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Sample records for gas density factors

  1. Gas density fluctuations in the Perseus Cluster: clumping factor and velocity power spectrum

    NASA Astrophysics Data System (ADS)

    Zhuravleva, I.; Churazov, E.; Arévalo, P.; Schekochihin, A. A.; Allen, S. W.; Fabian, A. C.; Forman, W. R.; Sanders, J. S.; Simionescu, A.; Sunyaev, R.; Vikhlinin, A.; Werner, N.

    2015-07-01

    X-ray surface brightness fluctuations in the core of the Perseus Cluster are analysed, using deep observations with the Chandra observatory. The amplitude of gas density fluctuations on different scales is measured in a set of radial annuli. It varies from 7 to 12 per cent on scales of ˜10-30 kpc within radii of 30-220 kpc from the cluster centre. Using a statistical linear relation between the observed amplitude of density fluctuations and predicted velocity, the characteristic velocity of gas motions on each scale is calculated. The typical amplitudes of the velocity outside the central 30 kpc region are 90-140 km s-1 on ˜20-30 kpc scales and 70-100 km s-1 on smaller scales ˜7-10 kpc. The velocity power spectrum (PS) is consistent with cascade of turbulence and its slope is in a broad agreement with the slope for canonical Kolmogorov turbulence. The gas clumping factor estimated from the PS of the density fluctuations is lower than 7-8 per cent for radii ˜30-220 kpc from the centre, leading to a density bias of less than 3-4 per cent in the cluster core. Uncertainties of the analysis are examined and discussed. Future measurements of the gas velocities with the Astro-H, Athena and Smart-X observatories will directly measure the gas density-velocity perturbation relation and further reduce systematic uncertainties in this analysis.

  2. Densities and filling factors of the diffuse ionized gas in the Solar neighbourhood

    NASA Astrophysics Data System (ADS)

    Berkhuijsen, E. M.; Müller, P.

    2008-10-01

    Aims: We analyse electron densities and filling factors of the diffuse ionized gas (DIG) in the Solar neighbourhood. Methods: We have combined dispersion measures and emission measures towards 38 pulsars at distances known to better than 50%, from which we derived the mean density in clouds, N_c, and their volume filling factor, F_v, averaged along the line of sight. The emission measures were corrected for absorption by dust and contributions from beyond the pulsar distance. Results: The scale height of the electron layer for our sample is 0.93± 0.13 kpc and the midplane electron density is 0.023± 0.004 cm-3, in agreement with earlier results. The average density along the line of sight is < n_e> = 0.018± 0.002 cm-3 and is nearly constant. Since < n_e> = F_vN_c, an inverse relationship between Fv and Nc is expected. We find F_v(N_c) = (0.011± 0.003) N_c-1.20± 0.13, which holds for the ranges N_c= 0.05-1 cm-3 and F_v= 0.4-0.01. Near the Galactic plane the dependence of Fv on Nc is significantly stronger than away from the plane. Fv does not systematically change along or perpendicular to the Galactic plane, but the spread about the mean value of 0.08± 0.02 is considerable. The total pathlength through the ionized regions increases linearly to about 80 pc towards |z| = 1 kpc. Conclusions: Our study of Fv and Nc of the DIG is the first one based on a sample of pulsars with known distances. We confirm the existence of a tight, nearly inverse correlation between Fv and Nc in the DIG. The exact form of this relation depends on the regions in the Galaxy probed by the pulsar sample. The inverse F_v-Nc relation is consistent with a hierarchical, fractal density distribution in the DIG caused by turbulence. The observed near constancy of < n_e> then is a signature of fractal structure in the ionized medium, which is most pronounced outside the thin disk.

  3. Acoustic measurements of gas density

    NASA Technical Reports Server (NTRS)

    Shakkottai, P.; Kwack, E. Y.; Back, L. H.

    1990-01-01

    Sound transmission through gases in an enclosure is considered. Analytical results are given in terms of geometrical parameters, wave numbers, and source type for simple model problems, and are compared with data obtained by Haran (1983). It is concluded that density measurements can be made in a gas contained in an enclosure by measuring the sound pressure level at a receiver located near a dipole source driven at a constant velocity amplitude at low frequencies.

  4. Simulation of AlGaN/GaN high-electron-mobility transistor gauge factor based on two-dimensional electron gas density and electron mobility

    NASA Astrophysics Data System (ADS)

    Chu, Min; Koehler, Andrew D.; Gupta, Amit; Nishida, Toshikazu; Thompson, Scott E.

    2010-11-01

    The gauge factor of AlGaN/GaN high-electron-mobility transistor was determined theoretically, considering the effect of stress on the two-dimensional electron gas (2DEG) sheet carrier density and electron mobility. Differences in the spontaneous and piezoelectric polarization between the AlGaN and GaN layers, with and without external mechanical stress, were investigated to calculate the stress-altered 2DEG density. Strain was incorporated into a sp3d5-sp3 empirical tight-binding model to obtain the change in electron effective masses under biaxial and uniaxial stress. The simulated longitudinal gauge factor (-7.9±5.2) is consistent with experimental results (-2.4±0.5) obtained from measurements eliminating parasitic charge trapping effects through continuous subbandgap optical excitation.

  5. Critical density of a soliton gas

    NASA Astrophysics Data System (ADS)

    El, G. A.

    2016-02-01

    We quantify the notion of a dense soliton gas by establishing an upper bound for the integrated density of states of the quantum-mechanical Schrödinger operator associated with the Korteweg-de Vries soliton gas dynamics. As a by-product of our derivation, we find the speed of sound in the soliton gas with Gaussian spectral distribution function.

  6. Photoionization and High Density Gas

    NASA Technical Reports Server (NTRS)

    Kallman, T.; Bautista, M.; White, Nicholas E. (Technical Monitor)

    2002-01-01

    We present results of calculations using the XSTAR version 2 computer code. This code is loosely based on the XSTAR v.1 code which has been available for public use for some time. However it represents an improvement and update in several major respects, including atomic data, code structure, user interface, and improved physical description of ionization/excitation. In particular, it now is applicable to high density situations in which significant excited atomic level populations are likely to occur. We describe the computational techniques and assumptions, and present sample runs with particular emphasis on high density situations.

  7. Critical density of a soliton gas.

    PubMed

    El, G A

    2016-02-01

    We quantify the notion of a dense soliton gas by establishing an upper bound for the integrated density of states of the quantum-mechanical Schrödinger operator associated with the Korteweg-de Vries soliton gas dynamics. As a by-product of our derivation, we find the speed of sound in the soliton gas with Gaussian spectral distribution function. PMID:26931586

  8. ?Linear Gas Jet with Tailored Density Profile"

    SciTech Connect

    KRISHNAN, Mahadevan

    2012-12-10

    Supersonic, highly collimated gas jets and gas-filled capillary discharge waveguides are two primary targets of choice for Laser Plasma Accelerators (LPA) . Present gas jets have lengths of only 2-4 mm at densities of 1-4E19 cm-3, sufficient for self trapping and electron acceleration to energies up to ~150 MeV. Capillary structures 3 cm long have been used to accelerate beams up to 1 GeV. Capillary discharges used in LPAs serve to guide the pump laser and optimize the energy gain. A wall-stabilized capillary discharge provides a transverse profile across the channel that helps guide the laser and combat diffraction. Gas injection via a fast nozzle at one end provides some longitudinal density control, to improve the coupling. Gas jets with uniform or controlled density profiles may be used to control electron bunch injection and are being integrated into capillary experiments to add tuning of density. The gas jet for electron injection has not yet been optimized. Our Ph-I results have provided the LPA community with an alternative path to realizing a 2-3GeV electron bunch using just a gas jet. For example, our slit/blade combination gives a 15-20mm long acceleration path with tunable density profile, serving as an alternative to a 20-mm long capillary discharge with gas injection at one end. In Ph-II, we will extend these results to longer nozzles, to see whether we can synthesize 30 or 40-mm long plasma channels for LPAs.

  9. Gravitational star formation thresholds and gas density in three galaxies

    NASA Technical Reports Server (NTRS)

    Oey, M. S.; Kennicutt, R. C., Jr.

    1990-01-01

    It has long been held that the star formation rate (SFR) may be described as a power law of the gas density, p(exp n), as given by Schmidt (1959). However, this relation has as yet remained poorly defined and is likewise poorly understood. In particular, most studies have been investigations of global gas and star formation properties of galaxies, due to lack of adequate high-resolution data for detailed studies of individual galaxies. The three spiral galaxies in this study have published maps of both H2 (as traced by CO), and HI, thereby enabling the authors to investigate the relationship between total gas surface density and SFR. The purpose of the present investigation is the comparison of spatially-resolved total surface gas density in three galaxies (NGC 6946, M51, and M83) to sigma sub c as given by the above model. CO, HI and H alpha data for NGC 6946 were taken from Tacconi-Garman (1988), and for M51 and M83 from Lord (1987). The authors used a CO-H2 conversion of N(H2)/I sub CO(exp cos i = 2.8 x 10(exp 20) atoms cm(-2)/(K kms(-1), and summed the H2 and HI data for each galaxy to obtain the total hydrogen gas density. This total was then multiplied by a factor of 1.36 to include the contribution of helium to the total surface gas density. The authors assumed distances to NGC 6946, M51, and M83 to be 6.0, 9.6, and 8.9 Mpc respectively, with inclination angles of 30, 20, and 26 degrees. H alpha flux was used as the measure of SFR for NGC 6946, and SFR for the remaining two galaxies was taken directly from Lord as computed from H alpha measurements. The results of these full-disk studies thus show a remarkable correlation between the total gas density and the threshold densities given by the gravitational stability criterion. In particular, the threshold density appears to mark a lower boundary to the range of gas densities in these galaxies, which may have consequence in determining appropriate models for star formation and gas dynamics. More evidence is

  10. Instability Analysis of a Low-Density Gas Jet Injected into a High-Density Gas

    NASA Technical Reports Server (NTRS)

    Lawson, Anthony Layiwola

    2001-01-01

    The objective of this study was to determine the effects of buoyancy on the absolute instability of low-density gas jets injected into high-density gas mediums. Most of the existing analyses of low-density gas jets injected into a high-density ambient have been carried out neglecting effects of gravity. In order to investigate the influence of gravity on the near-injector development of the flow, a linear temporal stability analysis and a spatio-temporal stability analysis of a low-density round jet injected into a high-density ambient gas were performed. The flow was assumed to be isothermal and locally parallel; viscous and diffusive effects were ignored. The variables were represented as the sum of the mean value and a normal-mode small disturbance. An ordinary differential equation governing the amplitude of the pressure disturbance was derived. The velocity and density profiles in the shear layer, and the Froude number (signifying the effects of gravity) were the three important parameters in this equation. Together with the boundary conditions, an eigenvalue problem was formulated. Assuming that the velocity and density profiles in the shear layer to be represented by hyperbolic tangent functions, the eigenvalue problem was solved for various values of Froude number. The temporal growth rates and the phase velocity of the disturbances were obtained. It was found that the presence of variable density within the shear layer resulted in an increase in the temporal amplification rate of the disturbances and an increase in the range of unstable frequencies, accompanied by a reduction in the phase velocities of the disturbances. Also, the temporal growth rates of the disturbances were increased as the Froude number was reduced (i.e. gravitational effects increased), indicating the destabilizing role played by gravity. The spatio-temporal stability analysis was performed to determine the nature of the absolute instability of the jet. The roles of the density ratio

  11. Density PDFs of diffuse gas in the Milky Way

    NASA Astrophysics Data System (ADS)

    Berkhuijsen, E. M.; Fletcher, A.

    2012-09-01

    The probability distribution functions (PDFs) of the average densities of the diffuse ionized gas (DIG) and the diffuse atomic gas are close to lognormal, especially when lines of sight at |b| < 5∘ and |b|≥ 5∘ are considered separately. Our results provide strong support for the existence of a lognormal density PDF in the diffuse ISM, consistent with a turbulent origin of density structure in the diffuse gas.

  12. THE MOLECULAR GAS DENSITY IN GALAXY CENTERS AND HOW IT CONNECTS TO BULGES

    SciTech Connect

    Fisher, David B.; Bolatto, Alberto; Drory, Niv; Combes, Francoise; Blitz, Leo; Wong, Tony

    2013-02-20

    In this paper we present gas density, star formation rate (SFR), stellar masses, and bulge-disk decompositions for a sample of 60 galaxies. Our sample is the combined sample of the BIMA SONG, CARMA STING, and PdBI NUGA surveys. We study the effect of using CO-to-H{sub 2} conversion factors that depend on the CO surface brightness, and also that of correcting SFRs for diffuse emission from old stellar populations. We estimate that SFRs in bulges are typically lower by 20% when correcting for diffuse emission. Using the surface brightness dependent conversion factor, we find that over half of the galaxies in our sample have {Sigma}{sub mol} > 100 M {sub Sun} pc{sup -2}. Though our sample is not complete in any sense, our results are enough to rule out the assumption that bulges are uniformly gas-poor systems. We find a trend between gas density of bulges and bulge Sersic index; bulges with lower Sersic index have higher gas density. Those bulges with low Sersic index (pseudobulges) have gas fractions that are similar to that of disks. Conversely, the typical molecular gas fraction in classical bulges is more similar to that of an elliptical galaxy. We also find that there is a strong correlation between bulges with the highest gas surface density and the galaxy being barred. However, we also find that classical bulges with low gas surface density can be barred as well. Our results suggest that understanding the connection between the central surface density of gas in disk galaxies and the presence of bars should also take into account the total gas content of the galaxy. Finally, we show that when using the corrected SFRs and gas densities, the correlation between SFR surface density and gas surface density of bulges is similar to that of disks. This implies that at the scale of the bulges the timescale for converting gas into stars is comparable to those results found in disks.

  13. The Molecular Gas Density in Galaxy Centers and how it Connects to Bulges

    NASA Astrophysics Data System (ADS)

    Fisher, David B.; Bolatto, Alberto; Drory, Niv; Combes, Francoise; Blitz, Leo; Wong, Tony

    2013-02-01

    In this paper we present gas density, star formation rate (SFR), stellar masses, and bulge-disk decompositions for a sample of 60 galaxies. Our sample is the combined sample of the BIMA SONG, CARMA STING, and PdBI NUGA surveys. We study the effect of using CO-to-H2 conversion factors that depend on the CO surface brightness, and also that of correcting SFRs for diffuse emission from old stellar populations. We estimate that SFRs in bulges are typically lower by 20% when correcting for diffuse emission. Using the surface brightness dependent conversion factor, we find that over half of the galaxies in our sample have Σmol > 100 M ⊙ pc-2. Though our sample is not complete in any sense, our results are enough to rule out the assumption that bulges are uniformly gas-poor systems. We find a trend between gas density of bulges and bulge Sérsic index; bulges with lower Sérsic index have higher gas density. Those bulges with low Sérsic index (pseudobulges) have gas fractions that are similar to that of disks. Conversely, the typical molecular gas fraction in classical bulges is more similar to that of an elliptical galaxy. We also find that there is a strong correlation between bulges with the highest gas surface density and the galaxy being barred. However, we also find that classical bulges with low gas surface density can be barred as well. Our results suggest that understanding the connection between the central surface density of gas in disk galaxies and the presence of bars should also take into account the total gas content of the galaxy. Finally, we show that when using the corrected SFRs and gas densities, the correlation between SFR surface density and gas surface density of bulges is similar to that of disks. This implies that at the scale of the bulges the timescale for converting gas into stars is comparable to those results found in disks.

  14. Reliability factors in gas lasers

    NASA Astrophysics Data System (ADS)

    Malk, E. G.; Ramsay, I. A.

    1982-07-01

    Two types of gas lasers, the helium-neon laser and the sealed off, waveguide carbon dioxide laser, are discussed. The beneficial influence of hard seals on the HeNe laser is briefly described, and the resulting improved mean time between failures is described and discussed, showing a summary of lifetest data. Rejection percentages at 80 percent of the rated power in 18 months of elapsed time is determined to be 10 percent for one family of HeNe lasers and 7.6 percent for another family. An optical failure mode for HeNe lasers and the scientific investigation leading to its elimination are described. Finally, CO2 waveguide laser reliability is discussed in terms of the lifetime degradation factors involved in the operation of these lasers.

  15. Growth of arc in high-pressure, pulsed glow discharge by gas density depletion

    NASA Astrophysics Data System (ADS)

    Imada, Go; Yatsui, Kiyoshi; Masuda, Wataru

    2000-10-01

    Effects of gas density depletion on arc formation of high-pressure, pulsed glow discharge have been investigated by eliminating the other factors which may affect the discharge stability, such as shock waves, residual ions, electrode heating, and discharge products. The gas density depletion has been simulated by utilizing a subsonic gas flow between the curved electrodes combined with a convergent nozzle and a divergent diffuser. A comparison has been made on the discharge in the aerodynamically created gas density depletion with the second discharge in the double-pulse discharge within a stable gas. We have found that the large gas density depletion, Δρ/ρ0˜-3.6% corresponding to a pulse repetition rate (PRR) of ˜50 Hz, tends to cause an arc-like filament or an arc without the shocks, ions, electrode heating, and products. However, the second discharge in the double-pulse discharge becomes an arc in much smaller gas density depletion (Δρ/ρ0˜-1.2% corresponding to PRR ˜3 Hz). Therefore, the collapse of high-pressure, pulsed glow discharge is most likely caused by some factor other than the gas density depletion.

  16. Multiple Point Dynamic Gas Density Measurements Using Molecular Rayleigh Scattering

    NASA Technical Reports Server (NTRS)

    Seasholtz, Richard; Panda, Jayanta

    1999-01-01

    A nonintrusive technique for measuring dynamic gas density properties is described. Molecular Rayleigh scattering is used to measure the time-history of gas density simultaneously at eight spatial locations at a 50 kHz sampling rate. The data are analyzed using the Welch method of modified periodograms to reduce measurement uncertainty. Cross-correlations, power spectral density functions, cross-spectral density functions, and coherence functions may be obtained from the data. The technique is demonstrated using low speed co-flowing jets with a heated inner jet.

  17. Suppression of Density Fluctuations in a Quantum Degenerate Fermi Gas

    SciTech Connect

    Sanner, Christian; Su, Edward J.; Keshet, Aviv; Gommers, Ralf; Shin, Yong-il; Huang Wujie; Ketterle, Wolfgang

    2010-07-23

    We study density profiles of an ideal Fermi gas and observe Pauli suppression of density fluctuations (atom shot noise) for cold clouds deep in the quantum degenerate regime. Strong suppression is observed for probe volumes containing more than 10 000 atoms. Measuring the level of suppression provides sensitive thermometry at low temperatures. After this method of sensitive noise measurements has been validated with an ideal Fermi gas, it can now be applied to characterize phase transitions in strongly correlated many-body systems.

  18. Electron density and gas density measurements in a millimeter-wave discharge

    NASA Astrophysics Data System (ADS)

    Schaub, S. C.; Hummelt, J. S.; Guss, W. C.; Shapiro, M. A.; Temkin, R. J.

    2016-08-01

    Electron density and neutral gas density have been measured in a non-equilibrium air breakdown plasma using optical emission spectroscopy and two-dimensional laser interferometry, respectively. A plasma was created with a focused high frequency microwave beam in air. Experiments were run with 110 GHz and 124.5 GHz microwaves at powers up to 1.2 MW. Microwave pulses were 3 μs long at 110 GHz and 2.2 μs long at 124.5 GHz. Electron density was measured over a pressure range of 25 to 700 Torr as the input microwave power was varied. Electron density was found to be close to the critical density, where the collisional plasma frequency is equal to the microwave frequency, over the pressure range studied and to vary weakly with input power. Neutral gas density was measured over a pressure range from 150 to 750 Torr at power levels high above the threshold for initiating breakdown. The two-dimensional structure of the neutral gas density was resolved. Intense, localized heating was found to occur hundreds of nanoseconds after visible plasma formed. This heating led to neutral gas density reductions of greater than 80% where peak plasma densities occurred. Spatial structure and temporal dynamics of gas heating at atmospheric pressure were found to agree well with published numerical simulations.

  19. Low density gas dynamic wall boundary conditions

    NASA Technical Reports Server (NTRS)

    Collins, F. G.

    1986-01-01

    Low density nozzles or large expansion ratio nozzles used in space experience rarefaction effects near their exit in the form of velocity slip and temperature jump at the walls. In addition, the boundary layers become very thick and there is a very strong viscous/inviscid interaction. For these reasons no existing design technique has been found to accurately predict the nozzle flow properties up to the nozzle exit. The objective of this investigation was to examine the slip boundary conditions and formulate them in a form appropriate for use with a full Navier-Stokes numerical code. The viscous/inviscid interaction would automatically be accounted for by using a compressible Navier-Stokes code. Through examination of the interaction of molecules with solid surfaces, a model for the distribution function of the reflected molecules has been determined and this distribution function has been used to develop a new slip boundary condition that can be shown to yield more realistic surface boundary conditions.

  20. THE DEPENDENCE OF STAR FORMATION EFFICIENCY ON GAS SURFACE DENSITY

    SciTech Connect

    Burkert, Andreas; Hartmann, Lee E-mail: lhartm@umich.edu

    2013-08-10

    Studies by Lada et al. and Heiderman et al. have suggested that star formation mostly occurs above a threshold in gas surface density {Sigma} of {Sigma}{sub c} {approx} 120 M{sub Sun} pc{sup -2} (A{sub K} {approx} 0.8). Heiderman et al. infer a threshold by combining low-mass star-forming regions, which show a steep increase in the star formation rate per unit area {Sigma}{sub SFR} with increasing {Sigma}, and massive cores forming luminous stars which show a linear relation. We argue that these observations do not require a particular density threshold. The steep dependence of {Sigma}{sub SFR}, approaching unity at protostellar core densities, is a natural result of the increasing importance of self-gravity at high densities along with the corresponding decrease in evolutionary timescales. The linear behavior of {Sigma}{sub SFR} versus {Sigma} in massive cores is consistent with probing dense gas in gravitational collapse, forming stars at a characteristic free-fall timescale given by the use of a particular molecular tracer. The low-mass and high-mass regions show different correlations between gas surface density and the area A spanned at that density, with A {approx} {Sigma}{sup -3} for low-mass regions and A {approx} {Sigma}{sup -1} for the massive cores; this difference, along with the use of differing techniques to measure gas surface density and star formation, suggests that connecting the low-mass regions with massive cores is problematic. We show that the approximately linear relationship between dense gas mass and stellar mass used by Lada et al. similarly does not demand a particular threshold for star formation and requires continuing formation of dense gas. Our results are consistent with molecular clouds forming by galactic hydrodynamic flows with subsequent gravitational collapse.

  1. Gas density effect on dropsize of simulated fuel sprays

    NASA Technical Reports Server (NTRS)

    Ingebo, Robert D.

    1989-01-01

    Two-phase flow in pneumatic two-fluid fuel nozzles was investigated experimentally to determine the effect of atomizing-gas density and gas mass-flux on liquid-jet breakup in sonic-velocity gas-flow. Dropsize data were obtained for the following atomizing-gases: nitrogen; argon; carbon dioxide; and helium. They were selected to cover a gas molecular-weight range of 4 to 44. Atomizing-gas mass-flux ranged from 6 to 50 g/sq cm-sec and four differently sized two-fluid fuel nozzles were used having orifice diameters that varied from 0.32 to 0.56 cm. The ratio of liquid-jet diameter to SMD, D sub o/D sub 32, was correlated with aerodynamic and liquid-surface forces based on the product of the Weber and Reynolds number, and gas-to-liquid density ratio, rho sub g/rho sub 1. To correlate spray dropsize with breakup forces produced by using different atomizing-gases, a new molecular-scale dimensionless group was derived. The derived dimensionless group was used to obtain an expression for the ratio of liquid-jet diameter to SMD, D sub o/D sub 32. The mathematical expression of this phenomenon incorporates the product of the Weber and Reynolds number, liquid viscosity, surface tension, acoustic gas velocity, the RMS velocity of gas molecules, the acceleration of gas molecules due to gravity, and gas viscosity. The mathematical expression encompassing these parameters agrees well with the atomization theory for liquid-jet breakup in high velocity gas flow. Also, it was found that at the same gas mass-flux, helium was considerably more effective than nitrogen in producing small droplet sprays with SMD's in the order of 5 micrometers.

  2. Gas density effect on dropsize of simulated fuel sprays

    NASA Technical Reports Server (NTRS)

    Ingebo, Robert D.

    1989-01-01

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

  3. Measurements of the negative ion density in reactive gas plasmas

    NASA Astrophysics Data System (ADS)

    Shindo, Masako; Ueda, Yoko; Kawai, Yoshinobu; Ishii, Nobuo

    1999-11-01

    The reactive gas plasmas, such as C_4F_8, SiH4 and SF6 gas plasmas, have been widely used in plasma etching or CVD. The radicals and ions species in these plasmas have been reported in a lot of study. However, the negative ion density has not been measured quantitatively, since the conventional Langmuir probe cannot be used due to film depositions on its surface. In this study, the negative ion density in the reactive gas plasmas was measured with a heated Langmuir probe and an 8-mm microwave interferometer as a function of gas flow rate and radial position. Furthermore, the following equation was suggested to estimate the negative ion density only from the probe measurements: fracI_+(X )I_+(Ar) = [ fracI_-(X)I_-(Ar) + fracN_-(X )N_+(Ar)√fracT_e(X)T_e(Ar) ] √fracM_+(Ar)M_+(X), where N- denotes negative ion density and the other characteristics represent the conventional ones. The positive ion mass M+ should be assumed properly. It was confirmed that this equation provides the negative ion density both in the magnetized plasmas, such as ECR plasmas, and non-magnetized plasmas.

  4. High-density carbon ablator ignition path with low-density gas-filled rugby hohlraum

    NASA Astrophysics Data System (ADS)

    Amendt, Peter; Ho, Darwin D.; Jones, Ogden S.

    2015-04-01

    A recent low gas-fill density (0.6 mg/cc 4He) cylindrical hohlraum experiment on the National Ignition Facility has shown high laser-coupling efficiency (>96%), reduced phenomenological laser drive corrections, and improved high-density carbon capsule implosion symmetry [Jones et al., Bull. Am. Phys. Soc. 59(15), 66 (2014)]. In this Letter, an ignition design using a large rugby-shaped hohlraum [Amendt et al., Phys. Plasmas 21, 112703 (2014)] for high energetics efficiency and symmetry control with the same low gas-fill density (0.6 mg/cc 4He) is developed as a potentially robust platform for demonstrating thermonuclear burn. The companion high-density carbon capsule for this hohlraum design is driven by an adiabat-shaped [Betti et al., Phys. Plasmas 9, 2277 (2002)] 4-shock drive profile for robust high gain (>10) 1-D ignition performance and large margin to 2-D perturbation growth.

  5. High-density carbon ablator ignition path with low-density gas-filled rugby hohlraum

    SciTech Connect

    Amendt, Peter; Ho, Darwin D.; Jones, Ogden S.

    2015-04-15

    A recent low gas-fill density (0.6 mg/cc {sup 4}He) cylindrical hohlraum experiment on the National Ignition Facility has shown high laser-coupling efficiency (>96%), reduced phenomenological laser drive corrections, and improved high-density carbon capsule implosion symmetry [Jones et al., Bull. Am. Phys. Soc. 59(15), 66 (2014)]. In this Letter, an ignition design using a large rugby-shaped hohlraum [Amendt et al., Phys. Plasmas 21, 112703 (2014)] for high energetics efficiency and symmetry control with the same low gas-fill density (0.6 mg/cc {sup 4}He) is developed as a potentially robust platform for demonstrating thermonuclear burn. The companion high-density carbon capsule for this hohlraum design is driven by an adiabat-shaped [Betti et al., Phys. Plasmas 9, 2277 (2002)] 4-shock drive profile for robust high gain (>10) 1-D ignition performance and large margin to 2-D perturbation growth.

  6. Effects of argon gas pressure on its metastable-state density in high-density plasmas

    SciTech Connect

    Seo, B. H.; Kim, J. H.; You, S. J.

    2015-05-15

    The effect of argon gas pressure on its metastable density in inductively coupled plasmas (ICPs) is investigated by using the laser-induced fluorescence method. Our results show that the metastable-state density of argon varies with the gas pressure depending on the measurement position; the density decreases with the pressure at a position far from the ICP antenna, whereas it increases with the pressure at a position near the antenna. This contrast in the metastable-state density trend with the pressure is explained by considering the electron temperature variations at the two measurement positions. The theoretical interpretation and calculation using a global model are also addressed in detail in this paper.

  7. A solid state gas density monitor for gas insulated substation equipment

    SciTech Connect

    Saaski, E.W.; Hartl, J.C.

    1982-07-01

    A solid state gas density monitor has been developed for SF/sub 6/ service in gas-insulated substation equipment that is based on principles and construction techniques similar to ionization-type fire alarms. The monitor has a resolution of .7kPa (.1 psi) at 20/sup 0/C and, depending on ion chamber voltage and geometry, exhibits a linearity of /sup +//sub -/1 to /sup +//sub -/4. kPa (/sup +//sub -/.15 to /sup +//sub -/.6 psi) at 20/sup 0/C over the density range 0.20 to 0.66 MPa (30 to 95 psia) at 20/sup 0/C. The monitor incorporates two level contact closure actuated by gas density falling below one of two pre-set alarm limits, and an LCD read-out for visual monitoring and instrument calibration. The display presents density in terms of equivalent psia at 68/sup 0/F. (20/sup 0/C.).

  8. Influence of factors on mammographic density in premenopausal Chinese women.

    PubMed

    Yang, Yaping; Liu, Jieqiong; Gu, Ran; Hu, Yue; Liu, Fengtao; Yun, Miaomiao; Xiao, Qiaozhen; Wu, Mei; Liu, Qiang; Su, Fengxi

    2016-07-01

    Mammographic density is an independent strong risk factor for breast cancer. However, the influence of factors on mammographic density in premenopausal women remains unclear. In the Southern Professional Women Breast Cancer Screening Project, we assessed the associations between mammographic density and its influential factors using multivariate logistic regression in premenopausal women adjusting for BMI, age, duration of breastfeeding, number of live births, and breast size. A total of 1699 premenopausal women aged 27 to 57 years, who had been screened by mammography, were enrolled in this cross-sectional study. Overall, 85.2% were categorized as having dense breasts (BI-RADS density 3 and 4) and 14.8% as having fatty breasts (BI-RADS density 1 and 2). In multivariate and logistic regression analysis, only BMI and age were significantly negatively correlated with mammographic density in premenopausal women (P<0.001). No significant associations between mammographic density and number of deliveries, breastfeeding duration, education level, family history of breast cancer, as well as breast size and sleep quality, were identified in the study. Age and BMI are negatively associated with mammographic density in premenopausal Chinese women. Information on the influential factors of mammographic density in premenopausal women might provide meaningful insights into breast cancer prevention. PMID:26075657

  9. The Factors Affecting Bone Density in Cirrhosis

    PubMed Central

    Hajiabbasi, Asghar; Shafaghi, Afshin; Fayazi, Haniyeh Sadat; Shenavar Masooleh, Irandokht; Hedayati Emami, Mohammad Hassan; Ghavidel Parsa, Pooneh; Amir Maafi, Alireza

    2015-01-01

    Background: Bone loss is common in cirrhosis. However, the prevalence of osteopenia and osteoporosis has been heterogeneous in different reports. Reduction in bone formation with or without increase in bone resorption appears to be responsible for bone loss in these patients. Objectives: We aimed to investigate bone loss in patients with cirrhosis at different anatomical sites and key factors that might affect it. Patients and Methods: In this cross-sectional study, 97 patients with cirrhosis who were referred to Razi Hospital, Rasht, Iran, from 2008 to 2010, were studied. Cirrhosis was diagnosed using biopsy and/or clinical and paraclinical findings. Bone mineral densitometry was done in L2 through L4 lumbar spine (LS) and femoral neck (FN), using dual-energy X-ray absorptiometry (DEXA) (QDR 1000, Hologic DEXA Inc, Waltham, Massachusetts, the United States). Statistical analysis was performed using SPSS 18. A P value < 0.05 was considered statistically significant. Results: A total of 97 patients with cirrhosis (55.7% male) and the mean age of 51 ± 13 years and median body mass index (BMI) of 22.7 kg/m2 were recruited over a two-year period. Etiologies of cirrhosis were hepatitis C (40.2%), hepatitis B (26.8%), cryptogenic (21.6%), and other causes (11.4%). Child A, B, and C, were seen in 16.5%, 47.4%, and 36.1% of patients, respectively. The DEXA results were abnormal in 78.4% of our participants (osteopenia, 45.4%; osteoporosis, 33%). BMI and calculated glomerular filtration rate (GFRc) had moderate positive and Child score had moderate negative significant correlation with T score in both anatomical sites. There was no significant association between abnormal DEXA and the causes of cirrhosis. The univariate analysis showed that the risk of abnormal results in DEXA was significantly higher in those with low BMI, current smoking, higher Child score, and low GFRc; however, in multivariate analysis, the abnormal results were more frequent in those with lower

  10. Gas-solid flow characteristics in high-density CFB

    NASA Astrophysics Data System (ADS)

    Wang, Xue-yao; Fan, Bao-guo; Wang, Sheng-dian; Xu, Xiang; Xiao, Yun-han

    2012-08-01

    The gas-solid flow characteristics in the riser of a high density CFB of square (0.27 m×0.27 m×10.4 m) or circular ( ϕ 0.187m×10.4 m) cross section, using Geldart B particles (quartz sand), was investigated experimentally. The influence of riser structure on the hydrodynamic behaviors of a high-density circulating fluidized bed was investigated. The solid circulation rate was up to 321 kg/(m2s) with the circular cross-section under the operating conditions of the main bed air velocity 12.1 m/s and loosen wind and back-feed wind flow 25.1 m3/h. Different operating conditions on realizing high density circulation was analyzed, while both solids circulation rate and particle holdup depended highly on operating conditions. The circulating gas-solid flow was accompanied by an evidently-dense character in the riser's bottom zone and became fully developed in the middle and upper zones.

  11. Technique for measuring gas conversion factors

    NASA Technical Reports Server (NTRS)

    Singh, J. J.; Sprinkle, D. R. (Inventor)

    1985-01-01

    A method for determining hydrocarbon conversion factors for a flowmeter. A mixture of air, O2 and C sub x H sub y is burned and the partial paressure of O2 in the resulting gas is forced to equal the partial pressure of O2 in air. The flowrate of O2 flowing into the mixture is measured by flowmeter and the flowrate of C sub x H sub y flowing into the mixture is measured by the flowmeter conversion factor is to be determined. These measured values are used to calculate the conversion factor.

  12. The effect of slot height and difference in gas densities for coaxial jets on jet mixing in constrained swirled flow

    NASA Astrophysics Data System (ADS)

    Shishkin, N. E.

    2015-07-01

    Experiments were conducted about the effect of height of annular slot on efficiency of film cooling in a tube flow. Nonisothermal nature of flows was modelled by mixing of jets with different densities: air with argon or with helium: the concentration of foreign gas on wall was measured. The influence of nearwall jet swirling and of proportions of densities of gas flows as key factors for laminarization of mixing was considered.

  13. Development of an ionization-type gas density monitor

    NASA Astrophysics Data System (ADS)

    Saaski, E. W.

    1980-12-01

    A battery operated electronic gas density monitor was developed for SF6 service in gas insulated substation equipment that is based on principles similar to ionization type fire alarms. The monitor has a resolution of 0.1 psia at 68 F and exhibits a linearity of from + or - 0.15 to + or - 0.6 psia at 68 F over the pressure range 30 to 75 psia, depending on ion chamber characteristics and operating voltage. A prototype unit exhibited a deviation from ideality of about 0.01% per degree Fahrenheit over the temperature range -30 F to 105 F and was found insensitive to water vapor in SF6 at levels in excess of 1000 ppM.

  14. Influence of Lifestyle Factors on Mammographic Density in Postmenopausal Women

    PubMed Central

    Brand, Judith S.; Czene, Kamila; Eriksson, Louise; Trinh, Thang; Bhoo-Pathy, Nirmala; Hall, Per; Celebioglu, Fuat

    2013-01-01

    Background Mammographic density is a strong risk factor for breast cancer. Apart from hormone replacement therapy (HRT), little is known about lifestyle factors that influence breast density. Methods We examined the effect of smoking, alcohol and physical activity on mammographic density in a population-based sample of postmenopausal women without breast cancer. Lifestyle factors were assessed by a questionnaire and percentage and area measures of mammographic density were measured using computer-assisted software. General linear models were used to assess the association between lifestyle factors and mammographic density and effect modification by body mass index (BMI) and HRT was studied. Results Overall, alcohol intake was positively associated with percent mammographic density (P trend  = 0.07). This association was modified by HRT use (P interaction  = 0.06): increasing alcohol intake was associated with increasing percent density in current HRT users (P trend  = 0.01) but not in non-current users (P trend  = 0.82). A similar interaction between alcohol and HRT was found for the absolute dense area, with a positive association being present in current HRT users only (P interaction  = 0.04). No differences in mammographic density were observed across categories of smoking and physical activity, neither overall nor in stratified analyses by BMI and HRT use. Conclusions Increasing alcohol intake is associated with an increase in mammography density, whereas smoking and physical activity do not seem to influence density. The observed interaction between alcohol and HRT may pose an opportunity for HRT users to lower their mammographic density and breast cancer risk. PMID:24349146

  15. Density of radiolytic gas bubbles in polymethyl methacrylate

    NASA Astrophysics Data System (ADS)

    Makkonen, T.; Tiainen, O. J. A.; Valkiainen, M.; Winberg, M.

    The density of the radiolytic gas bubbles in irradiated polymethyl methacrylate was measured during subsequent heat treatment as a function of radiation dose. The samples were irradiated in the core of the Triga Mark II reactor in Otaniemi. After the irradiation periods the samples were heat treated at 393 K. The number of the bubbles could be explained by a thermal activation model. The bubbles are born in material inhomogeneities and the threshold dose for the bubble initiation was about 25 Mrad for the heat treatment at 393 K under the atmospheric pressure.

  16. Momentum distribution function of the electron gas at metallic densities

    NASA Astrophysics Data System (ADS)

    Takada, Yasutami; Yasuhara, H.

    1991-10-01

    The momentum distribution function n(k) of the electron gas is calculated in the effective-potential-expansion method at metallic densities. The recently established self-consistency relation between n(k) and the correlation energy [Y. Takada and T. Kita, J. Phys. Soc. Jpn. 60, 25 (1991)] is employed to check the accuracy of our results. This check shows that the effective-potential-expansion method provides probably the exact and at least more accurate results of n(k) than all the other methods that have given n(k) thus far.

  17. Proton cooling in ultracold low-density electron gas

    NASA Astrophysics Data System (ADS)

    Bobrov, A. A.; Bronin, S. Y.; Manykin, E. A.; Zelener, B. B.; Zelener, B. V.; Khikhlukha, D. R.

    2015-11-01

    A sole proton energy loss processes in an electron gas and the dependence of these processes on temperature and magnetic field are studied using molecular dynamics techniques in present work. It appears that for electron temperatures less than 100 K many body collisions affect the proton energy loss and these collisions must be taken into account. The influence of a strong magnetic field on the relaxation processes is also considered in this work. Calculations were performed for electron densities 10 cm-3, magnetic field 1-3 Tesla, electron temperatures 10-50 K, initial proton energies 100-10000 K.

  18. High density fuel qualification for a gas turbine engine

    SciTech Connect

    Macleod, J.D.; Orbanski, B.; Hastings, P.R. Standard Aero, Ltd., Winnipeg, DND, Ottawa, )

    1992-01-01

    A program for the evaluation of gas turbine engine performance, carried out in the Engine Laboratory of the National Research Council of Canada, is described. Problems under consideration include performance alteration between JP-4 fuel and a high energy density fuel, called strategic military fuel (SMF); performance deterioration during the accelerated endurance test; and emission analysis. The T56 fuel control system is found to be capable of operation on the higher energy density fuel with no detrimental effects regarding control of the engine's normal operating regime. The deterioration of the engine performance during 150-hour endurance tests on SMF was very high, which was caused by an increase in turbine nozzle effective flow area and turbine blade untwist. The most significant performance losses during the endurance tests were on corrected output power, fuel flow, specific fuel consumption and compressor and turbine presure ratio. 9 refs.

  19. Factors influencing the density of aerobic granular sludge.

    PubMed

    Winkler, M-K H; Kleerebezem, R; Strous, M; Chandran, K; van Loosdrecht, M C M

    2013-08-01

    In the present study, the factors influencing density of granular sludge particles were evaluated. Granules consist of microbes, precipitates and of extracellular polymeric substance. The volume fractions of the bacterial layers were experimentally estimated by fluorescent in situ hybridisation staining. The volume fraction occupied by precipitates was determined by computed tomography scanning. PHREEQC was used to estimate potential formation of precipitates to determine a density of the inorganic fraction. Densities of bacteria were investigated by Percoll density centrifugation. The volume fractions were then coupled with the corresponding densities and the total density of a granule was calculated. The sensitivity of the density of the entire granule on the corresponding settling velocity was evaluated by changing the volume fractions of precipitates or bacteria in a settling model. Results from granules originating from a Nereda reactor for simultaneous phosphate COD and nitrogen removal revealed that phosphate-accumulating organisms (PAOs) had a higher density than glycogen-accumulating organisms leading to significantly higher settling velocities for PAO-dominated granules explaining earlier observations of the segregation of the granular sludge bed inside reactors. The model showed that a small increase in the volume fraction of precipitates (1-5 %) strongly increased the granular density and thereby the settling velocity. For nitritation-anammox granular sludge, mainly granular diameter and not density differences are causing a segregation of the biomass in the bed. PMID:23064481

  20. Plasma ionization frequency, edge-to-axis density ratio, and density on axis of a cylindrical gas discharge

    SciTech Connect

    Palacio Mizrahi, J. H.

    2014-06-15

    A rigorous derivation of expressions, starting from the governing equations, for the ionization frequency, edge-to-axis ratio of plasma density, plasma density at the axis, and radially averaged plasma density in a cylindrical gas discharge has been obtained. The derived expressions are simple and involve the relevant parameters of the discharge: Cylinder radius, axial current, and neutral gas pressure. The found expressions account for ion inertia, ion temperature, and changes in plasma ion collisionality.

  1. Simulations of Electron Density Perturbations in a Gas Discharge

    NASA Astrophysics Data System (ADS)

    Caplinger, James; Sotnikov, Vladimir; Main, Daniel

    2015-11-01

    Beginning with the idealized case of the Pierce diode, a series of particle-in-cell (PIC) simulations are conducted in order to characterize density perturbations in a laboratory gas discharge. This work is conducted to support future experimental investigations into electromagnetic scattering off of electron density perturbations excited by plasma flows. As a first step, 2D PIC simulations were conducted for the Pierce diode case, which is a simple model that exploits instabilities of a monochromatic electron beam between two grounded electrodes. These results were compared to the standard analytical solution. Departing from this idealized case we will include in the simulations electron-neutral collisions, particle creation from ionization, as well as an electric field generated by biased electrodes. A parameter study of electric field strength and collision frequency will be performed for values approaching the Pierce diode as well as extending to cases of expected laboratory parameters. If we can extract physical density spectra from simulations with parameters approaching experimental values, it may be possible to analyze electromagnetic scattering characteristics.

  2. Density measurement in air with a saturable absorbing seed gas

    NASA Technical Reports Server (NTRS)

    Baganoff, D.

    1981-01-01

    Resonantly enhanced scattering from the iodine molecule is studied experimentally for the purpose of developing a scheme for the measurement of density in a gas dynamic flow. A study of the spectrum of iodine, the collection of saturation data in iodine, and the development of a mathematical model for correlating saturation effects were pursued for a mixture of 0.3 torr iodine in nitrogen and for mixture pressures up to one atmosphere. For the desired pressure range, saturation effects in iodine were found to be too small to be useful in allowing density measurements to be made. The effects of quenching can be reduced by detuning the exciting laser wavelength from the absorption line center of the iodine line used (resonant Raman scattering). The signal was found to be nearly independent of pressure, for pressures up to one atmosphere, when the excitation beam was detuned 6 GHz from line center for an isolated line in iodine. The signal amplitude was found to be nearly equal to the amplitude for fluorescence at atmospheric pressure, which indicates a density measurement scheme is possible.

  3. Density fluctuations of a hard-core Bose gas in a one-dimensional lattice near the Mott insulating phase

    SciTech Connect

    Ates, C.; Moseley, Ch.; Ziegler, K.

    2005-06-15

    The characteristic oscillations of the density-density correlation function and the resulting structure factor are studied for a hard-core Bose gas in a one-dimensional lattice. Their wavelength diverges as the system undergoes a continuous transition from an incommensurate to a Mott insulating phase. The transition is associated with a unit static structure factor and a vanishing sound velocity. The qualitative picture is unchanged when a weak confining potential is applied to the system.

  4. Discharge dynamics and plasma density recovery by on/off switches of additional gas

    NASA Astrophysics Data System (ADS)

    Lee, Hyo-Chang; Kwon, Deuk-Chul; Oh, SeungJu; Kang, Hyun-Ju; Kim, Yu-Sin; Chung, Chin-Wook

    2016-06-01

    Measurement of the plasma density is investigated to study plasma dynamics by adding reactive gas (O2) or rare gas (He) in Ar plasmas. When the O2 or He gas is added, plasma density is suddenly decreased, while the plasma density recovers slowly with gas off. It is found that the recovery time is strongly dependent on the gas flow rate, and it can be explained by effect of gas residence time. When the He gas is off in the Ar plasma, the plasma density is overshot compared to the case of the O2 gas pulsing due to enhanced ionizations by metastable atoms. Analysis and calculation for correlation between the plasma density dynamics and the gas pulsing are also presented in detail.

  5. Acoustic device and method for measuring gas densities

    NASA Technical Reports Server (NTRS)

    Shakkottai, Parthasarathy (Inventor); Kwack, Eug Y. (Inventor); Back, Lloyd (Inventor)

    1992-01-01

    Density measurements can be made in a gas contained in a flow through enclosure by measuring the sound pressure level at a receiver or microphone located near a dipole sound source which is driven at constant velocity amplitude at low frequencies. Analytical results, which are provided in terms of geometrical parameters, wave numbers, and sound source type for systems of this invention, agree well with published data. The relatively simple designs feature a transmitter transducer at the closed end of a small tube and a receiver transducer on the circumference of the small tube located a small distance away from the transmitter. The transmitter should be a dipole operated at low frequency with the kL value preferable less that about 0.3.

  6. Pion transverse charge density from timelike form factor data

    SciTech Connect

    Gerald Miller, Mark Strikman, Christian Weiss

    2011-01-01

    The transverse charge density in the pion can be represented as a dispersion integral of the imaginary part of the pion form factor in the timelike region. This formulation incorporates information from e+e- annihilation experiments and allows one to reconstruct the transverse density much more accurately than from the spacelike pion form factor data alone. We calculate the transverse density using an empirical parametrization of the timelike pion form factor and estimate that it is determined to an accuracy of ~10% at a distance b ~ 0.1 fm, and significantly better at larger distances. The density is found to be close to that obtained from a zero-width rho meson pole over a wide range and shows a pronounced rise at small distances. The resulting two-dimensional image of the fast-moving pion can be interpreted in terms of its partonic structure in QCD. We argue that the singular behavior of the charge density at the center requires a substantial presence of pointlike configurations in the pion's partonic wave function, which can be probed in other high-momentum transfer processes.

  7. Factors Associated with Mammographic Density in Postmenopausal Women

    PubMed Central

    Caglayan, Kasim; Alkis, Ismet; Arslan, Ergin; Okur, Aylin; Banli, Oktay; Engin-Ustün, Yaprak

    2015-01-01

    Objectives Breast density increases the risk of breast cancer, but also in the interpretation of mammography is also important. This study examine the risk factors affecting breast density in postmenopausal women. Methods Between January 2013 and January 2014, 215 patients admitted to The Clinics of Gynecology and Obstetrics with complaints of menopause were taken. According to the results of mammography, Group I (non-dense, n = 175) and Group II (dense, n = 40) were created. The informations of the caseswere analyzed retrospectively. Results In Group I, body mass index (BMI), number of pregnancies, parity were significantly higher than group II (P < 0.05). In group II, the withdrawal period of menstruation and progesterone levels were significantly higher (P < 0.05). In logistic regression analysis, BMI for dense breasts and number of pregnancies were found to be an independent risk factor (P < 0.05). Conclusion Increased BMI, pregnancy and parity, result of reduction in density , but longer duration of menopause and increased progesterone cause an increase in density. BMI and the number of pregnancy was found to be independent risk factors for reducing breast density. PMID:26357645

  8. Does nitrogen gas bubbled through a low density polymer gel dosimeter solution affect the polymerization process?

    PubMed Central

    Shahbazi-Gahrouei, Daryoush; Gholami, Mehrdad; Pourfallah, Tayyeb Allahverdi; Keshtkar, Mohammad

    2015-01-01

    Background: On account of the lower electron density in the lung tissue, the dose distribution in the lung cannot be verified with the existing polymer gel dosimeters. Thus, the aims of this study are to make a low density polymer gel dosimeter and investigate the effect of nitrogen gas bubbles on the R2 responses and its homogeneity. Materials and Methods: Two different types of low density polymer gel dosimeters were prepared according to a composition proposed by De Deene, with some modifications. In the first type, no nitrogen gas was perfused through the gel solution and water. In the second type, to expel the dissolved oxygen, nitrogen gas was perfused through the water and gel solution. The post-irradiation times in the gels were 24 and 5 hours, respectively, with and without perfusion of nitrogen gas through the water and gel solution. Results: In the first type of gel, there was a linear correlation between the doses and R2 responses from 0 to 12 Gy. The fabricated gel had a higher dynamic range than the other low density polymer gel dosimeter; but its background R2 response was higher. In the second type, no difference in R2 response was seen in the dose ranges from 0 to 18 Gy. Both gels had a mass density between 0.35 and 0.45 g.cm-3 and CT values of about -650 to -750 Hounsfield units. Conclusion: It appeared that reactions between gelatin-free radicals and monomers, due to an increase in the gel temperature during rotation in the household mixer, led to a higher R2-background response. In the second type of gel, it seemed that the collapse of the nitrogen bubbles was the main factor that affected the R2-responses. PMID:26015914

  9. Implementing an Inexpensive and Accurate Introductory Gas Density Activity with High School Students

    ERIC Educational Resources Information Center

    Cunningham, W. Patrick; Joseph, Christopher; Morey, Samantha; Santos Romo, Ana; Shope, Cullen; Strang, Jonathan; Yang, Kevin

    2015-01-01

    A simplified activity examined gas density while employing cost-efficient syringes in place of traditional glass bulbs. The exercise measured the density of methane, with very good accuracy and precision, in both first-year high school and AP chemistry settings. The participating students were tasked with finding the density of a gas. The…

  10. Molecular Gas in Starburts ARP 220 & NGC 6240: Understanding Mergers using High Density Gas Tracers

    NASA Astrophysics Data System (ADS)

    Manohar, Swarnima; Scoville, Nicholas; Sheth, Kartik

    2015-01-01

    NGC 6240 and Arp 220 can be considered the founding members of a very active class of objects called Ultraluminous Infrared Galaxies or ULIRGs. They are in different stages of mergers and hence are excellent case studies to enhance our knowledge about the merging process. We have imaged the dense star-forming regions of these galaxies at sub-arcsec resolution with ALMA and CARMA. Multi-band imaging allows multilevel excitation analysis of HCN, HCO+ and CS transitions which will constrain the properties of the gas as a function of position and velocity (across line profiles). We are doing an extensive multilevel excitation analysis of the merger as a function of radius which enables in depth understanding of the gas dynamics and gas properties such as temperature and density. This in turn probes the homogeneity of the gas in the merging system and hence the regions that facilitate high star formation rates. This tandem use of CARMA with ALMA to map these systems at different merger stages will assemble a more integrated picture of the merger process. We are probing the distribution and dynamics of star forming gas and star formation activity in the dense disk structures to enable new theoretical understanding of the physics, dynamics, star formation activity and associated feedback in the most active and rapidly evolving galactic nuclei. Here we present our observations of Arp 220 and NGC 6240 from ALMA and CARMA.

  11. Molecular Gas in Local Mergers: Understanding Mergers using High Density Gas Tracers

    NASA Astrophysics Data System (ADS)

    Manohar, Swarnima; Scoville, N.; Sheth, K.

    2013-01-01

    NGC 6240 and Arp 220 can be considered the founding members of a very active class of objects called Ultraluminous Infrared Galaxies or ULIRGs. They are in different stages of mergers and hence are excellent case studies to enhance our knowledge about the merging process. We have imaged the dense star-forming regions of these galaxies at sub-arcsec resolution with ALMA and CARMA. Multi-band imaging will allow multilevel excitation analysis of HCN, HCO+ and CS transitions which will be used to constrain the properties of the gas as a function of position and velocity (across line profiles). We aim to do an extensive multilevel excitation analysis of the merger as a function of radius which will enable in depth understanding of the gas dynamics and gas properties such as temperature and density. This will in turn probe the homogeneity of the gas in the merging system and hence the regions that facilitate high star formation rates. This tandem use of CARMA with ALMA to map these systems at different merger stages will help assemble a more integrated picture of the merger process. We will probe the distribution and dynamics of star forming gas and star formation activity in the dense disk structures to enable new theoretical understanding of the physics, dynamics, star formation activity and associated feedback in the most active and rapidly evolving galactic nuclei. Here we present preliminary observations of Arp 220 and NGC 6240 from ALMA and CARMA.

  12. Molecular Gas in Starburts: Understanding Mergers using High Density Gas Tracers

    NASA Astrophysics Data System (ADS)

    Manohar, Swarnima; Scoville, N.; Walter, F.; Sheth, K.

    2014-01-01

    NGC 6240 and Arp 220 can be considered the founding members of a very active class of objects called Ultraluminous Infrared Galaxies or ULIRGs. They are in different stages of mergers and hence are excellent case studies to enhance our knowledge about the merging process. We have imaged the dense star-forming regions of these galaxies at sub-arcsec resolution with ALMA and CARMA. Multi-band imaging allows multilevel excitation analysis of HCN, HCO+ and CS transitions which will constrain the properties of the gas as a function of position and velocity (across line profiles). We are doing an extensive multilevel excitation analysis of the merger as a function of radius which enables in depth understanding of the gas dynamics and gas properties such as temperature and density. This in turn probes the homogeneity of the gas in the merging system and hence the regions that facilitate high star formation rates. This tandem use of CARMA with ALMA to map these systems at different merger stages will assemble a more integrated picture of the merger process. We are probing the distribution and dynamics of star forming gas and star formation activity in the dense disk structures to enable new theoretical understanding of the physics, dynamics, star formation activity and associated feedback in the most active and rapidly evolving galactic nuclei. Here we present preliminary observations of Arp 220 and NGC 6240 from ALMA and CARMA.

  13. Reproductive factors related to childbearing and mammographic breast density.

    PubMed

    Yaghjyan, Lusine; Colditz, Graham A; Rosner, Bernard; Bertrand, Kimberly A; Tamimi, Rulla M

    2016-07-01

    We investigated the associations of reproductive factors related to childbearing with percent breast density, absolute dense and nondense areas, by menopausal status. This study included 4110 cancer-free women within the Nurses' Health Study and Nurses' Health Study II cohorts. Percent breast density, absolute dense and nondense areas were measured from digitized mammography film images with computerized techniques. All density measures were square root-transformed in all the analyses to improve normality. The data on reproductive variables and other breast cancer risk factors were obtained from biennial questionnaires, at the time of the mammogram date. As compared to nulliparous women, parous postmenopausal women had lower percent density (β = -0.60, 95 % CI -0.84; -0.37), smaller absolute dense area (β = -0.66, 95 % CI -1.03; -0.29), and greater nondense area (β = 0.72, 95 % CI 0.27; 1.16). Among parous women, number of children was inversely associated with percent density in pre- (β per one child = -0.12, 95 % CI -0.20; -0.05) and postmenopausal women (β per one child = -0.07, 95 % CI -0.12; -0.02). The positive associations of breastfeeding with absolute dense and nondense areas were limited to premenopausal women, while the positive association of the age at first child's birth with percent density and the inverse association with nondense area were limited to postmenopausal women. Women with greater number of children and younger age at first child's birth have more favorable breast density patterns that could explain subsequent breast cancer risk reduction. PMID:27351801

  14. Density probability distribution functions of diffuse gas in the Milky Way

    NASA Astrophysics Data System (ADS)

    Berkhuijsen, E. M.; Fletcher, A.

    2008-10-01

    In a search for the signature of turbulence in the diffuse interstellar medium (ISM) in gas density distributions, we determined the probability distribution functions (PDFs) of the average volume densities of the diffuse gas. The densities were derived from dispersion measures and HI column densities towards pulsars and stars at known distances. The PDFs of the average densities of the diffuse ionized gas (DIG) and the diffuse atomic gas are close to lognormal, especially when lines of sight at |b| < 5° and |b| >= 5° are considered separately. The PDF of at high |b| is twice as wide as that at low |b|. The width of the PDF of the DIG is about 30 per cent smaller than that of the warm HI at the same latitudes. The results reported here provide strong support for the existence of a lognormal density PDF in the diffuse ISM, consistent with a turbulent origin of density structure in the diffuse gas.

  15. Star Formation as a Function of Neutral Hydrogen Gas Density in Local Group Galaxies

    NASA Astrophysics Data System (ADS)

    Carlson, Erika K.; Madore, Barry F.; Freedman, Wendy L.

    2016-06-01

    We present a study of the efficiency and timescales of star formation as a function of local neutral hydrogen gas density in four Local Group galaxies: M33, NGC 6822, the LMC, and the SMC. In this work, we conceptualize the process of star formation as a cycle of two major phases – (1) a gas dynamics phase in which neutral hydrogen gas coalesces into clouds, and (2) a stellar phase in which stars have formed and interrupt further gas coalescence during their active lifetimes. By examining the spatial distribution and number densities of stars on maps of neutral hydrogen, we estimate the timescale of the gas coalescence phase relative to the timescale of the stellar phase and infer an efficiency of star formation as a function of neutral hydrogen gas density. From these timescales and efficiencies, we will calculate star formation rates as a function of neutral hydrogen gas density in these galaxies.

  16. Stealing the Gas: Giant Impacts and the Large Diversity in Exoplanet Densities

    NASA Astrophysics Data System (ADS)

    Inamdar, Niraj K.; Schlichting, Hilke E.

    2016-02-01

    Although current sensitivity limits are such that true solar system analogs remain challenging to detect, numerous planetary systems have been discovered that are very different from our own solar system. The majority of systems harbor a new class of planets, bodies that are typically several times more massive than the Earth but orbit their host stars well inside the orbit of Mercury. These planets frequently show evidence for large hydrogen and helium envelopes containing several percent of the planet’s mass and display a large diversity in mean densities. Here we show that this wide range can be achieved by one or two late giant impacts, which are frequently needed to achieve long-term orbital stability in multiple planet systems once the gas disk has disappeared. We demonstrate using hydrodynamical simulations that a single collision between similarly sized exoplanets can easily reduce the envelope-to-core-mass ratio by a factor of two and show that this leads to a corresponding increase in the observed mean density by factors of two to three. In addition, we investigate how envelope mass loss depends on envelope mass, planet radius, semimajor axis, and the mass distribution inside the envelope. We propose that a small number of giant impacts may be responsible for the large observed spread in mean densities, especially for multiple-planet systems that contain planets with very different densities and have not been significantly sculpted by photoevaporation.

  17. Effects of Mean Flow Profiles on Instability of a Low-Density Gas Jet Injected into a High-Density Gas

    NASA Technical Reports Server (NTRS)

    Vedantam, Nanda Kishore

    2003-01-01

    The objective of this study was to investigate the effects of the mean flow profiles on the instability characteristics in the near-injector region of low-density gas jets injected into high-density ambient gas mediums. To achieve this, a linear temporal stability analysis and a spatio-temporal stability analysis of a low-density round gas jet injected vertically upwards into a high-density ambient gas were performed by assuming three different sets of mean velocity and density profiles. The flow was assumed to be isothermal and locally parallel. Viscous and diffusive effects were ignored. The mean flow parameters were represented as the sum of the mean value and a small normal-mode fluctuation. A second order differential equation governing the pressure disturbance amplitude was derived from the basic conservation equations. The first set of mean velocity and density profiles assumed were those used by Monkewitz and Sohn for investigating absolute instability in hot jets. The second set of velocity and density profiles assumed for this study were the ones used by Lawson. And the third set of mean profiles included a parabolic velocity profile and a hyperbolic tangent density profile. The effects of the inhomogeneous shear layer and the Froude number (signifying the effects of gravity) on the temporal and spatio-temporal results for each set of mean profiles were delineated. Additional information is included in the original extended abstract.

  18. Linear Stability Analysis of Gravitational Effects on a Low-Density Gas Jet Injected into a High-Density Medium

    NASA Technical Reports Server (NTRS)

    Lawson, Anthony L.; Parthasarathy, Ramkumar N.

    2005-01-01

    The objective of this study was to determine the effects of buoyancy on the absolute instability of low-density gas jets injected into high-density gas mediums. Most of the existing analyses of low-density gas jets injected into a high-density ambient have been carried out neglecting effects of gravity. In order to investigate the influence of gravity on the near-injector development of the flow, a spatio-temporal stability analysis of a low-density round jet injected into a high-density ambient gas was performed. The flow was assumed to be isothermal and locally parallel; viscous and diffusive effects were ignored. The variables were represented as the sum of the mean value and a normal-mode small disturbance. An ordinary differential equation governing the amplitude of the pressure disturbance was derived. The velocity and density profiles in the shear layer, and the Froude number (signifying the effects of gravity) were the three important parameters in this equation. Together with the boundary conditions, an eigenvalue problem was formulated. Assuming that the velocity and density profiles in the shear layer to be represented by hyperbolic tangent functions, the eigenvalue problem was solved for various values of Froude number. The Briggs-Bers criterion was combined with the spatio-temporal stability analysis to determine the nature of the absolute instability of the jet whether absolutely or convectively unstable. The roles of the density ratio, Froude number, Schmidt number, and the lateral shift between the density and velocity profiles on the absolute instability of the jet were determined. Comparisons of the results with previous experimental studies show good agreement when the effects of these variables are combined together. Thus, the combination of these variables determines how absolutely unstable the jet will be.

  19. 40 CFR Table Mm-1 to Subpart Mm of... - Default Factors for Petroleum Products and Natural Gas Liquids 1 2

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... and Natural Gas Liquids 1 2 MM Table MM-1 to Subpart MM of Part 98 Protection of Environment... Factors for Petroleum Products and Natural Gas Liquids 1 2 Products Column A: density(metric tons/bbl... Natural Gas Liquids Aviation Gasoline 0.1120 85.00 0.3490 Special Naphthas 0.1222 84.76 0.3798...

  20. 40 CFR Table Mm-1 to Subpart Mm of... - Default Factors for Petroleum Products and Natural Gas Liquids 1 2

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... and Natural Gas Liquids 1 2 MM Table MM-1 to Subpart MM of Part 98 Protection of Environment... Factors for Petroleum Products and Natural Gas Liquids 1 2 Products Column A: density(metric tons/bbl... Natural Gas Liquids Aviation Gasoline 0.1120 85.00 0.3490 Special Naphthas 0.1222 84.76 0.3798...

  1. 40 CFR Table Mm-1 to Subpart Mm of... - Default Factors for Petroleum Products and Natural Gas Liquids 1 2

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... and Natural Gas Liquids 1 2 MM Table MM-1 to Subpart MM of Part 98 Protection of Environment... Factors for Petroleum Products and Natural Gas Liquids 1 2 Products Column A: density(metric tons/bbl... Natural Gas Liquids Aviation Gasoline 0.1120 85.00 0.3490 Special Naphthas 0.1222 84.76 0.3798...

  2. 40 CFR Table Mm-1 to Subpart Mm of... - Default Factors for Petroleum Products and Natural Gas Liquids 1 2

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... and Natural Gas Liquids 1 2 MM Table MM-1 to Subpart MM of Part 98 Protection of Environment... Factors for Petroleum Products and Natural Gas Liquids 1 2 Products Column A: density(metric tons/bbl... Natural Gas Liquids Aviation Gasoline 0.1120 85.00 0.3490 Special Naphthas 0.1222 84.76 0.3798...

  3. Electromagnetic form factors and charge densities from hadrons to nuclei

    SciTech Connect

    Miller, Gerald A.

    2009-10-15

    A simple exact covariant model in which a scalar particle {psi} is modeled as a bound state of two different particles is used to elucidate relativistic aspects of electromagnetic form factors F(Q{sup 2}). The model form factor is computed using an exact covariant calculation of the lowest order triangle diagram. The light-front technique of integrating over the minus component of the virtual momentum gives the same result and is the same as the one obtained originally by Gunion et al. [Phys. Rev. D 8, 287 (1973)] by using time-ordered perturbation theory in the infinite-momentum frame. The meaning of the transverse density {rho}(b) is explained by providing a general derivation, using three spatial coordinates, of its relationship with the form factor. This allows us to identify a mean-square transverse size ={integral}d{sup 2}b b{sup 2}{rho}(b)=-4(dF/dQ{sup 2})(Q{sup 2}=0). The quantity is a true measure of hadronic size because of its direct relationship with the transverse density. We show that the rest-frame charge distribution is generally not observable by studying the explicit failure to uphold current conservation. Neutral systems of two charged constituents are shown to obey the conventional lore that the heavier one is generally closer to the transverse origin than the lighter one. It is argued that the negative central charge density of the neutron arises, in pion-cloud models, from pions of high longitudinal momentum that reside at the center. The nonrelativistic limit is defined precisely, and the ratio of the binding energy B to the mass M of the lightest constituent is shown to govern the influence of relativistic effects. It is shown that the exact relativistic formula for F(Q{sup 2}) is the same as the familiar one of the three-dimensional Fourier transform of a square of a wave function for very small values of B/M, but this only occurs for values of B/M less than about 0.001. For masses that mimic the quark-diquark model of

  4. Real-time gas density measurement using a ring cavity terahertz parametric oscillator

    NASA Astrophysics Data System (ADS)

    Ohno, S.; Guo, R.; Minamide, H.; Ito, H.

    2007-05-01

    We carried out real-time measurement of gas density using monochromatic terahertz waves. The THz-wave absorbance is useful to measure the density of a gas having a characteristic spectrum in the THz region. We used the ring cavity THz-wave parametric oscillator (ring-TPO) as a monochromatic tunable THz-wave source. One can change the oscillation frequency of ring-TPO with a rotating galvano mirror forming the ring cavity. The frequency can be changed by synchronization with a repeating pump-pulse of 500 Hz. We demonstrated real-time measurement of the gas density in R-22, which had some spectral structure in THz frequency region. The gas density in the sample cell was changed by controlling the pressure to lower than 1 atm. When the gas density in the cell was the most tenuous, the maximum sensitivity was about 5%, which was limited by the fluctuation of THz-wave intensity.

  5. Relation between plasma plume density and gas flow velocity in atmospheric pressure plasma

    SciTech Connect

    Yambe, Kiyoyuki; Taka, Shogo; Ogura, Kazuo

    2014-04-15

    We have studied atmospheric pressure plasma generated using a quartz tube, helium gas, and copper foil electrode by applying RF high voltage. The atmospheric pressure plasma in the form of a bullet is released as a plume into the atmosphere. To study the properties of the plasma plume, the plasma plume current is estimated from the difference in currents on the circuit, and the drift velocity is measured using a photodetector. The relation of the plasma plume density n{sub plu}, which is estimated from the current and the drift velocity, and the gas flow velocity v{sub gas} is examined. It is found that the dependence of the density on the gas flow velocity has relations of n{sub plu} ∝ log(v{sub gas}). However, the plasma plume density in the laminar flow is higher than that in the turbulent flow. Consequently, in the laminar flow, the density increases with increasing the gas flow velocity.

  6. Phase-field simulations of gas density within bubbles under irradiation

    SciTech Connect

    Paul C. Millett; Anter El-Azab; Michael Tonks

    2011-05-01

    Phase-field simulations are used to study the evolution of gas density within irradiation-induced bubbles. In our simulations, the dpa rate, gas production rate, and defect diffusivities are systematically varied to understand their effect on bubble nucleation rates, bubble densities, and the distribution of gas concentration within bubbles and in the solid regions. We find that gas densities within bubbles fluctuate drastically in the early nucleation stages, when growth rates are highest, but converge to steady-state values during the later coarsening stages. The steady-state gas densities within bubbles correspond with the ratio of total accumulated vacancy content divided by the total accumulated gas content, in agreement with a thermodynamic analysis concerning free-energy minimization.

  7. Factors associated with bone mineral density in healthy African women

    PubMed Central

    Kelly, Cliff; Gati, Brenda; Greenspan, Susan; Dai, James Y.; Bragg, Vivian; Livant, Edward; Piper, Jeanna M.; Nakabiito, Clemensia; Magure, Tsitsi; Marrazzo, Jeanne M.; Chirenje, Z. Mike; Riddler, Sharon A.

    2015-01-01

    Summary There is a paucity of normative bone mineral density (BMD) data in healthy African women. Baseline total hip and lumbar spine BMD was measured in premenopausal women. BMD distribution was comparable to that of a reference population and was impacted by several factors including contraception and duration of lactation. Introduction Normative data on bone mineral density (BMD) and the cumulative impact of lactation, contraceptive use, and other factors on BMD in healthy African women have not been well studied. Objectives The objective of this study was to determine the factors associated with BMD in healthy premenopausal women in Uganda and Zimbabwe. Methods Baseline total hip (TH) and lumbar spine (LS) BMD was measured by dual x-ray absorptiometry in 518 healthy, premenopausal black women enrolling in VOICE, an HIV-1 chemoprevention trial, at sites in Uganda and Zimbabwe. Contraceptive and lactation histories, physical activity assessment, calcium intake, and serum vitamin D levels were assessed. Independent factors associated with BMD were identified using an analysis of covariance model. Results The study enrolled 331 women from Zimbabwe and 187 women from Uganda. Median age was 29 years (IQR 25, 32) and median body mass index (BMI) was 24.8 kg/m2 (IQR 22.2, 28.6). In univariate analyses, lower TH BMD values were associated with residence in Uganda (p<0.001), lower BMI (p<0.001), and any use of and duration of depot-medroxyprogresterone acetate. Use of oral contraceptives, progestin-only implants, and higher physical activity levels were protective against reduced BMD. Similarly, lower LS BMD values were associated with these same factors but also higher parity and history of breastfeeding. In a multivariable analysis, lower TH and LS BMD values were associated with enrollment in Uganda, lower BMI, and lower physical activity level; contraceptive use was associated with lower spine BMD, and breastfeeding contributed to lower total hip BMD. Conclusions

  8. Modeling of neutral gas dynamics in high-density plasmas

    NASA Astrophysics Data System (ADS)

    Canupp, Patrick Wellington

    This thesis describes a physical model of chemically reactive neutral gas flow and discusses numerical solutions of this model for the flow in an inductively coupled plasma etch reactor. To obtain these solutions, this research develops an efficient, implicit numerical method. As a result of the enhanced numerical stability of the scheme, large time steps advance the solution from initial conditions to a final steady state in fewer iterations and with less computational expense than simpler explicit methods. This method would incorporate suitably as a module in currently existing large scale plasma simulation tools. In order to demonstrate the accuracy of the numerical technique, this thesis presents results from two simulations of flows that possess theoretical solutions. The first case is the inviscid flow of a gas through a converging nozzle. A comparison of the numerical solution to isentropic flow theory shows that the numerical technique capably captures the essential flow features of this environment. The second case is the Couette flow of a gas between two parallel plates. The simulation results compare well with the exact solution for this flow. After establishing the accuracy of the numerical technique, this thesis discusses results for the flow of chemically reactive gases in a chlorine plasma etch reactor. This research examines the influence of the plasma on the neutral gas and the dynamics exhibited by the neutral gas in the reactor. This research finds that the neutral gas temperature strongly depends on the rate at which inelastic, electron-impact dissociation reactions occur and on atomic chlorine wall recombination rates. Additionally, the neutral gas Aow in the reactor includes a significant mass flux of etch product from the wafer surface. Resolution of these effects is useful for neutral gas simulation. Finally, this thesis demonstrates that continuum fluid models provide reasonable accuracy for these low pressure reactor flows due to the fact

  9. Biofuels and the Greenhouse Gas Factor

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Biofuels have been scrutinized for their potential to be used as a fuel substitute to offset a portion of the greenhouse gas (GHG) emissions produced by fossil fuel combustion. But quantifying that offset is complex. Bioenergy crops offset their greenhouse-gas contributions in three key ways: by rem...

  10. Gas pycnometry for density determination of plutonium parts

    SciTech Connect

    Collins, S.; Randolph, H.W.

    1997-08-19

    The traditional method for plutonium density determination is by measuring the weight loss of the component when it is immersed in a liquid of known density, Archimedes` Principle. The most commonly used heavy liquids that are compatible for plutonium measurement are freon and monobromobenzene, but these pose serious environmental and health hazards. The contaminated liquid is also a radiological waste concern with difficult disposition. A gaseous medium would eliminate these environmental and health concerns. A collaborative research effort between the Savannah River Technology Center and Los Alamos National Laboratory was undertaken to determine the feasibility of a gaseous density measurement process for plutonium hemishells.

  11. Neutron radiography of a static density gradient of 3He gas at cryogenic temperatures

    NASA Astrophysics Data System (ADS)

    Wichmann, G.; Antognini, A.; Eggenberger, A.; Kirch, K.; Piegsa, F. M.; Soler, U.; Stahn, J.; Taqqu, D.

    2016-04-01

    We demonstrate a stationary helium gas density gradient which is needed for a proposed novel low-energy μ+ beam line. In a closed system with constant pressure the corresponding density gradient is only a function of the temperature. In a neutron radiography experiment two gas cells with different geometries were filled with 3He gas at constant pressures of about 10 mbar. Temperatures in the range from 6 K to 40 K were applied and density distributions with a maximum to minimum density ratio of larger than 3 were realized. The distribution was investigated employing the strongly neutron absorbing isotope 3He. A simple one-dimensional approach derived from Fourier's law describes the obtained gas density with a deviation < 2 %.

  12. Density measurement in air with saturable absorbing seed gas

    NASA Technical Reports Server (NTRS)

    Baganoff, D.

    1982-01-01

    Approaches which have the potential to make density measurements in a compressible flow, where one or more laser beams are used as probes, were investigated. Saturation in sulfur hexafluoride iodine and a crossed beam technique where one beam acts as a saturating beam and the other is at low intensity and acts as a probe beam are considered. It is shown that a balance between an increase in fluorescence intensity with increasing pressure from line broadening and the normal decrease in intensity with increasing pressure from quenching can be used to develop a linear relation between fluorescence intensity and number density and lead to a new density measurement scheme. The method is used to obtain a density image of the cross section of an iodine seeded underexpanded supersonic jet of nitrogen, by illuminating the cross section by a sheet of laser light.

  13. Factors Affecting Bone Mineral Density in Adults with Cerebral Palsy

    PubMed Central

    Yoon, Young Kwon; Kim, Ae Ryoung; Kim, On Yoo; Lee, Kilchan; Suh, Young Joo

    2012-01-01

    Objective To clarify factors affecting bone mineral density (BMD) in adults with cerebral palsy (CP). Method Thirty-five patients with CP participated in this study. Demographic data including gender, age, body mass index (BMI), subtype according to neuromotor type and topographical distribution, ambulatory function, and functional independence measure (FIM) were investigated. The BMD of the lumbar spine and femur were measured using Dual-energy X-ray absorptiometry, and the factors affecting BMD were analyzed. Results The BMD had no significant association with factors such as gender, age, and subtype in adults with CP. However, BMI was significantly correlated with the BMD of lumbar spine and femur (p<0.05). The FIM score was also positively correlated with the BMD of femur (p<0.05). Moreover, CP patients with higher ambulatory function had significantly higher BMD of femur (p<0.05). Conclusion These findings suggest that BMI and functional levels such as FIM and ambulatory function can affect BMD in adults with CP. The results might be used as basic data, suggesting the importance of treatment including weight bearing exercise and gait training in adults with CP. PMID:23342308

  14. Estimation of current density distribution of PAFC by analysis of cell exhaust gas

    SciTech Connect

    Kato, S.; Seya, A.; Asano, A.

    1996-12-31

    To estimate distributions of Current densities, voltages, gas concentrations, etc., in phosphoric acid fuel cell (PAFC) stacks, is very important for getting fuel cells with higher quality. In this work, we leave developed a numerical simulation tool to map out the distribution in a PAFC stack. And especially to Study Current density distribution in the reaction area of the cell, we analyzed gas composition in several positions inside a gas outlet manifold of the PAFC stack. Comparing these measured data with calculated data, the current density distribution in a cell plane calculated by the simulation, was certified.

  15. A CENSUS OF THE HIGH-DENSITY MOLECULAR GAS IN M82

    SciTech Connect

    Naylor, B. J.; Bradford, C. M.; Bock, J. J.; Nguyen, H. T.; Zmuidzinas, J.; Aguirre, J. E.; Earle, L.; Glenn, J.; Kamenetzky, J.; Maloney, P. R.; Inami, H.; Matsuhara, H.

    2010-10-10

    We present a three-pointing study of the molecular gas in the starburst nucleus of M82 based on 190-307 GHz spectra obtained with Z-Spec at the Caltech Submillimeter Observatory. We present intensity measurements, detections, and upper limits, for 20 transitions, including several new detections of CS, HNC, C{sub 2}H, H{sub 2}CO, and CH{sub 3}CCH lines. We combine our measurements with previously published measurements at other frequencies for HCN, HNC, CS, C{sup 34}S, and HCO{sup +} in a multi-species likelihood analysis constraining gas mass, density and temperature, and the species' relative abundances. We find some (1.7-2.7) x 10{sup 8} M{sub sun} of gas with n{sub H{sub 2}} between (1-6) x 10{sup 4} cm{sup -3} and T > 50 K. While the mass and temperature are comparable to values inferred from mid-J CO transitions, the thermal pressure is a factor of 10-20 greater. The molecular interstellar medium is largely fragmented and is subject to ultraviolet irradiation from the star clusters. It is also likely subject to cosmic rays and mechanical energy input from the supernovae, and is warmer on average than the molecular gas in the massive star formation (SF) regions in the Milky Way. The typical conditions in the dense gas in M82's central kiloparsec appear unfavorable for further SF; if any appreciable stellar populations are currently forming, they are likely biased against low-mass stars, producing a top-heavy initial mass function.

  16. Electron temperature and density measurement of tungsten inert gas arcs with Ar-He shielding gas mixture

    NASA Astrophysics Data System (ADS)

    Kühn-Kauffeldt, M.; Marques, J.-L.; Forster, G.; Schein, J.

    2013-10-01

    The diagnostics of atmospheric welding plasma is a well-established technology. In most cases the measurements are limited to processes using pure shielding gas. However in many applications shielding gas is a mixture of various components including metal vapor in gas metal arc welding (GMAW). Shielding gas mixtures are intentionally used for tungsten inert gas (TIG) welding in order to improve the welding performance. For example adding Helium to Argon shielding gas allows the weld geometry and porosity to be influenced. Yet thermal plasmas produced with gas mixtures or metal vapor still require further experimental investigation. In this work coherent Thomson scattering is used to measure electron temperature and density in these plasmas, since this technique allows independent measurements of electron and ion temperature. Here thermal plasmas generated by a TIG process with 50% Argon and 50% Helium shielding gas mixture have been investigated. Electron temperature and density measured by coherent Thomson scattering have been compared to the results of spectroscopic measurements of the plasma density using Stark broadening of the 696.5 nm Argon spectral line. Further investigations of MIG processes using Thomson scattering technique are planned.

  17. Metal Oxide Gas Sensors: Sensitivity and Influencing Factors

    PubMed Central

    Wang, Chengxiang; Yin, Longwei; Zhang, Luyuan; Xiang, Dong; Gao, Rui

    2010-01-01

    Conductometric semiconducting metal oxide gas sensors have been widely used and investigated in the detection of gases. Investigations have indicated that the gas sensing process is strongly related to surface reactions, so one of the important parameters of gas sensors, the sensitivity of the metal oxide based materials, will change with the factors influencing the surface reactions, such as chemical components, surface-modification and microstructures of sensing layers, temperature and humidity. In this brief review, attention will be focused on changes of sensitivity of conductometric semiconducting metal oxide gas sensors due to the five factors mentioned above. PMID:22294916

  18. Dust and Gas in the Disk of HL Tauri: Surface Density, Dust Settling, and Dust-to-gas Ratio

    NASA Astrophysics Data System (ADS)

    Pinte, C.; Dent, W. R. F.; Ménard, F.; Hales, A.; Hill, T.; Cortes, P.; de Gregorio-Monsalvo, I.

    2016-01-01

    The recent ALMA observations of the disk surrounding HL Tau reveal a very complex dust spatial distribution. We present a radiative transfer model accounting for the observed gaps and bright rings as well as radial changes of the emissivity index. We find that the dust density is depleted by at least a factor of 10 in the main gaps compared to the surrounding rings. Ring masses range from 10-100 M⊕ in dust, and we find that each of the deepest gaps is consistent with the removal of up to 40 M⊕ of dust. If this material has accumulated into rocky bodies, these would be close to the point of runaway gas accretion. Our model indicates that the outermost ring is depleted in millimeter grains compared to the central rings. This suggests faster grain growth in the central regions and/or radial migration of the larger grains. The morphology of the gaps observed by ALMA—well separated and showing a high degree of contrast with the bright rings over all azimuths—indicates that the millimeter dust disk is geometrically thin (scale height ≈1 AU at 100 AU) and that a large amount of settling of large grains has already occurred. Assuming a standard dust settling model, we find that the observations are consistent with a turbulent viscosity coefficient of a few 10-4. We estimate the gas/dust ratio in this thin layer to be of the order of 5 if the initial ratio is 100. The HCO+ and CO emission is consistent with gas in Keplerian motion around a 1.7 M⊙ star at radii from ≤10-120 AU.

  19. Comet Halley neutral gas density profile along the Vega 1 trajectory measured by NGE. [Neutral Gas Experiment (NGE)

    NASA Technical Reports Server (NTRS)

    Curtis, C. C.; Fan, C. Y.; Hsieh, K. C.; Hunten, D. M.; Ip, WING-H.; Keppler, E.; Richter, A. K.; Umlauft, G.; Afonin, V. V.; Dyachkov, A. V.

    1986-01-01

    Data from the Vega 1 permitted the determination of the total neutral gas density profile along the spacecraft trajectory. Discounting small fluctuations, the field ionization source instrument measured a density profile which varied approximately as the inverse radial distance squared. Data from the electron impact ionization instrument yielded a series of calibration points; e.g., the neutral density at 100,000 km is 10,000/cc. The combined data provide a calibrated total density profile, and imply a neutral production rate of 10 to the 30th power molecules/sec.

  20. Production of centimeter-scale, high-density plasmas with a linear gas jet

    SciTech Connect

    Coverdale, C.A.; Darrow, C.B.; Jones, R.; Sawyer, W.; Crane, J.; Ditmire, T.; Perry, M.D. ); Filbert, P.C. )

    1995-01-01

    A novel linear gas jet has been developed and used to produce centimeter-scale, 10[sup 19] cm[sup [minus]3] electron density plasmas. Long regions of high density are important to many types of experiments, including x-ray laser and laser-plasma interaction studies. This new type of gas jet has been characterized by stimulated Raman backscatter emission from the plasma.

  1. New applications for Coriolis flow and density measurement in the natural gas industry

    SciTech Connect

    Valentine, J.; Keilty, M.

    1995-11-01

    Simultaneous, highly accurate measurement of mass, density and temperature makes the Coriolis instrumentation ideal technology for a wide variety of natural gas applications. This paper describes the technology, discusses the benefits of using Coriolis instrumentation, and describes several applications related to the oil and gas production industries utilizing the Coriolis meter.

  2. Design of a high density cold gas attitude control system

    NASA Technical Reports Server (NTRS)

    Hall, Sarah E.; Lewis, Mark J.; Akin, David L.

    1993-01-01

    A comparison of the experimental results of a nitrous oxide cold gas thruster with the predicted performance from a numerical simulation of nozzle operations is discussed. Tests were conducted in a vacuum chamber to verify analytical predictions of both nitrogen and nitrous oxide. Preliminary results indicate an Isp for N2O of 61, and an Isp of 69 for N2. Based on the results of this research, parameters are presented for a nitrous oxide-based reaction control system for a small spacecraft currently under development.

  3. Method For Enhanced Gas Monitoring In High Density Flow Streams

    DOEpatents

    Von Drasek, William A.; Mulderink, Kenneth A.; Marin, Ovidiu

    2005-09-13

    A method for conducting laser absorption measurements in high temperature process streams having high levels of particulate matter is disclosed. An impinger is positioned substantially parallel to a laser beam propagation path and at upstream position relative to the laser beam. Beam shielding pipes shield the beam from the surrounding environment. Measurement is conducted only in the gap between the two shielding pipes where the beam propagates through the process gas. The impinger facilitates reduced particle presence in the measurement beam, resulting in improved SNR (signal-to-noise) and improved sensitivity and dynamic range of the measurement.

  4. 3D simulations of gas puff effects on edge density and ICRF coupling in ASDEX Upgrade

    NASA Astrophysics Data System (ADS)

    Zhang, W.; Bobkov, V.; Lunt, T.; Noterdaeme, J.-M.; Coster, D.; Bilato, R.; Jacquet, P.; Brida, D.; Feng, Y.; Wolfrum, E.; Guimarais, L.; the ASDEX Upgrade Team

    2016-03-01

    In recent experiments, a local gas puff was found to be an effective way to tailor the scrape-off layer (SOL) density and improve the ion cyclotron range of frequency (ICRF) power coupling in tokamaks. In order to quantitatively reproduce these experiments, to understand the corresponding physics and to optimize the gas valve positions and rates, simulations were carried out with the 3D edge plasma transport code EMC3-EIRENE in ASDEX Upgrade. An inter-ELM phase of an H-mode discharge with a moderate gas puff rate (1.2  ×  1022 electrons s-1) is used in our simulations. We simulated cases with gas puff in the lower divertor, the outer mid-plane and the top of the machine while keeping other conditions the same. Compared with the lower divertor gas puff, the outer mid-plane gas puff can increase the local density in front of the antennas most effectively, while a toroidally uniform but significantly smaller enhancement is found for the top gas puff. Good agreement between our simulations and experiments is obtained. With further simulations, the mechanisms of SOL density tailoring via local gas puffing and the strategies of gas puff optimization are discussed in the paper.

  5. [Greenhouse gas emission from reservoir and its influence factors].

    PubMed

    Zhao, Xiao-jie; Zhao, Tong-qian; Zheng, Hua; Duan, Xiao-nan; Chen, Fa-lin; Ouyang, Zhi-yun; Wang, Xiao-ke

    2008-08-01

    Reservoirs are significant sources of emissions of the greenhouse gases. Discussing greenhouse gas emission from the reservoirs and its influence factors are propitious to evaluate emission of the greenhouse gas accurately, reduce gas emission under hydraulic engineering and hydropower development. This paper expatiates the mechanism of the greenhouse gas production, sums three approaches of the greenhouse gas emission, which are emissions from nature emission of the reservoirs, turbines and spillways and downstream of the dam, respectively. Effects of greenhouse gas emission were discussed from character of the reservoirs, climate, pH of the water, vegetation growing in the reservoirs and so on. Finally, it has analyzed the heterogeneity of the greenhouse gas emission as well as the root of the uncertainty and carried on the forecast with emphasis to the next research. PMID:18839604

  6. Improving emissions factors for estimating urban natural gas leakage

    NASA Astrophysics Data System (ADS)

    Phillips, Nathan

    2013-04-01

    Emissions factors for pipeline natural gas leaks are in need of refinement. In addition to limitations from the small sample sizes of leaks that were initially used to develop emissions factors, a further limitation to emissions factors is lack of knowledge of characteristic statistical distributions of pipeline leak rates. For example, leaks were implicitly assumed to be normally distributed so that an average leak rate was used for pipelines of a given construction. Our natural gas leak data from Boston, USA, in which we found over 3,000 natural gas leaks, indicates that leaks rates are highly skewed, with relatively few leaks likely contributing disproportionately to the total. The long-tailed distribution of gas leak rates is mirrored by a similarly skewed distribution of surface methane concentrations in air. These data suggest that emissions factors should be based on correctly specified statistical distributions, and that fixing relatively few large leaks first may provide the most environmental benefit per cost.

  7. Dominant factors in controlling marine gas pools in South China

    USGS Publications Warehouse

    Xu, S.; Watney, W.L.

    2007-01-01

    In marine strata from Sinian to Middle Triassic in South China, there develop four sets of regional and six sets of local source rocks, and ten sets of reservoir rocks. The occurrence of four main formation periods in association with five main reconstruction periods, results in a secondary origin for the most marine gas pools in South China. To improve the understanding of marine gas pools in South China with severely deformed geological background, the dominant control factors are discussed in this paper. The fluid sources, including the gas cracked from crude oil, the gas dissolved in water, the gas of inorganic origin, hydrocarbons generated during the second phase, and the mixed pool fluid source, were the most significant control factors of the types and the development stage of pools. The period of the pool formation and the reconstruction controlled the pool evolution and the distribution on a regional scale. Owing to the multiple periods of the pool formation and the reconstruction, the distribution of marine gas pools was complex both in space and in time, and the gas in the pools is heterogeneous. Pool elements, such as preservation conditions, traps and migration paths, and reservoir rocks and facies, also served as important control factors to marine gas pools in South China. Especially, the preservation conditions played a key role in maintaining marine oil and gas accumulations on a regional or local scale. According to several dominant control factors of a pool, the pool-controlling model can be constructed. As an example, the pool-controlling model of Sinian gas pool in Weiyuan gas field in Sichuan basin was summed up. ?? Higher Education Press and Springer-Verlag 2007.

  8. Density measurement in air with a saturable absorbing seed gas

    NASA Technical Reports Server (NTRS)

    Baganoff, D.

    1982-01-01

    A method for making density measurements in a compressible flow by using off resonance laser induced fluorescence is studied. The seed molecule chosen for study is the iodine molecule which is excited with the 514.5 nm line of the argon ion laser whose output is frequency tuned, by as much as 3 GHz, relative to a strong iodine transition using an intracavity etalon. The theory which was developed to analyze the effect will be used in conjunction with two experiments being conducted to further study the method an acoustic resonance tube in which controlled perturbations about a uniform state are produced, and a small supersonic jet in which the conditions of the flow vary widely from point to point.

  9. Electron Density Measurements in UV-Preionized XeCl and CO2 Laser Gas Mixtures

    NASA Astrophysics Data System (ADS)

    Takagi, Shigeyuki; Sato, Saburo; Goto, Tatsumi

    1989-11-01

    A Langmuir probe technique has been used to measure electron densities and temperatures in UV-preionized XeCl excimer and CO2 laser gas mixtures in a laser tube. For this experiment, only pin electrodes (preionization sparks) were operated with no discharge between the main electrodes. The measured electron densities were about 108 cm-3 in both the excimer and CO2 laser gases, compared with 1010 cm-3 in pure He gas. The electron density was found to increase due to the proximity of the main electrodes. The coefficients of absorption for excimer and CO2 laser gas were obtained from the characteristics of the electron densities vs the distance from the UV source. Based on the absorption coefficient for XeCl, 0.9 cm-1 atm-1, we propose pin-electrode arrangements for spatially uniform preionization.

  10. Generation of thin, near critical density gas targets for laser plasma interaction experiments

    NASA Astrophysics Data System (ADS)

    Salehi, Fatholah; Goers, Andy; Hine, George; Feder, Linus; Miao, Bo; Milchberg, Howard

    2015-11-01

    We present the design and characterization of a thin (200µm FWHM), high density pulsed gas jet which we use to study near critical and overcritical laser plasma interactions. We show that cryogenic cooling of the pulsed jet provides the necessary density enhancement for reaching overcritical plasma densities at 800 nm (> 1 . 7 × >102 1 cm-3) with pure hydrogen gas at plenum pressures below 1000 psi. Further, we present 2D and 3D PIC simulations showing the interaction of femtosecond pulses with our experimentally measured near critical gas density profile. The simulations show electron and ion acceleration at drive pulse energies as low as a few tens of millijoules. This work supported by DTRA and the US Department of Energy.

  11. Background gas density and beam losses in NIO1 beam source.

    PubMed

    Sartori, E; Veltri, P; Cavenago, M; Serianni, G

    2016-02-01

    NIO1 (Negative Ion Optimization 1) is a versatile ion source designed to study the physics of production and acceleration of H- beams up to 60 keV. In ion sources, the gas is steadily injected in the plasma source to sustain the discharge, while high vacuum is maintained by a dedicated pumping system located in the vessel. In this paper, the three dimensional gas flow in NIO1 is studied in the molecular flow regime by the Avocado code. The analysis of the gas density profile along the accelerator considers the influence of effective gas temperature in the source, of the gas temperature accommodation by collisions at walls, and of the gas particle mass. The calculated source and vessel pressures are compared with experimental measurements in NIO1 during steady gas injection. PMID:26932000

  12. Background gas density and beam losses in NIO1 beam source

    NASA Astrophysics Data System (ADS)

    Sartori, E.; Veltri, P.; Cavenago, M.; Serianni, G.

    2016-02-01

    NIO1 (Negative Ion Optimization 1) is a versatile ion source designed to study the physics of production and acceleration of H- beams up to 60 keV. In ion sources, the gas is steadily injected in the plasma source to sustain the discharge, while high vacuum is maintained by a dedicated pumping system located in the vessel. In this paper, the three dimensional gas flow in NIO1 is studied in the molecular flow regime by the Avocado code. The analysis of the gas density profile along the accelerator considers the influence of effective gas temperature in the source, of the gas temperature accommodation by collisions at walls, and of the gas particle mass. The calculated source and vessel pressures are compared with experimental measurements in NIO1 during steady gas injection.

  13. Star Formation and Gas Densities in the Dwarf Irregular Galaxy Sextans A

    NASA Astrophysics Data System (ADS)

    Plummer, Julia D.; Hunter, Deidre A.

    1995-12-01

    As a step in understanding the process of star formation in irregular galaxies, we have analysed the irregular galaxy Sextans A. Irregular galaxies provide star-forming systems that are unperturbed by spiral density waves. Sextans A is a tiny galaxy, 1.3 Mpc distant, just beyond the dynamic boundary of the Local Group. We studied the star formation properties of this galaxy using UBV and Hα images. Stars are not currently forming in the center of this galaxy, though they have in the past. The current star formation is in clumps in the outer parts of the galaxy and is not evenly distributed. The total Hα luminosity found for Sextans A is 9 x 10(38) erg/s, which corresponds to a star formation rate of 6 x 10(-3) Mmathordsun /yr for standard assumptions. The rate per unit area, within the Holmberg radius, is 6 x 10(-10) Mmathordsun /yr/pc(2) . Skillman et al. (1988) derived a total HI mass of 6 x 10(7) Mmathordsun . At its present rate, Sextans A will use up all of its gas in 12 x 10(9) yr, including the He contribution. We have also compared the star formation and gas density in Sextans A to critical gas surface density models (Toomre 1964, Quirk 1972, Kennicutt 1988). We used a published rotation curve to calculate the critical gas density necessary for the instabilities that produce star-forming clouds (Skillman et al. 1988). The ratio of observed to critical gas density is low in Sextans A, at the low end of values found by Kennicutt (1988) for spiral galaxies. The current star formation is located in the region of the galaxy with higher radially averaged observed gas densities relative to the critical density. This suggests that Sextans A has a difficult time forming gas clouds, resulting in an observed low star formation rate. This research was funded by the REU program at Northern Arizona University.

  14. Effects of Mean Flow Profiles on the Instability of a Low-Density Gas Jet Injected into a High-Density Gas

    NASA Technical Reports Server (NTRS)

    Vedantam, NandaKishore; Parthasarathy, Ramkumar N.

    2004-01-01

    The effects of the mean velocity profiles on the instability characteristics in the near-injector region of axisymmetric low density gas jets injected vertically upwards into a high-density gas medium were investigated using linear inviscid stability analysis. The flow was assumed to be isothermal and locally parallel. Three velocity profiles, signifying different changes in the mean velocity in the shear layer, were used in the analysis. The effects of the inhomogeneous shear layer and the Froude number (signifying the effects of gravity) on the instability for each set of mean profiles were delineated. At a large Froude number (negligible gravity), a critical density ratio was found for the three profiles at which the jet became absolutely unstable. The critical density ratio for each velocity profile was increased as the Froude number was reduced. A critical Froude number was found for the three sets of profiles, below which the jet was absolutely unstable for all the density ratios less than unity, which demarcated the jet flow into the momentum-driven regime and the buoyancy-driven regime.

  15. Linear Temporal Stability Analysis of a Low-Density Round Gas Jet Injected into a High-Density Gas

    NASA Technical Reports Server (NTRS)

    Lawson, Anthony L.; Parthasarathy, Ramkumar N.

    2002-01-01

    It has been observed in previous experimental studies that round helium jets injected into air display a repetitive structure for a long distance, somewhat similar to the buoyancy-induced flickering observed in diffusion flames. In order to investigate the influence of gravity on the near-injector development of the flow, a linear temporal stability analysis of a round helium jet injected into air was performed. The flow was assumed to be isothermal and locally parallel; viscous and diffusive effects were ignored. The variables were represented as the sum of the mean value and a normal-mode small disturbance. An ordinary differential equation governing the amplitude of the pressure disturbance was derived. The velocity and density profiles in the shear layer, and the Froude number (signifying the effects of gravity) were the three important parameters in this equation. Together with the boundary conditions, an eigenvalue problem was formulated. Assuming that the velocity and density profiles in the shear layer to be represented by hyperbolic tangent functions, the eigenvalue problem was solved for various values of Froude number. The temporal growth rates and the phase velocity of the disturbances were obtained. The temporal growth rates of the disturbances increased as the Froude number was reduced (i.e. gravitational effects increased), indicating the destabilizing role played by gravity.

  16. Solution of an associating lattice-gas model with density anomaly on a Husimi lattice

    NASA Astrophysics Data System (ADS)

    Oliveira, Tiago J.; Stilck, Jürgen F.; Barbosa, Marco Aurélio A.

    2010-11-01

    We study a model of a lattice gas with orientational degrees of freedom which resemble the formation of hydrogen bonds between the molecules. In this model, which is the simplified version of the Henriques-Barbosa model, no distinction is made between donors and acceptors in the bonding arms. We solve the model in the grand-canonical ensemble on a Husimi lattice built with hexagonal plaquettes with a central site. The ground state of the model, which was originally defined on the triangular lattice, is exactly reproduced by the solution on this Husimi lattice. In the phase diagram, one gas and two liquid [high density liquid (HDL) and low density liquid (LDL)] phases are present. All phase transitions (GAS-LDL, GAS-HDL, and LDL-HDL) are discontinuous, and the three phases coexist at a triple point. A line of temperatures of maximum density in the isobars is found in the metastable GAS phase, as well as another line of temperatures of minimum density appears in the LDL phase, part of it in the stable region and another in the metastable region of this phase. These findings are at variance with simulational results for the same model on the triangular lattice, which suggested a phase diagram with two critical points. However, our results show very good quantitative agreement with the simulations, both for the coexistence loci and the densities of particles and of hydrogen bonds. We discuss the comparison of the simulations with our results.

  17. Characteristics of excitation discharge of an excimer laser in gas density depletion

    NASA Astrophysics Data System (ADS)

    Imada, Go; Masuda, Wataru; Yatsui, Kiyoshi

    1998-12-01

    The influences of gas density depletion on the highly- repetitive, high-pressure, pulsed glow discharge for excitation of excimer laser have been investigated eliminating the other instabilities, such as shock waves, residual ions, discharge products and electrode heating. The gas density depletion is simulated by utilizing a subsonic flow between the curved electrodes. The comparison has been made on the discharge occurred in the presence of the gas density depletion with the second discharge on the double-pulse experiment. We have found that the big gas density non uniformity, (Delta) (rho) /(rho) 0 approximately 3.6% corresponding to a pulse repetition rate (PRR) of approximately 20 Hz, tends to cause the arc discharge without the shocks, ions, discharge products and electrode heating. On the other hand, the second discharge on the double-pulse experiment becomes arc discharge in much smaller non uniformity ((Delta) (rho) /(rho) 0 approximately 1.2% corresponding to PRR approximately 3 Hz). The arc discharge in the double-pulse experiment might be driven by the residual ions and/or discharge products other than gas density depletion except for PRR greater than 20 Hz.

  18. Human respiration at rest in rapid compression and at high pressures and gas densities

    NASA Technical Reports Server (NTRS)

    Gelfand, R.; Lambertsen, C. J.; Strauss, R.; Clark, J. M.; Puglia, C. D.

    1983-01-01

    The ventilation (V), end-tidal PCO2 (PACO2), and CO2 elimination rate were determined in men at rest breathing CO2-free gas over the pressure range 1-50 ATA and the gas density range 0.4-25 g/l, during slow and rapid compressions, at stable elevated ambient pressures and during slow decompressions. Progressive increase in pulmonary gas flow resistance due to elevation of ambient pressure and inspired gas density to the He-O2 equivalent of 5000 feet of seawater was found to produce a complex pattern of change in PACO2. It was found that as both ambient pressure and pulmonary gas flow resistance were progressively raised, PACO2 at first increased, went through a maximum, and then declined towards values near the 1 ATA level. It is concluded that this pattern of PACO2 change results from the interaction on ventilation of the increase in pulmonary resistance due to the elevation of gas density with the increase in respiratory drive postulated as due to generalized central nervous system excitation associated with exposure to high hydrostatic pressure. It is suggested that a similar interaction exists between increased gas flow resistance and the increase in respiratory drive related to nitrogen partial pressure and the resulting narcosis.

  19. A CORRELATION BETWEEN SURFACE DENSITIES OF YOUNG STELLAR OBJECTS AND GAS IN EIGHT NEARBY MOLECULAR CLOUDS

    SciTech Connect

    Gutermuth, R. A.; Pipher, J. L.; Megeath, S. T.; Allen, T. S.; Myers, P. C.; Allen, L. E.

    2011-10-01

    We report the discovery and characterization of a power-law correlation between the local surface densities of Spitzer-identified, dusty young stellar objects (YSOs) and the column density of gas (as traced by near-IR extinction) in eight molecular clouds within 1 kpc and with 100 or more known YSOs. This correlation, which appears in data smoothed over size scales of {approx}1 pc, varies in quality from cloud to cloud; those clouds with tight correlations, MonR2 and Ophiuchus, are fit with power laws of slope 2.67 and 1.87, respectively. The spread in the correlation is attributed primarily to local gas disruption by stars that formed there or to the presence of very young subregions at the onset of star formation. We explore the ratio of the number of Class II to Class I sources, a proxy for the star formation age of a region, as a function of gas column density; this analysis reveals a declining Class II to Class I ratio with increasing column density. We show that the observed star-gas correlation is consistent with a star formation law where the star formation rate per area varies with the gas column density squared. We also propose a simple picture of thermal fragmentation of dense gas in an isothermal, self-gravitating layer as an explanation for the power law. Finally, we briefly compare the star-gas correlation and its implied star formation law with other recent proposed of star formation laws at similar and larger size scales from nearby star-forming regions.

  20. Gas-phase silicon atom densities in the chemical vapor deposition of silicon from silane

    SciTech Connect

    Coltrin, M.E.; Breiland, W.G.; Ho, P.

    1993-12-31

    Silicon atom number density profiles have been measured using laser-induced fluorescence during the chemical vapor deposition of silicon from silane. Measurements were obtained in a rotating-disk reactor as a function of silane partial pressure and the amount of hydrogen added to the carrier gas. Absolute number densities were obtained using an atomic absorption technique. Results were compared with calculated density profiles from a model of the coupled fluid flow, gas-phase and surface chemistry for an infinite-radius rotating disk. An analysis of the reaction mechanism showed that the unimolecular decomposition of SiH{sub 2} is not the dominant source of Si atoms. Profile shapes and positions, and all experimental trends are well matched by the calculations. However, the calculated number density is up to 100 times smaller than measured.

  1. Observing the gas temperature drop in the high-density nucleus of L 1544

    NASA Astrophysics Data System (ADS)

    Crapsi, A.; Caselli, P.; Walmsley, M. C.; Tafalla, M.

    2007-07-01

    Context: The thermal structure of a starless core is crucial for our understanding of the physics in these objects and hence for our understanding of star formation. Theory predicts a gas temperature drop in the inner 5000 AU of the pre-stellar core L 1544, but there has been no observational proof of this. Aims: We performed VLA observations of the NH{3} (1, 1) and (2, 2) transitions towards L 1544 in order to measure the temperature gradient between the high density core nucleus and the surrounding core envelope. Our VLA observation for the first time provide measurements of gas temperature in a core with a resolution smaller than 1000 AU. We have also obtained high resolution Plateau de Bure observations of the 110 GHz 111-101 para-NH2D line in order to further constrain the physical parameters of the high density nucleus. Methods: We combine our interferometric NH{3} and NH2D observations with available single dish measurements in order to estimate the effects of flux loss from extended components upon our data. We have estimated the temperature gradient using a model of the source to fit our data in the u,v plane. As the NH{3}(1, 1) line is extremely optically thick, this also involved fitting a gradient in the NH{3} abundance. In this way, we also measure the [ NH2D] /[ NH{3}] abundance ratio in the inner nucleus. Results: We find that indeed the temperature decreases toward the core nucleus from 12 K down to 5.5 K resulting in an increase of a factor of 50% in the estimated density of the core from the dust continuum if compared with the estimates done with constant temperature of 8.75 K. Current models of the thermal equilibrium can describe consistently the observed temperature and density in this object, simultaneously fitting our temperature profile and the continuum emission. We also found a remarkably high abundance of deuterated ammonia with respect to the ammonia abundance (50% ± 20%), which proves the persistence of nitrogen bearing molecules at

  2. Can mammographic assessments lead to consider density as a risk factor for breast cancer?

    PubMed

    Colin, C; Prince, V; Valette, P J

    2013-03-01

    Admitting that mammographic breast density is an important independent risk factor for breast cancer in the general population, has a crucial economical health care impact, since it might lead to increasing screening frequency or reinforcing additional modalities. Thus, the impact of density as a risk factor has to be carefully investigated and might be debated. Some authors suggested that high density would be either a weak factor or confused with a masking effect. Others concluded that most of the studies have methodological biases in basic physics to quantify percentage of breast density, as well as in mammographic acquisition parameters. The purpose of this review is to evaluate mammographic procedures and density assessments in published studies regarding density as a breast cancer risk. No standardization was found in breast density assessments and compared density categories. High density definitions varied widely from 25 to 75% of dense tissues on mammograms. Some studies showed an insufficient follow-up to reveal masking effect related to mammographic false negatives. Evaluating breast density impact needs thorough studies with consensual mammographic procedures, methods of density measurement, breast density classification as well as a standardized definition of high breast density. Digital mammography, more effective in dense breasts, should help to re-evaluate the issue of density as a risk factor for breast cancer. PMID:20133095

  3. Density fluctuations in a quasi-one-dimensional Bose gas as observed in free expansion

    NASA Astrophysics Data System (ADS)

    Gawryluk, Krzysztof; Gajda, Mariusz; Brewczyk, Mirosław

    2015-10-01

    We study, within the framework of the classical-field approximation, the density correlations of a weakly interacting expanding Bose gas for the whole range of temperatures across the Bose-Einstein condensation threshold. We focus on elongated quasi-one-dimensional systems where there is a huge discrepancy between the existing theory and experimental results [A. Perrin et al., Nat. Phys. 8, 195 (2012), 10.1038/nphys2212]. We find that the density correlation function is not reduced for temperatures below the critical one as it is predicted for the ideal gas or for a weakly interacting system within the Bogoliubov approximation. This behavior of the density correlations agrees with the above-mentioned experiment with the elongated system. Although the system was much larger than that studied here, we believe that the behavior of the density correlation function found there is quite generic. Our theoretical study indicates also large density fluctuations in the trap in the quasicondensate regime where only phase fluctuations were expected. We argue that the enhanced density fluctuations can originate in the presence of interactions in the system, or more precisely in the presence of spontaneous dark solitons in the elongated gas at thermal equilibrium.

  4. Density functional theory screening of gas-treatment strategies for stabilization of high energy-density lithium metal anodes

    NASA Astrophysics Data System (ADS)

    Koch, Stephan L.; Morgan, Benjamin J.; Passerini, Stefano; Teobaldi, Gilberto

    2015-11-01

    To explore the potential of molecular gas treatment of freshly cut lithium foils in non-electrolyte-based passivation of high-energy-density Li anodes, density functional theory (DFT) has been used to study the decomposition of molecular gases on metallic lithium surfaces. By combining DFT geometry optimization and Molecular Dynamics, the effects of atmospheric (N2, O2, CO2) and hazardous (F2, SO2) gas decomposition on Li(bcc) (100), (110), and (111) surfaces on relative surface energies, work functions, and emerging electronic and elastic properties are investigated. The simulations suggest that exposure to different molecular gases can be used to induce and control reconstructions of the metal Li surface and substantial changes (up to over 1 eV) in the work function of the passivated system. Contrary to the other considered gases, which form metallic adlayers, SO2 treatment emerges as the most effective in creating an insulating passivation layer for dosages ≤1 mono-layer. The substantial Li → adsorbate charge transfer and adlayer relaxation produce marked elastic stiffening of the interface, with the smallest change shown by nitrogen-treated adlayers.

  5. Maximization of ICRF power by SOL density tailoring with local gas injection

    NASA Astrophysics Data System (ADS)

    Jacquet, P.; Goniche, M.; Bobkov, V.; Lerche, E.; Pinsker, R. I.; Pitts, R. A.; Zhang, W.; Colas, L.; Hosea, J.; Moriyama, S.; Wang, S.-J.; Wukitch, S.; Zhang, X.; Bilato, R.; Bufferand, H.; Guimarais, L.; Faugel, H.; Hanson, G. R.; Kocan, M.; Monakhov, I.; Noterdaeme, J.-M.; Petrzilka, V.; Shaw, A.; Stepanov, I.; Sips, A. C. C.; Van Eester, D.; Wauters, T.; JET contributors, the; the ASDEX Upgrade Team; the DIII-D Team; ITPA ‘Integrated Operation Scenarios' members, the; experts

    2016-04-01

    Experiments have been performed under the coordination of the International Tokamak Physics Activity (ITPA) on several tokamaks, including ASDEX Upgrade (AUG), JET and DIII-D, to characterize the increased Ion cyclotron range of frequency (ICRF) antenna loading achieved by optimizing the position of gas injection relative to the RF antennas. On DIII-D, AUG and JET (with the ITER-Like Wall) a 50% increase in the antenna loading was observed when injecting deuterium in ELMy H-mode plasmas using mid-plane inlets close to the powered antennas instead of divertor injection and, with smaller improvement when using gas inlets located at the top of the machine. The gas injection rate required for such improvements (~0.7  ×  1022 el s-1 in AUG, ~1.0  ×  1022 el s-1 in JET) is compatible with the use of this technique to optimize ICRF heating during the development of plasma scenarios and no degradation of confinement was observed when using the mid-plane or top inlets compared with divertor valves. An increase in the scrape-off layer (SOL) density was measured when switching gas injection from divertor to outer mid-plane or top. On JET and DIII-D, the measured SOL density increase when using main chamber puffing is consistent with the antenna coupling resistance increase provided that the distance between the measurement lines of sight and the injection location is taken into account. Optimized gas injection was also found to be beneficial for reducing tungsten (W) sputtering at the AUG antenna limiters, and also to reduce slightly the W and nickel (Ni) content in JET plasmas. Modeling the specific effects of divertor/top/mid-plane injection on the outer mid-plane density was carried out using both the EDGE2D-EIRENE and EMC3-EIRENE plasma boundary code packages; simulations indeed indicate that outer mid-plane gas injection maximizes the density in the mid-plane close to the injection point with qualitative agreement with the AUG SOL density measurements

  6. Gas amplification factor in neon-nitrogen filled proportional counters

    NASA Astrophysics Data System (ADS)

    Othman, A.

    1988-07-01

    The gas amplification factor in a cylindrical proportional counter filled with NeN 2 Penning mixtures has been measured (over the range 1 < A < 6.4 × 10 3) to verify the validity of the gas gain formulae of Rose and Korff, Khristov, Williams and Sara, Diethorn and Zastawny. This factor has been found to obey Zastawny's formula over the range of variables studied. The formula of Diethorn can be fitted only for small nitrogen concentrations (below 5 × 10 -4). Constants appropriate to the Zastawny and Diethorn formulae have been determined over a wide range of N 2 concentrations from spectroscopically pure Ne up to 11.1% N 2.

  7. Improved parameterization of interatomic potentials for rare gas dimers with density-based energy decomposition analysis

    NASA Astrophysics Data System (ADS)

    Zhou, Nengjie; Lu, Zhenyu; Wu, Qin; Zhang, Yingkai

    2014-06-01

    We examine interatomic interactions for rare gas dimers using the density-based energy decomposition analysis (DEDA) in conjunction with computational results from CCSD(T) at the complete basis set (CBS) limit. The unique DEDA capability of separating frozen density interactions from density relaxation contributions is employed to yield clean interaction components, and the results are found to be consistent with the typical physical picture that density relaxations play a very minimal role in rare gas interactions. Equipped with each interaction component as reference, we develop a new three-term molecular mechanical force field to describe rare gas dimers: a smeared charge multipole model for electrostatics with charge penetration effects, a B3LYP-D3 dispersion term for asymptotically correct long-range attractions that is screened at short-range, and a Born-Mayer exponential function for the repulsion. The resulted force field not only reproduces rare gas interaction energies calculated at the CCSD(T)/CBS level, but also yields each interaction component (electrostatic or van der Waals) which agrees very well with its corresponding reference value.

  8. Improved parameterization of interatomic potentials for rare gas dimers with density-based energy decomposition analysis.

    PubMed

    Zhou, Nengjie; Lu, Zhenyu; Wu, Qin; Zhang, Yingkai

    2014-06-01

    We examine interatomic interactions for rare gas dimers using the density-based energy decomposition analysis (DEDA) in conjunction with computational results from CCSD(T) at the complete basis set (CBS) limit. The unique DEDA capability of separating frozen density interactions from density relaxation contributions is employed to yield clean interaction components, and the results are found to be consistent with the typical physical picture that density relaxations play a very minimal role in rare gas interactions. Equipped with each interaction component as reference, we develop a new three-term molecular mechanical force field to describe rare gas dimers: a smeared charge multipole model for electrostatics with charge penetration effects, a B3LYP-D3 dispersion term for asymptotically correct long-range attractions that is screened at short-range, and a Born-Mayer exponential function for the repulsion. The resulted force field not only reproduces rare gas interaction energies calculated at the CCSD(T)/CBS level, but also yields each interaction component (electrostatic or van der Waals) which agrees very well with its corresponding reference value. PMID:24908000

  9. Improved parameterization of interatomic potentials for rare gas dimers with density-based energy decomposition analysis

    PubMed Central

    Zhou, Nengjie; Lu, Zhenyu; Wu, Qin; Zhang, Yingkai

    2014-01-01

    We examine interatomic interactions for rare gas dimers using the density-based energy decomposition analysis (DEDA) in conjunction with computational results from CCSD(T) at the complete basis set (CBS) limit. The unique DEDA capability of separating frozen density interactions from density relaxation contributions is employed to yield clean interaction components, and the results are found to be consistent with the typical physical picture that density relaxations play a very minimal role in rare gas interactions. Equipped with each interaction component as reference, we develop a new three-term molecular mechanical force field to describe rare gas dimers: a smeared charge multipole model for electrostatics with charge penetration effects, a B3LYP-D3 dispersion term for asymptotically correct long-range attractions that is screened at short-range, and a Born-Mayer exponential function for the repulsion. The resulted force field not only reproduces rare gas interaction energies calculated at the CCSD(T)/CBS level, but also yields each interaction component (electrostatic or van der Waals) which agrees very well with its corresponding reference value. PMID:24908000

  10. Energy Factor Analysis for Gas Heat Pump Water Heaters

    SciTech Connect

    Gluesenkamp, Kyle R

    2016-01-01

    Gas heat pump water heaters (HPWHs) can improve water heating efficiency with zero GWP and zero ODP working fluids. The energy factor (EF) of a gas HPWH is sensitive to several factors. In this work, expressions are derived for EF of gas HPWHs, as a function of heat pump cycle COP, tank heat losses, burner efficiency, electrical draw, and effectiveness of supplemental heat exchangers. The expressions are used to investigate the sensitivity of EF to each parameter. EF is evaluated on a site energy basis (as used by the US DOE for rating water heater EF), and a primary energy-basis energy factor (PEF) is also defined and included. Typical ranges of values for the six parameters are given. For gas HPWHs, using typical ranges for component performance, EF will be 59 80% of the heat pump cycle thermal COP (for example, a COP of 1.60 may result in an EF of 0.94 1.28). Most of the reduction in COP is due to burner efficiency and tank heat losses. Gas-fired HPWHs are theoretically be capable of an EF of up to 1.7 (PEF of 1.6); while an EF of 1.1 1.3 (PEF of 1.0 1.1) is expected from an early market entry.

  11. Electron density measurement in gas discharge plasmas by optical and acoustic methods

    NASA Astrophysics Data System (ADS)

    Biagioni, A.; Anania, M. P.; Bellaveglia, M.; Chiadroni, E.; Cianchi, A.; Di Giovenale, D.; Di Pirro, G.; Ferrario, M.; Filippi, F.; Mostacci, A.; Pompili, R.; Shpakov, V.; Vaccarezza, C.; Villa, F.; Zigler, A.

    2016-08-01

    Plasma density represents a very important parameter for both laser wakefield and plasma wakefield acceleration, which use a gas-filled capillary plasma source. Several techniques can be used to measure the plasma density within a capillary discharge, which are mainly based on optical diagnostic methods, as for example the well-known spectroscopic method using the Stark broadening effect. In this work, we introduce a preliminary study on an alternative way to detect the plasma density, based on the shock waves produced by gas discharge in a capillary. Firstly, the measurements of the acoustic spectral content relative to the laser-induced plasmas by a solid target allowed us to understand the main properties of the acoustic waves produced during this kind of plasma generation; afterwards, we have extended such acoustic technique to the capillary plasma source in order to calibrate it by comparison with the stark broadening method.

  12. Molecular Rayleigh Scattering Techniques Developed for Measuring Gas Flow Velocity, Density, Temperature, and Turbulence

    NASA Technical Reports Server (NTRS)

    Mielke, Amy F.; Seasholtz, Richard G.; Elam, Kristie A.; Panda, Jayanta

    2005-01-01

    Nonintrusive optical point-wise measurement techniques utilizing the principles of molecular Rayleigh scattering have been developed at the NASA Glenn Research Center to obtain time-averaged information about gas velocity, density, temperature, and turbulence, or dynamic information about gas velocity and density in unseeded flows. These techniques enable measurements that are necessary for validating computational fluid dynamics (CFD) and computational aeroacoustic (CAA) codes. Dynamic measurements allow the calculation of power spectra for the various flow properties. This type of information is currently being used in jet noise studies, correlating sound pressure fluctuations with velocity and density fluctuations to determine noise sources in jets. These nonintrusive techniques are particularly useful in supersonic flows, where seeding the flow with particles is not an option, and where the environment is too harsh for hot-wire measurements.

  13. Bulk-density distributions of solids in the freeboard of a gas-solid fluidized bed

    SciTech Connect

    Shen, B.C.; Fan, L.T.; Walawender, W.P.

    1995-05-01

    The freeboard region above the bubbling zone of a gas-solid fluidized bed provides the space not only for the disengagement of particles but also for additional contact and reaction between the particles and gas. The flow pattern and behavior of particles as well as their bulk-density distribution in the freeboard have a significant impact on the efficiency of fluidization. The results of numerous previous experimental studies indicate that the bulk density of solids essentially decreases exponentially as a function of the height of the freeboard. In the present work, this distribution has been obtained by first derived the Fokker-Planck equation from the linearized equation of motion of a single particle and then transforming this Fokker-Planck equation into that for the bulk-density distribution of solids. Its simplification to the one-dimensional case readily gives rise to an exponential distribution and agrees well with the available experimental data.

  14. The probability density function in molecular gas in the G333 and Vela C molecular clouds

    NASA Astrophysics Data System (ADS)

    Cunningham, Maria

    2015-08-01

    The probability density function (PDF) is a simple analytical tool for determining the hierarchical spatial structure of molecular clouds. It has been used frequently in recent years with dust continuum emission, such as that from the Herschel space telescope and ALMA. These dust column density PDFs universally show a log-normal distribution in low column density gas, characteristic of unbound turbulent gas, and a power-law tail at high column densities, indicating the presence of gravitationally bound gas. We have recently conducted a PDF analysis of the molecular gas in the G333 and Vela C giant molecular cloud complexes, using transitions of CO, HCN, HNC, HCO+ and N2H+.The results show that CO and its isotopologues trace mostly the log-normal part of the PDF, while HCN and HCO+ trace both a log-normal part and a power law part to the distribution. On the other hand, HNC and N2H+ mostly trace only the power law tail. The difference between the PDFs of HCN and HNC is surprising, as is the similarity between HNC and the N2H+ PDFs. The most likely explanation for the similar distributions of HNC and N2H+ is that N2H+ is known to be enhanced in cool gas below 20K, where CO is depleted, while the reaction that forms HNC or HCN favours the former at similar low temperatures. The lack of evidence for a power law tail in 13CO and C18O, in conjunction for the results for the N2H+ PDF suggest that depletion of CO in the dense cores of these molecular clouds is significant. In conclusion, the PDF has proved to be a surprisingly useful tool for investigating not only the spatial distribution of molecular gas, but also the wide scale chemistry of molecular clouds.

  15. Investigating the Effect of Complexity Factors in Gas Law Problems

    ERIC Educational Resources Information Center

    Schuttlefield, Jennifer D.; Kirk, John; Pienta, Norbert J.; Tang, Hui

    2012-01-01

    Undergraduate students were asked to complete gas law questions using a Web-based tool as a first step in our understanding of the role of cognitive load in chemistry word questions and in helping us assess student problem-solving. Each question contained five different complexity factors, which were randomly assigned by the tool so that a…

  16. Pair distribution function of the spin-polarized electron gas: A first-principles analytic model for all uniform densities

    NASA Astrophysics Data System (ADS)

    Gori-Giorgi, Paola; Perdew, John P.

    2002-10-01

    We construct analytic formulas that represent the coupling-constant-averaged pair distribution function gxc(rs,ζ,kFu) of a three-dimensional nonrelativistic ground-state electron gas constrained to a uniform density with density parameter rs=(9π/4)1/3/kF and relative spin polarization ζ over the whole range 0∞) oscillations averaged out. The pair distribution function gxc at the physical coupling constant is then given by differentiation with respect to rs. Our formulas are constructed using only known theoretical constraints plus the correlation energy ɛc(rs,ζ), and accurately reproduce the gxc of the quantum Monte Carlo method and of the fluctuation-dissipation theorem with the Richardson-Ashcroft dynamical local-field factor. Our gxc is correct even in the high-density (rs-->0) and low-density (rs-->∞) limits. When the spin resolution of ɛc into ↑↑, ↓↓, and ↑↓ contributions is known, as it is in the high- and low-density limits, our formulas also yield the spin resolution of gxc. Because of these features, our formulas may be useful for the construction of density functionals for nonuniform systems. We also analyze the kinetic energy of correlation into contributions from density fluctuations of various wave vectors. The exchange and long-range correlation parts of our gxc(rs,ζ,kFu)-1 are analytically Fourier transformable, so that the static structure factor Sxc(rs,ζ,k/kF) is easily evaluated.

  17. Mammographic density and its interaction with other breast cancer risk factors in an Asian population

    PubMed Central

    Wong, C S; Lim, G H; Gao, F; Jakes, R W; Offman, J; Chia, K S; Duffy, S W

    2011-01-01

    Background: Joint effects of mammographic density and other risk factors on breast cancer risk remain unclear. Methods: From The Singapore Breast Screening Project, we selected 491 cases and 982 controls. Mammographic density was measured quantitatively. Data analysis was by conditional logistic regression. Results: Density was a significant risk factor, adjusting for other factors. Density of 76–100% had an odds ratio of 5.54 (95% CI 2.38–12.90) compared with 0–10%. Density had significant interactions with body mass index and oral contraceptive use (P=0.02). Conclusions: Percent density increases breast cancer risk in addition to effects of other risk factors, and modifies the effects of BMI and OCs. PMID:21245860

  18. Dwarf galaxy dark matter density profiles inferred from stellar and gas kinematics

    SciTech Connect

    Adams, Joshua J.; Simon, Joshua D.; Fabricius, Maximilian H.; Bender, Ralf; Thomas, Jens; Van den Bosch, Remco C. E.; Van de Ven, Glenn; Barentine, John C.; Gebhardt, Karl; Hill, Gary J.; Murphy, Jeremy D.; Swaters, R. A. E-mail: jja439@gmail.com

    2014-07-01

    We present new constraints on the density profiles of dark matter (DM) halos in seven nearby dwarf galaxies from measurements of their integrated stellar light and gas kinematics. The gas kinematics of low-mass galaxies frequently suggest that they contain constant density DM cores, while N-body simulations instead predict a cuspy profile. We present a data set of high-resolution integral-field spectroscopy on seven galaxies and measure the stellar and gas kinematics simultaneously. Using Jeans modeling on our full sample, we examine whether gas kinematics in general produce shallower density profiles than are derived from the stars. Although two of the seven galaxies show some localized differences in their rotation curves between the two tracers, estimates of the central logarithmic slope of the DM density profile, γ, are generally robust. The mean and standard deviation of the logarithmic slope for the population are γ = 0.67 ± 0.10 when measured in the stars and γ = 0.58 ± 0.24 when measured in the gas. We also find that the halos are not under-concentrated at the radii of half their maximum velocities. Finally, we search for correlations of the DM density profile with stellar velocity anisotropy and other baryonic properties. Two popular mechanisms to explain cored DM halos are an exotic DM component or feedback models that strongly couple the energy of supernovae into repeatedly driving out gas and dynamically heating the DM halos. While such models do not yet have falsifiable predictions that we can measure, we investigate correlations that may eventually be used to test models. We do not find a secondary parameter that strongly correlates with the central DM density slope, but we do find some weak correlations. The central DM density slope weakly correlates with the abundance of α elements in the stellar population, anti-correlates with H I fraction, and anti-correlates with vertical orbital anisotropy. We expect, if anything, the opposite of these

  19. Distribution of E/N and N/e/ in a cross-flow electric discharge laser. [electric field to neutral gas density and electron number density

    NASA Technical Reports Server (NTRS)

    Dunning, J. W., Jr.; Lancashire, R. B.; Manista, E. J.

    1976-01-01

    Measurements have been conducted of the effect of the convection of ions and electrons on the discharge characteristics in a large scale laser. The results are presented for one particular distribution of ballast resistance. Values of electric field, current density, input power density, ratio of electric field to neutral gas density (E/N), and electron number density were calculated on the basis of measurements of the discharge properties. In a number of graphs, the E/N ratio, current density, power density, and electron density are plotted as a function of row number (downstream position) with total discharge current and gas velocity as parameters. From the dependence of the current distribution on the total current, it appears that the electron production in the first two rows significantly affects the current flowing in the succeeding rows.

  20. Probing Milky Way's hot gas halo density distribution using the dispersion measure of pulsars

    NASA Astrophysics Data System (ADS)

    Zhezher, Ya. V.; Nugaev, E. Ya.; Rubtsov, G. I.

    2016-03-01

    A number of recent studies indicates a significant amount of ionized gas in a form of the hot gas halo around the Milky Way. The halo extends over the region of 100 kpc and may be acountable for the missing baryon mass. In this paper we calculate the contribution of the proposed halo to the dispersion measure (DM) of the pulsars. The Navarro, Frenk, and White (NFW), Maller and Bullock (MB), and Feldmann, Hooper, and Gnedin (FHG) density distibutions are considered for the gas halo. The data set includes pulsars with the distance known independently from the DM, e.g., pulsars in globular clusters, LMC, SMC and pulsars with known parallax. The results exclude the NFW distribution for the hot gas, while the more realisticMB and FHG models are compatible with the observed dispersion measure.

  1. Phase Separation, Density Fluctuations, and Boiling Near the Liquid-Gas Critical Point

    NASA Astrophysics Data System (ADS)

    Hegseth, John; Oprisan, Ana; Roy, Arun; Nikolayev, Vadim; Beysens, Daniel; Garrabos, Yves; Lecoutre-Chabot, Carole

    2002-11-01

    A pure liquid-gas mixture is one of the simplest examples of a soft-matter system. In fact, when co-existing gas and liquid phases of pure fluid are heated to their critical point, large-scale density fluctuations make the fluid extremely compressible (to external forces), expandable (to heating), slows the diffusive transport, and decreases the surface tension. In principle these properties and others either diverge to infinity or converge to zero at the critical temperature. These properties lead to some very unusual behavior: large density gradients at the laboratory scale, a large mechanical response to heating, and perfect wetting of a solid wall by the liquid phase (zero contact-angle). We have further simplified this system by performing experiments in weightlessness (Mir spaces station). By controlling the fluid's temperature, these properties may be varied over large ranges in a single sample. When the fluid is driven out of equilibrium by a fast temperature quench from the single-phase (supercritical fluid) state into the two-phase state, we have observed universal growth laws of minority domains (gas bubbles) during phase separation. Prior to this quench we have also observed density fluctuations using optical microscopy near the critical point. When heat is applied to a liquid-gas mixture, we have observed a spectacular spreading of a gas bubble along a hot solid wall as well as gas bubble over-heating (where the interior of a gas bubble gains a higher temperature than the heating wall). Although this gas phase over-heating appears to violate the second law, it is really a transient our-of-equilibrium effect. Inside of these unusual bubbles we also have observed unusually large variations in liquid wetting film thickness that often appear to evolve into spreading contact lines on the sapphire wall when heat is applied. We have observed coarsening and growth of minority domains (gas bubbles) in SF6 near its liquid-gas critical point. Phase separation in

  2. Effects of dry bulk density and particle size fraction on gas transport parameters in variably saturated landfill cover soil.

    PubMed

    Wickramarachchi, Praneeth; Kawamoto, Ken; Hamamoto, Shoichiro; Nagamori, Masanao; Moldrup, Per; Komatsu, Toshiko

    2011-12-01

    Landfill sites are emerging in climate change scenarios as a significant source of greenhouse gases. The compacted final soil cover at landfill sites plays a vital role for the emission, fate and transport of landfill gases. This study investigated the effects of dry bulk density, ρ(b), and particle size fraction on the main soil-gas transport parameters - soil-gas diffusivity (D(p)/D(o), ratio of gas diffusion coefficients in soil and free air) and air permeability (k(a)) - under variably-saturated moisture conditions. Soil samples were prepared by three different compaction methods (Standard and Modified Proctor compaction, and hand compaction) with resulting ρ(b) values ranging from 1.40 to 2.10 g cm(-3). Results showed that D(p) and k(a) values for the '+gravel' fraction (<35 mm) became larger than for the '-gravel' fraction (<2mm) under variably-saturated conditions for a given soil-air content (ε), likely due to enhanced gas diffusion and advection through less tortuous, large-pore networks. The effect of dry bulk density on D(p) and k(a) was most pronounced for the '+gravel' fraction. Normalized ratios were introduced for all soil-gas parameters: (i) for gas diffusivity D(p)/D(f), the ratio of measured D(p) to D(p) in total porosity (f), (ii) for air permeability k(a)/k(a)(,pF4.1), the ratio of measured k(a) to k(a) at 1235 kPa matric potential (=pF 4.1), and (iii) for soil-air content, the ratio of soil-air content (ε) to total porosity (f) (air saturation). Based on the normalized parameters, predictive power-law models for D(p)(ε/f) and k(a)(ε/f) models were developed based on a single parameter (water blockage factor M for D(p) and P for k(a)). The water blockage factors, M and P, were found to be linearly correlated to ρ(b) values, and the effects of dry bulk density on D(p) and k(a) for both '+gravel' and '-gravel' fractions were well accounted for by the new models. PMID:21813272

  3. Emission and afterglow properties of an expanding RF plasma with nonuniform neutral gas density

    NASA Astrophysics Data System (ADS)

    Chaplin, Vernon H.; Bellan, Paul M.

    2016-08-01

    We describe some notable aspects of the light emission and afterglow properties in pulsed, high-density ( 1018-1020 m-3 ) argon inductively coupled discharges initiated following fast gas injection. The plasma was created in a long, narrow discharge tube and then expanded downstream of the radiofrequency (RF) antenna into a large chamber. Fast camera images of the expanding plasma revealed a multi-phase time-dependent emission pattern that did not follow the ion density distribution. Dramatic differences in visible brightness were observed between discharges with and without an externally applied magnetic field. These phenomena were studied by tracking excited state populations using passive emission spectroscopy and are discussed in terms of the distinction between ionizing and recombining phase plasmas. Additionally, a method is presented for inferring the unknown neutral gas pressure in the discharge tube from the time-dependent visible and infrared emission measured by a simple photodiode placed near the antenna. In magnetized discharges created with fast gas injection, the downstream ion density rose by Δni˜1018 m-3 in the first ˜100 μs after the RF power was turned off. The conditions conducive to this afterglow density rise are investigated in detail, and the effect is tentatively attributed to pooling ionization.

  4. Gas temperature and density measurements based on spectrally resolved Rayleigh-Brillouin scattering

    NASA Technical Reports Server (NTRS)

    Seasholtz, Richard G.; Lock, James A.

    1992-01-01

    The use of molecular Rayleigh scattering for measurements of gas density and temperature is evaluated. The technique used is based on the measurement of the spectrum of the scattered light, where both temperature and density are determined from the spectral shape. Planar imaging of Rayleigh scattering from air using a laser light sheet is evaluated for ambient conditions. The Cramer-Rao lower bounds for the shot-noise limited density and temperature measurement uncertainties are calculated for an ideal optical spectrum analyzer and for a planar mirror Fabry-Perot interferometer used in a static, imaging mode. With this technique, a single image of the Rayleigh scattered light can be analyzed to obtain density (or pressure) and temperature. Experimental results are presented for planar measurements taken in a heated air stream.

  5. Measuring direct drive ICF remaining ablator areal density using a gas Cherenkov detector

    NASA Astrophysics Data System (ADS)

    Rubery, Michael; Horsfield, Colin; Herrmann, Hans; Kim, Yongho; Hoffmann, Nelson; Mack, Joseph; Young, Carl; Evans, Scott; Sedillo, Tom; Caldwell, Steven; Grafil, Elliot; Stoeffl, Wolfgang; Milnes, James; Atomic Weapons Establishment PLC Team; Los Alamos National Laboratory Team; Lawrence Livermore National Laboratory Team; Photek Ltd Team

    2013-10-01

    Neutrons from a compressed direct drive ICF target produce γ rays through inelastic interactions with ablator material. The inelastic γ intensity is proportional to the remaining ablator areal density at bang time and the neutron yield. Remaining ablator areal density is an important metric for the quality of the implosion and is strongly correlated with fuel temperature and compression. This contribution describes how a background signal routinely measured on the gas Cherenkov detectors can be used to infer the intensity of the low-energy inelastic gammas from the ablator on the same trace as the DT fusion γ signal, which is directly proportional to the neutron yield; therefore allowing the remaining ablator areal density to be measured in a self consistent manner. Results from recent experiments at the Omega laser facility designed to prove the technique are discussed. In addition, Monte Carlo modelling shows the technique can be used to measure remaining ablator areal density for both plastic and glass capsules.

  6. Investigation of the on-axis atom number density in the supersonic gas jet under high gas backing pressure by simulation

    SciTech Connect

    Chen, Guanglong; Xu, Yi; Cao, Yunjiu; Mi, Yiming; Zhang, Xiuli; Wang, Lili; Boldarev, A. S.; Geng, Xiaotao; Kim, Dong Eon

    2015-10-15

    The supersonic gas jets from conical nozzles are simulated using 2D model. The on-axis atom number density in gas jet is investigated in detail by comparing the simulated densities with the idealized densities of straight streamline model in scaling laws. It is found that the density is generally lower than the idealized one and the deviation between them is mainly dependent on the opening angle of conical nozzle, the nozzle length and the gas backing pressure. The density deviation is then used to discuss the deviation of the equivalent diameter of a conical nozzle from the idealized d{sub eq} in scaling laws. The investigation on the lateral expansion of gas jet indicates the lateral expansion could be responsible for the behavior of the density deviation. These results could be useful for the estimation of cluster size and the understanding of experimental results in laser-cluster interaction experiments.

  7. 40 CFR Table W - 7 of Subpart W-Default Methane Emission Factors for Natural Gas Distribution

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... Emission Factors for Natural Gas Distribution W Table W Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR PROGRAMS (CONTINUED) MANDATORY GREENHOUSE GAS REPORTING Petroleum and Natural Gas... for Natural Gas Distribution Natural gas distribution Emission factor (scf/hour/component)...

  8. The effective density of randomly moving electrons and related characteristics of materials with degenerate electron gas

    SciTech Connect

    Palenskis, V.

    2014-04-15

    Interpretation of the conductivity of metals, of superconductors in the normal state and of semiconductors with highly degenerate electron gas remains a significant issue if consideration is based on the classical statistics. This study is addressed to the characterization of the effective density of randomly moving electrons and to the evaluation of carrier diffusion coefficient, mobility, and other parameters by generalization of the widely published experimental results. The generalized expressions have been derived for various kinetic parameters attributed to the non-degenerate and degenerate electron gas, by analyzing a random motion of the single type carriers in homogeneous materials. The values of the most important kinetic parameters for different metals are also systematized and discussed. It has been proved that Einstein's relation between the diffusion coefficient and the drift mobility of electrons is held for any level of degeneracy if the effective density of randomly moving carriers is properly taken into account.

  9. Single-particle spectral density of a Bose gas in the two-fluid hydrodynamic regime

    SciTech Connect

    Arahata, Emiko; Nikuni, Tetsuro; Griffin, Allan

    2011-11-15

    In Bose superfluids, the single-particle Green's function can be directly related to the superfluid velocity-velocity correlation function in the hydrodynamic regime. An explicit expression for the single-particle spectral density was originally written down by Hohenberg and Martin in 1965, starting from the two-fluid equations for a superfluid. We give a simple derivation of their results. Using these results, we calculate the relative weights of first and second sound modes in the single-particle spectral density as a function of temperature in a uniform Bose gas. We show that the second sound mode makes a dominant contribution to the single-particle spectrum in a relatively high-temperature region. We also discuss the possibility of experimental observation of the second sound mode in a Bose gas by photoemission spectroscopy.

  10. Thermodynamics of the low-density excluded-volume hadron gas

    NASA Astrophysics Data System (ADS)

    Redlich, Krzysztof; Zalewski, Kacper

    2016-01-01

    We consider the thermodynamics of excluded-volume particles at finite temperature and chemical potential in the low-density approximation. We assume Boltzmann statistics and study the influence of the excluded volume on an ideal gas thermodynamics at the same temperature, pressure, and number of particles. We show that considering the change of the free enthalpy due to the excluded volume, and using the Maxwell identities, one can derive relevant thermodynamic functions and parameters of multicomponent gases. The derivation is quite general, because particles may have different sizes and shapes which can also depend on their momenta. Besides its simplicity and generality, our approach has the advantage of eliminating the transcendental equations occurring in earlier studies. A representative example of the excluded-volume thermodynamics is the single-component gas of hard spheres. For this case, using a virial expansion, the validity limits of the low-density approximation are also discussed.

  11. The topological features of the intracule density of the uniform electron gas

    NASA Astrophysics Data System (ADS)

    Fradera, X.; Sarasola, C.; Ugalde, J. M.; Boyd, R. J.

    1999-05-01

    The Laplacian of the self-consistent-field radial intracule density of the uniform electron gas has been analyzed. It reaches its absolute maximum at the electron-electron coalescence point with a value of 0.3 ρ2, where ρ is the electron charge density. Then, it decreases as the interlectronic distance increases and has an attenuated oscillatory decay at larger distances. Further examination of this function yields an onion-like representation of the spatial structure of the uniform electron gas from the viewpoint of an arbitrary reference electron. Our calculations demonstrate that the radius of the first layer is 13.069 rs and the remaining layers obey a simple relationship with respect to the layer number with a separation of 6.065 rs between adjacent layers.

  12. Electron density and temperature of gas-temperature-dependent cryoplasma jet

    SciTech Connect

    Noma, Yuri; Hyuk Choi, Jai; Muneoka, Hitoshi; Terashima, Kazuo

    2011-03-01

    A microsize cryoplasma jet was developed and analyzed at plasma gas temperatures ranging from room temperature down to 5 K. Experimental results obtained from optical emission spectroscopy and current-voltage measurements indicate that the average electron density and electron temperature of the cryoplasma jet depend on the gas temperature. In particular, the electron temperature in the cryoplasma starts to decrease rapidly near 60 K from about 13 eV at 60 K to 2 eV at 5 K, while the electron density increases from about 10{sup 9} to approximately 10{sup 12} cm{sup -3} from room temperature to 5 K. This phenomenon induces an increase in the Coulomb interaction between electrons, which can be explained by the virial equation of state.

  13. Buoyancy Effects on Flow Structure and Instability of Low-Density Gas Jets

    NASA Technical Reports Server (NTRS)

    Pasumarthi, Kasyap Sriramachandra

    2004-01-01

    A low-density gas jet injected into a high-density ambient gas is known to exhibit self-excited global oscillations accompanied by large vortical structures interacting with the flow field. The primary objective of the proposed research is to study buoyancy effects on the origin and nature of the flow instability and structure in the near-field of low-density gas jets. Quantitative rainbow schlieren deflectometry, Computational fluid dynamics (CFD) and Linear stability analysis were the techniques employed to scale the buoyancy effects. The formation and evolution of vortices and scalar structure of the flow field are investigated in buoyant helium jets discharged from a vertical tube into quiescent air. Oscillations at identical frequency were observed throughout the flow field. The evolving flow structure is described by helium mole percentage contours during an oscillation cycle. Instantaneous, mean, and RMS concentration profiles are presented to describe interactions of the vortex with the jet flow. Oscillations in a narrow wake region near the jet exit are shown to spread through the jet core near the downstream location of the vortex formation. The effects of jet Richardson number on characteristics of vortex and flow field are investigated and discussed. The laminar, axisymmetric, unsteady jet flow of helium injected into air was simulated using CFD. Global oscillations were observed in the flow field. The computed oscillation frequency agreed qualitatively with the experimentally measured frequency. Contours of helium concentration, vorticity and velocity provided information about the evolution and propagation of vortices in the oscillating flow field. Buoyancy effects on the instability mode were evaluated by rainbow schlieren flow visualization and concentration measurements in the near-field of self-excited helium jets undergoing gravitational change in the microgravity environment of 2.2s drop tower at NASA John H. Glenn Research Center. The jet

  14. HIGH-DENSITY MOLECULAR GAS PROPERTIES OF THE STARBURST GALAXY NGC 1614 REVEALED WITH ALMA

    SciTech Connect

    Imanishi, Masatoshi; Nakanishi, Kouichiro

    2013-09-15

    We present the results of HCN/HCO{sup +}/HNC J = 4-3 transition line observations of the nearby starburst galaxy NGC 1614, obtained with ALMA Cycle 0. We find that high density molecular gas traced with these lines shows a velocity structure such that the northern (southern) side of the nucleus is redshifted (blueshifted) with respect to the nuclear velocity of this galaxy. The redshifted and blueshifted emission peaks are offset by {approx}0.''6 at the northern and southern sides of the nucleus, respectively. At these offset positions, observations at infrared >3 {mu}m indicate the presence of active dusty starbursts, supporting the picture that high-density molecular gas is the site of active starbursts. The enclosed dynamical mass within the central {approx}2'' in radius, derived from the dynamics of the high-density molecular gas, is {approx}10{sup 9} M{sub Sun }, which is similar to previous estimates. Finally, the HCN emission is weaker than HCO{sup +} but stronger than HNC for J = 4-3 for all starburst regions of NGC 1614, as seen for J = 1-0 transition lines in starburst-dominated galaxies.

  15. R-Z Density Mapping and CFD Simulation of Gas Puff Nozzle Flow

    NASA Astrophysics Data System (ADS)

    McKee, Erik; Valenzuela, Julio; Krasheninnikov, Igor; Frazier, Alister; Covington, Aaron; Beg, Farhat; Darling, Tim; Nevada Terawatt Facility Team; University of San Diego Team

    2015-11-01

    Laser induced fluorescence (LIF) is a technique in which a tracer is added to the gas flow for measurement of its spatial and temporal density profile. The Nd:YAG EKSPLA laser 20mJ/150ps at the fourth harmonic 266nm wavelength is focused down to a <1mm pencil beam to excite the acetone tracer. The use of anr ICCD gating camera is necessary because the 4ns short-lived fluorescence state is an order-of-magnitude dimmer than the 200us long-lived phosphorescence state. Mapping the density profile in time and space requires multiple shots. Once the temporal and spatial density profile is obtained, it can be used and benchmarked for two independent CFD software programs using transient solvers: OpenFOAM and FLUENT. The measurements and simulations serve as the initial conditions for (i) Gas Puff experiments that utilize special nozzle contours to inject the gas load between the electrode gap on pulsed-power machines and (ii) use with future MHD modeling efforts. Support for this work is provided by DOE/NNSA grant DE-NA0002075 and funded by the US Department of Energy, ARPA-E, Control Number 1184-1527.

  16. Testing the gas mass density profile of galaxy clusters with distance duality relation

    NASA Astrophysics Data System (ADS)

    Cao, Shuo; Biesiada, Marek; Zheng, Xiaogang; Zhu, Zong-Hong

    2016-03-01

    In this paper, assuming the validity of distance duality relation, η = DL(z)(1 + z)-2/DA(z) = 1, where DA(z) and DL(z) are the angular and the luminosity distance, respectively, we explore two kinds of gas mass density profiles of clusters: the isothermal β model and the non-isothermal double-β model. In our analysis, performed on 38 massive galaxy clusters observed by Chandra (within the redshift range of 0.14 < z < 0.89), we use two types of cluster gas mass fraction data corresponding to different mass density profiles fitted to the X-ray data. Using two general parameterizations of η(z) (phenomenologically allowing for distance duality violation), we find that the non-isothermal double-β model agrees better with the distance duality relation, while the isothermal β model tends to be marginally incompatible with the Etherington theorem at 68.3 per cent confidence level (CL). However, current accuracy of the data does not allow to distinguish between the two models for the gas-density distribution at a significant level.

  17. Density functional theory of gas-liquid phase separation in dilute binary mixtures.

    PubMed

    Okamoto, Ryuichi; Onuki, Akira

    2016-06-22

    We examine statics and dynamics of phase-separated states of dilute binary mixtures using density functional theory. In our systems, the difference of the solvation chemical potential between liquid and gas [Formula: see text] (the Gibbs energy of transfer) is considerably larger than the thermal energy [Formula: see text] for each solute particle and the attractive interaction among the solute particles is weaker than that among the solvent particles. In these conditions, the saturated vapor pressure increases by [Formula: see text], where [Formula: see text] is the solute density added in liquid. For [Formula: see text], phase separation is induced at low solute densities in liquid and the new phase remains in gaseous states, even when the liquid pressure is outside the coexistence curve of the solvent. This explains the widely observed formation of stable nanobubbles in ambient water with a dissolved gas. We calculate the density and stress profiles across planar and spherical interfaces, where the surface tension decreases with increasing interfacial solute adsorption. We realize stable solute-rich bubbles with radius about 30 nm, which minimize the free energy functional. We then study dynamics around such a bubble after a decompression of the surrounding liquid, where the bubble undergoes a damped oscillation. In addition, we present some exact and approximate expressions for the surface tension and the interfacial stress tensor. PMID:27115676

  18. In-Shell Bulk Density as an Estimator of Farmers Stock Grade Factors

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The objective of this research was to determine whether or not bulk density can be used to accurately estimate farmer stock grade factors such as total sound mature kernels and other kernels. Physical properties including bulk density, pod size and kernel size distributions are measured as part of t...

  19. Density-conserving shape factors for particle simulations in cylindrical and spherical coordinates

    SciTech Connect

    Ruyten, W.M. )

    1993-04-01

    It is shown that, in cylindrical and spherical coordinates, particle-to- grid weighting based on conventional particle-in-cell (PIC) and cloud-in-cell (CIC) shape factors results in non-uniform grid densities even for uniform particle distributions. Instead, alternative, density-conserving weighting schemes are discussed, including modified PIC and CIC weighting. 10 refs., 5 figs.

  20. Density-conserving shape factors for particle simulations in cylindrical and spherical coordinates

    NASA Technical Reports Server (NTRS)

    Ruyten, Wilhelmus M.

    1993-01-01

    It is established that a particle-to-grid weighting which is based on both conventional particle-in-cell (PIC) and cloud-in-cell (CIC) shape factors will yield nonuniform grid densities, even in the case of uniform particle distributions, in both cylindrical and spherical coordinates. In view of this, alternative density-conserving weighting schemes are discussed which encompass modified PIC and CIC weighting. These alternative shape factors are mathematically no more complicated than the conventional nondensity-conserving expressions.

  1. The factors controlling species density in herbaceous plant communities: An assessment

    USGS Publications Warehouse

    Grace, J.B.

    1999-01-01

    This paper evaluates both the ideas and empirical evidence pertaining to the control of species density in herbaceous plant communities. While most theoretical discussions of species density have emphasized the importance of habitat productivity and disturbance regimes, many other factors (e.g. species pools, plant litter accumulation, plant morphology) have been proposed to be important. A review of literature presenting observations on the density of species in small plots (in the vicinity of a few square meters or less), as well as experimental studies, suggests several generalizations: (1) Available data are consistent with an underlying unimodal relationship between species density and total community biomass. While variance in species density is often poorly explained by predictor variables, there is strong evidence that high levels of community biomass are antagonistic to high species density. (2) Community biomass is just one of several factors affecting variations in species density. Multivariate analyses typically explain more than twice as much variance in species density as can be explained by community biomass alone. (3) Disturbance has important and sometimes complex effects on species density. In general, the evidence is consistent with the intermediate disturbance hypothesis but exceptions exist and effects can be complex. (4) Gradients in the species pool can have important influences on patterns of species density. Evidence is mounting that a considerable amount of the observed variability in species density within a landscape or region may result from environmental effects on the species pool. (5) Several additional factors deserve greater consideration, including time lags, species composition, plant morphology, plant density and soil microbial effects. Based on the available evidence, a conceptual model of the primary factors controlling species density is presented here. This model suggests that species density is controlled by the effects of

  2. Gas Transport Parameters for Landfill Final Cover Soil: Measurements and Model Modification by Dry Bulk Density

    NASA Astrophysics Data System (ADS)

    Wickramarachchi, P. N.; Kawamoto, K.; Hamamoto, S.; Nagamori, M.; Moldrup, P.; Komatsu, T.

    2011-12-01

    Landfill sites have been emerging in greenhouse warming scenarios as a significant source of atmospheric methane (CH4). Until recently, landfill management strategies have mainly addressed the problem of preventing groundwater contamination and reduction of leachate generation. Being one of the largest sources of anthropogenic CH4 emission, the final cover system should also be designed for minimizing the greenhouse gases migration into the atmosphere or the areas surrounding the landfill while securing the hydraulic performance. Compared to the intensive research efforts on hydraulic performances of landfill final cover soil, few studies about gas transport characteristics of landfill cover soils have been done. However, recent soil-gas studies implied that the effects of soil physical properties such as bulk density (i.e., compaction level), soil particle size are key parameters to understand landfill gaseous performance. The gas exchange through the final cover soils is controlled by advective and diffusive gas transport. Air permeability (ka) governs the advective gas transport while the soil-gas diffusion coefficient (Dp) governs diffusive gas transport. In this study, the effects of compaction level and particle size fraction effects on ka and Dp for landfill final cover soil was investigated. The disturbed soil samples were taken from landfill final cover in Japan. A compaction tests were performed for the soil samples with two different size fractions (< 35 mm and < 2.0 mm). In the compaction tests at field water content , the soil samples were repacked into soil cores (i.d. 15-cm, length 12-cm, 2120 cm3) at two different compaction levels [(MP):2700 kN/m2 and (SP):600 kN/m2]. After the compaction tests, ka and Dp were measured and then samples were saturated and subsequently drained at different soil-water matric potential of 0.98, 2.94, 9.81, 1235 kPa and with air-dried and oven-dried conditions. Results showed that measured Dp and ka values for the

  3. Space Charge Neutralization of DEMO Relevant Negative Ion Beams at Low Gas Density

    SciTech Connect

    Surrey, Elizabeth; Porton, Michael

    2011-09-26

    The application of neutral beams to future power plant devices (DEMO) is dependent on achieving significantly improved electrical efficiency and the most promising route to achieving this is by implementing a photoneutralizer in place of the traditional gas neutralizer. A corollary of this innovation would be a significant reduction in the background gas density through which the beam is transported between the accelerator and the neutralizer. This background gas is responsible for the space charge neutralization of the beam, enabling distances of several metres to be traversed without significant beam expansion. This work investigates the sensitivity of a D{sup -} beam to reduced levels of space charge compensation for energies from 100 keV to 1.5 MeV, representative of a scaled prototype experiment, commissioning and full energy operation. A beam transport code, following the evolution of the phase space ellipse, is employed to investigate the effect of space charge on the beam optics. This shows that the higher energy beams are insensitive to large degrees of under compensation, unlike the lower energies. The probable degree of compensation at low gas density is then investigated through a simple, two component beam-plasma model that allows the potential to be negative. The degree of under-compensation is dependent on the positive plasma ion energy, one source of which is dissociation of the gas by the beam. The subsequent space charge state of the beam is shown to depend upon the relative times for equilibration of the dissociation energy and ionization by the beam ions.

  4. Effects of dry bulk density and particle size fraction on gas transport parameters in variably saturated landfill cover soil

    SciTech Connect

    Wickramarachchi, Praneeth; Kawamoto, Ken; Hamamoto, Shoichiro; Nagamori, Masanao; Moldrup, Per; Komatsu, Toshiko

    2011-12-15

    Highlights: > The effects of soil physical properties on gas transport parameters were investigated. > Higher values of D{sub p} and k{sub a} exhibited in the '+gravel' than the '-gravel' fraction at same soil-air content ({epsilon}). > Recent power law models for D{sub p} (WLR) and k{sub a} (RPL) were modified. > Model parameters were linearly related to easily measurable dry bulk density ({rho}{sub b}). - Abstract: Landfill sites are emerging in climate change scenarios as a significant source of greenhouse gases. The compacted final soil cover at landfill sites plays a vital role for the emission, fate and transport of landfill gases. This study investigated the effects of dry bulk density, {rho}{sub b}, and particle size fraction on the main soil-gas transport parameters - soil-gas diffusivity (D{sub p}/D{sub o}, ratio of gas diffusion coefficients in soil and free air) and air permeability (k{sub a}) - under variably-saturated moisture conditions. Soil samples were prepared by three different compaction methods (Standard and Modified Proctor compaction, and hand compaction) with resulting {rho}{sub b} values ranging from 1.40 to 2.10 g cm{sup -3}. Results showed that D{sub p} and k{sub a} values for the '+gravel' fraction (<35 mm) became larger than for the '-gravel' fraction (<2 mm) under variably-saturated conditions for a given soil-air content ({epsilon}), likely due to enhanced gas diffusion and advection through less tortuous, large-pore networks. The effect of dry bulk density on D{sub p} and k{sub a} was most pronounced for the '+gravel' fraction. Normalized ratios were introduced for all soil-gas parameters: (i) for gas diffusivity D{sub p}/D{sub f}, the ratio of measured D{sub p} to D{sub p} in total porosity (f), (ii) for air permeability k{sub a}/k{sub a,pF4.1}, the ratio of measured k{sub a} to k{sub a} at 1235 kPa matric potential (=pF 4.1), and (iii) for soil-air content, the ratio of soil-air content ({epsilon}) to total porosity (f) (air

  5. Microstructural analysis of mass transport phenomena in gas diffusion media for high current density operation in PEM fuel cells

    NASA Astrophysics Data System (ADS)

    Kotaka, Toshikazu; Tabuchi, Yuichiro; Mukherjee, Partha P.

    2015-04-01

    Cost reduction is a key issue for commercialization of fuel cell electric vehicles (FCEV). High current density operation is a solution pathway. In order to realize high current density operation, it is necessary to reduce mass transport resistance in the gas diffusion media commonly consisted of gas diffusion layer (GDL) and micro porous layer (MPL). However, fundamental understanding of the underlying mass transport phenomena in the porous components is not only critical but also not fully understood yet due to the inherent microstructural complexity. In this study, a comprehensive analysis of electron and oxygen transport in the GDL and MPL is conducted experimentally and numerically with three-dimensional (3D) microstructural data to reveal the structure-transport relationship. The results reveal that the mass transport in the GDL is strongly dependent on the local microstructural variations, such as local pore/solid volume fractions and connectivity. However, especially in the case of the electrical conductivity of MPL, the contact resistance between carbon particles is the dominant factor. This suggests that reducing the contact resistance between carbon particles and/or the number of contact points along the transport pathway can improve the electrical conductivity of MPL.

  6. Velocity and density profiles of granular flow in channels using a lattice gas automaton

    SciTech Connect

    Peng, G.; Ohta, T.

    1997-06-01

    We have performed two-dimensional lattice-gas-automaton simulations of granular flow between two parallel planes. We find that the velocity profiles have nonparabolic distributions, while simultaneously the density profiles are nonuniform. Under nonslip boundary conditions, deviation of velocity profiles from the parabolic form of Newtonian fluids is found to be characterized solely by ratio of maximal velocity at the center to the average velocity, though the ratio depends on the model parameters in a complex manner. We also find that the maximal velocity (u{sub max}) at the center is a linear function of the driving force (g) as u{sub max}={alpha}g{minus}{delta} with nonzero {delta} in contrast with Newtonian fluids. Regarding density profiles, we observe that densities near the boundaries are higher than those in the center. The width of higher densities (above the average density) relative to the channel width is a decreasing function of a variable which scales with the driving force (g), energy dissipation parameter ({epsilon}), and the width of the system (L) as g{sup {mu}}L{sup {nu}}/{epsilon} with exponents {mu}=1.4{plus_minus}0.1 and {nu}=0.5{plus_minus}0.1. A phenomenological theory based on a scaling argument is presented to interpret these findings. {copyright} {ital 1997} {ital The American Physical Society}

  7. GAS SURFACE DENSITY, STAR FORMATION RATE SURFACE DENSITY, AND THE MAXIMUM MASS OF YOUNG STAR CLUSTERS IN A DISK GALAXY. I. THE FLOCCULENT GALAXY M 33

    SciTech Connect

    Gonzalez-Lopezlira, Rosa A.; Pflamm-Altenburg, Jan; Kroupa, Pavel

    2012-12-20

    We analyze the relationship between maximum cluster mass M{sub max} and surface densities of total gas ({Sigma}{sub gas}), molecular gas ({Sigma}{sub H{sub 2}}), and star formation rate ({Sigma}{sub SFR}) in the flocculent galaxy M 33, using published gas data and a catalog of more than 600 young star clusters in its disk. By comparing the radial distributions of gas and most massive cluster masses, we find that M{sub max}{proportional_to}{Sigma}{sup 4.7{+-}0.4}{sub gas}, M{sub max}{proportional_to}{Sigma}{sup 1.3{+-}0.1}{sub H{sub 2}}, and M{sub max}{proportional_to}{Sigma}{sup 1.0{+-}0.1}{sub SFR}. We rule out that these correlations result from the size of the sample; hence, the change of the maximum cluster mass must be due to physical causes.

  8. Body density and diving gas volume of the northern bottlenose whale (Hyperoodon ampullatus)

    PubMed Central

    Miller, Patrick; Narazaki, Tomoko; Isojunno, Saana; Aoki, Kagari; Smout, Sophie; Sato, Katsufumi

    2016-01-01

    ABSTRACT Diving lung volume and tissue density, reflecting lipid store volume, are important physiological parameters that have only been estimated for a few breath-hold diving species. We fitted 12 northern bottlenose whales with data loggers that recorded depth, 3-axis acceleration and speed either with a fly-wheel or from change of depth corrected by pitch angle. We fitted measured values of the change in speed during 5 s descent and ascent glides to a hydrodynamic model of drag and buoyancy forces using a Bayesian estimation framework. The resulting estimate of diving gas volume was 27.4±4.2 (95% credible interval, CI) ml kg−1, closely matching the measured lung capacity of the species. Dive-by-dive variation in gas volume did not correlate with dive depth or duration. Estimated body densities of individuals ranged from 1028.4 to 1033.9 kg m−3 at the sea surface, indicating overall negative tissue buoyancy of this species in seawater. Body density estimates were highly precise with ±95% CI ranging from 0.1 to 0.4 kg m−3, which would equate to a precision of <0.5% of lipid content based upon extrapolation from the elephant seal. Six whales tagged near Jan Mayen (Norway, 71°N) had lower body density and were closer to neutral buoyancy than six whales tagged in the Gully (Nova Scotia, Canada, 44°N), a difference that was consistent with the amount of gliding observed during ascent versus descent phases in these animals. Implementation of this approach using longer-duration tags could be used to track longitudinal changes in body density and lipid store body condition of free-ranging cetaceans. PMID:27296044

  9. Body density and diving gas volume of the northern bottlenose whale (Hyperoodon ampullatus).

    PubMed

    Miller, Patrick; Narazaki, Tomoko; Isojunno, Saana; Aoki, Kagari; Smout, Sophie; Sato, Katsufumi

    2016-08-15

    Diving lung volume and tissue density, reflecting lipid store volume, are important physiological parameters that have only been estimated for a few breath-hold diving species. We fitted 12 northern bottlenose whales with data loggers that recorded depth, 3-axis acceleration and speed either with a fly-wheel or from change of depth corrected by pitch angle. We fitted measured values of the change in speed during 5 s descent and ascent glides to a hydrodynamic model of drag and buoyancy forces using a Bayesian estimation framework. The resulting estimate of diving gas volume was 27.4±4.2 (95% credible interval, CI) ml kg(-1), closely matching the measured lung capacity of the species. Dive-by-dive variation in gas volume did not correlate with dive depth or duration. Estimated body densities of individuals ranged from 1028.4 to 1033.9 kg m(-3) at the sea surface, indicating overall negative tissue buoyancy of this species in seawater. Body density estimates were highly precise with ±95% CI ranging from 0.1 to 0.4 kg m(-3), which would equate to a precision of <0.5% of lipid content based upon extrapolation from the elephant seal. Six whales tagged near Jan Mayen (Norway, 71°N) had lower body density and were closer to neutral buoyancy than six whales tagged in the Gully (Nova Scotia, Canada, 44°N), a difference that was consistent with the amount of gliding observed during ascent versus descent phases in these animals. Implementation of this approach using longer-duration tags could be used to track longitudinal changes in body density and lipid store body condition of free-ranging cetaceans. PMID:27296044

  10. Molecular density functional theory for water with liquid-gas coexistence and correct pressure

    SciTech Connect

    Jeanmairet, Guillaume Levesque, Maximilien; Sergiievskyi, Volodymyr; Borgis, Daniel

    2015-04-21

    The solvation of hydrophobic solutes in water is special because liquid and gas are almost at coexistence. In the common hypernetted chain approximation to integral equations, or equivalently in the homogenous reference fluid of molecular density functional theory, coexistence is not taken into account. Hydration structures and energies of nanometer-scale hydrophobic solutes are thus incorrect. In this article, we propose a bridge functional that corrects this thermodynamic inconsistency by introducing a metastable gas phase for the homogeneous solvent. We show how this can be done by a third order expansion of the functional around the bulk liquid density that imposes the right pressure and the correct second order derivatives. Although this theory is not limited to water, we apply it to study hydrophobic solvation in water at room temperature and pressure and compare the results to all-atom simulations. The solvation free energy of small molecular solutes like n-alkanes and hard sphere solutes whose radii range from angstroms to nanometers is now in quantitative agreement with reference all atom simulations. The macroscopic liquid-gas surface tension predicted by the theory is comparable to experiments. This theory gives an alternative to the empirical hard sphere bridge correction used so far by several authors.

  11. Optimizing the hohlraum gas density for better symmetry control of indirect drive implosion experiments

    NASA Astrophysics Data System (ADS)

    Izumi, Nobuhiko; Hall, G. N.; Nagel, S. R.; Khan, S.; Rygg, R. R.; MacKinnon, A. J.; Ho, D. D.; Berzak Hopkins, L.; Jones, O. S.; Town, R. P. J.; Bradley, D. K.

    2014-10-01

    To achieve a spherically symmetric implosion, control of drive uniformity is essential. Both the ablation pressure and the mass ablation rate on the capsule surface should be made as uniform as possible for the duration of the drive. For an indirect drive implosion, the drive uniformity changes during the pulse because of: (1) the dynamic movement of the laser spots due to blow-off of the hohlraum wall, and (2) cross-beam energy transfer caused by laser-plasma interaction in the hohlraum. To tamp the wall blow-off, we use gas filled hohlraums. The cross-beam energy transfer can be controlled by applying a wave length separation between the cones of the laser beams. However, both of those dynamic effects are sensitive to the initial density of the hohlraum gas fill. To assess this, we performed implosion experiments with different hohlraum gas densities and tested the effect on drive asymmetry. The uniformity of the acceleration was measured by in-flight x-ray backlit imaging of the capsule. The uniformity of the core assembly was observed by imaging the self emission x-ray from the core. We will report on the experimental results and compare them to hydrodynamic simulations. Prepared by LLNL under Contract DE-AC52-07NA27344. LLNL-ABS-626372.

  12. Validity of power functionals for a homogeneous electron gas in reduced-density-matrix-functional theory

    NASA Astrophysics Data System (ADS)

    Putaja, A.; Eich, F. G.; Baldsiefen, T.; Räsänen, E.

    2016-03-01

    Physically valid and numerically efficient approximations for the exchange and correlation energy are critical for reduced-density-matrix-functional theory to become a widely used method in electronic structure calculations. Here we examine the physical limits of power functionals of the form f (n ,n') =(nn')α for the scaling function in the exchange-correlation energy. To this end we obtain numerically the minimizing momentum distributions for the three- and two-dimensional homogeneous electron gas, respectively. In particular, we examine the limiting values for the power α to yield physically sound solutions that satisfy the Lieb-Oxford lower bound for the exchange-correlation energy and exclude pinned states with the condition n (k )<1 for all wave vectors k . The results refine the constraints previously obtained from trial momentum distributions. We also compute the values for α that yield the exact correlation energy and its kinetic part for both the three- and two-dimensional electron gas. In both systems, narrow regimes of validity and accuracy are found at α ≳0.6 and at rs≳10 for the density parameter, corresponding to relatively low densities.

  13. Simulations of gas puff effects on edge density and ICRF coupling in ASDEX upgrade using EMC3-Eirene

    SciTech Connect

    Zhang, W.; Lunt, T.; Bobkov, V.; Coster, D.; Brida, D.; Noterdaeme, J.-M.; Jacquet, P.; Feng, Y.

    2015-12-10

    Simulations were carried out with the 3D plasma transport code EMC3-EIRENE, to study the deuterium gas (D{sub 2}) puff effects on edge density and the coupling of Ion Cyclotron Range of Frequency (ICRF) power in ASDEX Upgrade. Firstly we simulated an inter-ELM phase of an H-mode discharge with a moderate (1.2 × 10{sup 22} electrons/s) lower divertor gas puff. Then we changed the gas source positions to the mid-plane or top of machine while keeping other conditions the same. Cases with different mid-plane or top gas valves are investigated. Our simulations indicate that compared to lower divertor gas puffing, the mid-plane gas puff can enhance the local density in front of the antennas most effectively, while a rather global (toroidally uniform) but significantly smaller enhancement is found for top gas puffing. Our results show quantitative agreement with the experiments.

  14. Effective mass and Landé g-factor in Si-MOSFETs near the critical density

    NASA Astrophysics Data System (ADS)

    Limouny, Lhoussine; El Kaaouachi, Abdelhamid; Liang, Chi-Te

    2014-02-01

    We analyze the electrical resistivity and conductivity of a dilute two-dimensional electron gas (2DEG) in a Si metal-oxide-semiconductor field-effect transistor. When a magnetic field is applied parallel to the plane of the 2DEG, a signature of complete spin polarization, as evidenced by the saturation of the resistivity, is observed. We measured the effective mass and the Landé g-factor near the metal-insulator transition (MIT) and found that the Landé g-factor remained almost constant and close to its value in bulk silicon. In contrast, we have observed a sharp increase in the effective mass near the critical density of the MIT. Our new results suggest that the sharp increase in the previously-observed spin susceptibility is mainly due to the enhanced effective mass. Therefore, renormalization of the effective mass could play an important role in a dilute spinpolarized 2DEG. The data indicate that electron-electron interactions strongly modify the effective mass but only weakly affect the g-factor in a dilute 2DEG. Moreover, our results indicate that B c , which corresponds to the magnetic field at which the magnetoresistivity reaches saturation, vanishes at a characteristic density n χ higher than the critical density n c of the MIT. This is in contrast to the existing experimental results, and further studies are required if this discrepancy is to be understood.

  15. Dust and gas density evolution at a radial pressure bump in protoplanetary disks

    NASA Astrophysics Data System (ADS)

    Taki, Tetsuo; Fujimoto, Masaki; Ida, Shigeru

    2016-06-01

    We investigate the simultaneous evolution of dust and gas density profiles at a radial pressure bump located in a protoplanetary disk. If dust particles are treated as test particles, a radial pressure bump traps dust particles that drift radially inward. As the dust particles become more concentrated at the gas pressure bump, however, the drag force from dust to gas (back-reaction), which is ignored in a test-particle approach, deforms the pressure bump. We find that the pressure bump is completely deformed by the back-reaction when the dust-to-gas mass ratio reaches ~ 1 for a slower bump restoration. The direct gravitational instability of dust particles is inhibited by the bump destruction. In the dust-enriched region, the radial pressure support becomes ~ 10-100 times lower than the global value set initially. Although the pressure bump is a favorable place for streaming instability (SI), the flattened pressure gradient inhibits SI from forming large particle clumps corresponding to 100-1000 km sized bodies, which has been previously proposed. If SI occurs there, the dust clumps formed would be 10-100 times smaller, that is, of about 1-100 km.

  16. Spontaneous separation of large-spin Fermi gas in the harmonic trap: a density functional study

    PubMed Central

    Sun, Zongli; Gu, Qiang

    2016-01-01

    The component separation of the trapped large-spin Fermi gas is studied within density functional theory. The ground state and ferromagnetic transition in the gas, with and without the spin mixing collision, are calculated. In the absence of spin mixing, two patterns of separation are observed as the interaction between atoms increases, whereas only one of them corresponds to a ferromagnetic transition. The phase diagram suggests that the pattern which the system chooses depends on the interaction strength in the collision channels. With the presence of spin mixing, the distribution of phase region changes because of the interplay between different collision channels. Specifically, the spin exchange benefits the FM transition, while it suppresses the component separation of CS-II pattern. PMID:27549012

  17. Column Density Maps of the I-GALFA HI Survey: Evidence for Dark Gas?

    NASA Astrophysics Data System (ADS)

    Gibson, Steven J.; Koo, B.; Douglas, K. A.; Newton, J. H.; Peek, J. E.; Hughes, J. M.; Spraggs, M.; Park, G.; Kang, J.; Heiles, C. E.; Korpela, E. J.

    2014-01-01

    The gas in galactic disks, including our own, occurs in a wide range of temperatures and densities, most of which are unsuitable for star formation. Somehow, diffuse atomic clouds are collected into colder, denser molecular clouds that can collapse under their own gravity. The molecular condensation process is not directly observable, and the gas itself is often ``dark'' to standard probes like optically thin HI 21cm emission or the CO 2.6mm line. However, the presence of this dark gas can often be inferred from infrared dust emission in excess of what is expected for the observed HI and CO content. We have mapped apparent HI column densities in the Inner-Galaxy Arecibo L-band Feed Array (I-GALFA) survey, which covers a 1600 square degree region at 4-arcminute resolution in the first Galactic quadrant. We compare these ``naive'' HI columns to others derived from Planck first-release CO and dust maps and NE2001 model dispersion measures to identify a number of areas with potentially significant dark gas. We discuss whether optically thick HI or CO-free H2 is more likely to dominate the dark column, and we consider the effects of possible biases on our results. We acknowledge support from the National Science Foundation, the NASA Kentucky Space Grant Consortium, Western Kentucky University, and the Gatton Academy. I-GALFA (www.naic.edu igalfa) is a GALFA-HI survey observed with the 7-beam ALFA receiver on the 305-meter William E. Gordon Telescope. The Arecibo Observatory is a U.S. National Science Foundation facility operated under sequential cooperative agreements with Cornell University and SRI International, the latter in alliance with the Ana G. Mendez-Universidad Metropolitana and the Universities Space Research Association.

  18. Supersonic beams at high particle densities: model description beyond the ideal gas approximation.

    PubMed

    Christen, Wolfgang; Rademann, Klaus; Even, Uzi

    2010-10-28

    Supersonic molecular beams constitute a very powerful technique in modern chemical physics. They offer several unique features such as a directed, collision-free flow of particles, very high luminosity, and an unsurpassed strong adiabatic cooling during the jet expansion. While it is generally recognized that their maximum flow velocity depends on the molecular weight and the temperature of the working fluid in the stagnation reservoir, not a lot is known on the effects of elevated particle densities. Frequently, the characteristics of supersonic beams are treated in diverse approximations of an ideal gas expansion. In these simplified model descriptions, the real gas character of fluid systems is ignored, although particle associations are responsible for fundamental processes such as the formation of clusters, both in the reservoir at increased densities and during the jet expansion. In this contribution, the various assumptions of ideal gas treatments of supersonic beams and their shortcomings are reviewed. It is shown in detail that a straightforward thermodynamic approach considering the initial and final enthalpy is capable of characterizing the terminal mean beam velocity, even at the liquid-vapor phase boundary and the critical point. Fluid properties are obtained using the most accurate equations of state available at present. This procedure provides the opportunity to naturally include the dramatic effects of nonideal gas behavior for a large variety of fluid systems. Besides the prediction of the terminal flow velocity, thermodynamic models of isentropic jet expansions permit an estimate of the upper limit of the beam temperature and the amount of condensation in the beam. These descriptions can even be extended to include spinodal decomposition processes, thus providing a generally applicable tool for investigating the two-phase region of high supersaturations not easily accessible otherwise. PMID:20961156

  19. Liquid polymorphism and density anomaly in a three-dimensional associating lattice gas.

    PubMed

    Girardi, Mauricio; Balladares, Aline L; Henriques, Vera B; Barbosa, Marcia C

    2007-02-14

    The authors investigate the phase diagram of a three-dimensional associating lattice gas (ALG) model. This model combines orientational icelike interactions and "van der Waals" that might be repulsive, representing, in this case, a penalty for distortion of hydrogen bonds. These interactions can be interpreted as two competing distances, making the connection between this model and continuous isotropic soft-core potentials. The authors present Monte Carlo studies of the ALG model showing the presence of two liquid phases, two critical points, and density anomaly. PMID:17313225

  20. Two-Dimensional Plasma Density Distributions in Low-Pressure Gas Discharges

    SciTech Connect

    Berlin, E.V.; Dvinin, S.A.; Mikheev, V.V.; Omarov, M.O.; Sviridkina, V. S.

    2004-12-15

    The plasma density distribution in a two-dimensional nonuniform positive column of a low-pressure gas discharge is studied in the hydrodynamic approximation with allowance for ion inertia. Exact solutions are derived for discharges in a rectangular and a cylindrical chamber. Asymptotic solutions near the coordinate origin and near the critical surface are considered. It is shown that, for potential plasma flows, the flow velocity component normal to the plasma boundary is equal to the ion acoustic velocity. The results obtained can be used to analyze the processes occurring in low-pressure plasmochemical reactors.

  1. Fission-gas release from uranium nitride at high fission rate density

    NASA Technical Reports Server (NTRS)

    Weinstein, M. B.; Kirchgessner, T. A.; Tambling, T. N.

    1973-01-01

    A sweep gas facility has been used to measure the release rates of radioactive fission gases from small UN specimens irradiated to 8-percent burnup at high fission-rate densities. The measured release rates have been correlated with an equation whose terms correspond to direct recoil release, fission-enhanced diffusion, and atomic diffusion (a function of temperature). Release rates were found to increase linearly with burnups between 1.5 and 8 percent. Pore migration was observed after operation at 1550 K to over 6 percent burnup.

  2. The application of laser Rayleigh scattering to gas density measurements in hypersonic helium flows

    NASA Technical Reports Server (NTRS)

    Hoppe, J. C.; Honaker, W. C.

    1979-01-01

    Measurements of the mean static free-stream gas density have been made in two Langley Research Center helium facilities, the 3-inch leg of the high-Reynolds-number helium complex and the 22-inch hypersonic helium tunnel. Rayleigh scattering of a CW argon ion laser beam at 514.5 nm provided the basic physical mechanism. The behavior of the scattered signal was linear, confirmed by a preliminary laboratory study. That study also revealed the need to introduce baffles to reduce stray light. A relatively simple optical system and associated photon-counting electronics were utilized to obtain data for densities from 10 to the 23rd to 10 to the 25th per cu m. The major purpose, to confirm the applicability of this technique in the hypersonic helium flow, was accomplished.

  3. The high density phase of the k-NN hard core lattice gas model

    NASA Astrophysics Data System (ADS)

    Nath, Trisha; Rajesh, R.

    2016-07-01

    The k-NN hard core lattice gas model on a square lattice, in which the first k next nearest neighbor sites of a particle are excluded from being occupied by another particle, is the lattice version of the hard disc model in two dimensional continuum. It has been conjectured that the lattice model, like its continuum counterpart, will show multiple entropy-driven transitions with increasing density if the high density phase has columnar or striped order. Here, we determine the nature of the phase at full packing for k up to 820 302 . We show that there are only eighteen values of k, all less than k  =  4134, that show columnar order, while the others show solid-like sublattice order.

  4. Long-range density-matrix-functional theory: Application to a modified homogeneous electron gas

    SciTech Connect

    Pernal, Katarzyna

    2010-05-15

    We propose a method that employs functionals of the one-electron reduced density matrix (density matrix) to capture long-range effects of electron correlation. The complementary short-range regime is treated with density functionals. In an effort to find approximations for the long-range density-matrix functional, a modified power functional is applied to the homogeneous electron gas with Coulomb interactions replaced by their corresponding long-range counterparts. For the power {beta}=1/2 and the range-separation parameter {omega}=1/r{sub s}, the functional reproduces the correlation and the kinetic correlation energies with a remarkable accuracy for intermediate and large values of r{sub s}. Analysis of the Euler equation corresponding to this functional reveals correct r{sub s} expansion of the correlation energy in the limit of large r{sub s}. The first expansion coefficient is in very good agreement with that obtained from the modified Wigner-Seitz model.

  5. Standardisation of gas mixtures for estimating carbon monoxide transfer factor.

    PubMed Central

    Kendrick, A. H.; Laszlo, G.

    1993-01-01

    BACKGROUND--The American Thoracic Society recommends that the inspired concentration used for the estimation of carbon monoxide transfer factor (TLCO) mixture should be 0.25-0.35% carbon monoxide, 10-14% helium, 17-21% oxygen, balance nitrogen. Inspired oxygen influences alveolar oxygen and hence carbon monoxide uptake, such that transfer factor increases by 0.35% per mm Hg decrease in alveolar oxygen. To aid in the standardisation of TLCO either a known inspired oxygen concentration should be used, or TLCO should be corrected to a standard inspired oxygen concentration. The range of gas mixtures used in practice and the implications for cost and accuracy have been investigated. METHODS--A questionnaire was sent to 185 respiratory units in the UK requesting information on (1) the method used to estimate TLCO, (2) the manufacturer of the equipment, (3) the mixture used, (4) whether "medical quality" gas was ordered, and (5) the level of satisfaction with supplier service. RESULTS--Replies were received from 106 units. Most used the single breath breath holding method for which 17 different test mixtures were ordered. One unit also used the single breath exhalation method. Inspired oxygen ranged from 17.94% to 25%, giving a wide variation in alveolar oxygen and hence TLCO. Forty seven units ordered a specific inspired oxygen, the rest ordering "air" as balance. The cost per litre of gas varied greatly, with the mixture 14% helium, 0.28% carbon monoxide, balance air (17.9% oxygen) and 10% helium, 0.28% carbon monoxide, balance air (18.8% oxygen) being cheapest to produce. Ordering a specific inspired oxygen concentration increased the cost. Large cylinders of gas were cheaper for the same mixture. The mixture for the exhalation method was the most expensive. Sixty seven units ordered "medical quality" gas and six assumed this was supplied. Twenty nine (27%) were dissatisfied with their supplier due to (1) poor service, (2) long delivery times, (3) costs, or (4

  6. Accurate ab initio potential for the krypton dimer and transport properties of the low-density krypton gas.

    PubMed

    Waldrop, Jonathan M; Song, Bo; Patkowski, Konrad; Wang, Xiaopo

    2015-05-28

    A new highly accurate potential energy curve for the krypton dimer was constructed using coupled-cluster calculations up to the singles, doubles, triples, and perturbative quadruples level, including corrections for core-core and core-valence correlation and for relativistic effects. The ab initio data points were fitted to an analytic potential which was used to compute the most important transport properties of the krypton gas. The viscosity, thermal conductivity, self-diffusion coefficient, and thermal diffusion factor were calculated by the kinetic theory at low density and temperatures from 116 to 5000 K. The comparisons with literature experimental data as well as with values from other pair potentials indicate that our new potential is superior to all previous ones. The transport property values computed in this work are recommended as standard values over the complete temperature range. PMID:26026447

  7. Factors associated with low bone density in patients referred for assessment of bone health

    PubMed Central

    2013-01-01

    Background To identify factors that predict low bone mineral density (BMD) in pediatric patients referred for dual-energy x-ray absorptiometry assessments. Methods This is a retrospective cohort study of 304 children and adolescents referred for dual-energy x-ray absorptiometry assessments at a tertiary care center. Outcomes included risk factors which predicted a significant low bone density for age, defined as BMD Z-score ≤ -2.0 SD. A univariate analysis involved Chi-square, Fisher’s Exact test, and analysis of variance, and multivariate logistic regression models were constructed to determine predictors of low bone mineral density. Results In the multivariate logistic regression model, predictors of low bone mineral density included low body mass index Z-score (odds ratio 0.52, 95% confidence interval 0.39 – 0.69), low height Z-score (OR 0.71, 95% CI 0.57 – 0.88), vitamin D insufficiency (OR 3.97, 95% CI 2.08 – 7.59), and history of bone marrow transplant (OR 5.78, 95% CI 1.00 – 33.45). Conclusions Underlying health problems and associated treatments can impair bone mineral accrual. We identified risk factors most predictive of low bone mineral density in subjects referred for bone density measurement. Recognition of these factors may allow for earlier assessment to maximize bone mass in at-risk children. PMID:23388217

  8. Effects of hepatocyte growth factor on glutathione synthesis, growth, and apoptosis is cell density-dependent

    SciTech Connect

    Yang Heping; Magilnick, Nathaniel; Xia Meng; Lu, Shelly C.

    2008-01-15

    Hepatocyte growth factor (HGF) is a potent hepatocyte mitogen that exerts opposing effects depending on cell density. Glutathione (GSH) is the main non-protein thiol in mammalian cells that modulates growth and apoptosis. We previously showed that GSH level is inversely related to cell density of hepatocytes and is positively related to growth. Our current work examined whether HGF can modulate GSH synthesis in a cell density-dependent manner and how GSH in turn influence HGF's effects. We found HGF treatment of H4IIE cells increased cell GSH levels only under subconfluent density. The increase in cell GSH under low density was due to increased transcription of GSH synthetic enzymes. This correlated with increased protein levels and nuclear binding activities of c-Jun, c-Fos, p65, p50, Nrf1 and Nrf2 to the promoter region of these genes. HGF acts as a mitogen in H4IIE cells under low cell density and protects against tumor necrosis factor {alpha} (TNF{alpha})-induced apoptosis by limiting JNK activation. However, HGF is pro-apoptotic under high cell density and exacerbates TNF{alpha}-induced apoptosis by potentiating JNK activation. The increase in cell GSH under low cell density allows HGF to exert its full mitogenic effect but is not necessary for its anti-apoptotic effect.

  9. Technical Factors Influencing Cone Packing Density Estimates in Adaptive Optics Flood Illuminated Retinal Images

    PubMed Central

    Lombardo, Marco; Serrao, Sebastiano; Lombardo, Giuseppe

    2014-01-01

    Purpose To investigate the influence of various technical factors on the variation of cone packing density estimates in adaptive optics flood illuminated retinal images. Methods Adaptive optics images of the photoreceptor mosaic were obtained in fifteen healthy subjects. The cone density and Voronoi diagrams were assessed in sampling windows of 320×320 µm, 160×160 µm and 64×64 µm at 1.5 degree temporal and superior eccentricity from the preferred locus of fixation (PRL). The technical factors that have been analyzed included the sampling window size, the corrected retinal magnification factor (RMFcorr), the conversion from radial to linear distance from the PRL, the displacement between the PRL and foveal center and the manual checking of cone identification algorithm. Bland-Altman analysis was used to assess the agreement between cone density estimated within the different sampling window conditions. Results The cone density declined with decreasing sampling area and data between areas of different size showed low agreement. A high agreement was found between sampling areas of the same size when comparing density calculated with or without using individual RMFcorr. The agreement between cone density measured at radial and linear distances from the PRL and between data referred to the PRL or the foveal center was moderate. The percentage of Voronoi tiles with hexagonal packing arrangement was comparable between sampling areas of different size. The boundary effect, presence of any retinal vessels, and the manual selection of cones missed by the automated identification algorithm were identified as the factors influencing variation of cone packing arrangements in Voronoi diagrams. Conclusions The sampling window size is the main technical factor that influences variation of cone density. Clear identification of each cone in the image and the use of a large buffer zone are necessary to minimize factors influencing variation of Voronoi diagrams of the cone

  10. Dynamical correlation effects on structure factor of spin-polarized two-dimensional electron gas

    SciTech Connect

    Singh, Gurvinder; Moudgil, R. K.; Kumar, Krishan; Garg, Vinayak

    2015-06-24

    We report a theoretical study on static density structure factor S(q) of a spin-polarized two-dimensional electron gas over a wide range of electron number density r{sub s}. The electron correlations are treated within the dynamical version of the self-consistent mean-field theory of Singwi, Tosi, Land, and Sjolander, the so-called qSTLS approach. The calculated S(q) exhibits almost perfect agreement with the quantum Monte Carlo simulation data at r{sub s}=1. However, the extent of agreement somewhat diminishes with increasing r{sub s}, particularly for q around 2k{sub F}. Seen in conjunction with the success of qSTLS theory in dealing with correlations in the unpolarized phase, our study suggests that the otherwise celebrated qSTLS theory is not that good in treating the like-spin correlations.

  11. Correlation between density and oxidation temperature for pyrolytic-gas passivated ultrathin silicon oxide films

    NASA Astrophysics Data System (ADS)

    Yamada, Hiroshi

    2004-01-01

    Pyrolytic-gas passivation (PGP) with a small amount nitrogen gas enhances the breakdown reliability of silicon oxide gate films. To clarify the reliability retention of the PGP-grown films oxidized at low temperature, densities (ρox's) of the 3.5-6.5-nm-thick PGP-grown films on Si(100) oxidized at 700-900 °C were investigated. Since ρox's correlate well with the reliability and are useful as an index of the intrinsic structural characteristics of the films. Moreover, changes in ρox and nitrogen content corresponding to oxidation temperature are similar to those in breakdown reliability and interface state density (Dit), respectively. In addition, ρox's of the 700 °C-grown PGP films do not deteriorate as much when compared with those of the films grown by normal ultradry oxidation at 800 °C and their Dit's are less than about 6×1010/eV cm2. This suggests that PGP probably improves the reliability by generating the higher-ρox microscopic structure with few Si dangling bonds and effective passivation. .

  12. High-speed digital holography for neutral gas and electron density imaging.

    PubMed

    Granstedt, E M; Thomas, C E; Kaita, R; Majeski, R; Baylor, L R; Meitner, S J; Combs, S K

    2016-05-01

    An instrument was developed using digital holographic reconstruction of the wavefront from a CO2 laser imaged on a high-speed commercial IR camera. An acousto-optic modulator is used to generate 1-25 μs pulses from a continuous-wave CO2 laser, both to limit the average power at the detector and also to freeze motion from sub-interframe time scales. Extensive effort was made to characterize and eliminate noise from vibrations and second-surface reflections. Mismatch of the reference and object beam curvature initially contributed substantially to vibrational noise, but was mitigated through careful positioning of identical imaging lenses. Vibrational mode amplitudes were successfully reduced to ≲1 nm for frequencies ≳50 Hz, and the inter-frame noise across the 128 × 128 pixel window which is typically used is ≲2.5 nm. To demonstrate the capabilities of the system, a piezo-electric valve and a reducing-expanding nozzle were used to generate a super-sonic gas jet which was imaged with high spatial resolution (better than 0.8 lp/mm) at high speed. Abel inversions were performed on the phase images to produce 2-D images of localized gas density. This system could also be used for high spatial and temporal resolution measurements of plasma electron density or surface deformations. PMID:27250423

  13. Very high-density planets: a possible remnant of gas giants.

    PubMed

    Mocquet, A; Grasset, O; Sotin, C

    2014-04-28

    Data extracted from the Extrasolar Planets Encyclopaedia (see http://exoplanet.eu) show the existence of planets that are more massive than iron cores that would have the same size. After meticulous verification of the data, we conclude that the mass of the smallest of these planets is actually not known. However, the three largest planets, Kepler-52b, Kepler-52c and Kepler-57b, which are between 30 and 100 times the mass of the Earth, have indeed density larger than an iron planet of the same size. This observation triggers this study that investigates under which conditions these planets could represent the naked cores of gas giants that would have lost their atmospheres during their migration towards the star. This study shows that for moderate viscosity values (10(25) Pa s or lower), large values of escape rate and associated unloading stress rate during the atmospheric loss process lead to the explosion of extremely massive planets. However, for moderate escape rate, the bulk viscosity and finite-strain incompressibility of the cores of giant planets can be large enough to retain a very high density during geological time scales. This would make those a new kind of planet, which would help in understanding the interior structure of the gas giants. However, this new family of exoplanets adds some degeneracy for characterizing terrestrial exoplanets. PMID:24664925

  14. Level density of a Fermi gas and integer partitions: A Gumbel-like finite-size correction

    SciTech Connect

    Roccia, Jerome; Leboeuf, Patricio

    2010-04-15

    We investigate the many-body level density of a gas of noninteracting fermions. We determine its behavior as a function of the temperature and the number of particles. As the temperature increases, and beyond the usual Sommerfeld expansion that describes the degenerate gas behavior, corrections due to a finite number of particles lead to Gumbel-like contributions. We discuss connections with the partition problem in number theory, extreme value statistics, and differences with respect to the Bose gas.

  15. Spatial association between dissection density and environmental factors over the entire conterminous United States

    NASA Astrophysics Data System (ADS)

    Luo, Wei; Jasiewicz, Jaroslaw; Stepinski, Tomasz; Wang, Jinfeng; Xu, Chengdong; Cang, Xuezhi

    2016-01-01

    Previous studies of land dissection density (D) often find contradictory results regarding factors controlling its spatial variation. We hypothesize that the dominant controlling factors (and the interactions between them) vary from region to region due to differences in each region's local characteristics and geologic history. We test this hypothesis by applying a geographical detector method to eight physiographic divisions of the conterminous United States and identify the dominant factor(s) in each. The geographical detector method computes the power of determinant (q) that quantitatively measures the affinity between the factor considered and D. Results show that the factor (or factor combination) with the largest q value is different for physiographic regions with different characteristics and geologic histories. For example, lithology dominates in mountainous regions, curvature dominates in plains, and glaciation dominates in previously glaciated areas. The geographical detector method offers an objective framework for revealing factors controlling Earth surface processes.

  16. Flowing afterglow measurements of the density dependence of gas-phase ion-ion mutual neutralization reactions

    SciTech Connect

    Shuman, Nicholas S.; Viggiano, Albert A.; Johnsen, Rainer

    2013-05-28

    We have studied the dependence of several ion-ion mutual neutralization (MN) reactions on helium density in the range from 1.6 Multiplication-Sign 10{sup 16} to 1.5 Multiplication-Sign 10{sup 17} cm{sup -3} at 300 K, using the Variable Electron and Neutral Density Attachment Mass Spectrometry method. The rate coefficients of the reactions Ar{sup +}+ Br{sub 2}{sup -}, Ar{sup +}+ SF{sub 6}{sup -}, and Ar{sup +}+ C{sub 7}F{sub 14}{sup -} were found to be independent of gas density over the range studied, in disagreement with earlier observations that similar MN reactions are strongly enhanced at the same gas densities. The cause of the previous enhancement with density is traced to the use of 'orbital-motion-limit' theory to infer ion densities from the currents collected by ion-attracting Langmuir probes in a region where it is not applicable.

  17. Factors Affecting the Incidence of Angel Wing in White Roman Geese: Stocking Density and Genetic Selection

    PubMed Central

    Lin, M. J.; Chang, S. C.; Lin, T. Y.; Cheng, Y. S.; Lee, Y. P.; Fan, Y. K.

    2016-01-01

    The present study investigated stocking density and genetic lines, factors that may alter the severity and incidence of angel wing (AW), in White Roman geese. Geese (n = 384) from two genetically selected lines (normal- winged line, NL, and angel-winged line, AL, respectively) and one commercial line (CL) were raised in four pens. Following common commercial practice, low-stocking-density (LD), medium-stocking-density, and high-stocking-density treatments were respectively administered to 24, 32, and 40 geese per pen at 0 to 3 weeks (1.92 m2/pen) and 4 to 6 weeks (13.2 m2/pen) of age and to 24, 30, and 36 geese at 7 to 14 weeks (20.0 m2/pen) of age. The results revealed that stocking density mainly affected body weight gain in geese younger than 4 weeks, and that geese subjected to LD had a high body weight at 2 weeks of age. However, the effect of stocking density on the severity score of AW (SSAW) and incidence of AW (IAW) did not differ significantly among the treatments. Differences were observed among the genetic stocks; that is, SSAW and IAW were significantly higher in AL than in NL and CL. Genetic selection generally aggravates AW, complicating its elimination. To effectively reduce IAW, stocking density, a suspected causal factor, should be lower than that presently applied commercially. PMID:26954185

  18. Associations between soy, diet, reproductive factors, and mammographic density in Singapore Chinese women.

    PubMed

    Ursin, Giske; Sun, Can-Lan; Koh, Woon-Puay; Khoo, Kei-Siong; Gao, Fei; Wu, Anna H; Yu, Mimi C

    2006-01-01

    Although the evidence is not completely consistent, soy intake has been inversely associated with breast cancer risk, and the strongest results have been observed in certain Asian populations. To address this issue and to examine the association between mammographic density and reproductive factors in this population, we conducted a cross-sectional analysis of mammograms and validated food-frequency questionnaires from 380 Chinese women living in Singapore. Percent mammographic density, a biomarker for breast cancer risk, was assessed using a validated computer-assisted method. We used generalized linear models to estimate mean mammographic density by quartiles of soy intake and intake of other dietary factors while adjusting for potential confounders. Percent mammographic density was inversely associated with age, body mass index, parity, breastfeeding, and soy intake. The difference in mammographic density between the highest and lowest quartiles of soy intake was 4-5%; this difference was statistically significant for soy protein and soy isoflavone intake and is similar in magnitude to what has been reported in Western populations when women undergo menopause or commence hormone therapy. We found no evidence that high fiber, fruit, or vegetable intake has protective effects on mammographic density. Our results suggest that the effect of soy intake on percent mammographic density is moderate but possibly of clinical relevance. PMID:17474857

  19. Factors Affecting the Incidence of Angel Wing in White Roman Geese: Stocking Density and Genetic Selection.

    PubMed

    Lin, M J; Chang, S C; Lin, T Y; Cheng, Y S; Lee, Y P; Fan, Y K

    2016-06-01

    The present study investigated stocking density and genetic lines, factors that may alter the severity and incidence of angel wing (AW), in White Roman geese. Geese (n = 384) from two genetically selected lines (normal- winged line, NL, and angel-winged line, AL, respectively) and one commercial line (CL) were raised in four pens. Following common commercial practice, low-stocking-density (LD), medium-stocking-density, and high-stocking-density treatments were respectively administered to 24, 32, and 40 geese per pen at 0 to 3 weeks (1.92 m(2)/pen) and 4 to 6 weeks (13.2 m(2)/pen) of age and to 24, 30, and 36 geese at 7 to 14 weeks (20.0 m(2)/pen) of age. The results revealed that stocking density mainly affected body weight gain in geese younger than 4 weeks, and that geese subjected to LD had a high body weight at 2 weeks of age. However, the effect of stocking density on the severity score of AW (SSAW) and incidence of AW (IAW) did not differ significantly among the treatments. Differences were observed among the genetic stocks; that is, SSAW and IAW were significantly higher in AL than in NL and CL. Genetic selection generally aggravates AW, complicating its elimination. To effectively reduce IAW, stocking density, a suspected causal factor, should be lower than that presently applied commercially. PMID:26954185

  20. Effects of density stratification in driving zonal flow in gas giants

    NASA Astrophysics Data System (ADS)

    Gastine, T.; Wicht, J.

    2011-12-01

    The banded structures at the surfaces of Jupiter and Saturn are associated with prograde and retrograde zonal flows. The depth of these jets remains however poorly known. Theoretical scenarios range from ``shallow models'', that assume that zonal flows are restricted to a very thin layer close to the surface; to ``deep models'' that suppose that the jets involve the whole molecular shell (typically 104 kms). The latter idea was supported by fully 3-D numerical simulations (e.g. Heimpel, 2005) using the Boussinesq approximation, meaning that the background properties (temperature, density, ...) are constant with radius (Christensen, 2002). While this approximation is suitable for liquid iron cores of planets, it is more questionable in the envelopes of gas giants, where density increases by several orders of magnitude (Guillot, 1999). The anelastic approximation provides a more realistic framework to simulate the dynamics of zonal flows as it allows compressibility effects, while filtering out fast acoustic waves (Lantz & Fan, 1999). Recent anelastic simulations suggest that including compressibility effects yields interesting differences to Boussinesq approaches (Jones, 2009; Showman et al., 2011). Here, we therefore adopt an anelastic formulation to simulate 3-D compressible flows in rapidly rotating shells. We have conducted a systematic parametric study on the effects of background density stratification and analysed the influences on both convective flows and zonal jets. Despite the strong dependence of convection on the density stratification (i.e. the typical lengthscale of convective flows decreases when compressibility increases), the comparison between Boussinesq and anelastic simulations reveals striking common features: the latitudinal extent, the amplitude and the number of zonal jets is found to be nearly independent of the density stratification, provided convection is strongly driven. Mass-weighted properties of the flow (and notably a mass

  1. A Herschel-SPIRE survey of the Mon R2 giant molecular cloud: analysis of the gas column density probability density function

    NASA Astrophysics Data System (ADS)

    Pokhrel, R.; Gutermuth, R.; Ali, B.; Megeath, T.; Pipher, J.; Myers, P.; Fischer, W. J.; Henning, T.; Wolk, S. J.; Allen, L.; Tobin, J. J.

    2016-09-01

    We present a far-IR survey of the entire Mon R2 giant molecular cloud (GMC) with Herschel-Spectral and Photometric Imaging REceiver cross-calibrated with Planck-High Frequency Instrument data. We fit the spectral energy distributions of each pixel with a greybody function and an optimal beta value of 1.8. We find that mid-range column densities obtained from far-IR dust emission and near-IR extinction are consistent. For the entire GMC, we find that the column density histogram, or column density probability distribution function (N-PDF), is lognormal below ˜1021 cm-2. Above this value, the distribution takes a power law form with an index of -2.15. We analyse the gas geometry, N-PDF shape, and young stellar object (YSO) content of a selection of subregions in the cloud. We find no regions with pure lognormal N-PDFs. The regions with a combination of lognormal and one power-law N-PDF have a YSO cluster and a corresponding centrally concentrated gas clump. The regions with a combination of lognormal and two power-law N-PDF have significant numbers of typically younger YSOs but no prominent YSO cluster. These regions are composed of an aggregate of closely spaced gas filaments with no concentrated dense gas clump. We find that for our fixed scale regions, the YSO count roughly correlates with the N-PDF power-law index. The correlation appears steeper for single power-law regions relative to two power-law regions with a high column density cut-off, as a greater dense gas mass fraction is achieved in the former. A stronger correlation is found between embedded YSO count and the dense gas mass among our regions.

  2. Strong cylindrical shock wave in a self-gravitating rotational axisymmetric dusty gas with density varying exponentially

    NASA Astrophysics Data System (ADS)

    Nath, Gorakh

    2016-07-01

    The propagation of a strong cylindrical shock wave in a self-gravitating and rotational axisymmetric dusty gas, having variable azimuthal and axial fluid velocities is investigated. The dusty gas is assumed to be a mixture of small solid particles and perfect gas. The equilibrium flow conditions are assumed to be maintained. The density of the mixture and the fluid velocities in the ambient medium are assumed to be varying and obeying an exponential law. The shock wave moves with variable velocity and the total energy of the wave is non-constant. Non-similarity solutions are obtained and the effects of variation of the mass concentration of solid particles in the mixture, the ratio of the density of solid particles to the initial density of the gas, and the gravitational parameter on the flow variables in the region behind the shock are investigated at a given time. Also, a comparison between the isothermal and adiabatic flow is made.

  3. Breast cancer risk factors in relation to breast density (United States)

    PubMed Central

    Tosteson, Anna N. A.; Kasales, Claudia; Weiss, Julia; Goodrich, Martha; Hatch, Elizabeth E.; Carney, Patricia A.

    2006-01-01

    Objectives Evaluate known breast cancer risk factors in relation to breast density. Methods We examined factors in relation to breast density in 144,018 New Hampshire (NH) women with at least one mammogram recorded in a statewide mammography registry. Mammographic breast density was measured by radiologists using the BI-RADS classification; risk factors of interest were obtained from patient intake forms and questionnaires. Results Initial analyses showed a strong inverse influence of age and body mass index (BMI) on breast density. In addition, women with late age at menarche, late age at first birth, premenopausal women, and those currently using hormone therapy (HT) tended to have higher breast density, while those with greater parity tended to have less dense breasts. Analyses stratified on age and BMI suggested interactions, which were formally assessed in a multivariable model. The impact of current HT use, relative to nonuse, differed across age groups, with an inverse association in younger women, and a positive association in older women (p < 0.0001 for the interaction). The positive effects of age at menarche and age at first birth, and the inverse influence of parity were less apparent in women with low BMI than in those with high BMI (p = 0.04, p < 0.0001 and p = 0.01, respectively, for the interactions). We also noted stronger positive effects for age at first birth in postmenopausal women (p = 0.004 for the interaction). The multivariable model indicated a slight positive influence of family history of breast cancer. Conclusions The influence of age at menarche and reproductive factors on breast density is less evident in women with high BMI. Density is reduced in young women using HT, but increased in HT users of age 50 or more. PMID:17111260

  4. Unequal density effect on static structure factor of coupled electron layers

    SciTech Connect

    Saini, L. K. Nayak, Mukesh G.

    2014-04-24

    In order to understand the ordered phase, if any, in a real coupled electron layers (CEL), there is a need to take into account the effect of unequal layer density. Such phase is confirmed by a strong peak in a static structure factor. With the aid of quantum/dynamical version of Singwi, Tosi, Land and Sjölander (so-called qSTLS) approximation, we have calculated the intra- and interlayer static structure factors, S{sub ll}(q) and S{sub 12}(q), over a wide range of density parameter r{sub sl} and interlayer spacing d. In our present study, the sharp peak in S{sub 22}(q) has been found at critical density with sufficiently lower interlayer spacing. Further, to find the resultant effect of unequal density on intra- and interlayer static structure factors, we have compared our results with that of the recent CEL system with equal layer density and isolated single electron layer.

  5. GAS SURFACE DENSITY, STAR FORMATION RATE SURFACE DENSITY, AND THE MAXIMUM MASS OF YOUNG STAR CLUSTERS IN A DISK GALAXY. II. THE GRAND-DESIGN GALAXY M51

    SciTech Connect

    Gonzalez-Lopezlira, Rosa A.; Pflamm-Altenburg, Jan; Kroupa, Pavel

    2013-06-20

    We analyze the relationship between maximum cluster mass and surface densities of total gas ({Sigma}{sub gas}), molecular gas ({Sigma}{sub H{sub 2}}), neutral gas ({Sigma}{sub H{sub I}}), and star formation rate ({Sigma}{sub SFR}) in the grand-design galaxy M51, using published gas data and a catalog of masses, ages, and reddenings of more than 1800 star clusters in its disk, of which 223 are above the cluster mass distribution function completeness limit. By comparing the two-dimensional distribution of cluster masses and gas surface densities, we find for clusters older than 25 Myr that M{sub 3rd}{proportional_to}{Sigma}{sub H{sub I}{sup 0.4{+-}0.2}}, whereM{sub 3rd} is the median of the five most massive clusters. There is no correlation with{Sigma}{sub gas},{Sigma}{sub H2}, or{Sigma}{sub SFR}. For clusters younger than 10 Myr, M{sub 3rd}{proportional_to}{Sigma}{sub H{sub I}{sup 0.6{+-}0.1}} and M{sub 3rd}{proportional_to}{Sigma}{sub gas}{sup 0.5{+-}0.2}; there is no correlation with either {Sigma}{sub H{sub 2}} or{Sigma}{sub SFR}. The results could hardly be more different from those found for clusters younger than 25 Myr in M33. For the flocculent galaxy M33, there is no correlation between maximum cluster mass and neutral gas, but we have determined M{sub 3rd}{proportional_to}{Sigma}{sub gas}{sup 3.8{+-}0.3}, M{sub 3rd}{proportional_to}{Sigma}{sub H{sub 2}{sup 1.2{+-}0.1}}, and M{sub 3rd}{proportional_to}{Sigma}{sub SFR}{sup 0.9{+-}0.1}. For the older sample in M51, the lack of tight correlations is probably due to the combination of strong azimuthal variations in the surface densities of gas and star formation rate, and the cluster ages. These two facts mean that neither the azimuthal average of the surface densities at a given radius nor the surface densities at the present-day location of a stellar cluster represent the true surface densities at the place and time of cluster formation. In the case of the younger sample, even if the clusters have not yet

  6. Filling factors and scale heights of the diffuse ionized gas in the Milky Way

    NASA Astrophysics Data System (ADS)

    Berkhuijsen, E. M.; Mitra, D.; Mueller, P.

    2006-01-01

    The combination of dispersion measures of pulsars, distances from the model of Cordes & Lazio (\\cite{cordes+lazio02}) and emission measures from the WHAM survey enabled a statistical study of electron densities and filling factors of the diffuse ionized gas (DIG) in the Milky Way. The emission measures were corrected for absorption and contributions from beyond the pulsar distance. For a sample of 157 pulsars at |b|>5° and 60° < ℓ < 360°, located in mainly interarm regions within about 3 kpc from the Sun, we find that: (1) The average volume filling factor along the line of sight /line{f}v and the mean density in ionized clouds /line{n}c are inversely correlated: /line{f}v(/line{n}c ) = (0.0184± 0.0011) /line{n}c{ -1.07± 0.03} for the ranges 0.03 < /line{n}c < 2 {cm-3 and 0.8 > /line{f}v > 0.01. This relationship is very tight. The inverse correlation of /line{f}v and /line{n}c causes the well-known constancy of the average electron density along the line of sight. As /line{f}v(z) increases with distance from the Galactic plane |z|, the average size of the ionized clouds increases with |z|. (2) For |z| < 0.9 kpc the local density in clouds nc (z) and local filling factor f(z) are inversely correlated because the local electron density ne (z) = f(z) nc (z) is constant. We suggest that f(z) reaches a maximum value of >0.3 near |z| = 0.9 kpc, whereas nc (z) continues to decrease to higher |z|, thus causing the observed flattening in the distribution of dispersion measures perpendicular to the Galactic plane above this height. (3) For |z| < 0.9 kpc the local distributions nc (z), f(z) and ne2(z) have the same scale height which is in the range 250 < h ⪉ 500 pc. (4) The average degree of ionization of the warm atomic gas /line{I}w (z) increases towards higher |z| similarly to /line{f}v (z). Towards |z| = 1 kpc, /line{f}v (z) = 0.24± 0.05 and /line{I}w (z) = 0.24± 0.02. Near |z| = 1 kpc most of the warm, atomic hydrogen is ionized.

  7. Detection of coating fluorophores' densities in improved Q-factor cavities

    NASA Astrophysics Data System (ADS)

    Kandas, Ishac; Shehata, Nader; Daengngam, Chalongrat; Ashry, Islam; Xu, Yong

    2015-08-01

    This work investigates the relationship between the Q factor of a silica-microsphere coated with nonlinear optical molecules and the surface density of the molecules. Two types of nonlinear molecules are studied: poly {1-[p-(3'-carboxy-4'-hydroxyphenylazo) benzenesulfonamido]-1, 2-ethandiyl} (PCBS), and Procion Brown MX-GRN (PB). In our experiments, we coat silica microspheres with ionic self-assembled multilayer (ISAM) films with different thickness values as well as different PCBS/PB chromophore densities. The Q factors of the coated microspheres are limited to the range of 106-107, which can be attributed to the optical absorption of the coated chromophores. This work can be used to experimentally determine the effective density of chromophores assembled on the silica microsphere. It may also find applications in chemical / biological sensing.

  8. Measurement of chromophores density using high Q-factor silica microspheres

    NASA Astrophysics Data System (ADS)

    Kandas, Ishac; Shehata, Nader; Daengngam, Chalongrat; Ashry, Islam; Xu, Yong

    2016-01-01

    This work investigates the relationship between the Q factor of a silica microsphere coated with nonlinear optical molecules and the surface density of the nonlinear molecules. Two types of nonlinear molecules are studied: poly{1-[p-(3‧-carboxy-4‧-hydroxyphenylazo) benzenesulfonamido]-1,2-ethandiyl} (PCBS), and Procion Brown MX-GRN (PB). In our experiments, we coat silica microspheres with ionic self-assembled multilayer films with different thicknesses as well as with different PCBS/PB chromophores densities. The Q factors of the coated microspheres are measured to be within the range of 106 to 107, which can be attributed to the optical absorption of the coated chromophores. This work can be used to experimentally determine the effective density of chromophores assembled on the silica microsphere. It may also find applications in chemical/biological sensing.

  9. Polynomial approximations of thermodynamic properties of arbitrary gas mixtures over wide pressure and density ranges

    NASA Technical Reports Server (NTRS)

    Allison, D. O.

    1972-01-01

    Computer programs for flow fields around planetary entry vehicles require real-gas equilibrium thermodynamic properties in a simple form which can be evaluated quickly. To fill this need, polynomial approximations were found for thermodynamic properties of air and model planetary atmospheres. A coefficient-averaging technique was used for curve fitting in lieu of the usual least-squares method. The polynomials consist of terms up to the ninth degree in each of two variables (essentially pressure and density) including all cross terms. Four of these polynomials can be joined to cover, for example, a range of about 1000 to 11000 K and 0.00001 to 1 atmosphere (1 atm = 1.0133 x 100,000 N/m sq) for a given thermodynamic property. Relative errors of less than 1 percent are found over most of the applicable range.

  10. Gas-phase reactions of pd with acetone: A theoretical investigation using density functional theory

    NASA Astrophysics Data System (ADS)

    Dai, Guo-Liang; Wang, Chuan-Feng

    2012-12-01

    The gas-phase reaction of palladium atom with acetone is investigated using density functional theory. Geometries and energies of the reactants, intermediates, and products involved are calculated. Both ground and excited state potential energy surfaces are investigated in detail. The present results show that the title reaction start with the formation of an η2-CH3COCH3-metal complex, followed by C-O, C-H, and C-C activation. These reactions can lead to four different products (PdO + C3H6, PdCH2COCH3 + H, PdCH2 + CH3CHO, and PdCOCH2 + CH4). The present results may be helpful in understanding the mechanism of the title reaction and further experimental investigation of the reaction.

  11. Electron beam fluorescence system to measure gas density in impulse facilities

    NASA Technical Reports Server (NTRS)

    Hoppe, J. C.

    1974-01-01

    Very rapid measurements, ranging from a few microsecond to milliseconds in duration, characterize studies made in shock regions or behind them. A system to measure gas density under such conditions in a 15.24-cm (6-in.) expansion tube is described. The basic elements are an electron beam of moderate energy and high current capability, an optical detector, and the associated electronics and data readout equipment. A heated-cathode electron gun, capable of pulsed operation and delivering up to 200 milliamperes current, provides the source of electrons. Optics include a simple collector lens, aperture, collimator lens, filters, and a photomultiplier tube. The photomultiplier output signal was recorded by means of photographed oscilloscope traces for pulsed beam operation.

  12. Infrared and density functional theory studies of formic acid hydrate clusters in noble gas matrices

    NASA Astrophysics Data System (ADS)

    Ito, Fumiyuki

    2016-08-01

    Infrared absorption spectra of formic acid hydrate clusters (HCOOH)m(H2O)n have been measured in noble gas matrices (Ar and Kr). The concentration dependence of the spectra and the comparison with a previous experimental study on HCOOH(H2O) and HCOOH(H2O)2 [Geoge et al., Spectrochim. Acta, Part A 60 (2004) 3225] led to the identification of large clusters. Density functional theory calculations at the B3LYP-DCP/6-31+G(2d,2p) level were carried out to determine the anharmonic vibrational properties of the clusters, enabling a consistent assignment of the observed vibrational peaks to specific clusters.

  13. Fermi Edge Polaritons in a Microcavity Containing a High Density Two-Dimensional Electron Gas

    NASA Astrophysics Data System (ADS)

    Gabbay, A.; Preezant, Yulia; Cohen, E.; Ashkinadze, B. M.; Pfeiffer, L. N.

    2007-10-01

    Sharp, near band gap lines are observed in the reflection and photoluminescence spectra of GaAs/AlGaAs structures consisting of a modulation doped quantum well (MDQW) that contains a high density two-dimensional electron gas (2DEG) and is embedded in a microcavity (MC). The energy dependence of these lines on the MC-confined photon energy shows level anticrossings and Rabi splittings very similar to those observed in systems of undoped QW’s embedded in a MC. The spectra are analyzed by calculating the optical susceptibility of the MDQW in the near band gap spectral range and using it within the transfer matrix method. The calculated reflection spectra indicate that the sharp spectral lines are due to k∥=0 cavity polaritons that are composed of e-h pair excitations just above the 2DEG Fermi edge and are strongly coupled to the MC-confined photons.

  14. Gas-phase pyrolysis mechanisms of 3-anilino-1-propanol: Density functional theory study

    NASA Astrophysics Data System (ADS)

    Zhao, Jing; Tang, Ming-Sheng; Wei, Dong-Hui; Zhao, Chu-Feng; Zhang, Wen-Jing; Wang, Hong-Ming

    The gas-phase pyrolytic decomposition mechanisms of 3-anilino-1-propanol with the products of aniline, ethylene, and formaldehyde or N-methyl aniline and aldehyde were studied by density functional theory. The geometries of the reactant, transition states, and intermediates were optimized at the B3LYP/6-31G (d, p) level. Vibration analysis was carried out to confirm the transition state structures, and the intrinsic reaction coordinate method was performed to search the minimum energy path. Four possible reaction channels are shown, including two concerted reactions of direct pyrolytic decomposition and two indirect channels in which the reactant first becomes a ring-like intermediate, followed by concerted pyrogenation. One of the concerted reactions in the direct pyrolytic decomposition has the lowest activation barrier among all the four channels, and so, it occurs more often than others. The results appear to be consistent with the experimental outcomes.

  15. Form factor dispersion at La M5,4 edges and average density of resonant atoms.

    PubMed

    Smadici, S; Lee, J C T; Logvenov, G; Bozovic, I; Abbamonte, P

    2014-01-15

    Resonant soft x-ray scattering on complex oxide superlattices shows very large variations in the superlattice reflection position and intensity near La M5,4 edges. Resonant dispersion of the La x-ray form factor describes the observations well. We determine the average density of resonant La atoms and the thickness of superlattice layers. PMID:24318961

  16. A Factor Analytic Approach to the Study of Spatial Density Effects on Preschoolers.

    ERIC Educational Resources Information Center

    Loo, Chalsa M.

    1979-01-01

    Behavior of preschoolers was studied with respect to five factors: verbally-abusive interaction, activity-toy play, avoidance, negative affect-agression, and desire-to-leave-a-crowded-room. Under high density conditions, more girls exhibited reduced activity level and toy involvement, along with increased negative feelings, than boys. (MA)

  17. Self-tuning method for monitoring the density of a gas vapor component using a tunable laser

    DOEpatents

    Hagans, K.; Berzins, L.; Galkowski, J.; Seng, R.

    1996-08-27

    The present invention relates to a vapor density monitor and laser atomic absorption spectroscopy method for highly accurate, continuous monitoring of vapor densities, composition, flow velocity, internal and kinetic temperatures and constituent distributions. The vapor density monitor employs a diode laser, preferably of an external cavity design. By using a diode laser, the vapor density monitor is significantly less expensive and more reliable than prior art vapor density monitoring devices. In addition, the compact size of diode lasers enables the vapor density monitor to be portable. According to the method of the present invention, the density of a component of a gas vapor is calculated by tuning the diode laser to a frequency at which the amount of light absorbed by the component is at a minimum or a maximum within about 50 MHz of that frequency. Laser light from the diode laser is then transmitted at the determined frequency across a predetermined pathlength of the gas vapor. By comparing the amount of light transmitted by the diode laser to the amount of light transmitted after the laser light passes through the gas vapor, the density of the component can be determined using Beer`s law. 6 figs.

  18. Self-tuning method for monitoring the density of a gas vapor component using a tunable laser

    DOEpatents

    Hagans, Karla; Berzins, Leon; Galkowski, Joseph; Seng, Rita

    1996-01-01

    The present invention relates to a vapor density monitor and laser atomic absorption spectroscopy method for highly accurate, continuous monitoring of vapor densities, composition, flow velocity, internal and kinetic temperatures and constituent distributions. The vapor density monitor employs a diode laser, preferably of an external cavity design. By using a diode laser, the vapor density monitor is significantly less expensive and more reliable than prior art vapor density monitoring devices. In addition, the compact size of diode lasers enables the vapor density monitor to be portable. According to the method of the present invention, the density of a component of a gas vapor is calculated by tuning the diode laser to a frequency at which the amount of light absorbed by the component is at a minimum or a maximum within about 50 MHz of that frequency. Laser light from the diode laser is then transmitted at the determined frequency across a predetermined pathlength of the gas vapor. By comparing the amount of light transmitted by the diode laser to the amount of light transmitted after the laser light passes through the gas vapor, the density of the component can be determined using Beer's law.

  19. Dust-to-gas ratio, XCO factor and CO-dark gas in the Galactic anticentre: an observational study

    NASA Astrophysics Data System (ADS)

    Chen, B.-Q.; Liu, X.-W.; Yuan, H.-B.; Huang, Y.; Xiang, M.-S.

    2015-04-01

    We investigate the correlation between extinction and H I and CO emission at intermediate and high Galactic latitudes (|b| > 10°) within the footprint of the Xuyi Schmidt Telescope Photometric Survey of the Galactic anticentre (XSTPS-GAC) on small and large scales. In Paper I, we present a three-dimensional (3D) dust extinction map within the footprint of XSTPS-GAC, covering a sky area of over 6000 deg2 at a spatial angular resolution of 6 arcmin. In the current work, the map is combined with data from gas tracers, including H I data from the Galactic Arecibo L-band Feed Array H I survey and CO data from the Planck mission, to constrain the values of dust-to-gas ratio DGR = AV/N(H) and CO-to-H2 conversion factor XCO = N(H2)/WCO for the entire GAC footprint excluding the Galactic plane, as well as for selected star-forming regions (such as the Orion, Taurus and Perseus clouds) and a region of diffuse gas in the northern Galactic hemisphere. For the whole GAC footprint, we find DGR = (4.15 ± 0.01) × 10-22 mag cm2 and XCO = (1.72 ± 0.03) × 1020 cm- 2 (K km s- 1)- 1. We have also investigated the distribution of `CO-dark' gas (DG) within the footprint of GAC and found a linear correlation between the DG column density and the V-band extinction: N(DG) ˜eq 2.2 × 10^{21} (A_V - AcV) cm^{-2}. The mass fraction of DG is found to be fDG ˜ 0.55 towards the Galactic anticentre, which is respectively about 23 and 124 per cent of the atomic and CO-traced molecular gas in the same region. This result is consistent with the theoretical work of Papadopoulos et al. but much larger than that expected in the H2 cloud models by Wolfire et al.

  20. A Herschel - SPIRE Survey of the Mon R2 Giant Molecular Cloud: Analysis of the Gas Column Density Probability Density Function

    NASA Astrophysics Data System (ADS)

    Pokhrel, R.; Gutermuth, R.; Ali, B.; Megeath, T.; Pipher, J.; Myers, P.; Fischer, W. J.; Henning, T.; Wolk, S. J.; Allen, L.; Tobin, J. J.

    2016-06-01

    We present a far-IR survey of the entire Mon R2 GMC with Herschel - SPIRE cross-calibrated with Planck - HFI data. We fit the SEDs of each pixel with a greybody function and an optimal beta value of 1.8. We find that mid-range column densities obtained from far-IR dust emission and near-IR extinction are consistent. For the entire GMC, we find that the column density histogram, or N-PDF, is lognormal below ˜ 1021 cm-2. Above this value, the distribution takes a power law form with an index of -2.15. We analyze the gas geometry, N-PDF shape, and YSO content of a selection of subregions in the cloud. We find no regions with pure lognormal N-PDFs. The regions with a combination of lognormal and one power law N-PDF have a YSO cluster and a corresponding centrally concentrated gas clump. The regions with a combination of lognormal and two power law N-PDF have significant numbers of typically younger YSOs but no prominent YSO cluster. These regions are composed of an aggregate of closely spaced gas filaments with no concentrated dense gas clump. We find that for our fixed scale regions, the YSO count roughly correlates with the N-PDF power law index. The correlation appears steeper for single power law regions relative to two power law regions with a high column density cut-off, as a greater dense gas mass fraction is achieved in the former. A stronger correlation is found between embedded YSO count and the dense gas mass among our regions.

  1. Evolution and Instability of Galactic Gas Disks inresponse to A Spiral Density-wave Potential

    NASA Astrophysics Data System (ADS)

    Yuan, Chi; Yen, D. C.; Wang, H. H.

    2006-12-01

    We revisit the classic problem of the response of the gas in a galactic disk to an imposed spiral density-wave potential of stellar origin. The results show the distinct difference between waves generated by resonance excitation and forced oscillation. To avoid the confusion of mixing these two types of waves, we systematically reduce the strength of the spiral potential or the force near the primary Lindblad resonances. So we can study the original problem of shock formation and star formation problem formulated by Roberts (1969). For the cases without self-gravitation of the gas disk, in addition to the primary doubly periodic shocks, the presence of the branch-like structures which correspond to the ultra-harmonic resonances is pronounced. On the other hand, once the self-gravitation is included, unlike the work of Chakrabarti et al. (2003), the sub-structures associated with the ultra-harmonics are not necessarily enhanced by the self-gravity. Their growth may be deteriorated by the growth of the primary shocks. Sub-structures other than those identified with the ultra-harmonics may result from shear instability of Rayleigh's kind or gravitational instability of Toomre's kind. They are responsible for the branches, feathers or chaotic sub-structures observed in nearby galaxies in far infra-red. The work is in parts supported by a grant from National Science Council, Taiwan NSC95-2752-M-001-009-PAE.

  2. The Carina Nebula and Gum 31 molecular complex - I. Molecular gas distribution, column densities, and dust temperatures

    NASA Astrophysics Data System (ADS)

    Rebolledo, David; Burton, Michael; Green, Anne; Braiding, Catherine; Molinari, Sergio; Wong, Graeme; Blackwell, Rebecca; Elia, Davide; Schisano, Eugenio

    2016-03-01

    We report high-resolution observations of the 12CO(1-0) and 13CO(1-0) molecular lines in the Carina Nebula and the Gum 31 region obtained with the 22-m Mopra telescope as part of The Mopra Southern Galactic Plane CO Survey. We cover 8 deg2 from l = 285° to 290°, and from b = -1.5° to +0.5°. The molecular gas column density distributions from both tracers have a similar range of values. By fitting a grey-body function to the observed infrared spectral energy distribution from Herschel maps, we derive gas column densities and dust temperatures. The gas column density has values in the range from 6.3 × 1020 to 1.4 × 1023 cm-2, while the dust temperature has values in the range from 17 to 43 K. The gas column density derived from the dust emission is approximately described by a lognormal function for a limited range of column densities. A high-column-density tail is clearly evident for the gas column density distribution, which appears to be a common feature in regions with active star formation. There are regional variations in the fraction of the mass recovered by the CO emission lines with respect to the total mass traced by the dust emission. These variations may be related to changes in the radiation field strength, variation of the atomic to molecular gas fraction across the observed region, differences in the CO molecule abundance with respect to H2, and evolutionary stage differences of the molecular clouds that compose the Carina Nebula-Gum 31 complex.

  3. Modification of generalized vector form factors and transverse charge densities of the nucleon in nuclear matter

    NASA Astrophysics Data System (ADS)

    Jung, Ju-Hyun; Yakhshiev, Ulugbek; Kim, Hyun-Chul

    2016-03-01

    We investigate the medium modification of the generalized vector form factors of the nucleon, which include the electromagnetic and energy-momentum tensor form factors, based on an in-medium modified π -ρ -ω soliton model. We find that the vector form factors of the nucleon in nuclear matter fall off faster than those in free space, which implies that the charge radii of the nucleon become larger in nuclear medium than in free space. We also compute the corresponding transverse charge densities of the nucleon in nuclear matter, which clearly reveal the increasing of the nucleon size in nuclear medium.

  4. Tunable one-dimensional electron gas carrier densities at nanostructured oxide interfaces.

    PubMed

    Zhuang, Houlong L; Zhang, Lipeng; Xu, Haixuan; Kent, P R C; Ganesh, P; Cooper, Valentino R

    2016-01-01

    The emergence of two-dimensional metallic states at the LaAlO3/SrTiO3 (LAO/STO) heterostructure interface is known to occur at a critical thickness of four LAO layers. This insulator to-metal transition can be explained through the "polar catastrophe" mechanism arising from the divergence of the electrostatic potential at the LAO surface. Here, we demonstrate that nanostructuring can be effective in reducing or eliminating this critical thickness. Employing a modified "polar catastrophe" model, we demonstrate that the nanowire heterostructure electrostatic potential diverges more rapidly as a function of layer thickness than in a regular heterostructure. Our first-principles calculations indicate that for nanowire heterostructures a robust one-dimensional electron gas (1DEG) can be induced, consistent with recent experimental observations of 1D conductivity at LAO/STO steps. Similar to LAO/STO 2DEGs, we predict that the 1D charge density decays laterally within a few unit cells away from the nanowire; thus providing a mechanism for tuning the carrier dimensionality between 1D and 2D conductivity. Our work provides insight into the creation and manipulation of charge density at an oxide heterostructure interface and therefore may be beneficial for future nanoelectronic devices and for the engineering of novel quantum phases. PMID:27151049

  5. Tunable one-dimensional electron gas carrier densities at nanostructured oxide interfaces

    PubMed Central

    Zhuang, Houlong L.; Zhang, Lipeng; Xu, Haixuan; Kent, P. R. C.; Ganesh, P.; Cooper, Valentino R.

    2016-01-01

    The emergence of two-dimensional metallic states at the LaAlO3/SrTiO3 (LAO/STO) heterostructure interface is known to occur at a critical thickness of four LAO layers. This insulator to-metal transition can be explained through the “polar catastrophe” mechanism arising from the divergence of the electrostatic potential at the LAO surface. Here, we demonstrate that nanostructuring can be effective in reducing or eliminating this critical thickness. Employing a modified “polar catastrophe” model, we demonstrate that the nanowire heterostructure electrostatic potential diverges more rapidly as a function of layer thickness than in a regular heterostructure. Our first-principles calculations indicate that for nanowire heterostructures a robust one-dimensional electron gas (1DEG) can be induced, consistent with recent experimental observations of 1D conductivity at LAO/STO steps. Similar to LAO/STO 2DEGs, we predict that the 1D charge density decays laterally within a few unit cells away from the nanowire; thus providing a mechanism for tuning the carrier dimensionality between 1D and 2D conductivity. Our work provides insight into the creation and manipulation of charge density at an oxide heterostructure interface and therefore may be beneficial for future nanoelectronic devices and for the engineering of novel quantum phases. PMID:27151049

  6. Tunable one-dimensional electron gas carrier densities at nanostructured oxide interfaces

    NASA Astrophysics Data System (ADS)

    Zhuang, Houlong L.; Zhang, Lipeng; Xu, Haixuan; Kent, P. R. C.; Ganesh, P.; Cooper, Valentino R.

    2016-05-01

    The emergence of two-dimensional metallic states at the LaAlO3/SrTiO3 (LAO/STO) heterostructure interface is known to occur at a critical thickness of four LAO layers. This insulator to-metal transition can be explained through the “polar catastrophe” mechanism arising from the divergence of the electrostatic potential at the LAO surface. Here, we demonstrate that nanostructuring can be effective in reducing or eliminating this critical thickness. Employing a modified “polar catastrophe” model, we demonstrate that the nanowire heterostructure electrostatic potential diverges more rapidly as a function of layer thickness than in a regular heterostructure. Our first-principles calculations indicate that for nanowire heterostructures a robust one-dimensional electron gas (1DEG) can be induced, consistent with recent experimental observations of 1D conductivity at LAO/STO steps. Similar to LAO/STO 2DEGs, we predict that the 1D charge density decays laterally within a few unit cells away from the nanowire; thus providing a mechanism for tuning the carrier dimensionality between 1D and 2D conductivity. Our work provides insight into the creation and manipulation of charge density at an oxide heterostructure interface and therefore may be beneficial for future nanoelectronic devices and for the engineering of novel quantum phases.

  7. Tunable one-dimensional electron gas carrier densities at nanostructured oxide interfaces

    DOE PAGESBeta

    Zhang, Lipeng; Xu, Haixuan; Kent, Paul R. C.; Ganesh, Panchapakesan; Cooper, Valentino R.; Zhuang, Houlong L.

    2016-05-06

    The emergence of two-dimensional metallic states at the LaAlO3/SrTiO3 (LAO/STO) heterostructure interface is known to occur at a critical thickness of four LAO over layers. This insulator-to-metal transition can be explained through the polar catastrophe mechanism arising from the divergence of the electrostatic potential at the LAO surface. Here, we demonstrate that nanostructuring can be effective in reducing or eliminating this critical thickness. Employing a modified polar catastrophe" model, we demonstrate that the nanowire heterostructure electrostatic potential diverges more rapidly as a function of layer thickness than in a regular heterostructure. Our first principles calculations indicate that for nanowire heterostructuremore » geometries a one-dimensional electron gas (1DEG) can be induced, consistent with recent experimental observations of 1D conductivity in LAO/STO steps. Similar to LAO/STO 2DEGs, we predict that the 1D charge density will decay laterally within a few unit cells away from the nanowire; thus providing a mechanism for tuning the carrier behavior between 1D and 2D conductivity. Furthermore, our work provides insight into the creation and manipulation of charge density at an oxide heterostructure interface and therefore may be beneficial for future nanoelectronic devices and for the engineering of novel quantum phases.« less

  8. Tunable One-Dimensional Electron Gas Carrier Densities at Nanostructured Oxide Interfaces

    SciTech Connect

    Zhang, Lipeng; Xu, Haixuan; Kent, Paul R; Ganesh, Panchapakesan; Cooper, Valentino R

    2016-01-01

    The emergence of two-dimensional metallic states at the LaAlO3/SrTiO3 (LAO/STO) heterostructure interface is known to occur at a critical thickness of four LAO over layers. This insulator-to-metal transition can be explained through the polar catastrophe mechanism arising from the divergence of the electrostatic potential at the LAO surface. Here, we demonstrate that nanostructuring can be effective in reducing or eliminating this critical thickness. Employing a modified polar catastrophe" model, we demonstrate that the nanowire heterostructure electrostatic potential diverges more rapidly as a function of layer thickness than in a regular heterostructure. Our first principles calculations indicate that for nanowire heterostructure geometries a one-dimensional electron gas (1DEG) can be induced, consistent with recent experimental observations of 1D conductivity in LAO/STO steps. Similar to LAO/STO 2DEGs, we predict that the 1D charge density will decay laterally within a few unit cells away from the nanowire; thus providing a mechanism for tuning the carrier behavior between 1D and 2D conductivity. In essence, our work provides insight into the creation and manipulation of charge density at an oxide heterostructure interface and therefore may be beneficial for future nanoelectronic devices and for the engineering of novel quantum phases.

  9. Diagrammatic expansion for positive density-response spectra: Application to the electron gas

    NASA Astrophysics Data System (ADS)

    Uimonen, A.-M.; Stefanucci, G.; Pavlyukh, Y.; van Leeuwen, R.

    2015-03-01

    In a recent paper [Phys. Rev. B 90, 115134 (2014), 10.1103/PhysRevB.90.115134] we put forward a diagrammatic expansion for the self-energy which guarantees the positivity of the spectral function. In this work we extend the theory to the density-response function. We write the generic diagram for the density-response spectrum as the sum of "partitions." In a partition the original diagram is evaluated using time-ordered Green's functions on the left half of the diagram, antitime-ordered Green's functions on the right half of the diagram, and lesser or greater Green's function gluing the two halves. As there exists more than one way to cut a diagram in two halves, to every diagram corresponds more than one partition. We recognize that the most convenient diagrammatic objects for constructing a theory of positive spectra are the half-diagrams. Diagrammatic approximations obtained by summing the squares of half-diagrams do indeed correspond to a combination of partitions which, by construction, yield a positive spectrum. We develop the theory using bare Green's functions and subsequently extend it to dressed Green's functions. We further prove a connection between the positivity of the spectral function and the analytic properties of the polarizability. The general theory is illustrated with several examples and then applied to solve the long-standing problem of including vertex corrections without altering the positivity of the spectrum. In fact already the first-order vertex diagram, relevant to the study of gradient expansion, Friedel oscillations, etc., leads to spectra which are negative in certain frequency domain. We find that the simplest approximation to cure this deficiency is given by the sum of the zeroth-order bubble diagram, the first-order vertex diagram, and a partition of the second-order ladder diagram. We evaluate this approximation in the three-dimensional homogeneous electron gas and show the positivity of the spectrum for all frequencies and

  10. Impact of density and environmental factors on population fluctuations in a migratory passerine.

    PubMed

    Pasinelli, Gilberto; Schaub, Michael; Häfliger, Guido; Frey, Monika; Jakober, Hans; Müller, Mathis; Stauber, Wolfgang; Tryjanowski, Piotr; Zollinger, Jean-Luc; Jenni, Lukas

    2011-01-01

    1. Populations of plants and animals typically fluctuate because of the combined effects of density-dependent and density-independent processes. The study of these processes is complicated by the fact that population sizes are typically not known exactly, because population counts are subject to sampling variance. Although the existence of sampling variance is broadly acknowledged, relatively few studies on time-series data have accounted for it, which can result in wrong inferences about population processes. 2. To increase our understanding of population dynamics, we analysed time series from six Central European populations of the migratory red-backed shrike Lanius collurio by simultaneously assessing the strength of density dependence, process and sampling variance. In addition, we evaluated hypotheses predicting effects of factors presumed to operate on the breeding grounds, at stopover sites in eastern Africa during fall and spring migration and in the wintering grounds in southern Africa. We used both simple and state-space formulations of the Gompertz equation to model population size. 3. Across populations and modelling approaches, we found consistent evidence for negative density-dependent population regulation. Further, process variance contributed substantially to variation in population size, while sampling variance did not. Environmental conditions in eastern and southern Africa appear to influence breeding population size, as rainfall in the Sahel during fall migration and in the south African wintering areas were positively related to population size in the following spring in four of six populations. In contrast, environmental conditions in the breeding grounds were not related to population size. 4. Our findings suggest negative density-dependent regulation of red-backed shrike breeding populations and are consistent with the long-standing hypothesis that conditions in the African staging and wintering areas influence population numbers of species

  11. Estimated uncertainty of calculated liquefied natural gas density from a comparison of NBS and Gaz de France densimeter test facilities

    SciTech Connect

    Siegwarth, J.D.; LaBrecque, J.F.; Roncier, M.; Philippe, R.; Saint-Just, J.

    1982-12-16

    Liquefied natural gas (LNG) densities can be measured directly but are usually determined indirectly in custody transfer measurement by using a density correlation based on temperature and composition measurements. An LNG densimeter test facility at the National Bureau of Standards uses an absolute densimeter based on the Archimedes principle, while a test facility at Gaz de France uses a correlation method based on measurement of composition and density. A comparison between these two test facilities using a portable version of the absolute densimeter provides an experimental estimate of the uncertainty of the indirect method of density measurement for the first time, on a large (32 L) sample. The two test facilities agree for pure methane to within about 0.02%. For the LNG-like mixtures consisting of methane, ethane, propane, and nitrogen with the methane concentrations always higher than 86%, the calculated density is within 0.25% of the directly measured density 95% of the time.

  12. Optimization of the particle density to maximize the SERS enhancement factor of periodic plasmonic nanostructure array.

    PubMed

    Wei, Shuhua; Zheng, Mengjie; Xiang, Quan; Hu, Hailong; Duan, Huigao

    2016-09-01

    Low-cost surface-enhanced Raman scattering (SERS) substrate with the largest possible enhancement factor is highly desirable for SERS-based sensing applications. In this work, we systematically investigated how the density of plasmonic nanostructures affects the intensity of SERS signal. By directly depositing of metallic layer on electron-beam-lithography defined dielectric nanoposts, plasmonic structures array with different densities were reliably fabricated for SERS measurements. Two main experimental phenomena were obtained: (1) the SERS intensity did not increase monotonically when increasing the density of plasmonic structures, and (2) these ultra-dense plasmonic structures resulted in the maximal SERS intensity. These results could be well explained based on finite-difference time domain (FDTD) simulations and provide robust experimental evidences to guide the design of the best possible SERS substrate. PMID:27607665

  13. Factors limiting the domestic density of Triatoma infestans in north-west Argentina: a longitudinal study.

    PubMed Central

    Cecere, M. C.; Gürtler, R. E.; Chuit, R.; Cohen, J. E.

    1998-01-01

    Reported are the environmental and demographic risk factors associated with the domestic infestation and density of Triatoma infestans in three heavily infested rural villages in Santiago del Estero Province, Argentina. In a one-factor unadjusted analysis, the number of T. infestans captured per person-hour was associated significantly and negatively with the use of domestic insecticides by householders, type of thatch used in the roofs and the age of the house; and positively with the following: degree of cracking of the indoor walls and presence of hens nesting indoors. In one model, using multiple linear regression and a backward stepwise elimination procedure, most of the variation in the overall abundance of T. infestans was explained by insecticide use and the presence of hens nesting indoors; in another model using the same procedure it was explained by insecticide use, bug density in 1988 and previous spraying with deltamethrin in 1985. Variations in bug density per capture stratum (household goods, beds, walls and roof) were explained by the bug density in other strata and by one or two of the following risk factors: hens nesting indoors, type of roof, presence of cracks in the walls and number of people living in the house. Bug density might be locally controlled by the availability of refuges in the roofs and walls, by the presence of hens nesting indoors and by the use of domestic insecticides. Certain local materials, such as a grass known as simbol, could be successfully used in rural housing improvement programmes aimed at reducing the availability of refuges for insects in the roof. PMID:9803588

  14. Gas density does not affect pulmonary acoustic transmission in normal men.

    PubMed

    Mahagnah, M; Gavriely, N

    1995-03-01

    Fremitus, the transmission of sound and vibration from the mouth to the chest wall, has long been used clinically to examine the pulmonary system. Recently, modern technology has become available to measure the acoustic transfer function (TF) and transit times (TT) of the pulmonary system. Because sound speed is inversely proportional to the square root of gas density in free gas, but not in porous media, we measured the effect of air and Heliox (80% He-20% O2) breathing on pulmonary sound transmission in six healthy subjects to investigate the mechanism of sound transmission. Wide-band noise (75-2,000 Hz) was "injected" into the mouth and picked up over the trachea and chest wall. The averaged power spectra, TF, phase, and coherence were calculated using a fast Fourier transform-based algorithm. The phase data were used to calculate TT as a function of frequency. TF was found to consist of a low-pass filter property with essentially flat transmitted energy to 300 Hz and exponential decline to 600 Hz at the anterior right upper lobe (CR) and flat transmission to 100 Hz with exponential decline to 150 Hz at the right posterior base (BR). TF was not affected by breathing Heliox. The average TT values, calculated from the slopes of the averaged phase, were 1.5 +/- 0.5 ms for trachea to CR and 5.2 +/- 0.5 ms for trachea to BR transmission during air breathing. During Heliox breathing, the values of TT were 1.5 +/- 0.5 ms and 4.9 +/- 0.5 ms from the trachea to CR and from the trachea to BR locations, respectively. These results suggest that sound transmission in the respiratory system is dominated by wave propagation through the parenchymal porous structure. PMID:7775338

  15. Gas kinetics and dust dynamics in low-density comet comae

    NASA Astrophysics Data System (ADS)

    Davidsson, Björn J. R.; Gulkis, Samuel; Alexander, Claudia; Allmen, Paul von; Kamp, Lucas; Lee, Seungwon; Warell, Johan

    2010-11-01

    Extensive regions of low-density cometary comae are characterized by important deviations from the Maxwell-Boltzmann velocity distribution, i.e. breakdown of thermodynamic equilibrium. The consequences of this on the shapes of emission and absorption lines, and for the acceleration of solid bodies due to gas drag, have rarely been investigated. These problems are studied here to aid in the development of future coma models, and in preparation for observations of Comet 67P/Churyumov-Gerasimenko from the ESA Rosetta spacecraft. Two topics in particular, related to Rosetta, are preparation for in situ observations of water, carbon monoxide, ammonia, and methanol emission lines by the mm/sub-mm spectrometer MIRO, as well as gas drag forces on dust grains and on the Rosetta spacecraft itself. Direct Simulation Monte Carlo (DSMC) modeling of H 2O/CO mixtures in spherically symmetric geometries at various heliocentric distances are used to study the evolution of the (generally non-Maxwellian) velocity distribution function throughout the coma. Such distribution functions are then used to calculate Doppler broadening profiles and drag forces. It is found that deviation from thermodynamic equilibrium indeed is commonplace, and already at 2.5 AU from the Sun the entire comet coma displays manifestations of such breakdown, e.g., non-equal partitioning of energy between kinetic and rotational modes, causing substantial differences between translational and rotational temperatures. We exemplify how deviations from thermodynamic equilibrium affect the properties of Doppler broadened line profiles. Upper limits on the size of liftable dust grains as well as terminal grain velocities are presented. Furthermore, it is demonstrated that the drag-to-gravity force ratio is likely to decrease with decreasing cometocentric distance, which may be of relevance both for Rosetta and for the lander probe Philae.

  16. Monte Carlo study of voxel S factor dependence on tissue density and atomic composition

    NASA Astrophysics Data System (ADS)

    Amato, Ernesto; Italiano, Antonio; Baldari, Sergio

    2013-11-01

    Voxel dosimetry is a common approach to the internal dosimetry of non-uniform activity distributions in nuclear medicine therapies with radiopharmaceuticals and in the estimation of the radiation hazard due to internal contamination of radionuclides. Aim of the present work is to extend our analytical approach for the calculation of voxel S factors to materials different from the soft tissue. We used a Monte Carlo simulation in GEANT4 of a voxelized region of each material in which the source of monoenergetic electrons or photons was uniformly distributed within the central voxel, and the energy deposition was scored over the surrounding 11×11×11 voxels. Voxel S factors were obtained for the following standard ICRP materials: Adipose tissue, Bone cortical, Brain, Lung, Muscle skeletal and Tissue soft with 1 g cm-3 density. Moreover, we considered the standard ICRU materials: Bone compact and Muscle striated. Voxel S factors were represented as a function of the “normalized radius”, defined as the ratio between the source-target voxel distance and the voxel side. We found that voxel S factors and related analytical fit functions are mainly affected by the tissue density, while the material composition gives only a slight contribution to the difference between data series, which is negligible for practical purposes. Our results can help in broadening the dosimetric three-dimensional approach based on voxel S factors to other tissues where diagnostic and therapeutic radionuclides can be taken up and radiation can propagate.

  17. Stochastic seasonality and nonlinear density-dependent factors regulate population size in an African rodent

    USGS Publications Warehouse

    Leirs, H.; Stenseth, N.C.; Nichols, J.D.; Hines, J.E.; Verhagen, R.; Verheyen, W.

    1997-01-01

    Ecology has long been troubled by the controversy over how populations are regulated. Some ecologists focus on the role of environmental effects, whereas others argue that density-dependent feedback mechanisms are central. The relative importance of both processes is still hotly debated, but clear examples of both processes acting in the same population are rare. Keyfactor analysis (regression of population changes on possible causal factors) and time-series analysis are often used to investigate the presence of density dependence, but such approaches may be biased and provide no information on actual demographic rates. Here we report on both density-dependent and density-independent effects in a murid rodent pest species, the multimammate rat Mastomys natalensis (Smith, 1834), using statistical capture-recapture models. Both effects occur simultaneously, but we also demonstrate that they do not affect all demographic rates in the same way. We have incorporated the obtained estimates of demographic rates in a population dynamics model and show that the observed dynamics are affected by stabilizing nonlinear density-dependent components coupled with strong deterministic and stochastic seasonal components.

  18. Factors regulating viable cell density in the intervertebral disc: blood supply in relation to disc height

    PubMed Central

    Boubriak, Olga A; Watson, Natasha; Sivan, Sarit S; Stubbens, Naomi; Urban, Jill P G

    2013-01-01

    The intervertebral disc is an avascular tissue, maintained by a small population of cells that obtain nutrients mainly by diffusion from capillaries at the disc–vertebral body interface. Loss of this nutrient supply is thought to lead to disc degeneration, but how nutrient supply influences viable cell density is unclear. We investigated two factors that influence nutrient delivery to disc cells and hence cell viability: disc height and blood supply. We used bovine caudal discs as our model as these show a gradation in disc height. We found that although disc height varied twofold from the largest to the smallest disc studied, it had no significant effect on cell density, unlike the situation found in articular cartilage. The density of blood vessels supplying the discs was markedly greater for the largest disc than the smallest disc, as was the density of pores allowing capillary penetration through the bony endplate. Results indicate that changes in blood vessels in the vertebral bodies supplying the disc, as well as changes in endplate architecture appear to influence density of cells in intervertebral discs. PMID:23311982

  19. Homeostatic maintenance of ponderosa pine gas exchange in response to stand density changes.

    PubMed

    McDowell, Nate G; Adams, Henry D; Bailey, John D; Hess, Marcey; Kolb, Thomas E

    2006-06-01

    Homeostatic maintenance of gas exchange optimizes carbon gain per water loss. Homeostasis is regulated by short-term physiological and long-term structural mechanisms, both of which may respond to changes in resource availability associated with competition. Therefore, stand density regulation via silvicultural manipulations may facilitate growth and survival through mechanisms operating at both short and long timescales. We investigated the responses of ponderosa pine (Pinus ponderosa) to stand basal area manipulations in Arizona, USA. Stand basal area was manipulated to seven replicated levels in 1962 and was maintained for four decades by decadal thinning. We measured basal area increment (BAI) to assess the response and sustainability of wood growth, carbon isotope discrimination (A) inferred from annual rings to assess the response of crown gas exchange, and ratios of leaf area to sapwood area (A(l):A(s)) to assess longer term structural acclimation. Basal area treatments increased soil water potential (r2 = 0.99) but did not affect photosynthetic capacity. BAI increased within two years of thinning, and the 40-year mean BAI was negatively correlated with stand basal area (r2 = 0.98). delta was negatively correlated with stand basal area for years 5 through 12 after thinning (r2 = 0.90). However, delta was relatively invariant with basal area for the period 13-40 years after initial thinning despite maintenance of treatment basal areas via repeated decadal thinnings. Independent gas exchange measurements verified that the ratio of photosynthesis to stomatal conductance was invariant with basal area, but absolute values of both were elevated at lower basal areas. A(l):A(s) was negatively correlated with basal area (r2 = 0.93). We hypothesize that increased A(l):A(s) is a homeostatic response to increased water availability that maximizes water-use efficiency and whole-tree carbon uptake. Elevated A(l):A(s) of trees at low basal areas was associated with greater

  20. Lyα Emission from Green Peas: The Role of Circumgalactic Gas Density, Covering, and Kinematics

    NASA Astrophysics Data System (ADS)

    Henry, Alaina; Scarlata, Claudia; Martin, Crystal L.; Erb, Dawn

    2015-08-01

    We report Hubble Space Telescope/Cosmic Origins Spectrograph observations of the Lyα emission and interstellar absorption lines in a sample of 10 star-forming galaxies at z ˜ 0.2. Selected on the basis of high equivalent width optical emission lines, the sample, dubbed “Green Peas,” make some of the best analogs for young galaxies in an early universe. We detect Lyα emission in all ten galaxies, and 9/10 show double-peaked line profiles suggestive of low H i column density. We measure Lyα/Hα flux ratios of 0.5-5.6, implying that 5%-60% of Lyα photons escape the galaxies. These data confirm previous findings that low-ionization metal absorption (LIS) lines are weaker when Lyα escape fraction and equivalent width are higher. However, contrary to previously favored interpretations of this trend, increased Lyα output cannot be the result of a varying H i covering: the Lyman absorption lines (Lyβ and higher) show a covering fraction near unity for gas with NH i ≳ 1016 cm-2. Moreover, we detect no correlation between Lyα escape and the outflow velocity of the LIS lines, suggesting that kinematic effects do not explain the range of Lyα/Hα flux ratios in these galaxies. In contrast, we detect a strong anticorrelation between the Lyα escape fraction and the velocity separation of the Lyα emission peaks, driven primarily by the velocity of the blue peak. As this velocity separation is sensitive to H i column density, we conclude that Lyα escape in these Green Peas is likely regulated by the H i column density rather than outflow velocity or H i covering fraction. Based on observations made with the NASA/ESA Hubble Space Telescope, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555. These observations are associated with programs 12928 and 11727.

  1. Development of 3-dimensional time-dependent density functional theory and its application to gas diffusion in nanoporous materials.

    PubMed

    Liu, Yu

    2016-05-11

    I developed a novel time-dependent density functional theory (TDDFT) and applied it to complicated 3-dimensional systems for the first time. Superior to conventional TDDFT, the diffusion coefficient is modeled as a function of density profile, which is self-determined by the entropy scaling rule instead using an input parameter. The theory was employed to mimic gas diffusion in a nanoporous material. The TDDFT prediction on the transport diffusivity was reasonable compared to simulations. Moreover, the time-dependent density profiles gave an insight into the microscopic mechanism of the diffusion process. PMID:27121986

  2. Density response of a trapped Fermi gas: A crossover from the pair vibration mode to the Goldstone mode

    SciTech Connect

    Korolyuk, A.; Kinnunen, J. J.; Toermae, P.

    2011-09-15

    We consider the density response of a trapped two-component Fermi gas. Combining the Bogoliubov-deGennes method with the random phase approximation allows the study of both collective and single-particle excitations. Calculating the density response across a wide range of interactions, we observe a crossover from a weakly interacting pair vibration mode to a strongly interacting Goldstone mode. The crossover is associated with a depressed collective mode frequency and an increased damping rate, in agreement with density response experiments performed in strongly interacting atomic gases.

  3. Departures from local thermodynamic equilibrium in cutting arc plasmas derived from electron and gas density measurements using a two-wavelength quantitative Schlieren technique

    SciTech Connect

    Prevosto, L.; Mancinelli, B.; Artana, G.; Kelly, H.

    2011-03-15

    A two-wavelength quantitative Schlieren technique that allows inferring the electron and gas densities of axisymmetric arc plasmas without imposing any assumption regarding statistical equilibrium models is reported. This technique was applied to the study of local thermodynamic equilibrium (LTE) departures within the core of a 30 A high-energy density cutting arc. In order to derive the electron and heavy particle temperatures from the inferred density profiles, a generalized two-temperature Saha equation together with the plasma equation of state and the quasineutrality condition were employed. Factors such as arc fluctuations that influence the accuracy of the measurements and the validity of the assumptions used to derive the plasma species temperature were considered. Significant deviations from chemical equilibrium as well as kinetic equilibrium were found at elevated electron temperatures and gas densities toward the arc core edge. An electron temperature profile nearly constant through the arc core with a value of about 14000-15000 K, well decoupled from the heavy particle temperature of about 1500 K at the arc core edge, was inferred.

  4. 40 CFR Table W - 1A of Subpart W-Default Whole Gas Emission Factors for Onshore Petroleum and Natural Gas Production

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... Emission Factors for Onshore Petroleum and Natural Gas Production W Table W Protection of Environment... Petroleum and Natural Gas Systems Definitions. Pt. 98, Subpt. W, Table W-1A Table W-1A of Subpart W—Default Whole Gas Emission Factors for Onshore Petroleum and Natural Gas Production Onshore petroleum...

  5. Drift and diffusion of spin and charge density waves in a two-dimensional electron gas

    NASA Astrophysics Data System (ADS)

    Yang, Luyi; Koralek, J. D.; Orenstein, J.; Tibbetts, D. R.; Reno, J. L.; Lilly, M. P.

    2011-03-01

    We use transient grating spectroscopy (TGS) to study the persistent spin helix (PSH) state and electron-hole density wave (EHDW) in a 2D electron gas in the presence of an in-plane electric field parallel to the wavevector of the PSH or EHDW. By directly measuring the phase, we can measure the PSH and EHDW displacement with 10 nm spatial and sub-picosecond time resolution. We obtain both the spin diffusion and mobility and ambipolar diffusion and mobility from the TGS measurements of PSH and EHDW, respectively. The spin transresistivity extracted from the spin diffusion is in excellent agreement with the RPA theory of spin Coulomb drag (SCD). The spin mobility data indicate that SCD may also play a role in the spin wave drifting process. From the ambipolar diffusion and mobility, we obtain the transresistivity of electrons and holes in the same layer, which is much stronger than is typically seen in the conventional Coulomb drag experiments on coupled quantum wells.

  6. Noble gas adsorption in two-dimensional zeolites: a combined experimental and density functional theory study

    NASA Astrophysics Data System (ADS)

    Wang, Mengen; Zhong, Jianqiang; Boscoboinik, Jorge Anibal; Lu, Deyu

    Zeolites are important industrial catalysts with porous three-dimensional structures. The catalytically active sites are located inside the pores, thus rendering them inaccessible for surface science measurements. We synthesized a two-dimensional (2D) zeolite model system, consisting of an (alumino)silicate bilayer weakly bound to a Ru (0001) surface. The 2D zeolite is suitable for surface science studies; it allows a detailed characterization of the atomic structure of the active site and interrogation of the model system during the catalytic reaction. As an initial step, we use Ar adsorption to obtain a better understanding of the atomic structure of the 2D zeolite. In addition, atomic level studies of rare gas adsorption and separation by zeolite are important for its potential application in nuclear waste sequestration. Experimental studies found that Ar atoms can be trapped inside the 2D-zeolite, raising an interesting question on whether Ar atoms are trapped inside the hexagonal prism nano-cages or at the interface between the (alumino)silicate bilayer and Ru(0001), or both. DFT calculations using van der Waals density functionals were carried out to determine the preferred Ar adsorption sites and the corresponding adsorption energies. This research used resources of the Center for Functional Nanomaterials, which is a U.S. DOE Office of Science Facility, at Brookhaven National Laboratory under Contract No. DE-SC0012704.

  7. Density-induced processes in quantum gas mixtures in optical lattices

    NASA Astrophysics Data System (ADS)

    Jürgensen, Ole; Sengstock, Klaus; Lühmann, Dirk-Sören

    2012-10-01

    We show that off-site processes and multiorbital physics have a crucial impact on the phase diagram of quantum gas mixtures in optical lattices. In particular, we discuss Bose-Fermi mixtures where the intra- and interspecies interactions induce competing density-induced hopping processes, the so-called bond-charge interactions. Furthermore, higher bands strongly influence tunneling and on-site interactions. We apply a multiorbital interaction-induced dressing of the lowest band, which leads to renormalized hopping processes. These corrections give rise to an extended Hubbard model with intrinsically occupation-dependent parameters. The resulting decrease of the tunneling competes with a decrease of the total on-site interaction energy, both affecting the critical lattice depth of the superfluid to Mott-insulator transition. In contrast to the standard Bose-Fermi Hubbard model, we predict a large shift of the transition to shallower lattice depths with increasing Bose-Fermi attraction. The applied theoretical model allows an accurate prediction of the modified tunneling amplitudes and the critical lattice depth, both being recently observed experimentally.

  8. Novelty detection by multivariate kernel density estimation and growing neural gas algorithm

    NASA Astrophysics Data System (ADS)

    Fink, Olga; Zio, Enrico; Weidmann, Ulrich

    2015-01-01

    One of the underlying assumptions when using data-based methods for pattern recognition in diagnostics or prognostics is that the selected data sample used to train and test the algorithm is representative of the entire dataset and covers all combinations of parameters and conditions, and resulting system states. However in practice, operating and environmental conditions may change, unexpected and previously unanticipated events may occur and corresponding new anomalous patterns develop. Therefore for practical applications, techniques are required to detect novelties in patterns and give confidence to the user on the validity of the performed diagnosis and predictions. In this paper, the application of two types of novelty detection approaches is compared: a statistical approach based on multivariate kernel density estimation and an approach based on a type of unsupervised artificial neural network, called the growing neural gas (GNG). The comparison is performed on a case study in the field of railway turnout systems. Both approaches demonstrate their suitability for detecting novel patterns. Furthermore, GNG proves to be more flexible, especially with respect to dimensionality of the input data and suitability for online learning.

  9. Density Functional Computations and Mass Spectrometric Measurements. Can this Coupling Enlarge the Knowledge of Gas-Phase Chemistry?

    NASA Astrophysics Data System (ADS)

    Marino, T.; Russo, N.; Sicilia, E.; Toscano, M.; Mineva, T.

    A series of gas-phase properties of the systems has been investigated by using different exchange-correlation potentials and basis sets of increasing size in the framework of Density Functional theory with the aim to determine a strategy able to give reliable results with reasonable computational efforts.

  10. Generation and characterization of high-density gas jets from a 150 micron diameter nozzle in air

    NASA Astrophysics Data System (ADS)

    Hahn, Luke; Bartas, Kevin; Tay, Yan; Kuk, Donghoon; Kim, Ki-Yong

    This work characterizes argon and nitrogen gas jets in unconventional atmospheric pressure instead of the conventional vacuum pressure, and then compares the results directly to that of the conventional technique of creating gas jet targets. A Mach-Zehnder interferometer was used to estimate the number density of the gas jet, and a Rayleigh scattering setup was used to determine if either of the techniques formed atomic clusters and if so, estimating relative quantity. The diameter of the cylindrical nozzle used for is around 150 μm with backing pressures ranging from 13 bars to 69 bars. The highest backing pressure gives us a maximum phase shift value of 9 rad, number density 4.5 ×1020 cm-3. Another characteristic property of these jets is the shock diamond formation due to the flows interaction with atmospheric air particles. The highest number density for a shock diamond was ~1020 cm-3 which does not necessarily occur at higher backing pressure. Also, the distance from the first shock diamond to the nozzle orifice does increase with increasing backing pressure, consistent with a theory. This type of high-density, thin gas jets can be used as a laser target for creating dense plasmas and producing energetic particles and X-rays in the atmospheric conditions. Work supported by DOE, Fusion Energy Sciences under Award No. DE-SC0010706.

  11. The Effects of Fuel and Cylinder Gas Densities on the Characteristics of Fuel Sprays for Oil Engines

    NASA Technical Reports Server (NTRS)

    Joachim, W F; Beardsley, Edward G

    1928-01-01

    This investigation was conducted as a part of a general research on fuel-injection engines for aircraft. The purpose of the investigation was to determine the effects of fuel and cylinder gas densities with several characteristics of fuel sprays for oil engines. The start, growth, and cut-off of single fuel sprays produced by automatic injection valves were recorded on photographic film by means of special high-speed motion-picture apparatus. This equipment, which has been described in previous reports, is capable of taking twenty-five consecutive pictures of the moving spray at the rate of 4,000 per second. The penetrations of the fuel sprays increased and the cone angles and relative distributions decreased with increase in the specific gravity of the fuel. The density of the gas into which the fuel sprays were injected controlled their penetration. This was the only characteristic of the chamber gas that had a measurable effect upon the fuel sprays. Application of fuel-spray penetration data to the case of an engine, in which the pressure is rising during injection, indicated that fuel sprays may penetrate considerably farther than when injected into a gas at a density equal to that of the gas in an engine cylinder at top center.

  12. Anamnestic risk factor questionnaire as reliable diagnostic instrument for osteoporosis (reduced bone morphogenic density)

    PubMed Central

    2011-01-01

    Background Osteoporosis is a major health problem worldwide, and is included in the WHO list of the top 10 major diseases. However, it is often undiagnosed until the first fracture occurs, due to inadequate patient education and lack of insurance coverage for screening tests. Anamnestic risk factors like positive family anamnesis or early menopause are assumed to correlate with reduced BMD. Methods In our study of 78 patients with metaphyseal long bone fractures, we searched for a correlation between anamnestic risk factors, bone specific laboratory values, and the bone morphogenic density (BMD). Each indicator was examined as a possible diagnostic instrument for osteoporosis. The secondary aim of this study was to demonstrate the high prevalence of osteoporosis in patients with metaphyseal fractures. Results 76.9% of our fracture patients had decreased bone density and 43.6% showed manifest osteoporosis in DXA (densitometry) measurements. Our questionnaire, identifying anamnestic risk factors, correlated highly significantly (p = 0.01) with reduced BMD, whereas seven bone-specific laboratory values (p = 0.046) correlated significantly. Conclusions Anamnestic risk factors correlate with pathological BMD. The medical questionnaire used in this study would therefore function as a cost-effective primary diagnostic instrument for identification of osteoporosis patients. PMID:21849030

  13. Cryopegs as destabilization factor of intra-permafrost gas hydrates

    NASA Astrophysics Data System (ADS)

    Chuvilin, Evgeny; Bukhanov, Boris; Istomin, Vladimir

    2016-04-01

    A characteristic feature of permafrost soils in the Arctic is widespread intra-permafrost unfrozen brine lenses - cryopegs. They are often found in permafrost horizons in the north part of Western Siberia, in particular, on the Yamal Peninsula. Cryopegs depths in permafrost zone can be tens and hundreds of meters from the top of frozen strata. The chemical composition of natural cryopegs is close to sea waters, but is characterized by high mineralization. They have a sodium-chloride primary composition with a minor amount of sulphate. Mineralization of cryopegs brine is often hundreds of grams per liter, and the temperature is around -6…-8 °C. The formation of cryopegs in permafrost is associated with processes of long-term freezing of sediments and cryogenic concentration of salts and salt solutions in local areas. The cryopegs' formation can take place in the course of permafrost evolution at the sea transgressions and regressions during freezing of saline sea sediments. Very important feature of cryopegs in permafrost is their transformation in the process of changing temperature and pressure conditions. As a result, the salinity and chemical composition are changed and in addition the cryopegs' location can be changed during their migration. The cryopegs migration violates the thermodynamic conditions of existence intra-permafrost gas hydrate formations, especially the relic gas hydrates deposits, which are situated in the shallow permafrost up to 100 meters depth in a metastable state [1]. The interaction cryopegs with gas hydrates accumulations can cause decomposition of intra-permafrost hydrates. Moreover, the increasing of salt and unfrozen water content in sedimentary rocks sharply reduce the efficiency of gas hydrates self-preservation in frozen soils. It is confirmed by experimental investigations of interaction of frozen gas hydrate bearing sediments with salt solutions [2]. So, horizons with elevated pressure can appear, as a result of gas hydrate

  14. Scaling of stomatal size and density optimizes allocation of leaf epidermal space for gas exchange in angiosperms

    NASA Astrophysics Data System (ADS)

    de Boer, Hugo Jan; Price, Charles A.; Wagner-Cremer, Friederike; Dekker, Stefan C.; Franks, Peter J.; Veneklaas, Erik J.

    2015-04-01

    Stomata on plant leaves are key traits in the regulation of terrestrial fluxes of water and carbon. The basic morphology of stomata consists of a diffusion pore and two guard cells that regulate the exchange of CO2 and water vapour between the leaf interior and the atmosphere. This morphology is common to nearly all land plants, yet stomatal size (defined as the area of the guard cell pair) and stomatal density (the number of stomata per unit area) range over three orders of magnitude across species. Evolution of stomatal sizes and densities is driven by selection pressure on the anatomical maximum stomatal conductance (gsmax), which determines the operational range of leaf gas exchange. Despite the importance of stomata traits for regulating leaf gas exchange, a quantitative understanding of the relation between adaptation of gsmax and the underlying co-evolution of stomatal sizes and densities is still lacking. Here we develop a theoretical framework for a scaling relationship between stomatal sizes and densities within the constraints set by the allocation of epidermal space and stomatal gas exchange. Our theory predicts an optimal scaling relationship that maximizes gsmax and minimizes epidermal space allocation to stomata. We test whether stomatal sizes and densities reflect this optimal scaling with a global compilation of stomatal trait data on 923 species reflecting most major clades. Our results show optimal scaling between stomatal sizes and densities across all species in the compiled data set. Our results also show optimal stomatal scaling across angiosperm species, but not across gymnosperm and fern species. We propose that the evolutionary flexibility of angiosperms to adjust stomatal sizes underlies their optimal allocation of leaf epidermal space to gas exchange.

  15. Geological and environmental factors involved in natural gas accidents

    NASA Astrophysics Data System (ADS)

    Sommer, Sheldone E.

    1981-07-01

    Variability in soil mineralogy, texture, and pavement cover are involved in events leading to undetected gas leaks and subsequent explosions in Bowie, Md. and Washington, D.C. These geologic parameters are involved in selectively removing the gas odorant additive t-butyl merceptan as the gas came into contact with the soil near the pipeline breaks. This removal resulted in an accumulation of combustable natural gas without detectable odor. Soil samples from drill holes and near surface sites were utilized to map soil type, texture, and mineralogy. Residual methane content of the samples was also measured. The data from two dissimilar sites indicates that finegrained soil enriched in montmorillonite preferentially removes the odorant.

  16. A theory for accelerated slow crack growth in medium-density polyethylene fuel-gas pipes

    SciTech Connect

    Chaoui, K.

    1989-01-01

    In the present work, a new testing procedure is developed for medium density polyethylene (MDPE) fuel gas pipes to produce brittle fracture at laboratory scale within a shorter period of time as compared to existing procedures. In the proposed procedure, the intrinsic resistance of (MDPE) pipes is studied under fatigue mode and ambient environment. Because of the lack of theoretical foundations in the existing procedures, brittle fracture in such structural components is addressed using the crack layer formalism in order to assess the controlling damage mechanisms and extract characteristic parameters representative of the phenomena occurring as a result of failure. It is found that crack propagation behavior is split into a brittle regime which extends up to half of the specimen width and a ductile regime which controls most of the second half. Damage analysis revealed that the brittle regime is led by a craze zone which becomes diffuse and larger as ductility increases. Crack and its surrounding damage are treated as a single macroscopic entity called a crack layer (CL). The portion where damage accumulates under the effects of the stress field at the crack tip is defined as the active zone. This zone is a major energy sink and thus, controls the crack propagation rate. The driving force and the instability conditions for CL propagation are commonly given in terms of the energy available and the energy required for propagation which is expressed as the product of the resistance moment R{sub 1} and the specific enthalpy of damage. In the present case, the analysis is limited to the brittle regime which is of a great interest in the long-term failure of MDPE pipes under service conditions. Also, the analysis uses the entire brittle fracture history to evaluate the resistance moment for the crazing mechanism and to extract the specific enthalpy of damage {Psi}*.

  17. Environmental Factors Associated with High Fly Densities and Diarrhea in Vellore, India.

    PubMed

    Collinet-Adler, Stefan; Babji, Sudhir; Francis, Mark; Kattula, Deepthi; Premkumar, Prasanna Samuel; Sarkar, Rajiv; Mohan, Venkat Ragava; Ward, Honorine; Kang, Gagandeep; Balraj, Vinohar; Naumova, Elena N

    2015-09-01

    Diarrhea causes significant morbidity and mortality in Indian children under 5 years of age. Flies carry enteric pathogens and may mediate foodborne infections. In this study, we characterized fly densities as a determinant of infectious diarrhea in a longitudinal cohort of 160 urban and 80 rural households with 1,274 individuals (27% under 5 years of age) in Vellore, India. Household questionnaires on living conditions were completed at enrollment. Fly abundance was measured during the wet and dry seasons using fly ribbons placed in kitchens. PCRs for enteric bacteria, viruses, and protozoa were performed on 60 fly samples. Forty-three (72%) fly samples were positive for the following pathogens: norovirus (50%), Salmonella spp. (46.7%), rotavirus (6.7%), and Escherichia coli (6.7%). Ninety-one episodes of diarrhea occurred (89% in children under 5 years of age). Stool pathogens isolated in 24 of 77 (31%) samples included E. coli, Shigella spp., Vibrio spp., Giardia, Cryptosporidium, and rotavirus. Multivariate log-linear models were used to explore the relationships between diarrhea and fly densities, controlling for demographics, hygiene, and human-animal interactions. Fly abundance was 6 times higher in rural than urban sites (P < 0.0001). Disposal of garbage close to homes and rural living were significant risk factors for high fly densities. The presence of latrines was protective against high fly densities and diarrhea. The adjusted relative risks of diarrheal episodes and duration of diarrhea, associated with fly density at the 75th percentile, were 1.18 (95% confidence interval [CI], 1.03 to 1.34) and 1.15 (95% CI, 1.02 to 1.29), respectively. Flies harbored enteric pathogens, including norovirus, a poorly documented pathogen on flies. PMID:26116684

  18. Environmental Factors Associated with High Fly Densities and Diarrhea in Vellore, India

    PubMed Central

    Collinet-Adler, Stefan; Babji, Sudhir; Francis, Mark; Kattula, Deepthi; Premkumar, Prasanna Samuel; Sarkar, Rajiv; Mohan, Venkat Ragava; Ward, Honorine; Kang, Gagandeep; Balraj, Vinohar

    2015-01-01

    Diarrhea causes significant morbidity and mortality in Indian children under 5 years of age. Flies carry enteric pathogens and may mediate foodborne infections. In this study, we characterized fly densities as a determinant of infectious diarrhea in a longitudinal cohort of 160 urban and 80 rural households with 1,274 individuals (27% under 5 years of age) in Vellore, India. Household questionnaires on living conditions were completed at enrollment. Fly abundance was measured during the wet and dry seasons using fly ribbons placed in kitchens. PCRs for enteric bacteria, viruses, and protozoa were performed on 60 fly samples. Forty-three (72%) fly samples were positive for the following pathogens: norovirus (50%), Salmonella spp. (46.7%), rotavirus (6.7%), and Escherichia coli (6.7%). Ninety-one episodes of diarrhea occurred (89% in children under 5 years of age). Stool pathogens isolated in 24 of 77 (31%) samples included E. coli, Shigella spp., Vibrio spp., Giardia, Cryptosporidium, and rotavirus. Multivariate log-linear models were used to explore the relationships between diarrhea and fly densities, controlling for demographics, hygiene, and human-animal interactions. Fly abundance was 6 times higher in rural than urban sites (P < 0.0001). Disposal of garbage close to homes and rural living were significant risk factors for high fly densities. The presence of latrines was protective against high fly densities and diarrhea. The adjusted relative risks of diarrheal episodes and duration of diarrhea, associated with fly density at the 75th percentile, were 1.18 (95% confidence interval [CI], 1.03 to 1.34) and 1.15 (95% CI, 1.02 to 1.29), respectively. Flies harbored enteric pathogens, including norovirus, a poorly documented pathogen on flies. PMID:26116684

  19. Analyses of substantially different plasma current densities and safety factors reconstructed from magnetic diagnostics data

    NASA Astrophysics Data System (ADS)

    Zaitsev, F. S.; Kostomarov, D. P.; Suchkov, E. P.; Drozdov, V. V.; Solano, E. R.; Murari, A.; Matejcik, S.; Hawkes, N. C.; Contributors, JET-EFDA

    2011-10-01

    The problem of plasma current density and safety factor reconstruction using magnetic field measurements is considered. In the traditional formulation, the problem is strongly ill-posed. In particular, substantially different current densities and safety factors can be equally well attributed to the same set of measurements, given their experimental errors. In other words, the problem can be strongly unstable with respect to the input data. Different constraints are used in practice to make the problem more stable. This paper presents an accurate mathematical formulation of the inverse problem and its variants. A numerical algorithm is provided, which permits us to study the stability with respect to variations in the input data, to find all substantially different solutions, or to prove their absence, and to determine the confidence intervals of the reconstructions. The proposed method also allows establishing the maximum error for a given diagnostic (additional constraint), below which the diagnostic efficiently extracts one solution among several substantially different ones. Examples of very different current density and safety factor reconstructions for measurements with finite accuracy are presented for the original formulation of the inverse problem. Cases of MAST, JET and ITER-like plasmas are considered. It is shown that including the motional Stark effect (MSE) measurements as a constraint, provided the accuracy of MSE measurements is sufficient, allows identifying one solution among several very different ones, obtained without such a constraint. The maximum MSE diagnostics error for efficient identification of this solution is estimated for JET. The approach of this paper can be used for a wide range of ill-posed problems in physics and can help in selecting additional conditions, which can identify the most likely solution among several.

  20. Vascular density, angiogenesis and pro-angiogenic factors in uterine fibroids.

    PubMed

    Sajewicz, Marek; Konarska, Monika; Wrona, Anna Natalia; Aleksandrovych, Veronika; Bereza, Tomasz; Komnata, Kinga; Solewski, Bernard; Maleszka, Aleksandra; Depukat, Paweł; Warchoł, Łukasz

    2016-01-01

    Angiogenesis is a process of development of new vessels from the preexisting vascular network of a host. This is process which is seen in many physiological situations but it accompanies also a development of different lesions, i.e. neoplasms. Uterine fibroids are one of the most frequent lesions which affect human internal female genital tracts. Authors briefly review most important pro-angiogenic factors, based on their own observation as well as reviewing current literature. They pay much attention to vascular density which is significantly changed in the uterine tumors. PMID:27513836

  1. Charge density distributions and charge form factors of the N=82 and N=126 isotonic nuclei

    SciTech Connect

    Wang Zaijun; Fan Ying; Ren Zhongzhou

    2006-01-15

    Charge form factors for N=82 and N=126 isotonic nuclei are calculated with the relativistic eikonal approximation, in which the charge density distributions are from the relativistic mean-field theory. The variations of charge form factors with proton number are discussed in detail. It is found that the most sensitive parts of the charge form factors are those around the minimums and maximums. For an increasing proton number, the charge form factors near the extrema have an upward shift. As the protons increase and occupy a new shell, the minimums and maximums of the charge form factors could also have a significant inward shift. The results can be useful for the study of behaviors of valence-proton wave functions for such nuclei as can be considered as a core plus proton(s), and thus the proton-halo phenomenon. In addition, the results can also be useful for future electron-unstable nucleus scattering experiments and provide tests of the reliability of the relativistic mean-field theory for the unstable nuclei.

  2. The Effects of Physicochemical Factors and Cell Density on Nitrite Transformation in a Lipid-Rich Chlorella.

    PubMed

    Liang, Fang; Du, Kui; Wen, Xiaobin; Luo, Liming; Geng, Yahong; Li, Yeguang

    2015-12-28

    To understand the effects of physicochemical factors on nitrite transformation by microalgae, a lipid-rich Chlorella with high nitrite tolerance was cultured with 8 mmol/l sodium nitrite as sole nitrogen source under different conditions. The results showed that nitrite transformation was mainly dependent on the metabolic activities of algal cells rather than oxidation of nitrite by dissolved oxygen. Light intensity, temperature, pH, NaHCO3 concentrations, and initial cell densities had significant effects on the rate of nitrite transformation. Single-factor experiments revealed that the optimum conditions for nitrite transformation were light intensity: 300 μmol/m(2); temperature: 30°C; pH: 7-8; NaHCO3 concentration: 2.0 g/l; and initial cell density: 0.15 g/l; and the highest nitrite transformation rate of 1.36 mmol/l/d was achieved. There was a positive correlation between nitrite transformation rate and the growth of Chlorella. The relationship between nitrite transformation rate (mg/l/d) and biomass productivity (g/l/d) could be described by the regression equation y = 61.3x (R(2) = 0.9665), meaning that 61.3 mg N element was assimilated by 1.0 g dry biomass on average, which indicated that the nitrite transformation is a process of consuming nitrite as nitrogen source by Chlorella. The results demonstrated that the Chlorella suspension was able to assimilate nitrite efficiently, which implied the feasibility of using flue gas for mass production of Chlorella without preliminary removal of NOX. PMID:26323272

  3. Cultivar and Tree Density As Key Factors in the Long-Term Performance of Super High-Density Olive Orchards.

    PubMed

    Díez, Concepción M; Moral, Juan; Cabello, Diego; Morello, Pablo; Rallo, Luis; Barranco, Diego

    2016-01-01

    Super high-density (SHD) olive orchards are rapidly expanding since the first plantation was set up in Spain in the 1990s. Because there are no long-term studies characterizing these systems, it is unknown if densities above a certain threshold could trigger competition among fully-grown trees, compromising their development. Over 14 years we have evaluated the performance of the major olive cultivars currently planted in SHD systems ("Arbequina," Arbequina IRTA-i·18, "Arbosana," "Fs-17," and "Koroneiki") and nine SHD designs ranging from 780 to 2254 trees ha(-1) for the cultivar "Arbequina." Remarkably, the accumulated fruit and oil production of the five cultivars increased linearly over time. Our data indicated the favorable long-term performance of the evaluated cultivars with an average annual oil production of 2.3 t ha(-1). Only "Fs-17" did not perform well to the SHD system in our conditions and it yielded about half (1.2 t ha(-1)) of the other cultivars. In the density trial for "Arbequina," both fruit and oil accumulated production increased over time as a function of tree density. Thus, the accumulated oil yield ranged from 16.1 t ha(-1) for the lowest density (780 trees ha(-1)) to 29.9 t ha(-1) for the highest (2254 trees ha(-1)). In addition, we note that the accumulated production per surface unit showed a better correlation with the hedgerow length than the tree density. Thus, the current planting designs of SHD olive orchards can be further improved taking this parameter into account. Despite observations that some irregular patterns of crop distribution have arisen, our olive hedgerows are still fully productive after 14 years of planting. This result contradicts previous experiences that showed declines in production 7 or 8 years after planting due to high vigor, shading, and limited ventilation. PMID:27602035

  4. Propagation of a strong spherical shock wave in a gravitating or non-gravitating dusty gas with exponentially varying density

    NASA Astrophysics Data System (ADS)

    Nath, G.; Vishwakarma, J. P.

    2016-06-01

    The propagation of a strong spherical shock wave in a dusty gas with or without self-gravitational effects is investigated in the case of isothermal and adiabatic flows. The dusty gas is assumed to be a mixture of small solid particles and perfect gas. The equilibrium flow conditions are assumed to be maintained, and the density of the mixture is assumed to be varying and obeying an exponential law. Non-similarity solutions are obtained and the effects of variations of the mass concentration of solid particles in the mixture and the ratio of the density of solid particles to the initial density of the gas, and the presence of self-gravitational field on the flow variables are investigated at given times. Our analysis reveals that after inclusion of gravitational field effects surprisingly the shock strength increases and remarkable differences are found in the distribution of flow variables. An increase in time also, increases the shock strength. Further, it is investigated that the consideration of isothermal flow increases the shock strength, and removes the singularity in the density distribution. Also, the presence of gravitational field increases the compressibility of the medium, due to which it is compressed and therefore the distance between the inner contact surface and the shock surface is reduced. The shock waves in self-gravitating dusty gas can be important for description of shocks in supernova explosions, in the study of central part of star burst galaxies, star formation and shocks in stellar explosion, nuclear explosion, in industry, rupture of a pressurized vessel and explosion in the ionosphere. Other potential applications of this study include analysis of data from exploding wire experiments and cylindrically symmetric hypersonic flow problems associated with meteors or re-entry of vehicles etc. A comparison is made between the solutions in the cases of the gravitating and the non-gravitating media. The obtained solutions are applicable for

  5. Clinical and Microbiological Factors Associated with High Nasopharyngeal Pneumococcal Density in Patients with Pneumococcal Pneumonia

    PubMed Central

    Alpkvist, Helena; Athlin, Simon; Nauclér, Pontus; Herrmann, Björn; Abdeldaim, Guma; Slotved, Hans-Christian; Hedlund, Jonas; Strålin, Kristoffer

    2015-01-01

    Background We aimed to study if certain clinical and/or microbiological factors are associated with a high nasopharyngeal (NP) density of Streptococcus pneumoniae in pneumococcal pneumonia. In addition, we aimed to study if a high NP pneumococcal density could be useful to detect severe pneumococcal pneumonia. Methods Adult patients hospitalized for radiologically confirmed community-acquired pneumonia were included in a prospective study. NP aspirates were collected at admission and were subjected to quantitative PCR for pneumococcal DNA (Spn9802 DNA). Patients were considered to have pneumococcal etiology if S. pneumoniae was detected in blood culture and/or culture of respiratory secretions and/or urinary antigen test. Results Of 166 included patients, 68 patients had pneumococcal DNA detected in NP aspirate. Pneumococcal etiology was noted in 57 patients (84%) with positive and 8 patients (8.2%) with negative test for pneumococcal DNA (p<0.0001). The median NP pneumococcal density of DNA positive patients with pneumococcal etiology was 6.83 log10 DNA copies/mL (range 1.79–9.50). In a multivariate analysis of patients with pneumococcal etiology, a high pneumococcal density was independently associated with severe pneumonia (Pneumonia Severity Index risk class IV-V), symptom duration ≥2 days prior to admission, and a medium/high serum immunoglobulin titer against the patient’s own pneumococcal serotype. NP pneumococcal density was not associated with sex, age, smoking, co-morbidity, viral co-infection, pneumococcal serotype, or bacteremia. Severe pneumococcal pneumonia was noted in 28 study patients. When we studied the performance of PCR with different DNA cut-off levels for detection of severe pneumococcal pneumonia, we found sensitivities of 54–82% and positive predictive values of 37–56%, indicating suboptimal performance. Conclusions Pneumonia severity, symptom duration ≥2 days, and a medium/high serum immunoglobulin titer against the patient

  6. Fibroblast growth factor 23 contributes to diminished bone mineral density in childhood inflammatory bowel disease

    PubMed Central

    2012-01-01

    Background Diminished bone mineral density (BMD) is of significant concern in pediatric inflammatory bowel disease (IBD). Exact etiology is debatable. The recognition of fibroblast growth factor 23 (FGF23), a phosphaturic hormone related to tumor necrosis factor alpha (TNF-α) makes it plausible to hypothesize its possible relation to this pathology. Methods In this follow up case control study, BMD as well as serum levels of FGF23, calcium, phosphorus, alkaline phosphatase, creatinine, parathyroid hormone, 25 hydroxy vitamin D3 and 1, 25 dihydroxy vitamin D3 were measured in 47 children with IBD during flare and reassessed in the next remission. Results Low BMD was frequent during IBD flare (87.2%) with significant improvement after remission (44.7%). During disease flare, only 21.3% of patients had vitamin D deficiency, which was severe in 12.8%. During remission, all patients had normal vitamin D except for two patients with Crohn’s disease (CD) who remained vitamin D deficient. Mean value of serum FGF23 was significantly higher among patients with IBD during flare compared to controls. It showed significant improvement during remission but not to the control values. 1, 25 dihydroxy vitamin D3, FGF23, serum calcium and urinary phosphorus were significant determinants of BMD in IBD patients. Conclusions We can conclude that diminished BMD in childhood IBD is a common multifactorial problem. Elevated FGF23 would be a novel addition to the list of factors affecting bone mineral density in this context. Further molecular studies are warranted to display the exact interplay of these factors. PMID:22551310

  7. Genetic Sharing with Cardiovascular Disease Risk Factors and Diabetes Reveals Novel Bone Mineral Density Loci

    PubMed Central

    Thompson, Wesley K.; McEvoy, Linda K.; Schork, Andrew J.; Zuber, Verena; LeBlanc, Marissa; Bettella, Francesco; Mills, Ian G.; Desikan, Rahul S.; Djurovic, Srdjan; Gautvik, Kaare M.; Dale, Anders M.; Andreassen, Ole A.

    2015-01-01

    Bone Mineral Density (BMD) is a highly heritable trait, but genome-wide association studies have identified few genetic risk factors. Epidemiological studies suggest associations between BMD and several traits and diseases, but the nature of the suggestive comorbidity is still unknown. We used a novel genetic pleiotropy-informed conditional False Discovery Rate (FDR) method to identify single nucleotide polymorphisms (SNPs) associated with BMD by leveraging cardiovascular disease (CVD) associated disorders and metabolic traits. By conditioning on SNPs associated with the CVD-related phenotypes, type 1 diabetes, type 2 diabetes, systolic blood pressure, diastolic blood pressure, high density lipoprotein, low density lipoprotein, triglycerides and waist hip ratio, we identified 65 novel independent BMD loci (26 with femoral neck BMD and 47 with lumbar spine BMD) at conditional FDR < 0.01. Many of the loci were confirmed in genetic expression studies. Genes validated at the mRNA levels were characteristic for the osteoblast/osteocyte lineage, Wnt signaling pathway and bone metabolism. The results provide new insight into genetic mechanisms of variability in BMD, and a better understanding of the genetic underpinnings of clinical comorbidity. PMID:26695485

  8. NO density and gas temperature measurements in atmospheric pressure nanosecond repetitively pulsed (NRP) discharges by Mid-IR QCLAS

    NASA Astrophysics Data System (ADS)

    Simeni Simeni, Marien; Stancu, Gabi-Daniel; Laux, Christophe

    2014-10-01

    Nitric oxide is a key species for many processes: in combustion, in human skin physiology... Recently, NO-ground state absolute density measurements produced by atmospheric pressure NRP discharges were carried out in air as a function of the discharge parameters, using Quantum Cascade Laser Absorption Spectroscopy. These measurements were space averaged and performed in the post-discharge region in a large gas volume. Here we present radial profiles of NO density and temperature measured directly in the discharge for different configurations. Small plasma volume and species densities, high temperature and EM noise environment make the absorption diagnostic challenging. For this purpose the QCLAS sensitivity was improved using a two-detector system. We conducted lateral absorbance measurements with a spatial resolution of 300 μm for two absorption features at 1900.076 and 1900.517 cm-1. The radial temperature and NO density distributions were obtained from the Abel inverted lateral measurements. Time averaged NO densities of about 1.E16 cm-3 and gas temperature of about 1000K were obtained in the center of the discharge. PLASMAFLAME Project (Grant No ANR-11-BS09-0025).

  9. Geochemical and geologic factors effecting the formulation of gas hydrate: Task No. 5, Final report

    SciTech Connect

    Kvenvolden, K.A.; Claypool, G.E.

    1988-01-01

    The main objective of our work has been to determine the primary geochemical and geological factors controlling gas hydrate information and occurrence and particularly in the factors responsible for the generation and accumulation of methane in oceanic gas hydrates. In order to understand the interrelation of geochemical/geological factors controlling gas hydrate occurrence, we have undertaken a multicomponent program which has included (1) comparison of available information at sites where gas hydrates have been observed through drilling by the Deep Sea Drilling Project (DSDP) on the Blake Outer Ridge and Middle America Trench; (2) regional synthesis of information related to gas hydrate occurrences of the Middle America Trench; (3) development of a model for the occurrence of a massive gas hydrate as DSDP Site 570; (4) a global synthesis of gas hydrate occurrences; and (5) development of a predictive model for gas hydrate occurrence in oceanic sediment. The first three components of this program were treated as part of a 1985 Department of Energy Peer Review. The present report considers the last two components and presents information on the worldwide occurrence of gas hydrates with particular emphasis on the Circum-Pacific and Arctic basins. A model is developed to account for the occurrence of oceanic gas hydrates in which the source of the methane is from microbial processes. 101 refs., 17 figs., 6 tabs.

  10. Rigorous investigation of the reduced density matrix for the ideal Bose gas in harmonic traps by a loop-gas-like approach

    SciTech Connect

    Beau, Mathieu; Savoie, Baptiste

    2014-05-15

    In this paper, we rigorously investigate the reduced density matrix (RDM) associated to the ideal Bose gas in harmonic traps. We present a method based on a sum-decomposition of the RDM allowing to treat not only the isotropic trap, but also general anisotropic traps. When focusing on the isotropic trap, the method is analogous to the loop-gas approach developed by Mullin [“The loop-gas approach to Bose-Einstein condensation for trapped particles,” Am. J. Phys. 68(2), 120 (2000)]. Turning to the case of anisotropic traps, we examine the RDM for some anisotropic trap models corresponding to some quasi-1D and quasi-2D regimes. For such models, we bring out an additional contribution in the local density of particles which arises from the mesoscopic loops. The close connection with the occurrence of generalized-Bose-Einstein condensation is discussed. Our loop-gas-like approach provides relevant information which can help guide numerical investigations on highly anisotropic systems based on the Path Integral Monte Carlo method.

  11. Cultivar and Tree Density As Key Factors in the Long-Term Performance of Super High-Density Olive Orchards

    PubMed Central

    Díez, Concepción M.; Moral, Juan; Cabello, Diego; Morello, Pablo; Rallo, Luis; Barranco, Diego

    2016-01-01

    Super high-density (SHD) olive orchards are rapidly expanding since the first plantation was set up in Spain in the 1990s. Because there are no long-term studies characterizing these systems, it is unknown if densities above a certain threshold could trigger competition among fully-grown trees, compromising their development. Over 14 years we have evaluated the performance of the major olive cultivars currently planted in SHD systems (“Arbequina,” Arbequina IRTA-i·18, “Arbosana,” “Fs-17,” and “Koroneiki”) and nine SHD designs ranging from 780 to 2254 trees ha−1 for the cultivar “Arbequina.” Remarkably, the accumulated fruit and oil production of the five cultivars increased linearly over time. Our data indicated the favorable long-term performance of the evaluated cultivars with an average annual oil production of 2.3 t ha−1. Only “Fs-17” did not perform well to the SHD system in our conditions and it yielded about half (1.2 t ha−1) of the other cultivars. In the density trial for “Arbequina,” both fruit and oil accumulated production increased over time as a function of tree density. Thus, the accumulated oil yield ranged from 16.1 t ha−1 for the lowest density (780 trees ha−1) to 29.9 t ha−1 for the highest (2254 trees ha−1). In addition, we note that the accumulated production per surface unit showed a better correlation with the hedgerow length than the tree density. Thus, the current planting designs of SHD olive orchards can be further improved taking this parameter into account. Despite observations that some irregular patterns of crop distribution have arisen, our olive hedgerows are still fully productive after 14 years of planting. This result contradicts previous experiences that showed declines in production 7 or 8 years after planting due to high vigor, shading, and limited ventilation. PMID:27602035

  12. Clinicopathological significance of vascular endothelial growth factor, thymidine phosphorylase and microvessel density in colorectal cancer.

    PubMed

    Kimura, Yutaka; Morohashi, Satoko; Yoshizawa, Tadashi; Suzuki, Takahiro; Morohashi, Hajime; Sakamoto, Yoshiyuki; Koyama, Motoi; Murata, Akihiko; Kijima, Hiroshi; Hakamada, Kenichi

    2016-02-01

    Colorectal cancer is a common malignant disease, the incidence of which is increasing worldwide, therefore, identifying novel prognostic factors to improve adjuvant therapeutic strategies or postoperative monitoring is required. Angiogenesis, which is assessed by microvessel density (MVD), is significant in tumor growth and metastasis. However, the association between angiogenesis and clinical outcome remains controversial. In the present study, 84 surgically resected cases of colorectal cancer were examined to clarify the clinicopathological significance of vascular endothelial growth factor (VEGF), thymidine phosphorylase (TP) and cluster of differentiation (CD)34 expression levels. VEGF expression was identified to be significantly correlated with TP expression (r=0.45; P<0.0001) and MVD in the high VEGF expression group was observed to be significantly greater than that in the low VEGF expression group (P=0.0194). In the Dukes' stage D group, the MVD in the high TP expression group was significantly greater than that in the low TP expression group (P=0.0149). High VEGF expression was subsequently correlated with a short overall survival rate for patients exhibiting lymph node metastasis (P=0.0128); however, there was no significant difference in overall survival rate regarding the expression levels of TP and CD34. The results of the present study indicate that VEGF expression may serve as a prognostic factor for colorectal cancer patients exhibiting lymph node metastasis. Furthermore, angiogenesis, as assessed by MVD, is an important prognostic factor for tumor growth at the primary site. PMID:26676225

  13. Genetic variation in Transforming Growth Factor beta 1 and mammographic density in Singapore Chinese women

    PubMed Central

    Lee, Eunjung; Van den Berg, David; Hsu, Chris; Ursin, Giske; Koh, Woon-Puay; Yuan, Jian-Min; Stram, Daniel O.; Yu, Mimi C.; Wu, Anna H.

    2013-01-01

    Transforming growth factor-beta (TGF-β) plays a critical role in normal mammary development and morphogenesis. Decreased TGF-β signaling has been associated with increased mammographic density. Percent mammographic density (PMD) adjusted for age and body mass index (BMI) is a strong risk factor and predictor of breast cancer risk. PMD is highly heritable, but few genetic determinants have been identified. We investigated the association between genetic variation in TGFB1 and PMD using a cross-sectional study of 2,038 women who were members of the population-based Singapore Chinese Health Study cohort. We assessed PMD using a computer-assisted method. We used linear regression to examine the association between 9 tagging SNPs of TGFB1 and PMD and their interaction with parity, adjusting for age, BMI, and dialect group. We calculated ‘P-values adjusted for correlated tests’ (PACT) to account for multiple testing. The strongest association was observed for rs2241716. Adjusted PMD was higher by 1.5% per minor allele (PACT =0.04). When stratifying by parity, this association was limited to nulliparous women. For nulliparous women, adjusted PMD was higher by 8.6% per minor allele (PACT=0.003; P for interaction with parity=0.002). Three additional TGFB1 tagging SNPs, which were in linkage disequilibrium with rs2241716, were statistically significantly associated with adjusted PMD (PACT<0.05) for nulliparous women. However, none of these three SNPs showed statistically significant association after adjusting for rs2241716. Our data support that TGFB1 genetic variation may be an important genetic determinant of mammographic density measure that predicts breast cancer risk, particularly in nulliparous women. PMID:23333936

  14. Factors in Daily Physical Activity Related to Calcaneal Mineral Density in Men

    NASA Technical Reports Server (NTRS)

    Hutchinson, Teresa M.; Whalen, Robert T.; Cleek, Tammy M.; Vogel, John M.; Arnaud, Sara B.

    1995-01-01

    To determine the factors in daily physical activity that influence the mineral density of the calcaneus, we recorded walking steps and the type and duration of exercise in 43 healthy 26-to 51-yr-old men. Areal (g/sq cm) calcaneal bone mineral density (CBMD) was measured by single energy x-ray densitometry. Subjects walked a mean (+/- SD) of 7902(+/-2534) steps per day or approximately 3.9(+/-1.2) miles daily. Eight subjects reported no exercise activities. The remaining 35 subjects spent 143(2-772) (median and range) min/wk exercising. Twenty-eight men engaged in exercise activities that generate single leg peak vertical ground reaction forces (GRF(sub z)) of 2 or more body weights (high loaders, HL), and 15 reported exercise or daily activities that typically generate GRF(sub z) less than 1.5 body weights (low loaders, LL). CBMD was 12% higher in HL than LL (0.668 +/- 0.074 g/sq cm vs 0.597 +/- 0.062 g/sq cm, P less than 0.004). In the HL group, CBMD correlated to reported minutes of high load exercise (r = 0.41, P less than 0.03). CBMD was not related to the number of daily walking steps (N = 43, r = 0.03, NS). The results of this study support the concept that the dominant factor in daily physical activity relating to bone mineral density is the participation in site specific high loading activities, i.e., for the calcaneus, high calcaneal loads.

  15. Density profiles of CDM microhalos and their implications for annihilation boost factors

    SciTech Connect

    Anderhalden, Donnino; Diemand, Juerg E-mail: diemand@physik.uzh.ch

    2013-04-01

    In a standard cold dark matter (CDM) cosmology, microhalos at the CDM cutoff scale are the first and smallest objects expected to form in the universe. Here we present results of high resolution simulations of three representative roughly Earth-mass microhalos in order to determine their inner density profile. We find that CDM microhalos in simulations without a cutoff in the power spectrum roughly follow the NFW density profile, just like the much larger CDM halos on galaxy and galaxy cluster scales. But having a cutoff in the initial power spectrum at a typical neutralino free streaming scale of 10{sup −7}M{sub s}un makes their inner density profiles considerably steeper, i.e. ρ∝r{sup −(1.3−1.4)}, in good agreement with the results from Ishiyama et al. (2010). An extrapolation of the halo and subhalo mass functions down to the cutoff scale indicates that microhalos are extremely abundant throughout the present day dark matter distribution and might contribute significantly to indirect dark matter detection signals. Assuming a transition from a NFW to a steeper inner profile (ρ∝r{sup −1.4}) two orders of magnitude above the cutoff scale, the total boost factor for a Milky Way sized dark matter halo increases from about 3.5 to 4. We further find that CDM microhalo concentrations are consistent with the Bullock et al. (2001) model and clearly rule out simplistic power law models for the mass dependence of concentrations and subhalo annihilation, which would erroneously lead to very large boost factors (a few hundred for galaxy halos and over 1000 for clusters)

  16. Nerve growth factor induces sensitization of nociceptors without evidence for increased intraepidermal nerve fiber density.

    PubMed

    Hirth, Michael; Rukwied, Roman; Gromann, Alois; Turnquist, Brian; Weinkauf, Benjamin; Francke, Klaus; Albrecht, Philip; Rice, Frank; Hägglöf, Björn; Ringkamp, Matthias; Engelhardt, Maren; Schultz, Christian; Schmelz, Martin; Obreja, Otilia

    2013-11-01

    Nerve growth factor (NGF) is involved in the long-term sensitization of nociceptive processing linked to chronic pain. Functional and structural ("sprouting") changes can contribute. Thus, humans report long-lasting hyperalgesia to mechanical and electrical stimulation after intradermal NGF injection and NGF-induced sprouting has been reported to underlie cancer bone pain and visceral pain. Using a human-like animal model we investigated the relationship between the structure and function of unmyelinated porcine nociceptors 3 weeks after intradermal NGF treatment. Axonal and sensory characteristics were studied by in vivo single-fiber electrophysiology and immunohistochemistry. C fibers recorded extracellularly were classified based on mechanical response and activity-dependent slowing (ADS) of conduction velocity. Intraepidermal nerve fiber (IENF) densities were assessed by immunohistochemistry in pigs and in human volunteers using the same NGF model. NGF increased conduction velocity and reduced ADS and propagation failure in mechano-insensitive nociceptors. The proportion of mechano-sensitive C nociceptors within NGF-treated skin areas increased from 45.1% (control) to 71% and their median mechanical thresholds decreased from 40 to 20 mN. After NGF application, the mechanical receptive fields of nociceptors increased from 25 to 43 mm(2). At the structural level, however, IENF density was not increased by NGF. In conclusion, intradermal NGF induces long-lasting axonal and mechanical sensitization in porcine C nociceptors that corresponds to hyperalgesia observed in humans. Sensitization is not accompanied by increased IENF density, suggesting that NGF-induced hyperalgesia might not depend on changes in nerve fiber density but could be linked to the recruitment of previously silent nociceptors. PMID:23891896

  17. Predicting Fractures in an International Cohort using Risk Factor Algorithms, Without Bone Mineral Density

    PubMed Central

    Sambrook, Philip N; Flahive, Julie; Hooven, Fred H; Boonen, Steven; Chapurlat, Roland; Lindsay, Robert; Nguyen, Tuan V; Díez-Perez, Adolfo; Pfeilschifter, Johannes; Greenspan, Susan L; Hosmer, David; Netelenbos, J Coen; Adachi, Jonathan D; Watts, Nelson B; Cooper, Cyrus; Roux, Christian; Rossini, Maurizio; Siris, Ethel S; Silverman, Stuart; Saag, Kenneth G; Compston, Juliet E; LaCroix, Andrea; Gehlbach, Stephen

    2016-01-01

    Clinical risk factors are associated with increased probability of fracture in postmenopausal women. We sought to compare prediction models using self-reported clinical risk factors, excluding bone-mineral density (BMD), to predict incident fracture among postmenopausal women. The GLOW study enrolled women aged ≥55 years were seen at 723 primary care practices in 10 countries. The population comprised 19,586 women aged ≥60 years who were not receiving anti-osteoporosis medication and were followed annually for 2 years. Self-administered questionnaires were used to collect data on characteristics, fracture risk factors, previous fractures, and health status. The main outcome measure compares the c index for models using the WHO Fracture Risk (FRAX), the Garvan Fracture Risk Calculator (FRC), and a simple model using age and prior fracture. Over 2 years, 880 women reported incident fractures including 69 hip fractures, 468 “major fractures” (as defined by FRAX) and 583 “osteoporotic fractures” (as defined by FRC). Using baseline clinical risk factors, both FRAX and FRC showed moderate ability to correctly order hip fracture times (c index for hip fracture: 0.78 and 0.76, respectively). C indices for “major” and “osteoporotic” fractures showed lower values, at 0.61 and 0.64. Neither algorithm was better than the model based on age+fracture history alone (c index for hip fracture: 0.78). In conclusion, estimation of fracture risk in an international primary care population of postmenopausal women can be made using clinical risk factors alone, without BMD. However, more sophisticated models incorporating multiple clinical risk factors including falls were not superior to more parsimonious models in predicting future fracture in this population. PMID:21887705

  18. Assessing the accuracy of the van der Waals density functionals for rare-gas and small molecular systems

    NASA Astrophysics Data System (ADS)

    Callsen, Martin; Hamada, Ikutaro

    2015-05-01

    The precise description of chemical bonds with different natures is a prerequisite for an accurate electronic structure method. The van der Waals density functional is a promising approach that meets such a requirement. Nevertheless, the accuracy should be assessed for a variety of materials to test the robustness of the method. We present benchmark calculations for weakly interacting molecular complexes and rare-gas systems as well as covalently bound molecular systems, in order to assess the accuracy and applicability of rev-vdW-DF2, a recently proposed variant [I. Hamada, Phys. Rev. B 89, 121103 (2014), 10.1103/PhysRevB.89.121103] of the van der Waals density functional. It is shown that although the calculated atomization energies for small molecules are less accurate rev-vdW-DF2 describes the interaction energy curves for the weakly interacting molecules and rare-gas complexes, as well as the bond lengths of diatomic molecules, reasonably well.

  19. A new equation of state for better liquid density prediction of natural gas systems

    NASA Astrophysics Data System (ADS)

    Nwankwo, Princess C.

    Equations of state formulations, modifications and applications have remained active research areas since the success of van der Waal's equation in 1873. The need for better reservoir fluid modeling and characterization is of great importance to petroleum engineers who deal with thermodynamic related properties of petroleum fluids at every stage of the petroleum "life span" from its drilling, to production through the wellbore, to transportation, metering and storage. Equations of state methods are far less expensive (in terms of material cost and time) than laboratory or experimental forages and the results are interestingly not too far removed from the limits of acceptable accuracy. In most cases, the degree of accuracy obtained, by using various EOS's, though not appreciable, have been acceptable when considering the gain in time. The possibility of obtaining an equation of state which though simple in form and in use, could have the potential of further narrowing the present existing bias between experimentally determined and popular EOS estimated results spurred the interest that resulted in this study. This research study had as its chief objective, to develop a new equation of state that would more efficiently capture the thermodynamic properties of gas condensate fluids, especially the liquid phase density, which is the major weakness of other established and popular cubic equations of state. The set objective was satisfied by a new semi analytical cubic three parameter equation of state, derived by the modification of the attraction term contribution to pressure of the van der Waal EOS without compromising either structural simplicity or accuracy of estimating other vapor liquid equilibria properties. The application of new EOS to single and multi-component light hydrocarbon fluids recorded far lower error values than does the popular two parameter, Peng-Robinson's (PR) and three parameter Patel-Teja's (PT) equations of state. Furthermore, this research

  20. Adsorption of SF6 decomposed gas on anatase (101) and (001) surfaces with oxygen defect: a density functional theory study.

    PubMed

    Zhang, Xiaoxing; Chen, Qinchuan; Tang, Ju; Hu, Weihua; Zhang, Jinbin

    2014-01-01

    The detection of partial discharge by analyzing the components of SF6 gas in gas-insulated switchgears is important to the diagnosis and assessment of the operational state of power equipment. A gas sensor based on anatase TiO2 is used to detect decomposed gases in SF6. In this paper, first-principle density functional theory calculations are adopted to analyze the adsorption of SO2, SOF2, and SO2F2, the primary decomposition by-products of SF6 under partial discharge, on anatase (101) and (001) surfaces. Simulation results show that the perfect anatase (001) surface has a stronger interaction with the three gases than that of anatase (101), and both surfaces are more sensitive and selective to SO2 than to SOF2 and SO2F2. The selection of a defect surface to SO2, SOF2, and SO2F2 differs from that of a perfect surface. This theoretical result is corroborated by the sensing experiment using a TiO2 nanotube array (TNTA) gas sensor. The calculated values are analyzed to explain the results of the Pt-doped TNTA gas sensor sensing experiment. The results imply that the deposited Pt nanoparticles on the surface increase the active sites of the surface and the gas molecules may decompose upon adsorption on the active sites. PMID:24755845

  1. Adsorption of SF6 decomposed gas on anatase (101) and (001) surfaces with oxygen defect: A density functional theory study

    NASA Astrophysics Data System (ADS)

    Zhang, Xiaoxing; Chen, Qinchuan; Tang, Ju; Hu, Weihua; Zhang, Jinbin

    2014-04-01

    The detection of partial discharge by analyzing the components of SF6 gas in gas-insulated switchgears is important to the diagnosis and assessment of the operational state of power equipment. A gas sensor based on anatase TiO2 is used to detect decomposed gases in SF6. In this paper, first-principle density functional theory calculations are adopted to analyze the adsorption of SO2, SOF2, and SO2F2, the primary decomposition by-products of SF6 under partial discharge, on anatase (101) and (001) surfaces. Simulation results show that the perfect anatase (001) surface has a stronger interaction with the three gases than that of anatase (101), and both surfaces are more sensitive and selective to SO2 than to SOF2 and SO2F2. The selection of a defect surface to SO2, SOF2, and SO2F2 differs from that of a perfect surface. This theoretical result is corroborated by the sensing experiment using a TiO2 nanotube array (TNTA) gas sensor. The calculated values are analyzed to explain the results of the Pt-doped TNTA gas sensor sensing experiment. The results imply that the deposited Pt nanoparticles on the surface increase the active sites of the surface and the gas molecules may decompose upon adsorption on the active sites.

  2. Steady temperature and density distributions in a gas containing heat sources

    NASA Technical Reports Server (NTRS)

    Davison, H. W.

    1971-01-01

    Computer program, STADDIG, is based on steady state, one dimensional heat transfer calculation using cylindrical coordinates. Program allows for conduction across gas and container walls. Heat is dissipated from walls by forced convection cooling with incompressible coolant. Heat sources are included in coolant, gas, and walls.

  3. Computational modeling of Krypton gas puffs with tailored mass density profiles on Z

    SciTech Connect

    Jennings, C. A.; Ampleford, D. J.; Lamppa, D. C.; Hansen, S. B.; Jones, B.; Harvey-Thompson, A. J.; Jobe, M.; Strizic, T.; Reneker, J.; Rochau, G. A.; Cuneo, M. E.

    2015-05-15

    Large diameter multi-shell gas puffs rapidly imploded by high current (∼20 MA, ∼100 ns) on the Z generator of Sandia National Laboratories are able to produce high-intensity Krypton K-shell emission at ∼13 keV. Efficiently radiating at these high photon energies is a significant challenge which requires the careful design and optimization of the gas distribution. To facilitate this, we hydrodynamically model the gas flow out of the nozzle and then model its implosion using a 3-dimensional resistive, radiative MHD code (GORGON). This approach enables us to iterate between modeling the implosion and gas flow from the nozzle to optimize radiative output from this combined system. Guided by our implosion calculations, we have designed gas profiles that help mitigate disruption from Magneto-Rayleigh–Taylor implosion instabilities, while preserving sufficient kinetic energy to thermalize to the high temperatures required for K-shell emission.

  4. Computational modeling of Krypton gas puffs with tailored mass density profiles on Z

    SciTech Connect

    Jennings, Christopher A.; Ampleford, David J.; Lamppa, Derek C.; Hansen, Stephanie B.; Jones, Brent Manley; Harvey-Thompson, Adam James; Jobe, Marc Ronald Lee; Reneker, Joseph; Rochau, Gregory A.; Cuneo, Michael Edward; Strizic, T.

    2015-05-18

    Large diameter multi-shell gas puffs rapidly imploded by high current (~20 MA, ~100 ns) on the Z generator of Sandia National Laboratories are able to produce high-intensity Krypton K-shell emission at ~13 keV. Efficiently radiating at these high photon energies is a significant challenge which requires the careful design and optimization of the gas distribution. To facilitate this, we hydrodynamically model the gas flow out of the nozzle and then model its implosion using a 3-dimensional resistive, radiative MHD code (GORGON). This approach enables us to iterate between modeling the implosion and gas flow from the nozzle to optimize radiative output from this combined system. Furthermore, guided by our implosion calculations, we have designed gas profiles that help mitigate disruption from Magneto-Rayleigh–Taylor implosion instabilities, while preserving sufficient kinetic energy to thermalize to the high temperatures required for K-shell emission.

  5. Computational modeling of Krypton gas puffs with tailored mass density profiles on Z

    DOE PAGESBeta

    Jennings, Christopher A.; Ampleford, David J.; Lamppa, Derek C.; Hansen, Stephanie B.; Jones, Brent Manley; Harvey-Thompson, Adam James; Jobe, Marc Ronald Lee; Reneker, Joseph; Rochau, Gregory A.; Cuneo, Michael Edward; et al

    2015-05-18

    Large diameter multi-shell gas puffs rapidly imploded by high current (~20 MA, ~100 ns) on the Z generator of Sandia National Laboratories are able to produce high-intensity Krypton K-shell emission at ~13 keV. Efficiently radiating at these high photon energies is a significant challenge which requires the careful design and optimization of the gas distribution. To facilitate this, we hydrodynamically model the gas flow out of the nozzle and then model its implosion using a 3-dimensional resistive, radiative MHD code (GORGON). This approach enables us to iterate between modeling the implosion and gas flow from the nozzle to optimize radiativemore » output from this combined system. Furthermore, guided by our implosion calculations, we have designed gas profiles that help mitigate disruption from Magneto-Rayleigh–Taylor implosion instabilities, while preserving sufficient kinetic energy to thermalize to the high temperatures required for K-shell emission.« less

  6. Fibroblast growth factor 23 signaling in hippocampal cells: impact on neuronal morphology and synaptic density.

    PubMed

    Hensel, Niko; Schön, Anne; Konen, Timo; Lübben, Verena; Förthmann, Benjamin; Baron, Olga; Grothe, Claudia; Leifheit-Nestler, Maren; Claus, Peter; Haffner, Dieter

    2016-06-01

    Endocrine fibroblast growth factor 23 (FGF23) is predominantly secreted by osteocytes and facilitates renal phosphate excretion. However, FGF23 is also present in cerebrospinal fluid. In chronic kidney disease, FGF23 serum levels are excessively elevated and associated with learning and memory deficits. Structural plasticity of the hippocampus such as formation of new synapses or an altered dendritic arborization comprises a cellular and morphological correlate of memory formation. Therefore, we hypothesize that FGF23 alters hippocampal neuron morphology and synapses. To address this, we prepared primary murine hippocampal cultures and incubated them with recombinant FGF23 alone or together with a soluble isoform of its co-receptor α-Klotho. Neuronal expression of a fluorescent reporter allowed for a detailed evaluation of the neuronal morphology by Sholl analysis. Additionally, we evaluated synaptic density, identified by stainings, for synaptic markers. We show an enhanced number of primary neurites combined with a reduced arborization, resulting in a less complex morphology of neurons treated with FGF23. Moreover, FGF23 enhances the synaptic density in a FGF-receptor (FGF-R) dependent manner. Finally, we addressed the corresponding signaling events downstream of FGF-R employing a combination of western blots and quantitative immunofluorescence. Interestingly, FGF23 induces phospholipase Cγ activity in primary hippocampal neurons. Co-application of soluble α-Klotho leads to activation of the Akt-pathway and modifies FGF23-impact on neuronal morphology and synaptic density. Compared with other FGFs, this alternative signaling pattern is a possible reason for differential effects of FGF23 on hippocampal neurons and may thereby contribute to learning and memory deficits in chronic kidney disease patients. In this study, we show that fibroblast growth factor 23 inhibits neuronal ramification and enhances the synaptic density in primary hippocampal cultures

  7. FACTORS INFLUENCING THE DEPOSITION OF A COMPOUND THAT PARTITIONS BETWEEN GAS AND PARTICULATE PHASES

    EPA Science Inventory

    How will atmospheric deposition behave for a compound when it reversibly sorbs between gas and atmospheric particulate phases? Two factors influence the answer. What physical mechanisms occur in the sorption process? What are the concentration and composition of atmospheric par...

  8. Factors Influencing Density-Dependent Groundwater Flow in the Michigan Basin

    NASA Astrophysics Data System (ADS)

    Sykes, J. F.; Normani, S. D.; Yin, Y.

    2010-12-01

    Regional-scale density-dependent groundwater flow is analyzed in an approximately 18000 sq km domain of the Michigan basin centered on a site at Tiverton Ontario near the shore of Lake Huron for a proposed deep geologic repository (DGR) for low and intermediate level nuclear waste. Flow was also analyzed in an approximately 600 km west-to-east cross-section through the center of the basin. Both domains extend from the Precambrian basement to the surface and include minimal upscaling of the complex stratigraphy in the basin. The model FRAC3DVS-OPG was used for all analyses. The hydraulic gradients across the basin are small as both Lake Huron and Lake Michigan have the same water surface elevation. As a result, groundwater flow in the basin is expected to be stagnant. Hydrogeologic parameters for the models were developed from borehole and petrophysics data from the DGR site for units from the Cambrian sandstone to the Devonian. Literature data were used for the shallower units in Michigan. Excluding the surficial drift, the hydraulic conductivity in the basin ranges from 3x10e-6 m/s in the Cambrian to less than 10e-14 m/s in the Ordovician sediments. Groundwater flow is sensitive to the distribution of total dissolved solids concentration with concentrations ranging up to 384 g/L in the Guelph formation in the Silurian. Both TDS data from porewater and groundwater at the DGR site and literature data for TDS versus depth were assigned to the sedimentary rock. The TDS distribution with depth for the Precambrian rock was assigned using both data for the Canadian Shield and a literature based model. Data at the DGR site indicates that the Cambrian is overpressured with respect to the surface while the Ordovician sediments are underpressured. It is hypothesized that the underpressures are the result of the presence of a gas phase in the units. The steps in determining a converged solution for saturated density-dependent flow were as follows: (1) solve steady state

  9. Factors associated with graft survival and endothelial cell density after Descemet's stripping automated endothelial keratoplasty.

    PubMed

    Ishii, Nobuhito; Yamaguchi, Takefumi; Yazu, Hiroyuki; Satake, Yoshiyuki; Yoshida, Akitoshi; Shimazaki, Jun

    2016-01-01

    Postoperative endothelial cell loss leads to graft failure after corneal transplantation, and is one of the important issues for long-term prognosis. The objective of this study was to identify clinical factors affecting graft survival and postoperative endothelial cell density (ECD) after Descemet's stripping automated endothelial keratoplasty (DSAEK). A total of 198 consecutive Japanese patients (225 eyes) who underwent DSAEK were analysed using Cox proportional hazard regression and multiple linear regression models. The candidate factors included recipient age; gender; diagnosis; pre-existing iris damage state, scored based on its severity; the number of previous intraocular surgeries; graft ECD; graft diameter; simultaneous cataract surgery; surgeons experience; intraoperative iris damage; postoperative rebubbling; and graft rejection. Eyes with higher pre-existing iris damage score and more number of previous intraocular surgery had a significantly higher risk of graft failure (HR = 8.53; P < 0.0001, and HR = 2.66; P = 0.026, respectively). Higher pre-existing iris damage score, lower graft ECD, and smaller graft diameter were identified as significant predisposing factors for lower postoperative ECD. The results show that iris damage status before DSAEK may be clinically useful in predicting the postoperative course. Avoiding intraoperative iris damage, especially in eyes with low ECD can change the prognosis of future DSAEK. PMID:27121659

  10. Manifestly Hermitian semiclassical expansion for the one-particle density matrix of a two-dimensional Fermi gas

    NASA Astrophysics Data System (ADS)

    Bencheikh, K.; van Zyl, B. P.; Berkane, K.

    2016-08-01

    The semiclassical ℏ expansion of the one-particle density matrix for a two-dimensional Fermi gas is calculated within the Wigner transform method of B. Grammaticos and A. Voros [Ann. Phys. (N.Y.) 123, 359 (1979), 10.1016/0003-4916(79)90343-9], originally developed in the context of nuclear physics. The method of Grammaticos and Voros has the virtue of preserving both the Hermiticity and idempotency of the density matrix to all orders in the ℏ expansion. As a topical application, we use our semiclassical expansion to go beyond the local-density approximation for the construction of the total dipole-dipole interaction energy functional of a two-dimensional, spin-polarized dipolar Fermi gas. We find a finite, second-order gradient correction to the Hartree-Fock energy, which takes the form ɛ (∇ρ ) 2/√{ρ } , with ɛ being small (|ɛ |≪1 ) and negative. We test the quality of the corrected energy by comparing it with the exact results available for harmonic confinement. Even for small particle numbers, the gradient correction to the dipole-dipole energy provides a significant improvement over the local-density approximation.

  11. Non-linear optics and local-field factors in liquid chloroform: A time-dependent density-functional theory study

    NASA Astrophysics Data System (ADS)

    Strubbe, David A.; Andrade, Xavier; Rubio, Angel; Louie, Steve G.

    2009-03-01

    Chloroform is often used as a solvent and reference when measuring non-linear optical properties of organic molecules. We calculate directly the non-linear susceptibilities of liquid chloroform at optical frequencies, using molecular dynamics and the Sternheimer equation in time-dependent density-functional theory [X. Andrade et al., J. Chem. Phys. 126, 184106 (2007)]. We compare the results to those of chloroform in the gas and solid phases, and experimental values, and make an ab initio calculation of the local-field factors which are needed to extract molecular properties from liquid calculations and experimental measurements.

  12. Risk Factors for Low Bone Mineral Density in Individuals Residing in a Facility for the People with Intellectual Disability

    ERIC Educational Resources Information Center

    Jaffe, J. S.; Timell, A. M.; Elolia, R.; Thatcher, S. S.

    2005-01-01

    Background: Individuals with intellectual disability (ID) are known to have a high prevalence of both low bone mineral density (BMD) and fractures with significant attendant morbidity. Effective strategies aimed at reducing fractures will be facilitated by the identification of predisposing risk factors. Methods: Bone mineral density was measured…

  13. Temperature, density, and composition in the disturbed thermosphere from Esro 4 gas analyzer measurements - A global model

    NASA Technical Reports Server (NTRS)

    Jacchia, L. G.; Slowey, J. W.; Von Zahn, U.

    1977-01-01

    An analysis of density measurements of Ar, N2, O, and He made at 280 km with the gas analyzer aboard the polar-orbiting satellite Esro 4 has yielded a global model of the variations in temperature, density, and composition that occur in the disturbed thermosphere. In the model the increase of temperature over quiet conditions is a nonlinear function of the planetary geomagnetic index, its latitude profile being approximated by a fourth-power sin phi law, where phi is the 'invariant' magnetic latitude. A density wave proceeding from high latitudes is approximated by a fourth power cos phi law. A strong nonlinearity in the relation between the temperature variations and the variations in the height of the homopause explains a previously found behavioral difference in the variation of atomic oxygen during magnetic storms and during periods of sustained geomagnetic activity.

  14. A Method to Simulate Linear Stability of Impulsively Accelerated Density Interfaces in Ideal-MHD and Gas Dynamics

    SciTech Connect

    Ravi Samtaney

    2009-02-10

    We present a numerical method to solve the linear stability of impulsively accelerated density interfaces in two dimensions such as those arising in the Richtmyer-Meshkov instability. The method uses an Eulerian approach, and is based on an unwind method to compute the temporally evolving base state and a flux vector splitting method for the perturbations. The method is applicable to either gas dynamics or magnetohydrodynamics. Numerical examples are presented for cases in which a hydrodynamic shock interacts with a single or double density interface, and a doubly shocked single density interface. Convergence tests show that the method is spatially second order accurate for smooth flows, and between first and second order accurate for flows with shocks.

  15. Factors associated with arrival densities of grasshopper sparrow (Ammodramus Savannarum) and baird's sparrow (A. Bairdii) in the upper great plains

    USGS Publications Warehouse

    Ahlering, M.A.; Johnson, D.H.; Faaborg, J.

    2009-01-01

    Although critical to habitat and population management, the proximate cues that birds use to establish territories are largely unknown. Understanding these cues is important for birds, such as many grassland birds, that exhibit high annual variability in population density and make new habitat-selection decisions annually. Identifying the actual cues used is difficult in the field, but the factors associated with the arrival densities of birds can help uncover variables that are involved in or correlated with cues used for selection. During the summers of 2002-2004, we investigated how weather and local vegetation factors were related to arrival densities of Grasshopper Sparrows (Ammodramus savannarum) and Baird's Sparrows (A. bairdii) at three locations across North Dakota and Saskatchewan. Spring densities of Grasshopper Sparrows were positively correlated with concurrent May precipitation, whereas densities of Baird's Sparrows were negatively correlated with the previous winter's snowfall. We used a model-selection approach to evaluate the vegetation characteristics associated with arrival densities of birds. Grasshopper Sparrow densities showed a strong negative relationship to woody cover, and Baird's Sparrow densities showed a negative relationship to vegetation height and vegetation density near the ground. Our results provide a first detailed look at habitat and weather associations immediately after arrival in spring and an important first step in uncovering factors that may be involved in habitat selection in two grassland species. Received 13 August 2008, accepted 20 April 2009. ?? The American Ornithologists' Union, 2009.

  16. 40 CFR Table W - 5 of Subpart W-Default Methane Emission Factors for Liquefied Natural Gas (LNG) Storage

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... Emission Factors for Liquefied Natural Gas (LNG) Storage W Table W Protection of Environment ENVIRONMENTAL... Natural Gas Systems Definitions. Pt. 98, Subpt. W, Table W-5 Table W-5 of Subpart W—Default Methane Emission Factors for Liquefied Natural Gas (LNG) Storage LNG storage Emission factor...

  17. From slant column densities to trace gas profiles: Post processing data from the new MAX-DOAS network in Mexico City

    NASA Astrophysics Data System (ADS)

    Friedrich, M. M.; Stremme, W.; Rivera, C. I.; Arellano, E. J.; Grutter, M.

    2014-12-01

    The new MAX-DOAS network in Mexico City provides results of O4, HCHO and NO2 slant column densities (SCD). Here, we present a new numerical code developed to retrieve gas profiles of NO2 and HCHO using radiative transfer simulations. We present first results of such profiles from the MAX-DOAS station located at UNAM campus. The code works in two steps: First, the O4 slant column density information is used to retrieve an aerosol profile. As an a-priori aerosol profile, we use averaged ceilometer data measured at UNAM and scaled to the total optical depth provided by the Aeronet data base. In the second step, the retrieved aerosol profile information is used together with the trace gas (HCHO or NO2) SCDs to retrieve the trace gas profiles. The inversion is based on a gauss-newton iteration scheme and uses constrained least square fitting with either optimal estimation or Tihkonov regularization. For the latter, the regulation matrix is currently constructed from the discrete first derivative operator. The forward model uses the radiative transfer code VLIDORT. The inputs to VLIDORT are calculated using temperature and pressure information from daily radiosounde measurements and aerosol single scattering optical depths and asymmetry factors from the Aeronet data base for Mexico City. For the gas absorption cross sections we use the same values as were used for the SCD calculation from the recorded spectra using QDOAS. Besides demonstrating the functionality of the algorithm showing profile retrievals of simulated SCDs with added random noise, we present HCHO and NO2 profiles retrieved from SCDs calculated from the MAX-DOAS measurements at UNAM campus at selected days.

  18. Illuminating epidermal growth factor receptor densities on filopodia through plasmon coupling.

    PubMed

    Wang, Jing; Boriskina, Svetlana V; Wang, Hongyun; Reinhard, Björn M

    2011-08-23

    Filopodia have been hypothesized to act as remote sensors of the cell environment, but many details of the sensor function remain unclear. We investigated the distribution of the epidermal growth factor (EGF) receptor (EGFR) density on filopodia and on the dorsal cell membrane of A431 human epidermoid carcinoma cells using a nanoplasmonic enabled imaging tool. We targeted cell surface EGFR with 40 nm diameter Au nanoparticles (NPs) using a high affinity multivalent labeling strategy and determined relative NP binding affinities spatially resolved through plasmon coupling. Distance-dependent near-field interactions between the labels generated a NP density (ρ)-dependent spectral response that facilitated a spatial mapping of the EGFR density distribution on subcellular length scales in an optical microscope in solution. The measured ρ values were significantly higher on filopodia than on the cellular surface, which is indicative of an enrichment of EGFR on filopodia. A detailed characterization of the spatial distribution of the NP immunolabels through scanning electron microscopy (SEM) confirmed the findings of the all-optical plasmon coupling studies and provided additional structural details. The NPs exhibited a preferential association with the sides of the filopodia. We calibrated the ρ-dependent spectral response of the Au immunolabels through correlation of optical spectroscopy and SEM. The experimental dependence of the measured plasmon resonance wavelength (λ(res)) of the interacting immunolabels on ρ was well described by the fit λ(res) = 595.0 nm - 46.36 nm exp(-ρ/51.48) for ρ ≤ 476 NPs/μm(2). The performed correlated spectroscopic/SEM studies pave the way toward quantitative immunolabeling studies of EGFR and other important cell surface receptors in an optical microscope. PMID:21761914

  19. Estimates of density, detection probability, and factors influencing detection of burrowing owls in the Mojave Desert

    USGS Publications Warehouse

    Crowe, D.E.; Longshore, K.M.

    2010-01-01

    We estimated relative abundance and density of Western Burrowing Owls (Athene cunicularia hypugaea) at two sites in the Mojave Desert (200304). We made modifications to previously established Burrowing Owl survey techniques for use in desert shrublands and evaluated several factors that might influence the detection of owls. We tested the effectiveness of the call-broadcast technique for surveying this species, the efficiency of this technique at early and late breeding stages, and the effectiveness of various numbers of vocalization intervals during broadcasting sessions. Only 1 (3) of 31 initial (new) owl responses was detected during passive-listening sessions. We found that surveying early in the nesting season was more likely to produce new owl detections compared to surveying later in the nesting season. New owls detected during each of the three vocalization intervals (each consisting of 30 sec of vocalizations followed by 30 sec of silence) of our broadcasting session were similar (37, 40, and 23; n 30). We used a combination of detection trials (sighting probability) and double-observer method to estimate the components of detection probability, i.e., availability and perception. Availability for all sites and years, as determined by detection trials, ranged from 46.158.2. Relative abundance, measured as frequency of occurrence and defined as the proportion of surveys with at least one owl, ranged from 19.232.0 for both sites and years. Density at our eastern Mojave Desert site was estimated at 0.09 ?? 0.01 (SE) owl territories/km2 and 0.16 ?? 0.02 (SE) owl territories/km2 during 2003 and 2004, respectively. In our southern Mojave Desert site, density estimates were 0.09 ?? 0.02 (SE) owl territories/km2 and 0.08 ?? 0.02 (SE) owl territories/km 2 during 2004 and 2005, respectively. ?? 2010 The Raptor Research Foundation, Inc.

  20. Critical parameters governing energy density of Li-storage cathode materials unraveled by confirmatory factor analysis

    NASA Astrophysics Data System (ADS)

    Sohn, Kee-Sun; Han, Su Cheol; Park, Woon Bae; Pyo, Myoungho

    2016-03-01

    Despite extensive effort during the past few decades, a comprehensive understanding of the key variables governing the electrochemical properties of cathode materials in Li-ion batteries is still far from complete. To elucidate the critical parameters affecting energy density (ED) and capacity (Q) retention in layer and spinel cathodes, we data-mine the existing experimental data via confirmatory factor analysis (CFA) based on a structural equation model (SEM), which is a proven, versatile tool in understanding complex problems in the social science. The data sets are composed of 18 and 15 parameters extracted from 38 layer and 33 spinel compounds, respectively. CFA reveals the irrelevance of Q retention to all the parameters we adopt, but it also reveals the sensitive variations of ED with specific parameters. We validate the usefulness of CFA in material science and pinpointed critical parameters for high-ED cathodes, hoping to suggest a new insight in materials design.

  1. Direct phase-sensitive identification of a d-form factor density wave in underdoped cuprates

    PubMed Central

    Fujita, Kazuhiro; Hamidian, Mohammad H.; Edkins, Stephen D.; Kim, Chung Koo; Kohsaka, Yuhki; Azuma, Masaki; Takano, Mikio; Takagi, Hidenori; Eisaki, Hiroshi; Uchida, Shin-ichi; Allais, Andrea; Lawler, Michael J.; Kim, Eun-Ah; Sachdev, Subir; Davis, J. C. Séamus

    2014-01-01

    The identity of the fundamental broken symmetry (if any) in the underdoped cuprates is unresolved. However, evidence has been accumulating that this state may be an unconventional density wave. Here we carry out site-specific measurements within each CuO2 unit cell, segregating the results into three separate electronic structure images containing only the Cu sites [Cu(r)] and only the x/y axis O sites [Ox(r) and Oy(r)]. Phase-resolved Fourier analysis reveals directly that the modulations in the Ox(r) and Oy(r) sublattice images consistently exhibit a relative phase of π. We confirm this discovery on two highly distinct cuprate compounds, ruling out tunnel matrix-element and materials-specific systematics. These observations demonstrate by direct sublattice phase-resolved visualization that the density wave found in underdoped cuprates consists of modulations of the intraunit-cell states that exhibit a predominantly d-symmetry form factor. PMID:24989503

  2. Unique Features of High-Density Lipoproteins in the Japanese: In Population and in Genetic Factors

    PubMed Central

    Yokoyama, Shinji

    2015-01-01

    Despite its gradual increase in the past several decades, the prevalence of atherosclerotic vascular disease is low in Japan. This is largely attributed to difference in lifestyle, especially food and dietary habits, and it may be reflected in certain clinical parameters. Plasma high-density lipoprotein (HDL) levels, a strong counter risk for atherosclerosis, are indeed high among the Japanese. Accordingly, lower HDL seems to contribute more to the development of coronary heart disease (CHD) than an increase in non-HDL lipoproteins at a population level in Japan. Interestingly, average HDL levels in Japan have increased further in the past two decades, and are markedly higher than in Western populations. The reasons and consequences for public health of this increase are still unknown. Simulation for the efficacy of raising HDL cholesterol predicts a decrease in CHD of 70% in Japan, greater than the extent by reducing low-density lipoprotein cholesterol predicted by simulation or achieved in a statin trial. On the other hand, a substantial portion of hyperalphalipoproteinemic population in Japan is accounted for by genetic deficiency of cholesteryl ester transfer protein (CETP), which is also commonly unique in East Asian populations. It is still controversial whether CETP mutations are antiatherogenic. Hepatic Schistosomiasis is proposed as a potential screening factor for historic accumulation of CETP deficiency in East Asia. PMID:25849946

  3. Plasma density evolution during nanosecond discharge in hydrogen gas at (1-3) × 105 Pa pressure

    NASA Astrophysics Data System (ADS)

    Yatom, S.; Krasik, Ya E.

    2014-05-01

    The results of a study of the nanosecond discharge in H2 gas at pressures of (1-3) × 105 Pa using fast-framing photography and space- and time-resolved spectroscopy are presented. The discharge is initiated by the application of a high-voltage pulse with an amplitude of ˜100 kV and duration of ˜5 ns to a blade cathode placed at a distance of 20 mm from the anode. The results show the dynamics of the discharge formation and the build-up of the plasma electron density in the discharge channels close to and at a distance from the edge of the cathode. The results obtained are compared to those obtained in recent studies of similar discharges in air and He gas. It was shown that the time and space evolution of the plasma light emission in the H2 gas discharge is very similar to that in air. Namely, the generation of the plasma is mainly confined to the plasma channels initiated at the top and bottom edges of the cathode electrode and that there are no new plasma channels formed from the explosive emission centres along the blade as it was obtained in earlier experiments with He gas. Spectroscopic measurements showed that the plasma density reaches 2 × 1017 cm-3 and 1.6 × 1016 cm-3 in the vicinity of the cathode and the middle of the anode-cathode gap, respectively, for a plasma electron temperature of <1.5 eV. The values of plasma electron density and the previously presented results of electric field measurements allow calculation of the resistance of the plasma channels.

  4. Harmonic distortion and power factor assessment in city street gas discharge lamps

    SciTech Connect

    Rios, S.; Castaneda, R.; Veas, D.

    1996-04-01

    The current and voltage harmonic spectrum, and power factor in gas discharge lamps: Sodium (Na)-high pressure and Mercury (Hg) in actual use in public street lighting have been measured. A sample of nearby 360 gas discharge lamps (Na, Hg) of different rated power was obtained by simple random sampling over a universe of approximately 15,000 lamps. An equivalent current harmonic spectrum for gas discharge lamps is proposed, which is independent of the type of gas and the lamp rated power. This current spectrum can be used to integrate gas discharge lamp models for harmonic distortion level assessment in distribution networks. The relation of this equivalent current harmonic spectrum with: (1) lamp voltage waveform, (2) type of lamp (Na, Hg), and (3) power factor-capacitor lamp, is analyzed.

  5. Fluorocarbon seal replaces metal piston ring in low density gas environment

    NASA Technical Reports Server (NTRS)

    Morath, W. D.; Morgan, N. E.

    1967-01-01

    Reinforced fluorocarbon cupseal, which provides an integral lip-type seal, replaces the metal piston rings in piston-cylinder configurations used in the compression of low density gases. The fluorocarbon seal may be used as cryogenic compressor piston seals.

  6. Clinical relevance of the biochemical, metabolic, and genetic factors that influence low-density lipoprotein heterogeneity.

    PubMed

    Kwiterovich, Peter O

    2002-10-17

    Traditional risk factors for coronary artery disease (CAD) predict about 50% of the risk of developing CAD. The Adult Treatment Panel (ATP) III has defined emerging risk factors for CAD, including small, dense low-density lipoprotein (LDL). Small, dense LDL is often accompanied by increased triglycerides (TGs) and low high-density lipoprotein (HDL). An increased number of small, dense LDL particles is often missed when the LDL cholesterol level is normal or borderline elevated. Small, dense LDL particles are present in families with premature CAD and hyperapobetalipoproteinemia, familial combined hyperlipidemia, LDL subclass pattern B, familial dyslipidemic hypertension, and syndrome X. The metabolic syndrome, as defined by ATP III, incorporates a number of the components of these syndromes, including insulin resistance and intra-abdominal fat. Subclinical inflammation and elevated procoagulants also appear to be part of this atherogenic syndrome. Overproduction of very low-density lipoproteins (VLDLs) by the liver and increased secretion of large, apolipoprotein (apo) B-100-containing VLDL is the primary metabolic characteristic of most of these patients. The TG in VLDL is hydrolyzed by lipoprotein lipase (LPL) which produces intermediate-density lipoprotein. The TG in intermediate-density lipoprotein is hydrolyzed further, resulting in the generation of LDL. The cholesterol esters in LDL are exchanged for TG in VLDL by the cholesterol ester tranfer proteins, followed by hydrolysis of TG in LDL by hepatic lipase which produces small, dense LDL. Cholesterol ester transfer protein mediates a similar lipid exchange between VLDL and HDL, producing a cholesterol ester-poor HDL. In adipocytes, reduced fatty acid trapping and retention by adipose tissue may result from a primary defect in the incorporation of free fatty acids into TGs. Alternatively, insulin resistance may promote reduced retention of free fatty acids by adipocytes. Both these abnormalities lead to

  7. Risk factors for transient dysfunction of gas exchange after cardiac surgery

    PubMed Central

    Rodrigues, Cristiane Delgado Alves; Moreira, Marcos Mello; Lima, Núbia Maria Freire Vieira; de Figueirêdo, Luciana Castilho; Falcão, Antônio Luis Eiras; Petrucci, Orlando; Dragosavac, Desanka

    2015-01-01

    Objective A retrospective cohort study was preformed aiming to verify the presence of transient dysfunction of gas exchange in the postoperative period of cardiac surgery and determine if this disorder is linked to cardiorespiratory events. Methods We included 942 consecutive patients undergoing cardiac surgery and cardiac procedures who were referred to the Intensive Care Unit between June 2007 and November 2011. Results Fifteen patients had acute respiratory distress syndrome (2%), 199 (27.75%) had mild transient dysfunction of gas exchange, 402 (56.1%) had moderate transient dysfunction of gas exchange, and 39 (5.4%) had severe transient dysfunction of gas exchange. Hypertension and cardiogenic shock were associated with the emergence of moderate transient dysfunction of gas exchange postoperatively (P=0.02 and P=0.019, respectively) and were risk factors for this dysfunction (P=0.0023 and P=0.0017, respectively). Diabetes mellitus was also a risk factor for transient dysfunction of gas exchange (P=0.03). Pneumonia was present in 8.9% of cases and correlated with the presence of moderate transient dysfunction of gas exchange (P=0.001). Severe transient dysfunction of gas exchange was associated with patients who had renal replacement therapy (P=0.0005), hemotherapy (P=0.0001), enteral nutrition (P=0.0012), or cardiac arrhythmia (P=0.0451). Conclusion Preoperative hypertension and cardiogenic shock were associated with the occurrence of postoperative transient dysfunction of gas exchange. The preoperative risk factors included hypertension, cardiogenic shock, and diabetes. Postoperatively, pneumonia, ventilator-associated pneumonia, renal replacement therapy, hemotherapy, and cardiac arrhythmia were associated with the appearance of some degree of transient dysfunction of gas exchange, which was a risk factor for reintubation, pneumonia, ventilator-associated pneumonia, and renal replacement therapy in the postoperative period of cardiac surgery and cardiac

  8. Factors controlling sulfur gas exchange in Sphagnum-dominated wetlands

    NASA Technical Reports Server (NTRS)

    Demello, William Zamboni; Hines, Mark E.; Bayley, Suzanne E.

    1992-01-01

    Atmosphere-peatland exchange of reduced sulfur gases was determined seasonally in fen in NH, and in an artificially-acidified fen at the Experimental Lakes Area (ELA) in Canada. Dimethyl sulfide (DMS) dominated gas fluxes at rates as high as 400 nmol/m(sup -2)hr(sup -1). DMS fluxes measured using enclosures were much higher than those calculated using a stagnant-film model, suggesting that Sphagnum regulated efflux. Temperature controlled diel and seasonal variability in DMS emissions. Use of differing enclosure techniques indicated that vegetated peatlands consume atmospheric carbonyl sulfide. Sulfate amendments caused DMS and methane thiol concentrations in near-surface pore waters to increase rapidly, but fluxes of these gases to the atmosphere were not affected. However, emission data from sites experiencing large differences in rates of sulfate deposition from the atmosphere suggested that chronic elevated sulfate inputs enhance DMS emissions from northern wetlands.

  9. Effect of Environmental Factors on Sulfur Gas Emissions from Drywall

    SciTech Connect

    Maddalena, Randy

    2011-08-20

    Problem drywall installed in U.S. homes is suspected of being a source of odorous and potentially corrosive indoor pollutants. The U.S. Consumer Product Safety Commission's (CPSC) investigation of problem drywall incorporates three parallel tracks: (1) evaluating the relationship between the drywall and reported health symptoms; (2) evaluating the relationship between the drywall and electrical and fire safety issues in affected homes; and (3) tracing the origin and the distribution of the drywall. To assess the potential impact on human health and to support testing for electrical and fire safety, the CPSC has initiated a series of laboratory tests that provide elemental characterization of drywall, characterization of chemical emissions, and in-home air sampling. The chemical emission testing was conducted at Lawrence Berkeley National Laboratory (LBNL). The LBNL study consisted of two phases. In Phase 1 of this study, LBNL tested thirty drywall samples provided by CPSC and reported standard emission factors for volatile organic compounds (VOCs), aldehydes, reactive sulfur gases (RSGs) and volatile sulfur compounds (VSCs). The standard emission factors were determined using small (10.75 liter) dynamic test chambers housed in a constant temperature environmental chamber. The tests were all run at 25 C, 50% relative humidity (RH) and with an area-specific ventilation rate of {approx}1.5 cubic meters per square meter of emitting surface per hour [m{sup 3}/m{sup 2}/h]. The thirty samples that were tested in Phase 1 included seventeen that were manufactured in China in 2005, 2006 and 2009, and thirteen that were manufactured in North America in 2009. The measured emission factors for VOCs and aldehydes were generally low and did not differ significantly between the Chinese and North American drywall. Eight of the samples tested had elevated emissions of volatile sulfur-containing compounds with total RSG emission factors between 32 and 258 micrograms per square meter

  10. High-Resolution Simulations of Gas-Solids Jet Penetration Into a High Density Riser Flow

    SciTech Connect

    Li, Tingwen

    2011-05-01

    High-resolution simulations of a gas-solids jet in a 0.3 m diameter and 15.9 m tall circulating fluidized bed (CFB) riser were conducted with the open source software-MFIX. In the numerical simulations, both gas and solids injected through a 1.6 cm diameter radial-directed tube 4.3 m above the bottom distributor were tracked as tracers, which enable the analysis of the characteristics of a two-phase jet. Two jetting gas velocities of 16.6 and 37.2 m/s were studied with the other operating conditions fixed. Reasonable flow hydrodynamics with respect to overall pressure drop, voidage, and solids velocity distributions were predicted. Due to the different dynamic responses of gas and particles to the crossflow, a significant separation of gas and solids within the jet region was predicted for both cases. In addition, the jet characteristics based on tracer concentration and tracer mass fraction profiles at different downstream levels are discussed. Overall, the numerical predictions compare favorably to the experimental measurements made at NETL.

  11. THE RELATION BETWEEN GAS DENSITY AND VELOCITY POWER SPECTRA IN GALAXY CLUSTERS: QUALITATIVE TREATMENT AND COSMOLOGICAL SIMULATIONS

    SciTech Connect

    Zhuravleva, I.; Allen, S. W.; Churazov, E. M.; Gaspari, M.; Schekochihin, A. A.; Lau, E. T.; Nagai, D.; Nelson, K.; Parrish, I. J.

    2014-06-10

    We address the problem of evaluating the power spectrum of the velocity field of the intracluster medium using only information on the plasma density fluctuations, which can be measured today by Chandra and XMM-Newton observatories. We argue that for relaxed clusters there is a linear relation between the rms density and velocity fluctuations across a range of scales, from the largest ones, where motions are dominated by buoyancy, down to small, turbulent scales: (δρ{sub k}/ρ){sup 2}=η{sub 1}{sup 2}(V{sub 1,k}/c{sub s}){sup 2}, where δρ {sub k}/ρ is the spectral amplitude of the density perturbations at wavenumber k, V{sub 1,k}{sup 2}=V{sub k}{sup 2}/3 is the mean square component of the velocity field, c{sub s} is the sound speed, and η{sub 1} is a dimensionless constant of the order of unity. Using cosmological simulations of relaxed galaxy clusters, we calibrate this relation and find η{sub 1} ≈ 1 ± 0.3. We argue that this value is set at large scales by buoyancy physics, while at small scales the density and velocity power spectra are proportional because the former are a passive scalar advected by the latter. This opens an interesting possibility to use gas density power spectra as a proxy for the velocity power spectra in relaxed clusters across a wide range of scales.

  12. Development and evaluation of probability density functions for a set of human exposure factors

    SciTech Connect

    Maddalena, R.L.; McKone, T.E.; Bodnar, A.; Jacobson, J.

    1999-06-01

    The purpose of this report is to describe efforts carried out during 1998 and 1999 at the Lawrence Berkeley National Laboratory to assist the U.S. EPA in developing and ranking the robustness of a set of default probability distributions for exposure assessment factors. Among the current needs of the exposure-assessment community is the need to provide data for linking exposure, dose, and health information in ways that improve environmental surveillance, improve predictive models, and enhance risk assessment and risk management (NAS, 1994). The U.S. Environmental Protection Agency (EPA) Office of Emergency and Remedial Response (OERR) plays a lead role in developing national guidance and planning future activities that support the EPA Superfund Program. OERR is in the process of updating its 1989 Risk Assessment Guidance for Superfund (RAGS) as part of the EPA Superfund reform activities. Volume III of RAGS, when completed in 1999 will provide guidance for conducting probabilistic risk assessments. This revised document will contain technical information including probability density functions (PDFs) and methods used to develop and evaluate these PDFs. The PDFs provided in this EPA document are limited to those relating to exposure factors.

  13. Factors associated with decreased bone mineral density in postmenopausal women with schizophrenia

    PubMed Central

    Liang, Ying; Huang, Jian; Tian, Jing-bin; Cao, Yuan-yuan; Zhang, Guo-ling; Wang, Chun-gang; Cao, Ying; Li, Jian-rong

    2016-01-01

    Objective This study examined the risk factors for decreased bone mineral density (BMD) in postmenopausal women with schizophrenia. Methods Cluster sampling method was adopted in this large-sample, cross-sectional study. A total of 219 postmenopausal female inpatients with schizophrenia were selected and interviewed in Beijing. The average age of the patients was 60.4±7.0 years. Clinical assessment instruments included the Positive and Negative Syndrome Scale (PANSS) and a questionnaire with detailed general information and disease-related investigations. Laboratory measurements included prolactin (PRL), estradiol, progesterone, thyroid stimulating hormone, FT3, and FT4. BMD testing was performed by dual-energy X-ray absorptiometry. Results The prevalence of osteoporosis or osteopenia was 66.2% (n=145). Decreased BMD was associated with age, illness duration, therapeutic dose (equivalent chlorpromazine dose), treatment duration, PANSS-negative scores, body mass index (BMI), daily exercises (min/d), drinking (unit/wk), PRL, and estradiol. Multiple logistic regression analysis revealed that age, treatment duration, PANSS-negative score, BMI, and PRL were significantly associated with decreased BMD. Conclusion Prevalence of BMD loss was higher in Chinese postmenopausal women with schizophrenia compared to the normal BMD group. A combination of demographic and clinical factors play important roles in determining decreased BMD, including older age, longer treatment duration, more PANSS-negative scores, higher BMI, and higher PRL level. PMID:26937181

  14. Importance of network density of nanotube: Effect on nitrogen dioxide gas sensing by solid state resistive sensor

    NASA Astrophysics Data System (ADS)

    Mishra, Prabhash; Grachyova, D. V.; Moskalenko, A. S.; Shcherbak, M. A.; Pavelyev, V. S.

    2016-04-01

    Dispersion of single-walled carbon nanotubes (SWCNTs) is an established fact, however, its effect on toxic gas sensing for the development of solid state resistive sensor was not well reported. In this report, the dispersion quality of SWCNTs has been investigated and improved, and this well-dispersed SWCNTs network was used for sensor fabrication to monitor nitrogen dioxide gas. Ultraviolet (UV)-visible spectroscopic studies shows the strength of SWNTs dispersion and scanning electron microscopy (SEM) imaging provides the morphological properties of the sensor device. In this gas sensor device, two sets of resistive type sensors were fabricated that consisting of a pair of interdigitated electrodes (IDEs) using dielectrophoresis technique with different SWCNTs network density. With low-density SWCNTs networks, this fabricated sensor exhibits a high response for nitrogen dioxide sensing. The sensing of nitrogen dioxide is mainly due to charge transfer from absorbed molecules to sidewalls of nanotube and tube-tube screening acting a major role for the transport properties of charge carriers.

  15. A pressure gauge based on gas density measurement from analysis of the thermal noise of an atomic force microscope cantilever

    SciTech Connect

    Seo, Dongjin; Ducker, William A.; Paul, Mark R.

    2012-05-15

    We describe a gas-density gauge based on the analysis of the thermally-driven fluctuations of an atomic force microscope (AFM) cantilever. The fluctuations are modeled as a ring-down of a simple harmonic oscillator, which allows fitting of the resonance frequency and damping of the cantilever, which in turn yields the gas density. The pressure is obtained from the density using the known equation of state. In the range 10-220 kPa, the pressure readings from the cantilever gauge deviate by an average of only about 5% from pressure readings on a commercial gauge. The theoretical description we use to determine the pressure from the cantilever motion is based upon the continuum hypothesis, which sets a minimum pressure for our analysis. It is anticipated that the cantilever gauge could be extended to measure lower pressures given a molecular theoretical description. Alternatively, the gauge could be calibrated for use in the non-continuum range. Our measurement technique is similar to previous AFM cantilever measurements, but the analysis produces improved accuracy.

  16. Measurement and Evaluation of the Gas Density and Viscosity of Pure Gases and Mixtures Using a Micro-Cantilever Beam.

    PubMed

    Badarlis, Anastasios; Pfau, Axel; Kalfas, Anestis

    2015-01-01

    Measurement of gas density and viscosity was conducted using a micro-cantilever beam. In parallel, the validity of the proposed modeling approach was evaluated. This study also aimed to widen the database of the gases on which the model development of the micro-cantilever beams is based. The density and viscosity of gases are orders of magnitude lower than liquids. For this reason, the use of a very sensitive sensor is essential. In this study, a micro-cantilever beam from the field of atomic force microscopy was used. Although the current cantilever was designed to work with thermal activation, in the current investigation, it was activated with an electromagnetic force. The deflection of the cantilever beam was detected by an integrated piezo-resistive sensor. Six pure gases and sixteen mixtures of them in ambient conditions were investigated. The outcome of the investigation showed that the current cantilever beam had a sensitivity of 240 Hz/(kg/m³), while the accuracy of the determined gas density and viscosity in ambient conditions reached ±1.5% and ±2.0%, respectively. PMID:26402682

  17. Measurement and Evaluation of the Gas Density and Viscosity of Pure Gases and Mixtures Using a Micro-Cantilever Beam

    PubMed Central

    Badarlis, Anastasios; Pfau, Axel; Kalfas, Anestis

    2015-01-01

    Measurement of gas density and viscosity was conducted using a micro-cantilever beam. In parallel, the validity of the proposed modeling approach was evaluated. This study also aimed to widen the database of the gases on which the model development of the micro-cantilever beams is based. The density and viscosity of gases are orders of magnitude lower than liquids. For this reason, the use of a very sensitive sensor is essential. In this study, a micro-cantilever beam from the field of atomic force microscopy was used. Although the current cantilever was designed to work with thermal activation, in the current investigation, it was activated with an electromagnetic force. The deflection of the cantilever beam was detected by an integrated piezo-resistive sensor. Six pure gases and sixteen mixtures of them in ambient conditions were investigated. The outcome of the investigation showed that the current cantilever beam had a sensitivity of 240 Hz/(kg/m3), while the accuracy of the determined gas density and viscosity in ambient conditions reached ±1.5% and ±2.0%, respectively. PMID:26402682

  18. Characterization factors for water consumption and greenhouse gas emissions based on freshwater fish species extinction.

    PubMed

    Hanafiah, Marlia M; Xenopoulos, Marguerite A; Pfister, Stephan; Leuven, Rob S E W; Huijbregts, Mark A J

    2011-06-15

    Human-induced changes in water consumption and global warming are likely to reduce the species richness of freshwater ecosystems. So far, these impacts have not been addressed in the context of life cycle assessment (LCA). Here, we derived characterization factors for water consumption and global warming based on freshwater fish species loss. Calculation of characterization factors for potential freshwater fish losses from water consumption were estimated using a generic species-river discharge curve for 214 global river basins. We also derived characterization factors for potential freshwater fish species losses per unit of greenhouse gas emission. Based on five global climate scenarios, characterization factors for 63 greenhouse gas emissions were calculated. Depending on the river considered, characterization factors for water consumption can differ up to 3 orders of magnitude. Characterization factors for greenhouse gas emissions can vary up to 5 orders of magnitude, depending on the atmospheric residence time and radiative forcing efficiency of greenhouse gas emissions. An emission of 1 ton of CO₂ is expected to cause the same impact on potential fish species disappearance as the water consumption of 10-1000 m³, depending on the river basin considered. Our results make it possible to compare the impact of water consumption with greenhouse gas emissions. PMID:21574555

  19. Gas Flux and Density Surrounding a Cylindrical Aperture in the Free Molecular Flow Regime

    NASA Technical Reports Server (NTRS)

    Soulas, George C.

    2011-01-01

    The equations for rigorously calculating the particle flux and density surrounding a cylindrical aperture in the free molecular flow regime are developed and presented. The fundamental equations for particle flux and density from a reservoir and a diffusely reflecting surface will initially be developed. Assumptions will include a Maxwell-Boltzmann speed distribution, equal particle and wall temperatures, and a linear flux distribution along the cylindrical aperture walls. With this information, the equations for axial flux and density surrounding a cylindrical aperture will be developed. The cylindrical aperture will be divided into multiple volumes and regions to rigorously determine the surrounding axial flux and density, and appropriate limits of integration will be determined. The results of these equations will then be evaluated. The linear wall flux distribution assumption will be assessed. The axial flux and density surrounding a cylindrical aperture with a thickness-to-radius ratio of 1.25 will be presented. Finally, the equations determined in this study will be verified using multiple methods.

  20. [Effects of increased planting density with reduced nitrogen fertilizer application on rice yield, N use efficiency and greenhouse gas emission in Northeast China].

    PubMed

    Zhu, Xiang-cheng; Zhang, Zhen-ping; Zhang, Jun; Deng, Ai-xing; Zhang, Wei-jian

    2016-02-01

    The traditional rice growing practice has to change to save resource and protect environment, and it' s necessary to develop new technology in rice cultivation. Therefore, a two-year field experiment of Japonica rice (Liaoxing 1) was conducted in Northeast China in 2012 and 2013 to investigate the integrated effects of dense planting with less basal nitrogen (N) and unchanged top-dressing N (IR) on rice yield, N use efficiency (NUE) and greenhouse gas emissions. Compared with traditional practice (CK), we increased the rice seedling density by 33.3% and reduced the basal N rate by 20%. The results showed that the average N agronomy efficiency and partial factor productivity were improved by 49.6% (P<0.05) and 20.4% (P<0.05), respectively, while the area and yield-scaled greenhouse gas emissions were reduced by 9.9% and 12.7% (P<0.05), respectively. Although IR cropping mode decreased panicle number and biomass production, it significantly enhanced rice seed setting rate and harvest index, resulting in an unchanged or even highei yield. NH4+-N and NO3(-)-N concentrations in rice rhizosphere soil were reduced, resulting in an increment of N recovery efficiency. Generally, proper dense planting with less basal N applicatior could be a good approach for the trade-off between rice yield, NUE and greenhouse gas emission. PMID:27396117

  1. Bone mineral density and factors influencing it in Asian Indian population with type 2 diabetes mellitus

    PubMed Central

    Kamalanathan, Sadishkumar; Nambiar, Vimal; Shivane, Vyankatesh; Bandgar, Tushar; Menon, Padmavathy; Shah, Nalini

    2014-01-01

    Objective: To assess bone mineral density (BMD) in type 2 diabetes mellitus (T2DM) patients and its relation, if any, to clinical, hormonal and metabolic factors. Materials and Methods: A prospective evaluation of 194 T2DM patients (97 men and 97 women) was carried out. BMD was done with dual energy X-ray absorptiometry (DXA) at the lumbar spine and total hip. Physical activity, nutritional intake and sunlight exposure were calculated. Biochemical and hormonal tests included serum 25 hydroxy vitamin D [25(OH) D], parathyroid hormone, estrogen, testosterone and urinary calcium-creatinine ratio. Glycosylated hemoglobin and complete lipid profiles were done in patients with diabetes. Five hundred and seventy one non-diabetic controls (262 males and 309 females) were evaluated for BMD alone. Results: BMD was normal (Z score > -2) in 156 (80.5%) and low (Z score ≤ -2) in 38 (19.5%) patients in the diabetes study group. BMD in the diabetes group was significantly higher than the control group in both sexes at the hip and spine. The difference was no longer significant on analysis of a BMI matched control subgroup. Weight and BMI showed significant correlation to BMD. Duration of T2DM, degree of glycemic control, use of drugs like statins and thiazolidinediones, 25(OH) D levels, calcium intake, sunlight exposure and physical activity did not significantly affect BMD in this cohort of individuals with diabetes. Conclusions: Bone mineral density of Asian Indian T2DM subjects was similar to that of healthy volunteers in this study. PMID:25364679

  2. Supernova matter at subnuclear densities as a resonant Fermi gas: enhancement of neutrino rates.

    PubMed

    Bartl, A; Pethick, C J; Schwenk, A

    2014-08-22

    At low energies nucleon-nucleon interactions are resonant and therefore supernova matter at subnuclear densities has many similarities to atomic gases with interactions dominated by a Feshbach resonance. We calculate the rates of neutrino processes involving nucleon-nucleon collisions and show that these are enhanced in mixtures of neutrons and protons at subnuclear densities due to the large scattering lengths. As a result, the rate for neutrino pair bremsstrahlung and absorption is significantly larger below 10(13) g cm(-3) compared to rates used in supernova simulations. PMID:25192083

  3. A transported probability density function/photon Monte Carlo method for high-temperature oxy-natural gas combustion with spectral gas and wall radiation

    NASA Astrophysics Data System (ADS)

    Zhao, X. Y.; Haworth, D. C.; Ren, T.; Modest, M. F.

    2013-04-01

    A computational fluid dynamics model for high-temperature oxy-natural gas combustion is developed and exercised. The model features detailed gas-phase chemistry and radiation treatments (a photon Monte Carlo method with line-by-line spectral resolution for gas and wall radiation - PMC/LBL) and a transported probability density function (PDF) method to account for turbulent fluctuations in composition and temperature. The model is first validated for a 0.8 MW oxy-natural gas furnace, and the level of agreement between model and experiment is found to be at least as good as any that has been published earlier. Next, simulations are performed with systematic model variations to provide insight into the roles of individual physical processes and their interplay in high-temperature oxy-fuel combustion. This includes variations in the chemical mechanism and the radiation model, and comparisons of results obtained with versus without the PDF method to isolate and quantify the effects of turbulence-chemistry interactions and turbulence-radiation interactions. In this combustion environment, it is found to be important to account for the interconversion of CO and CO2, and radiation plays a dominant role. The PMC/LBL model allows the effects of molecular gas radiation and wall radiation to be clearly separated and quantified. Radiation and chemistry are tightly coupled through the temperature, and correct temperature prediction is required for correct prediction of the CO/CO2 ratio. Turbulence-chemistry interactions influence the computed flame structure and mean CO levels. Strong local effects of turbulence-radiation interactions are found in the flame, but the net influence of TRI on computed mean temperature and species profiles is small. The ultimate goal of this research is to simulate high-temperature oxy-coal combustion, where accurate treatments of chemistry, radiation and turbulence-chemistry-particle-radiation interactions will be even more important.

  4. Modeling high-pressure adsorption of gas mixtures on activated carbon and coal using a simplified local-density model

    SciTech Connect

    Fitzgerald, J.E.; Robinson, R.L.; Gasem, K.A.M.

    2006-11-07

    The simplified local-density (SLD) theory was investigated regarding its ability to provide accurate representations and predictions of high-pressure supercritical adsorption isotherms encountered in coalbed methane (CBM) recovery and CO{sub 2} sequestration. Attention was focused on the ability of the SLD theory to predict mixed-gas adsorption solely on the basis of information from pure gas isotherms using a modified Peng-Robinson (PR) equation of state (EOS). An extensive set of high-pressure adsorption measurements was used in this evaluation. These measurements included pure and binary mixture adsorption measurements for several gas compositions up to 14 MPa for Calgon F-400 activated carbon and three water-moistened coals. Also included were ternary measurements for the activated carbon and one coal. For the adsorption of methane, nitrogen, and CO{sub 2} on dry activated carbon, the SLD-PR can predict the component mixture adsorption within about 2.2 times the experimental uncertainty on average solely on the basis of pure-component adsorption isotherms. For the adsorption of methane, nitrogen, and CO{sub 2} on two of the three wet coals, the SLD-PR model can predict the component adsorption within the experimental uncertainties on average for all feed fractions (nominally molar compositions of 20/80, 40/60, 60/40, and 80/20) of the three binary gas mixture combinations, although predictions for some specific feed fractions are outside of their experimental uncertainties.

  5. Adsorption of binary gas mixtures in heterogeneous carbon predicted by density functional theory: on the formation of adsorption azeotropes.

    PubMed

    Ritter, James A; Pan, Huanhua; Balbuena, Perla B

    2010-09-01

    Classical density functional theory (DFT) was used to predict the adsorption of nine different binary gas mixtures in a heterogeneous BPL activated carbon with a known pore size distribution (PSD) and in single, homogeneous, slit-shaped carbon pores of different sizes. By comparing the heterogeneous results with those obtained from the ideal adsorbed solution theory and with those obtained in the homogeneous carbon, it was determined that adsorption nonideality and adsorption azeotropes are caused by the coupled effects of differences in the molecular size of the components in a gas mixture and only slight differences in the pore sizes of a heterogeneous adsorbent. For many binary gas mixtures, selectivity was found to be a strong function of pore size. As the width of a homogeneous pore increases slightly, the selectivity for two different sized adsorbates may change from being greater than unity to less than unity. This change in selectivity can be accompanied by the formation of an adsorption azeotrope when this same binary mixture is adsorbed in a heterogeneous adsorbent with a PSD, like in BPL activated carbon. These results also showed that the selectivity exhibited by a heterogeneous adsorbent can be dominated by a small number of pores that are very selective toward one of the components in the gas mixture, leading to adsorption azeotrope formation in extreme cases. PMID:20712330

  6. Impact of using high-density polyethylene geomembrane layer as landfill intermediate cover on landfill gas extraction.

    PubMed

    Chen, Zezhi; Gong, Huijuan; Zhang, Mengqun; Wu, Weili; Liu, Yu; Feng, Jin

    2011-05-01

    Clay is widely used as a traditional cover material for landfills. As clay becomes increasingly costly and scarce, and it also reduces the storage capacity of landfills, alternative materials with low hydraulic conductivity are employed. In developing countries such as China, landfill gas (LFG) is usually extracted for utilization during filling stage, therefore, the intermediate covering system is an important part in a landfill. In this study, a field test of LFG extraction was implemented under the condition of using high-density polyethylene (HDPE) geomembrane layer as the only intermediate cover on the landfill. Results showed that after welding the HDPE geomembranes together to form a whole airtight layer upon a larger area of landfill, the gas flow in the general pipe increased 25% comparing with the design that the HDPE geomembranes were not welded together, which means that the gas extraction ability improved. However as the heat isolation capacity of the HDPE geomembrane layer is low, the gas generation ability of a shallow landfill is likely to be weakened in cold weather. Although using HDPE geomembrane layer as intermediate cover is acceptable in practice, the management and maintenance of it needs to be investigated in order to guarantee its effective operation for a long term. PMID:21232931

  7. The Molecular Gas in Luminous Infrared Galaxies. II. Extreme Physical Conditions and Their Effects on the X co Factor

    NASA Astrophysics Data System (ADS)

    Papadopoulos, Padelis P.; van der Werf, Paul; Xilouris, E.; Isaak, Kate G.; Gao, Yu

    2012-05-01

    In this work, we conclude the analysis of our CO line survey of luminous infrared galaxies (LIRGs: L IR >~ 1011 L ⊙) in the local universe (Paper I) by focusing on the influence of their average interstellar medium (ISM) properties on the total molecular gas mass estimates via the so-called X co = M(H2)/L co, 1-0 factor. One-phase radiative transfer models of the global CO spectral line energy distributions (SLEDs) yield an X co distribution with langX corang ~ (0.6 ± 0.2) M ⊙ (K km s-1 pc2)-1 over a significant range of average gas densities, temperatures, and dynamic states. The latter emerges as the most important parameter in determining X co, with unbound states yielding low values and self-gravitating states yielding the highest ones. Nevertheless, in many (U)LIRGs where available higher-J CO lines (J = 3-2, 4-3, and/or J = 6-5) or HCN line data from the literature allow a separate assessment of the gas mass at high densities (>=104 cm-3) rather than a simple one-phase analysis, we find that near-Galactic X co ~ (3-6) M ⊙ (K km s-1 pc2)-1 values become possible. We further show that in the highly turbulent molecular gas in ULIRGs, a high-density component will be common and can be massive enough for its high X co to dominate the average value for the entire galaxy. Using solely low-J CO lines to constrain X co in such environments (as has been the practice up until now) may have thus resulted in systematic underestimates of molecular gas mass in ULIRGs, as such lines are dominated by a warm, diffuse, and unbound gas phase with low X co but very little mass. Only well-sampled high-J CO SLEDs (J = 3-2 and higher) and/or multi-J observations of heavy rotor molecules (e.g., HCN) can circumvent such a bias, and the latter type of observations may have actually provided early evidence of it in local ULIRGs. The only way that the global X co of such systems could be significantly lower than Galactic is if the average dynamic state of the dense gas is strongly

  8. Endocan-expressing microvessel density as a prognostic factor for survival in human gastric cancer

    PubMed Central

    Chang, Yuan; Niu, Wei; Lian, Pei-Long; Wang, Xian-Qiang; Meng, Zhi-Xin; Liu, Yi; Zhao, Rui

    2016-01-01

    AIM: To investigate the expression of endocan in tumour vessels and the relationships between endocan and the expression of vascular endothelial growth factor (VEGF) and prognosis in gastric cancer. METHODS: This study included 142 patients with confirmed gastric cancer in a single cancer centre between 2008 and 2009. Clinicopathologic features were determined, and an immunohistochemical analysis of endocan-expressing microvessel density (MVD) (endocan-MVD), VEGF and vascular endothelial growth factor receptor 2 (VEGFR2) was performed. Potential relationships between endocan-MVD and clinicopathological variables were assessed using a Student’s t-test or an analysis of variance test. Spearman’s rank correlation was applied to evaluate the relationship between endocan-MVD and the expression of VEGF/VEGFR2. Long-term survival of these patients was analysed using univariate and multivariate analyses. RESULTS: Positive staining of endocan was observed in most of the gastric cancer tissues (108/142) and in fewer of the normal gastric tissues. Endocan-MVD was not associated with gender or histological type (P > 0.05), while endocan-MVD was associated with tumour size, Borrmann type, tumour differentiation, tumour invasion, lymph node metastasis and TNM stage (P < 0.05). According to the Spearman’s rank correlation analysis, endocan-MVD had a positive correlation with VEGF (r = 0.167, P = 0.047) and VEGFR2 (r = 0.410, P = 0.000). The univariate analysis with a log-rank test indicated that the patients with a high level of endocan-MVD had a significantly poorer overall survival rate than those with a low level of endocan-MVD (17.9% vs 64.0%, P = 0.000). The multivariate analysis showed that a high level of endocan-MVD was a valuable prognostic factor. CONCLUSION: Endocan-MVD significantly correlates with the expression of VEGF and VEGFR2 and is a valuable prognostic factor for survival in human gastric cancer. PMID:27340359

  9. Gedanken densities and exact constraints in density functional theory

    SciTech Connect

    Perdew, John P.; Ruzsinszky, Adrienn; Sun, Jianwei; Burke, Kieron

    2014-05-14

    Approximations to the exact density functional for the exchange-correlation energy of a many-electron ground state can be constructed by satisfying constraints that are universal, i.e., valid for all electron densities. Gedanken densities are designed for the purpose of this construction, but need not be realistic. The uniform electron gas is an old gedanken density. Here, we propose a spherical two-electron gedanken density in which the dimensionless density gradient can be an arbitrary positive constant wherever the density is non-zero. The Lieb-Oxford lower bound on the exchange energy can be satisfied within a generalized gradient approximation (GGA) by bounding its enhancement factor or simplest GGA exchange-energy density. This enhancement-factor bound is well known to be sufficient, but our gedanken density shows that it is also necessary. The conventional exact exchange-energy density satisfies no such local bound, but energy densities are not unique, and the simplest GGA exchange-energy density is not an approximation to it. We further derive a strongly and optimally tightened bound on the exchange enhancement factor of a two-electron density, which is satisfied by the local density approximation but is violated by all published GGA's or meta-GGA’s. Finally, some consequences of the non-uniform density-scaling behavior for the asymptotics of the exchange enhancement factor of a GGA or meta-GGA are given.

  10. System and Method for Determining Gas Optical Density Changes in a Non-Linear Measurement Regime

    NASA Technical Reports Server (NTRS)

    Sachse, Glen W. (Inventor); Rana, Mauro (Inventor)

    2007-01-01

    Each of two sensors, positioned to simultaneously detect electromagnetic radiation absorption along a path, is calibrated to define a unique response curve associated therewith that relates a change in voltage output for each sensor to a change in optical density. A ratio-of-responses curve is defined by a ratio of the response curve associated with the first sensor to the response curve associated with the second sensor. A ratio of sensor output changes is generated using outputs from the sensors. An operating point on the ratio-of-responses curve is established using the ratio of sensor output changes. The established operating point is indicative of an optical density. When the operating point is in the non-linear response region of at least one of the sensors, the operating point and optical density corresponding thereto can be used to establish an actual response of at least one of the sensors whereby the actual sensor output can be used in determining changes in the optical density.

  11. Metallic state of the free-electron gas within the self-interaction-corrected local-spin-density approximation

    NASA Astrophysics Data System (ADS)

    Pederson, Mark R.; Heaton, Richard A.; Harrison, Joseph G.

    1989-01-01

    The uniform-density electron gas is studied within the framework of the Wannier-function (WF) formulation of the self-interaction-corrected local-spin-density approximation (SIC-LSD). While the results of the present work follow rigorously from a variational formulation, they may also be qualitatively understood in terms of the local-bonding-site concept introduced by Mott in his theory of the metal-insulator transition. SIC-LSD admits metallic-state solutions at ordinary electron densities just as in traditional LSD theory. The result of introducing SIC to the metallic state is an overall downward shift of the LSD eigenvalues. This shift is largest for states near k=0 and vanishes for states near the Fermi energy ɛF. As such, the orbital energies at ɛF are found to be in exact agreement with both the exchange-only version of LSD and Hartree-Fock (HF). Beyond metallic-state solutions, this formulation of SIC-LSD also admits insulator solutions at very low electron densities and may thus have important application to the problem of Wigner crystallization.

  12. Correlation Energy of 3D Spin-Polarized Electron Gas: A Single Interpolation Between High- and Low-Density Limits

    NASA Astrophysics Data System (ADS)

    Sun, Jianwei; Perdew, John; Seidl, Michael

    2008-03-01

    We present an analytic model for the correlation energy per electron ec(rs,ζ) in the three-dimensional (3D) uniform electron gas, covering the full range 0<=rs<∞ and 0<=ζ<=1 of the density parameter rs and the relative spin polarization ζ. An interpolation is made between the exactly known high-density (rs->0) and low-density (rs->∞) limits, using a formula which (unlike previous ones) has the right analytic structures in both limits. We find that there is almost enough information available from these limits to determine the correlation energy over the full range. By minimal fitting to numerical quantum Monte Carlo data, we predict the value of b1(ζ) at ζ=0 close to the theoretical value [1], where b1(ζ) is the coefficient of the rsterm in the high-density expansion. The model finds correlation energies for the unpolarized (ζ=0) and fully polarized (ζ=1) cases in excellent agreement with Monte Carlo data. [1] T. Endo, M. Horiuchi, Y. Takada and H. Yasuhara, Phys. Rev. B 59, 7367 (1999)

  13. THE PHYSICAL ORIGINS OF THE MORPHOLOGY-DENSITY RELATION: EVIDENCE FOR GAS STRIPPING FROM THE SLOAN DIGITAL SKY SURVEY

    SciTech Connect

    Van der Wel, Arjen; Bell, Eric F.; Skibba, Ramin A.; Rix, Hans-Walter; Holden, Bradford P.

    2010-05-10

    We provide a physical interpretation and explanation of the morphology-density relation for galaxies, drawing on stellar masses, star formation rates, axis ratios, and group halo masses from the Sloan Digital Sky Survey. We first re-cast the classical morphology-density relation in more quantitative terms, using low star formation rate (quiescence) as a proxy for early-type morphology and dark matter halo mass from a group catalog as a proxy for environmental density: for galaxies of a given stellar mass the quiescent fraction is found to increase with increasing dark matter halo mass. Our novel result is that-at a given stellar mass-quiescent galaxies are significantly flatter in dense environments, implying a higher fraction of disk galaxies. Supposing that the denser environments differ simply by a higher incidence of quiescent disk galaxies that are structurally similar to star-forming disk galaxies of similar mass, explains simultaneously and quantitatively these quiescence-environment and shape-environment relations. Our findings add considerable weight to the slow removal of gas as the main physical driver of the morphology-density relation, at the expense of other explanations.

  14. 40 CFR Table W - 4 of Subpart W-Default Total Hydrocarbon Emission Factors for Underground Natural Gas Storage

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 40 Protection of Environment 22 2012-07-01 2012-07-01 false 4 of Subpart W-Default Total Hydrocarbon Emission Factors for Underground Natural Gas Storage W Table W Protection of Environment... Total Hydrocarbon Emission Factors for Underground Natural Gas Storage Underground natural gas...

  15. 40 CFR Table W - 2 of Subpart W-Default Total Hydrocarbon Emission Factors for Onshore Natural Gas Processing

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 40 Protection of Environment 22 2012-07-01 2012-07-01 false 2 of Subpart W-Default Total Hydrocarbon Emission Factors for Onshore Natural Gas Processing W Table W Protection of Environment... Total Hydrocarbon Emission Factors for Onshore Natural Gas Processing Onshore natural gas...

  16. A comparison of planar, laser-induced fluorescence, and high-sensitivity interferometry techniques for gas-puff nozzle density measurements

    SciTech Connect

    Jackson, S. L.; Weber, B. V.; Mosher, D.; Phipps, D. G.; Stephanakis, S. J.; Commisso, R. J.; Qi, N.; Failor, B. H.; Coleman, P. L.

    2008-10-15

    The distribution of argon gas injected by a 12-cm-diameter triple-shell nozzle was characterized using both planar, laser-induced fluorescence (PLIF) and high-sensitivity interferometry. PLIF is used to measure the density distribution at a given time by detecting fluorescence from an acetone tracer added to the gas. Interferometry involves making time-dependent, line-integrated gas density measurements at a series of chordal locations that are then Abel inverted to obtain the gas density distribution. Measurements were made on nominally identical nozzles later used for gas-puff Z-pinch experiments on the Saturn pulsed-power generator. Significant differences in the mass distributions obtained by the two techniques are presented and discussed, along with the strengths and weaknesses of each method.

  17. High contrast Kr gas jet Kα x-ray source for high energy density physics experimentsa)

    NASA Astrophysics Data System (ADS)

    Kugland, N. L.; Neumayer, P.; Döppner, T.; Chung, H.-K.; Constantin, C. G.; Girard, F.; Glenzer, S. H.; Kemp, A.; Niemann, C.

    2008-10-01

    A high contrast 12.6keV Kr Kα source has been demonstrated on the petawatt-class Titan laser facility using strongly clustering Kr gas jet targets. The contrast ratio (Kα to continuum) is 65, with a competitive ultrashort pulse laser to x-ray conversion efficiency of 10-5. Filtered shadowgraphy indicates that the Kr Kα and Kβ x rays are emitted from a roughly 1×2mm2 emission volume, making this source suitable for area backlighting and scattering. Spectral calculations indicate a typical bulk electron temperature of 50-70eV (i.e., mean ionization state 13-16), based on the observed ratio of Kα to Kβ. Kr gas jets provide a debris-free high energy Kα source for time-resolved diagnosis of dense matter.

  18. Optical gas sensing responses in transparent conducting oxides with large free carrier density

    NASA Astrophysics Data System (ADS)

    Ohodnicki, P. R.; Andio, M.; Wang, C.

    2014-07-01

    Inherent advantages of optical-based sensing devices motivate a need for materials with useful optical responses that can be utilized as thin film functional sensor layers. Transparent conducting metal oxides with large electrical conductivities as typified by Al-doped ZnO (AZO) display attractive properties for high temperature optical gas sensing through strong optical transduction of responses conventionally monitored through changes in measured electrical resistivity. An enhanced optical sensing response in the near-infrared and ultraviolet/visible wavelength ranges is demonstrated experimentally and linked with characteristic modifications to the dielectric constant due to a relatively high concentration of free charge carriers. The impact of light scattering on the magnitude and wavelength dependence of the sensing response is also discussed highlighting the potential for tuning the optical sensing response by controlling the surface roughness of a continuous film or the average particle size of a nanoparticle-based film. The physics underpinning the optical sensing response for AZO films on planar substrates yields significant insight into the measured sensing response for optical fiber-based evanescent wave absorption spectroscopy sensors employing an AZO sensing layer. The physics of optical gas sensing discussed here provides a pathway towards development of sensing materials for extreme temperature optical gas sensing applications. As one example, preliminary results are presented for a Nb-doped TiO2 film with sufficient stability and relatively large sensing responses at sensing temperatures greater than 500 °C.

  19. Comparison of surface vacuum ultraviolet emissions with resonance level number densities. II. Rare-gas plasmas and Ar-molecular gas mixtures

    SciTech Connect

    Boffard, John B. Lin, Chun C.; Wang, Shicong; Wendt, Amy E.; Culver, Cody; Radovanov, Svetlana; Persing, Harold

    2015-03-15

    Vacuum ultraviolet (VUV) emissions from excited plasma species can play a variety of roles in processing plasmas, including damaging the surface properties of materials used in semiconductor processing. Depending on their wavelength, VUV photons can easily transmit thin upper dielectric layers and affect the electrical characteristics of the devices. Despite their importance, measuring VUV fluxes is complicated by the fact that few materials transmit at VUV wavelengths, and both detectors and windows are easily damaged by plasma exposure. The authors have previously reported on measuring VUV fluxes in pure argon plasmas by monitoring the concentrations of Ar(3p{sup 5}4s) resonance atoms that produce the VUV emissions using noninvasive optical emission spectroscopy in the visible/near-infrared wavelength range [Boffard et al., J. Vac. Sci. Technol., A 32, 021304 (2014)]. Here, the authors extend this technique to other rare-gases (Ne, Kr, and Xe) and argon-molecular gas plasmas (Ar/H{sub 2}, Ar/O{sub 2}, and Ar/N{sub 2}). Results of a model for VUV emissions that couples radiation trapping and the measured rare-gas resonance level densities are compared to measurements made with both a calibrated VUV photodiode and a sodium salicylate fluorescence detection scheme. In these more complicated gas mixtures, VUV emissions from a variety of sources beyond the principal resonance levels of the rare gases are found to contribute to the total VUV flux.

  20. High-density lipoprotein is a potential growth factor for adrenocortical cells

    SciTech Connect

    Murao, Koji . E-mail: mkoji@kms.ac.jp; Imachi, Hitomi; Cao, Wenming; Yu, Xiao; Li, Junhua; Yoshida, Kazuya; Ahmed, Rania A.M.; Matsumoto, Kensuke; Nishiuchi, Takamasa; Ishida, Toshihiko; Wong, Norman C.W.

    2006-05-26

    The entry of cholesterol contained within high-density lipoprotein (HDL) into adrenocortical cells is mediated by a human homologue of SR-BI, CD36, and LIMPII Analogous-1 (CLA-1) and thus augmenting their growth. To address the role of CLA-1, we created a mutant mCLA that lacked the C-terminal tail. HDL CE selective uptake by cells carrying the mCLA-1 receptor was fully active and equivalent to those transfected with full-length CLA-1 (fCLA-1). Expression of mCLA inhibited the proliferation of an adrenocortical cell line and the incorporation of [{sup 3}H]thymidine into the cells. This effect was sensitive to wortmannin, an inhibitor of phosphoinositide 3-kinase (PI3K). Our transcriptional studies revealed that the inhibitory action of mCLA required the transcriptional factor AP-1 and the effect of HDL on AP-1 activation was also abrogated by wortmannin. These findings raise the possibility that the inhibitors of the effects of HDL may be of therapeutic value for adrenocortical tumor.

  1. Bone Mineral Density in the Noninstitutionalized Elderly: Influence of Sociodemographic and Anthropometric Factors

    PubMed Central

    Cristina de Sousa e Silva Araujo, Ellen; Pagotto, Valéria; Silveira, Erika Aparecida

    2016-01-01

    Objective. Analysis of bone mineral density (BMD) in the elderly and its associated factors according to sex. Methods. A cross-sectional study is presented herein, with a random sample of 132 noninstitutionalized elderly people. Individuals who did not use diuretics were excluded. BMD was obtained from examination of total body densitometry and its association with sociodemographic variables, lifestyle, anthropometric, and body composition was verified. Results. Mean BMD for men was 1.17 ± 0.12 g/cm2 and for women was 1.04 ± 0.11 g/cm2. Higher education was associated with higher BMD values in men (p < 0.05). There was a reduction in BMD in the age group 75–79 years of age in women and over 80 years of age in men (p < 0.05). Underweight was associated with significantly low BMD for both sexes (p < 0.01), while normal weight was associated with low BMD in women (p < 0.001). Discussion. The elderly with low schooling and in older age groups are more probable to also present low BMD. Lower levels of body mass index also indicated towards low BMD. PMID:27127504

  2. Atomic-scale electronic structure of the cuprate d-symmetry form factor density wave state

    NASA Astrophysics Data System (ADS)

    Hamidian, M. H.; Edkins, S. D.; Kim, Chung Koo; Davis, J. C.; MacKenzie, A. P.; Eisaki, H.; Uchida, S.; Lawler, M. J.; Kim, E.-A.; Sachdev, S.; Fujita, K.

    2016-02-01

    Research on high-temperature superconducting cuprates is at present focused on identifying the relationship between the classic `pseudogap’ phenomenon and the more recently investigated density wave state. This state is generally characterized by a wavevector Q parallel to the planar Cu-O-Cu bonds along with a predominantly d-symmetry form factor (dFF-DW). To identify the microscopic mechanism giving rise to this state, one must identify the momentum-space states contributing to the dFF-DW spectral weight, determine their particle-hole phase relationship about the Fermi energy, establish whether they exhibit a characteristic energy gap, and understand the evolution of all these phenomena throughout the phase diagram. Here we use energy-resolved sublattice visualization of electronic structure and reveal that the characteristic energy of the dFF-DW modulations is actually the `pseudogap’ energy Δ1. Moreover, we demonstrate that the dFF-DW modulations at E = -Δ1 (filled states) occur with relative phase π compared to those at E = Δ1 (empty states). Finally, we show that the conventionally defined dFF-DW Q corresponds to scattering between the `hot frontier’ regions of momentum-space beyond which Bogoliubov quasiparticles cease to exist. These data indicate that the cuprate dFF-DW state involves particle-hole interactions focused at the pseudogap energy scale and between the four pairs of `hot frontier’ regions in momentum space where the pseudogap opens.

  3. Real-Gas Correction Factors for Hypersonic Flow Parameters in Helium

    NASA Technical Reports Server (NTRS)

    Erickson, Wayne D.

    1960-01-01

    The real-gas hypersonic flow parameters for helium have been calculated for stagnation temperatures from 0 F to 600 F and stagnation pressures up to 6,000 pounds per square inch absolute. The results of these calculations are presented in the form of simple correction factors which must be applied to the tabulated ideal-gas parameters. It has been shown that the deviations from the ideal-gas law which exist at high pressures may cause a corresponding significant error in the hypersonic flow parameters when calculated as an ideal gas. For example the ratio of the free-stream static to stagnation pressure as calculated from the thermodynamic properties of helium for a stagnation temperature of 80 F and pressure of 4,000 pounds per square inch absolute was found to be approximately 13 percent greater than that determined from the ideal-gas tabulation with a specific heat ratio of 5/3.

  4. Monte Carlo modeling of electron density in hypersonic rarefied gas flows

    SciTech Connect

    Fan, Jin; Zhang, Yuhuai; Jiang, Jianzheng

    2014-12-09

    The electron density distribution around a vehicle employed in the RAM-C II flight test is calculated with the DSMC method. To resolve the mole fraction of electrons which is several orders lower than those of the primary species in the free stream, an algorithm named as trace species separation (TSS) is utilized. The TSS algorithm solves the primary and trace species separately, which is similar to the DSMC overlay techniques; however it generates new simulated molecules of trace species, such as ions and electrons in each cell, basing on the ionization and recombination rates directly, which differs from the DSMC overlay techniques based on probabilistic models. The electron density distributions computed by TSS agree well with the flight data measured in the RAM-C II test along a decent trajectory at three altitudes 81km, 76km, and 71km.

  5. Greenhouse Gas Emissions of Indianapolis using a High-Density Surface Tower Network and an Atmospheric Inversion

    NASA Astrophysics Data System (ADS)

    Lauvaux, T.; Miles, N. L.; Davis, K. J.; Richardson, S.; Deng, A.; Sarmiento, D. P.; Wu, K.; Sweeney, C.; Karion, A.; Hardesty, R. M.; Brewer, A.; Turnbull, J. C.; Iraci, L. T.; Hillyard, P. W.; Podolske, J. R.; Gurney, K. R.; Patarasuk, R.; Cambaliza, M. O. L.; Shepson, P. B.; Whetstone, J. R.

    2014-12-01

    The Indianapolis Flux Experiment (INFLUX) was designed to develop and evaluate methods of detection and attribution of greenhouse gas fluxes from urban environments. Determination of greenhouse gas fluxes and uncertainty bounds is essential for the evaluation of the effectiveness of mitigation strategies. Indianapolis is intended to serve as a test bed for these methods; the results will inform efforts at measuring emissions from urban centers worldwide, including megacities. The generally accepted method for determining urban greenhouse gas emissions is inventories, which are compiled from records of land use and human activity. Atmospheric methods, in which towers are instrumented with sensors to measure greenhouse gas mole fractions and these data are used in an inversion model, have the potential to provide independent determination of emissions. The current INFLUX observation network includes twelve in-situ tower-based, continuous measurements of CO2. A subset of five towers additionally measure CH4, and a different subset measure CO. The subset measuring CO also include weekly flask samples of a wide variety of trace gases including 14CO2. Here we discuss the observed urban spatial and temporal patterns in greenhouse gas mole fraction in Indianapolis, with the critical result being the detectability of city emissions with this high-density network. We also present the first atmospheric inversion results for both CO2 and CH4, compare these results to inventories, and discuss the effects of critical assumptions in the inversion framework. The construction of unbiased atmospheric modeling systems and well-defined prior errors remains an important step in atmospheric emissions monitoring over urban areas. In order to minimize transport model errors, we developed a WRF-Chem FDDA modeling system ingesting surface and profile measurements of horizontal mean wind, temperature, and moisture. We demonstrate the impact of the meteorological data assimilation system on

  6. Measurement of viscosity, density, and gas solubility of refrigerant blends in selected synthetic lubricants. Final report

    SciTech Connect

    Cavestri, R.C.

    1995-05-15

    The lubricants tested in this project were chosen based on the results of liquid/liquid miscibility tests. EMKARATE RL32S and Emery 2968A were selected. The Vapor Liquid Equilibrium (VLE) viscosity reduction and gas fractionation of each was measured with three different refrigerant blends: (1) R-404A; (2) R-507; and (3) R-407C. In addition, the four single refrigerants that make up the blends, HFC-32, HFC-125, HFC-134a, and HFC-143a, were also measured. Lubricants found to have the lowest liquid/liquid miscibilities had nearly equal viscosity reduction profiles as did the more miscible lubricants. Analytical methodology consisted of maintaining equally both the composition of the head space vapor above the lubricant/refrigerant mixture, and the composition of the liquid blend refrigerant. Blends with large temperature glides were re-evaluated in order to test the concept of head space quality and a vented piston hydraulic cylinder assembly was developed to perform this task. Fluid property data, above critical temperature and pressure conditions, is presented for the two lubricants with HFC-32, HFC-125, HFC-143a refrigerants. This research shows that the lubricant EMKARATE RL32S, which had the lowest (poorest) liquid/liquid miscibilities with the selected refrigerants, also had nearly equal viscosity reduction profiles to the more miscible Emery 2968A lubricant. The analytical methodology consisted of maintaining the composition of the refrigerant gas above the lubricant to be equal in composition to that of the pure liquid refrigerant blend being introduced into the lubricant. Refrigerant blends with large temperature glides were re-evaluated in order to validate the concept of the importance of the composition of the gas over the lubricant. To do perform this task, a special vented piston hydraulic cylinder assembly was developed. Fluid property data is also presented for HFC-32, HFC-125, and HFC-143a above the critical temperature and pressure of each.

  7. Serum fibroblast growth factor 23, serum iron and bone mineral density in premenopausal women.

    PubMed

    Imel, Erik A; Liu, Ziyue; McQueen, Amie K; Acton, Dena; Acton, Anthony; Padgett, Leah R; Peacock, Munro; Econs, Michael J

    2016-05-01

    Fibroblast growth factor 23 (FGF23) circulates as active protein and inactive fragments. Low iron status increases FGF23 gene expression, and iron deficiency is common. We hypothesized that in healthy premenopausal women, serum iron influences C-terminal and intact FGF23 concentrations, and that iron and FGF23 associate with bone mineral density (BMD). Serum iron, iron binding capacity, percent iron saturation, phosphorus, and other biochemistries were measured in stored fasting samples from healthy premenopausal white (n=1898) and black women (n=994), age 20-55years. Serum C-terminal and intact FGF23 were measured in a subset (1631 white and 296 black women). BMD was measured at the lumbar spine and femur neck. Serum phosphorus, calcium, alkaline phosphatase and creatinine were lower in white women than black women (p<0.001). Serum iron (p<0.0001) and intact FGF23 (p<0.01) were higher in white women. C-terminal FGF23 did not differ between races. Phosphorus correlated with intact FGF23 (white women, r=0.120, p<0.0001; black women r=0.163, p<0.01). However, phosphorus correlated with C-terminal FGF23 only in black women (r=0.157, p<0.01). Intact FGF23 did not correlate with iron. C-terminal FGF23 correlated inversely with iron (white women r=-0.134, p<0.0001; black women r=-0.188, p<0.01), having a steeper slope at iron <50mcg/dl than ≥50mcg/dl. Longitudinal changes in iron predicted changes in C-terminal FGF23. Spine BMD correlated with iron negatively (r=-0.076, p<0.01) in white women; femur neck BMD correlated with iron negatively (r=-0.119, p<0.0001) in black women. Both relationships were eliminated in weight-adjusted models. BMD did not correlate with FGF23. Serum iron did not relate to intact FGF23, but was inversely related to C-terminal FGF23. Intact FGF23 correlated with serum phosphorus. In weight-adjusted models, BMD was not related to intact FGF23, C-terminal FGF23 or iron. The influence of iron on FGF23 gene expression is not important in

  8. Experimental study of dense pyroclastic density currents using sustained, gas-fluidized granular flows

    NASA Astrophysics Data System (ADS)

    Rowley, Pete J.; Roche, Olivier; Druitt, Timothy H.; Cas, Ray

    2014-09-01

    We present the results of laboratory experiments on the behaviour of sustained, dense granular flows in a horizontal flume, in which high-gas pore pressure was maintained throughout the flow duration by continuous injection of gas through the flume base. The flows were fed by a sustained (0.5-30 s) supply of fine (75 ± 15 μm) particles from a hopper; the falling particles impacted an impingement surface at concentrations of ~3 to 45 %, where they densified rapidly to generate horizontally moving, dense granular flows. When the gas supplied through the flume base was below the minimum fluidization velocity of the particles (i.e. aerated flow conditions), three flow phases were identified: (i) an initial dilute spray of particles travelling at 1-2 m s-1, followed by (ii) a dense granular flow travelling at 0.5-1 m s-1, then by (iii) sustained aggradation of the deposit by a prolonged succession of thin flow pulses. The maximum runout of the phase 2 flow was linearly dependent on the initial mass flux, and the frontal velocity had a square-root dependence on mass flux. The frontal propagation speed during phase 3 had a linear relationship with mass flux. The total mass of particles released had no significant control on either flow velocity or runout in any of the phases. High-frequency flow unsteadiness during phase 3 generated deposit architectures with progradational and retrogradational packages and multiple internal erosive contacts. When the gas supplied through the flume base was equal to the minimum fluidization velocity of the particles (i.e. fluidized flow conditions), the flows remained within phase 2 for their entire runout, no deposit formed and the particles ran off the end of the flume. Sustained granular flows differ significantly from instantaneous flows generated by lock-exchange mechanisms, in that the sustained flows generate (by prolonged progressive aggradation) deposits that are much thicker than the flowing layer of particles at any given

  9. A DIRECT MEASUREMENT OF THE TOTAL GAS COLUMN DENSITY IN ORION KL

    SciTech Connect

    Plume, R.; Bergin, E. A.; Wang, S.; Crockett, N. R.; Phillips, T. G.; Lis, D. C.; Caux, E.; Comito, C.; Schilke, P.; Goldsmith, P. F.

    2012-01-01

    The large number of high-J lines of C{sup 18}O available via the Herschel Space Observatory provide an unprecedented ability to model the total CO column density in hot cores. Using the emission from all the observed lines (up to J = 15-14), we sum the column densities in each individual level to obtain the total column after correcting for the population in the unobserved states. With additional knowledge of source size, V{sub LSR}, and line width, and both local thermodynamic equilibrium (LTE) and non-LTE modeling, we have determined the total C{sup 18}O column densities in the Extended Ridge, Outflow/Plateau, Compact Ridge, and Hot Core components of Orion KL to be 1.4 Multiplication-Sign 10{sup 16} cm{sup -2}, 3.5 Multiplication-Sign 10{sup 16} cm{sup -2}, 2.2 Multiplication-Sign 10{sup 16} cm{sup -2}, and 6.2 Multiplication-Sign 10{sup 16} cm{sup -2}, respectively. We also find that the C{sup 18}O/C{sup 17}O abundance ratio varies from 1.7 in the Outflow/Plateau, 2.3 in the Extended Ridge, 3.0 in the Hot Core, and to 4.1 in the Compact Ridge. This is in agreement with models in which regions with higher ultraviolet radiation fields selectively dissociate C{sup 17}O, although care must be taken when interpreting these numbers due to the size of the uncertainties in the C{sup 18}O/C{sup 17}O abundance ratio.

  10. Evolution of the cosmological mass density of neutral gas from Sloan Digital Sky Survey II - Data Release 7

    NASA Astrophysics Data System (ADS)

    Noterdaeme, P.; Petitjean, P.; Ledoux, C.; Srianand, R.

    2009-10-01

    We present the results of a search for damped Lyman-α (DLA) systems in the Sloan Digital Sky Survey II (SDSS), Data Release 7. We use a fully automatic procedure to identify DLAs and derive their column densities. The procedure is checked against the results of previous searches for DLAs in SDSS. We discuss the agreements and differences and show the robustness of our procedure. For each system, we obtain an accurate measurement of the absorber's redshift, the H I column density and the equivalent width of associated metal absorption lines, without any human intervention. We find 1426 absorbers with 2.15 < z < 5.2 with log N(H I) ≥ 20, out of which 937 systems have log N(H I) ≥ 20.3. This is the largest DLA sample ever built, made available to the scientific community through the electronic version of this paper. In the course of the survey, we discovered the intervening DLA with highest H I column density known to date with log N(H I) = 22.0±0.1. This single system provides a strong constraint on the high-end of the N(H I) frequency distribution now measured with high accuracy. We show that the presence of a DLA at the blue end of a QSO spectrum can lead to important systematic errors and propose a method to avoid them. This has important consequences for the measurement of the cosmological mass density of neutral gas at z ~ 2.2 and therefore on our understanding of galaxy evolution over the past 10 billion years. We find a significant decrease of the cosmological mass density of neutral gas in DLAs, Ω_g^DLA, from z = 4 to z = 2.2, consistent with the result of previous SDSS studies. However, and contrary to other SDSS studies, we find that Ω_g^DLA(z = 2.2) is about twice the value at z = 0. This implies that Ω_g^DLA keeps decreasing at z < 2.2. Catalog is only available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/505/1087

  11. Low bone mineral density and associated risk factors in HIV-infected patients

    PubMed Central

    Chiţu-Tișu, Cristina-Emilia; Barbu, Ecaterina-Constanţa; Lazăr, Mihai; Ion, Daniela Adriana; Bădărău, Ioana Anca

    2016-01-01

    Background Aging of persons with human immunodeficiency virus (HIV) resulted in high rates of osteopenia and osteoporosis. Multiple cohort studies have reported an increased prevalence of bone demineralization among HIV-infected individuals. The aim of this study was to evaluate bone mineral density (BMD) and risk factors for osteopenia/osteoporosis among HIV-positive patients attending the National Institute for Infectious Diseases “Prof.Dr. Matei Balș”, Bucharest, Romania. Methods We performed a cross-sectional study that enrolled 60 patients with HIV. The association between BMD and lifestyle habits (smoking), body mass index (BMI), nadir cluster of differentiation 4 (CD4) cell count, current CD4 cell count, HIV viral load and history of combination antiretroviral therapy (cART) were investigated. The BMD was measured at the lumbar spine, hips and total body using dual-energy X-ray absorptiometry (DEXA). Results In the present study, DEXA evaluation showed an overall prevalence of osteoporosis of 16.66% (ten patients) and a prevalence of osteopenia of 48.33% (29 patients). In men, low BMI and cigarette smoking showed significant association with the diagnosis of lumbar spine demineralization (p=0.034 and p=0.041, respectively). Duration of exposure to cART classes in relation to BMD was also evaluated. The use of non-nucleoside reverse-transcriptase inhibitors (NNRTIs) was associated with low lumbar spine BMD in all patients (p=0.015). Reduced BMD was significantly associated with protease inhibitors (PIs)-containing treatment (p=0.043) in women. Conclusion At lumbar spine DEXA, male gender was statistically associated with reduced BMD. At the left hip Ward’s area, decreased BMD T scores were significantly associated with aging. The reduced BMD was higher in patients receiving PI- or NNRTI-containing regimens. PMID:27482514

  12. Atomic-scale electronic structure of the cuprate d-symmetry form factor density wave state

    DOE PAGESBeta

    M. H. Hamidian; Kim, Chung Koo; Edkins, S. D.; Davis, J. C.; Mackenzie, A. P.; Eisaki, H.; Uchida, S.; Lawler, M. J.; Kim, E. -A.; Sachdev, S.; et al

    2015-10-26

    Research on high-temperature superconducting cuprates is at present focused on identifying the relationship between the classic ‘pseudogap’ phenomenon1, 2 and the more recently investigated density wave state3–13. This state is generally characterized by a wavevector Q parallel to the planar Cu–O–Cu bonds 4–13 along with a predominantly d-symmetry form factor 14–17 (dFF-DW). To identify the microscopic mechanism giving rise to this state 18–30, one must identify the momentum-space states contributing to the dFF-DW spectral weight, determine their particle–hole phase relationship about the Fermi energy, establish whether they exhibit a characteristic energy gap, and understand the evolution of all these phenomenamore » throughout the phase diagram. Here we use energy-resolved sublattice visualization14 of electronic structure and reveal that the characteristic energy of the dFF-DW modulations is actually the ‘pseudogap’ energy Δ1. Moreover, we demonstrate that the dFF-DW modulations at E = –Δ1 (filled states) occur with relative phase π compared to those at E = Δ1 (empty states). Lastly, we show that the conventionally defined dFF-DW Q corresponds to scattering between the ‘hot frontier’ regions of momentum-space beyond which Bogoliubov quasiparticles cease to exist30–32. These data indicate that the cuprate dFF-DW state involves particle–hole interactions focused at the pseudogap energy scale and between the four pairs of ‘hot frontier’ regions in momentum space where the pseudogap opens.« less

  13. Novel Bayes Factors That Capture Expert Uncertainty in Prior Density Specification in Genetic Association Studies

    PubMed Central

    Spencer, Amy V.; Cox, Angela; Lin, Wei‐Yu; Easton, Douglas F.; Michailidou, Kyriaki

    2015-01-01

    ABSTRACT Bayes factors (BFs) are becoming increasingly important tools in genetic association studies, partly because they provide a natural framework for including prior information. The Wakefield BF (WBF) approximation is easy to calculate and assumes a normal prior on the log odds ratio (logOR) with a mean of zero. However, the prior variance (W) must be specified. Because of the potentially high sensitivity of the WBF to the choice of W, we propose several new BF approximations with logOR ∼N(0,W), but allow W to take a probability distribution rather than a fixed value. We provide several prior distributions for W which lead to BFs that can be calculated easily in freely available software packages. These priors allow a wide range of densities for W and provide considerable flexibility. We examine some properties of the priors and BFs and show how to determine the most appropriate prior based on elicited quantiles of the prior odds ratio (OR). We show by simulation that our novel BFs have superior true‐positive rates at low false‐positive rates compared to those from both P‐value and WBF analyses across a range of sample sizes and ORs. We give an example of utilizing our BFs to fine‐map the CASP8 region using genotype data on approximately 46,000 breast cancer case and 43,000 healthy control samples from the Collaborative Oncological Gene‐environment Study (COGS) Consortium, and compare the single‐nucleotide polymorphism ranks to those obtained using WBFs and P‐values from univariate logistic regression. PMID:25727067

  14. Atomic-scale electronic structure of the cuprate d-symmetry form factor density wave state

    SciTech Connect

    M. H. Hamidian; Kim, Chung Koo; Edkins, S. D.; Davis, J. C.; Mackenzie, A. P.; Eisaki, H.; Uchida, S.; Lawler, M. J.; Kim, E. -A.; Sachdev, S.; Fujita, K.

    2015-10-26

    Research on high-temperature superconducting cuprates is at present focused on identifying the relationship between the classic ‘pseudogap’ phenomenon1, 2 and the more recently investigated density wave state3–13. This state is generally characterized by a wavevector Q parallel to the planar Cu–O–Cu bonds 4–13 along with a predominantly d-symmetry form factor 14–17 (dFF-DW). To identify the microscopic mechanism giving rise to this state 18–30, one must identify the momentum-space states contributing to the dFF-DW spectral weight, determine their particle–hole phase relationship about the Fermi energy, establish whether they exhibit a characteristic energy gap, and understand the evolution of all these phenomena throughout the phase diagram. Here we use energy-resolved sublattice visualization14 of electronic structure and reveal that the characteristic energy of the dFF-DW modulations is actually the ‘pseudogap’ energy Δ1. Moreover, we demonstrate that the dFF-DW modulations at E = –Δ1 (filled states) occur with relative phase π compared to those at E = Δ1 (empty states). Lastly, we show that the conventionally defined dFF-DW Q corresponds to scattering between the ‘hot frontier’ regions of momentum-space beyond which Bogoliubov quasiparticles cease to exist30–32. These data indicate that the cuprate dFF-DW state involves particle–hole interactions focused at the pseudogap energy scale and between the four pairs of ‘hot frontier’ regions in momentum space where the pseudogap opens.

  15. Serum LDL (Low Density Lipoprotein) As a Risk Factor for Ischemic Stroke.

    PubMed

    Biswas, N; Sangma, M A

    2016-07-01

    Atherosclerosis is the main risk factor of ischaemic stroke. Dyslipidaemia is the main cause of atherosclerosis. High levels of LDL, also called "bad" cholesterol, seem to provoke stroke. This case control study was conducted in Mymensingh Medical College Hospital during the period of January 2012 to December 2012. The study was carried out to measure the level of serum LDL (Low Density Lipoprotein) of ischaemic stroke patients admitted in Medicine wards of Mymensingh Medical College Hospital and the result of this study was compared with the level of LDL cholesterol in age matched controls. Sample size was 384 which had been selected by inclusion and exclusion criteria. Out of 384 samples 192 were cases and 192 were controls. Mean age ±SD was 57.0±10.85 years in cases and 57.43±10.64 years in controls. Elderly people are the most vulnerable group for developing stroke. LDL cholesterol level was more than 130mg/dl was found 88.54% among cases and 33.85% among controls, the difference was statistically significant (p<0.05). Mean LDL level ±SD were 145±13.59mg/dl in cases and 125.01±10.73mg/dl in controls. Odds ratio of LDL cholesterol were 15.0979 and 95% confidence limits were 8.8396 to 25.7869 among cases and controls. This study explored study population with higher LDL cholesterol was over fifteen times more likely to developed ischaemic stroke. Early detection of high LDL cholesterol in the way to prevent ischaemic stroke and thereby reduced the morbidity and mortality of ischaemic stroke. PMID:27612886

  16. High-density Two-Dimensional Small Polaron Gas in a Delta-Doped Mott Insulator

    PubMed Central

    Ouellette, Daniel G.; Moetakef, Pouya; Cain, Tyler A.; Zhang, Jack Y.; Stemmer, Susanne; Emin, David; Allen, S. James

    2013-01-01

    Heterointerfaces in complex oxide systems open new arenas in which to test models of strongly correlated material, explore the role of dimensionality in metal-insulator-transitions (MITs) and small polaron formation. Close to the quantum critical point Mott MITs depend on band filling controlled by random disordered substitutional doping. Delta-doped Mott insulators are potentially free of random disorder and introduce a new arena in which to explore the effect of electron correlations and dimensionality. Epitaxial films of the prototypical Mott insulator GdTiO3 are delta-doped by substituting a single (GdO)+1 plane with a monolayer of charge neutral SrO to produce a two-dimensional system with high planar doping density. Unlike metallic SrTiO3 quantum wells in GdTiO3 the single SrO delta-doped layer exhibits thermally activated DC and optical conductivity that agree in a quantitative manner with predictions of small polaron transport but with an extremely high two-dimensional density of polarons, ~7 × 1014 cm−2. PMID:24257578

  17. Tuning the conductivity threshold and carrier density of two-dimensional electron gas at oxide interfaces through interface engineering

    SciTech Connect

    Ma, H. J. Harsan E-mail: ariando@nus.edu.sg; Zeng, S. W.; Annadi, A.; Ariando E-mail: ariando@nus.edu.sg; Huang, Z.; Venkatesan, T.

    2015-08-15

    The two-dimensional electron gas (2DEG) formed at the perovskite oxides heterostructures is of great interest because of its potential applications in oxides electronics and nanoscale multifunctional devices. A canonical example is the 2DEG at the interface between a polar oxide LaAlO{sub 3} (LAO) and non-polar SrTiO{sub 3} (STO). Here, the LAO polar oxide can be regarded as the modulating or doping layer and is expected to define the electronic properties of 2DEG at the LAO/STO interface. However, to practically implement the 2DEG in electronics and device design, desired properties such as tunable 2D carrier density are necessary. Here, we report the tuning of conductivity threshold, carrier density and electronic properties of 2DEG in LAO/STO heterostructures by insertion of a La{sub 0.5}Sr{sub 0.5}TiO{sub 3} (LSTO) layer of varying thicknesses, and thus modulating the amount of polarization of the oxide over layers. Our experimental result shows an enhancement of carrier density up to a value of about five times higher than that observed at the LAO/STO interface. A complete thickness dependent metal-insulator phase diagram is obtained by varying the thickness of LAO and LSTO providing an estimate for the critical thickness needed for the metallic phase. The observations are discussed in terms of electronic reconstruction induced by polar oxides.

  18. Hysteresis phenomena of the two dimensional electron gas density in lattice-matched InAlN/GaN heterostructures

    SciTech Connect

    Sang, Ling; Yang, Xuelin Cheng, Jianpeng; Guo, Lei; Hu, Anqi; Xiang, Yong; Yu, Tongjun; Xu, Fujun; Tang, Ning; Jia, Lifang; He, Zhi; Wang, Maojun; Wang, Xinqiang; Shen, Bo; Ge, Weikun

    2015-08-03

    High-temperature transport properties in high-mobility lattice-matched InAlN/GaN heterostructures have been investigated. An interesting hysteresis phenomenon of the two dimensional electron gas (2DEG) density is observed in the temperature-dependent Hall measurements. After high-temperature thermal cycles treatment, the reduction of the 2DEG density is observed, which is more serious in thinner InAlN barrier samples. This reduction can then be recovered by light illumination. We attribute these behaviors to the shallow trap states with energy level above the Fermi level in the GaN buffer layer. The electrons in the 2DEG are thermal-excited when temperature is increased and then trapped by these shallow trap states in the buffer layer, resulting in the reduction and hysteresis phenomenon of their density. Three trap states are observed in the GaN buffer layer and C{sub Ga} may be one of the candidates responsible for the observed behaviors. Our results provide an alternative approach to assess the quality of InAlN/GaN heterostructures for applications in high-temperature electronic devices.

  19. The mechanism of small-gas detonation in mechanically activated low-density powder mixtures

    NASA Astrophysics Data System (ADS)

    Rashkovskii, S. A.; Dolgoborodov, A. Yu.

    2015-06-01

    A mechanism of supersonic propagation of the energy-release wave in mechanically activated small-gas explosive powder mixtures is proposed. It is shown that, under certain conditions, this process exhibits all the signs of detonation and should be recognized as a kind of thereof. On the other hand, this kind of detonation is fundamentally different from classical detonation, e.g., in gases. Instead of a shock wave, the powder mixture features propagation of a compression wave, in which the powder exhibits densification due to the mutual displacement of particles rather than contraction of the particle material. A chemical reaction is initiated by the mutual friction of particles in the compression wave.

  20. Start-phase ionization dynamics in the laser plasma at low gas target densities

    NASA Astrophysics Data System (ADS)

    Belik, V. P.; Demidov, R. A.; Kalmykov, S. G.; Mozharov, A. M.; Petrenko, M. V.; Sasin, M. E.

    2013-12-01

    In Xe laser-produced-plasma sources of short-wave radiation, the laser-energy-to-EUV conversion efficiency (CE) proves substantially less than theoretical expectations. In the present work, a calculated estimate has been made which indicates that a long period of the primary ionization, lasting up to a moment when high-Z ions appear to emit short-wave photons, can be one of main causes for this. During that period the plasma remains low-ionized and absorbs weakly the laser energy. The estimate above has been experimentally confirmed with spectroscopic data and those on the effective ion charge derived from measured absorption of the laser radiation in the plasma. A preionization of the gas target with an ultraviolet (UV) excimer laser pulse is proposed as a method to accelerate the ionization process and consequently, to enhance CE.

  1. Extended performance gas Cherenkov detector for gamma-ray detection in high-energy density experiments.

    PubMed

    Herrmann, H W; Kim, Y H; Young, C S; Fatherley, V E; Lopez, F E; Oertel, J A; Malone, R M; Rubery, M S; Horsfield, C J; Stoeffl, W; Zylstra, A B; Shmayda, W T; Batha, S H

    2014-11-01

    A new Gas Cherenkov Detector (GCD) with low-energy threshold and high sensitivity, currently known as Super GCD (or GCD-3 at OMEGA), is being developed for use at the OMEGA Laser Facility and the National Ignition Facility (NIF). Super GCD is designed to be pressurized to ≤400 psi (absolute) and uses all metal seals to allow the use of fluorinated gases inside the target chamber. This will allow the gamma energy threshold to be run as low at 1.8 MeV with 400 psi (absolute) of C2F6, opening up a new portion of the gamma ray spectrum. Super GCD operating at 20 cm from TCC will be ∼400 × more efficient at detecting DT fusion gammas at 16.7 MeV than the Gamma Reaction History diagnostic at NIF (GRH-6m) when operated at their minimum thresholds. PMID:25430303

  2. Extended performance gas Cherenkov detector for gamma-ray detection in high-energy density experimentsa)

    NASA Astrophysics Data System (ADS)

    Herrmann, H. W.; Kim, Y. H.; Young, C. S.; Fatherley, V. E.; Lopez, F. E.; Oertel, J. A.; Malone, R. M.; Rubery, M. S.; Horsfield, C. J.; Stoeffl, W.; Zylstra, A. B.; Shmayda, W. T.; Batha, S. H.

    2014-11-01

    A new Gas Cherenkov Detector (GCD) with low-energy threshold and high sensitivity, currently known as Super GCD (or GCD-3 at OMEGA), is being developed for use at the OMEGA Laser Facility and the National Ignition Facility (NIF). Super GCD is designed to be pressurized to ≤400 psi (absolute) and uses all metal seals to allow the use of fluorinated gases inside the target chamber. This will allow the gamma energy threshold to be run as low at 1.8 MeV with 400 psi (absolute) of C2F6, opening up a new portion of the gamma ray spectrum. Super GCD operating at 20 cm from TCC will be ˜400 × more efficient at detecting DT fusion gammas at 16.7 MeV than the Gamma Reaction History diagnostic at NIF (GRH-6m) when operated at their minimum thresholds.

  3. Extended performance gas Cherenkov detector for gamma-ray detection in high-energy density experiments

    SciTech Connect

    Herrmann, H. W. Kim, Y. H.; Young, C. S.; Fatherley, V. E.; Lopez, F. E.; Oertel, J. A.; Batha, S. H.; Malone, R. M.; Rubery, M. S.; Horsfield, C. J.; Stoeffl, W.; Zylstra, A. B.; Shmayda, W. T.

    2014-11-15

    A new Gas Cherenkov Detector (GCD) with low-energy threshold and high sensitivity, currently known as Super GCD (or GCD-3 at OMEGA), is being developed for use at the OMEGA Laser Facility and the National Ignition Facility (NIF). Super GCD is designed to be pressurized to ≤400 psi (absolute) and uses all metal seals to allow the use of fluorinated gases inside the target chamber. This will allow the gamma energy threshold to be run as low at 1.8 MeV with 400 psi (absolute) of C{sub 2}F{sub 6}, opening up a new portion of the gamma ray spectrum. Super GCD operating at 20 cm from TCC will be ∼400 × more efficient at detecting DT fusion gammas at 16.7 MeV than the Gamma Reaction History diagnostic at NIF (GRH-6m) when operated at their minimum thresholds.

  4. The measurement of electron number density in helium micro hollow gas discharge using asymmetric He I lines

    NASA Astrophysics Data System (ADS)

    Jovović, J.; Šišović, N. M.

    2015-09-01

    The electron number density N e in helium micro hollow gas discharge (MHGD) is measured by means of optical emission spectroscopy (OES) techniques. The structure of MHGD is a gold-alumina-gold sandwich with 250 μm alumina thickness and 100 μm diameter hole. The electron temperature T e and gas temperature T g in the discharge is determined using the relative intensity of He I lines and {{\\text{N}}2}+≤ft({{\\text{B}}2}Σ\\text{u}+- {{X}2}Σ\\text{g}+\\right) R branch lines in the frame of BP technique, respectively. The simple procedure based on spectral line broadening theory was developed in MATLAB to generate synthetic neutral line asymmetric profiles. The synthetic profiles were compared with an experimental He I 447.1 nm and He I 492.2 nm line to obtain N e from the centre of a micro hollow gas discharge (MHGD) source in helium. The N e results were compared with N e values obtained from the forbidden-to-allowed (F/A) intensity ratio technique. The comparison confirmed higher N e determined using a F/A ratio due to large uncertainty of the method. Applying the fitting formula for a He I 492.2 nm line derived from computer simulation (CS) gives the same N e values as the one determined using the MATLAB procedure in this study. The dependence of N e on gas pressure and electric current is investigated as well.

  5. A Survey of Metal Lines at High Redshift. II. SDSS Absorption Line Studies—O VI Line Density, Space Density, and Gas Metallicity at z abs ~ 3.0

    NASA Astrophysics Data System (ADS)

    Frank, S.; Mathur, S.; Pieri, M.; York, D. G.

    2010-09-01

    We have analyzed a large data set of O VI absorber candidates found in the spectra of 3702 Sloan Digital Sky Survey (SDSS) quasars, focusing on a subsample of 387 active galactic nuclei sight lines with an average S/N >=5.0, allowing for the detection of absorbers above a rest-frame equivalent width limit of W r >= 0.19 Å for the O VI 1032 Å component. Accounting for random interlopers mimicking an O VI doublet, we derive for the first time a secure lower limit for the redshift number density ΔN/Δz for redshifts z abs >= 2.8. With extensive Monte Carlo simulations, we quantify the losses of absorbers due to blending with the ubiquitous Lyα forest lines and estimate the success rate of retrieving each individual candidate as a function of its redshift, the emission redshift of the quasar, the strength of the absorber, and the measured signal-to-noise ratio (S/N) of the spectrum by modeling typical Lyman forest spectra. These correction factors allow us to derive the "incompleteness and S/N-corrected" redshift number densities of O VI absorbers: ΔN O VI,c /Δzc (2.8 < z < 3.2) = 4.6 ± 0.3, ΔN O VI,c /Δzc (3.2 < z < 3.6) = 6.7 ± 0.8, and ΔN O VI,c /Δzc (3.6 < z < 4.0) = 8.4 ± 2.9. We can place a secure lower limit for the contribution of O VI to the closure mass density at the redshifts probed here: ΩO VI (2.8 < z < 3.2) >= 1.9 × 10-8 h -1. We show that the strong lines we probe account for over 65% of the mass in the O VI absorbers; the weak absorbers, while dominant in line number density, do not contribute significantly to the mass density. Making a conservative assumption about the ionization fraction, {O VI}/{O}, and adopting the Anders & Grevesse solar abundance values, we derive the mean metallicity of the gas probed in our search: ζ(2.8 < z < 3.2) >= 3.6 × 10-4 h, in good agreement with other studies. These results demonstrate that large spectroscopic data sets such as SDSS can play an important role in QSO absorption line studies, in spite of

  6. Volcanic tremor induced by gas-liquid two-phase flow: Implications of density wave oscillation

    NASA Astrophysics Data System (ADS)

    Fujita, Eisuke; Araki, Kazuhiro; Nagano, Katsuhiro

    2011-09-01

    We model the source mechanism of volcanic tremor at shallow depths of a volcano by hydrothermal dynamics. Steam-water two-phase flow in the pipe is formulated, and its instability, known as density wave oscillation, can produce monotonic characteristics similar to those of a volcanic tremor. The oscillation is closely related to the heat supplied to the system and we quantitatively obtain the upper and lower limits of the heating quantity to realize this monotonic oscillation. This source mechanism can be realized only when the effect of gravity is small (i.e., horizontal flow), since the effect of depressurization due to upwelling is significant for bubble growth with vertical flow including gravity, and heating and vaporization are less important.

  7. Behavior of a plasma in a high-density gas-embedded Z-pinch configuration

    SciTech Connect

    Shlachter, J.S.

    1982-05-01

    The theoretical analysis of a high density Z-pinch (HDZP) begins with an examination of the steady state energy balance between ohmic heating and bremsstrahlung radiation losses for a plasma column in pressure equilibrium. The model is then expanded to include the time-varying internal energy and results in a quasi-equilibrium prescription for the load current through a constant radius plasma channel. This set of current waveforms is useful in the design of experimental systems. The behavior of a plasma for physically realizable conditions is first examined by allowing adiabatic changes in the column radius. A more complete model is then developed by incorporating inertial effects into the momentum equation, and the resultant global MHD computational model is compared with more sophisticated, and costly, one- and two-dimensional computer simulations. These comparisons demonstrate the advantages of the global MHD description over previously developed zero-dimensional models.

  8. Gravitational Effects on Near Field Flow Structure of Low Density Gas Jets

    NASA Technical Reports Server (NTRS)

    Griffin, D. W.; Yep, T. W.; Agrawal, A. K.

    2005-01-01

    Experiments were conducted in Earth gravity and microgravity to acquire quantitative data on near field flow structure of helium jets injected into air. Microgravity conditions were simulated in the 2.2- second drop tower at NASA Glenn Research Center. The jet flow was observed by quantitative rainbow schlieren deflectometry, a non-intrusive line of site measurement technique for the whole field. The flow structure was characterized by distributions of angular deflection and helium mole percentage obtained from color schlieren images taken at 60 Hz. Results show that the jet in microgravity was up to 70 percent wider than that in Earth gravity. The global jet flow oscillations observed in Earth gravity were absent in microgravity, providing direct experimental evidence that the flow instability in the low density jet was buoyancy induced. The paper provides quantitative details of temporal flow evolution as the experiment undergoes change in gravity in the drop tower.

  9. Gravitational Effects on Near Field Flow Structure of Low Density Gas Jets

    NASA Technical Reports Server (NTRS)

    Yep, Tze-Wing; Agrawal, Ajay K.; Griffin, DeVon; Salzman, Jack (Technical Monitor)

    2001-01-01

    Experiments were conducted in Earth gravity and microgravity to acquire quantitative data on near field flow structure of helium jets injected into air. Microgravity conditions were simulated in the 2.2-second drop tower at NASA Glenn Research Center. The jet flow was observed by quantitative rainbow schlieren deflectometry, a non-intrusive line of site measurement technique for the whole field. The flow structure was characterized by distributions of angular deflection and helium mole percentage obtained from color schlieren images taken at 60 Hz. Results show that the jet flow was significantly influenced by the gravity. The jet in microgravity was up to 70 percent wider than that in Earth gravity. The jet flow oscillations observed in Earth gravity were absent in microgravity, providing direct experimental evidence that the flow instability in the low density jet was buoyancy induced. The paper provides quantitative details of temporal flow evolution as the experiment undergoes a change in gravity in the drop tower.

  10. Pollutant Emission Factors from Residential Natural Gas Appliances: A Literature Review

    SciTech Connect

    Traynor, G.W.; Apte, M.G.; Chang, G.-M.

    1996-08-01

    There is a need to reduce air pollutant emissions in some U.S. urban regions to meet federal and state air quality guidelines. Opportunities exist for reducing pollutant emissions from natural gas appliances in the residential sector. A cost-benefit analysis on various pollutant-reducing strategies is needed to evaluate these opportunities. The effectiveness of these pollutant-reducing strategies (e.g., low-emission burners, energy conservation) can then be ranked among themselves and compared with other pollutant-reducing strategies available for the region. A key step towards conducting a cost-benefit analysis is to collect information on pollutant emissions from existing residential natural gas appliances. An extensive literature search was conducted to collect data on residential natural-gas-appliance pollutant emission factors. The literature primarily describes laboratory tests and may not reflect actual emission factor distributions in the field. Pollutant emission factors for appliances operated at over 700 test conditions are summarized for nitrogen oxides, carbon monoxide, fine particulate matter, formaldehyde, and methane. The appliances for which pollutant emissions are summarized include forced-air furnaces; stand-alone space heaters (vented and unvented); water heaters; cooking range burners, ovens, and broilers; and pilot lights. The arithmetic means of the nitrogen oxides and fine particulate matter emission factor distributions agree well with the Environmental Protection Agency published emission factor values for domestic gas appliances (in report AP-42). However, the carbon monoxide and methane distribution means are much higher than the relevant AP-42 values. Formaldehyde emission factors are not addressed in AP-42, but the emission factor mean for formaldehyde is comparable to the AP-42 emission factor value for total hydrocarbon emissions.

  11. Beyond Cultural Factors to Understand Immigrant Mental Health: Neighborhood Ethnic Density and the Moderating Role of Pre-migration and Post-migration Factors

    PubMed Central

    Arévalo, Sandra P.; Tucker, Katherine L; Falcón, Luis M

    2015-01-01

    Pre-migration and post-migration factors may influence the health of immigrants. Using a cross-national framework that considers the effects of the sending and receiving social contexts, we examined the extent to which pre-migration and post-migration factors, including individual and neighborhood level factors, influence depressive symptoms at a 2-year follow-up time point. Data come from the Boston Puerto Rican Health Study, a population-based prospective cohort of Puerto Ricans between the ages of 45 and 75 y. The association of neighborhood ethnic density with depressive symptomatology at follow-up was significantly modified by sex and level of language acculturation. Men, but not women, experienced protective effects of ethnic density. The interaction of neighborhood ethnic density with language acculturation had a non-linear effect on depressive symptomatology, with lowest depressive symptomatology in the second highest quartile of language acculturation, relative to the lowest and top two quartiles among residents of high ethnic density neighborhoods. Results from this study highlight the complexity, and interplay, of a number of factors that influence the health of immigrants, and emphasize the significance of moving beyond cultural variables to better understand why the health of some immigrant groups deteriorates at faster rates overtime. PMID:26057720

  12. Star formation laws in the Andromeda galaxy: gas, stars, metals and the surface density of star formation

    NASA Astrophysics Data System (ADS)

    Rahmani, S.; Lianou, S.; Barmby, P.

    2016-03-01

    We use hierarchical Bayesian regression analysis to investigate star formation laws in the Andromeda galaxy (M31) in both local (30, 155 and 750 pc) and global cases. We study and compare the well-known Kennicutt-Schmidt law, the extended Schmidt law and the metallicity/star formation correlation. Using a combination of Hα and 24 μm emission, a combination of far-ultraviolet and 24 μm, and the total infrared emission, we estimate the total star formation rate (SFR) in M31 to be between 0.35 ± 0.04 and 0.4 ± 0.04 M⊙ yr-1. We produce a stellar mass surface density map using IRAC 3.6 μm emission and measured the total stellar mass to be 6.9 × 1010 M⊙. For the Kennicutt-Schmidt law in M31, we find the power-law index N to be between 0.49 and 1.18; for all the laws, the power-law index varies more with changing gas tracer than with SFR tracer. The power-law index also changes with distance from the centre of the galaxy. We also applied the commonly used ordinary least-squares fitting method and showed that using different fitting methods leads to different power-law indices. There is a correlation between the surface density of SFR and the stellar mass surface density, which confirms that the Kennicutt-Schmidt law needs to be extended to consider the other physical properties of galaxies. We found a weak correlation between metallicity, the SFR and the stellar mass surface density.

  13. The effects of density-dependent form factors for (e, e'p) reaction in quasi-elastic region

    NASA Astrophysics Data System (ADS)

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

    2016-04-01

    Within the framework of a relativistic single particle model, the effects of density-dependent electromagnetic form factors on the exclusive (e,e'p) reaction are investigated in the quasi-elastic region. The density-dependent electromagnetic form factors are generated from a quark-meson coupling model and used to calculate the cross sections in two different densities, either at the normal density of ρ_0 ˜ 0.15 fm^-3 or at the lower density, 0.5ρ_0 . Then these cross sections are analyzed in the two different kinematics: One is that the momentum of the outgoing nucleon is along the momentum transfer. The other is that the angle between the momentum of the outgoing nucleon and the momentum transfer is varied at fixed magnitude of the momentum of the outgoing nucleon. Our theoretical differential reduced cross sections are compared with the NIKHEF data for the 208 Pb( e, e'p) reaction, which is related to the probability that a bound nucleon from a given orbit can be knocked-out of the nucleus. The effects of the density-dependent form factors increase the differential cross sections for both knocked-out proton and neutron by an amount of a few percent. Moreover they are shown to be almost the same within only a few percent, i.e., nearly independent of the shell location of knockout nucleons. These results are quite consistent with the characteristics of double magic nuclei which have relatively sharp smearing in the density distribution.

  14. Gas amplification factor in Kr + ISO-pentane filled proportional counters

    NASA Astrophysics Data System (ADS)

    Kowalski, T. Z.

    1983-11-01

    The gas amplification factor, A, has been measured for krypton/iso-pentane mixtures (over the range 1 < A < 5 × 104) to verify the validity of the formulae of Rose and Korff, Curran and Craggs, Diethorn, Williams and Sara, Khristov and Zastawny. Only the expressions of Zastawny and Diethorn can be fitted over a limited range of A.

  15. Correlation energy, structure factor, radial distribution function, and momentum distribution of the spin-polarized uniform electron gas

    NASA Astrophysics Data System (ADS)

    Ortiz, G.; Ballone, P.

    1994-07-01

    The properties of the three-dimensional uniform electron gas in the Fermi liquid regime are analyzed using variational Monte Carlo (VMC) and fixed-node diffusion Monte Carlo methods. Our study extends those of Ceperley [Phys. Rev. B 18, 3126 (1978)] and Ceperley and Alder [Phys. Rev. Lett. 45, 566 (1980)] to larger system sizes with improved statistics and, more importantly, to partial spin polarization. The density range 0.8<=rs<=10, which is the most relevant for density functional computations, is studied in detail. We analyze the size dependence of the simulation results and present an extended set of correlation energies extrapolated to the thermodynamic limit. Using the VMC method we analyze the spin dependence of the correlation energy, and we compare our results to several interpolation formulas used in density functional calculations. We summarize our results by a simple interpolation formula. In addition, we present results for the radial distribution function, the structure factor, the momentum distribution, and triplet correlation functions, and we discuss the comparison with many-body semianalytic theories.

  16. ALMA OBSERVATIONS OF A HIGH-DENSITY CORE IN TAURUS: DYNAMICAL GAS INTERACTION AT THE POSSIBLE SITE OF A MULTIPLE STAR FORMATION

    SciTech Connect

    Tokuda, Kazuki; Onishi, Toshikazu; Saigo, Kazuya; Kawamura, Akiko; Fukui, Yasuo; Inutsuka, Shu-ichiro; Tachihara, Kengo; Matsumoto, Tomoaki; Machida, Masahiro N.; Tomida, Kengo

    2014-07-01

    Starless dense cores eventually collapse dynamically, forming protostars inside them, and the physical properties of the cores determine the nature of the forming protostars. We report ALMA observations of dust continuum emission and molecular rotational lines toward MC27 or L1521F, which is considered to be very close to the first protostellar core phase. We found a few starless high-density cores, one of which has a very high density of ∼10{sup 7} cm{sup –3}, within a region of several hundred AU around a very low-luminosity protostar detected by Spitzer. A very compact bipolar outflow with a dynamical timescale of a few hundred years was found toward the protostar. The molecular line observation shows several cores with an arc-like structure, possibly due to the dynamical gas interaction. These complex structures revealed in the present observations suggest that the initial condition of star formation is highly dynamical in nature, which is considered to be a key factor in understanding fundamental issues of star formation such as the formation of multiple stars and the origin of the initial mass function of stars.

  17. Density, Demography, and Influential Environmental Factors on Overwintering Populations of Sogatella furcifera (Hemiptera: Delphacidae) in Southern Yunnan, China.

    PubMed

    Hu, Shao-Ji; Fu, Da-Ying; Han, Zhong-Liang; Ye, Hui

    2015-01-01

    Sogatella furcifera (Horváth) (Hemiptera: Delphacidae) is the most serious pest on rice in southwestern China. Yunnan province is within this region and is a major overwintering area for S. furcifera in China. This field study was carried out over 4 yr (2010-2013) and focused on S. furcifera distribution, population density, and demography, as well as the relationship between various environmental factors and the distribution and density of overwintering S. furcifera in Yunnan. Our study demonstrated that overwintering populations of S. furcifera mainly occurred in valleys and lowlands below 25.02°N and 1,608 m above sea level (a.s.l.), where ratooning rice was present [corrected]. The overwintering range of S. furcifera has expanded in Yunnan compared with 20 yr ago, and regional climate change is believed to be the main contributing cause for this expansion. Environmental factor analysis showed that the mean air temperature of the coldest quarter and precipitation of the coldest quarter were two key factors that were strongly linked to the overwintering distribution and density of S. furcifera in Yunnan. Wintertime temperature was the principal influencing factor to determine the distribution and density of S. furcifera, while the effect of precipitation was indirect in that it influenced the insect's distribution via its host. This study documented the major overwintering areas of S. furcifera in Yunnan, which can be used to predict outbreak potential in the following spring. Hence, key climatic factors, overwintering distribution, and density of S. furcifera should be used when forecasting outbreaks in spring. PMID:25978998

  18. Density, Demography, and Influential Environmental Factors on Overwintering Populations of Sogatella furcifera (Hemiptera: Delphacidae) in Southern Yunnan, China

    PubMed Central

    Hu, Shao-Ji; Fu, Da-Ying; Han, Zhong-Liang; Ye, Hui

    2015-01-01

    Sogatella furcifera (Horváth) (Hemiptera: Delphacidae) is the most serious pest on rice in southwestern China. Yunnan province is within this region and is a major overwintering area for S. furcifera in China. This field study was carried out over 4 yr (2010–2013) and focused on S. furcifera distribution, population density, and demography, as well as the relationship between various environmental factors and the distribution and density of overwintering S. furcifera in Yunnan. Our study demonstrated that overwintering populations of S. furcifera mainly occurred in valleys and lowlands below 25.02°N and 1,680 m above sea level (a.s.l.), where ratooning rice was present. The overwintering range of S. furcifera has expanded in Yunnan compared with 20 yr ago, and regional climate change is believed to be the main contributing cause for this expansion. Environmental factor analysis showed that the mean air temperature of the coldest quarter and precipitation of the coldest quarter were two key factors that were strongly linked to the overwintering distribution and density of S. furcifera in Yunnan. Wintertime temperature was the principal influencing factor to determine the distribution and density of S. furcifera, while the effect of precipitation was indirect in that it influenced the insect’s distribution via its host. This study documented the major overwintering areas of S. furcifera in Yunnan, which can be used to predict outbreak potential in the following spring. Hence, key climatic factors, overwintering distribution, and density of S. furcifera should be used when forecasting outbreaks in spring. PMID:25978998

  19. A van der Waals density functional built upon the electron-gas foundation

    NASA Astrophysics Data System (ADS)

    Hyldgaard, Per; Berland, Kristian; Schröder, Elsebeth

    2015-03-01

    The vdW-DF method is designed to be a systematic extension of the constraint-based generalized-gradient approximation (GGA) and can therefore serve as general purpose density functional [PRB 90, 075148 (2014)]. Yet the early versions can have issues both with bulk systems and with weak chemisorption. We present a recent nonempirical version, vdW-DF-cx [J. Chem. Phys. 140, 18A539 (2014), PRB 89, 035412 (2014)], that resolves these issues. The version is designed to have a consistent combination of exchange and correlation. We show that it performs well for inter-molecular binding and that it can even be better than PBE for describing cohesion and structure of molecules and solids. These results validate the robustness of the vdW-DF plasmon-pole model, which we show is closed linked to the exchange correlation hole of constraint-based GGA. The work was supported by the Swedish Research Council (VR), by the Chalmers Areas of Advance: Materials, and by the Swedish National Infrastructure for Computing.

  20. How well do static electronic dipole polarizabilities from gas-phase experiments compare with density functional and MP2 computations?

    SciTech Connect

    Thakkar, Ajit J. Wu, Taozhe

    2015-10-14

    Static electronic dipole polarizabilities for 135 molecules are calculated using second-order Møller-Plesset perturbation theory and six density functionals recently recommended for polarizabilities. Comparison is made with the best gas-phase experimental data. The lowest mean absolute percent deviations from the best experimental values for all 135 molecules are 3.03% and 3.08% for the LC-τHCTH and M11 functionals, respectively. Excluding the eight extreme outliers for which the experimental values are almost certainly in error, the mean absolute percent deviation for the remaining 127 molecules drops to 2.42% and 2.48% for the LC-τHCTH and M11 functionals, respectively. Detailed comparison enables us to identify 32 molecules for which the discrepancy between the calculated and experimental values warrants further investigation.

  1. Density Functional Theory and Reaction Kinetics Studies of the Water–Gas Shift Reaction on Pt–Re Catalysts

    SciTech Connect

    Carrasquillo-Flores, Ronald; Gallo, Jean Marcel R.; Hahn, Konstanze; Dumesic, James A.; Mavrikakis, Manos

    2013-11-05

    Periodic, self-consistent density functional theory calculations (DFT-GGA-PW91) on Pt(111) and Pt3Re(111) surfaces, reaction kinetics measurements, and microkinetic modeling are employed to study the mechanism of the water–gas shift (WGS) reaction over Pt and Pt–Re catalysts. The values of the reaction rates and reaction orders predicted by the model are in agreement with the ones experimentally determined; the calculated apparent activation energies are matched to within 6% of the experimental values. The primary reaction pathway is predicted to take place through adsorbed carboxyl (COOH) species, whereas formate (HCOO) is predicted to be a spectator species. We conclude that the clean Pt(111) is a good representation of the active site for the WGS reaction on Pt catalysts, whereas the active sites on the Pt–Re alloy catalyst likely contain partially oxidized metal ensembles.

  2. Low-density real gas flows about hypersonic vehicles. Interim report, 25 September 1986-25 September 1987

    SciTech Connect

    Hoffman, J.J.; Wong, R.S.; Bussing, T.R.; Birch, S.F.

    1988-03-01

    Phase I results include selection of the three components of the computational of the computational algorithm (a Navier-Stokes solution algorithm, a chemistry solution algorithm, and vectorization and parallel-processing requirements for both algorithms). Development of a nonequilibrium air-chemistry reaction model is included, as well as studies of leeside models, turbulence models, and wall catalysis effects appropriate to the hypersonic flows to be considered. Mach 20 test cases were performed using the Navier-Stokes and chemistry algorithms, and a comprehensive sensitivity study was completed for the selection of an air-chemistry model. Transport property calculations are also discussed. The components of the computational algorithm developed during Phase I will be assembled during Phase II into a unified computer code capable of accurately and efficiently calculating low-density real gas flows about hypersonic vehicles.

  3. THE SPACE DENSITY OF EXTENDED ULTRAVIOLET (XUV) DISKS IN THE LOCAL UNIVERSE AND IMPLICATIONS FOR GAS ACCRETION ONTO GALAXIES

    SciTech Connect

    Lemonias, Jenna J.; Schiminovich, David; Thilker, David; Bianchi, Luciana; Wyder, Ted K.; Martin, D. Christopher; Seibert, Mark; Madore, Barry F.; Treyer, Marie A.; Heckman, Timothy M.; Rich, R. Michael

    2011-06-01

    We present results of the first unbiased search for extended ultraviolet (XUV)-disk galaxies undertaken to determine the space density of such galaxies. Our sample contains 561 local (0.001 < z < 0.05) galaxies that lie in the intersection of available Galaxy Evolution Explorer (GALEX) deep imaging (exposure time >1.5 x 10{sup 4} s) and Sloan Digital Sky Survey DR7 footprints. We explore modifications to the standard classification scheme for our sample that includes both disk- and bulge-dominated galaxies. Visual classification of each galaxy in the sample reveals an XUV-disk frequency of up to 20% for the most nearby portion of our sample. On average over the entire sample (out to z = 0.05) the frequency ranges from a hard limit of 4%-14%. The GALEX imaging allows us to detect XUV disks beyond 100 Mpc. The XUV regions around XUV-disk galaxies are consistently bluer than the main bodies. We find a surprisingly high frequency of XUV emission around luminous red (NUV-r > 5) and green valley (3 < NUV-r < 5) galaxies. The XUV-disk space density in the local universe is >(1.5-4.2) x 10{sup -3} Mpc{sup -3}. Using the XUV emission as an indicator of recent gas accretion, we estimate that the cold gas accretion rate onto these galaxies is >(1.7-4.6) x 10{sup -3} M{sub sun} Mpc{sup -3} yr{sup -1}. The number of XUV disks in the green valley and the estimated accretion rate onto such galaxies points to the intriguing possibility that 7%-18% of galaxies in this population are transitioning away from the red sequence.

  4. Temperature, Density, Ionization Rate, and Morphology of Diffuse Gas Near the Galactic Center Probed by H_3^+

    NASA Astrophysics Data System (ADS)

    Oka, Takeshi; Geballe, Thomas R.; Goto, Miwa; Usuda, Tomonori

    2014-06-01

    Since last year, infrared spectra of H_3^+ and CO have been obtained toward nine stars (designated by us α+, β, γ, γ-, δ, θ, κ, λ, and λ-) along the Galactic plane from 138 pc to the west of Sgr A* to 115 pc east, using IRCS of the Subaru Telescope and GNIRS of the Gemini North Observatory. All of the objects lie within the Central Molecular Zone (CMZ), a region of radius ˜150 pc at the center of the Galaxy. All sightlines except that toward λ (a red giant not suitable for H_3^+ spectroscopy) have high H_3^+ column densities on the order of a few times 1015 cm-2. The metastable R(3,3)^l absorption line was sought on seven sightlines (α+, β, γ, γ-, δ, θ, κ), each of which showed significant signal except κ for which detection of this line was inconclusive. These results indicate that the long (at least several tens of parsecs) columns of warm (T ˜ 250 K) and diffuse (n ≤ 100 cm-3) gas in which a high ionization rate of ζ of a few times 10-15 s-1 exists, found earlier by us on sightlines passing through the central 30 pc of the CMZ are present over nearly the entire CMZ. The velocity profiles of the H_3^+ absorption lines provide information on the morphology of the diffuse gas in the CMZ. The velocity profile toward star λ- (2MASS J17482472-2824313) observed by GNIRS is particularly noteworthy. The sightline toward this star, located 115 pc to the east of Sgr A*, shows the presence of warm diffuse gas near 0 radial velocity and complements an identical result at the west end (on sightlines toward α+ and previously observed sources α and β). Stars nearer to the center of the CMZ show the warm diffuse gas at negative velocities only. Although many more stars need to be observed, the results to date suggest the existence of an expanding molecular ring of diffuse gas which is, unlike previously reported, not rotating but purely expanding. Oka, T., Geballe, T. R., Goto, M., Usuda, T., and McCall, B. J. 2005, ApJ, 632 882 Goto, M., Usuda, T

  5. A study of factors affecting the human cone photoreceptor density measured by adaptive optics scanning laser ophthalmoscope

    PubMed Central

    Park, Sung Pyo; Chung, Jae Keun; Greenstein, Vivienne; Tsang, Stephen H.; Chang, Stanley

    2015-01-01

    To investigate the variation in human cone photoreceptor packing density with various demographic or clinical factors, cone packing density was measured using a Canon prototype adaptive optics scanning laser ophthalmoscope and compared as a function of retinal eccentricity, refractive error, axial length, age, gender, race/ethnicity and ocular dominance. We enrolled 192 eyes of 192 subjects with no ocular pathology. Cone packing density was measured at three different retinal eccentricities (0.5 mm, 1.0 mm, and 1.5 mm from the foveal center) along four meridians. Cone density decreased from 32,200 to 11,600 cells/mm2 with retinal eccentricity (0.5 mm to 1.5 mm from the fovea, P < 0.001). A trend towards a slightly negative correlation was observed between age and density (r = −0.117, P = 0.14). There was, however, a statistically significant negative correlation (r = −0.367, P = 0.003) between axial length and cone density. Gender, ocular dominance, and race/ethnicity were not important determinants of cone density (all, P > 0.05). In addition, to assess the spatial arrangement of the cone mosaics, the nearest-neighbor distances (NNDs) and the Voronoi domains were analyzed. The results of NND and Voronoi analysis were significantly correlated with the variation of the cone density. Average NND and Voronoi area were gradually increased (all, P ≤ 0.001) and the degree of regularity of the cone mosaics was decreased (P ≤ 0.001) with increasing retinal eccentricity. In conclusion, we demonstrated cone packing density decreases as a function of retinal eccentricity and axial length and the results of NND and Voronoi analysis is a useful index for cone mosaics arrangements. The results also serve as a reference for further studies designed to detect or monitor cone photoreceptors in patients with retinal diseases. PMID:23276813

  6. Factors controlling the variances of seismic velocity, density, thermal conductivity and heat production of cores from the KTB Pilot Hole

    NASA Astrophysics Data System (ADS)

    Huenges, Ernst

    This paper presents a statistical analysis of about 50000 petrophysical data measured on core samples from the Continental Deep Drilling Project (KTB) of the Federal Republic of Germany. The scattering of the data must be taken into consideration using empirical relationships between pairs of parameters, e.g., sound velocity, density, heat production and thermal conductivity. Such covariances of parameters were calculated and used to find the principle components by applying factor analysis. The reduction of parameters by factor analysis may help other scientists to concentrate on the essential parameters to be measured. About 50% of the variance of all data can be explained by one background variable, the so-called “lithology factor”. The variables that load a factor are either highly correlated or anticorrelated. The lithology factor combines gamma spectroscopy data, density and the mineral contents of quartz, amphibole, garnet and white mica. Seismic velocities and porosity data, however, were less well related to the lithology factor. Therefore, the KTB data indicate that correlation between seismic velocity and one of the lithology factor loading variables is unlikely. The lithology factor distinguishes 3 major “rock types”: metabasites, gneisses and an intermediate type. The variance of the petrophysical parameters within the rock types, plotted in crossplots, show the level of validity of commonly used relationships among these parameters. Measurements under ambient and simulated in-situ conditions are included to enable discussion of chemical, mineralogical and microstructural characteristics of the rocks.

  7. Theoretical infrared spectral density of H-bonds in liquid and gas phases: Anharmonicities and dampings effects

    NASA Astrophysics Data System (ADS)

    Rekik, Najeh; Oujia, Brahim; Wójcik, Marek J.

    2008-09-01

    The main purpose of the present paper is to show how both anharmonicities of the fast and the slow modes, multiple Fermi resonances and damping mechanisms introduced within the strong anharmonic coupling theory, are susceptible to explain some analogies in the infrared spectra of hydrogen bonded systems, when passing from the condensed to the gas phase. The high-frequency mode X-H→⋯Y described by double well potential is supposed to be anharmonically coupled to the H-bond stretching mode X←-H⋯Y→ described by Morse potential and to first overtones of some bending modes through Fermi resonances. The relaxation of the fast and bending modes and of the H-bond bridge is incorporated by aid of previous results [N. Rekik, B. Ouari, P. Blaise, O. Henri-Rousseau, J. Mol. Struct. 687 (2004) 125]. The spectral density is obtained as the Fourier transform of the autocorrelation function of the dipole moment operator within linear response theory. Numerical results show that mixing of all these effects results in a broad and complicated structure and expects to provide efficient energy relaxation pathways by using large dampings parameters for the condensed phase and weaker dampings for the gas one.

  8. Theoretical and experimental studies of radiative and gas dynamic properties of substances at high energy density in matter

    NASA Astrophysics Data System (ADS)

    Orlov, N. Yu; Denisov, O. B.; Vergunova, G. A.; Rosmej, O. N.

    2015-11-01

    Mathematical modelling of radiative and gas-dynamic processes in substances at high energy density is carried out for experiments, where both laser and heavy ion beams are used. Important features of the theoretical model, known as the ion model (IM), which is used for quantum mechanical calculations of radiative opacity, are discussed. Reliability of (IM) results is tested with experiment, where measurements of x-pinch radiation energy yield for two exploding wire materials, NiCr and Alloy 188 were made. Theoretical estimations of radiative efficiency are compared with experimental results, and (IM) calculations agree well with the experimental data. Subsequently, the theoretical approach was used for temperature diagnostics of CHO plasma target in combined laser-heavy ion beam experiments. Joint radiative and gas-dynamic calculations are performed for comparison with experiment, where hohlraum radiation transmits through the CHO plasma target, and the share of absorbed radiation energy is compared with experiment. Study of radiative properties of CHO plasma with little admixture of gold is carried out as well. Specific dependence of the Rosseland mean on plasma temperature is discussed for gold plasma.

  9. Dairy cattle management factors that influence on-farm density of European starlings in Ohio, 2007-2009.

    PubMed

    Medhanie, Genet A; Pearl, David L; McEwen, Scott A; Guerin, Michele T; Jardine, Claire M; LeJeune, Jeffrey T

    2015-06-15

    Potential dairy farm management and environmental factors that attract European starlings (Sturnus vulgaris) to dairy farms were explored. During the period from 2007 to 2009, 150 dairy farms were each visited twice (once during the summer and again in the fall) and the number of starlings was recorded. Risk factors were assessed for possible association with the number of starlings per milking cow (starling density), using a zero-inflated negative binomial model. Starling density was higher on farms visited in 2007 compared to those visited in 2008 or 2009. The interaction term between feeding method and feeding site was significantly associated with starling density on farm; generally, feeding outdoors was associated with increased starling density. The odds of a zero starling count (compared to a count greater than zero) was higher on farms that removed manure from barns weekly or less frequently than weekly compared to those that removed manure daily or after every milking. The odds of a zero starling count decreased with increasing distance of a farm from the closest night roost. Identifying on farm risk factors that expose farms to starlings will help farmers develop strategies that minimize the number of birds on their farms and thereby reduce physical damage to the farms as well as the potential for pathogen transmission from birds to cattle and humans. PMID:25940010

  10. Menstrual and reproductive factors in relation to mammographic density: the Study of Women’s Health Across the Nation (SWAN)

    PubMed Central

    Butler, Lesley M.; Gold, Ellen B.; Greendale, Gail A.; Crandall, Carolyn J.; Modugno, Francesmary; Oestreicher, Nina; Quesenberry, Charles P.; Habel, Laurel A.

    2009-01-01

    Menstrual and reproductive factors may increase breast cancer risk through a pathway that includes increased mammographic density. We assessed whether known or suspected menstrual and reproductive breast cancer risk factors were cross-sectionally associated with mammographic density, by measuring area of radiographic density and total breast area on mammograms from 801 participants in the Study of Women’s Health Across the Nation (SWAN), a multi-ethnic cohort of pre- and early perimenopausal women. From multivariable linear regression, the following menstrual or reproductive factors were independently associated with percent mammographic density (area of dense breast/breast area): older age at menarche (β = 10.3, P < 0.01, for >13 vs. <12 years), premenstrual cravings and bloating (β = −3.36, P = 0.02), younger age at first full-term birth (β = −8.12, P < 0.01 for ≤23 years versus no births), greater number of births (β = −6.80, P < 0.01 for ≥3 births versus no births), and premenopausal status (β = 3.78, P < 0.01 versus early perimenopausal). Only number of births remained associated with percent density after adjustment for age, race/ethnicity, study site, body mass index (BMI), and smoking. In addition, stratified analyses revealed that the association with number of births was confined to women within the lowest BMI tertile (β = −12.2, P < 0.01 for ≥3 births versus no births). Our data support a mechanism for parity and breast cancer that involves mammographic density among pre- and early perimenopausal women that may be modified by body size. PMID:18066689

  11. Influence of Gas Flow and Improvement of Homogeneity on the Distribution of Critical Current Density in YBCO Coated Conductor Processed by TFA-MOD Method

    NASA Astrophysics Data System (ADS)

    Shiohara, Kei; Higashikawa, Kohei; Kawaguchi, Teppei; Inoue, Masayoshi; Kiss, Takanobu; Yoshizumi, Masateru; Izumi, Teruo

    Using a scanning Hall-probe microscopy, we have investigated in-plane distribution of critical current density in TFA-MOD processed YBCO coated conductors. We compared the distributions of critical current density for two kinds of coated conductors processed with different directions of gas flow at the calcinations. As a result, it was found that the direction of the gas flow largely influenced the distribution of critical current density. For example, the maximum value of critical current density was 1.5 times higher than the average for a sample processed with a gas flow in width direction. On the other hand, the distribution of critical current density was relatively uniform for the one with a gas flow in axial direction perpendicular to the surface of the conductor. These findings will be very important information for the optimization of the manufacturer processes for the conductors. Actually, a very uniform distribution of critical current density has been observed for a coated conductor produced by an optimized process. This demonstrates a high potential of TFA-MOD processed YBCO coated conductors for practical applications.

  12. Effect of Kr Gas Dilution on O Atom Density in Inductively Coupled Kr/O2 Plasma

    NASA Astrophysics Data System (ADS)

    Hori, Masaru; Ikuma, Soichi; Goto, Toshio

    2003-10-01

    Oxygen-based plasmas have been used for the low temperature oxidation of materials. It has been reported that the high quality SiO2 film was formed at a low temperature by Kr dilution O2 plasma. From the viewpoint of developing the low temperature oxidation processes used for the gate dielectric film in LCD devices, a quantitative study on the behavior of O atom in the Kr/O2 mixture plasma is strongly required. In this study, we measured the absolute O atom and metastable Kr atom densities in an inductively coupled Kr/O2 plasma using vacuum ultraviolet absorption spectroscopy technique. The transition lines used for absorption measurements were ^3S0 - ^3P_2, ^3S0 - ^3P1 and ^3S0 - ^3P0 at 130.2 nm for O atom and ^3D3 - ^3P2 at 811.3 nm for metastable Kr atom. The absolute O atom density was almost constant on 4×10^13 cm-3 although the Kr dilution ratio was increased from 0 to 99% at an RF power of 200W, a pressure of 107 Pa, and a total gas flow rate of 100 sccm. The effect of metastable Kr atom on the production of the O atom has been discussed.

  13. Temperature and electron density distributions of laser-induced plasmas generated with an iron sample at different ambient gas pressures

    NASA Astrophysics Data System (ADS)

    Aguilera, J. A.; Aragón, C.

    2002-09-01

    Intensity, temperature and electron density distributions of laser-induced plasmas (LIPs) have been measured by emission spectroscopy with two-dimensional spatial resolution and temporal resolution. The plasmas have been generated with an iron sample at different pressures of air, in the range 10-1000 mbar. An experimental system based in an imaging spectrometer equipped with an intensified CCD detector has been used to obtain the spectra with two-dimensional spatial resolution. The evolution of the intensity distributions is described by the blast wave model only at initial times. The temperature distributions are shown to correspond to a slight difference between the intensity distributions of two Fe I emission lines that have a high difference of their upper energy levels (3.38 eV). The electron density distributions have similar features to those of the temperature distributions. The features of the intensity and temperature distributions show a significant change with the ambient gas pressure: they have separated maxima in the plasmas generated at pressures below 100 mbar, whereas at higher pressures, the maxima of the two distributions coincide.

  14. Water-gas Shift Reaction on oxide/Cu(111): Rational Catalyst Screening from Density Functional Theory

    SciTech Connect

    Liu, P.

    2010-11-28

    Developing improved catalysts based on a fundamental understanding of reaction mechanism has become one of the grand challenges in catalysis. A theoretical understanding and screening the metal-oxide composite catalysts for the water-gas shift (WGS) reaction is presented here. Density functional theory was employed to identify the key step for the WGS reaction on the Au, Cu-oxide catalysts, where the calculated reaction energy for water dissociation correlates well with the experimental measured WGS activity. Accordingly, the calculated reaction energy for water dissociation was used as the scaling descriptor to screen the inverse model catalysts, oxide/Cu(111), for the better WGS activity. Our calculations predict that the WGS activity increases in a sequence: Cu(111), ZnO/Cu(111) < TiO{sub 2}/Cu(111), ZrO{sub 2}/Cu(111) < MoO{sub 3}/Cu(111). Our results imply that the high performances of Au, Cu-oxide nanocatalysts in the WGS reaction rely heavily on the direct participation of both oxide and metal sites. The degree that the oxide is reduced by Cu plays an important role in determining the WGS activity of oxide/Cu catalysts. The reducible oxide can be transformed from the fully oxidized form to the reduced form due to the interaction with Cu and, therefore, the transfer of electron density from Cu, which helps in releasing the bottleneck water dissociation and, therefore, facilitating the WGS reaction on copper.

  15. Water-gas shift reaction on oxide/Cu(111): Rational catalyst screening from density functional theory

    NASA Astrophysics Data System (ADS)

    Liu, Ping

    2010-11-01

    Developing improved catalysts based on a fundamental understanding of reaction mechanism has become one of the grand challenges in catalysis. A theoretical understanding and screening the metal-oxide composite catalysts for the water-gas shift (WGS) reaction is presented here. Density functional theory was employed to identify the key step for the WGS reaction on the Au, Cu-oxide catalysts, where the calculated reaction energy for water dissociation correlates well with the experimental measured WGS activity. Accordingly, the calculated reaction energy for water dissociation was used as the scaling descriptor to screen the inverse model catalysts, oxide/Cu(111), for the better WGS activity. Our calculations predict that the WGS activity increases in a sequence: Cu(111), ZnO/Cu(111) < TiO2/Cu(111), ZrO2/Cu(111) < MoO3/Cu(111). Our results imply that the high performances of Au, Cu-oxide nanocatalysts in the WGS reaction rely heavily on the direct participation of both oxide and metal sites. The degree that the oxide is reduced by Cu plays an important role in determining the WGS activity of oxide/Cu catalysts. The reducible oxide can be transformed from the fully oxidized form to the reduced form due to the interaction with Cu and, therefore, the transfer of electron density from Cu, which helps in releasing the bottleneck water dissociation and, therefore, facilitating the WGS reaction on copper.

  16. DEPENDENCE OF THE TURBULENT VELOCITY FIELD ON GAS DENSITY IN L1551

    SciTech Connect

    Yoshida, Atsushi; Kitamura, Yoshimi; Kawabe, Ryohei E-mail: kitamura@isas.jaxa.j

    2010-08-01

    We have carried out mapping observations of the entire L1551 molecular cloud with about 2 pc x 2 pc size in the {sup 12}CO(1-0) line with the Nobeyama 45 m radio telescope at the high effective resolution of 22'' (corresponding to 0.017 pc at the distance of 160 pc), and analyzed the {sup 12}CO data together with the {sup 13}CO(1-0) and C{sup 18}O(1-0) data from the Nobeyama Radio Observatory database. We derived the new non-thermal line width-size relations, {sigma}{sub NT} {proportional_to} L {sup {gamma}}, for the three molecular lines, corrected for the effect of optical depth and the line-of-sight integration. To investigate the characteristic of the intrinsic turbulence, the effects of the outflows were removed. The derived relations are ({sigma}{sub NT}/km s{sup -1}) = (0.18 {+-} 0.010)(L/pc){sup 0.45{+-}0.095}, (0.20 {+-} 0.020)(L/pc){sup 0.48{+-}0.091}, and (0.22 {+-} 0.050) (L/pc){sup 0.54{+-}0.21} for the {sup 12}CO, {sup 13}CO, and C{sup 18}O lines, respectively, suggesting that the line width-size relation of the turbulence very weakly depends on our observed molecular lines, i.e., the relation does not change between the density ranges of 10{sup 2}-10{sup 3} and 10{sup 3}-10{sup 4} cm{sup -3}. In addition, the relations indicate that incompressible turbulence is dominant at the scales smaller than 0.6 pc in L1551. The power spectrum indices converted from the relations, however, seem to be larger than that of the Kolmogorov spectrum for incompressible flow. The disagreement could be explained by the anisotropy in the turbulent velocity field in L1551, as expected in MHD turbulence. Actually, the autocorrelation functions of the centroid velocity fluctuations show larger correlation along the direction of the magnetic field measured for the whole Taurus cloud, which is consistent with the results of numerical simulations for incompressible MHD flow.

  17. Intra unit cell electronic structure of the d-symmetry form factor density wave in the underdoped cuprates - Part II

    NASA Astrophysics Data System (ADS)

    Edkins, Stephen; Fujita, Kazuhiro; Hamidian, Mohammad; Kim, Chung Koo; MacKenzie, Andrew; Eisaki, Hiroshi; Uchida, Shinichi; Lawler, Michael; Kim, Eun-Ah; Sachdev, Subir; Davis, Seamus

    2015-03-01

    A central issue of cuprate superconductivity research is to understand the nature of the unknown phase called the pseudogap and its relationship to the d-wave superconductivity. To approach this we use spectroscopic imaging STM to study the electronic structure of Bi2Sr2CaCu2O8+δ. Using our recently developed technique of sub-lattice phase-resolved electronic structure visualization within each CuO2 unit-cell, we discovered a d-symmetry form factor density wave within the cuprate pseudogap state. In this talk, part II, we report on the electronic structure of the density wave and its interplay with superconductivity.

  18. Digging for answers: contributions of density- and frequency-dependent factors on ectoparasite burden in a social mammal.

    PubMed

    Archer, Elizabeth K; Bennett, Nigel C; Faulkes, Chris G; Lutermann, Heike

    2016-02-01

    Due to the density-dependent nature of parasite transmission parasites are generally assumed to constrain the evolution of sociality. However, evidence for a correlation between group size and parasite burden is equivocal, particularly for mammals. Host contact rates may be modified by mobility of the host and parasite as well as social barriers. In the current study, we used the common mole-rat (Cryptomys hottentotus hottentotus), a social subterranean rodent, as a model system to investigate the effect of host density and frequency of contact rates on ectoparasite burdens. To address these factors we used a study species that naturally varies in population densities and intergroup contact rates across its geographic range. We found that ectoparasite prevalence, abundance and species richness decreased with increasing host density at a regional scale. At the same time, measures of parasite burden increased with intergroup contact rates. Ectoparasite burdens decreased with colony size at the group level possibly as a result of increased grooming rates. Equating group size with population density might be too simplistic an approach when assessing parasite distributions in social mammals. Our data suggest that frequency-dependent mechanisms may play a much greater role at a population level than density-dependent mechanisms in determining parasite distributions in social species. We suggest that future studies should explicitly consider behavioural mechanisms that may affect parasite distribution. PMID:26546084

  19. Rare human nerve growth factor-β mutation reveals relationship between C-afferent density and acute pain evaluation.

    PubMed

    Perini, Irene; Tavakoli, Mitra; Marshall, Andrew; Minde, Jan; Morrison, India

    2016-08-01

    The rare nerve growth factor-β (NGFB) mutation R221W causes a selective loss of thinly myelinated fibers and especially unmyelinated C-fibers. Carriers of this mutation show altered pain sensation. A subset presents with arthropathic symptoms, with the homozygous most severely affected. The aim of the present study was to investigate the relationship between peripheral afferent loss and pain evaluation by performing a quantification of small-fiber density in the cornea of the carriers, relating density to pain evaluation measures. In vivo corneal confocal microscopy (CCM) was used to quantify C-fiber loss in the cornea of 19 R221W mutation carriers (3 homozygous) and 19 age-matched healthy control subjects. Pain evaluation data via the Situational Pain Questionnaire (SPQ) and the severity of neuropathy based on the Neuropathy Disability Score (NDS) were assessed. Homozygotes, heterozygotes, and control groups differed significantly in corneal C-nerve fiber density, with the homozygotes showing a significant afferent reduction. Importantly, peripheral C-fiber loss correlated negatively with pain evaluation, as revealed by SPQ scores. This study is the first to investigate the contribution of small-fiber density to the perceptual evaluation of pain. It demonstrates that the lower the peripheral small-fiber density, the lower the degree of reported pain intensity, indicating a functional relationship between small-fiber density and higher level pain experience. PMID:27146986

  20. A Desorbed Gas Molecular Ionization Mechanism for Arcing Onset in Solar Arrays Immersed in a Low-Density Plasma

    NASA Technical Reports Server (NTRS)

    Galofaro, J.; Vayner, B.; Ferguson, D.; Degroot, W.

    2002-01-01

    Previous experimental studies have hypothesized that the onset of Solar Array Arc (SAA) initiation in low-density space plasmas is caused by a desorbed gas molecular ionization mechanism. Indeed past investigations performed at the NASA Glenn Plasma Interaction Facility tend to not only support the desorbed gas molecular ionization mechanism, but have gone as far as identifying the crucial molecular species that must be present for molecular ion dominated process to occur. When electrical breakdown occurs at a triple junction site on a solar array panel, a quasi-neutral plasma cloud is ejected. Assuming the main component of the expelled plasma cloud by weight is due to water vapor, the fastest process available is due to HO molecules and OH(+) ions, or more succinctly, dissociative molecular-ion dominated recombination processes: H2O(+) + e(-) yields H* + OH*. Recently published spectroscopic observations of solar array arc spectra in ground tests have revealed the well-known molecular OH band (302 to 309nm), as well as the molecular SiH band (387nm peak), and the molecular CH band (432nm peak). Note that the OH band is observed in emission arcs where water vapor is present. Strong atomic lines were also observed for H(sub beta) at 486nm and H(sub alpha) at 656.3nm in prior ground testing. Independent supporting evidence of desorbed gas molecular ionization mechanisms also come from measurements of arc current pulse widths at different capacitances. We will revisit an earlier first order approximation demonstrating the dependence of arc current pulse widths on the square root of the capacitance. The simple arc current pulse width model will be then be used to estimate the temperature of the arc plasma (currently believed to be somewhere in the range of 3 to 5 eV). The current paper then seeks to extend the outlined work by including numerous vacuum chamber measurements obtained with a quadrupole mass spectrometer. A small solar array was mounted inside the vacuum

  1. Alcohol Outlet Density, Drinking Contexts and Intimate Partner Violence: A Review of Environmental Risk Factors

    PubMed Central

    Mair, Christina; Todd, Michael

    2015-01-01

    Alcohol use is a robust predictor of intimate partner violence (IPV). A critical barrier to progress in preventing alcohol-related IPV is that little is known about how an individual’s specific drinking contexts (where, how often, and with whom one drinks) are related to IPV, or how these contexts are affected by environmental characteristics, such as alcohol outlet density and neighborhood disadvantage. The putative mechanism is the social environment in which drinking occurs that may promote or strengthen aggressive norms. Once these contexts are known, specific prevention measures can be put in place, including policy-oriented (e.g., regulating outlet density) and individually-oriented (e.g., brief interventions to reduce risk for spousal aggression) measures targeting at-risk populations. This paper reviews applicable theories and empirical research evidence that links IPV to drinking contexts and alcohol outlet density, highlights research gaps, and make recommendations for future research. PMID:25725018

  2. Breast density and parenchymal texture measures as potential risk factors for estrogen-receptor positive breast cancer

    NASA Astrophysics Data System (ADS)

    Keller, Brad M.; Chen, Jinbo; Conant, Emily F.; Kontos, Despina

    2014-03-01

    Accurate assessment of a woman's risk to develop specific subtypes of breast cancer is critical for appropriate utilization of chemopreventative measures, such as with tamoxifen in preventing estrogen-receptor positive breast cancer. In this context, we investigate quantitative measures of breast density and parenchymal texture, measures of glandular tissue content and tissue structure, as risk factors for estrogen-receptor positive (ER+) breast cancer. Mediolateral oblique (MLO) view digital mammograms of the contralateral breast from 106 women with unilateral invasive breast cancer were retrospectively analyzed. Breast density and parenchymal texture were analyzed via fully-automated software. Logistic regression with feature selection and was performed to predict ER+ versus ER- cancer status. A combined model considering all imaging measures extracted was compared to baseline models consisting of density-alone and texture-alone features. Area under the curve (AUC) of the receiver operating characteristic (ROC) and Delong's test were used to compare the models' discriminatory capacity for receptor status. The density-alone model had a discriminatory capacity of 0.62 AUC (p=0.05). The texture-alone model had a higher discriminatory capacity of 0.70 AUC (p=0.001), which was not significantly different compared to the density-alone model (p=0.37). In contrast the combined density-texture logistic regression model had a discriminatory capacity of 0.82 AUC (p<0.001), which was statistically significantly higher than both the density-alone (p<0.001) and texture-alone regression models (p=0.04). The combination of breast density and texture measures may have the potential to identify women specifically at risk for estrogen-receptor positive breast cancer and could be useful in triaging women into appropriate risk-reduction strategies.

  3. 40 CFR Table W - 2 of Subpart W of Part 98-Default Total Hydrocarbon Emission Factors for Onshore Natural Gas...

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 22 2013-07-01 2013-07-01 false 2 of Subpart W of Part 98-Default Total Hydrocarbon Emission Factors for Onshore Natural Gas Processing W Table W Protection of... of Part 98—Default Total Hydrocarbon Emission Factors for Onshore Natural Gas Processing...

  4. 40 CFR Table W - 4 of Subpart W of Part 98-Default Total Hydrocarbon Emission Factors for Underground Natural Gas...

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 21 2014-07-01 2014-07-01 false 4 of Subpart W of Part 98-Default Total Hydrocarbon Emission Factors for Underground Natural Gas Storage W Table W Protection of... of Part 98—Default Total Hydrocarbon Emission Factors for Underground Natural Gas Storage...

  5. 40 CFR Table W - 2 of Subpart W of Part 98-Default Total Hydrocarbon Emission Factors for Onshore Natural Gas...

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 21 2014-07-01 2014-07-01 false 2 of Subpart W of Part 98-Default Total Hydrocarbon Emission Factors for Onshore Natural Gas Processing W Table W Protection of... of Part 98—Default Total Hydrocarbon Emission Factors for Onshore Natural Gas Processing...

  6. 40 CFR Table W - 4 of Subpart W of Part 98-Default Total Hydrocarbon Emission Factors for Underground Natural Gas...

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 22 2013-07-01 2013-07-01 false 4 of Subpart W of Part 98-Default Total Hydrocarbon Emission Factors for Underground Natural Gas Storage W Table W Protection of... of Part 98—Default Total Hydrocarbon Emission Factors for Underground Natural Gas Storage...

  7. 40 CFR Table W - 3 of Subpart W-Default Total Hydrocarbon Emission Factors for Onshore Natural Gas Transmission...

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 40 Protection of Environment 22 2012-07-01 2012-07-01 false 3 of Subpart W-Default Total Hydrocarbon Emission Factors for Onshore Natural Gas Transmission Compression W Table W Protection of...—Default Total Hydrocarbon Emission Factors for Onshore Natural Gas Transmission Compression...

  8. Measurement and interpretation of threshold stress intensity factors for steels in high-pressure hydrogen gas.

    SciTech Connect

    Nibur, Kevin A.

    2010-11-01

    Threshold stress intensity factors were measured in high-pressure hydrogen gas for a variety of low alloy ferritic steels using both constant crack opening displacement and rising crack opening displacement procedures. The sustained load cracking procedures are generally consistent with those in ASME Article KD-10 of Section VIII Division 3 of the Boiler and Pressure Vessel Code, which was recently published to guide design of high-pressure hydrogen vessels. Three definitions of threshold were established for the two test methods: K{sub THi}* is the maximum applied stress intensity factor for which no crack extension was observed under constant displacement; K{sub THa} is the stress intensity factor at the arrest position for a crack that extended under constant displacement; and K{sub JH} is the stress intensity factor at the onset of crack extension under rising displacement. The apparent crack initiation threshold under constant displacement, K{sub THi}*, and the crack arrest threshold, K{sub THa}, were both found to be non-conservative due to the hydrogen exposure and crack-tip deformation histories associated with typical procedures for sustained-load cracking tests under constant displacement. In contrast, K{sub JH}, which is measured under concurrent rising displacement and hydrogen gas exposure, provides a more conservative hydrogen-assisted fracture threshold that is relevant to structural components in which sub-critical crack extension is driven by internal hydrogen gas pressure.

  9. Measurement and interpretation of threshold stress intensity factors for steels in high-pressure hydrogen gas.

    SciTech Connect

    Dadfarnia, Mohsen; Nibur, Kevin A.; San Marchi, Christopher W.; Sofronis, Petros; Somerday, Brian P.; Foulk, James W., III; Hayden, Gary A.

    2010-07-01

    Threshold stress intensity factors were measured in high-pressure hydrogen gas for a variety of low alloy ferritic steels using both constant crack opening displacement and rising crack opening displacement procedures. The sustained load cracking procedures are generally consistent with those in ASME Article KD-10 of Section VIII Division 3 of the Boiler and Pressure Vessel Code, which was recently published to guide design of high-pressure hydrogen vessels. Three definitions of threshold were established for the two test methods: K{sub THi}* is the maximum applied stress intensity factor for which no crack extension was observed under constant displacement; K{sub THa} is the stress intensity factor at the arrest position for a crack that extended under constant displacement; and K{sub JH} is the stress intensity factor at the onset of crack extension under rising displacement. The apparent crack initiation threshold under constant displacement, K{sub THi}*, and the crack arrest threshold, K{sub THa}, were both found to be non-conservative due to the hydrogen exposure and crack-tip deformation histories associated with typical procedures for sustained-load cracking tests under constant displacement. In contrast, K{sub JH}, which is measured under concurrent rising displacement and hydrogen gas exposure, provides a more conservative hydrogen-assisted fracture threshold that is relevant to structural components in which sub-critical crack extension is driven by internal hydrogen gas pressure.

  10. Intra unit cell electronic structure of the d-symmetry form factor density wave in the underdoped cuprates - Part I

    NASA Astrophysics Data System (ADS)

    Fujita, Kazuhiro; Hamidian, Mohammad; Edkins, Stephen; Kim, Chung Koo; MacKenzie, Andy; Eisaki, Hiroshi; Uchida, Shin-Ichi; Lawler, Michael; Kim, Eun-Ah; Sachdev, Subir; Davis, J. C.

    2015-03-01

    A central issue of cuprate superconductivity research is to understand the nature of the unknown phase called the pseudogap and its relationship to the d-wave superconductivity. To approach this we use spectroscopic imaging STM to study the electronic structure of Bi2Sr2CaCu2O8+δ. Using our recently developed technique of sub-lattice phase-resolved electronic structure visualization within each CuO2 unit-cell, we discovered a d-symmetry form factor density wave within the cuprate pseudogap state. In this talk, part I, we demonstrate that d-symmetry is the predominant form factor in the density wave within pseudogap states and show how this situation evolves upon doping.

  11. Human factors engineering in oil and gas--a review of industry guidance.

    PubMed

    Robb, Martin; Miller, Gerald

    2012-01-01

    Oil and gas exploration and production activities are carried out in hazardous environments in many parts of the world. Recent events in the Gulf of Mexico highlight those risks and underline the importance of considering human factors during facility design. Ergonomic factors such as machinery design, facility and accommodation layout and the organization of work activities have been systematically considered over the past twenty years on a limited number of offshore facility design projects to a) minimize the occupational risks to personnel, b) support operations and maintenance tasks and c) improve personnel wellbeing. During this period, several regulators and industry bodies such as the American Bureau of Shipping (ABS), the American Society of Testing and Materials (ASTM), the UK's Health and Safety Executive (HSE), Oil and Gas Producers (OGP), and Norway's Petroleum Safety Authority (PSA) have developed specific HFE design standards and guidance documents for the application of Human Factors Engineering (HFE) to the design and operation of Oil and Gas projects. However, despite the existence of these guidance and recommended design practise documents, and documented proof of their value in enhancing crew safety and efficiency, HFE is still not well understood across the industry and application across projects is inconsistent. This paper summarizes the key Oil and Gas industry bodies' HFE guidance documents, identifies recurring themes and current trends in the use of these standards, provides examples of where and how these HFE standards have been used on past major offshore facility design projects, and suggests criteria for selecting the appropriate HFE strategy and tasks for future major oil and gas projects. It also provides a short history of the application of HFE to the offshore industry, beginning with the use of ASTM F 1166 to a major operator's Deepwater Gulf of Mexico facility in 1990 and the application of HFE to diverse world regions. This

  12. Single-particle spectral density of the unitary Fermi gas: Novel approach based on the operator product expansion, sum rules and the maximum entropy method

    SciTech Connect

    Gubler, Philipp; Yamamoto, Naoki; Hatsuda, Tetsuo; Nishida, Yusuke

    2015-05-15

    Making use of the operator product expansion, we derive a general class of sum rules for the imaginary part of the single-particle self-energy of the unitary Fermi gas. The sum rules are analyzed numerically with the help of the maximum entropy method, which allows us to extract the single-particle spectral density as a function of both energy and momentum. These spectral densities contain basic information on the properties of the unitary Fermi gas, such as the dispersion relation and the superfluid pairing gap, for which we obtain reasonable agreement with the available results based on quantum Monte-Carlo simulations.

  13. Comparative Study on Extinction Process of Gas-Blasted Air and CO2 Arc Discharge Using Two-Dimensional Electron Density Imaging Sensor

    NASA Astrophysics Data System (ADS)

    Inada, Yuki; Kamiya, Tomoki; Matsuoka, Shigeyasu; Kumada, Akiko; Ikeda, Hisatoshi; Hidaka, Kunihiko; Nakano, Tomoyuki; Murai, Kosuke; Tanaka, Yasunori; Shinkai, Takeshi

    2015-09-01

    Systematic comparison of the electron density images for various kinds of arc-quenching gas media inside high-voltage circuit breakers is a promising method for the effective search and development of SF6-alternative gases. However, electron density imaging over the decaying arcs around the nozzle throat of the circuit breakers is extremely difficult by using the conventional arc generation setup and localized type sensing systems, due to the nozzle opaqueness and spatiotemporal instability of long-gap arc discharges around current zero. Here, we achieved two-dimensional electron density imaging over the decaying arcs around the nozzle throat first in the world, by a combination of the development of a unique gas flow nozzle integrating a cubic quartz cell and the single-shot recordings using Shack-Hartmann sensors. Shack-Hartmann sensors were applied to gas-blasted air and CO2 arc discharges under current-zero phases after sudden switch-off of stationary arc currents. These experimental results showed that the electron densities and arc diameters took the minimums in the upper stream nozzle regions with the maximum blasting gas speeds. In addition, CO2 had a shorter electron density decaying time constant than air, which is consistent with the previous theoretical studies on higher interruption performance of CO2 compared with air.

  14. Small-bandgap polymer solar cells with unprecedented short-circuit current density and high fill factor.

    PubMed

    Choi, Hyosung; Ko, Seo-Jin; Kim, Taehyo; Morin, Pierre-Olivier; Walker, Bright; Lee, Byoung Hoon; Leclerc, Mario; Kim, Jin Young; Heeger, Alan J

    2015-06-01

    Small-bandgap polymer solar cells (PSCs) with a thick bulk heterojunction film of 340 nm exhibit high power conversion efficiencies of 9.40% resulting from high short-circuit current density (JSC ) of 20.07 mA cm(-2) and fill factor of 0.70. This remarkable efficiency is attributed to maximized light absorption by the thick active layer and minimized recombination by the optimized lateral and vertical morphology through the processing additive. PMID:25899940

  15. Design factors for a super high energy density Ni-MH battery for military uses

    SciTech Connect

    Brown, J.T.; Klein, M.G.

    1997-12-01

    The nickel-metal hydride battery is a relatively new commercial product which meets the needs for a more environmentally friendly battery than either the lead-acid or nickel-cadmium couples. While the presently available product also provides significantly improved performance over these other batteries, it is believed possible to develop a new generation of Ni-MH batteries with perhaps 80% greater density by using improved hydrogen storage alloys with the capability to store up to 2% by weight hydrogen, improved nickel electrodes which can stably cycle with an electron transfer of greater than 1.5 per nickel atom, and utilizing improved new cell and battery packaging designs which minimize inactive battery weight and volume. This could raise the energy density of today`s commercial product (55--70 Wh/kg) to greater than 120 Wh/kg.

  16. An annular gas seal analysis using empirical entrance and exit region friction factors

    NASA Technical Reports Server (NTRS)

    Elrod, D. A.; Childs, D. W.; Nelson, C. C.

    1990-01-01

    Wall shear stress results from stationary-rotor flow tests of five annular gas seals are used to develop entrance and exit region friction factor models. The friction factor models are used in a bulk-flow seal analysis which predicts leakage and rotor-dynamic coefficients. The predictions of the analysis are compared to experimental results and to the predictions of Nelson's analysis (1985). The comparisons are for smooth-rotor seals with smooth and honeycomb-stators. The present analysis predicts the destabilizing cross-coupled stiffness of a seal better than Nelson's analysis. Both analyses predict direct damping well and direct stiffness poorly.

  17. Longitudinal bone mineral content and density in Rett syndrome and their contributing factors.

    PubMed

    Jefferson, Amanda; Fyfe, Sue; Downs, Jenny; Woodhead, Helen; Jacoby, Peter; Leonard, Helen

    2015-05-01

    Bone mass and density are low in females with Rett syndrome. This study used Dual energy x-ray absorptiometry to measure annual changes in z-scores for areal bone mineral density (aBMD) and bone mineral content (BMC) in the lumbar spine and total body in an Australian Rett syndrome cohort at baseline and then after three to four years. Bone mineral apparent density (BMAD) was calculated in the lumbar spine. Annual changes in lean tissue mass (LTM) and bone area (BA) were also assessed. The effects of age, genotype, mobility, menstrual status and epilepsy diagnosis on these parameters were also investigated. The baseline sample included 97 individuals who were representative of the total live Australian Rett syndrome population under 30years in 2005 (n=274). Of these 74 had a follow-up scan. Less than a quarter of females were able to walk on their own at follow-up. Bone area and LTM z-scores declined over the time between the baseline and follow-up scans. Mean height-standardised z-scores for the bone outcomes were obtained from multiple regression models. The lumbar spine showed a positive mean annual BMAD z-score change (0.08) and a marginal decrease in aBMD (-0.04). The mean z-score change per annum for those 'who could walk unaided' was more positive for LS BMAD (p=0.040). Total body BMD mean annual z-score change from baseline to follow-up was negative (-0.03). However this change was positive in those who had achieved menses prior to the study (0.03, p=0,040). Total body BMC showed the most negative change (-0.60), representing a decrease in bone mineral content over time. This normalised to a z-score change of 0.21 once adjusted for the reduced lean tissue mass mean z-score change (-0.21) and bone area mean z-score change (-0.14). Overall, the bone mineral content, bone mineral density, bone area and lean tissue mass z-scores for all outcome measures declined, with the TB BMC showing significant decreases. Weight, height and muscle mass appear to have

  18. Relationship between insulin-like growth factor I, dehydroepiandrosterone sulfate and proresorptive cytokines and bone density in cystic fibrosis

    PubMed Central

    Binello, E.; LeBoff, M. S.; Wohl, M. E.; Rosen, C. J.; Colin, A. A.

    2011-01-01

    Introduction Patients with cystic fibrosis (CF) are known to be at risk for early osteoporosis, and the mechanisms that mediate bone loss are still being delineated. The aim of the present investigation was to investigate if a correlation exists in these patients between skeletal measurements by dual-energy x-ray absorptiometry (DXA) and two anabolic factors, dehydroepiandrosterone (DHEA) and insulin-like growth factor I (IGF-I), and proresorptive factors such as the cytokines interleukin-1β, tumor necrosis factor α, and interleukin-6. Methods We studied 32 outpatients (18 females; mean age: 26.2 ± 7.9 years) at a tertiary care medical center. The subjects had venous samples obtained, underwent anthropometric and bone mineral density (BMD) measurements, and completed a health survey. Serum IGF-I concentrations were below the age-adjusted mean in 78% of the participants, and DHEA sulfate (DHEAS) concentrations were low in 72%. Serum concentrations of all cytokines were on the low side of normal; nonetheless, there was a modest inverse correlation between IL-1β and BMD at all sites. Results In univariate analyses, IGF-I and DHEAS were significant correlates of BMD or bone mineral content. In final multivariate models controlling for anthropometric and other variables of relevance to bone density, only IGF-I was identified as a significant independent skeletal predictor. While alterations in DHEAS, IGF-I, and specific cytokines may contribute to skeletal deficits in patients with CF, of these factors a low IGF-I concentration appears to be most strongly correlated with BMD. Conclusions These findings may have therapeutic implications for enhancing bone density in these patients. PMID:16541207

  19. Exponents of the spectral functions and dynamical structure factor of the 1D Lieb-Liniger Bose gas

    NASA Astrophysics Data System (ADS)

    Carmelo, J. M. P.; Sacramento, P. D.

    2016-06-01

    We study the (k , ω) -plane finite-energy line shape of the zero-temperature one-boson removal spectral function (ω < 0) , one-boson addition spectral function (ω > 0) , and charge dynamical structure factor (ω > 0) of the 1D Lieb-Liniger Bose gas with repulsive boson interaction c > 0. Our analysis of the problem focuses on the line shape at finite excitation energies in the vicinity of these functions spectrum upper (ω < 0) or lower (ω > 0) threshold. Specifically, we derive the exact momentum, interaction, and density dependences of the exponents controlling such a line shape in each of the N = 1 , 2 , 3 , … momentum subdomains k ∈ [(N - 1) 2 πn , N 2 πn ] . Here n = N / L is the boson density, N the boson number, and L the system length. In the thermodynamic limit considered in our study nearly all spectral weight of the dynamical correlation functions is for large values of n / c contained in the N = 1 momentum subdomain k ∈ [ 0 , 2 πn ] . As n / c decreases a small fraction of that weight is transferred to the remaining set of N = 2 , 3 , 4 , … momentum subdomains, particularly to the N = 2 subdomain. In the case of the momentum subdomain k ∈ [ 0 , 2 πn ] , our exact results agree with those of previous studies. For that subdomain the above exponents are plotted as a function of the momentum for several n / c values. Our derivation of the line shapes of the three dynamical correlation functions relies on the use of a simplified form of the pseudofermion dynamical theory of the fermionic 1D Hubbard model suitably modified in this paper for the 1D Bose gas.

  20. Strong optical and UV intermediate-width emission lines in the quasar SDSS J232444.80–094600.3: dust-free and intermediate-density gas at the skin of dusty torus?

    NASA Astrophysics Data System (ADS)

    Li, Zhen-Zhen; Zhou, Hong-Yan; Hao, Lei; Wang, Shu-Fen; Ji, Tuo; Liu, Bo

    2016-09-01

    Emission lines from the broad emission line region (BELR) and the narrow emission line region (NELR) of active galactic nuclei (AGNs) have been extensively studied. However, emission lines are rarely detected between these two regions. We present a detailed analysis of quasar SDSS J232444.80–094600.3 (SDSS J2324–0946), which is remarkable for its strong intermediate-width emission lines (IELs) with FWHM ≈ 1800 km s‑1. The IEL component is present in different emission lines, including the permitted lines Lyα λ1216, CIV λ1549, semiforbidden line [CIII] λ1909, and forbidden lines [OIII] λλ4959, 5007. With the aid of photo-ionization models, we found that the IELs are produced by gas with a hydrogen density of nH ∼ 106.2 ∼ 106.3 cm‑3, a distance from the central ionizing source of R ∼ 35 – 50 pc, a covering factor of ∼ 6%, and a dust-to-gas ratio of ≤ 4% that of the SMC. We suggest that the strong IELs of this quasar are produced by nearly dust-free and intermediate-density gas located at the skin of the dusty torus. Such strong IELs, which serve as a useful diagnostic, can provide an avenue to study the properties of gas between the BELR and the NELR.

  1. ALMA Observations of a High-density Core in Taurus: Dynamical Gas Interaction at the Possible Site of a Multiple Star Formation

    NASA Astrophysics Data System (ADS)

    Tokuda, Kazuki; Onishi, Toshikazu; Saigo, Kazuya; Kawamura, Akiko; Fukui, Yasuo; Matsumoto, Tomoaki; Inutsuka, Shu-ichiro; Machida, Masahiro N.; Tomida, Kengo; Tachihara, Kengo

    2015-08-01

    It is crucially important to observe dense cores in order to investigate the initial condition of star formation since protostars are formed via dynamical collapse of dense cores, inhering the physical properties from their natal dense cores. Here we present the results of ALMA Cycle 0 and Cycle 1 observations of dust continuum emission and molecular rotational lines toward a dense core, MC27 (aka L1521F), which is considered to be very close to the first protostellar core phase.The Cycle 0 observations revealed complex structures at the center. We found a few starless high-density cores, one of which (MMS2) has a very high density of ~107 cm-3, around the very low-luminousity protostar detected by Spitzer. A very compact bipolar outflow with a dynamical timescale of a few hundred years was found toward the protostar. The HCO+ (3-2) observation shows several cores associated with an arc-like structure whose length is ~2000 AU, possibly due to the dynamical gas interaction. These complex structures suggest that the initial condition of star formation is highly dynamical in nature, which is considered to be a key factor in understanding fundamental issues of star formation such as origins of the stellar multiplicity and the initial mass function. These initial Cycle 0 results were published by Tokuda et al. (2014). Matsumoto et al. (2015) investigated the arc-like structures by performing numerical simulations.Detailed column density distribution with the size from ~100 to ~10000 AU scale are revealed by combining the 12m array data with the 7m array data of the ALMA Compact Array as well as with the single dish MAMBO data. Our preliminary analysis shows that the averaged radial column density distribution of the inner part (r < 2000 AU) is N(H2)~r-0.4, clearly flatter than that of the outer part, ~r-1.3. We detected the above-mentioned complex structure inside the inner flatter region, which may reflect the dynamical status of the dense core. The Cycle 1

  2. Variation in Inflammatory Cytokine/Growth-Factor Genes and Mammographic Density in Premenopausal Women Aged 50–55

    PubMed Central

    Ozhand, Ali; Lee, Eunjung; Wu, Anna H.; Ellingjord-Dale, Merete; Akslen, Lars A.; McKean-Cowdin, Roberta; Ursin, Giske

    2013-01-01

    Background Mammographic density (MD) has been found to be an independent risk factor for breast cancer. Although data from twin studies suggest that MD has a strong genetic component, the exact genes involved remain to be identified. Alterations in stromal composition and the number of epithelial cells are the most predominant histopathological determinants of mammographic density. Interactions between the breast stroma and epithelium are critically important in the maturation and development of the mammary gland and the cross-talk between these cells are mediated by paracrine growth factors and cytokines. The potential impact of genetic variation in growth factors and cytokines on MD is largely unknown. Methods We investigated the association between 89 single nucleotide polymorphisms (SNPs) in 7 cytokine/growth-factor genes (FGFR2, IGFBP1, IGFBP3, TGFB1, TNF, VEGF, IL6) and percent MD in 301 premenopausal women (aged 50 to 55 years) participating in the Norwegian Breast Cancer Screening Program. We evaluated the suggestive associations in 216 premenopausal Singapore Chinese Women of the same age. Results We found statistically significant associations between 9 tagging SNPs in the IL6 gene and MD in Norwegian women; the effect ranged from 3–5% in MD per variant allele (p-values = 0.02 to 0.0002). One SNP in the IL6 (rs10242595) significantly influenced MD in Singapore Chinese women. Conclusion Genetic variations in IL6 may be associated with MD and therefore may be an indicator of breast cancer risk in premenopausal women. PMID:23762340

  3. Optimum extracted H{sup {minus}} and D{sup {minus}} current densities from gas-pressure-limited high-power hydrogen/deuterium tandem ion sources

    SciTech Connect

    Hiskes, J.R.

    1993-07-14

    The tandem hydrogen/deuterium ion source is modelled for the purpose of identifying the maximum current densities that can be extracted subject to the gas-pressure constraints proposed for contemporary beam-line systems. Optimum useful extracted current densities are found to be in the range of approximately 7 to 10 mA cm{sup {minus}2}. The sensitivity of these current densities is examined subject to uncertainties in the underlying atomic/molecular rate processes; A principal uncertainty remains the quantification of the molecular vibrational distribution following H{sub 3{sup +}} wall collisions.

  4. Test of a nonempirical density functional for short-range van der Waals interaction in rare-gas dimers

    NASA Astrophysics Data System (ADS)

    Tao, Jianmin

    2005-03-01

    It is known that the nonempirical generalized gradient approximation (GGA) of Perdew, Burke, and Ernzerhof (PBE) provides a much more realistic description of the short-range part of the van der Waals (vdW) interaction than does the local spin density (LSD) approximation. In the present work, the ability of the higher-level nonempirical meta-GGA of Tao, Perdew, Staroverov, and Scuseria (TPSS) [Phys. Rev. Lett. 91, 146401 (2003)] to describe vdW interaction is tested self-consistently in rare-gas dimers with Z <=36. The one-parameter hybrid version (TPSSh) of the TPSS exchange-correlation functional is also included in this test. Calculations show that both TPSS and TPSSh functionals correctly yield vdW bonds in these dimers and significantly improve the prediction of bond lengths and binding energies over LSD. The rather close agreement of TPSS with PBE for these dimers confirms a principle of the TPSS construction: preservation of the PBE large-gradient behavior. Compared with the PBE GGA, TPSS and TPSSh yield a slightly weaker binding. The typically too-long bond lengths and too-small binding energies of TPSS meta-GGA suggest the need for some long-range vdW interaction correction which is discussed.

  5. Enhanced diesel fuel fraction from waste high-density polyethylene and heavy gas oil pyrolysis using factorial design methodology.

    PubMed

    Joppert, Ney; da Silva, Alexsandro Araujo; da Costa Marques, Mônica Regina

    2015-02-01

    Factorial Design Methodology (FDM) was developed to enhance diesel fuel fraction (C9-C23) from waste high-density polyethylene (HDPE) and Heavy Gas Oil (HGO) through co-pyrolysis. FDM was used for optimization of the following reaction parameters: temperature, catalyst and HDPE amounts. The HGO amount was constant (2.00 g) in all experiments. The model optimum conditions were determined to be temperature of 550 °C, HDPE = 0.20 g and no FCC catalyst. Under such conditions, 94% of pyrolytic oil was recovered, of which diesel fuel fraction was 93% (87% diesel fuel fraction yield), no residue was produced and 6% of noncondensable gaseous/volatile fraction was obtained. Seeking to reduce the cost due to high process temperatures, the impact of using higher catalyst content (25%) with a lower temperature (500 °C) was investigated. Under these conditions, 88% of pyrolytic oil was recovered (diesel fuel fraction yield was also 87%) as well as 12% of the noncondensable gaseous/volatile fraction. No waste was produced in these conditions, being an environmentally friendly approach for recycling the waste plastic. This paper demonstrated the usefulness of using FDM to predict and to optimize diesel fuel fraction yield with a great reduction in the number of experiments. PMID:25532672

  6. Homogeneous catalysis on the gas-phase dehydration reaction of tertiary alcohols by hydrogen bromide. Density functional theory calculation

    NASA Astrophysics Data System (ADS)

    Maldonado, Alexis; Rosas, Felix; Mora, Jose R.; Brusco, Yannely; Córdova-Sintjago, Tania C.; Chuchani, Gabriel

    2015-02-01

    The gas-phase thermal dehydration mechanism of tert-butanol, 2-methyl-2-butanol, 2-methyl-2-pentanol and 2,3-dimethyl-2-butanol by homogeneous catalysis of hydrogen bromide was examined by density functional theory calculations with the hybrid functionals: M062X, CAMB3LYP and WB97XD. Reasonable agreements were found between theoretical and experimental enthalpy values at the WB97XD/6-311++G(d,p) level. The dehydration mechanism of tert-butanol with and without catalysis was evaluated in order to examine the catalyst effect on the mechanism. The elimination reaction without catalysis involves a four-membered transition state (TS), while the reaction with catalysis involves a six-membered TS. The mechanism without catalysis has enthalpy activation over 150 kJ mol-1 greater than the catalysed reaction. In all these reactions, the elongation of the C-O bond is significant in the TS. The un-catalysed reaction is controlled by breaking of C-O bond, and it was found to be more synchronous (Sy ≈ 0.91) than the hydrogen bromide catalysed reactions (Sy ≈ 0.75-0.78); the latter reactions are dominated by the three reaction coordinates associated with water formation. No significant effect on the enthalpies of activation was observed when the size of the alkyl chain was increased.

  7. Using Clinical Factors and Mammographic Breast Density to Estimate Breast Cancer Risk: Development and Validation of a New Predictive Model

    PubMed Central

    Tice, Jeffrey A.; Cummings, Steven R.; Smith-Bindman, Rebecca; Ichikawa, Laura; Barlow, William E.; Kerlikowske, Karla

    2009-01-01

    Background Current models for assessing breast cancer risk are complex and do not include breast density, a strong risk factor for breast cancer that is routinely reported with mammography. Objective To develop and validate an easy-to-use breast cancer risk prediction model that includes breast density. Design Empirical model based on Surveillance, Epidemiology, and End Results incidence, and relative hazards from a prospective cohort. Setting Screening mammography sites participating in the Breast Cancer Surveillance Consortium. Patients 1 095 484 women undergoing mammography who had no previous diagnosis of breast cancer. Measurements Self-reported age, race or ethnicity, family history of breast cancer, and history of breast biopsy. Community radiologists rated breast density by using 4 Breast Imaging Reporting and Data System categories. Results During 5.3 years of follow-up, invasive breast cancer was diagnosed in 14 766 women. The breast density model was well calibrated overall (expected–observed ratio, 1.03 [95% CI, 0.99 to 1.06]) and in racial and ethnic subgroups. It had modest discriminatory accuracy (concordance index, 0.66 [CI, 0.65 to 0.67]). Women with low-density mammograms had 5-year risks less than 1.67% unless they had a family history of breast cancer and were older than age 65 years. Limitation The model has only modest ability to discriminate between women who will develop breast cancer and those who will not. Conclusion A breast cancer prediction model that incorporates routinely reported measures of breast density can estimate 5-year risk for invasive breast cancer. Its accuracy needs to be further evaluated in independent populations before it can be recommended for clinical use. PMID:18316752

  8. Translationally invariant calculations of form factors, nucleon densities and momentum distributions for finite nuclei with short-range correlations included

    NASA Astrophysics Data System (ADS)

    Shebeko, A. V.; Grigorov, P. A.; Iurasov, V. S.

    2012-11-01

    Relying upon our previous treatment of the density matrices for nuclei (in general, nonrelativistic self-bound finite systems) we are studying a combined effect of center-of-mass motion and short-range nucleon-nucleon correlations on the nucleon density and momentum distributions in light nuclei (4He and 16O). Their intrinsic ground-state wave functions are constructed in the so-called fixed center-of-mass approximation, starting with mean-field Slater determinants modified by some correlator ( e.g., after Jastrow or Villars). We develop the formalism based upon the Cartesian or boson representation, in which the coordinate and momentum operators are linear combinations of the creation and annihilation operators for oscillatory quanta in the three different space directions, and get the own "Tassie-Barker" factors for each distribution and point out other model-independent results. After this separation of the center-of-mass motion effects we propose additional analytic means in order to simplify the subsequent calculations ( e.g., within the Jastrow approach or the unitary correlation operator method). The charge form factors, densities and momentum distributions of 4He and 16O evaluated by using the well-known cluster expansions are compared with data, our exact (numerical) results and microscopic calculations.

  9. Spatial Distributions of Electron, CF, and CF2 Radical Densities and Gas Temperature in DC-Superposed Dual-Frequency Capacitively Coupled Plasma Etch Reactor Employing Cyclic-C4F8/N2/Ar Gas

    NASA Astrophysics Data System (ADS)

    Yamaguchi, Tsuyoshi; Kimura, Tetsuya; Koshimizu, Chishio; Takeda, Keigo; Kondo, Hiroki; Ishikawa, Kenji; Sekine, Makoto; Hori, Masaru

    2011-05-01

    On a plasma etch reactor for a wafer of 300 mm in diameter, the spatial distributions of the absolute densities of CF and CF2 radicals, electron density (ne), and the gas temperature (Tg) of N2 were measured employing the dual frequency of negative dc voltage superposed to a very high frequency (VHF) of 60 MHz capacitively coupled plasma (DS-2f-CCP) with the cyclic- (c-)C4F8/Ar/N2 gas mixture. The dc bias was superposed on the upper electrode with a frequency of 60 MHz. The distributions of electron and radical densities were uniform within a diameter of about 260 mm, and took a monotonic decay in regions outside a diameter of 260 mm on the reactor for 300 mm wafers in the reactor. It was found that only CF2 density at the radial position between 150 and 180 mm, corresponding to the position of the Si focus ring, dropped, while CF density took a uniform distribution over a diameter of 260 mm. Additionally, at this position, the rotational temperature of N2 gas increased to be 100 K larger than that at the center position. CF2 radical density was markedly affected by the modified surface loss probability of the material owing to coupling with surface temperature.

  10. Simulation and Experimental Studies on Substrate Temperature and Gas Density Field in Hfcvd Diamond Films Growth on WC-Co Drill Tools

    NASA Astrophysics Data System (ADS)

    Zhang, Jianguo; Zhang, Tao; Wang, Xinchang; Shen, Bin; Sun, Fanghong

    2013-04-01

    Uniform temperature and gas density field inside the reactor play an important role on synthesis of high-quality diamond films using hot filament chemical vapor deposition (HFCVD) method. In the present study, the finite volume method (FVM) is adopted to simulate the temperature and gas density distribution during the deposition process. Temperature-measuring experiments are conducted to verify the correctness of the simulation results. Thereafter, the deposition parameters are optimized using this model as D (filament separation) = 35 mm, H (filament-substrate distance) = -10 mm and N (number of gas inlet) = 3. Finally, experiments of depositing diamond films on WC-Co drill tools are carried out with the optimal deposition parameters. The results of the characterization by SEM and Raman spectrum exhibit that as-fabricated diamond-coated tools present a layer of high-quality diamond films with homogeneous surface and uniform thickness, further validating the accuracy of the parameter optimization using the simulation method.

  11. Simulation model of speed-density characteristics for mixed bicycle flow—Comparison between cellular automata model and gas dynamics model

    NASA Astrophysics Data System (ADS)

    Zhang, Shuichao; Ren, Gang; Yang, Renfa

    2013-10-01

    The mixed bicycle flow refers to the bicycle flow containing electric bicycles. The traffic characteristics data of the mixed bicycle flow was collected by the virtual coil method in Nanjing and Ningbo, China. And the speed-density characteristics of the mixed bicycle flow with different proportions of electric bicycles were obtained. The results show that the overall speed of the mixed bicycle flow containing electric bicycles is higher than that of pure bicycle flow when the density is relatively low. The speed decreases when the density is higher than 0.08 bic/m2; the speed-density characteristics of the bicycles and the electric bicycles tend to be the same when the density is higher than 0.25 bic/m2. And when the density reaches 0.58 bic/m2, the mixed bicycle flow becomes blocked and the speed is zero. The cellular automata model and gas dynamics model were also adopted to simulate the speed-density characteristics of the mixed bicycle flow. The simulation results of the cellular automata model are effectively consistent with the actual survey data when the density is lower than 0.225 bic/m2; the simulation results of the gas dynamics model are effectively consistent with the actual survey data when the density is higher than 0.300 bic/m2; but both of the two types of simulation models are inapplicable when the density is between 0.225 and 0.300 bic/m2. These results will be used in the management of mixed bicycles and the research of vehicle-bicycle conflict and so on.

  12. 2D hydrodynamic simulations of a variable length gas target for density down-ramp injection of electrons into a laser wakefield accelerator

    NASA Astrophysics Data System (ADS)

    Kononenko, O.; Lopes, N. C.; Cole, J. M.; Kamperidis, C.; Mangles, S. P. D.; Najmudin, Z.; Osterhoff, J.; Poder, K.; Rusby, D.; Symes, D. R.; Warwick, J.; Wood, J. C.; Palmer, C. A. J.

    2016-09-01

    In this work, two-dimensional (2D) hydrodynamic simulations of a variable length gas cell were performed using the open source fluid code OpenFOAM. The gas cell was designed to study controlled injection of electrons into a laser-driven wakefield at the Astra Gemini laser facility. The target consists of two compartments: an accelerator and an injector section connected via an aperture. A sharp transition between the peak and plateau density regions in the injector and accelerator compartments, respectively, was observed in simulations with various inlet pressures. The fluid simulations indicate that the length of the down-ramp connecting the sections depends on the aperture diameter, as does the density drop outside the entrance and the exit cones. Further studies showed, that increasing the inlet pressure leads to turbulence and strong fluctuations in density along the axial profile during target filling, and consequently, is expected to negatively impact the accelerator stability.

  13. Intramolecular vibrational energy redistribution and intermolecular energy transfer of benzene in supercritical CO 2: measurements from the gas phase up to liquid densities

    NASA Astrophysics Data System (ADS)

    von Benten, R.; Charvat, A.; Link, O.; Abel, B.; Schwarzer, D.

    2004-03-01

    Femtosecond pump probe spectroscopy was employed to measure intramolecular vibrational energy redistribution (IVR) and intermolecular vibrational energy transfer (VET) of benzene in the gas phase and in supercritical (sc) CO 2. We observe two IVR time scales the faster of which proceeds within τ IVR(1)<0.5 ps. The slower IVR component has a time constant of τ IVR(2)=(48±5) ps in the gas phase and in scCO 2 is accelerated by interactions with the solvent. At the highest CO 2 density it is reduced to τ IVR(2)=(6±1) ps. The corresponding IVR rate constants show a similar density dependence as the VET rate constants. Model calculations suggest that both quantities correlate with the local CO 2 density in the immediate surrounding of the benzene molecule.

  14. Importance of Relativistic Effects and Electron Correlation in Structure Factors and Electron Density of Diphenyl Mercury and Triphenyl Bismuth.

    PubMed

    Bučinský, Lukáš; Jayatilaka, Dylan; Grabowsky, Simon

    2016-08-25

    This study investigates the possibility of detecting relativistic effects and electron correlation in single-crystal X-ray diffraction experiments using the examples of diphenyl mercury (HgPh2) and triphenyl bismuth (BiPh3). In detail, the importance of electron correlation (ECORR), relativistic effects (REL) [distinguishing between total, scalar and spin-orbit (SO) coupling relativistic effects] and picture change error (PCE) on the theoretical electron density, its topology and its Laplacian using infinite order two component (IOTC) wave functions is discussed. This is to develop an understanding of the order of magnitude and shape of these different effects as they manifest in the electron density. Subsequently, the same effects are considered for the theoretical structure factors. It becomes clear that SO and PCE are negligible, but ECORR and scalar REL are important in low- and medium-order reflections on absolute and relative scales-not in the high-order region. As a further step, Hirshfeld atom refinement (HAR) and subsequent X-ray constrained wavefunction (XCW) fitting have been performed for the compound HgPh2 with various relativistic and nonrelativistic wave functions against the experimental structure factors. IOTC calculations of theoretical structure factors and relativistic HAR as well as relativistic XCW fitting are presented for the first time, accounting for both scalar and spin-orbit relativistic effects. PMID:27434184

  15. Causal Factors of Weld Porosity in Gas Tungsten Arc Welding of Powder Metallurgy Produced Titanium Alloys

    SciTech Connect

    Muth, Thomas R; Yamamoto, Yukinori; Frederick, David Alan; Contescu, Cristian I; Chen, Wei; Lim, Yong Chae; Peter, William H; Feng, Zhili

    2013-01-01

    ORNL undertook an investigation using gas tungsten arc (GTA) welding on consolidated powder metallurgy (PM) titanium (Ti) plate, to identify the causal factors behind observed porosity in fusion welding. Tramp element compounds of sodium and magnesium, residual from the metallothermic reduction of titanium chloride used to produce the titanium, were remnant in the starting powder and were identified as gas forming species. PM-titanium made from revert scrap where sodium and magnesium were absent, showed fusion weld porosity, although to a lesser degree. We show that porosity was attributable to hydrogen from adsorbed water on the surface of the powders prior to consolidation. The removal / minimization of both adsorbed water on the surface of titanium powder and the residues from the reduction process prior to consolidation of titanium powders, are critical to achieve equivalent fusion welding success similar to that seen in wrought titanium produced via the Kroll process.

  16. Coupled Monte Carlo Probability Density Function/ SPRAY/CFD Code Developed for Modeling Gas-Turbine Combustor Flows

    NASA Technical Reports Server (NTRS)

    1995-01-01

    The success of any solution methodology for studying gas-turbine combustor flows depends a great deal on how well it can model various complex, rate-controlling processes associated with turbulent transport, mixing, chemical kinetics, evaporation and spreading rates of the spray, convective and radiative heat transfer, and other phenomena. These phenomena often strongly interact with each other at disparate time and length scales. In particular, turbulence plays an important role in determining the rates of mass and heat transfer, chemical reactions, and evaporation in many practical combustion devices. Turbulence manifests its influence in a diffusion flame in several forms depending on how turbulence interacts with various flame scales. These forms range from the so-called wrinkled, or stretched, flamelets regime, to the distributed combustion regime. Conventional turbulence closure models have difficulty in treating highly nonlinear reaction rates. A solution procedure based on the joint composition probability density function (PDF) approach holds the promise of modeling various important combustion phenomena relevant to practical combustion devices such as extinction, blowoff limits, and emissions predictions because it can handle the nonlinear chemical reaction rates without any approximation. In this approach, mean and turbulence gas-phase velocity fields are determined from a standard turbulence model; the joint composition field of species and enthalpy are determined from the solution of a modeled PDF transport equation; and a Lagrangian-based dilute spray model is used for the liquid-phase representation with appropriate consideration of the exchanges of mass, momentum, and energy between the two phases. The PDF transport equation is solved by a Monte Carlo method, and existing state-of-the-art numerical representations are used to solve the mean gasphase velocity and turbulence fields together with the liquid-phase equations. The joint composition PDF

  17. Water quality, weather and environmental factors associated with fecal indicator organism density in beach sand at two recreational marine beaches.

    PubMed

    Heaney, Christopher D; Exum, Natalie G; Dufour, Alfred P; Brenner, Kristen P; Haugland, Richard A; Chern, Eunice; Schwab, Kellogg J; Love, David C; Serre, Marc L; Noble, Rachel; Wade, Timothy J

    2014-11-01

    Recent studies showing an association between fecal indicator organisms (FIOs) in sand and gastrointestinal (GI) illness among beachgoers with sand contact have important public health implications because of the large numbers of people who recreate at beaches and engage in sand contact activities. Yet, factors that influence fecal pollution in beach sand remain unclear. During the 2007 National Epidemiological and Environmental Assessment of Recreational (NEEAR) Water Study, sand samples were collected at three locations (60 m apart) on weekend days (Sat, Sun) and holidays between June and September at two marine beaches - Fairhope Beach, AL and Goddard Beach, RI - with nearby publicly-owned treatment works (POTWs) outfalls. F(+) coliphage, enterococci, Bacteroidales, fecal Bacteroides spp., and Clostridium spp. were measured in sand using culture and qPCR-based calibrator-cell equivalent methods. Water samples were also collected on the same days, times and transects as the 144 sand samples and were assayed using the same FIO measurements. Weather and environmental data were collected at the time of sample collection. Mean FIO concentrations in sand varied over time, but not space. Enterococci CFU and CCE densities in sand were not correlated, although other FIOs in sand were. The strongest correlation between FIO density in sand and water was fecal Bacteroides CCE, followed by enterococci CFU, Clostridium spp. CCE, and Bacteroidales CCE. Overall, the factors associated with FIO concentrations in sand were related to the sand-water interface (i.e., sand-wetting) and included daily average densities of FIOs in water, rainfall, and wave height. Targeted monitoring that focuses on daily trends of sand FIO variability, combined with information about specific water quality, weather, and environmental factors may inform beach monitoring and management decisions to reduce microbial burdens in beach sand. The views expressed in this paper are those of the authors and do

  18. Water quality, weather and environmental factors associated with fecal indicator organism density in beach sand at two recreational marine beaches

    PubMed Central

    Heaney, Christopher D.; Exum, Natalie G.; Dufour, Alfred P.; Brenner, Kristen P.; Haugland, Richard A.; Chern, Eunice; Schwab, Kellogg J.; Love, David C.; Serre, Marc L.; Noble, Rachel; Wade, Timothy J.

    2015-01-01

    Recent studies showing an association between fecal indicator organisms (FIOs) in sand and gastrointestinal (GI) illness among beachgoers with sand contact have important public health implications because of the large numbers of people who recreate at beaches and engage in sand contact activities. Yet, factors that influence fecal pollution in beach sand remain unclear. During the 2007 National Epidemiological and Environmental Assessment of Recreational (NEEAR) Water Study, sand samples were collected at three locations (60 m apart) on weekend days (Sat, Sun) and holidays between June and September at two marine beaches — Fairhope Beach, AL and Goddard Beach, RI — with nearby publicly-owned treatment works (POTWs) outfalls. F+ coliphage, enterococci, Bacteroidales, fecal Bacteroides spp., and Clostridium spp. were measured in sand using culture and qPCR-based calibrator-cell equivalent methods. Water samples were also collected on the same days, times and transects as the 144 sand samples and were assayed using the same FIO measurements. Weather and environmental data were collected at the time of sample collection. Mean FIO concentrations in sand varied over time, but not space. Enterococci CFU and CCE densities in sand were not correlated, although other FIOs in sand were. The strongest correlation between FIO density in sand and water was fecal Bacteroides CCE, followed by enterococci CFU, Clostridium spp. CCE, and Bacteroidales CCE. Overall, the factors associated with FIO concentrations in sand were related to the sand–water interface (i.e., sand-wetting) and included daily average densities of FIOs in water, rainfall, and wave height. Targeted monitoring that focuses on daily trends of sand FIO variability, combined with information about specific water quality, weather, and environmental factors may inform beach monitoring and management decisions to reduce microbial burdens in beach sand. The views expressed in this paper are those of the authors

  19. Targeting of Tumor Necrosis Factor Receptor 1 to Low Density Plasma Membrane Domains in Human Endothelial Cells*

    PubMed Central

    D'Alessio, Alessio; Kluger, Martin S.; Li, Jie H.; Al-Lamki, Rafia; Bradley, John R.; Pober, Jordan S.

    2010-01-01

    TNFR1 (tumor necrosis factor receptor 1) localizes to caveolae of human endothelial-derived EA.hy926 cells. Transduced TNFR1 molecules lacking amino acid residues 229–244 (spanning the transmembrane/intercellular boundary) are expressed on the cell surface equivalently to full-length TNFR1 molecules but incompletely localize to caveolae. A peptide containing this sequence pulls down CAV-1 (caveolin-1) and TNFR1 from cell lysates but fails to do so following disruption of caveolae with methyl-β-cyclodextrin. We previously reported that methyl-β-cyclodextrin eliminates caveolae and blocks tumor necrosis factor (TNF)-induced internalization of TNFR1 but not TNF-induced activation of NF-κB in EA.hy926 cells. Both CAV-1 and FLOT-2 (flotillin-2), organizing proteins of caveolae and lipid rafts, respectively, associate with caveolae in EA.hy926 cells. Small interfering RNA-mediated knockdown of CAV-1 but not FLOT-2 strikingly reduces caveolae number. Both knockdowns reduce total TNFR1 protein expression, but neither prevents TNFR1 localization to low density membrane domains, TNF-induced internalization of TNFR1, or NF-κB activation by TNF. Both CAV-1 and FLOT-2 knockdowns reduce TNF-mediated activation of stress-activated protein kinase (SAPK). However, both knockdowns reduce expression of TRAF2 (TNF receptor-associated factor-2) protein, and small interfering RNA targeting of TRAF2 also selectively inhibits SAPK activation. We conclude that TNFR1 contains a membrane-proximal sequence that targets the receptor to caveolae/lipid rafts. Neither TNFR1 targeting to nor internalization from these low density membrane domains depends upon CAV-1 or FLOT-2. Furthermore, both NF-κB and SAPK activation appear independent of both TNFR1 localization to low density membrane domains and to TNF-induced receptor internalization. PMID:20511226

  20. The Penetration Behavior of an Annular Gas-Solid Jet Impinging on a Liquid Bath: The Effects of the Density and Size of Solid Particles

    NASA Astrophysics Data System (ADS)

    Chang, J. S.; Sohn, H. Y.

    2012-08-01

    Top-blow injection of a gas-solid jet through a circular lance is used in the Mitsubishi Continuous Smelting Process. One problem associated with this injection is the severe erosion of the hearth refractory below the lances. A new configuration of the lance to form an annular gas-solid jet rather than the circular jet was designed in this laboratory. With this new configuration, the solid particles fed through the center tube leave the lance at a much lower velocity than the gas, and the penetration behavior of the jet is significantly different from that with a circular lance where the solid particles leave the lance at the same high velocity as the gas. In previous cold-model investigations in this laboratory, the effects of the gas velocity, particle feed rate, lance height of the annular lance, and the cross-sectional area of the gas jet were studied and compared with the circular lance. This study examined the effect of the density and size of the solid particles on the penetration behavior of the annular gas-solid jet, which yielded some unexpected results. The variation in the penetration depth with the density of the solid particles at the same mass feed rate was opposite for the circular lance and the annular lance. In the case of the circular lance, the penetration depth became shallower as the density of the solid particles increased; on the contrary, for the annular lance, the penetration depth became deeper with the increasing density of particles. However, at the same volumetric feed rate of the particles, the density effect was small for the circular lance, but for the annular lance, the jets with higher density particles penetrated more deeply. The variation in the penetration depth with the particle diameter was also different for the circular and the annular lances. With the circular lance, the penetration depth became deeper as the particle size decreased for all the feed rates, but with the annular lance, the effect of the particle size was

  1. A new method to improve multiplication factor in micro-pixel avalanche photodiodes with high pixel density

    NASA Astrophysics Data System (ADS)

    Sadygov, Z.; Ahmadov, F.; Khorev, S.; Sadigov, A.; Suleymanov, S.; Madatov, R.; Mehdiyeva, R.; Zerrouk, F.

    2016-07-01

    Presented is a new model describing development of the avalanche process in time, taking into account the dynamics of electric field within the depleted region of the diode and the effect of parasitic capacitance shunting individual quenching micro-resistors on device parameters. Simulations show that the effective capacitance of a single pixel, which defines the multiplication factor, is the sum of the pixel capacitance and a parasitic capacitance shunting its quenching micro-resistor. Conclusions obtained as a result of modeling open possibilities of improving the pixel gain in micropixel avalanche photodiodes with high pixel density (or low pixel capacitance).

  2. Methanogenic pathways of coal-bed gas in the Powder River Basin, United States: The geologic factor

    USGS Publications Warehouse

    Flores, R.M.; Rice, C.A.; Stricker, G.D.; Warden, A.; Ellis, M.S.

    2008-01-01

    Coal-bed gas of the Tertiary Fort Union and Wasatch Formations in the Powder River Basin in Wyoming and Montana, U.S. was interpreted as microbial in origin by previous studies based on limited data on the gas and water composition and isotopes associated with the coal beds. To fully evaluate the microbial origin of the gas and mechanisms of methane generation, additional data for 165 gas and water samples from 7 different coal-bed methane-bearing coal-bed reservoirs were collected basinwide and correlated to the coal geology and stratigraphy. The C1/(C2 + C3) ratio and vitrinite reflectance of coal and organic shale permitted differentiation between microbial gas and transitional thermogenic gas in the central part of the basin. Analyses of methane ??13C and ??D, carbon dioxide ??13C, and water ??D values indicate gas was generated primarily from microbial CO2 reduction, but with significant gas generated by microbial methyl-type fermentation (aceticlastic) in some areas of the basin. Microbial CO2 reduction occurs basinwide, but is generally dominant in Paleocene Fort Union Formation coals in the central part of the basin, whereas microbial methyl-type fermentation is common along the northwest and east margins. Isotopically light methane ??13C is distributed along the basin margins where ??D is also depleted, indicating that both CO2-reduction and methyl-type fermentation pathways played major roles in gas generation, but gas from the latter pathway overprinted gas from the former pathway. More specifically, along the northwest basin margin gas generation by methyl-type fermentation may have been stimulated by late-stage infiltration of groundwater recharge from clinker areas, which flowed through highly fractured and faulted coal aquifers. Also, groundwater recharge controlled a change in gas composition in the shallow Eocene Wasatch Formation with the increase of nitrogen and decrease of methane composition of the coal-bed gas. Other geologic factors, such as

  3. A hierarchy of factors influence discontinuous gas exchange in the grasshopper Paracinema tricolor (Orthoptera: Acrididae).

    PubMed

    Groenewald, Berlizé; Chown, Steven L; Terblanche, John S

    2014-10-01

    The evolutionary origin and maintenance of discontinuous gas exchange (DGE) in tracheate arthropods are poorly understood and highly controversial. We investigated prioritization of abiotic factors in the gas exchange control cascade by examining oxygen, water and haemolymph pH regulation in the grasshopper Paracinema tricolor. Using a full-factorial design, grasshoppers were acclimated to hypoxic or hyperoxic (5% O2, 40% O2) gas conditions, or dehydrated or hydrated, whereafter their CO2 release was measured under a range of O2 and relative humidity (RH) conditions (5%, 21%, 40% O2 and 5%, 60%, 90% RH). DGE was significantly less common in grasshoppers acclimated to dehydrating conditions compared with the other acclimations (hypoxia, 98%; hyperoxia, 100%; hydrated, 100%; dehydrated, 67%). Acclimation to dehydrating conditions resulted in a significant decrease in haemolymph pH from 7.0±0.3 to 6.6±0.1 (mean ± s.d., P=0.018) and also significantly increased the open (O)-phase duration under 5% O2 treatment conditions (5% O2, 44.1±29.3 min; 40% O2, 15.8±8.0 min; 5% RH, 17.8±1.3 min; 60% RH, 24.0±9.7 min; 90% RH, 20.6±8.9 min). The observed acidosis could potentially explain the extension of the O-phase under low RH conditions, when it would perhaps seem more useful to reduce the O-phase to lower respiratory water loss. The results confirm that DGE occurrence and modulation are affected by multiple abiotic factors. A hierarchical framework for abiotic factors influencing DGE is proposed in which the following stressors are prioritized in decreasing order of importance: oxygen supply, CO2 excretion and pH modulation, oxidative damage protection and water savings. PMID:25063854

  4. A new insight on the gas phase retro-Diels-Alder reaction of bicyclic compounds: density functional theory calculations

    NASA Astrophysics Data System (ADS)

    Mora, Jose R.; Lezama, Jesús; Córdova-Sintjago, Tania C.; Chuchani, Gabriel

    2015-11-01

    The mechanisms of the gas-phase thermal decomposition of bicyclo[2.2.1]heptadiene and 3,7,7-trimethylbicyclo[2.2.1]hept-2-ene were examined by density functional theory calculations with the hybrid functionals: B3LYP, CAM-B3LYP, MPW1PW91, and PBEPBE. Reasonable agreements were found between theoretical and experimental values with the B3LYP hybrid functional. Three molecular concerted pathways for bicyclo[2.2.1]heptadiene decomposition are proposed. The retro-Diels-Alder (retro-DA) pathway yields cyclopentadiene and acetylene through a nearly synchronous transition state structure (Sy = 0.97). The other two reaction channels are stepwise with a common step with the formation of the intermediate bicyclo[4.1.0] heptadiene. This reaction is dominated by C-C bond breaking leading to the methylene migration by an early transition state in the reaction coordinate (Sy = 0.91). The rearrangements of the latter intermediate producing toluene were also studied. The retro-DA elimination of 3,7,7-trimethylbicyclo[2.2.1]hept-2-ene gives 1,5,5-trimethyl-cyclopenta-1,3-diene in a less synchronous process (Sy = 0.77). This fact may be due to the electronic effects of the methyl substituent. The latter product is unstable and undergoes methyl migrations to give a more stable isomer 1,2,3-trimethylcyclopenta-1,3-diene. The stepwise mechanism for the retro-DA reaction through a biradical intermediate appears to be unfavourable because the barrier is bigger than that for the concerted reaction.

  5. Symmetric reflection line resonator and its quality factor modulation by a two-dimensional electron gas

    SciTech Connect

    Zhang, Miao-Lei; Deng, Guang-Wei; Li, Shu-Xiao; Li, Hai-Ou; Cao, Gang; Tu, Tao; Xiao, Ming; Guo, Guang-Can; Guo, Guo-Ping; Jiang, Hong-Wen; Siddiqi, Irfan

    2014-02-24

    We have designed and fabricated a half-wavelength reflection line resonator that consists of a pair of coupled microstrip lines on a GaAs/AlGaAs heterostructure. By changing the top gate voltage on a small square with a two-dimensional electron gas under the resonator, the quality factor was tuned over a large range from 2700 to below 600. Apart from being of fundamental interest, this gate modulation technique has the potential for use in on-chip resonator applications.

  6. X-RAY SCALING RELATION IN EARLY-TYPE GALAXIES: DARK MATTER AS A PRIMARY FACTOR IN RETAINING HOT GAS

    SciTech Connect

    Kim, Dong-Woo; Fabbiano, Giuseppina

    2013-10-20

    We have revisited the X-ray scaling relations of early-type galaxies (ETG) by investigating, for the first time, the L{sub X,Gas}-M{sub Total} relation in a sample of 14 ETGs. In contrast to the large scatter (a factor of 10{sup 2}-10{sup 3}) in the L{sub X,Total}-L{sub B} relation, we found a tight correlation between these physically motivated quantities with an rms deviation of a factor of three in L{sub X,Gas} = 10{sup 38}-10{sup 43} erg s{sup –1} or M{sub Total} = a few × 10{sup 10} to a few × 10{sup 12} M{sub ☉}. More striking, this relation becomes even tighter with an rms deviation of a factor of 1.3 among the gas-rich galaxies (with L{sub X,Gas} > 10{sup 40} erg s{sup –1}). In a simple power-law form, the new relation is (L{sub X,Gas}/10{sup 40} erg s{sup –1}) = (M{sub Total}/3.2 × 10{sup 11} M{sub ☉}){sup 3}. This relation is also consistent with the steep relation between the gas luminosity and temperature, L{sub X,Gas} ∼ T{sub Gas} {sup 4.5}, identified by Boroson et al., if the gas is virialized. Our results indicate that the total mass of an ETG is the primary factor in regulating the amount of hot gas. Among the gas-poor galaxies (with L{sub X,Gas} < a few × 10{sup 39} erg s{sup –1}), the scatter in the L{sub X,Gas}-M{sub Total} (and L{sub X,Gas}-T{sub Gas}) relation increases, suggesting that secondary factors (e.g., rotation, flattening, star formation history, cold gas, environment, etc.) may become important.

  7. Soil biotransformation of thiodiglycol, the hydrolysis product of mustard gas: understanding the factors governing remediation of mustard gas contaminated soil.

    PubMed

    Li, Hong; Muir, Robert; McFarlane, Neil R; Soilleux, Richard J; Yu, Xiaohong; Thompson, Ian P; Jackman, Simon A

    2013-02-01

    Thiodiglycol (TDG) is both the precursor for chemical synthesis of mustard gas and the product of mustard gas hydrolysis. TDG can also react with intermediates of mustard gas degradation to form more toxic and/or persistent aggregates, or reverse the pathway of mustard gas degradation. The persistence of TDG have been observed in soils and in the groundwater at sites contaminated by mustard gas 60 years ago. The biotransformation of TDG has been demonstrated in three soils not previously exposed to the chemical. TDG biotransformation occurred via the oxidative pathway with an optimum rate at pH 8.25. In contrast with bacteria isolated from historically contaminated soil, which could degrade TDG individually, a consortium of three bacterial strains isolated from the soil never contaminated by mustard gas was able to grow on TDG in minimal medium and in hydrolysate derived from an historical mustard gas bomb. Exposure to TDG had little impacts on the soil microbial physiology or on community structure. Therefore, the persistency of TDG in soils historically contaminated by mustard gas might be attributed to the toxicity of mustard gas to microorganisms and the impact to soil chemistry during the hydrolysis. TDG biodegradation may form part of a remediation strategy for mustard gas contaminated sites, and may be enhanced by pH adjustment and aeration. PMID:22752796

  8. Factors That Contribute to Low Bone Density in Postmenopausal Women in Different Amazonian Communities

    PubMed Central

    Borba-Pinheiro, Cláudio Joaquim; Drigo, Alexandre Janotta; de Alencar Carvalho, Mauro César Gurgel; da Silva, Nádia Souza Lima; Dantas, Estélio Henrique Martin

    2011-01-01

    Background: The aim of this study was to verify socioeconomic differences, nutrition, body balance and quality of life (QoL) in postmenopausal women with low bone mineral density (BMD) in two Amazonian communities. Methods: A total of 42 female volunteers participated in the study. The volunteers were separated into two groups: Villa (n = 20; 53 ± 5.5 years) and City (n = 22; 56 ± 7.9 years). The following evaluation instruments were used: dual energy X-ray absorptiometry (DXA); a socioeconomic questionnaire; a QoL questionnaire; a dietary habits questionnaire; and a balance test. Parametric and nonparametric tests were used. Results: The data showed significant differences in socioeconomic level (Δ%=+15.9%, p = 0.000), lumbar spine L2-L4 (Δ% = +0.10%, p = 0.007), balance (Δ% = +4.3%, p = 0.03) and some important aspects of nutrition, such as the consumption of milk (Δ%=+34%, p = 0.01) and alcohol (+14.8%, p = 0.0001). These significant differences also contributed to the total QoL score (Δ%=+76.2%, p = 0.000) and the majority of the QoL-related functions. Conclusion: This study verified that socioeconomic level, nutritional status, physical activity levels and QoL can influence the BMD of postmenopausal women. The study suggests new strategies for official health organizations to use in order to prevent and treat osteoporosis. In addition, this study can provide an orientation to physical activity, nutrition and medical professionals. PMID:22870468

  9. Fracture density as a controlling factor of postglacial fluvial incision rate, Granite Range, Alaska.

    NASA Astrophysics Data System (ADS)

    Champagnac, J.-D.; Sternai, P.; Herman, F.; Guralnik, B.; Beaud, F.

    2012-04-01

    The relations between lithosphere and atmosphere to shape the landscape are disputed since the last two decades. The classical "chicken or egg" problem raised the idea that erosion can promote creation of topography thanks to isostatic compensation of eroded material and subsequent positive feedback. Quaternary glaciations and high erosion rates are supposed to be the main agent of such process. More recently, "tectonic activity" has been considered not only as a rock uplift agent, but also as a rock crusher, that in turn promote erosion, thanks to the reduction of size of individual rock elements, more easily transported. The Granite Range in Alaska presents a contrasted morphology: its western part shows preserved glacial landscape, whereas its eastern part presents a strong fluvial / hillslope imprint, and only a few relicts of glacial surfaces. We quantify these differences by 1) qualitative appreciation of the landscape, 2) quantification of post-glacial erosion, and 3) hypsometric quantification of the landscape. On the field, the eastern part appears to be highly fractured, with many, large, penetrative faults, associated with km-thick fault gouges and cataclasites. The westernmost part shows massive bedrock, with minor, localised faults. Remote-sensed fracture mapping confirms this: fracture density is much higher to the east, where hypsometric parameters (HI and HIP) display anomalies, and where high post-glacial incision (up to 600m) is observed. We provide here an impressive case study for tectonic-erosion interactions through rock crushing effect, and document that half of the sediments coming out of the range come from the ~10% of the most fractured area, all other being equal. This challenges the usual view of tectonic "driving" rock uplift, while erosion removes material: In our case, tectonics is the main erosional agent, rivers and glaciers being (efficient) transport agents.

  10. Forebody and base region real gas flow in severe planetary entry by a factored implicit numerical method. II - Equilibrium reactive gas

    NASA Technical Reports Server (NTRS)

    Davy, W. C.; Green, M. J.; Lombard, C. K.

    1981-01-01

    The factored-implicit, gas-dynamic algorithm has been adapted to the numerical simulation of equilibrium reactive flows. Changes required in the perfect gas version of the algorithm are developed, and the method of coupling gas-dynamic and chemistry variables is discussed. A flow-field solution that approximates a Jovian entry case was obtained by this method and compared with the same solution obtained by HYVIS, a computer program much used for the study of planetary entry. Comparison of surface pressure distribution and stagnation line shock-layer profiles indicates that the two solutions agree well.

  11. Absolute CF{sub 2} density and gas temperature measurements by absorption spectroscopy in dual-frequency capacitively coupled CF{sub 4}/Ar plasmas

    SciTech Connect

    Liu, Wen-Yao; Xu, Yong Peng, Fei; Gong, Fa-Ping; Li, Xiao-Song; Zhu, Ai-Min; Liu, Yong-Xin; Wang, You-Nian

    2014-10-15

    Broadband ultraviolet absorption spectroscopy has been used to determine the CF{sub 2} radical density in dual-frequency capacitively coupled CF{sub 4}/Ar plasmas, using the CF{sub 2} A{sup ~1}B{sub 1}←X{sup ~1}A{sub 1} system of absorption spectrum. The rotational temperature of ground state CF{sub 2} and excited state CF was also estimated by using A{sup ~1}B{sub 1}←X{sup ~1}A{sub 1} system and B{sup 2}Δ−X{sup 2}Π system, respectively. The translational gas temperature was deduced from the Doppler width of the Ar{sup *}({sup 3}P{sub 2}) and Ar{sup *}({sup 3}P{sub 0}) metastable atoms absorption line by using the tunable diode laser absorption spectroscopy. The rotational temperatures of the excited state CF are about 100 K higher than those of ground state CF{sub 2}, and about 200 K higher than the translational gas temperatures. The dependences of the radical CF{sub 2} density, electron density, electron temperature, rotational temperature, and gas temperature on the high frequency power and pressure have been analyzed. Furthermore, the production and loss mechanisms of CF{sub 2} radical and the gas heating mechanisms have also been discussed.

  12. 40 CFR Table W - 5 of Subpart W of Part 98-Default Methane Emission Factors for Liquefied Natural Gas (LNG) Storage

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... Methane Emission Factors for Liquefied Natural Gas (LNG) Storage W Table W Protection of Environment... Petroleum and Natural Gas Systems Definitions. Pt. 98, Subpt. W, Table W-5 Table W-5 of Subpart W of Part 98—Default Methane Emission Factors for Liquefied Natural Gas (LNG) Storage LNG storage Emission factor...

  13. 40 CFR Table W - 5 of Subpart W of Part 98-Default Methane Emission Factors for Liquefied Natural Gas (LNG) Storage

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... Methane Emission Factors for Liquefied Natural Gas (LNG) Storage W Table W Protection of Environment... Petroleum and Natural Gas Systems Definitions. Pt. 98, Subpt. W, Table W-5 Table W-5 of Subpart W of Part 98—Default Methane Emission Factors for Liquefied Natural Gas (LNG) Storage LNG storage Emission factor...

  14. Flying-Fox Species Density - A Spatial Risk Factor for Hendra Virus Infection in Horses in Eastern Australia

    PubMed Central

    Smith, Craig; Skelly, Chris; Kung, Nina; Roberts, Billie; Field, Hume

    2014-01-01

    Hendra virus causes sporadic but typically fatal infection in horses and humans in eastern Australia. Fruit-bats of the genus Pteropus (commonly known as flying-foxes) are the natural host of the virus, and the putative source of infection in horses; infected horses are the source of human infection. Effective treatment is lacking in both horses and humans, and notwithstanding the recent availability of a vaccine for horses, exposure risk mitigation remains an important infection control strategy. This study sought to inform risk mitigation by identifying spatial and environmental risk factors for equine infection using multiple analytical approaches to investigate the relationship between plausible variables and reported Hendra virus infection in horses. Spatial autocorrelation (Global Moran’s I) showed significant clustering of equine cases at a distance of 40 km, a distance consistent with the foraging ‘footprint’ of a flying-fox roost, suggesting the latter as a biologically plausible basis for the clustering. Getis-Ord Gi* analysis identified multiple equine infection hot spots along the eastern Australia coast from far north Queensland to central New South Wales, with the largest extending for nearly 300 km from southern Queensland to northern New South Wales. Geographically weighted regression (GWR) showed the density of P. alecto and P. conspicillatus to have the strongest positive correlation with equine case locations, suggesting these species are more likely a source of infection of Hendra virus for horses than P. poliocephalus or P. scapulatus. The density of horses, climate variables and vegetation variables were not found to be a significant risk factors, but the residuals from the GWR suggest that additional unidentified risk factors exist at the property level. Further investigations and comparisons between case and control properties are needed to identify these local risk factors. PMID:24936789

  15. Flying-fox species density--a spatial risk factor for Hendra virus infection in horses in eastern Australia.

    PubMed

    Smith, Craig; Skelly, Chris; Kung, Nina; Roberts, Billie; Field, Hume

    2014-01-01

    Hendra virus causes sporadic but typically fatal infection in horses and humans in eastern Australia. Fruit-bats of the genus Pteropus (commonly known as flying-foxes) are the natural host of the virus, and the putative source of infection in horses; infected horses are the source of human infection. Effective treatment is lacking in both horses and humans, and notwithstanding the recent availability of a vaccine for horses, exposure risk mitigation remains an important infection control strategy. This study sought to inform risk mitigation by identifying spatial and environmental risk factors for equine infection using multiple analytical approaches to investigate the relationship between plausible variables and reported Hendra virus infection in horses. Spatial autocorrelation (Global Moran's I) showed significant clustering of equine cases at a distance of 40 km, a distance consistent with the foraging 'footprint' of a flying-fox roost, suggesting the latter as a biologically plausible basis for the clustering. Getis-Ord Gi* analysis identified multiple equine infection hot spots along the eastern Australia coast from far north Queensland to central New South Wales, with the largest extending for nearly 300 km from southern Queensland to northern New South Wales. Geographically weighted regression (GWR) showed the density of P. alecto and P. conspicillatus to have the strongest positive correlation with equine case locations, suggesting these species are more likely a source of infection of Hendra virus for horses than P. poliocephalus or P. scapulatus. The density of horses, climate variables and vegetation variables were not found to be a significant risk factors, but the residuals from the GWR suggest that additional unidentified risk factors exist at the property level. Further investigations and comparisons between case and control properties are needed to identify these local risk factors. PMID:24936789

  16. Measurement of plasma density in the discharge maintained in a nonuniform gas flow by a high-power terahertz-wave gyrotron

    NASA Astrophysics Data System (ADS)

    Sidorov, A. V.; Razin, S. V.; Golubev, S. V.; Safronova, M. I.; Fokin, A. P.; Luchinin, A. G.; Vodopyanov, A. V.; Glyavin, M. Yu.

    2016-04-01

    We performed measurements of plasma density in a "point-like" discharge, which is generated in a nonuniform flow of a gas (argon) under the action of high-power terahertz gyrotron radiation with a frequency of 0.67 THz, a power of 40 kW, and a pulse duration of 20 μs. The nonuniform flow was produced by injecting the gas to the vacuum chamber through a small hole (0.14 mm in diameter) under a background pressure at a level of 0.01 Torr. The discharge developed and was localized only in a small region of space (about 1 mm) near the gas injection hole, where the pressure was high (close to the atmospheric one) and the breakdown conditions (the "point-like" discharge) were fulfilled. The density of electrons in the discharge was measured by observing the Stark broadening of the atomic radiation line Hα of hydrogen (656.3 nm) which was present in the discharge as a minor admixture. The plasma density in the discharge was equal to about 2 × 1016 cm-3, which exceeds the cut-off density for a frequency of 0.67 THz used to maintain the discharge.

  17. Dynamic density functional theory with hydrodynamic interactions: theoretical development and application in the study of phase separation in gas-liquid systems.

    PubMed

    Kikkinides, E S; Monson, P A

    2015-03-01

    Building on recent developments in dynamic density functional theory, we have developed a version of the theory that includes hydrodynamic interactions. This is achieved by combining the continuity and momentum equations eliminating velocity fields, so the resulting model equation contains only terms related to the fluid density and its time and spatial derivatives. The new model satisfies simultaneously continuity and momentum equations under the assumptions of constant dynamic or kinematic viscosity and small velocities and/or density gradients. We present applications of the theory to spinodal decomposition of subcritical temperatures for one-dimensional and three-dimensional density perturbations for both a van der Waals fluid and for a lattice gas model in mean field theory. In the latter case, the theory provides a hydrodynamic extension to the recently studied dynamic mean field theory. We find that the theory correctly describes the transition from diffusive phase separation at short times to hydrodynamic behaviour at long times. PMID:25747098

  18. Dynamic density functional theory with hydrodynamic interactions: Theoretical development and application in the study of phase separation in gas-liquid systems

    SciTech Connect

    Kikkinides, E. S.; Monson, P. A.

    2015-03-07

    Building on recent developments in dynamic density functional theory, we have developed a version of the theory that includes hydrodynamic interactions. This is achieved by combining the continuity and momentum equations eliminating velocity fields, so the resulting model equation contains only terms related to the fluid density and its time and spatial derivatives. The new model satisfies simultaneously continuity and momentum equations under the assumptions of constant dynamic or kinematic viscosity and small velocities and/or density gradients. We present applications of the theory to spinodal decomposition of subcritical temperatures for one-dimensional and three-dimensional density perturbations for both a van der Waals fluid and for a lattice gas model in mean field theory. In the latter case, the theory provides a hydrodynamic extension to the recently studied dynamic mean field theory. We find that the theory correctly describes the transition from diffusive phase separation at short times to hydrodynamic behaviour at long times.

  19. Dynamic density functional theory with hydrodynamic interactions: Theoretical development and application in the study of phase separation in gas-liquid systems

    NASA Astrophysics Data System (ADS)

    Kikkinides, E. S.; Monson, P. A.

    2015-03-01

    Building on recent developments in dynamic density functional theory, we have developed a version of the theory that includes hydrodynamic interactions. This is achieved by combining the continuity and momentum equations eliminating velocity fields, so the resulting model equation contains only terms related to the fluid density and its time and spatial derivatives. The new model satisfies simultaneously continuity and momentum equations under the assumptions of constant dynamic or kinematic viscosity and small velocities and/or density gradients. We present applications of the theory to spinodal decomposition of subcritical temperatures for one-dimensional and three-dimensional density perturbations for both a van der Waals fluid and for a lattice gas model in mean field theory. In the latter case, the theory provides a hydrodynamic extension to the recently studied dynamic mean field theory. We find that the theory correctly describes the transition from diffusive phase separation at short times to hydrodynamic behaviour at long times.

  20. Molecular gas in low-metallicity starburst galaxies:. Scaling relations and the CO-to-H2 conversion factor

    NASA Astrophysics Data System (ADS)

    Amorín, R.; Muñoz-Tuñón, C.; Aguerri, J. A. L.; Planesas, P.

    2016-04-01

    Context. Tracing the molecular gas-phase in low-mass star-forming galaxies becomes extremely challenging due to significant UV photo-dissociation of CO molecules in their low-dust, low-metallicity ISM environments. Aims: We aim to study the molecular content and the star-formation efficiency of a representative sample of 21 blue compact dwarf galaxies (BCDs), previously characterized on the basis of their spectrophotometric properties. Methods: We present CO (1-0) and (2-1) observations conducted at the IRAM-30m telescope. These data are further supplemented with additional CO measurements and multiwavelength ancillary data from the literature. We explore correlations between the derived CO luminosities and several galaxy-averaged properties. Results: We detect CO emission in seven out of ten BCDs observed. For two galaxies these are the first CO detections reported so far. We find the molecular content traced by CO to be correlated with the stellar and Hi masses, star formation rate (SFR) tracers, the projected size of the starburst, and its gas-phase metallicity. BCDs appear to be systematically offset from the Schmidt-Kennicutt (SK) law, showing lower average gas surface densities for a given ΣSFR, and therefore showing extremely low (≲0.1 Gyr) H2 and H2 +Hi depletion timescales. The departure from the SK law is smaller when considering H2 +Hi rather than H2 only, and is larger for BCDs with lower metallicity and higher specific SFR. Thus, the molecular fraction (ΣH2/ ΣHI) and CO depletion timescale (ΣH2/ ΣSFR) of BCDs is found to be strongly correlated with metallicity. Using this, and assuming that the empirical correlation found between the specific SFR and galaxy-averaged H2 depletion timescale of more metal-rich galaxies extends to lower masses, we derive a metallicity-dependent CO-to-H2 conversion factor αCO,Z ∝ (Z/Z⊙)- y, with y = 1.5(±0.3)in qualitative agreement with previous determinations, dust-based measurements, and recent model

  1. Influence factors on the flue gas desulfurization in the circulating fluidized bed reactor

    SciTech Connect

    Gao, J.; Tang, D.; Liu, H.; Suzuki, Yoshizo; Kito, Nobo

    1997-12-31

    This paper describes a dry SO{sub 2} removal method -- the absorbent (Ca(OH){sub 2}) was injected into the Circulating Fluidized Bed (CFB) reactor at the coolside of the duct to abate SO{sub 2} in the flue gas -- with the potential to significantly enhance desulfurization performance over that of existing dry/semi-dry Flue Gas Desulfurization (FGD) technology such as Spray Drying. A patent for coolside Flue Gas Desulfurization in the Circulating Fluidized Bed reactor (CFB-FGD) was approved by the China Patent Bureau in September of 1995 and the additional laboratory experiment was carried out in an electrically heated bench scale quartz circulating fluidized bed reactor of 2350mm in height and 23mm in diameter in January, 1996. The influences of steam, ratio of calcium and sulfur, reactor temperature, and absorbent utilization efficiency were invested. The results show that: (1) Water steam plays a key role in the reaction of Ca(OH){sub 2} and SO{sub 2} in the CFB reactor; (2) There is a positive effect of Ca/S on SO{sub 2} removal efficiency; (3) The temperature is an another key factor for SO{sub 2} removal efficiency for the CFB-FGD process; (4) The absorbent can be enhanced in the CFB reactor; (5) The CFB reactor is better than the dry/semi-dry FDG technology. SO{sub 2} removal efficiency can be as high as 84.8%.

  2. Reduced vascular endothelial growth factor and capillary density in the occipital cortex in dementia with Lewy bodies.

    PubMed

    Miners, Scott; Moulding, Hayley; de Silva, Rohan; Love, Seth

    2014-07-01

    In dementia with Lewy bodies (DLB), blood flow tends to be reduced in the occipital cortex. We previously showed elevated activity of the endothelin and angiotensin pathways in Alzheimer's disease (AD). We have measured endothelin-1 (ET-1) level and angiotensin-converting enzyme (ACE) activity in the occipital cortex in DLB and control brains. We also measured vascular endothelial growth factor (VEGF); factor VIII-related antigen (FVIIIRA) to indicate microvessel density; myelin-associated glycoprotein (MAG), a marker of ante-mortem hypoperfusion; total α-synuclein (α-syn) and α-synuclein phosphorylated at Ser129 (α-syn-p129). In contrast to findings in AD, ACE activity and ET-1 level were unchanged in DLB compared with controls. VEGF and FVIIIRA levels were, however, significantly lower in DLB. VEGF correlated positively with MAG concentration (in keeping with a relationship between reduction in VEGF and hypoperfusion), and negatively with α-syn and α-syn-p129 levels. Both α-syn and α-syn-p129 levels increased in human SH-SY5Y neuroblastoma cells after oxygen-glucose deprivation (OGD), and VEGF level was reduced in SH-SY5Y cells overexpressing α-syn. Taken together, our findings suggest that reduced microvessel density rather than vasoconstriction is responsible for lower occipital blood flow in DLB, and that the loss of microvessels may result from VEGF deficiency, possible secondary to the accumulation of α-syn. PMID:24521289

  3. Competition among native and invasive Impatiens species: the roles of environmental factors, population density and life stage

    PubMed Central

    Čuda, Jan; Skálová, Hana; Janovský, Zdeněk; Pyšek, Petr

    2015-01-01

    Many invasive species are considered competitively superior to native species, with the strongest competition expected in species with similar niches and/or in closely related species. However, competition outcome is strongly context-dependent as competitive strength varies along environmental gradients, and life stages, and also depends on abundances. To explore the importance of these factors, we examined competition effects in an experiment with three Impatiens species (Balsaminaceae) widespread in central Europe and sharing similar life-history characteristics and habitats: the native I. noli-tangere, and two invasive species, I. parviflora and I. glandulifera. We compared their competitive strength and reciprocal impacts under two levels of water and light availability, two overall planting densities and three competitor densities. We assessed species performance (ability to complete the life-cycle, biomass and fecundity) and temporal competition dynamics in a garden pot experiment. Environmental variables had lower explanatory power than overall planting and competitor density, which indicates the importance of competitive interactions when evaluating plant performance and potential invasion success. Despite poor and delayed germination, the invasive I. glandulifera attained dominance even at a high competitor density and was competitively superior across all treatments, exceeding the height of both congeners. Impatiens parviflora was competitively weakest, having a negligible impact on both native I. noli-tangere and invasive I. glandulifera. The intermediate competitive strength of the native I. noli-tangere probably results from its intermediate height, and good germination rate and timing. The difference in height among species increased during the experiment when I. glandulifera was involved; this species continues growing until autumn, enhancing its competitive superiority. The results provide a mechanistic understanding for the competitive exclusion of

  4. Competition among native and invasive Impatiens species: the roles of environmental factors, population density and life stage.

    PubMed

    Čuda, Jan; Skálová, Hana; Janovský, Zdeněk; Pyšek, Petr

    2015-01-01

    Many invasive species are considered competitively superior to native species, with the strongest competition expected in species with similar niches and/or in closely related species. However, competition outcome is strongly context-dependent as competitive strength varies along environmental gradients, and life stages, and also depends on abundances. To explore the importance of these factors, we examined competition effects in an experiment with three Impatiens species (Balsaminaceae) widespread in central Europe and sharing similar life-history characteristics and habitats: the native I. noli-tangere, and two invasive species, I. parviflora and I. glandulifera. We compared their competitive strength and reciprocal impacts under two levels of water and light availability, two overall planting densities and three competitor densities. We assessed species performance (ability to complete the life-cycle, biomass and fecundity) and temporal competition dynamics in a garden pot experiment. Environmental variables had lower explanatory power than overall planting and competitor density, which indicates the importance of competitive interactions when evaluating plant performance and potential invasion success. Despite poor and delayed germination, the invasive I. glandulifera attained dominance even at a high competitor density and was competitively superior across all treatments, exceeding the height of both congeners. Impatiens parviflora was competitively weakest, having a negligible impact on both native I. noli-tangere and invasive I. glandulifera. The intermediate competitive strength of the native I. noli-tangere probably results from its intermediate height, and good germination rate and timing. The difference in height among species increased during the experiment when I. glandulifera was involved; this species continues growing until autumn, enhancing its competitive superiority. The results provide a mechanistic understanding for the competitive exclusion of

  5. Emission factors for hydraulically fractured gas wells derived using well- and battery-level reported data for Alberta, Canada.

    PubMed

    Tyner, David R; Johnson, Matthew R

    2014-12-16

    A comprehensive technical analysis of available industry-reported well activity and production data for Alberta in 2011 has been used to derive flaring, venting, and diesel combustion greenhouse gas and criteria air contaminant emission factors specifically linked to drilling, completion, and operation of hydraulically fractured natural gas wells. Analysis revealed that in-line ("green") completions were used at approximately 53% of wells completed in 2011, and in other cases the majority (99.5%) of flowback gases were flared rather than vented. Comparisons with limited analogous data available in the literature revealed that reported total flared and vented natural gas volumes attributable to tight gas well-completions were ∼ 6 times larger than Canadian Association of Petroleum Producers (CAPP) estimates for natural gas well-completion based on wells ca. 2000, but 62% less than an equivalent emission factor that can be derived from U.S. EPA data. Newly derived emission factors for diesel combustion during well drilling and completion are thought to be among the first such data available in the open literature, where drilling-related emissions for tight gas wells drilled in Alberta in 2011 were found to have increased by a factor of 2.8 relative to a typical well drilled in Canada in 2000 due to increased drilling lengths. From well-by-well analysis of production phase flared, vented, and fuel usage natural gas volumes reported at 3846 operating tight gas wells in 2011, operational emission factors were developed. Overall results highlight the importance of operational phase GHG emissions at upstream well sites (including on-site natural gas fuel use), and the critical levels of uncertainty in current estimates of liquid unloading emissions. PMID:25402949

  6. Magnetic anisotropy of heteronuclear dimers in the gas phase and supported on graphene: relativistic density-functional calculations.

    PubMed

    Błoński, Piotr; Hafner, Jürgen

    2014-04-01

    The structural and magnetic properties of mixed PtCo, PtFe, and IrCo dimers in the gas phase and supported on a free-standing graphene layer have been calculated using density-functional theory, both in the scalar-relativistic limit and self-consistently including spin-orbit coupling. The influence of the strong magnetic moments of the 3d atoms on the spin and orbital moments of the 5d atoms, and the influence of the strong spin-orbit coupling contributed by the 5d atom on the orbital moments of the 3d atoms have been studied in detail. The magnetic anisotropy energy is found to depend very sensitively on the nature of the eigenstates in the vicinity of the Fermi level, as determined by band filling, exchange splitting and spin-orbit coupling. The large magnetic anisotropy energy of free PtCo and IrCo dimers relative to the easy direction parallel to the dimer axis is coupled to a strong anisotropy of the orbital magnetic moments of the Co atom for both dimers, and also on the Ir atom in IrCo. In contrast the PtFe dimer shows a weak perpendicular anisotropy and only small spin and orbital anisotropies of opposite sign on the two atoms. For dimers supported on graphene, the strong binding within the dimer and the stronger interaction of the 3d atom with the substrate stabilizes an upright geometry. Spin and orbital moments on the 3d atom are strongly quenched, but due to the weaker binding within the dimer the properties of the 5d atom are more free-atom-like with increased spin and orbital moments. The changes in the magnetic moment are reflected in the structure of the electronic eigenstates near the Fermi level, for all three dimers the easy magnetic direction is now parallel to the dimer axis and perpendicular to the graphene layer. The already very large magnetic anisotropy energy (MAE) of IrCo is further enhanced by the interaction with the support, the MAE of PtFe changes sign, and that of the PtCo dimer is reduced. These changes are discussed in relation to

  7. High density ozone monitoring using gas sensitive semi-conductor sensors in the Lower Fraser Valley, British Columbia.

    PubMed

    Bart, Mark; Williams, David E; Ainslie, Bruce; McKendry, Ian; Salmond, Jennifer; Grange, Stuart K; Alavi-Shoshtari, Maryam; Steyn, Douw; Henshaw, Geoff S

    2014-04-01

    A cost-efficient technology for accurate surface ozone monitoring using gas-sensitive semiconducting oxide (GSS) technology, solar power, and automated cell-phone communications was deployed and validated in a 50 sensor test-bed in the Lower Fraser Valley of British Columbia, over 3 months from May-September 2012. Before field deployment, the entire set of instruments was colocated with reference instruments for at least 48 h, comparing hourly averaged data. The standard error of estimate over a typical range 0-50 ppb for the set was 3 ± 2 ppb. Long-term accuracy was assessed over several months by colocation of a subset of ten instruments each at a different reference site. The differences (GSS-reference) of hourly average ozone concentration were normally distributed with mean -1 ppb and standard deviation 6 ppb (6000 measurement pairs). Instrument failures in the field were detected using network correlations and consistency checks on the raw sensor resistance data. Comparisons with modeled spatial O3 fields demonstrate the enhanced monitoring capability of a network that was a hybrid of low-cost and reference instruments, in which GSS sensors are used both to increase station density within a network as well as to extend monitoring into remote areas. This ambitious deployment exposed a number of challenges and lessons, including the logistical effort required to deploy and maintain sites over a summer period, and deficiencies in cell phone communications and battery life. Instrument failures at remote sites suggested that redundancy should be built into the network (especially at critical sites) as well as the possible addition of a "sleep-mode" for GSS monitors. At the network design phase, a more objective approach to optimize interstation distances, and the "information" content of the network is recommended. This study has demonstrated the utility and affordability of the GSS technology for a variety of applications, and the effectiveness of this

  8. Transportation Energy Futures Series: Effects of the Built Environment on Transportation: Energy Use, Greenhouse Gas Emissions, and Other Factors

    SciTech Connect

    Porter, C. D.; Brown, A.; Dunphy, R. T.; Vimmerstedt, L.

    2013-03-01

    Planning initiatives in many regions and communities aim to reduce transportation energy use, decrease emissions, and achieve related environmental benefits by changing land use. This report reviews and summarizes findings from existing literature on the relationship between the built environment and transportation energy use and greenhouse gas emissions, identifying results trends as well as potential future actions. The indirect influence of federal transportation and housing policies, as well as the direct impact of municipal regulation on land use are examined for their effect on transportation patterns and energy use. Special attention is given to the 'four D' factors of density, diversity, design and accessibility. The report concludes that policy-driven changes to the built environment could reduce transportation energy and GHG emissions from less than 1% to as much as 10% by 2050, the equivalent of 16%-18% of present-day urban light-duty-vehicle travel. This is one of a series of reports produced as a result of the Transportation Energy Futures (TEF) project, a Department of Energy-sponsored multi-agency project initiated to pinpoint underexplored strategies for abating GHGs and reducing petroleum dependence related to transportation.

  9. Transportation Energy Futures Series. Effects of the Built Environment on Transportation. Energy Use, Greenhouse Gas Emissions, and Other Factors

    SciTech Connect

    Porter, C. D.; Brown, A.; Dunphy, R. T.; Vimmerstedt, L.

    2013-03-15

    Planning initiatives in many regions and communities aim to reduce transportation energy use, decrease emissions, and achieve related environmental benefits by changing land use. This report reviews and summarizes findings from existing literature on the relationship between the built environment and transportation energy use and greenhouse gas emissions, identifying results trends as well as potential future actions. The indirect influence of federal transportation and housing policies, as well as the direct impact of municipal regulation on land use are examined for their effect on transportation patterns and energy use. Special attention is given to the 'four D' factors of density, diversity, design and accessibility. The report concludes that policy-driven changes to the built environment could reduce transportation energy and GHG emissions from less than 1% to as much as 10% by 2050, the equivalent of 16%-18% of present-day urban light-duty-vehicle travel. This is one of a series of reports produced as a result of the Transportation Energy Futures (TEF) project, a Department of Energy-sponsored multi-agency project initiated to pinpoint underexplored strategies for abating GHGs and reducing petroleum dependence related to transportation.

  10. The CO-to-H2 Conversion Factor and Dust-to-gas Ratio on Kiloparsec Scales in Nearby Galaxies

    NASA Astrophysics Data System (ADS)

    Sandstrom, K. M.; Leroy, A. K.; Walter, F.; Bolatto, A. D.; Croxall, K. V.; Draine, B. T.; Wilson, C. D.; Wolfire, M.; Calzetti, D.; Kennicutt, R. C.; Aniano, G.; Donovan Meyer, J.; Usero, A.; Bigiel, F.; Brinks, E.; de Blok, W. J. G.; Crocker, A.; Dale, D.; Engelbracht, C. W.; Galametz, M.; Groves, B.; Hunt, L. K.; Koda, J.; Kreckel, K.; Linz, H.; Meidt, S.; Pellegrini, E.; Rix, H.-W.; Roussel, H.; Schinnerer, E.; Schruba, A.; Schuster, K.-F.; Skibba, R.; van der Laan, T.; Appleton, P.; Armus, L.; Brandl, B.; Gordon, K.; Hinz, J.; Krause, O.; Montiel, E.; Sauvage, M.; Schmiedeke, A.; Smith, J. D. T.; Vigroux, L.

    2013-11-01

    We present ~kiloparsec spatial resolution maps of the CO-to-H2 conversion factor (αCO) and dust-to-gas ratio (DGR) in 26 nearby, star-forming galaxies. We have simultaneously solved for αCO and the DGR by assuming that the DGR is approximately constant on kiloparsec scales. With this assumption, we can combine maps of dust mass surface density, CO-integrated intensity, and H I column density to solve for both αCO and the DGR with no assumptions about their value or dependence on metallicity or other parameters. Such a study has just become possible with the availability of high-resolution far-IR maps from the Herschel key program KINGFISH, 12CO J = (2-1) maps from the IRAM 30 m large program HERACLES, and H I 21 cm line maps from THINGS. We use a fixed ratio between the (2-1) and (1-0) lines to present our αCO results on the more typically used 12CO J = (1-0) scale and show using literature measurements that variations in the line ratio do not affect our results. In total, we derive 782 individual solutions for αCO and the DGR. On average, αCO = 3.1 M ⊙ pc-2 (K km s-1)-1 for our sample with a standard deviation of 0.3 dex. Within galaxies, we observe a generally flat profile of αCO as a function of galactocentric radius. However, most galaxies exhibit a lower αCO value in the central kiloparsec—a factor of ~2 below the galaxy mean, on average. In some cases, the central αCO value can be factors of 5-10 below the standard Milky Way (MW) value of αCO, MW = 4.4 M ⊙ pc-2 (K km s-1)-1. While for αCO we find only weak correlations with metallicity, the DGR is well-correlated with metallicity, with an approximately linear slope. Finally, we present several recommendations for choosing an appropriate αCO for studies of nearby galaxies.

  11. Impact of gas/particle partitioning of semivolatile organic compounds on source apportionment with positive matrix factorization.

    PubMed

    Xie, Mingjie; Hannigan, Michael P; Barsanti, Kelley C

    2014-08-19

    To quantify and minimize the influence of gas/particle (G/P) partitioning on receptor-based source apportionment using particle-phase semivolatile organic compound (SVOC) data, positive matrix factorization (PMF) coupled with a bootstrap technique was applied to three data sets mainly composed of "measured-total" (measured particle- + gas-phase), "particle-only" (measured particle-phase) and "predicted-total" (measured particle-phase + predicted gas-phase) SVOCs to apportion carbonaceous aerosols. Particle- (PM2.5) and gas-phase SVOCs were collected using quartz fiber filters followed by PUF/XAD-4/PUF adsorbents and measured using gas chromatography-mass spectrometry (GC-MS). Concentrations of gas-phase SVOCs were also predicted from their particle-phase concentrations using absorptive partitioning theory. Five factors were resolved for each data set, and the factor profiles were generally consistent across the three PMF solutions. Using a previous source apportionment study at the same receptor site, those five factors were linked to summertime biogenic emissions (odd n-alkane factor), unburned fossil fuels (light SVOC factor), road dust and/or cooking (n-alkane factor), motor vehicle emissions (PAH factor), and lubricating oil combustion (sterane factor). The "measured-total" solution was least influenced by G/P partitioning and used as reference. Two out of the five factors (odd n-alkane and PAH factors) exhibited consistent contributions for "particle-only" vs "measured-total" and "predicted-total" vs "measured-total" solutions. Factor contributions of light SVOC and n-alkane factors were more consistent for "predicted-total" vs "measured-total" than "particle-only" vs "measured-total" solutions. The remaining factor (sterane factor) underestimated the contribution by around 50% from both "particle-only" and "predicted-total" solutions. The results of this study confirm that when measured gas-phase SVOCs are not available, "predicted-total" SVOCs should be used

  12. Neutral gas temperature measurements of high-power-density fluorocarbon plasmas by fitting swan bands of C{sub 2} molecules

    SciTech Connect

    Bai Bo; Sawin, Herbert H.; Cruden, Brett A.

    2006-01-01

    The neutral gas temperature of fluorocarbon plasmas in a remote toroidal transformer-coupled source was measured to be greater than 5000 K, under the conditions of a power density greater than 15 W/cm{sup 3} and pressures above 2 torr. The rovibrational bands of C{sub 2} molecules (swan bands, d {sup 3}{pi}{sub g}{yields}a {sup 3}{pi}{sub u}) were fitted to obtain the rotational temperature that was assumed to equal the translational temperature. This rotational-translational temperature equilibrium assumption was supported by the comparison with the rotational temperature of second positive system of added N{sub 2}. For the same gas mixture, the neutral gas temperature is nearly a linear function of plasma power, since the conduction to chamber wall and convection are the major energy-loss processes, and they are both proportional to neutral gas temperature. The dependence of the neutral gas temperature on O{sub 2} flow rate and pressure can be well represented through the power dependence, under the condition of constant current operation. An Arrhenius type of dependence between the etching rate of oxide film and the neutral gas temperature is observed, maybe indicating the importance of the pyrolytic dissociation in the plasma formation process when the temperature is above 5000 K.

  13. Development of a high-density gas-jet target for nuclear astrophysics and reaction studies with rare isotope beams. Final Report

    SciTech Connect

    Uwe, Greife

    2014-08-12

    The purpose of this project was to develop a high-density gas jet target that will enable a new program of transfer reaction studies with rare isotope beams and targets of hydrogen and helium that is not currently possible and will have an important impact on our understanding of stellar explosions and of the evolution of nuclear shell structure away from stability. This is the final closeout report for the project.

  14. Factors associated with graft survival and endothelial cell density after Descemet’s stripping automated endothelial keratoplasty

    PubMed Central

    Ishii, Nobuhito; Yamaguchi, Takefumi; Yazu, Hiroyuki; Satake, Yoshiyuki; Yoshida, Akitoshi; Shimazaki, Jun

    2016-01-01

    Postoperative endothelial cell loss leads to graft failure after corneal transplantation, and is one of the important issues for long-term prognosis. The objective of this study was to identify clinical factors affecting graft survival and postoperative endothelial cell density (ECD) after Descemet’s stripping automated endothelial keratoplasty (DSAEK). A total of 198 consecutive Japanese patients (225 eyes) who underwent DSAEK were analysed using Cox proportional hazard regression and multiple linear regression models. The candidate factors included recipient age; gender; diagnosis; pre-existing iris damage state, scored based on its severity; the number of previous intraocular surgeries; graft ECD; graft diameter; simultaneous cataract surgery; surgeons experience; intraoperative iris damage; postoperative rebubbling; and graft rejection. Eyes with higher pre-existing iris damage score and more number of previous intraocular surgery had a significantly higher risk of graft failure (HR = 8.53; P < 0.0001, and HR = 2.66; P = 0.026, respectively). Higher pre-existing iris damage score, lower graft ECD, and smaller graft diameter were identified as significant predisposing factors for lower postoperative ECD. The results show that iris damage status before DSAEK may be clinically useful in predicting the postoperative course. Avoiding intraoperative iris damage, especially in eyes with low ECD can change the prognosis of future DSAEK. PMID:27121659

  15. Factors influencing the late phase of recovery after bone mineral density loss in allogeneic stem cell transplantation survivors.

    PubMed

    Anandi, P; Jain, N A; Tian, X; Wu, C O; Pophali, P A; Koklanaris, E; Ito, S; Savani, B N; Barrett, J; Battiwalla, M

    2016-08-01

    Accelerated bone mineral density loss (BMDL) occurs early after allogeneic stem cell transplantation (SCT) and is related to factors such as steroids and chronic GvHD. In order to understand the natural history of BMDL of SCT in the longer term, we evaluated a longitudinal cohort of 148 survivors with a median follow-up of 12 years (range 3-22 years). All women received hormone replacement therapy, and routine calcium/vitamin D supplementation was recommended but ∼50% of patients still had suboptimal vitamin D levels and bisphosphonates were rarely utilized. BMD significantly improved from 5 to 20+ years but the femoral neck and forearm remained vulnerable sites. Younger age, higher pretransplant body mass index (BMI) and increment in BMI post transplant were significantly associated with increased BMD and protected against osteopenia/osteoporosis. These findings support consideration of BMD loss in SCT survivors in two phases, an early phase of BMD loss (3-5 years) followed by a later phase of BMD recovery, with different protective and aggravating factors. Treatment- and transplant-related factors (such as steroids, immunosuppressives, chronic GvHD, vitamin D) are known to impact the early phase of BMD loss but age and BMI are more influential in the late phase of BMD recovery. PMID:27042843

  16. 40 CFR Table W - 3 of Subpart W of Part 98-Default Total Hydrocarbon Emission Factors for Onshore Natural Gas...

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 22 2013-07-01 2013-07-01 false 3 of Subpart W of Part 98-Default Total Hydrocarbon Emission Factors for Onshore Natural Gas Transmission Compression W Table W Protection...-3 of Subpart W of Part 98—Default Total Hydrocarbon Emission Factors for Onshore Natural...

  17. 40 CFR Table W - 3 of Subpart W of Part 98-Default Total Hydrocarbon Emission Factors for Onshore Natural Gas...

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 21 2014-07-01 2014-07-01 false 3 of Subpart W of Part 98-Default Total Hydrocarbon Emission Factors for Onshore Natural Gas Transmission Compression W Table W Protection...-3 of Subpart W of Part 98—Default Total Hydrocarbon Emission Factors for Onshore Natural...

  18. Axial- and radial-resolved electron density and excitation temperature of aluminum plasma induced by nanosecond laser: Effect of the ambient gas composition and pressure

    SciTech Connect

    Dawood, Mahmoud S.; Hamdan, Ahmad E-mail: Joelle.margot@umontreal.ca; Margot, Joëlle E-mail: Joelle.margot@umontreal.ca

    2015-11-15

    The spatial variation of the characteristics of an aluminum plasma induced by a pulsed nanosecond XeCl laser is studied in this paper. The electron density and the excitation temperature are deduced from time- and space- resolved Stark broadening of an ion line and from a Boltzmann diagram, respectively. The influence of the gas pressure (from vacuum up to atmospheric pressure) and compositions (argon, nitrogen and helium) on these characteristics is investigated. It is observed that the highest electron density occurs near the laser spot and decreases by moving away both from the target surface and from the plume center to its edge. The electron density increases with the gas pressure, the highest values being occurred at atmospheric pressure when the ambient gas has the highest mass, i.e. in argon. The excitation temperature is determined from the Boltzmann plot of line intensities of iron impurities present in the aluminum target. The highest temperature is observed close to the laser spot location for argon at atmospheric pressure. It decreases by moving away from the target surface in the axial direction. However, no significant variation of temperature occurs along the radial direction. The differences observed between the axial and radial direction are mainly due to the different plasma kinetics in both directions.

  19. Analysis of factors influencing the performance of CMS membranes for gas separation

    NASA Astrophysics Data System (ADS)

    Williams, Paul Jason

    2007-12-01

    Carbon molecular sieve (CMS) membranes represent the most attractive pure component materials to compete against polymer membranes for high performance gas separations. CMS membranes are formed from the thermal decomposition of polymer precursors and can therefore be formed into continuous defect free membranes with excellent gas separation performance. Over the last 20 years, CMS membranes have been produced in a variety of geometries and have a wide range of separation performance applicable to several important gas separations. Though research into CMS membrane formation is quite extensive, the relationship between synthesis factors and separation performance is still not well understood. The goal of this study was to elucidate the effect of two different synthesis factors on the separation performance of CMS membranes to allow more control over separation performance. The foci of this study were to clarify (1) the effect of pyrolysis atmosphere and (2) the effect of polymer precursor composition. Dense flat CMS membranes were synthesized from 6FDA:BPDA-DAM precursor at 550°C using several pyrolysis atmospheres including vacuum pyrolysis (<0.05 torr), helium and argon flowing at atmospheric pressure, and helium and argon flowing at reduced pressures. The separation performance of CMS membranes produced under different pyrolysis atmospheres suggests that the amount of oxygen available during pyrolysis has a significant affect on the microstructure of membrane. CMS membranes were produced from 6FDA:BPDA(1:1)-DAM and 6FDA:BPDA(1:1)-DAM under identical pyrolysis conditions to determine the utility of polymer precursor composition as an engineering tool to fine-tune the performance of CMS membranes. In a second study utilizing 6FDA-6FpDA and 6FDA-6FmDA precursors, the separation performance of CMS membranes was shown to be dependent on the intrinsic precursor free volume. These studies have shown that two factors to be considered when choosing a polymer precursor

  20. INCIDENCE DENSITY, PROPORTIONATE MORTALITY, AND RISK FACTORS OF ASPERGILLOSIS IN MAGELLANIC PENGUINS IN A REHABILITATION CENTER FROM BRAZIL.

    PubMed

    Silva Filho, Rodolfo Pinho da; Xavier, Melissa Orzechowski; Martins, Aryse Moreira; Ruoppolo, Valéria; Mendoza-Sassi, Raúl Andrés; Adornes, Andréa Corrado; Cabana, Ângela Leitzke; Meireles, Mário Carlos Araújo

    2015-12-01

    Aspergillosis, an opportunistic mycosis caused by the Aspergillus genus, affects mainly the respiratory system and is considered one of the most significant causes of mortality in captive penguins. This study aimed to examine a 6-yr period of cases of aspergillosis in penguins at the Centro de Recuperação de Animais Marinhos (CRAM-FURG), Rio Grande, Brazil. A retrospective cohort study was conducted using the institution's records of penguins received from January 2004 to December 2009. Animals were categorized according to the outcome "aspergillosis," and analyzed by age group, sex, oil fouling, origin, prophylactic administration of itraconazole, period in captivity, body mass, hematocrit, and total plasma proteins. A total of 327 Magellanic penguins (Spheniscus magellanicus) was studied, 66 of which died of aspergillosis. Proportionate mortality by aspergillosis was 48.5%, and incidence density was 7.3 lethal aspergillosis cases per 100 penguins/mo. Approximately 75% of the aspergillosis cases occurred in penguins that had been transferred from other rehabilitation centers, and this was considered a significant risk factor for the disease. Significant differences were also observed between the groups in regard to the period of time spent in captivity until death, hematocrit and total plasma proteins upon admission to the center, and body mass gain during the period in captivity. The findings demonstrate the negative impacts of aspergillosis on the rehabilitation of Magellanic penguins, with a high incidence density and substantial mortality. PMID:26667521

  1. Magneto-transport analysis of an ultra-low-density two-dimensional hole gas in an undoped strained Ge/SiGe heterostructure

    DOE PAGESBeta

    Laroche, D.; Huang, S. -H.; Chuang, Y.; Li, J. -Y.; Liu, C. W.; Lu, T. M.

    2016-06-01

    We report the magneto-transport, scattering mechanisms, and e ective mass analysis of an ultralow density two-dimensional hole gas capacitively induced in an undoped strained Ge/Si0:2Ge0:8 heterostructure. This fabrication technique allows hole densities as low as p 1:1 1010 cm² to be achieved, more than one order of magnitude lower than previously reported in doped Ge/SiGe heterostructures. The power-law exponent of the electron mobility versus density curve, / n , is found to be 0:29 over most of the density range, implying that background impurity scattering is the dominant scattering mechanism at intermediate densities in such devices. A charge migration modelmore » is used to explain the mobility decrease at the highest achievable densities. The hole e ective mass is deduced from the temperature dependence of Shubnikov-de Haas oscillations. At p 1:0 1011cm², the e ective mass m is 0:105 m0, which is signi cantly larger than masses obtained from modulation-doped Ge/SiGe two-dimensional hole gases.« less

  2. Magneto-transport analysis of an ultra-low-density two-dimensional hole gas in an undoped strained Ge/SiGe heterostructure

    NASA Astrophysics Data System (ADS)

    Laroche, D.; Huang, S.-H.; Chuang, Y.; Li, J.-Y.; Liu, C. W.; Lu, T. M.

    2016-06-01

    We report the magneto-transport, scattering mechanisms, and effective mass analysis of an ultra-low density two-dimensional hole gas capacitively induced in an undoped strained Ge/Si0.2Ge0.8 heterostructure. This fabrication technique allows hole densities as low as p ˜ 1.1 × 1010 cm-2 to be achieved, more than one order of magnitude lower than previously reported in doped Ge/SiGe heterostructures. The power-law exponent of the electron mobility versus density curve, μ ∝ nα, is found to be α ˜ 0.29 over most of the density range, implying that background impurity scattering is the dominant scattering mechanism at intermediate densities in such devices. A charge migration model is used to explain the mobility decrease at the highest achievable densities. The hole effective mass is deduced from the temperature dependence of Shubnikov-de Haas oscillations. At p ˜ 1.0 × 1011 cm-2, the effective mass m* is ˜0.105 m0, which is significantly larger than masses obtained from modulation-doped Ge/SiGe two-dimensional hole gases.

  3. Measuring Ambient Densities and Lorentz Factors of Gamma-Ray Bursts from GeV and Optical Observations

    NASA Astrophysics Data System (ADS)

    Hascoët, Romain; Vurm, Indrek; Beloborodov, Andrei M.

    2015-11-01

    The Fermi satellite detected GeV flashes from cosmological gamma-ray bursts (GRBs). In two GRBs, an optical counterpart of the GeV flash was detected. Such flashes are predicted by the model of a blast wave running into a medium loaded with copious {e}+/- pairs. Here we examine a sample of seven bursts with the best GeV+optical data and further test the model. We find that the observed light curves are in agreement with the theoretical predictions, which allows us to measure three parameters for each burst: the Lorentz factor of the explosion, its isotropic kinetic energy, and the external density. With the possible exception of GRB 090510 (the only short burst in the sample), the ambient medium is consistent with a wind from a Wolf-Rayet progenitor. The wind density parameter A=ρ {r}2 varies in the sample around 1011 g cm-1. The initial Lorentz factor of the blast wave varies from 200 to 540, and correlates with the burst luminosity. Radiative efficiency of the prompt emission varies between 0.1 and 0.8. For the two bursts with a detected optical flash, GRB 120711A and GRB 130427A, we also estimate the magnetization of the external blast wave. Remarkably, despite its small number of free parameters, the model reproduces the entire optical light curve of GRB 120711A (with its sharp peak, fast decay, plateau, and break) as well as the GeV data. The spectra of GeV flashes are predicted to extend above 0.1 TeV, where they can be detected by ground-based Cherenkov telescopes.

  4. Sedimentation of a two-dimensional colloidal mixture exhibiting liquid-liquid and gas-liquid phase separation: a dynamical density functional theory study.

    PubMed

    Malijevský, Alexandr; Archer, Andrew J

    2013-10-14

    We present dynamical density functional theory results for the time evolution of the density distribution of a sedimenting model two-dimensional binary mixture of colloids. The interplay between the bulk phase behaviour of the mixture, its interfacial properties at the confining walls, and the gravitational field gives rise to a rich variety of equilibrium and non-equilibrium morphologies. In the fluid state, the system exhibits both liquid-liquid and gas-liquid phase separation. As the system sediments, the phase separation significantly affects the dynamics and we explore situations where the final state is a coexistence of up to three different phases. Solving the dynamical equations in two-dimensions, we find that in certain situations the final density profiles of the two species have a symmetry that is different from that of the external potentials, which is perhaps surprising, given the statistical mechanics origin of the theory. The paper concludes with a discussion on this. PMID:24116640

  5. Fabrication of graded density impactor via underwater shock wave and quasi-isentropic compression testing at two-stage gas gun facility

    NASA Astrophysics Data System (ADS)

    Sun, Wei; Li, Xiaojie; Hokamoto, Kazuyuki

    2014-12-01

    We show direct evidence that underwater shock wave enables us to bond multithin plates with flat, parallel, and high-strength interfaces, which are key requirements for functionally graded material (also called graded density impactor). This phenomenon is ascribed to the super short duration of the high-speed underwater shock wave, reducing the surface tension, diffusion, evaporation, deposition, and viscous flow of matter. Thin magnesium, aluminum, titanium, copper, and molybdenum foils were welded together and designed with the increase in density. Experimental evidence and numerical simulation show that well bonding between the multilayer structures. Microstructure examinations reveal that the dominant interfacial form shifts from waviness to linearity. Graded density impactor with multilayer structure is proved that can produce quasi-isentropic compression in two-stage gas gun experiment with a designed pressure loading profile, which suggests a feasible method to simulate the conditions we want to study that were previously inaccessible in a precisely controlled laboratory environment.

  6. THE MOLECULAR GAS IN LUMINOUS INFRARED GALAXIES. II. EXTREME PHYSICAL CONDITIONS AND THEIR EFFECTS ON THE X{sub co} FACTOR

    SciTech Connect

    Papadopoulos, Padelis P.; Van der Werf, Paul; Xilouris, E.; Isaak, Kate G.; Gao, Yu E-mail: pvdwerf@strw.leidenuniv.nl E-mail: kisaak@rssd.esa.int

    2012-05-20

    In this work, we conclude the analysis of our CO line survey of luminous infrared galaxies (LIRGs: L{sub IR} {approx}> 10{sup 11} L{sub Sun }) in the local universe (Paper I) by focusing on the influence of their average interstellar medium (ISM) properties on the total molecular gas mass estimates via the so-called X{sub co} = M(H{sub 2})/L{sub co,1-0} factor. One-phase radiative transfer models of the global CO spectral line energy distributions (SLEDs) yield an X{sub co} distribution with (X{sub co}) {approx} (0.6 {+-} 0.2) M{sub Sun} (K km s{sup -1} pc{sup 2}){sup -1} over a significant range of average gas densities, temperatures, and dynamic states. The latter emerges as the most important parameter in determining X{sub co}, with unbound states yielding low values and self-gravitating states yielding the highest ones. Nevertheless, in many (U)LIRGs where available higher-J CO lines (J = 3-2, 4-3, and/or J = 6-5) or HCN line data from the literature allow a separate assessment of the gas mass at high densities ({>=}10{sup 4} cm{sup -3}) rather than a simple one-phase analysis, we find that near-Galactic X{sub co} {approx} (3-6) M{sub Sun} (K km s{sup -1} pc{sup 2}){sup -1} values become possible. We further show that in the highly turbulent molecular gas in ULIRGs, a high-density component will be common and can be massive enough for its high X{sub co} to dominate the average value for the entire galaxy. Using solely low-J CO lines to constrain X{sub co} in such environments (as has been the practice up until now) may have thus resulted in systematic underestimates of molecular gas mass in ULIRGs, as such lines are dominated by a warm, diffuse, and unbound gas phase with low X{sub co} but very little mass. Only well-sampled high-J CO SLEDs (J = 3-2 and higher) and/or multi-J observations of heavy rotor molecules (e.g., HCN) can circumvent such a bias, and the latter type of observations may have actually provided early evidence of it in local ULIRGs. The only

  7. Regression approaches to derive generic and fish group-specific probability density functions of bioconcentration factors for metals.

    PubMed

    Tanaka, Taku; Ciffroy, Philippe; Stenberg, Kristofer; Capri, Ettore

    2010-11-01

    In the framework of environmental multimedia modeling studies dedicated to environmental and health risk assessments of chemicals, the bioconcentration factor (BCF) is a parameter commonly used, especially for fish. As for neutral lipophilic substances, it is assumed that BCF is independent of exposure levels of the substances. However, for metals some studies found the inverse relationship between BCF values and aquatic exposure concentrations for various aquatic species and metals, and also high variability in BCF data. To deal with the factors determining BCF for metals, we conducted regression analyses to evaluate the inverse relationships and introduce the concept of probability density function (PDF) for Cd, Cu, Zn, Pb, and As. In the present study, for building the regression model and derive the PDF of fish BCF, two statistical approaches are applied: ordinary regression analysis to estimate a regression model that does not consider the variation in data across different fish family groups; and hierarchical Bayesian regression analysis to estimate fish group-specific regression models. The results show that the BCF ranges and PDFs estimated for metals by both statistical approaches have less uncertainty than the variation of collected BCF data (the uncertainty is reduced by 9%-61%), and thus such PDFs proved to be useful to obtain accurate model predictions for environmental and health risk assessment concerning metals. PMID:20886641

  8. Prevalence and Risk Factors of Low Bone Mineral Density in Korean HIV-Infected Patients: Impact of Abacavir and Zidovudine

    PubMed Central

    Kim, Hee-Sung; Chin, Bum Sik

    2013-01-01

    Low bone mineral density (BMD) is common in HIV-infected patients. We aimed to describe the prevalence of low BMD and risk factors in Korean HIV-infected patients and to assess the effects of antiretroviral therapy (ART) on BMD. We retrospectively evaluated 224 HIV infected-patients. The prevalence of osteopenia and osteoporosis were 41.5% and 12.9%. These were much higher in 53 patients aged 50 yr and older (52.8% and 34.0%). Older age, lower body mass index, and ART > 3 months were independent risk factors for low BMD. Osteoporosis was more prevalent in patients on the abacavir-based regimen for < 1 yr than ≥ 1 yr; however, it was more prevalent in patients on the zidovudine-based regimen for ≥ 1 yr than < 1 yr (P = 0.017). Osteoporosis in patients on the abacavir-based regimen was more common in the spine than in the femur (P = 0.01). Given such a high prevalence of low BMD, close monitoring of BMD for HIV-infected patients on ART is required. The different prevalence of osteoporosis over time and affected areas between two regimens suggest they may play roles in different mechanisms in bone loss. PMID:23772145

  9. Investigation of Controlling Factors Impacting Water Quality in Shale Gas Produced Brine

    NASA Astrophysics Data System (ADS)

    Fan, W.; Hayes, K. F.; Ellis, B. R.

    2014-12-01

    The recent boom in production of natural gas from unconventional reservoirs has generated a substantial increase in the volume of produced brine that must be properly managed to prevent contamination of fresh water resources. Produced brine, which includes both flowback and formation water, is often highly saline and may contain elevated concentrations of naturally occurring radioactive material and other toxic elements. These characteristics present many challenges with regard to designing effective treatment and disposal strategies for shale gas produced brine. We will present results from a series of batch experiments where crushed samples from two shale formations in the Michigan Basin, the Antrim and Utica-Collingwood shales, were brought into contact with synthetic hydraulic fracturing fluids under in situ temperature and pressure conditions. The Antrim has been an active shale gas play for over three decades, while the Utica-Collingwood formation (a grouped reservoir consisting of the Utica shale and Collingwood limestone) is an emerging shale gas play. The goal of this study is to investigate the influence of water-rock interactions in controlling produced water quality. We evaluate toxic element leaching from shale samples in contact with model hydraulic fracturing fluids under system conditions corresponding to reservoir depths up to 1.5 km. Experimental results have begun to elucidate the relative importance of shale mineralogy, system conditions, and chemical additives in driving changes in produced water quality. Initial results indicate that hydraulic fracturing chemical additives have a strong influence on the extent of leaching of toxic elements from the shale. In particular, pH was a key factor in the release of uranium (U) and divalent metals, highlighting the importance of the mineral buffering capacity of the shale. Low pH values persisted in the Antrim and Utica shale experiments and resulted in higher U extraction efficiencies than that

  10. A New Method to Modify Two-Dimensional Electron Gas Density by GaN Cap Etching

    NASA Astrophysics Data System (ADS)

    Li, Zhongda; Chow, T. Paul

    2013-08-01

    We have experimentally demonstrated a new method for modifying the two-dimensional electron density (2DEG) at the AlGaN/GaN interface by etching of the GaN cap layer on top of the AlGaN. GaN MOS capacitors have been fabricated on samples with partially or fully etched GaN cap, and the 2DEG density has been extracted. The results show a linear relation between the 2DEG density and the thickness of the GaN cap being etched. We have also fabricated van der Pauw structures and obtained the 2DEG density using Hall measurements, and the results are consistent with that from the GaN MOS capacitors.

  11. Factors influencing self-sealing of sclerotomy performed under gas tamponade in 23-gauge transconjunctival sutureless vitrectomy

    PubMed Central

    Takashina, Hirotsugu; Watanabe, Akira; Mitooka, Katsuya; Tsuneoka, Hiroshi

    2014-01-01

    Background The purpose of this study was to investigate factors influencing self-sealing of sclerotomy performed under gas tamponade in 23-gauge transconjunctival sutureless vitrectomy. Methods This study was a retrospective review of 84 patients (84 eyes) who underwent 23-gauge transconjunctival sutureless vitrectomy under gas tamponade by a single surgeon. At the end of surgery, the sclerotomy was massaged to promote self-sealing. Factors influencing massage time were examined using multiple regression analysis. Independent variables were age, surgical time, vitreous incarceration, intraocular manipulation, and axial length. Results Significant factors were intraocular manipulation and vitreous incarceration in the examination of all sclerotomies, age only in the examination of infusion sites, and vitreous incarceration only in the examination of manipulation sites. Conclusion In sclerotomy performed with gas tamponade using 23-gauge transconjunctival sutureless vitrectomy, intraocular manipulation influenced self-sealing of sclerotomy the most, followed by vitreous incarceration, and then age. PMID:25336910

  12. CARMA SURVEY TOWARD INFRARED-BRIGHT NEARBY GALAXIES (STING). III. THE DEPENDENCE OF ATOMIC AND MOLECULAR GAS SURFACE DENSITIES ON GALAXY PROPERTIES

    SciTech Connect

    Wong, Tony; Xue, Rui; Bolatto, Alberto D.; Fisher, David B.; Vogel, Stuart N.; Leroy, Adam K.; Blitz, Leo; Rosolowsky, Erik; Bigiel, Frank; Ott, Jürgen; Rahman, Nurur; Walter, Fabian

    2013-11-01

    We investigate the correlation between CO and H I emission in 18 nearby galaxies from the CARMA Survey Toward IR-Bright Nearby Galaxies (STING) at sub-kpc and kpc scales. Our sample, spanning a wide range in stellar mass and metallicity, reveals evidence for a metallicity dependence of the H I column density measured in regions exhibiting CO emission. Such a dependence is predicted by the equilibrium model of McKee and Krumholz, which balances H{sub 2} formation and dissociation. The observed H I column density is often smaller than predicted by the model, an effect we attribute to unresolved clumping, although values close to the model prediction are also seen. We do not observe H I column densities much larger than predicted, as might be expected were there a diffuse H I component that did not contribute to H{sub 2} shielding. We also find that the H{sub 2} column density inferred from CO correlates strongly with the stellar surface density, suggesting that the local supply of molecular gas is tightly regulated by the stellar disk.

  13. CARMA Survey toward Infrared-bright Nearby Galaxies (STING). III. The Dependence of Atomic and Molecular Gas Surface Densities on Galaxy Properties

    NASA Astrophysics Data System (ADS)

    Wong, Tony; Xue, Rui; Bolatto, Alberto D.; Leroy, Adam K.; Blitz, Leo; Rosolowsky, Erik; Bigiel, Frank; Fisher, David B.; Ott, Jürgen; Rahman, Nurur; Vogel, Stuart N.; Walter, Fabian

    2013-11-01

    We investigate the correlation between CO and H I emission in 18 nearby galaxies from the CARMA Survey Toward IR-Bright Nearby Galaxies (STING) at sub-kpc and kpc scales. Our sample, spanning a wide range in stellar mass and metallicity, reveals evidence for a metallicity dependence of the H I column density measured in regions exhibiting CO emission. Such a dependence is predicted by the equilibrium model of McKee and Krumholz, which balances H2 formation and dissociation. The observed H I column density is often smaller than predicted by the model, an effect we attribute to unresolved clumping, although values close to the model prediction are also seen. We do not observe H I column densities much larger than predicted, as might be expected were there a diffuse H I component that did not contribute to H2 shielding. We also find that the H2 column density inferred from CO correlates strongly with the stellar surface density, suggesting that the local supply of molecular gas is tightly regulated by the stellar disk.

  14. Variation Trend and Driving Factors of Greenhouse Gas Emissions from Chinese Magnesium Production.

    PubMed

    Gao, Feng; Liu, Yu; Nie, Zuo-Ren; Gong, Xianzheng; Wang, Zhihong

    2015-11-01

    As the largest magnesium producer in the world, China is facing a great challenge of greenhouse gas (GHG) emissions reduction. In this paper, the variation trend and driving factors of GHG emissions from Chinese magnesium production were evaluated and the measures of technology and policy for effectively mitigating GHG emissions were provided. First, the energy-related and process-oriented GHG inventory is compiled for magnesium production in China. Then, the driving forces for the changes of the energy-related emission were analyzed by the method of Logarithmic Mean Divisia Index (LMDI) decomposition. Results demonstrated that Chinese magnesium output from 2003 to 2013 increased by 125%, whereas GHG emissions only increased by 16%. The emissions caused by the fuels consumption decline most significantly (from 28.4 to 6.6 t CO2eq/t Mg) among all the emission sources. The energy intensity and the energy structure were the main offsetting factors for the increase of GHG emissions, while the scale of production and the international market demand were the main contributors for the total increase. Considering the improvement of technology application and more stringent policy measures, the annual GHG emissions from Chinese primary magnesium production will be controlled within 22 million tons by 2020. PMID:26458120

  15. Density of atoms in Ar*(3p{sup 5}4s) states and gas temperatures in an argon surfatron plasma measured by tunable laser spectroscopy

    SciTech Connect

    Huebner, S.; Carbone, E. A. D.; Mullen, J. J. A. M. van der; Sadeghi, N.

    2013-04-14

    This study presents the absolute argon 1 s (in Paschens's notation) densities and the gas temperature, T{sub g}, obtained in a surfatron plasma in the pressure range 0.65gas pressures of p<10 mbar, changes to a Voigt shape at p>10 mbar, for which the pressure broadening can no more be neglected. T{sub g} is in the range of 480-750 K, increasing with pressure and decreasing with the distance from the microwave launcher. Taking into account the line of sight effects of the absorption measurements, a good agreement is found with our previous measurements by Rayleigh scattering of T{sub g} at the tube center. In the studied pressure range, the Ar(4 s) atom densities are in the order of 10{sup 16}-10{sup 18} m{sup -3}, increasing towards the end of the plasma column, decreasing with the pressure. In the low pressure side, a broad minimum is found around 10densities increase slightly with rising pressure. For the studied pressure range and all axial positions, the density ratio: 1s{sub 5}/1s{sub 4}/1s{sub 3} is very close to a Boltzmann equilibrium by electron impact mixing at the local T{sub e}, which was previously measured by Thomson scattering. The Ar(4 s) densities are successfully compared to a detailed Collisional Radiative Model.

  16. Quality of diet and potential renal acid load as risk factors for reduced bone density in elderly women

    PubMed Central

    Pedone, Claudio; Napoli, Nicola; Lauretani, Fulvio; Pozzilli, Paolo; Ferrucci, Luigi; Antonelli-Incalzi, Raffaele

    2010-01-01

    Background Bone mass density (BMD) may be influenced by the general dietary pattern and the potential renal acid load (PRAL). Objective To evaluate the association between PRAL and BMD. Methods We evaluated BMD using computed tomography and dietary intake using the EPIC questionnaire in 543 community-living women aged 60 years and older. We grouped the participants according to tertiles of total, trabecular and cortical BMD, and compared demographic, anthropometric and nutritional characteristics across groups. Analyses were repeated using tertiles of BMD variation over a 6-years follow-up. Results Total BMD was inversely associated with age, time since menopause, and creatinine clearance. The intake of PUFAs was slightly higher among women with the highest total BMD, none of the other nutrients taken into account nor PRAL was associated with total BMD. Similar results were found for trabecular BMD, with the exception that alcohol intake was associated with lower bone density. Cortical BMD was associated with vitamin D intake (1.6, 1.8, and 1.8 mcg/day in first, second and third tertile, respectively) and serum 25-OH vitamin D (38.8, 43.2, and 49.5 nmol/L in the first, second, and third tertile, respectively). In the longitudinal analysis, a lower BMI was associated with greater loss of total BMD, while lower serum 25-hydroxy vitamin D at baseline was associated with smaller loss of cortical BMD. Conclusions We found no relationship between dietary acid load and BMD. We also confirmed the role of well recognized risk factor for osteoporosis and found a possible protective effect of PUFA intake on BMD. PMID:20005315

  17. Correlations in the low-density Fermi gas: Fermi-liquid state, dimerization, and Bardeen-Cooper-Schrieffer pairing

    NASA Astrophysics Data System (ADS)

    Fan, H. H.; Krotscheck, E.; Lichtenegger, T.; Mateo, D.; Zillich, R. E.

    2015-08-01

    We present ground-state calculations for low-density Fermi gases described by two model interactions, an attractive square-well potential and a Lennard-Jones potential, of varying strength. We use the optimized Fermi-hypernetted chain integral equation method, which has been proved to provide, in the density regimes of interest here, an accuracy of better than 1%. We first examine the low-density expansion of the energy and compare it with the exact answer of H. Huang and C. N. Yang [Phys. Rev. 105, 767 (1957), 10.1103/PhysRev.105.767]. It is shown that a locally correlated wave function of the Jastrow-Feenberg type does not recover the quadratic term in the expansion of the energy in powers of a0kF , where a0 is the vacuum s -wave scattering length and kF the Fermi wave number. The problem is cured by adding second-order perturbation corrections in a correlated basis. Going to higher densities and/or more strongly coupled systems, we encounter an instability of the normal state of the system which is characterized by a divergence of the in-medium scattering length. We interpret this divergence as a phonon-exchange-driven dimerization of the system, similar to what occurs at zero density when the vacuum scattering length a0 diverges. We then study, in the stable regime, the superfluid gap and its dependence on the density and the interaction strength. We identify two corrections to low-density expansions: One is medium corrections to the pairing interaction, and the other is finite-range corrections. We show that the most important finite-range corrections are a direct manifestation of the many-body nature of the system.

  18. What experimental factors influence the accuracy of retention projections in gas chromatography-mass spectrometry?

    PubMed

    Wilson, Michael B; Barnes, Brian B; Boswell, Paul G

    2014-12-19

    Programmed-temperature gas chromatographic (GC) retention information is difficult to share because it depends on so many experimental factors that vary among laboratories. Though linear retention indexing cannot properly account for experimental differences, retention times can be accurately calculated, or "projected", from shared isothermal retention vs. temperature (T) relationships, but only if the temperature program and hold-up time vs. T profile produced by a GC is known with great precision. The effort required to measure these profiles were previously impractical, but we recently showed that they can be easily back-calculated from the programmed-temperature retention times of a set of 25 n-alkanes using open-source software at www.retentionprediction.org/gc. In a multi-lab study, the approach was shown to account for both intentional and unintentional differences in the temperature programs, flow rates, and inlet pressures produced by the GCs. Here, we tested 16 other experimental factors and found that only 5 could reduce accuracy in retention projections: injection history, exposure to very high levels of oxygen at high temperature, a very low transfer line temperature, an overloaded column, and a very short column (≤15m). We find that the retention projection methodology acts as a hybrid of conventional retention projection and retention indexing, drawing on the advantages of both; it properly accounts for a wide range of experimental conditions while accommodating the effects of experimental factors not properly taken into account in the calculations. Finally, we developed a four-step protocol to efficiently troubleshoot a GC system after it is found to be yielding inaccurate retention projections. PMID:25482038

  19. What Experimental Factors Influence the Accuracy of Retention Projections in Gas Chromatography-Mass Spectrometry?

    PubMed Central

    Wilson, Michael B.; Barnes, Brian B.; Boswell, Paul G.

    2014-01-01

    Programmed-temperature gas chromatographic (GC) retention information is difficult to share because it depends on so many experimental factors that vary among laboratories. Though linear retention indexing cannot properly account for experimental differences, retention times can be accurately calculated, or “projected”, from shared isothermal retention vs. temperature (T) relationships, but only if the temperature program and hold-up time vs. T profile produced by a GC is known with great precision. The effort required to measure these profiles were previously impractical, but we recently showed that they can be easily back-calculated from the programmed-temperature retention times of a set of 25 n-alkanes using open-source software at www.retentionprediction.org/gc. In a multi-lab study, the approach was shown to account for both intentional and unintentional differences in the temperature programs, flow rates, and inlet pressures produced by the GCs. Here, we tested 16 other experimental factors and found that only 5 could reduce accuracy in retention projections: injection history, exposure to very high levels of oxygen at high temperature, a very low transfer line temperature, an overloaded column, and a very short column (≤ 15 m). We find that the retention projection methodology acts as a hybrid of conventional retention projection and retention indexing, drawing on the advantages of both; it properly accounts for a wide range of experimental conditions while accommodating the effects of experimental factors not properly taken into account in the calculations. Finally, we developed a four-step protocol to efficiently troubleshoot a GC system after it is found to be yielding inaccurate retention projections. PMID:25482038

  20. Expression of vascular endothelial growth factor (VEGF), hypoxia inducible factor-1alpha (HIF-1alpha), and microvessel density in endometrial tissue in women with adenomyosis.

    PubMed

    Goteri, Gaia; Lucarini, Guendalina; Montik, Nina; Zizzi, Antonio; Stramazzotti, Daniela; Fabris, Guidalberto; Tranquilli, Andrea Luigi; Ciavattini, Andrea

    2009-03-01

    Adenomyosis is a disease with a mysterious pathogenesis, defined by an abnormal displacement of the eutopic endometrium deeply and haphazardly inside the myometrium. Angiogenesis has been indicated to play an important role and our aim was to investigate whether vascular endothelial growth factor (VEGF) and hypoxia-inducible factor-1alpha (HIF-1alpha) expression and microvessel density (MVD) were different in women with and without adenomyosis. Immunohistochemistry was performed in endometrial tissues in 23 patients who underwent radical hysterectomy for adenomyosis (14) and for ovarian cysts and fibroids (9) at an Academic Hospital. Compared to women without the disease, VEGF expression was increased in endometrium with a normal location in patients with adenomyosis, although not associated to a significant increase of HIF-1alpha and MVD. Moreover, the endometrium with an abnormal location in patients with adenomyosis showed an increased VEGF and HIF-1alpha expression, particularly in the epithelial cells, associated to an increase of MVD, compared with the endometrium in a normal location in the same group of patients. Our present findings suggest that VEGF-mediated angiogenesis might be associated with the development of adenomyosis. In the ectopic foci the abnormal location might contribute to increased HIF-1a expression, stimulation of VEGF production, and increased vessel formation. In endometrium with a normal location, instead, where VEGF increased expression seems not to be correlated with HIF-1alpha increased expression nor with an increased MVD, other mechanisms might be reasonably postulated. Additional studies are required to explore new targeted and more effective treatment modalities. PMID:19188818

  1. Factors affecting fish assemblages associated with gas platforms in the Mediterranean Sea

    NASA Astrophysics Data System (ADS)

    Consoli, Pierpaolo; Romeo, Teresa; Ferraro, Maria; Sarà, Gianluca; Andaloro, Franco

    2013-03-01

    Understanding the role played by offshore platforms in marine ecosystems is acquiring increasing importance worldwide. In this work, underwater visual census techniques were applied to describe spatial and temporal patterns of fish assemblages associated with extractive platforms. Data were collected during three seasons according to the following spatial factors: Location (Adriatic and Ionian Seas), Depth (0-6 m and 12-18 m) and Distance from the platform (external and internal). Both univariate and multivariate analyses showed highly significant differences for each factor assessed in this study, as well as for the interaction among said factors. Results indicated that artificial structures in both the Adriatic and Ionian Seas act as artificial reefs attracting reef-dwelling or partially reef-dwelling species, which are not present far from the platforms in open waters. Results also showed significant differences between Ionian and Adriatic fish assemblages, with a higher mean density of fish and a greater mean number of species in the latter basin. Boops boops, Chromis chromis and several species belonging to the Blennidae family most contributed to these differences. This is likely due to the eutrophication that involves the coast of the northern and central Adriatic, allowing a high production of fish, especially planctivorous. Thanks to the eutrophication, platforms located in this basin are characterized by a greater abundance of fouling organisms which offer a perfect habitat for cryptobenthic species, such as Blennids. Moreover, Thalassoma pavo and Scorpaena maderensis, thermophilic species, were more abundant in the Ionian platforms than in the Adriatic ones thus contributing to the dissimilarities between these two basins. Present results could bear strong implications for the environmental management of drilling and production activities in different basins. Assessing biodiversity in these highly complex contexts is a challenge for the near future, and

  2. Simulation study of geometric shape factor approach to estimating earth emitted flux densities from wide field-of-view radiation measurements

    NASA Technical Reports Server (NTRS)

    Weaver, W. L.; Green, R. N.

    1980-01-01

    A study was performed on the use of geometric shape factors to estimate earth-emitted flux densities from radiation measurements with wide field-of-view flat-plate radiometers on satellites. Sets of simulated irradiance measurements were computed for unrestricted and restricted field-of-view detectors. In these simulations, the earth radiation field was modeled using data from Nimbus 2 and 3. Geometric shape factors were derived and applied to these data to estimate flux densities on global and zonal scales. For measurements at a satellite altitude of 600 km, estimates of zonal flux density were in error 1.0 to 1.2%, and global flux density errors were less than 0.2%. Estimates with unrestricted field-of-view detectors were about the same for Lambertian and non-Lambertian radiation models, but were affected by satellite altitude. The opposite was found for the restricted field-of-view detectors.

  3. Osteoclastogenesis inhibitory factor/osteoprotegerin ameliorates the decrease in both bone mineral density and bone strength in immobilized rats.

    PubMed

    Mochizuki, Shin-ichi; Fujise, Nobuaki; Higashio, Kanji; Tsuda, Eisuke

    2002-01-01

    Rat models of immobilization-induced osteopenia are characterized by uncoupling of bone metabolism, i.e., increased bone resorption and decreased bone formation in trabecular bone. Using such a rat model, the efficacy of osteoclastogenesis inhibitory factor (OCIF)/osteoprotegerin, a novel secreted protein that inhibits osteoclastogenesis, in reducing bone loss was investigated. Male Fischer rats were neurectomized and injected intramuscularly with either OCIF (0.2, 1.0, or 5.0 mg/kg body weight) or vehicle once daily for 7 days. On the eighth day after sciatic neurectomy, significant bone loss was observed in the vehicle-injected rats. OCIF ameliorated the decrease in bone mineral density (BMD) of both the proximal and distal femur in a dose-dependent manner. OCIF also ameliorated the decrease in bone strength of the femoral neck at the highest dose. A high correlation (r = 0.805) was detected between the BMD of the distal femur and the bone strength of the femoral neck. When OCIF was administered intermittently to the immobilized rats twice weekly (on days 1 and 4) after immobilization, it also ameliorated the decrease in BMD of the distal femur. These results suggest that OCIF has therapeutic potential for the treatment of immobilization-induced osteopenia. PMID:11810411

  4. High-density lipoprotein modulates thrombosis by preventing von Willebrand factor self-association and subsequent platelet adhesion.

    PubMed

    Chung, Dominic W; Chen, Junmei; Ling, Minhua; Fu, Xiaoyun; Blevins, Teri; Parsons, Scott; Le, Jennie; Harris, Jeff; Martin, Thomas R; Konkle, Barbara A; Zheng, Ying; López, José A

    2016-02-01

    The ability of von Willebrand factor (VWF) to initiate platelet adhesion depends on the number of monomers in individual VWF multimers and on the self-association of individual VWF multimers into larger structures. VWF self-association is accelerated by shear stress. We observed that VWF self-association occurs during adsorption of VWF onto surfaces, assembly of secreted VWF into hyperadhesive VWF strings on the endothelial surface, and incorporation of fluid-phase VWF into VWF fibers. VWF adsorption under static conditions increased with increased VWF purity and was prevented by a component of plasma. We identified that component as high-density lipoprotein (HDL) and its major apolipoprotein ApoA-I. HDL and ApoA-I also prevented VWF on the endothelium from self-associating into longer strands and inhibited the attachment of fluid-phase VWF onto vessel wall strands. Platelet adhesion to VWF fibers was reduced in proportion to the reduction in self-associated VWF. In a mouse model of thrombotic microangiopathy, HDL also largely prevented the thrombocytopenia induced by injection of high doses of human VWF. Finally, a potential role for ApoA-I in microvascular occlusion associated with thrombotic thrombocytopenic purpura and sepsis was revealed by the inverse relationship between the concentration of ApoA-I and that of hyperadhesive VWF. These results suggest that interference with VWF self-association would be a new approach to treating thrombotic disorders. PMID:26552698

  5. Biological impact of vascular endothelial growth factor on vessel density and survival in multiple myeloma and plasmacytoma.

    PubMed

    Swelam, Wael M; Al Tamimi, Dalal M

    2010-11-15

    We compared the differences in a number of angiogenesis-related immunohistochemical parameters, including microvascular density (MVD) and tumor cell activity, between multiple myeloma (MM) and solitary plasmacytoma (SP). Tissue sections from tumors of MM and SP were immunohistochemically stained and analyzed using ImageJ image analysis software for the expression of vascular endothelial growth factor (VEGF), VEGF receptors (Flt-1 and Flk-1), inducible nitric oxide (iNOS), and anti-apoptotic (Bcl-2) protein. Tumor tissues were cytologically graded as high-, intermediate-, or low-grade. Two pathologists determined the MVD of each section independently by recording the average number of CD34+ blood vessels in 500 unit fields. The arithmetic means for MVD were statistically analyzed using the Student's t-test and the significance level was calculated at P-value <0.001. The results indicate a direct correlation between upregulation of iNOS/VEGF in high-grade tumors. For MM, an increase in MVD is also correlated with a high-grade. Tumor survival signaling by Bcl-2 in both SP and MM emphasizes the fact that VEGF has a bimodal role that is mainly angiogenic in MM and tumorigenic, promoting tumor cell survival in SP. PMID:20709463

  6. The importance of low serum levels of high-density lipoprotein cholesterol (HDL-C) as a cardiovascular risk factor.

    PubMed

    Espinosa-Larrañaga, Francisco; Vejar-Jalaf, Margarita; Medina-Santillán, Roberto

    2005-10-01

    In order to discuss and establish a joint position on the treatment of low serum levels of high-density lipoprotein cholesterol (HDL-C), a group of experts involved in the care of people with dyslipidaemia and at risk of cardiovascular disease met in Miami, Florida, U.S., on 5th and 6th March 2005. The experts came from the Latin American countries Argentina, Brazil, Chile, Colombia, Ecuador, Guatemala, Mexico and Venezuela and had at least five years of experience in the care of patients with dyslipidaemia and low HDL-C. The main objective of the meeting was to discuss and propose a treatment for low serum HDL-C levels as a cardiovascular risk factor in patients and to create a group of useful recommendations in this regard, applicable to the daily clinical practice of physicians dealing with patients with dyslipidaemia and cardiovascular disease. This document describes the methodology developed to obtain these recommendations and presents the results of this academic meeting. PMID:16342610

  7. Effects of retinoids on differentiation, lipid metabolism, epidermal growth factor, and low-density lipoprotein binding in squamous carcinoma cells

    SciTech Connect

    Ponec, M.; Weerheim, A. ); Havekes, L. ); Boonstra, J. )

    1987-08-01

    The relationship among keratinocyte differentiation capacity, lipid synthesis, low-density lipoprotein (LDL) metabolism, plasma membrane composition, and epidermal growth factor (EGF) binding has been studied in SCC-12F2 cells. The differentiation capacity of the cells, i.e., ionophore-induced cornified envelope formation, was inhibited by various retinoids and stimulated by hydrocortisone. Retinoids that caused a significant reduction of cornified envelope formation, i.e., retinoic acid and 13-cis-retinoic acid, caused only minor changes in lipid synthesis and plasma membrane composition. Arotinoid ethylsulfone, having a minor effect on cornified envelope formation, caused a drastic inhibition of cholesterol synthesis resulting in changes in the plasma membrane composition. Hydrocortisone stimulated cornified envelope formation but had only minor effects on lipid synthesis and plasma membrane composition. Of all retinoids tested, only arotinoid ethylsulfone caused a drastic increase in EGF binding, while hydrocortisone had no effect. These results clearly demonstrate that the plasma membrane composition is not related to keratinocyte differentiation capacity, but most likely does determine EGF binding. Furthermore, EGF binding does not determine keratinocyte differentiation capacity.

  8. Collective modes in a saturated lithium-ammonia solution as a probe of the response of the low-density homogeneous electron gas

    NASA Astrophysics Data System (ADS)

    Petrillo, C.; Sacchetti, F.; Guarini, E.; Bove, L. E.; Demmel, F.

    2011-09-01

    The ion dynamics of a saturated lithium ammonia solution was investigated by inelastic neutron scattering with optimized resolution. The experimental dispersion curve and mode damping, here carefully probed in a wave-vector range extending well below and above 1 Å-1, display visible anomalies around 0.8 Å-1. We relate the dispersion relation anomaly to the shape of the electron gas dielectric function, which screens the ion-ion potential in a way peculiar of the low electron density of the system. The increase of the damping around 0.8 Å-1 also supports the presence of a new decay channel for the collective excitations. An interpretation of these effects, based on the low electron-density properties of the lithium-ammonia solution, is proposed.

  9. Ultra-bright, high-energy-density γ-ray emission from a gas-filled gold cone-capillary

    NASA Astrophysics Data System (ADS)

    Zhu, Xing-Long; Yin, Yan; Yu, Tong-Pu; Liu, Jin-Jin; Zou, De-Bin; Ge, Zhe-Yi; Wang, Wei-Quan; Shao, Fu-Qiu

    2015-09-01

    We propose a new scheme to obtain a compact ultra-bright, high-energy-density γ ray source by ultra-intense laser interaction with a near-critical-density (NCD) plasmas filled gold cone-capillary. By using the particle-in-cell code EPOCH, it is shown that NCD electrons are accelerated by the laser ponderomotive force in the gold cone and emit strong radiation. Considering the effect of large radiation back-reaction force, some electrons are kicked into the laser field. The trapped electrons oscillate significantly in the transverse direction and emit ultra-bright γ ray in the forward direction. By attaching a capillary to the gold cone, the trapped electrons are able to keep oscillating for a long distance and the radiation emission can be significantly enhanced. Three-dimensional simulations show that the total γ photon flux with the photon energy in the range of 3 MeV to 30 MeV is approximately 1013/shot, and the corresponding peak brightness is in the order of 1023 photons/s/mm2/mrad2/0.1%BW. The average energy-density of the radiated γ photons is about 1017J /m3 , which is six orders of magnitude higher than the threshold of high-energy-density physics. The energy conversion efficiency from the laser to the γ photons is estimated to be about 5% at the irradiation of a laser with intensity ˜1.37 ×1022W /cm2 .

  10. High-density lipoprotein cholesterol as an independent risk factor in cardiovascular disease: assessing the data from Framingham to the Veterans Affairs High--Density Lipoprotein Intervention Trial.

    PubMed

    Boden, W E

    2000-12-21

    The Framingham Heart Study found that high-density lipoprotein cholesterol (HDL-C) was the most potent lipid predictor of coronary artery disease risk in men and women >49 years of age. The Air Force/Texas Coronary Atheros