter-like) conditions, manifest as long delays in activity onset after light offset, severely reduces the amplitude of the diurnal rhythm of plasma corticosterone. Such a pronounced reduction in the glucocorticoid rhythm may alter rhythmic gene expression in the

  5. The frequency of hippocampal theta rhythm is modulated on a circadian period and is entrained by food availability

    PubMed Central

    Munn, Robert G. K.; Tyree, Susan M.; McNaughton, Neil; Bilkey, David K.

    2015-01-01

    The hippocampal formation plays a critical role in the generation of episodic memory. While the encoding of the spatial and contextual components of memory have been extensively studied, how the hippocampus encodes temporal information, especially at long time intervals, is less well understood. The activity of place cells in hippocampus has previously been shown to be modulated at a circadian time-scale, entrained by a behavioral stimulus, but not entrained by light. The experimental procedures used in the previous study of this phenomenon, however, necessarily conflated two alternative entraining stimuli, the exposure to the recording environment and the availability of food, making it impossible to distinguish between these possibilities. Here we demonstrate that the frequency of theta-band hippocampal EEG varies with a circadian period in freely moving animals and that this periodicity mirrors changes in the firing rate of hippocampal neurons. Theta activity serves, therefore, as a proxy of circadian-modulated hippocampal neuronal activity. We then demonstrate that the frequency of hippocampal theta driven by stimulation of the reticular formation also varies with a circadian period. Because this effect can be observed without having to feed the animal to encourage movement we were able to identify what stimulus entrains the circadian oscillation. We show that with reticular-activated recordings started at various times of the day the frequency of theta varies quasi-sinusoidally with a 25 h period and phase-aligned when referenced to the animal’s regular feeding time, but not the recording start time. Furthermore, we show that theta frequency consistently varied with a circadian period when the data obtained from repeated recordings started at various times of the day were referenced to the start of food availability in the recording chamber. This pattern did not occur when data were referenced to the start of the recording session or to the actual time of

  6. Spatio-temporal behavior of brightness temperature in Tel-Aviv and its application to air temperature monitoring.

    PubMed

    Pelta, Ran; Chudnovsky, A Alexandra; Schwartz, Joel

    2016-01-01

    This study applies remote sensing technology to assess and examine the spatial and temporal Brightness Temperature (BT) profile in the city of Tel-Aviv, Israel over the last 30 years using Landsat imagery. The location of warmest and coldest zones are constant over the studied period. Distinct diurnal and temporal BT behavior divide the city into four different segments. As an example of future application, we applied mixed regression models with daily random slopes to correlate Landsat BT data with monitored air temperature (Tair) measurements using 14 images for 1989-2014. Our preliminary results show a good model performance with R(2) = 0.81. Furthermore, based on the model's results, we analyzed the spatial profile of Tair within the study domain for representative days. PMID:26499933

  7. Oxidation Behavior of Germanium- and/or Silicon-Bearing Near-α Titanium Alloys in Air

    NASA Astrophysics Data System (ADS)

    Kitashima, Tomonori; Yamabe-Mitarai, Yoko

    2015-06-01

    The effect of germanium (Ge) and/or silicon (Si) addition on the oxidation behavior of the near-α alloy Ti-5Al-2Sn-4Zr-2Mo was investigated in air at 973 K (700 °C). Ge addition decreased the oxidation resistance because of the formation of a Ge-rich layer in the substrate at the TiO2/substrate interface, enhancing Sn segregation at the interface. In addition, a small amount of Ge dissolved in the external Al2O3 layer. These results reduced the aluminum activity at the interface, suppressed the formation of Al2O3, and increased the diffusivity of oxygen in the oxide scales. The addition of 0.2 and 0.9 wt pct Si was beneficial for improving oxidation resistance. The effect of germanide and silicide precipitates in the matrix on the oxide growth process was also discussed.

  8. Estimated Entrainment of Dungeness Crab During Dredging For The Columbia River Channel Improvement Project

    SciTech Connect

    Pearson, Walter H.; Williams, Greg D.; Skalski, John R.

    2002-12-01

    The studies reported here focus on issues regarding the entrainment of Dungeness crab related to the proposed Columbia River Channel Improvement Project and provided direct measurements of crab entrainment rates at three locations (Desdomona Shoals, Upper Sands, and Miller Sands) from RM4 to RM24 during summer 2002. Entrainment rates for all age classes of crabs ranged from zero at Miller Sands to 0.224 crabs per cy at Desdemona Shoals in June 2002. The overall entrainment rate at Desdomona Shoals in September was 0.120 crabs per cy. A modified Dredge Impact Model (DIM) used the summer 2002 entrainment rates to project crab entrainment and adult equivalent loss and loss to the fishery for the Channel Improvement Project. To improve the projections, entrainment data from Flavel Bar is needed. The literature, analyses of salinity intrusion scenarios, and the summer 2002 site-specific data on entrainment and salinity all indicate that bottom salinity influences crab distribution and entrainment, especially at lower salinities. It is now clear from field measurements of entrainment rates and salinity during a period of low river flow (90-150 Kcfs) and high salinity intrusion that entrainment rates are zero where bottom salinity is less than 16 o/oo most of the time. Further, entrainment rates of 2+ and older crab fall with decreasing salinity in a clear and consistent manner. More elaboration of the crab distribution- salinity model, especially concerning salinity and the movements of 1+ crab, is needed.

  9. The discovery of human auditory-motor entrainment and its role in the development of neurologic music therapy.

    PubMed

    Thaut, Michael H

    2015-01-01

    The discovery of rhythmic auditory-motor entrainment in clinical populations was a historical breakthrough in demonstrating for the first time a neurological mechanism linking music to retraining brain and behavioral functions. Early pilot studies from this research center were followed up by a systematic line of research studying rhythmic auditory stimulation on motor therapies for stroke, Parkinson's disease, traumatic brain injury, cerebral palsy, and other movement disorders. The comprehensive effects on improving multiple aspects of motor control established the first neuroscience-based clinical method in music, which became the bedrock for the later development of neurologic music therapy. The discovery of entrainment fundamentally shifted and extended the view of the therapeutic properties of music from a psychosocially dominated view to a view using the structural elements of music to retrain motor control, speech and language function, and cognitive functions such as attention and memory. PMID:25725919

  10. Developmental Exposure to Concentrated Ambient Ultrafine Particulate Matter Air Pollution in Mice Results in Persistent and Sex-Dependent Behavioral Neurotoxicity and Glial Activation

    PubMed Central

    Allen, Joshua L.; Liu, Xiufang; Weston, Douglas; Prince, Lisa; Oberdörster, Günter; Finkelstein, Jacob N.; Johnston, Carl J.; Cory-Slechta, Deborah A.

    2014-01-01

    The brain appears to be a target of air pollution. This study aimed to further ascertain behavioral and neurobiological mechanisms of our previously observed preference for immediate reward (Allen, J. L., Conrad, K., Oberdorster, G., Johnston, C. J., Sleezer, B., and Cory-Slechta, D. A. (2013). Developmental exposure to concentrated ambient particles and preference for immediate reward in mice. Environ. Health Perspect. 121, 32–38), a phenotype consistent with impulsivity, in mice developmentally exposed to inhaled ultrafine particles. It examined the impact of postnatal and/or adult concentrated ambient ultrafine particles (CAPS) or filtered air on another behavior thought to reflect impulsivity, Fixed interval (FI) schedule-controlled performance, and extended the assessment to learning/memory (novel object recognition (NOR)), and locomotor activity to assist in understanding behavioral mechanisms of action. In addition, levels of brain monoamines and amino acids, and markers of glial presence and activation (GFAP, IBA-1) were assessed in mesocorticolimbic brain regions mediating these cognitive functions. This design produced four treatment groups/sex of postnatal/adult exposure: Air/Air, Air/CAPS, CAPS/Air, and CAPS/CAPS. FI performance was adversely influenced by CAPS/Air in males, but by Air/CAPS in females, effects that appeared to reflect corresponding changes in brain mesocorticolimbic dopamine/glutamate systems that mediate FI performance. Both sexes showed impaired short-term memory on the NOR. Mechanistically, cortical and hippocampal changes in amino acids raised the potential for excitotoxicity, and persistent glial activation was seen in frontal cortex and corpus callosum of both sexes. Collectively, neurodevelopment and/or adulthood CAPS can produce enduring and sex-dependent neurotoxicity. Although mechanisms of these effects remain to be fully elucidated, findings suggest that neurodevelopment and/or adulthood air pollution exposure may

  11. Developmental exposure to concentrated ambient ultrafine particulate matter air pollution in mice results in persistent and sex-dependent behavioral neurotoxicity and glial activation.

    PubMed

    Allen, Joshua L; Liu, Xiufang; Weston, Douglas; Prince, Lisa; Oberdörster, Günter; Finkelstein, Jacob N; Johnston, Carl J; Cory-Slechta, Deborah A

    2014-07-01

    The brain appears to be a target of air pollution. This study aimed to further ascertain behavioral and neurobiological mechanisms of our previously observed preference for immediate reward (Allen, J. L., Conrad, K., Oberdorster, G., Johnston, C. J., Sleezer, B., and Cory-Slechta, D. A. (2013). Developmental exposure to concentrated ambient particles and preference for immediate reward in mice. Environ. Health Perspect. 121, 32-38), a phenotype consistent with impulsivity, in mice developmentally exposed to inhaled ultrafine particles. It examined the impact of postnatal and/or adult concentrated ambient ultrafine particles (CAPS) or filtered air on another behavior thought to reflect impulsivity, Fixed interval (FI) schedule-controlled performance, and extended the assessment to learning/memory (novel object recognition (NOR)), and locomotor activity to assist in understanding behavioral mechanisms of action. In addition, levels of brain monoamines and amino acids, and markers of glial presence and activation (GFAP, IBA-1) were assessed in mesocorticolimbic brain regions mediating these cognitive functions. This design produced four treatment groups/sex of postnatal/adult exposure: Air/Air, Air/CAPS, CAPS/Air, and CAPS/CAPS. FI performance was adversely influenced by CAPS/Air in males, but by Air/CAPS in females, effects that appeared to reflect corresponding changes in brain mesocorticolimbic dopamine/glutamate systems that mediate FI performance. Both sexes showed impaired short-term memory on the NOR. Mechanistically, cortical and hippocampal changes in amino acids raised the potential for excitotoxicity, and persistent glial activation was seen in frontal cortex and corpus callosum of both sexes. Collectively, neurodevelopment and/or adulthood CAPS can produce enduring and sex-dependent neurotoxicity. Although mechanisms of these effects remain to be fully elucidated, findings suggest that neurodevelopment and/or adulthood air pollution exposure may represent

  12. MODELING THE EFFECT OF WATER VAPOR ON THE INTERFACIAL BEHAVIOR OF HIGH-TEMPERATURE AIR IN CONTACT WITH Fe20Cr SURFACES

    SciTech Connect

    Chialvo, Ariel A; Brady, Michael P; Keiser, James R; Cole, David R

    2011-01-01

    The purpose of this communication is to provide an atomistic view, via molecular dynamic simulation, of the contrasting interfacial behavior between high temperature dry- and (10-40 vol%) wet-air in contact with stainless steels as represented by Fe20Cr. It was found that H2O preferentially adsorbs and displaces oxygen at the metal/fluid interface. Comparison of these findings with experimental studies reported in the literature is discussed. Keywords: Fe-Cr alloys, metal-fluid interfacial behavior, wet-air, molecular simulation

  13. Fission product transport and behavior during two postulated loss of flow transients in the air

    SciTech Connect

    Adams, J.P.; Carboneau, M.L.

    1991-01-01

    This document discusses fission product behavior during two postulated loss-of-flow accidents (leading to high- and low-pressure core degradation, respectively) in the Advanced Test Reactor (ATR). These transients are designated ATR Transient LCPI5 (high-pressure) and LPP9 (low-pressure). Normally, transients of this nature would be easily mitigated using existing safety systems and procedures. In these analyses, failure of these safety systems was assumed so that core degradation and fission product release could be analyzed. A probabilistic risk assessment indicated that the probability of occurrence for these two transients is of the order of 10{sup {minus}5 }and 10{sup {minus}7} per reactor year for LCP15 and LPP9, respectively.

  14. Fission product transport and behavior during two postulated loss of flow transients in the air

    SciTech Connect

    Adams, J.P.; Carboneau, M.L.

    1991-12-31

    This document discusses fission product behavior during two postulated loss-of-flow accidents (leading to high- and low-pressure core degradation, respectively) in the Advanced Test Reactor (ATR). These transients are designated ATR Transient LCPI5 (high-pressure) and LPP9 (low-pressure). Normally, transients of this nature would be easily mitigated using existing safety systems and procedures. In these analyses, failure of these safety systems was assumed so that core degradation and fission product release could be analyzed. A probabilistic risk assessment indicated that the probability of occurrence for these two transients is of the order of 10{sup {minus}5 }and 10{sup {minus}7} per reactor year for LCP15 and LPP9, respectively.

  15. Electrification of particulate entrained fluid flows-Mechanisms, applications, and numerical methodology

    NASA Astrophysics Data System (ADS)

    Wei, Wei; Gu, Zhaolin

    2015-10-01

    distribution and mechanical behaviors of liquid surface can be predicted by using this method. The methodology combining particle charging model with Computational Fluid Dynamics (CFD) and Discrete element method (DEM) is applicable to study the particle charging/charged processes in gas-solid two phase flows, the influence factors of particle charging, such as gas-particle interaction, contact force, contact area, and various velocities, are described systematically. This review would explore a clear understanding of the particulate charging and provide theoretical references to control and utilize the charging/charged particulate entrained fluid system.

  16. The Behavior of Methane-Air Partially Premixed Flames Under Normal- and Zero-G Conditions

    NASA Technical Reports Server (NTRS)

    Puri, Ishwar K.; Aggarwal, Suresh K.; Choi, Chun Wai; Hegde, Uday

    2001-01-01

    Partially premixed flames (PPFs) represent a class of hybrid flames containing multiple reaction zones. These flames are established when less than stoichiometric quantity of oxidizer is molecularly mixed with the fuel stream before entering the reaction zone where additional oxidizer is available for complete combustion. This mode of combustion can be used to exploit the advantages of both nonpremixed and premixed flames regarding operational safety, lower pollutant emissions and flame stabilization. A double flame containing a fuel-rich premixed reaction zone, which is anchored by a nonpremixed reaction zone, is one example of a partially premixed flame. A triple flame is also a PPF that contains three reaction zones, namely, a fuel-rich premixed zone, a fuel-lean premixed zone, and a nonpremixed reaction zone. Herein we focus on two aspects of our investigation, one involving the development of optical diagnostics that can be used on a microgravity rig, which has been recently fabricated, and the other on the numerically predicted differences between normal- and zero-gravity PPFs. Both the measurements and simulations examine the detailed structure of methane-air PPFs stabilized on a Wolfhard-Parker slot burner.

  17. Novel alloys to improve the electrochemical behavior of zinc anodes for zinc/air battery

    NASA Astrophysics Data System (ADS)

    Lee, Chang Woo; Sathiyanarayanan, K.; Eom, Seung Wook; Yun, Mun Soo

    In our continued efforts for improving the performance of zinc anodes for a Zn/air battery, we now report the preparation of three alloys and improved performances of anodes made up with these alloys. The alloys contained zinc, nickel, and indium with different weight percentages and were calcined at two different temperatures. Out of the six alloys, the alloy which has a composition of zinc 90%, nickel 7.5% and Indium 2.5% and fired at 500 °C is found to be the best. In the case of the hydrogen evolution reaction, this alloy had its potential shifted to a more negative potential. As far as the cyclic voltammograms were concerned, the difference between the anodic and cathodic part was minimal when compared with other alloys. Surprisingly, this alloy had reversibility even after 100 cycles of the cyclic voltammogram. This is a clear indication that dendrite formation was reduced to a considerable extent. Images taken with a scanning electron microscope also indicated reduced dendrite formation.

  18. Tribological behavior of micron-scale polycrystalline silicon structural films in ambient air

    NASA Astrophysics Data System (ADS)

    Alsem, D. H.; van der Hulst, R.; Stach, E. A.; Dugger, M. T.; De Hosson, J. Th. M.; Ritchie, R. O.

    2009-02-01

    As tribological properties are critical factors in the reliability of microelectromechanical systems, it is important to understand the physical processes and parameters governing wear and friction in silicon structural films. Dynamic friction, wear volumes and wear morphology have been studied for polysilicon devices from the Sandia SUMMiT VTM process actuated in ambient air at μN loads. A total of seven devices were tested. Roughly half of the devices showed a peak in the friction coefficient at three times the initial value with failure after 105 cycles. The other half of the devices behaved similarly initially; however, following the friction coefficient peak they displayed a lower steady-state friction regime with no failure for millions of cycles. Additionally, the nanoscale wear coefficient and roughness increased in the first ~105 cycles and then slowly decayed over several million cycles. Transmission electron microscopy studies revealed amorphous oxygen-rich debris. These measurements show that after a short adhesive wear regime, abrasive wear is the governing mechanism with failures attributed to differences in the local nanoscale surface morphology. Changing the relative humidity, sliding speed and load was found to influence the friction coefficient, but re-oxidation of worn polysilicon surfaces was only found to have an effect after periods of inactivity.

  19. Beneficial effects of environmental enrichment and food entrainment in the R6/2 mouse model of Huntington's disease

    PubMed Central

    Skillings, Elizabeth A; Wood, Nigel I; Morton, A Jennifer

    2014-01-01

    Background In addition to their cognitive and motor deficits, R6/2 mice show a progressive disintegration in circadian rhythms that mirrors the problems associated with sleep-wake disturbances experienced by patients with Huntington's disease (HD). It has been shown previously that motor and cognitive performance, as well as survival, can be improved in transgenic mouse models of HD through the provision of environmental enrichment. Methods We compared the effect of two different overnight entrainment paradigms presented either separately or in combination. The first was environmental enrichment, the second was temporal food-entrainment. Environmental enrichment was provided in the dark period (the natural active period for mice) in the form of access to a Perspex playground containing running wheels, tunnels, climbing frame, ropes and chew blocks. Food entrainment was imposed by allowing access to food only during the dark period. We assessed a number of different aspects of function in the mice, measuring general health (by SHIRPA testing, body temperature and body weight measurements), cognitive performance in the touchscreen and locomotor behavior in the open field. Results There were no significant differences in cognitive performance between groups on different schedules. Environmental enrichment delayed the onset of general health deterioration, while food entrainment slowed the loss of body weight, aided the maintenance of body temperature and improved locomotor behavior. Effects were limited however, and in combination had deleterious effects on survival. Conclusions Our results support previous studies showing that environmental enrichment can be beneficial and might be used to enhance the quality of life of HD patients. However, improvements are selective and ‘enrichment’ per se is likely to only be useful as an adjunct to a more direct therapy. PMID:25328844

  20. Assessment of Circadian and Light-Entrainable Parameters in Mice Using Wheel-Running Activity.

    PubMed

    Banks, Gareth T; Nolan, Patrick M

    2011-01-01

    In most organisms, physiological variables are regulated by an internal clock. This endogenous circadian (∼24-hr) clock enables organisms to anticipate daily environmental changes and modify behavioral and physiological functions appropriately. Processes regulated by the circadian clock include sleep-wake and locomotor activity, core body temperature, metabolism, water/food intake, and available hormone levels. At the core of the mammalian circadian system are molecular oscillations within the hypothalamic suprachiasmatic nucleus. These oscillations are modifiable by signals from the environment (so called zeitgebers or time-givers) and, once integrated within the suprachiasmatic nucleus, are conveyed to remote neural circuits where output rhythms are regulated. Disrupting any of a number of neural processes can affect how rhythms are generated and relayed to the periphery and disturbances in circadian/entrainment parameters are associated with numerous human conditions. These non-invasive protocols can be used to determine whether circadian/entrainment parameters are affected in mouse mutants or treatment groups. Curr. Protoc. Mouse Biol. 1:369-381 © 2011 by John Wiley & Sons, Inc. PMID:26068996

  1. Methamphetamine and dopamine receptor D1 regulate entrainment of murine circadian oscillators.

    PubMed

    Mohawk, Jennifer A; Pezuk, Pinar; Menaker, Michael

    2013-01-01

    We investigated the effect of methamphetamine (MA) injections on the circadian organization of behavior and individual tissues in the mouse. Scheduled, daily injections of MA resulted in anticipatory activity, with an increase in locomotor activity immediately prior to the time of injection. Daily MA also shifted the peak time of PER2 expression in the liver, pituitary, and salivary glands. It has been suggested that reward pathways, and dopamine signaling in particular, may underlie the effects of MA on the circadian system. To test this hypothesis, we examined the effect of the D1 receptor antagonist SCH23390 (SCH) on circadian rhythms. The MA-induced shift in the phase of pituitary and salivary glands was attenuated by pretreatment with the D1 antagonist SCH23390 (SCH). Interestingly, daily SCH, administered alone, also affected some circadian oscillators. The livers and lungs (but not pituitaries or salivary glands) of mice treated with daily injections of SCH displayed disrupted rhythms of PER2 expression, suggesting that D1 receptor signaling is important for entrainment of these organs. From these results, we conclude that MA has widespread effects within the circadian system, and that these effects are mediated, at least in part, by the dopaminergic system. This study also identifies a role for dopamine signaling in normal entrainment of circadian oscillators. PMID:23626822

  2. Fluid dynamics of pressurized, entrained coal gasifiers. Tenth quarterly technical progress report, April 1, 1996--June 30, 1996

    SciTech Connect

    Louge, M.Y.

    1996-10-01

    Pressurized, entrained gasification is a promising new technology for the clean and efficient combustion of coal. Its principle is to operate a coal gasifier at a high inlet gas velocity to increase the inflow of reactants, and at an elevated pressure to raise the overall efficiency of the process. Unfortunately, because of the extraordinary difficulties involved in performing measurements in hot, pressurized, high-velocity pilot plants, its fluid dynamics are largely unknown. Thus the designer cannot predict with certainty crucial phenomena Re erosion, heat transfer and solid capture. In this context, we are conducting a study of the fluid dynamics of Pressurized Entrained Coal Gasifiers (PECGs). The idea is to simulate the flows in generic industrial PECGs using dimensional similitude. To this end, we employ a unique entrained gas-solid flow facility with the flexibility to recycle -rather than discard- gases other than air. By matching five dimensionless parameters, suspensions in mixtures of helium, carbon dioxide and sulfur hexafluoride simulate the effects of pressure and scale-up on the fluid dynamics of PECGs. Because it operates under cold, atmospheric conditions, the laboratory facility is ideal for detailed measurements.

  3. Effects of Wet Air and Synthetic Combustion Gas Atmospheres on the Oxidation Behavior of Mo-Si-B Alloys

    SciTech Connect

    Kramer, M.J.; Thom, A.J.; Mandal, P.; Behrani, V.; Akinc, M.

    2003-04-24

    Continuing our work on understanding the oxidation behavior of multiphase composite alloys based on the Mo-Si-B system, we investigated three alloys in the Mo-Si-B system, designated as A1, A2, and A3. The nominal phase assemblages of these alloys are: A1 = Mo{sub 5}Si{sub 3}B{sub x} (T1)-MoSi{sub 2}-MoB, A2 = T1-Mo{sub 5}SiB{sub 2} (T2)-Mo{sub 3}Si, and A3 = Mo-T2-Mo{sub 3}Si. Our previous work showed that for exposures to 1100 C, all alloys formed a protective oxide scale in dry air. Exposures to wet air containing about 150 Torr water promoted the formation of a multiphase layer near the scale/alloy interface composed of Mo and MoO{sub 2}. Interrupted mass loss measurements indicated a near zero mass change. In the present study, isothermal mass measurements were conducted in order to quantitatively determine the oxidation rate constants at 1000 C in both dry and wet air. These measurements are critical for understanding the nature of scale development during the initial exposure, as well as the nature of scale stability during the long-term exposure. Isothermal measurements were also conducted at 1600 C in dry air to make an initial determination of alloy stability with respect to Vision 21 goals. We also conducted alloy oxidation testing in a synthetic oxidizing combustion atmosphere. Alloys were exposed up to 300 hours at 1100 C to a gas mixture having an approximate gas composition of N{sub 2} - 13 CO{sub 2} - 10 H{sub 2}O - 4 O{sub 2}. This gas composition simulates oxidizing flue gas, but does not contain a sulfidizing agent that would also be present in flue gas. The oxidized samples were carefully analyzed by SEM/EDS. This analysis will be discussed to provide an understanding of the role of water vapor and the synthetic combustion atmosphere on the oxidative stability of Mo-Si-B alloys.

  4. Late Quaternary behavior of the East African monsoon and the importance of the Congo Air Boundary

    NASA Astrophysics Data System (ADS)

    Tierney, Jessica E.; Russell, James M.; Sinninghe Damsté, Jaap S.; Huang, Yongsong; Verschuren, Dirk

    2011-04-01

    Both Atlantic and Indian Ocean climate dynamics exert influence over tropical African hydroclimate, producing complex patterns of convergence and precipitation. To isolate the Indian Ocean influence on African paleohydrology, we analyzed the deuterium/hydrogen ratio of higher plant leaf waxes ( δD wax) in a 25 000-year sediment record from Lake Challa (3° S, 38° E) in the easternmost area of the African tropics. Whereas both the seismic record of inferred lake level fluctuations and the Branched and Isoprenoidal Tetraether (BIT) index proxy record changes in hydrology within the Challa basin, δD wax, as a proxy for the isotopic composition of precipitation ( δD P) is interpreted as a tracer of large-scale atmospheric circulation that integrates the history of the moisture transported to the Lake Challa area. Specifically, based on modern-day isotope-rainfall relationships, we argue that Lake Challa δD wax reflects the intensity of East African monsoon circulation. The three hydrological proxy records show generally similar trends for the last 25 000 years, but there are important differences between them, primarily during the middle Holocene. We interpret this deviation of δD wax from local hydrological history as a decoupling of East African monsoon intensity - which heavily influences the isotopes of precipitation in East Africa today - from rainfall amount in the Challa basin. In combination, the hydrological proxy data from Lake Challa singularly highlight zonal gradients in tropical African climate that occur over a variety of timescales, suggesting that the Congo Air Boundary plays a fundamental role in controlling hydroclimate in the African tropics.

  5. Thermal creep-assisted dust lifting on Mars: Wind tunnel experiments for the entrainment threshold velocity

    NASA Astrophysics Data System (ADS)

    Küpper, Markus; Wurm, Gerhard

    2015-07-01

    In this work we present laboratory measurements on the reduction of the threshold friction velocity necessary for lifting dust if the dust bed is illuminated. Insolation of a porous soil establishes a temperature gradient. At low ambient pressure this gradient leads to thermal creep gas flow within the soil. This flow leads to a subsurface overpressure which supports lift imposed by wind. The wind tunnel was run with Mojave Mars Simulant and air at 3, 6, and 9mbar, to cover most of the pressure range at Martian surface levels. Our first measurements imply that the insolation of the Martian surface can reduce the entrainment threshold velocity between 4% and 19% for the conditions sampled with our experiments. An insolation activated soil might therefore provide additional support for aeolian particle transport at low wind speeds.

  6. Combustion Model of Supersonic Rocket Exhausts in an Entrained Flow Enclosure

    NASA Technical Reports Server (NTRS)

    Vu, Bruce T.; Oliveira, Justin

    2011-01-01

    This paper describes the Computational Fluid Dynamics (CFD) model developed to simulate the supersonic rocket exhaust in an entrained flow cylinder. The model can be used to study the plume-induced environment due to static firing tests of the Taurus-II launch vehicle. The finite-rate chemistry is used to model the combustion process involving rocket propellant (RP-1) and liquid oxidizer (LOX). A similar chemical reacting model is also used to simulate the mixing of rocket plume and ambient air. The model provides detailed information on the gas concentration and other flow parameters within the enclosed region, thus allowing different operating scenarios to be examined in an efficient manner. It is shown that the real gas influence is significant and yields better agreement with the theory.

  7. Combustion Model of Supersonic Rocket Exhausts in an Entrained Flow Enclosure

    NASA Technical Reports Server (NTRS)

    Vu, Bruce; Oliveira, Justin

    2011-01-01

    This paper describes the Computation Fluid Dynamics (CFD) model developed to simulate the supersonic rocket exhaust in an entrained flow cylinder. The model can be used to study the plume-induced environment due to static firing test of the Taurus II launch vehicle. The finite rate chemistry is used to model the combustion process involving rocket propellant (RP 1) and liquid oxidizer (LOX). A similar chemical reacting model is also used to simulate the mixing of rocket plume and ambient air. The model provides detailed information on the gas concentration and other flow parameters within the enclosed region thus allowing different operating scenarios to be examined in an efficient manner. It is shown that the real gas influence is significant and yields better agreement with the theory.

  8. Gradient layer entrainment in a thermohaline system with mixed layer circulation

    SciTech Connect

    Incropera, F.P.; Lents, C.E.; Viskanta, R.

    1986-11-01

    Entrainment of salt-stratified fluid into a bottom mixed layer is investigated under conditions for which mixing is driven by bottom heating and/or an imposed horizontal flow. Entrainment rate measurements and mixed layer flow visualization suggest that entrainment is strongly influenced by a shear mechanism involving both horizontal and vertical fluid velocity components. Under certain conditions, imposition of the horizontal flow inhibits the buoyancy flow and entrainment rates for combined mixing are less than those for pure buoyant mixing. Attempts to correlate entrainment rates in terms of conventional dimensionless parameters were unsuccessful.

  9. The microstructure and dissolution behavior of lipid-monolayer-coated, air-filled microbubble

    NASA Astrophysics Data System (ADS)

    Pu, Gang

    Suspensions of lipid-coated microbubbles are currently being developed for use as ultrasound contrast agents, drug delivery vehicles and blood substitutes. In our study, first, we examined the effect of lipid acyl chain length and the cooling rate on the microbubble surface domain morphology. The average domain size decreased with increasing cooling rate for all acyl chain lengths. The shape factor increased with chain length for the highest cooling rate. Second, we investigated the effect of microstructure on molecular oxygen permeation through condensed phospholipid monolayers. Oxygen permeability was shown to increase linearly with domain boundary density at a constant phospholipid acyl chain length and, accordingly, was shown to decrease exponentially with increasing chain length at a constant domain boundary density. Modification of the energy barrier theory to account for microstructural effects, in terms of the domain boundary density, provides a general equation to model passive transport through polycrystalline monolayer films. Last, we demonstrated that the phase conditions and microstructure of the shell were critical to determine the dissolution behaviors of the lipid-coated microbubble. For these two-phase coexistence bubbles, a transition from primary collapse, as loss of expanded phase due to vesiculation, to secondary collapse, as the rapid propagation of monolayer folds and simultaneous deformation, was observed. For very rigid monolayers, we observed substantial surface buckling with simultaneous nucleation and growth of folds.

  10. Creep-rupture behavior of 6 candidate stirling engine iron-base superalloys in high pressure hydrogen. Volume 1: Air creep-rupture behavior

    NASA Technical Reports Server (NTRS)

    Bhattacharyya, S.

    1982-01-01

    Four wrought alloys (A-286, IN 800H, N-155, and 19-9DL) and two cast alloys (CRM-6D and XF-818) were tested to determine their creep-rupture behavior. The wrought alloys were used in the form of sheets of 0.89 mm (0.035 in.) average thickness. The cast alloy specimens were investment cast and machined to 6.35 mm (0.250 in.) gage diameter. All specimens were tested to rupture in air at different times up to 3000 h over the temperature range of 650 C to 925 C (1200 F to 1700 F). Rupture life, minimum creep rate, and time to 1% creep strain were statistically analyzed as a function of stress at different temperatures. Temperature-compensated analysis was also performed to obtain the activation energies for rupture life, time to 1% creep strain, and the minimum creep rate. Microstructural and fracture analyses were also performed. Based on statistical analyses, estimates were made for stress levels at different temperatures to obtain 3500 h rupture life and time to 1% creep strain. Test results are to be compared with similar data being obtained for these alloys under 15 MPa (2175 psi) hydrogen.

  11. Magnetized neutron stars with superconducting cores: effect of entrainment

    NASA Astrophysics Data System (ADS)

    Palapanidis, K.; Stergioulas, N.; Lander, S. K.

    2015-09-01

    We construct equilibrium configurations of magnetized, two-fluid neutron stars using an iterative numerical method. Working in Newtonian framework we assume that the neutron star has two regions: the core, which is modelled as a two-component fluid consisting of type-II superconducting protons and superfluid neutrons, and the crust, a region composed of normal matter. Taking a new step towards more complete equilibrium models, we include the effect of entrainment, which implies that a magnetic force acts on neutrons, too. We consider purely poloidal field cases and present improvements to an earlier numerical scheme for solving equilibrium equations, by introducing new convergence criteria. We find that entrainment results in qualitative differences in the structure of field lines along the magnetic axis.

  12. Fast biomass pyrolysis with an entrained-flow reactor

    NASA Astrophysics Data System (ADS)

    Bohn, M. S.; Benham, C.

    1982-02-01

    A tubular entrained flow reactor has been used to study the effect of process control variables on fast biomass pyrolysis. In this type of reactor, finely ground biomass particles are entrained by carrier gas and transported through a reactor tube which is heated to about 900 C. Biomass particles pyrolyze as a result of heat transfer from the reactor wall yielding a gas composed primarily of carbon monoxide, carbon dioxide, hydrogen, methane, and unsaturated hydrocarbons. In this experimental program three dependent variables, percent conversion to gas, gas composition, and process heat, have been measured as a function of several process control variables. These process variables include reactor temperature, carrier gas to biomass flow ratio, reactor residence time, biomass particle size, and reactor Reynolds number. The data allow one to design and predict the performance of large scale reactors and also elucidates heat transfer mechanisms in fast biomass pyrolysis.

  13. Numerical Modeling of Deep Mantle Flow: Thermochemical Convection and Entrainment

    NASA Astrophysics Data System (ADS)

    Mulyukova, Elvira; Steinberger, Bernhard; Dabrowski, Marcin; Sobolev, Stephan

    2013-04-01

    One of the most robust results from tomographic studies is the existence of two antipodally located Large Low Shear Velocity Provinces (LLSVPs) at the base of the mantle, which appear to be chemically denser than the ambient mantle. Results from reconstruction studies (Torsvik et al., 2006) infer that the LLSVPs are stable, long-lived, and are sampled by deep mantle plumes that rise predominantly from their margins. The origin of the dense material is debated, but generally falls within three categories: (i) a primitive layer that formed during magma ocean crystallization, (ii) accumulation of a dense eclogitic component from the recycled oceanic crust, and (iii) outer core material leaking into the lower mantle. A dense layer underlying a less dense ambient mantle is gravitationally stable. However, the flow due to thermal density variations, i.e. hot rising plumes and cold downwelling slabs, may deform the layer into piles with higher topography. Further deformation may lead to entrainment of the dense layer, its mixing with the ambient material, and even complete homogenisation with the rest of the mantle. The amount of the anomalous LLSVP-material that gets entrained into the rising plumes poses a constraint on the survival time of the LLSVPs, as well as on the plume buoyancy, on the lithospheric uplift associated with plume interaction and geochemical signature of the erupted lavas observed at the Earth's surface. Recent estimates for the plume responsible for the formation of the Siberian Flood Basalts give about 15% of entrained dense recycled oceanic crust, which made the hot mantle plume almost neutrally buoyant (Sobolev et al., 2011). In this numerical study we investigate the mechanics of entrainment of a dense basal layer by convective mantle flow. We observe that the types of flow that promote entrainment of the dense layer are (i) upwelling of the dense layer when it gets heated enough to overcome its stabilizing chemical density anomaly, (ii

  14. Entrainment parameters in a cold superfluid neutron star core

    SciTech Connect

    Chamel, Nicolas; Haensel, Pawel

    2006-04-15

    Hydrodynamic simulations of neutron star cores that are based on a two-fluid description in terms of a neutron-proton superfluid mixture require the knowledge of the Andreev-Bashkin entrainment matrix which relates the momentum of one constituent to the currents of both constituents. This matrix is derived for arbitrary nuclear asymmetry at zero temperature and in the limits of small relative currents in the framework of the energy density functional theory. The Skyrme energy density functional is considered as a particular case. General analytic formulas for the entrainment parameters and various corresponding effective masses are obtained. These formulas are applied to the liquid core of a neutron star composed of homogeneous plasma of nucleons, electrons, and possibly muons in {beta} equilibrium.

  15. Synchrony and entrainment properties of robust circadian oscillators

    PubMed Central

    Bagheri, Neda; Taylor, Stephanie R.; Meeker, Kirsten; Petzold, Linda R.; Doyle, Francis J.

    2008-01-01

    Systems theoretic tools (i.e. mathematical modelling, control, and feedback design) advance the understanding of robust performance in complex biological networks. We highlight phase entrainment as a key performance measure used to investigate dynamics of a single deterministic circadian oscillator for the purpose of generating insight into the behaviour of a population of (synchronized) oscillators. More specifically, the analysis of phase characteristics may facilitate the identification of appropriate coupling mechanisms for the ensemble of noisy (stochastic) circadian clocks. Phase also serves as a critical control objective to correct mismatch between the biological clock and its environment. Thus, we introduce methods of investigating synchrony and entrainment in both stochastic and deterministic frameworks, and as a property of a single oscillator or population of coupled oscillators. PMID:18426774

  16. Updrafts, Downdrafts, Entrainment, and Detrainment in the Giga-LES

    NASA Astrophysics Data System (ADS)

    Krueger, S. K.; Glenn, I.

    2012-12-01

    We are investigating the properties of evolving three-dimensional updraft and downdraft "cores" in a model dataset from the Giga-LES, a large-domain LES (large-eddy simulation) of tropical oceanic deep convection (Khairoutdinov et al. 2009). We have also applied the analysis method developed by Kuang and Bretherton (2006) to investigate various aspects of the ensemble characteristics of cumulus convection in the Giga-LES. Our results agree with those of Kuang and Bretherton for the cumulus updraft properties. We have examined the relative merits of different entrainment and cloud-top-height assumptions in spectral plume models of cumulus updrafts, the characteristics of downdrafts, and the nature of a rapid transition from shallow to deep convection.isualization of cumulus clouds from the Giga-LES. The realistic structure is associated with entrainment.

  17. Entrainment and thrust augmentation in pulsatile ejector flows

    NASA Technical Reports Server (NTRS)

    Sarohia, V.; Bernal, L.; Bui, T.

    1981-01-01

    This study comprised direct thrust measurements, flow visualization by use of a spark shadowgraph technique, and mean and fluctuating velocity measurements with a pitot tube and linearized constant temperature hot-wire anemometry respectively. A gain in thrust of as much as 10 to 15% was observed for the pulsatile ejector flow as compared to the steady flow configuration. From the velocity profile measurements, it is concluded that this enhanced augmentation for pulsatile flow as compared to a nonpulsatile one was accomplished by a corresponding increased entrainment by the primary jet flow. It is also concluded that the augmentation and total entrainment by a constant area ejector critically depends upon the inlet geometry of the ejector. Experiments were performed to evaluate the influence of primary jet to ejector area ratio, ejector length, and presence of a diffuser on pulsatile ejector performance.

  18. Neural entrainment to the rhythmic structure of music.

    PubMed

    Tierney, Adam; Kraus, Nina

    2015-02-01

    The neural resonance theory of musical meter explains musical beat tracking as the result of entrainment of neural oscillations to the beat frequency and its higher harmonics. This theory has gained empirical support from experiments using simple, abstract stimuli. However, to date there has been no empirical evidence for a role of neural entrainment in the perception of the beat of ecologically valid music. Here we presented participants with a single pop song with a superimposed bassoon sound. This stimulus was either lined up with the beat of the music or shifted away from the beat by 25% of the average interbeat interval. Both conditions elicited a neural response at the beat frequency. However, although the on-the-beat condition elicited a clear response at the first harmonic of the beat, this frequency was absent in the neural response to the off-the-beat condition. These results support a role for neural entrainment in tracking the metrical structure of real music and show that neural meter tracking can be disrupted by the presentation of contradictory rhythmic cues. PMID:25170794

  19. Entrainment of respiratory frequency to exercise rhythm during hypoxia.

    PubMed

    Paterson, D J; Wood, G A; Marshall, R N; Morton, A R; Harrison, A B

    1987-05-01

    Breathing frequency (f) is often reported as having an integer-multiple relationship to limb movement (entrainment) during rhythmic exercise. To investigate the strength of this coupling while running under hypoxic conditions, two male Caucasians and four male Nepalese porters were tested in the Annapurna region of the Himalayas at altitudes of 915, 2,135, 3,200, 4,420, and 5,030 m. In an additional study in a laboratory at sea level, three male and four female subjects inspired various O2-N2 mixtures [fraction of inspired O2 (FIO2) = 20.93, 17.39, 14.40, 11.81%] that were administered in a single-blind randomized fashion during a treadmill run (40% FIO2 maximum O2 consumption). Breathing and gait signals were stored on FM tape and later processed on a PDP 11/73 computer. The subharmonic relationships between these signals were determined from Fourier analysis (power spectrum), and the coincidence of coupling occurrence was statistically modeled. Entrainment decreased linearly during increasing hypoxia (P less than 0.01). Moreover, a significant linear increase in f occurred during hypoxia (P less than 0.05), whereas stride frequency and metabolic rate remained constant, suggesting that hypoxic-induced increases in f decreased the degree of entrainment. PMID:3597249

  20. microRNA modulation of circadian clock period and entrainment

    PubMed Central

    Cheng, Hai-Ying M.; Papp, Joseph W.; Varlamova, Olga; Dziema, Heather; Russell, Brandon; Curfman, John P.; Nakazawa, Takanobu; Shimizu, Kimiko; Okamura, Hitoshi; Impey, Soren; Obrietan, Karl

    2007-01-01

    microRNAs (miRNAs) are a class of small, non-coding, RNAs that regulate the stability or translation of mRNA transcripts. Although recent work has implicated miRNAs in development and in disease, the expression and function of miRNAs in the adult mammalian nervous system has not been extensively characterized. Here, we examine the role of two brain-specific miRNAs, miR-219 and miR-132, in modulating the circadian clock located in the suprachiasmatic nucleus. miR-219 is a target of the CLOCK/BMAL1 complex, exhibits robust circadian rhythms of expression and the in vivo knockdown of miR-219 lengthens the circadian period. miR-132 is induced by photic entrainment cues via a MAPK/CREB-dependent mechanism, modulates clock gene expression, and attenuates the entraining effects of light. Collectively, these data reveal miRNAs as clock- and light-regulated genes and provide a mechanistic examination of their roles as effectors of pacemaker activity and entrainment. PMID:17553428

  1. Entrainment of coarse grains using a discrete particle model

    SciTech Connect

    Valyrakis, Manousos; Arnold, Roger B. Jr.

    2014-10-06

    Conventional bedload transport models and incipient motion theories relying on a time-averaged boundary shear stress are incapable of accounting for the effects of fluctuating near-bed velocity in turbulent flow and are therefore prone to significant errors. Impulse, the product of an instantaneous force magnitude and its duration, has been recently proposed as an appropriate criterion for quantifying the effects of flow turbulence in removing coarse grains from the bed surface. Here, a discrete particle model (DPM) is used to examine the effects of impulse, representing a single idealized turbulent event, on particle entrainment. The results are classified according to the degree of grain movement into the following categories: motion prior to entrainment, initial dislodgement, and energetic displacement. The results indicate that in all three cases the degree of particle motion depends on both the force magnitude and the duration of its application and suggest that the effects of turbulence must be adequately accounted for in order to develop a more accurate method of determining incipient motion. DPM is capable of simulating the dynamics of grain entrainment and is an appropriate tool for further study of the fundamental mechanisms of sediment transport.

  2. Presence of strong harmonics during visual entrainment: a magnetoencephalography study.

    PubMed

    Heinrichs-Graham, Elizabeth; Wilson, Tony W

    2012-09-01

    Visual neurons are known to synchronize their firing with stimuli that flicker at a constant rate (e.g. 12Hz). These so-called visual steady-state responses (VSSR) are a well-studied phenomenon, yet the underlying mechanisms are widely disagreed upon. Furthermore, there is limited evidence that visual neurons may simultaneously synchronize at harmonics of the stimulation frequency. We utilized magnetoencephalography (MEG) to examine synchronization at harmonics of the visual stimulation frequency (18Hz). MEG data were analyzed for event-related-synchronization (ERS) at the fundamental frequency, 36, 54, and 72Hz. We found strong ERS in all bands. Only 31% of participants showed maximum entrainment at the fundamental; others showed stronger entrainment at either 36 or 54Hz. The cortical foci of these responses indicated that the harmonics involved cortices that were partially distinct from the fundamental. These findings suggest that spatially-overlapping subpopulations of neurons are simultaneously entrained at different harmonics of the stimulus frequency. PMID:22569101

  3. An Examination of Some Behavioral Correlates of Air Force Undergraduate Pilot Training through the Use of the Porter and Lawler Performance/Satisfaction Model.

    ERIC Educational Resources Information Center

    Lohmann, David P.

    The study tested the applicability of portions of the Porter and Lawler model in a cognitive training environment and examined the relationships among some behavioral variables in Air Force Undergraduate Pilot Training. The variables analyzed were the Maslow need hierarchy, effort, abilities, role perceptions, performance, satisfaction and the…

  4. Entrainment of granular substrate by pyroclastic flows: an experimental study and its implications for flow dynamics

    NASA Astrophysics Data System (ADS)

    Roche, O.; Niño, Y.; Mangeney, A.; Brand, B. D.; Valentine, G. A.

    2012-12-01

    Pyroclastic flows deposits may contain lithics entrained from an unconsolidated granular substrate on which the flows emplaced. In order to address this issue, analog experiments on dense gas-particle flows propagating on a horizontal granular layer were carried out to elucidate the entrainment mechanisms and to infer the dynamics of pyroclastic flows. The experimental flows were generated from the release of gas-fluidized columns of fine (80 μm) particles in a horizontal channel whose base was made of an unconsolidated granular layer. The flows consisted of a fluidized air-particles mixture, and the small hydraulic permeability of the material allowed for long-lived high interstitial pore fluid pressure during emplacement. Basal pore pressure measurements in preliminary experiments involving a rigid substrate revealed that the sliding head of the flows generated a dynamic underpressure (relative to atmosphere) proportional to the square of the front velocity. As such underpressure at the flow base was likely to promote an upward pressure gradient that could cause uplift of particles of a granular substrate, we did a theoretical analysis in order to determine the critical underpressure and the corresponding flow velocity (Uc) at which uplift could occur. This analysis showed that Uc~(dρpg/Cρ)1/2 for spherical particles, where d and ρp are the particle diameter and density, respectively, C is an empirical constant, and is ρ is the bulk flow density. It was validated with experiments on flows propagating on 3 cm-thick substrates of steel beads of diameter d=1.6 mm. The beads were first dragged horizontally individually due to basal shear, and onset of uplift did occur at Uc~0.9 m/s. The beads uplifted were incorporated within the flow base, to a height that increased up to 6-8 mm at flow velocities up to 2.5-3 m/s, and were entrained over distances of several tens of cm representing a significant part of the flow runout. The flow deposits hence had a well

  5. Effects of cumulus entrainment and multiple cloud types on a January global climate model simulation

    NASA Technical Reports Server (NTRS)

    Yao, Mao-Sung; Del Genio, Anthony D.

    1989-01-01

    An improved version of the GISS Model II cumulus parameterization designed for long-term climate integrations is used to study the effects of entrainment and multiple cloud types on the January climate simulation. Instead of prescribing convective mass as a fixed fraction of the cloud base grid-box mass, it is calculated based on the closure assumption that the cumulus convection restores the atmosphere to a neutral moist convective state at cloud base. This change alone significantly improves the distribution of precipitation, convective mass exchanges, and frequencies in the January climate. The vertical structure of the tropical atmosphere exhibits quasi-equilibrium behavior when this closure is used, even though there is no explicit constraint applied above cloud base.

  6. The neuroergonomic evaluation of human machine interface design in air traffic control using behavioral and EGG/ERP measures.

    PubMed

    Giraudet, L; Imbert, J-P; Bérenger, M; Tremblay, S; Causse, M

    2015-11-01

    The Air Traffic Control (ATC) environment is complex and safety-critical. Whilst exchanging information with pilots, controllers must also be alert to visual notifications displayed on the radar screen (e.g., warning which indicates a loss of minimum separation between aircraft). Under the assumption that attentional resources are shared between vision and hearing, the visual interface design may also impact the ability to process these auditory stimuli. Using a simulated ATC task, we compared the behavioral and neural responses to two different visual notification designs--the operational alarm that involves blinking colored "ALRT" displayed around the label of the notified plane ("Color-Blink"), and the more salient alarm involving the same blinking text plus four moving yellow chevrons ("Box-Animation"). Participants performed a concurrent auditory task with the requirement to react to rare pitch tones. P300 from the occurrence of the tones was taken as an indicator of remaining attentional resources. Participants who were presented with the more salient visual design showed better accuracy than the group with the suboptimal operational design. On a physiological level, auditory P300 amplitude in the former group was greater than that observed in the latter group. One potential explanation is that the enhanced visual design freed up attentional resources which, in turn, improved the cerebral processing of the auditory stimuli. These results suggest that P300 amplitude can be used as a valid estimation of the efficiency of interface designs, and of cognitive load more generally. PMID:26200718

  7. Prediction of thermal behaviors of an air-cooled lithium-ion battery system for hybrid electric vehicles

    NASA Astrophysics Data System (ADS)

    Choi, Yong Seok; Kang, Dal Mo

    2014-12-01

    Thermal management has been one of the major issues in developing a lithium-ion (Li-ion) hybrid electric vehicle (HEV) battery system since the Li-ion battery is vulnerable to excessive heat load under abnormal or severe operational conditions. In this work, in order to design a suitable thermal management system, a simple modeling methodology describing thermal behavior of an air-cooled Li-ion battery system was proposed from vehicle components designer's point of view. A proposed mathematical model was constructed based on the battery's electrical and mechanical properties. Also, validation test results for the Li-ion battery system were presented. A pulse current duty and an adjusted US06 current cycle for a two-mode HEV system were used to validate the accuracy of the model prediction. Results showed that the present model can give good estimations for simulating convective heat transfer cooling during battery operation. The developed thermal model is useful in structuring the flow system and determining the appropriate cooling capacity for a specified design prerequisite of the battery system.

  8. Oxidation Behavior of a Pd43Cu27Ni10P20 Bulk Metallic Glass and Foam in Dry Air

    NASA Astrophysics Data System (ADS)

    Kai, W.; Ren, I. F.; Barnard, B.; Liaw, P. K.; Demetriou, M. D.; Johnson, W. L.

    2010-07-01

    The oxidation behavior of both Pd43Cu27Ni10P20 bulk metallic glass (Pd4-BMG) and its amorphous foam containing 45 pct porosity (Pd4-AF) was investigated over the temperature range of 343 K (70 °C) to 623 K (350 °C) in dry air. The results showed that virtually no oxidation occurred in the Pd4-BMG at T < 523 K (250 °C), revealing the alloy’s favorable oxidation resistance in this temperature range. In addition, the oxidation kinetics at T ≥ 523 K (250 °C) followed a parabolic-rate law, and the parabolic-rate constants ( k p values) generally increased with temperature. It was found that the oxidation k p values of the Pd4-AF are slightly lower than those of the Pd4-BMG, indicating that the porous structure contributes to improving the overall oxidation resistance. The scale formed on the alloys was composed exclusively of CuO at T ≥ 548 K (275 °C), whose thickness gradually increased with increasing temperature. In addition, the amorphous structure remained unchanged at T ≤ 548 K (275 °C), while a triplex-phase structure developed after the oxidation at higher temperatures, consisting of Pd2Ni2P, Cu3P, and Pd3P.

  9. Comparison of Short-Term Oxidation Behavior of Model and Commercial Chromia-Forming Ferritic Stainless Steels in Air with Water Vapor

    SciTech Connect

    Brady, Michael P; Keiser, James R; More, Karren Leslie; Fayek, Mostafa; Walker, Larry R; Meisner, Roberta Ann; Anovitz, Lawrence {Larry} M; Wesolowski, David J; Cole, David R

    2012-01-01

    A high-purity Fe-20Cr and commercial type 430 ferritic stainless steel were exposed at 700 and 800 C in dry air and air with 10% water vapor (wet air) and characterized by SEM, XRD, STEM, SIMS, and EPMA. The Fe-20Cr alloy formed a fast growing Fe-rich oxide scale at 700 C in wet air after 24 h exposure, but formed a thin chromia scale at 700 C in dry air and at 800 C in both dry air and wet air. In contrast, thin spinel + chromia base scales with a discontinuous silica subscale were formed on 430 stainless steel under all conditions studied. Extensive void formation was observed at the alloy-oxide interface for the Fe-20Cr in both dry and wet conditions, but not for the 430 stainless steel. The Fe-20Cr alloy was found to exhibit a greater relative extent of subsurface Cr depletion than the 430 stainless steel, despite the former's higher Cr content. Depletion of Cr in the Fe-20Cr after 24 h exposure was also greater at 700 C than 800 C. The relative differences in oxidation behavior are discussed in terms of the coarse alloy grain size of the high-purity Fe-20Cr material, and the effects of Mn, Si, and C on the oxide scale formed on the 430 stainless steel.

  10. Audience entrainment during live contemporary dance performance: physiological and cognitive measures.

    PubMed

    Bachrach, Asaf; Fontbonne, Yann; Joufflineau, Coline; Ulloa, José Luis

    2015-01-01

    Perceiving and synchronizing to a piece of dance is a remarkable skill in humans. Research in this area is very recent and has been focused mainly on entrainment produced by regular rhythms. Here, we investigated entrainment effects on spectators perceiving a non-rhythmic and extremely slow performance issued from contemporary dance. More specifically, we studied the relationship between subjective experience and entrainment produced by perceiving this type of performance. We defined two types of entrainment. Physiological entrainment corresponded to cardiovascular and respiratory coordinated activities. Cognitive entrainment was evaluated through cognitive tasks that quantified time distortion. These effects were thought to reflect attunement of a participant' internal temporal clock to the particularly slow pace of the danced movement. Each participant' subjective experience-in the form of responses to questionnaires-were collected and correlated with cognitive and physiological entrainment. We observe: (a) a positive relationship between psychological entrainment and attention to breathing (their own one or that of dancers); and (b) a positive relationship between cognitive entrainment (reflected as an under-estimation of time following the performance) and attention to their own breathing, and attention to the muscles' dancers. Overall, our results suggest a close relationship between attention to breathing and entrainment. This proof-of-concept pilot study was intended to prove the feasibility of a quantitative situated paradigm. This research is inscribed in a large-scale interdisciplinary project of dance spectating (labodanse.org). PMID:25999831

  11. Audience entrainment during live contemporary dance performance: physiological and cognitive measures

    PubMed Central

    Bachrach, Asaf; Fontbonne, Yann; Joufflineau, Coline; Ulloa, José Luis

    2015-01-01

    Perceiving and synchronizing to a piece of dance is a remarkable skill in humans. Research in this area is very recent and has been focused mainly on entrainment produced by regular rhythms. Here, we investigated entrainment effects on spectators perceiving a non-rhythmic and extremely slow performance issued from contemporary dance. More specifically, we studied the relationship between subjective experience and entrainment produced by perceiving this type of performance. We defined two types of entrainment. Physiological entrainment corresponded to cardiovascular and respiratory coordinated activities. Cognitive entrainment was evaluated through cognitive tasks that quantified time distortion. These effects were thought to reflect attunement of a participant’ internal temporal clock to the particularly slow pace of the danced movement. Each participant’ subjective experience—in the form of responses to questionnaires—were collected and correlated with cognitive and physiological entrainment. We observe: (a) a positive relationship between psychological entrainment and attention to breathing (their own one or that of dancers); and (b) a positive relationship between cognitive entrainment (reflected as an under-estimation of time following the performance) and attention to their own breathing, and attention to the muscles’ dancers. Overall, our results suggest a close relationship between attention to breathing and entrainment. This proof-of-concept pilot study was intended to prove the feasibility of a quantitative situated paradigm. This research is inscribed in a large-scale interdisciplinary project of dance spectating (labodanse.org). PMID:25999831

  12. Doing Duo - a case study of entrainment in William Forsythe's choreography "Duo".

    PubMed

    Waterhouse, Elizabeth; Watts, Riley; Bläsing, Bettina E

    2014-01-01

    Entrainment theory focuses on processes in which interacting (i.e., coupled) rhythmic systems stabilize, producing synchronization in the ideal sense, and forms of phase related rhythmic coordination in complex cases. In human action, entrainment involves spatiotemporal and social aspects, characterizing the meaningful activities of music, dance, and communication. How can the phenomenon of human entrainment be meaningfully studied in complex situations such as dance? We present an in-progress case study of entrainment in William Forsythe's choreography Duo, a duet in which coordinated rhythmic activity is achieved without an external musical beat and without touch-based interaction. Using concepts of entrainment from different disciplines as well as insight from Duo performer Riley Watts, we question definitions of entrainment in the context of dance. The functions of chorusing, turn-taking, complementary action, cues, and alignments are discussed and linked to supporting annotated video material. While Duo challenges the definition of entrainment in dance as coordinated response to an external musical or rhythmic signal, it supports the definition of entrainment as coordinated interplay of motion and sound production by active agents (i.e., dancers) in the field. Agreeing that human entrainment should be studied on multiple levels, we suggest that entrainment between the dancers in Duo is elastic in time and propose how to test this hypothesis empirically. We do not claim that our proposed model of elasticity is applicable to all forms of human entrainment nor to all examples of entrainment in dance. Rather, we suggest studying higher order phase correction (the stabilizing tendency of entrainment) as a potential aspect to be incorporated into other models. PMID:25374522

  13. Entrainment of Solvent in Aqueous Stream from CINC V-5 Contactor

    SciTech Connect

    Fink, S. D.; Restivo, M. L.; Peters, T. B.; Fowley, M. D.; Burns, D. B.; Smith, W. M. Jr.; Fondeur, F. F.; Crump, S. L.; Norato, M. A.; Herman, D. T.; Nash, C. A.

    2005-04-29

    spectroscopy and droplet size measurement by a MicroTrac{trademark} S3000. Interfacial tension measurements also showed sensitivity to purity of the solvent suggesting that this technique may prove valuable for future process diagnostics. The study highlighted limitations of the current gas chromatography configuration for determination of modifier content of samples. Additional development of analytical methods for determining composition--and particularly modifier content--of organic and mixed aqueous-organic samples is warranted. Infrared spectroscopy shows particular promise. Additional full-scale studies are warranted to investigate the entrainment of organic in the aqueous effluent from the extraction operation. Since waste composition may differ appreciably for the process, this stream may exhibit much wider variance in hydraulic behavior, organic entrainment, and may pose a greater risk for poor hydraulics. Conducting contactor studies at SRNL allowed numerous personnel to view operations and facilitated the training of staff members. Members of the Design Authority, Engineering, and Training groups benefited from tours. Consideration should be given to procuring and installing a full-scale contactor at SRNL for future support and for assistance during commissioning of the MCU. Additional study of surface and interfacial tension is recommended. This tool may also offer economical and rapid process diagnostics for future operations.

  14. Acute management of vascular air embolism

    PubMed Central

    Shaikh, Nissar; Ummunisa, Firdous

    2009-01-01

    Vascular air embolism (VAE) is known since early nineteenth century. It is the entrainment of air or gas from operative field or other communications into the venous or arterial vasculature. Exact incidence of VAE is difficult to estimate. High risk surgeries for VAE are sitting position and posterior fossa neurosurgeries, cesarean section, laparoscopic, orthopedic, surgeries invasive procedures, pulmonary overpressure syndrome, and decompression syndrome. Risk factors for VAE are operative site 5 cm above the heart, creation of pressure gradient which will facilitate entry of air into the circulation, orogenital sex during pregnancy, rapid ascent in scuba (self contained underwater breathing apparatus) divers and barotrauma or chest trauma. Large bolus of air can lead to right ventricular air lock and immediate fatality. In up to 35% patient, the foramen ovale is patent which can cause paradoxical arterial air embolism. VAE affects cardiovascular, pulmonary and central nervous system. High index of clinical suspicion is must to diagnose VAE. The transesophgeal echocardiography is the most sensitive device which will detect smallest amount of air in the circulation. Treatment of VAE is to prevent further entrainment of air, reduce the volume of air entrained and haemodynamic support. Mortality of VAE ranges from 48 to 80%. VAE can be prevented significantly by proper positioning during surgery, optimal hydration, avoiding use of nitrous oxide, meticulous care during insertion, removal of central venous catheter, proper guidance, and training of scuba divers. PMID:20009308

  15. Acute management of vascular air embolism.

    PubMed

    Shaikh, Nissar; Ummunisa, Firdous

    2009-09-01

    Vascular air embolism (VAE) is known since early nineteenth century. It is the entrainment of air or gas from operative field or other communications into the venous or arterial vasculature. Exact incidence of VAE is difficult to estimate. High risk surgeries for VAE are sitting position and posterior fossa neurosurgeries, cesarean section, laparoscopic, orthopedic, surgeries invasive procedures, pulmonary overpressure syndrome, and decompression syndrome. Risk factors for VAE are operative site 5 cm above the heart, creation of pressure gradient which will facilitate entry of air into the circulation, orogenital sex during pregnancy, rapid ascent in scuba (self contained underwater breathing apparatus) divers and barotrauma or chest trauma. Large bolus of air can lead to right ventricular air lock and immediate fatality. In up to 35% patient, the foramen ovale is patent which can cause paradoxical arterial air embolism. VAE affects cardiovascular, pulmonary and central nervous system. High index of clinical suspicion is must to diagnose VAE. The transesophgeal echocardiography is the most sensitive device which will detect smallest amount of air in the circulation. Treatment of VAE is to prevent further entrainment of air, reduce the volume of air entrained and haemodynamic support. Mortality of VAE ranges from 48 to 80%. VAE can be prevented significantly by proper positioning during surgery, optimal hydration, avoiding use of nitrous oxide, meticulous care during insertion, removal of central venous catheter, proper guidance, and training of scuba divers. PMID:20009308

  16. Comprehensive modeling and numerical investigation of entrained-flow coal gasifiers

    NASA Astrophysics Data System (ADS)

    Silaen, Armin Karen

    Numerical simulations of coal gasification process inside a generic 2-stage entrained-flow gasifier are carried out using the commercial CFD solver ANSYS/FLUENT. The 3-D Navier-Stokes equations and eight species transport equations are solved with three heterogeneous global reactions, three homogeneous reactions, and one thermal cracking equation of volatiles. Finite rates are used for the heterogeneous solid-gas reactions. Both finite rate and eddy-breakup combustion models are calculated for each homogeneous gas-gas reaction, and the smaller of the two rates is used. Lagrangian-Eulerian method is employed. The Eulerian method calculates the continuous phase while the Lagrangian method tracks each coal particle. Fundamental study is carried out to investigate effects of five turbulence models (standard k-epsilon, k-o, RSM, k-o SST, and k-epsilon RNG) and four devolatilization models (Kobayashi, single rate, constant rate, and CPD) on gasification simulation. A study is also conducted to investigate the effects of different operation parameters on gasification process including coal mixture (dry vs. slurry), oxidant (oxygen-blown vs. air-blown), and different coal distributions between two stages. Finite-rate model and instantaneous gasification model are compared. It is revealed that the instantaneous gasification approach can provide an overall evaluation of relative changes of gasifier performance in terms of temperature, heating value, and gasification efficiency corresponding to parametric variations, but not adequately capture the local gasification process predicted by the finite rate model in most part of the gasifier. Simulations are performed to help with design modifications of a small industrial demonstration entrained-flow gasifier. It is discovered that the benefit of opening the slag tap on the quench-type gasifier wider by allowing slag to move successfully without clogging is compromised by increased heat losses, reduced gasification performance

  17. An experimental investigation of flow patterns and liquid entrainment in a horizontal-tube evaporator

    NASA Astrophysics Data System (ADS)

    Barnhart, John Steven

    An experimental study of two-phase flow patterns and droplet entrainment in a horizontal-tube evaporator was conducted. Measurements were made with serpentine aluminum and glass evaporators with geometries typical of those used for domestic refrigeration. The refrigerant in the majority of tests was R134a, which will replace R12 for refrigeration and automotive air-conditioning in 1995. The phenomenon of primary interest was the nonequilibrium transport of droplets within superheated vapor at the evaporator exit. Of particular concern were substantial variations in the liquid rate with time, and corresponding fluctuations in exit temperature. These variations are due to the formation of slugs which rapidly transport a surplus of liquid toward the exit. A flow loop was constructed to circulate oil-free refrigerant through the evaporator under widely varying conditions. Liquid carry over (expressed as a dimensionless entrained mass fraction, EMF) was measured as a function of inlet quality, heat flux, mass flux, and exit superheat. A laser-based phase/Doppler particle analyzer was used to measure droplet diameters and velocities at the evaporator exit. Tests with three refrigerants over wide ranges of operating conditions revealed time-averaged EMF's of no more than 0.1 percent. Analysis of variance showed exit superheat to have the strongest effect, followed by mass flux, inlet quality, and heat flux. Time-averaged EMF's varied with operating conditions by several orders of magnitude, decreasing with increasing superheat level (due to lower entrainment rates near the exit and more rapid droplet vaporization) and mass flux and inlet quality (due to reduced slug formation). The incidence of slug flow and its effect on evaporator exit conditions were documented in time-resolved experiments, using techniques such as auto- and cross-correlation and Fourier transform. Time-resolved EMF's as high as one percent were observed, as well as sharp reductions in exit superheat

  18. Influence of the Entrainment Interface Layer on Cloud Microphysical Properties near Stratocumulus Top

    NASA Astrophysics Data System (ADS)

    Chuang, P. Y.; Carman, J. K.; Rossiter, D. L.

    2010-12-01

    Entrainment across the stratocumulus-topped boundary layer is a key process governing the cloud properties and evolution. This process is not well-represented even in high-resolution large-eddy simulations, in part due to the sharp gradients in temperature, buoyancy and (usually) humidity that occur at the top of the boundary layer. In summer 2008, the Physics of Stratocumulus Top (POST) field campaign conduct extensive measurements in the vicinity of cloud top, including the so-called entrainment interface layer or EIL that separates boundary layer and free tropospheric air. Roughly half of the fifteen flights occurred during the day (near solar noon) while the remaining flights occurred during late evening-to-night when solar input was minimal. A wide diversity of EIL properties has been revealed over the course of the campaign. EIL vertical thickness diagnosed using total water varies from fairly thin (~20 m) to very thick (>100 m). The thickness and intensity of the turbulent layer in this interfacial region also varies substantially, with the top of the significantly turbulent region ranging from 10 m to 50 m above cloud top. Shear in the vicinity of cloud top also varied strongly from day-to-day. While almost all cases exhibited strong jumps in potential temperature, there are a number of cases where the jump in total water was very small-to-none, and one case where total water was higher in the free troposphere by 1.4 g/kg. POST thus demonstrates that the cloud-top interfacial region exhibits a rich and diverse range of properties. This study focuses on how this EIL diversity affects the stratocumulus cloud itself. We build on our study of the EIL dynamic and thermodynamic properties to investigate the influence of the EIL on the microphysical properties of the stratocumulus in the vicinity of cloud top. Entrainment of the overlying warmer and (usually) drier air can strongly impact the amount of liquid water as well as the size and concentration of cloud

  19. The role of organic compounds in cloud formation: Relative importance of entrainment, co-condensation and particle-phase properties

    NASA Astrophysics Data System (ADS)

    Lowe, Samuel; Partridge, Daniel; Topping, David; Riipinen, Ilona

    2016-04-01

    The organic fraction of atmospheric aerosols is widely acknowledged to affect the cloud nucleating potential of aerosols. Cloud droplet formation through activation of non-volatile CCN is considered to be relatively well understood, however, there are fewer systematic studies on the activation of aerosols containing semi-volatile organic compounds that co-condense alongside water vapour, thus enhancing CCN activity. Although the significance of co-condensation of organic vapours for cloud droplet number concentration predictions has recently been identified, it remains uncertain how this process may interact with atmospheric dynamics. In addition to co-condensation of existing in-cloud material, additional semi-volatile mass can be entrained from the surrounding environment. Reduced cloud droplet number concentrations are expected as the parcel is diluted with clean air; however, additional soluble mass in the particle phase promotes droplet activation. The extent of increased droplet activation due to co-condensation relies also on the physiochemical properties of the organic compounds, as seen in several other phase partitioning sensitivity studies. In this work we study the simultaneous impact of entrainment and co-condensation, the relative importance of these two processes at different atmospheric conditions, their interactions with each other, and the particle-phase chemistry in terms of cloud microphysical properties and their parametric sensitivities. To assess the importance of the entrainment of semi-volatile materials as compared with their co-condensation and chemical properties, a pseudo-adiabatic cloud parcel model with a detailed description of bin microphysics is employed. We have added the co-condensation process to the model such that it is coupled with the parametric entrainment representation. The effects of entrainment and co-condensation are benchmarked independently and simultaneously against a control simulation. Furthermore, we probe the

  20. SEQUENTIAL RADIOCHEMICAL ANALYSIS FOR RUTHENIUM, STRONTIUM AND CESIUM IN ENVIRONMENTAL AIR

    EPA Science Inventory

    In routine surveillance operations, the radionuclide measurement of air discharged from an operating nuclear facility involves the entrainment of radionuclides on selective filter or absorptive media, and the determination of their gross beta activity. However, a more sensitive t...

  1. Behaviorism

    ERIC Educational Resources Information Center

    Moore, J.

    2011-01-01

    Early forms of psychology assumed that mental life was the appropriate subject matter for psychology, and introspection was an appropriate method to engage that subject matter. In 1913, John B. Watson proposed an alternative: classical S-R behaviorism. According to Watson, behavior was a subject matter in its own right, to be studied by the…

  2. Entrainment characteristics of unsteady subsonic jets. [for V/STOL aircraft

    NASA Technical Reports Server (NTRS)

    Platzer, M. F.; Simmons, J. M.; Bremhorst, K.

    1979-01-01

    The effectiveness of jet unsteadiness in enhancing flow entrainment was assessed. It was conducted that entrainment depends on the type and amount of jet unsteadiness. Apparently, the mere introduction of jet unsteadiness by small sinusoidal flow angle variations is insufficient to enhance entrainment but, it should be noted that the results were obtained at measuring stations which are all many nozzle widths downstream of the jet nozzle. Thus, no fully conclusive statement can be made at this time about the entrainment close to the nozzle. The high entrainment of the fluidically oscillated jet was caused by the high-frequency content of this square wave type of oscillation but more detailed measurements are clearly needed, in particular for the fluidically oscillated and the pulsed jets. Practical ejector application requires the proper trade-off between entrainment and primary nozzle thrust efficiency.

  3. Effects of continuous chlorination on entrained estuarine plankton

    SciTech Connect

    Erickson, S.J.; Foulk, H.R.

    1980-01-01

    Technical report: The effects of continuous chlorination in running sea water on entrained plankton were examined. The concentration of ATP was used as an indicator of biomass because: it is present in all living cells; the concentration is proportional to the living biomass; and dead cells lose ATP rapidly. Effects were measured by bioluminescence; luciferin-luciferase reagents from firefly lanterns were used to analyze ATP concentration. Results indicate that ATP measurement is an accurate, effective means of evaluating damage done to planktonic organisms by continuous chlorination. Further studies of the effects of low-concentration, continuous chlorination are recommended. (13 references, 1 table)

  4. Porous Sphere in Stratified Environments: Entrainment and Diffusion

    NASA Astrophysics Data System (ADS)

    Camassa, Roberto; Falcon, Claudia; Khatri, Shilpa; McLaughlin, Richard; UNC Joint Fluids Lab Team

    2014-11-01

    A theoretical, experimental, and numerical study of porous spheres falling in stratified fluids will be presented. The systematic justification of asymptotic regimes resulting in asymptotic models with ``heat bath'' boundary conditions for salinity are derived in low Reynolds number regimes. Violation of these asymptotic scalings will be discussed in the context of experiments and mathematical modeling. In particular the presence of a salt depletion or enrichment wake left behind by the settling, ab/de-sorbing sphere, and its competition with entrainment, will be presented and highlighted. Experimental results with microporous spheres as well calibrated manufactured drilled spheres will be compared. Supported by: NSF CMG, NSF RTG, ONR.

  5. IDMS and DWPF SRAT offgas flux and particle entrainment

    SciTech Connect

    Ritter, J.A.

    1992-11-11

    Bench scale experiments showed that the peak H2 generation rate increases with an increase in the PHA addition/evaporation rate. A 2,500 gal Slurry Mix Evaporator Condensate Tank (SMECT) was installed in the IDMS to allow performing PHA addition and evaporation both at the same rate and continuously. The SMECT allowed prototypic boil-up rates to be used, which allowed the investigation of hydrogen evolution in a more prototypic fashion and also made it possible to investigate solids entrainment. in the offgas. The results of these investigations are discussed in this report.

  6. Cloud microphysical relationships and their implication on entrainment and mixing mechanism for the stratocumulus clouds measured during the VOCALS project

    DOE PAGESBeta

    Yum, Seong Soo; Wang, Jian; Liu, Yangang; Senum, Gunnar; Springston, Stephen; McGraw, Robert; Yeom, Jae Min

    2015-05-27

    Cloud microphysical data obtained from G-1 aircraft flights over the southeastern pacific during the VOCALS-Rex field campaign were analyzed for evidence of entrainment mixing of dry air from above cloud top. Mixing diagram analysis was made for the horizontal flight data recorded at 1 Hz and 40 Hz. The dominant observed feature, a positive relationship between cloud droplet mean volume (V) and liquid water content (L), suggested occurrence of homogeneous mixing. On the other hand, estimation of the relevant scale parameters (i.e., transition length scale and transition scale number) consistently indicated inhomogeneous mixing. Importantly, the flight altitudes of the measurementsmore » were significantly below cloud top. We speculate that mixing of the entrained air near the cloud top may have indeed been inhomogeneous; but due to vertical circulation mixing, the correlation between V and L became positive at the measurement altitudes in mid-level of clouds, because during their descent, cloud droplets evaporate, faster in more diluted cloud parcels, leading to a positive correlation between V and L regardless of the mixing mechanism near the cloud top.« less

  7. Cloud microphysical relationships and their implication on entrainment and mixing mechanism for the stratocumulus clouds measured during the VOCALS project

    SciTech Connect

    Yum, Seong Soo; Wang, Jian; Liu, Yangang; Senum, Gunnar; Springston, Stephen; McGraw, Robert; Yeom, Jae Min

    2015-05-27

    Cloud microphysical data obtained from G-1 aircraft flights over the southeastern pacific during the VOCALS-Rex field campaign were analyzed for evidence of entrainment mixing of dry air from above cloud top. Mixing diagram analysis was made for the horizontal flight data recorded at 1 Hz and 40 Hz. The dominant observed feature, a positive relationship between cloud droplet mean volume (V) and liquid water content (L), suggested occurrence of homogeneous mixing. On the other hand, estimation of the relevant scale parameters (i.e., transition length scale and transition scale number) consistently indicated inhomogeneous mixing. Importantly, the flight altitudes of the measurements were significantly below cloud top. We speculate that mixing of the entrained air near the cloud top may have indeed been inhomogeneous; but due to vertical circulation mixing, the correlation between V and L became positive at the measurement altitudes in mid-level of clouds, because during their descent, cloud droplets evaporate, faster in more diluted cloud parcels, leading to a positive correlation between V and L regardless of the mixing mechanism near the cloud top.

  8. Cloud microphysical relationships and their implication on entrainment and mixing mechanisms for marine and continental stratocumulus clouds

    NASA Astrophysics Data System (ADS)

    Yum, S. S.; Yeom, J. M.; Wang, J.; Liu, Y.; Senum, G.; Springston, S. R.; McGraw, R. L.; Lu, C.

    2015-12-01

    Cloud microphysical data obtained from aircraft measurements of stratocumulus clouds over the southeastern pacific during the VOCALS-Rex field campaign and over the Great Plains region in Oklahoma during the RACORO field campaign were analyzed for evidence of entrainment mixing of air from above cloud top. Mixing diagram analysis was made for the horizontal flight data recorded at various rates (1 Hz, 10 Hz and 40 Hz). For the maritime stratocumulus clouds, the dominant observed feature, a positive relationship between cloud droplet mean volume (V) and liquid water content (L), suggested occurrence of homogeneous mixing. On the other hand, estimation of the relevant scale parameters (i.e., transition length scale and transition scale number) consistently indicated inhomogeneous mixing. Importantly, the flight altitudes of the measurements were significantly below cloud top. We speculate that mixing of the entrained air near the cloud top may have indeed been inhomogeneous; but due to vertical circulation mixing the correlation between V and L became positive at the measurement altitudes in mid-level of clouds, because during their descent, cloud droplets evaporate, faster in more diluted cloud parcels, leading to a positive correlation between V and L regardless of the mixing mechanism near the cloud top. For the continental stratocumulus clouds, the positive relationship between V and L was even more pronounced while the scale parameters were less indicative of inhomogeneous mixing. Finding evidence for vertical circulation mixing was difficult for these clouds because flight plans in this campaign were not designed to investigate such process.

  9. A viscoplastic lubrication model for entrainment by avalanches and debris flows, and comparison with experiments

    NASA Astrophysics Data System (ADS)

    Bates, Belinda; Ancey, Christophe

    2015-04-01

    Recently, experiments were designed and carried out examining how a viscoplastic avalanche begins to entrain a shallow layer of identical fluid lying in its path, much like a snow avalanche or mud flow which suddenly encounters an entrainable layer, described as a yield stress material. This represents a simplified problem, investigated in order to gain some physical insight into entrainment by avalanches. These experiments serve as a test for mathematical models of entraining gravity currents. Two classes of entrainment behaviour were observed: either the avalanche ``glided'' out over the entrainable bed, immediately shearing it in the downstream direction and progressively incorporating fluid down to the rigid base, or the avalanche seemed to ``roll'' out onto the entrainable bed, with strong motion in the slope-normal direction in the bed after yield. This difference in behaviour was dictated by the magnitude of the flume's slope. For the steeper flows studied (20 and 24 degrees), entrainment was principally in the former class, whereas for shallower slope angle (12 and 16 degrees) entrainment more closely resembled the latter type. This would suggest that there is a competition between the normal and shear stresses exerted on the bed, with bed-yield and entrainment occurring when these stresses exceed a critical value. An interesting phenomenon that was observed in all cases was a sort of buckling of the bed, downstream of the avalanche front. This was far more significant in the flows down shallower slopes, and regular waves were created in the bed with wavelength dependent on the flow depth. Based on theoretical comparisons with non-entraining Herschel Bulkley flows, the physics of entraining flows are investigated numerically for shallow viscoplastic gravity currents on different slopes. The predictions are compared with the experimental values for velocity field and surface height. The model was successful in reproducing velocities of the correct order, but

  10. Irregular Speech Rate Dissociates Auditory Cortical Entrainment, Evoked Responses, and Frontal Alpha

    PubMed Central

    Kayser, Stephanie J.; Ince, Robin A.A.; Gross, Joachim

    2015-01-01

    The entrainment of slow rhythmic auditory cortical activity to the temporal regularities in speech is considered to be a central mechanism underlying auditory perception. Previous work has shown that entrainment is reduced when the quality of the acoustic input is degraded, but has also linked rhythmic activity at similar time scales to the encoding of temporal expectations. To understand these bottom-up and top-down contributions to rhythmic entrainment, we manipulated the temporal predictive structure of speech by parametrically altering the distribution of pauses between syllables or words, thereby rendering the local speech rate irregular while preserving intelligibility and the envelope fluctuations of the acoustic signal. Recording EEG activity in human participants, we found that this manipulation did not alter neural processes reflecting the encoding of individual sound transients, such as evoked potentials. However, the manipulation significantly reduced the fidelity of auditory delta (but not theta) band entrainment to the speech envelope. It also reduced left frontal alpha power and this alpha reduction was predictive of the reduced delta entrainment across participants. Our results show that rhythmic auditory entrainment in delta and theta bands reflect functionally distinct processes. Furthermore, they reveal that delta entrainment is under top-down control and likely reflects prefrontal processes that are sensitive to acoustical regularities rather than the bottom-up encoding of acoustic features. SIGNIFICANCE STATEMENT The entrainment of rhythmic auditory cortical activity to the speech envelope is considered to be critical for hearing. Previous work has proposed divergent views in which entrainment reflects either early evoked responses related to sound encoding or high-level processes related to expectation or cognitive selection. Using a manipulation of speech rate, we dissociated auditory entrainment at different time scales. Specifically, our

  11. Impact of entrainment and impingement on fish populations in the Hudson River estuary. Volume I. Entrainment-impact estimates for six fish populations inhabiting the Hudson River estuary

    SciTech Connect

    Boreman, J.; Barnthouse, L.W.; Vaughn, D.S.; Goodyear, C.P.; Christensen, S.W.; Kumar, K.D.; Kirk, B.L.; Van Winkle, W.

    1982-01-01

    This volume is concerned with the estimation of the direct (or annual) entrainment impact of power plants on populations of striped bass, white perch, Alosa spp. (blueback herring and alewife), American shad, Atlantic tomcod, and bay anchovy in the Hudson River estuary. Entrainment impact results from the killing of fish eggs, larvae, and young juveniles that are contained in the cooling water cycled through a power plant. An Empirical Transport Model (ETM) is presented as the means of estimating a conditional entrainment mortality rate (defined as the fraction of a year class which would be killed due to entrainment in the absence of any other source of mortality). Most of this volume is concerned with the estimation of several parameters required by the ETM: physical input parameters (e.g., power-plant withdrawal flow rates); the longitudinal distribution of ichthyoplankton in time and space; the duration of susceptibility of the vulnerable organisms; the W-factors, which express the ratios of densities of organisms in power plant intakes to densities of organisms in the river; and the entrainment mortality factors (f-factors), which express the probability that an organism will be killed if it is entrained. Once these values are obtained, the ETM is used to estimate entrainment impact for both historical and projected conditions.

  12. Examination of turbulent entrainment-mixing mechanisms using a combined approach

    SciTech Connect

    Lu, C.; Liu, Y.; Niu, S.

    2011-10-01

    Turbulent entrainment-mixing mechanisms are investigated by applying a combined approach to the aircraft measurements of three drizzling and two nondrizzling stratocumulus clouds collected over the U.S. Department of Energy's Atmospheric Radiation Measurement Southern Great Plains site during the March 2000 cloud Intensive Observation Period. Microphysical analysis shows that the inhomogeneous entrainment-mixing process occurs much more frequently than the homogeneous counterpart, and most cases of the inhomogeneous entrainment-mixing process are close to the extreme scenario, having drastically varying cloud droplet concentration but roughly constant volume-mean radius. It is also found that the inhomogeneous entrainment-mixing process can occur both near the cloud top and in the middle level of a cloud, and in both the nondrizzling clouds and nondrizzling legs in the drizzling clouds. A new dimensionless number, the scale number, is introduced as a dynamical measure for different entrainment-mixing processes, with a larger scale number corresponding to a higher degree of homogeneous entrainment mixing. Further empirical analysis shows that the scale number that separates the homogeneous from the inhomogeneous entrainment-mixing process is around 50, and most legs have smaller scale numbers. Thermodynamic analysis shows that sampling average of filament structures finer than the instrumental spatial resolution also contributes to the dominance of inhomogeneous entrainment-mixing mechanism. The combined microphysical-dynamical-thermodynamic analysis sheds new light on developing parameterization of entrainment-mixing processes and their microphysical and radiative effects in large-scale models.

  13. Refractive index matched suspensions as a tool for investigating entrainment by avalanches and debris flows

    NASA Astrophysics Data System (ADS)

    Bates, Belinda; Ancey, Christophe

    2015-04-01

    Geophysical gravity flows such as avalanches and debris flows are complicated mixtures of fluid and solids, often containing particle sizes of many orders of magnitude. In a debris flow, for example, the composition varies from head to tail, and from bottom to top due to particle size segregation and recirculation. In addition the solid components may have different masses and mechanical properties. For this reason, a complete understanding of substrate entrainment by this type of flow is still out of reach. A common strategy for advancing our understanding of the physics of processes like entrainment is to use a greatly simplified laboratory model of a debris flow, and take internal and bulk measurements. This idealized technique forms the basis of this study, in which a two-phase, monodisperse suspension of PMMA beads in a refractive-index matched suspending fluid flowed down a flume, encountering an entrainable region of the same suspension on the way. This study represents the first attempt of taking continuous internal velocity measurements inside a flowing, entraining model avalanche or debris flow in the laboratory. Interior PIV measurements of flow velocity were taken in the entrainable region, along with surface height measurements, to shed some light on the entrainment mechanisms and to see how the bulk flow responded. Further, some differential pressure measurements were made in the entrainable bed to see if pore-pressure peaks had any correlation with significant events during entrainment. We present our preliminary findings and discuss the suitability of the method to entrainment investigations.

  14. Ifluence of crystallization and entrainment of cooler material on the emplacement of basaltic aa lava flows

    NASA Technical Reports Server (NTRS)

    Crisp, Joy; Baloga, Stephen

    1994-01-01

    A theoretical model is used to describe and investigate the effects of simultaneous crystallization, radiation loss, and entrainment of cooler material on the temperature of a well-mixed core of an active aa lava flow. Entrainment of crust, levee debris, and base material into the interior of active flows has been observed, but the degree of assimilation and the thermal consequences are difficult to quantify. The rate of entrainment can be constrained by supplementing the theoretical model with information on the crystallization along the path of the flow and estimation of the radiative loss from the flow interior. Application of the model is demonstrated with the 1984 Mauna Loa flow, which was erupted about 30 C undercooled. Without any entrainment of cooler material, the high crystallization rates would have driven temperatures in the core wall above temperatures measured by thermocouple and estimated from glass geothermometry. One plausible scenario for this flow, which agrees with available temperature and crystallinity measurements, has a high initial rate of entrainment during the first 8 hours of travel (a mass ratio of entrained material to fluid core of about 15% if the average temperature of the entrained material was 600 C), which counterbalances the latent heat from approximately 40% crystallization. In this scenario, the model suggests an additional 5% crystallization and a 5% entrainment mass ratio over the subsequent 16-hour period. Measurements of crystallization, radiative losses, and entrainment factors are necessary for understanding the detailed thermal histories of active lava flows.

  15. Effects of frequency on fatigue behavior of type 316 low-carbon, nitrogen-added stainless steel in air and mercury for the spallation neutron source

    NASA Astrophysics Data System (ADS)

    Tian, H.; Liaw, P. K.; Fielden, D. E.; Brooks, C. R.; Brotherton, M. D.; Jiang, L.; Yang, B.; Wang, H.; Strizak, J. P.; Mansur, L. K.

    2006-01-01

    The high-cycle fatigue behavior of type 316 low-carbon, nitrogen-added (LN) stainless steel (SS), the prime-candidate target-container material for the spallation neutron source (SNS), was investigated in air and mercury. Test frequencies ranged from 0.2 to 10 Hz with an R ratio of -1, and 10 to 700 Hz with an R ratio of 0.1. During tension-compression fatigue studies, a significant increase in the specimen temperature was observed at 10 Hz in air, which decreased the fatigue life of the 316 LN SS relative to that at 0.2 Hz. Companion tests in air were carried out, while cooling the specimen with nitrogen gas at 10 Hz in air. In these experiments, fatigue lives were comparable at 10 Hz in air with nitrogen cooling and at 0.2 Hz in air. During tension-tension fatigue studies, a higher specimen temperature was observed at 700 than at 10 Hz. After cooling the specimen, comparable fatigue lives were found at 10 and at 700 Hz. The frequency effect on the fatigue life in mercury was found to be much less than that in air, due to the fact that mercury acts as an effective coolant during the fatigue experiment. Striation spacing on the fracture surface at different test frequencies was closely examined, relative to calculated Δ K values, during fatigue of the 316 LN SS. Specimen self-heating has to be considered in understanding fatigue characteristics of 316 LN SS in air and mercury.

  16. Stress rupture and creep behavior of a low pressure plasma-sprayed NiCoCrAlY coating alloy in air and vacuum

    NASA Technical Reports Server (NTRS)

    Hebsur, M. G.; Miner, R. V.

    1987-01-01

    The creep behavior of a NiCoCrAlY coating alloy in air and vacuum at 660 and 850 C is studied. The microstructure of the coating alloy is described. Analysis of the creep curves reveal that the secondary creep rates, the transition from secondary to tertiary creep, and the strain-to-failure are affected by the environment, preexposure, stress, and temperature. It is observed that the rupture lives of the NiCoCrAlY alloy at 660 and 850 C are greater in air than in vacuum. Several mechanisms that may explain the lack of crack growth from surface-connected pores during tests in air are proposed.

  17. Targeted Mutation of the Calbindin D28K Gene Disrupts Circadian Rhythmicity and Entrainment

    PubMed Central

    Kriegsfeld, Lance J; Mei, Dan Feng; Yan, Lily; Witkovsky, Paul; LeSauter, Joseph; Hamada, Toshiyuki; Silver, Rae

    2009-01-01

    The suprachiasmatic nucleus (SCN) is the principal circadian pacemaker in mammals. A salient feature of the SCN is that cells of a particular phenotype are topographically organized; this organization defines functionally distinct subregions that interact to generate coherent rhythmicity. In Syrian hamsters (Mesocricetus auratus), a dense population of directly retinorecipient calbindinD28K (CalB) neurons in the caudal SCN marks a subregion critical for circadian rhythmicity. In mouse SCN, a dense cluster of CalB neurons occurs during early postnatal development but in the adult, CalB neurons are dispersed through the SCN. In the adult retina CalB colocalizes with melanopsin-expressing ganglion cells. In the present study, we explored the role of CalB in modulating circadian function and photic entrainment by investigating mice with a targeted mutation of the CalB gene (CalB-/- mice). In constant darkness (DD), CalB-/- animals either become arrhythmic (40%) or exhibit low-amplitude locomotor rhythms with marked activity during subjective day (60%). Rhythmic clock gene expression is blunted in these latter animals. Importantly, CalB-/- mice exhibit anomalies in entrainment revealed following transfer from a light:dark cycle to DD. Paradoxically, responses to acute light pulses measured by behavioral phase shifts, SCN FOS protein and Period1 mRNA expression are normal. Together, the developmental pattern of CalB expression in mouse SCN, the presence of CalB in photoresponsive ganglion cells, and the abnormalities seen in CalB-/- mice suggest an important role for CalB in mouse circadian function. PMID:18588531

  18. Newborn primate infants are entrained by low intensity lighting

    PubMed Central

    Rivkees, Scott A.; Hofman, Paul L.; Fortman, Jeffrey

    1997-01-01

    At the present time we do not know when the circadian timing system of human infants becomes responsive to light. Because of human study limitations, it is not currently possible to address this issue in clinical studies. Therefore, to provide insights into when the circadian system of humans becomes responsive to light, baboons were studied. We first assessed if the biological clock located in suprachiasmatic nuclei (SCN) is responsive to light at birth. When term newborn infants were exposed to bright light at night (5000 lux), SCN metabolic activity and c-fos mRNA expression increased, indicating the presence of photic responsiveness. When photic entrainment of developing rhythmicity was examined in infants, low intensity (200 lux) cycled lighting was sufficient to entrain circadian phase. However, low intensity lighting was not sufficient to induce changes in SCN metabolic activity or c-fos mRNA expression. Phase–response studies indicated that light exposure (200 lux) before the onset of activity most effectively shifted circadian phase. These data provide direct evidence that the SCN are responsive to visually mediated light information in a primate at birth. Further consideration of lighting conditions that infants are exposed to is therefore warranted. PMID:8990202

  19. Enhanced entrainability of genetic oscillators by period mismatch

    PubMed Central

    Hasegawa, Yoshihiko; Arita, Masanori

    2013-01-01

    Biological oscillators coordinate individual cellular components so that they function coherently and collectively. They are typically composed of multiple feedback loops, and period mismatch is unavoidable in biological implementations. We investigated the advantageous effect of this period mismatch in terms of a synchronization response to external stimuli. Specifically, we considered two fundamental models of genetic circuits: smooth and relaxation oscillators. Using phase reduction and Floquet multipliers, we numerically analysed their entrainability under different coupling strengths and period ratios. We found that a period mismatch induces better entrainment in both types of oscillator; the enhancement occurs in the vicinity of the bifurcation on their limit cycles. In the smooth oscillator, the optimal period ratio for the enhancement coincides with the experimentally observed ratio, which suggests biological exploitation of the period mismatch. Although the origin of multiple feedback loops is often explained as a passive mechanism to ensure robustness against perturbation, we study the active benefits of the period mismatch, which include increasing the efficiency of the genetic oscillators. Our findings show a qualitatively different perspective for both the inherent advantages of multiple loops and their essentiality. PMID:23389900

  20. Phase Sensitivity and Entrainment in a Modeled Bursting Neuron

    PubMed Central

    Demir, S. S.; Butera, R. J.; DeFranceschi, A. A.; Clark, J. W.; Byrne, J. H.

    1997-01-01

    A model of neuron R15 in Aplysia was used to study the mechanisms determining the phase-response curve (PRC) of the cell in response to both extrinsic current pulses and modeled synaptic input and to compare entrainment predictions from PRCs with those from actual simulations. Over the range of stimulus parameters studied, the PRCs of the model exhibited minimal dependence upon stimulus amplitude, and a strong dependence upon stimulus duration. State-space analysis of the effect of transient current pulses provided several important insights into the relationship between the PRC and the underlying dynamics of the model, such as a correlation between the prestimulus concentration of Ca2+ and the poststimulus phase of the oscillation. The system nullclines were also found to provide well-defined limits upon the perturbatory extent of a hyperpolarizing input. These results demonstrated that experimentally applied current pulses are sufficient to determine the shape of the PRC in response to a synaptic input, provided that the duration of the current pulse is of a duration similar to that of the evoked synaptic current. Furthermore, we found that predictions of phase-locked 1:m entrainment from PRCs were valid, even when the duration of the periodically applied pulses were a significant portion of the control limit cycle. ImagesFIGURE 5FIGURE 7FIGURE 8 PMID:9017188

  1. Debris entrainment and landform genesis during tidewater glacier surges

    NASA Astrophysics Data System (ADS)

    Lovell, Harold; Fleming, Edward J.; Benn, Douglas I.; Hubbard, Bryn; Lukas, Sven; Rea, Brice R.; Noormets, Riko; Flink, Anne E.

    2015-08-01

    The englacial entrainment of basal debris during surges presents an opportunity to investigate processes acting at the glacier bed. The subsequent melt-out of debris-rich englacial structures during the quiescent phase produces geometrical ridge networks on glacier forelands that are diagnostic of surge activity. We investigate the link between debris entrainment and proglacial geomorphology by analyzing basal ice, englacial structures, and ridge networks exposed at the margins of Tunabreen, a tidewater surge-type glacier in Svalbard. The basal ice facies display clear evidence for brittle and ductile tectonic deformation, resulting in overall thickening of the basal ice sequence. The formation of debris-poor dispersed facies ice is the result of strain-induced metamorphism of meteoric ice near the bed. Debris-rich englacial structures display a variety of characteristics and morphologies and are interpreted to represent the incorporation and elevation of subglacial till via the squeezing of till into basal crevasses and hydrofracture exploitation of thrust faults, reoriented crevasse squeezes, and preexisting fractures. These structures are observed to melt-out and form embryonic geometrical ridge networks at the base of a terrestrially grounded ice cliff. Ridge networks are also located at the terrestrial margins of Tunabreen, neighboring Von Postbreen, and in a submarine position within Tempelfjorden. Analysis of network characteristics allows these ridges to be linked to different formational mechanisms of their parent debris-rich englacial structures. This in turn provides an insight into variations in the dominant tectonic stress regimes acting across the glacier during surges.

  2. Altered streamflow and sediment entrainment in the Gunnison Gorge

    USGS Publications Warehouse

    Elliott, J.G.; Parker, R.S.

    1997-01-01

    The Gunnison River in the Gunnison Gorge is a canyon river where upstream dams regulate mainstem discharge but do not affect debris-flow sediment supply from tributaries entering below the reservoirs. Regulation since 1966 has altered flood frequency, streambed mobility, and fluvial geomorphology creating potential resource-management issues. The duration of moderate streamflows between 32.3 and 85.0 m3/s has increased threefold since 1966. This, along with flood-peak attenuation, has facilitated fine-sediment deposition and vegetation encroachment on stream banks. The Shields equation and on-site channel geometry and bed-material measurements were used to assess changes in sediment entrainment in four alluvial reaches. Sand and fine gravel are transported through riffle/pool reaches at most discharges, but the cobbles and boulders composing the streambed in many reaches now are infrequently entrained. Periodic debris flows add coarse sediment to rapids and can increase pool elevation and the streambed area affected by backwater and fine-sediment accumulation. Debris-flow supplied boulders accumulate on fans and in rapids and constrict the channel until reworked by larger floods. The response to streamflow-regime changes in the Gunnison Gorge could serve as an analog for alluvial reaches in other regulated canyon rivers.

  3. Colloidal quantum dots entrained in microstructured optical fibers

    NASA Astrophysics Data System (ADS)

    Holton, Carvel E.; Meissner, Kenith E.; Herz, Erik; Kominsky, Daniel; Pickrell, Gary R.

    2004-06-01

    We present the initial results of entraining colloidal quantum dots emitting at wavelengths from 0.5um through 1.2um, in various micro-structured optical fibers. Conventional and non-conventional, micro-structured optical fibers fabricated at Virginia Tech"s Fiber & ElectroOptics Research Center (FEORC) have been combined with semiconductor, colloidal quantum dots fabricated by the VT Advanced Biomedical Center (VTabc). The results are presented primarily in the form of visual verification and analysis of entrainment phenomena, for a cross-section of colloidal dot and micro-structured fiber forms. Unique optical, electro-optical and material properties resulting from the combinations are visibly suggested in the results. Core/clad/free space propagation properties and effects of emitted and absorbed light fields are observed to be dependent on the structure, aspect ratio and materials of the fibers as well as the properties of the colloidal quantum dots. Basic spectral data on representative free-space materials will be presented in the current paper. The presentation will explore in passing, the research options available to such quantum dot-fiber combinations, including advanced sensors, sources and filters.

  4. Regulation of MAPK/ERK Signaling and Photic Entrainment of the Suprachiasmatic Nucleus Circadian Clock by Raf Kinase Inhibitor Protein

    PubMed Central

    Antoun, Ghadi; Cannon, Pascale Bouchard; Cheng, Hai-Ying Mary

    2013-01-01

    Activation of the MAPK/ERK signaling cascade in the suprachiasmatic nucleus (SCN) is a key event that couples light to circadian clock entrainment. However, we do not fully understand the mechanisms that shape the properties of MAPK/ERK signaling in the SCN, and how these mechanisms may influence overt circadian rhythms. Here we show that Raf kinase inhibitor protein (RKIP) controls the kinetics of light-induced MAPK/ERK activity in the SCN and photic entrainment of behavioral rhythms. Light triggers robust phosphorylation of RKIP in the murine SCN and dissociation of RKIP and c-Raf. Overexpression of a nonphosphorylatable form of RKIP in the SCN of transgenic mice blocks light-induced ERK1/2 activation in the SCN and severely dampens light-induced phase delays in behavioral rhythms. Conversely, in RKIP knock-out (RKIP−/−) mice, light-induced ERK1/2 activity in the SCN is prolonged in the early and late subjective night, resulting in augmentation of the phase-delaying and -advancing effects of light. Reentrainment to an advancing light cycle was also accelerated in RKIP−/− mice. In relation to the molecular clockwork, genetic deletion of RKIP potentiated light-evoked PER1 and PER2 protein expression in the SCN in the early night. Additionally, RKIP−/− mice displayed enhanced transcriptional activation of mPeriod1 and the immediate early gene c-Fos in the SCN in response to a phase-delaying light pulse. Collectively, our data reveal an important role of RKIP in the regulation of MAPK/ERK signaling in the SCN and photic entrainment of the SCN clock. PMID:22492043

  5. Experimental studies on an air-air jet exhaust pump

    SciTech Connect

    Chou, S.K.

    1986-01-01

    Industrial ventilation employing an air-air jet exhaust pump connected to a compressed-air line was investigated. The motive air supply pressure was maintained between 2 and 3 bar. A unique ejector housing was constructed to receive both the convergent-divergent primary nozzle and the mixing chamber. The entire unit adapts readily to any existing compressed-air system. The mixing chamber was so constructed that the length of its cylindrical section may be changed. Pressure variations along the mixing chamber were recorded, and this offered a valuable appreciation of the effects of the length-to-diameter ratios. Results indicate the influence of the supply air pressure and pressure ratio on the jet entrainment capacity and efficiency. It has also been shown that the present design is capable of achieving the maximum reported jet-pump efficiency of around 25% corresponding to a nozzle-to-mixing chamber area ratio of 0.15.

  6. Investigation of entrainment and thermal properties of a cryogenic dense-gas cloud using optical measurement techniques.

    PubMed

    Kunsch, J P; Rösgen, T

    2006-09-01

    Cryogenic dense-gas clouds have been investigated in a heavy-gas channel under controlled source and ambient conditions. Advantage is taken from new, non-intrusive optical measurement techniques (e.g. image correlation velocimetry, ICV, and background oriented Schlieren, BOS) providing detailed pictures of the temperature and velocity field in relevant regions of the cloud. The ice particles in the cloud, formed by nucleation, represent a natural seeding to be used as tracers, which have the advantage of behaving passively. Two layers can be identified in a cryogenic gas cloud: a lower cold layer, which is visible due to the presence of ice particles, and an invisible upper layer, where the ice particles have melted, mostly due to heat addition by air entrainment into the upper layer. A two-layer model has been applied to a generic element of the cloud, where detailed experimental data regarding velocity and temperature are available. Thermal- and dilution behaviour can be interpreted by means of the model which is presented in detail. A global entrainment parameter is deduced allowing a simple comparison with existing experimental information obtained by other traditional experimental techniques. The numerical values of the present entrainment parameter agree well with the correlations proposed by other authors. Thermal effects, such as heat transfer from the ground, appear to be very important. In addition, the visible height of the cloud can be predicted in relative good agreement with the experimental observations, by means of a thermal balance including the phase transition of the ice particles. PMID:16621256

  7. Combined air and water pollution control system

    NASA Technical Reports Server (NTRS)

    Wolverton, Billy C. (Inventor); Jarrell, Lamont (Inventor)

    1990-01-01

    A bioaquatic air pollution control system for controlling both water and atmospheric pollution is disclosed. The pollution control system includes an exhaust for directing polluted gases out of a furnace and a fluid circulating system which circulates fluid, such as waste water, from a source, past the furnace where the fluid flow entrains the pollutants from the furnace. The combined fluid and pollutants are then directed through a rock/plant/microbial filtering system. A suction pump pumps the treated waste water from the filter system past the exhaust to again entrain more pollutants from the furnace where they are combined with the fluid (waste water) and directed to the filter system.

  8. Basal entrainment by Newtonian gravity-driven flows

    NASA Astrophysics Data System (ADS)

    Bates, Belinda; Andreini, Nicolas; Ancey, Christophe

    2016-04-01

    Gravity-driven flows can erode the bed along which they descend and increase their mass by a factor of 10 or more. This process is called basal entrainment. Although documented by field observations and laboratory experiments, it remains poorly understood. We look into this issue by studying eroding dam-break waves. More specifically we would like to determine what happens when a viscous gravity-driven flow generated by releasing a fixed volume of incompressible Newtonian fluid encounters a stationary erodible layer (composed of fluid with the same density and viscosity). Models based on depth-averaged mass and momentum balance equations deal with bed-flow interfaces as shock waves. In contrast, we use an approach involving the long-wave approximation of the Navier-Stokes equations (lubrication theory), and in this context, bed-flow interfaces are acceleration waves that move quickly across thin stationary layers. The incoming flow digs down into the bed, pushing up downstream material, thus advancing the flow front. Extending the method used by Huppert [J. Fluid Mech. 121, 43--58 (1982)] for modelling viscous dam-break waves, we end up with a nonlinear diffusion equation for the flow depth, which is solved numerically. Theory is compared with experimental results. Excellent agreement is found in the limit of low Reynolds numbers (i.e., for flow Reynolds numbers lower than 20) for the front position over time and flow depth profile. The Newtonian model has sometimes been used to describe the flow behaviour of natural materials such as snow and debris suspensions, but the majority of existing approaches rely on more elaborate constitutive equations. So there is no direct application of the results presented here to real flow conditions. Yet, our study sheds light on the mechanisms involved in basal entrainment. We provide evidence that the whole layer of loose material is entrained quickly once the flow makes contact with the erodible layer. As this process occurs

  9. Photic Resetting and Entrainment in CLOCK-Deficient Mice

    PubMed Central

    Dallmann, Robert; DeBruyne, Jason P.; Weaver, David R.

    2012-01-01

    Mice lacking CLOCK protein have a relatively subtle circadian phenotype, including a slightly shorter period in constant darkness, differences in phase resetting after 4-hr light pulses in the early and late night, and a variably advanced phase angle of entrainment in a light-dark (LD) cycle (DeBruyne et al., Neuron 50:465–477, 2006). The present series of experiments was conducted to more fully characterize the circadian phenotype of Clock−/− mice under various lighting conditions. A phase-response curve (PRC) to 4-hour light pulses in free-running mice was conducted; the results confirm that Clock−/− mice exhibit very large phase advances after 4 hrs light pulses in the late subjective night, but have relatively normal responses to light at other phases. The abnormal shape of the PRC to light may explain the tendency of CLOCK-deficient mice to begin activity before lights-out when housed in a 12 hrs light: 12 hrs dark lighting schedule. To assess this relationship further, Clock−/− and wild-type control mice were entrained to skeleton lighting cycles (1L:23D, and 1L:10D:1L:12D). Comparing entrainment under the two types of skeleton photoperiods revealed that exposure to 1 hr light in the morning leads to a phase advance of activity onset (expressed the following afternoon) in Clock−/− mice, but not in the controls. Constant light typically causes an intensity-dependent increase in circadian period in mice, but this did not occur in CLOCK-deficient mice. The failure of Clock−/− mice to respond to the period-lengthening effect of constant light likely results from the increased functional impact of light falling in the phase advance zone of the PRC. Collectively, these experiments reveal that alterations in the response of CLOCK-deficient mice to light in several paradigms are likely due to an imbalance in the shape of the PRC to light. PMID:21921293

  10. Entrainment and Mixing of the Faroe Bank Channel Overflow

    NASA Astrophysics Data System (ADS)

    Fer, Ilker

    2010-05-01

    The continuous, swift flow of cold water over the sill of the Faroe Bank Channel, the deepest passage from the Nordic Seas to the North Atlantic Ocean, contributes to the ventilation of the deep North Atlantic Ocean. The amount of bulk entrainment and mixing of the overflow along its path was previously estimated from coarsely spaced currentmeters and water-mass considerations; however remain poorly constrained. The spatial distribution of mixing remains unknown due to lack of direct measurements. Here we report from the first direct turbulence measurements conducted in June 2008, supplemented by moored observations. The shipboard survey covers the first 120 km downstream of the sill, and includes vertical profiles of hydrography and velocity (from a conductivity-temperature-depth package equipped with lowered-acoustic Doppler current profilers), and of turbulent dissipation rate from a vertical microstructure profiler (Rockland Sci. Int.). The dynamic properties and mixing of the overflow plume as it descends toward the Iceland Basin are described. The plume has a vertical structure composed of a 70 ± 35 m thick well-mixed bottom layer overlaid by a 120 ± 60 m thick stratified interfacial layer. The vigorously turbulent plume is associated with intense mixing and enhanced turbulent dissipation near the bottom and at the plume-ambient interface, but with a quiescent core. The latter is due to weak shear production of turbulent kinetic energy near the velocity maximum, located typically deeper than the interface. Enhanced mixing at the stratified and highly-sheared interface is mostly due to coexisting shear instabilities and internal wave-turbulence transition. Entrainment velocity inferred from dissipation measurements show strong lateral variability. A pronounced transverse circulation is observed consistent with rotating plume dynamics. The transverse circulation actively dilutes the bottom layer of the plume. The bulk entrainment parameterizations mainly

  11. Strain-cycling fatigue behavior of ten structural metals tested in liquid helium (4 K), in liquid nitrogen (78 K), and in ambient air (300 K)

    NASA Technical Reports Server (NTRS)

    Nachtigall, A. J.

    1974-01-01

    Strain-cycling fatigue behavior of 10 different structural alloys and metals was investigated in liquid helium (4 K), in liquid nitrogen (78 K), and in ambient air (300 K). At high cyclic lives, fatigue resistance increased with decreasing temperature for all the materials investigated. At low cyclic lives, fatigue resistance generally decreased with decreasing temperature for the materials investigated. Only for Inconel 718 did fatigue resistance increase with decreasing temperature over the entire life range investigated. Comparison of the experimental fatigue behavior with that predicted by the Manson method of universal slopes showed that the fatigue behavior of these materials can be predicted for cryogenic temperatures by using material tensile properties obtained at those same temperatures.

  12. Non-parametric entrainment by natural twilight in the microchiropteran bat, Hipposideros speoris inside a cave.

    PubMed

    Joshi, D S; Vanlalnghaka, C

    2005-01-01

    The study aimed to determine the influence of repeated natural dawn and dusk twilight pulses in entraining the circadian flight activity rhythm of the microchiropteran bat, Hipposideros speoris, free-running in constant darkness in a natural cave. The bats were exposed to repeated dawn or dusk twilight pulses at eight circadian phases. All bats exposed to dawn twilight pulses were entrained by advancing transients, and the stable entrainment was reached when the onset of activity occurred about 12 h before the lights-on of the pulses, irrespective of the initial phase at which the bats were exposed to twilight. All bats exposed to dusk twilight pulses, however, were entrained by delaying transients, and the stable entrainment was reached when the onset of activity occurred about 1.6 h after the lights-on of the pulses. The entrainment caused by dawn and dusk twilight pulses is discussed in the context of the postulated two photoreceptors: the short wavelength sensitive (S) photoreceptors mediating entrainment via dusk twilight, and the medium wavelength sensitive (M) photoreceptors mediating entrainment via dawn twilight. PMID:16147895

  13. LIDAR OBSERVATIONS OF MIXED LAYER DYNAMICS: TESTS OF PARAMETERIZED ENTRAINMENT MODELS OF MIXED LAYER GROWTH RATE

    EPA Science Inventory

    Lidar measurements of the atmospheric boundary layer height, the entrainment zone, wind speed and direction, ancillary temperature profiles and surface flux data were used to test current parameterized entrainment models of mixed layer growth rate. Six case studies under clear ai...

  14. Determination of human EEG alpha entrainment ERD/ERS using the continuous complex wavelet transform

    NASA Astrophysics Data System (ADS)

    Chorlian, David B.; Porjesz, Bernice; Begleiter, Henri

    2003-04-01

    Alpha entrainment caused by exposure to a background stimulus continuously flickering at a rate of 8 1/3 Hz was affected by the appearance of a foreground target stimulus to which the subjects were requested to press a button. With the use of bipolar derivations (to reduce volume conduction effects), scalp recorded EEG potentials were subjected to a continuous wavelet transform using complex Morlet wavelets at a range of scales. Complex Morlet wavelets were used to calculate efficiently instantaneous amplitudes and phases on a per-trial basis, rather than using the Hilbert transform on band-pass filtered data. Multiple scales were employed to contrast the pattern of alpha activity with those in other bands, and to determine whether the harmonics observed in the spectral analysis of the data were simply a result of the non-sinusoidal response to the entraining signal or a distinct neural phenomenon. We were thus able to calculate desynchronization/resynchronization for both the entrained and non-entrained alpha activity. The occurance of the target stimulus caused a sharp increase in amplitude in both the entrained and non-entrained alpha activity, followed by a sharp decrease, and then a return to baseline, over a period of 2.5 seconds. However, the entrained alpha activity showed a much more rapid recovery than non-entrained activity.

  15. The importance of entrainment and bulking on debris flow runout modeling: examples from the Swiss Alps

    NASA Astrophysics Data System (ADS)

    Frank, F.; McArdell, B. W.; Huggel, C.; Vieli, A.

    2015-11-01

    This study describes an investigation of channel-bed entrainment of sediment by debris flows. An entrainment model, developed using field data from debris flows at the Illgraben catchment, Switzerland, was incorporated into the existing RAMMS debris-flow model, which solves the 2-D shallow-water equations for granular flows. In the entrainment model, an empirical relationship between maximum shear stress and measured erosion is used to determine the maximum potential erosion depth. Additionally, the average rate of erosion, measured at the same field site, is used to constrain the erosion rate. The model predicts plausible erosion values in comparison with field data from highly erosive debris flow events at the Spreitgraben torrent channel, Switzerland in 2010, without any adjustment to the coefficients in the entrainment model. We find that by including bulking due to entrainment (e.g., by channel erosion) in runout models a more realistic flow pattern is produced than in simulations where entrainment is not included. In detail, simulations without entrainment show more lateral outflow from the channel where it has not been observed in the field. Therefore the entrainment model may be especially useful for practical applications such as hazard analysis and mapping, as well as scientific case studies of erosive debris flows.

  16. Separation of Function for Classical and Ganglion Cell Photoreceptors with Respect to Circadian Rhythm Entrainment and Induction of Photosomnolence

    PubMed Central

    Morin, L.P.; Studholme, K.M.

    2011-01-01

    Four studies were performed to further clarify the contribution of rod/cone and intrinsically photoreceptive retinal ganglion cells to measures of entrainment, light-induced locomotor suppression and photosomnolence. Wildtype (WT), retinally degenerate (rd/rd) and melanopsin-less (OPN4−/−) mouse strains were compared. In Expt. 1, mice were exposed to a graded photoperiod in which approximately 0.26 μW/cm2 irradiance diminished to dark over a 6 hr interval. This method enabled “phase angle titration,” with individual animals assuming activity onsets according to their sensitivity to light. WT and OPN4−/− animals entrained with identical phase angles (effective irradiance=0.078 μW/cm2), but rd/rd mice required a more intense irradiance (0.161 μW/cm2) and entrainment occurred about 2.5 hr earlier. In Expt. 2, all three strains preferred the dark side of a divided light-dark chamber until the irradiance dropped to 0.5 μW/cm2 at which point, rd/rd mice no longer showed a preference. Expts. 3 and 4 determined that WT and rd/rd mice showed equivalent light-induced locomotor suppression, but the response was greatly impaired in OPN4−/− mice. Closer examination of open field locomotion using infrared video-based methods and Any-mazetm software revealed two opposing effects of light. Locomotor suppression was equivalent in WT and rd/rd mice. Responses by OPN4−/− mice varied from being absent (N=17) to normal (similar to WT and rd/rd mice; N=8). Light onset was associated with a significant, but brief, locomotion increase in WT and OPN4−/− mice, but not in rd/rd mice. Any-mazetm analysis supports the view that light-induced locomotor quiescence is followed by behavioral sleep (photosomnolence), a fact that was visually validated from the raw video files. The data show that a) classical photoreceptors, most likely rods, allow mice to prefer and entrain to very dim light such as found in natural twilight; b) the presence of melanopsin photopigment

  17. Emissions from vehicles, tailpipe and vehicle re-entrained road dust

    NASA Astrophysics Data System (ADS)

    Zhu, Dongzi

    Emissions from transportation are some of the largest sources of urban air pollution. Transportation emissions originate from both the engine-through combustion processes and non-tailpipe re-suspended road dust emissions induced by vehicle travel on unpaved and paved roads. Gaseous and particulate emissions from transportation sources have negative impacts on human health, visibility and may influence the global radiation balance. Fugitive dust emissions originating from vehicle travel on paved and unpaved roads constitute a significant fraction of the PM10 in many areas of the western US impacting their attainment status of National Ambient Air Quality Standards. The research used three novel instrument platforms developed at the Desert Research Institute. The In-Plume Emissions Test Stand (IPETS) was designed to provide characterization of exhaust emissions from in-use individual vehicles or engines by analyzing air as close as 1 m from the exhaust port. Real-world emission factors can be quantified by in-plume measurements and provide more realistic measures for emission inventories, source modeling, and receptor modeling than certification measurements. The Testing Re-entrained Aerosol Kinetic Emissions from Roads (TRAKER) provides an effective alternate approach to the EPA AP-42 road dust emissions estimation techniques by sampling 1000s of km of roads versus isolated 3 m sections. The Portable Deposition Monitoring Platform (PDMP incorporates PM and meteorological instruments to characterize the downwind change in particle concentrations to define depositional losses in different environments. The research outcome provides important knowledge for understanding diesel engine emissions, road dust emissions and aerosol deposition process near road sources.

  18. Venous air embolus during scalp incision.

    PubMed

    Spence, Nicole Z; Faloba, Kathryn; Sonabend, Adam M; Bruce, Jeffrey N; Anastasian, Zirka H

    2016-06-01

    Venous air embolism (VAE) is a known complication of sitting craniotomy. Clinical consequences of VAE can range from tachypnea to cardiovascular collapse. The entrainment of air typically occurs during bone work, but we describe a case in which a VAE was recognized while working on the scalp. Monitoring techniques are critical for early treatment of VAE to avoid more serious complications, and our case illustrates the need to implement monitors early and remain vigilant throughout the procedure. PMID:26765767

  19. Simulator Of Rain In Flowing Air

    NASA Technical Reports Server (NTRS)

    Clayton, Richard M.; Cho, Young I.; Shakkottai, Parthasarathy; Back, Lloyd H.

    1989-01-01

    Report describes relatively inexpensive apparatus that creates simulated precipitation from drizzle to heavy rain in flowing air. Small, positive-displacement pump and water-injecting device positioned at low-airspeed end of converging section of wind tunnel 10 in. in diameter. Drops injected by array entrained in flow of air as it accelerates toward narrower outlet, 15 in. downstream. Outlet 5 in. in diameter.

  20. Entrainment of Dungeness Crab in the Desdemona Shoals Reach of the Lower Columbia River Navigation Channel

    SciTech Connect

    Pearson, Walter H.; Kohn, Nancy P.; Skalski, J. R.

    2006-09-30

    Proposed dredging of the Columbia River has raised concerns about related impacts on Dungeness crab in the Columbia River Estuary (CRE). This study follows two major efforts, sponsored by the Portland District of the U. S. Army Corps of Engineers (USACE) to quantify the number of crabs entrained by a hopper dredge working in the CRE. From June 2002 through September 2002, Pacific Northwest National Laboratory (PNNL) conducted direct measurements of crab entrainment in the CRE from the mouth of the Columbia River (MCR, river mile -3 to +3) upriver as far as Miller Sands (river mile 21 to 24). These studies constituted a major step in quantifying crab entrainment in the CRE, and allowed statistically bounded projections of adult equivalent loss (AEL) for Dungeness crab populations under a range of future construction dredging and maintenance dredging scenarios (Pearson et al. 2002, 2003). In 2004, PNNL performed additional measurements to improve estimates of crab entrainment at Desdemona Shoals and at Flavel Bar, a reach near Astoria that had not been adequately sampled in 2002 (Figure 1). The 2004 data were used to update the crab loss projections for channel construction to 43 ft MLLW. In addition, a correlation between bottom salinity and adult (age 2+ and 3+, >100 mm carapace width) crab entrainment was developed using 2002 data, and elaborated upon with the 2004 data. This crab salinity model was applied to forecasting seasonal (monthly) entrainment rates and AEL using seasonal variations in salinity (Pearson et al. 2005). In the previous studies, entrainment rates in Desdemona Shoals were more variable than in any of the other reaches. Pearson et al. (2005) concluded that ?the dynamics behind the variable entrainment rates at Desdemona Shoals are not fully understood,? as well as finding that juvenile crab entrainment was not significantly correlated with salinity as it was for older crab. The present study was undertaken to address the question of whether the

  1. Right Heart Vortex Entrainment Volume and Right Ventricular Diastolic Dysfunction

    NASA Astrophysics Data System (ADS)

    Browning, James; Hertzberg, Jean; Fenster, Brett; Schroeder, Joyce

    2014-11-01

    Recent advances in cardiac magnetic resonance imaging (CMR) have allowed for the 3-dimensional characterization of blood flow in the right ventricle (RV) and right atrium (RA). In this study, we investigate and quantify differences in the characteristics of coherent rotating flow structures (vortices) in the RA and RV between subjects with right ventricular diastolic dysfunction (RVDD) and normal controls. Fifteen RVDD subjects and 10 age-matched controls underwent same day 3D time resolved CMR and echocardiography. Echocardiography was used to determine RVDD stage as well as pulmonary artery systolic pressure (PASP). CMR data was used for RA and RV vortex quantification and visualization during early and late ventricular diastole. RA and RV vortex entrainment volume is quantified and visualized using the Lambda-2 criterion, and the results are compared between healthy subjects and those with RVDD. The resulting trends are discussed and hypotheses are presented regarding differences in vortex characteristics between healthy and RVDD subjects cohorts.

  2. Entrainment of heterogeneous glycolytic oscillations in single cells

    NASA Astrophysics Data System (ADS)

    Gustavsson, Anna-Karin; Adiels, Caroline B.; Mehlig, Bernhard; Goksör, Mattias

    2015-03-01

    Cell signaling, gene expression, and metabolism are affected by cell-cell heterogeneity and random changes in the environment. The effects of such fluctuations on cell signaling and gene expression have recently been studied intensively using single-cell experiments. In metabolism heterogeneity may be particularly important because it may affect synchronisation of metabolic oscillations, an important example of cell-cell communication. This synchronisation is notoriously difficult to describe theoretically as the example of glycolytic oscillations shows: neither is the mechanism of glycolytic synchronisation understood nor the role of cell-cell heterogeneity. To pin down the mechanism and to assess its robustness and universality we have experimentally investigated the entrainment of glycolytic oscillations in individual yeast cells by periodic external perturbations. We find that oscillatory cells synchronise through phase shifts and that the mechanism is insensitive to cell heterogeneity (robustness) and similar for different types of external perturbations (universality).

  3. Near-field entrainment in black smoker plumes

    NASA Astrophysics Data System (ADS)

    Smith, J. E.; Germanovich, L. N.; Lowell, R. P.

    2013-12-01

    In this work, we study the entrainment rate of the ambient fluid into a plume in the extreme conditions of hydrothermal venting at ocean floor depths that would be difficult to reproduce in the laboratory. Specifically, we investigate the flow regime in the lower parts of three black smoker plumes in the Main Endeavour Field on the Juan de Fuca Ridge discharging at temperatures of 249°C, 333°C, and 336°C and a pressure of 21 MPa. Such flow conditions are typical for ocean floor hydrothermal venting but would be difficult to reproduce in the laboratory. The centerline temperature was measured at several heights in the plume above the orifice. Using a previously developed turbine flow meter, we also measured the mean flow velocity at the orifice. Measurements were conducted during dives 4452 and 4518 on the submersible Alvin. Using these measurements, we obtained a range of 0.064 - 0.068 for values of the entrainment coefficient α, which is assumed constant near the orifice. This is half the value of α ≈ 0.12 - 0.13 that would be expected for plume flow regimes based on the existing laboratory results and field measurements in lower temperature and pressure conditions. In fact, α = 0.064 - 0.068 is even smaller than the value of α ≈ 0.075 characteristic of jet flow regimes and appears to be the lowest reported in the literature. Assuming that the mean value α = 0.066 is typical for hydrothermal venting at ocean floor depths, we then characterized the flow regimes of 63 black smoker plumes located on the Endeavor Segment of the Juan de Fuca Ridge. Work with the obtained data is ongoing, but current results indicate that approximately half of these black smokers are lazy in the sense that their plumes exhibit momentum deficits compared to the pure plume flow that develops as the plume rises. The remaining half produces forced plumes that show the momentum excess compared to the pure plumes. The lower value of the entrainment coefficient has important

  4. Low frequency entrainment of oscillatory bursts in hair cells.

    PubMed

    Shlomovitz, Roie; Fredrickson-Hemsing, Lea; Kao, Albert; Meenderink, Sebastiaan W F; Bruinsma, Robijn; Bozovic, Dolores

    2013-04-16

    Sensitivity of mechanical detection by the inner ear is dependent upon a highly nonlinear response to the applied stimulus. Here we show that a system of differential equations that support a subcritical Hopf bifurcation, with a feedback mechanism that tunes an internal control parameter, captures a wide range of experimental results. The proposed model reproduces the regime in which spontaneous hair bundle oscillations are bistable, with sporadic transitions between the oscillatory and the quiescent state. Furthermore, it is shown, both experimentally and theoretically, that the application of a high-amplitude stimulus to the bistable system can temporarily render it quiescent before recovery of the limit cycle oscillations. Finally, we demonstrate that the application of low-amplitude stimuli can entrain bundle motility either by mode-locking to the spontaneous oscillation or by mode-locking the transition between the quiescent and oscillatory states. PMID:23601313

  5. Low Frequency Entrainment of Oscillatory Bursts in Hair Cells

    PubMed Central

    Shlomovitz, Roie; Fredrickson-Hemsing, Lea; Kao, Albert; Meenderink, Sebastiaan W.F.; Bruinsma, Robijn; Bozovic, Dolores

    2013-01-01

    Sensitivity of mechanical detection by the inner ear is dependent upon a highly nonlinear response to the applied stimulus. Here we show that a system of differential equations that support a subcritical Hopf bifurcation, with a feedback mechanism that tunes an internal control parameter, captures a wide range of experimental results. The proposed model reproduces the regime in which spontaneous hair bundle oscillations are bistable, with sporadic transitions between the oscillatory and the quiescent state. Furthermore, it is shown, both experimentally and theoretically, that the application of a high-amplitude stimulus to the bistable system can temporarily render it quiescent before recovery of the limit cycle oscillations. Finally, we demonstrate that the application of low-amplitude stimuli can entrain bundle motility either by mode-locking to the spontaneous oscillation or by mode-locking the transition between the quiescent and oscillatory states. PMID:23601313

  6. Turbulent mixing and entrainment in a gravity current

    SciTech Connect

    Ecke, Robert E; Odier, Philippe; Chen, Jun

    2010-01-01

    We present an experimental study of the mixing processes in a gravity current. The turbulent transport of momentum and buoyancy can be described in a very direct and compact form by a Prandtl mixing length model: the turbulent vertical fluxes of momentum and buoyancy are found to scale quadratically with the vertical mean gradients of velocity and density. The scaling coefficient is the square of the mixing lenth, approximately constant over the mixing zone of the stratified shear layer. We show how, in different flow configurations, this length can be related to the shear length of the flow ({var_epsilon}/{partial_derivative}{sub z}u{sup 3}){sup 1/2}. We also study the fluctuations of the momentum and density turbulent fluxes, showing how they relate to the mixing phenomena, and to the entrainment/detrainment balance.

  7. Phase-selective entrainment of nonlinear oscillator ensembles

    NASA Astrophysics Data System (ADS)

    Zlotnik, Anatoly; Nagao, Raphael; Kiss, István Z.; Li-Shin, Jr.

    2016-03-01

    The ability to organize and finely manipulate the hierarchy and timing of dynamic processes is important for understanding and influencing brain functions, sleep and metabolic cycles, and many other natural phenomena. However, establishing spatiotemporal structures in biological oscillator ensembles is a challenging task that requires controlling large collections of complex nonlinear dynamical units. In this report, we present a method to design entrainment signals that create stable phase patterns in ensembles of heterogeneous nonlinear oscillators without using state feedback information. We demonstrate the approach using experiments with electrochemical reactions on multielectrode arrays, in which we selectively assign ensemble subgroups into spatiotemporal patterns with multiple phase clusters. The experimentally confirmed mechanism elucidates the connection between the phases and natural frequencies of a collection of dynamical elements, the spatial and temporal information that is encoded within this ensemble, and how external signals can be used to retrieve this information.

  8. Spontaneous tempo and rhythmic entrainment in a bonobo (Pan paniscus).

    PubMed

    Large, Edward W; Gray, Patricia M

    2015-11-01

    The emergence of speech and music in the human species represent major evolutionary transitions that enabled the use of complex, temporally structured acoustic signals to coordinate social interaction. While the fundamental capacity for temporal coordination with complex acoustic signals has been shown in a few distantly related species, the extent to which nonhuman primates exhibit sensitivity to auditory rhythms remains controversial. In Experiment 1, we assessed spontaneous motor tempo and tempo matching in a bonobo (Pan paniscus), in the context of a social drumming interaction. In Experiment 2, the bonobo spontaneously entrained and synchronized her drum strikes within a range around her spontaneous motor tempo. Our results are consistent with the hypothesis that the evolution of acoustic communication builds upon fundamental neurodynamic mechanisms that can be found in a wide range of species, and are recruited for social interactions. PMID:26147705

  9. Entrainment of Human Alpha Oscillations Selectively Enhances Visual Conjunction Search

    PubMed Central

    Müller, Notger G.; Vellage, Anne-Katrin; Heinze, Hans-Jochen; Zaehle, Tino

    2015-01-01

    The functional role of the alpha-rhythm which dominates the human electroencephalogram (EEG) is unclear. It has been related to visual processing, attentional selection and object coherence, respectively. Here we tested the interaction of alpha oscillations of the human brain with visual search tasks that differed in their attentional demands (pre-attentive vs. attentive) and also in the necessity to establish object coherence (conjunction vs. single feature). Between pre- and post-assessment elderly subjects received 20 min/d of repetitive transcranial alternating current stimulation (tACS) over the occipital cortex adjusted to their individual alpha frequency over five consecutive days. Compared to sham the entrained alpha oscillations led to a selective, set size independent improvement in the conjunction search task performance but not in the easy or in the hard feature search task. These findings suggest that cortical alpha oscillations play a specific role in establishing object coherence through suppression of distracting objects. PMID:26606255

  10. Phase-selective entrainment of nonlinear oscillator ensembles

    DOE PAGESBeta

    Zlotnik, Anatoly V.; Nagao, Raphael; Kiss, Istvan Z.; Li, Jr -Shin

    2016-03-18

    The ability to organize and finely manipulate the hierarchy and timing of dynamic processes is important for understanding and influencing brain functions, sleep and metabolic cycles, and many other natural phenomena. However, establishing spatiotemporal structures in biological oscillator ensembles is a challenging task that requires controlling large collections of complex nonlinear dynamical units. In this report, we present a method to design entrainment signals that create stable phase patterns in ensembles of heterogeneous nonlinear oscillators without using state feedback information. We demonstrate the approach using experiments with electrochemical reactions on multielectrode arrays, in which we selectively assign ensemble subgroups intomore » spatiotemporal patterns with multiple phase clusters. As a result, the experimentally confirmed mechanism elucidates the connection between the phases and natural frequencies of a collection of dynamical elements, the spatial and temporal information that is encoded within this ensemble, and how external signals can be used to retrieve this information.« less

  11. Phase-selective entrainment of nonlinear oscillator ensembles

    PubMed Central

    Zlotnik, Anatoly; Nagao, Raphael; Kiss, István Z.; Li, Jr-Shin

    2016-01-01

    The ability to organize and finely manipulate the hierarchy and timing of dynamic processes is important for understanding and influencing brain functions, sleep and metabolic cycles, and many other natural phenomena. However, establishing spatiotemporal structures in biological oscillator ensembles is a challenging task that requires controlling large collections of complex nonlinear dynamical units. In this report, we present a method to design entrainment signals that create stable phase patterns in ensembles of heterogeneous nonlinear oscillators without using state feedback information. We demonstrate the approach using experiments with electrochemical reactions on multielectrode arrays, in which we selectively assign ensemble subgroups into spatiotemporal patterns with multiple phase clusters. The experimentally confirmed mechanism elucidates the connection between the phases and natural frequencies of a collection of dynamical elements, the spatial and temporal information that is encoded within this ensemble, and how external signals can be used to retrieve this information. PMID:26988313

  12. Entrainment of Human Alpha Oscillations Selectively Enhances Visual Conjunction Search.

    PubMed

    Müller, Notger G; Vellage, Anne-Katrin; Heinze, Hans-Jochen; Zaehle, Tino

    2015-01-01

    The functional role of the alpha-rhythm which dominates the human electroencephalogram (EEG) is unclear. It has been related to visual processing, attentional selection and object coherence, respectively. Here we tested the interaction of alpha oscillations of the human brain with visual search tasks that differed in their attentional demands (pre-attentive vs. attentive) and also in the necessity to establish object coherence (conjunction vs. single feature). Between pre- and post-assessment elderly subjects received 20 min/d of repetitive transcranial alternating current stimulation (tACS) over the occipital cortex adjusted to their individual alpha frequency over five consecutive days. Compared to sham the entrained alpha oscillations led to a selective, set size independent improvement in the conjunction search task performance but not in the easy or in the hard feature search task. These findings suggest that cortical alpha oscillations play a specific role in establishing object coherence through suppression of distracting objects. PMID:26606255

  13. Phase-selective entrainment of nonlinear oscillator ensembles.

    PubMed

    Zlotnik, Anatoly; Nagao, Raphael; Kiss, István Z; Li, Jr-Shin

    2016-01-01

    The ability to organize and finely manipulate the hierarchy and timing of dynamic processes is important for understanding and influencing brain functions, sleep and metabolic cycles, and many other natural phenomena. However, establishing spatiotemporal structures in biological oscillator ensembles is a challenging task that requires controlling large collections of complex nonlinear dynamical units. In this report, we present a method to design entrainment signals that create stable phase patterns in ensembles of heterogeneous nonlinear oscillators without using state feedback information. We demonstrate the approach using experiments with electrochemical reactions on multielectrode arrays, in which we selectively assign ensemble subgroups into spatiotemporal patterns with multiple phase clusters. The experimentally confirmed mechanism elucidates the connection between the phases and natural frequencies of a collection of dynamical elements, the spatial and temporal information that is encoded within this ensemble, and how external signals can be used to retrieve this information. PMID:26988313

  14. Gastrin-releasing peptide mediates photic entrainable signals to dorsal subsets of suprachiasmatic nucleus via induction of Period gene in mice.

    PubMed

    Aida, Reiko; Moriya, Takahiro; Araki, Miwa; Akiyama, Masashi; Wada, Keiji; Wada, Etsuko; Shibata, Shigenobu

    2002-01-01

    The suprachiasmatic nucleus (SCN), locus of the central circadian clock, consists of two neuronal populations (i.e., a light-recipient ventral SCN subpopulation directly entrained by light and a dorsal SCN subpopulation with an autonomous oscillatory function possessing an indirect or weak light response). However, the mechanism underlying the transmission of photic signals from the ventral to dorsal SCN remains unclear. Because gastrin-releasing peptide (GRP), expressed mainly in the ventral SCN, exerts phase-shifting actions, loss of the GRP receptor intuitively implies a reduction of photic information from the ventral to dorsal SCN. Therefore, using GRP receptor-deficient mice, we examined the involvement of GRP and the GRP receptor in light- and GRP-induced entrainment by the assessment of behavioral rhythm and induction of mousePeriod (mPer) gene in the SCN, which is believed to be a critical for photic entrainment. Administration of GRP during nighttime dose dependently produced a phase delay of behavior in wild-type but not GRP receptor-deficient mice. This phase-shift by GRP was closely associated with induction of mPer1 and mPer2 mRNA as well as c-Fos protein in the dorsal portion of the SCN, where the GRP receptor was also expressed abundantly. Both the light-induced phase shift in behavior and the induction of mPer mRNA and c-Fos protein in the dorsal SCN were attenuated in GRP receptor-deficient mice. Our present studies suggest that GRP neurons in the retinorecipient ventral area of the SCN convey the photic entrainable signals from the ventral SCN to the dorsal SCN via induction of the mPer gene. PMID:11752203

  15. Experimental study of near-field entrainment of moderately overpressured jets

    USGS Publications Warehouse

    Solovitz, S.A.; Mastin, L.G.; Saffaraval, F.

    2011-01-01

    Particle image velocimetry (PIV) experiments have been conducted to study the velocity flow fields in the developing flow region of high-speed jets. These velocity distributions were examined to determine the entrained mass flow over a range of geometric and flow conditions, including overpressured cases up to an overpressure ratio of 2.83. In the region near the jet exit, all measured flows exhibited the same entrainment up until the location of the first shock when overpressured. Beyond this location, the entrainment was reduced with increasing overpressure ratio, falling to approximately 60 of the magnitudes seen when subsonic. Since entrainment ratios based on lower speed, subsonic results are typically used in one-dimensional volcanological models of plume development, the current analytical methods will underestimate the likelihood of column collapse. In addition, the concept of the entrainment ratio normalization is examined in detail, as several key assumptions in this methodology do not apply when overpressured.

  16. Isospin dependence of entrainment in superfluid neutron stars in a relativistic model

    NASA Astrophysics Data System (ADS)

    Kheto, Apurba; Bandyopadhyay, Debades

    2014-01-01

    We study the entrainment effect between superfluid neutrons and charge neutral fluid (called the proton fluid) which is made of protons and electrons in a neutron star interior within the two-fluid formalism and using a relativistic model where baryon-baryon interaction is mediated by the exchange of σ, ω, and ρ mesons. This model of strong interaction also includes scalar self-interactions. The entrainment matrix and entrainment parameter are calculated using the parameter sets of Glendenning (GL) and another non-linear (NL3) interaction. The inclusion of ρ mesons strongly influences the entrainment parameter (ɛmom) in a superfluid neutron star. The entrainment parameter is constant at the core and drops rapidly at the surface. It takes values within the physical range.

  17. How oil properties and layer thickness determine the entrainment of spilled surface oil.

    PubMed

    Zeinstra-Helfrich, Marieke; Koops, Wierd; Murk, Albertinka J

    2016-09-15

    Viscosity plays an important role in dispersion of spilled surface oil, so does adding chemical dispersants. For seven different oil grades, entrainment rate and initial droplet size distribution were investigated using a plunging jet apparatus with coupled camera equipment and subsequent image analysis. We found that amount of oil entrained is proportional to layer thickness and largely independent of oil properties: A dispersant dose of 1:200 did not result in a significantly different entrainment rate compared to no dispersants. Oil viscosity had a minor to no influence on entrainment rate, until a certain threshold above which entrainment was impeded. The mean droplet size scales with the modified Weber number as described by Johansen. The obtained results can help improve dispersion algorithms in oil spill fate and transport models, to aid making an informed decision about application of dispersants. PMID:27345705

  18. Out-of-synchrony speech entrainment in developmental dyslexia.

    PubMed

    Molinaro, Nicola; Lizarazu, Mikel; Lallier, Marie; Bourguignon, Mathieu; Carreiras, Manuel

    2016-08-01

    Developmental dyslexia is a reading disorder often characterized by reduced awareness of speech units. Whether the neural source of this phonological disorder in dyslexic readers results from the malfunctioning of the primary auditory system or damaged feedback communication between higher-order phonological regions (i.e., left inferior frontal regions) and the auditory cortex is still under dispute. Here we recorded magnetoencephalographic (MEG) signals from 20 dyslexic readers and 20 age-matched controls while they were listening to ∼10-s-long spoken sentences. Compared to controls, dyslexic readers had (1) an impaired neural entrainment to speech in the delta band (0.5-1 Hz); (2) a reduced delta synchronization in both the right auditory cortex and the left inferior frontal gyrus; and (3) an impaired feedforward functional coupling between neural oscillations in the right auditory cortex and the left inferior frontal regions. This shows that during speech listening, individuals with developmental dyslexia present reduced neural synchrony to low-frequency speech oscillations in primary auditory regions that hinders higher-order speech processing steps. The present findings, thus, strengthen proposals assuming that improper low-frequency acoustic entrainment affects speech sampling. This low speech-brain synchronization has the strong potential to cause severe consequences for both phonological and reading skills. Interestingly, the reduced speech-brain synchronization in dyslexic readers compared to normal readers (and its higher-order consequences across the speech processing network) appears preserved through the development from childhood to adulthood. Thus, the evaluation of speech-brain synchronization could possibly serve as a diagnostic tool for early detection of children at risk of dyslexia. Hum Brain Mapp 37:2767-2783, 2016. © 2016 Wiley Periodicals, Inc. PMID:27061643

  19. Laser Cladding to Improve Oxidation Behavior of Air Plasma-Sprayed Ni-20Cr Coating on Stainless Steel Substrate

    NASA Astrophysics Data System (ADS)

    Rauf, M. Mudassar; Shahid, Muhammad; Nusair Khan, A.; Mehmood, K.

    2015-09-01

    Air plasma-sprayed Ni-20Cr coating on stainless steel (AISI-304) substrate was re-melted using CO2 laser to remove the inherent defects, i.e., porosity, splat boundaries, and oxides of air plasma-sprayed coating. The (1) uncoated, (2) air plasma-sprayed, and (3) laser-re-melted specimens were exposed to cyclic oxidation at 900 °C for a hundred cycles run. The oxidation products were characterized using XRD and SEM. Weight changes were determined after every 4th cycle; Uncoated samples showed severe oxidation indicated by substantial weight loss, whereas air plasma-coated samples demonstrated noticeable weight gain. However, oxidation resistance of laser-cladded samples was found to be significantly improved as the samples showed negligible weight change; porosity within the coating was minimized with an improvement in interface quality causing reduction in delamination damage.

  20. Circadian rhythm in larval release by the crab Rhithropanopeus harrisii: entrainment model.

    PubMed

    Forward, Richard B; Moeller, Bianca P; Cohen, Jonathan H

    2014-04-01

    The subtidal crab Rhithropanopeus harrisii has a circadian rhythm in larval release; under constant conditions eggs hatch in the 2-3-h interval after the time of sunset in nontidal estuaries. Eggs that are removed from the female hatch rhythmically, indicating that the circadian rhythm resides in the embryos. The model for entrainment is that mature embryos have functional sensory systems that detect and entrain to environmental cycles. This model was reexamined by confirming that the visual system of advanced embryos responds to light and thus could mediate entrainment to the light/dark cycle. We then determined whether the hatching rhythm of mature embryos that are removed from the female can be entrained to new light/dark cycles. Contrary to expectations, these embryos did not entrain to new cycles. Instead, they remained entrained to the light/dark cycle to which they were exposed when still attached to the female, suggesting that the female entrains the rhythm. Indeed, hatching by embryos collected from the field when they had not yet developed eye pigments, kept in constant conditions attached to their mother, exhibited the circadian hatching rhythm. They could also be entrained to a new photoperiod in the laboratory. The role of the female is further supported by experiments showing that the hatching rhythm in embryos carried by females lacking one but not both eyes can be entrained to a new cycle in the laboratory. Thus, the revised model is that the female perceives the light/dark cycle and entrains the circadian rhythm in the embryos. PMID:24797091

  1. The performative pleasure of imprecision: a diachronic study of entrainment in music performance.

    PubMed

    Geeves, Andrew; McIlwain, Doris J; Sutton, John

    2014-01-01

    This study focuses in on a moment of live performance in which the entrainment amongst a musical quartet is threatened. Entrainment is asymmetric in so far as there is an ensemble leader who improvises and expands the structure of a last chorus of a piece of music beyond the limits tacitly negotiated during prior rehearsals and performances. Despite the risk of entrainment being disturbed and performance interrupted, the other three musicians in the quartet follow the leading performer and smoothly transition into unprecedented performance territory. We use this moment of live performance to work back through the fieldwork data, building a diachronic study of the development and bases of entrainment in live music performance. We introduce the concept of entrainment and profile previous theory and research relevant to entrainment in music performance. After outlining our methodology, we trace the evolution of the structure of the piece of music from first rehearsal to final performance. Using video clip analysis, interviews and field notes we consider how entrainment shaped and was shaped by the moment of performance in focus. The sense of trust between quartet musicians is established through entrainment processes, is consolidated via smooth adaptation to the threats of disruption. Non-verbal communicative exchanges, via eye contact, gesture, and spatial proximity, sustain entrainment through phase shifts occurring swiftly and on the fly in performance contexts. These exchanges permit smooth adaptation promoting trust. This frees the quartet members to play with the potential disturbance of equilibrium inherent in entrained relationships and to play with this tension in an improvisatory way that enhances audience engagement and the live quality of performance. PMID:25400567

  2. The performative pleasure of imprecision: a diachronic study of entrainment in music performance

    PubMed Central

    Geeves, Andrew; McIlwain, Doris J.; Sutton, John

    2014-01-01

    This study focuses in on a moment of live performance in which the entrainment amongst a musical quartet is threatened. Entrainment is asymmetric in so far as there is an ensemble leader who improvises and expands the structure of a last chorus of a piece of music beyond the limits tacitly negotiated during prior rehearsals and performances. Despite the risk of entrainment being disturbed and performance interrupted, the other three musicians in the quartet follow the leading performer and smoothly transition into unprecedented performance territory. We use this moment of live performance to work back through the fieldwork data, building a diachronic study of the development and bases of entrainment in live music performance. We introduce the concept of entrainment and profile previous theory and research relevant to entrainment in music performance. After outlining our methodology, we trace the evolution of the structure of the piece of music from first rehearsal to final performance. Using video clip analysis, interviews and field notes we consider how entrainment shaped and was shaped by the moment of performance in focus. The sense of trust between quartet musicians is established through entrainment processes, is consolidated via smooth adaptation to the threats of disruption. Non-verbal communicative exchanges, via eye contact, gesture, and spatial proximity, sustain entrainment through phase shifts occurring swiftly and on the fly in performance contexts. These exchanges permit smooth adaptation promoting trust. This frees the quartet members to play with the potential disturbance of equilibrium inherent in entrained relationships and to play with this tension in an improvisatory way that enhances audience engagement and the live quality of performance. PMID:25400567

  3. A Novel Quantitative Trait Locus on Mouse Chromosome 18, “era1,” Modifies the Entrainment of Circadian Rhythms

    PubMed Central

    Wisor, Jonathan P.; Striz, Martin; DeVoss, Jason; Murphy, Greer M.; Edgar, Dale M.; O'Hara, Bruce F.

    2007-01-01

    Study Objectives: The mammalian circadian clock in the suprachiasmatic nuclei (SCN) of the hypothalamus conveys 24-h rhythmicity to sleep-wake cycles, locomotor activity, and other behavioral and physiological processes. The timing of rhythms relative to the light/dark (LD12:12) cycle is influenced in part by the endogenous circadian period and the time of day specific sensitivity of the clock to light. We now describe a novel circadian rhythm phenotype, and a locus influencing that phenotype, in a segregating population of mice. Methods: By crossbreeding 2 genetically distinct nocturnal strains of mice (Cast/Ei and C57BL/6J) and backcrossing the resulting progeny to Cast/Ei, we have produced a novel circadian phenotype, called early runner mice. Results: Early runner mice entrain to a light/dark cycle at an advanced phase, up to 9 hours before dark onset. This phenotype is not significantly correlated with circadian period in constant darkness and is not associated with disruption of molecular circadian rhythms in the SCN, as assessed by analysis of period gene expression. We have identified a genomic region that regulates this phenotype—a major quantitative trait locus on chromosome 18 (near D18Mit184) that we have named era1 for Early Runner Activity locus one. Phase delays caused by light exposure early in the subjective night were of smaller magnitude in backcross offspring that were homozygous Cast/Ei at D18Mit184 than in those that were heterozygous at this locus. Conclusion: Genetic variability in the circadian response to light may, in part, explain the variance in phase angle of entrainment in this segregating mouse population. Citation: Wisor JP; Striz M; DeVoss J; Murphy GM; Edgar DM; O'Hara BF. A novel quantitative trait locus on mouse chromosome 18, “era1,” modifies the entrainment of circadian rhythms. SLEEP 2007;30(10):1255-1263. PMID:17969459

  4. Understanding run-in behavior of diamond-like carbon friction and preventing diamond-like carbon wear in humid air.

    PubMed

    Marino, Matthew J; Hsiao, Erik; Chen, Yongsheng; Eryilmaz, Osman L; Erdemir, Ali; Kim, Seong H

    2011-10-18

    The friction behavior of diamond-like carbon (DLC) is very sensitive to the test environment. For hydrogen-rich DLC tested in dry argon and hydrogen, there was always an induction period, so-called "run-in" period, during which the friction coefficient was high and gradually decreased before DLC showed an ultralow friction coefficient (less than 0.01) behavior. Regardless of friction coefficients and hydrogen contents, small amounts of wear were observed in dry argon, hydrogen, oxygen, and humid argon environments. Surprisingly, there were no wear or rubbing scar on DLC surfaces tested in n-pentanol vapor conditions, although the friction coefficient was relatively high among the five test environments. Ex situ X-ray photoelectron and near-edge X-ray absorption fine-structure spectroscopy analyses failed to reveal any differences in chemical composition attributable to the environment dependence of DLC friction and wear. The failure of getting chemical information of oxygenated surface species from the ex situ analysis was found to be due to facile oxidation of the DLC surface upon exposure to air. The removal or wear of this surface oxide layer is responsible for the run-in behavior of DLC. It was discovered that the alcohol vapor can also prevent the oxidized DLC surface from wear in humid air conditions. PMID:21888344

  5. Reduced bleed air extraction for DC-10 cabin air conditioning

    NASA Technical Reports Server (NTRS)

    Newman, W. H.; Viele, M. R.; Hrach, F. J.

    1980-01-01

    It is noted that a significant fuel savings can be achieved by reducing bleed air used for cabin air conditioning. Air in the cabin can be recirculated to maintain comfortable ventilation rates but the quality of the air tends to decrease due to entrainment of smoke and odors. Attention is given to a development system designed and fabricated under the NASA Engine Component Improvement Program to define the recirculation limit for the DC-10. It is shown that with the system, a wide range of bleed air reductions and recirculation rates is possible. A goal of 0.8% fuel savings has been achieved which results from a 50% reduction in bleed extraction from the engine.

  6. A Closer Look at Cost Behavior Patterns and the Implementation of New Programs. AIR 1985 Annual Forum Paper.

    ERIC Educational Resources Information Center

    Lundy, Harold W.

    The way that planning tools can be used to evaluate the economic consequences of implementing new academic programs at Grambling State University (GSU) is considered. The focus is projecting cost behavior for planning and decision making. The following planning tools are examined: cost-volume-revenue analysis, cost behavior analysis and least…

  7. Flow Dynamics and Sediment Entrainment in Natural Turbidity Currents Inferred from Numerical Modeling

    NASA Astrophysics Data System (ADS)

    Traer, M. M.; Hilley, G. E.; Fildani, A.

    2009-12-01

    Submarine turbidity currents derive their momentum from gravity acting upon the density contrast between sediment-laden and clear water, and so unlike fluvial systems, the dynamics of such flows are inextricably linked to the rates at which they deposit and entrain sediment. We have analyzed the sensitivity of the growth and maintenance of turbidity currents to sediment entrainment and deposition using the layer-averaged equations of conservation of fluid and sediment mass, and conservation of momentum and turbulent kinetic energy. Our model results show that the dynamics of turbidity currents are extremely sensitive to the functional form and empirical constants of the relationship between sediment entrainment and friction velocity. Data on the relationship between sediment entrainment and friction velocity for submarine density flows are few and as a result, entrainment formulations are populated with data from sub-aerial flows not driven by the density contrast between clear and turbid water. If we entertain the possibility that sediment entrainment in sub-aerial rivers is different than in dense underflows, flow parameters such as velocity, height, and concentration were found nearly impossible to predict beyond a few hundred meters based on the limited laboratory data available that constrain the sediment entrainment process in turbidity currents. The sensitivity of flow dynamics to the functional relationship between friction velocity and sediment entrainment indicates that independent calibration of a sediment entrainment law in the submarine environment is necessary to realistically predict the dynamics of these flows and the resulting patterns of erosion and deposition. To calibrate such a relationship, we have developed an inverse methodology that utilizes existing submarine channel morphology as a means of constraining the sediment entrainment function parameters. We use a Bayesian Metropolis-Hastings sampler to determine the sediment entrainment

  8. On the pollutant removal, dispersion, and entrainment over two-dimensional idealized street canyons

    NASA Astrophysics Data System (ADS)

    Liu, Chun-Ho; Wong, Colman C. C.

    2014-01-01

    Pollutant dispersion over urban areas is not that well understood, in particular at the street canyon scale. This study is therefore conceived to examine how urban morphology modifies the pollutant removal, dispersion, and entrainment over urban areas. An idealized computational domain consisting of 12 two-dimensional (2D) identical street canyons of unity aspect ratio is employed. The large-eddy simulation (LES) is used to calculate the turbulent flows and pollutant transport in the urban boundary layer (UBL). An area source of uniform pollutant concentration is applied on the ground of the first street canyon. A close examination on the roof-level turbulence reveals patches of low-speed air masses in the streamwise flows and narrow high-speed downdrafts in the shear layer. Different from the flows over a smooth surface, the turbulence intensities are peaked near the top of the building roughness. The pollutant is rather uniformly distributed inside a street canyon but disperses quickly in the UBL over the buildings. Partitioning the vertical pollutant flux into its mean and turbulent components demystifies that the pollutant removal is mainly governed by turbulence. Whereas, mean wind carries pollutant into and out of a street canyon simultaneously. In addition to wind speed promotion, turbulent mixing is thus required to dilute the ground-level pollutants, which are then removed from the street canyon to the UBL. Atmospheric flows slow down rapidly after the leeward buildings, leading to updrafts carrying pollutants away from the street canyons (the basic pollutant removal mechanism).

  9. Fish entrainment rates through towboat propellers in the Upper Mississippi and Illinois rivers

    USGS Publications Warehouse

    Jack, Killgore K.; Miranda, L.E.; Murphy, C.E.; Wolff, D.M.; Hoover, J.J.; Keevin, T.M.; Maynord, S.T.; Cornish, M.A.

    2011-01-01

    Aspecially designed netwas used to study fish entrainment and injury through towboat propellers in 13 pools of the Upper Mississippi and Illinois rivers. The net was attached to the stern of a 48.8-m-long towboat with twin propellers (in Kort propulsion nozzles), and sampling typically took place while the towboat pushed 15 loaded barges upstream at a time. In total, 254 entrainment samples over 894 km of the 13 study pools were collected. The sampling efforts produced 16,005 fish representing 15 families and at least 44 species; fish ranged in total length from 3 to 123 cm, but only 12.5-cm or longer fish were analyzed because smaller fish could escape through the mesh of the trawl. Clupeidae (68% of total catch) and Sciaenidae (21%) were the dominant families. We detected no effects of towboat operation variables (speed and engine [i.e., propeller] revolutions per minute [RPM]) on entrainment rate (i.e., fish/km), but entrainment rate showed a wedge-shaped distribution relative to hydraulic and geomorphic characteristics of the channel. Entrainment rate was low (30 fish/km). Although total entrainment rate was not related to engine RPM, the probability of being struck by a propeller increased with fish length and engine RPM. Limits on engine RPM in narrow, shallow, and sluggish reaches could reduce entrainment impact, particularly for large-bodied fish. ?? American Fisheries Society 2011.

  10. Entrainment Across a Sheared Density Interface in High Richardson Number Cavity Flow

    NASA Astrophysics Data System (ADS)

    Williamson, Nicholas; Kirkpartick, Michael; Armfield, Steve

    2015-11-01

    The turbulent entrainment of fluid across a sharp density interface has been examined experimentally in a purging cavity flow. In the experiments, a long straight cavity with sloped entry and exit boundaries is located in the base of a straight open channel. Saline fluid is entrained from the cavity into the overflow. The cavity geometry has been designed to ensure there is no separation of the overflow in the cavity region with the goal of obtaining a single mode of entrainment, related only to the interface properties rather than to cavity specific mechanisms. The bulk entrainment rate has been measured and correlated with bulk Richardson number over Ri = 1 . 0 - 20 at Reynolds number Re = 7100 - 15100 . The entrainment rate is shown to scale with the local bulk Richardson number E ~= CRi - 1 . 38 , very close to the established result for entrainment across a sharp two layer density interface in a recirculating water channel (Strang and Fernando, J Fluid Mech., 428, 2001) but with an order of magnitude lower coefficient C. Experiments instrumented with PIV/LIF were used to relate the bulk Ri to the local gradient Richardson number of the interface. In the cavity setting the interface appears to remain sharper, resulting in larger Rig and reduced entrainment.

  11. Quadrupedal Locomotion-Respiration Entrainment and Metabolic Economy in Cross-Country Skiers.

    PubMed

    Boldt, Kevin; Killick, Anthony; Herzog, Walter

    2016-02-01

    A 1:1 locomotion-respiration entrainment is observed in galloping quadrupeds, and is thought to improve running economy. However, this has not been tested directly in animals, as animals cannot voluntarily disrupt this entrainment. The purpose of this study was to evaluate metabolic economy in a human gait involving all four limbs, cross-country skiing, in natural entrainment and forced nonentrainment. Nine elite cross-country skiers roller skied at constant speed using the 2-skate technique. In the first and last conditions, athletes used the natural entrained breathing pattern: inhaling with arm recovery and exhaling with arm propulsion, and in the second condition, the athletes disentrained their breathing pattern. The rate of oxygen uptake (VO2) and metabolic rate (MR) were measured via expired gas analysis. Propulsive forces were measured with instrumented skis and poles. VO2 and MR increased by 4% and 5% respectively when skiers used the disentrained compared with the entrained breathing pattern. There were no differences in ski or pole forces or in timing of the gait cycle between conditions. We conclude that breathing entrainment reduces metabolic cost of cross-country skiing by approximately 4%. Further, this reduction is likely a result of the entrainment rather than alterations in gait mechanics. PMID:26252735

  12. Fish and opossum shrimp entrainment in the Mt. Elbert Pumped-Storage Power Plant

    SciTech Connect

    Maiolie, M.A.

    1987-01-01

    Impacts of operating the Mt. Elbert Pumped-Storage Power Plant on fish and opossum shrimp (mysis relicta) were investigated from 1981 to 1985 at Twin Lakes, Colorado to determine any negative effects on the Twin Lakes fishery. Daytime generation cycles entrained shrimp at densities averaging 0.05 to 0.23 shrimp/m/sup 3/ of discharge. Eight hour daytime generation cycles would entrain 50,000 to 300,000 shrimp at these rates. Generation cycles which occurred after dark entrained many times more shrimp with densities as high as 1.21 shrimp/m/sup 3/ of discharge. Entrainment density during nighttime pump-back cycles was much greater; averaging 2 to 17 shrimp/m/sup 3/ discharged. Six to 44 million shrimp were entrained during typical 8 h pump-back cycles. Differences between daytime and nighttime entrainment rates appeared to be caused by migration of shrimp into the water column at night making them more vulnerable to entrainment. Losses were estimated to have reduced Lower Twin Lake shrimp abundance by 39% in 1985.

  13. Entrainment and mixing processes in downslope gravity currents.

    NASA Astrophysics Data System (ADS)

    Shishova, Anna; Gritsenko, Vladimir

    2010-05-01

    Downslope density currents play a significant role in vertical water exchange in near-shore zones of lakes, seas and oceans. Entrainment and mixing processes at the density currents' interface has been described by many authors (e.g., Barenblatt, Benjamin, Britter & Linden, Simpson, Turner, Holyer & Huppert, Baines), however further understanding is still required. Main objective of the present work is the analysis of mixing processes, associated with density current propagating along the bottom, based on examination of simulated flows. The simulations were carried out by using a non-linear two-dimensional XZ-model, which solves the following system of equations: D?/Dt = (g/ρ0) (δσ/δz) + νT??; ?φ = ?; Dρ/Dt = kT?ρ; Dc/Dt = kT?c, where ? - is the flow vorticity, φ - stream function, g=982 cm/s2, ρ0=1 g/cm3 - fresh water density, ρ - saline water density, x, z - horizontal and vertical coordinates, respectively; t - time; D/Dt = δ/δt + uδ/δx + wδ/δz; ? = δ2/δx2 + δ2/δz2; νT = ν0 + c×νeff, kT = 0.5νT - turbulent diffusivity and viscosity coefficients, νeff = √Re×ν 0; Re = u0×h0/ν0; ν0 = 0.015 cm2/s; ν eff = 0 at t=0; c=c(x, z, t), 0.0≤c≤1.0 - dimensionless concentration of tracer of the bottom current water mass. For description and comprehension of specific features of mixing processes in downslope currents the approach suggested by Baines (J. Fluid Mech. 2001, vol. 443) is used, based upon employing local parameters and local averaging. Following Baines, four dimensionless parameters were chosen for the description of the basic flow: slope angle ?, Richardson number Ri = g'd3cosq/Q2, Reynolds number Re = Q/ν and M = Q/(g'D3)0,5= QN3/g'2 - the ambient fluid stratification coefficient; here, ν - kinematical viscosity, d - average thickness of the downflow. Two important additional parameters were defined: N - buoyancy frequency, and an associated parameter D - the depth below the source where the initial density of the fluid in

  14. High Prevalence of Substance Use among Men who have Sex with Men in Buenos Aires, Argentina: Implications for HIV Risk Behavior

    PubMed Central

    Balán, Iván C.; Carballo-Diéguez, Alex; Dolezal, Curtis; Marone, Rubén; Pando, María A.; Barreda, Victoria; Ávila, María M

    2012-01-01

    Five hundred gay and other men who have sex with men (G&MSM) from Buenos Aires, Argentina completed an assessment regarding substance use and sexual behavior. During the past two months, 78% of participants consumed alcohol and 61% drugs. Over 20% of participants reporting alcohol, marijuana, cocaine sulfate, or tranquilizer use, did so daily. Heavy alcohol use was more likely among participants with greater mood reactivity (AOR = 1.64) and less likely among those who identified as gay (AOR=0.38). Weekly drug use was less likely among older (AOR=0.98), and gay-identified participants (AOR=0.50), but more likely among participants with greater mood reactivity (AOR=1.49). Drug use was correlated with unprotected anal and vaginal intercourse with men, women, and transvestites among non-gay identified participants (r= 0.22). Findings highlight the need to reduce substance use and sexual risk behavior in this population. PMID:23196860

  15. Photic entrainment of Period mutant mice is predicted from their phase response curves

    PubMed Central

    Pendergast, Julie S.; Friday, Rio C.; Yamazaki, Shin

    2010-01-01

    A fundamental property of circadian clocks is that they entrain to environmental cues. The circadian genes, Period1 and Period2, are involved in entrainment of the mammalian circadian system. To investigate the roles of the Period genes in photic entrainment, we constructed phase response curves (PRC) to light pulses for C57BL/6J wild-type, Per1−/−, Per2−/−, and Per3−/− mice and tested whether the PRCs accurately predict entrainment to non-24 light-dark cycles (T-cycles) and constant light (LL). The PRCs of wild-type and Per3−/− mice are similar in shape and amplitude and have relatively large delay zones and small advance zones, resulting in successful entrainment to T26, but not T21, with similar phase angles. Per1−/− mice have a high-amplitude PRC, resulting in entrainment to a broad range of T-cycles. Per2−/− mice also entrain to a wide range of T-cycles because the advance portion of their PRC is larger than wild-types. Period aftereffects following entrainment to T-cycles were similar among all genotypes. We found that the ratio of the advance portion to the delay portion of the PRC accurately predicts the lengthening of the period of the activity rhythm in LL. Wild-type, Per1−/−, and Per3−/− mice had larger delay zones than advance zones and lengthened (>24hrs) periods in LL, while Per2−/− mice had delay and advance zones that were equal in size and no period lengthening in LL. Together, these results demonstrate that PRCs are powerful tools for predicting and understanding photic entrainment of circadian mutant mice. PMID:20826680

  16. Power, Control, and Gender: Training as Catalyst for Dysfunctional Behavior at the United States Air Force Academy

    ERIC Educational Resources Information Center

    Callahan, Jamie L.

    2005-01-01

    I explore the role of training practices at the United States Air Force Academy (USAFA) in perpetuating power and control issues and the potential consequences of those practices. I argue that trainee responses to control deprivation may have resulted in alleged sexual assaults by male cadets and the eating disorders manifested by female cadets.…

  17. Laboratory experiments investigating entrainment by debris flows and associated increased mobility

    NASA Astrophysics Data System (ADS)

    Moberly, D.; Maki, L.; Hill, K. M.

    2014-12-01

    As debris flows course down a steep hillside they entrain bed materials such as loose sediments. The entrainment of materials not only increases the size of the debris flows but the mobility as well. The mechanics underlying the particle entrainment and the associated increased mobility are not well-understood. Existing models for the entrainment process include those that explicitly consider stress ratios, the angle of inclination, and the particle fluxes relative to those achieved under steady conditions. Others include an explicit consideration of the physics of the granular state: the visco-elastic nature of particle flows and, alternatively, the role of macroscopic force chains. Understanding how well these different approaches account for entrainment and deposition rates is important for accurate debris flow modeling, both in terms of the rate of growth and also in terms of the increased mobility associated with the entrainment. We investigate how total and instantaneous entrainment and deposition vary with macroscopic stresses and particle-scale interactions for different particle sizes and different fluid contents using laboratory experiments in an instrumented experimental laboratory debris flow flume. The flume has separate, independent water supplies for the bed and "supply" (parent debris flow), and the bed is instrumented with pore pressure sensors and a basal stress transducer. We monitor flow velocities, local structure, and instantaneous entrainment and deposition rates using a high speed camera. We have found that systems with a mixture of particle sizes are less erosive and more depositional than systems of one particle size under otherwise the same conditions. For both mixtures and single-sized particle systems, we have observed a relatively linear relationship between total erosion and the slope angle for dry flows. Increasing fluid content typically increases entrainment. Measurements of instantaneous entrainment indicate similar dependencies

  18. Investigation of Pressurized Entrained-Flow Kraft Black Liquor Gasification in an Industrially Relevant Environment

    SciTech Connect

    Kevin Whitty

    2008-06-30

    The University of Utah's project 'Investigation of Pressurized Entrained-Flow Kraft Black Liquor Gasification in an Industrially Relevant Environment' (U.S. DOE Cooperative Agreement DE-FC26-04NT42261) was a response to U.S. DOE/NETL solicitation DE-PS36-04GO94002, 'Biomass Research and Development Initiative' Topical Area 4-Kraft Black Liquor Gasification. The project began September 30, 2004. The objective of the project was to improve the understanding of black liquor conversion in high pressure, high temperature reactors that gasify liquor through partial oxidation with either air or oxygen. The physical and chemical characteristics of both the gas and condensed phase were to be studied over the entire range of liquor conversion, and the rates and mechanisms of processes responsible for converting the liquor to its final smelt and syngas products were to be investigated. This would be accomplished by combining fundamental, lab-scale experiments with measurements taken using a new semi-pilot scale pressurized entrained-flow gasifier. As a result of insufficient availability of funds and changes in priority within the Office of Biomass Programs of the U.S. Department of Energy, the research program was terminated in its second year. In total, only half of the budgeted funding was made available for the program, and most of this was used during the first year for construction of the experimental systems to be used in the program. This had a severe impact on the program. As a consequence, most of the planned research was unable to be performed. Only studies that relied on computational modeling or existing experimental facilities started early enough to deliver useful results by the time to program was terminated Over the course of the program, small scale (approx. 1 ton/day) entrained-flow gasifier was designed and installed at the University of Utah's off-campus Industrial Combustion and Gasification Research Facility. The system is designed to operate at

  19. Integrated perfusion and separation systems for entrainment of insulin secretion from islets of Langerhans.

    PubMed

    Yi, Lian; Wang, Xue; Dhumpa, Raghuram; Schrell, Adrian M; Mukhitov, Nikita; Roper, Michael G

    2015-02-01

    A microfluidic system was developed to investigate the entrainment of insulin secretion from islets of Langerhans to oscillatory glucose levels. A gravity-driven perfusion system was integrated with a microfluidic system to deliver sinusoidal glucose waveforms to the islet chamber. Automated manipulation of the height of the perfusion syringes allowed precise control of the ratio of two perfusion solutions into a chamber containing 1-10 islets. Insulin levels in the perfusate were measured using an online competitive electrophoretic immunoassay with a sampling period of 10 s. The insulin immunoassay had a detection limit of 3 nM with RSDs of calibration points ranging from 2-8%. At 11 mM glucose, insulin secretion from single islets was oscillatory with a period ranging from 3-6 min. Application of a small amplitude sinusoidal wave of glucose with a period of 5 or 10 min, shifted the period of the insulin oscillations to this forcing period. Exposing groups of 6-10 islets to a sinusoidal glucose wave synchronized their behavior, producing a coherent pulsatile insulin response from the population. These results demonstrate the feasibility of the developed system for the study of oscillatory insulin secretion and can be easily modified for investigating the dynamic nature of other hormones released from different cell types. PMID:25474044

  20. Oil in Water: An Experimental Study of Splashing and Entrainment from Droplets and Jets

    NASA Astrophysics Data System (ADS)

    Mittal, Raina; Halper, Kristen; Mittal, Rajat

    2015-11-01

    This study is motivated by the interaction between oil and water that is associated with events such as oil spills, oil slicks and underwater oil leaks. For instance, the impact of rain drops on a floating oil slick can lead to the formation of satellite droplets and oil entrainment into the water, that could subsequently lead to further dispersion of the oil slick. Furthermore, the dynamics of high speed jets of oil in water is relevant to underwater oil leaks, but the motion of such oil jets is not well studied. In the current study, we use high-speed videography with various types of commonly available oils to study the impact of water droplets on oil slicks of varying thicknesses. Results show that an oil slick with intermediate thickness leads to the most significant formation of satellite droplets. This behavior seems to be related to the competing effect of oil viscosity and surface tension on the dynamics of splashing. We also use high-speed videography to study the motion and dispersion of underwater oil jets and correlate the breakup of the jet with the inclination of the jet.

  1. Synchronizing an aging brain: can entraining circadian clocks by food slow Alzheimer’s disease?

    PubMed Central

    Kent, Brianne A.

    2014-01-01

    Alzheimer’s disease (AD) is a global epidemic. Unfortunately, we are still without effective treatments or a cure for this disease, which is having devastating consequences for patients, their families, and societies around the world. Until effective treatments are developed, promoting overall health may hold potential for delaying the onset or preventing neurodegenerative diseases such as AD. In particular, chronobiological concepts may provide a useful framework for identifying the earliest signs of age-related disease as well as inexpensive and noninvasive methods for promoting health. It is well reported that AD is associated with disrupted circadian functioning to a greater extent than normal aging. However, it is unclear if the central circadian clock (i.e., the suprachiasmatic nucleus) is dysfunctioning, or whether the synchrony between the central and peripheral clocks that control behavior and metabolic processes are becoming uncoupled. Desynchrony of rhythms can negatively affect health, increasing morbidity and mortality in both animal models and humans. If the uncoupling of rhythms is contributing to AD progression or exacerbating symptoms, then it may be possible to draw from the food-entrainment literature to identify mechanisms for re-synchronizing rhythms to improve overall health and reduce the severity of symptoms. The following review will briefly summarize the circadian system, its potential role in AD, and propose using a feeding-related neuropeptide, such as ghrelin, to synchronize uncoupled rhythms. Synchronizing rhythms may be an inexpensive way to promote healthy aging and delay the onset of neurodegenerative disease such as AD. PMID:25225484

  2. Laboratory simulations show diabatic heating drives cumulus-cloud evolution and entrainment.

    PubMed

    Narasimha, Roddam; Diwan, Sourabh Suhas; Duvvuri, Subrahmanyam; Sreenivas, K R; Bhat, G S

    2011-09-27

    Clouds are the largest source of uncertainty in climate science, and remain a weak link in modeling tropical circulation. A major challenge is to establish connections between particulate microphysics and macroscale turbulent dynamics in cumulus clouds. Here we address the issue from the latter standpoint. First we show how to create bench-scale flows that reproduce a variety of cumulus-cloud forms (including two genera and three species), and track complete cloud life cycles--e.g., from a "cauliflower" congestus to a dissipating fractus. The flow model used is a transient plume with volumetric diabatic heating scaled dynamically to simulate latent-heat release from phase changes in clouds. Laser-based diagnostics of steady plumes reveal Riehl-Malkus type protected cores. They also show that, unlike the constancy implied by early self-similar plume models, the diabatic heating raises the Taylor entrainment coefficient just above cloud base, depressing it at higher levels. This behavior is consistent with cloud-dilution rates found in recent numerical simulations of steady deep convection, and with aircraft-based observations of homogeneous mixing in clouds. In-cloud diabatic heating thus emerges as the key driver in cloud development, and could well provide a major link between microphysics and cloud-scale dynamics. PMID:21918112

  3. Phase Entrainment of Human Delta Oscillations Can Mediate the Effects of Expectation on Reaction Speed

    PubMed Central

    Stefanics, Gábor; Hangya, Balázs; Hernádi, István; Winkler, István; Lakatos, Péter; Ulbert, István

    2015-01-01

    The more we anticipate a response to a predictable stimulus, the faster we react. This empirical observation has been confirmed and quantified by many investigators suggesting that the processing of behaviorally relevant stimuli is facilitated by probability-based confidence of anticipation. However, the exact neural mechanisms underlying this phenomenon are largely unknown. Here we show that performance changes related to different levels of expectancy originate in dynamic modulation of delta oscillation phase. Our results obtained in rhythmic auditory target detection tasks indicated significant entrainment of the EEG delta rhythm to the onset of the target tones with increasing phase synchronization at higher levels of predictability. Reaction times correlated with the phase of the delta band oscillation at target onset. The fastest reactions occurred during the delta phase that most commonly coincided with the target event in the high expectancy conditions. These results suggest that low-frequency oscillations play a functional role in human anticipatory mechanisms, presumably by modulating synchronized rhythmic fluctuations in the excitability of large neuronal populations and by facilitating efficient task-related neuronal communication among brain areas responsible for sensory processing and response execution. PMID:20943899

  4. Melatonin is a redundant entraining signal in the rat circadian system.

    PubMed

    Houdek, Pavel; Nováková, Marta; Polidarová, Lenka; Sládek, Martin; Sumová, Alena

    2016-07-01

    The role of melatonin in maintaining proper function of the circadian system has been proposed but very little evidence for such an effect has been provided. To ascertain the role, the aim of the study was to investigate impact of long-term melatonin absence on regulation of circadian system. The parameters of behavior and circadian clocks of rats which were devoid of the melatonin signal due to pinealectomy (PINX) for more than one year were compared with those of intact age-matched controls. PINX led to a decrease in spontaneous locomotor activity and a shortening of the free-running period of the activity rhythm driven by the central clock in the suprachiasmatic nuclei (SCN) in constant darkness. However, the SCN-driven rhythms in activity and feeding were not affected and remained well entrained in the light/dark cycle. In contrast, in these conditions PINX had a significant effect on amplitudes of the clock gene expression rhythms in the duodenum and also partially in the liver. These results demonstrate the significant impact of long-term melatonin absence on period of the central clock in the SCN and the amplitudes of the peripheral clocks in duodenum and liver and suggest that melatonin might be a redundant but effective endocrine signal for these clocks. PMID:27167607

  5. Oscillatory phase dynamics in neural entrainment underpin illusory percepts of time.

    PubMed

    Herrmann, Björn; Henry, Molly J; Grigutsch, Maren; Obleser, Jonas

    2013-10-01

    Neural oscillatory dynamics are a candidate mechanism to steer perception of time and temporal rate change. While oscillator models of time perception are strongly supported by behavioral evidence, a direct link to neural oscillations and oscillatory entrainment has not yet been provided. In addition, it has thus far remained unaddressed how context-induced illusory percepts of time are coded for in oscillator models of time perception. To investigate these questions, we used magnetoencephalography and examined the neural oscillatory dynamics that underpin pitch-induced illusory percepts of temporal rate change. Human participants listened to frequency-modulated sounds that varied over time in both modulation rate and pitch, and judged the direction of rate change (decrease vs increase). Our results demonstrate distinct neural mechanisms of rate perception: Modulation rate changes directly affected listeners' rate percept as well as the exact frequency of the neural oscillation. However, pitch-induced illusory rate changes were unrelated to the exact frequency of the neural responses. The rate change illusion was instead linked to changes in neural phase patterns, which allowed for single-trial decoding of percepts. That is, illusory underestimations or overestimations of perceived rate change were tightly coupled to increased intertrial phase coherence and changes in cerebro-acoustic phase lag. The results provide insight on how illusory percepts of time are coded for by neural oscillatory dynamics. PMID:24089487

  6. Synchronizing an aging brain: can entraining circadian clocks by food slow Alzheimer's disease?

    PubMed

    Kent, Brianne A

    2014-01-01

    Alzheimer's disease (AD) is a global epidemic. Unfortunately, we are still without effective treatments or a cure for this disease, which is having devastating consequences for patients, their families, and societies around the world. Until effective treatments are developed, promoting overall health may hold potential for delaying the onset or preventing neurodegenerative diseases such as AD. In particular, chronobiological concepts may provide a useful framework for identifying the earliest signs of age-related disease as well as inexpensive and noninvasive methods for promoting health. It is well reported that AD is associated with disrupted circadian functioning to a greater extent than normal aging. However, it is unclear if the central circadian clock (i.e., the suprachiasmatic nucleus) is dysfunctioning, or whether the synchrony between the central and peripheral clocks that control behavior and metabolic processes are becoming uncoupled. Desynchrony of rhythms can negatively affect health, increasing morbidity and mortality in both animal models and humans. If the uncoupling of rhythms is contributing to AD progression or exacerbating symptoms, then it may be possible to draw from the food-entrainment literature to identify mechanisms for re-synchronizing rhythms to improve overall health and reduce the severity of symptoms. The following review will briefly summarize the circadian system, its potential role in AD, and propose using a feeding-related neuropeptide, such as ghrelin, to synchronize uncoupled rhythms. Synchronizing rhythms may be an inexpensive way to promote healthy aging and delay the onset of neurodegenerative disease such as AD. PMID:25225484

  7. Application of the k-epsilon turbulence model to the simulation of a fully pulsed free air jet

    NASA Astrophysics Data System (ADS)

    Graham, L. J. W.; Bremhorst, K.

    1993-03-01

    The work describes application of the k-epsilon turbulence model to a fully pulsed air jet. The standard model failed to predict the change in slope of the velocity decay where the jet changes from pulsed to steady jet behavior. A change in one of the constants of the k-epsilon model based on the behavior of the periodic velocity component relative to the intrinsic component yielded satisfactory results. Features of the pulsed jet which were successfully simulated included the flow reversal near the edge of the jet, increased entrainment when compared to steady jets and large radial outflow near the leading edge of the pulse and large radial inflow near the outer edge of the jet for the remainder of the pulse.

  8. Evidence of micro-continent entrainment during crustal accretion.

    PubMed

    Pilia, S; Rawlinson, N; Cayley, R A; Bodin, T; Musgrave, R; Reading, A M; Direen, N G; Young, M K

    2015-01-01

    Simple models involving the gradual outboard accretion of material along curvilinear subduction zones are often inconsistent with field-based evidence. A recent study using 3-D geodynamic modelling has shown that the entrainment of an exotic continental fragment within a simple subduction system can result in a complex phase of growth. Although kinematic models based on structural mapping and high-resolution gravity and magnetic maps indicate that the pre-Carboniferous Tasmanides in southeastern Australia may have been subjected to this process, to date there has been little corroboration from crustal scale geophysical imaging. Here, we apply Bayesian transdimensional tomography to ambient noise data recorded by the WOMBAT transportable seismic array to constrain a detailed (20 km resolution in some areas) 3-D shear velocity model of the crust beneath southeast Australia. We find that many of the velocity variations that emerge from our inversion support the recently developed geodynamic and kinematic models. In particular, the full thickness of the exotic continental block, responsible for orocline formation and the tectonic escape of the back arc region, is imaged here for the first time. Our seismic results provide the first direct evidence that exotic continental fragments may profoundly affect the development of an accretionary orogen. PMID:25645934

  9. Kinematics of flow and sediment particles at entrainment and deposition

    NASA Astrophysics Data System (ADS)

    Antico, Federica; Sanches, Pedro; Aleixo, Rui; Ferreira, Rui M. L.

    2015-04-01

    A cohesionless granular bed subjected to a turbulent open-channel flow is analysed. The key objective is to clarify the kinematics of entrainment and deposition of individual sediment particles. In particular, we quantify a) the turbulent flow field in the vicinity of particles at the instants of their entrainment and of their deposition; b) the initial particle velocity and the particle velocity immediately before returning to rest. The experimental work was performed at the Hydraulics Laboratory of IST-UL in a 12.5 m long, 0.405 m wide glass-walled flume recirculating water and sediment through independent circuits. The granular bed was a 4.0 m long and 2.5 cm deep reach filled with 5 mm diameter glass beads packed (with some vibration) to a void fraction of 0.356, typical of random packing. Upstream the mobile bed reach the bed was composed of glued particles to ensure the development of a boundary layer with the same roughness. Laboratory tests were run under conditions of weak beadload transport with Shields parameters in the range 0.007 to 0.03. Froude numbers ranged from 0.63 to 0.95 while boundary Reynolds numbers were in the range 130 to 300. It was observed that the bed featured patches of regular arrangements: face centered cubic (fcc) or hexagonal close packing (hcp) blocks alternate with and body centered cubic (bcc) blocks. The resulting bed surface exhibits cleavage lines between blocks and there are spatial variations of bed elevation. The option for artificial sediment allowed for a simplified description of particle positioning at the instant of entrainment. In particular support and pivoting angles are found analytically. Skin friction angles were determind experimentally. The only relevant variables are exposure (defined as the ratio of the actual frontal projection of the exposed area to the area of a circle with 5 mm diameter) and protrusion (defined as the vertical distance between the apex of the particle and the mean local bed elevation

  10. Glucocorticoids as entraining signals for peripheral circadian oscillators.

    PubMed

    Pezük, Pinar; Mohawk, Jennifer A; Wang, Laura A; Menaker, Michael

    2012-10-01

    Mammalian circadian organization is governed by pacemaker neurons in the brain that communicate with oscillators in peripheral tissues. Adrenal glucocorticoids are important time-giving signals to peripheral circadian oscillators. We investigated the rhythm of Per1-luc expression in pineal, pituitary, salivary glands, liver, lung, kidney, cornea as well as suprachiasmatic nucleus from adrenalectomized and sham-operated rats kept under light-dark cycles, or exposed to single 6-h phase delays or advances of their light cycles. Adrenalectomy shifted the phases of Per1-luc in liver, kidney, and cornea and caused phase desynchrony and significant dampening in the rhythmicity of cornea. Treatment with hydrocortisone shifted the phases of Per1-luc in most of the tissues examined, even those that were not affected by adrenalectomy. The rhythm in cornea recovered in animals given hydrocortisone in vivo or when corneas were treated with dexamethasone in vitro. Adrenalectomy increased the rate of reentrainment after phase shifts in liver, kidney, cornea, pineal, lung, and suprachiasmatic nucleus but not in pituitary and salivary glands. Our data show that glucocorticoids act as strong entraining signals for peripheral circadian oscillators and may feed back on central oscillators as well. PMID:22893723

  11. Basal entrainment by Newtonian gravity-driven flows

    NASA Astrophysics Data System (ADS)

    Bates, Belinda M.; Andreini, Nicolas; Ancey, Christophe

    2016-05-01

    Gravity-driven flows can erode the bed along which they descend and increase their mass by a factor of 10 or more. This process is called "basal entrainment." Although documented by field observations and laboratory experiments, it remains poorly understood. This paper examines what happens when a viscous gravity-driven flow generated by releasing a fixed volume of incompressible Newtonian fluid encounters a stationary layer (composed of fluid with the same density and viscosity). Models based on depth-averaged mass and momentum balance equations deal with bed-flow interfaces as shock waves. In contrast, we use an approach involving the long-wave approximation of the Navier-Stokes equations (lubrication theory), and in this context, bed-flow interfaces are acceleration waves that move quickly across thin stationary layers. The incoming flow digs down into the bed, pushing up downstream material, thus advancing the flow front. Extending the method used by Huppert ["The propagation of two-dimensional and axisymmetric viscous gravity currents over a rigid horizontal surface," J. Fluid Mech. 121, 43-58 (1982)] for modeling viscous dam-break waves, we end up with a nonlinear diffusion equation for the flow depth, which is solved numerically. Theory is compared with experimental results. Excellent agreement is found in the limit of low Reynolds numbers (i.e., for flow Reynolds numbers lower than 20) for the front position over time and flow depth profile.

  12. Changes in music tempo entrain movement related brain activity.

    PubMed

    Daly, Ian; Hallowell, James; Hwang, Faustina; Kirke, Alexis; Malik, Asad; Roesch, Etienne; Weaver, James; Williams, Duncan; Miranda, Eduardo; Nasuto, Slawomir J

    2014-01-01

    The neural mechanisms of music listening and appreciation are not yet completely understood. Based on the apparent relationship between the beats per minute (tempo) of music and the desire to move (for example feet tapping) induced while listening to that music it is hypothesised that musical tempo may evoke movement related activity in the brain. Participants are instructed to listen, without moving, to a large range of musical pieces spanning a range of styles and tempos during an electroencephalogram (EEG) experiment. Event-related desynchronisation (ERD) in the EEG is observed to correlate significantly with the variance of the tempo of the musical stimuli. This suggests that the dynamics of the beat of the music may induce movement related brain activity in the motor cortex. Furthermore, significant correlations are observed between EEG activity in the alpha band over the motor cortex and the bandpower of the music in the same frequency band over time. This relationship is observed to correlate with the strength of the ERD, suggesting entrainment of motor cortical activity relates to increased ERD strength. PMID:25571015

  13. Colour as a signal for entraining the mammalian circadian clock.

    PubMed

    Walmsley, Lauren; Hanna, Lydia; Mouland, Josh; Martial, Franck; West, Alexander; Smedley, Andrew R; Bechtold, David A; Webb, Ann R; Lucas, Robert J; Brown, Timothy M

    2015-04-01

    Twilight is characterised by changes in both quantity ("irradiance") and quality ("colour") of light. Animals use the variation in irradiance to adjust their internal circadian clocks, aligning their behaviour and physiology with the solar cycle. However, it is currently unknown whether changes in colour also contribute to this entrainment process. Using environmental measurements, we show here that mammalian blue-yellow colour discrimination provides a more reliable method of tracking twilight progression than simply measuring irradiance. We next use electrophysiological recordings to demonstrate that neurons in the mouse suprachiasmatic circadian clock display the cone-dependent spectral opponency required to make use of this information. Thus, our data show that some clock neurons are highly sensitive to changes in spectral composition occurring over twilight and that this input dictates their response to changes in irradiance. Finally, using mice housed under photoperiods with simulated dawn/dusk transitions, we confirm that spectral changes occurring during twilight are required for appropriate circadian alignment under natural conditions. Together, these data reveal a new sensory mechanism for telling time of day that would be available to any mammalian species capable of chromatic vision. PMID:25884537

  14. Laser Blow Off and Impurity Entrainment in CSDX

    NASA Astrophysics Data System (ADS)

    Gosselin, Jordan James; Thakur, Saikat; Tynan, George

    2015-11-01

    Material migration in tokamaks is especially important when considering the lifetime of plasma facing components. However, the flow geometry in the scrape off layer can be complex and diagnostic access is limited. To study the impurity transport in a simple geometry, a laser blow off apparatus was installed on the Controlled Shear Decorelation eXperiment (a 3m long linear helicon source operated plasma machine with an electron temperature of 4 eV and density of 1013 per cm3). The parallel velocity and diffusion coefficients for the impurity are determined by modeling the impurity injection with the 1-D advection-diffusion equation. The parallel velocity of the impurity cloud found with the model agrees very well with laser induced fluorescence (LIF) measurements of the parallel plasma ion velocity. This indicates that the bismuth impurities are fully entrained in the plasma, which is consistent with classical collisional theories. This material is based upon work supported by the U.S. Department of Energy, Office of Science, under Award Number DE-FG02-07ER54912.

  15. Evidence of micro-continent entrainment during crustal accretion

    PubMed Central

    Pilia, S.; Rawlinson, N.; Cayley, R. A.; Bodin, T.; Musgrave, R.; Reading, A. M.; Direen, N. G.; Young, M. K.

    2015-01-01

    Simple models involving the gradual outboard accretion of material along curvilinear subduction zones are often inconsistent with field-based evidence. A recent study using 3-D geodynamic modelling has shown that the entrainment of an exotic continental fragment within a simple subduction system can result in a complex phase of growth. Although kinematic models based on structural mapping and high-resolution gravity and magnetic maps indicate that the pre-Carboniferous Tasmanides in southeastern Australia may have been subjected to this process, to date there has been little corroboration from crustal scale geophysical imaging. Here, we apply Bayesian transdimensional tomography to ambient noise data recorded by the WOMBAT transportable seismic array to constrain a detailed (20 km resolution in some areas) 3-D shear velocity model of the crust beneath southeast Australia. We find that many of the velocity variations that emerge from our inversion support the recently developed geodynamic and kinematic models. In particular, the full thickness of the exotic continental block, responsible for orocline formation and the tectonic escape of the back arc region, is imaged here for the first time. Our seismic results provide the first direct evidence that exotic continental fragments may profoundly affect the development of an accretionary orogen. PMID:25645934

  16. Weather entrainment and multispectral diel activity rhythm of desert hamsters.

    PubMed

    Wan, Xinrong; Zhang, Xinjie; Huo, Yingjun; Wang, Guiming

    2013-10-01

    The circadian rhythm of animals is an adaptation to predictable variation in environmental conditions. Multiple internal oscillators may allow animals to cope with environmental oscillations in different frequencies. Heat stress and dramatic differences between night and day temperatures are the main selective pressures of the diel activity of desert mammals, particularly small-sized rodents. We tested the hypotheses that the diel activities of desert hamsters (Phodopus roborovskii) would be entrained by ambient humidity and temperature. We predicted that increases in night temperature and humidity would improve the propensity to perform activities of the hamster. We observed hourly activities of desert hamsters under semi natural conditions for 24 consecutive hours, with seven replicates in 7 different days. We fit generalized linear mixed models to observed proportions of active hamsters, temperatures, and relative humidity. Observed diel activities of desert hamsters consisted of three harmonic oscillations in the periodicities of 24 h, 12 h, and 6 h, respectively. Furthermore, probabilities to perform activities were positively related to night temperature and humidity. Therefore, the diel activities of desert hamsters are synchronized by atmospheric humidity, temperatures, and environmental cues of ultradian fluctuations. PMID:23810901

  17. MODELING AND DESIGN FOR A DIRECT CARBON FUEL CELL WITH ENTRAINED FUEL AND OXIDIZER

    SciTech Connect

    Alan A. Kornhauser; Ritesh Agarwal

    2005-04-01

    The novel molten carbonate fuel cell design described in this report uses porous bed electrodes. Molten carbonate, with carbon fuel particles and oxidizer entrained, is circulated through the electrodes. Carbon may be reacted directly, without gasification, in a molten carbonate fuel cell. The cathode reaction is 2CO{sub 2} + O{sub 2} 4e{sup -} {yields} 2CO{sub 3}{sup =}, while the anode reaction can be either C + 2CO{sub 3}{sup =} {yields} 3CO{sub 2} + 4e{sup -} or 2C + CO{sub 3}{sup =} {yields} 3CO + 2e{sup -}. The direct carbon fuel cell has an advantage over fuel cells using coal-derived synthesis gas in that it provides better overall efficiency and reduces equipment requirements. Also, the liquid electrolyte provides a means for transporting the solid carbon. The porous bed cell makes use of this carbon transport ability of the molten salt electrolyte. A one-dimensional model has been developed for predicting the performance of this cell. For the cathode, dependent variables are superficial O{sub 2} and CO{sub 2} fluxes in the gas phase, superficial O{sub 2} and CO{sub 2} fluxes in the liquid phase, superficial current density through the electrolyte, and electrolyte potential. The variables are related by correlations, from the literature, for gas-liquid mass transfer, liquid-solid mass transfer, cathode current density, electrode overpotential, and resistivity of a liquid with entrained gas. For the anode, dependent variables are superficial CO{sub 2} flux in the gas phase, superficial CO{sub 2} flux in the liquid phase, superficial C flux, superficial current density through the electrolyte, and electrolyte potential. The same types of correlations relate the variables as in the cathode, with the addition of a correlation for resistivity of a fluidized bed. CO production is not considered, and axial dispersion is neglected. The model shows behavior typical of porous bed electrodes used in electrochemical processes. Efficiency is comparable to that of

  18. Interaction behaviors at the interface between liquid Al-Si and solid Ti-6Al-4V in ultrasonic-assisted brazing in air.

    PubMed

    Chen, Xiaoguang; Yan, Jiuchun; Gao, Fei; Wei, Jinghui; Xu, Zhiwu; Fan, Guohua

    2013-01-01

    Power ultrasonic vibration (20 kHz, 6 μm) was applied to assist the interaction between a liquid Al-Si alloy and solid Ti-6Al-4V substrate in air. The interaction behaviors, including breakage of the oxide film on the Ti-6Al-4V surface, chemical dissolution of solid Ti-6Al-4V, and interfacial chemical reactions, were investigated. Experimental results showed that numerous 2-20 μm diameter-sized pits formed on the Ti-6Al-4V surface. Propagation of ultrasonic waves in the liquid Al-Si alloy resulted in ultrasonic cavitation. When this cavitation occurred at or near the liquid/solid interface, many complex effects were generated at the small zones during the bubble implosion, including micro-jets, hot spots, and acoustic streaming. The breakage behavior of oxide films on the solid Ti-6Al-4V substrate, excessive chemical dissolution of solid Ti-6Al-4V into liquid Al-Si, abnormal interfacial chemical reactions at the interface, and phase transformation between the intermetallic compounds could be wholly ascribed to these ultrasonic effects. An effective bond between Al-Si and Ti-6Al-4V can be produced by ultrasonic-assisted brazing in air. PMID:22824641

  19. Flame behaviors of propane/air premixed flame propagation in a closed rectangular duct with a 90-deg bend

    NASA Astrophysics Data System (ADS)

    He, Xuechao; Sun, Jinhua; Yuen, K. K.; Ding, Yibin; Chen, Sining

    2008-11-01

    Experiments of flame propagation in a small, closed rectangular duct with a 90° bend were performed for a propane-air mixture. The high speed camera and Schlieren techniques were used to record images of flame propagation process in the combustion pipe. Meanwhile, the fine thermocouples and ion current probes were applied to measure the temperature distribution and reaction intensity of combustion. The characteristics of propane-air flame and its microstructure were analyzed in detail by the experimental results. In the test, the special tulip flame formation was observed. Around the bend, the flame tip proceeded more quickly at the lower side with the flame front elongated toward the axial direction. And transition to turbulent flame occurred. It was suggested that fluctuations of velocity, ion current and temperature were mainly due to the comprehensive effects of multi-wave and the intense of turbulent combustion.

  20. Hydrogen Balmer α line behavior in Laser-Induced Breakdown Spectroscopy depth scans of Au, Cu, Mn, Pb targets in air

    NASA Astrophysics Data System (ADS)

    Senesi, G. S.; Benedetti, P. A.; Cristoforetti, G.; Legnaioli, S.; Palleschi, V.

    2010-07-01

    The behavior of hydrogen spectral emission of the plasmas obtained by Laser-Induced Breakdown Spectroscopy (LIBS) measurement of four metal targets (Au, Cu, Mn, Pb) in air was investigated. The plasma was produced by a pulsed Nd:YAG laser emitting in the fundamental wavelength. A systematic study of the spatial-integrated plasma emission obtained by an in-depth scanning of the target was performed for each metal, both in single pulse and collinear double-pulse configurations. Further, a spatial-resolved analysis of the emission of plasma produced on the Al target by a single laser pulse was performed, in order to describe the spatial distribution of emitters deriving from the target and air elements. The line intensities of the main plasma components (target metal, nitrogen, oxygen and hydrogen) were measured in both experimental conditions. Results show that the hydrogen line intensity varies greatly as a function of the metal considered, and exhibits a marked decrease after the first laser shots. However, differently from emission lines due to surface impurities, the hydrogen line intensity reaches a constant level deep inside the target. The spatial-resolved measurements indicate that hydrogen atoms in the plasma mainly derive from the target surface and, only at a minor extent, from the dissociation of molecular hydrogen present in the surrounding air. These findings show that the calculation of plasma electron number density through the measurement of the Stark broadening of hydrogen Balmer α line is possible also in depth scanning measurements.