WorldWideScience

Sample records for density contrasts distributions

  1. Study delay and dispersion effects in dynamic susceptibility contrast MRI based on local density random walk distribution

    Science.gov (United States)

    Li, Xingfeng; Tian, Jie; Wang, Xiaoxiang; Dai, Jianping; Ai, Lin

    2004-04-01

    The aim of this study was to assess the validation of the local density random walk (LDRW) function to correct the delayed and dispersed arterial input function (AIF) data derived from dynamic susceptibility contrast magnetic resonance imaging (DSC-MRI). Instead of using the gamma-variate function to smooth and extrapolate the AIF curves, we suggested a method which was based on diffusion with drift approach. Forty-seven AIF curves from ten patients were segmented to test the effectiveness of the proposed method. The results of the comparisons with the gamma-variate function showed that the LDRW distribution function may provide a new means for more accurate correction of AIF curves.

  2. Density Distribution Sunflower Plots

    OpenAIRE

    Dupont, William D; W. Dale Plummer Jr.

    2003-01-01

    Density distribution sunflower plots are used to display high-density bivariate data. They are useful for data where a conventional scatter plot is difficult to read due to overstriking of the plot symbol. The x-y plane is subdivided into a lattice of regular hexagonal bins of width w specified by the user. The user also specifies the values of l, d, and k that affect the plot as follows. Individual observations are plotted when there are less than l observations per bin as in a conventio...

  3. Density contrast indicators in cosmological dust models

    Indian Academy of Sciences (India)

    Filipe C Mena; Reza Tavakol

    2000-10-01

    We discuss ways of quantifying structuration in relativistic cosmological settings, by employing a family of covariant density constrast indicators. We study the evolution of these indicators with time in the context of inhomogeneous Szekeres models. We find that different observers (having either different spatial locations or different indicators) see different evolutions for the density contrast, which may or may not be monotonically increasing with time. We also find that monotonicity seems to be related to the initial conditions of the model, which may be of potential interest in connection with debates regarding gravitational entropy and the arrow of time.

  4. Density Distribution Sunflower Plots

    Directory of Open Access Journals (Sweden)

    William D. Dupont

    2003-01-01

    Full Text Available Density distribution sunflower plots are used to display high-density bivariate data. They are useful for data where a conventional scatter plot is difficult to read due to overstriking of the plot symbol. The x-y plane is subdivided into a lattice of regular hexagonal bins of width w specified by the user. The user also specifies the values of l, d, and k that affect the plot as follows. Individual observations are plotted when there are less than l observations per bin as in a conventional scatter plot. Each bin with from l to d observations contains a light sunflower. Other bins contain a dark sunflower. In a light sunflower each petal represents one observation. In a dark sunflower, each petal represents k observations. (A dark sunflower with p petals represents between /2-pk k and /2+pk k observations. The user can control the sizes and colors of the sunflowers. By selecting appropriate colors and sizes for the light and dark sunflowers, plots can be obtained that give both the overall sense of the data density distribution as well as the number of data points in any given region. The use of this graphic is illustrated with data from the Framingham Heart Study. A documented Stata program, called sunflower, is available to draw these graphs. It can be downloaded from the Statistical Software Components archive at http://ideas.repec.org/c/boc/bocode/s430201.html . (Journal of Statistical Software 2003; 8 (3: 1-5. Posted at http://www.jstatsoft.org/index.php?vol=8 .

  5. Relationship Between Collateral Status, Contrast Transit, and Contrast Density in Acute Ischemic Stroke.

    Science.gov (United States)

    Kawano, Hiroyuki; Bivard, Andrew; Lin, Longting; Spratt, Neil J; Miteff, Ferdinand; Parsons, Mark W; Levi, Christopher R

    2016-03-01

    Collateral circulation is recognized to influence the life expectancy of the ischemic penumbra in acute ischemic stroke. The best method to quantify collateral status on acute imaging is uncertain. We aimed to determine the relationship between visual collateral status, quantitative collateral assessments, baseline computed tomographic perfusion measures, and tissue outcomes on follow-up imaging. Sixty-six consecutive patients with acute ischemic stroke clinically eligible for recanalization therapy and with M1 or M2 middle cerebral artery occlusion were evaluated. We compared the visual collateral scoring with measures of contrast peak time delay and contrast peak density. We also compared these measures for their ability to predict perfusion lesion and infarct core volumes, final infarct, and infarct growth. Shorter contrast peak time delay (P=0.041) and higher contrast peak density (P=0.002) were associated with good collateral status. Shorter contrast peak time delay correlated with higher contrast peak density (β=-4.413; P=0.037). In logistic regression analysis after adjustment for age, sex, onset-computed tomographic time, and occlusion site, higher contrast peak density was independently associated with good collateral status (P=0.009). Multiple regression analysis showed that higher contrast peak density was an independent predictor of smaller perfusion lesion volume (P=0.029), smaller ischemic core volume (P=0.044), smaller follow-up infarct volume (P=0.005), and smaller infarct growth volume (P=0.010). Visual collateral status, contrast peak density, and contrast peak time delay were inter-related, and good collateral status was strongly associated with contrast peak density. Contrast peak density in collateral vessel may be an important factor in tissue fate in acute ischemic stroke. © 2016 American Heart Association, Inc.

  6. From Density Contrast to Compositional Difference on Pluto and Charon

    Science.gov (United States)

    Bierson, C. J.; Nimmo, F.; McKinnon, W. B.

    2016-12-01

    Leading up to the New Horizons encounter, modeling work suggested that if Pluto and Charon formed in a giant impact Charon would be more ice rich than Pluto [1,2]. Conversely, if Pluto and Charon both formed in-situ they should have the same bulk composition. New Horizons has confirmed that Pluto and Charon have distinct bulk densities, 1854 ± 11 kg m-3 and 1701 ± 33 kg m-3 respectively [3]. The question is whether this density contrast necessarily implies a compositional difference. We investigate if differences in the porous structure of Pluto and Charon could explain this observed density contrast. We couple a thermal model [4] with a model of viscous pore closure [5]. We include both the temperature dependence and the effect of porosity on thermal conductivity of the ice mantle. Due to the both lower gravity and lower heat flux, Charon can maintain a thicker porous layer over the age of the solar system. This effect however, only produces a bulk density contrast between Pluto and Charon of 60 kg m-3 , compared with the observed density contrast of 153±44 kg m-3. Other factors such as a modern ocean on Pluto, larger compression in Pluto's interior, and chemical water-rock interactions are also considered. None of these processes, even when combined, can explain the observed density contrast. From this we conclude that Pluto and Charon must be compositionally distinct. We will discuss the implications this compositional difference has for the formation and evolution of the Pluto-Charon system. References: [1] Canup, Science (2005). [2] Canup, The Astronomical Journal (2010). [3] Nimmo et al. arXiv preprint (2016). [4] Robuchon and Nimmo. Icarus (2011) [5] Besserer et al. JGR: Planets (2013)

  7. Moho Density Contrast in Central Eurasia from GOCE Gravity Gradients

    Directory of Open Access Journals (Sweden)

    Mehdi Eshagh

    2016-05-01

    Full Text Available Seismic data are primarily used in studies of the Earth’s inner structure. Since large parts of the world are not yet sufficiently covered by seismic surveys, products from the Earth’s satellite observation systems have more often been used for this purpose in recent years. In this study we use the gravity-gradient data derived from the Gravity field and steady-state Ocean Circulation Explorer (GOCE, the elevation data from the Shuttle Radar Topography Mission (SRTM and other global datasets to determine the Moho density contrast at the study area which comprises most of the Eurasian plate (including parts of surrounding continental and oceanic tectonic plates. A regional Moho recovery is realized by solving the Vening Meinesz-Moritz’s (VMM inverse problem of isostasy and a seismic crustal model is applied to constrain the gravimetric solution. Our results reveal that the Moho density contrast reaches minima along the mid-oceanic rift zones and maxima under the continental crust. This spatial pattern closely agrees with that seen in the CRUST1.0 seismic crustal model as well as in the KTH1.0 gravimetric-seismic Moho model. However, these results differ considerably from some previously published gravimetric studies. In particular, we demonstrate that there is no significant spatial correlation between the Moho density contrast and Moho deepening under major orogens of Himalaya and Tibet. In fact, the Moho density contrast under most of the continental crustal structure is typically much more uniform.

  8. RHOCUBE: 3D density distributions modeling code

    Science.gov (United States)

    Nikutta, Robert; Agliozzo, Claudia

    2016-11-01

    RHOCUBE models 3D density distributions on a discrete Cartesian grid and their integrated 2D maps. It can be used for a range of applications, including modeling the electron number density in LBV shells and computing the emission measure. The RHOCUBE Python package provides several 3D density distributions, including a powerlaw shell, truncated Gaussian shell, constant-density torus, dual cones, and spiralling helical tubes, and can accept additional distributions. RHOCUBE provides convenient methods for shifts and rotations in 3D, and if necessary, an arbitrary number of density distributions can be combined into the same model cube and the integration ∫ dz performed through the joint density field.

  9. The density curve of F distribution

    Institute of Scientific and Technical Information of China (English)

    LIU Xiaopeng; LIU Kunhui

    2004-01-01

    Employing the properties of special function,we discuss the positional relation between two density curves with different parameters for F distribution in this paper.Some varying regularities about the position of density curve of F distribution have been obtained.

  10. Information Theory and the Earth's Density Distribution

    Science.gov (United States)

    Rubincam, D. P.

    1979-01-01

    An argument for using the information theory approach as an inference technique in solid earth geophysics. A spherically symmetric density distribution is derived as an example of the method. A simple model of the earth plus knowledge of its mass and moment of inertia lead to a density distribution which was surprisingly close to the optimum distribution. Future directions for the information theory approach in solid earth geophysics as well as its strengths and weaknesses are discussed.

  11. Distribution of milled peat density in stockpiles

    Energy Technology Data Exchange (ETDEWEB)

    Kuntsevich, V.B. (and others)

    1987-01-01

    The interaction of pile density and spontaneous heating and/or combustion for a range of peat types and decomposition degrees was investigated. Up to a self-heating temperature of 75 degrees C, density distribution was normal throughout the pile but thereafter it increased locally with temperature and involved weight losses of 28-52% of the original peat in the semi-coke zone. The results are tabulated. 4 refs., 1 fig., 1 tab.

  12. Complexity Analysis of Peat Soil Density Distribution

    Science.gov (United States)

    Sampurno, Joko; Diah Faryuni, Irfana; Dzar Eljabbar Latief, Fourier; Srigutomo, Wahyu

    2016-08-01

    The distributions of peat soil density have been identified using fractal analysis method. The study was conducted on 5 peat soil samples taken from a ground field in Pontianak, West Kalimantan, at the coordinates (0 ° 4 '2:27 "S, 109 ° 18' 48.59" E). In this study, we used micro computerized tomography (pCT Scanner) at 9.41 micro meter per pixel resolution under peat soil samples to provide 2-D high-resolution images L1-L5 (200 200 pixels) that were used to detect the distribution of peat soil density. The method for determining the fractal dimension and intercept was the 2-D Fourier analysis method. The method was used to obtain the log log-plot of magnitude with frequency. Fractal dimension was obtained from the straight regression line that interpolated the points in the interval with the largest coefficient determination. Intercept defined by the point of intersection on the -axis. The conclusion was that the distributions of peat soil density showing the fractal behaviour with the heterogeneity of the samples from the highest to the lowest were L5, L1, L4, L3 and L2. Meanwhile, the range of density values of the samples from the highest to the lowest was L3, L2, L4, L5 and L1. The study also concluded that the behaviour of the distribution of peat soil density was a weakly anisotropic.

  13. THE DENSITY DISTRIBUTION IN TURBULENT BISTABLE FLOWS

    Energy Technology Data Exchange (ETDEWEB)

    Gazol, Adriana [Centro de Radioastronomia y Astrofisica, UNAM, A. P. 3-72, c.p. 58089 Morelia, Michoacan (Mexico); Kim, Jongsoo, E-mail: a.gazol@crya.unam.mx, E-mail: jskim@kasi.re.kr [Korea Astronomy and Space Science Institute, 61-1, Hwaam-Dong, Yuseong-Ku, Daejeon 305-348 (Korea, Republic of)

    2013-03-01

    We numerically study the volume density probability distribution function (n-PDF) and the column density probability distribution function ({Sigma}-PDF) resulting from thermally bistable turbulent flows. We analyze three-dimensional hydrodynamic models in periodic boxes of 100 pc by side, where turbulence is driven in the Fourier space at a wavenumber corresponding to 50 pc. At low densities (n {approx}< 0.6 cm{sup -3}), the n-PDF is well described by a lognormal distribution for an average local Mach number ranging from {approx}0.2 to {approx}5.5. As a consequence of the nonlinear development of thermal instability (TI), the logarithmic variance of the distribution of the diffuse gas increases with M faster than in the well-known isothermal case. The average local Mach number for the dense gas (n {approx}> 7.1 cm{sup -3}) goes from {approx}1.1 to {approx}16.9 and the shape of the high-density zone of the n-PDF changes from a power law at low Mach numbers to a lognormal at high M values. In the latter case, the width of the distribution is smaller than in the isothermal case and grows slower with M. At high column densities, the {Sigma}-PDF is well described by a lognormal for all of the Mach numbers we consider and, due to the presence of TI, the width of the distribution is systematically larger than in the isothermal case but follows a qualitatively similar behavior as M increases. Although a relationship between the width of the distribution and M can be found for each one of the cases mentioned above, these relations are different from those of the isothermal case.

  14. Detection of low-contrast signals in low optical density. Effects of film contrast and noise on signal detection

    Energy Technology Data Exchange (ETDEWEB)

    Kondoh, Yasufumi; Hamada, Tomohiro; Mochizuki, Yuji; Yoshida, Yukito; Murakami, Yasunori [Oita Medical Univ., Hasama (Japan). Hospital; Higashida, Yoshiharu

    1998-04-01

    Observer performance tests were conducted to establish the effects of the noise and film contrast of screen-film systems on the detection of low-contrast signals. Three screen-film systems with different noise levels and film contrast were used in the experiments. The observer performance tests were carried out by the contrast-detail (C-D) diagram method and receiver operating characteristic (ROC) analysis. The results of observer performance tests with the C-D diagram method and ROC analysis indicated that the screen-film system with low noise level and high film contrast provided higher detectability than the system with low noise and low contrast. The screen-film system with high contrast showed greater improvement in detectability than the system with low contrast and low noise at low optical densities, despite the increase in noise. (author)

  15. High seed dispersal ability of Pinus canariensis in stands of contrasting density inferred from genotypic data

    Directory of Open Access Journals (Sweden)

    Unai López de Heredia

    2015-04-01

    Full Text Available Aim of the study: Models that combine parentage analysis from molecular data with spatial information of seeds and seedlings provide a framework to describe and identify the factors involved in seed dispersal and recruitment of forest species. In the present study we used a spatially explicit method (the gene shadow model in order to assess primary and effective dispersal in Pinus canariensis. Area of study: Pinus canariensis is endemic to the Canary Islands (Spain. Sampling sites were a high density forest in southern slopes of Tenerife and a low density stand in South Gran Canaria. Materials and methods: We fitted models based on parentage analysis from seeds and seedlings collected in two sites with contrasting stand density, and then compared the resulting dispersal distributions. Main results: The results showed that: 1 P. canariensis has a remarkable dispersal ability compared to other pine species; 2 there is no discordance between primary and effective dispersals, suggesting limited secondary dispersal by animals and lack of Janzen-Connell effect; and 3 low stand densities enhance the extent of seed dispersal, which was higher in the low density stand. Research highlights: The efficient dispersal mechanism of P. canariensis by wind inferred by the gene shadow model is congruent with indirect measures of gene flow, and has utility in reconstructing past demographic events and in predicting future distribution ranges for the species.

  16. An experimental study of the effects of density and viscosity contrasts on macrodispersion in porous media

    Science.gov (United States)

    Kretz, V.; Berest, P.; Hulin, J. P.; Salin, D.

    2003-02-01

    We study the vertical miscible displacements of two fluids of different densities and/or viscosities in two model porous media, constructed using different arrangements of blocks of packed glass beads with different sizes. The two configurations have the same permeability distributions but different spatial arrangements and structural features. Time variations of the mean fluid concentration in different sections along the samples are monitored by an acoustic technique. For stable viscosity or density contrasts, the spreading of the displacement front is predominantly macrodispersive. For fluids of the same viscosity but different densities, the macrodispersivities approach at large velocities, where the displacement is stable, the passive tracer limit, ld∞, which is controlled only by the heterogeneity of the medium. This is true, regardless of the density contrast. At lower velocities, where gravity instabilities can exist, the normalized dispersivities ld/ld∞ vary exponentially with the normalized flow rate, with opposite exponents in the stable and unstable configurations. These results are compared to existing theoretical works based on stochastic approaches and linear stability analyses.

  17. Density Matrix for Mesoscopic Distributed Parameter Circuits

    Institute of Scientific and Technical Information of China (English)

    JI Ying-Hua; WANG Qi; LUO Hai-Mei; LEI Min-Sheng

    2005-01-01

    Under the Born-von-Karmann periodic boundary condition, we propose a quantization scheme for nondissipative distributed parameter circuits (i.e. a uniform periodic transmission line). We find the unitary operator for diagonalizing the Hamiltonian of the uniform periodic transmission line. The unitary operator is expressed in a coordinate representation that brings convenience to deriving the density matrix p(q, q',β). The quantum fluctuations of charge and current at a definite temperature have been studied. It is shown that quantum fluctuations of distributed parameter circuits, which also have distributed properties, are related to both the circuit parameters and the positions and the mode of signals and temperature T. The higher the temperature is, the stronger quantum noise the circuit exhibits.

  18. Protostellar fragmentation in a power-law density distribution

    CERN Document Server

    Burkert, A; Bodenheimer, P

    1997-01-01

    Hydrodynamical calculations in three space dimensions of the collapse of an isothermal, rotating 1 M\\sol protostellar cloud are presented. The initial density stratification is a power law with density $\\rho \\propto r^{-p}$, with $p=1$. The case of the singular isothermal sphere ($p=2$) is not considered; however $p=1$ has been shown observationally to be a good representation of the density distribution in molecular cloud cores just before the beginning of collapse. The collapse is studied with two independent numerical methods, an SPH code with 200,000 particles, and a finite-difference code with nested grids which give high spatial resolution in the inner regions. Although previous numerical studies have indicated that such a power-law distribution would not result in fragmentation into a binary system, both codes show, in contrast, that multiple fragmentation does occur in the central regions of the protostar. Thus the process of binary formation by fragmentation is shown to be consistent with the fact th...

  19. Intravenous contrast injection significantly affects bone mineral density measured on CT

    NARCIS (Netherlands)

    Pompe, Esther; Willemink, Martin J.; Dijkhuis, Gawein R.; Verhaar, Harald J. J.|info:eu-repo/dai/nl/111379628; Mohamed Hoesein, Firdaus A A|info:eu-repo/dai/nl/341235512; de Jong, Pim A.|info:eu-repo/dai/nl/287955672

    2015-01-01

    OBJECTIVE: The objective is to evaluate the effect of intravenous contrast media on bone mineral density (BMD) assessment by comparing unenhanced and contrast-enhanced computed tomography (CT) examinations performed for other indications. METHODS: One hundred and fifty-two patients (99 without and 5

  20. Intravenous contrast injection significantly affects bone mineral density measured on CT

    NARCIS (Netherlands)

    Pompe, Esther; Willemink, Martin J.; Dijkhuis, Gawein R.; Verhaar, Harald J. J.; Mohamed Hoesein, Firdaus A A; de Jong, Pim A.

    2015-01-01

    OBJECTIVE: The objective is to evaluate the effect of intravenous contrast media on bone mineral density (BMD) assessment by comparing unenhanced and contrast-enhanced computed tomography (CT) examinations performed for other indications. METHODS: One hundred and fifty-two patients (99 without and 5

  1. Diffusion and near-equilibrium distribution of MRI and CT contrast agents in articular cartilage

    Science.gov (United States)

    Silvast, Tuomo S.; Kokkonen, Harri T.; Jurvelin, Jukka S.; Quinn, Thomas M.; Nieminen, Miika T.; Töyräs, Juha

    2009-11-01

    Charged contrast agents have been used both in vitro and in vivo for estimation of the fixed charge density (FCD) in articular cartilage. In the present study, the effects of molecular size and charge on the diffusion and equilibrium distribution of several magnetic resonance imaging (MRI) and computed tomography (CT) contrast agents were investigated. Full thickness cartilage disks (Ø = 4.0 mm, n = 64) were prepared from fresh bovine patellae. Contrast agent (gadopentetate: Magnevist®, gadodiamide: Omniscan™, ioxaglate: Hexabrix™ or sodium iodide: NaI) diffusion was allowed either through the articular surface or through the deep cartilage. CT imaging of the samples was conducted before contrast agent administration and after 1, 5, 9, 16, 25 and 29 h (and with three samples after 2, 3, 4 and 5 days) diffusion using a clinical peripheral quantitative computed tomography (pQCT) instrument. With all contrast agents, the diffusion through the deep cartilage was slower when compared to the diffusion through the articular surface. With ioxaglate, gadopentetate and gadodiamide it took over 29 h for diffusion to reach the near-equilibrium state. The slow diffusion of the contrast agents raise concerns regarding the validity of techniques for FCD estimation, as these contrast agents may not reach the equilibrium state that is assumed. However, since cartilage composition, i.e. deep versus superficial, had a significant effect on diffusion, imaging of the nonequilibrium diffusion process might enable more accurate assessment of cartilage integrity.

  2. On the evolution of the cosmic-mass-density contrast and the cosmological constant

    CERN Document Server

    Palle, D

    2003-01-01

    We study the evolution of the cosmic-mass-density contrast beyond the Robertson-Walker geometry including the small contribution of acceleration. We derive a second-order evolution equation for the density contrast within the spherical model for CDM collisionless fluid including the cosmological constant, the expansion and the non-vanishing vector of acceleration. While the mass-density is not seriously affected by acceleration, the mass-density contrast changes its shape at smaller redshifts even for a small amount of the acceleration parameter. This could help to resolve current controversial results in cosmology from measurements of WMAP, gravitational lensing, XMM X-ray cluster or type Ia supernovae data, etc.

  3. Characteristic density contrasts in the evolution of superclusters. The case of A2142 supercluster

    Science.gov (United States)

    Gramann, Mirt; Einasto, Maret; Heinämäki, Pekka; Teerikorpi, Pekka; Saar, Enn; Nurmi, Pasi; Einasto, Jaan

    2015-09-01

    Context. The formation and evolution of the cosmic web in which galaxy superclusters are the largest relatively isolated objects is governed by a gravitational attraction of dark matter and antigravity of dark energy (cosmological constant). Aims: We study the characteristic density contrasts in the spherical collapse model for several epochs in the supercluster evolution and their dynamical state. Methods: We analysed the density contrasts for the turnaround, future collapse, and zero gravity in different ΛCDM models and applied them to study the dynamical state of the supercluster A2142 with an almost spherical main body, making it a suitable test object to apply a model that assumes sphericity. Results: We present characteristic density contrasts in the spherical collapse model for different cosmological parameters. The analysis of the supercluster A2142 shows that its high-density core has already started to collapse. The zero-gravity line outlines the outer region of the main body of the supercluster. In the course of future evolution, the supercluster may split into several collapsing systems. Conclusions: The various density contrasts presented in our study and applied to the supercluster A2142 offer a promising way to characterise the dynamical state and expected future evolution of galaxy superclusters.

  4. Distributed Atmospheric Neutral Density Explorer (DANDE)

    Science.gov (United States)

    2010-08-31

    Rolla) 331 Toomey Hall 400 West 13th Street Rolla, MO 65409-0050 AFOSR / RSE 875 North Randolph Street, Suit 325 Room 3112 Arlington, Virginia...22203-1768 AFOSR/ RSE AFRL-OSR-VA-TR-2012-0737 1) DISTRIBUTION STATEMENT A: Approved for public release; distribution is unlimited The DANDE program...systems. Standard terms apply U U U UU 2 Kent Miller, RSE (Program Manager) 703.696.8573 To: technicalreports@afosr.af.mil Subject: Progress

  5. Unstable density distribution associated with equatorial plasma bubble

    Science.gov (United States)

    Kherani, E. A.; Bharuthram, R.; Singh, S.; Lakhina, G. S.; de Meneses, F. Carlos

    2016-04-01

    In this work, we present a simulation study of equatorial plasma bubble (EPB) in the evening time ionosphere. The fluid simulation is performed with a high grid resolution, enabling us to probe the steepened updrafting density structures inside EPB. Inside the density depletion that eventually evolves as EPB, both density and updraft are functions of space from which the density as implicit function of updraft velocity or the density distribution function is constructed. In the present study, this distribution function and the corresponding probability distribution function are found to evolve from Maxwellian to non-Maxwellian as the initial small depletion grows to EPB. This non-Maxwellian distribution is of a gentle-bump type, in confirmation with the recently reported distribution within EPB from space-borne measurements that offer favorable condition for small scale kinetic instabilities.

  6. CONTRAST

    DEFF Research Database (Denmark)

    Kristensen, Thomas Krogsgaard

    2007-01-01

    Dette er en afrapportering fra den årlige CONTRAST workshop, der i 2007 blev afholdt i Yaoundé, Cameroon.......Dette er en afrapportering fra den årlige CONTRAST workshop, der i 2007 blev afholdt i Yaoundé, Cameroon....

  7. Initial Distribution Spread: A density forecasting approach

    CERN Document Server

    Machete, Reason L

    2012-01-01

    Ensemble forecasting of nonlinear systems involves the use of a model to run forward a discrete ensemble (or set) of initial states. Data assimilation techniques tend to focus on estimating the true state of the system, even though model error limits the value of such efforts. This paper argues for choosing the initial ensemble in order to optimise forecasting performance rather than estimate the true state of the system. Density forecasting and choosing the initial ensemble are treated as one problem. Forecasting performance can be quantified by some scoring rule. In the case of the logarithmic scoring rule, theoretical arguments and empirical results are presented. It turns out that, if the underlying noise dominates model error, we can diagnose the noise spread.

  8. Einasto as a new approach for noncommutativity density distribution?

    CERN Document Server

    Hernandez-Almada, Alberto

    2016-01-01

    In this paper we analyze the galaxy rotation curves using a density profile that comes from noncommutativity (NC) theory. We will refer to this distribution as NC density. In this case, we use the Einasto's density profile as a reference due that it is a generalized case of NC distribution and is one of the most successful phenomenological profiles to describe the rotation curve of galaxies. Based on these results, we open a discussion if Einasto's profile could be used as an extension of NC density and if could be applied to other studies treated by this theory.

  9. Ion Density Distribution in an Inductively Coupled Plasma Chamber

    Institute of Scientific and Technical Information of China (English)

    陈俊芳; 赵文锋; 吴先球; 樊双莉; 符斯列

    2004-01-01

    The ion density distribution in the reaction chamber was diagnosed by a Langmuir probe. The rules of the ion density distribution were obtained under the pressures of 9 Pa, 13 Pa,27 Pa and 53 Pa in the reaction chamber, different radio-frequency powers and different positions.The result indicates that the ion density decreases as the pressure increases, and increases as the power decreases. The ion density of axial position z = 0 achieves 5.8×10 10 on the center of coil under the power of 200 w and pressure of 9 Pa in the reaction chamber.

  10. Density and Macroporosity Distribution of Near Earth Asteroids

    Science.gov (United States)

    Dotson, Jessie L.; Mathias, Donovan

    2017-01-01

    The density of near earth asteroids is a fundamental property which can illuminate the structure of the asteroid, provide clues about it’s collisional history and is key in assessing the hazard of an impact of an NEA with Earth. A low density can be indicative of a rubble pile structure whereas a higher density can imply a monolith and/or a higher metal content. Unfortunately, measuring the density of asteroids is extremely difficult, has only been attempted for a tiny fraction of NEAs and usually results in measurements with large uncertainties. In the absence of density measurements for a specific object, understanding the range and distribution of likely densities can allow for probabilistic assessments of the population and facilitate estimates of the range of reasonable masses for a specific object. We have developed a candidate macroporosity distribution for near earth asteroids based on measurements of meteorite densities and asteroid densities. The macroporosity of an asteroid can be used to aid extrapolation from meteorite physical properties to asteroid physical properties. In addition, we discuss estimating an asteroid density distribution from the macroporosity distribution.

  11. Characteristic density contrasts in the evolution of superclusters. The case of A2142 supercluster

    CERN Document Server

    Gramann, Mirt; Heinämäki, Pekka; Teerikorpi, Pekka; Saar, Enn; Nurmi, Pasi; Einasto, Jaan

    2015-01-01

    The formation and evolution of the cosmic web in which galaxy superclusters are the largest relatively isolated objects is governed by a gravitational attraction of the dark matter and antigravity of the dark energy (cosmological constant). We study the characteristic density contrasts in the spherical collapse model for several epochs in the supercluster evolution and their dynamical state. We analyse the density contrasts for the turnaround, for the future collapse and for the zero-gravity in different LCDM models and apply them to study the dynamical state of the supercluster A2142 with an almost spherical main body. The analysis of the supercluster A2142 shows that its high-density core has already started to collapse. The zero-gravity line outlines the outer region of the main body of the supercluster. In the course of future evolution the supercluster may split into several collapsing systems. The various density contrasts presented in our study and applied to the supercluster A2142 offer a promising wa...

  12. Forms of density regulation and (quasi-) stationary distributions of population sizes in birds

    DEFF Research Database (Denmark)

    Sæther, Bernt-Erik; Engen, Steinar; Grøtan, Vidar;

    2008-01-01

    that have grown from very small population sizes followed by a period of fluctuations around K. We then use these parameters to estimate the quasi-stationary distribution of population size. There were often large uncertainties in these parameters specifying the form of density regulation that were...... generally independent of the duration of the study period. In contrast, precision in the estimates of environmental variance increased with the length of the time series. In most of the populations, a large proportion of the probability density of the (quasi-) stationary distribution of population sizes......The theta-logistic model of density regulation is an especially flexible class of density regulation models where different forms of non-linear density regulation can be expressed by only one parameter, u. Estimating the parameters of the thetalogistic model is, however, challenging. This is mainly...

  13. Wigner Function of Density Operator for Negative Binomial Distribution

    Institute of Scientific and Technical Information of China (English)

    HE Min-Hua; XU Xing-Lei; ZHANG Duan-Ming; LI Hong-Qi; PAN Gui-Jun; YIN Yan-Ping; CHEN Zhi-Yuan

    2008-01-01

    By using the technique of integration within an ordered product (IWOP) of operator we derive Wigner function of density operator for negative binomial distribution of radiation field in the mixed state case, then we derive the Wigner function of squeezed number state, which yields negative binomial distribution by virtue of the entangled state representation and the entangled Wigner operator.

  14. Estimation of current density distribution under electrodes for external defibrillation

    Directory of Open Access Journals (Sweden)

    Papazov Sava P

    2002-12-01

    Full Text Available Abstract Background Transthoracic defibrillation is the most common life-saving technique for the restoration of the heart rhythm of cardiac arrest victims. The procedure requires adequate application of large electrodes on the patient chest, to ensure low-resistance electrical contact. The current density distribution under the electrodes is non-uniform, leading to muscle contraction and pain, or risks of burning. The recent introduction of automatic external defibrillators and even wearable defibrillators, presents new demanding requirements for the structure of electrodes. Method and Results Using the pseudo-elliptic differential equation of Laplace type with appropriate boundary conditions and applying finite element method modeling, electrodes of various shapes and structure were studied. The non-uniformity of the current density distribution was shown to be moderately improved by adding a low resistivity layer between the metal and tissue and by a ring around the electrode perimeter. The inclusion of openings in long-term wearable electrodes additionally disturbs the current density profile. However, a number of small-size perforations may result in acceptable current density distribution. Conclusion The current density distribution non-uniformity of circular electrodes is about 30% less than that of square-shaped electrodes. The use of an interface layer of intermediate resistivity, comparable to that of the underlying tissues, and a high-resistivity perimeter ring, can further improve the distribution. The inclusion of skin aeration openings disturbs the current paths, but an appropriate selection of number and size provides a reasonable compromise.

  15. Probability distribution functions in the finite density lattice QCD

    CERN Document Server

    Ejiri, S; Aoki, S; Kanaya, K; Saito, H; Hatsuda, T; Ohno, H; Umeda, T

    2012-01-01

    We study the phase structure of QCD at high temperature and density by lattice QCD simulations adopting a histogram method. We try to solve the problems which arise in the numerical study of the finite density QCD, focusing on the probability distribution function (histogram). As a first step, we investigate the quark mass dependence and the chemical potential dependence of the probability distribution function as a function of the Polyakov loop when all quark masses are sufficiently large, and study the properties of the distribution function. The effect from the complex phase of the quark determinant is estimated explicitly. The shape of the distribution function changes with the quark mass and the chemical potential. Through the shape of the distribution, the critical surface which separates the first order transition and crossover regions in the heavy quark region is determined for the 2+1-flavor case.

  16. Quantitative imaging of electron density and effective atomic number using phase contrast CT

    Energy Technology Data Exchange (ETDEWEB)

    Qi Zhihua; Zambelli, Joseph; Bevins, Nicholas; Chen Guanghong, E-mail: gchen7@wisc.ed [Department of Medical Physics, University of Wisconsin-Madison, WI 53705 (United States)

    2010-05-07

    Compared to single energy CT, which only provides information for x-ray linear attenuation coefficients, dual-energy CT is able to obtain both the electron density and effective atomic number for different materials in a quantitative way. In this study, as an alternative to dual-energy CT, a novel quantitative imaging method based on phase contrast CT is presented. Rather than requiring two projection data sets with different x-ray energy spectra, diffraction-grating-based phase contrast CT is capable of reconstructing images of both linear attenuation and refractive index decrement from the same projection data using a single x-ray energy spectra. From the two images, quantitative information of both the electron density and effective atomic number can be extracted. Two physical phantoms were constructed and used to validate the presented method. Experimental results demonstrate that (1) electron density can be accurately determined from refractive index decrement through a linear relationship, and (2) the effective atomic number can be explicitly derived from the ratio of the linear attenuation to refractive index decrement using a power function plus a constant. The presented method will provide insight into the technique of material separation and find its use in medical and industrial applications.

  17. Quantitative imaging of electron density and effective atomic number using phase contrast CT

    Science.gov (United States)

    Qi, Zhihua; Zambelli, Joseph; Bevins, Nicholas; Chen, Guang-Hong

    2010-05-01

    Compared to single energy CT, which only provides information for x-ray linear attenuation coefficients, dual-energy CT is able to obtain both the electron density and effective atomic number for different materials in a quantitative way. In this study, as an alternative to dual-energy CT, a novel quantitative imaging method based on phase contrast CT is presented. Rather than requiring two projection data sets with different x-ray energy spectra, diffraction-grating-based phase contrast CT is capable of reconstructing images of both linear attenuation and refractive index decrement from the same projection data using a single x-ray energy spectra. From the two images, quantitative information of both the electron density and effective atomic number can be extracted. Two physical phantoms were constructed and used to validate the presented method. Experimental results demonstrate that (1) electron density can be accurately determined from refractive index decrement through a linear relationship, and (2) the effective atomic number can be explicitly derived from the ratio of the linear attenuation to refractive index decrement using a power function plus a constant. The presented method will provide insight into the technique of material separation and find its use in medical and industrial applications.

  18. Density distribution in a heavy-medium cyclone

    Institute of Scientific and Technical Information of China (English)

    Wang Yuling; Zhao Yuemin; Yang Jianguo

    2011-01-01

    Heavy-medium cyclones are widely used to upgrade run-of-mine coal. But the understanding of flow in a cyclone containing a dense medium is still incomplete. By introducing turbulent diffusion into calculations of centrifugal settling a theoretical distribution function giving the density field can be deduced. Qualitative analysis of the density field in every part of a cylindrical cyclone suggests an optimum design that has exhibited good separation effectiveness and anti-wear performance when in commercial operation.

  19. Extraction of density distributions and particle locations from hologram images

    Energy Technology Data Exchange (ETDEWEB)

    Ikeda, Koh; Okamoto, Koji [Tokyo Univ., Tokai, Ibaraki (Japan). Nuclear Engineering Research Lab.; Kato, Fumitake; Shimizu, Isao

    1996-11-01

    In this study, the simultaneous measurement technique for three-dimensional density and three-dimensional velocity distributions was evaluated. The Holographic Particle Image Velocimetry (HPIV) was the technique to record the three-dimensional position of the tracer particle on the hologram. In the hologram, the interferogram between reference beam and particle scattering were recorded. When there were density distributions in the interrogation region, the plane optical wave may be modulated because of the difference of the refraction indices. Then, both of the plane wave modulated by density and the spherical wave by particle scatter were interfered with the reference beam, being recorded on the hologram. With reconstructing the hologram, the both of the modulated plane wave and spherical wave were reconstructed. Since the plane wave and spherical wave had low and high frequency, respectively, the plane wave was reconstructed with the low-pass filter, resulting in the information of the density distributions to be obtained. With the high-pass filter, the particle three-dimensional positions was determined, i.e., the same procedure with the original HPIV technique. In the experiment, a jet of carbon-dioxide into air with mist were measured. Both mist particle position and the fringe shift caused by the density distribution were well observed, showing the effectiveness of the proposed technique. (author)

  20. Technical Note: Contrast solution density and cross section errors in inhomogeneity-corrected dose calculation for breast balloon brachytherapy

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Leonard H.; Zhang Miao; Howell, Roger W.; Yue, Ning J.; Khan, Atif J. [Department of Radiation Oncology, University of Medicine and Dentistry of New Jersey: Robert Wood Johnson Medical School and Cancer Institute of New Jersey, New Brunswick, New Jersey 08903 (United States); Department of Radiology, University of Medicine and Dentistry of New Jersey: New Jersey Medical School, Newark, New Jersey 07103 (United States); Department of Radiation Oncology, University of Medicine and Dentistry of New Jersey: Robert Wood Johnson Medical School and Cancer Institute of New Jersey, New Brunswick, New Jersey 08903 (United States)

    2013-01-15

    Purpose: Recent recommendations by the American Association of Physicists in Medicine Task Group 186 emphasize the importance of understanding material properties and their effect on inhomogeneity-corrected dose calculation for brachytherapy. Radiographic contrast is normally injected into breast brachytherapy balloons. In this study, the authors independently estimate properties of contrast solution that were expected to be incorrectly specified in a commercial brachytherapy dose calculation algorithm. Methods: The mass density and atomic weight fractions of a clinical formulation of radiographic contrast solution were determined using manufacturers' data. The mass density was verified through measurement and compared with the density obtained by the treatment planning system's CT calibration. The atomic weight fractions were used to determine the photon interaction cross section of the contrast solution for a commercial high-dose-rate (HDR) brachytherapy source and compared with that of muscle. Results: The density of contrast solution was 10% less than that obtained from the CT calibration. The cross section of the contrast solution for the HDR source was 1.2% greater than that of muscle. Both errors could be addressed by overriding the density of the contrast solution in the treatment planning system. Conclusions: The authors estimate the error in mass density and cross section parameters used by a commercial brachytherapy dose calculation algorithm for radiographic contrast used in a clinical breast brachytherapy practice. This approach is adaptable to other clinics seeking to evaluate dose calculation errors and determine appropriate density override values if desired.

  1. Simulation of distribution of radiation energy density in water balls

    Institute of Scientific and Technical Information of China (English)

    TANG Shi-Biao; MA Qing-Li; YIN Ze-Jie; TANG Yu; HUANG Huan; RAO Nan-Xia; ZHU Da-Ming

    2005-01-01

    The distribution of energy deposition density in radiate region and its surrounding areas from γ-rays was simulated and analyzed for a water-ball model with Geant4 package ( Geant4.7.0,2005 ) developed by CERN (the Center of European Research of Nucleus). The results show that the distribution depends strongly on the collimating condition of radiation beam. A well-collimated beam would reduce radiation effects on surrounding areas.

  2. Intravenous contrast injection significantly affects bone mineral density measured on CT

    Energy Technology Data Exchange (ETDEWEB)

    Pompe, Esther; Willemink, Martin J.; Dijkhuis, Gawein R.; Verhaar, Harald J.J.; Hoesein, Firdaus A.A.M.; Jong, Pim A. de [University Medical Center Utrecht, Department of Radiology and Internal Medicine-Geriatrics, Postbus 85500, Postbox: E.03.511, GA, Utrecht (Netherlands)

    2014-09-05

    The objective is to evaluate the effect of intravenous contrast media on bone mineral density (BMD) assessment by comparing unenhanced and contrast-enhanced computed tomography (CT) examinations performed for other indications. One hundred and fifty-two patients (99 without and 53 with malignant neoplasm) who underwent both unenhanced and two contrast-enhanced (arterial and portal venous phase) abdominal CT examinations in a single session between June 2011 and July 2013 were included. BMD was evaluated on the three examinations as CT-attenuation values in Hounsfield Units (HU) in the first lumbar vertebra (L1). CT-attenuation values were significantly higher in both contrast-enhanced phases, compared to the unenhanced phase (p < 0.01). In patients without malignancies, mean ± standard deviation (SD) HU-values increased from 128.8 ± 48.6 HU for the unenhanced phase to 142.3 ± 47.2 HU for the arterial phase and 147.0 ± 47.4 HU for the portal phase (p < 0.01). In patients with malignancies, HU-values increased from 112.1 ± 38.1 HU to 126.2 ± 38.4 HU and 130.1 ± 37.3 HU (p < 0.02), respectively. With different thresholds to define osteoporosis, measurements in the arterial and portal phase resulted in 7-25 % false negatives. Our study showed that intravenous contrast injection substantially affects BMD-assessment on CT and taking this into account may improve routine assessment of low BMD in nonquantitative CT. (orig.)

  3. Spatial Distribution of City Tweets and Their Densities

    CERN Document Server

    Jiang, Bin; Yin, Junjun; Sandberg, Mats

    2016-01-01

    Social media outlets such as Twitter constitute valuable data sources for understanding human activities in the virtual world from a geographic perspective. This paper examines spatial distribution of tweets and densities within cities. The cities refer to natural cities that are automatically aggregated from a country's small street blocks, so called city blocks. We adopted street blocks (rather than census tracts) as the basic geographic units and topological center (rather than geometric center) in order to assess how tweets and densities vary from the center to the peripheral border. We found that, within a city from the center to the periphery, the tweets first increase and then decrease, while the densities decrease in general. These increases and decreases fluctuate dramatically, and differ significantly from those if census tracts are used as the basic geographic units. We also found that the decrease of densities from the center to the periphery is less significant, and even disappears, if an arbitra...

  4. Subchondral bone density distribution in the human femoral head

    Energy Technology Data Exchange (ETDEWEB)

    Wright, David A.; Meguid, Michael; Lubovsky, Omri; Whyne, Cari M. [Sunnybrook Research Institute, Orthopaedic Biomechanics Laboratory, Toronto, Ontario (Canada)

    2012-06-15

    This study aims to quantitatively characterize the distribution of subchondral bone density across the human femoral head using a computed tomography derived measurement of bone density and a common reference coordinate system. Femoral head surfaces were created bilaterally for 30 patients (14 males, 16 females, mean age 67.2 years) through semi-automatic segmentation of reconstructed CT data and used to map bone density, by shrinking them into the subchondral bone and averaging the greyscale values (linearly related to bone density) within 5 mm of the articular surface. Density maps were then oriented with the center of the head at the origin, the femoral mechanical axis (FMA) aligned with the vertical, and the posterior condylar axis (PCA) aligned with the horizontal. Twelve regions were created by dividing the density maps into three concentric rings at increments of 30 from the horizontal, then splitting into four quadrants along the anterior-posterior and medial-lateral axes. Mean values for each region were compared using repeated measures ANOVA and a Bonferroni post hoc test, and side-to-side correlations were analyzed using a Pearson's correlation. The regions representing the medial side of the femoral head's superior portion were found to have significantly higher densities compared to other regions (p < 0.05). Significant side-to-side correlations were found for all regions (r {sup 2} = 0.81 to r {sup 2} = 0.16), with strong correlations for the highest density regions. Side-to-side differences in measured bone density were seen for two regions in the anterio-lateral portion of the femoral head (p < 0.05). The high correlation found between the left and right sides indicates that this tool may be useful for understanding 'normal' density patterns in hips affected by unilateral pathologies such as avascular necrosis, fracture, developmental dysplasia of the hip, Perthes disease, and slipped capital femoral head epiphysis. (orig.)

  5. Calculation of the electron density distribution in silicon by the density-functional method. Comparison with X-ray results

    NARCIS (Netherlands)

    Velders, G.J.M.; Feil, D.

    1989-01-01

    Quantum-chemical density-functional theory (DFT) calculations, using the local-density approximation (LDA), have been performed for hydrogen-bounded silicon clusters to determine the electron density distribution of the Si-Si bond. The density distribution in the bonding region is compared with calc

  6. Density Distribution Sunflower Plots in Stata Version 8

    OpenAIRE

    Dupont, William D

    2004-01-01

    Density distribution sunflower plots are used to display high-density bivariate data. They are useful for data where a conventional scatter plot is difficult to read due to overstriking of the plot symbol. The x-y plane is subdivided into a lattice of regular hexagonal bins of width w specified by the user. The user also specifies the values of l, d, and k that affect the plot as follows. Individual observations are plotted when there are less than l observations per bin as in a conventional ...

  7. Crystal structure and electron density distribution in niobium carbide

    Energy Technology Data Exchange (ETDEWEB)

    Will, G.; Platzbecker, R. [Bonn Univ. (Germany). Abt. fuer Mineralogie und Kristallographie

    2001-09-01

    In this paper the bonding properties, e. g. the charge distribution between the atoms and the deformation of niobium carbide densities have been studied. The crystal studied had the composition NbC{sub 0.98}. Careful and redundant data collection (74 unique reflections out of 2087 reflections measured) gave the basis for a detailed study. IAM models (independent atom model), high order and multipole refinements were made resulting in R values of R=0.4% and R=0.07%. In the corresponding deformation density maps electron accumulations between the niobium atoms were detected, but no bonding to the carbon atoms. (orig.)

  8. Modeling of branching density and branching distribution in low-density polyethylene polymerization

    NARCIS (Netherlands)

    Kim, D.M.; Iedema, P.D.

    2008-01-01

    Low-density polyethylene (ldPE) is a general purpose polymer with various applications. By this reason, many publications can be found on the ldPE polymerization modeling. However, scission reaction and branching distribution are only recently considered in the modeling studies due to difficulties i

  9. Galaxy rotation curves with log-normal density distribution

    CERN Document Server

    Marr, John H

    2015-01-01

    The log-normal distribution represents the probability of finding randomly distributed particles in a micro canonical ensemble with high entropy. To a first approximation, a modified form of this distribution with a truncated termination may represent an isolated galactic disk, and this disk density distribution model was therefore run to give the best fit to the observational rotation curves for 37 representative galaxies. The resultant curves closely matched the observational data for a wide range of velocity profiles and galaxy types with rising, flat or descending curves in agreement with Verheijen's classification of 'R', 'F' and 'D' type curves, and the corresponding theoretical total disk masses could be fitted to a baryonic Tully Fisher relation (bTFR). Nine of the galaxies were matched to galaxies with previously published masses, suggesting a mean excess dynamic disk mass of dex0.61+/-0.26 over the baryonic masses. Although questionable with regard to other measurements of the shape of disk galaxy g...

  10. Student Difficulties in Learning Density: A Distributed Cognition Perspective

    Science.gov (United States)

    Xu, Lihua; Clarke, David

    2012-08-01

    Density has been reported as one of the most difficult concepts for secondary school students (e.g. Smith et al. 1997). Discussion about the difficulties of learning this concept has been largely focused on the complexity of the concept itself or student misconceptions. Few, if any, have investigated how the concept of density was constituted in classroom interactions, and what consequences these interactions have for individual students' conceptual understanding. This paper reports a detailed analysis of two lessons on density in a 7th Grade Australian science classroom, employing the theory of Distributed Cognition (Hollan et al. 1999; Hutchins 1995). The analysis demonstrated that student understanding of density was shaped strongly by the public classroom discussion on the density of two metal blocks. It also revealed the ambiguities associated with the teacher demonstration and the student practical work. These ambiguities contributed to student difficulties with the concept of density identified in this classroom. The results of this study suggest that deliberate effort is needed to establish shared understanding not only about the purpose of the activities, but also about the meaning of scientific language and the utility of tools. It also suggests the importance of appropriate employment of instructional resources in order to facilitate student scientific understanding.

  11. The use of dilute Calogen as a fat density oral contrast medium in upper abdominal computed tomography, compared with the use of water and positive oral contrast media.

    Science.gov (United States)

    Ramsay, D W; Markham, D H; Morgan, B; Rodgers, P M; Liddicoat, A J

    2001-08-01

    Oral contrast media are commonly given prior to computed tomography (CT) examination of the upper abdomen. Although positive oral contrast media are normally used, there is increasing interest in using negative agents such as water and less commonly fat density products. The aim of this study was to compare a positive oral contrast medium, water, and a diluted emulsion of arachis oil Calogen, a fat density food supplement) for assessment of the upper abdomen. Seventy-one patients referred for upper abdominal CT were randomized to receive either 500 ml water, 2% sodium diatrizoate or a dilute suspension of Calogen. The CT images were scored independently by three radiologists. Distension and anatomical identification was assessed for the stomach, duodenum and jejunum; with anatomical identification recorded for the pancreas, retroperitoneum, liver, gallbladder and spleen. Dilute Calogen produced a significant improvement (P < 0.01) in distension and anatomical visualization of the stomach and proximal duodenum. Only minimal differences were demonstrated between the three contrast media for visualization of more distal small bowel or identification of the other upper abdominal viscera. Significantly more artifacts were caused by positive contrast media than with the Calogen mixture. A dilute suspension of Calogen as an oral contrast medium is recommended when disease is suspected within the stomach or proximal duodenum.

  12. New Fitting Formula for Cosmic Nonlinear Density Distribution

    Science.gov (United States)

    Shin, Jihye; Kim, Juhan; Pichon, Christophe; Jeong, Donghui; Park, Changbom

    2017-07-01

    We have measured the probability distribution function (PDF) of a cosmic matter density field from a suite of N-body simulations. We propose the generalized normal distribution of version 2 ({{ N }}{{v}2}) as an alternative fitting formula to the well-known log-normal distribution. We find that {{ N }}{{v}2} provides a significantly better fit than that of the log-normal distribution for all smoothing radii (2, 5, 10, 25 [Mpc h -1]) that we studied. The improvement is substantial in the underdense regions. The development of non-Gaussianities in the cosmic matter density field is captured by continuous evolution of the skewness and shift parameters of the {{ N }}{{v}2} distribution. We present the redshift evolution of these parameters for aforementioned smoothing radii and various background cosmology models. All the PDFs measured from large and high-resolution N-body simulations that we use in this study can be obtained from the web site https://astro.kias.re.kr/jhshin.

  13. Vertical distribution of zooplankton: density dependence and evidence for an ideal free distribution with costs

    Directory of Open Access Journals (Sweden)

    Lampert Winfried

    2005-04-01

    Full Text Available Abstract Background In lakes with a deep-water algal maximum, herbivorous zooplankton are faced with a trade-off between high temperature but low food availability in the surface layers and low temperature but sufficient food in deep layers. It has been suggested that zooplankton (Daphnia faced with this trade-off distribute vertically according to an "Ideal Free Distribution (IFD with Costs". An experiment has been designed to test the density (competition dependence of the vertical distribution as this is a basic assumption of IFD theory. Results Experiments were performed in large, indoor mesocosms (Plankton Towers with a temperature gradient of 10°C and a deep-water algal maximum established below the thermocline. As expected, Daphnia aggregated at the interface between the two different habitats when their density was low. The distribution spread asymmetrically towards the algal maximum when the density increased until 80 % of the population dwelled in the cool, food-rich layers at high densities. Small individuals stayed higher in the water column than large ones, which conformed with the model for unequal competitors. Conclusion The Daphnia distribution mimics the predictions of an IFD with costs model. This concept is useful for the analysis of zooplankton distributions under a large suite of environmental conditions shaping habitat suitability. Fish predation causing diel vertical migrations can be incorporated as additional costs. This is important as the vertical location of grazing zooplankton in a lake affects phytoplankton production and species composition, i.e. ecosystem function.

  14. Quantification of volume, mass, and density of thrombus formation using brightfield and differential interference contrast microscopy

    Science.gov (United States)

    Baker-Groberg, Sandra M.; Phillips, Kevin G.; McCarty, Owen J. T.

    2013-01-01

    Flow chamber assays, in which blood is perfused over surfaces of immobilized extracellular matrix proteins, are used to investigate the formation of platelet thrombi and aggregates under shear flow conditions. Elucidating the dynamic response of thrombi/aggregate formation to different coagulation pathway perturbations in vitro has been used to develop an understanding of normal and pathological cardiovascular states. Current microscopy techniques, such as differential interference contrast (DIC) or fluorescent confocal imaging, respectively, do not provide a simple, quantitative understanding of the basic physical features (volume, mass, and density) of platelet thrombi/aggregate structures. The use of two label-free imaging techniques applied, for the first time, to platelet aggregate and thrombus formation are introduced: noninterferometric quantitative phase microscopy, to determine mass, and Hilbert transform DIC microscopy, to perform volume measurements. Together these techniques enable a quantitative biophysical characterization of platelet aggregates and thrombi formed on three surfaces: fibrillar collagen, fibrillar collagen +0.1 nM tissue factor (TF), and fibrillar collagen +1 nM TF. It is demonstrated that label-free imaging techniques provide quantitative insight into the mechanisms by which thrombi and aggregates are formed in response to exposure to different combinations of procoagulant agonists under shear flow.

  15. Distribution, density, and biomass of introduced small mammals in the southern mariana islands

    Science.gov (United States)

    Wiewel, A.S.; Adams, A.A.Y.; Rodda, G.H.

    2009-01-01

    Although it is generally accepted that introduced small mammals have detrimental effects on island ecology, our understanding of these effects is frequently limited by incomplete knowledge of small mammal distribution, density, and biomass. Such information is especially critical in the Mariana Islands, where small mammal density is inversely related to effectiveness of Brown Tree Snake (Boiga irregularis) control tools, such as mouse-attractant traps. We used mark-recapture sampling to determine introduced small mammal distribution, density, and biomass in the major habitats of Guam, Rota, Saipan, and Tinian, including grassland, Leucaena forest, and native limestone forest. Of the five species captured, Rattus diardii (sensu Robins et al. 2007) was most common across habitats and islands. In contrast, Mus musculus was rarely captured at forested sites, Suncus murinus was not captured on Rota, and R. exulans and R. norvegicus captures were uncommon. Modeling indicated that neophobia, island, sex, reproductive status, and rain amount influenced R. diardii capture probability, whereas time, island, and capture heterogeneity influenced S. murinus and M. musculus capture probability. Density and biomass were much greater on Rota, Saipan, and Tinian than on Guam, most likely a result of Brown Tree Snake predation pressure on the latter island. Rattus diardii and M. musculus density and biomass were greatest in grassland, whereas S. murinus density and biomass were greatest in Leucaena forest. The high densities documented during this research suggest that introduced small mammals (especially R. diardii) are impacting abundance and diversity of the native fauna and flora of the Mariana Islands. Further, Brown Tree Snake control and management tools that rely on mouse attractants will be less effective on Rota, Saipan, and Tinian than on Guam. If the Brown Tree Snake becomes established on these islands, high-density introduced small mammal populations will likely

  16. Evolution of column density distributions within Orion~A

    CERN Document Server

    Stutz, A M

    2015-01-01

    We compare the structure of star-forming molecular clouds in different regions of Orion A to determine how the column density probability distribution function (N-PDF) varies with environmental conditions such as the fraction of young protostars. A correlation between the N-PDF slope and Class 0 protostar fraction has been previously observed in a low-mass star-formation region (Perseus) by Sadavoy; here we test if a similar correlation is observed in a high-mass star-forming region. We use Herschel data to derive a column density map of Orion A. We use the Herschel Orion Protostar Survey catalog for accurate identification and classification of the Orion A young stellar object (YSO) content, including the short-lived Class 0 protostars (with a $\\sim$ 0.14 Myr lifetime). We divide Orion A into eight independent 13.5 pc$^2$ regions; in each region we fit the N-PDF distribution with a power-law, and we measure the fraction of Class 0 protostars. We use a maximum likelihood method to measure the N-PDF power-law ...

  17. Seagrass species distribution, density and coverage at Panggang Island, Jakarta

    Science.gov (United States)

    Wahab, Iswandi; Madduppa, Hawis; Kawaroe, Mujizat

    2017-01-01

    This study aimed to assess species distribution, density and coverage of seagrass in Panggang Island, within Kepulauan Seribu Marine National Park, northern Jakarta. Seagrass sampling was conducted between March to April 2016 at three observation stations in the West, East, and South of Panggang Island. A total of 6 seagrass species was recorded during sampling period, including Cymodocea rotundata, C. serulata, Halodule uninervis, Syiringodium isoetifolium, Enhalus acoroides, and Thalassia hempricii. All species were observed in the South station, while in the West and East station found only three species (C. rotundata, E. acoroides, and T. hemprichii). While, C. rotundata and T. hemprichii were observed at all station. The highest density was observed for C. rotundata (520 ind/m2) and for T. hempricii (619 ind/m2) in the West station and South Station, respectively. The lowest density was observed in South Station for C. serulata (18 ind/m2), Halodule uninervis (20 ind/m2), and Syiringodium isoetifolium (15 ind/m2). Seagrass coverage of Thalassia hempricii was the highest (43.60%) and the lowest observed at Syiringodium isoetifolium (0.40%). This could be basic information for the management of seagrass ecosystem in the Kepulauan Seribu Marine National Park.

  18. Differential Density Statistics of Galaxy Distribution and the Luminosity Function

    CERN Document Server

    Albani, V V L; Ribeiro, M B; Stöger, W R; Albani, Vinicius V. L.; Iribarrem, Alvaro S.; Ribeiro, Marcelo B.; Stoeger, William R.

    2006-01-01

    This paper uses data obtained from the galaxy luminosity function (LF) to calculate two types of radial number densities statistics of the galaxy distribution as discussed in Ribeiro (2005), namely the differential density $\\gamma$ and the integral differential density $\\gamma^\\ast$. By applying the theory advanced by Ribeiro and Stoeger (2003), which connects the relativistic cosmology number counts with the astronomically derived LF, the differential number counts $dN/dz$ are extracted from the LF and used to calculate both $\\gamma$ and $\\gamma^\\ast$ with various cosmological distance definitions, namely the area distance, luminosity distance, galaxy area distance and redshift distance. LF data are taken from the CNOC2 galaxy redshift survey and $\\gamma$ and $\\gamma^\\ast$ are calculated for two cosmological models: Einstein-de Sitter and an $\\Omega_{m_0}=0.3$, $\\Omega_{\\Lambda_0}=0.7$ standard cosmology. The results confirm the strong dependency of both statistics on the distance definition, as predicted in...

  19. Effects of edge contrast on redback salamander distribution in even-aged northern hardwoods

    Science.gov (United States)

    Richard M. DeGraaf; Mariko. Yamasaki

    2002-01-01

    Terrestrial salamanders are sensitive to forest disturbance associated with even-aged management. We studied the distribution of redback salamanders (Plethodon cinereus) for 4 yr at edges between even-aged northern hardwood stands along three replicate transects in each of three edge contrast types: regeneration/mature, sapling/mature, and...

  20. Bone Mineral Density Estimations From Routine Multidetector Computed Tomography: A Comparative Study of Contrast and Calibration Effects

    Science.gov (United States)

    Kaesmacher, Johannes; Liebl, Hans; Baum, Thomas; Kirschke, Jan Stefan

    2017-01-01

    Introduction Phantom-based (synchronous and asynchronous) and phantomless (internal tissue calibration based) assessment of bone mineral density (BMD) in routine MDCT (multidetector computed tomography) examinations potentially allows for diagnosis of osteoporosis. Although recent studies investigated the effects of contrast-medium application on phantom-calibrated BMD measurements, it remains uncertain to what extent internal tissue-calibrated BMD measurements are also susceptible to contrast-medium associated density variation. The present study is the first to systemically evaluate BMD variations related to contrast application comparing different calibration techniques. Purpose To compare predicative performance of different calibration techniques for BMD measurements obtained from triphasic contrast-enhanced MDCT. Materials and Methods Bone mineral density was measured on nonenhanced (NE), arterial (AR) and portal-venous (PV) contrast phase MDCT images of 46 patients using synchronous (SYNC) and asynchronous (ASYNC) phantom calibration as well as internal calibration (IC). Quantitative computed tomography (QCT) served as criterion standard. Density variations were analyzed for each contrast phase and calibration technique, and respective linear fitting was performed. Results Both asynchronous calibration-derived BMD values (NE-ASYNC) and values estimated using IC (NE-IC) on NE MDCT images did reasonably well in predicting QCT BMD (root-mean-square deviation, 8.0% and 7.8%, respectively). Average NE-IC BMD was 2.7% lower when compared with QCT (P = 0.017), whereas no difference could be found for NE-ASYNC (P = 0.957). All average BMD estimates derived from contrast-enhanced scans differed significantly from QCT BMD (all P 6.0 mg/mL). All regression fits revealed a consistent linear dependency (R2 range, 0.861–0.963). Overall accuracy and goodness of fit tended to decrease from AR to PV contrast phase. Highest precision and best linear fit could be reached

  1. Effects of Horizontal Density Distribution on Internal Bond Strength of Flakeboard

    Institute of Scientific and Technical Information of China (English)

    MEIChangtong; DAIChunping; ZHOUDingguo

    2005-01-01

    Horizontal density variation is a structural phenomenon of non-veneer wood composites. The variation and distribution characteristics of horizontal density have impacts on the products properties. In this study, veneer strip simulated flake boards with 4 kinds of density distribution were made using a mat model. The density variation of the modeled mats was discussed, as well as the relationship between sample size and density variation. The effects of density and density distribution of non-veneer composites on the internal bond strength were analyzed. Result shows that the horizontal density of random formed particleboard follows normal distribution. Density has remarkable influence on internal bond strength (IB). Increasing density helps to improve IB at lower density stage, but has negative impacts on IB at higher density stage.Density variation between testing specimens depends on their sizes. Properly increasing specimen size can decrease the variation of the IBs.

  2. Carbon density and distribution of six Chinese temperate forests

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    Quantifying forest carbon(C) storage and distribution is important for forest C cycling studies and terrestrial ecosystem modeling.Forest inventory and allometric approaches were used to measure C density and allocation in six representative temperate forests of similar stand age(42-59 years old) and growing under the same climate in northeastern China.The forests were an aspen-birch forest,a hardwood forest,a Korean pine plantation,a Dahurian larch plantation,a mixed deciduous forest,and a Mongolian oak forest.There were no significant differences in the C densities of ecosystem components(except for detritus) although the six forests had varying vegetation compositions and site conditions.However,the differences were significant when the C pools were normalized against stand basal area.The total ecosystem C density varied from 186.9 tC hm-2 to 349.2 tC hm-2 across the forests.The C densities of vegetation,detritus,and soil ranged from 86.3-122.7 tC hm-2,6.5-10.5 tC hm-2,and 93.7-220.1 tC hm-2,respectively,which accounted for 39.7% ± 7.1%(mean ± SD),3.3% ± 1.1%,and 57.0% ± 7.9% of the total C densities,respectively.The overstory C pool accounted for > 99% of the total vegetation C pool.The foliage biomass,small root(diameter < 5mm) biomass,root-shoot ratio,and small root to foliage biomass ratio varied from 2.08-4.72 tC hm-2,0.95-3.24 tC hm-2,22.0%-28.3%,and 34.5%-122.2%,respectively.The Korean pine plantation had the lowest foliage production efficiency(total biomass/foliage biomass:22.6 g g-1) among the six forests,while the Dahurian larch plantation had the highest small root production efficiency(total biomass/small root biomass:124.7 g g-1).The small root C density decreased with soil depth for all forests except for the Mongolian oak forest,in which the small roots tended to be vertically distributed downwards.The C density of coarse woody debris was significantly less in the two plantations than in the four naturally regenerated forests.The variability

  3. A multi-wavelength, high-contrast contact radiography system for the study of low-density aerogel foams.

    Science.gov (United States)

    Opachich, Y P; Koch, J A; Haugh, M J; Romano, E; Lee, J J; Huffman, E; Weber, F A; Bowers, J W; Benedetti, L R; Wilson, M; Prisbrey, S T; Wehrenberg, C E; Baumann, T F; Lenhardt, J M; Cook, A; Arsenlis, A; Park, H-S; Remington, B A

    2016-07-01

    A multi-wavelength, high contrast contact radiography system has been developed to characterize density variations in ultra-low density aerogel foams. These foams are used to generate a ramped pressure drive in materials strength experiments at the National Ignition Facility and require precision characterization in order to reduce errors in measurements. The system was used to characterize density variations in carbon and silicon based aerogels to ∼10.3% accuracy with ∼30 μm spatial resolution. The system description, performance, and measurement results collected using a 17.8 mg/cc carbon based JX-6 (C20H30) aerogel are discussed in this manuscript.

  4. Vegetation factors influencing density and distribution of wild large herbivores in a southern African savannah

    NARCIS (Netherlands)

    Gandiwa, E.

    2014-01-01

    Understanding factors influencing large herbivore densities and distribution in terrestrial ecosystems is a fundamental goal of ecology. This study examined environmental factors influencing the density and distribution of wild large herbivores in Gonarezhou National Park, Zimbabwe. Vegetation and s

  5. Vegetation factors influencing density and distribution of wild large herbivores in a southern African savannah

    NARCIS (Netherlands)

    Gandiwa, E.

    2014-01-01

    Understanding factors influencing large herbivore densities and distribution in terrestrial ecosystems is a fundamental goal of ecology. This study examined environmental factors influencing the density and distribution of wild large herbivores in Gonarezhou National Park, Zimbabwe. Vegetation and

  6. Angular momentum of disc galaxies with a lognormal density distribution

    CERN Document Server

    Marr, John Herbert

    2015-01-01

    Whilst most galaxy properties scale with galaxy mass, similar scaling relations for angular momentum are harder to demonstrate. A lognormal (LN) density distribution for disc mass provides a good overall fit to the observational data for disc rotation curves for a wide variety of galaxy types and luminosities. In this paper, the total angular momentum J and energy $\\vert{}$E$\\vert{}$ were computed for 38 disc galaxies from the published rotation curves and plotted against the derived disc masses, with best fit slopes of 1.683$\\pm{}$0.018 and 1.643$\\pm{}$0.038 respectively, using a theoretical model with a LN density profile. The derived mean disc spin parameter was $\\lambda{}$=0.423$\\pm{}$0.014. Using the rotation curve parameters V$_{max}$ and R$_{max}$ as surrogates for the virial velocity and radius, the virial mass estimator $M_{disc}\\propto{}R_{max}V_{max}^2$ was also generated, with a log-log slope of 1.024$\\pm{}$0.014 for the 38 galaxies, and a proportionality constant ${\\lambda{}}^*=1.47\\pm{}0.20\\time...

  7. Cut-rose production in response to planting density in two contrasting cultivars

    NARCIS (Netherlands)

    Burema, B.S.; Buck-Sorlin, G.H.; Damen, T.; Vos, J.; Heuvelink, E.; Marcelis, L.F.M.

    2010-01-01

    Growing in lower planting density, rose plants produce more assimilates, which can be used to produce more and/or heavier flowering shoots. The effect of planting density was investigated during a period including the first five flowering flushes of a young crop. In a heated greenhouse two cut-rose

  8. Cut-rose production in response to planting density in two contrasting cultivars

    NARCIS (Netherlands)

    Burema, B.S.; Buck-Sorlin, G.H.; Damen, T.; Vos, J.; Heuvelink, E.; Marcelis, L.F.M.

    2010-01-01

    Growing in lower planting density, rose plants produce more assimilates, which can be used to produce more and/or heavier flowering shoots. The effect of planting density was investigated during a period including the first five flowering flushes of a young crop. In a heated greenhouse two cut-rose

  9. Efficiency of Contrast-Enhanced Fat-Suppressed Proton Density Images for Shoulder MRI: Comparison with Contrast-enhanced Fat-suppressed T1 Weighted Image and Arthroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Kwan Sub; Ha, Doo Hoe; Lee, Sang Min; Yoo, Ko Eun; Kim, Jae Wha [Bundang CHA General Hospital, Pocheon (Korea, Republic of)

    2009-03-15

    This study was designed to evaluate the efficiency of contrast-enhanced fat-suppressed proton-density images (CE-FS-PDI) for shoulder MRI. We retrospectively reviewed 54 shoulder MR precontrast fat-suppressed proton-density images (FS-PDI), CE-FS-PDI and contrast-enhanced fat-suppressed T1 weighted images (CE-FS-T1WI). Signal-to-noise ratios (SNRs) and contrast-to-noise ratios (CNRs) of the posterior labrum, infraspinatus muscle, synovium, biceps brachii long head tendon and subcutaneous fat were analyzed on each sequence. Subsequently, 53 cases were reviewed where patients had undergone both shoulder arthroscopy and shoulder MRI. We analyzed the diagnostic agreement rates between the CE-FS-PDI and CE-FS-T1WI and the diagnostic accuracy of arthroscopically proven tears of the supraspinatus tendon. On CE-FS-PDI, the SNRs and CNRs of all structures were statistically higher than on precontrast FSPDI and CE-FS-T1WI. Diagnostic agreement rates between CE-FS-PDI and CE-FS-T1WI were 70-96% in labrums and 75-96% in rotator cuffs. The diagnostic accuracy rates for a tear of the supraspinatus tendon were 83% on CE-FS-PDI and 75% on CE-FS-T1WI, respectively. The SNR and CNR on CE-FS-PDI were increased in the shoulder structures, and the diagnostic rate for a tear of the supraspinatus tendon on CE-FS-PDI was superior as compared to CE-FS-T1WI. Therefore, CE-FS-PDI will be useful for shoulder MRI.

  10. Estimating Leaf Bulk Density Distribution in a Tree Canopy Using Terrestrial LiDAR and a Straightforward Calibration Procedure

    Directory of Open Access Journals (Sweden)

    François Pimont

    2015-06-01

    Full Text Available Leaf biomass distribution is a key factor for modeling energy and carbon fluxes in forest canopies and for assessing fire behavior. We propose a new method to estimate 3D leaf bulk density distribution, based on a calibration of indices derived from T-LiDAR. We applied the method to four contrasted plots in a mature Quercus pubescens forest. Leaf bulk densities were measured inside 0.7 m-diameter spheres, referred to as Calibration Volumes. Indices were derived from LiDAR point clouds and calibrated over the Calibration Volume bulk densities. Several indices were proposed and tested to account for noise resulting from mixed pixels and other theoretical considerations. The best index and its calibration parameter were then used to estimate leaf bulk densities at the grid nodes of each plot. These LiDAR-derived bulk density distributions were used to estimate bulk density vertical profiles and loads and above four meters compared well with those assessed by the classical inventory-based approach. Below four meters, the LiDAR-based approach overestimated bulk densities since no distinction was made between wood and leaf returns. The results of our method are promising since they demonstrate the possibility to assess bulk density on small plots at a reasonable operational cost.

  11. Differential growth response to arbuscular mycorrhizal fungi and plant density in two wild plants belonging to contrasting functional types.

    Science.gov (United States)

    Pérez, Marisela; Urcelay, Carlos

    2009-10-01

    The effect of arbuscular mycorrhizal fungi (AMF) on plant growth was examined in two wild plant species belonging to contrasting functional types: an annual forb (Bidens pilosa, Asteraceae) and a deciduous shrub (Acacia caven, Fabaceae) at three contrasting plant densities (one, two, and three individuals per pot). AMF had a slightly negative effect on B. pilosa when the species grew in isolation while they positively affected A. caven. Positive effects of AMF on shoot mass of A. caven decreased at higher plant densities, while shoot mass of individuals of B. pilosa showed less marked differences between plant densities. When considering total biomass per pot, AMF positively affected A. caven growth while negatively affecting B. pilosa, at all three plant densities. Root/shoot ratio per pot was negatively affected by AMF but not plant density in both species. These findings highlight the importance of including plants belonging to different life forms and/or traits in research regarding the interaction between AMF and intraspecific plant competition.

  12. Wood density variations of Norway spruce (Picea abies (L. Karst. under contrasting climate conditions in southwestern Germany

    Directory of Open Access Journals (Sweden)

    Marieke van der Maaten-Theunissen

    2013-07-01

    Full Text Available We analyzed inter-annual variations in ring width and maximum wood density of Norway spruce (Picea abies (L. Karst. at different altitudes in Baden-Württemberg, southwestern Germany, to determine the climate response of these parameters under contrasting climate conditions. In addition, we compared maximum, average and minimum wood density between sites. Bootstrapped correlation coefficients of ring width and maximum wood density with monthly temperature and precipitation, revealed a different climate sensitivity of both parameters. Ring width showed strong correlations with climate variables in the previous year and in the first half of the growing season. Further, a negative relationship with summer temperature was observed at the low-altitude sites. Maximum wood density correlated best with temperature during the growing season, whereby strongest correlations were found between September temperature and maximum wood density at the high-altitude sites. Observed differences in maximum, average and minimum wood density are suggested to relate to the local climate; with lower temperatures and higher water availability having a negative effect on wood density

  13. Non-invasive prediction of hemodynamically significant coronary artery stenoses by contrast density difference in coronary CT angiography

    Energy Technology Data Exchange (ETDEWEB)

    Hell, Michaela M., E-mail: michaela.hell@uk-erlangen.de [Department of Cardiology, University of Erlangen (Germany); Dey, Damini [Department of Biomedical Sciences, Biomedical Imaging Research Institute, Cedars-Sinai Medical Center, Taper Building, Room A238, 8700 Beverly Boulevard, Los Angeles, CA 90048 (United States); Marwan, Mohamed; Achenbach, Stephan; Schmid, Jasmin; Schuhbaeck, Annika [Department of Cardiology, University of Erlangen (Germany)

    2015-08-15

    Highlights: • Overestimation of coronary lesions by coronary computed tomography angiography and subsequent unnecessary invasive coronary angiography and revascularization is a concern. • Differences in plaque characteristics and contrast density difference between hemodynamically significant and non-significant stenoses, as defined by invasive fractional flow reserve, were assessed. • At a threshold of ≥24%, contrast density difference predicted hemodynamically significant lesions with a specificity of 75%, sensitivity of 33%, PPV of 35% and NPV of 73%. • The determination of contrast density difference required less time than transluminal attenuation gradient measurement. - Abstract: Objectives: Coronary computed tomography angiography (CTA) allows the detection of obstructive coronary artery disease. However, its ability to predict the hemodynamic significance of stenoses is limited. We assessed differences in plaque characteristics and contrast density difference between hemodynamically significant and non-significant stenoses, as defined by invasive fractional flow reserve (FFR). Methods: Lesion characteristics of 59 consecutive patients (72 lesions) in whom invasive FFR was performed in at least one coronary artery with moderate to high-grade stenoses in coronary CTA were evaluated by two experienced readers. Coronary CTA data sets were acquired on a second-generation dual-source CT scanner using retrospectively ECG-gated spiral acquisition or prospectively ECG-triggered axial acquisition mode. Plaque volume and composition (non-calcified, calcified), remodeling index as well as contrast density difference (defined as the percentage decline in luminal CT attenuation/cross-sectional area over the lesion) were assessed using a semi-automatic software tool (Autoplaq). Additionally, the transluminal attenuation gradient (defined as the linear regression coefficient between intraluminal CT attenuation and length from the ostium) was determined

  14. Correlations Between the Gradient of Contrast Density, Evaluated by Cardio CT, and Functional Significance of Coronary Artery Stenosis

    Directory of Open Access Journals (Sweden)

    Orzan Marius

    2016-06-01

    Full Text Available Background: Assessment of the hemodynamic significance of a coronary artery stenosis is a challenging task, being extremely important for the establishment of indication for revascularization in atherosclerotic coronary artery stenosis. The aim of this study was to evaluate the role of a new marker reflecting the functional significance of a coronary artery stenosis, represented by the attenuation degree of contrast density along the stenosis by Coronary CT.

  15. The mapping of electronic energy distributions using experimental electron density.

    Science.gov (United States)

    Tsirelson, Vladimir G

    2002-08-01

    It is demonstrated that the approximate kinetic energy density calculated using the second-order gradient expansion with parameters of the multipole model fitted to experimental structure factors reproduces the main features of this quantity in a molecular or crystal position space. The use of the local virial theorem provides an appropriate derivation of approximate potential energy density and electronic energy density from the experimental (model) electron density and its derivatives. Consideration of these functions is not restricted by the critical points in the electron density and provides a comprehensive characterization of bonding in molecules and crystals.

  16. Interleaved variable density sampling with a constrained parallel imaging reconstruction for dynamic contrast-enhanced MR angiography.

    Science.gov (United States)

    Wang, Kang; Busse, Reed F; Holmes, James H; Beatty, Philip J; Brittain, Jean H; Francois, Christopher J; Reeder, Scott B; Du, Jiang; Korosec, Frank R

    2011-08-01

    For MR applications such as contrast-enhanced MR angiography, it is desirable to achieve simultaneously high spatial and temporal resolution. The current clinical standard uses view-sharing methods combined with parallel imaging; however, this approach still provides limited spatial and temporal resolution. To improve on the clinical standard, we present an interleaved variable density (IVD) sampling method that pseudorandomly undersamples each individual frame of a 3D Cartesian ky-kz plane combined with parallel imaging acceleration. From this dataset, time-resolved images are reconstructed with a method that combines parallel imaging with a multiplicative constraint. Total acceleration factors on the order of 20 are achieved for contrast-enhanced MR angiography of the lower extremities, and improvements in temporal fidelity of the depiction of the contrast bolus passage are demonstrated relative to the clinical standard. Copyright © 2011 Wiley-Liss, Inc.

  17. 10 CFR 960.5-2-1 - Population density and distribution.

    Science.gov (United States)

    2010-01-01

    ... 10 Energy 4 2010-01-01 2010-01-01 false Population density and distribution. 960.5-2-1 Section 960... Population density and distribution. (a) Qualifying condition. The site shall be located such that, during... specified in § 960.5-1(a)(1). (b) Favorable conditions. (1) A low population density in the general region...

  18. Ion energy distributions and densities in the plume of Enceladus

    Science.gov (United States)

    Sakai, Shotaro; Cravens, Thomas E.; Omidi, Nojan; Perry, Mark E.; Waite, J. Hunter

    2016-10-01

    Enceladus has a dynamic plume that is emitting gas, including water vapor, and dust. The gas is ionized by solar EUV radiation, charge exchange, and electron impact and extends throughout the inner magnetosphere of Saturn. The charge exchange collisions alter the plasma composition. Ice grains (dust) escape from the vicinity of Enceladus and form the E ring, including a portion that is negatively charged by the local plasma. The inner magnetosphere within 10 RS (Saturn radii) contains a complex mixture of plasma, neutral gas, and dust that links back to Enceladus. In this paper we investigate the energy distributions, ion species and densities of water group ions in the plume of Enceladus using test particle and Monte Carlo methods that include collisional processes such as charge exchange and ion-neutral chemical reactions. Ion observations from the Cassini Ion and Neutral Mass Spectrometer (INMS) for E07 are presented for the first time. We use the modeling results to interpret observations made by the Cassini Plasma Spectrometer (CAPS) and the INMS. The low energy ions, as observed by CAPS, appear to be affected by a vertical electric field (EZ=-10 μV/m) in the plume. The EZ field may be associated with the charged dust and/or the pressure gradient of plasma. The model results, along with the results of earlier models, show that H3O+ ions created by chemistry are predominant in the plume, which agrees with INMS and CAPS data, but the INMS count rate in the plume for the model is several times greater than the data, which we do not fully understand. This composition and the total ion count found in the plume agree with INMS and CAPS data. On the other hand, the Cassini Langmuir Probe measured a maximum plume ion density more than 30,000 cm-3, which is far larger than the maximum ion density from our model, 900 cm-3. The model results also demonstrate that most of the ions in the plume are from the external magnetospheric flow and are not generated by local

  19. Number size distribution measurements of biological aerosols under contrasting environments and seasons from southern tropical India

    Science.gov (United States)

    Valsan, Aswathy; Cv, Biju; Krishna, Ravi; Huffman, Alex; Poschl, Ulrich; Gunthe, Sachin

    2016-04-01

    Biological aerosols constitute a wide range of dead and alive biological materials and structures that are suspended in the atmosphere. They play an important role in the atmospheric physical, chemical and biological processes and health of living being by spread of diseases among humans, plants, and, animals. The atmospheric abundance, sources, physical properties of PBAPs as compared to non-biological aerosols, however, is poorly characterized. Though omnipresent, their concentration and composition exhibit large spatial and temporal variations depending up on their sources, land-use, and local meteorology. The Indian tropical region, which constitutes approximately 18% of the world's total population exhibits vast geographical extend and experiences a distinctive meteorological phenomenon by means of Indian Summer Monsoon (IMS). Thus, the sources, properties and characteristics of biological aerosols are also expected to have significant variations over the Indian subcontinent depending upon the location and seasons. Here we present the number concentration and size distribution of Fluorescent Biological Aerosol Particles (FBAP) from two contrasting locations in Southern tropical India measured during contrasting seasons using Ultra Violet Aerodynamic Particle Sizer (UV-APS). Measurements were carried out at a pristine high altitude continental site, Munnar (10.09 N, 77.06 E; 1605 m asl) during two contrasting seasons, South-West Monsoon (June-August, 2014) and winter (Jan - Feb, 2015) and in Chennai, a coastal urban area, during July - November 2015. FBAP concentrations at both the locations showed large variability with higher concentrations occurring at Chennai. Apart from regional variations, the FBAP concentrations also exhibited variations over two different seasons under the same environmental condition. In Munnar the FBAP concentration increased by a factor of four from South-West Monsoon to winter season. The average size distribution of FBAP at both

  20. Helical CT of the abdomen: whole milk as a low-density oral contrast agent; Tomografia helicoidal do abdome: avaliacao do leite integral como contraste oral de baixa densidade

    Energy Technology Data Exchange (ETDEWEB)

    Collares, Felipe Birchal; Diniz, Renata Lopes Furletti Caldeira; Motta, Emilia Guerra Pinto Coelho; Moreira, Wanderval; Ribeiro, Marcelo Almeida [Hospital Mater Dei, Belo Horizonte, MG (Brazil). Dept. de Radiologia

    2000-08-01

    We evaluated 90 abdominal helical computed tomography scans from patients who received 1% iodine solution, whole milk or no oral contrast agent before scanning. Four parameters were evaluated: gastrointestinal distension, mural visualization, pancreas-duodenum discrimination and bowel loop discrimination. Better results were obtained with the use of whole milk compared to iodine contrast or no oral contrast agent. Whole milk is an effective low density oral contrast agent. (author)

  1. Student Difficulties in Learning Density: A Distributed Cognition Perspective

    Science.gov (United States)

    Xu, Lihua; Clarke, David

    2012-01-01

    Density has been reported as one of the most difficult concepts for secondary school students (e.g. Smith et al. 1997). Discussion about the difficulties of learning this concept has been largely focused on the complexity of the concept itself or student misconceptions. Few, if any, have investigated how the concept of density was constituted in…

  2. The intravertebral distribution of bone density: correspondence to intervertebral disc health and implications for vertebral strength

    Science.gov (United States)

    Jackman, T. M.; Morgan, S. R.; Barest, G. D.; Morgan, E. F.

    2015-01-01

    Summary This study's goal was to determine associations among the intravertebral heterogeneity in bone density, bone strength, and intervertebral disc (IVD) health. Results indicated that predictions of vertebral strength can benefit from considering the magnitude of the density heterogeneity and the congruence between the spatial distribution of density and IVD health. Introduction This study aims to determine associations among the intravertebral heterogeneity in bone density, bone strength, and IVD health Methods Regional measurements of bone density were performed throughout 30 L1 vertebral bodies using microcomputed tomography (μCT) and quantitative computed tomography (QCT). The magnitude of the intravertebral heterogeneity in density was defined as the interquartile range and quartile coefficient of variation in regional densities. The spatial distribution of density was quantified using ratios of regional densities representing different anatomical zones (e.g., anterior to posterior regional densities). Cluster analysis was used to identify groups of vertebrae with similar spatial distributions of density. Vertebral strength was measured in compression. IVD health was assessed using two scoring systems. Results QCT- and μCT-based measures of the magnitude of the intravertebral heterogeneity in density were strongly correlated with each other (p<0.005). Accounting for the interquartile range in regional densities improved predictions of vertebral strength as compared to predictions based only on mean density (R2=0.59 vs. 0.43; F-test p-value=0.018). Specifically, after adjustment for mean density, vertebral bodies with greater heterogeneity in density exhibited higher strength. No single spatial distribution of density was associated with high vertebral strength. Analyses of IVD scores suggested that the health of the adjacent IVDs may modulate the effect of a particular spatial distribution of density on vertebral strength. Conclusions Noninvasive

  3. Predicting cetacean habitats from their energetic needs and the distribution of their prey in two contrasted tropical regions.

    Science.gov (United States)

    Lambert, Charlotte; Mannocci, Laura; Lehodey, Patrick; Ridoux, Vincent

    2014-01-01

    To date, most habitat models of cetaceans have relied on static and oceanographic covariates, and very few have related cetaceans directly to the distribution of their prey, as a result of the limited availability of prey data. By simulating the distribution of six functional micronekton groups between the surface and ≃1,000 m deep, the SEAPODYM model provides valuable insights into prey distributions. We used SEAPODYM outputs to investigate the habitat of three cetacean guilds with increasing energy requirements: sperm and beaked whales, Globicephalinae and Delphininae. We expected High Energy Requirements cetaceans to preferentially forage in habitats of high prey biomass and/or production, where they might easily meet their high energetic needs, and Low Energy Requirements cetaceans to forage in habitats of either high or low prey biomass and/or production. Cetacean sightings were collected from dedicated aerial surveys in the South West Indian Ocean (SWIO) and French Polynesia (FP). We examined cetacean densities in relation to simulated distributions of their potential prey using Generalised Additive Models and predicted their habitats in both regions. Results supported their known diving abilities, with Delphininae mostly related to prey present in the upper layers of the water column, and Globicephalinae and sperm and beaked whales also related to prey present in deeper layers. Explained deviances ranged from 9% for sperm and beaked whales in the SWIO to 47% for Globicephalinae in FP. Delphininae and Globicephalinae appeared to select areas where high prey biomass and/or production were available at shallow depths. In contrast, sperm and beaked whales showed less clear habitat selection. Using simulated prey distributions as predictors in cetacean habitat models is crucial to understand their strategies of habitat selection in the three dimensions of the ocean.

  4. On the possibility of kinetic energy density evaluation from the experimental electron-density distribution

    Energy Technology Data Exchange (ETDEWEB)

    Abramov, Yu.A. [National Inst. for Research in Inorganic Materials, Tsukuba, Ibaraki (Japan)

    1997-05-01

    A simple new approach for the evaluation of the electronic kinetic energy density, G(r), from the experimental (multipole-fitted) electron density is proposed. It allows a quantitative and semi-quantitative description of the G(r) behavior at the bond critical points of compounds with closed-shell and shared interactions, respectively. This can provide information on the values of the kinetic electron energy densities at the bond critical points, which appears to be useful for quantum-topological studies of chemical interactions using experimental electron densities. (orig.).

  5. High-density speckle contrast optical tomography (SCOT) for three dimensional tomographic imaging of the small animal brain.

    Science.gov (United States)

    Dragojević, Tanja; Varma, Hari M; Hollmann, Joseph L; Valdes, Claudia P; Culver, Joseph P; Justicia, Carles; Durduran, Turgut

    2017-06-01

    High-density speckle contrast optical tomography (SCOT) utilizing tens of thousands of source-detector pairs, was developed for in vivo imaging of blood flow in small animals. The reduction in cerebral blood flow (CBF) due to local ischemic stroke in a mouse brain was transcanially imaged and reconstructed in three dimensions. The reconstructed volume was then compared with corresponding magnetic resonance images demonstrating that the volume of reduced CBF agrees with the infarct zone at twenty-four hours. Copyright © 2017 The Authors. Published by Elsevier Inc. All rights reserved.

  6. Redox-induced lower mantle density contrast and effect on mantle structure and primitive oxygen

    Science.gov (United States)

    Gu, Tingting; Li, Mingming; McCammon, Catherine; Lee, Kanani K. M.

    2016-09-01

    The mantle comprises nearly three-quarters of Earth's volume and through convection connects the deep interior with the lithosphere and atmosphere. The composition of the mantle determines volcanic emissions, which are intimately linked to evolution of the primitive atmosphere. Fundamental questions remain on how and when the proto-Earth mantle became oxidized, and whether redox state is homogeneous or developed large-scale structures. Here we present experiments in which we subjected two synthetic samples of nearly identical composition that are representative of the lower mantle (enstatite chondrite), but synthesized under different oxygen fugacities, to pressures and temperatures up to 90 GPa and 2,400 K. In addition to the mineral bridgmanite, compression of the more reduced material also produced Al2O3 as a separate phase, and the resulting assemblage is about 1 to 1.5% denser than in experiments with the more oxidized material. Our geodynamic simulations suggest that such a density difference can cause a rapid ascent and accumulation of oxidized material in the upper mantle, with descent of the denser reduced material to the core-mantle boundary. We suggest that the resulting heterogeneous redox conditions in Earth's interior can contribute to the large low-shear velocity provinces in the lower mantle and the evolution of atmospheric oxygen.

  7. Data assimilation of depth-distributed satellite chlorophyll-α in two Mediterranean contrasting sites

    KAUST Repository

    Kalaroni, S.

    2016-04-12

    A new approach for processing the remote sensing chlorophyll-α (Chl-α) before assimilating into an ecosystem model is applied in two contrasting, regarding productivity and nutrients availability, Mediterranean sites: the DYFAMED and POSEIDON E1-M3A fixed point open ocean observatories. The new approach derives optically weighted depth-distributed Chl-α profiles from satellite data based on the model simulated Chl-α vertical distribution and light attenuation coefficient. We use the 1D version of the operational ecological 3D POSEIDON model, based on the European Regional Seas Ecosystem Model (ERSEM). The required hydrodynamic properties are obtained (off-line) from the POSEIDON operational 3D hydrodynamic Mediterranean basin scale model. The data assimilation scheme is the Singular Evolutive Interpolated Kalman (SEIK) filter, the ensemble variant of the Singular Evolutive Extended Kalman (SEEK) filter. The performance of the proposed assimilation approach was evaluated against the Chl-α satellite data and the seasonal averages of available in-situ data for nitrate, phosphate and Chl-α. An improvement of the model simulated near-surface and subsurface maximum Chl-α concentrations is obtained, especially at the DYFAMED site. Model nitrate is improved with assimilation, particularly with the new approach assimilating depth-distributed Chl-α, while model phosphate is slightly worse after assimilation. Additional sensitivity experiments were performed, showing a better performance of the new approach under different scenarios of model Chl-α deviation from pseudo-observations of surface Chl-α.

  8. Data assimilation of depth-distributed satellite chlorophyll-α in two Mediterranean contrasting sites

    Science.gov (United States)

    Kalaroni, S.; Tsiaras, K.; Petihakis, G.; Hoteit, I.; Economou-Amilli, A.; Triantafyllou, G.

    2016-08-01

    A new approach for processing the remote sensing chlorophyll-α (Chl-α) before assimilating into an ecosystem model is applied in two contrasting, regarding productivity and nutrients availability, Mediterranean sites: the DYFAMED and POSEIDON E1-M3A fixed point open ocean observatories. The new approach derives optically weighted depth-distributed Chl-α profiles from satellite data based on the model simulated Chl-α vertical distribution and light attenuation coefficient. We use the 1D version of the operational ecological 3D POSEIDON model, based on the European Regional Seas Ecosystem Model (ERSEM). The required hydrodynamic properties are obtained (off-line) from the POSEIDON operational 3D hydrodynamic Mediterranean basin scale model. The data assimilation scheme is the singular evolutive interpolated Kalman (SEIK) filter, the ensemble variant of the singular evolutive extended Kalman (SEEK) filter. The performance of the proposed assimilation approach was evaluated against the Chl-α satellite data and the seasonal averages of available in situ data for nitrate, phosphate and Chl-α. An improvement of the model simulated near-surface and subsurface maximum Chl-α concentrations is obtained, especially at the DYFAMED site. Model nitrate is improved with assimilation, particularly with the new approach assimilating depth-distributed Chl-α, while model phosphate is slightly worse after assimilation. Additional sensitivity experiments were performed, showing a better performance of the new approach under different scenarios of model Chl-α deviation from pseudo-observations of surface Chl-α.

  9. Gravity data inversion to determine 3D topographycal density contrast of Banten area, Indonesia based on fast Fourier transform

    Science.gov (United States)

    Windhari, Ayuty; Handayani, Gunawan

    2015-04-01

    The 3D inversion gravity anomaly to estimate topographical density using a matlab source code from gridded data provided by Parker Oldenburg algorithm based on fast Fourier transform was computed. We extend and improved the source code of 3DINVERT.M invented by Gomez Ortiz and Agarwal (2005) using the relationship between Fourier transform of the gravity anomaly and the sum of the Fourier transform from the topography density. We gave density contrast between the two media to apply the inversion. FFT routine was implemented to construct amplitude spectrum to the given mean depth. The results were presented as new graphics of inverted topography density, the gravity anomaly due to the inverted topography and the difference between the input gravity data and the computed ones. It terminates when the RMS error is lower than pre-assigned value used as convergence criterion or until maximum of iterations is reached. As an example, we used the matlab program on gravity data of Banten region, Indonesia.

  10. Measurement of depth-resolved thermal deformation distribution using phase-contrast spectral optical coherence tomography.

    Science.gov (United States)

    Zhang, Yun; Dong, Bo; Bai, Yulei; Ye, Shuangli; Lei, Zhenkun; Zhou, Yanzhou

    2015-10-19

    An updated B-scan method is proposed for measuring the evolution of thermal deformation fields in polymers. In order to measure the distributions of out-of-plane deformation and normal strain field, phase-contrast spectral optical coherence tomography (PC-SOCT) was performed with the depth range and resolution of 4.3 mm and 10.7 μm, respectively, as thermal loads were applied to three different multilayer samples. The relation between temperature and material refractive index was predetermined before the measurement. After accounting for the refractive index, the thermal deformation fields in the polymer were obtained. The measured thermal expansion coefficient of silicone sealant was approximately equal to its reference value. This method allows correctly assessing the mechanical properties in semitransparent polymers.

  11. Contrast of the Distribution SRET in the Potosi Highlands in Mexico

    Directory of Open Access Journals (Sweden)

    Campos-Aranda D.F.

    2011-04-01

    Full Text Available First, the importance of maximum daily rainfall predictions as the base for designing flood estimation is pointed out, particularly when recording rain-gages and hydrometric information are not available. Besides, the advantages of regional methods when the data show outliers are cited and the two main objectives of this work are formulated. Next, the pluviometric information used is described. Late, four procedures of regional fit of the General Extreme Values (GEV distribution are described and applied, based in the L moment technique, which are: (1 station–year method, (2 fit through averaging probability weighted moments, (3 median standardized values method and (4 fit through regional shape parameter. Three probabilistic models are applied to the pluviometric records: GVE, Log–Pearson type III and square–root exponential type (SRET. Finally, the predictions of probabilistic models and the regional results are contrasted; then several conclusions are formulated, which point out the simplicity and greater accuracy of the SRET function.

  12. Global distribution of a key trophic guild contrasts with common latitudinal diversity patterns.

    Science.gov (United States)

    Boyero, Luz; Pearson, Richard G; Dudgeon, David; Graça, Manuel A S; Gessner, Mark O; Albariño, Ricardo J; Ferreira, Verónica; Yule, Catherine M; Boulton, Andrew J; Arunachalam, Muthukumarasamy; Callisto, Marcos; Chauvet, Eric; Ramírez, Alonso; Chará, Julián; Moretti, Marcelo S; Gonçalves, José F; Helson, Julie E; Chará-Serna, Ana M; Encalada, Andrea C; Davies, Judy N; Lamothe, Sylvain; Cornejo, Aydeè; Li, Aggie O Y; Buria, Leonardo M; Villanueva, Verónica D; Zúñiga, María C; Pringle, Catherine M

    2011-09-01

    Most hypotheses explaining the general gradient of higher diversity toward the equator are implicit or explicit about greater species packing in the tropics. However, global patterns of diversity within guilds, including trophic guilds (i.e., groups of organisms that use similar food resources), are poorly known. We explored global diversity patterns of a key trophic guild in stream ecosystems, the detritivore shredders. This was motivated by the fundamental ecological role of shredders as decomposers of leaf litter and by some records pointing to low shredder diversity and abundance in the tropics, which contrasts with diversity patterns of most major taxa for which broad-scale latitudinal patterns haven been examined. Given this evidence, we hypothesized that shredders are more abundant and diverse in temperate than in tropical streams, and that this pattern is related to the higher temperatures and lower availability of high-quality leaf litter in the tropics. Our comprehensive global survey (129 stream sites from 14 regions on six continents) corroborated the expected latitudinal pattern and showed that shredder distribution (abundance, diversity and assemblage composition) was explained by a combination of factors, including water temperature (some taxa were restricted to cool waters) and biogeography (some taxa were more diverse in particular biogeographic realms). In contrast to our hypothesis, shredder diversity was unrelated to leaf toughness, but it was inversely related to litter diversity. Our findings markedly contrast with global trends of diversity for most taxa, and with the general rule of higher consumer diversity at higher levels of resource diversity. Moreover, they highlight the emerging role of temperature in understanding global patterns of diversity, which is of great relevance in the face of projected global warming.

  13. Hydroacoustic Estimates of Fish Density Distributions in Cougar Reservoir, 2011

    Energy Technology Data Exchange (ETDEWEB)

    Ploskey, Gene R.; Zimmerman, Shon A.; Hennen, Matthew J.; Batten, George W.; Mitchell, T. D.

    2012-09-01

    Day and night mobile hydroacoustic surveys were conducted once each month from April through December 2011 to quantify the horizontal and vertical distributions of fish throughout Cougar Reservoir, Lane County, Oregon.

  14. Formal Difference Analysis and Unification on p-Norm Distribution Density Functions

    Institute of Scientific and Technical Information of China (English)

    LIU Zhengcai; ZHU Jianjun; WANG Huaiyu

    2006-01-01

    The cause of the formal difference of p-norm distribution density functions is analyzed, two problems in the deduction of p-norm formulating are improved, and it is proved that two different forms of p-norm distribution density functions are equivalent. This work is useful for popularization and application of the p-norm theory to surveying and mapping.

  15. HI column density distribution function at z=0 : Connection to damped Ly alpha statistics

    NARCIS (Netherlands)

    Zwaan, Martin; Verheijen, MAW; Briggs, FH

    We present a measurement of the HI column density distribution function f(N-HI) at the present epoch for column densities > 10(20) cm(-2). These high column densities compare to those measured in damped Ly alpha lines seen in absorption against background quasars. Although observationally rare, it

  16. HI column density distribution function at z=0 : Connection to damped Ly alpha statistics

    NARCIS (Netherlands)

    Zwaan, Martin; Verheijen, MAW; Briggs, FH

    1999-01-01

    We present a measurement of the HI column density distribution function f(N-HI) at the present epoch for column densities > 10(20) cm(-2). These high column densities compare to those measured in damped Ly alpha lines seen in absorption against background quasars. Although observationally rare, it a

  17. Neutron density distributions of neutron-rich nuclei studied with the isobaric yield ratio difference

    Energy Technology Data Exchange (ETDEWEB)

    Ma, Chun-Wang; Bai, Xiao-Man; Yu, Jiao; Wei, Hui-Ling [Henan Normal University, Institute of Particle and Nuclear Physics, Xinxiang (China)

    2014-09-15

    The isobaric yield ratio difference (IBD) between two reactions of similar experimental setups is found to be sensitive to nuclear density differences between projectiles. In this article, the IBD probe is used to study the density variation in neutron-rich {sup 48}Ca. By adjusting diffuseness in the neutron density distribution, three different neutron density distributions of {sup 48}Ca are obtained. The yields of fragments in the 80A MeV {sup 40,} {sup 48}Ca + {sup 12}C reactions are calculated by using a modified statistical abrasion-ablation model. It is found that the IBD results obtained from the prefragments are sensitive to the density distribution of the projectile, while the IBD results from the final fragments are less sensitive to the density distribution of the projectile. (orig.)

  18. Specification of Density Functional Approximation by Radial Distribution Function of Bulk Fluid

    Institute of Scientific and Technical Information of China (English)

    ZHOUShi-Qi

    2002-01-01

    A systematic methodology is proposed to deal with the weighted density approximation version of classical density functional theory by employing the knowledge of radial distribution function of bulk fluid.The present methodology results from the concept of universality of the free energy density functional combined with the test particle method.It is shown that the new method is very accurate for the predictions of density distribution of a hard sphere fluid at different confining geometries.The physical foundation of the present methodology is also applied to the quantum density functional theory.

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

    Energy Technology Data Exchange (ETDEWEB)

    Kato, S.; Seya, A. [Fuji Electric Co., Ltd., Ichihara-shi (Japan); Asano, A. [Fuji Electric Corporate, Ltd., Yokosuka-shi (Japan)

    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.

  20. Distribution of local density of states in superstatistical random matrix theory

    Energy Technology Data Exchange (ETDEWEB)

    Abul-Magd, A.Y. [Department of Mathematics, Faculty of Science, Zagazig University, Zagazig (Egypt)]. E-mail: a_y_abul_magd@hotmail.com

    2007-07-02

    We expose an interesting connection between the distribution of local spectral density of states arising in the theory of disordered systems and the notion of superstatistics introduced by Beck and Cohen and recently incorporated in random matrix theory. The latter represents the matrix-element joint probability density function as an average of the corresponding quantity in the standard random-matrix theory over a distribution of level densities. We show that this distribution is in reasonable agreement with the numerical calculation for a disordered wire, which suggests to use the results of theory of disordered conductors in estimating the parameter distribution of the superstatistical random-matrix ensemble.

  1. Using ultrasound tomography to identify the distributions of density throughout the breast

    Science.gov (United States)

    Sak, Mark; Duric, Neb; Littrup, Peter; Sherman, Mark E.; Gierach, Gretchen L.

    2016-04-01

    Women with high breast density are at increased risk of developing breast cancer. Breast density has usually been defined using mammography as the ratio of fibroglandular tissue to total breast area. Ultrasound tomography (UST) is an emerging modality that can also be used to measure breast density. UST creates tomographic sound speed images of the patient's breast which is useful as sound speed is directly proportional to tissue density. Furthermore, the volumetric and quantitative information contained in the sound speed images can be used to describe the distribution of breast density. The work presented here measures the UST sound speed density distributions of 165 women with negative screening mammography. Frequency distributions of the sound speed voxel information were examined for each patient. In a preliminary analysis, the UST sound speed distributions were averaged across patients and grouped by various patient and density-related factors (e.g., age, body mass index, menopausal status, average mammographic breast density). It was found that differences in the distribution of density could be easily visualized for different patient groupings. Furthermore, findings suggest that the shape of the distributions may be used to identify participants with varying amounts of dense and non-dense tissue.

  2. Numerical analysis of atomic density distribution in arc driven negative ion sources

    Energy Technology Data Exchange (ETDEWEB)

    Yamamoto, T., E-mail: t.yamamoto@ppl.appi.keio.ac.jp; Shibata, T.; Hatayama, A. [Graduate School of Science and Technology, Keio University, 3-14-1 Hiyoshi, Yokohama 223-8522 (Japan); Kashiwagi, M.; Hanada, M. [Japan Atomic Energy Agency (JAEA), 801-1 Mukouyama, Naka 311-0193 (Japan); Sawada, K. [Faculty of Engineering, Shinshu University, 4-17-1 Wakasato, Nagano 380-8553 (Japan)

    2014-02-15

    The purpose of this study is to calculate atomic (H{sup 0}) density distribution in JAEA 10 ampere negative ion source. A collisional radiative model is developed for the calculation of the H{sup 0} density distribution. The non-equilibrium feature of the electron energy distribution function (EEDF), which mainly determines the H{sup 0} production rate, is included by substituting the EEDF calculated from 3D electron transport analysis. In this paper, the H{sup 0} production rate, the ionization rate, and the density distribution in the source chamber are calculated. In the region where high energy electrons exist, the H{sup 0} production and the ionization are enhanced. The calculated H{sup 0} density distribution without the effect of the H{sup 0} transport is relatively small in the upper region. In the next step, the effect should be taken into account to obtain more realistic H{sup 0} distribution.

  3. Millimeter-wave Line Ratios and Sub-beam Volume Density Distributions

    Science.gov (United States)

    Leroy, Adam K.; Usero, Antonio; Schruba, Andreas; Bigiel, Frank; Kruijssen, J. M. Diederik; Kepley, Amanda; Blanc, Guillermo A.; Bolatto, Alberto D.; Cormier, Diane; Gallagher, Molly; Hughes, Annie; Jiménez-Donaire, Maria J.; Rosolowsky, Erik; Schinnerer, Eva

    2017-02-01

    We explore the use of mm-wave emission line ratios to trace molecular gas density when observations integrate over a wide range of volume densities within a single telescope beam. For observations targeting external galaxies, this case is unavoidable. Using a framework similar to that of Krumholz & Thompson, we model emission for a set of common extragalactic lines from lognormal and power law density distributions. We consider the median density of gas that produces emission and the ability to predict density variations from observed line ratios. We emphasize line ratio variations because these do not require us to know the absolute abundance of our tracers. Patterns of line ratio variations have the potential to illuminate the high-end shape of the density distribution, and to capture changes in the dense gas fraction and median volume density. Our results with and without a high-density power law tail differ appreciably; we highlight better knowledge of the probability density function (PDF) shape as an important area. We also show the implications of sub-beam density distributions for isotopologue studies targeting dense gas tracers. Differential excitation often implies a significant correction to the naive case. We provide tabulated versions of many of our results, which can be used to interpret changes in mm-wave line ratios in terms of adjustments to the underlying density distributions.

  4. Subchondral bone density distribution of the talus in clinically normal Labrador Retrievers.

    Science.gov (United States)

    Dingemanse, W; Müller-Gerbl, M; Jonkers, I; Vander Sloten, J; van Bree, H; Gielen, I

    2016-03-15

    Bones continually adapt their morphology to their load bearing function. At the level of the subchondral bone, the density distribution is highly correlated with the loading distribution of the joint. Therefore, subchondral bone density distribution can be used to study joint biomechanics non-invasively. In addition physiological and pathological joint loading is an important aspect of orthopaedic disease, and research focusing on joint biomechanics will benefit veterinary orthopaedics. This study was conducted to evaluate density distribution in the subchondral bone of the canine talus, as a parameter reflecting the long-term joint loading in the tarsocrural joint. Two main density maxima were found, one proximally on the medial trochlear ridge and one distally on the lateral trochlear ridge. All joints showed very similar density distribution patterns and no significant differences were found in the localisation of the density maxima between left and right limbs and between dogs. Based on the density distribution the lateral trochlear ridge is most likely subjected to highest loads within the tarsocrural joint. The joint loading distribution is very similar between dogs of the same breed. In addition, the joint loading distribution supports previous suggestions of the important role of biomechanics in the development of OC lesions in the tarsus. Important benefits of computed tomographic osteoabsorptiometry (CTOAM), i.e. the possibility of in vivo imaging and temporal evaluation, make this technique a valuable addition to the field of veterinary orthopaedic research.

  5. Contrast-enhanced ultrasonography for the detection and characterization of prostate cancer: Correlation with microvessel density and Gleason score

    Energy Technology Data Exchange (ETDEWEB)

    Jiang, J. [Xinhua Hospital Affiliated to Shanghai Jiaotong University School of Medicine, 1665 Kongjiang Road, Shanghai 200092 (China); Chen, Y., E-mail: joychen_1266@163.com [Xinhua Hospital Affiliated to Shanghai Jiaotong University School of Medicine, 1665 Kongjiang Road, Shanghai 200092 (China); Zhu, Y.; Yao, X.; Qi, J. [Xinhua Hospital Affiliated to Shanghai Jiaotong University School of Medicine, 1665 Kongjiang Road, Shanghai 200092 (China)

    2011-08-15

    Aim: To determine whether there is a correlation between the peak intensity of the lesion at contrast-enhanced ultrasonography and the microvessel density (MVD) and Gleason score in biopsy specimens of prostate cancer. Materials and methods: Contrast-enhanced ultrasonography using cadence-contrast pulse sequence (CPS) technology was performed in 147 patients with suspected prostate cancer before biopsy. An auto-tracking contrast quantification (ACQ) software was used to analyse the peak intensity (PI) of the lesion. The Gleason score and MVD immunoreactivity were determined in the prostate biopsy specimens. Ultrasound findings were correlated with biopsy findings. Results: Prostate cancer was detected in 73 of 147 patients. The PI values of prostate cancer patients were significantly higher than those of non-malignant patients [9.81 (4.23) versus 5.69 (3.19) dB; p < 0.01]. The mean (SD) PIs of prostate cancer lesions with a Gleason score of 6-9 were 7.08 (3.80), 8.65 (4.08), 9.76 (3.75), and 9.85 (4.13) dB, respectively. The PI value increased significantly with a higher Gleason score (p < 0.01). The mean (SD) MVDs observed in prostate cancer lesions with a Gleason score of 6-9 were 52.50 (10.54), 56.85 (10.31), 59.91 (9.29), and 66.04 (11.82), respectively. There was a positive correlation between PI and MVD in prostate cancer, with a correlation coefficient of 0.617. No correlation was found between PI value and age, prostate specific antigen (PSA) or prostate specific antigen density (PSAD) level (p > 0.05). Conclusion: The PI obtained by CPS harmonic ultrasonography appears to be of value as an indicator of MVD and increases with a higher Gleason score. CPS harmonic ultrasonography could be promising as a useful imaging technique in the detection and characterization of prostate cancer.

  6. Evolving Molecular Cloud Structure and the Column Density Probability Distribution Function

    CERN Document Server

    Ward, Rachel L; Sills, Alison

    2014-01-01

    The structure of molecular clouds can be characterized with the probability distribution function (PDF) of the mass surface density. In particular, the properties of the distribution can reveal the nature of the turbulence and star formation present inside the molecular cloud. In this paper, we explore how these structural characteristics evolve with time and also how they relate to various cloud properties as measured from a sample of synthetic column density maps of molecular clouds. We find that, as a cloud evolves, the peak of its column density PDF will shift to surface densities below the observational threshold for detection, resulting in an underlying lognormal distribution which has been effectively lost at late times. Our results explain why certain observations of actively star-forming, dynamically older clouds, such as the Orion molecular cloud, do not appear to have any evidence of a lognormal distribution in their column density PDFs. We also study the evolution of the slope and deviation point ...

  7. Ground State Density Distribution of Bose-Fermi Mixture in a One-Dimensional Harmonic Trap

    Institute of Scientific and Technical Information of China (English)

    HAO Ya-Jiang

    2011-01-01

    By the density-functional calculation we investigate the ground-state properties of Bose-Fermi mixture confined in one-dimensional harmonic traps. The homogeneous mixture of bosons and polarized fermions with contact interaction can be exactly solved by the Bethe-ansatz method. After giving the exact formula of ground state energy density, we employ the local-density approximation to determine the density distribution of each component. It is shown that with the increase in interaction, the total density distribution evolves to Fermi-like distribution and the system exhibits phase separation between two components when the interaction is strong enough but finite. While in the infinite interaction limit both bosons and fermions display the completely same Fermi-like distributions and phase separation disappears.

  8. Relationship between the shape and density distribution of the femur and its natural frequencies of vibration.

    Science.gov (United States)

    Campoli, G; Baka, N; Kaptein, B L; Valstar, E R; Zachow, S; Weinans, H; Zadpoor, A A

    2014-10-17

    It has been recently suggested that mechanical loads applied at frequencies close to the natural frequencies of bone could enhance bone apposition due to the resonance phenomenon. Other applications of bone modal analysis are also suggested. For the above-mentioned applications, it is important to understand how patient-specific bone shape and density distribution influence the natural frequencies of bones. We used finite element models to study the effects of bone shape and density distribution on the natural frequencies of the femur in free boundary conditions. A statistical shape and appearance model that describes shape and density distribution independently was created, based on a training set of 27 femora. The natural frequencies were then calculated for different shape modes varied around the mean shape while keeping the mean density distribution, for different appearance modes around the mean density distribution while keeping the mean bone shape, and for the 27 training femora. Single shape or appearance modes could cause up to 15% variations in the natural frequencies with certain modes having the greatest impact. For the actual femora, shape and density distribution changed the natural frequencies by up to 38%. First appearance mode that describes the general cortical bone thickness and trabecular bone density had one of the strongest impacts. The first appearance mode could therefore provide a sensitive measure of general bone health and disease progression. Since shape and density could cause large variations in the calculated natural frequencies, patient-specific FE models are needed for accurate estimation of bone natural frequencies.

  9. Phase contrast imaging of high-intensity laser hole boring of solid-density wires at LCLS-MEC

    Science.gov (United States)

    Schumaker, W.; Brown, S.; Curry, C.; Gauthier, M.; Gamboa, E.; Goede, S.; Fletcher, L.; Kim, J.; MacDonald, M.; Mishra, R.; Roedel, C.; Glenzer, S.; Fiuza, F.; Granados, E.; Nagler, B.; Zhou, Z.; MacKinnon, A.; Obst, L.; Ziel, K.; Pak, A.; Williams, G.; Fajardo, M.

    2016-10-01

    High-intensity, relativistic (a0 > 1) laser plasma interactions on solid surfaces produce a rich mix of dynamics on the laser timescale (Weibel instabilities, surface effects, sheath formation, etc.) and hydrodynamic timescale (hole-boring, shocks, etc.). Probing these interactions optically is difficult due to critical density layer obscuring the surface of the target, whereas probing with hard X-rays from K-alpha sources does not sufficiently resolve these interactions temporally as they are typically many ps in duration. Presented here are the first experimental measurements of laser hole-boring on a carbon wire surfaces performed at the LCLS-MEC facility. With laser intensities of up to 1019 W / cm2 , we observe the dissociation of micron-sized wires over 100 ps timescale with peak hole boring velocities up to 0.001 c using phase-contrast imaging. This work was funded by DOE FES under FWP #100182.

  10. Proton and neutron density distributions at supranormal density in low- and medium-energy heavy-ion collisions

    Science.gov (United States)

    Stone, J. R.; Danielewicz, P.; Iwata, Y.

    2017-07-01

    Background: The distribution of protons and neutrons in the matter created in heavy-ion collisions is one of the main points of interest for the collision physics, especially at supranormal densities. These distributions are the basis for predictions of the density dependence of the symmetry energy and the density range that can be achieved in a given colliding system. We report results of the first systematic simulation of proton and neutron density distributions in central heavy-ion collisions within the beam energy range of Ebeam≤800 MeV /nucl . The symmetric 40Ca+40Ca , 48Ca+48Ca , 100Sn+100Sn , and 120Sn+120Sn and asymmetric 40Ca+48Ca and 100Sn+120Sn systems were chosen for the simulations. Purpose: We simulate development of proton and neutron densities and asymmetries as a function of initial state, beam energy, and system size in the selected collisions in order to guide further experiments pursuing the density dependence of the symmetry energy. Methods: The Boltzmann-Uhlenbeck-Uehling (pBUU) transport model with four empirical models for the density dependence of the symmetry energy was employed. Results of simulations using pure Vlasov dynamics were added for completeness. In addition, the time-dependent Hartree-Fock (TDHF) model, with the SV-bas Skyrme interaction, was used to model the heavy-ion collisions at Ebeam≤40 MeV /nucl . Maximum proton and neutron densities ρpmax and ρnmax, reached in the course of a collision, were determined from the time evolution of ρp and ρn. Results: The highest total densities predicted at Ebeam=800 MeV /nucl . were of the order of ˜2.5 ρ0 (ρ0=0.16 fm-3 ) for both Sn and Ca systems. They were found to be only weakly dependent on the initial conditions, beam energy, system size, and a model of the symmetry energy. The proton-neutron asymmetry δ =(ρnmax-ρpmax) /(ρnmax+ρpmax) at maximum density does depend, though, on these parameters. The highest value of δ found in all systems and at all investigated beam

  11. Atomic force microscopy contrast with CO functionalized tips in hydrogen-bonded molecular layers: Does the real tip charge distribution play a role?

    Science.gov (United States)

    Ellner, Michael; Pou, Pablo; Pérez, Rubén

    2017-08-01

    The interplay of van der Waals (vdW), electrostatic (ES), and short-range (SR) interactions on both the intra- and intermolecular contrast observed in high-resolution atomic force microscopy (HR-AFM) is explored in a hydrogen-bonded monolayer of triazine molecules. Our efficient model to simulate AFM images uses the three-dimensional (3D) charge distribution of both tip and sample to calculate the ES interaction, takes into account the tilting of the CO molecule, and reproduces with high accuracy density functional theory calculations. In spite of triazine's hexagonal structure, the intramolecular contrast has triangular symmetry, reflecting the charge density of the molecule. Stripelike intermolecular features, which join the molecules in the H-bond directions, originate from the overlap of the charge density of the atoms in neighboring molecules and are sharpened by the CO tilt. We demonstrate the existence of different potential energy surface minima for the CO tilt and discuss its influence on imaging. Our results clearly show that the ES interaction maps represent a local 3D average of the ES potential of the sample weighted by the tip's charge density, while the SR interaction resembles a local 3D average of the charge density of the sample. However, the strong cancellation of both contributions results in a net interaction dominated by the ES and vdW far from the molecules, and by the SR at short distance. This cancellation, which essentially removes the dependence on the detailed charge distribution of the tip, explains why AFM images can be reproduced using only sample properties such as the z component of the electric field and the charge density of the molecule, and the success of simple models that only incorporate pairwise, point-charge interactions.

  12. Inversion of the Abel equation for toroidal density distributions

    CERN Document Server

    Ciotti, L

    1999-01-01

    In this paper I present three new results of astronomical interest concerning the theory of Abel inversion. 1) I show that in the case of a spatial emissivity that is constant on toroidal surfaces and projected along the symmetry axis perpendicular to the torus' equatorial plane, it is possible to invert the projection integral. From the surface (i.e. projected) brightness profile one then formally recovers the original spatial distribution as a function of the toroidal radius. 2) By applying the above-described inversion formula, I show that if the projected profile is described by a truncated off-center gaussian, the functional form of the related spatial emissivity is very simple and - most important - nowhere negative for any value of the gaussian parameters, a property which is not guaranteed - in general - by Abel inversion. 3) Finally, I show how a generic multimodal centrally symmetric brightness distribution can be deprojected using a sum of truncated off-center gaussians, recovering the spatial emis...

  13. Specification of Density Functional Approximation by Radial Distribution Function of Bulk Fluid

    Institute of Scientific and Technical Information of China (English)

    ZHOU Shi-Qi

    2002-01-01

    A systematic methodology is proposed to deal with the weighted density approximation version of clas-sical density functional theory by employing the knowledge of radial distribution function of bulk fluid. The presentmethodology results from the concept of universality of the free energy density functional combined with the test particlemethod. It is shown that the new method is very accurate for the predictions of density distribution ofa hard sphere fluidat different confining geometries. The physical foundation of the present methodology is also applied to the quantumdensity functional theory.

  14. Evaluation of mobile dislocation density based on distribution function of dislocation segments

    Institute of Scientific and Technical Information of China (English)

    周志敏; 孙艳蕊; 周海涛

    2004-01-01

    A function is offered to represent the distribution of reduced length of dislocation segments. The segment distribution of materials, e. g. , MgO and Cu, can be well described by taking appropriate values of parametersm and n. Based on this function, a model for evaluating the mobile dislocation density is developed. Provided the total dislocation density and applied stress are known, the mobile dislocation density could be readily assessed by using this model. For pure copper the mobile dislocation density and strain rates at deferent strains are evaluated. The calculated results are consistent with the known experimental data.

  15. Pauling bond strength, bond length and electron density distribution

    Energy Technology Data Exchange (ETDEWEB)

    Gibbs, Gerald V.; Ross, Nancy L.; Cox, David F.; Rosso, Kevin M.; Iversen, Bo B.; Spackman, M. A.

    2014-01-18

    A power law regression equation, = 1.46(<ρ(rc)>/r)-0.19, connecting the average experimental bond lengths, , with the average accumulation of the electron density at the bond critical point, <ρ(rc)>, between bonded metal M and oxygen atoms, determined at ambient conditions for oxide crystals, where r is the row number of the M atom, is similar to the regression equation R(M-O) = 1.39(ρ(rc)/r)-0.21 determined for three perovskite crystals for pressures as high as 80 GPa. The two equations are also comparable with those, = 1.43(/r)-0.21, determined for a large number of oxide crystals at ambient conditions and = 1.39(/r)-0.22, determined for geometry optimized hydroxyacid molecules, that connect the bond lengths to the average Pauling electrostatic bond strength, , for the M-O bonded interactions. On the basis of the correspondence between the two sets of equations connecting ρ(rc) and the Pauling bond strength s with bond length, it appears that Pauling’s simple definition of bond strength closely mimics the accumulation of the electron density between bonded pairs of atoms. The similarity of the expressions for the crystals and molecules is compelling evidence that the M-O bonded interactions for the crystals and molecules 2 containing the same bonded interactions are comparable. Similar expressions, connecting bond lengths and bond strength, have also been found to hold for fluoride, nitride and sulfide molecules and crystals. The Brown-Shannon bond valence, σ, power law expression σ = [R1/(R(M-O)]N that has found wide use in crystal chemistry, is shown to be connected to a more universal expression determined for oxides and the perovskites, <ρ(rc)> = r[(1.41)/]4.76, demonstrating that the bond valence for a bonded interaction is likewise closely connected to the accumulation of the electron density between the bonded atoms. Unlike the Brown-Shannon expression, it is universal in that it holds for the M

  16. Contrasting tropical cyclone and non-tropical cyclone related rainfall drop size distribution at Darwin, Australia

    Science.gov (United States)

    Deo, Anil; Walsh, Kevin J. E.

    2016-11-01

    In this study the rainfall drop size distribution (DSD) during the passage of seven tropical cyclones (TCs) over Darwin is compared and contrasted with that associated with non-tropical cyclone (non-TC) events, using the impact disdrometer data at the Darwin Atmospheric Radiation and Measurement (ARM) site. The disparity of the DSD with respect to rainfall types (between TC and non-TC conditions) and distance from TC centre is also examined. It is shown that TC DSDs are statistically different from the non-TC DSDs, the former encompassing a larger concentration of small to moderate drop sizes. The TC mass-weighted mean diameter (Dm) is lower than the non-TC values at all rain rates and also for the different precipitation types (convective, transition and stratiform). The TC DSD varies with distance from the TC centre, as rainfall near the TC centre (< 60 km) comprises of relatively smaller drops which are strongly evident at small to moderate rain rates (< 30 mm h- 1). Such variations in the DSD have implications for the parameters used in the algorithm that converts radar reflectivity to rainfall rate in TCs, as well as for the analytical expressions used in describing the observed DSD employed in cloud modelling parameterizations.

  17. Contrasting genetic structure in two co-distributed species of old world fruit bat.

    Science.gov (United States)

    Chen, Jinping; Rossiter, Stephen J; Flanders, Jonathan R; Sun, Yanhong; Hua, Panyu; Miller-Butterworth, Cassandra; Liu, Xusheng; Rajan, Koilmani E; Zhang, Shuyi

    2010-01-01

    The fulvous fruit bat (Rousettus leschenaulti) and the greater short-nosed fruit bat (Cynopterus sphinx) are two abundant and widely co-distributed Old World fruit bats in Southeast and East Asia. The former species forms large colonies in caves while the latter roots in small groups in trees. To test whether these differences in social organization and roosting ecology are associated with contrasting patterns of gene flow, we used mtDNA and nuclear loci to characterize population genetic subdivision and phylogeographic histories in both species sampled from China, Vietnam and India. Our analyses from R. leschenaulti using both types of marker revealed little evidence of genetic structure across the study region. On the other hand, C. sphinx showed significant genetic mtDNA differentiation between the samples from India compared with China and Vietnam, as well as greater structuring of microsatellite genotypes within China. Demographic analyses indicated signatures of past rapid population expansion in both taxa, with more recent demographic growth in C. sphinx. Therefore, the relative genetic homogeneity in R. leschenaulti is unlikely to reflect past events. Instead we suggest that the absence of substructure in R. leschenaulti is a consequence of higher levels of gene flow among colonies, and that greater vagility in this species is an adaptation associated with cave roosting.

  18. Contrasting genetic structure in two co-distributed species of old world fruit bat.

    Directory of Open Access Journals (Sweden)

    Jinping Chen

    Full Text Available The fulvous fruit bat (Rousettus leschenaulti and the greater short-nosed fruit bat (Cynopterus sphinx are two abundant and widely co-distributed Old World fruit bats in Southeast and East Asia. The former species forms large colonies in caves while the latter roots in small groups in trees. To test whether these differences in social organization and roosting ecology are associated with contrasting patterns of gene flow, we used mtDNA and nuclear loci to characterize population genetic subdivision and phylogeographic histories in both species sampled from China, Vietnam and India. Our analyses from R. leschenaulti using both types of marker revealed little evidence of genetic structure across the study region. On the other hand, C. sphinx showed significant genetic mtDNA differentiation between the samples from India compared with China and Vietnam, as well as greater structuring of microsatellite genotypes within China. Demographic analyses indicated signatures of past rapid population expansion in both taxa, with more recent demographic growth in C. sphinx. Therefore, the relative genetic homogeneity in R. leschenaulti is unlikely to reflect past events. Instead we suggest that the absence of substructure in R. leschenaulti is a consequence of higher levels of gene flow among colonies, and that greater vagility in this species is an adaptation associated with cave roosting.

  19. A phase contrast imaging–interferometer system for detection of multiscale electron density fluctuations on DIII-D

    Energy Technology Data Exchange (ETDEWEB)

    Davis, E. M.; Rost, J. C.; Porkolab, M.; Marinoni, A. [MIT Plasma Science and Fusion Center, Cambridge, Massachusetts 02139 (United States); Van Zeeland, M. A. [General Atomics, San Diego, California 92121 (United States)

    2016-11-15

    Heterodyne interferometry and phase contrast imaging (PCI) are robust, mature techniques for measuring low-k and high-k electron density fluctuations, respectively. This work describes the first-ever implementation of a combined PCI–interferometer. The combined system uses a single 10.6 μm probe beam, two interference schemes, and two detectors to measure electron density fluctuations at large spatiotemporal bandwidth (10 kHz

  20. Edge distribution and density in the characteristic sequence

    CERN Document Server

    Malliaris, M E

    2009-01-01

    The characteristic sequence of hypergraphs $$ associated to a formula $\\phi(x;y)$, introduced in [arXiv:0908.4111], is defined by $P_n(y_1,... y_n) = (\\exists x) \\bigwedge_{i\\leq n} \\phi(x;y_i)$. This paper continues the study of characteristic sequences, showing that graph-theoretic techniques, notably Szemer\\'edi's celebrated regularity lemma, can be naturally applied to the study of model-theoretic complexity via the characteristic sequence. Specifically, we relate classification-theoretic properties of $\\phi$ and of the $P_n$ (considered as formulas) to density between components in Szemer\\'edi-regular decompositions of graphs in the characteristic sequence. In addition, we use Szemer\\'edi regularity to calibrate model-theoretic notions of independence by describing the depth of independence of a constellation of sets and showing that certain failures of depth imply Shelah's strong order property $SOP_3$; this sheds light on the interplay of independence and order in unstable theories.

  1. The force distribution probability function for simple fluids by density functional theory.

    Science.gov (United States)

    Rickayzen, G; Heyes, D M

    2013-02-28

    Classical density functional theory (DFT) is used to derive a formula for the probability density distribution function, P(F), and probability distribution function, W(F), for simple fluids, where F is the net force on a particle. The final formula for P(F) ∝ exp(-AF(2)), where A depends on the fluid density, the temperature, and the Fourier transform of the pair potential. The form of the DFT theory used is only applicable to bounded potential fluids. When combined with the hypernetted chain closure of the Ornstein-Zernike equation, the DFT theory for W(F) agrees with molecular dynamics computer simulations for the Gaussian and bounded soft sphere at high density. The Gaussian form for P(F) is still accurate at lower densities (but not too low density) for the two potentials, but with a smaller value for the constant, A, than that predicted by the DFT theory.

  2. Reinvestigation of the charge density distribution in arc discharge fusion system

    Energy Technology Data Exchange (ETDEWEB)

    Sheng, Lin Horng; Yee, Lee Kim; Nan, Phua Yeong; Thung, Yong Yun; Khok, Yong Thian; Rahman, Faidz Abd [Centre of Photonics and Advance Material, Universiti Tunku Abdul Rahman Kuala Lumpur (Malaysia)

    2015-04-24

    A continual arc discharge system has been setup and the light intensity of arc discharge has been profiled. The mathematical model of local energy density distribution in arc discharge fusion has been simulated which is in good qualitative agreement with light intensity profile of arc discharge in the experiments. Eventually, the local energy density distribution of arc discharge system is able to be precisely manipulated to act as heat source in the fabrication of fused fiber devices.

  3. Bayesian Contrast Measures and Clutter Distribution Determinants of Human Target Detection.

    Science.gov (United States)

    Novak, Ana; Armstrong, Nicholas; Caelli, Terry; Blair, Iain

    2017-03-01

    Human target detection is known to be dependent on a number of components: one, basic electro-optics including image contrast, the target size, pixel resolution, and contrast sensitivity; two, target shape, image type and features, types of clutter; and three, context and task requirements. Here, we consider a Bayesian approach to investigating how these components contribute to target detection. To this end, we develop and compare three different formulations for contrast: mean contrast, perceptual contrast, and a Bayesian-based histogram contrast statistic. Results on past detection data show how the latter contrast measure correlates well with human performance factoring out all other dimensions. As for clutter, our findings show that with large targets, there are effectively no clutter effects. Furthermore, clutter does not have a major effect on detection when it is not contiguous with the target even when it is smaller. However, except for large targets, when the target is contiguous with the clutter, detection clearly decreases as a function of the similarity of target and clutter features-creating type of "clutter camouflage". This Bayesian formulation uses priors based on the contrast histogram statistics derived from all the images, the image context, and implies that human observers have adapted their criteria to fit with the image set, context, and task.

  4. DIRECT EXPANSIONS FOR THE DISTRIBUTION FUNCTIONS AND DENSITY FUNCTIONS OF x2-TYPE AND t-TYPE DISTRIBUTED RANDOM VARIABLES

    Institute of Scientific and Technical Information of China (English)

    ZHENGZUKANG

    1996-01-01

    Suppose that Z1,Z2…,Zn are independent normal random variables with common mean μ and variance σ2. Then S2=∑n n=1 (zi-z)2/σ2 and T =(n-1的平方根)-Z/(S2/n的平方根) have x2n-1 distribution and tn-1 distribution respectively. If the normal assumption fails, there will be the remainders of the distribution functions and density functions. This paper gives the direct expansions of distribution functions and density functions of S2 and T up to o(n-1). They are more intuitive and convenient than usual Edgeworth expansions.

  5. A Comprehensive Survey of Pelagic Megafauna: Their Distribution, Densities, and Taxonomic Richness in the Tropical Southwest Indian Ocean

    Directory of Open Access Journals (Sweden)

    Sophie Laran

    2017-05-01

    Full Text Available The distribution and density of pelagic megafauna (marine mammals, seabirds, elasmobranches, and sea turtles are important indicators of marine biodiversity, reflecting the condition of the underlying ecosystems. A dedicated aerial survey was conducted in the tropical Southwest Indian Ocean to map their distribution, the taxonomic diversity, and to estimate their densities to serve as a baseline for the area. This large survey across three ecological sub-regions revealed contrasting spatial distributions: maps of taxonomic richness of marine mammals and seabirds revealed different “hotspots” in the area. Densities were estimated for eight cetacean taxa with small and large Delphininae, or small Globicephalinae dominating, and for seven seabird taxa, with terns and noddies dominating. At the community level, the Southwest Indian Ocean megafauna was structured by the marine environment with strong differences between the Mozambique Channel and the Mascarene Islands, or between shelf and slope/oceanic habitats. Our results illustrate how multi-taxa aerial surveys are relevant and cost-effective monitoring tools for marine megafauna, allowing a community-wide approach.

  6. A High Power Density DC-DC Converter for Distributed PV Architectures

    Energy Technology Data Exchange (ETDEWEB)

    Agamy, Mohammed S; Chi, Song; Elasser, Ahmed; Harfman-Todorovic, Maja; Jiang, Yan; Mueller, Frank; Tao, Fengfeng

    2012-06-01

    In order to maximize solar energy harvesting capabilities, power converters have to be designed for high efficiency and good MPPT and voltage/current performance. When many converters are used in distributed systems, power density also becomes an important factor as it allows for simpler system integration. In this paper a high power density string dc-dc converter suitable for distributed medium to large scale PV installation is presented. A simple partial power processing topology, implemented with all silicon carbide devices provides high efficiency as well as high power density. A 3.5kW, 100kHz converter is designed and tested to verify the proposed methods.

  7. Theoretical discussion for electron-density distribution in multicusp ion source

    Science.gov (United States)

    Zhan, Hualin; Hu, Chundong; Xie, Yahong; Wu, Bin; Wang, Jinfang; Liang, Lizheng; Wei, Jianglong

    2011-03-01

    By introducing some ideas of magnetohydrodynamics (MHD) and kinetic theories, some useful solutions for electron-density distribution in the radial direction in multicusp ion source are obtained. Therefore, some conclusions are made in this perspective: 1, the electron-density distributions in a specific region in the sheath are the same with or without magnetic field; 2, the influence of magnetic field on the electron density obeys exponential law, which should take into account the collision term as well if the magnetic field is strong; 3, the result derived from the Boltzmann equation is qualitatively consistent with some given experimental results.

  8. Isovector coupling channel and central properties of the charge density distribution in heavy spherical nuclei

    Indian Academy of Sciences (India)

    S Haddad

    2010-09-01

    The influence of the isovector coupling channel on the central depression parameter and the central value of the charge density distribution in heavy spherical nuclei was studied. The isovector coupling channel leads to about 50% increase of the central depression parameter, and weakens the dependency of both central depression parameter and central density on the asymmetry, impressively contributing to the semibubble form of the charge density distribution in heavy nuclei, and increasing the probability of larger nuclei with higher proton numbers and higher neutron-to-proton ratios stable.

  9. Compensation in Root Water Uptake Models Combined with Three-Dimensional Root Length Density Distribution

    NARCIS (Netherlands)

    Heinen, M.

    2014-01-01

    A three-dimensional root length density distribution function is introduced that made it possible to compare two empirical uptake models with a more mechanistic uptake model. Adding a compensation component to the more empirical model resulted in predictions of root water uptake distributions

  10. Statistical link between the structure of molecular clouds and their density distribution

    CERN Document Server

    Donkov, Sava; Klessen, Ralf S

    2016-01-01

    We introduce the concept of a class of equivalence of molecular clouds represented by an abstract spherically symmetric, isotropic object. This object is described by use of abstract scales in respect to a given mass density distribution. Mass and average density are ascribed to each scale and thus are linked to the density distribution: a power-law type and an arbitrary continuous one. In the latter case, we derive a differential relationship between the mean density at a given scale and the structure parameter which defines the mass-density relationship. The two-dimensional (2D) projection of the cloud along the line of sight is also investigated. Scaling relations of mass and mean density are derived in the considered cases of power-law and arbitrary continuous distributions. We obtain relations between scaling exponents in the 2D and 3D cases. The proposed classes of equivalence are representative for the general structure of real clouds with various types of column-density distributions: power law, logno...

  11. Basement depth estimation from gravity anomalies: two 2.5D approaches coupled with the exponential density contrast model

    Science.gov (United States)

    Chakravarthi, V.; Mallesh, K.; Ramamma, B.

    2017-03-01

    We develop two automatic techniques in the spatial domain using the exponential density contrast model (EDCM) to trace the bottom surface of a 2.5D sedimentary basin from the observed gravity anomalies. The interface between the sediments and basement is described with a finite strike polygonal source, whose depth ordinates become the unknown parameters to be estimated. The proposed automatic modeling technique makes use of the forward difference approximation and the inversion solves a system of normal equations using the ridge regression to estimate the unknown parameters. Furthermore, the proposed inversion technique simultaneously estimates the regional gravity background that is associated with the residual gravity anomaly. In either case, forward modeling is realized in the spatial domain through a method that combines both analytical and numerical approaches. The utility of each algorithm was successfully tested on a theoretically produced noisy residual gravity dataset. The validity of the inversion technique is also exemplified with the noisy gravity anomalies attributable to a synthetic structure in the presence of regional gravity background. We demonstrate that the magnitude of gravity anomaly is offset dependent and that it would influence the modeling result. Additionally, some applications with real gravity datasets from the Gediz and Büyük Menderes grabens in western Turkey using the derived EDCMs have produced geologically reasonable results which are in close agreement with those reported previously.

  12. The Probability Density Functions to Diameter Distributions for Scots Pine Oriental Beech and Mixed Stands

    Directory of Open Access Journals (Sweden)

    Aydın Kahriman

    2011-11-01

    Full Text Available Determine the diameter distribution of a stand and its relations with stand ages, site index, density and mixture percentage is very important both biologically and economically. The Weibull with two parameters, Weibull with three parameters, Gamma with two parameters, Gamma with three parameters, Beta, Lognormal with two parameters, Lognormal with three parameters, Normal, Johnson SB probability density functions were used to determination of diameter distributions. This study aimed to compared based on performance of describing different diameter distribution and to describe the best successful function of diameter distributions. The data were obtaited from 162 temporary sample plots measured Scots pine and Oriental beech mixed stands in Black Sea Region. The results show that four parameter Johnson SB function for both scots pine and oriental beech is the best successful function to describe diameter distributions based on error index values calculated by difference between observed and predicted diameter distributions.

  13. Density Distributions of H and H2 in Pulsed Microwave hydrogen Plasmas

    Institute of Scientific and Technical Information of China (English)

    DUAN Xu-Ru(段旭如); H.Lange; QIAN shang-Jie(钱尚介); N.Lang

    2003-01-01

    Temporal distribution of the H atom and Hz densities in a pulsed microwave hydrogen plasmas has been measured simultaneously by two-photon absorption laser-induced fluorescence (TALIF). The measurement of the H-atom absolute density obtained by NO2 titration in a flow tube reactor shows that the density of H2 could be determined by the measured effective lifetime of the TALIF signal via the quenching equation. The H-atom density of about 1.5×1015cm-3 in both pulsed and stationary phases does not obviously change. It is found that the gas temperature volume effect plays an important role in governing the distributions of the H-atom density and it is mole fraction. The calculated gas temperature is in good consistent with the rotational temperature of H2measured by optical emission spectroscopy in pulsed phase.

  14. Kink and Sausage Modes in Nonuniform Magnetic Slabs with Continuous Transverse Density Distributions

    CERN Document Server

    Yu, Hui; Chen, Shao-Xia; Guo, Ming-Zhe

    2015-01-01

    We examine the influence of a continuous density structuring transverse to coronal slabs on the dispersive properties of fundamental standing kink and sausage modes supported therein. We derive generic dispersion relations (DRs) governing linear fast waves in pressureless straight slabs with general transverse density distributions, and focus on the cases where the density inhomogeneity takes place in a layer of arbitrary width and in arbitrary form. The physical relevance of the solutions to the DRs is demonstrated by the corresponding time-dependent computations. For all profiles examined, the lowest-order kink modes are trapped regardless of longitudinal wavenumber $k$. A continuous density distribution introduces a difference to their periods of $\\lesssim 13\\%$ when $k$ is the observed range, relative to the case where the density profile takes a step-function form. Sausage modes and other branches of kink modes are leaky at small $k$, and their periods and damping times are heavily influenced by how the ...

  15. First principles study of the electron density distribution in a pair of bare metallic electrodes

    Energy Technology Data Exchange (ETDEWEB)

    Ma, Chun-Lan [Suzhou University of Science and Technology, School of Mathematics and Physics, Suzhou (China); Chen, Yu-Chang; Nghiem, Diu; Tseng, Allen; Huang, Pao-Chieh [National Chiao Tung University, Department of Electrophysics, Hsinchu (China)

    2011-07-15

    Self-consistent calculations of electron density distribution from first principles for a series of semi-infinite metals show that the electron density almost drops to zero at 8.5 a.u. away from a metal surface. The electron densities in a series of bimetallic-electrode systems with a distance between the two electrodes of 21.7 a.u. are further investigated. Spin-polarized calculations of electron density for nonmagnetic and magnetic bimetallic-electrode systems are compared. Our work is helpful for first principles investigation of spin-dependent metal-molecule-metal tunneling junctions. (orig.)

  16. Modeling Spatiotemporal Precipitation: Effects of Density, Interpolation, and Land Use Distribution

    Directory of Open Access Journals (Sweden)

    Christopher L. Shope

    2015-01-01

    Full Text Available Characterization of precipitation is critical in quantifying distributed catchment-wide discharge. The gauge network is a key driver in hydrologic modeling to characterize discharge. The accuracy of precipitation is dependent on the location of stations, the density of the network, and the interpolation scheme. Our study examines 16 weather stations in a 64 km2 catchment. We develop a weighted, distributed approach for gap-filling the observed meteorological dataset. We analyze five interpolation methods (Thiessen, IDW, nearest neighbor, spline, and ordinary Kriging at five gauge densities. We utilize precipitation in a SWAT model to estimate discharge in lumped parameter simulations and in a distributed approach at the multiple densities (1, 16, 50, 142, and 300 stations. Gauge density has a substantial impact on distributed discharge and the optimal gauge density is between 50 and 142 stations. Our results also indicate that the IDW interpolation scheme was optimum, although the Kriging and Thiessen polygon methods produced similar results. To further examine variability in discharge, we characterized the land use and soil distribution throughout each of the subbasins. The optimal rain gauge position and distribution of the gauges drastically influence catchment-wide runoff. We found that it is best to locate the gauges near less permeable locations.

  17. Distribution and speciation of ambient selenium in contrasted soils, from mineral to organic rich.

    Science.gov (United States)

    Tolu, Julie; Thiry, Yves; Bueno, Maïté; Jolivet, Claudy; Potin-Gautier, Martine; Le Hécho, Isabelle

    2014-05-01

    Selenium adsorption onto oxy-hydroxides mainly controls its mobility in volcanic soils, red earths and soils poor in organic matter (OM) while the influence of OM was emphasized in podzol and peat soils. This work aims at deciphering how those solid phases influence ambient Se mobility and speciation under less contrasted conditions in 26 soils spanning extensive ranges of OM (1-32%), Fe/Al oxy-hydroxides (0.3-6.1%) contents and pH (4.0-8.3). The soil collection included agriculture, meadow and forest soils to assess the influence of OM quality as well. Trace concentrations of six ambient Se species (Se(IV), Se(VI) and 4 organo-Se compounds) were analyzed by HPLC-ICP-MS in three extractants (ultrapure water, phosphate and sodium hydroxide) targeting Se associated to different soil phases. The Kd values determined from ultrapure water extraction were higher than those reported in commonly used short-term experiments after Se-spiking. Correlations of ambient Se content and distribution with soil parameters explained this difference by an involvement of slow processes in Se retention in soils. The 26 Kd values determined here for a wide variety of soils thus represent a relevant database for long-term prediction of Se mobility. For soils containing less than 20% OM, ambient Se solubility is primarily controlled by its adsorption onto crystalline oxy-hydroxides. However, OM plays an important role in Se mobility by forming organo-mineral associations that may protect adsorbed Se from leaching and/or create anoxic zones (aggregates) where Se is immobilized after its reduction. Although for the first time, inorganic Se(IV), Se(VI) and organo-Se compounds were simultaneously investigated in a large soil collection, high Se proportions remain unidentified in each soil extract, most probably due to Se incorporation and/or binding to colloidal-sized OM. Variations of environmental factors regulating the extent of OM-mineral associations/aggregation may thus lead to changes

  18. Non-parametric kernel density estimation of species sensitivity distributions in developing water quality criteria of metals.

    Science.gov (United States)

    Wang, Ying; Wu, Fengchang; Giesy, John P; Feng, Chenglian; Liu, Yuedan; Qin, Ning; Zhao, Yujie

    2015-09-01

    Due to use of different parametric models for establishing species sensitivity distributions (SSDs), comparison of water quality criteria (WQC) for metals of the same group or period in the periodic table is uncertain and results can be biased. To address this inadequacy, a new probabilistic model, based on non-parametric kernel density estimation was developed and optimal bandwidths and testing methods are proposed. Zinc (Zn), cadmium (Cd), and mercury (Hg) of group IIB of the periodic table are widespread in aquatic environments, mostly at small concentrations, but can exert detrimental effects on aquatic life and human health. With these metals as target compounds, the non-parametric kernel density estimation method and several conventional parametric density estimation methods were used to derive acute WQC of metals for protection of aquatic species in China that were compared and contrasted with WQC for other jurisdictions. HC5 values for protection of different types of species were derived for three metals by use of non-parametric kernel density estimation. The newly developed probabilistic model was superior to conventional parametric density estimations for constructing SSDs and for deriving WQC for these metals. HC5 values for the three metals were inversely proportional to atomic number, which means that the heavier atoms were more potent toxicants. The proposed method provides a novel alternative approach for developing SSDs that could have wide application prospects in deriving WQC and use in assessment of risks to ecosystems.

  19. Comparative analysis of Vening-Meinesz Moritz isostatic models using the constant and variable crust-mantle density contrast – a case study of Zealandia

    Indian Academy of Sciences (India)

    Mohammad Bagherbandi; Robert Tenzer

    2013-04-01

    We compare three different numerical schemes of treating the Moho density contrast in gravimetric inverse problems for finding the Moho depths. The results are validated using the global crustal model CRUST2.0, which is determined based purely on seismic data. Firstly, the gravimetric recovery of the Moho depths is realized by solving Moritz’s generalization of the Vening-Meinesz inverse problem of isostasy while the constant Moho density contrast is adopted. The Pratt-Hayford isostatic model is then facilitated to estimate the variable Moho density contrast. This variable Moho density contrast is subsequently used to determine the Moho depths. Finally, the combined least-squares approach is applied to estimate jointly the Moho depths and density contract based on a priori error model. The EGM2008 global gravity model and the DTM2006.0 global topographic/bathymetric model are used to generate the isostatic gravity anomalies. The comparison of numerical results reveals that the optimal isostatic inverse scheme should take into consideration both the variable depth and density of compensation. This is achieved by applying the combined least-squares approach for a simultaneous estimation of both Moho parameters. We demonstrate that the result obtained using this method has the best agreement with the CRUST2.0 Moho depths. The numerical experiments are conducted at the regional study area of New Zealand’s continental shelf.

  20. The use of dilute calogen[reg] as a fat density oral contrast medium in upper abdominal computed tomography, compared with the use of water and positive oral contrast media

    Energy Technology Data Exchange (ETDEWEB)

    Ramsay, Duncan W.; Markham, Derrian H.; Morgan, Bruno; Rodgers, Peter M.; Liddicoat, Amanda J

    2001-08-01

    AIM: Oral contrast media are commonly given prior to computed tomography (CT) examination of the upper abdomen. Although positive oral contrast media are normally used, there is increasing interest in using negative agents such as water and less commonly fat density products. The aim of this study was to compare a positive oral contrast medium, water, and a diluted emulsion of arachis oil (Calogen[reg], a fat density food supplement) for assessment of the upper abdomen. MATERIALS AND METHODS: Seventy-one patients referred for upper abdominal CT were randomized to receive either 500 ml water, 2% sodium diatrizoate or a dilute suspension of Calogen[reg]. The CT images were scored independently by three radiologists. Distension and anatomical identification was assessed for the stomach, duodenum and jejunum; with anatomical identification recorded for the pancreas, retroperitoneum, liver, gallbladder and spleen. RESULTS: Dilute Calogen[reg] produced a significant improvement (P < 0.01) in distension and anatomical visualization of the stomach and proximal duodenum. Only minimal differences were demonstrated between the three contrast media for visualization of more distal small bowel or identification of the other upper abdominal viscera. Significantly more artifacts were caused by positive contrast media than with the Calogen[reg] mixture. CONCLUSION: A dilute suspension of Calogen[reg] as an oral contrast medium is recommended when disease is suspected within the stomach or proximal duodenum. Ramsay, D.W. et al. (2001)

  1. Density distribution of a dust cloud in three-dimensional complex plasmas

    Science.gov (United States)

    Naumkin, V. N.; Zhukhovitskii, D. I.; Molotkov, V. I.; Lipaev, A. M.; Fortov, V. E.; Thomas, H. M.; Huber, P.; Morfill, G. E.

    2016-09-01

    We propose a method of determination of the dust particle spatial distribution in dust clouds that form in three-dimensional (3D) complex plasmas under microgravity conditions. The method utilizes the data obtained during the 3D scanning of a cloud, and it provides reasonably good accuracy. Based on this method, we investigate the particle density in a dust cloud realized in gas discharge plasma in the PK-3 Plus setup onboard the International Space Station. We find that the treated dust clouds are both anisotropic and inhomogeneous. One can isolate two regimes in which a stationary dust cloud can be observed. At low pressures, the particle density decreases monotonically with the increase of the distance from the discharge center; at higher pressures, the density distribution has a shallow minimum. Regardless of the regime, we detect a cusp of the distribution at the void boundary and a slowly varying density at larger distances (in the foot region). A theoretical interpretation of the obtained results is developed that leads to reasonable estimates of the densities for both the cusp and the foot. The modified ionization equation of state, which allows for violation of the local quasineutrality in the cusp region, predicts the spatial distributions of ion and electron densities to be measured in future experiments.

  2. The Velocity and Density Distribution of Earth-Intersecting Meteoroids: Implications for Environment Models

    Science.gov (United States)

    Moorhead, A. V.; Brown, P. G.; Campbell-Brown, M. D.; Moser, D. E.; Blaauw, R. C.; Cooke, W. J.

    2017-01-01

    Meteoroids are known to damage spacecraft: they can crater or puncture components, disturb a spacecraft's attitude, and potentially create secondary electrical effects. Because the damage done depends on the speed, size, density, and direction of the impactor, accurate environment models are critical for mitigating meteoroid-related risks. Yet because meteoroid properties are derived from indirect observations such as meteors and impact craters, many characteristics of the meteoroid environment are uncertain. In this work, we present recent improvements to the meteoroid speed and density distributions. Our speed distribution is derived from observations made by the Canadian Meteor Orbit Radar. These observations are de-biased using modern descriptions of the ionization efficiency. Our approach yields a slower meteoroid population than previous analyses (see Fig. 1 for an example) and we compute the uncertainties associated with our derived distribution. We adopt a higher fidelity density distribution than that used by many older models. In our distribution, meteoroids with TJ less than 2 are assigned to a low-density population, while those with TJ greater than 2 have higher densities (see Fig. 2). This division and the distributions themselves are derived from the densities reported by Kikwaya et al. These changes have implications for the environment: for instance, the helion/antihelion sporadic sources have lower speeds than the apex and toroidal sources and originate from high-T(sub J) parent bodies. Our on-average slower and denser distributions thus imply that the helion and antihelion sources dominate the meteoroid environment even more completely than previously thought. Finally, for a given near-Earth meteoroid cratering rate, a slower meteoroid population produces a comparatively higher rate of satellite attitude disturbances.

  3. Suction/Inspiration against resistance or standardized Mueller maneuver : a new breathing technique to improve contrast density within the pulmonary artery: a pilot CT study.

    Science.gov (United States)

    Gutzeit, Andreas; Froehlich, Johannes M; Wälti, Stephan; Roos, Justus E; Meissnitzer, Matthias; Hergan, Klaus; von Weymarn, Constantin; Czell, David; Goyen, Matthias; Reischauer, Carolin

    2015-11-01

    Our aim was to prospectively investigate whether the recently introduced suction/inspiration against resistance breathing method leads to higher computed tomography (CT) contrast density in the pulmonary artery compared to standard breathing. The present study was approved by the Medical Ethics committee and all subjects gave written informed consent. Fifteen patients, each without suspicious lung emboli, were randomly assigned to four different groups with different breathing maneuvers (suction against resistance, Valsalva, inspiration, expiration) during routine CT. Contrast enhancement in the central and peripheral sections of the pulmonary artery were measured and compared with one another. Peripheral enhancement during suction yielded increased mean densities of 138.14 Hounsfield units (HU) (p = 0.001), compared to Valsalva and a mean density of 67.97 HU superior to inspiration (p = 0.075). Finally, suction in comparison to expiration resulted in a mean increase of 30.51 HU (p = 0.42). Central parts of pulmonary arteries presented significantly increased enhancement values (95.74 HU) for suction versus the Valsalva technique (p = 0.020), while all other mean densities were in favour of suction (versus inspiration: p = 0.201; versus expiration: p = 0.790) without reaching significance. Suction/Inspiration against resistance is a promising technique to improve contrast density within pulmonary vessels, especially in the peripheral parts, in comparison to other breathing maneuvers. • Suction/Inspiration against resistance is promising to improve contrast density within the pulmonary artery. • Patients potentially suffering pulmonary embolism are able to follow suction/inspiration against resistance. • Contrast density after suction is superior in comparison to other breathing maneuvers.

  4. Millimeter-Wave Line Ratios and Sub-beam Volume Density Distributions

    CERN Document Server

    Leroy, Adam K; Schruba, Andreas; Bigiel, Frank; Kruijssen, J M Diederik; Kepley, Amanda; Blanc, Guillermo A; Bolatto, Alberto D; Cormier, Diane; Gallagher, Molly; Hughes, Annie; Jimenez-Donaire, Maria J; Rosolowsky, Erik; Schinnerer, Eva

    2016-01-01

    We explore the use of mm-wave emission line ratios to trace molecular gas density when observations integrate over a wide range of volume densities within a single telescope beam. For observations targeting external galaxies, this case is unavoidable. Using a framework similar to that of Krumholz and Thompson (2007), we model emission for a set of common extragalactic lines from lognormal and power law density distributions. We consider the median density of gas producing emission and the ability to predict density variations from observed line ratios. We emphasize line ratio variations, because these do not require knowing the absolute abundance of our tracers. Patterns of line ratio variations have the prospect to illuminate the high-end shape of the density distribution, and to capture changes in the dense gas fraction and median volume density. Our results with and without a high density power law tail differ appreciably; we highlight better knowledge of the PDF shape as an important area. We also show th...

  5. Spin-density distribution in the tetragonal cluster compound Cu4OCl6daca4

    Science.gov (United States)

    Zaharko, O.; Brown, P. J.; Mys'Kiv, M.

    2010-05-01

    The spin-density distribution in Cu4OCl6daca4 (daca=diallylcyanamide) , a system containing tetrahedra of Cu2+ ions, has been determined using single-crystal polarized neutron diffraction at temperature 10 K and magnetic field 9 T. The data have been analyzed both with a spherical atom model and using a maximum entropy reconstruction. The magnetic moment on the Cu2+ ion is reduced to 0.35(1)μB and significant delocalization of spin density [0.16(3)μB] is found within the Cu4OCl6 core. The experimental spin-density distribution is compared with the predictions of ab initio density-functional calculations.

  6. Optimum distribution of heat exchanger inventory for power density optimization of an endoreversible closed Brayton cycle

    Energy Technology Data Exchange (ETDEWEB)

    Lingen Chen; Junlin Zheng; Fengrui Sun [Naval Univ. of Engineering, Faculty 306, Wuhan (China); Chih Wu [U.S. Naval Academy, Mechanical Engineering Dept., Annapolis, MD (United States)

    2001-02-07

    In this paper, the power density (defined as the ratio of the power output to the maximum specific volume in the cycle) is taken as the objective for performance optimisations of an endoreversible closed Brayton cycle coupled to constant-temperature heat reservoirs in the viewpoint of finite-time thermodynamics (FTT) or entropy generation minimisation (EGM). The optimum heat conductance distribution corresponding to the optimum power density of the hot- and cold-side heat exchangers for the fixed heat exchanger inventory is analysed using numerical examples. The influence of some design parameters on the optimum heat conductance distribution and the maximum power density and the optimum pressure ratio corresponding to the maximum power density are provided. The power plant design with optimisation leads to higher efficiency and smaller size. (Author)

  7. Field line distribution of density at L=4.8 inferred from observations by CLUSTER

    Directory of Open Access Journals (Sweden)

    S. Schäfer

    2009-02-01

    Full Text Available For two events observed by the CLUSTER spacecraft, the field line distribution of mass density ρ was inferred from Alfvén wave harmonic frequencies and compared to the electron density ne from plasma wave data and the oxygen density nO+ from the ion composition experiment. In one case, the average ion mass M≈ρ/ne was about 5 amu (28 October 2002, while in the other it was about 3 amu (10 September 2002. Both events occurred when the CLUSTER 1 (C1 spacecraft was in the plasmatrough. Nevertheless, the electron density ne was significantly lower for the first event (ne=8 cm−3 than for the second event (ne=22 cm−3, and this seems to be the main difference leading to a different value of M. For the first event (28 October 2002, we were able to measure the Alfvén wave frequencies for eight harmonics with unprecedented precision, so that the error in the inferred mass density is probably dominated by factors other than the uncertainty in frequency (e.g., magnetic field model and theoretical wave equation. This field line distribution (at L=4.8 was very flat for magnetic latitude |MLAT|≲20° but very steeply increasing with respect to |MLAT| for |MLAT|≳40°. The total variation in ρ was about four orders of magnitude, with values at large |MLAT| roughly consistent with ionospheric values. For the second event (10 September 2002, there was a small local maximum in mass density near the magnetic equator. The inferred mass density decreases to a minimum 23% lower than the equatorial value at |MLAT|=15.5°, and then steeply increases as one moves along the field line toward the ionosphere. For this event we were also able to examine the spatial dependence of the electron density using measurements of ne from all four CLUSTER spacecraft. Our analysis indicates that the density varies with L at L~5 roughly like L−4, and that ne is also locally peaked at the magnetic equator, but with a smaller peak. The value of ne reaches a density minimum

  8. Numerical Simulation of Current Density Distribution in Keyhole Double-Sided Arc Welding

    Institute of Scientific and Technical Information of China (English)

    Junsheng SUN; Chuansong WU; Min ZHANG; Houxiao WANG

    2004-01-01

    In the double-sided arc welding system (DSAW) composing of PAW+TIG arcs, the PAW arc is guided by the TIG arc so that the current mostly flows through the direction of the workpiece thickness and the penetration is greatly improved. To analyze the current density distribution in DSAW is beneficial to understanding of this process.Considering all kinds of dynamic factors acting on the weldpool, this paper discusses firstly the surface deformation of the weldpool and the keyhole formation in PAW+TIG DSAW process on the basis of the magnetohydrodynamic theory and variation principles. Hence, a model of the current density distribution is developed. Through numerical simulation, the current density distribution in PAW+TIG DSAW process is quantitatively analyzed. It shows that the minimal radius of keyhole formed in PAW+TIG DSAW process is 0.5 mm and 89.5 percent of current flows through the keyhole.

  9. Electron density distribution in Si and Ge using multipole, maximum entropy method and pair distribution function analysis

    Indian Academy of Sciences (India)

    R Saravanan; K S Syed Ali; S Israel

    2008-04-01

    The local, average and electronic structure of the semiconducting materials Si and Ge has been studied using multipole, maximum entropy method (MEM) and pair distribution function (PDF) analyses, using X-ray powder data. The covalent nature of bonding and the interaction between the atoms are clearly revealed by the two-dimensional MEM maps plotted on (1 0 0) and (1 1 0) planes and one-dimensional density along [1 0 0], [1 1 0] and [1 1 1] directions. The mid-bond electron densities between the atoms are 0.554 e/Å3 and 0.187 e/Å3 for Si and Ge respectively. In this work, the local structural information has also been obtained by analyzing the atomic pair distribution function. An attempt has been made in the present work to utilize the X-ray powder data sets to refine the structure and electron density distribution using the currently available versatile methods, MEM, multipole analysis and determination of pair distribution function for these two systems.

  10. Age differences in the variability and distribution of sleep spindle and rapid eye movement densities.

    Directory of Open Access Journals (Sweden)

    Kevin R Peters

    Full Text Available The present study had two main objectives. The first objective was to compare the sleep architecture of young and older adults, with an emphasis on sleep spindle density and REM density. The second objective was to examine two aspects of age differences that have not been considered in previous studies: age differences in the variability of sleep measures as well as the magnitude of age differences in phasic events across the distribution of values (i.e., at each decile rather than a single measure of location such as the mean or median. A total of 24 young (mean age=20.75 ± 1.78 years and 24 older (mean age=71.17 ± 6.15 years adults underwent in-home polysomnography. Whole-night spindle density was significantly higher in young adults than older adults. The two age groups did not differ significantly in whole-night REM density, although significant increases in REM density across the night were observed in both age groups. These results suggest that spindle density is more affected by age than REM density. Although age differences were observed in the degree of absolute variability (older adults had significantly larger variances than young adults for sleep efficiency and time spent awake after sleep onset, a similar pattern was also observed within the two age groups: the four sleep measures with the lowest degrees of relative variability were the same and included time spent in REM and Stage 2 sleep, total sleep time, and sleep efficiency. The distributional analysis of age differences in sleep spindle density revealed that the largest age differences were initially observed in the middle of the distributions, but as the night progressed, they were seen at the upper end of the distributions. The results reported here have potential implications for the causes and functional implications of age-related changes in sleep architecture.

  11. Approximation to Distribution of Product of Random Variables Using Orthogonal Polynomials for Lognormal Density

    CERN Document Server

    Zheng, Zhong; Hämäläinen, Jyri; Tirkkonen, Olav

    2012-01-01

    We derive a closed-form expression for the orthogonal polynomials associated with the general lognormal density. The result can be utilized to construct easily computable approximations for probability density function of a product of random variables. As an example, we have calculated the approximative distribution for the product of correlated Nakagami-m variables. Simulations indicate that accuracy of the proposed approximation is good.

  12. Density Estimation for Protein Conformation Angles Using a Bivariate von Mises Distribution and Bayesian Nonparametrics.

    Science.gov (United States)

    Lennox, Kristin P; Dahl, David B; Vannucci, Marina; Tsai, Jerry W

    2009-06-01

    Interest in predicting protein backbone conformational angles has prompted the development of modeling and inference procedures for bivariate angular distributions. We present a Bayesian approach to density estimation for bivariate angular data that uses a Dirichlet process mixture model and a bivariate von Mises distribution. We derive the necessary full conditional distributions to fit the model, as well as the details for sampling from the posterior predictive distribution. We show how our density estimation method makes it possible to improve current approaches for protein structure prediction by comparing the performance of the so-called "whole" and "half" position distributions. Current methods in the field are based on whole position distributions, as density estimation for the half positions requires techniques, such as ours, that can provide good estimates for small datasets. With our method we are able to demonstrate that half position data provides a better approximation for the distribution of conformational angles at a given sequence position, therefore providing increased efficiency and accuracy in structure prediction.

  13. Biotic and abiotic factors predicting the global distribution and population density of an invasive large mammal

    Science.gov (United States)

    Lewis, Jesse S.; Farnsworth, Matthew L.; Burdett, Chris L.; Theobald, David M.; Gray, Miranda; Miller, Ryan S.

    2017-01-01

    Biotic and abiotic factors are increasingly acknowledged to synergistically shape broad-scale species distributions. However, the relative importance of biotic and abiotic factors in predicting species distributions is unclear. In particular, biotic factors, such as predation and vegetation, including those resulting from anthropogenic land-use change, are underrepresented in species distribution modeling, but could improve model predictions. Using generalized linear models and model selection techniques, we used 129 estimates of population density of wild pigs (Sus scrofa) from 5 continents to evaluate the relative importance, magnitude, and direction of biotic and abiotic factors in predicting population density of an invasive large mammal with a global distribution. Incorporating diverse biotic factors, including agriculture, vegetation cover, and large carnivore richness, into species distribution modeling substantially improved model fit and predictions. Abiotic factors, including precipitation and potential evapotranspiration, were also important predictors. The predictive map of population density revealed wide-ranging potential for an invasive large mammal to expand its distribution globally. This information can be used to proactively create conservation/management plans to control future invasions. Our study demonstrates that the ongoing paradigm shift, which recognizes that both biotic and abiotic factors shape species distributions across broad scales, can be advanced by incorporating diverse biotic factors. PMID:28276519

  14. Distribution and density of Cubitermes Wasmann (Isoptera: Termitidae mounds in the northern Kruger National Park

    Directory of Open Access Journals (Sweden)

    V.W. Meyer

    2000-07-01

    Full Text Available This paper provides fundamental information on distribution and density of the genus Cubitermes, Wasm. quantified for future monitoring. After distribution trends have been established, changes in Cubitermes density over time can be brought into contention with other factors in the Kruger National Park, such as the impact of fire frequency, water distribution, and elephant density on these insects. At least ten 2 ha belt-transects were undertaken in each of the 20 northern landscape zones of the KNP. Termite mounds were recorded and their activity within was determined. Cubitermes accounts for 29.8% of all active termite mounds in the northern KNP, with an average density of 0.33 mounds/ha. Cubitermes favours the Nwambiya Sandveld (zone 32. These termites occur in high density in the Klipkoppies 1 land type (Gorge, but in low densities in the Phalaborwa 10-12, Bulweni 1-3, Letaba 1-7 and Pafuri 3-6 land types. Cubitermes mounds tend to occur in high numbers on the Nzhelele formation (Mn (sandstones; quartzite; basalt. Mounds of this genus in the Far North are highly concentrated on the Gaudam and Moriah soil series of the Hutton form, suggesting that these termites prefer very sandy soils with medium to coarse particles.

  15. Distribution of Magnetic Flux Density in Soft-Contact EMCC Rectangular Mold

    Institute of Scientific and Technical Information of China (English)

    ZHANG Lin-tao; WANG En-gang; DENG An-yuan; HE Ji-cheng

    2006-01-01

    The distribution of the magnetic flux density in a soft-contact electromagnetic continuous casting (EMCC) rectangular mold was investigated. The experimental results show that with an increase in electric power, the magnetic flux density increases. The position where the maximum magnetic flux density appears will shift up when the coil moves to the top of the mold. At the same time, the maximum magnetic flux density will increase and the effective acting range of electromagnetic pressure will widen. As a result, in practice, the coil should be placed near the top part of the mold. The meniscus should be controlled near the top part of the coil, as this not only remarkably improves the billet surface quality but also saves energy. With the same electric power input, the higher the frequency, the lower the magnetic flux density.

  16. Kink and Sausage Modes in Nonuniform Magnetic Slabs with Continuous Transverse Density Distributions

    Science.gov (United States)

    Yu, Hui; Li, Bo; Chen, Shao-Xia; Guo, Ming-Zhe

    2015-11-01

    We examine the influence of a continuous density structuring transverse to coronal slabs on the dispersive properties of fundamental standing kink and sausage modes supported therein. We derive generic dispersion relations (DRs) governing linear fast waves in pressureless straight slabs with general transverse density distributions, and focus on cases where the density inhomogeneity takes place in a layer of arbitrary width and in arbitrary form. The physical relevance of the solutions to the DRs is demonstrated by the corresponding time-dependent computations. For all profiles examined, the lowest order kink modes are trapped regardless of longitudinal wavenumber k. A continuous density distribution introduces a difference to their periods of ≲13% when k is the observed range relative to the case where the density profile takes a step function form. Sausage modes and other branches of kink modes are leaky at small k, and their periods and damping times are heavily influenced by how the transverse density profile is prescribed, in particular the length scale. These modes have sufficiently high quality to be observable only for physical parameters representative of flare loops. We conclude that while the simpler DR pertinent to a step function profile can be used for the lowest order kink modes, the detailed information on the transverse density structuring needs to be incorporated into studies of sausage modes and higher order kink modes.

  17. KINK AND SAUSAGE MODES IN NONUNIFORM MAGNETIC SLABS WITH CONTINUOUS TRANSVERSE DENSITY DISTRIBUTIONS

    Energy Technology Data Exchange (ETDEWEB)

    Yu, Hui; Li, Bo; Chen, Shao-Xia; Guo, Ming-Zhe, E-mail: bbl@sdu.edu.cn [Shandong Provincial Key Laboratory of Optical Astronomy and Solar-Terrestrial Environment, Institute of Space Sciences, Shandong University, Weihai, 264209 (China)

    2015-11-20

    We examine the influence of a continuous density structuring transverse to coronal slabs on the dispersive properties of fundamental standing kink and sausage modes supported therein. We derive generic dispersion relations (DRs) governing linear fast waves in pressureless straight slabs with general transverse density distributions, and focus on cases where the density inhomogeneity takes place in a layer of arbitrary width and in arbitrary form. The physical relevance of the solutions to the DRs is demonstrated by the corresponding time-dependent computations. For all profiles examined, the lowest order kink modes are trapped regardless of longitudinal wavenumber k. A continuous density distribution introduces a difference to their periods of ≲13% when k is the observed range relative to the case where the density profile takes a step function form. Sausage modes and other branches of kink modes are leaky at small k, and their periods and damping times are heavily influenced by how the transverse density profile is prescribed, in particular the length scale. These modes have sufficiently high quality to be observable only for physical parameters representative of flare loops. We conclude that while the simpler DR pertinent to a step function profile can be used for the lowest order kink modes, the detailed information on the transverse density structuring needs to be incorporated into studies of sausage modes and higher order kink modes.

  18. Fractal-Based Exponential Distribution of Urban Density and Self-Affine Fractal Forms of Cities

    CERN Document Server

    Chen, Yanguang

    2016-01-01

    Urban population density always follows the exponential distribution and can be described with Clark's model. Because of this, the spatial distribution of urban population used to be regarded as non-fractal pattern. However, Clark's model differs from the exponential function in mathematics because that urban population is distributed on the fractal support of landform and land-use form. By using mathematical transform and empirical evidence, we argue that there are self-affine scaling relations and local power laws behind the exponential distribution of urban density. The scale parameter of Clark's model indicating the characteristic radius of cities is not a real constant, but depends on the urban field we defined. So the exponential model suggests local fractal structure with two kinds of fractal parameters. The parameters can be used to characterize urban space filling, spatial correlation, self-affine properties, and self-organized evolution. The case study of the city of Hangzhou, China, is employed to ...

  19. Fractal dimension of the topological charge density distribution in SU(2) lattice gluodynamics

    Energy Technology Data Exchange (ETDEWEB)

    Buividovich, P.V. [Joint Institute for Nuclear Research, Dubna (Russian Federation); Institute for Theoretical and Experimental Physics ITEP, Moscow (Russian Federation); Kalaydzhyan, T. [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany); Institute for Theoretical and Experimental Physics ITEP, Moscow (Russian Federation); Polikarpov, M.I. [Institute for Theoretical and Experimental Physics ITEP, Moscow (Russian Federation)

    2011-11-15

    We study the effect of cooling on the spatial distribution of the topological charge density in quenched SU(2) lattice gauge theory with overlap fermions. We show that as the gauge field configurations are cooled, the Hausdorff dimension of regions where the topological charge is localized gradually changes from d=2/3 towards the total space dimension. Hence the cooling procedure destroys some of the essential properties of the topological charge distribution. (orig.)

  20. Modeling the Images of Relativistic Jets Lensed by Galaxies with Different Mass Surface Density Distributions

    OpenAIRE

    Larchenkova, T. I.; Lutovinov, A. A.; Lyskova, N. S.

    2011-01-01

    The images of relativistic jets from extragalactic sources produced by gravitational lensing by galaxies with different mass surface density distributions are modeled. In particular, the following models of the gravitational lens mass distribution are considered: a singular isothermal ellipsoid, an isothermal ellipsoid with a core, two- and three-component models with a galactic disk, halo, and bulge. The modeled images are compared both between themselves and with available observations. Dif...

  1. A mathematical model of the current density distribution in electrochemical cells - AUTHORS’ REVIEW

    Directory of Open Access Journals (Sweden)

    PREDRAG M. ŽIVKOVIĆ

    2011-06-01

    Full Text Available An approach based on the equations of electrochemical kinetics for the estimation of the current density distribution in electrochemical cells is presented. This approach was employed for a theoretical explanation of the phenomena of the edge and corner effects. The effects of the geometry of the system, the kinetic parameters of the cathode reactions and the resistivity of the solution are also discussed. A procedure for a complete analysis of the current distribution in electrochemical cells is presented.

  2. Unilateral ventricular reflux and asymmetric ventricular distribution of intrathecally introduced contrast medium or tracer

    Energy Technology Data Exchange (ETDEWEB)

    Deisenhammer, E.; Hammer, B.

    Fourteen cases of totally or predominantly unilateral ventricular reflux and stasis of intrathecally injected radioisotope or contrast medium were demonstrated by scintigraphy or computed tomographic cisternography. All showed asymmetric enlargement of the lateral ventricles and nine had ipsilateral brain lesions. Four case reports are presented. The pathophysiologic mechanism of communicating hydrocephalus and possible causes of unilateral ventricular reflux are discussed, as well as indications for ventricular shunt installation.

  3. Statistical Evidence for the Preference of Frailty Distributions with Regularly-Varying-at-Zero Densities

    DEFF Research Database (Denmark)

    Missov, Trifon I.; Schöley, Jonas

    to this criterion admissible distributions are, for example, the gamma, the beta, the truncated normal, the log-logistic and the Weibull, while distributions like the log-normal and the inverse Gaussian do not satisfy this condition. In this article we show that models with admissible frailty distributions......Missov and Finkelstein (2011) prove an Abelian and its corresponding Tauberian theorem regarding distributions for modeling unobserved heterogeneity in fixed-frailty mixture models. The main property of such distributions is the regular variation at zero of their densities. According...... and a Gompertz baseline provide a better fit to adult human mortality data than the corresponding models with non-admissible frailty distributions. We implement estimation procedures for mixture models with a Gompertz baseline and frailty that follows a gamma, truncated normal, log-normal, or inverse Gaussian...

  4. Distributed Density Estimation Based on a Mixture of Factor Analyzers in a Sensor Network

    Directory of Open Access Journals (Sweden)

    Xin Wei

    2015-08-01

    Full Text Available Distributed density estimation in sensor networks has received much attention due to its broad applicability. When encountering high-dimensional observations, a mixture of factor analyzers (MFA is taken to replace mixture of Gaussians for describing the distributions of observations. In this paper, we study distributed density estimation based on a mixture of factor analyzers. Existing estimation algorithms of the MFA are for the centralized case, which are not suitable for distributed processing in sensor networks. We present distributed density estimation algorithms for the MFA and its extension, the mixture of Student’s t-factor analyzers (MtFA. We first define an objective function as the linear combination of local log-likelihoods. Then, we give the derivation process of the distributed estimation algorithms for the MFA and MtFA in details, respectively. In these algorithms, the local sufficient statistics (LSS are calculated at first and diffused. Then, each node performs a linear combination of the received LSS from nodes in its neighborhood to obtain the combined sufficient statistics (CSS. Parameters of the MFA and the MtFA can be obtained by using the CSS. Finally, we evaluate the performance of these algorithms by numerical simulations and application example. Experimental results validate the promising performance of the proposed algorithms.

  5. Measurements and predictions of the air distribution systems in high compute density (Internet) data centers

    Energy Technology Data Exchange (ETDEWEB)

    Cho, Jinkyun [HIMEC (Hanil Mechanical Electrical Consultants) Ltd., Seoul 150-103 (Korea); Department of Architectural Engineering, Yonsei University, Seoul 120-749 (Korea); Lim, Taesub; Kim, Byungseon Sean [Department of Architectural Engineering, Yonsei University, Seoul 120-749 (Korea)

    2009-10-15

    When equipment power density increases, a critical goal of a data center cooling system is to separate the equipment exhaust air from the equipment intake air in order to prevent the IT server from overheating. Cooling systems for data centers are primarily differentiated according to the way they distribute air. The six combinations of flooded and locally ducted air distribution make up the vast majority of all installations, except fully ducted air distribution methods. Once the air distribution system (ADS) is selected, there are other elements that must be integrated into the system design. In this research, the design parameters and IT environmental aspects of the cooling system were studied with a high heat density data center. CFD simulation analysis was carried out in order to compare the heat removal efficiencies of various air distribution systems. The IT environment of an actual operating data center is measured to validate a model for predicting the effect of different air distribution systems. A method for planning and design of the appropriate air distribution system is described. IT professionals versed in precision air distribution mechanisms, components, and configurations can work more effectively with mechanical engineers to ensure the specification and design of optimized cooling solutions. (author)

  6. Suction/inspiration against resistance or standardized Mueller maneuver: a new breathing technique to improve contrast density within the pulmonary artery: a pilot CT study

    Energy Technology Data Exchange (ETDEWEB)

    Gutzeit, Andreas [Paracelsus Medical University Salzburg, Department of Radiology, Salzburg (Austria); Hirslanden Hospital St. Anna, Institute of Radiology and Nuclear Medicine, Clinical Research Unit, Lucerne (Switzerland); Kantonsspital Winterthur, Department of Radiology, Winterthur (Switzerland); Froehlich, Johannes M.; Weymarn, Constantin von; Goyen, Matthias [Hirslanden Hospital St. Anna, Institute of Radiology and Nuclear Medicine, Clinical Research Unit, Lucerne (Switzerland); Waelti, Stephan [Cantonal Hospital St. Gallen, Department of Radiology and Nuclear Medicine, St. Gallen (Switzerland); Roos, Justus E. [Duke University Medical Center, Department of Radiology, Durham, NC (United States); Meissnitzer, Matthias; Hergan, Klaus [Paracelsus Medical University Salzburg, Department of Radiology, Salzburg (Austria); Czell, David [Cantonal Hospital Winterthur, Department of Neurology, Winterthur (Switzerland); Reischauer, Carolin [Paracelsus Medical University Salzburg, Department of Radiology, Salzburg (Austria); Hirslanden Hospital St. Anna, Institute of Radiology and Nuclear Medicine, Clinical Research Unit, Lucerne (Switzerland)

    2015-11-15

    Our aim was to prospectively investigate whether the recently introduced suction/inspiration against resistance breathing method leads to higher computed tomography (CT) contrast density in the pulmonary artery compared to standard breathing. The present study was approved by the Medical Ethics committee and all subjects gave written informed consent. Fifteen patients, each without suspicious lung emboli, were randomly assigned to four different groups with different breathing maneuvers (suction against resistance, Valsalva, inspiration, expiration) during routine CT. Contrast enhancement in the central and peripheral sections of the pulmonary artery were measured and compared with one another. Peripheral enhancement during suction yielded increased mean densities of 138.14 Hounsfield units (HU) (p = 0.001), compared to Valsalva and a mean density of 67.97 HU superior to inspiration (p = 0.075). Finally, suction in comparison to expiration resulted in a mean increase of 30.51 HU (p = 0.42). Central parts of pulmonary arteries presented significantly increased enhancement values (95.74 HU) for suction versus the Valsalva technique (p = 0.020), while all other mean densities were in favour of suction (versus inspiration: p = 0.201; versus expiration: p = 0.790) without reaching significance. Suction/Inspiration against resistance is a promising technique to improve contrast density within pulmonary vessels, especially in the peripheral parts, in comparison to other breathing maneuvers. (orig.)

  7. Using regional bird density distribution models to evaluate protected area networks and inform conservation planning

    Science.gov (United States)

    John D. Alexander; Jaime L. Stephens; Sam Veloz; Leo Salas; Josée S. Rousseau; C. John Ralph; Daniel A. Sarr

    2017-01-01

    As data about populations of indicator species become available, proactive strategies that improve representation of biological diversity within protected area networks should consider finer-scaled evaluations, especially in regions identified as important through course-scale analyses. We use density distribution models derived from a robust regional bird...

  8. The electron density distribution in the hydrogen bond. A quantum chemical and crystallographic study

    NARCIS (Netherlands)

    Feil, Dirk

    1990-01-01

    With the help of Hartree—Fock—Slater calculations in which very large basis sets are employed, the polarisation of the water molecule by an electric field is explored. The various features in the electron density distribution are encountered again in the long hydrogen bond in the water dimer, showin

  9. The COSMOS density field: a reconstruction using both weak lensing and galaxy distributions

    NARCIS (Netherlands)

    Amara, A.; Lilly, S.; Kovač, K.; Rhodes, J.; Massey, R.; Zamorani, G.; Carollo, C. M.; Contini, T.; Kneib, J.-P.; Le Fevre, O.; Mainieri, V.; Renzini, A.; Scodeggio, M.; Bardelli, S.; Bolzonella, M.; Bongiorno, A.; Caputi, K.; Cucciati, O.; de la Torre, S.; de Ravel, L.; Franzetti, P.; Garilli, B.; Iovino, A.; Kampczyk, P.; Knobel, C.; Lamareille, F.; Le Borgne, J.-F.; Le Brun, V.; Maier, C.; Mignoli, M.; Pello, R.; Peng, Y.; Montero, E. Perez; Presotto, V.; Silverman, J.; Tanaka, M.; Tasca, L.; Tresse, L.; Vergani, D.; Zucca, E.; Barnes, L.; Bordoloi, R.; Cappi, A.; Cimatti, A.; Coppa, G.; Koekoemoer, A.; López-Sanjuan, C.; McCracken, H. J.; Moresco, M.; Nair, P.; Pozzetti, L.; Welikala, N.

    2012-01-01

    The COSMOS field has been the subject of a wide range of observations, with a number of studies focusing on reconstructing the 3D dark matter density field. Typically, these studies have focused on one given method or tracer. In this paper, we reconstruct the distribution of mass in the COSMOS field

  10. The COSMOS density field : a reconstruction using both weak lensing and galaxy distributions

    NARCIS (Netherlands)

    Amara, A.; Lilly, S.; Kovač, K.; Rhodes, J.; Massey, R.; Zamorani, G.; Carollo, C. M.; Contini, T.; Kneib, J. -P; Le Fevre, O.; Mainieri, V.; Renzini, A.; Scodeggio, M.; Bardelli, S.; Bolzonella, M.; Bongiorno, A.; Caputi, K.; Cucciati, O.; de la Torre, S.; de Ravel, L.; Franzetti, P.; Garilli, B.; Iovino, A.; Kampczyk, P.; Knobel, C.; Lamareille, F.; Le Borgne, J. -F; Le Brun, V.; Maier, C.; Mignoli, M.; Pello, R.; Peng, Y.; Montero, E. Perez; Presotto, V.; Silverman, J.; Tanaka, M.; Tasca, L.; Tresse, L.; Vergani, D.; Zucca, E.; Barnes, L.; Bordoloi, R.; Cappi, A.; Cimatti, A.; Coppa, G.; Koekoemoer, A.; López-Sanjuan, C.; McCracken, H. J.; Moresco, M.; Nair, P.; Pozzetti, L.; Welikala, N.

    2012-01-01

    The COSMOS field has been the subject of a wide range of observations, with a number of studies focusing on reconstructing the 3D dark matter density field. Typically, these studies have focused on one given method or tracer. In this paper, we reconstruct the distribution of mass in the COSMOS field

  11. Response of a galactic disc to vertical perturbations : Strong dependence on density distribution

    NARCIS (Netherlands)

    Pranav, Pratyush; Jog, Chanda J.

    We study the self-consistent, linear response of a galactic disc to non-axisymmetric perturbations in the vertical direction as due to a tidal encounter, and show that the density distribution near the disc mid-plane has a strong impact on the radius beyond which distortions like warps develop. The

  12. Control of ion density distribution by magnetic traps for plasma electrons

    Energy Technology Data Exchange (ETDEWEB)

    Baranov, Oleg; Romanov, Maxim [Plasma Laboratory, National Aerospace University ' KhAI,' Kharkov 61070 (Ukraine); Fang Jinghua [Plasma Nanoscience Centre Australia (PNCA), CSIRO Materials Science and Engineering, P.O. Box 218, Lindfield, New South Wales 2070 (Australia); School of Physics, University of Melbourne, Parkville, VIC 3010 (Australia); Cvelbar, Uros [Jozef Stefan Institute, Jamova cesta 39, SI-1000 Ljubljana (Slovenia); Ostrikov, Kostya [Plasma Nanoscience Centre Australia (PNCA), CSIRO Materials Science and Engineering, P.O. Box 218, Lindfield, New South Wales 2070 (Australia); University of Sydney, Sydney, NSW 2006 (Australia)

    2012-10-01

    The effect of a magnetic field of two magnetic coils on the ion current density distribution in the setup for low-temperature plasma deposition is investigated. The substrate of 400 mm diameter is placed at a distance of 325 mm from the plasma duct exit, with the two magnetic coils mounted symmetrically under the substrate at a distance of 140 mm relative to the substrate centre. A planar probe is used to measure the ion current density distribution along the plasma flux cross-sections at distances of 150, 230, and 325 mm from the plasma duct exit. It is shown that the magnetic field strongly affects the ion current density distribution. Transparent plastic films are used to investigate qualitatively the ion density distribution profiles and the effect of the magnetic field. A theoretical model is developed to describe the interaction of the ion fluxes with the negative space charge regions associated with the magnetic trapping of the plasma electrons. Theoretical results are compared with the experimental measurements, and a reasonable agreement is demonstrated.

  13. Using aerial surveys to estimate density and distribution of harbour porpoises in Dutch waters

    NARCIS (Netherlands)

    Scheidat, M.; Verdaat, J.P.; Aarts, G.M.

    2012-01-01

    To investigate harbour porpoise density and distribution in Dutch waters, dedicated line transect distance sampling aerial surveys were conducted from May 2008 to March 2010. In total 10,557 km were covered on survey effort during 16 survey days in February to May, August, November and December. Usi

  14. Weight Distributions of Regular Low-Density Parity-Check Codes over Finite Fields

    CERN Document Server

    Yang, Shengtian; Chen, Yan; Zhang, Zhaoyang; Qiu, Peiliang

    2010-01-01

    The average weight distribution of a regular low-density parity-check (LDPC) code ensemble over a finite field is thoroughly analyzed. In particular, a precise asymptotic approximation of the average weight distribution is derived for the small-weight case, and a series of fundamental qualitative properties of the asymptotic growth rate of the average weight distribution are proved. Based on this analysis, a general result, including all previous results as special cases, is established for the minimum distance of individual codes in a regular LDPC code ensemble.

  15. Chemical bonding and charge density distribution analysis of undoped and lanthanum doped barium titanate ceramics

    Indian Academy of Sciences (India)

    J MANGAIYARKKARASI; R SARAVANAN; MUKHLIS M ISMAIL

    2016-12-01

    A-site deficient, Lanthanum substituted Ba1−xLa2x/3TiO3 (x=0.000, 0.005, 0.015, 0.020 and 0.025) ceramics have been synthesized by chemical route. The effects of lanthanum dopant on the BaTiO3 lattice and the electron density distributions in the unit cell of the samples were investigated. Structural studies suggested the reduction in cell parameters and shrinkage in cell volume with the increase in lanthanum content. Chemical bonding and electron density distributions were examined through high resolution maximum entropy method (MEM). The mid bond electron density values revealed the enhancement of covalent nature between titanium and oxygen ions and predominant ionic nature between barium and oxygen ions. Average grain sizes were estimated for the undoped and doped samples. SEM investigations showed the existence of smaller grains with large voids in between them.

  16. Influence of Mobile Users' Density Distribution on the CDMA Base Station Power

    Science.gov (United States)

    Lebl, Aleksandar; Mitić, Dragan; Popović, Miroslav; Markov, Žarko; Mileusnić, Mladen; Matić, Vladimir

    2016-12-01

    In this paper we analyze the influence of users' density distribution in one cell of CDMA mobile network (ie adjusted power control on the forward link) on base station emission power. This influence is analyzed for different circles radii around base station within which same emission power is generated for all mobile users, and for different values of propagation loss coefficient. It is proved that emission power in this cell must be increased comparing to the similar cell, which uses complete power control. The power increase is greater when greater number of users are situated near base station, and for greater values of propagation loss coefficient. The results are presented, illustrated by numerical examples and verified by simulation for three users' density distributions: uniform, decreasing and increasing density from the base station to the cell rim. The simulation process, which is based on random traffic process, is presented briefly.

  17. Determination of nanoparticle size distribution together with density or molecular weight by 2D analytical ultracentrifugation

    KAUST Repository

    Carney, Randy P.

    2011-06-07

    Nanoparticles are finding many research and industrial applications, yet their characterization remains a challenge. Their cores are often polydisperse and coated by a stabilizing shell that varies in size and composition. No single technique can characterize both the size distribution and the nature of the shell. Advances in analytical ultracentrifugation allow for the extraction of the sedimentation (s) and diffusion coefficients (D). Here we report an approach to transform the s and D distributions of nanoparticles in solution into precise molecular weight (M), density (?P) and particle diameter (dp) distributions. M for mixtures of discrete nanocrystals is found within 4% of the known quantities. The accuracy and the density information we achieve on nanoparticles are unparalleled. A single experimental run is sufficient for full nanoparticle characterization, without the need for standards or other auxiliary measurements. We believe that our method is of general applicability and we discuss its limitations. 2011 Macmillan Publishers Limited. All rights reserved.

  18. Spin and charge distribution in iron porphyrin models: a coupled cluster and density-functional study.

    Science.gov (United States)

    Johansson, Mikael P; Sundholm, Dage

    2004-02-15

    We recently performed detailed analyses of the electronic structure of low-spin iron porphyrins using density-functional theory (DFT). Both the spin-density distributions of the oxidized, ferric forms, as well as the changes in total charge density upon reduction to the ferrous forms have been explored. Here, we compare the DFT results with wave-function theory, more specifically, with the approximate singles and doubles coupled-cluster method (CC2). Different spin states are considered by studying representative models of low spin, intermediate spin, and high spin species. The CC2 calculations corroborate the DFT results; the spin density exhibits the same amount of molecular spin polarization, and the charge delocalization is of comparable magnitude. Slight differences in the descriptions are noted and discussed.

  19. Contrasting Size Distributions of Chondrules and Inclusions in Allende CV3

    Science.gov (United States)

    Fisher, Kent R.; Tait, Alastair W.; Simon, Jusin I.; Cuzzi, Jeff N.

    2014-01-01

    There are several leading theories on the processes that led to the formation of chondrites, e.g., sorting by mass, by X-winds, turbulent concentration, and by photophoresis. The juxtaposition of refractory inclusions (CAIs) and less refractory chondrules is central to these theories and there is much to be learned from their relative size distributions. There have been a number of studies into size distributions of particles in chondrites but only on relatively small scales primarily for chondrules, and rarely for both Calcium Aluminum-rich Inclusions (CAIs) and chondrules in the same sample. We have implemented macro-scale (25 cm diameter sample) and high-resolution microscale sampling of the Allende CV3 chondrite to create a complete data set of size frequencies for CAIs and chondrules.

  20. Probabilistic electron density distribution in CdTe at RT and 200K

    Energy Technology Data Exchange (ETDEWEB)

    Saravanan, R. [Department of Physics, The Madura College, Madurai - 625 011, Tamil Nadu (India); Israel, S. [Department of Physics, American College, Madurai - 625 002, Tamil Nadu (India); Ono, Y.; Kajitani, T. [Department of Applied Physics, Graduate School of Engineering, Tohoku University, Sendai 980-8579 (Japan); Ohno, K. [Institute for Materials Research, Tohoku University, Sendai, 980-8577 (Japan); Isshiki, M. [Institute for Advanced Materials Processing, Tohoku University, Sendai, 980-8577 (Japan); Rajaram, R.K. [School of Physics, Madurai Kamaraj University, Madurai - 625 021, Tamil Nadu (India)

    2006-03-15

    The bonding between the atoms in the II-VI compound semiconductors has always been a subject of rigorous research because of their tremendous applications in a variety of fields. The bonding and ionic character in CdTe at 300 and 200 K have been determined quantitatively as well as qualitatively using single crystal X-ray data sets and MEM (Maximum Entropy Method) as the tool for the reconstruction of the electron densities distributed within the unit cell. The ab-initio band calculation of the total and valence charge densities have been carried out theoretically by means of the local density approximation (LDA) method in support of the experimentally derived MEM maps. The difference density maps show fewer errors between the theoretical and experimental charge density and thus gives credence to the results accordingly. Along the bonding direction [111], the mid-bond electron densities are found to be 0.233 e/Aa{sup 3} and 0.284 e/Aa{sup 3} at 300 K and 200 K at distances 1.4026 Aa and 1.4036 Aa respectively. The densities along [100] and [110] show an increase in the charge concentration at the bond at lower temperatures. copyright 2006 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim. (orig.)

  1. Modeling environmental effects on charge density distributions in polar organometallics: validation of embedded cluster models for the methyl lithium crystal.

    Science.gov (United States)

    Götz, Kathrin; Meier, Florian; Gatti, Carlo; Burow, Asbjörn M; Sierka, Marek; Sauer, Joachim; Kaupp, Martin

    2010-11-15

    The charge density and its Laplacian at the Li-C and C-H bond critical points and other features of the electron density distribution of the methyl lithium crystal have been compared by density functional methods for (i) the isolated (LiCH(3))(4) tetramer or larger clusters, (ii) for quantum mechanically treated clusters in polarizable continuum model (PCM) surroundings, (iii) for clusters augmented by the periodic electrostatic embedded cluster model (PEECM), and for (iv) the periodic crystal. Comparisons with identical functional and basis sets indicate that both PCM and PEECM embedding of only a tetramer did not fully account for the environmental effect. In contrast, embedding of a full unit cell gave results that were essentially converged to the periodic crystal data. Effects of basis set and exchange correlation functional on the QTAIM bond descriptors are of a comparable order of magnitude as the crystal environmental effects. In this context, embedded cluster computations provide distinct advantages over explicit solid-state calculations with respect to their freedom of the choice of computational and theoretical level. This is demonstrated by embedded MP2 calculations.

  2. Implementation of a phase detection algorithm for dynamic cardiac computed tomography analysis based on time dependent contrast agent distribution.

    Directory of Open Access Journals (Sweden)

    Carsten Kendziorra

    Full Text Available This paper presents a phase detection algorithm for four-dimensional (4D cardiac computed tomography (CT analysis. The algorithm detects a phase, i.e. a specific three-dimensional (3D image out of several time-distributed 3D images, with high contrast in the left ventricle and low contrast in the right ventricle. The purpose is to use the automatically detected phase in an existing algorithm that automatically aligns the images along the heart axis. Decision making is based on the contrast agent distribution over time. It was implemented in KardioPerfusion--a software framework currently being developed for 4D CT myocardial perfusion analysis. Agreement of the phase detection algorithm with two reference readers was 97% (95% CI: 82-100%. Mean duration for detection was 0.020 s (95% CI: 0.018-0.022 s, which was 800 times less than the readers needed (16±7 s, p<03001. Thus, this algorithm is an accurate and fast tool that can improve work flow of clinical examinations.

  3. Dynamics of the spatial electron density distribution of EUV-induced plasmas

    Science.gov (United States)

    van der Horst, R. M.; Beckers, J.; Osorio, E. A.; Banine, V. Y.

    2015-11-01

    We studied the temporal evolution of the electron density distribution in a low pressure pulsed plasma induced by high energy extreme ultraviolet (EUV) photons using microwave cavity resonance spectroscopy (MCRS). In principle, MCRS only provides space averaged information about the electron density. However, we demonstrate here the possibility to obtain spatial information by combining multiple resonant modes. It is shown that EUV-induced plasmas, albeit being a rather exotic plasma, can be explained by known plasma physical laws and processes. Two stages of plasma behaviour are observed: first the electron density distribution contracts, after which it expands. It is shown that the contraction is due to cooling of the electrons. The moment when the density distribution starts to expand is related to the inertia of the ions. After tens of microseconds, the electrons reached the wall of the cavity. The speed of this expansion is dependent on the gas pressure and can be divided into two regimes. It is shown that the acoustic dominated regime the expansion speed is independent of the gas pressure and that in the diffusion dominated regime the expansion depends reciprocal on the gas pressure.

  4. Linearized image reconstruction method for ultrasound modulated electrical impedance tomography based on power density distribution

    Science.gov (United States)

    Song, Xizi; Xu, Yanbin; Dong, Feng

    2017-04-01

    Electrical resistance tomography (ERT) is a promising measurement technique with important industrial and clinical applications. However, with limited effective measurements, it suffers from poor spatial resolution due to the ill-posedness of the inverse problem. Recently, there has been an increasing research interest in hybrid imaging techniques, utilizing couplings of physical modalities, because these techniques obtain much more effective measurement information and promise high resolution. Ultrasound modulated electrical impedance tomography (UMEIT) is one of the newly developed hybrid imaging techniques, which combines electric and acoustic modalities. A linearized image reconstruction method based on power density is proposed for UMEIT. The interior data, power density distribution, is adopted to reconstruct the conductivity distribution with the proposed image reconstruction method. At the same time, relating the power density change to the change in conductivity, the Jacobian matrix is employed to make the nonlinear problem into a linear one. The analytic formulation of this Jacobian matrix is derived and its effectiveness is also verified. In addition, different excitation patterns are tested and analyzed, and opposite excitation provides the best performance with the proposed method. Also, multiple power density distributions are combined to implement image reconstruction. Finally, image reconstruction is implemented with the linear back-projection (LBP) algorithm. Compared with ERT, with the proposed image reconstruction method, UMEIT can produce reconstructed images with higher quality and better quantitative evaluation results.

  5. Measurements of solar flux density distribution on a plane receiver due to a flat heliostat

    Energy Technology Data Exchange (ETDEWEB)

    Elsayed, M.M.; Fathalah, K.A.; Al-Rabghi, O.M. [King Abdulaziz Univ., Jeddah (Saudi Arabia)

    1995-06-01

    An experimental facility is designed and manufactured to measure the solar flux density distribution on a central flat receiver due to a single flat heliostat. The tracking mechanism of the heliostat is controlled by two stepping motors, one for tilt angle control and the other for azimuth angle control. A x-y traversing mechanism is also designed and mounted on a vertical central receiver plane, where the solar flux density is to be measured. A miniature solar sensor is mounted on the platform of the traversing mechanism, where it is used to measure the solar flux density distribution on the receiver surface. The sensor is connected to a data acquisition card in a host computer. The two stepping motors of the heliostat tracking mechanism and the two stepping motors of the traversing mechanism are all connected to a controller card in the same host computer. A software `TOWER` is prepared to let the heliostat track the sun, move the platform of the traversing mechanism to the points of a preselected grid, and to measure the solar flux density distribution on the receiver plane. Measurements are carried out using rectangular flat mirrors of different dimensions at several distances from the central receiver. Two types of images were identified on the receiver plane - namely, apparent (or visible) and mirror-reflected radiation images. Comparison between measurements and a mathematical model validates the mathematical model. 13 refs., 12 figs., 1 tab.

  6. Density distribution of a dust cloud in three-dimensional complex plasmas

    CERN Document Server

    Naumkin, V N; Molotkov, V I; Lipaev, A M; Fortov, V E; Thomas, H M; Huber, P; Morfill, G E

    2016-01-01

    We propose a novel method of determination of the dust particle spatial distribution in dust clouds that form in three-dimensional (3D) complex plasmas under microgravity conditions. The method utilizes the data obtained during the 3D scanning of a cloud and provides a reasonably good accuracy. Based on this method, we investigate the particle density in a dust cloud realized in gas discharge plasma in the PK-3 Plus setup onboard the International Space Station. We find that the treated dust clouds are both anisotropic and inhomogeneous. One can isolate two regimes, in which a stationary dust cloud can be observed. At low pressures, the particle density decreases monotonically with the increase of the distance from the discharge center; at higher pressures, the density distribution has a shallow minimum. Regardless of the regime, we detect a cusp of the distribution at the void boundary and a slowly varying density at larger distances (in the foot region). A theoretical interpretation of obtained results is d...

  7. Experimental Infection of Taenia saginata eggs in Bali Cattle: Distribution and Density of Cysticercus bovis

    Directory of Open Access Journals (Sweden)

    Nyoman Sadra Dharmawan

    2009-12-01

    Full Text Available The objective of this study was to observe the development, distribution, and infection density ofTaenia saginata metacestodes in Bali cattle. Three Bali cattle were experimentally infected with T. saginataeggs which were collected from taeniasis patients. The experimental animal was inoculated with : i1000,00 T. saginata; ii 500,000 eggs; and iii 1,000,000 eggs, respectivelly 100,000 (cattle 1, 500,000(cattle 2, and 1,000,000 (cattle 3 T. saginata eggs, respectively. To observe the development of cysticerci,all cattle were slaughtered at 24 weeks post infection. To observe their distribution and density, slicingwas done to the cattle?s tissues. The study results showed that cysts were found distributed to all muscletissues and some visceral organs such as heart, diaphragm, lungs, and kidney of the cattle infected with100,000 and 500,000 T. saginata eggs. Density of the cyst was in the range of 11 to 95 cysts per 100 gramsof tissue. The highest density was noted in the heart (58/100 grams and in diaphragm (55/100 grams.This study has confirmed that T. saginata eggs derived from taeniasis patient in Bali, if infected to Balicattle can develop and spread to all muscle tissues and some visceral organs. From this study it wasconcluded that it is necessary to include the heart in the meat inspection at slaughter house for possibilityof T. saginata cyst infection.$?

  8. Distributions of colorectal cancer in two Chinese cities with contrasting colorectal cancer epidemiology.

    Science.gov (United States)

    Leung, Wai K; Chen, Wei-Qing; Gu, Li; Long, Dan; Law, W L

    2015-12-01

    The incidence of colorectal cancer (CRC) is rising rapidly in Chinese. We studied the anatomic distributions and characteristics of CRC in Hong Kong (HK) and Chongqing (CQ) with different CRC epidemiology. It was a retrospective study conducted in three large regional hospitals of the two cities. We identified all patients newly diagnosed with CRC between 2003 and 2012. The distribution and characteristics of CRC of the two cities were compared. Of CRC, 3664 new cases were diagnosed within the study period. CRC was more common in men (>56%) in both cities. The mean age at diagnosis was significantly younger in CQ, the lower prevalence area, than in HK (62.1 vs 70.4 years; P < 0.001). Rectal cancer was the predominant (61.3%) cancer in CQ, but only 18% of cancers in HK were rectal cancer (P = 0.0001). Right-sided colonic cancer, however, was more common in HK than CQ (27.2% vs 17.4%; P < 0.001). Women had more right-sided colonic cancer than men in both cities (P < 0.002), and there was an age-related increase in right-sided colonic cancer in HK but not in CQ. Multivariate analysis showed that older age, female, and living in HK were independent risk factors associated with right-sided colonic cancer. There are significant differences in the distribution of CRC between HK and CQ. The discrepancy may be partly accounted by older population and an increase in proximal colonic cancer, particularly in women, in HK. © 2015 Journal of Gastroenterology and Hepatology Foundation and Wiley Publishing Asia Pty Ltd.

  9. A comparative analysis of the density distributions and the structure models of $^{9}$Li

    Indian Academy of Sciences (India)

    M AYGUN

    2017-03-01

    In the present study, we have analysed the elastic scattering cross-section data of $^{9}$Li + $^{12}$C system at $E_{lab}$ = 540 MeV and $^{9}$Li + $^{208}$Pb system at $E_{c.m.}$ = 28.3 MeV for some cluster models and various density distributions of the $^{9}$Li nucleus. First, we have obtained five different density distributions of the $^{9}$Li nucleus to generate real potentials with the help of double-folding model. For these densities, we have calculated the elastic scattering angular distributions. Secondly, using a simple approach, we have investigated some cluster models of the $^{9}$Li nucleus consisting of $^{6}$He + $^{3}$H and $^{8}$Li + n systems. We have presented the comparison of elastic scattering angular distributions for each system with each other as well as with the experimental data. Finally, we have given the cross-section values obtained from the theoretical calculations for all the systems studied in this paper.

  10. A comparative analysis of the density distributions and the structure models of 9Li

    Science.gov (United States)

    Aygun, M.

    2017-03-01

    In the present study, we have analysed the elastic scattering cross-section data of 9Li + 12C system at E lab = 540 MeV and 9Li + 208Pb system at E c.m. = 28.3 MeV for some cluster models and various density distributions of the 9Li nucleus. First, we have obtained five different density distributions of the 9Li nucleus to generate real potentials with the help of double-folding model. For these densities, we have calculated the elastic scattering angular distributions. Secondly, using a simple approach, we have investigated some cluster models of the 9Li nucleus consisting of 6He + 3H and 8Li + n systems. We have presented the comparison of elastic scattering angular distributions for each system with each other as well as with the experimental data. Finally, we have given the cross-section values obtained from the theoretical calculations for all the systems studied in this paper.

  11. Ternary-fission mass distribution of 252Cf: A level-density approach

    Science.gov (United States)

    Balasubramaniam, M.; Karthikraj, C.; Selvaraj, S.; Arunachalam, N.

    2014-11-01

    We study here the ternary-fission mass distribution of the 252Cf nucleus for a fixed third fragment 48Ca using the level-density approach within the framework of statistical theory. For the evaluation of nuclear level densities, the single-particle energies of the finite-range droplet model are used. Our results for temperatures T =1 and 2 MeV reproduce qualitatively the experimental expectation of ternary fragmentation of 132Sn +72Ni +48Ca . In addition, different possible ternary-fission modes are highlighted.

  12. Changes of the electron density distribution during MHD activity in CHS

    Energy Technology Data Exchange (ETDEWEB)

    Soltwish, H. [Ruhr-University Bochum, Institute for Experimental Physics, Bochum (Germany); Tanaka, K. [National Inst. for Fusion Science, Toki, Gifu (Japan)

    2000-09-01

    Density oscillations induced by MHD activities were observed in NBI heated plasmas on CHS by using an HCN laser interferometer. The accompanied changes of the density profiles were also observed. The oscillations are composition of m=0 sawteeth like crash and m=2 sinusoidal oscillations as a post courser of the crash. Possible models of the oscillation structure are examined in order to explain experimental data of the interferometer. Rotating plasma core, which is hollow profile and keeps constant elongation of the flux surface can explain amplitude and phase distribution of the sinusoidal oscillation. (author)

  13. Measurement for titanium density distribution on Ti:sapphire rods for high intensity pump source

    Energy Technology Data Exchange (ETDEWEB)

    Usami, Tsutomu; Nishimura, Akihiko; Sugiyama, Akira [Japan Atomic Energy Research Inst., Kizu, Kyoto (Japan). Kansai Research Establishment

    2001-10-01

    A Ti:sapphire rod of 190 mm length made by Czochralski (CZ) technique was used in the flashlamp pumped high intensity laser for Yb:glass chirped pulse amplification. In the absorption spectroscopy of the rod immersed in an index matching liquid of methylene iodide, heterogeneous Ti{sup 3+} density distribution was measured along the direction of length. It has been first clarified that the Ti:sapphire rod grown by the CZ technique has 20% difference of the Ti{sup 3+} density at the both ends. (author)

  14. Incommensurate density modulation in a Na-rich plagioclase feldspar: Z-contrast imaging and single-crystal X-ray diffraction study.

    Science.gov (United States)

    Xu, Huifang; Jin, Shiyun; Noll, Bruce C

    2016-12-01

    Plagioclase feldspars are the most abundant mineral in the Earth's crust. Intermediate plagioclase feldspars commonly display incommensurately modulated or aperiodic structures. Z-contrast images show both Ca-Na ordering and density modulation. The local structure of lamellae domains has I1-like symmetry. The neighboring lamellae domains are in an inversion twinning relationship. With a state-of-the-art X-ray diffraction unit, second-order satellite reflections (f-reflections) are observed for the first time in andesine (An45), a Na-rich e-plagioclase. The f-reflections indicate a structure with a density modulation which is close to a Ca-rich e-plagioclase. The similarity between this e-andesine structure and previously solved e-labradorite structure is confirmed. Refinement of the structure shows density modulation of ∼ 7 mol % in compositional variation of the anorthite (An) component. The results from Z-contrast imaging and low-temperature single X-ray diffraction (XRD) provide a structure consistent with density modulation. The discovery of f-reflections in Na-rich e-plagioclase extends the composition range of e1 structure with density modulation to as low as at least An45, which is the lower end of the composition range of Bøggild intergrowth. The new result supports the loop-shaped solvus for Bøggild intergrowth, below which is a homogenous stable area for e1 structure in the phase diagram. The phase transition between e2 structure without density modulation and e1 structure with density modulation should happen at low temperature. There is a change in modulation period accompanying the phase transition, as well as higher occupancy of Al in the T1o site. The andesine with density modulation also indicates extremely slow cooling of its host rock.

  15. Limit Distribution Theory for Maximum Likelihood Estimation of a Log-Concave Density.

    Science.gov (United States)

    Balabdaoui, Fadoua; Rufibach, Kaspar; Wellner, Jon A

    2009-06-01

    We find limiting distributions of the nonparametric maximum likelihood estimator (MLE) of a log-concave density, i.e. a density of the form f(0) = exp varphi(0) where varphi(0) is a concave function on R. Existence, form, characterizations and uniform rates of convergence of the MLE are given by Rufibach (2006) and Dümbgen and Rufibach (2007). The characterization of the log-concave MLE in terms of distribution functions is the same (up to sign) as the characterization of the least squares estimator of a convex density on [0, infinity) as studied by Groeneboom, Jongbloed and Wellner (2001b). We use this connection to show that the limiting distributions of the MLE and its derivative are, under comparable smoothness assumptions, the same (up to sign) as in the convex density estimation problem. In particular, changing the smoothness assumptions of Groeneboom, Jongbloed and Wellner (2001b) slightly by allowing some higher derivatives to vanish at the point of interest, we find that the pointwise limiting distributions depend on the second and third derivatives at 0 of H(k), the "lower invelope" of an integrated Brownian motion process minus a drift term depending on the number of vanishing derivatives of varphi(0) = log f(0) at the point of interest. We also establish the limiting distribution of the resulting estimator of the mode M(f(0)) and establish a new local asymptotic minimax lower bound which shows the optimality of our mode estimator in terms of both rate of convergence and dependence of constants on population values.

  16. Distribution of aquatic macrophytes in contrasting river systems: a critique of compositional-based assessment of water quality.

    Science.gov (United States)

    Demars, Benoît O L; Edwards, Anthony C

    2009-01-01

    A brief summary of the historical developments relating to plant distribution and aquatic macrophyte-nutrient indices provided a means of assessing the general context and validity of previous assumptions. This has particular current relevance because of the prominent use of bioindicators for defining nutrient enrichment. A survey of 161 sites distributed across two broadly contrasting groups of rivers (circum-neutral versus alkaline) recorded 110 species of aquatic macrophytes and these have been statistically analyzed to (i) rank and separate the individual effects of local environmental conditions and spatial isolation on species distribution in the two contrasting groups of sites; (ii) calculate a macrophyte index based on plant cover and species indicator values (Mean Trophic Rank, MTR); and finally (iii) investigate the implications for biomonitoring. Chemical, physical and hydrological site attributes together with spatial isolation, each explained a significant and at least partially independent influence over plant species distribution. It was extremely difficult, however, to separate the single effects of different site attributes on plant distribution. While some plant species are more restricted to certain environmental conditions, many appeared indifferent to the range of those being tested. The role played by nutrients (nitrogen (N) and phosphorus (P)) were either mostly indistinguishable from other site attributes (e.g., nitrate from conductivity) or subordinate (e.g., soluble reactive phosphorus, ammonium). It is therefore very unlikely that macrophyte species composition could provide a reliable bioindicator of the surrounding nutrient (N, P) status. The calculation of the plant index illustrated this unreliability by showing that strong correlations existed with many environmental variables, not just inorganic N and P.

  17. Development of a spatially distributed model of fish population density for habitat assessment of rivers

    Science.gov (United States)

    Sui, Pengzhe; Iwasaki, Akito; Ryo, Masahiro; Saavedra, Oliver; Yoshimura, Chihiro

    2013-04-01

    Flow conditions play an important role in sustaining biodiversity of river ecosystem. However, their relations to freshwater fishes, especially to fish population density, have not been clearly described. This study, therefore, aimed to propose a new methodology to quantitatively link habitat conditions, including flow conditions and other physical conditions, to population density of fish species. We developed a basin-scale fish distribution model by integrating the concept of habitat suitability assessment with a distributed hydrological model (DHM) in order to estimate fish population density with particular attention to flow conditions. Generalized linear model (GLM) was employed to evaluate the relationship between population density of fish species and major environmental factors. The target basin was Sagami River in central Japan, where the river reach was divided into 10 sections by estuary, confluences of tributaries, and river-crossing structures (dams, weirs). The DHM was employed to simulate river discharge from 1998 to 2005, which was used to calculate 10 flow indices including mean discharge, 25th and 75th percentile discharge, duration of low and high flows, number of floods. In addition, 5 water quality parameters and 13 other physical conditions (such as basin area, river width, mean diameter of riverbed material, and number of river-crossing structures upstream and downstream) of each river section were considered as environmental variables. In case of Sagami River, 10 habitat variables among them were then selected based on their correlations to avoid multicollinearity. Finally, the best GLM was developed for each species based on Akaike's information criterion. As results, population densities of 16 fish species in Sagami River were modelled, and correlation coefficients between observed and calculated population densities for 10 species were more than 0.70. The key habitat factors for population density varied among fish species. Minimum

  18. Analytical method for reconstruction pin to pin of the nuclear power density distribution

    Energy Technology Data Exchange (ETDEWEB)

    Pessoa, Paulo O.; Silva, Fernando C.; Martinez, Aquilino S., E-mail: ppessoa@con.ufrj.br, E-mail: fernando@con.ufrj.br, E-mail: aquilino@imp.ufrj.br [Coordenacao dos Programas de Pos-Graduacao em Engenharia (COPPE/UFRJ), Rio de Janeiro, RJ (Brazil)

    2013-07-01

    An accurate and efficient method for reconstructing pin to pin of the nuclear power density distribution, involving the analytical solution of the diffusion equation for two-dimensional neutron energy groups in homogeneous nodes, is presented. The boundary conditions used for analytic as solution are the four currents or fluxes on the surface of the node, which are obtained by Nodal Expansion Method (known as NEM) and four fluxes at the vertices of a node calculated using the finite difference method. The analytical solution found is the homogeneous distribution of neutron flux. Detailed distributions pin to pin inside a fuel assembly are estimated by the product of homogeneous flux distribution by local heterogeneous form function. Furthermore, the form functions of flux and power are used. The results obtained with this method have a good accuracy when compared with reference values. (author)

  19. Predicting above-ground density and distribution of small mammal prey species at large spatial scales.

    Science.gov (United States)

    Olson, Lucretia E; Squires, John R; Oakleaf, Robert J; Wallace, Zachary P; Kennedy, Patricia L

    2017-01-01

    Grassland and shrub-steppe ecosystems are increasingly threatened by anthropogenic activities. Loss of native habitats may negatively impact important small mammal prey species. Little information, however, is available on the impact of habitat variability on density of small mammal prey species at broad spatial scales. We examined the relationship between small mammal density and remotely-sensed environmental covariates in shrub-steppe and grassland ecosystems in Wyoming, USA. We sampled four sciurid and leporid species groups using line transect methods, and used hierarchical distance-sampling to model density in response to variation in vegetation, climate, topographic, and anthropogenic variables, while accounting for variation in detection probability. We created spatial predictions of each species' density and distribution. Sciurid and leporid species exhibited mixed responses to vegetation, such that changes to native habitat will likely affect prey species differently. Density of white-tailed prairie dogs (Cynomys leucurus), Wyoming ground squirrels (Urocitellus elegans), and leporids correlated negatively with proportion of shrub or sagebrush cover and positively with herbaceous cover or bare ground, whereas least chipmunks showed a positive correlation with shrub cover and a negative correlation with herbaceous cover. Spatial predictions from our models provide a landscape-scale metric of above-ground prey density, which will facilitate the development of conservation plans for these taxa and their predators at spatial scales relevant to management.

  20. Foliar Nutrient Distribution Patterns in Sympatric Maple Species Reflect Contrasting Sensitivity to Excess Manganese.

    Directory of Open Access Journals (Sweden)

    Denise R Fernando

    Full Text Available Sugar maple and red maple are closely-related co-occurring tree species significant to the North American forest biome. Plant abiotic stress effects including nutritional imbalance and manganese (Mn toxicity are well documented within this system, and are implicated in enhanced susceptibility to biotic stresses such as insect attack. Both tree species are known to overaccumulate foliar manganese (Mn when growing on unbuffered acidified soils, however, sugar maple is Mn-sensitive, while red maple is not. Currently there is no knowledge about the cellular sequestration of Mn and other nutrients in these two species. Here, electron-probe x-ray microanalysis was employed to examine cellular and sub-cellular deposition of excessively accumulated foliar Mn and other mineral nutrients in vivo. For both species, excess foliar Mn was deposited in symplastic cellular compartments. There were striking between-species differences in Mn, magnesium (Mg, sulphur (S and calcium (Ca distribution patterns. Unusually, Mn was highly co-localised with Mg in mesophyll cells of red maple only. The known sensitivity of sugar maple to excess Mn is likely linked to Mg deficiency in the leaf mesophyll. There was strong evidence that Mn toxicity in sugar maple is primarily a symplastic process. For each species, leaf-surface damage due to biotic stress including insect herbivory was compared between sites with acidified and non-acidified soils. Although it was greatest overall in red maple, there was no difference in biotic stress damage to red maple leaves between acidified and non-acidified soils. Sugar maple trees on buffered non-acidified soil were less damaged by biotic stress compared to those on unbuffered acidified soil, where they are also affected by Mn toxicity abiotic stress. This study concluded that foliar nutrient distribution in symplastic compartments is a determinant of Mn sensitivity, and that Mn stress hinders plant resistance to biotic stress.

  1. Density distribution of {sup 14}Be from reaction cross-section measurements

    Energy Technology Data Exchange (ETDEWEB)

    Moriguchi, T. [Institute of Physics, University of Tsukuba, Tsukuba, Ibaraki 305-8571 (Japan); Ozawa, A., E-mail: ozawa@tac.tsukuba.ac.jp [Institute of Physics, University of Tsukuba, Tsukuba, Ibaraki 305-8571 (Japan); Ishimoto, S. [High Energy Accelerator Research Organization (KEK), Tsukuba, Ibaraki 305-0801 (Japan); Abe, Y. [Institute of Physics, University of Tsukuba, Tsukuba, Ibaraki 305-8571 (Japan); Fukuda, M. [Department of Physics, Osaka University, Osaka 560-0043 (Japan); Hachiuma, I. [Department of Physics, Saitama University, Saitama 338-8570 (Japan); Ishibashi, Y.; Ito, Y. [Institute of Physics, University of Tsukuba, Tsukuba, Ibaraki 305-8571 (Japan); Kuboki, T. [Department of Physics, Saitama University, Saitama 338-8570 (Japan); Lantz, M. [RIKEN Nishina Center, Wako, Saitama 351-0198 (Japan); Nagae, D. [Institute of Physics, University of Tsukuba, Tsukuba, Ibaraki 305-8571 (Japan); Namihira, K. [Department of Physics, Saitama University, Saitama 338-8570 (Japan); Nishimura, D. [Department of Physics, Osaka University, Osaka 560-0043 (Japan); Ohtsubo, T. [Department of Physics, Niigata University, Niigata 950-2181 (Japan); Ooishi, H. [Institute of Physics, University of Tsukuba, Tsukuba, Ibaraki 305-8571 (Japan); Suda, T. [RIKEN Nishina Center, Wako, Saitama 351-0198 (Japan); Suzuki, H. [Institute of Physics, University of Tsukuba, Tsukuba, Ibaraki 305-8571 (Japan); Suzuki, T. [Department of Physics, Saitama University, Saitama 338-8570 (Japan); Takechi, M.; Tanaka, K. [RIKEN Nishina Center, Wako, Saitama 351-0198 (Japan); and others

    2014-09-15

    We measured the reaction cross sections of the two-neutron halo nucleus {sup 14}Be with proton and carbon targets at about 41 and 76 MeV/nucleon. Based on a Glauber model calculation, we deduced the matter density distribution of {sup 14}Be in which previously measured interaction cross sections at relativistic energies were also included. An s-wave dominance in {sup 14}Be has been confirmed, although the halo tail of {sup 14}Be is not distributed as much as that of {sup 11}Li. Significant mixing of the p-wave in addition to the s- and d-wave is also suggested.

  2. Correction of distribution density of deep sea manganese nodules based on their occurrence type

    Energy Technology Data Exchange (ETDEWEB)

    Kang, Jung-Seock; Kong, Gee-Soo [Korea Institute of Geoscience and Mineral Resources, Taejeon(Korea)

    2001-06-01

    This study aims to improve the method for more exact estimation of the distribution density and amount of seabed manganese modules in the Korean districts of northeastern Pacific, which are registered at International Seabed Authority(ISA). As the result of the study, correction formulas are obtained, and the grade of correction shows great differences depending upon the type of nodule occurrence. Four types of nodule occurrence are recognized based on the combination of shape, size and distribution density. The abundance of nodules are calculated from the area ratios of grabbing nodules and the correlation modules of sample abundances, and finally are obtained the correction formulas multiplying the corrective coefficients (experimental values between the recoveries and the covered ratios) to the bottom abundances. (author). 7 refs., 6 tabs., 6 figs.

  3. Inter-annual and seasonal trends in cetacean distribution, density and abundance off southern California

    Science.gov (United States)

    Campbell, Gregory S.; Thomas, Len; Whitaker, Katherine; Douglas, Annie B.; Calambokidis, John; Hildebrand, John A.

    2015-02-01

    Trends in cetacean density and distribution off southern California were assessed through visual line-transect surveys during thirty-seven California Cooperative Oceanic Fisheries Investigations (CalCOFI) cruises from July 2004-November 2013. From sightings of the six most commonly encountered cetacean species, seasonal, annual and overall density estimates were calculated. Blue whales (Balaenoptera musculus), fin whales (Balaenoptera physalus) and humpback whales (Megaptera novaeangliae) were the most frequently sighted baleen whales with overall densities of 0.91/1000 km2 (CV=0.27), 2.73/1000 km2 (CV=0.19), and 1.17/1000 km2 (CV=0.21) respectively. Species specific density estimates, stratified by cruise, were analyzed using a generalized additive model to estimate long-term trends and correct for seasonal imbalances. Variances were estimated using a non-parametric bootstrap with one day of effort as the sampling unit. Blue whales were primarily observed during summer and fall while fin and humpback whales were observed year-round with peaks in density during summer and spring respectively. Short-beaked common dolphins (Delphinus delphis), Pacific white-sided dolphins (Lagenorhynchus obliquidens) and Dall's porpoise (Phocoenoidesdalli) were the most frequently encountered small cetaceans with overall densities of 705.83/1000 km2 (CV=0.22), 51.98/1000 km2 (CV=0.27), and 21.37/1000 km2 (CV=0.19) respectively. Seasonally, short-beaked common dolphins were most abundant in winter whereas Pacific white-sided dolphins and Dall's porpoise were most abundant during spring. There were no significant long-term changes in blue whale, fin whale, humpback whale, short-beaked common dolphin or Dall's porpoise densities while Pacific white-sided dolphins exhibited a significant decrease in density across the ten-year study. The results from this study were fundamentally consistent with earlier studies, but provide greater temporal and seasonal resolution.

  4. COMPARATIVE ANALYSIS OF SOLID INK DENSITY, PRINT CONTRAST AND PRINT GLOSS OF METALIZED BOARD PRINTED WITH SHEET FED OFFSET PRINTING PROCESS AND DRY TONER BASED DIGITAL PRINTING PROCESS

    OpenAIRE

    Aman Bhardwaj*, Vandana

    2016-01-01

    Metalized boards are frequently used in the packaging industry. In our study, we compare the Print properties of metalized board printed with the primer coat on sheet fed offset and dry toner based digital printing process. Metalized boards are give good print properties when printed with digital printing process for short run jobs. Comparatively high contrast is found in less solid ink density in digital printing.  

  5. Control of Grafting Density and Distribution in Graft Polymers by Living Ring-Opening Metathesis Copolymerization.

    Science.gov (United States)

    Lin, Tzu-Pin; Chang, Alice B; Chen, Hsiang-Yun; Liberman-Martin, Allegra L; Bates, Christopher M; Voegtle, Matthew J; Bauer, Christina A; Grubbs, Robert H

    2017-03-15

    Control over polymer sequence and architecture is crucial to both understanding structure-property relationships and designing functional materials. In pursuit of these goals, we developed a new synthetic approach that enables facile manipulation of the density and distribution of grafts in polymers via living ring-opening metathesis polymerization (ROMP). Discrete endo,exo-norbornenyl dialkylesters (dimethyl DME, diethyl DEE, di-n-butyl DBE) were strategically designed to copolymerize with a norbornene-functionalized polystyrene (PS), polylactide (PLA), or polydimethylsiloxane (PDMS) macromonomer mediated by the third-generation metathesis catalyst (G3). The small-molecule diesters act as diluents that increase the average distance between grafted side chains, generating polymers with variable grafting density. The grafting density (number of side chains/number of norbornene backbone repeats) could be straightforwardly controlled by the macromonomer/diluent feed ratio. To gain insight into the copolymer sequence and architecture, self-propagation and cross-propagation rate constants were determined according to a terminal copolymerization model. These kinetic analyses suggest that copolymerizing a macromonomer/diluent pair with evenly matched self-propagation rate constants favors randomly distributed side chains. As the disparity between macromonomer and diluent homopolymerization rates increases, the reactivity ratios depart from unity, leading to an increase in gradient tendency. To demonstrate the effectiveness of our method, an array of monodisperse polymers (PLA(x)-ran-DME(1-x))n bearing variable grafting densities (x = 1.0, 0.75, 0.5, 0.25) and total backbone degrees of polymerization (n = 167, 133, 100, 67, 33) were synthesized. The approach disclosed in this work therefore constitutes a powerful strategy for the synthesis of polymers spanning the linear-to-bottlebrush regimes with controlled grafting density and side chain distribution, molecular

  6. On the reliability of observational measurements of column density probability distribution functions

    CERN Document Server

    Ossenkopf, Volker; Schneider, Nicola; Federrath, Christoph; Klessen, Ralf S

    2016-01-01

    Probability distribution functions (PDFs) of column densities are an established tool to characterize the evolutionary state of interstellar clouds. Using simulations, we show to what degree their determination is affected by noise, line-of-sight contamination, field selection, and the incomplete sampling in interferometric measurements. We solve the integrals that describe the convolution of a cloud PDF with contaminating sources and study the impact of missing information on the measured column density PDF. The effect of observational noise can be easily estimated and corrected for if the root mean square (rms) of the noise is known. For $\\sigma_{noise}$ values below 40\\,\\% of the typical cloud column density, $N_{peak}$, this involves almost no degradation of the accuracy of the PDF parameters. For higher noise levels and narrow cloud PDFs the width of the PDF becomes increasingly uncertain. A contamination by turbulent foreground or background clouds can be removed as a constant shield if the PDF of the c...

  7. Inter-annual and seasonal trends in cetacean distribution, density and abundance off southern California

    OpenAIRE

    2015-01-01

    Funding was provided by the Chief of Naval Operations Environmental Readiness Division, the United States Navy’s Pacific Fleet, the Naval Postgraduate School Grant #N00244-11-1-027, and the Naval Facilities Engineering Command Living Marine Resources Program. Trends in cetacean density and distribution off southern California were assessed through visual line-transect surveys during thirty-seven California Cooperative Oceanic Fisheries Investigations (CalCOFI) cruises from July 2004–Novemb...

  8. Contrasted glass-whole rock compositions and phenocryst re-distribution, IPOD Sites 417 and 418

    Science.gov (United States)

    Staudigel, H.; Bryan, W. B.

    1982-01-01

    Major element composition ranges of closely associated basalt glass-whole rock pairs from individual small cooling units approach the total known range of basalt glass and whole rock compositions at IPOD sites 417 and 418. The whole rock samples fall into two groups: one is depleted in MgO and distinctly enriched in plagioclase but has lost some olivine and/or pyroxene relative to its corresponding glass; and the other is enriched in MgO and in phenocrysts of olivine and pyroxene as well as plagioclase compared to its corresponding glass. By analogy with observed phenocryst distributions in lava pillows, tubes, and dikes, and with some theoretical studies, we infer that bulk rock compositions are strongly affected by phenocryst redistribution due to gravity settling, flotation, and dynamic sorting after eruption, although specific models are not well constrained by the one-dimensional geometry of drill core. Compositional trends or groupings in whole rock data resulting from such late-stage processes should not be confused with more fundamental compositional effects produced in deep chambers or during partial melting.

  9. Epipactis helleborine shows strong mycorrhizal preference towards ectomycorrhizal fungi with contrasting geographic distributions in Japan.

    Science.gov (United States)

    Ogura-Tsujita, Yuki; Yukawa, Tomohisa

    2008-09-01

    Epipactis helleborine (L.) Crantz, one of the most widespread orchid species, occurs in a broad range of habitats. This orchid is fully myco-heterotrophic in the germination stage and partially myco-heterotrophic in the adult stage, suggesting that a mycorrhizal partner is one of the key factors that determines whether E. helleborine successfully colonizes a specific environment. We focused on the coastal habitat of Japanese E. helleborine and surveyed the mycorrhizal fungi from geographically different coastal populations that grow in Japanese black pine (Pinus thunbergii Parl.) forests of coastal sand dunes. Mycorrhizal fungi and plant haplotypes were then compared with those from inland populations. Molecular phylogenetic analysis of large subunit rRNA sequences of fungi from its roots revealed that E. helleborine is mainly associated with several ectomycorrhizal taxa of the Pezizales, such as Wilcoxina, Tuber, and Hydnotrya. All individuals from coastal dunes were exclusively associated with a pezizalean fungus, Wilcoxina, which is ectomycorrhizal with pine trees growing on coastal dunes. Wilcoxina was not detected in inland forests. Coastal populations were indistinguishable from inland populations based on plant trnL intron haplotypes. Our results indicate that mycorrhizal association with geographically restricted pezizalean ectomycorrhizal fungi is a key control upon this orchid species' distribution across widely different forest habitats.

  10. Contrasting activity profile of two distributed cortical networks as a function of attentional demands.

    Science.gov (United States)

    Popa, Daniela; Popescu, Andrei T; Paré, Denis

    2009-01-28

    Recent human functional MRI (fMRI) studies have revealed that two widely distributed groups of cortical areas display inverse changes in activity when attentional demands increase, with one group showing higher (task-on) and the second lower (task-off) blood oxygen level-dependent (BOLD) signals. Moreover, task-on and task-off regions also exhibit slow (cat homologues of task-on and task-off regions. In all states of vigilance, LFP power was lower in task-off than task-on regions with no difference in firing rates. Both sets of regions displayed slow (0.5-0.15 Hz) cyclical modulations in LFP power in all frequency bands but with large and variable phase differences such that task-on and task-off regions were often anticorrelated. Inversely correlated LFP power fluctuations were state-dependent in that they were much more frequent in waking and paradoxical sleep than in slow-wave sleep. Moreover, consistent with fMRI findings, when attentional demands increased, LFP power in task-on and task-off regions changed in opposite directions, further augmenting and decreasing, respectively. At odds with previous fMRI studies, however, the decreased LFP power in task-off regions was associated with increased firing rates, suggesting that the engagement of task-off regions might not be reduced but in fact enhanced during attention.

  11. Estimation of electrical conductivity distribution within the human head from magnetic flux density measurement.

    Science.gov (United States)

    Gao, Nuo; Zhu, S A; He, Bin

    2005-06-01

    We have developed a new algorithm for magnetic resonance electrical impedance tomography (MREIT), which uses only one component of the magnetic flux density to reconstruct the electrical conductivity distribution within the body. The radial basis function (RBF) network and simplex method are used in the present approach to estimate the conductivity distribution by minimizing the errors between the 'measured' and model-predicted magnetic flux densities. Computer simulations were conducted in a realistic-geometry head model to test the feasibility of the proposed approach. Single-variable and three-variable simulations were performed to estimate the brain-skull conductivity ratio and the conductivity values of the brain, skull and scalp layers. When SNR = 15 for magnetic flux density measurements with the target skull-to-brain conductivity ratio being 1/15, the relative error (RE) between the target and estimated conductivity was 0.0737 +/- 0.0746 in the single-variable simulations. In the three-variable simulations, the RE was 0.1676 +/- 0.0317. Effects of electrode position uncertainty were also assessed by computer simulations. The present promising results suggest the feasibility of estimating important conductivity values within the head from noninvasive magnetic flux density measurements.

  12. Reconciliation of size-density bivariate distributions over a separating node

    Institute of Scientific and Technical Information of China (English)

    Bidarahalli Venkoba Rao; Vivek Ganvir; Sirigeri Jois Gopalakrishna

    2008-01-01

    Data reconciliation considers the restoration of mass balance among the noise prone measured data by way of component adjustments for the various particle size or particle density classes or assays over the separating node. In this paper, the method of Lagrange multipliers has been extended to balance bivariate feed and product size-density distributions of coal particles split from a settling column. The settling suspension in the column was split into two product fractions at 40% height from the bottom after a minute settling of homogenized suspension at start. Reconciliation of data assists to estimate solid flow split of particles to the settled stream as well as helps to calculate the profiles of partition curves of the marginal particle size or particle density distributions. In general, Lagrange multiplier method with uniform weighting of its components may not guarantee a smooth partition surface and thus the reconciled data needs further refinement to establish the nature of the surface. In order to overcome this difficulty, a simple alternative method of reconciling bivariate size-density data using partition surface concept is explored in this paper.

  13. The Column Density Distribution of the Low-Redshift Lyman-Alpha Forest in Illustris

    CERN Document Server

    Gurvich, Alex; Bird, Simeon

    2016-01-01

    We investigate the low-redshift Lyman-alpha forest column density distribution in the Illustris simulation. We show that Illustris reproduces observations extremely well in the column density range 10^12.5-10^14.5 cm^-2, relevant for the "photon underproduction crisis." We attribute this to the inclusion of AGN feedback, which changes the gas distribution so as to mimic the effect of extra photons, as well as the use of the Faucher-Giguere (2009) ultra-violet background, which is more ionizing at z=0.1 than the Haardt & Madau (2012) background previously considered. We show that the difference between simulations run with smoothed particle hydrodynamics and simulations using a moving mesh is small in this column density range. We further consider the effect of supernova feedback, Voigt profile fitting and finite resolution, all of which we show to be small. Finally, we identify a discrepancy between our simulations and observations at column densities 10^14-10^16 cm^-2, where Illustris produces too few ab...

  14. The Stellar Number Density Distribution in the Local Solar Neighborhood is North-South Asymmetric

    Energy Technology Data Exchange (ETDEWEB)

    Yanny, Brian [Fermilab; Gardner, Susan [Kentucky U.

    2013-10-17

    We study the number density distribution of a sample of K and M dwarf stars, matched North and South of the Galactic plane within a distance of 2 kpc from the sun, using observations from the Ninth Data Release of the Sloan Digital Sky Survey. We determine distances using the photometric parallax method, and in this context systematic effects exist which could potentially impact the determination of the number density profile with height from the Galactic plane --- and ultimately affect a number density North-South asymmetry. They include: (i) the calibration of the various photometric parallax relations, (ii) the ability to separate dwarfs from giants in our sample, (iii) the role of stellar population differences such as age and metallicity, (iv) the ability to determine the offset of the sun from the Galactic plane, and (v) the correction for reddening from dust in the Galactic plane, though our stars are at high Galactic latitudes. We find the various analyzed systematic effects to have a negligible impact on our observed asymmetry, and using a new and larger sample of stars we confirm and refine the earlier discovery of Widrow et al. of a significant Galactic North-South asymmetry in the stellar number density distribution.

  15. Marine litter distribution and density in European seas, from the shelves to deep basins.

    Directory of Open Access Journals (Sweden)

    Christopher K Pham

    Full Text Available Anthropogenic litter is present in all marine habitats, from beaches to the most remote points in the oceans. On the seafloor, marine litter, particularly plastic, can accumulate in high densities with deleterious consequences for its inhabitants. Yet, because of the high cost involved with sampling the seafloor, no large-scale assessment of distribution patterns was available to date. Here, we present data on litter distribution and density collected during 588 video and trawl surveys across 32 sites in European waters. We found litter to be present in the deepest areas and at locations as remote from land as the Charlie-Gibbs Fracture Zone across the Mid-Atlantic Ridge. The highest litter density occurs in submarine canyons, whilst the lowest density can be found on continental shelves and on ocean ridges. Plastic was the most prevalent litter item found on the seafloor. Litter from fishing activities (derelict fishing lines and nets was particularly common on seamounts, banks, mounds and ocean ridges. Our results highlight the extent of the problem and the need for action to prevent increasing accumulation of litter in marine environments.

  16. Contrasting genetic diversity patterns in two sister kelp species co-distributed along the coast of Brittany, France.

    Science.gov (United States)

    Robuchon, Marine; Le Gall, Line; Mauger, Stéphane; Valero, Myriam

    2014-06-01

    We investigated patterns of genetic structure in two sister kelp species to explore how distribution width along the shore, zonation, latitudinal distribution and historical factors contribute to contrasting patterns of genetic diversity. We implemented a hierarchical sampling scheme to compare patterns of genetic diversity and structure in these two kelp species co-distributed along the coasts of Brittany (France) using a total of 12 microsatellites, nine for Laminaria hyperborea and 11 for Laminaria digitata, of which eight amplified in both species. The genetic diversity and connectivity of L. hyperborea populations were greater than those of L. digitata populations in accordance with the larger cross-shore distribution width along the coast and the greater depth occupied by L. hyperborea populations in contrast to L. digitata populations. In addition, marginal populations showed reduced genetic diversity and connectivity, which erased isolation-by-distance patterns in both species. As L. digitata encounters its southern range limit in southern Brittany (SBr) while L. hyperborea extends down to mid-Portugal, it was possible to distinguish the effect of habitat continuity from range edge effects. We found that L. digitata did not harbour high regional diversity at its southern edge, as expected in a typical rear edge, suggesting that refuges from the last glacial maximum for L. digitata were probably not located in SBr, but most likely further north. For both species, the highest levels of genetic diversity were found in the Iroise Sea and Morlaix Bay, the two regions in which they are being currently harvested. Preserving genetic diversity of these two foundation species in these areas should, thus, be a priority for the management of this resource in Brittany.

  17. Beam hardening and smoothing correction effects on performance of micro-ct SkyScan 1173 for imaging low contrast density materials

    Energy Technology Data Exchange (ETDEWEB)

    Sriwayu, Wa Ode [Physics Departement, Haluoleo University Indonesia (Indonesia); Haryanto, Freddy; Khotimah, Siti Nurul; Latief, Fourier Dzar Eljabbar [Physics Departement, ITB Indonesia email : ayoe-fisika@yahoo.com (Indonesia)

    2015-04-16

    We have designed and fabricated phantom mimicking breast cancer composition known as a region that has low contrast density. The used compositions are a microcalcifications, fatty tissues and tumor mass by using Al{sub 2}O{sub 3}, C{sub 27}H{sub 46}O, and hard nylon materials. Besides, phantom also has a part to calculate low cost criteria /CNR (Contrast to Noise Ratio). Uniformity will be measured at water distillation medium located in a part of phantom scale contrast. Phantom will be imaged by using micro ct-sky scan 1173 high energy type, and then also can be quantified CT number to examine SkyScan 1173 performance in imaging low contrast density materials. Evaluation of CT number is done at technique configuration parameter using voltage of 30 kV, exposure 0.160 mAs, and camera resolution 560x560 pixel, the effect of image quality to reconstruction process is evaluated by varying image processing parameters in the form of beam hardening corrections with amount of 25%, 66% and100% with each smoothing level S10,S2 and S7. To obtain the better high quality image, the adjustment of beam hardening correction should be 66% and smoothing level reach maximal value at level 10.

  18. Fabrication Flaw Density and Distribution In Repairs to Reactor Pressure Vessel and Piping Welds

    Energy Technology Data Exchange (ETDEWEB)

    GJ Schuster, FA Simonen, SR Doctor

    2008-04-01

    The Pacific Northwest National Laboratory is developing a generalized fabrication flaw distribution for the population of nuclear reactor pressure vessels and for piping welds in U.S. operating reactors. The purpose of the generalized flaw distribution is to predict component-specific flaw densities. The estimates of fabrication flaws are intended for use in fracture mechanics structural integrity assessments. Structural integrity assessments, such as estimating the frequency of loss-of-coolant accidents, are performed by computer codes that require, as input, accurate estimates of flaw densities. Welds from four different reactor pressure vessels and a collection of archived pipes have been studied to develop empirical estimates of fabrication flaw densities. This report describes the fabrication flaw distribution and characterization in the repair weld metal of vessels and piping. This work indicates that large flaws occur in these repairs. These results show that repair flaws are complex in composition and sometimes include cracks on the ends of the repair cavities. Parametric analysis using an exponential fit is performed on the data. The relevance of construction records is established for describing fabrication processes and product forms. An analysis of these records shows there was a significant change in repair frequency over the years when these components were fabricated. A description of repair flaw morphology is provided with a discussion of fracture mechanics significance. Fabrication flaws in repairs are characterized using optimized-access, high-sensitivity nondestructive ultrasonic testing. Flaw characterizations are then validated by other nondestructive evaluation techniques and complemented by destructive testing.

  19. Response of a galactic disc to vertical perturbations : Strong dependence on density distribution

    CERN Document Server

    Pranav, Pratyush

    2010-01-01

    We study the self-consistent, linear response of a galactic disc to non-axisymmetric perturbations in the vertical direction as due to a tidal encounter, and show that the density distribution near the disc mid-plane has a strong impact on the radius beyond which distortions like warps develop. The self-gravity of the disc resists distortion in the inner parts. Applying this approach to a galactic disc with an exponential vertical profile, Saha & Jog showed that warps develop beyond 4-6 disc scalelengths, which could hence be only seen in HI. The real galactic discs, however, have less steep vertical density distributions that lie between a sech and an exponential profile. Here we calculate the disc response for such a general sech^(2/n) density distribution, and show that the warps develop from a smaller radius of 2-4 disc scalelengths. This naturally explains why most galaxies show stellar warps that start within the optical radius. Thus a qualitatively different picture of ubiquitous optical warps emer...

  20. High contrast Kr gas jet K alpha x-ray source for high energy density physics experiments.

    Science.gov (United States)

    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 12.6 keV Kr K alpha source has been demonstrated on the petawatt-class Titan laser facility using strongly clustering Kr gas jet targets. The contrast ratio (K alpha to continuum) is 65, with a competitive ultrashort pulse laser to x-ray conversion efficiency of 10(-5). Filtered shadowgraphy indicates that the Kr K alpha and K beta x rays are emitted from a roughly 1x2 mm(2) emission volume, making this source suitable for area backlighting and scattering. Spectral calculations indicate a typical bulk electron temperature of 50-70 eV (i.e., mean ionization state 13-16), based on the observed ratio of K alpha to K beta. Kr gas jets provide a debris-free high energy K alpha source for time-resolved diagnosis of dense matter.

  1. Effects of the distribution density of a biomass combined heat and power plant network on heat utilisation efficiency in village-town systems.

    Science.gov (United States)

    Zhang, Yifei; Kang, Jian

    2017-11-01

    The building of biomass combined heat and power (CHP) plants is an effective means of developing biomass energy because they can satisfy demands for winter heating and electricity consumption. The purpose of this study was to analyse the effect of the distribution density of a biomass CHP plant network on heat utilisation efficiency in a village-town system. The distribution density is determined based on the heat transmission threshold, and the heat utilisation efficiency is determined based on the heat demand distribution, heat output efficiency, and heat transmission loss. The objective of this study was to ascertain the optimal value for the heat transmission threshold using a multi-scheme comparison based on an analysis of these factors. To this end, a model of a biomass CHP plant network was built using geographic information system tools to simulate and generate three planning schemes with different heat transmission thresholds (6, 8, and 10 km) according to the heat demand distribution. The heat utilisation efficiencies of these planning schemes were then compared by calculating the gross power, heat output efficiency, and heat transmission loss of the biomass CHP plant for each scenario. This multi-scheme comparison yielded the following results: when the heat transmission threshold was low, the distribution density of the biomass CHP plant network was high and the biomass CHP plants tended to be relatively small. In contrast, when the heat transmission threshold was high, the distribution density of the network was low and the biomass CHP plants tended to be relatively large. When the heat transmission threshold was 8 km, the distribution density of the biomass CHP plant network was optimised for efficient heat utilisation. To promote the development of renewable energy sources, a planning scheme for a biomass CHP plant network that maximises heat utilisation efficiency can be obtained using the optimal heat transmission threshold and the nonlinearity

  2. Curve fitting of the corporate recovery rates: the comparison of Beta distribution estimation and kernel density estimation.

    Directory of Open Access Journals (Sweden)

    Rongda Chen

    Full Text Available Recovery rate is essential to the estimation of the portfolio's loss and economic capital. Neglecting the randomness of the distribution of recovery rate may underestimate the risk. The study introduces two kinds of models of distribution, Beta distribution estimation and kernel density distribution estimation, to simulate the distribution of recovery rates of corporate loans and bonds. As is known, models based on Beta distribution are common in daily usage, such as CreditMetrics by J.P. Morgan, Portfolio Manager by KMV and Losscalc by Moody's. However, it has a fatal defect that it can't fit the bimodal or multimodal distributions such as recovery rates of corporate loans and bonds as Moody's new data show. In order to overcome this flaw, the kernel density estimation is introduced and we compare the simulation results by histogram, Beta distribution estimation and kernel density estimation to reach the conclusion that the Gaussian kernel density distribution really better imitates the distribution of the bimodal or multimodal data samples of corporate loans and bonds. Finally, a Chi-square test of the Gaussian kernel density estimation proves that it can fit the curve of recovery rates of loans and bonds. So using the kernel density distribution to precisely delineate the bimodal recovery rates of bonds is optimal in credit risk management.

  3. Dynamics and density distributions in a capillary-discharge waveguide with an embedded supersonic jet

    Energy Technology Data Exchange (ETDEWEB)

    Matlis, N. H., E-mail: nmatlis@gmail.com; Gonsalves, A. J.; Steinke, S.; Tilborg, J. van; Shaw, B.; Mittelberger, D. E.; Geddes, C. G. R. [Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States); Matlis, E. H. [Department of Aerospace and Mechanical Engineering, University of Notre Dame, Notre Dame, Indiana 46556 (United States); Leemans, W. P. [Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States); Department of Physics, University of California, Berkeley, California 94720 (United States)

    2015-11-28

    We present an analysis of the gas dynamics and density distributions within a capillary-discharge waveguide with an embedded supersonic jet. This device provides a target for a laser plasma accelerator which uses longitudinal structuring of the gas-density profile to enable control of electron trapping and acceleration. The functionality of the device depends sensitively on the details of the density profile, which are determined by the interaction between the pulsed gas in the jet and the continuously-flowing gas in the capillary. These dynamics are captured by spatially resolving recombination light from several emission lines of the plasma as a function of the delay between the jet and the discharge. We provide a phenomenological description of the gas dynamics as well as a quantitative evaluation of the density evolution. In particular, we show that the pressure difference between the jet and the capillary defines three regimes of operation with qualitatively different longitudinal density profiles and show that jet timing provides a sensitive method for tuning between these regimes.

  4. Density,Storage and Distribution of Carbon in Mangrove Ecosystem in Guangdong’s Coastal Areas

    Institute of Scientific and Technical Information of China (English)

    Na; LI; Pimao; CHEN; Chuanxin; QIN

    2015-01-01

    Using the mangrove plants and sediment of the typical mangrove areas in Guangdong’s coastal areas,P. R. China as the research object,the density,storage and spatial distribution of carbon are studied. The study method is the combination of the wild field analysis and laboratory testing method. The results show that the carbon density of the sediment will gradually decrease because of the increased depth,and has nothing to do with the difference of the area and tree species. The average carbon density of 50 cm sediment is 0. 007 g C / g. The carbon density is obviously different in different components of different mangrove species in different regions. The total carbon storage in different regions is in the following order: Zhuhai > Gaoqiao > Shenzhen > Shuidong Bay > Guanghai Bay > Raoping > Daya Bay > Chenghai. The carbon density and carbon storage are obviously higher in mangrove covered area than blank area. It shows that mangroves have very strong carbon sink function.

  5. Asymmetric Velocity Distributions from Halo Density Profiles in the Eddington Approach

    Directory of Open Access Journals (Sweden)

    J. D. Vergados

    2015-01-01

    Full Text Available We show how to obtain the energy distribution f(E in our vicinity starting from WIMP density profiles in a self-consistent way by employing the Eddington approach and adding reasonable angular momentum dependent terms in the expression of the energy. We then show how we can obtain the velocity dispersions and the asymmetry parameter β in terms of the parameters describing the angular momentum dependence. From this expression, for f(E, we proceed to construct an axially symmetric WIMP a velocity distribution, which, for a gravitationally bound system, automatically has a velocity upper bound and is characterized by the same asymmetriy β. This approach is tested and clarified by constructing analytic expressions in a simple model, with adequate structure. We then show how such velocity distributions can be used in determining the event rates, including modulation, in both the standard and the directional WIMP searches.

  6. Extension of the statistical modal energy distribution analysis for estimating energy density in coupled subsystems

    Science.gov (United States)

    Totaro, N.; Guyader, J. L.

    2012-06-01

    The present article deals with an extension of the Statistical modal Energy distribution Analysis (SmEdA) method to estimate kinetic and potential energy density in coupled subsystems. The SmEdA method uses the modal bases of uncoupled subsystems and focuses on the modal energies rather than the global energies of subsystems such as SEA (Statistical Energy Analysis). This method permits extending SEA to subsystems with low modal overlap or to localized excitations as it does not assume the existence of modal energy equipartition. We demonstrate that by using the modal energies of subsystems computed by SmEdA, it is possible to estimate energy distribution in subsystems. This approach has the same advantages of standard SEA, as it uses very short calculations to analyze damping effects. The estimation of energy distribution from SmEdA is applied to an academic case and an industrial example.

  7. Conservation implications of brown hyaena (Parahyaena brunnea population densities and distribution across landscapes in Botswana

    Directory of Open Access Journals (Sweden)

    Christiaan W. Winterbach

    2017-05-01

    Full Text Available The brown hyaena (Parahyaena brunnea is endemic to southern Africa. The largest population of this near-threatened species occurs in Botswana, but limited data were available to assess distribution and density. Our objectives were to use a stratified approach to collate available data and to collect more data to assess brown hyaena distribution and density across land uses in Botswana. We conducted surveys using track counts, camera traps and questionnaires and collated our results and available data to estimate the brown hyaena population based on the stratification of Botswana for large carnivores. Brown hyaenas occur over 533 050 km² (92% of Botswana. Our density estimates ranged from 0 brown hyaenas/100 km² in strata of northern Botswana to 2.94 (2.16–3.71 brown hyaenas/100 km² in the southern stratum of the Central Kalahari Game Reserve. We made assumptions regarding densities in strata that lacked data, using the best references available. We estimated the brown hyaena population in Botswana as 4642 (3133–5993 animals, with 6.8% of the population in the Northern Conservation Zone, 73.1% in the Southern Conservation Zone, 2.0% in the smaller conservation zones and 18.1% in the agricultural zones. The similar densities of brown hyaenas in the Central Kalahari Game Reserve and the Ghanzi farms highlight the potential of agricultural areas in Botswana to conserve this species. The conservation of brown hyaenas in the agricultural landscape of Botswana is critical for the long-term conservation of the species; these areas provide important links between populations in South Africa, Namibia and Zimbabwe.Conservation implications: Botswana contains the core of the brown hyaena population in southern Africa, and conflict mitigation on agricultural land is crucial to maintaining connectivity among the range countries.

  8. Modeling Bubble Flow and Current Density Distribution in an Alkaline Electrolysis Cell

    Directory of Open Access Journals (Sweden)

    Ravichandra S. Jupudi

    2009-12-01

    Full Text Available The effect of bubbles on the current density distribution over the electrodes of an alkaline electrolyzer cell is studied using a two-dimensional computational fluid dynamics model. Model includes Eulerian-Eulerian two-phase flow methodology to model the multiphase flow of Hydrogen and Oxygen with water and the behavior of each phase is accounted for using first principle. Hydrogen/Oxygen evolution, flow field and current density distribution are incorporated in the model to account for the complicated physics involved in the process. Fluent 6.2 is used to solve two-phase flow and electrochemistry is incorporated using UDF (User Defined Function feature of Fluent. Model is validated with mesh refinement study and by comparison with experimental measurements. Model is found to replicate the effect of cell voltage and inter-electrode gap (distance between the electrodes on current density accurately. Further, model is found to capture the existence of optimum cell height. The validated model is expected to be a very useful tool in the design and optimization of alkaline electrolyzer cells.

  9. The Structure, Density, and Local Environment Distribution in Ab Initio Liquid Water

    Science.gov (United States)

    Santra, Biswajit; Distasio, Robert A., Jr.; Wu, Xifan; Car, Roberto

    2014-03-01

    We have performed extensive ab initio molecular dynamics (AIMD) simulations of liquid water at ambient conditions in the canonical (NVT) and isothermal-isobaric (NPT) ensembles to understand the individual and collective importance of exact exchange, van der Waals interactions, and nuclear quantum effects on the structural properties of liquid water. AIMD simulations which include these effects result in oxygen-oxygen radial distribution functions which are in excellent agreement with experiments and a liquid water structure having an equilibrium density within 1% of the experimental value of 1 g/cm3. A detailed analysis of the distribution of local structure in ambient liquid water has revealed that the inherent potential energy surface is bimodal with respect to high- and low-density molecular environments, consistent with the existence of polymorphism in the amorphous phases of water. With these findings in mind, the methodology presented herein overcomes the well-known limitations of semi-local density functional theory (GGA-DFT) providing a detailed and accurate microscopic description of ambient liquid water. DOE: DE-SC0008626, DOE: DE-SC0005180, NSF: CHE-0956500.

  10. Experimental Measurements of Longitudinal and Transverse Dispersion in Miscible Fluids with a High Viscosity and Density Contrast

    Science.gov (United States)

    Alkindi, A.; Bijeljic, B.; Muggeridge, A.

    2008-12-01

    Diffusion and advective dispersion may have a significant influence on the mixing between miscible fluids during displacement processes in porous media. This is particularly important when intimate mixing may result in important changes to the fluid behaviour. For example in oil recovery, mixing between injected and connate water will tend to reduce the efficiency of low salinity water injection. On the other hand recovery may be increased if injected gas mixes with high viscosity oil increasing its mobility. Most experimental data for longitudinal and transverse dispersion have been obtained using fluid pairs with very similar viscosities and densities. The traditional description (Perkins and Johnston, 1963) suggests that longitudinal dispersion decreases as mobility ratio increases. It also suggests that gravity will tend to reduce transverse dispersion. We provide experimental measurements of longitudinal (KL) and transverse (KT) dispersion at low Reynolds number as a function of Peclet number for the first contact miscible ethanol- glycerol fluid system flowing in a porous media formed from glass beads. These fluids have a high viscosity ratio of over 1000 and a significant density difference of 470 kg m-3. We show that both KL and KT are similar to values measured for a water-brine system but that KT is reduced when the less dense ethanol is flowing above the denser glycerol.

  11. Theoretical study of the central depression of nuclear charge density distribution by electron scattering

    Institute of Scientific and Technical Information of China (English)

    LIU Jian; CHU Yan-Yun; REN Zhong-Zhou; WANG Zai-Jun

    2012-01-01

    The charge form factors of elastic electron scattering for isotones with N =20 and N =28 are calculated using the phase-shift analysis method,with corresponding charge density distributions from relativistic mean-field theory.The results show that there are sharp variations at the inner parts of charge distributions with the proton number decreasing.The corresponding charge form factors are divided into two groups because of the unique properties of the s-states wave functions,though the proton numbers change uniformly in two isotonic chains.Meanwhile,the shift regularities of the minima are also discussed,and we give a clear relation between the minima of the charge form factors and the corresponding charge radii.This relation is caused by the diffraction effect of the electron.Under this conclusion,we calculate the charge density distributions and the charge form factors of the A =44 nuclei chain.The results are also useful for studying the central depression in light exotic nuclei.

  12. THE STEADY-STATE WIND MODEL FOR YOUNG STELLAR CLUSTERS WITH AN EXPONENTIAL STELLAR DENSITY DISTRIBUTION

    Energy Technology Data Exchange (ETDEWEB)

    Silich, Sergiy; Tenorio-Tagle, Guillermo; Martinez-Gonzalez, Sergio [Instituto Nacional de Astrofisica Optica y Electronica, AP 51, 72000 Puebla (Mexico); Bisnovatyi-Kogan, Gennadiy, E-mail: silich@inaoep.mx, E-mail: gkogan@iki.rssi.ru [Space Research Institute, 84/32 Profsoyuznaya, Moscow 117810 (Russian Federation)

    2011-12-20

    A hydrodynamic model for steady-state, spherically symmetric winds driven by young stellar clusters with an exponential stellar density distribution is presented. Unlike in most previous calculations, the position of the singular point R{sub sp}, which separates the inner subsonic zone from the outer supersonic flow, is not associated with the star cluster edge, but calculated self-consistently. When the radiative losses of energy are negligible, the transition from the subsonic to the supersonic flow occurs always at R{sub sp} Almost-Equal-To 4R{sub c} , where R{sub c} is the characteristic scale for the stellar density distribution, irrespective of other star cluster parameters. This is not the case in the catastrophic cooling regime, when the temperature drops abruptly at a short distance from the star cluster center, and the transition from the subsonic to the supersonic regime occurs at a much smaller distance from the star cluster center. The impact from the major star cluster parameters to the wind inner structure is thoroughly discussed. Particular attention is paid to the effects which radiative cooling provides to the flow. The results of the calculations for a set of input parameters, which lead to different hydrodynamic regimes, are presented and compared to the results from non-radiative one-dimensional numerical simulations and to those from calculations with a homogeneous stellar mass distribution.

  13. Laser ultrasonics for bulk-density distribution measurement on green ceramic tiles

    Science.gov (United States)

    Revel, G. M.; Cavuto, A.; Pandarese, G.

    2016-10-01

    In this paper a Laser Ultrasonics (LUT) system is developed and applied to measure bulk density distribution of green ceramic tiles, which are porous materials with low heat conductivity. Bulk density of green ceramic bodies is a fundamental parameter to be kept under control in the industrial production of ceramic tiles. The LUT system proposed is based on a Nd:YAG pulsed laser for excitation and an air-coupled electro-capacitive transducer for detection. The paper reports experimental apparent bulk-density measurements on white ceramic bodies after a calibration procedures. The performances observed are better than those previously achieved by authors using air-coupled ultrasonic probes for both emission and detection, allowing to reduce average uncertainty down to about ±6 kg/m3 (±0.3%), thanks to the increase in excitation efficiency and lateral resolution, while maintaining potential flexibility for on-line application. The laser ultrasonic procedure proposed is available for both on-line and off-line application. In this last case it is possible to obtain bulk density maps with high spatial resolution by a 2D scan without interrupting the production process.

  14. Vertical foliage distribution determines the radial pattern of sap flux density in Picea abies.

    Science.gov (United States)

    Fiora, Alessandro; Cescatti, Alessandro

    2008-09-01

    Understanding the causes determining the radial pattern of sap flux density is important both for improving knowledge of sapwood functioning and for up-scaling sap flow measurements to canopy transpiration and ecosystem water use. To investigate the anatomical connection between whorls and annual sapwood rings, pruning-induced variation in the radial pattern of sap flux density was monitored with Granier probes in a 35-year-old Picea abies (L.) Karst tree that was pruned from the crown bottom up. Modifications in the radial pattern of sap flux density were quantified by a shape index (SI), which varies with the relative contribution of the outer and inner sapwood to tree transpiration. The SI progressively diminished during bottom up pruning, indicating a significant reduction in sap flow contribution of the inner sapwood. Results suggest that the radial pattern of sap flux density depends mainly on the vertical distribution of foliage in the crown, with lower shaded branches hydraulically connected with inner sapwood and upper branches connected with the outer rings.

  15. Understanding star formation in molecular clouds I. A universal probability distribution of column densities ?

    CERN Document Server

    Schneider, N; Csengeri, T; Klessen, R; Federrath, C; Tremblin, P; Girichidis, P; Bontemps, S; Andre, Ph

    2014-01-01

    Column density maps of molecular clouds are one of the most important observables in the context of molecular cloud- and star-formation (SF) studies. With Herschel it is now possible to reveal rather precisely the column density of dust, which is the best tracer of the bulk of material in molecular clouds. However, line-of-sight (LOS) contamination from fore- or background clouds can lead to an overestimation of the dust emission of molecular clouds, in particular for distant clouds. This implies too high values for column density and mass, and a misleading interpretation of probability distribution functions (PDFs) of the column density. In this paper, we demonstrate by using observations and simulations how LOS contamination affects the PDF. We apply a first-order approximation (removing a constant level) to the molecular clouds of Auriga and Maddalena (low-mass star-forming), and Carina and NGC3603(both high-mass SF regions). In perfect agreement with the simulations, we find that the PDFs become broader, ...

  16. A class of multivariate infinitely divisible distributions related to arcsine density

    CERN Document Server

    Maejima, Makoto; Sato, Ken-iti; 10.3150/10-BEJ348

    2012-01-01

    Two transformations $\\mathcal{A}_1$ and $\\mathcal{A}_2$ of L\\'{e}vy measures on $\\mathbb{R}^d$ based on the arcsine density are studied and their relation to general Upsilon transformations is considered. The domains of definition of $\\mathcal{A}_1$ and $\\mathcal{A}_2$ are determined and it is shown that they have the same range. The class of infinitely divisible distributions on $\\mathbb{R}^d$ with L\\'{e}vy measures being in the common range is called the class $A$ and any distribution in the class $A$ is expressed as the law of a stochastic integral $\\int_0^1\\cos(2^{-1}\\uppi t)\\,\\mathrm{d}X_t$ with respect to a L\\'{e}vy process $\\{X_t\\}$. This new class includes as a proper subclass the Jurek class of distributions. It is shown that generalized type $G$ distributions are the image of distributions in the class $A$ under a mapping defined by an appropriate stochastic integral. $\\mathcal{A}_2$ is identified as an Upsilon transformation, while $\\mathcal{A}_1$ is shown not to be.

  17. Beam energy distribution influences on density modulation efficiency in seeded free-electron lasers

    Directory of Open Access Journals (Sweden)

    Guanglei Wang

    2015-06-01

    Full Text Available The beam energy spread at the entrance of an undulator system is of paramount importance for efficient density modulation in high-gain seeded free-electron lasers (FELs. In this paper, the dependences of high harmonic bunching efficiency in high-gain harmonic generation (HGHG, echo-enabled harmonic generation (EEHG and phase-merging enhanced harmonic generation (PEHG schemes on the electron beam energy spread distribution are studied. Theoretical investigations and multidimensional numerical simulations are applied to the cases of uniform and saddle beam energy distributions and compared to a traditional Gaussian distribution. It shows that the uniform and saddle electron energy distributions significantly enhance the bunching performance of HGHG FELs, while they almost have no influence on EEHG and PEHG schemes. A further start-to-end simulation example demonstrated that, with the saddle distribution of sliced beam energy spread controlled by a laser heater, the 30th harmonic can be directly generated by a single-stage HGHG scheme for a soft x-ray FEL facility.

  18. Comparative assessment of surface fluxes from different sources using probability density distributions

    Science.gov (United States)

    Gulev, Sergey; Tilinina, Natalia; Belyaev, Konstantin

    2015-04-01

    Surface turbulent heat fluxes from modern era and first generation reanalyses (NCEP-DOE, ERA-Interim, MERRA NCEP-CFSR, JRA) as well as from satellite products (SEAFLUX, IFREMER, HOAPS) were intercompared using framework of probability distributions for sensible and latent heat fluxes. For approximation of probability distributions and estimation of extreme flux values Modified Fisher-Tippett (MFT) distribution has been used. Besides mean flux values, consideration is given to the comparative analysis of (i) parameters of the MFT probability density functions (scale and location), (ii) extreme flux values corresponding high order percentiles of fluxes (e.g. 99th and higher) and (iii) fractional contribution of extreme surface flux events in the total surface turbulent fluxes integrated over months and seasons. The latter was estimated using both fractional distribution derived from MFT and empirical estimates based upon occurrence histograms. The strongest differences in the parameters of probability distributions of surface fluxes and extreme surface flux values between different reanalyses are found in the western boundary current extension regions and high latitudes, while the highest differences in the fractional contributions of surface fluxes may occur in mid ocean regions being closely associated with atmospheric synoptic dynamics. Generally, satellite surface flux products demonstrate relatively stronger extreme fluxes compared to reanalyses, even in the Northern Hemisphere midlatitudes where data assimilation input in reanalyses is quite dense compared to the Southern Ocean regions.

  19. Size and CT density of iodine-containing ethosomal vesicles obtained by membrane extrusion: potential for use as CT contrast agents.

    Science.gov (United States)

    Na, Bomin; Choi, Byoung Wook; Kim, Bumsang

    2013-11-01

    Computed tomography (CT) is the primary non-invasive imaging technique used for most patients with suspected liver disease. In order to improve liver-specific imaging properties and prevent toxic effects in patients with compromised renal function, we investigated the encapsulation of iodine within ethosomal vesicles. As a first step in the development of novel contrast agents using ethosomes for CT imaging applications, iodine was entrapped within ethosomes and iodine-containing ethosomes of the desired size were obtained by extrusion using a polycarbonate membrane with a defined pore size. Ethosomes containing iodine showed a relatively high CT density, which decreased when they were extruded, due to the rupture and re-formation of the lipid bilayer of the ethosome. However, when a solution with a high iodine concentration was used as a dispersion media during the extrusion process, the decrease in CT density could be prevented. In addition, ethosomes containing iodine were taken up efficiently by macrophages, which are abundant in the liver, and these ethosomes exhibited no cellular toxicity. These results demonstrate that iodine could be entrapped within ethosomal vesicles, giving the ethosomes a relatively high CT density, and that the extrusion technique used in this study could conveniently and reproducibly produce ethosomal vesicles with a desired size. Therefore, ethosomes containing iodine, as prepared in this study, have potential as contrast agents with applications in CT imaging.

  20. Modal density and modal distribution of bending wave vibration fields in ribbed plates

    DEFF Research Database (Denmark)

    Dickow, Kristoffer Ahrens; Brunskog, Jonas; Ohlrich, Mogens

    2013-01-01

    Plates reinforced by ribs or joists are common elements in lightweight building structures, as well as in other engineering structures such as vehicles, ships, and aircraft. These structures, however, are often not well suited for simple structural acoustic prediction models such as statistical...... energy analysis. One reason is that the modal density is not uniformly distributed due to the spatial periodicity introduced by the ribs. This phenomenon is investigated in the present paper, using a modal model of a ribbed plate. The modal model uses the Fourier sine modes, and the coupling between...... the plate and ribs is incorporated using Hamilton's principle. This model is then used to investigate the modal density of the considered spatially periodic structure, and a grouping of the modes in different dominating directions is proposed. Suggestions are also given regarding how to proceed towards...

  1. Excitations and magnetization density distribution in the dilute ferromagnetic semiconductor Yb14MnSb11

    Science.gov (United States)

    Stone, M. B.; Garlea, V. O.; Gillon, B.; Cousson, A.; Christianson, A. D.; Lumsden, M. D.; Nagler, S. E.; Mandrus, D.; Sales, B. C.

    2017-01-01

    Yb14MnSb11 is a rare example of a Kondo lattice compound with ferromagnetic dominated RKKY interactions. As a ferromagnetic semiconductor with Tc≈53 K, it is also a potential compound for exploration of spintronic devices. Here we describe measurements which answer remaining questions regarding the energy scales of the exchange interactions, the valence, and the magnetization density distribution in this system. We find that the system consists of RKKY exchange coupled Mn2 + sites with nearest and next nearest exchange interactions dominating the magnetic spectrum with no significant magnetization density localized on other atomic sites. The extended spread of a negative magnetization around each of the Mn ions supports a Kondo screening cloud scenario for Yb14MnSb11 .

  2. Local distortion in Co-doped LSMO from entropy-maximized charge density distribution

    Energy Technology Data Exchange (ETDEWEB)

    Syed Ali, K.S. [Department of Physics, The Madura College, Madurai 625011 (India); Saravanan, R., E-mail: saragow@dataone.i [Department of Physics, The Madura College, Madurai 625011 (India); Pashchenko, A.V.; Pashchenko, V.P. [Galkin Donetsk Institute of Physics and Technology, National Academy of Sciences of Ukraine, Donetsk 83114 (Ukraine)

    2010-07-09

    Perovskite structure manganites La{sub 0.67}Sr{sub 0.22}Mn{sub 1.11-x}Co{sub x}O{sub 3} were prepared by the solid state reaction method. An X-ray analysis of the structure was undertaken using the Rietveld technique on the experimental powder X-ray diffraction data and, then, a charge density distribution study was undertaken, using the maximum entropy method (MEM). The charge density in the unit cell was reconstructed and the effect of Co{sup 3+} doping in the Mn-O matrix was studied. Local distortions due to Co doping were analyzed and the results are now discussed.

  3. Distribution of the Current Density in Electrolyte of the Pem Fuel Cell

    Directory of Open Access Journals (Sweden)

    Eugeniusz Kurgan

    2004-01-01

    Full Text Available In this paper water management in proton exchange membrane (PEM fuel cell is considered. Firt mass convervation law for water is applied. Next proton transport is described by the Nernst-Planck equation and liqid water convection velocity is eliminated by the Schlogl equation. Electro-osmotic drag coefficient is related to hydrogen index and experimentally determined swelling coefficient. Three partial differential equations for molar water concentration Cw, electric potential ϕ and water pressure Pw are formulated. Current density vector i is derived from proton flux expression. These equations together with adequate boundary conditions were solved using finite element method. The distribution of electric potential and current density in function of geometrical parametres is investigated. At the end some illustrative example is given.

  4. Results of Current Density Distribution Mapping in PEM Fuel Cells Dependent on Operation Parameters

    Directory of Open Access Journals (Sweden)

    Zbigniew A. Styczynski

    2013-07-01

    Full Text Available This paper presents in situ measurements of a newly developed current density measurement system for proton exchange membrane fuel cells (PEMFC. While the functional principle and technical evaluation of the measurement system were presented in a previous paper, this paper analyzes the influence of various operation parameters, including multiple start-stop operation, at the anode, cathode and cooling locations on the distribution and long-term development of the current density. The system was operated for 500 h over two years with long periods of inactivity between measurements. The measurement results are evaluated and provide additional information on how to optimize the operation modes of fuel cells, including the start and stop of such systems as well as the water balance.

  5. [gamma]-ray CT examination of density gradients in slip ceramics: correlation with stress distribution

    Energy Technology Data Exchange (ETDEWEB)

    Sawicka, B.D. (AECL Research, Chalk River Labs., Ontario (Canada)); Murphy, J.G.; Taheri, F.; Kanary, L.E. (Advanced Materials Engineering Centre, Halifax, Nova Scotia (Canada))

    1992-06-01

    Residual stresses caused by processing techniques reduce the safe allowable design life of components. This is especially critical for brittle materials, like ceramics, which do not exhibit plastic deformation. During development of the manufacturing process for an experimental high-precision ceramic component, a characteristic cracking pattern occurred in a series of prototypes, which suggested development of stresses during densification, either during drying or sintering. To examine parameters which may influence the development of these residual stresses, a series of simple geometry specimens were prepared and characterized for density gradients using computed tomography (CT). Using the measured values of density gradients, a model of the sintering process was made and the resultant stress distribution in the parts calculated. Results indicate that the use of nonlinear finite element analysis in conjunction with hypoelastic materials modeling qualitatively represents the sintering stresses.

  6. γ-ray CT examination of density gradients in slip cast ceramics: correlation with stress distribution

    Science.gov (United States)

    Sawicka, B. D.; Murphy, J. G.; Taheri, F.; Kanary, L. E.

    1992-06-01

    Residual stresses caused by processing techniques reduce the safe allowable design life of components. This is especially critical for brittle materials, like ceramics, which do not exhibit plastic deformation. During development of the manufacturing process for an experimental high-precision ceramic component, a characteristic cracking pattern occurred in a series of prototypes, which suggested development of stresses during densification, either during drying or sintering. To examine parameters which may influence the development of these residual stresses, a series of simple geometry specimens were prepared and characterized for density gradients using computed tomography (CT). Using the measured values of density gradients, a model of the sintering process was made and the resultant stress distribution in the parts calculated. Results indicate that the use of nonlinear finite element analysis in conjunction with hypoelastic materials modelling qualitatively represents the sintering stresses.

  7. Density, distribution, and activity of the ocelot Leopardus pardalis (Carnivora: Felidae in Southeast Mexican rainforests

    Directory of Open Access Journals (Sweden)

    Gabriela Pérez-Irineo

    2014-12-01

    Full Text Available The ocelot Leopardus pardalis is of particular significance in terrestrial communities due to its ecological role within the group of small-sized felids and as a mesopredator. However, despite the reduction of ocelot habitat in Southeast Mexico, there are still very few ecological studies. This research aimed to contribute with some ecological aspects of the species in this region. For this, 29 camera trap stations were established in a rain forest in Los Chimalapas (an area of 22km2 during a two years period (March 2011-June, 2013, in Oaxaca state, Southeast Mexico. Data allowed the estimation of the population density, activity pattern, sex ratio, residence time, and spatial distribution. Population density was calculated using Capture-Recapture Models for demographically open populations; besides, circular techniques were used to determine if nocturnal and diurnal activity varied significantly over the seasons, and Multiple Discriminant Analysis was used to determine which of the selected environmental variables best explained ocelot abundance in the region. A total of 103 ocelot records were obtained, with a total sampling effort of 8 529 trap-days. Density of 22-38individuals/100km2 was estimated. Ocelot population had a high proportion of transient individuals in the zone (55%, and the sex ratio was statistically equal to 1:1. Ocelot activity was more frequent at night (1:00-6:00h, but it also exhibited diurnal activity throughout the study period. Ocelot spatial distribution was positively affected by the proximity to the village as well as by the amount of prey. The ocelot population here appears to be stable, with a density similar to other regions in Central and South America, which could be attributed to the diversity of prey species and a low degree of disturbance in Los Chimalapas. Rev. Biol. Trop. 62 (4: 1421-1432. Epub 2014 December 01.

  8. Diurnal and seasonal variability in radial distribution of sap flux density: Implications for estimating stand transpiration.

    Science.gov (United States)

    Fiora, Alessandro; Cescatti, Alessandro

    2006-09-01

    Daily and seasonal patterns in radial distribution of sap flux density were monitored in six trees differing in social position in a mixed coniferous stand dominated by silver fir (Abies alba Miller) and Norway spruce (Picea abies (L.) Karst) in the Alps of northeastern Italy. Radial distribution of sap flux was measured with arrays of 1-cm-long Granier probes. The radial profiles were either Gaussian or decreased monotonically toward the tree center, and seemed to be related to social position and crown distribution of the trees. The ratio between sap flux estimated with the most external sensor and the mean flux, weighted with the corresponding annulus areas, was used as a correction factor (CF) to express diurnal and seasonal radial variation in sap flow. During sunny days, the diurnal radial profile of sap flux changed with time and accumulated photosynthetic active radiation (PAR), with an increasing contribution of sap flux in the inner sapwood during the day. Seasonally, the contribution of sap flux in the inner xylem increased with daily cumulative PAR and the variation of CF was proportional to the tree diameter, ranging from 29% for suppressed trees up to 300% for dominant trees. Two models were developed, relating CF with PAR and tree diameter at breast height (DBH), to correct daily and seasonal estimates of whole-tree and stand sap flow obtained by assuming uniform sap flux density over the sapwood. If the variability in the radial profile of sap flux density was not accounted for, total stand transpiration would be overestimated by 32% during sunny days and 40% for the entire season.

  9. Energy density distribution of shaped waves inside scattering media mapped onto a complete set of diffusion modes

    CERN Document Server

    Ojambati, Oluwafemi S; Vellekoop, Ivo M; Lagendijk, Ad; Vos, Willem L

    2016-01-01

    We show that the spatial distribution of the energy density of optimally shaped waves inside a scattering medium can be described by considering only a few of the lowest eigenfunctions of the diffusion equation. Taking into account only the fundamental eigenfunction, the total internal energy inside the sample is underestimated by only 2%. The spatial distribution of the shaped energy density is very similar to the fundamental eigenfunction, up to a cosine distance of about 0.01. We obtained the energy density inside a quasi-1D disordered waveguide by numerical calculation of the joined scattering matrix. Computing the transmission-averaged energy density over all transmission channels yields the ensemble averaged energy density of shaped waves. From the averaged energy density obtained, we reconstruct its spatial distribution using the eigenfunctions of the diffusion equation. The results from our study have exciting applications in controlled biomedical imaging, efficient light harvesting in solar cells, en...

  10. Dynamic contrast optical coherence tomography: quantitative measurement of microvascular transit-time distributions in vivo (Conference Presentation)

    Science.gov (United States)

    Merkle, Conrad W.; Srinivasan, Vivek J.

    2016-03-01

    Transit time is a fundamental microcirculatory parameter that is critical in determining oxygen delivery from capillaries to surrounding tissue. Recently, it was demonstrated theoretically that capillary transit-time heterogeneity potentially leads to non-uniform oxygen extraction in micro-domains. However, in spite of its importance, capillary transit-time distribution has been challenging to quantify comprehensively and efficiently at the microscopic level. Here, we introduce a method, called Dynamic Contrast Optical Coherence Tomography (DyC-OCT), based on dynamic cross-sectional OCT imaging of the kinetics of an intravascular tracer during its passage through the field-of-view. DyC-OCT is used to quantitatively measure the transit-time distribution in microvascular networks in cross-section at the single-capillary level. Transit-time metrics are derived from analysis of the temporal characteristics of the dynamic scattering signal, related to tracer concentration, using indicator-dilution theory. Since DyC-OCT does not require calibration of the optical focus, quantitative accuracy is achieved even deep in highly scattering brain tissue where the focal spot degrades. After direct validation of DyC-OCT against the dilution curves measured using a fluorescent plasma label in the surface pial vessels of a mouse brain, imaged through a thinned-skull, glass coverslip-reinforced cranial window, the laminar transit-time distribution was investigated in microvasculature across the entire depth of the mouse somatosensory cortex. Laminar trends were identified, with the earliest transit times in the middle cortical layers, and the lowest heterogeneity in cortical layer 4. The new DyC-OCT technique affords a novel perspective of microvascular networks, with the unique capability of performing simultaneous measurements of transit-time distributions across cortical laminae.

  11. Characterization of three dimensional volumetric strain distribution during passive tension of the human tibialis anterior using Cine Phase Contrast MRI.

    Science.gov (United States)

    Jensen, Elisabeth R; Morrow, Duane A; Felmlee, Joel P; Murthy, Naveen S; Kaufman, Kenton R

    2016-10-03

    Intramuscular pressure correlates strongly with muscle tension and is a promising tool for quantifying individual muscle force. However, clinical application is impeded by measurement variability that is not fully understood. Previous studies point to regional differences in IMP, specifically increasing pressure with muscle depth. Based on conservation of mass, intramuscular pressure and volumetric strain distributions may be inversely related. Therefore, we hypothesized volumetric strain would decrease with muscle depth. To test this we quantified 3D volumetric strain in the tibialis anterior of 12 healthy subjects using Cine Phase Contrast Magnetic Resonance Imaging. Cine Phase Contrast data were collected while a custom apparatus rotated the subjects' ankle continuously between neutral and plantarflexion. A T2-weighted image stack was used to define the resting tibials anterior position. Custom and commercial post-processing software were used to quantify the volumetric strain distribution. To characterize regional strain changes, the muscle was divided into superior-inferior sections and either medial-lateral or anterior-posterior slices. Mean volumetric strain was compared across the sections and slices. As hypothesized, volumetric strain demonstrated regional differences with a decreasing trend from the anterior (superficial) to the posterior (deep) muscle regions. Statistical tests showed significant main effects and interactions of superior-inferior and anterior-posterior position as well as superior-inferior and medial-lateral position on regional strain. These data support our hypothesis and imply a potential relationship between regional volumetric strain and intramuscular pressure. This finding may advance our understanding of intramuscular pressure variability sources and lead to more reliable measurement solutions in the future. Copyright © 2016 Elsevier Ltd. All rights reserved.

  12. Spin Density Distribution in Open-Shell Transition Metal Systems: A Comparative Post-Hartree-Fock, Density Functional Theory, and Quantum Monte Carlo Study of the CuCl2 Molecule.

    Science.gov (United States)

    Caffarel, Michel; Giner, Emmanuel; Scemama, Anthony; Ramírez-Solís, Alejandro

    2014-12-09

    We present a comparative study of the spatial distribution of the spin density of the ground state of CuCl2 using Density Functional Theory (DFT), quantum Monte Carlo (QMC), and post-Hartree-Fock wave function theory (WFT). A number of studies have shown that an accurate description of the electronic structure of the lowest-lying states of this molecule is particularly challenging due to the interplay between the strong dynamical correlation effects in the 3d shell and the delocalization of the 3d hole over the chlorine atoms. More generally, this problem is representative of the difficulties encountered when studying open-shell metal-containing molecular systems. Here, it is shown that qualitatively different results for the spin density distribution are obtained from the various quantum-mechanical approaches. At the DFT level, the spin density distribution is found to be very dependent on the functional employed. At the QMC level, Fixed-Node Diffusion Monte Carlo (FN-DMC) results are strongly dependent on the nodal structure of the trial wave function. Regarding wave function methods, most approaches not including a very high amount of dynamic correlation effects lead to a much too high localization of the spin density on the copper atom, in sharp contrast with DFT. To shed some light on these conflicting results Full CI-type (FCI) calculations using the 6-31G basis set and based on a selection process of the most important determinants, the so-called CIPSI approach (Configuration Interaction with Perturbative Selection done Iteratively) are performed. Quite remarkably, it is found that for this 63-electron molecule and a full CI space including about 10(18) determinants, the FCI limit can almost be reached. Putting all results together, a natural and coherent picture for the spin distribution is proposed.

  13. A density functional for liquid {sup 4}He including the pair distribution function

    Energy Technology Data Exchange (ETDEWEB)

    Szybisz, Leszek [Laboratorio TANDAR, Departamento de Fisica, Comision Nacional de Energia Atomica, Av. del Libertador 8250, RA-1429 Buenos Aires (Argentina) and Departamento de Fisica, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Ciudad Universitaria, RA-1428 Buenos Aires (Argentina) and Consejo Nacional de Investigaciones Cientificas y Tecnicas, Av. Rivadavia 1917, RA-1033 Buenos Aires (Argentina)]. E-mail: szybisz@tandar.cnea.gov.ar; Urrutia, Ignacio [Laboratorio TANDAR, Departamento de Fisica, Comision Nacional de Energia Atomica, Av. del Libertador 8250, RA-1429 Buenos Aires (Argentina) and Comision de Investigaciones Cientificas de la Prov. de Buenos Aires, Calle 526 entre 10 y 11, RA-1900 La Plata (Argentina)]. E-mail: iurrutia@cnea.gov.ar

    2005-04-25

    A new semi-microscopic functional for studying adsorption of {sup 4}He on solid surfaces is presented. In this proposal the helium-helium interaction is screened at small distances by the pair distribution function g(r) and, in addition, the contribution which plays an important role in the interpretation of the experimental static response function is written in terms of the gradient of g(r). This functional reproduces the usual test properties. Moreover, a detailed comparison with results of the Orsay-Trento density functional is performed.

  14. Distributed material density and anisotropy for optimized eigenfrequency of 2D continua

    DEFF Research Database (Denmark)

    Pedersen, Pauli; Pedersen, Niels Leergaard

    2015-01-01

    with respect to material density and from this values of the element OC. Each factor of this expression has a physical interpretation. Stated alternatively, the optimization problem of material distribution is converted into a problem of determining a design of uniform OC values. The constitutive matrices...... are described by non-dimensional matrices with unity norms of trace and Frobenius, and thus this part of the optimized design has no influence on the mass distribution. Gradients of eigenfrequency with respect to the components of these non-dimensional constitutive matrices are therefore simplified......, and an additional optimization criterion shows that the optimized redesign of anisotropy are described directly by the element strains. The fact that all components of an optimal constitutive matrix are expressed by the components of a strain state, imply a reduced number of independent components of an optimal...

  15. Modeling the Images of Relativistic Jets Lensed by Galaxies with Different Mass Surface Density Distributions

    CERN Document Server

    Larchenkova, T I; Lyskova, N S

    2011-01-01

    The images of relativistic jets from extragalactic sources produced by gravitational lensing by galaxies with different mass surface density distributions are modeled. In particular, the following models of the gravitational lens mass distribution are considered: a singular isothermal ellipsoid, an isothermal ellipsoid with a core, two- and three-component models with a galactic disk, halo, and bulge. The modeled images are compared both between themselves and with available observations. Different sets of parameters are shown to exist for the gravitationally lensed system B0218+357 in multicomponent models. These sets allow the observed geometry of the system and the intensity ratio of the compact core images to be obtained, but they lead to a significant variety in the Hubble constant determined from the modeling results.

  16. Density and spatial distribution of Parkia biglobosa pattern in Benin under climate change

    Directory of Open Access Journals (Sweden)

    Fafunkè Titilayo Dotchamou

    2016-06-01

    Full Text Available Parkia biglobosa is an indigenous species which, traditionally contributes to the resilience of the agricultural production system in terms of food security, source of income, poverty reduction and ecosystem stability. Therefore, it is important to improve knowledge on its density, current and future spatial distribution. The main objective of this study is to evaluate the tree density, the climate change effects on the spatial distribution of the species in the future for better conservation. The modeling of the current and future geographical distribution of the species is based on the principle of Maximum Entropy (MaxEnt on a total of 286 occurrence points from field work and Global Biodiversity Information Facility GBIF-Data Portal-(www.gbif.org. Two climatic models (HadGEM2_ES and Csiro_mk3_6_0 have been used under two scenarios RCP 2.6 and RCP 8.5 for the projection of the species distribution at the horizon 2050. The correlation analyses and Jackknife test have helped to identify seven variables which are less correlated (r < 0.80 with highest modeling participation. The soil, annual precipitation (BIO12 and temperature (diurnal average Deviation are the variables which have mostly contributed to performance of the models. Currently, 53% of national territory, spread from north to south is very suitable to the cultivation of P. biglobosa. The scenarios have predicted at the horizon 2050, a loss of the habitats which are currently very suitable for the cultivation and conservation of P. biglobosa, to the benefit of moderate and weak habitats. 51% and 57% are the highest proportion of this lost which will be registered with HadGEM2_ES model under two scenarios. These results revealed that the suitable habitat of the species is threatened by climate change in Benin. In order to limit damage such as decreased productivity, extinction of species, some appropriate solutions must be found.

  17. Beam energy distribution influences on density modulation efficiency in seeded free-electron lasers

    CERN Document Server

    Wang, Guanglei; Deng, Haixiao; Zhang, Weiqing; Wu, Guorong; Dai, Dongxu; Wang, Dong; Zhao, Zhentang; Yang, Xueming

    2015-01-01

    The beam energy spread at the entrance of undulator system is of paramount importance for efficient density modulation in high-gain seeded free-electron lasers (FELs). In this paper, the dependences of high harmonic micro-bunching in the high-gain harmonic generation (HGHG), echo-enabled harmonic generation (EEHG) and phase-merging enhanced harmonic generation (PEHG) schemes on the electron energy spread distribution are studied. Theoretical investigations and multi-dimensional numerical simulations are applied to the cases of uniform and saddle beam energy distributions and compared to a traditional Gaussian distribution. It shows that the uniform and saddle electron energy distributions significantly enhance the performance of HGHG-FELs, while they almost have no influence on EEHG and PEHG schemes. A numerical example demonstrates that, with about 84keV RMS uniform and/or saddle slice energy spread, the 30th harmonic radiation can be directly generated by a single-stage seeding scheme for a soft x-ray FEL f...

  18. Contrasting distributions of groundwater arsenic and uranium in the western Hetao basin, Inner Mongolia: Implication for origins and fate controls

    Science.gov (United States)

    Guo, Huaming; Jia, Yongfeng; Wanty, Richard B.; Jiang, Yuxiao; Zhao, Weiguang; Xiu, Wei; Shen, Jiaxing; Li, Yuan; Cao, Yongsheng; Wu, Yang; Zhang, Di; Wei, Chao; Zhang, Yilong; Cao, Wengeng; Foster, Andrea L.

    2016-01-01

    Although As concentrations have been investigated in shallow groundwater from the Hetao basin, China, less is known about U and As distributions in deep groundwater, which would help to better understand their origins and fate controls. Two hundred and ninety-nine groundwater samples, 122 sediment samples, and 14 rock samples were taken from the northwest portion of the Hetao basin, and analyzed for geochemical parameters. Results showed contrasting distributions of groundwater U and As, with high U and low As concentrations in the alluvial fans along the basin margins, and low U and high As concentrations downgradient in the flat plain. The probable sources of both As and U in groundwater were ultimately traced to the bedrocks in the local mountains (the Langshan Mountains). Chemical weathering of U-bearing rocks (schist, phyllite, and carbonate veins) released and mobilized U as UO2(CO3)22 − and UO2(CO3)34 − species in the alluvial fans under oxic conditions and suboxic conditions where reductions of Mn and NO3− were favorable (OSO), resulting in high groundwater U concentrations. Conversely, the recent weathering of As-bearing rocks (schist, phyllite, and sulfides) led to the formation of As-bearing Fe(III) (hydr)oxides in sediments, resulting in low groundwater As concentrations. Arsenic mobilization and U immobilization occurred in suboxic conditions where reduction of Fe(III) oxides was favorable and reducing conditions (SOR). Reduction of As-bearing Fe(III) (hydr)oxides, which were formed during palaeo-weathering and transported and deposited as Quaternary aquifer sediments, was believed to release As into groundwater. Reduction of U(VI) to U(IV) would lead to the formation of uraninite, and therefore remove U from groundwater. We conclude that the contrasting distributions of groundwater As and U present a challenge to ensuring safe drinking water in analogous areas, especially with high background values of U and As.

  19. Prey distribution, physical habitat features, and guild traits interact to produce contrasting shorebird assemblages among foraging patches.

    Directory of Open Access Journals (Sweden)

    Beth M VanDusen

    Full Text Available Worldwide declines in shorebird populations, driven largely by habitat loss and degradation, motivate environmental managers to preserve and restore the critical coastal habitats on which these birds depend. Effective habitat management requires an understanding of the factors that determine habitat use and value to shorebirds, extending from individuals to the entire community. While investigating the factors that influenced shorebird foraging distributions among neighboring intertidal sand flats, we built upon species-level understandings of individual-based, small-scale foraging decisions to develop more comprehensive guild- and community-level insights. We found that densities and community composition of foraging shorebirds varied substantially among elevations within some tidal flats and among five flats despite their proximity (all located within a 400-m stretch of natural, unmodified inlet shoreline. Non-dimensional multivariate analyses revealed that the changing composition of the shorebird community among flats and tidal elevations correlated significantly (ρ(s = 0.56 with the spatial structure of the benthic invertebrate prey community. Sediment grain-sizes affected shorebird community spatial patterns indirectly by influencing benthic macroinvertebrate community compositions. Furthermore, combining sediment and macroinvertebrate information produced a 27% increase in correlation (ρ(s = 0.71 with shorebird assemblage patterns over the correlation of the bird community with the macroinvertebrate community alone. Beyond its indirect effects acting through prey distributions, granulometry of the flats influenced shorebird foraging directly by modifying prey availability. Our study highlights the importance of habitat heterogeneity, showing that no single patch type was ideal for the entire shorebird community. Generally, shorebird density and diversity were greatest at lower elevations on flats when they became exposed; these

  20. Multicellular automaticity of cardiac cell monolayers: effects of density and spatial distribution of pacemaker cells

    Science.gov (United States)

    Elber Duverger, James; Boudreau-Béland, Jonathan; Le, Minh Duc; Comtois, Philippe

    2014-11-01

    Self-organization of pacemaker (PM) activity of interconnected elements is important to the general theory of reaction-diffusion systems as well as for applications such as PM activity in cardiac tissue to initiate beating of the heart. Monolayer cultures of neonatal rat ventricular myocytes (NRVMs) are often used as experimental models in studies on cardiac electrophysiology. These monolayers exhibit automaticity (spontaneous activation) of their electrical activity. At low plated density, cells usually show a heterogeneous population consisting of PM and quiescent excitable cells (QECs). It is therefore highly probable that monolayers of NRVMs consist of a heterogeneous network of the two cell types. However, the effects of density and spatial distribution of the PM cells on spontaneous activity of monolayers remain unknown. Thus, a simple stochastic pattern formation algorithm was implemented to distribute PM and QECs in a binary-like 2D network. A FitzHugh-Nagumo excitable medium was used to simulate electrical spontaneous and propagating activity. Simulations showed a clear nonlinear dependency of spontaneous activity (occurrence and amplitude of spontaneous period) on the spatial patterns of PM cells. In most simulations, the first initiation sites were found to be located near the substrate boundaries. Comparison with experimental data obtained from cardiomyocyte monolayers shows important similarities in the position of initiation site activity. However, limitations in the model that do not reflect the complex beat-to-beat variation found in experiments indicate the need for a more realistic cardiomyocyte representation.

  1. Current density distribution mapping in PEM fuel cells as an instrument for operational measurements

    Energy Technology Data Exchange (ETDEWEB)

    Geske, M.; Heuer, M.; Heideck, G.; Styczynski, Z. A. [Otto-von-Guericke University Magdeburg, Chair Electric Power Networks and Renewable Energy Sources, Magdeburg (Germany)

    2010-07-01

    A newly developed measurement system for current density distribution mapping has enabled a new approach for operational measurements in proton exchange membrane fuel cells (PEMFC). Taking into account previously constructed measurement systems, a method based on a multi layer printed circuit board was chosen for the development of the new system. This type of system consists of a sensor, a special electronic device and the control and visualization PC. For the acquisition of the current density distribution values, a sensor device was designed and installed within a multilayer printed circuit board with integrated shunt resistors. Varying shunt values can be taken into consideration with a newly developed and evaluated calibration method. The sensor device was integrated in a PEM fuel cell stack to prove the functionality of the whole measurement system. A software application was implemented to visualize and save the measurement values. Its functionality was verified by operational measurements within a PEMFC system. Measurement accuracy and possible negative reactions of the sensor device during PEMFC operation are discussed in detail in this paper. The developed system enables operational measurements for different operating phases of PEM fuel cells. Additionally, this can be seen as a basis for new opportunities of optimization for fuel cell design and operation modes. (author)

  2. Density distribution of particles upon jamming after an avalanche in a 2D silo

    Directory of Open Access Journals (Sweden)

    Rodolfo O. Uñac

    2015-05-01

    Full Text Available We present a complete analysis of the density distribution of particles in a two dimensional silo after discharge. Simulations through a pseudo-dynamic algorithm are performed for filling and subsequent discharge of a plane silo. Particles are monosized hard disks deposited in the container and subjected to a tapping process for compaction. Then, a hole of a given size is open at the bottom of the silo and the discharge is triggered. After a clogging at the opening is produced, and equilibrium is restored, the final distribution of the remaining particles at the silo is analyzed by dividing the space into cells with different geometrical arrangements to visualize the way in which the density depression near the opening is propagated throughout the system. The different behavior as a function of the compaction degree is discussed. Received: 9 December 2014, Accepted: 13 April 2015; Edited by: L. A. Pugnaloni; Reviewed by: F. Vivanco, Dpto. de Física, Universidad de Santiago de Chile, Chile; DOI: http://dx.doi.org/10.4279/PIP.070007 Cite as: R. O. Uñac, J. L. Sales, M. V. Gargiulo, A. M. Vidales, Papers in Physics 7, 070007 (2015

  3. Evaluation of ion current density distribution on an extraction electrode of a radio frequency ion thruster

    Science.gov (United States)

    Masherov, P.; Riaby, V.; Abgaryan, V.

    2017-01-01

    The radial distributions of ion current density on an ion extracting electrode of a radio frequency (RF) ion thruster (RIT) with an inductive plasma source were obtained using probe diagnostics of the RF xenon plasma. Measurements were carried out using a plane wall probe simulator and the VGPS-12 Probe System of Plasma Sensors Co. At xenon flow rate q  =  2 sccm plasma pressure was 2 · 10-3 Torr, incident RF generator power varied in the range P g  =  50-250 W with RF power absorbed by plasma up to P p  =  220 W. Ion current densities were determined using semi- and double-logarithmic probe characteristics by linear extrapolations of their ion branches to probe floating potentials. The same parameters were also measured in undisturbed plasma by a classic cylindrical probe. They exceeded plane probe data by more than two times, showing the effectiveness of plasma sheath reproduction of the RIT ion extracting electrode by the plane wall probe simulator. Slight non-uniformity of the resulting plasma distributions and simplified RIT model design showed that the studied device with flat antenna coil and ferrite core could be considered as a promising prospect for RITs of new generation.

  4. Vegetation in Bangalore's Slums: Composition, Species Distribution, Density, Diversity, and History

    Science.gov (United States)

    Gopal, Divya; Nagendra, Harini; Manthey, Michael

    2015-06-01

    There is widespread acknowledgement of the need for biodiversity and greening to be part of urban sustainability efforts. Yet we know little about greenery in the context of urban poverty, particularly in slums, which constitute a significant challenge for inclusive development in many rapidly growing cities. We assessed the composition, density, diversity, and species distribution of vegetation in 44 slums of Bangalore, India, comparing these to published studies on vegetation diversity in other land-use categories. Most trees were native to the region, as compared to other land-use categories such as parks and streets which are dominated by introduced species. Of the most frequently encountered tree species, Moringa oleifera and Cocos nucifera are important for food, while Ficus religiosa plays a critical cultural and religious role. Tree density and diversity were much lower in slums compared to richer residential neighborhoods. There are also differences in species preferences, with most plant (herb, shrub and vines) species in slums having economic, food, medicinal, or cultural use, while the species planted in richer residential areas are largely ornamental. Historic development has had an impact on species distribution, with older slums having larger sized tree species, while recent slums were dominated by smaller sized tree species with greater economic and food use. Extensive focus on planting trees and plant species with utility value is required in these congested neighborhoods, to provide livelihood support.

  5. The Steady State Wind Model for Young Stellar Clusters with an Exponential Stellar Density Distribution

    CERN Document Server

    Silich, Sergiy; Tenorio-Tagle, Guillermo; Martinez-Gonzalez, Sergio

    2011-01-01

    A hydrodynamic model for steady state, spherically-symmetric winds driven by young stellar clusters with an exponential stellar density distribution is presented. Unlike in most previous calculations, the position of the singular point R_sp, which separates the inner subsonic zone from the outer supersonic flow, is not associated with the star cluster edge, but calculated self-consistently. When the radiative losses of energy are negligible, the transition from the subsonic to the supersonic flow occurs always at R_sp ~ 4 R_c, where R_c is the characteristic scale for the stellar density distribution, irrespective of other star cluster parameters. This is not the case in the catastrophic cooling regime, when the temperature drops abruptly at a short distance from the star cluster center and the transition from the subsonic to the supersonic regime occurs at a much smaller distance from the star cluster center. The impact from the major star cluster parameters to the wind inner structure is thoroughly discusse...

  6. Current Density Distribution Mapping in PEM Fuel Cells as An Instrument for Operational Measurements

    Directory of Open Access Journals (Sweden)

    Martin Geske

    2010-04-01

    Full Text Available A newly developed measurement system for current density distribution mapping has enabled a new approach for operational measurements in proton exchange membrane fuel cells (PEMFC. Taking into account previously constructed measurement systems, a method based on a multi layer printed circuit board was chosen for the development of the new system. This type of system consists of a sensor, a special electronic device and the control and visualization PC. For the acquisition of the current density distribution values, a sensor device was designed and installed within a multilayer printed circuit board with integrated shunt resistors. Varying shunt values can be taken into consideration with a newly developed and evaluated calibration method. The sensor device was integrated in a PEM fuel cell stack to prove the functionality of the whole measurement system. A software application was implemented to visualize and save the measurement values. Its functionality was verified by operational measurements within a PEMFC system. Measurement accuracy and possible negative reactions of the sensor device during PEMFC operation are discussed in detail in this paper. The developed system enables operational measurements for different operating phases of PEM fuel cells. Additionally, this can be seen as a basis for new opportunities of optimization for fuel cell design and operation modes.

  7. Soleus aponeurosis strain distribution following chronic unloading in humans: an in vivo MR phase-contrast study.

    Science.gov (United States)

    Lee, Hae-Dong; Finni, Taija; Hodgson, John A; Lai, Alex M; Edgerton, V Reggie; Sinha, Shantanu

    2006-06-01

    The in vivo strain properties of human skeletal muscle-tendon complexes are poorly understood, particularly following chronic periods of reduced load bearing. We studied eight healthy volunteers who underwent 4 wk of unilateral lower limb suspension (ULLS) to induce chronic unloading. Before and after the ULLS, maximum isometric ankle plantar flexion torque was determined by using a magnetic resonance (MR)-compatible dynamometry. Volumes of the triceps surae muscles and strain distribution of the soleus aponeurosis and the Achilles tendon at a constant submaximal plantar flexion (20% pre-maximal voluntary contraction) were measured by using MRI and velocity-encoded, phase-contrast MRI techniques. Following ULLS, volumes of the soleus and the medial gastrocnemius and the maximum isometric ankle plantar flexion (maximum voluntary contraction) decreased by 5.5+/-1.9, 7.5+/-2.7, and 48.1+/-6.1%, respectively. The strain of the aponeurosis along the length of the muscle before the ULLS was 0.3+/-0.3%, ranging from -1.5 to 2.7% in different locations of the aponeurosis. Following ULLS, the mean strain was -6.4+/-0.3%, ranging from -1.6 to 1.3%. The strain distribution of the midregion of the aponeurosis was significantly influenced by the ULLS, whereas the more distal component showed no consistent changes. Achilles tendon strain was not affected by the ULLS. These results raise the issue as to whether these changes in strain distribution affect the functional properties of the triceps surae and whether the probability of strain injuries within the triceps surae increases following chronic unloading in those regions of this muscle complex in which unusual strains occur.

  8. The TWINS exospheric neutral H-density distribution under solar minimum conditions

    Directory of Open Access Journals (Sweden)

    J. H. Zoennchen

    2011-12-01

    Full Text Available Terrestrial exospheric atomic hydrogen (H resonantly scatters solar Lyman-α (121.567 nm radiation, observed as the glow of the H-geocorona. The Two Wide-angle Imaging Neutral-atom Spectrometers (TWINS satellites are equiped with two Lyman-α line-of-sight Detectors (LADs each. Since during the past solar minimum conditions the relevant solar control parameters practically did not vary, we are using LAD data between June and September 2008 to create a time averaged hydrogen geocorona model representative for these solar minimum conditions. In this averaged model we assume that the H-geocorona is longitudinally symmetric with respect to the earth-sun line. We find a 3-dimensional H-density distribution in the range from 3 to 8 earth radii which with some caution can also be extrapolated to larger distances. For lower geocentric distances than 3 earth radii a best fitting r-dependent Chamberlain (1963-like model is adapted. Main findings are larger than conventionally expected H-densities at heights above 5 RE and a pronounced day-to-night side H-density asymmetry. The H-geocorona presented here should serve as a reference H-atmosphere for the earth during solar minimum conditions.

  9. Finding Frequent Pattern with Transaction and Occurrences based on Density Minimum Support Distribution

    Directory of Open Access Journals (Sweden)

    Preeti Khare

    2012-09-01

    Full Text Available The importance of data mining is increasing exponentially since last decade and in recent time where there is very tough competition in the market where the quality of information and information on time play a very crucial role in decision making of policy has attracted a great deal of attention in the information industry and in society as a whole. In this approach we also use density minimum support so that we reduce the execution time. A frequent superset means it contains more transactions then the minimum support. It utilize the concept that if the item set is not frequent but the superset may be frequent which is consider for the further data mining task. By this approach we can store the transaction on the daily basis, then we provide three different density zone based on the transaction and minimum support which is low (L, Medium (M, High (H. Based on this approach we categorize the item set for pruning. Our approach is based on apriori algorithm but provides better reduction in time because of the prior separation in the data, which is useful for selecting according to the density wise distribution in India. Our algorithm provides the flexibility for improved association and dynamic support. Comparative result shows the effectiveness of our algorithm.

  10. Distribution characteristics of terrestrial heat flow density in Jiyang depression of Shengli Oilfield, East China

    Institute of Scientific and Technical Information of China (English)

    GONG Yuling; WANG Liangshu; LIU Shaowen; LI Cheng; HAN Yongbing; LI Hua; LIU Bo; CAI Jingong

    2004-01-01

    Based on the geo-temperature data of 13 systematically continuous temperature log curves and 700 testing oil boreholes in Jiyang depression, Shengli Oilfield, and the measured thermal conductivities of 47 rock samples, the terrestrial heat flow densities of 114 boreholes of Jiyang depression and its surrounding areas are determined, including 13 of those data derived from systemically continuous temperature logging. The results show that Jiyang depression has a relatively high background heat flow with an average value (65.8 ± 5.4) mW/m2. The lateral variation of heat flow in basin has negative correlation with basement depth. Moreover, heat flow of uplift areas with shallower basement is high, so are those of regions with volcanic rocks, and those of depression areas with deep basement are relatively low. The heat flow densities of different structural units of Jiyang depression can be summarized as follows: The average heat flow value of Zhanhua sag is (67.4 ± 5.3) mW/m2, higher than that of the whole basin, that of Dongying sag is (66.0 ± 6.1) mW/m2, and that of Chezhen sag is (65.1 ± 3.7) mW/m2. It is apparent that these latter two values are approximate to the average value of the whole Jiyang depression,while the average value of Huimin sag is (63.6±5.0) mW/m2, lower than that of the whole basin. In fact, the basement depth and the distribution framework of uplift and depression areas are all controlled by the process of lithosphere extension. In addition, the distribution of volcanic rocks in basin is also relatively close to this extension geodynamic process. In summary, the distribution characteristics of terrestrial heat flow of Jiyang depression is determined by the Cenozoic tectono-thermal events of this region.

  11. Quantitative Analysis of Depth, Distribution, and Density of Cysts in Acanthamoeba Keratitis Using Confocal Microscopy.

    Science.gov (United States)

    Huang, Ping; Tepelus, Tudor; Vickers, Laura A; Baghdasaryan, Elmira; Huang, Jianyan; Irvine, John A; Hsu, Hugo Y; Sadda, Srinivas; Lee, Olivia L

    2017-08-01

    To quantify the density, distribution, and depth of invasion of cysts in the corneas of eyes with acanthamoeba keratitis (AK) by in vivo confocal microscopy (IVCM) with a novel scanning pattern. The medical records of patients with AK evaluated at the Doheny Eye Center UCLA between September 2014 and July 2016 were reviewed retrospectively. Patients with clinically diagnosed AK underwent IVCM at various time points during their clinical course. Five corneal locations were scanned at each time point: the central area and 4 standard points on the peripheral cornea corresponding to temporal, nasal, inferior, and superior locations. The IVCM scans were manually graded to quantify the maximum depth of invasion and density of cysts. Twenty-one eyes of 18 patients with visible cysts on IVCM were included. Mean cyst density at presentation was 214.1 ± 120.2/mm (range: 64-484 cells/mm), and the average cyst depth was 164.3 ± 81.2 μm (range: 17-290 μm). In 17 eyes, the average cyst depth was 139.4 ± 68.6 μm (range: 17-245 μm), mean cyst density was 177.9 ± 99.6/mm, and an average of 1.4 ± 1.3 quadrants was infiltrated at presentation, and reached clinical resolution with medical treatment without surgical intervention. Four eyes that ultimately underwent therapeutic penetrating keratoplasty had cysts in all 4 quadrants and deeper cyst infiltration; the average cyst depth in these corneas was 270.5 ± 17.5 μm (range: 252-290). Eyes with AK requiring therapeutic keratoplasty were more likely to have a deeper and more diffuse penetration of cysts in the cornea compared with those resolving with medical treatment.

  12. Correction: Number density distribution of solvent molecules on a substrate: a transform theory for atomic force microscopy.

    Science.gov (United States)

    Amano, Ken-Ichi; Liang, Yunfeng; Miyazawa, Keisuke; Kobayashi, Kazuya; Hashimoto, Kota; Fukami, Kazuhiro; Nishi, Naoya; Sakka, Tetsuo; Onishi, Hiroshi; Fukuma, Takeshi

    2016-08-07

    Correction for 'Number density distribution of solvent molecules on a substrate: a transform theory for atomic force microscopy' by Ken-ichi Amano et al., Phys. Chem. Chem. Phys., 2016, 18, 15534-15544.

  13. Distribution of lipid biomarkers and carbon isotope fractionation in contrasting trophic environments of the South East Pacific

    Directory of Open Access Journals (Sweden)

    I. Tolosa

    2008-06-01

    Full Text Available The distribution of lipid biomarkers and their stable carbon isotope composition was investigated on suspended particles from different contrasting trophic environments at six sites in the South East Pacific. High algal biomass with diatom-related lipids (24-methylcholesta-5,24(28-dien-3β-ol, C25 HBI alkenes, C16:4 FA, C20:5 FA was characteristic in the upwelling zone, whereas haptophyte lipids (long-chain (C37-C39 unsaturated ketones were proportionally most abundant in the nutrient-poor settings of the centre of the South Pacific Gyre and on its easter edge. The dinoflagellate–sterol, 4α-23,24-trimethylcholest-22(E-en-3β-ol, was a minor contributor in all of the studied area and the cyanobacteria-hydrocarbon, C17n-alkane, was at maximum in the high nutrient low chlorophyll regime of the subequatorial waters near the Marquesas archipelago.

    The taxonomic and spatial variability of the relationships between carbon photosynthetic fractionation and environmental conditions for four specific algal taxa (diatoms, haptophytes, dinoflagellates and cyanobacteria was also investigated. The carbon isotope fractionation factor (εp of the 24-methylcholesta-5,24(28-dien-3β-ol diatom marker, varied over a range of 16% along the different trophic systems. In contrast, εp of dinoflagellate, cyanobacteria and alkenone markers varied only by 7–10‰. The low fractionation factors and small variations between the different phytoplankton markers measured in the upwelling area likely reveals uniformly high specific growth rates within the four phytoplankton taxa, and/or that transport of inorganic carbon into phytoplankton cells may not only occur by diffusion but also by other carbon concentrating mechanisms (CCM. In contrast, in the oligotrophic zone, i.e. gyre and eastgyre, relatively high εp values, especially for the diatom marker

  14. T1 weighted Brain Images at 7 Tesla Unbiased for Proton Density, T2* contrast and RF Coil Receive B1 Sensitivity with Simultaneous Vessel Visualization

    Science.gov (United States)

    Van de Moortele, Pierre-François; Auerbach, Edwards J.; Olman, Cheryl; Yacoub, Essa; Uğurbil, Kâmil; Moeller, Steen

    2009-01-01

    At high magnetic field, MR images exhibit large, undesirable signal intensity variations commonly referred to as “intensity field bias”. Such inhomogeneities mostly originate from heterogeneous RF coil B1 profiles and, with no appropriate correction, are further pronounced when utilizing rooted sum of square reconstruction with receive coil arrays. These artifacts can significantly alter whole brain high resolution T1-weighted (T1w) images that are extensively utilized for clinical diagnosis, for gray/white matter segmentation as well as for coregistration with functional time series. In T1 weighted 3D-MPRAGE sequences, it is possible to preserve a bulk amount of T1 contrast through space by using adiabatic inversion RF pulses that are insensitive to transmit B1 variations above a minimum threshold. However, large intensity variations persist in the images, which are significantly more difficult to address at very high field where RF coil B1 profiles become more heterogeneous. Another characteristic of T1w MPRAGE sequences is their intrinsic sensitivity to Proton Density and T2* contrast, which cannot be removed with post-processing algorithms utilized to correct for receive coil sensitivity. In this paper, we demonstrate a simple technique capable of producing normalized, high resolution T1w 3D-MPRAGE images that are devoid of receive coil sensitivity, Proton Density and T2* contrast. These images, which are suitable for routinely obtaining whole brain tissue segmentation at 7 Tesla, provide higher T1 contrast specificity than standard MPRAGE acquisitions. Our results show that removing the Proton Density component can help identifying small brain structures and that T2* induced artifacts can be removed from the images. The resulting unbiased T1w images can also be used to generate Maximum Intensity Projection angiograms, without additional data acquisition, that are inherently registered with T1w structural images. In addition, we introduce a simple technique

  15. Spatial Distribution and Density of Dolines in the NW Part of Velika Kapela from GIS Based Buffer Analysis

    OpenAIRE

    Mladen Pahernik

    2000-01-01

    GIS based buffer analysis methods were applied for analysing spatial distribution and density of dolinas in the NW part of Velika Kapela. Results extracted from existing spatial databases indicated spatial distribution of faults, as well as a degree of relationship between direction and density of dolinas with identified lineaments. By comparing faults identified from dolina analysis, with faults identified during on-situ mapping, major tectonic blocks or units within researched area were ide...

  16. The impact of local stellar radiation on the HI column density distribution

    CERN Document Server

    Rahmati, Alireza; Pawlik, Andreas H; Raičević, Milan

    2013-01-01

    It is often assumed that local sources of ionizing radiation have little impact on the distribution of HI in the post-reionization Universe. While this is a good assumption for the IGM, analytic arguments suggest that local sources may typically be more important than the background radiation for high column density absorbers (N_HI > 10^17 /cm^2). We post-process cosmological simulations with accurate radiation transport to investigate the impact of local stellar sources on the HI distribution. We demonstrate that the limited numerical resolution and the simplified treatment of the ISM that are typical of current cosmological simulations provide significant challenges, but that many of the problems can be overcome by taking two steps. First, using ISM particles rather than stellar particles as sources results in a much better sampling of the source distribution. Second, by rescaling the source luminosities so that the amount of radiation escaping into the IGM agrees with that required to produce the observed ...

  17. Experimental determination of two-dimensional critical current density distribution in YBCO coated conductors

    Energy Technology Data Exchange (ETDEWEB)

    Amemiya, Naoyuki; Shinkai, Yoshichika [Faculty of Engineering, Yokohama National University, Tokiwadai, Hodogaya, Yokohama (Japan); Iijima, Yasuhiro; Kakimoto, Kazuomi; Takeda, Kaoru [Materials Research Laboratory, Fujikura Ltd., Kiba, Koto, Tokyo (Japan)

    2001-08-01

    The critical current density (J{sub c}) distribution in YBCO coated conductors is attracting interest from the viewpoint of its influence on their AC loss characteristics as well as from material science and process engineering. A two-dimensional J{sub c} distribution in a YBCO coated conductor made by the IBAD (ion-beam assisted deposition) and the PLD (pulse-laser deposition) method can be determined by the magnetic-knife method with spatial resolutions of 0.2 mm lateral and 10 mm longitudinal directions, respectively. In an up-to-date 80A-class YBCO coated conductor, the J{sub c} is relatively uniform in the central part and reaches mbox{l_brace}7$x$10{sup 9} A m{sup -2}, {r_brace} while the J{sub c} fluctuates spatially in the central part of a tape fabricated earlier and with less critical current. Near the edges of the tapes, the J{sub c} is higher or lower than in the central part and the experimentally determined J{sub c} distributions are far from uniform. This suggests that a presumption of a uniform J{sub c} for AC loss estimations is not always reasonable and can lead to a large error in the estimated AC losses. (author)

  18. Recovering the nonlinear density field from the galaxy distribution with a Poisson-Lognormal filter

    CERN Document Server

    Kitaura, Francisco S; Metcalf, R Benton

    2009-01-01

    We present a general expression for a lognormal filter given an arbitrary nonlinear galaxy bias. We derive this filter as the maximum a posteriori solution assuming a lognormal prior distribution for the matter field with a given mean field and modeling the observed galaxy distribution by a Poissonian process. We have performed a three-dimensional implementation of this filter with a very efficient Newton-Krylov inversion scheme. Furthermore, we have tested it with a dark matter N-body simulation assuming a unit galaxy bias relation and compared the results with previous density field estimators like the inverse weighting scheme and Wiener filtering. Our results show good agreement with the underlying dark matter field for overdensities even above delta~1000 which exceeds by one order of magnitude the regime in which the lognormal is expected to be valid. The reason is that for our filter the lognormal assumption enters as a prior distribution function, but the maximum a posteriori solution is also conditione...

  19. Radial power density distribution of MOX fuel rods in the IFA-651

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Byung Ho; Koo, Yang Hyun; Joo, Hyung Kook; Cheon, Jin Sik; Oh, Je Yong; Sohn, Dong Seong [Korea Atomic Energy Research Institute, Taejeon (Korea)

    2002-04-01

    Two MOX fuel rods, which were fabricated in the Paul Scherrer Institute (PSI), Switzerland in cooperation with Korea Atomic Energy Research Institute, have been irradiated in the HBWR from June, 2000 in the framework of OECD-HRP together with a reference MOX fuel rod supplied by the BNFL. Since fuel temperature, which is influenced by radial power distribution, is basic in analyzing fuel behavior, it is required to consider radial power distribution in the HBWR. A subroutine FACTOR{sub H}BWR that calculates radial power density distribution for three MOX fuel rods has been developed based on neutron physics results and DEPRESS program. The developed subroutine FACTOR{sub H}BWR gives good agreement with the physics calculation except slight under-prediction at the outer part of the pellet above the burnup of 20 MWd/kgHM. The subroutine will be incorporated into a computer code COSMOS and used to analyze the in-reactor behavior of the three MOX fuel rods during the Halden irradiation test. 24 figs., 4 tabs. (Author)

  20. Landscape-scale distribution and density of raptor populations wintering in anthropogenic-dominated desert landscapes

    Science.gov (United States)

    Duerr, Adam E.; Miller, Tricia A.; Cornell Duerr, Kerri L; Lanzone, Michael J; Fesnock, Amy; Katzner, Todd Eli

    2015-01-01

    Anthropogenic development has great potential to affect fragile desert environments. Large-scale development of renewable energy infrastructure is planned for many desert ecosystems. Development plans should account for anthropogenic effects to distributions and abundance of rare or sensitive wildlife; however, baseline data on abundance and distribution of such wildlife are often lacking. We surveyed for predatory birds in the Sonoran and Mojave Deserts of southern California, USA, in an area designated for protection under the “Desert Renewable Energy Conservation Plan”, to determine how these birds are distributed across the landscape and how this distribution is affected by existing development. We developed species-specific models of resight probability to adjust estimates of abundance and density of each individual common species. Second, we developed combined-species models of resight probability for common and rare species so that we could make use of sparse data on the latter. We determined that many common species, such as red-tailed hawks, loggerhead shrikes, and especially common ravens, are associated with human development and likely subsidized by human activity. Species-specific and combined-species models of resight probability performed similarly, although the former model type provided higher quality information. Comparing abundance estimates with past surveys in the Mojave Desert suggests numbers of predatory birds associated with human development have increased while other sensitive species not associated with development have decreased. This approach gave us information beyond what we would have collected by focusing either on common or rare species, thus it provides a low-cost framework for others conducting surveys in similar desert environments outside of California.

  1. Size distribution and radial density profile of synaptic vesicles by SAXS and light scattering

    Energy Technology Data Exchange (ETDEWEB)

    Castorph, Simon; Salditt, Tim [Institute for X-ray Physics, Goettingen (Germany); Holt, Matthew; Jahn, Reinhard [Max Plank Institute for Biophysical Chemistry, Goettingen (Germany); Sztucki, Michael [European Synchrotron Radiation Facility, Grenoble (France)

    2008-07-01

    Synaptic vesicles are small membraneous organelles within the nerve terminal, encapsulating neurotransmitters by a lipid bilayer. The transport of the neurotransmitter, the fusion at the plasma membrane, and the release of the stored neurotransmitters into the synaptic cleft are since long know as essential step in nerve conduction of the chemical synapse. A detailed structural view of these molecular mechanisms is still lacking, not withstanding the enormous progress in the field during recent years. From measurements and quantitative fitting of small angle X-ray scattering curves and dynamic light scattering the averaged structural properties of synaptic vesicles can be determined. We present SAXS measurements and fits revealing the width of the size distribution function and details of the radial scattering length profile of synaptic vesicles from rat brain. Representative values for the inner and outer radius and the size polydispersity as well as the density and width of the outer protein layer are obtained.

  2. Non-anomalous magnetization density distribution in CeB6

    Science.gov (United States)

    Givord, F.; Boucherle, J.-X.; Burlet, P.; Gillon, B.; Kunii, S.

    2003-05-01

    Results of polarized neutron diffraction on the compound CeB6 are used to obtain its magnetization density distribution. The measurements are performed at two different points of the magnetic phase diagram (phase I and II). The data are analysed in direct space using the maximum entropy method, as well as in reciprocal space using the cerium form factor expansion and anisotropy. The conclusion is that, in both phases, the magnetization is localized on the cerium sites only. This result is in contradiction to a recent paper by Saitoh et al (2002 J. Phys. Soc. Japan 71 2369), claiming that, in phase II, a localized spin moment was observed at non-atomic sites.

  3. PERFORMANCE OPTIMIZATION OF LINEAR INDUCTION MOTOR BY EDDY CURRENT AND FLUX DENSITY DISTRIBUTION ANALYSIS

    Directory of Open Access Journals (Sweden)

    M. S. MANNA

    2011-12-01

    Full Text Available The development of electromagnetic devices as machines, transformers, heating devices confronts the engineers with several problems. For the design of an optimized geometry and the prediction of the operational behaviour an accurate knowledge of the dependencies of the field quantities inside the magnetic circuits is necessary. This paper provides the eddy current and core flux density distribution analysis in linear induction motor. Magnetic flux in the air gap of the Linear Induction Motor (LIM is reduced to various losses such as end effects, fringes, effect, skin effects etc. The finite element based software package COMSOL Multiphysics Inc. USA is used to get the reliable and accurate computational results for optimization the performance of Linear Induction Motor (LIM. The geometrical characteristics of LIM are varied to find the optimal point of thrust and minimum flux leakage during static and dynamic conditions.

  4. Twisted accretion discs. Pt. 2. Variation in density distribution and application to interacting binaries

    Energy Technology Data Exchange (ETDEWEB)

    Kumar, Sanjiv

    1986-11-15

    Accretion discs formed out of the symmetry plane of a compact object are likely to be twisted due to the effects of precession. The radius at which they align with the compact object spin axis depends on viscosity and surface-density distribution along with the dominant external forcing on the disc. Only isothermal discs are treated because of their tractability. The results are applied to X-ray binaries with resonably well-determined parameters which exhibit long-term periodic behaviour, particularly Her X-1. It is found that the case for alignment in Her X-1 and 2S0614 + 091 is inconclusive, but alignment is ruled out in SMCX-1 and LMC X-4, in this model.

  5. Production of Transverse Controllable Laser Density Distribution in Fermilab/NICADD Photoinjector

    CERN Document Server

    Li, Jianliang; Tikhoplav, Rodion

    2005-01-01

    The Fermilab/NICADD photoinjector laboratory consist of a photoemission electron source based on an L band rf-gun. The CsTe photocathode is illuminated by an ultrashort UV laser. The transport line from the laser to the photocathode was recently upgraded to allow imaging of an object plane located ~20 m from the photocathode. This upgrade allows the generation of transverse laser distributions with controlled nonuniformity, yielding the production of an electron beam with various transverse densities patterns. Measuring the evolution of the artificial pattern on the electron bunch provides information that can be used to benchmark numerical simulations and investigate the impact of space charge. Preliminary data on these investigations are presented in the present paper.

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

    CERN Document Server

    Nugaev, Emin Ya; Zhezher, Yana V

    2015-01-01

    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 & White (NFW), Maller & Bullock (MB) and Feldmann, Hooper & 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 realistic MB and FHG models are compatible with the observed dispersion measure.

  7. Simulation of die wall friction's effect on density distribution in metallic powder compaction

    Institute of Scientific and Technical Information of China (English)

    周照耀; 赵伟斌; 陈普庆; 陈维平; 邵明; 王郡文

    2002-01-01

    A computer simulation procedure for metal powder die compaction was described. Friction behavior of metal powder during cold compaction was simulated by the finite element method. The movement of powder relative to the die wall was taken into consideration by utilizing the shear friction model. Friction between the powder and the rigid die wall leads to inhomogeneous density distribution during the compaction process. The floating die technique and double punch pressing can attain more homogenous compacts than the fixed die technique can do. The results obtained from numerical analysis agree well with the experimental results. Simulation model was built in MSC.Mentat, and MSC.Marc software was used to calculate the powder compaction process.

  8. The internal density distribution of comet 67P/C-G based on 3D models

    Science.gov (United States)

    Jorda, Laurent; Faurschou Hviid, Stubbe; Capanna, Claire; Gaskell, Robert W.; Gutiérrez, Pedro; Preusker, Frank; Scholten, Frank; Rodionov, Sergey; OSIRIS Team

    2016-10-01

    The OSIRIS camera aboard the Rosetta spacecraft observed the nucleus of comet 67P/C-G from the mapping phase in summer 2014 until now. The images have allowed the reconstruction in three-dimension of nucleus surface with stereophotogrammetry (Preusker et al., Astron. Astrophys.) and stereophotoclinometry (Jorda et al., Icarus) techniques. We use the reconstructed models to constrain the internal density distribution based on: (i) the measurement of the offset between the center of mass and the center of figure of the object, and (ii) the assumption that flat areas observed at the surface of the comet correspond to iso-gravity surfaces. The results of our analysis will be presented, and the consequences for the internal structure and formation of the nucleus of comet 67P/C-G will be discussed.

  9. Calculation of photodetachment cross sections and photoelectron angular distributions of negative ions using density functional theory

    Science.gov (United States)

    Liu, Yuan; Ning, Chuangang

    2015-10-01

    Recently, the development of photoelectron velocity map imaging makes it much easier to obtain the photoelectron angular distributions (PADs) experimentally. However, explanations of PADs are only qualitative in most cases, and very limited works have been reported on how to calculate PAD of anions. In the present work, we report a method using the density-functional-theory Kohn-Sham orbitals to calculate the photodetachment cross sections and the anisotropy parameter β. The spherical average over all random molecular orientation is calculated analytically. A program which can handle both the Gaussian type orbital and the Slater type orbital has been coded. The testing calculations on Li-, C-, O-, F-, CH-, OH-, NH2-, O2-, and S2- show that our method is an efficient way to calculate the photodetachment cross section and anisotropy parameter β for anions, thus promising for large systems.

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

    Science.gov (United States)

    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.

  11. Communication: Investigation of the electron momentum density distribution of nanodiamonds by electron energy-loss spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Feng, Zhenbao; Yang, Bing; Lin, Yangming; Su, Dangsheng, E-mail: dssu@imr.ac.cn [Shenyang National Laboratory of Materials Science, Institute of Metal Research, Chinese Academy of Sciences, Wenhua Road 72, Shenyang 110016 (China)

    2015-12-07

    The electron momentum distribution of detonation nanodiamonds (DND) was investigated by recording electron energy-loss spectra at large momentum transfer in the transmission electron microscope (TEM), which is known as electron Compton scattering from solid (ECOSS). Compton profile of diamond film obtained by ECOSS was found in good agreement with prior photon experimental measurement and theoretical calculation that for bulk diamond. Compared to the diamond film, the valence Compton profile of DND was found to be narrower, which indicates a more delocalization of the ground-state charge density for the latter. Combining with other TEM characterizations such as high-resolution transmission electron spectroscopy, diffraction, and energy dispersive X-ray spectroscopy measurements, ECOSS was shown to be a great potential technique to study ground-state electronic properties of nanomaterials.

  12. Analysis of Observation Data of Earth-Rockfill Dam Based on Cloud Probability Distribution Density Algorithm

    Directory of Open Access Journals (Sweden)

    Han Liwei

    2014-07-01

    Full Text Available Monitoring data on an earth-rockfill dam constitutes a form of spatial data. Such data include much uncertainty owing to the limitation of measurement information, material parameters, load, geometry size, initial conditions, boundary conditions and the calculation model. So the cloud probability density of the monitoring data must be addressed. In this paper, the cloud theory model was used to address the uncertainty transition between the qualitative concept and the quantitative description. Then an improved algorithm of cloud probability distribution density based on a backward cloud generator was proposed. This was used to effectively convert certain parcels of accurate data into concepts which can be described by proper qualitative linguistic values. Such qualitative description was addressed as cloud numerical characteristics-- {Ex, En, He}, which could represent the characteristics of all cloud drops. The algorithm was then applied to analyze the observation data of a piezometric tube in an earth-rockfill dam. And experiment results proved that the proposed algorithm was feasible, through which, we could reveal the changing regularity of piezometric tube’s water level. And the damage of the seepage in the body was able to be found out.

  13. Current distribution and enhancement of the engineering critical current density in multifilament Bi-2223 tapes

    DEFF Research Database (Denmark)

    Wang, W.G.; Jensen, M.B.; Kindl, B.;

    2000-01-01

    The spatial distribution of the critical current density (Jc) and engineering critical current density (Je) along the tape width direction was studied by a cutting technique on Bi-2223 multifilamentary tapes. In general, an increase of Jc towards the centre of the tape was measured. We attribute...... this tendency to the stress-strain experienced in the tape during the rolling process. Jc of 50 kA/cm2 and Jeof 18 kA/cm2 was measured at the centre part (185 μm wide and 200 μm thick) of a tape cut from a 500 meters long tape (average Je of 8 kA/cm2). The low Jc of the edge part is a result of the porous...... microstructure with a great amount of secondary phases. Local variation of Jc was measured within the centre segment of the tape. This indicates the influence of other factors on Jc, such as filament shape, connectivity of the filaments, and sausaging. Enhancement of Je has been pursued in which average Je of 12...

  14. Hysteresis in Carbon Nanotube Transistors: Measurement and Analysis of Trap Density, Energy Level, and Spatial Distribution.

    Science.gov (United States)

    Park, Rebecca Sejung; Shulaker, Max Marcel; Hills, Gage; Suriyasena Liyanage, Luckshitha; Lee, Seunghyun; Tang, Alvin; Mitra, Subhasish; Wong, H-S Philip

    2016-04-26

    We present a measurement technique, which we call the Pulsed Time-Domain Measurement, for characterizing hysteresis in carbon nanotube field-effect transistors, and demonstrate its applicability for a broad range of 1D and 2D nanomaterials beyond carbon nanotubes. The Pulsed Time-Domain Measurement enables the quantification (density, energy level, and spatial distribution) of charged traps responsible for hysteresis. A physics-based model of the charge trapping process for a carbon nanotube field-effect transistor is presented and experimentally validated using the Pulsed Time-Domain Measurement. Leveraging this model, we discover a source of traps (surface traps) unique to devices with low-dimensional channels such as carbon nanotubes and nanowires (beyond interface traps which exist in today's silicon field-effect transistors). The different charge trapping mechanisms for interface traps and surface traps are studied based on their temperature dependencies. Through these advances, we are able to quantify the interface trap density for carbon nanotube field-effect transistors (∼3 × 10(13) cm(-2) eV(-1) near midgap), and compare this against a range of previously studied dielectric/semiconductor interfaces.

  15. The column density distribution of hard X-ray radio galaxies

    CERN Document Server

    Panessa, F; Landi, R; Bazzano, A; Dallacasa, D; La Franca, F; Malizia, A; Venturi, T; Ubertini, P

    2016-01-01

    In order to investigate the role of absorption in AGN with jets, we have studied the column density distribution of a hard X-ray selected sample of radio galaxies, derived from the INTEGRAL/IBIS and Swift/BAT AGN catalogues (~7-10% of the total AGN population). The 64 radio galaxies have a typical FRII radio morphology and are characterized by high 20-100 keV luminosities (from 10^42 to 10^46 erg/s) and high Eddington ratios (Log L_{Bol}/L_{Edd} typically larger than ~0.01). The observed fraction of absorbed AGN (N_{H} > 10^{22} cm^{-2}) is around 40% among the total sample, and ~75% among type 2 AGN. The majority of obscured AGN are narrow line objects, while unobscured AGN are broad line objects, obeying to the zeroth-order predictions of unified models. A significant anti-correlation between the radio core dominance parameter and the X-ray column density is found. The observed fraction of Compton thick AGN is ~2-3%, in comparison with the 5-7% found in radio-quiet hard X-ray selected AGN. We have estimated...

  16. Visualization of High-Dimensional Point Clouds Using Their Density Distribution's Topology.

    Science.gov (United States)

    Oesterling, P; Heine, C; Janicke, H; Scheuermann, G; Heyer, G

    2011-11-01

    We present a novel method to visualize multidimensional point clouds. While conventional visualization techniques, like scatterplot matrices or parallel coordinates, have issues with either overplotting of entities or handling many dimensions, we abstract the data using topological methods before presenting it. We assume the input points to be samples of a random variable with a high-dimensional probability distribution which we approximate using kernel density estimates on a suitably reconstructed mesh. From the resulting scalar field we extract the join tree and present it as a topological landscape, a visualization metaphor that utilizes the human capability of understanding natural terrains. In this landscape, dense clusters of points show up as hills. The nesting of hills indicates the nesting of clusters. We augment the landscape with the data points to allow selection and inspection of single points and point sets. We also present optimizations to make our algorithm applicable to large data sets and to allow interactive adaption of our visualization to the kernel window width used in the density estimation.

  17. The role of body mass index, insulin, and adiponectin in the relation between fat distribution and bone mineral density

    NARCIS (Netherlands)

    M.C. Zillikens (Carola); A.G. Uitterlinden (André); J.P.T.M. van Leeuwen (Hans); A.L. Berends (Anne); P. Henneman (Peter); J.A.P. Willems van Dijk (Ko); B.A. Oostra (Ben); C.M. van Duijn (Cock); H.A.P. Pols (Huib); F. Rivadeneira Ramirez (Fernando)

    2010-01-01

    textabstractDespite the positive association between body mass index (BMI) and bone mineral density (BMD) and content (BMC), the role of fat distribution in BMD/BMC remains unclear. We examined relationships between BMD/BMC and various measurements of fat distribution and studied the role of BMI, in

  18. The molecular electron density distribution meeting place of X-ray diffraction and quantum chemistry intermediate - between theory and experiment

    NARCIS (Netherlands)

    Feil, Dirk

    1992-01-01

    Quantum chemistry and the concepts used daily in chemistry are increasingly growing apart. Among the concepts that are able to bridge the gap between theory and experimental practice, electron density distribution has an important place. The study of this distribution has led to new developments in

  19. Patchy distributions of competitors affect the growth of a clonal plant when the competitor density is high.

    Directory of Open Access Journals (Sweden)

    Wei Xue

    Full Text Available Environments are patchy in not only abiotic factors but also biotic ones. Many studies have examined effects of spatial heterogeneity in abiotic factors such as light, water and nutrients on the growth of clonal plants, but few have tested those in biotic factors. We conducted a greenhouse experiment to examine how patchy distributions of competitors affect the growth of a rhizomatous wetland plant Bolboschoenus planiculmis and whether such effects depend on the density of the competitors. We grew one ramet of B. planiculmis in the center of each of the experimental boxes without competitors (Schoenoplectus triqueter, with a homogeneous distribution of the competitors of low or high density, and with a patchy distribution of the competitors of low or high density. The presence of competitors markedly decreased the growth (biomass, number of ramets, number of tubers and rhizome length of the B. planiculmis clones. When the density of the competitors was low, the growth of B. planiculmis did not differ significantly between the competitor patches and competitor-free patches. However, when the density of the competitors was high, the growth of B. planiculmis was significantly higher in the competitor-free patches than in the competitor patches. Therefore, B. planiculmis can respond to patchy distributions of competitors by placing more ramets in competition-free patches when the density of competitors is high, but cannot do so when the density of competitors is low.

  20. Patchy distributions of competitors affect the growth of a clonal plant when the competitor density is high.

    Science.gov (United States)

    Xue, Wei; Huang, Lin; Dong, Bi-Cheng; Zhang, Ming-Xiang; Yu, Fei-Hai

    2013-01-01

    Environments are patchy in not only abiotic factors but also biotic ones. Many studies have examined effects of spatial heterogeneity in abiotic factors such as light, water and nutrients on the growth of clonal plants, but few have tested those in biotic factors. We conducted a greenhouse experiment to examine how patchy distributions of competitors affect the growth of a rhizomatous wetland plant Bolboschoenus planiculmis and whether such effects depend on the density of the competitors. We grew one ramet of B. planiculmis in the center of each of the experimental boxes without competitors (Schoenoplectus triqueter), with a homogeneous distribution of the competitors of low or high density, and with a patchy distribution of the competitors of low or high density. The presence of competitors markedly decreased the growth (biomass, number of ramets, number of tubers and rhizome length) of the B. planiculmis clones. When the density of the competitors was low, the growth of B. planiculmis did not differ significantly between the competitor patches and competitor-free patches. However, when the density of the competitors was high, the growth of B. planiculmis was significantly higher in the competitor-free patches than in the competitor patches. Therefore, B. planiculmis can respond to patchy distributions of competitors by placing more ramets in competition-free patches when the density of competitors is high, but cannot do so when the density of competitors is low.

  1. Distribution characteristics of coronal electric current density as an indicator for the occurrence of a solar flare

    Science.gov (United States)

    Kang, Jihye; Magara, Tetsuya; Inoue, Satoshi; Kubo, Yuki; Nishizuka, Naoto

    2016-10-01

    In this paper we investigate the distribution characteristics of the coronal electric current density in a flare-producing active region (AR12158; SOL2014-09-10) by reconstructing nonlinear force-free (NLFF) fields from photospheric magnetic field data. A time series of NLFF fields shows the spatial distribution and its temporal development of coronal current density in this active region. A fractal dimensional analysis shows that a concentrated coronal current forms a structure of fractal spatiality. Furthermore, the distribution function of coronal current density is featured with a double power-law profile, and the value of electric current density at the breaking point of a double power-law fitting function shows a noticeable time variation toward the onset of an X-class flare. We discuss that this quantity will be a useful indicator for the occurrence of a flare.

  2. Distribution characteristics of coronal electric current density as an indicator for the occurrence of a solar flare

    Science.gov (United States)

    Kang, Jihye; Magara, Tetsuya; Inoue, Satoshi; Kubo, Yuki; Nishizuka, Naoto

    2016-12-01

    In this paper we investigate the distribution characteristics of the coronal electric current density in a flare-producing active region (AR12158; SOL2014-09-10) by reconstructing nonlinear force-free (NLFF) fields from photospheric magnetic field data. A time series of NLFF fields shows the spatial distribution and its temporal development of coronal current density in this active region. A fractal dimensional analysis shows that a concentrated coronal current forms a structure of fractal spatiality. Furthermore, the distribution function of coronal current density is featured with a double power-law profile, and the value of electric current density at the breaking point of a double power-law fitting function shows a noticeable time variation toward the onset of an X-class flare. We discuss that this quantity will be a useful indicator for the occurrence of a flare.

  3. Spatial distributions of the energy and energy flux density of partially coherent electromagnetic beams in atmospheric turbulence.

    Science.gov (United States)

    Li, Jianlong; Lü, Baida; Zhu, Shifu

    2009-07-06

    The formulas of the energy and energy flux density of partially coherent electromagnetic beams in atmospheric turbulence are derived by using Maxwell's equations. Expressions expressed by elements of electric cross spectral density matrixes of the magnetic and the mutual cross spectral density matrix are obtained for the partially coherent electromagnetic beams. Taken the partially coherent Cosh-Gaussian (ChG) electromagnetic beam as a typical example, the spatial distributions of the energy and energy flux density in atmospheric turbulence are numerically calculated. It is found that the turbulence shows a broadening effect on the spatial distributions of the energy and energy flux density. Some interesting results are obtained and explained with regard to their physical nature.

  4. Tailoring the mass distribution and functional group density of dimethylsiloxane-based films by thermal evaporation

    Directory of Open Access Journals (Sweden)

    Tino Töpper

    2016-05-01

    Full Text Available The tailoring of molecular weight distribution and the functional group density of vinyl-terminated polydimethylsiloxane (PDMS by molecular beam deposition is demonstrated herein. Thermally evaporated PDMS and its residue are characterized using gel permeation chromatography and nuclear magnetic resonance. Thermal fragmentation of vinyl groups occurs for evaporation temperatures above 487 K (214 °C. At a background pressure of 10−6 mbar, the maximum molecular weight distribution is adjusted from (700 ± 100 g/mol to (6100 ± 100 g/mol with a polydispersity index of 1.06 ± 0.02. The content of vinyl-termination per repeating unit of PDMS is tailored from (2.8 ± 0.2% to (5.6 ± 0.1%. Molecular weights of vinyl-terminated PDMS evaporated at temperatures above 388 K (115 °C correspond to those attributed to trimethyl-terminated PDMS. Side groups of linear PDMS dominate intermolecular interactions and vapor pressure.

  5. Mammographic Breast Density in Chinese Women: Spatial Distribution and Autocorrelation Patterns.

    Directory of Open Access Journals (Sweden)

    Christopher W K Lai

    Full Text Available Mammographic breast density (MBD is a strong risk factor for breast cancer. The spatial distribution of MBD in the breast is variable and dependent on physiological, genetic, environmental and pathological factors. This pilot study aims to define the spatial distribution and autocorrelation patterns of MBD in Chinese women aged 40-60. By analyzing their digital mammographic images using a public domain Java image processing program for segmentation and quantification of MBD, we found their left and right breasts were symmetric to each other in regard to their breast size (Total Breast Area, the amount of BMD (overall PD and Moran's I values. Their MBD was also spatially autocorrelated together in the anterior part of the breast in those with a smaller breast size, while those with a larger breast size tend to have their MBD clustered near the posterior part of the breast. Finally, we observed that the autocorrelation pattern of MBD was dispersed after a 3-year observation period.

  6. Estimation of the mass density contrasts and the 3D geometrical shape of the source bodies, in the Yilgarn area, Eastern Goldfields, Western Australia

    DEFF Research Database (Denmark)

    Strykowski, Gabriel; Boschetti, F.; Papp, G.

    2005-01-01

    , a rough 3D shape of the source is modelled-a model consisting of the vertical mass columns of equal height. The horizontal extension is implied by the surface gravity signal. Subsequently, the shape of each source body is modified to obtain a better fit to the surface gravity data. In each modification......) and only weakly constrained by the seismic information. The result was the reconstruction of the 'rough' 3D geometry of the source bodies and the estimation of a constant mass density contrast to the surroundings. A possible extension of this technique for detailed studies of the geological model......We invert 2D surface gravity data constrained both by geological and seismic information. We use a number of pre-processing tools in order to reduce the general multi-body inversion into several single-body inversions, whereby we can reduce the overall complexity of the inversion task. This is done...

  7. Density, distribution, and genetic structure of grizzly bears in the Cabinet-Yaak Ecosystem

    Science.gov (United States)

    Macleod, Amy C.; Boyd, Kristina L; Boulanger, John; Royle, J. Andrew; Kasworm, Wayne F.; Paetkau, David; Proctor, Michael F; Annis, Kim; Graves, Tabitha A.

    2016-01-01

    The conservation status of the 2 threatened grizzly bear (Ursus arctos) populations in the Cabinet-Yaak Ecosystem (CYE) of northern Montana and Idaho had remained unchanged since designation in 1975; however, the current demographic status of these populations was uncertain. No rigorous data on population density and distribution or analysis of recent population genetic structure were available to measure the effectiveness of conservation efforts. We used genetic detection data from hair corral, bear rub, and opportunistic sampling in traditional and spatial capture–recapture models to generate estimates of abundance and density of grizzly bears in the CYE. We calculated mean bear residency on our sampling grid from telemetry data using Huggins and Pledger models to estimate the average number of bears present and to correct our superpopulation estimates for lack of geographic closure. Estimated grizzly bear abundance (all sex and age classes) in the CYE in 2012 was 48–50 bears, approximately half the population recovery goal. Grizzly bear density in the CYE (4.3–4.5 grizzly bears/1,000 km2) was among the lowest of interior North American populations. The sizes of the Cabinet (n = 22–24) and Yaak (n = 18–22) populations were similar. Spatial models produced similar estimates of abundance and density with comparable precision without requiring radio-telemetry data to address assumptions of geographic closure. The 2 populations in the CYE were demographically and reproductively isolated from each other and the Cabinet population was highly inbred. With parentage analysis, we documented natural migrants to the Cabinet and Yaak populations by bears born to parents in the Selkirk and Northern Continental Divide populations. These events supported data from other sources suggesting that the expansion of neighboring populations may eventually help sustain the CYE populations. However, the small size, isolation, and inbreeding documented by this study

  8. A neural code for looming and receding motion is distributed over a population of electrosensory ON and OFF contrast cells.

    Science.gov (United States)

    Clarke, Stephen E; Longtin, André; Maler, Leonard

    2014-04-16

    Object saliency is based on the relative local-to-background contrast in the physical signals that underlie perceptual experience. As such, contrast-detecting neurons (ON/OFF cells) are found in many sensory systems, responding respectively to increased or decreased intensity within their receptive field centers. This differential sensitivity suggests that ON and OFF cells initiate segregated streams of information for positive and negative sensory contrast. However, while recording in vivo from the ON and OFF cells of Apteronotus leptorhynchus, we report that the reversal of stimulus motion triggers paradoxical responses to electrosensory contrast. By considering the instantaneous firing rates of both ON and OFF cell populations, a bidirectionally symmetric representation of motion is achieved for both positive and negative contrast stimuli. Whereas the firing rates of the individual contrast detecting neurons convey scalar information, such as object distance, it is their sequential activation over longer timescales that track changes in the direction of movement.

  9. Digital evaluation of the influence of interruption of the fixation process on radiographic contrast and base-plus-fog density in three commercial brands of radiographic films

    Directory of Open Access Journals (Sweden)

    Paula Verona Ragusa da Silva

    Full Text Available INTRODUCTION : With the interest in anticipating access to the result of intraoral radiography, the radiographic processing is frequently neglected, compromising image quality. OBJECTIVE : The aim of this study was to evaluate the influence of interrupting the fixation process on the radiographic contrast and base-plus-fog density (BPFD in three brands of periapical films. MATERIAL AND METHOD : Ninety radiographs were taken of an aluminum stepwedge and a lead plate for each brand, and they were divided according to the time of initial immersion in the fixative in: control group (without interrupting the fixing, 5, 10, 20, 30 and 40 seconds. During processing, films had the fixing stage stopped and were exposed to a negatoscope for 1 minute, then the fixation time of 10 minutes was completed. The radiographs were digitized and exported to Image Tool 3.0.software. RESULT : Kodak(r film showed no statistically significant differences between groups, while Agfa(r film presented difference in BPFD compared with Group 5 seconds, and Dentix(r film showed statistical difference in all groups in comparison with the control group. CONCLUSION : Under the conditions studied, Kodak(r film is not influenced by disruption of fixation as regards BPFD and image contrast, enabling early access to the results of radiographs, whereas Agfa(r film requires at least 10 seconds of initial fixation, and Dentix(r film obtains better results when the process of fixation is not interrupted.

  10. Contrasting patterns of clonality and fine-scale genetic structure in two rare sedges with differing geographic distributions.

    Science.gov (United States)

    Binks, R M; Millar, M A; Byrne, M

    2015-09-01

    For plants with mixed reproductive capabilities, asexual reproduction is more frequent in rare species and is considered a strategy for persistence when sexual recruitment is limited. We investigate whether asexual reproduction contributes to the persistence of two co-occurring, rare sedges that both experience irregular seed set and if their differing geographic distributions have a role in the relative contribution of clonality. Genotypic richness was high (R=0.889±0.02) across the clustered populations of Lepidosperma sp. Mt Caudan and, where detected, clonal patches were small, both in ramet numbers (⩽3 ramets/genet) and physical size (1.3±0.1 m). In contrast, genotypic richness was lower in the isolated L. sp. Parker Range populations, albeit more variable (R=0.437±0.13), with genets as large as 17 ramets and up to 5.8 m in size. Aggregated clonal growth generated significant fine-scale genetic structure in both species but to a greater spatial extent and with additional genet-level structure in L. sp. Parker Range that is likely due to restricted seed dispersal. Despite both species being rare, asexual reproduction clearly has a more important role in the persistence of L. sp. Parker Range than L. sp. Mt Caudan. This is consistent with our prediction that limitations to sexual reproduction, via geographic isolation to effective gene exchange, can lead to greater contributions of asexual reproduction. These results demonstrate the role of population isolation in affecting the balance of alternate reproductive modes and the contextual nature of asexual reproduction in rare species.

  11. Joint Reconstruction of Absorbed Optical Energy Density and Sound Speed Distribution in Photoacoustic Computed Tomography: A numerical Investigation

    CERN Document Server

    Huang, Chao; Schoonover, Robert W; Wang, Lihong V; Anastasio, Mark A

    2015-01-01

    Photoacoustic computed tomography (PACT) is a rapidly emerging bioimaging modality that seeks to reconstruct an estimate of the absorbed optical energy density within an object. Conventional PACT image reconstruction methods assume a constant speed-of-sound (SOS), which can result in image artifacts when acoustic aberrations are significant. It has been demonstrated that incorporating knowledge of an object's SOS distribution into a PACT image reconstruction method can improve image quality. However, in many cases, the SOS distribution cannot be accurately and/or conveniently estimated prior to the PACT experiment. Because variations in the SOS distribution induce aberrations in the measured photoacoustic wavefields, certain information regarding an object's SOS distribution is encoded in the PACT measurement data. Based on this observation, a joint reconstruction (JR) problem has been proposed in which the SOS distribution is concurrently estimated along with the sought-after absorbed optical energy density ...

  12. The column density distribution of hard X-ray radio galaxies

    Science.gov (United States)

    Panessa, F.; Bassani, L.; Landi, R.; Bazzano, A.; Dallacasa, D.; La Franca, F.; Malizia, A.; Venturi, T.; Ubertini, P.

    2016-09-01

    In order to investigate the role of absorption in active galactic nuclei (AGN) with jets, we have studied the column density distribution of a hard X-ray selected sample of radio galaxies, derived from the INTEGRAL/Imager on Board the Integral Satellite (IBIS) and Swift/The Burst Alert Telescope (BAT) AGN catalogues (˜7-10 per cent of the total AGN population). The 64 radio galaxies have a typical FR II radio morphology and are characterized by high 20-100 keV luminosities (from 1042 to 1046 erg s-1) and high Eddington ratios (log LBol/LEdd typically larger than ˜0.01). The observed fraction of absorbed AGN (NH > 1022 cm-2) is around 40 per cent among the total sample, and ˜75 per cent among type 2 AGN. The majority of obscured AGN are narrow-line objects, while unobscured AGN are broad-line objects, obeying to the zeroth-order predictions of unified models. A significant anti-correlation between the radio core dominance parameter and the X-ray column density is found. The observed fraction of Compton thick AGN is ˜2-3 per cent, in comparison with the 5-7 per cent found in radio-quiet hard X-ray selected AGN. We have estimated the absorption and Compton thick fractions in a hard X-ray sample containing both radio galaxies and non-radio galaxies and therefore affected by the same selection biases. No statistical significant difference was found in the absorption properties of radio galaxies and non-radio galaxies sample. In particular, the Compton thick objects are likely missing in both samples and the fraction of obscured radio galaxies appears to decrease with luminosity as observed in hard X-ray non-radio galaxies.

  13. Winter distribution, density and size of Mesodesma mactroides (Bivalvia, Mactracea in Monte Hermoso beach (Argentina

    Directory of Open Access Journals (Sweden)

    Sandra Marcela Fiori

    2004-03-01

    Full Text Available The yellow clam Mesodesma mactroides (Deshayes, 1854 is a seasonal migrant that moves in spring to the sandy upper intertidal level. In this paper we analyze the spatial distribution of density and mean shell size of the yellow clam population in Monte Hermoso beach (Argentina in winter 1995, i.e., three months before the mass mortality occurred in November 1995. Sampling covered 32 km of beach, with a regular design of 22 transects. The major environmental gradient in the beach was determined using principal component analysis (PCA on the correlation matrix of the environmental data (beach morphology, slope, and sand granulometry. Correlation analysis was used to assess the relationship between the score of a site (transect on the first and second principal component, and clam mean density and mean shell size. Most of the beach seems to be habitable for clams, their spatial heterogeneity not having been explained by the measured variables since, although the first axis of the PCA has demonstrated an E-W physical gradient, clam density was not in correlation with it. Density was maximum near the piers, even though these are points with high tourist activity. It seems that non-extractive touristic activities do not affect population density but rather mean shell size, probably due to reduction of growth rates. The abundance of the winter population, as compared with the assessment done after the mass mortality of November, strongly suggests that a great part of the population was overwintering in the intertidal fringe.O molusco Mesodesma mactroides (Deshayes, 1854 é uma espécie migrante sazonal que na primavera move-se para o nível entremarés superior da praia. Neste estudo, analisamos a distribuição espacial da densidade e o tamanho médio da população do bivalve na praia de Monte Hermoso (Argentina no inverno de 1995, i. é, três meses antes da mortalidade massiva desses moluscos, acontecida em novembro de 1995. A amostragem cobriu 32

  14. Statistical tests for whether a given set of independent, identically distributed draws comes from a specified probability density.

    Science.gov (United States)

    Tygert, Mark

    2010-09-21

    We discuss several tests for determining whether a given set of independent and identically distributed (i.i.d.) draws does not come from a specified probability density function. The most commonly used are Kolmogorov-Smirnov tests, particularly Kuiper's variant, which focus on discrepancies between the cumulative distribution function for the specified probability density and the empirical cumulative distribution function for the given set of i.i.d. draws. Unfortunately, variations in the probability density function often get smoothed over in the cumulative distribution function, making it difficult to detect discrepancies in regions where the probability density is small in comparison with its values in surrounding regions. We discuss tests without this deficiency, complementing the classical methods. The tests of the present paper are based on the plain fact that it is unlikely to draw a random number whose probability is small, provided that the draw is taken from the same distribution used in calculating the probability (thus, if we draw a random number whose probability is small, then we can be confident that we did not draw the number from the same distribution used in calculating the probability).

  15. Distribution and density of mast cells in camel small intestine and influence of fixation techniques

    Directory of Open Access Journals (Sweden)

    MB Al-Zghoul

    2009-08-01

    Full Text Available This study was carried out to gather species-specific data on mast-cell density and distribution in camel small intestine under different fixation conditions and to elucidate the presence and cross-reactivity of tryptase in the camel small intestine using human specific anti-tryptase antibody. Tissue specimens from the jejunum, duodenum, and ileum were obtained from 9 healthy, 9-12 months old, male camels. Specimens were fixed either with carnoy’s fluid or formalinbuffered solution and stained with either methylene blue or immunohistochemically to identify mast cells. The present study demonstrated for the first time, the presence and cross-reactivity of tryptase in the camel small intestine using a specific mouse anti-human tryptase antibody. Mast cells were detected in all histological layers of the camel small intestine (mucosal, submucosal, muscularis externa and serosa. Among all locations examined in the duodenum, ileum and jejunum, no significant difference was observed in mast-cell counts among the lamina propria, muscularis mucosae, muscularis externa and the serosa. The only significant difference observed was the mast-cell count in submucosa region where the highest and lowest mast count was observed in the jejenual and ileal submucosa, respectively. Significant differences regarding the distribution of mast cell as well as the influence of the fixation method could be observed. This underlines the fact that data regarding mast cell heterogeneity from other species, obtained by different fixation methods, are not comparable. This fact has to be taken into account when evaluating mast cell subtypes under pathological conditions.

  16. Gamma distribution model describes maturational curves for delta wave amplitude, cortical metabolic rate and synaptic density.

    Science.gov (United States)

    Feinberg, I; Thode, H C; Chugani, H T; March, J D

    1990-01-23

    We analyzed the available ontogenetic data (birth to 30 years of age) for: amplitude of delta EEG (DA) waves during sleep; cortical metabolic rate (CMR) measured with positron emission tomography; and synaptic density (SD) in frontal cortex. Each is at the adult level at birth, increases to about twice this level by 3 years of age, and then gradually falls back to the adult level over the next two decades. Statistical analyses revealed that individual gamma distribution models fit each data set as well as did the best ad hoc polynomial. A test of whether a single gamma distribution model could describe all three data sets gave good results for DA and CMR but the fit was unsatisfactory for SD. However, because so few data were available for SD, this test was not conclusive. We proposed the following model to account for these changes. First, cortical neurons are stimulated by birth to enter a proliferative state (PS) that creates many connections. Next, as a result of interactions in the PS, neurons are triggered into a transient organizational state (OS) in which they make enduring connections. The OS has a finite duration (minutes to years), and is characterized by high rates of information-processing and metabolism. Levels of CMR, SD and DA, therefore, are proportional to the number of neurons in the OS at any time. Thus, the cortex after birth duplicates, over a vastly greater time scale, the overproduction and regression of neural elements that occurs repeatedly in embryonic development. Finally, we discussed the implications of post-natal brain changes for normal and abnormal brain function. Mental disorders that have their onset after puberty (notably schizophrenia and manic-depressive psychoses) might be caused by errors in these late maturational processes. In addition to age of onset, this neurodevelopmental hypothesis might explain several other puzzling features of these subtle disorders.

  17. Calculation of photodetachment cross sections and photoelectron angular distributions of negative ions using density functional theory

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Yuan [Department of Physics, State Key Laboratory of Low-Dimensional Quantum Physics, Tsinghua University, Beijing 100084 (China); Ning, Chuangang, E-mail: ningcg@tsinghua.edu.cn [Department of Physics, State Key Laboratory of Low-Dimensional Quantum Physics, Tsinghua University, Beijing 100084 (China); Collaborative Innovation Center of Quantum Matter, Beijing (China)

    2015-10-14

    Recently, the development of photoelectron velocity map imaging makes it much easier to obtain the photoelectron angular distributions (PADs) experimentally. However, explanations of PADs are only qualitative in most cases, and very limited works have been reported on how to calculate PAD of anions. In the present work, we report a method using the density-functional-theory Kohn-Sham orbitals to calculate the photodetachment cross sections and the anisotropy parameter β. The spherical average over all random molecular orientation is calculated analytically. A program which can handle both the Gaussian type orbital and the Slater type orbital has been coded. The testing calculations on Li{sup −}, C{sup −}, O{sup −}, F{sup −}, CH{sup −}, OH{sup −}, NH{sub 2}{sup −}, O{sub 2}{sup −}, and S{sub 2}{sup −} show that our method is an efficient way to calculate the photodetachment cross section and anisotropy parameter β for anions, thus promising for large systems.

  18. Monitoring the three-dimensional ionospheric electron density distribution using GPS observations over China

    Indian Academy of Sciences (India)

    Wen Debao; Yuan Yunbin; Ou Jikun

    2007-06-01

    In this paper, an IRI model assisted GPS-based Computerized Ionospheric Tomography (CIT) technique is developed to inverse the ionospheric electron density (IED) distribution over China. Essentially, an improved algebraic reconstruction technique (IART) is first proposed to reconstruct the ionospheric images with high resolution and high efficiency. A numerical experiment is used to validate the reliability of the method and its advantages to the classical algebraic reconstruction technique (ART). This is then used to reconstruct the IED images using the GPS data in China. The variations of the IED during magnetically quiet and disturbed days are reported and analyzed here. Reconstructed results during magnetically quiet days show some prominent ionospheric features such as the development of equatorial anomaly and the tilt of ionization crest. Meanwhile, ionospheric storm phase effects and disturbed features can also be revealed from the reconstructed IED image under storm conditions. Research shows that the positive storm phase effects usually happen in southern China, and the negative storm phase effects mainly occur in northern China. The equatorial anomaly crest moved to the north in the main phase of the storm. Ionosonde data recorded at Wuhan station provides the verification for the reliability of GPS-based CIT technique.

  19. SURFACE AREA, VOLUME, MASS, AND DENSITY DISTRIBUTIONS FOR SIZED BOMASS PARTICLES

    Energy Technology Data Exchange (ETDEWEB)

    Ramanathan Sampath

    2004-05-01

    This semi-annual technical progress report describes work performed at Morehouse College under DOE Grant No. DE-FC26-04NT42130 during the period July 01, 2004 to December 31, 2004 which covers the first six months of the project. Presently work is in progress to characterize surface area, volume, mass, and density distributions for sized biomass particles. During this reporting period, supply requests were processed and supplies including biomass test particles (hardwood sawdust AI14546) in the size range of 100-200 microns were obtained from a cofiring pilot plant research facility owned by Southern Company, Birmingham, AL. Morehouse has completed setting up of the gravimetric technique measurement system in the heat transfer laboratory, department of physics and dual degree engineering, Morehouse College. Simultaneously, REM, our subcontractor, has completed setting up of the electrodynamic balance (EDB) measurement system to characterize shape and mass for individual biomass particles. Testing of the gravimetric system, and calibration of the cameras and imaging systems using known sizes of polystyrene particles are in progress.

  20. Excessive magnetic field flux density distribution from overhead isolated powerline conductors due to neutral line current.

    Science.gov (United States)

    Netzer, Moshe

    2013-06-01

    Overhead isolated powerline conductors (hereinafter: "OIPLC") are the most compact form for distributing low voltage currents. From the known physics of magnetic field emission from 3-phase power lines, it is expected that excellent symmetry of the 120° shifted phase currents and where compact configuration of the 3-phase+neutral line exist, the phase current vectorial summation of the magnetic field flux density (MFFD) is expected to be extremely low. However, despite this estimation, an unexpectedly very high MFFD was found in at least three towns in Israel. This paper explains the reasons leading to high MFFD emissions from compact OIPLC and the proper technique to fix it. Analysis and measurement results had led to the failure hypothsis of neutral line poor connection design and poor grounding design of the HV-LV utility transformers. The paper elaborates on the low MFFD exposure level setup by the Israeli Environmental Protection Office which adopted a rather conservative precaution principal exposure level (2 mG averaged over 24 h).

  1. Cosmological Density Distribution Function from the Ellipsoidal Collapse Model in Real Space

    CERN Document Server

    Ohta, Y; Taruya, A; Ohta, Yasuhiro; Kayo, Issha; Taruya, Atsushi

    2004-01-01

    We calculate the one-point probability distribution function (PDF) for cosmic density in non-linear regime of the gravitational evolution. Under the local approximation that the evolution of cosmic fluid fields can be characterized by the Lagrangian local dynamics with finite degrees of freedom, the analytic expressions of PDF are derived taking account of the smoothing effect. The validity and the usefulness of the local approximation are then discussed comparing those results with N-body simulations in a Gaussian initial condition. Adopting the ellipsoidal collapse model (ECM) and the spherical collapse model (SCM) as Lagrangian local dynamics, we found that the PDFs from the local approximation excellently match the simulation results in the case of the cold dark matter initial spectrum. As for the scale-free initial spectra given by $P(k)\\propto k^n$, N-body result suffers from spurious numerical effects, which prevent us to give a detailed comparison. Nevertheless, at the quality of N-body data, the mode...

  2. Number density distribution of solvent molecules on a substrate: a transform theory for atomic force microscopy.

    Science.gov (United States)

    Amano, Ken-Ichi; Liang, Yunfeng; Miyazawa, Keisuke; Kobayashi, Kazuya; Hashimoto, Kota; Fukami, Kazuhiro; Nishi, Naoya; Sakka, Tetsuo; Onishi, Hiroshi; Fukuma, Takeshi

    2016-06-21

    Atomic force microscopy (AFM) in liquids can measure a force curve between a probe and a buried substrate. The shape of the measured force curve is related to hydration structure on the substrate. However, until now, there has been no practical theory that can transform the force curve into the hydration structure, because treatment of the liquid confined between the probe and the substrate is a difficult problem. Here, we propose a robust and practical transform theory, which can generate the number density distribution of solvent molecules on a substrate from the force curve. As an example, we analyzed a force curve measured by using our high-resolution AFM with a newly fabricated ultrashort cantilever. It is demonstrated that the hydration structure on muscovite mica (001) surface can be reproduced from the force curve by using the transform theory. The transform theory will enhance AFM's ability and support structural analyses of solid/liquid interfaces. By using the transform theory, the effective diameter of a real probe apex is also obtained. This result will be important for designing a model probe of molecular scale simulations.

  3. Number Density Distribution of Small Particles around a Large Particle: Structural Analysis of a Colloidal Suspension.

    Science.gov (United States)

    Amano, Ken-Ichi; Iwaki, Mitsuhiro; Hashimoto, Kota; Fukami, Kazuhiro; Nishi, Naoya; Takahashi, Ohgi; Sakka, Tetsuo

    2016-10-11

    Some colloidal suspensions contain two types of particles-small and large particles-to improve the lubricating ability, light absorptivity, and so forth. Structural and chemical analyses of such colloidal suspensions are often performed to understand their properties. In a structural analysis study, the observation of the number density distribution of small particles around a large particle (gLS) is difficult because these particles are randomly moving within the colloidal suspension by Brownian motion. We obtain gLS using the data from a line optical tweezer (LOT) that can measure the potential of mean force between two large colloidal particles (ΦLL). We propose a theory that transforms ΦLL into gLS. The transform theory is explained in detail and tested. We demonstrate for the first time that LOT can be used for the structural analysis of a colloidal suspension. LOT combined with the transform theory will facilitate structural analyses of the colloidal suspensions, which is important for both understanding colloidal properties and developing colloidal products.

  4. The Distribution of Mass Surface Densities in a High-Mass Protocluster

    CERN Document Server

    Lim, Wanggi; Kainulainen, Jouni; Ma, Bo; Butler, Micheal J

    2016-01-01

    We study the probability distribution function (PDF) of mass surface densities, $\\Sigma$, of infrared dark cloud (IRDC) G028.37+00.07 and its surrounding giant molecular cloud. This PDF constrains the physical processes, such as turbulence, magnetic fields and self-gravity, that are expected to be controlling cloud structure and star formation activity. The chosen IRDC is of particular interest since it has almost 100,000 solar masses within a radius of 8 parsecs, making it one of the most massive, dense molecular structures known and is thus a potential site for the formation of a "super star cluster." We study $\\Sigma$ in two ways. First, we use a combination of NIR and MIR extinction maps that are able to probe the bulk of the cloud structure up to $\\Sigma\\sim1\\:{\\rm{g\\:cm}^{-2}}\\:$($A_V\\simeq200$~mag). Second, we study the FIR and sub-mm dust continuum emission from the cloud utilizing Herschel PACS and SPIRE images and paying careful attention to the effects of foreground and background contamination. We...

  5. The Milky Way Hot Baryons and their Peculiar Density Distribution: a Relic of Nuclear Activity

    CERN Document Server

    Nicastro, F; Krongold, Y; Mathur, S; Elvis, M

    2016-01-01

    We know that our Galaxy is permeated by tenuous, hot, metal-rich gas. However much remains unknown about its origin, the portion of the Galaxy that it permeates, its total mass, as any role it may play in regulating activity in the Galaxy. In a Letter currently in the press with the ApJ, we show that this hot gas permeates both the disk of the Galaxy and a large spherical volume, centered on the Galactic nucleus, and extending out to distances of at least 60-200 kpc from the center. This gas displays a peculiar density distribution that peaks about 6 kpc from the Galaxy's center, likely witnessing a period of strong activity of the central super-massive black hole of the Milky Way that occurred 6 Myrs ago. With our study we are also able to update the total baryonic mass of the Galaxy to Mb = (0.8-4)x1e11 Solar Masses, sufficient to close the Galaxy's baryon census.

  6. Automatic measurement of contrast bolus distribution in carotid arteries using a C-arm angiography system to support interventional perfusion imaging

    Science.gov (United States)

    Fieselmann, Andreas; Ganguly, Arundhuti; Yu, Deuerling-Zheng; Boese, Jan; Hornegger, Joachim; Fahrig, Rebecca

    2011-03-01

    Brain perfusion CT using a C-arm angiography system capable of CT-like imaging could optimize patient treatment during stroke therapy procedures. For this application, an intra-arterial contrast bolus injection at the aortic arch could be used provided that the location of the injection catheter enables uniform distribution of the bolus into the two common carotid arteries (CCA). In this work, we present a novel method to support optimal injection catheter placement by providing additional quantitative information about the distribution of the contrast bolus into the CCAs. Our fully automatic method uses 2-D digital subtraction angiography (DSA) images following a test bolus injection. It segments both CCAs and computes the relative contrast distribution. We have tested the method in DSA data sets from 5 healthy pigs and our method achieved successful segmentation of both CCAs in all data sets. The results showed that the contrast is uniformly distributed (mean relative difference less or equal than 10%) if the injection location is properly chosen.

  7. 3D electron density distributions in the solar corona during solar minima: assessment for more realistic solar wind modeling

    CERN Document Server

    de Patoul, Judith; Riley, Pete

    2015-01-01

    Knowledge of the electron density distribution in the solar corona put constraints on the magnetic field configurations for coronal modeling and on initial conditions for solar wind modeling. We work with polarized SOHO/LASCO-C2 images from the last two recent minima of solar activity (1996-1997 and 2008-2010), devoid of coronal mass ejections. The goals are to derive the 4D electron density distributions in the corona by applying a newly developed time-dependent tomographic reconstruction method and to compare the results between the two solar minima and with two magnetohydrodynamic models. First, we confirm that the values of the density distribution in thermodynamic models are more realistic than in polytropic ones. The tomography provides more accurate distributions in the polar regions, and we find that the density in tomographic and thermodynamic solutions varies with the solar cycle in both polar and equatorial regions. Second, we find that the highest-density structures do not always correspond to the...

  8. Studies on remote sensing method of particle size and water density distribution in mists and clouds using laser radar techniques

    Science.gov (United States)

    Shimizu, H.; Kobayasi, T.; Inaba, H.

    1979-01-01

    A method of remote measurement of the particle size and density distribution of water droplets was developed. In this method, the size of droplets is measured from the Mie scattering parameter which is defined as the total-to-backscattering ratio of the laser beam. The water density distribution is obtained by a combination of the Mie scattering parameter and the extinction coefficient of the laser beam. This method was examined experimentally for the mist generated by an ultrasonic mist generator and applied to clouds containing rain and snow. Compared with the conventional sampling method, the present method has advantages of remote measurement capability and improvement in accuracy.

  9. Reexamining cluster radioactivity in trans-lead nuclei with consideration of specific density distributions in daughter nuclei and clusters

    Science.gov (United States)

    Qian, Yibin; Ren, Zhongzhou; Ni, Dongdong

    2016-08-01

    We further investigate the cluster emission from heavy nuclei beyond the lead region in the framework of the preformed cluster model. The refined cluster-core potential is constructed by the double-folding integral of the density distributions of the daughter nucleus and the emitted cluster, where the radius or the diffuseness parameter in the Fermi density distribution formula is determined according to the available experimental data on the charge radii and the neutron skin thickness. The Schrödinger equation of the cluster-daughter relative motion is then solved within the outgoing Coulomb wave-function boundary conditions to obtain the decay width. It is found that the present decay width of cluster emitters is clearly enhanced as compared to that in the previous case, which involved the fixed parametrization for the density distributions of daughter nuclei and clusters. Among the whole procedure, the nuclear deformation of clusters is also introduced into the calculations, and the degree of its influence on the final decay half-life is checked to some extent. Moreover, the effect from the bubble density distribution of clusters on the final decay width is carefully discussed by using the central depressed distribution.

  10. Bone mineral density measurements of the proximal femur from routine contrast-enhanced MDCT data sets correlate with dual-energy X-ray absorptiometry

    Energy Technology Data Exchange (ETDEWEB)

    Gruber, M. [Medical University of Vienna, Department of Radiology, Division of Neuroradiology and Musculoskeletal Radiology, Vienna (Austria); Bauer, J.S.; Dobritz, M.; Woertler, K.; Rummeny, E.J.; Baum, T. [Technische Universitaet Muenchen, Department of Radiology, Klinikum rechts der Isar, Munich (Germany); Beer, A.J. [Technische Universitaet Muenchen, Department of Nuclear Medicine, Munich (Germany); Wolf, P. [Technische Universitaet Muenchen, Institute for Medical Statistics and Epidemiology, Munich (Germany)

    2013-02-15

    To evaluate the utility of femoral bone mineral density (BMD) measurements in routine contrast-enhanced multi-detector computed tomography (ceMDCT) using dual-energy X-ray absorptiometry (DXA) as the reference standard. Forty-one patients (33 women, 8 men) underwent DXA measurement of the proximal femur. Subsequently, transverse sections of routine ceMDCT of these patients were used to measure BMD of the femoral head and femoral neck. The MDCT-to-DXA conversion equations for BMD and T-score were calculated using linear regression analysis. The conversion equations were applied to the MDCT data sets of 382 patients (120 women, 262 men) of whom 74 had osteoporotic fractures. A correlation coefficient of r = 0.84 (P < 0.05) was calculated for BMD{sub MDCT} values of the femoral head and DXA T-scores of the total proximal femur using the conversion equation T-score = 0.021 x BMD{sub MDCT} - 5.90. The correlation coefficient for the femoral neck was r = 0.79 (P < 0.05) with the conversion equation T-score = 0.016 x BMD{sub MDCT} - 4.28. Accordingly, converted T-scores for the femoral neck in patients with versus those without osteoporotic fractures were significantly different (female, -1.83 versus -1.47; male, -1.86 versus -1.47; P < 0.05). BMD measurements of the proximal femur were computed in routine contrast-enhanced MDCT and converted to DXA T-scores, which adequately differentiated patients with and without osteoporotic fractures. (orig.)

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

    CERN Document Server

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

    2015-01-01

    We report high resolution observations of the $^{12}$CO$(1\\rightarrow0)$ and $^{13}$CO$(1\\rightarrow0)$ molecular lines in the Carina Nebula and the Gum 31 region obtained with the 22-m Mopra telescope as part of the The Mopra Southern Galactic Plane CO Survey. We cover 8 deg$^2$ from $l = 285^{\\circ}$ to 290$^{\\circ}$, and from $b = -1.5^{\\circ}$ to +0.5$^{\\circ}$. 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 $6.3\\times\\ 10^{20}$ to $1.4\\times 10^{23}$ 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 log-normal function for a limited range of column densities. A high-column density tail is clearly evident for the gas column density dis...

  12. Research on lithospheric density distributions beneath North China Craton and its destruction mechanism by gravity and seismic observations

    Science.gov (United States)

    Wang, X.; Fang, J.; Hsu, H.

    2011-12-01

    North China Craton (NCC) has been a research hotspot for geoscientists all over the world. Partial North China Craton (NCC) has lost its lithospheric keel since Mesozoic. Researchers have reached a consensus on destruction of NCC' lithosphere, however, the destruction mechanism and dynamic processes still remain controversy. In this study, a three-dimensional density distribution of lithosphere beneath NCC is determined using gravity datum combined with P-wave travel times by sequential inversion method. After the analyses and discussions on our density results referred to other geophysical and geochemical researches and then gave our viewpoint about destruction mechanisms of NCC lithosphere from the standpoint of density distribution. A linear velocity-density relationship is used to achieve mutual transformations and constraints between density and velocity. As we know, the gravity anomalies measured on the ground surface are the integrated reflection of the interface undulations and underground density inhomogeneous. In order to invert the lithospheric density structures, we firstly separated the gravity effects of lithospheric density inhomogeneous by removing the effects of other contributions to the gravity field from the observed integrated gravity filed before density inversion. The method of Zhao et al.,(1994) is used for seismic tomography, while Algebraic Reconstruction Technique (ART) is applied in density inversion, which highly improved the calculation velocity compared to common least squares method. The inversion results indicate that, the lithospheric density beneath NCC is extremely inhomogeneous and its distributions are coherent with surface regional tectonics; Low density anomalies exist in lower crust beneath rift basins around Ordos block. High poisson' ratios are found in these regions (about 3.0), which may indicate partial melting occurred. Receive function studies prevailed thinned ( 8.2km/s) is also found in this region. The prominent

  13. Laboratory Studies of the Impact of Fish School Density and Individual Distribution on Acoustic Propagation and Scattering

    Science.gov (United States)

    2012-09-30

    obtained, all below resonance. Fig. 5. The 1-D acoustic resonator with live zebra fish (Danio rerio). Fig. 6. Preliminary measured...of one of the zebra fish used in the resonator measurements is shown. This data was processed to show bones in reddish/pink/white colors and the...DISTRIBUTION STATEMENT A. Approved for public release; distribution is unlimited. Laboratory Studies of the Impact of Fish School Density and

  14. Contrast Materials

    Science.gov (United States)

    ... Physician Resources Professions Site Index A-Z Contrast Materials What are contrast materials and how do they ... material? Pregnancy and contrast materials What are contrast materials and how do they work? Contrast materials, also ...

  15. Correlation between traffic density and particle size distribution in a street canyon and the dependence on wind direction

    Directory of Open Access Journals (Sweden)

    J. Voigtländer

    2006-05-01

    Full Text Available Combustion of fossil fuel in gasoline and diesel powered vehicles is a major source of aerosol particles in a city. In a street canyon, the number concentration of particles smaller than 300 nm in diameter, which can be inhaled and cause serious health effects, is dominated by particles originating from this source.

    In this study we measured both, particle number size distribution and traffic density continuously in a characteristic street canyon in Germany for a time period of 6 months. The street canyon with multistory buildings and 4 traffic lanes is very typical for larger cities. Thus, the measurements are also representative for many other street canyons. In contrast to previous studies, we measured and analyzed the particle number size distribution with high size resolution using a Twin Differential Mobility Analyzer (TDMPS. The measured size range was from 3 to 800 nm, separated into 40 size channels.

    Correlation coefficients between particle number concentration for integrated size ranges and traffic up to 0.5 counts were determined. Correlations were also calculated for each of the 40 size channels of the DMPS system, respectively. We found two maxima of the correlation coefficient for particles about 10 nm and in the size range 60–80 nm in diameter.

    Furthermore, correlations between traffic and particles in dependence of meteorological data were calculated. Relevant parameters were identified by a multiple regression method. In our experiment only wind parameters have influenced the particle number concentration significantly. Very high correlation coefficients (up to 0.85 could be observed in the lee side of the street canyon as well as particles in the range between 60 and 80 nm in diameter. These values are significantly higher than correlation coefficients for other wind directions and other particle sizes. A minimum was found in the luff side of the street. These findings are in good agreement

  16. Fish but Not Macroinvertebrates Promote Trophic Cascading Effects in High Density Submersed Plant Experimental Lake Food Webs in Two Contrasting Climate Regions

    Directory of Open Access Journals (Sweden)

    Carlos Iglesias

    2017-07-01

    Full Text Available Predators play a key role in the functioning of shallow lakes. Differences between the response of temperate and subtropical systems to fish predation have been proposed, but experimental evidence is scarce. To elucidate cascading effects produced by predators in contrasting climatic zones, we conducted a mesocosm experiment in three pairs of lakes in Uruguay and Denmark. We used two typical planktivorous-omnivorous fish species (Jenynsia multidentata + Cnesterodon decemmaculatus and Gasterosteus aculeatus + Perca fluviatilis and one littoral omnivorous-predatory macroinvertebrate (Palaemonetes argentinus and Gammarus lacustris, alone and combined, in numbers resembling natural densities. Fish predation on zooplankton increased phytoplankton biomass in both climate zones, whereas the effects of predatory macroinvertebrates on zooplankton and phytoplankton were not significant in either climate zone. Macroinvertebrates (that freely colonized the sampling devices were diminished by fish in both climate areas; however, periphyton biomass did not vary among treatments. Our experiments demonstrated that fish affected the structure of both planktonic and littoral herbivorous communities in both climate regions, with a visible positive cascading effect on phytoplankton biomass, but no effects on periphyton. Altogether, fish impacts appeared to be a strong driver of turbid water conditions in shallow lakes regardless of climatic zone by indirectly contributing to increasing phytoplankton biomass.

  17. Current density distributions and sputter marks in electron cyclotron resonance ion sources.

    Science.gov (United States)

    Panitzsch, Lauri; Peleikis, Thies; Böttcher, Stephan; Stalder, Michael; Wimmer-Schweingruber, Robert F

    2013-01-01

    Most electron cyclotron resonance ion sources use hexapolar magnetic fields for the radial confinement of the plasma. The geometry of this magnetic structure is then--induced by charged particles--mapped onto the inner side of the plasma electrode via sputtering and deposition. The resulting structures usually show two different patterns: a sharp triangular one in the central region which in some cases is even sputtered deep into the material (referred to as thin groove or sharp structure), and a blurred but still triangular-like one in the surroundings (referred to as broad halo). Therefore, both patterns seem to have different sources. To investigate their origins we replaced the standard plasma electrode by a custom-built plasma electrode acting as a planar, multi-segment current-detector. For different biased disc voltages, detector positions, and source biases (referred to the detector) we measured the electrical current density distributions in the plane of the plasma electrode. The results show a strong and sharply confined electron population with triangular shape surrounded by less intense and spatially less confined ions. Observed sputter- and deposition marks are related to the analysis of the results. Our measurements suggest that the two different patterns (thin and broad) indeed originate from different particle populations. The thin structures seem to be caused by the hot electron population while the broad marks seem to stem from the medium to highly charged ions. In this paper we present our measurements together with theoretical considerations and substantiate the conclusions drawn above. The validity of these results is also discussed.

  18. Distribution and correlates of non-high-density lipoprotein cholesterol and triglycerides in Lebanese school children.

    Science.gov (United States)

    Gannagé-Yared, Marie-Hélène; Farah, Vanessa; Chahine, Elise; Balech, Nicole; Ibrahim, Toni; Asmar, Nadia; Barakett-Hamadé, Vanda; Jambart, Selim

    2016-01-01

    The prevalence of dyslipidelmia in pediatric Middle-Eastern populations is unknown. Our study aims to investigate the distribution and correlates of non-high-density lipoprotein cholesterol (non-HDL-C) and triglycerides among Lebanese school children. A total of 969 subjects aged 8-18 years were included in the study (505 boys and 464 girls). Recruitment was done from 10 schools located in the Great Beirut and Mount-Lebanon areas. Non-fasting total cholesterol, triglycerides, and HDL-cholesterol (HDL-C) were measured. Non-HDL-C was calculated. Schools were categorized into 3 socioeconomic statuses (SESs; low, middle, and high). In the overall population, the prevalence of high non-HDL-C (>3.8 mmol/L), very high non-HDL-C (>4.9 mmol/L), and high triglycerides (>1.5 mmol/l) are respectively 9.2%, 1.24%, and 26.6%. There is no significant gender difference for non-HDL-C or triglycerides. Non-HDL-C and triglycerides are inversely correlated with age in girls (P triglycerides are higher in children from lower SES schools. After adjustment for age and body mass index (BMI), testosterone is inversely associated with triglycerides in boys (P triglycerides are independently associated with BMI and schools' SES in both girls and boys. This study confirms, in our population, the association between obesity and both high non-HDL-C and triglycerides, and between high triglycerides and low SES. Copyright © 2016 National Lipid Association. Published by Elsevier Inc. All rights reserved.

  19. A method for extracting multi-organ from four-phase contrasted CT images based on CT value distribution estimation using EM-algorithm

    Science.gov (United States)

    Sakashita, Makiko; Kitasaka, Takayuki; Mori, Kensaku; Suenaga, Yasuhito; Nawano, Shigeru

    2007-03-01

    This paper presents a method for extracting multi-organs from four-phase contrasted CT images taken at different contrast timings (non-contrast, early, portal, and late phases). First, we apply a median filter to each CT image and align four-phase CT images by performing non-rigid volumetric image registration. Then, a three-dimensional joint histogram of CT values is computed from three-phase (early-, portal-, and late-) CT images. We assume that this histogram is a mixture of normal distributions corresponding to the liver, spleen, kidney, vein, artery, muscle, and bone regions. The EM algorithm is employed to estimate each normal distribution. Organ labels are assigned to each voxel using the mahalanobis distance measure. Connected component analysis is applied to correct the shape of each organ region. After that, the pancreas region is extracted from non-contrasted CT images in which other extracted organs and vessel regions are excluded. The EM algorithm is also employed for estimating the distribution of CT values inside the pancreas. We applied this method to seven cases of four-phase CT images. Extraction results show that the proposed method extracted multi-organs satisfactorily.

  20. Dust extinction bias in the column density distribution of gamma-ray bursts; high column density, low redshift GRBs are more heavily obscured

    CERN Document Server

    Watson, Darach

    2012-01-01

    The afterglows of gamma-ray bursts (GRBs) have more soft X-ray absorption than expected from the foreground gas column in the Galaxy. While the redshift of the absorption can in general not be constrained from current X-ray observations, it has been assumed that the absorption is due to metals in the host galaxy of the GRB. The large sample of X-ray afterglows and redshifts now available allows the construction of statistically meaningful distributions of the metal column densities. We construct such a sample and show, as found in previous studies, that the typical absorbing column density (N_HX) increases substantially with redshift, with few high column density objects found at low to moderate redshifts. We show, however, that when highly extinguished bursts are included in the sample, using redshifts from their host galaxies, high column density sources are also found at low to moderate redshift. We infer from individual objects in the sample and from observations of blazars, that the increase in column de...

  1. Excitation temperature and electron number density distributions experienced by analyte species in an inductively coupled argon plasma

    Energy Technology Data Exchange (ETDEWEB)

    Kalnicky, D.J.

    1977-02-01

    Spatially resolved, radial excitation temperatures and radial electron number density distributions experienced by analyte species in the observation zone of 15 to 25 mm above the load coil of a toroidally shaped, inductively coupled argon plasma (ICP) are presented and related to the analytical performance of these plasmas. A comparison of radial temperatures measured with support gas (Ar I) lines and with a typical analyte thermometric species (Fe I) at 15 mm above the load coil is given. Radial (Fe I) excitation temperatures obtained at three observation heights (15, 20, and 25 mm) are compared for aerosol carrier gas flows of 1.0 l/min and 1.3 l/min. The addition of a large amount of an easily ionized element (6900 ..mu..g Na/ml) did not significantly change Fe I excitation temperature distributions at the respective aerosol carrier gas flows and observation heights. A comparison of radial electron number density distributions measured by the Saha-Eggert ionization and Stark broadening methods is given for an observation height of 15 mm above the load coil. The differences between the electron number density values obtained by these methods is discussed. The effect of addition of 6900 ..mu..g Na/ml on Saha-Eggert electron density distributions at these observation heights is also discussed. The computer programs employed in this investigation and discussions of the computational procedures incorporated in these programs are given.

  2. The influence of interpolation and station network density on the distributions and trends of climate variables in gridded daily data

    NARCIS (Netherlands)

    Hofstra, N.; New, M.; McSweeney, C.

    2010-01-01

    We study the influence of station network density on the distributions and trends in indices of area-average daily precipitation and temperature in the E-OBS high resolution gridded dataset of daily climate over Europe, which was produced with the primary purpose of Regional Climate Model evaluation

  3. Density Functional Theory Based on the Electron Distribution on the Energy Coordinate

    CERN Document Server

    Takahashi, Hideaki

    2016-01-01

    We introduced a new electron density n({\\epsilon}) by projecting the spatial electron density n(r) onto the energy coordinate {\\epsilon} defined with the external potential \\upsion (r) of interest. Then, a density functional theory (DFT) was formulated, where n({\\epsilon}) serves as a fundamental variable for the electronic energy. It was demonstrated that the Kohn-Sham equation can also be adapted to the DFT that employs the density n({\\epsilon}) as an argument to the exchange energy functional. An important attribute of the energy density is that it involves the spatially non-local population of the spin-adapted density n(r) at the bond dissociation. By taking advantage of this property we developed a prototype of the static correlation functional employing no empirical parameters, which realized a reasonable dissociation curve for H2 molecule.

  4. Planting densities and bird and rodent absence affect size distributions of four dicots in synthetic tallgrass communities.

    Science.gov (United States)

    Martínez-Garza, Cristina; Saha, Sonali; Torres, Veronica; Brown, Joel S; Howe, Henry F

    2004-05-01

    Variability in the size distributions of populations is usually studied in monocultures or in mixed plantings of two species. Variability of size distributions of populations in more complex communities has been neglected. The effects of seeding density (35 or 350 seeds/species/m2) and presence of small vertebrates on the variability of size distributions were studied for a total of 1,920 individuals of 4 species in replicated synthetic communities of 18 species in northern Illinois. End-of season height and above-ground biomass were measured for prairie perennials Dalea purpurea (purple prairie clover), Echinacea purpurea (purple coneflower), Desmanthus illinoensis (Illinois bundleflower) and Heliopsis helianthoides (early sunflower). Variability in biomass distribution of the four target species was twice as great at low than at high densities when small vertebrates were excluded. Our results suggest that inter- and intraspecific competition may affect all individuals more under high-density conditions, thereby reducing the variability in their biomass distributions within this community. This result, a consequence of plant-plant interaction, is obscured when small birds or mammals are present, presumably because either or both add variance that overwhelms the pattern.

  5. The use of airborne radar reflectometry to establish snow/firn density distribution on Devon Ice Cap, Canadian Arctic: A path to understanding complex heterogeneous internal layering patterns

    Science.gov (United States)

    Rutishauser, A.; Grima, C.; Sharp, M. J.; Blankenship, D. D.; Young, D. A.; Dowdeswell, J. A.

    2014-12-01

    The internal layer stratigraphy of polar ice sheets revealed by airborne radio-echo sounding (RES) contains valuable information about past ice sheet mass balance and dynamics. Internal layers in the Antarctic and Greenland ice sheets are considered to be isochrones and are continuous over several hundreds of kilometres. In contrast, internal layers in Canadian Arctic ice caps appear to be very heterogeneous and fragmentary, consisting of highly discontinuous layers that can be traced over only a few to several tens of kilometres. Internal layers most likely relate to former ice surfaces (the upper few meters of snow/firn), the properties which are directly influenced by atmospheric conditions including the air temperature, precipitation rate, and prevailing wind pattern. We hypothesize that the heterogeneous and complex nature of layers in the Canadian Arctic results from highly variable snow and firn conditions at the surface. Characterizing surface properties such as variations in the snow/firn density from dry to wet snow/firn, as well as high-density shallow ice layers and lenses of refrozen water can help to elucidate the complex internal layer pattern in the Canadian Arctic ice caps. Estimates of the snow/firn surface density and roughness can be derived from reflectance and scattering information using the surface radar returns from RES measurements. Here we present estimates of the surface snow/firn density distribution over Devon Ice Cap in the Canadian Arctic derived by the Radar Statistical Reconnaissance (RSR) methodology (Grima et al., 2014, Planetary & Space Sciences) using data collected by recent airborne radar sounding programs. The RSR generates estimates of the statistical distribution of surface echo amplitudes over defined areas along a survey transect. The derived distributions are best-fitted with a theoretical stochastic envelope, parameterized with the signal reflectance and scattering, in order to separate those two components. Finally

  6. Polarization curve measurements combined with potential probe sensing for determining current density distribution in vanadium redox-flow batteries

    Science.gov (United States)

    Becker, Maik; Bredemeyer, Niels; Tenhumberg, Nils; Turek, Thomas

    2016-03-01

    Potential probes are applied to vanadium redox-flow batteries for determination of effective felt resistance and current density distribution. During the measurement of polarization curves in 100 cm2 cells with different carbon felt compression rates, alternating potential steps at cell voltages between 0.6 V and 2.0 V are applied. Polarization curves are recorded at different flow rates and states of charge of the battery. Increasing compression rates lead to lower effective felt resistances and a more uniform resistance distribution. Low flow rates at high or low state of charge result in non-linear current density distribution with high gradients, while high flow rates give rise to a nearly linear behavior.

  7. Polar observations of electron density distribution in the Earth’s magnetosphere. 1. Statistical results

    Directory of Open Access Journals (Sweden)

    H. Laakso

    Full Text Available Forty-five months of continuous spacecraft potential measurements from the Polar satellite are used to study the average electron density in the magnetosphere and its dependence on geomagnetic activity and season. These measurements offer a straightforward, passive method for monitoring the total electron density in the magnetosphere, with high time resolution and a density range that covers many orders of magnitude. Within its polar orbit with geocentric perigee and apogee of 1.8 and 9.0 RE, respectively, Polar encounters a number of key plasma regions of the magnetosphere, such as the polar cap, cusp, plasmapause, and auroral zone that are clearly identified in the statistical averages presented here. The polar cap density behaves quite systematically with season. At low distance (~2 RE, the density is an order of magnitude higher in summer than in winter; at high distance (>4 RE, the variation is somewhat smaller. Along a magnetic field line the density declines between these two altitudes by a factor of 10–20 in winter and by a factor of 200–1000 in summer. A likely explanation for the large gradient in the summer is a high density of heavy ions that are gravitationally bound in the low-altitude polar cap. The geomagnetic effects are also significant in the polar cap, with the average density being an order of magnitude larger for high Kp; for an individual case, the polar cap density may increase even more dramatically. The plasma density in the cusp is controlled primarily by the solar wind variables, but nevertheless, they can be characterized to some extent in terms of the Kp index. We also investigate the local time variation of the average density at the geosynchronous distance that appears to be in accordance with previous geostationary observations. The average density decreases with increasing Kp at all MLT sectors

  8. Current Density Distribution on the Perimeter of Waveguide Exciter Cylindrical Vibrator Conductor

    OpenAIRE

    Zakharia, Yosyp

    2010-01-01

    On ground of electrodynamic analysis the surface current distribution nonuniformity on the perimeter of waveguide-exciter cylindrical conductor is found. Considerable influence of current distribution nonuniformity on exciter input reactance is established. It is also showed, that the current distribution on the vibrator perimeter, for conductor radius no greater then 0,07 of waveguide cross section breadth, approximately uniform is.

  9. The law of distribution of light beam direction fluctuations in telescopes. [normal density functions

    Science.gov (United States)

    Divinskiy, M. L.; Kolchinskiy, I. G.

    1974-01-01

    The distribution of deviations from mean star trail directions was studied on the basis of 105 star trails. It was found that about 93% of the trails yield a distribution in agreement with the normal law. About 4% of the star trails agree with the Charlier distribution.

  10. Development of bulk density, total C distribution and OC saturation in fine mineral fractions during paddy soil evolution

    Science.gov (United States)

    Wissing, Livia; Kölbl, Angelika; Cao, Zhi-Hong; Kögel-Knabner, Ingrid

    2010-05-01

    Paddy soils are described as important accumulator for OM (Zhang and He, 2004). In southeast China, paddy soils have the second highest OM stocks (Zhao et al, 1997) and thus a large proportion of the terrestrial carbon is conserved in wetland rice soils. The paddy soil management is believed to be favorable for accumulation of organic matter, as its content in paddy soils is statistically higher than that of non-paddy soils (Cai, 1996). However, the mechanism of OM storage and the development of OM distribution during paddy soil evolution is largely unknown. The aim of the project is to identify the role of organo-mineral complexes for the stabilization of organic carbon during management-induced paddy soil formation in a chronosequence ranging from 50 to 2000 years of paddy soil use. The soil samples were analysed for bulk density, total organic carbon (TOC) and total inorganic carbon (TIC) concentrations of bulk soils and the concentration of organic carbon as well as the organic carbon stocks of physical soil fractions. First results indicate distinctly different depth distributions between paddy and non-paddy (control) sites. The paddy soils are characterized by relatively low bulk densities in the puddled layer (between 0.9 and 1.3 g cm-3) and high values in the plough pan (1.4 to 1.6 g cm-3) and the non-paddy soils by relatively homogeneous values throughout the profiles (1.3 to 1.4 g cm-3). In contrast to the carbonate-rich non-paddy sites, we found a significant loss of carbonates during paddy soil formation, resulting in decalcification of the upper 20 cm after 100 yr of paddy soil use, and decalcification of the total soil profile in 700, 1000 and 2000 yr old paddy soils. The calculation of the organic carbon stocks of each horizon indicate that paddy sites always have higher values in topsoils compared to non-paddy sites, and show increasing values with increasing soil age. The capacity of fine mineral fractions to preserve OC was calculated according to

  11. The Differential Entropy of the Joint Distribution of Eigenvalues of Random Density Matrices

    Directory of Open Access Journals (Sweden)

    Laizhen Luo

    2016-09-01

    Full Text Available We derive exactly the differential entropy of the joint distribution of eigenvalues of Wishart matrices. Based on this result, we calculate the differential entropy of the joint distribution of eigenvalues of random mixed quantum states, which is induced by taking the partial trace over the environment of Haar-distributed bipartite pure states. Then, we investigate the differential entropy of the joint distribution of diagonal entries of random mixed quantum states. Finally, we investigate the relative entropy between these two kinds of distributions.

  12. Contrast in manganese nodule distribution on either side of 79~'E fracture zone in central Indian Basin

    Digital Repository Service at National Institute of Oceanography (India)

    Kodagali, V.N.

    Seabed topography is one of the prime factors in controlling the distribution of manganese nodules. Study of the nodule abundance on either side of the 79~'E fracture zone in the Central Indian Basin (idenfitied from multibeam bathymetric data...

  13. A Study on Effects on Current Density Distribution, Inductance Gradient, and Contact Force by Variation of Armature and Rail Structure

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Bok Ki [Kwangwoon University, Seoul (Korea)

    2001-02-01

    The distribution of current in the conductors influenced by armature geometry and velocity is an important parameter for determining performance of an electromagnetic launcher(EML). The electric current in the early launching stage tends to flow on the outer surface of the conductors, resulting in very high local electric current density. However, the tendency for current to concentrate on the surface is driven by the velocity skin effect later in launching stage. The high current density produces high local heating and, consequently, increases armature wear which causes several defects on EML system. This paper investigates the effect of rail/armature geometry on current density distribution, launcher inductance gradient (L'), and contact force. Three geometrical parameters are used to characterize the railgun system. These are the ratio of contact length, relative position of contact leading edge to root trailing edge, and the ratio of rail overhang to the rail height. The distribution of current density, L',contact force between various configurations of the armature and the rail are analyzed and compared by using the EMAP3D program. (author). 6 refs., 9 figs., 3 tabs.

  14. Floating macro-litter along the Mediterranean French coast: Composition, density, distribution and overlap with cetacean range.

    Science.gov (United States)

    Di-Méglio, Nathalie; Campana, Ilaria

    2017-02-23

    This study investigated the composition, density and distribution of floating macro-litter along the Liguro-Provençal basin with respect to cetaceans presence. Survey transects were performed in summer between 2006 and 2015 from sailing vessels with simultaneous cetaceans observations. During 5171km travelled, 1993 floating items were recorded, widespread in the whole study area. Plastics was the predominant category, with bags/packaging always representing >45% of total items. Overall mean density (14.98 items/km(2)) was stable with significant increase reported only in 2010-2011; monthly analysis showed lower litter densities in July-September, suggesting possible seasonal patterns. Kernel density estimation for plastics revealed ubiquitous distribution rather than high accumulation areas, mainly due to the circulation dynamics of this area. The presence range of cetaceans (259 sightings, 6 species) corresponded by ~50% with plastic distribution, indicating high potential of interaction, especially in the eastern part of the area, but effective risks for marine species might be underrepresented.

  15. Perfusion parameters of dynamic contrast-enhanced magnetic resonance imaging in patients with rectal cancer: Correlation with microvascular density and vascular endothelial growth factor expression

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Yeo Eun [Dept. of Radiology, Seoul Medical Center, Seoul (Korea, Republic of); Lim, Joon Seok; Kim, Myeong Jin; Kim, Ki Whang; Choi, Jun Jeong [Yonsei University Health System, Seoul (Korea, Republic of); Kim, Dae Hong [Molecular Imaging and Therapy Branch, National Cancer Center, Goyang (Korea, Republic of); Myoung, Sung Min [Dept. of Medical Information, Jungwon University, Goesan (Korea, Republic of)

    2013-12-15

    To determine whether quantitative perfusion parameters of dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) correlate with immunohistochemical markers of angiogenesis in rectal cancer. Preoperative DCE-MRI was performed in 63 patients with rectal adenocarcinoma. Transendothelial volume transfer (K{sup trans}) and fractional volume of the extravascular-extracellular space (Ve) were measured by Interactive Data Language software in rectal cancer. After surgery, microvessel density (MVD) and vascular endothelial growth factor (VEGF) expression scores were determined using immunohistochemical staining of rectal cancer specimens. Perfusion parameters (K{sup trans}, Ve) of DCE-MRI in rectal cancer were found to be correlated with MVD and VEGF expression scores by Spearman's rank coefficient analysis. T stage and N stage (negative or positive) were correlated with perfusion parameters and MVD. Significant correlation was not found between any DCE-MRI perfusion parameters and MVD (rs = -0.056 and p 0.662 for K{sup trans}; rs = -0.103 and p = 0.416 for Ve), or between any DCE-MRI perfusion parameters and the VEGF expression score (rs = -0.042, p 0.741 for K{sup trans}; r = 0.086, p = 0.497 for Ve) in rectal cancer. TN stage showed no significant correlation with perfusion parameters or MVD (p > 0.05 for all). DCE-MRI perfusion parameters, K{sup trans} and Ve, correlated poorly with MVD and VEGF expression scores in rectal cancer, suggesting that these parameters do not simply denote static histological vascular properties.

  16. Study of Different Tissue Density Effects on the Dose Distribution of a 103Pd Brachytherapy Source Model MED3633

    Directory of Open Access Journals (Sweden)

    Ali Asghar Mowlavi

    2010-09-01

    Full Text Available Introduction: Clinical application of encapsulated radioactive brachytherapy sources has a major role in cancer treatment. In the present research, the effects of different tissue densities on the dose distribution of a 103Pd brachytherapy source in a spherical phantom of 50 cm radius have been studied. Material and Methods: As is well known, absorbed dose in tissue depends to its density, but this difference is not clear in measurements. Therefore, we applied the MCNP code to evaluate the effect of density on the dose distribution. 103Pd brachytherapy sources are used to treat prostate, breast and other cancers. Results: Absorbed dose has been calculated and presented around a source placed in the center of the phantom for different tissue densities. Also, we derived anisotropy and radial dose functions and compared our Monte Carlo results with experimental results of Rivard and Li et al. for F(1, θ and g(r in 1.040 g/cm3 tissue. Conclusion: The results of this study show that relative dose variations around the source center are very considerable at different densities, because of the presence of a photoabsorber (Au-Cu alloy in the source core. Dose variation exceeds 80% at the point (Z = 2.4 mm, Y = 0 mm. Computed values of anisotropy and radial dose functions are in good agreement with the experimental results of Rivard and Li et al.

  17. Electron density distribution and bonding in ZnSe and PbSe using maximum entropy method (MEM)

    Indian Academy of Sciences (India)

    K S Syed Ali; R Saravanan; S Israel; R K Rajaram

    2006-04-01

    The study of electronic structure of materials and bonding is an important part of material characterization. The maximum entropy method (MEM) is a powerful tool for deriving accurate electron density distribution in crystalline materials using experimental data. In this paper, the attention is focused on producing electron density distribution of ZnSe and PbSe using JCPDS X-ray powder diffraction data. The covalent/ionic nature of the bonding and the interaction between the atoms are clearly revealed by the MEM maps. The mid bond electron densities between atoms in these systems are found to be 0.544 e/Å3 and 0.261 e/Å3, respectively for ZnSe and PbSe. The bonding in these two systems has been studied using two-dimensional MEM electron density maps on the (100) and (110) planes, and the one-dimensional electron density profiles along [100], [110] and [111] directions. The thermal parameters of the individual atoms have also been reported in this work. The algorithm of the MEM procedure has been presented.

  18. The Rapidity Density Distributions and Longitudinal Expansion Dynamics of Identified Pions from the STAR Beam Energy Scan

    Science.gov (United States)

    Flores, Christopher E.

    2016-12-01

    The Beam Energy Scan (BES) at the Relativistic Heavy-Ion Collider was proposed to characterize the properties of the medium produced in heavy-ion interactions over a broad range of baryon chemical potential. The aptitude of the STAR detector for mid-rapidity measurements has previously been leveraged to measure identified particle yields and spectra to extract bulk properties for the BES energies for | y | ≤ 0.1. However, to extract information on expansion dynamics and full phase space particle production, it is necessary to study identified particle rapidity density distributions. We present the first rapidity density distributions of identified pions from Au+Au collisions at √{sNN} = 7.7 , 11.5, and 19.6 GeV from the BES program as measured by the STAR detector. We use these distributions to obtain the full phase space yields of the pions to provide additional information of the system's chemistry. Further, we report the width of the rapidity density distributions compared to the width expected from Landau hydrodynamics. Finally, we interpret the results as a function of collision energy and discuss them in the context of previous energy scans done at the AGS and SPS.

  19. Direct asymmetry measurement of temperature and density spatial distributions in inertial confinement fusion plasmas from pinhole space-resolved spectra

    CERN Document Server

    Nagayama, T; Florido, R; Mayes, D; Tommasini, R; Koch, J A; Delettrez, J A; Regan, S P; Smalyuk, V A

    2014-01-01

    Two-dimensional space-resolved temperature and density images of an inertial confinement fusion (ICF) implosion core have been diagnosed for the first time. Argon-doped, direct-drive ICF experiments were performed at the Omega Laser Facility and a collection of two-dimensional space-resolved spectra were obtained from an array of gated, spectrally resolved pinhole images recorded by a multi-monochromatic x-ray imager. Detailed spectral analysis revealed asymmetries of the core not just in shape and size but in the temperature and density spatial distributions, thus characterizing the core with an unprecedented level of detail.

  20. Testing the influence of rain gauges' density and distribution on hydrological modeling results, a case study of Xiangjiang River basin

    Science.gov (United States)

    Xu, H.

    2012-04-01

    Hydrological models are important tools for flood forecasting, for the assessment of water resources under current and a changing climate. However, the accuracy of hydrological models is limited by many factors, of which, the most important one is perhaps the errors in the input data. For the lumped and semi-distributed hydrological models, the main input is the estimated areal precipitation, and the quality of which is very much dependent on the spatial distribution and density of rain gauges. Many researches have been reported on the development, calibration and validation of hydrological models, however, the influence of the precipitation gauges density and network distribution on the modeling results has received much less attention. One of the reasons for the limited study of this important issue is it needs a catchment with sufficient size, wide diversity of topography and climate, and dense raingauges with long and good quality data. In this study, a famous and widely used hydrological model, the Xinanjiang Model was applied to Xiangjiang River basin to examine the influence of rain gauges' density and distribution on the performance of the model in simulating the streamflow and other water balance components, like actual evapotranspiration and soil moisture content. The Xiangjiang River basin, one of the most important economic belts in Hunan Province, China and the primary inflow basin of Dongting Lake - China's second largest freshwater lake, has dense rain gauge network with long and high quality data. To perform the study, 18 different input data scenarios representing different density and distribution situations are used as input to the Xinanjiang model. The influences of different input scenarios on the modeling results as measured by Nash-Sutcliffe coefficient, relative bias, and peak errors are compared, and guidance for optimal planning of rain gauges is proposed. Keywords: Xinanjiang Model; Xiangjiang River basin; precipitation gauges network

  1. Unfolding the laws of star formation: the density distribution of molecular clouds.

    Science.gov (United States)

    Kainulainen, Jouni; Federrath, Christoph; Henning, Thomas

    2014-04-11

    The formation of stars shapes the structure and evolution of entire galaxies. The rate and efficiency of this process are affected substantially by the density structure of the individual molecular clouds in which stars form. The most fundamental measure of this structure is the probability density function of volume densities (ρ-PDF), which determines the star formation rates predicted with analytical models. This function has remained unconstrained by observations. We have developed an approach to quantify ρ-PDFs and establish their relation to star formation. The ρ-PDFs instigate a density threshold of star formation and allow us to quantify the star formation efficiency above it. The ρ-PDFs provide new constraints for star formation theories and correctly predict several key properties of the star-forming interstellar medium.

  2. Evolution of Quantum Phase Space Distribution: a Trajectory-Density Approach

    Institute of Scientific and Technical Information of China (English)

    ZHANG Xue-Feng; ZHENG Yu-Jun

    2009-01-01

    The trajectory-density method of a quantum system is developed by using local Koopman and Frobenius-Perron operators. We propose a new scheme of approximation from two sets of trajectory-density mixed equations. By examining the local generation and termination of trajectories, we show how they can be adopted to the propagation of negative values of the Wigner function even if it starts off positive everywhere.

  3. The study on the effect of pattern density distribution on the STI CMP process

    Science.gov (United States)

    Sub, Yoon Myung; Hian, Bernard Yap Tzen; Fong, Lee It; Anak, Philip Menit; Minhar, Ariffin Bin; Wui, Tan Kim; Kim, Melvin Phua Twang; Jin, Looi Hui; Min, Foo Thai

    2017-08-01

    The effects of pattern density on CMP characteristics were investigated using specially designed wafer for the characterization of pattern-dependencies in STI CMP [1]. The purpose of this study is to investigate the planarization behavior based on a direct STI CMP used in cerium (CeO2) based slurry system in terms of pattern density variation. The minimal design rule (DR) of 180nm generation technology node was adopted for the mask layout. The mask was successfully applied for evaluation of a cerium (CeO2) abrasive based direct STI CMP process. In this study, we described a planarization behavior of the loading-effects of pattern density variation which were characterized with layout pattern density and pitch variations using masks mentioned above. Furthermore, the characterizing pattern dependent on the variations of the dimensions and spacing features, in thickness remaining after CMP, were analyzed and evaluated. The goal was to establish a concept of library method which will be used to generate design rules reducing the probability of CMP-related failures. Details of the characterization were measured in various layouts showing different pattern density ranges and the effects of pattern density on STI CMP has been discussed in this paper.

  4. Estimating the amount and distribution of radon flux density from the soil surface in China.

    Science.gov (United States)

    Zhuo, Weihai; Guo, Qiuju; Chen, Bo; Cheng, Guan

    2008-07-01

    Based on an idealized model, both the annual and the seasonal radon ((222)Rn) flux densities from the soil surface at 1099 sites in China were estimated by linking a database of soil (226)Ra content and a global ecosystems database. Digital maps of the (222)Rn flux density in China were constructed in a spatial resolution of 25 km x 25 km by interpolation among the estimated data. An area-weighted annual average (222)Rn flux density from the soil surface across China was estimated to be 29.7+/-9.4 mBq m(-2)s(-1). Both regional and seasonal variations in the (222)Rn flux densities are significant in China. Annual average flux densities in the southeastern and northwestern China are generally higher than those in other regions of China, because of high soil (226)Ra content in the southeastern area and high soil aridity in the northwestern one. The seasonal average flux density is generally higher in summer/spring than winter, since relatively higher soil temperature and lower soil water saturation in summer/spring than other seasons are common in China.

  5. Classical probability density distributions with uncertainty relations for ground states of simple non-relativistic quantum-mechanical systems

    Science.gov (United States)

    Radożycki, Tomasz

    2016-11-01

    The probability density distributions for the ground states of certain model systems in quantum mechanics and for their classical counterparts are considered. It is shown, that classical distributions are remarkably improved by incorporating into them the Heisenberg uncertainty relation between position and momentum. Even the crude form of this incorporation makes the agreement between classical and quantum distributions unexpectedly good, except for the small area, where classical momenta are large. It is demonstrated that the slight improvement of this form, makes the classical distribution very similar to the quantum one in the whole space. The obtained results are much better than those from the WKB method. The paper is devoted to ground states, but the method applies to excited states too.

  6. Relation between Growth and Vertical Distribution of Fine Roots and Soil Density in the Weibei Loess Plateau

    Institute of Scientific and Technical Information of China (English)

    Zhao Zhong; Li Peng; Xue Wenpeng; Guo Shengwu

    2006-01-01

    The influence of woodland soil bulk density on the growth and distribution of fine root system of main planting tree species in the Weibei Loess Plateau was investigated by means of pot culture and field survey.Results indicated that in the woodland of Pinus tabulaeformis,soil bulk density increased with the depth at different sites,while in the woodland of Robinia pseudoacacia,soil bulk density was higher than that in P.tabulaeformis,and there was no clear difference across the profile.Further analysis implied that there existed negative correlations between soil bulk density and fine root length in the woodland of P.tabulaeformis.Results from pot culture indicated that although the effects of pot culture media on the free root growth and development of different tree species seedlings were different,all treated seedlings grew better in the soil matter with medium bulk density and porosity and with the biggest biomass.Bulk density of pot culture media had clear effects on the growth and development of P.tabulaeformis and R.pseudoacacia seedling roots,especially on the former,whereas it had little effect on that of Platycladus orientalis and Prunus armeniaca var.ansu,whose fine root biomass changed little in different pot culture media.

  7. Classification of boar spermatozoid head images using a model intracellular density distribution

    NARCIS (Netherlands)

    Sánchez, Lidia; Petkov, Nicolai; Alegre, Enrique; Sanfeliu, A; Cortes, ML

    2005-01-01

    We propose a novel classification method to identify boar spermatozoid heads which present an intracellular intensity distribution similar to a model. From semen sample images, head images are isolated and normalized. We define a model intensity distribution averaging a set of head images assumed as

  8. The functional significance of density and distribution of outgrowths on co-opted contact pairs in biological arresting systems

    Science.gov (United States)

    Filippov, Alexander E.; Popov, Valentin L.; Gorb, Stanislav N.

    2015-01-01

    Microstructures responsible for temporary arresting of contacting surfaces are widely distributed on surfaces in different organisms. Recent morphological studies show that these structures have different density of outgrowths and not ideal distribution pattern on both complementary parts of the contact. One can suggest that this difference is optimized by natural selection to get stronger mechanical arrest within the system. In this paper, we simulate such a system numerically, both in the frames of continuous contact and discrete dynamical models to prove this hypothesis and elucidate other aspects of optimization of such mechanical adhesive systems. PMID:25533090

  9. Biodiversity and the Lotka-Volterra theory of species interactions: open systems and the distribution of logarithmic densities.

    Science.gov (United States)

    Wilson, William G; Lundberg, Per

    2004-09-22

    Theoretical interest in the distributions of species abundances observed in ecological communities has focused recently on the results of models that assume all species are identical in their interactions with one another, and rely upon immigration and speciation to promote coexistence. Here we examine a one-trophic level system with generalized species interactions, including species-specific intraspecific and interspecific interaction strengths, and density-independent immigration from a regional species pool. Comparisons between results from numerical integrations and an approximate analytic calculation for random communities demonstrate good agreement, and both approaches yield abundance distributions of nearly arbitrary shape, including bimodality for intermediate immigration rates.

  10. Poor transferability of species distribution models for a pelagic predator, the grey petrel, indicates contrasting habitat preferences across ocean basins.

    Directory of Open Access Journals (Sweden)

    Leigh G Torres

    Full Text Available Species distribution models (SDMs are increasingly applied in conservation management to predict suitable habitat for poorly known populations. High predictive performance of SDMs is evident in validations performed within the model calibration area (interpolation, but few studies have assessed SDM transferability to novel areas (extrapolation, particularly across large spatial scales or pelagic ecosystems. We performed rigorous SDM validation tests on distribution data from three populations of a long-ranging marine predator, the grey petrel Procellaria cinerea, to assess model transferability across the Southern Hemisphere (25-65°S. Oceanographic data were combined with tracks of grey petrels from two remote sub-Antarctic islands (Antipodes and Kerguelen using boosted regression trees to generate three SDMs: one for each island population, and a combined model. The predictive performance of these models was assessed using withheld tracking data from within the model calibration areas (interpolation, and from a third population, Marion Island (extrapolation. Predictive performance was assessed using k-fold cross validation and point biserial correlation. The two population-specific SDMs included the same predictor variables and suggested birds responded to the same broad-scale oceanographic influences. However, all model validation tests, including of the combined model, determined strong interpolation but weak extrapolation capabilities. These results indicate that habitat use reflects both its availability and bird preferences, such that the realized distribution patterns differ for each population. The spatial predictions by the three SDMs were compared with tracking data and fishing effort to demonstrate the conservation pitfalls of extrapolating SDMs outside calibration regions. This exercise revealed that SDM predictions would have led to an underestimate of overlap with fishing effort and potentially misinformed bycatch mitigation

  11. Geometry-Independent Determination of Radial Density Distributions in Molecular Cloud Cores and Other Astronomical Objects

    CERN Document Server

    Krčo, Marko

    2016-01-01

    We present a geometry-independent method for determining the shapes of radial volume density profiles of astronomical objects whose geometries are unknown, based on a single column density map. Such profiles are often critical to understand the physics and chemistry of molecular cloud cores, in which star formation takes place. The method presented here does not assume any geometry for the object being studied, thus removing a significant source of bias. Instead it exploits contour self-similarity in column density maps which appears to be common in data for astronomical objects. Our method may be applied to many types of astronomical objects and observable quantities so long as they satisfy a limited set of conditions which we describe in detail. We derive the method analytically, test it numerically, and illustrate its utility using 2MASS-derived dust extinction in molecular cloud cores. While not having made an extensive comparison of different density profiles, we find that the overall radial density dist...

  12. The Relations Between Soil Water Retention Characteristics, Particle Size Distributions, Bulk Densities and Calcium Carbonate Contents for Danish Soils

    DEFF Research Database (Denmark)

    Jensen, Niels H.; Balstrøm, Thomas; Breuning-Madsen, Henrik

    2005-01-01

    A database containing about 800 soil profiles located in a 7-km grid covering Denmark has been used to develop a set of regression equations of soil water content at pressure heads –1, -10, -100 and –1500 kPa versus particle size distribution, organic matter, CaCO3 and bulk density. One purpose...... was to elaborate equations based of soil parameters available in the Danish Soil Classification's texture database on particle size distribution and organic matter. It was also tested if inclusion of bulk density or CaCO3 content (in CaCO3-containing samples) as predictors or grouping in surface and subsurface...... horizons or textural classes improved the regression equations. Compared to existing Danish equations based on much fewer observations the accuracies of the new equations were better. The equations also predicted the soil water content at the measured pressure heads more accurate than the pedotransfer...

  13. Variation of Eddy Current Density Distribution and its Effect on Crack Signal in Eddy Current Non-Destructive of Testing

    Directory of Open Access Journals (Sweden)

    Ladislav Janousek

    2006-01-01

    Full Text Available The paper deals with variation of eddy current density distribution along material depth and investigates an effect of the variation on a crack signal in eddy current non-destructive testing. Four coaxial rectangular tangential coils are used to induce eddy currents in a tested conductive object. The exciting coils are driven independently by phase-shifted AC currents; a ratio of amplitudes of the exciting currents is continuously changed to vary the distribution of eddy current density along material depth under a circular pick-up coil positioned in centre between the exciting coils. Dependences of a crack signal amplitude and its phase on the ratio are evaluated and special features are extracted. It is revealed that the dependences are strongly influenced by depth of a crack, and thus the extracted features can enhance evaluation of a detected crack.

  14. Density and distribution of Patella ferruginea in a Marine Protected Area (western Sardinia, Italy): Constraint analysis for population conservation

    OpenAIRE

    Coppa, S.; G. A. de Lucia; Massaro, G.; Magni, P

    2012-01-01

    The endemic limpet Patella ferruginea is the most endangered invertebrate of the Mediterranean Sea. Our study examined a population of P. ferruginea in the Marine Protected Area of Penisola del Sinis - Isola di Mal di Ventre (western Sardinia, Italy). During the summer 2009, we carried out a systematic census of P. ferruginea along a 8114 m georeferenced perimeter of coast in the no take-no entry zone to assess its density, spatial distribution, and morphometric characteristics. Our aim was t...

  15. Patchy Distributions of Competitors Affect the Growth of a Clonal Plant When the Competitor Density Is High

    OpenAIRE

    Wei Xue; Lin Huang; Bi-Cheng Dong; Ming-Xiang Zhang; Fei-Hai Yu

    2013-01-01

    Environments are patchy in not only abiotic factors but also biotic ones. Many studies have examined effects of spatial heterogeneity in abiotic factors such as light, water and nutrients on the growth of clonal plants, but few have tested those in biotic factors. We conducted a greenhouse experiment to examine how patchy distributions of competitors affect the growth of a rhizomatous wetland plant Bolboschoenus planiculmis and whether such effects depend on the density of the competitors. We...

  16. Retrieval of Droplet size Density Distribution from Multiple field of view Cross polarized Lidar Signals: Theory and Experimental Validation

    Science.gov (United States)

    2016-06-02

    is derived to facilitate use of secondary polarization. The model is supported by exper- imental MFOV lidar measurements carried out in a controlled ...Retrieval of droplet-size density distribution from multiple-field-of- view cross-polarized lidar signals: theory and experimental validation...Gilles Roy, Luc Bissonnette, Christian Bastille, and Gilles Vallee Multiple-field-of- view (MFOV) secondary-polarization lidar signals are used to

  17. Linear and angular momentum of electromagnetic fields generated by an arbitrary distribution of charge and current densities at rest

    CERN Document Server

    Thidé, B; Then, H; Tamburini, F

    2010-01-01

    Starting from Stratton-Panofsky-Phillips-Jefimenko equations for the electric and magnetic fields generated by completely arbitrary charge and current density distributions at rest, we derive far-zone approximations for the fields, containing all components, dominant as well as sub-dominant. Using these approximate formulas, we derive general formulas for the total electromagnetic linear momentum and angular momentum, valid at large distances from arbitrary, non-moving charge and current sources.

  18. Water distributions in polystyrene-block-poly[styrene-g-poly(ethylene oxide)] block grafted copolymer system in aqueous solutions revealed by contrast variation small angle neutron scattering study

    Science.gov (United States)

    Li, Xin; Hong, Kunlun; Liu, Yun; Shew, Chwen-Yang; Liu, Emily; Herwig, Kenneth W.; Smith, Gregory S.; Zhao, Junpeng; Zhang, Guangzhao; Pispas, Stergios; Chen, Wei-Ren

    2010-10-01

    We develop an experimental approach to analyze the water distribution around a core-shell micelle formed by polystyrene-block-poly[styrene-g-poly(ethylene oxide (PEO)] block copolymers in aqueous media at a fixed polymeric concentration of 10 mg/ml through contrast variation small angle neutron scattering (SANS) study. Through varying the D2O/H2O ratio, the scattering contributions from the water molecules and the micellar constituent components can be determined. Based on the commonly used core-shell model, a theoretical coherent scattering cross section incorporating the effect of water penetration is developed and used to analyze the SANS I(Q ). We have successfully quantified the intramicellar water distribution and found that the overall micellar hydration level increases with the increase in the molecular weight of hydrophilic PEO side chains. Our work presents a practical experimental means for evaluating the intramacromolecular solvent distributions of general soft matter systems.

  19. Complex Probability Distributions A Solution for the Long-Standing Problem of QCD at Finite Density

    CERN Document Server

    Azcoiti, V

    1996-01-01

    We show how the prescription of taking the absolute value of the fermion determinant in the integration measure of QCD at finite density, forgetting its phase, reproduces the correct thermodynamical limit. This prescription, which applies also to other gauge theories with non-positive-definite integration measure, also has the advantage of killing finite size effects due to extremely small mean values of the cosine of the phase of the fermion determinant. We also give an explanation for the pathological behaviour of quenched QCD at finite density.

  20. Reconstruction of the ionospheric 3D electron density distribution by assimilation of ionosonde measurements and operational TEC estimations

    Science.gov (United States)

    Gerzen, Tatjana; Wilken, Volker; Jakowski, Norbert; Hoque, Mainul M.

    2013-04-01

    New methods to generate maps of the F2 layer peak electron density of the ionosphere (NmF2) and to reconstruct the ionospheric 3D electron density distribution will be presented. For validation, reconstructed NmF2 maps will be compared with peak electron density measurements from independent ionosonde stations. The ionosphere is the ionized part of the upper Earth's atmosphere lying between about 50 km and 1000 km above the Earth's surface. From the applications perspective the electron density, Ne, is certainly one of the most important parameters of the ionosphere because of its strong impact on radio signal propagation. Especially the critical frequency, foF2, which is related to the F2 layer peak electron density, NmF2, according to the equation NmF2-m3 = 1.24 ? 1010(foF2-MHz)2 and builds the lower limit for the maximum usable frequency MUF, is of particular interest with regard to the HF radio communication applications. In a first order approximation the ionospheric delay of transionospheric radio waves of frequency f is proportional to 1-f2 and to the integral of the electron density (total electron content - TEC) along the ray path. Thus, the information about the total electron content along the receiver-to-satellite ray path can be obtained from the dual frequency measurements permanently transmitted by GNSS satellites. As data base for our reconstruction approaches we use the vertical sounding measurements of the ionosonde stations providing foF2 and routinely generated TEC maps in SWACI (http://swaciweb.dlr.de) at DLR Neustrelitz. The basic concept of our approach is the following one: To reconstruct NmF2 maps we assimilate the ionosonde data into the global Neustrelitz F2 layer Peak electron Density Model (NPDM) by means of a successive corrections method. The TEC maps are produced by assimilating actual ground based GPS measurements providing TEC into an operational version of Neustrelitz TEC Model (NTCM). Finally, the derived NmF2 and TEC maps in

  1. Theoretical Electron Density Distributions for Fe- and Cu-Sulfide Earth Materials: A Connection between Bond Length, Bond Critical Point Properties, Local Energy Densities, and Bonded Interactions

    Energy Technology Data Exchange (ETDEWEB)

    Gibbs, Gerald V.; Cox, David F.; Rosso, Kevin M.; Ross, Nancy L.; Downs, R. T.; Spackman, M. A.

    2007-03-01

    Bond critical point and local energy density properties together with net atomic charges were calculated for theoretical electron density distributions, F(r), generated for a variety of Fe and Cu metal-sulfide materials with high- and low-spin Fe atoms in octahedral coordination and high-spin Fe atoms in tetrahedral coordination. The electron density, F(rc), the Laplacian, 32F(rc), the local kinetic energy, G(rc), and the oxidation state of Fe increase as the local potential energy density, V(rc), the Fe-S bond lengths, and the coordination numbers of the Fe atoms decrease. The properties of the bonded interactions for the octahedrally coordinated low-spin Fe atoms for pyrite and marcasite are distinct from those for high-spin Fe atoms for troilite, smythite, and greigite. The Fe-S bond lengths are shorter and the values of F(rc) and 32F(rc) are larger for pyrite and marcasite, indicating that the accumulation and local concentration of F(r) in the internuclear region are greater than those involving the longer, high-spin Fe-S bonded interactions. The net atomic charges and the bonded radii calculated for the Fe and S atoms in pyrite and marcasite are also smaller than those for sulfides with high-spin octahedrally coordinated Fe atoms. Collectively, the Fe-S interactions are indicated to be intermediate in character with the low-spin Fe-S interactions having greater shared character than the highspin interactions. The bond lengths observed for chalcopyrite together with the calculated bond critical point properties are consistent with the formula Cu+Fe3+S2. The bond length is shorter and the F(rc) value is larger for the FeS4 tetrahedron displayed by metastable greigite than those displayed by chalcopyrite and cubanite, consistent with a proposal that the Fe atom in greigite is tetravalent. S-S bond paths exist between each of the surface S atoms of adjacent slabs of FeS6 octahedra comprising the layer sulfide smythite, suggesting that the neutral Fe3S4 slabs are

  2. Measuring surface state density and energy distribution in InAs nanowires

    Energy Technology Data Exchange (ETDEWEB)

    Halpern, Eliezer; Cohen, Gilad; Gross, Shahar; Henning, Alexander; Matok, Max; Rosenwaks, Yossi [Department of Physical Electronics, School of Electrical Engineering, Tel-Aviv University (Israel); Kretinin, Andrey V. [School of Physics and Astronomy, University of Manchester (United Kingdom); Shtrikman, Hadas [Department of Condensed Matter Physics, Braun Center for Submicrometer Research, Weizmann Institute of Science, Rehovot (Israel)

    2014-02-15

    Semiconducting nanowires are expected to have applications in various areas as transistors, sensors, resonators, solar cells, and thermoelectric systems. Understanding the surface properties is crucial for the fabrication of high-performance devices. Due to the large surface-to-volume ratio of nanowires, their surface electronic properties, like surface states, can a have a large effect on the performance of both electronic and optoelectronic devices. At present, determination of the surface state density depends on a combination of experimental measurements of the capacitance and/or drain current, in a nanowire field-effect transistor, and a fitting to simulation. This technique follows certain assumptions, which can severely harm the accuracy of the extracted density of states. In this report, we demonstrate a direct measurement of the surface state density of individual InAs and silicon nanowires. The method is based on measuring the surface potential of a nanowire field-effect transistor, with respect to a changing gate bias. The extracted density of states at the surface helps to explain various electronic phenomena in such devices. (copyright 2014 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  3. Marine litter distribution and density in European seas, from the shelves to deep basins

    NARCIS (Netherlands)

    Pham, C.K.; Ramirez-Llodra, E.; Alt, C.H.S.; Amaro, T.; Bergmann, M.; Canals, M.; Company, J.B.; Davies, J.; Duineveld, G.; Galgani, F.; Howell, K.L.; Huvenne, V.A.I.; Isidro, E.; Jones, D.O.B.; Lastras, G.; Morato, T.; Gomes-Pereira, J.N.; Purser, A.; Stewart, H.; Tojeira, I.; Tubau, X.; Van Rooij, D.; Tyler, P.A.

    2014-01-01

    Anthropogenic litter is present in all marine habitats, from beaches to the most remote points in the oceans. On the seafloor, marine litter, particularly plastic, can accumulate in high densities with deleterious consequences for its inhabitants. Yet, because of the high cost involved with sampling

  4. Using ultra-short pulses to determine particle size and density distributions

    NARCIS (Netherlands)

    Lee, Christopher James; van der Slot, Petrus J.M.; Boller, Klaus J.

    2007-01-01

    We analyze the time dependent response of strongly scattering media (SSM) to ultra-short pulses of light. A random walk technique is used to model the optical scattering of ultra-short pulses of light propagating through media with random shapes and various packing densities. The pulse spreading was

  5. Predicting above-ground density and distribution of small mammal prey species at large spatial scales

    Science.gov (United States)

    Lucretia E. Olson; John R. Squires; Robert J. Oakleaf; Zachary P. Wallace; Patricia L. Kennedy

    2017-01-01

    Grassland and shrub-steppe ecosystems are increasingly threatened by anthropogenic activities. Loss of native habitats may negatively impact important small mammal prey species. Little information, however, is available on the impact of habitat variability on density of small mammal prey species at broad spatial scales. We examined the relationship between small mammal...

  6. [Distribution of electroencephalograph power density in patients with severe obstructive sleep apnea during different sleep stages].

    Science.gov (United States)

    Deng, Y; Tian, X; Chen, B Y; Zhou, N; Xia, M; Bai, W W; Dou, M M; Liu, X Y

    2017-04-12

    Objective: To investigate the variation of electroencephalograph(EEG) power density during different sleep stages in OSA for understanding of the mechanisms underlying the brain dysfunction in OSA as well as its earlier diagnosis and treatment. Methods: Sixteen-channel EEGs from OSA patients and normal controls in stage wake, sleep stage 1, sleep stage 2, sleep stage 3 and rapid eye movement stage were analyzed by time-frequency analysis method. The EEG power density in different frequency bands (including δ, θ, α, σ, β and γ) was respectively compared between the 2 groups. The correlation between the variation in the EEG power and primary indices of polysomnography was further analyzed. Results: The EEG power density in δ band in stage wake [OSA: (0.82±0.13) μV(2)/Hz, Control: (0.66±0.02) μV(2)/Hz, t=4.309, Pdensity was significantly higher in frontal and central regions in stage wake [frontal: OSA: (0.90±0.02) μV(2)/Hz, Control: (0.66±0.02) μV(2)/Hz, t=8.539, Pdensity in central region in stage 1 and stage 3 was positively correlated with arousal index (r=0.877 in stage 1, 0.656 in stage 3), implying that sleep fragmentation was closely related to the variation of EEG power density during nocturnal sleep in OSA. Conclusions: The feature stages for OSA are stage wake, stage 1 and stage 3. The EEG power density in OSA (δ band) was significantly higher than that in the control. The EEG power density in OSA and the control shows differences in frontal and central regions in stage wake and stage 1, as well as in central region in stage 3. The results indicate that low-frequency EEG power density giving priority to frontal area and central area has improved in severe OSA, which may be related to the neurologic deficits in corresponding brain areas.

  7. Fission fragment charge and mass distributions in 239Pu(n,f) in the adiabatic nuclear energy density functional theory

    CERN Document Server

    Regnier, D; Schunck, N; Verriere, M

    2016-01-01

    Accurate knowledge of fission fragment yields is an essential ingredient of numerous applications ranging from the formation of elements in the r-process to fuel cycle optimization for nuclear energy. The need for a predictive theory applicable where no data is available is an incentive to develop a fully microscopic approach to fission dynamics. In this work, we calculate the pre-neutron emission charge and mass distributions of the fission fragments formed in the neutron-induced fission of 239Pu using a microscopic method based on nuclear energy density functional (EDF) method, where large amplitude collective motion is treated adiabatically using the time dependent generator coordinate method (TDGCM) under the Gaussian overlap approximation (GOA). Fission fragment distributions are extracted from the flux of the collective wave packet through the scission line. We find that the main characteristics of the fission charge and mass distributions can be well reproduced by existing energy functionals even in tw...

  8. Contrasting geographical distributions as a result of thermal tolerance and long-distance dispersal in two allegedly widespread tropical brown algae.

    Directory of Open Access Journals (Sweden)

    Ana Tronholm

    Full Text Available BACKGROUND: Many tropical marine macroalgae are reported from all three ocean basins, though these very wide distributions may simply be an artifact resulting from inadequate taxonomy that fails to take into account cryptic diversity. Alternatively, pantropical distributions challenge the belief of limited intrinsic dispersal capacity of marine seaweeds and the effectiveness of the north-south oriented continents as dispersal barriers. We aimed to re-assess the distribution of two allegedly circumtropical brown algae, Dictyota ciliolata and D. crenulata, and interpret the realized geographical range of the respective species in relation to their thermal tolerance and major tectonic and climatic events during the Cenozoic. METHODOLOGY/PRINCIPAL FINDINGS: Species delimitation was based on 184 chloroplast encoded psbA sequences, using a Generalized Mixed Yule Coalescent method. Phylogenetic relationships were inferred by analyzing a six-gene dataset. Divergence times were estimated using relaxed molecular clock methods and published calibration data. Distribution ranges of the species were inferred from DNA-confirmed records, complemented with credible literature data and herbarium vouchers. Temperature tolerances of the species were determined by correlating distribution records with local SST values. We found considerable conflict between traditional and DNA-based species definitions. Dictyota crenulata consists of several pseudocryptic species, which have restricted distributions in the Atlantic Ocean and Pacific Central America. In contrast, the pantropical distribution of D. ciliolata is confirmed and linked to its significantly wider temperature tolerance. CONCLUSIONS/SIGNIFICANCE: Tectonically driven rearrangements of physical barriers left an unequivocal imprint on the current diversity patterns of marine macroalgae, as witnessed by the D. crenulata-complex. The nearly circumglobal tropical distribution of D. ciliolata, however

  9. Analysis on insulator–metal transition in yttrium doped LSMO from electron density distribution

    Indian Academy of Sciences (India)

    S Israel; S Saravana Kumar; R Renuretson; R A J R Sheeba; R Saravanan

    2012-02-01

    Yttrium doped LSMO (La1−SrMnO3) was prepared using sol–gel technique and analysed for the insulator–metal transition fromcharge density variation in the unit cell with respect to different stoichiometric inclusion of yttrium. X-ray powder diffraction profiles of the samples were obtained and the well known Rietveld method and a versatile tool called maximum entropy method (MEM) were used for structural and profile refinement. The charge density in the unit cell was constructed using refined structure factors and was analysed. The charge ordering taking place in the insulator–metal transition was investigated and quantified. The insulator–metal transition was found to occur when 20% of La/Sr atoms were replaced by yttrium. The changes in the charge environment have also been analysed.

  10. Two-dimensional simulations of temperature and current-density distribution in electromigrated structures

    Science.gov (United States)

    Kießig, Birgit; Schäfer, Roland; von Löhneysen, Hilbert

    2014-01-01

    We report on the application of a feedback-controlled electromigration technique for the formation of nanometre-sized gaps in mesoscopic gold wires and rings. The effect of current density and temperature, linked via Joule heating, on the resulting gap size is investigated. Our experiments include in situ measurements of the evolution of the electrical resistance and of the structure of the device during electromigration. Experimentally, a good thermal coupling to the substrate turned out to be crucial to reach electrode spacings below 10 nm and to avoid overall melting of the nanostructures. This finding is supported by numerical calculations of the current-density and temperature profiles for structure layouts subjected to electromigration. The numerical method can be used for optimizing the layout so as to predetermine the location where electromigration leads to the formation of a gap.

  11. Effect of current density on distribution coefficient of solute at solid-liquid interface

    Institute of Scientific and Technical Information of China (English)

    常国威; 王自东; 吴春京; 胡汉起

    2003-01-01

    When current passes through the solid-liquid interface, the growth rate of crystal, solid-liquid interfaceenergy and radius of curvature at dendritic tip will change. Based on this fact, the theoretical relation between thedistribution of solute at solid-liquid interface and current density was established, and the effect of current on thedistribution coefficient of solute through effecting the rate of crystal growth, the solid-liquid interface energy and theradius of curvature at the dendritic tip was discussed. The results show that as the current density increases, thedistribution coefficient of solute tends to rise in a whole, and when the former is larger than about 400 A/cm2 , thelatter varies significantly.

  12. Effect of soil surface salt on the density and distribution of the snail Bithynia siamensis goniomphalos in northeast Thailand.

    Science.gov (United States)

    Suwannatrai, Apiporn; Suwannatrai, Kulwadee; Haruay, Surat; Piratae, Supawadee; Thammasiri, Chalida; Khampoosa, Panita; Kulsantiwong, Jutharat; Prasopdee, Sattrachai; Tarbsripair, Pairat; Suwanwerakamtorn, Rasamee; Sukchan, Somsak; Boonmars, Thidarut; Malone, John B; Kearney, Michael T; Tesana, Smarn

    2011-05-01

    Opisthorchis viverrini infection is associated with human cholangiocarcinoma and northeast Thailand has the highest incidence of this disease in the world. Bithynia siamensis goniomphalos is the major freshwater snail intermediate host of O. viverrini in this area and an analysis based on geographical information systems was used to determine the effect of variation in soil surface salt on the density and distribution of this snail. A malacological survey was carried out in 56 water bodies in the Khorat basin, northeast Thailand at locations with various soil surface salt levels. Mollusk samples were collected from 10 ecologically representative water body sites with 10-20 sampling stations in each. The shoreline of clear, shallow water bodies was found to be the preferred B. s. goniomphalos habitat. The snails were exclusively found in water with salinity levels ranging between 0.05 and 22.11 parts per thousand (ppt), which supports the notion that B. s. goniomphalos prefers water with some saline content over pure, freshwater. The highest snail population densities were in rice fields, ponds, road-side ditches and canals within a water salinity range of 2.5-5.0 ppt. However, the presence of B. s. goniomphalos was negatively correlated with water salinity (P ≤0.05), both with regard to density and distribution. The areas with the highest density of B. s. goniomphalos were those with less than 1% soil surface salt (potential index = 0.314), while the lowest densities were found in areas exceeding 50% soil surface salt (potential index = 0.015).

  13. Effect of soil surface salt on the density and distribution of the snail Bithynia siamensis goniomphalos in northeast Thailand

    Directory of Open Access Journals (Sweden)

    Apiporn Suwannatrai

    2011-05-01

    Full Text Available Opisthorchis viverrini infection is associated with human cholangiocarcinoma and northeast Thailand has the highest incidence of this disease in the world. Bithynia siamensis goniomphalos is the major freshwater snail intermediate host of O. viverrini in this area and an analysis based on geographical information systems was used to determine the effect of variation in soil surface salt on the density and distribution of this snail. A malacological survey was carried out in 56 water bodies in the Khorat basin, northeast Thailand at locations with various soil surface salt levels. Mollusk samples were collected from 10 ecologically representative water body sites with 10-20 sampling stations in each. The shoreline of clear, shallow water bodies was found to be the preferred B. s. goniomphalos habitat. The snails were exclusively found in water with salinity levels ranging between 0.05 and 22.11 parts per thousand (ppt, which supports the notion that B. s. goniomphalos prefers water with some saline content over pure, freshwater. The highest snail population densities were in rice fields, ponds, road-side ditches and canals within a water salinity range of 2.5-5.0 ppt. However, the presence of B. s. goniomphalos was negatively correlated with water salinity (P ≤0.05, both with regard to density and distribution. The areas with the highest density of B. s. goniomphalos were those with less than 1% soil surface salt (potential index = 0.314, while the lowest densities were found in areas exceeding 50% soil surface salt (potential index = 0.015.

  14. Distribution of trace elements in selected pulverized coals as a function of particle size and density

    Science.gov (United States)

    Senior, C.L.; Zeng, T.; Che, J.; Ames, M.R.; Sarofim, A.F.; Olmez, I.; Huggins, Frank E.; Shah, N.; Huffman, G.P.; Kolker, A.; Mroczkowski, S.; Palmer, C.; Finkelman, R.

    2000-01-01

    Trace elements in coal have diverse modes of occurrence that will greatly influence their behavior in many coal utilization processes. Mode of occurrence is important in determining the partitioning during coal cleaning by conventional processes, the susceptibility to oxidation upon exposure to air, as well as the changes in physical properties upon heating. In this study, three complementary methods were used to determine the concentrations and chemical states of trace elements in pulverized samples of four US coals: Pittsburgh, Illinois No. 6, Elkhorn and Hazard, and Wyodak coals. Neutron Activation Analysis (NAA) was used to measure the absolute concentration of elements in the parent coals and in the size- and density-fractionated samples. Chemical leaching and X-ray absorption fine structure (XAFS) spectroscopy were used to provide information on the form of occurrence of an element in the parent coals. The composition differences between size-segregated coal samples of different density mainly reflect the large density difference between minerals, especially pyrite, and the organic portion of the coal. The heavy density fractions are therefore enriched in pyrite and the elements associated with pyrite, as also shown by the leaching and XAFS methods. Nearly all the As is associated with pyrite in the three bituminous coals studied. The sub-bituminous coal has a very low content of pyrite and arsenic; in this coal arsenic appears to be primarily organically associated. Selenium is mainly associated with pyrite in the bituminous coal samples. In two bituminous coal samples, zinc is mostly in the form of ZnS or associated with pyrite, whereas it appears to be associated with other minerals in the other two coals. Zinc is also the only trace element studied that is significantly more concentrated in the smaller (45 to 63 ??m) coal particles.

  15. The effect of polymer charge density and charge distribution on the formation of multilayers

    CERN Document Server

    Voigt, U; Tauer, K; Hahn, M; Jäger, W; Klitzing, K V

    2003-01-01

    Polyelectrolyte multilayers which are built up by alternating adsorption of polyanions and polycations from aqueous solutions at a solid interface are investigated by reflectometry and ellipsometry. Below a degree of charge of about 70% the adsorption stops after a certain number of dipping cycles and no multilayer formation occurs. This indicates an electrostatically driven adsorption process. Below a charge density of 70% an adsorption can take place if the charged segments are combined as a block of the polymer.

  16. Radial Density Statistics of the Galaxy Distribution and the Luminosity Function

    CERN Document Server

    Iribarrem, Alvaro S; Stoeger, William R

    2012-01-01

    This paper discusses a connection between the relativistic number counts of cosmological sources and the observed galaxy luminosity function (LF). Observational differential number densities are defined and obtained from published LF data using such connection. We observe a distortion in the observational quantities that increases with higher redshift values as compared to the theoretical predictions. The use of different cosmological distance measures plays a role in such a distortion

  17. Distributed material density and anisotropy for optimized eigenfrequency of 2D continua

    DEFF Research Database (Denmark)

    Pedersen, Pauli; Pedersen, Niels Leergaard

    2015-01-01

    A practical approach to optimize a continuum/structural eigenfrequency is presented, including design of the distribution of material anisotropy. This is often termed free material optimization (FMO). An important aspect is the separation of the overall material distribution from the local design...... constitutive matrix. For 3D problems from 21 to 6 parameters, for 2D from 6 to 3 parameters, and for axisymmetric problems from 10 to 4 parameters....... are described by non-dimensional matrices with unity norms of trace and Frobenius, and thus this part of the optimized design has no influence on the mass distribution. Gradients of eigenfrequency with respect to the components of these non-dimensional constitutive matrices are therefore simplified...

  18. Distribution and density of mosquitoes in two endemic areas for bancroftian filariasis in Sorsogon, Philippines.

    Science.gov (United States)

    Cabrera, B D; Valeza, F

    1978-09-01

    Mosquito density in Rangas where abaca is in abundance is much higher, almost twice, than that of Putiao where abaca is absent. The adult density of Aedes poecilus over Aedes ananae in the two areas combined is 3 to 4 times whereas the larval density of the former is much lower than Aedes ananae. The banana axils is a favorite breeding place for Aedes poecilus but may also utilize the abaca axils. This finding is very favorable in the transmission of bancroftian filariasis because this species of banana is planted around houses even closer to human dwelling than the abaca plants. Aedes poecilus being more anthropophylic than zoophylic can be domesticated as Culex quinquefasciatus and Aedes aegypti which again is a factor in favor of ideal transmission of the disease. The fact that bananas are planted around houses both in villages and towns, transmission of the disease could easily occur in both places, which should be borne in mind when planning a control program. The number of dissected mosquitoes is too small to be of significance in vector determination.

  19. Lévy stable two-sided distributions: exact and explicit densities for asymmetric case.

    Science.gov (United States)

    Górska, K; Penson, K A

    2011-06-01

    We investigate functions g(α,β;x) which are heavy-tailed Lévy stable probability distributions of index 0econophysics, geology, hydrology, internet traffic, dynamics of human relations, etc. We present an ensemble of exact and explicit solutions of g(α,β;x) for all admissible rational values of α and β. We reproduce all the previously known cases and furnish distributions for values α and β which were previously inaccessible. We point out many instances of experimental and statistical data that could be described by our results.

  20. Contrasting nurse plants and nurse rocks: The spatial distribution of seedlings of two sub-Antarctic species

    Science.gov (United States)

    Haussmann, N. S.; McGeoch, M. A.; Boelhouwers, J. C.

    2010-05-01

    Positive plant interactions, such as those associated with nurse plants, have been suggested to dominate over negative interactions in environments with high abiotic stress. Here we demonstrate that the sub-Antarctic cushion plant species, Azorella selago (Apiaceae), positively affects the distribution of both its own seedlings and those of the perennial grass, Agrostis magellanica (Poaceae). As a result of the light weight and small size of seeds of both species, coupled with strong winds experienced in the study area, we consider it unlikely that these patterns are the result of very localized seed dispersal from the study cushions themselves. Instead, we suggest that both cushions and rocks act as seed traps, trapping seeds dispersed by wind, runoff and/or downslope sediment transport through frost creep. In addition, increased A. selago seedling numbers around cushions, but not around rocks, suggest that cushions provide a biological nurse effect, such as improving soil nutrient status or providing mychorrizae, to seedlings of their own kind.

  1. Charged particle density distributions in Au + Au collisions at relativistic heavy-ion collider energies

    Indian Academy of Sciences (India)

    Fauad Rami

    2003-05-01

    Charged particle pseudorapidity distributions have been measured in Au + Au collisions using the BRAHMS detector at RHIC. The results are presented as a function of the collision centrality and the center of mass energy. They are compared to the predictions of different parton scattering models and the important role of hard scattering processes at RHIC energies is discussed.

  2. Criticality of the net-baryon number probability distribution at finite density

    Directory of Open Access Journals (Sweden)

    Kenji Morita

    2015-02-01

    Full Text Available We compute the probability distribution P(N of the net-baryon number at finite temperature and quark-chemical potential, μ, at a physical value of the pion mass in the quark-meson model within the functional renormalization group scheme. For μ/T<1, the model exhibits the chiral crossover transition which belongs to the universality class of the O(4 spin system in three dimensions. We explore the influence of the chiral crossover transition on the properties of the net baryon number probability distribution, P(N. By considering ratios of P(N to the Skellam function, with the same mean and variance, we unravel the characteristic features of the distribution that are related to O(4 criticality at the chiral crossover transition. We explore the corresponding ratios for data obtained at RHIC by the STAR Collaboration and discuss their implications. We also examine O(4 criticality in the context of binomial and negative-binomial distributions for the net proton number.

  3. Density and distribution of Patella ferruginea in a Marine Protected Area (western Sardinia, Italy: Constraint analysis for population conservation

    Directory of Open Access Journals (Sweden)

    S. COPPA

    2012-04-01

    Full Text Available The endemic limpet Patella ferruginea is the most endangered invertebrate of the Mediterranean Sea. Our study examined a population of P. ferruginea in the Marine Protected Area of Penisola del Sinis - Isola di Mal di Ventre (western Sardinia, Italy. During the summer 2009, we carried out a systematic census of P. ferruginea along a 8114 m georeferenced perimeter of coast in the no take-no entry zone to assess its density, spatial distribution, and morphometric characteristics. Our aim was to provide a detailed map of the distribution of P. ferruginea and to investigate the effects of accessibility, wave exposure and slope of the coast on its occurrence. Patella ferrugineashowed the lowest mean density ever reported (0.02 ind/m and a unimodal population structure characterised by fewer females and juveniles. Accessibility had a major negative effect on the occurrence of P. ferruginea. Exposure was also an important factor in influencing its density, size composition and specimen position within the mesolittoral, while the slope had little influence. Morphometric analysis showed the dominance of the Rouxi form, while the Lamarcki form was confined to exposed sites. Our results demonstrate a highly endangered population of P. ferruginea and suggest that human pressure represents the main risk factor.

  4. Density and distribution of Patella ferruginea in a Marine Protected Area (western Sardinia, Italy: Constraint analysis for population conservation

    Directory of Open Access Journals (Sweden)

    S. COPPA

    2012-12-01

    Full Text Available The endemic limpet Patella ferruginea is the most endangered invertebrate of the Mediterranean Sea. Our study examined a population of P. ferruginea in the Marine Protected Area of Penisola del Sinis - Isola di Mal di Ventre (western Sardinia, Italy. During the summer 2009, we carried out a systematic census of P. ferruginea along a 8114 m georeferenced perimeter of coast in the no take-no entry zone to assess its density, spatial distribution, and morphometric characteristics. Our aim was to provide a detailed map of the distribution of P. ferruginea and to investigate the effects of accessibility, wave exposure and slope of the coast on its occurrence. Patella ferrugineashowed the lowest mean density ever reported (0.02 ind/m and a unimodal population structure characterised by fewer females and juveniles. Accessibility had a major negative effect on the occurrence of P. ferruginea. Exposure was also an important factor in influencing its density, size composition and specimen position within the mesolittoral, while the slope had little influence. Morphometric analysis showed the dominance of the Rouxi form, while the Lamarcki form was confined to exposed sites. Our results demonstrate a highly endangered population of P. ferruginea and suggest that human pressure represents the main risk factor.

  5. Evaluation of density and distribution of CART-immunoreactive structures in gastrointestinal tract of hypertensive rats.

    Science.gov (United States)

    Kasacka, Irena; Piotrowska, Zaneta

    2012-01-01

    The prevalence of CART (cocaine- and amphetamine-regulated transcript) throughout the organism, multiplicity of functions fulfilled by that peptide, and the collected evidence confirming CART contribution to blood pressure regulation prompted us to undertake the research aiming to identify, localize, and assess changes in CART-immunopositive structures of the gastrointestinal tract (GI tract) of rats with renovascular hypertension. The two-kidney one-clip model of arterial hypertension was used to evaluate the location and density of CART-containing structures in the stomach (cardia, fundus, and pylorus), duodenum, jejunum, ileum, and colon of hypertensive rats. The study was carried out on the GI tract of 20 rats. Ten rats were subjected to the renal artery clipping procedure and after a 6-week period each of them developed stable hypertension. An immunohistochemical localization of CART was performed on paraffin GI tract sections from all the study animals. CART was detected in the extensive population of neurons, particularly within the myenteric plexuses all along the GI tract, and also in neuroendocrine cells, being especially numerous in the stomach and a few in the small intestine. The hypertension significantly increased the density of CART-positive structures in the rat GI tract. The differences between the hypertensive rats and the control animals concerned not only the density of CART-immunoreactive structures but also the staining intensity. As this study provides novel findings, we are planning further molecular examinations to better understand the impact of hypertension on the functioning and activity of CART in the GI tract.

  6. X-ray derived experimental charge density distribution in GaF3 and VF3 solid systems

    Science.gov (United States)

    Sujatha, K.; Israel, S.; Anzline, C.; Niranjana Devi, R.; Sheeba, R. A. J. R.

    2016-09-01

    The electronic structure and bonding features of metal and transition metal fluorides in low oxidation states, GaF3 and VF3, have been studied from precise single crystal X-ray diffraction data using multipole and maximum entropy methods. The topology of the charge density is analyzed and the (3,-1) bond critical points are determined. Existences of ionic nature of bonding in low valent fluorine compounds are clearly evident. The spherical core of metal atom and aspherical or twisted core of transition metal atom reveal the fact that GaF3 is much more rigid than VF3. Aspherical cores of the polarized ligand atoms are also visible in the two-dimensional density distribution pictures. The true valence charge density surfaces with encapsulating the atomic basins maps are elucidated. An elongated saddle with mid-bond density of 0.6191 e/Å3, observed in the compound VF3, shows that its lattice is less rigid and has more ionic character than GaF3.

  7. A detailed numerical analysis of asymmetrical density distribution in Saturn's F ring during an encounter with Prometheus

    Science.gov (United States)

    Sutton, Phil J.; Kusmartsev, Feo V.

    2014-04-01

    Saturn's rings, reminiscent of an early Solar system present a unique opportunity to investigate experimentally some mechanisms thought to be responsible for planet and planetesimal formation in protoplanetary discs. Here, we extended the comparison of our numerical models of Prometheus encountering the F ring employing non-interacting and interacting particles. Higher resolution analysis revealed that the density increases known to exist at channel edges is more complex and localized than previously thought. Asymmetry between density increases on channel edges revealed that the channel edge facing way from Prometheus to be the most stable but with lowest maximum increases. However, on the channel edge facing Prometheus the interacting model showed large chaotic fluctuations in the maximum density of some clumps, much larger than those of the other channel. The likely cause of this asymmetry is a variance in localized turbulence introduced into the F ring by Prometheus. High-resolution velocity dispersion maps showed that there was a spatial link between the highest densities and the highest velocity dispersions in the interacting model. Thus, suggesting that the high velocity dispersion we see is the reason for the observed inhomogeneous distribution of fans (evidence of embedded moonlets) on some of the channel edges facing Prometheus.

  8. Dynamic simulation for tempo-spatial distribution of strain energy density in inhomogeneous stratified crust

    Institute of Scientific and Technical Information of China (English)

    CHEN Yu-kun; NIE Yong-an

    2000-01-01

    Through simulating the research on dynamic variations of strain energy density (SED) in seismogenic model with hard inclusion, the authors have gained further knowledge to such problems as the process of earthquake preparation, initial rupture, conditions of the initial rupture and fracture propagation direction, etc. Results of the research show that SED (strain energy density) in soft inclusion is very high during the initial period of earthquake preparation. And the increment of SED in the soft area decreases at the later stage of the process. Meanwhile, the increment increases quickly in hard inclusion and in the intersection zone of the inclusion with an erecting fault, where the increment of SED is maximum. Thus, the intersection zone between hard inclusion with larger elastic modulus and erecting fault becomes the place where the initial rupture or earthquake occurs. The fracture in the end part of the hard inclusion spreads along a direction nearly vertical to the erecting fault, so the theoretical fracture direction is consistent with that calculated by digital simulation.

  9. Size- and density-distributions and sources of polycyclic aromatic hydrocarbons in urban road dust.

    Science.gov (United States)

    Murakami, Michio; Nakajima, Fumiyuki; Furumai, Hiroaki

    2005-11-01

    Polycyclic aromatic hydrocarbons (PAHs) present in size- and density-fractionated road dust were measured to identify the important fractions in urban runoff and to analyse their sources. Road dust was collected from a residential area (Shakujii) and a heavy traffic area (Hongo Street). The sampling of road dust from the residential area was conducted twice in different seasons (autumn and winter). The collected road dust was separated into three or four size-fractions and further fractionated into light (1.7 g/cm3) fractions by using cesium chloride solution. Light particles constituted only 4.0+/-1.4%, 0.69+/-0.03% and 3.4+/-1.0% of the road dust by weight for Shakujii (November), Shakujii (February) and Hongo Street, respectively but contained 28+/-10%, 33+/-3% and 44+/-8% of the total PAHs, respectively. The PAH contents in the light fractions were 1-2 orders of magnitude higher than those in the heavy fractions. In the light fractions, the 12PAH contents in February were significantly higher than the 12PAH contents in November (P0.05). Cluster analysis revealed that there was a significant difference in the PAH profiles between locations rather than between size-fractions, density-fractions and sampling times. Multiple regression analysis indicated that asphalt/pavement was the major source of Shakujii road dust, and that tyre and diesel vehicle exhaust were the major sources of finer and coarser fractions collected from Hongo Street road dust, respectively.

  10. Stereoscopy of dust density waves under microgravity: Velocity distributions and phase-resolved single-particle analysis

    Energy Technology Data Exchange (ETDEWEB)

    Himpel, Michael, E-mail: himpel@physik.uni-greifswald.de; Killer, Carsten; Melzer, André [Institute of Physics, Ernst-Moritz-Arndt-University, 17489 Greifswald (Germany); Bockwoldt, Tim; Piel, Alexander [IEAP, Christian-Albrechts-Universität Kiel, D-24098 Kiel (Germany); Ole Menzel, Kristoffer [ABB Switzerland Ltd, Corporate Research Center, 5405 Dättwil (Switzerland)

    2014-03-15

    Experiments on dust-density waves have been performed in dusty plasmas under the microgravity conditions of parabolic flights. Three-dimensional measurements of a dust density wave on a single particle level are presented. The dust particles have been tracked for many oscillation periods. A Hilbert analysis is applied to obtain trajectory parameters such as oscillation amplitude and three-dimensional velocity amplitude. While the transverse motion is found to be thermal, the velocity distribution in wave propagation direction can be explained by harmonic oscillations with added Gaussian (thermal) noise. Additionally, it is shown that the wave properties can be reconstructed by means of a pseudo-stroboscopic approach. Finally, the energy dissipation mechanism from the kinetic oscillation energy to thermal motion is discussed and presented using phase-resolved analysis.

  11. Multidimensional metrics for estimating phage abundance, distribution, gene density, and sequence coverage in metagenomes

    Directory of Open Access Journals (Sweden)

    Ramy Karam Aziz

    2015-05-01

    Full Text Available Phages are the most abundant biological entities on Earth and play major ecological roles, yet the current sequenced phage genomes do not adequately represent their diversity, and little is known about the abundance and distribution of these sequenced genomes in nature. Although the study of phage ecology has benefited tremendously from the emergence of metagenomic sequencing, a systematic survey of phage genes and genomes in various ecosystems is still lacking, and fundamental questions about phage biology, lifestyle, and ecology remain unanswered. To address these questions and improve comparative analysis of phages in different metagenomes, we screened a core set of publicly available metagenomic samples for sequences related to completely sequenced phages using the web tool, Phage Eco-Locator. We then adopted and deployed an array of mathematical and statistical metrics for a multidimensional estimation of the abundance and distribution of phage genes and genomes in various ecosystems. Experiments using those metrics individually showed their usefulness in emphasizing the pervasive, yet uneven, distribution of known phage sequences in environmental metagenomes. Using these metrics in combination allowed us to resolve phage genomes into clusters that correlated with their genotypes and taxonomic classes as well as their ecological properties. We propose adding this set of metrics to current metaviromic analysis pipelines, where they can provide insight regarding phage mosaicism, habitat specificity, and evolution.

  12. Leaf Gas Exchange and Nutrient Use Efficiency Help Explain the Distribution of Two Neotropical Mangroves under Contrasting Flooding and Salinity

    Directory of Open Access Journals (Sweden)

    Pablo Cardona-Olarte

    2013-01-01

    Full Text Available Rhizophora mangle and Laguncularia racemosa cooccur along many intertidal floodplains in the Neotropics. Their patterns of dominance shift along various gradients, coincident with salinity, soil fertility, and tidal flooding. We used leaf gas exchange metrics to investigate the strategies of these two species in mixed culture to simulate competition under different salinity concentrations and hydroperiods. Semidiurnal tidal and permanent flooding hydroperiods at two constant salinity regimes (10 g L−1 and 40 g L−1 were simulated over 10 months. Assimilation (A, stomatal conductance (gw, intercellular CO2 concentration (Ci, instantaneous photosynthetic water use efficiency (PWUE, and photosynthetic nitrogen use efficiency (PNUE were determined at the leaf level for both species over two time periods. Rhizophora mangle had significantly higher PWUE than did L. racemosa seedlings at low salinities; however, L. racemosa had higher PNUE and gw and, accordingly, had greater intercellular CO2 (calculated during measurements. Both species maintained similar capacities for A at 10 and 40 g L−1 salinity and during both permanent and tidal hydroperiod treatments. Hydroperiod alone had no detectable effect on leaf gas exchange. However, PWUE increased and PNUE decreased for both species at 40 g L−1 salinity compared to 10 g L−1. At 40 g L−1 salinity, PNUE was higher for L. racemosa than R. mangle with tidal flooding. These treatments indicated that salinity influences gas exchange efficiency, might affect how gases are apportioned intercellularly, and accentuates different strategies for distributing leaf nitrogen to photosynthesis for these two species while growing competitively.

  13. Leaf gas exchange and nutrient use efficiency help explain the distribution of two Neotropical mangroves under contrasting flooding and salinity

    Science.gov (United States)

    Cardona-Olarte, Pablo; Krauss, Ken W.; Twilley, Robert R.

    2013-01-01

    Rhizophora mangle and Laguncularia racemosa co-occur along many intertidal floodplains in the Neotropics. Their patterns of dominance shift along various gradients, coincident with salinity, soil fertility, and tidal flooding. We used leaf gas exchange metrics to investigate the strategies of these two species in mixed culture to simulate competition under different salinity concentrations and hydroperiods. Semidiurnal tidal and permanent flooding hydroperiods at two constant salinity regimes (10 g L−1 and 40 g L−1) were simulated over 10 months. Assimilation (A), stomatal conductance (gw), intercellular CO2 concentration (Ci), instantaneous photosynthetic water use efficiency (PWUE), and photosynthetic nitrogen use efficiency (PNUE) were determined at the leaf level for both species over two time periods. Rhizophora mangle had significantly higher PWUE than did L. racemosa seedlings at low salinities; however, L. racemosa had higher PNUE and stomatal conductance and gw, accordingly, had greater intercellular CO2 (calculated) during measurements. Both species maintained similar capacities for assimilation at 10 and 40 g L−1 salinity and during both permanent and tidal hydroperiod treatments. Hydroperiod alone had no detectable effect on leaf gas exchange. However, PWUE increased and PNUE decreased for both species at 40 g L−1 salinity compared to 10 g L−1. At 40 g L−1 salinity, PNUE was higher for L. racemosa than R. mangle with tidal flooding. These treatments indicated that salinity influences gas exchange efficiency, might affect how gases are apportioned intercellularly, and accentuates different strategies for distributing leaf nitrogen to photosynthesis for these two species while growing competitively.

  14. AVERAGE GEOMETRICAL FEATURES OF THE ELECTRON WAVE PACKAGES DISTRIBUTION IN METALLIC CONDUCTORS WITH PULSED AXIAL CURRENT OF HIGH DENSITY

    Directory of Open Access Journals (Sweden)

    M. I. Baranov

    2016-11-01

    Full Text Available Purpose. Calculation and experimental determination of average geometrical features of distributing of macroscopic electron wave packages (EWP in round cylindrical metallic conductors with the pulsed axial current of high density. Methodology. Theoretical bases of the electrical engineering, bases of atomic and quantum physics, electrophysics bases of technique of high voltage and high pulsed currents. Results. The results of the conducted calculation and experimental researches are resulted on close determination of average geometrical features of distribution of longitudinal and radial EWP of macroscopic sizes in the indicated conductors. These descriptions are included by the average widths of «hot» and «cold» longitudinal and radial areas of conductor, and also average steps of division into the periods of similar areas. Results of the executed calculations and high temperature experiments for average geometrical features of longitudinal EWP in the zincked steel wire of diameter of 1.6 mm and length of 320 mm with the aperiodic impulse of current of temporal form 9 ms/160 ms and by amplitude 745 A coincide within the limits of 19 %. Originality. First with the use of methods of atomic and quantum physics the features of the stochastic distributing and mean values of basic geometrical sizes are analysed macroscopic longitudinal and radial EWP in round cylindrical metallic conductors with the pulsed axial current of high density. Practical value. Drawing on the got results in practice will allow more reliably to forecast geometrical sizes and places of localization of arising up in the probed metallic conductors with pulsed axial current of high density longitudinal and radial EWP.

  15. Approximation of the breast height diameter distribution of two-cohort stands by mixture models III Kernel density estimators vs mixture models

    Science.gov (United States)

    Rafal Podlaski; Francis A. Roesch

    2014-01-01

    Two-component mixtures of either the Weibull distribution or the gamma distribution and the kernel density estimator were used for describing the diameter at breast height (dbh) empirical distributions of two-cohort stands. The data consisted of study plots from the Å wietokrzyski National Park (central Poland) and areas close to and including the North Carolina section...

  16. Spatial distribution of Brucella antibodies with reference to indigenous cattle populations among contrasting agro-ecological zones of Uganda.

    Science.gov (United States)

    Kabi, Fredrick; Muwanika, Vincent; Masembe, Charles

    2015-09-01

    Indigenous cattle populations exhibit various degrees of agro-ecological fitness and provide desirable opportunities for investments to improve sustainable production for better rural small-scale farmers' incomes globally. However, they could be a source of infection to their attendants and other susceptible livestock if their brucellosis status remains unknown. This study investigated the spatial distribution of Brucella antibodies among indigenous cattle populations in Uganda. Sera from a total of 925 indigenous cattle (410 Ankole Bos taurus indicus, 50 Nganda and 465 East African Shorthorn Zebu (EASZ) - B. indicus) obtained randomly from 209 herds spread throughout Uganda were sequentially analysed for Brucella antibodies using the indirect (I) and competitive (C) enzyme linked Immuno-sorbent assays (ELISA). Recent incidences of abortion within the previous 12 months and routine hygienic practices during parturition were explored for public health risks. Brucella antibodies occurred in approximately 8.64% (80/925) and 28.70% (95% CI: 22.52, 34.89) of the sampled individual cattle and herds, respectively. Findings have shown that Ankole and EASZ cattle had similar seroprevalences. Indigenous cattle from the different study agro-ecological zones (AEZs) exhibited varying seroprevalences ranging from approximately 1.78% (95% CI: 0, 5.29) to 19.67% (95% CI: 8.99, 30.35) in the Lake Victoria Crescent (LVC) and North Eastern Drylands (NED) respectively. Significantly higher odds for Brucella antibodies occurred in the NED (OR: 3.40, 95% CI: 1.34, 8.57, p=0.01) inhabited by EASZ cattle compared to the KP (reference category) AEZ. Recent incidences of abortions within the previous 12 months were significantly (p<0.001) associated with seropositive herds. These findings add critical evidence to existing information on the widespread occurrence of brucellosis among indigenous cattle populations in Uganda and could guide allocation of meagre resources for awareness creation

  17. A study of the early detection of insect infestations and density/distribution of host plants

    Science.gov (United States)

    Hart, W. G.; Ingle, S. J.; Davis, M. R. (Principal Investigator)

    1974-01-01

    The author has identified the following significant results. Significant results have been obtained in the identification of citrus, sugarcane, winter vegetables, irrigated pastures, and unimproved pastures which contain brush. Land without vegetation, lakes, roads, and waterways can also be determined. Different densities of vegetation covering some cultivated areas are apparent. The practical applications of these results are many. The abundance of host plants of pests can be determined. Avenues of entry of pests can be plotted, facilitating control or preventing entry of pest species. The boundaries of areas to be quarantined can be accurately established after viewing the S-190B data. Better cultural methods can be employed such as planning where to plant certain crops that indirectly are detrimental to those already growing. This would relate to such factors as pesticide drift or alternate hosts of major pests.

  18. A microscopic "social norm" model to obtain realistic macroscopic velocity and density pedestrian distributions.

    Directory of Open Access Journals (Sweden)

    Francesco Zanlungo

    Full Text Available We propose a way to introduce in microscopic pedestrian models a "social norm" in collision avoiding and overtaking, i.e. the tendency, shared by pedestrians belonging to the same culture, to avoid collisions and perform overtaking in a preferred direction. The "social norm" is implemented, regardless of the specific collision avoiding model, as a rotation in the perceived velocity vector of the opponent at the moment of computation of the collision avoiding strategy, and justified as an expectation that the opponent will follow the same "social norm" (for example a tendency to avoid on the left and overtake on the right, as proposed in this work for Japanese pedestrians. By comparing with real world data, we show that the introduction of this norm allows for a better reproduction of macroscopic pedestrian density and velocity patterns.

  19. A comparison of the experimental and theoretical charge density distributions in two polymorphic modifications of piroxicam

    DEFF Research Database (Denmark)

    Lai, Felcia; Du, Jonathan J.; Williams, Peter A.;

    2016-01-01

    piroxicam molecules, (2a) and (2b), and two water molecules. Geometry differs between (1) and (2) due to the zwitterionic nature of (2) which results in the rotation of the pyridine ring around the C(10)-N(2) bond by approximately 180°. Consequently, the pyridine and amide are no longer co-planar and (2...... is distributed across the benzothiazine carboxamide moiety. The multipole derived lattice energy for (1) is -304 kJ mol(-1) and that for (2) is -571 kJ mol(-1), which is in agreement with the experimentally determined observations of higher solubility and dissolution rates of (1) compared to (2)....

  20. Statistical Distribution of the Vacuum Energy Density in Racetrack K\\"ahler Uplift Models in String Theory

    CERN Document Server

    Sumitomo, Yoske; Wong, Sam S C

    2013-01-01

    We study a racetrack model in the presence of the leading alpha'-correction in flux compactification in Type IIB string theory, for the purpose of getting conceivable de-Sitter vacua in the large compactified volume approximation. Unlike the K\\"ahler Uplift model studied previously, the alpha'-correction is more controllable for the meta-stable de-Sitter vacua in the racetrack case since the constraint on the compactified volume size is very much relaxed. We find that the vacuum energy density \\Lambda for de-Sitter vacua approaches zero exponentially as the volume grows. We also analyze properties of the probability distribution of \\Lambda in this class of models. As in other cases studied earlier, the probability distribution again peaks sharply at \\Lambda=0. We also study the Racetrack K\\"ahler Uplift model in the Swiss-Cheese type model.

  1. Probability density functions for description of diameter distribution in thinned stands of Tectona grandis

    Directory of Open Access Journals (Sweden)

    Julianne de Castro Oliveira

    2012-06-01

    Full Text Available The objective of this study was to evaluate the effectiveness of fatigue life, Frechet, Gamma, Generalized Gamma, Generalized Logistic, Log-logistic, Nakagami, Beta, Burr, Dagum, Weibull and Hyperbolic distributions in describing diameter distribution in teak stands subjected to thinning at different ages. Data used in this study originated from 238 rectangular permanent plots 490 m2 in size, installed in stands of Tectona grandis L. f. in Mato Grosso state, Brazil. The plots were measured at ages 34, 43, 55, 68, 81, 82, 92, 104, 105, 120, 134 and 145 months on average. Thinning was done in two occasions: the first was systematic at age 81months, with a basal area intensity of 36%, while the second was selective at age 104 months on average and removed poorer trees, reducing basal area by 30%. Fittings were assessed by the Kolmogorov-Smirnov goodness-of-fit test. The Log-logistic (3P, Burr (3P, Hyperbolic (3P, Burr (4P, Weibull (3P, Hyperbolic (2P, Fatigue Life (3P and Nakagami functions provided more satisfactory values for the k-s test than the more commonly used Weibull function.

  2. The Role of Core Mass in Controlling Evaporation: the Kepler Radius Distribution and the Kepler-36 Density Dichotomy

    CERN Document Server

    Lopez, Eric

    2013-01-01

    We use models of coupled thermal evolution and photo-evaporative mass loss to understand the formation and evolution of the Kepler-36 system. We show that the large contrast in mean planetary density observed by Carter et al. (2012) can be explained as a natural consequence of photo-evaporation from planets that formed with similar initial compositions. However, rather than being due to differences in XUV irradiation between the planets, we find that this contrast is due to the difference in the masses of the planets' rock/iron cores and the impact that this has on mass loss evolution. We explore in detail how our coupled models depend on irradiation, mass, age, composition, and the efficiency of mass loss. Based on fits to large numbers of coupled evolution and mass loss runs, we provide analytic fits to understand threshold XUV fluxes for significant atmospheric loss, as a function of core mass and mass loss efficiency. Finally we discuss these results in the context of recent studies of the radius distribu...

  3. Current Density Distributions and a Supersymmetric Action for Interacting Brane Systems

    CERN Document Server

    Bandos, I A; Bandos, Igor; Kummer, Wolfgang

    1999-01-01

    We propose a method to obtain a manifestly supersymmetric action functional for interacting brane systems. It is based on the induced map of the worldvolume of low-dimensional branes into the worldvolume of the space-time filling brane ((D-1)-brane), which may be either dynamical or auxiliary, and implies an identification of Grassmann coordinate fields of lower dimensional branes with an image of the Grassmann coordinate fields of that (D-1)-brane. With this identification the covariant current distribution forms with support on the superbrane worldvolumes become invariant under the target space supersymmetry and can be used to write the coupled superbrane action as an integral over the D-dimensional manifolds ((D-1)-brane worldvolume). We compare the equations derived from this new ('Goldstone fermion embedded') action with the ones produced by a more straightforward generalization of the free brane actions based on the incorporation of the boundary terms with Lagrange multipliers ('superspace embedded' act...

  4. Density and Distribution of Citemene Fields in a Miombo Woodland Environment in Zambia.

    Science.gov (United States)

    Sprague; Oyama

    1999-09-01

    / The Bemba people of northern Zambia practice citemene shifting cultivation. We utilized Landsat satellite images from 1984 and 1992 to map the distribution of citemene fields in those two years and to assess changes in the spatial sustainability of citemene cultivation in a miombo woodland study area. The citemene fields were concentrated within about 5-6 km of roads. Between 1984 and 1992, there was a decrease in the number of fields, and an increase in the average distance from the road. These changes may have been due to the introduction of semipermanent maize farming in the intervening years. The estimated cycle times for woodland utilization may have been long enough to maintain sustainability under traditional citemene cultivation practices. However, cycle times may be too short to maintain sustainability within the woodlands along roads.KEY WORDS: Shifting agriculture; GIS; Sustainability; Citemene; Miombo; Zambiahttp://link.springer-ny.com/link/service/journals/00267/bibs/24n2p273.html

  5. Radial distribution function of penetrable sphere fluids to the second order in density.

    Science.gov (United States)

    Santos, Andrés; Malijevský, Alexandr

    2007-02-01

    The simplest bounded potential is that of penetrable spheres, which takes a positive finite value epsilon if the two spheres are overlapped, being zero otherwise. In this paper we derive the cavity function to second order in density and the fourth virial coefficient as functions of T* identical with k(B)T/epsilon (where k(B is the Boltzmann constant and T is the temperature) for penetrable sphere fluids. The expressions are exact, except for the function represented by an elementary diagram inside the core, which is approximated by a polynomial form in excellent agreement with accurate results obtained by Monte Carlo integration. Comparison with the hypernetted-chain (HNC) and Percus-Yevick (PY) theories shows that the latter is better than the former for T* hard sphere limit), the PY solution is not accurate inside the overlapping region, where no practical cancellation of the neglected diagrams takes place. The exact fourth virial coefficient is positive for T* compressibility route is the best one for T* or similar to 0.7.

  6. Predicting Ligand Binding Sites on Protein Surfaces by 3-Dimensional Probability Density Distributions of Interacting Atoms

    Science.gov (United States)

    Jian, Jhih-Wei; Elumalai, Pavadai; Pitti, Thejkiran; Wu, Chih Yuan; Tsai, Keng-Chang; Chang, Jeng-Yih; Peng, Hung-Pin; Yang, An-Suei

    2016-01-01

    Predicting ligand binding sites (LBSs) on protein structures, which are obtained either from experimental or computational methods, is a useful first step in functional annotation or structure-based drug design for the protein structures. In this work, the structure-based machine learning algorithm ISMBLab-LIG was developed to predict LBSs on protein surfaces with input attributes derived from the three-dimensional probability density maps of interacting atoms, which were reconstructed on the query protein surfaces and were relatively insensitive to local conformational variations of the tentative ligand binding sites. The prediction accuracy of the ISMBLab-LIG predictors is comparable to that of the best LBS predictors benchmarked on several well-established testing datasets. More importantly, the ISMBLab-LIG algorithm has substantial tolerance to the prediction uncertainties of computationally derived protein structure models. As such, the method is particularly useful for predicting LBSs not only on experimental protein structures without known LBS templates in the database but also on computationally predicted model protein structures with structural uncertainties in the tentative ligand binding sites. PMID:27513851

  7. The Distribution and Density of Water Mice (Xeromys myoides) in the Maroochy River of Southeast Queensland, Australia.

    Science.gov (United States)

    Kaluza, Janina; Donald, R Lesley; Gynther, Ian C; Leung, Luke K-P; Allen, Benjamin L

    2016-01-01

    The water mouse is a small and vulnerable rodent present in coastal areas of south-west Papua New Guinea, and eastern Queensland and the Northern Territory of Australia. Current knowledge regarding the distribution of the water mouse is incomplete and the loss of one local population has been documented in southeast Queensland, a region where pressures from urban and industrial development are increasing. Water mouse populations have not been studied intensively enough to enable the primary factors responsible for the local decline to be identified. We surveyed the distribution and density of the water mouse along the Maroochy River of southeast Queensland, near the southern extent of the species' range, to gather baseline data that may prove valuable for detecting any future decline in this population's size or health. All areas of suitable habitat were surveyed on foot or by kayak or boat over a three-year period. We found 180 water mouse nests, of which ~94% were active. Permanent camera monitoring of one nest and limited supplementary live trapping suggested that up to three individual mice occupied active nests. Water mouse density was estimated to be 0.44 per hectare of suitable habitat along the Maroochy River. Should future monitoring reveal an adverse change in the water mouse population on the Maroochy River, a concerted effort should be made to identify contributing factors and address proximate reasons for the decline.

  8. The Distribution and Density of Water Mice (Xeromys myoides in the Maroochy River of Southeast Queensland, Australia.

    Directory of Open Access Journals (Sweden)

    Janina Kaluza

    Full Text Available The water mouse is a small and vulnerable rodent present in coastal areas of south-west Papua New Guinea, and eastern Queensland and the Northern Territory of Australia. Current knowledge regarding the distribution of the water mouse is incomplete and the loss of one local population has been documented in southeast Queensland, a region where pressures from urban and industrial development are increasing. Water mouse populations have not been studied intensively enough to enable the primary factors responsible for the local decline to be identified. We surveyed the distribution and density of the water mouse along the Maroochy River of southeast Queensland, near the southern extent of the species' range, to gather baseline data that may prove valuable for detecting any future decline in this population's size or health. All areas of suitable habitat were surveyed on foot or by kayak or boat over a three-year period. We found 180 water mouse nests, of which ~94% were active. Permanent camera monitoring of one nest and limited supplementary live trapping suggested that up to three individual mice occupied active nests. Water mouse density was estimated to be 0.44 per hectare of suitable habitat along the Maroochy River. Should future monitoring reveal an adverse change in the water mouse population on the Maroochy River, a concerted effort should be made to identify contributing factors and address proximate reasons for the decline.

  9. Density and Distribution of Xylocopa Nests (Hymenoptera: Apidae) in Caatinga Areas in the Surroundings of Passion Fruit Crops.

    Science.gov (United States)

    Martins, C F; de Siqueira, K M M; Kiill, L H P; Sá, I I S; Aguiar, C M L

    2014-08-01

    Due to their importance as pollinators of many plant species, this study aimed to know the nest density, spatial distribution, and nesting substrates used by Xylocopa species in the Caatinga, a xerophilous vegetation of Northeastern Brazil. Three areas of Caatinga in the surroundings of passion fruit crops were sampled. The bee species found in these areas were Xylocopa grisescens Lepeletier and Xylocopa frontalis (Olivier). All nests were in Commiphora leptophloeos (Burseraceae) trees (n = 113). Phytosociological analysis showed that this tree species presented the highest absolute density (212.5 individuals/ha) and index of importance value (52.7). The distribution pattern of the C. leptophloeos was aggregated. The nests were located in dead and dried branches with an average diameter of 5.3 ± 2.0 cm (n = 43). The mean number of nests/tree was 3.1 ± 2.8 (n = 113). The less disturbed area showed 6.7 nests/ha and 4.2 nests/tree. In the disturbed areas, 0.9 nests/ha and 2.4 to 2.7 nests/tree were observed. The availability of substrate for nesting in the studied areas and its importance as a limiting factor for nesting are discussed.

  10. Ejecta velocity distribution of impact craters formed on quartz sand: Effect of projectile density on crater scaling law

    Science.gov (United States)

    Tsujido, Sayaka; Arakawa, Masahiko; Suzuki, Ayako I.; Yasui, Minami

    2015-12-01

    In order to clarify the effects of projectile density on ejecta velocity distributions for a granular target, impact cratering experiments on a quartz sand target were conducted by using eight types of projectiles with different densities ranging from 11 g cm-3 to 1.1 g cm-3, which were launched at about 200 m s-1 from a vertical gas gun at Kobe University. The scaling law of crater size, the ejection angle of ejecta grains, and the angle of the ejecta curtain were also investigated. The ejecta velocity distribution obtained from each projectile was well described by the π-scaling theory of v0/√{gR} =k2(x0/R)-1/μ, where v0, g, R and x0 are the ejection velocity, gravitational acceleration, crater radius and ejection position, respectively, and k2 and μ are constants mostly depending on target material properties (Housen, K.R., Holsapple, K.A. [2011]. Icarus 211, 856-875). The value of k2 was found to be almost constant at 0.7 for all projectiles except for the nylon projectile, while μ increased with the projectile density, from 0.43 for the low-density projectile to 0.6-0.7 for the high-density projectile. On the other hand, the π-scaling theory for crater size gave a μ value of 0.57, which was close to the average of the μ values obtained from ejecta velocity distributions. The ejection angle, θ, of each grain decreased slightly with distance, from higher than 45° near the impact point to 30-40° at 0.6 R. The ejecta curtain angle is controlled by the two elementary processes of ejecta velocity distribution and ejection angle; it gradually increased from 52° to 63° with the increase of the projectile density. The comparison of our experimental results with the theoretical model of the crater excavation flow known as the Z-model revealed that the relationship between μ and θ obtained by our experiments could not be described by the Z-model (Maxwell, D.E. [1977]. In: Roddy, D.J., Pepin, R.O., Merrill, R.B. (Eds.), Impact and Explosion Cratering

  11. The use of salinity contrast for density difference compensation to improve the thermal recovery efficiency in high-temperature aquifer thermal energy storage systems

    NARCIS (Netherlands)

    van Lopik, J.H.; Hartog, N.; Zaadnoordijk, Willem Jan

    2016-01-01

    The efficiency of heat recovery in high-temperature (>60 °C) aquifer thermal energy storage (HT-ATES) systems is limited due to the buoyancy of the injected hot water. This study investigates the potential to improve the efficiency through compensation of the density difference by increased salinity

  12. Large organic-walled Protista ( Gromia) in the Arabian Sea: Density, diversity, distribution and ecology

    Science.gov (United States)

    Aranda da Silva, A.; Gooday, A. J.

    2009-03-01

    The genus Gromia includes large marine protists ('gromiids') with filose pseudopodia and sack-like organic tests. The first deep-water species were discovered in the 1990s on the Oman Margin of the Arabian Sea and subsequently found on the Pakistan Margin. We present a survey of gromiids in samples collected off Oman in 2002 and off Pakistan in 2003. In addition to the two species ( Gromia sphaerica and Gromia pyriformis) already described from this area, at least eight undescribed gromiid species were present. Sausage shaped, grape shaped and spherical morphotypes were represented among this material. On the Oman Margin, gromiids occurred in densities up to several thousand individuals m -2 at 1400 and 1700 m but were much less common at 1100 and 2000 m. Apart from G. pyriformis, which was fairly common (several hundred individuals m -2) at 1000 m, gromiids were uncommon in core samples taken off Pakistan, with 11 indiv. m -2 at 1200 m and 19 indiv. m -2 at 1850 m. On both margins, these protists occurred at depths >1000 m where bottom-water oxygen concentrations exceeded ˜0.2 ml l -1 (=8.92 μM l -1) land sediments were fully bioturbated and oxidised. However, they were not observed at similar oxygen levels above the OMZ. Most gromiids lived on the sediment surface with their apertures facing down and their pseudopodia presumably deployed into the sediment to feed on surficial material and associated bacteria. We conclude that these large protists may play an important ecological role in the bathyal Arabian Sea, particularly in carbon cycling but also in structuring the surficial sediments. In addition, their tests, particularly those of G. sphaerica, provide substrates for attached Foraminifera.

  13. Anatomic distribution of nerves and microvascular density in the human anterior vaginal wall: prospective study.

    Directory of Open Access Journals (Sweden)

    Ting Li

    Full Text Available BACKGROUND: The presence of the G-spot (an assumed erotic sensitive area in the anterior wall of the vagina remains controversial. We explored the histomorphological basis of the G-spot. METHODS: Biopsies were drawn from a 12 o'clock direction in the distal- and proximal-third areas of the anterior vagina of 32 Chinese subjects. The total number of protein gene product 9.5-immunoreactive nerves and smooth muscle actin-immunoreactive blood vessels in each specimen was quantified using the avidin-biotin-peroxidase assay. RESULTS: Vaginal innervation was observed in the lamina propria and muscle layer of the anterior vaginal wall. The distal-third of the anterior vaginal wall had significantly richer small-nerve-fiber innervation in the lamina propria than the proximal-third (p = 0.000 and in the vaginal muscle layer (p = 0.006. There were abundant microvessels in the lamina propria and muscle layer, but no small vessels in the lamina propria and few in the muscle layer. Significant differences were noted in the number of microvessels when comparing the distal- with proximal-third parts in the lamina propria (p = 0.046 and muscle layer (p = 0.002. CONCLUSIONS: Significantly increased density of nerves and microvessels in the distal-third of the anterior vaginal wall could be the histomorphological basis of the G-spot. Distal anterior vaginal repair could disrupt the normal anatomy, neurovascular supply and function of the G-spot, and cause sexual dysfunction.

  14. The use of salinity contrast for density difference compensation to improve the thermal recovery efficiency in high-temperature aquifer thermal energy storage systems

    Science.gov (United States)

    van Lopik, Jan H.; Hartog, Niels; Zaadnoordijk, Willem Jan

    2016-08-01

    The efficiency of heat recovery in high-temperature (>60 °C) aquifer thermal energy storage (HT-ATES) systems is limited due to the buoyancy of the injected hot water. This study investigates the potential to improve the efficiency through compensation of the density difference by increased salinity of the injected hot water for a single injection-recovery well scheme. The proposed method was tested through numerical modeling with SEAWATv4, considering seasonal HT-ATES with four consecutive injection-storage-recovery cycles. Recovery efficiencies for the consecutive cycles were investigated for six cases with three simulated scenarios: (a) regular HT-ATES, (b) HT-ATES with density difference compensation using saline water, and (c) theoretical regular HT-ATES without free thermal convection. For the reference case, in which 80 °C water was injected into a high-permeability aquifer, regular HT-ATES had an efficiency of 0.40 after four consecutive recovery cycles. The density difference compensation method resulted in an efficiency of 0.69, approximating the theoretical case (0.76). Sensitivity analysis showed that the net efficiency increase by using the density difference compensation method instead of regular HT-ATES is greater for higher aquifer hydraulic conductivity, larger temperature difference between injection water and ambient groundwater, smaller injection volume, and larger aquifer thickness. This means that density difference compensation allows the application of HT-ATES in thicker, more permeable aquifers and with larger temperatures than would be considered for regular HT-ATES systems.

  15. Spatial patterns of distribution, abundance, and species diversity of small odontocetes estimated using density surface modeling with line transect sampling

    Science.gov (United States)

    Kanaji, Yu; Okazaki, Makoto; Miyashita, Tomio

    2017-06-01

    Spatial patterns of distribution, abundance, and species diversity of small odontocetes including species in the Delphinidae and Phocoenidae families were investigated using long-term dedicated sighting survey data collected between 1983 and 2006 in the North Pacific. Species diversity indices were calculated from abundance estimated using density surface modeling of line-transect data. The estimated abundance ranged from 19,521 individuals in killer whale to 1,886,022 in pantropical spotted dolphin. The predicted density maps showed that the habitats of small odontocetes corresponded well with distinct oceanic domains. Species richness was estimated to be highest between 30 and 40°N where warm- and cold-water currents converge. Simpson's Diversity Index showed latitudinal diversity gradients of decreasing species numbers toward the poles. Higher diversity was also estimated in the coastal areas and the zonal areas around 35-42°N. Coastal-offshore gradients and latitudinal gradients are known for many taxa. The zonal areas around 35°N and 40°N coincide with the Kuroshio Current and its extension and the subarctic boundary, respectively. These results suggest that the species diversity of small odontocetes primarily follows general patterns of latitudinal and longitudinal gradients, while the confluence of faunas originating in distinct water masses increases species diversify in frontal waters around 30-40°N. Population densities tended to be higher for the species inhabiting higher latitudes, but were highest for intermediate latitudes at approximately 35-40°N. According to latitudinal gradients in water temperature and biological productivity, the costs for thermoregulation will decrease in warmer low latitudes, while feeding efficiency will increase in colder high latitudes. These trade-offs could optimize population density in intermediate latitudes.

  16. Density and distribution of megafauna at the Håkon Mosby Mud Volcano (the Barents Sea based on image analysis

    Directory of Open Access Journals (Sweden)

    E. Rybakova (Goroslavskaya

    2012-12-01

    Full Text Available During a survey of the Håkon Mosby Mud Volcano (HMMV, located on the Bear Island Fan in the southwest Barents Sea at ~ 1250 m water depth, different habitats inside the volcano caldera and outside it were photographed using a towed camera platform, an Ocean Floor Observation System (OFOS. Three transects were performed across the caldera and one outside, in the background area, each transect was ~ 2 km in length. We compared the density, taxa richness and diversity of non-symbiotrophic megafauna in areas inside the volcano caldera with different bacterial mat and pogonophoran tubeworm cover. Significant variations in megafaunal composition, density and distribution were found between considered areas. Total megafaunal density was highest in areas of dense pogonophoran populations (mean 52.9 ind. m−2 followed by areas of plain light-coloured sediment that were devoid of bacterial mats and tubeworms (mean 37.7 ind. m−2. The lowest densities were recorded in areas of dense bacterial mats (mean ≤ 1.4 ind. m−2. Five taxa contributed to most of the observed variation: the ophiuroid Ophiocten gracilis, lysianassid amphipods, the pycnogonid Nymphon macronix, the caprellid Metacaprella horrida and the fish Lycodes squamiventer. In agreement with previous studies, three zones within the HMMV caldera were distinguished, based on different habitats and megafaunal composition: "bacterial mats", "pogonophoran fields" and "plain light-coloured sediments". The zones were arranged almost concentrically around the central part of the caldera that was devoid of visible megafauna. The total number of taxa showed little variation inside (24 spp. and outside the caldera (26 spp.. The density, diversity and composition of megafauna varied substantially between plain light-coloured sediment areas inside the caldera and the HMMV background. Megafaunal density was lower in the background (mean 25.3 ind

  17. Density and distribution of megafauna at the Håkon Mosby mud volcano (the Barents Sea based on image analysis

    Directory of Open Access Journals (Sweden)

    E. Rybakova (Goroslavskaya

    2013-05-01

    Full Text Available During a survey of the Håkon Mosby mud volcano (HMMV, located on the Bear Island fan in the southwest Barents Sea at ∼1250 m water depth, different habitats inside the volcano caldera and outside it were photographed using a towed camera platform, an Ocean Floor Observation System (OFOS. Three transects were performed across the caldera and one outside, in the background area, each transect was ∼2 km in length. We compared the density, taxa richness and diversity of nonsymbiotrophic megafauna in areas inside the volcano caldera with different bacterial mat and pogonophoran tubeworm cover. Significant variations in megafaunal composition, density and distribution were found between considered areas. Total megafaunal density was highest in areas of dense pogonophoran populations (mean 52.9 ind. m−2 followed by areas of plain light-coloured sediment that were devoid of bacterial mats and tube worms (mean 37.7 ind. m−2. The lowest densities were recorded in areas of dense bacterial mats (mean ≤1.4 ind. m−2. Five taxa contributed to most of the observed variation: the ophiuroid Ophiocten gracilis, lysianassid amphipods, the pycnogonid Nymphon macronix, the caprellid Metacaprella horrida and the fish Lycodes squamiventer. In agreement with previous studies, three zones within the HMMV caldera were distinguished, based on different habitats and megafaunal composition: "bacterial mats", "pogonophoran fields" and "plain light-coloured sediments". The zones were arranged almost concentrically around the central part of the caldera that was devoid of visible megafauna. The total number of taxa showed little variation inside (24 spp. and outside the caldera (26 spp.. The density, diversity and composition of megafauna varied substantially between plain light-coloured sediment areas inside the caldera and the HMMV background. Megafaunal density was lower in the background (mean 25.3 ind. m−2 compared to areas of plain light-coloured sediments

  18. Extraction of the spatial distribution of electron temperature and density in Magnetized Liner Inertial Fusion implosion plasmas

    Science.gov (United States)

    Carpenter, Kyle; Mancini, Roberto

    2016-10-01

    We are testing polychromatic tomography to extract the spatial distribution of electron temperatures and densities in the cylindrical implosion plasmas created during MagLIF. Motivation for this technique stems from its successful application to spherical implosion core plasmas on Omega through the analysis of spatially resolved spectra (SRS) collected via pinhole imaging. In MagLIF, collections of SRS can be extracted from the images created by the slit imaging CRITR spectrometers. These spectra can be complemented with pinhole monochromatic images and spectra recorded with a spherical crystal spectrometer. One axially resolved and one radially resolved CRITR are field during MagLIF and information extracted from one of these SRS would be spatially integrated over a plane of finite thickness given by the spatial resolution of the instrument. In our method, we couple a model that creates synthetic sets of spectra, like those obtained from an experiment, with a Pareto genetic algorithm which searches in parameter space for the spatial distribution which best simultaneously and self-consistently fits the set of SRS/ Solutions obtained are used as the initial solution for a Levenberg-Marquadt minimization algorithm to provide a final ``fine-tuned'' solution. We are testing this method by creating synthetic ``experimental'' data and using the technique to search for the spatial distribution. The results of these feasibility studies will be discussed. The work is supported by a contract from Sandia National Laboratories.

  19. Effect of microvascular distribution and its density on interstitial fluid pressure in solid tumors: A computational model.

    Science.gov (United States)

    Mohammadi, M; Chen, P

    2015-09-01

    Solid tumors with different microvascular densities (MVD) have been shown to have different outcomes in clinical studies. Other studies have demonstrated the significant correlation between high MVD, elevated interstitial fluid pressure (IFP) and metastasis in cancers. Elevated IFP in solid tumors prevents drug macromolecules reaching most cancerous cells. To overcome this barrier, antiangiogenesis drugs can reduce MVD within the tumor and lower IFP. A quantitative approach is essential to compute how much reduction in MVD is required for a specific tumor to reach a desired amount of IFP for drug delivery purposes. Here we provide a computational framework to investigate how IFP is affected by the tumor size, the MVD, and location of vessels within the tumor. A general physiologically relevant tumor type with a heterogenous vascular structure surrounded by normal tissue is utilized. Then the continuity equation, Darcy's law, and Starling's equation are applied in the continuum mechanics model, which can calculate IFP for different cases of solid tumors. High MVD causes IFP elevation in solid tumors, and IFP distribution correlates with microvascular distribution within tumor tissue. However, for tumors with constant MVD but different microvascular structures, the average values of IFP were found to be the same. Moreover, for a constant MVD and vascular distribution, an increase in tumor size leads to increased IFP.

  20. NIHAO project II: Halo shape, phase-space density and velocity distribution of dark matter in galaxy formation simulations

    CERN Document Server

    Butsky, Iryna; Dutton, Aaron A; Wang, Liang; Stinson, Greg S; Penzo, Camilla; Kang, Xi; Keller, Ben W; Wadsley, James

    2015-01-01

    We show the effect of galaxy formation on the dark matter (DM) distribution across a wide range of halo masses. We focus on how baryon physics changes the dark matter halo shape, the so called "pseudo phase-space density distribution" and the velocity distribution within the virial radius, Rvir and in the solar neighborhood. This study is based on the NIHAO galaxy formation simulations, a large suite of cosmological zoom-in simulations. The galaxies reproduce key properties of observed galaxies, and hence offer unique insight into how baryons change the dark matter morphology and kinematics. When compared to dark matter only simulations, the NIHAO haloes have similar shapes at Rvir, but are substantially rounder inside ~0.1 Rvir. In DM-only simulations the inner halo has a minor-to-major axis ratio of c/a~0.5. In hydro simulations c/a increases with halo mass and integrated star formation efficiency, reaching ~0.8 at the Milky Way mass, reconciling a long-standing conflict between observations and DM only sim...

  1. Temperature Prediction Model for Bone Drilling Based on Density Distribution and In Vivo Experiments for Minimally Invasive Robotic Cochlear Implantation.

    Science.gov (United States)

    Feldmann, Arne; Anso, Juan; Bell, Brett; Williamson, Tom; Gavaghan, Kate; Gerber, Nicolas; Rohrbach, Helene; Weber, Stefan; Zysset, Philippe

    2016-05-01

    Surgical robots have been proposed ex vivo to drill precise holes in the temporal bone for minimally invasive cochlear implantation. The main risk of the procedure is damage of the facial nerve due to mechanical interaction or due to temperature elevation during the drilling process. To evaluate the thermal risk of the drilling process, a simplified model is proposed which aims to enable an assessment of risk posed to the facial nerve for a given set of constant process parameters for different mastoid bone densities. The model uses the bone density distribution along the drilling trajectory in the mastoid bone to calculate a time dependent heat production function at the tip of the drill bit. Using a time dependent moving point source Green's function, the heat equation can be solved at a certain point in space so that the resulting temperatures can be calculated over time. The model was calibrated and initially verified with in vivo temperature data. The data was collected in minimally invasive robotic drilling of 12 holes in four different sheep. The sheep were anesthetized and the temperature elevations were measured with a thermocouple which was inserted in a previously drilled hole next to the planned drilling trajectory. Bone density distributions were extracted from pre-operative CT data by averaging Hounsfield values over the drill bit diameter. Post-operative [Formula: see text]CT data was used to verify the drilling accuracy of the trajectories. The comparison of measured and calculated temperatures shows a very good match for both heating and cooling phases. The average prediction error of the maximum temperature was less than 0.7 °C and the average root mean square error was approximately 0.5 °C. To analyze potential thermal damage, the model was used to calculate temperature profiles and cumulative equivalent minutes at 43 °C at a minimal distance to the facial nerve. For the selected drilling parameters, temperature elevation profiles and

  2. The influence of interpolation and station network density on the distributions and trends of climate variables in gridded daily data

    Energy Technology Data Exchange (ETDEWEB)

    Hofstra, Nynke [University of Oxford, School of Geography and the Environment, Oxford (United Kingdom); Wageningen University, Environmental Systems Analysis Group, P.O. Box 47, Wageningen (Netherlands); New, Mark; McSweeney, Carol [University of Oxford, School of Geography and the Environment, Oxford (United Kingdom)

    2010-10-15

    We study the influence of station network density on the distributions and trends in indices of area-average daily precipitation and temperature in the E-OBS high resolution gridded dataset of daily climate over Europe, which was produced with the primary purpose of Regional Climate Model evaluation. Area averages can only be determined with reasonable accuracy from a sufficiently large number of stations within a grid-box. However, the station network on which E-OBS is based comprises only 2,316 stations, spread unevenly across approximately 18,000 0.22 grid-boxes. Consequently, grid-box data in E-OBS are derived through interpolation of stations up to 500 km distant, with the distance of stations that contribute significantly to any grid-box value increasing in areas with lower station density. Since more dispersed stations have less shared variance, the resultant interpolated values are likely to be over-smoothed, and extreme daily values even more so. We perform an experiment over five E-OBS grid boxes for precipitation and temperature that have a sufficiently dense local station network to enable a reasonable estimate of the area-average. We then create a series of randomly selected station sub-networks ranging in size from four to all stations within the E-OBS interpolation search radii. For each sub-network realisation, we estimate the grid-box average applying the same interpolation methodology as used for E-OBS, and then evaluate the effect of network density on the distribution of daily values, as well as trends in extremes indices. The results show that when fewer stations have been used for the interpolation, both precipitation and temperature are over-smoothed, leading to a strong tendency for interpolated daily values to be reduced relative to the ''true'' area-average. The smoothing is greatest for higher percentiles, and therefore has a disproportionate effect on extremes and any derived extremes indices. For many regions of the

  3. Volcanism on Mercury (dikes, lava flows, pyroclastics): Crust/mantle density contrasts, the evolution of compressive stress and the presence of mantle volatiles

    Science.gov (United States)

    Wilson, L.; Head, J. W., III

    2008-09-01

    Background. There is great uncertainty about the internal structure of Mercury and the composition of the mantle [e.g., 1, 2]. The high mean density of the body suggests that it may have lost parts of its crust and mantle in a giant impact at some stage after most of its initial accretion was sufficiently complete that at least partial separation of a core had occurred. It is the uncertainty about the timing of the giant impact, and hence the physico-chemical state of proto-Mercury at the time that it occurred, that leads to difficulties in predicting the interior structure and mantle composition. However, it seems reasonable to assume that the Mercury we see today has some combination of a relatively low-density crust and a relatively highdensity mantle; uncertainty remains about the presence and types of volatiles [2]. The second uncertainty is the nature of the surface plains units, specifically, are these lava flows and pyroclastics erupted from the interior, or impact-reworked earlier crust [3-5] (Figs. 1-2)? The detection of candidate pyroclastic deposits [4] has very important implications for mantle volatiles. Furthermore, whatever the surface composition, the presence of planet-wide systems of wrinkle ridges and thrust faults implies that a compressive crustal stress regime became dominant at some stage in the planet's history [3, 6]. If the plains units are indeed lava flows, then the fact that the products of the compressive regime deform many plains units suggests that the development of the compressive stresses may have played a vital role in determining when and if surface eruptions of mantle-derived magmas could occur. This would be analogous to the way in which the change with time from extensional to compressive global stresses in the lithosphere of the Moon influenced the viability of erupting magmas from deep mantle sources [7-9]. Analysis: To investigate the relationship between lithospheric stresses and magma eruption conditions [e.g., 9-11] we

  4. 3D analysis of synaptic vesicle density and distribution after acute foot-shock stress by using serial section transmission electron microscopy

    DEFF Research Database (Denmark)

    Khanmohammadi, M; Darkner, S; Nava, N

    2017-01-01

    distribution by fitting a one-dimensional parametrized distribution that took into account the location uncertainty due to section thickness. Our results showed a clear structural difference in synaptic vesicle density and distribution between stressed and control group with improved separation by 3D measures......Behavioural stress has shown to strongly affect neurotransmission within the neocortex. In this study, we analysed the effect of an acute stress model on density and distribution of neurotransmitter-containing vesicles within medial prefrontal cortex. Serial section transmission electron microscopy...... in comparison to the 2D measures. Our results showed that acute foot-shock stress exposure significantly affected both the spatial distribution and density of the synaptic vesicles within the presynaptic terminal....

  5. Modeling electron density distributions from X-ray diffraction to derive optical properties: Constrained wavefunction versus multipole refinement

    Science.gov (United States)

    Hickstein, Daniel D.; Cole, Jacqueline M.; Turner, Michael J.; Jayatilaka, Dylan

    2013-08-01

    The rational design of next-generation optical materials requires an understanding of the connection between molecular structure and the solid-state optical properties of a material. A fundamental challenge is to utilize the accurate structural information provided by X-ray diffraction to explain the properties of a crystal. For years, the multipole refinement has been the workhorse technique for transforming high-resolution X-ray diffraction datasets into the detailed electron density distribution of crystalline material. However, the electron density alone is not sufficient for a reliable calculation of the nonlinear optical properties of a material. Recently, the X-ray constrained wavefunction refinement has emerged as a viable alternative to the multipole refinement, offering several potential advantages, including the calculation of a wide range of physical properties and seeding the refinement process with a physically reasonable starting point. In this study, we apply both the multipole refinement and the X-ray constrained wavefunction technique to four molecules with promising nonlinear optical properties and diverse structural motifs. In general, both techniques obtain comparable figures of merit and generate largely similar electron densities, demonstrating the wide applicability of the X-ray constrained wavefunction method. However, there are some systematic differences between the electron densities generated by each technique. Importantly, we find that the electron density generated using the X-ray constrained wavefunction method is dependent on the exact location of the nuclei. The X-ray constrained wavefunction refinement makes smaller changes to the wavefunction when coordinates from the Hartree-Fock-based Hirshfeld atom refinement are employed rather than coordinates from the multipole refinement, suggesting that coordinates from the Hirshfeld atom refinement allow the X-ray constrained wavefunction method to produce more accurate wavefunctions. We

  6. A fast wire scanner, used to measure the transverse density distribution of beams circulating in an accelerator or storage ring.

    CERN Multimedia

    Maximilien Brice

    2002-01-01

    Fast wire scanners are used to measure the transverse density distribution of beams circulating in an accelerator or storage ring. In order to minimize blow-up of the beam through multiple Coulomb scattering, the wires are very thin (in the version shown here it is actually a twisted strand of carbon fibres with a total diameter of about 25 microns) and are swept through the beam at high speed (a linear motor, not mounted here, accelerates the wires to up to 20 m/s). One measures either the secondary emission current from the wire, or the signal from a scintillator/photomultiplier combination downstream from the wire scanner receiving the shower from nuclear reactions of beam particles with the wire nuclei. There are four such fast wire scanners in the 26 GeV PS and eight in the 1.4 GeV Booster.

  7. Measurements of transient electron density distributions by femtosecond X-ray diffraction; Messungen transienter Elektronendichteverteilungen durch Femtosekunden-Roentgenbeugung

    Energy Technology Data Exchange (ETDEWEB)

    Freyer, Benjamin

    2013-05-02

    This thesis concerns measurements of transient charge density maps by femtosecond X-ray diffraction. Different X-ray diffraction methods will be considered, particularly with regard to their application in femtosecond X-ray diffraction. The rotation method is commonly used in stationary X-ray diffraction. In the work in hand an X-ray diffraction experiment is demonstrated, which combines the method with ultrafast X-ray pulses. This experiment is the first implementation which makes use of the rotation method to map transient intensities of a multitude of Bragg reflections. As a prototype material Bismuth is used, which previously was studied frequently by femtosecond X-ray diffraction by measuring Bragg reflections successively. The experimental results of the present work are compared with the literature data. In the second part a powder-diffraction experiment will be presented, which is used to study the dynamics of the electron-density distribution on ultrafast time scales. The experiment investigates a transition metal complex after photoexcitation of the metal to ligand charge transfer state. Besides expected results, i. e. the change of the bond length between the metal and the ligand and the transfer of electronic charge from the metal to the ligand, a strong contribution of the anion to the charge transfer was found. Furthermore, the charge transfer has predominantly a cooperative character. That is, the excitation of a single complex causes an alteration of the charge density of several neighboring units. The results show that more than 30 transition-metal complexes and 60 anions contribute to the charge transfer. This collective response is a consequence of the strong coulomb interactions of the densely packed ions.

  8. Molecular weight​/branching distribution modeling of low-​density-​polyethylene accounting for topological scission and combination termination in continuous stirred tank reactor

    NARCIS (Netherlands)

    Yaghini, N.; Iedema, P.D.

    2014-01-01

    We present a comprehensive model to predict the molecular weight distribution (MWD),(1) and branching distribution of low-density polyethylene (IdPE),(2) for free radical polymerization system in a continuous stirred tank reactor (CSTR).(3) The model accounts for branching, by branching moment or ps

  9. Differences in estimates of size distribution of beryllium powder materials using phase contrast microscopy, scanning electron microscopy, and liquid suspension counter techniques.

    Science.gov (United States)

    Stefaniak, Aleksandr B; Hoover, Mark D; Dickerson, Robert M; Day, Gregory A; Breysse, Patrick N; Scripsick, Ronald C

    2007-02-28

    Accurate characterization of the physicochemical properties of aerosols generated for inhalation toxicology studies is essential for obtaining meaningful results. Great emphasis must also be placed on characterizing particle properties of materials as administered in inhalation studies. Thus, research is needed to identify a suite of techniques capable of characterizing the multiple particle properties (i.e., size, mass, surface area, number) of a material that may influence toxicity. The purpose of this study was to characterize the morphology and investigate the size distribution of a model toxicant, beryllium. Beryllium metal, oxides, and alloy particles were aerodynamically size-separated using an aerosol cyclone, imaged dry using scanning electron microscopy (SEM), then characterized using phase contrast microscopy (PCM), a liquid suspension particle counter (LPC), and computer-controlled SEM (CCSEM). Beryllium metal powder was compact with smaller sub-micrometer size particles attached to the surface of larger particles, whereas the beryllium oxides and alloy particles were clusters of primary particles. As expected, the geometric mean (GM) diameter of metal powder determined using PCM decreased with aerodynamic size, but when suspended in liquid for LPC or CCSEM analysis, the GM diameter decreased by a factor of two (p particles attached to the surface of larger particles and/or particle agglomerates detach in liquid, thereby shifting the particle size distribution downward. The GM diameters of the oxide materials were similar regardless of sizing technique, but observed differences were generally significant (p aerodynamic cluster size will dictate deposition in the lung, but primary particle size may influence biological activity. The GM diameter of alloy particles determined using PCM became smaller with decreasing aerodynamic size fraction; however, when suspended in liquid for CCSEM and LPC analyses, GM particle size decreased by a factor of two (p

  10. Simultaneous visualization of oxygen partial pressure, current density, and water droplets in serpentine fuel cell during power generation for understanding reaction distributions

    Science.gov (United States)

    Takanohashi, Kazuhiro; Suga, Takeo; Uchida, Makoto; Ueda, Toshihide; Nagumo, Yuzo; Inukai, Junji; Nishide, Hiroyuki; Watanabe, Masahiro

    2017-03-01

    Understanding the reaction distributions inside a polymer electrolyte fuel cell (PEFC) is essential for the higher performance and durability. We have developed a new see-through cell and visualized the distributions of oxygen partial pressure and current density inside a running PEFC at the temperature of 40 and 80 °C and the relative humidity of 53%. The oxygen utilization was changed from 0% to 80% by changing the current density. At higher oxygen utilizations, the current density was higher and therefore the water generation. Generated water droplets in the flow channel were also visualized, allowing for the simultaneous visualization of the distribution of the oxygen partial pressure, current density, and water droplets. By combining the observations of all three parameters, the reactions inside a membrane-electrode assembly were discussed.

  11. Contrastive Lexicology.

    Science.gov (United States)

    Hartmann, R. R. K.

    This paper deals with the relation between etymologically related words in different languages. A survey is made of seven stages in the development of contrastive lexicology. These are: prelinguistic word studies, semantics, lexicography, translation, foreign language learning, bilingualism, and finally contrastive analysis. Concerning contrastive…

  12. Vertical density contrast and mapping of basement, Conrad and Moho morphologies through 2D spectral analysis of gravity data in and around Odisha, India

    Science.gov (United States)

    Kumar, Arbind; S. Roy, P. N.; Das, L. K.

    2016-07-01

    Power spectrum analysis of Complete Bouguer Anomaly (CBA) map of Eastern Ghat Mobile Belt (EGMB) and its surroundings in India through Two Dimensional (2D) spectral analysis has provided estimates of the ensemble average depths for the density discontinuities which represent crustal inhomogeneities. The spectral analysis method has helped to estimate the depths of a perturbing body sources which are obtained from the negative slopes of the linear relationship between the logarithmic power spectrum and the wave-numbers of the gravity field. The detailed analysis reveals three horizontal discontinuities (i) Phanerozoic sediment thickness (ii) Basement depth and (iii) Conrad discontinuity. The average thickness of Phanerozoic sediments is estimated to be 3 km whereas depth of basement and Conrad discontinuity are at 7 km and 14.5 km respectively. Additionally Mohorovicic discontinuity also estimated at a depth of 32.8 km in the study region.

  13. Distribution, density and biological breeding of white wing pheasant (Phasianus colchicus principalis, Sclater, 1885 in Northeast of Iran

    Directory of Open Access Journals (Sweden)

    Nasrin Kayvanfar

    2014-01-01

    Full Text Available Common pheasant (Phasianus colchicus, Linnaeus, 1758 is an endemic naturally distributed in the Palearctic regions. White wing pheasant (P. c. principalis is distributed from Turkmenistan and north of Afghanistan along to Harir-Rud river in northeast of Iran. This study was the first attempt to determine the geographical range, density and breeding biology of white wing pheasant populations in northeast of Iran. To do so, 36 stations were defined in the breeding range of the species in two cities, namely Sarakhs and Dargaz in northeast of Iran. The breeding behaviors including egg lying, hatching and feeding behavior of chicks' were monitored and photographed using camera traps in 14 active nests in 10 stations. Collected data showed that white wing pheasant had a simple nest shape breeding season started in early April hatching began end of May and lasted 24±1 days (based on 14 active nests and finally enjoiyed little parental caring, particularly for the males. Comparative morphometrical data for eggs (length and width, nest and clutch size showed that there was a significant variation between the studied populations (P<0.05, ANOVA, in which the populations could be separated based on discriminant function analysis and the euclidean eendrogram. Comparision of morphometrical data of eggs in captive and wild nests showed that there was a significant length variation between them (P<0.05.

  14. Trait enactments as density distributions: The role of actors, situations, and observers in explaining stability and variability.

    Science.gov (United States)

    Fleeson, William; Law, Mary Kate

    2015-12-01

    The purposes of this article were to determine (a) whether the high consistency of individual differences in average aggregated behavior is because of actors' personalities or because of the consistency in the situations those actors encounter; and (b) whether the surprisingly high within-person variability in trait enactment is a real phenomenon corroborated by observers, or merely in individuals' heads. Although traits are supposed to describe what individuals are like in everyday life, little evidence exists about the enactment of trait content in everyday life. Past experience-sampling studies have found both highly variable and highly consistent trait enactment, but were restricted to self-report data and to naturally occurring situations. The current study used experience-sampling in controlled lab environments with 97 targets and 183 observers to address these shortcomings. Targets attended hour-long lab sessions 20× each and observers rated targets' behavior. Parameters of distributions were highly consistent (rs ∼ .80), revealing that actors were responsible for consistency, not situations. Nonetheless, observer ratings revealed that most variability in trait enactment was within-person, confirming that even when people put it on the line in ways that affected others, they still varied rapidly in the traits they enacted. In the face of 2 historically vexing objections to traits, this article supports the density distributions model of traits and argues that trait conceptualizations must accommodate large within-person variability.

  15. Pressure-induced changes in the electron density distribution in α-Ge near the α-β transition

    Energy Technology Data Exchange (ETDEWEB)

    Li, Rui [Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049 (China); HPCAT Geophysical Laboratory, Carnegie Institution of Washington, Argonne, Illinois 60439 (United States); University of Chinese Academy of Sciences, Chinese Academy of Sciences, Beijing 100049 (China); Liu, Jing [Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049 (China); Bai, Ligang; Shen, Guoyin, E-mail: gshen@ciw.edu [HPCAT Geophysical Laboratory, Carnegie Institution of Washington, Argonne, Illinois 60439 (United States); Tse, John S. [Department of Physics and Engineering Physics, University of Saskatchewan, Saskatoon, Saskatchewan S7N 5E2 (Canada)

    2015-08-17

    Electron density distributions in α-Ge have been determined under high pressure using maximum entropy method with structure factors obtained from single crystal synchrotron x-ray diffraction in a diamond anvil cell. The results show that the sp{sup 3} bonding is enhanced with increasing pressure up to 7.7(1) GPa. At higher pressures but below the α-β transition pressure of 11.0(1) GPa, the sp{sup 3}-like electron distribution progressively weakens with a concomitant increase of d-orbitals hybridization. The participation of d-orbitals in the electronic structure is supported by Ge Kβ{sub 2} (4p-1s) x-ray emission spectroscopy measurements showing the reduction of 4s character in the valence band at pressures far below the α-β transition. The gradual increase of d-orbitals in the valence level in the stability field of α-Ge is directly related to the eventual structural transition.

  16. Nitric oxide density distributions in the effluent of an RF argon APPJ: effect of gas flow rate and substrate

    Science.gov (United States)

    Iseni, S.; Zhang, S.; van Gessel, A. F. H.; Hofmann, S.; van Ham, B. T. J.; Reuter, S.; Weltmann, K.-D.; Bruggeman, P. J.

    2014-12-01

    The effluent of an RF argon atmospheric pressure plasma jet, the so-called kinpen, is investigated with focus on the nitric-oxide (NO) distribution for laminar and turbulent flow regimes. An additional dry air gas curtain is applied around the plasma effluent to prevent interaction with the ambient humid air. By means of laser-induced fluorescence (LIF) the absolute spatially resolved NO density is measured as well as the rotational temperature and the air concentration. While in the laminar case, the transport of NO is attributed to thermal diffusion; in the turbulent case, turbulent mixing is responsible for air diffusion. Additionally, measurements with a molecular beam mass-spectrometer (MBMS) absolutely calibrated for NO are performed and compared with the LIF measurements. Discrepancies are explained by the contribution of the N{{O}2} and {{N}2}O to the MBMS NO signal. Finally, the effect of a conductive substrate in front of the plasma jet on the spatial distribution of NO and air diffusion is also investigated.

  17. Surface current density distribution measurements of an electrically exploded foil via B-dot probe array data inversion

    Science.gov (United States)

    Ruden, E. L.; Amdahl, D. J.; Cooksey, R. H.; Robinson, P. R.; Analla, F. T.; Brown, D. J.; Kostora, M. R.; Camacho, J. F.

    2014-10-01

    Measurements are presented of the current per unit length as a function of the transverse distance from the center of a water-tamped 80 μm Al foil that narrows to a central width of 15.2 cm as it explodes into warm dense matter by Ohmic heating. Current is delivered by the discharge of a 36 μF capacitor bank charged to 30 kV and discharged to a peak current of 342 kA in 2.0 μs. The distribution is calculated by the linear regularized inversion of signals from an array of B-dot probes distributed along the foil's central half-width. The probes are far enough away from the foil (1 cm) be noninvasive and mechanically undisturbed during the time of interest. These results are compared to 3-D MHD ALEGRA simulations of the geometry driven by an external coupled two-loop lumped circuit model which accurately represents the driver. The goal of the effort is to test, in conjunction with other diagnostics, ab initio models of the equation of state and electrical conductivity of matter under conditions encountered in single-shot pulsed power devices (1 - 10 eV and 0.1 - 1 × solid density). This work was supported by AFOSR LRIR 11RD02COR.

  18. Unit-Sphere Anisotropic Multiaxial Stochastic-Strength Model Probability Density Distribution for the Orientation of Critical Flaws

    Science.gov (United States)

    Nemeth, Noel

    2013-01-01

    Models that predict the failure probability of monolithic glass and ceramic components under multiaxial loading have been developed by authors such as Batdorf, Evans, and Matsuo. These "unit-sphere" failure models assume that the strength-controlling flaws are randomly oriented, noninteracting planar microcracks of specified geometry but of variable size. This report develops a formulation to describe the probability density distribution of the orientation of critical strength-controlling flaws that results from an applied load. This distribution is a function of the multiaxial stress state, the shear sensitivity of the flaws, the Weibull modulus, and the strength anisotropy. Examples are provided showing the predicted response on the unit sphere for various stress states for isotropic and transversely isotropic (anisotropic) materials--including the most probable orientation of critical flaws for offset uniaxial loads with strength anisotropy. The author anticipates that this information could be used to determine anisotropic stiffness degradation or anisotropic damage evolution for individual brittle (or quasi-brittle) composite material constituents within finite element or micromechanics-based software

  19. Fission fragment charge and mass distributions in 239Pu(n ,f ) in the adiabatic nuclear energy density functional theory

    Science.gov (United States)

    Regnier, D.; Dubray, N.; Schunck, N.; Verrière, M.

    2016-05-01

    Background: Accurate knowledge of fission fragment yields is an essential ingredient of numerous applications ranging from the formation of elements in the r process to fuel cycle optimization for nuclear energy. The need for a predictive theory applicable where no data are available, together with the variety of potential applications, is an incentive to develop a fully microscopic approach to fission dynamics. Purpose: In this work, we calculate the pre-neutron emission charge and mass distributions of the fission fragments formed in the neutron-induced fission of 239Pu using a microscopic method based on nuclear density functional theory (DFT). Methods: Our theoretical framework is the nuclear energy density functional (EDF) method, where large-amplitude collective motion is treated adiabatically by using the time-dependent generator coordinate method (TDGCM) under the Gaussian overlap approximation (GOA). In practice, the TDGCM is implemented in two steps. First, a series of constrained EDF calculations map the configuration and potential-energy landscape of the fissioning system for a small set of collective variables (in this work, the axial quadrupole and octupole moments of the nucleus). Then, nuclear dynamics is modeled by propagating a collective wave packet on the potential-energy surface. Fission fragment distributions are extracted from the flux of the collective wave packet through the scission line. Results: We find that the main characteristics of the fission charge and mass distributions can be well reproduced by existing energy functionals even in two-dimensional collective spaces. Theory and experiment agree typically within two mass units for the position of the asymmetric peak. As expected, calculations are sensitive to the structure of the initial state and the prescription for the collective inertia. We emphasize that results are also sensitive to the continuity of the collective landscape near scission. Conclusions: Our analysis confirms

  20. Insights into the crystal chemistry of Earth materials rendered by electron density distributions: Pauling's rules revisited

    Energy Technology Data Exchange (ETDEWEB)

    Gibbs, Gerald V.; Ross, Nancy L.; Cox, David F.; Rosso, Kevin M.

    2014-05-20

    Pauling's first two rules are examined in terms of the accumulation of the electron density between bonded pairs of atoms for a relatively large number of oxide and silicate crystals and siloxane molecules. The distribution of the electron density shows that the radius of the oxygen atom is not fixed, but that it actually decreases systematically from ~1.40 Å to ~ 0.65 Å as the polarizing power and the electronegativity of the bonded metal atoms increase and the distribution of the O atom is progressively polarized and contracted along the bond vectors by the impact of the bonded interactions. The contractions result in an aspherical oxygen atom that displays as many different bonded “radii” as it has bonded interactions. The bonded radii for the metal atoms match the Shannon and Prewitt ionic radii for the more electropositive atoms like potassium and sodium, but they are systematically larger for the more electronegative atoms like aluminum, silicon and phosphorous. Pauling's first rule is based on the assumption that the radius of the oxide anion is fixed and that the radii of the cations are such that radius sum of the spherical oxide anion and a cation necessarily equals the separation between the cation-anion bonded pair with the coordination number of the cation being determined by the ratio of the radii of the cation and anion. In the case of the bonded radii, the sum of the bonded radii for the metal atoms and the oxide anion necessarily equals the bond lengths by virtue of the way that the bonded radii were determined in the partitioning of the electron density along the bond path into metal and O atom parts. But, the radius ratio for the O and M atoms is an unsatisfactory rule for determining the coordination number of the metal atom inasmuch as a bonded O atom is not, in general, spherical, and its size varies substantially along its bonded directions. But by counting the number of bond paths that radiate from a bonded atom, the

  1. Comparative study of species sensitivity distributions based on non-parametric kernel density estimation for some transition metals.

    Science.gov (United States)

    Wang, Ying; Feng, Chenglian; Liu, Yuedan; Zhao, Yujie; Li, Huixian; Zhao, Tianhui; Guo, Wenjing

    2017-02-01

    Transition metals in the fourth period of the periodic table of the elements are widely widespread in aquatic environments. They could often occur at certain concentrations to cause adverse effects on aquatic life and human health. Generally, parametric models are mostly used to construct species sensitivity distributions (SSDs), which result in comparison for water quality criteria (WQC) of elements in the same period or group of the periodic table might be inaccurate and the results could be biased. To address this inadequacy, the non-parametric kernel density estimation (NPKDE) with its optimal bandwidths and testing methods were developed for establishing SSDs. The NPKDE was better fit, more robustness and better predicted than conventional normal and logistic parametric density estimations for constructing SSDs and deriving acute HC5 and WQC for transition metals in the fourth period of the periodic table. The decreasing sequence of HC5 values for the transition metals in the fourth period was Ti > Mn > V > Ni > Zn > Cu > Fe > Co > Cr(VI), which were not proportional to atomic number in the periodic table, and for different metals the relatively sensitive species were also different. The results indicated that except for physical and chemical properties there are other factors affecting toxicity mechanisms of transition metals. The proposed method enriched the methodological foundation for WQC. Meanwhile, it also provided a relatively innovative, accurate approach for the WQC derivation and risk assessment of the same group and period metals in aquatic environments to support protection of aquatic organisms.

  2. Differences in estimates of size distribution of beryllium powder materials using phase contrast microscopy, scanning electron microscopy, and liquid suspension counter techniques

    Directory of Open Access Journals (Sweden)

    Day Gregory A

    2007-02-01

    Full Text Available Abstract Accurate characterization of the physicochemical properties of aerosols generated for inhalation toxicology studies is essential for obtaining meaningful results. Great emphasis must also be placed on characterizing particle properties of materials as administered in inhalation studies. Thus, research is needed to identify a suite of techniques capable of characterizing the multiple particle properties (i.e., size, mass, surface area, number of a material that may influence toxicity. The purpose of this study was to characterize the morphology and investigate the size distribution of a model toxicant, beryllium. Beryllium metal, oxides, and alloy particles were aerodynamically size-separated using an aerosol cyclone, imaged dry using scanning electron microscopy (SEM, then characterized using phase contrast microscopy (PCM, a liquid suspension particle counter (LPC, and computer-controlled SEM (CCSEM. Beryllium metal powder was compact with smaller sub-micrometer size particles attached to the surface of larger particles, whereas the beryllium oxides and alloy particles were clusters of primary particles. As expected, the geometric mean (GM diameter of metal powder determined using PCM decreased with aerodynamic size, but when suspended in liquid for LPC or CCSEM analysis, the GM diameter decreased by a factor of two (p

  3. Spatial distribution of electrons near the Fermi level in the metallic LaB6 through accurate X-ray charge density study

    Science.gov (United States)

    Kasai, Hidetaka; Nishibori, Eiji

    2017-01-01

    Charge densities of iso-structural metal hexaborides, a transparent metal LaB6 and a semiconductor BaB6, have been determined using the d > 0.22 Å ultra-high resolution synchrotron radiation X-ray diffraction data by a multipole refinement and a maximum entropy method (MEM). The quality of the experimental charge densities was evaluated by comparison with theoretical charge densities. The strong inter-octahedral and relatively weak intra-octahedral boron-boron bonds were observed in the charge densities. A difference of valence charge densities between LaB6 and BaB6 was calculated to reveal a small difference between isostructural metal and semiconductor. The weak electron lobes distributed around the inter B6 octahedral bond were observed in the difference density. We found the electron lobes are the conductive π-electrons in LaB6 from the comparison with the theoretical valence charge density. We successfully observed a spatial distribution of electrons near the Fermi level from the X-ray charge density study of the series of iso-structural solids. PMID:28120900

  4. The Column Density Distribution and Continuum Opacity of the Intergalactic and Circumgalactic Medium at Redshift langzrang = 2.4

    Science.gov (United States)

    Rudie, Gwen C.; Steidel, Charles C.; Shapley, Alice E.; Pettini, Max

    2013-06-01

    We present new high-precision measurements of the opacity of the intergalactic and circumgalactic medium (IGM; CGM) at langzrang = 2.4. Using Voigt profile fits to the full Lyα and Lyβ forests in 15 high-resolution high-S/N spectra of hyperluminous QSOs, we make the first statistically robust measurement of the frequency of absorbers with H I column densities 14 \\lesssim log (N_H\\,\\scriptsize{ I}/ {cm}^{-2}) \\lesssim 17.2. We also present the first measurements of the frequency distribution of H I absorbers in the volume surrounding high-z galaxies (the CGM, 300 pkpc), finding that the incidence of absorbers in the CGM is much higher than in the IGM. In agreement with Rudie et al., we find that there are fractionally more high-N H I absorbers than low-N H I absorbers in the CGM compared to the IGM, leading to a shallower power law fit to the CGM frequency distribution. We use these new measurements to calculate the total opacity of the IGM and CGM to hydrogen-ionizing photons, finding significantly higher opacity than most previous studies, especially from absorbers with log (N_H\\,\\scriptsize{ I}/ {cm}^{-2}) background and of ionizing sources at z ≈ 2-3. Based on data obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and the National Aeronautics and Space Administration, and was made possible by the generous financial support of the W. M. Keck Foundation.

  5. Vibronic Characteristics and Spin-Density Distributions in Bacteriochlorins as Revealed by Spectroscopic Studies of 16 Isotopologues. Implications for Energy- and Electron-Transfer in Natural Photosynthesis and Artificial Solar-Energy Conversion.

    Science.gov (United States)

    Diers, James R; Tang, Qun; Hondros, Christopher J; Chen, Chih-Yuan; Holten, Dewey; Lindsey, Jonathan S; Bocian, David F

    2014-06-26

    Vibronic characteristics and spin-density distributions in the core bacteriochlorin macrocycle were revealed by spectroscopic and theoretical studies of 16 isotopologues. The vibrational modes in copper bacteriochlorin isotopologues were examined via resonance Raman and Fourier-transform infrared spectroscopy. The resonance Raman spectra exhibit an exceptional sparcity of vibronically active modes of the core macrocycle, in contrast with the rich spectra of the natural bacteriochlorophylls. The Qy-excitation resonance Raman spectrum is dominated by a single mode at 727 cm(-1), which calculations suggest is due to a symmetrical accordion-like deformation of the five-atom Cm(CaNCa)pyrroleCm portion of the ring core. This deformation also dominates the vibronic features in the absorption and fluorescence spectra. The spin-density distributions in the π-cation radical of the zinc bacteriochlorin isotopologues were studied by electron paramagnetic resonance spectroscopy. The spectra indicate a significant electron/spin density (ρ ∼ 0.1) on each meso-carbon atom. This observation contradicts the predictions of early calculations that have been assumed to be correct for nearly four decades. Collectively, these findings have implications for how the structural features that characterize natural bacteriochlorophylls might influence energy- and electron-transfer processes in photosynthesis and alter the thinking on the design of synthetic, bacteriochlorin-based arrays for solar-energy conversion.

  6. Optimal densities of alkali metal atoms in an optically pumped K-Rb hybrid atomic magnetometer considering the spatial distribution of spin polarization.

    Science.gov (United States)

    Ito, Yosuke; Sato, Daichi; Kamada, Keigo; Kobayashi, Tetsuo

    2016-07-11

    An optically pumped K-Rb hybrid atomic magnetometer can be a useful tool for biomagnetic measurements due to the high spatial homogeneity of its sensor property inside a cell. However, because the property varies depending on the densities of potassium and rubidium atoms, optimization of the densities is essential. In this study, by using the Bloch equations of K and Rb and considering the spatial distribution of the spin polarization, we confirmed that the calculation results of spin polarization behavior are in good agreement with the experimental data. Using our model, we calculated the spatial distribution of the spin polarization and found that the optimal density of K atoms is 3 × 1019 m-3 and the optimal density ratio is nK/nRb ~ 400 to maximize the output signal and enhance spatial homogeneity of the sensor property.

  7. Density-dependence in space and time: opposite synchronous variations in population distribution and body condition in the Baltic Sea sprat (Sprattus sprattus over three decades.

    Directory of Open Access Journals (Sweden)

    Michele Casini

    Full Text Available Spatio-temporal density-dependent processes are crucial regulatory factors for natural populations. However, there is a lack of studies addressing spatial density-dependence in fish growth. A previous investigation has suggested spatio-temporal density-dependence in body condition of Baltic sprat. Here, we used different techniques, such as centre of gravity, distance, and homogeneity indices, to better characterize the spatial and temporal variations in sprat density and body condition in the Baltic Proper. Our results evidenced a negative spatio-temporal co-variation between the centres of gravity of density and maximum condition. In the 1980s-early 1990s both centres were located in the middle of the Baltic Proper. From the mid 1990s the centres progressively separated in space, as the sprat population moved towards the north-eastern Baltic Proper, and the centre of maximum condition towards the south-western areas. Moreover, at low abundances, sprat density and condition were homogeneously distributed in space, whereas at high abundances both density and condition showed pronounced geographical gradients. The ecological processes potentially explaining the observed patterns were discussed in the light of the Ideal Free Distribution theory. We provide evidence that the shift in the spatial distribution of cod, the main predator of sprat, has been the main factor triggering the overall spatial changes in sprat density, and thus condition, during the past thirty years. The spatial indices shown here, synthesizing the spatio-temporal patterns of fish distribution, can support the implementation of the EU Marine Strategy Framework Directive.

  8. Density-dependence in space and time: opposite synchronous variations in population distribution and body condition in the Baltic Sea sprat (Sprattus sprattus) over three decades.

    Science.gov (United States)

    Casini, Michele; Rouyer, Tristan; Bartolino, Valerio; Larson, Niklas; Grygiel, Włodzimierz

    2014-01-01

    Spatio-temporal density-dependent processes are crucial regulatory factors for natural populations. However, there is a lack of studies addressing spatial density-dependence in fish growth. A previous investigation has suggested spatio-temporal density-dependence in body condition of Baltic sprat. Here, we used different techniques, such as centre of gravity, distance, and homogeneity indices, to better characterize the spatial and temporal variations in sprat density and body condition in the Baltic Proper. Our results evidenced a negative spatio-temporal co-variation between the centres of gravity of density and maximum condition. In the 1980s-early 1990s both centres were located in the middle of the Baltic Proper. From the mid 1990s the centres progressively separated in space, as the sprat population moved towards the north-eastern Baltic Proper, and the centre of maximum condition towards the south-western areas. Moreover, at low abundances, sprat density and condition were homogeneously distributed in space, whereas at high abundances both density and condition showed pronounced geographical gradients. The ecological processes potentially explaining the observed patterns were discussed in the light of the Ideal Free Distribution theory. We provide evidence that the shift in the spatial distribution of cod, the main predator of sprat, has been the main factor triggering the overall spatial changes in sprat density, and thus condition, during the past thirty years. The spatial indices shown here, synthesizing the spatio-temporal patterns of fish distribution, can support the implementation of the EU Marine Strategy Framework Directive.

  9. Density functional studies on wurtzite piezotronic transistors: influence of different semiconductors and metals on piezoelectric charge distribution and Schottky barrier.

    Science.gov (United States)

    Liu, Wei; Zhang, Aihua; Zhang, Yan; Wang, Zhong Lin

    2016-05-20

    The mechanical-electrical coupling properties of piezoelectric semiconductors endow these materials with novel device applications in microelectromechanical systems, sensors, human-computer interfaces, etc. When an applied strain is exerted on a piezoelectric semiconductor, piezoelectric charges are generated at the surface or interface of the semiconductor, which can be utilized to control the electronic transport characteristics. This is the fundamental working mechanism of piezotronic devices, called the piezotronic effect. In the present report, a series of piezotronic transistors composed of different electrode metals and semiconductors is examined using density functional theory calculation. It is found that the influence of semiconductors on the piezotronic effect is larger than the impact of metals, and GaN and CdS are promising candidates for piezotronic and piezo-phototronic devices, respectively. The width of the piezoelectric charge distribution obtained in the present study can be used as a parameter in classical finite-element-method based simulations, which provide guidance on designing high-performance piezotronic devices.

  10. [Spatiotemporal distribution pattern of photosynthetic photon flux density in forest gaps of Korean pine broadleaved mixed forest].

    Science.gov (United States)

    Li, Meng; Duan, Wen-biao; Chen, Li-xin

    2011-04-01

    Taking the forest gaps of natural Pinus koraiensis broadleaved mixed forest in Xiao Xing'an Mountains as test object, and by the method of grids, the photosynthetic photon flux density (PPFD) in the gaps was continuously measured during growth season, and the spatiotemporal distribution patterns of the PPFD were analyzed by fundamental statistics and geostatistics methods. In the forest gaps, the high-value region of PPFD presented an obvious diurnal change, with the maximum PPFD appeared at 12:00 and in the northern part of the gaps. The mean monthly PPFD was the highest in June, and then decreased in the sequence of July, August, and September, with the largest coefficient of variation at different locations occurred in July and the medium variability in all the months. In different months, the intensity and the scale of PPFD spatial heterogeneity in the gaps differed, with the variation degree being the highest in June and the sill and proportion being the largest in July. The complex degree of the monthly PPFD patches also differed, with the maximum located in the northeast part of the gaps. The variation sequence of the mean monthly PPFD in understory and open ground was consistent with that in gap, and the mean monthly PPFD was the highest in open ground, medium in forest gap, and the lowest in understory.

  11. The dynamics of infection of Tribolium confusum by Hymenolepis diminuta: the influence of infective-stage density and spatial distribution.

    Science.gov (United States)

    Keymer, A E; Anderson, R M

    1979-10-01

    The mean parasite burden of a population of Tribolium confusum is shown to rise to a plateau as the exposure density of infective eggs of Hymenolepis diminuta increases. The level of this plateau is shown to be dependent on the nutritional status of the host population, being depressed from approximately 18 cysticeroids/beetle in hosts which have been starved prior to experimentation, to approximately 2 cysticercoids/beetle in satiated hosts. A simple model is used to describe the shape of this infection functional response in terms of the predator-prey interaction between hosts (T. confusum) and parasite infective stages (H. diminuta eggs). The distribution of successful infections/host is shown to be over-dispersed, even when hosts are exposed to infective stages arranged in a uniform spatial pattern. The over-dispersion of parasite numbers/host is shown to become more severe as the spatial pattern of infective stages changes from under-dispersed, through random, to over-dispersed. Experimental results are discussed in relation to the dynamics of parasite-host interactions, in which infection takes place by host ingestion of a free-living infective stage.

  12. Clinicopathological Features and Immunohistochemical Alterations of Keratinocyte Proliferation, Melanocyte Density, Smooth Muscle Hyperplasia and Nerve Fiber Distribution in Becker's Nevus

    Science.gov (United States)

    Sheng, Ping; Cheng, Yun-Long; Cai, Chuan-Chuan; Guo, Wei-Jin; Zhou, Ying; Shi, Ge

    2016-01-01

    Background Although Becker's nevus (BN) is a relatively common disease, the systematic studies of clinicopathological and immunohistochemical results are poorly reported. Objective To investigate the clinicopathological features and immunohistochemical alterations of keratinocyte proliferation, melanocyte density, smooth muscle hyperplasia and nerve fiber distribution in BN. Methods Clinical and pathological data were collected in 60 newly-diagnosed BN cases. Immunohistochemical stain of Ki-67, Melan-A, keratin 15, smooth muscle actin and protein gene product 9.5 was performed in 21 cases. Results The median diagnostic and onset age was 17 and 12 years, respectively. Skin lesions usually appeared on the upper trunk and upper limbs. The pathological features included the rete ridge elongation and fusion and basal hyperpigmentation. Epidermal Ki-67, Melan-A and keratin 15 expression and dermal nerve fiber length were significantly higher in lesional and perilesional skin than in normal skin (p<0.05~0.01), while smooth muscle actin expression was upregulated only in skin lesion (p<0.05). Conclusion Although the clinical diagnosis of BN is often straightforward, histopathology is helpful to differentiate from other pigmentary disorders. The hyperproliferation of keratinocytes, melanocytes, arrector pili muscle and dermal nerve fibers could be involved in the pathogenesis of BN. PMID:27904268

  13. Density functional studies on wurtzite piezotronic transistors: influence of different semiconductors and metals on piezoelectric charge distribution and Schottky barrier

    Science.gov (United States)

    Liu, Wei; Zhang, Aihua; Zhang, Yan; Wang, Zhong Lin

    2016-05-01

    The mechanical-electrical coupling properties of piezoelectric semiconductors endow these materials with novel device applications in microelectromechanical systems, sensors, human-computer interfaces, etc. When an applied strain is exerted on a piezoelectric semiconductor, piezoelectric charges are generated at the surface or interface of the semiconductor, which can be utilized to control the electronic transport characteristics. This is the fundamental working mechanism of piezotronic devices, called the piezotronic effect. In the present report, a series of piezotronic transistors composed of different electrode metals and semiconductors is examined using density functional theory calculation. It is found that the influence of semiconductors on the piezotronic effect is larger than the impact of metals, and GaN and CdS are promising candidates for piezotronic and piezo-phototronic devices, respectively. The width of the piezoelectric charge distribution obtained in the present study can be used as a parameter in classical finite-element-method based simulations, which provide guidance on designing high-performance piezotronic devices.

  14. Effects of nonthermal distribution of electrons and polarity of net dust-charge number density on nonplanar dust-ion-acoustic solitary waves.

    Science.gov (United States)

    Mamun, A A; Shukla, P K

    2009-09-01

    Effects of the nonthermal distribution of electrons as well as the polarity of the net dust-charge number density on nonplanar (viz. cylindrical and spherical) dust-ion-acoustic solitary waves (DIASWs) are investigated by employing the reductive perturbation method. It is found that the basic features of the DIASWs are significantly modified by the effects of nonthermal electron distribution, polarity of net dust-charge number density, and nonplanar geometry. The implications of our results in some space and laboratory dusty plasma environments are briefly discussed.

  15. 超声造影对增强计算机层析成像肝脏低密度病灶的诊断价值%Contrast-enhanced ultrasonography diagnostic value of the liver low-density focus on contrast-enhanced CT

    Institute of Scientific and Technical Information of China (English)

    薛改琴; 郭荣荣

    2011-01-01

    Objective To discuss the contrast-enhanced ultrasonography diagnostic value of the liver low-density focus on contrast-enhanced CT. Methods The contrast-enhanced ultrasonography results of 47 cases of the liver low-density focus on contrast-enhanced CT. were retrospectively analyzed. Results The pathological diagnosis in 47 focuses was metastatic carcinoma 20 cases, inflammatory pseudotumour 9 cases,hepatic hemangioma 6 cases, primary liver carcinoma 4 cases, cyst 2 cases, abscess 2 cases, tuberculosis 2 cases, FNH (focal liver nodular hyperplasia) 1 case, local adipose tissue infiltration of liver 1 case. 45 cases of contrast-enhanced ultrasonography diagnosis was consistent with pathological or clinical diagnosis. Cysts and inflammatory pseudotumour had not ultrasound contrast enhancement in the entire phase, but the crossed blood vessels was observed in inflammatory pseudotumour. The local adipose infiltration of liver had synchronous ultrasound contrast enhancement accompanied with liver tissue enhancement. 80% (12/15) of liver metastases of lack of blood supply showed fast contrast enhancement around the tumour edge and homogeneous and light contrast enhancement in the tumour center. 80 % (4/5) of liver metastases of rich of blood supply showed heavy and rapid contrast enhancement in the whole tumour. The enhancement degree in bscess and tuberculosis in the ultrasound contrast enhancement was correlated with necrosis degree, which showed fast and uneven contrast enhancement, hepatic hemangioma showed gradually contrast enhancement from its edge to center, whose enhancement time lasted for longer time than that of metastatic tumour with a statistically difference. FNH showed a typical contrast enhancement pattern, fast enhancement and fast weakening from center to edge. Hepatic cell carcinoma showed fast enhancement and fast weakening in the whole tumour. Conclusion Contrast-enhanced ultrasonography have diagnostic value of CT liver focus of low-density, which

  16. Experimental study of track density distribution on LR115 detector and deposition fraction of sup 2 sup 1 sup 8 Po in diffusion chamber

    CERN Document Server

    Koo, V S Y; Ho, J P Y; Nikezic, D; Yu, K N

    2002-01-01

    The radial distribution of track density on a solid-state nuclear track detector inside a diffusion chamber is a function of the fraction f of sup 2 sup 1 sup 8 Po decay before deposition. In the present work, procedures are proposed to determine f experimentally by determining the track density distribution on an LR115 detector in a diffusion chamber. First, a relatively tall diffusion chamber, with a height of 8 cm, was chosen. After exposure, the LR115 detector was etched. A transparent template with concentric circles was devised to study the radial distribution of sensitivity using an optical microscope. The distributions according to different values of f were also calculated using Monte Carlo simulations. By minimizing the deviations between these Monte Carlo curves and the experimental data, f was found to be 0.4.

  17. Intermolecular interactions, charge-density distribution and the electrostatic properties of pyrazinamide anti-TB drug molecule: an experimental and theoretical charge-density study.

    Science.gov (United States)

    Rajalakshmi, Gnanasekaran; Hathwar, Venkatesha R; Kumaradhas, Poomani

    2014-06-01

    An experimental charge-density analysis of pyrazinamide (a first line antitubercular drug) was performed using high-resolution X-ray diffraction data [(sin θ/λ)max = 1.1 Å(-1)] measured at 100 (2) K. The structure was solved by direct methods using SHELXS97 and refined by SHELXL97. The total electron density of the pyrazinamide molecule was modeled using the Hansen-Coppens multipole formalism implemented in the XD software. The topological properties of electron density determined from the experiment were compared with the theoretical results obtained from CRYSTAL09 at the B3LYP/6-31G** level of theory. The crystal structure was stabilized by N-H...N and N-H...O hydrogen bonds, in which the N3-H3B...N1 and N3-H3A...O1 interactions form two types of dimers in the crystal. Hirshfeld surface analysis was carried out to analyze the intermolecular interactions. The fingerprint plot reveals that the N...H and O...H hydrogen-bonding interactions contribute 26.1 and 18.4%, respectively, of the total Hirshfeld surface. The lattice energy of the molecule was calculated using density functional theory (B3LYP) methods with the 6-31G** basis set. The molecular electrostatic potential of the pyrazinamide molecule exhibits extended electronegative regions around O1, N1 and N2. The existence of a negative electrostatic potential (ESP) region just above the upper and lower surfaces of the pyrazine ring confirm the π-electron cloud.

  18. Describing contrast across scales

    Science.gov (United States)

    Syed, Sohaib Ali; Iqbal, Muhammad Zafar; Riaz, Muhammad Mohsin

    2017-06-01

    Due to its sensitive nature against illumination and noise distributions, contrast is not widely used for image description. On the contrary, the human perception of contrast along different spatial frequency bandwidths provides a powerful discriminator function that can be modeled in a robust manner against local illumination. Based upon this observation, a dense local contrast descriptor is proposed and its potential in different applications of computer vision is discussed. Extensive experiments reveal that this simple yet effective description performs well in comparison with state of the art image descriptors. We also show the importance of this description in multiresolution pansharpening framework.

  19. Hydrogen bonding and spin density distribution in the Qb semiquinone of bacterial reaction centers and comparison with the Qa site.

    Science.gov (United States)

    Martin, Erik; Samoilova, Rimma I; Narasimhulu, Kupala V; Lin, Tzu-Jen; O'Malley, Patrick J; Wraight, Colin A; Dikanov, Sergei A

    2011-04-13

    In the photosynthetic reaction center from Rhodobacter sphaeroides, the primary (Q(A)) and secondary (Q(B)) electron acceptors are both ubiquinone-10, but with very different properties and functions. To investigate the protein environment that imparts these functional differences, we have applied X-band HYSCORE, a 2D pulsed EPR technique, to characterize the exchangeable protons around the semiquinone (SQ) in the Q(A) and Q(B) sites, using samples of (15)N-labeled reaction centers, with the native high spin Fe(2+) exchanged for diamagnetic Zn(2+), prepared in (1)H(2)O and (2)H(2)O solvent. The powder HYSCORE method is first validated against the orientation-selected Q-band ENDOR study of the Q(A) SQ by Flores et al. (Biophys. J.2007, 92, 671-682), with good agreement for two exchangeable protons with anisotropic hyperfine tensor components, T, both in the range 4.6-5.4 MHz. HYSCORE was then applied to the Q(B) SQ where we found proton lines corresponding to T ≈ 5.2, 3.7 MHz and T ≈ 1.9 MHz. Density functional-based quantum mechanics/molecular mechanics (QM/MM) calculations, employing a model of the Q(B) site, were used to assign the observed couplings to specific hydrogen bonding interactions with the Q(B) SQ. These calculations allow us to assign the T = 5.2 MHz proton to the His-L190 N(δ)H···O(4) (carbonyl) hydrogen bonding interaction. The T = 3.7 MHz spectral feature most likely results from hydrogen bonding interactions of O1 (carbonyl) with both Gly-L225 peptide NH and Ser-L223 hydroxyl OH, which possess calculated couplings very close to this value. The smaller 1.9 MHz coupling is assigned to a weakly bound peptide NH proton of Ile-L224. The calculations performed with this structural model of the Q(B) site show less asymmetric distribution of unpaired spin density over the SQ than seen for the Q(A) site, consistent with available experimental data for (13)C and (17)O carbonyl hyperfine couplings. The implications of these interactions for Q

  20. Hydrogen bonding and spin density distribution in the QB semiquinone of bacterial reaction centers and comparison with the QA site

    Science.gov (United States)

    Martin, Erik; Samoilova, Rimma I.; Narasimhulu, Kupala V.; Lin, Tzu-Jen; O’Malley, Patrick J.; Wraight, Colin A.; Dikanov, Sergei A.

    2011-01-01

    In the photosynthetic reaction center from Rhodobacter sphaeroides, the primary (QA) and secondary (QB) electron acceptors are both ubiquinone-10, but with very different properties and functions. To investigate the protein environment that imparts these functional differences, we have applied X-band HYSCORE, a 2D pulsed EPR technique, to characterize the exchangeable protons around the semiquinone (SQ) in the QA and QB sites, using samples of 15N-labeled reaction centers, with the native high spin Fe2+ exchanged for diamagnetic Zn2+, prepared in 1H2O and 2H2O solvent. The powder HYSCORE method is first validated against the orientation-selected Q-band ENDOR study of the QA SQ by Flores et al. (Biophys. J. 2007, 92, 671–682), with good agreement for two exchangeable protons with anisotropic hyperfine tensor components, T, both in the range 4.6–5.4 MHz. HYSCORE was then applied to the QB SQ where we found proton lines corresponding to T~5.2, 3.7 MHz and T~1.9 MHz. Density functional-based quantum mechanics/molecular mechanics (QM/MM) calculations, employing a model of the QB site, were used to assign the observed couplings to specific hydrogen bonding interactions with the QB SQ. These calculations allow us to assign the T=5.2 MHz proton to the His-L190 NδH…O4 (carbonyl) hydrogen bonding interaction. The T =3.7 MHz spectral feature most likely results from hydrogen bonding interactions of O1 (carbonyl) with both Gly-L225 peptide NH and Ser-L223 hydroxyl OH, which possess calculated couplings very close to this value. The smaller 1.9 MHz coupling is assigned to a weakly bound peptide NH proton of Ile-L224. The calculations performed with this structural model of the QB site show less asymmetric distribution of unpaired spin density over the SQ than seen for the QA site, consistent with available experimental data for 13C and 17O carbonyl hyperfine couplings. The implications of these interactions for QB function and comparisons with the QA site are discussed

  1. Distribution, densities, and ecology of Siberian cranes in the Khroma River region of northern Yakutia in northeastern Russia

    Science.gov (United States)

    Bysykatova, Inga P.; Krapu, Gary L.; Germogenov, Nicolai I.; Buhl, Deborah A.; Aborn, David

    2014-01-01

    The Siberian crane (Grus leucogeranus) is the third rarest crane species in the world with a breeding range now centered on 3 core areas and a buffer zone in the arctic of northern Yakutia in northeastern Russia. During 16 July-2 August 2009, we undertook ground surveys within the Khroma River core breeding area, surrounding buffer zone, and lands lying to the west of the known rbeeding range to estimate densities and determine habitat use and social status of Siberian cranes. A total of 142 Siberian cranes were sighted (including 55 pairs) at 54 locations with 32 cranes (including 13 pairs) sighted outside the currently known breeding range in the lower drainages of the Syalakh and Syuryuktyakh Rivers. After adjusting for a probability of detection of 0.484 (95% CI = 0.281-0.833), Siberian crane densities in the Khroma core area and the buffer zone averaged 0.0921 cranes/km2 and 0.0363 cranes/km2, respectively. A majority of cranes (n = 93 [65%]) occurred in complexes of large basin wetlands, with use centered in those having extensive beds of pendant grass (Arctophila fulva). Of the 142 cranes seen, 110 (77%) were paired, 21 (15%) were singles, and 11 (8%) were in groups of 3-5. The Khroma core supports 1 of 2 large concentrations of breeding Siberian cranes remaining in the wild; therefore, we recommend that consideration be given to designating a nature reserve that would encompass the Khroma core, adjacent buffer zone, and lands to the west (including coastal tundra areas along the lower drainages of the Syalah and Syuryuktyah Rivers). Further research is needed to gain additional insight into Siberian crane distribution and numbers on lands beyond the currently delineated western boundary of the Siberian crane breeding range in the Ust-Yana District of northern Yakutia. Important gaps remain in information needed to effectively guide conservation efforts for the Eastern Population, and recent advances in remote tracking technology offer potential

  2. Forest Bird Distribution, Density and Trends in the Ka'u Region of Hawai'i Island

    Science.gov (United States)

    Gorresen, P. Marcos; Camp, Richard J.; Pratt, Thane K.

    2007-01-01

    An accurate and current measure of population status and trend is necessary for conservation and management efforts. Scott and Kepler (1985) provided a comprehensive review of the status of native Hawaiian birds based on the extensive Hawaii Forest Bird Survey (HFBS) of the main islands (Scott et al. 1986). At that time, they documented declining populations and decreasing ranges for most species, and the extinction of several species over the previous 50 years. Many native bird species continue to decline throughout Hawai`i (Camp et al. In review, Gorresen et al. In prep.). The focus of this study is the mid-to-high elevation rainforest on the southeast windward slopes of Mauna Loa Volcano (Figure 1). Known as Ka`u, the region encompasses forest lands protected by Kamehameha Schools, The Nature Conservancy, Hawai`i Volcanoes National Park (HVNP), and the State of Hawai'i's Ka`u Forest Reserve, Kapapala Forest Reserve and Kapapala Cooperative Game Management Area,. Together these lands support one of three main concentrations of native forest birds on the Hawai`i Island (the other two being centered on the Hakalau Forest National Wildlife Refuge and Kulani-Keauhou area in the north and central windward part of the island, respectively.) Because this region harbors important populations of native and endangered forest birds in some of the best remaining forest habitat on the island, it has been a focus of forest bird surveys since the 1970s. The Ka`u region was first quantitatively surveyed in 1976 by the Hawaii Forest Bird Survey (Scott et al. 1986). Surveys were conducted by State of Hawai`i Division of Forestry and Wildlife in 1993 and 2002 and by the U.S. National Park Service and the U.S. Geological Survey in 2004 and 2005. In this report, we present analyses of the density, distribution and trends of native and introduced forest bird within the Ka`u region of Hawai`i Island. The analyses cover only those species with sufficient detections to model detection

  3. 3D analysis of synaptic vesicle density and distribution after acute foot-shock stress by using serial section transmission electron microscopy.

    Science.gov (United States)

    Khanmohammadi, M; Darkner, S; Nava, N; Nyengaard, J R; Wegener, G; Popoli, M; Sporring, J

    2017-01-01

    Behavioural stress has shown to strongly affect neurotransmission within the neocortex. In this study, we analysed the effect of an acute stress model on density and distribution of neurotransmitter-containing vesicles within medial prefrontal cortex. Serial section transmission electron microscopy was employed to compare two groups of male rats: (1) rats subjected to foot-shock stress and (2) rats with sham stress as control group. Two-dimensional (2D) density measures are common in microscopic images and are estimated by following a 2D path in-section. However, this method ignores the slant of the active zone and thickness of the section. In fact, the active zone is a surface in three-dimension (3D) and the 2D measures do not accurately reflect the geometric configuration unless the active zone is perpendicular to the sectioning angle. We investigated synaptic vesicle density as a function of distance from the active zone in 3D. We reconstructed a 3D dataset by estimating the thickness of all sections and by registering all the image sections into a common coordinate system. Finally, we estimated the density as the average number of vesicles per area and volume and modelled the synaptic vesicle distribution by fitting a one-dimensional parametrized distribution that took into account the location uncertainty due to section thickness. Our results showed a clear structural difference in synaptic vesicle density and distribution between stressed and control group with improved separation by 3D measures in comparison to the 2D measures. Our results showed that acute foot-shock stress exposure significantly affected both the spatial distribution and density of the synaptic vesicles within the presynaptic terminal.

  4. Time-dependent density functional theory (TD-DFT) coupled with reference interaction site model self-consistent field explicitly including spatial electron density distribution (RISM-SCF-SEDD)

    Science.gov (United States)

    Yokogawa, D.

    2016-09-01

    Theoretical approach to design bright bio-imaging molecules is one of the most progressing ones. However, because of the system size and computational accuracy, the number of theoretical studies is limited to our knowledge. To overcome the difficulties, we developed a new method based on reference interaction site model self-consistent field explicitly including spatial electron density distribution and time-dependent density functional theory. We applied it to the calculation of indole and 5-cyanoindole at ground and excited states in gas and solution phases. The changes in the optimized geometries were clearly explained with resonance structures and the Stokes shift was correctly reproduced.

  5. Subtle changes in bone mineralization density distribution in most severely affected patients with chronic obstructive pulmonary disease.

    Science.gov (United States)

    Misof, B M; Roschger, P; Jorgetti, V; Klaushofer, K; Borba, V Z C; Boguszewski, C L; Cohen, A; Shane, E; Zhou, H; Dempster, D W; Moreira, C A

    2015-10-01

    Chronic obstructive pulmonary disease (COPD) is associated with low aBMD as measured by DXA and altered microstructure as assessed by bone histomorphometry and microcomputed tomography. Knowledge of bone matrix mineralization is lacking in COPD. Using quantitative backscatter electron imaging (qBEI), we assessed cancellous (Cn.) and cortical (Ct.) bone mineralization density distribution (BMDD) in 19 postmenopausal women (62.1 ± 7.3 years of age) with COPD. Eight had sustained fragility fractures, and 13 had received treatment with inhaled glucocorticoids. The BMDD outcomes from the patients were compared with healthy reference data and were correlated with previous clinical and histomorphometric findings. In general, the BMDD outcomes for the patients were not significantly different from the reference data. Neither the subgroups of with or without fragility fractures or of who did or did not receive inhaled glucocorticoid treatment, showed differences in BMDD. However, subgroup comparison according to severity revealed 10% decreased cancellous mineralization heterogeneity (Cn.CaWidth) for the most severely affected compared with less affected patients (p=0.042) and compared with healthy premenopausal controls (p=0.021). BMDD parameters were highly correlated with histomorphometric cancellous bone volume (BV/TV) and formation indices: mean degree of mineralization (Cn.CaMean) versus BV/TV (r=0.58, p=0.009), and Cn.CaMean and Ct.CaMean versus bone formation rate (BFR/BS) (r=-0.71, p50th percentile) BV/TV. The normality in most of the BMDD parameters and bone formation rates as well as the significant correlations between them suggests unaffected mineralization processes in COPD. Our findings also indicate no significant negative effect of treatment with inhaled glucocorticoids on the bone mineralization pattern. However, the observed concomitant occurrence of relatively lower bone volumes with lower bone matrix mineralization will both contribute to the reduced a

  6. Centrality dependence of the pseudorapidity density distribution for charged particles in Pb-Pb collisions at $\\sqrt{s_{NN}}$ = 2.76 TeV

    CERN Document Server

    Abbas, Ehab; Adam, Jaroslav; Adamova, Dagmar; Adare, Andrew Marshall; Aggarwal, Madan; Aglieri Rinella, Gianluca; Agnello, Michelangelo; Agocs, Andras Gabor; Agostinelli, Andrea; Ahammed, Zubayer; Ahmad, Arshad; Ahmad, Nazeer; Ahn, Sang Un; Ahn, Sul-Ah; Aimo, Ilaria; Ajaz, Muhammad; Akindinov, Alexander; Aleksandrov, Dmitry; Alessandro, Bruno; Alici, Andrea; Alkin, Anton; Almaraz Avina, Erick Jonathan; Alme, Johan; Alt, Torsten; Altini, Valerio; Altinpinar, Sedat; Altsybeev, Igor; Andrei, Cristian; Andronic, Anton; Anguelov, Venelin; Anielski, Jonas; Anson, Christopher Daniel; Anticic, Tome; Antinori, Federico; Antonioli, Pietro; Aphecetche, Laurent Bernard; Appelshauser, Harald; Arbor, Nicolas; Arcelli, Silvia; Arend, Andreas; Armesto, Nestor; Arnaldi, Roberta; Aronsson, Tomas Robert; Arsene, Ionut Cristian; Arslandok, Mesut; Asryan, Andzhey; Augustinus, Andre; Averbeck, Ralf Peter; Awes, Terry; Aysto, Juha Heikki; Azmi, Mohd Danish; Bach, Matthias Jakob; Badala, Angela; Baek, Yong Wook; Bailhache, Raphaelle Marie; Bala, Renu; Baldisseri, Alberto; Baltasar Dos Santos Pedrosa, Fernando; Ban, Jaroslav; Baral, Rama Chandra; Barbera, Roberto; Barile, Francesco; Barnafoldi, Gergely Gabor; Barnby, Lee Stuart; Barret, Valerie; Bartke, Jerzy Gustaw; Basile, Maurizio; Bastid, Nicole; Basu, Sumit; Bathen, Bastian; Batigne, Guillaume; Batyunya, Boris; Batzing, Paul Christoph; Baumann, Christoph Heinrich; Bearden, Ian Gardner; Beck, Hans; Behera, Nirbhay Kumar; Belikov, Iouri; Bellini, Francesca; Bellwied, Rene; Belmont-Moreno, Ernesto; Bencedi, Gyula; Beole, Stefania; Berceanu, Ionela; Bercuci, Alexandru; Berdnikov, Yaroslav; Berenyi, Daniel; Bergognon, Anais Annick Erica; Bertens, Redmer Alexander; Berzano, Dario; Betev, Latchezar; Bhasin, Anju; Bhati, Ashok Kumar; Bhom, Jihyun; Bianchi, Nicola; Bianchi, Livio; Bianchin, Chiara; Bielcik, Jaroslav; Bielcikova, Jana; Bilandzic, Ante; Bjelogrlic, Sandro; Blanco, F; Blanco, Francesco; Blau, Dmitry; Blume, Christoph; Boccioli, Marco; Boettger, Stefan; Bogdanov, Alexey; Boggild, Hans; Bogolyubsky, Mikhail; Boldizsar, Laszlo; Bombara, Marek; Book, Julian; Borel, Herve; Borissov, Alexander; Bossu, Francesco; Botje, Michiel; Botta, Elena; Braidot, Ermes; Braun-Munzinger, Peter; Bregant, Marco; Breitner, Timo Gunther; Broker, Theo Alexander; Browning, Tyler Allen; Broz, Michal; Brun, Rene; Bruna, Elena; Bruno, Giuseppe Eugenio; Budnikov, Dmitry; Buesching, Henner; Bufalino, Stefania; Buncic, Predrag; Busch, Oliver; Buthelezi, Edith Zinhle; Caffarri, Davide; Cai, Xu; Caines, Helen Louise; Calvo Villar, Ernesto; Camerini, Paolo; Canoa Roman, Veronica; Cara Romeo, Giovanni; Carena, Francesco; Carena, Wisla; Carlin Filho, Nelson; Carminati, Federico; Casanova Diaz, Amaya Ofelia; Castillo Castellanos, Javier Ernesto; Castillo Hernandez, Juan Francisco; Casula, Ester Anna Rita; Catanescu, Vasile; Cavicchioli, Costanza; Ceballos Sanchez, Cesar; Cepila, Jan; Cerello, Piergiorgio; Chang, Beomsu; Chapeland, Sylvain; Charvet, Jean-Luc Fernand; Chattopadhyay, Subhasis; Chattopadhyay, Sukalyan; Cherney, Michael Gerard; Cheshkov, Cvetan; Cheynis, Brigitte; Chibante Barroso, Vasco Miguel; Chinellato, David; Chochula, Peter; Chojnacki, Marek; Choudhury, Subikash; Christakoglou, Panagiotis; Christensen, Christian Holm; Christiansen, Peter; Chujo, Tatsuya; Chung, Suh-Urk; Cicalo, Corrado; Cifarelli, Luisa; Cindolo, Federico; Cleymans, Jean Willy Andre; Colamaria, Fabio; Colella, Domenico; Collu, Alberto; Conesa Balbastre, Gustavo; Conesa del Valle, Zaida; Connors, Megan Elizabeth; Contin, Giacomo; Contreras, Jesus Guillermo; Cormier, Thomas Michael; Corrales Morales, Yasser; Cortese, Pietro; Cortes Maldonado, Ismael; Cosentino, Mauro Rogerio; Costa, Filippo; Cotallo, Manuel Enrique; Crescio, Elisabetta; Crochet, Philippe; Cruz Alaniz, Emilia; Cruz Albino, Rigoberto; Cuautle, Eleazar; Cunqueiro, Leticia; Dainese, Andrea; Dalsgaard, Hans Hjersing; Dang, Ruina; Danu, Andrea; Das, Kushal; Das, Indranil; Das, Supriya; Das, Debasish; Dash, Ajay Kumar; Dash, Sadhana; De, Sudipan; de Barros, Gabriel; De Caro, Annalisa; de Cataldo, Giacinto; de Cuveland, Jan; De Falco, Alessandro; De Gruttola, Daniele; Delagrange, Hugues; Deloff, Andrzej; De Marco, Nora; Denes, Ervin; De Pasquale, Salvatore; Deppman, Airton; D'Erasmo, Ginevra; de Rooij, Raoul Stefan; Diaz Corchero, Miguel Angel; Di Bari, Domenico; Dietel, Thomas; Di Giglio, Carmelo; Di Liberto, Sergio; Di Mauro, Antonio; Di Nezza, Pasquale; Divia, Roberto; Djuvsland, Oeystein; Dobrin, Alexandru Florin

    2013-11-04

    We present the first wide-range measurement of the charged-particle pseudorapidity density distribution, for different centralities (the 0-5%, 5-10%, 10-20%, and 20-30% most central events) in Pb-Pb collisions at $\\sqrt{s_{NN}}$ = 2.76 TeV at the LHC. The measurement is performed using the full coverage of the ALICE detectors, -5.0 < $\\eta$ < 5.5, and employing a special analysis technique based on collisions arising from LHC ' satellite' bunches. We present the pseudorapidity density as a function of the number of participating nucleons as well as an extrapolation to the total number of produced charged particles ($N_{ch}$ = 17165 +/- 772 for the 0-5% most central collisions). From the measured d$N_{ch}$/d$\\eta$ distribution we derive the rapidity density distribution, d$N_{ch}$/dy, under simple assumptions. The rapidity density distribution is found to be significantly wider than the predictions of the Landau model, which reproduce data well at RHIC energies. We assess the validity of longitudinal sca...

  7. Centrality dependence of the pseudorapidity density distribution for charged particles in Pb–Pb collisions at √(s{sub NN})=2.76 TeV

    Energy Technology Data Exchange (ETDEWEB)

    Abbas, E. [Academy of Scientific Research and Technology (ASRT), Cairo (Egypt); Abelev, B. [Lawrence Livermore National Laboratory, Livermore, CA (United States); Adam, J. [Faculty of Nuclear Sciences and Physical Engineering, Czech Technical University in Prague, Prague (Czech Republic); Adamová, D. [Nuclear Physics Institute, Academy of Sciences of the Czech Republic, Řež u Prahy (Czech Republic); Adare, A.M. [Yale University, New Haven, CT (United States); Aggarwal, M.M. [Physics Department, Panjab University, Chandigarh (India); Aglieri Rinella, G. [European Organization for Nuclear Research (CERN), Geneva (Switzerland); Agnello, M. [Sezione INFN, Turin (Italy); Politecnico di Torino, Turin (Italy); Agocs, A.G. [Wigner Research Centre for Physics, Hungarian Academy of Sciences, Budapest (Hungary); Agostinelli, A. [Dipartimento di Fisica e Astronomia dell' Università and Sezione INFN, Bologna (Italy); Ahammed, Z. [Variable Energy Cyclotron Centre, Kolkata (India); Ahmad Masoodi, A.; Ahmad, N. [Department of Physics, Aligarh Muslim University, Aligarh (India); Ahn, S.U.; Ahn, S.A. [Korea Institute of Science and Technology Information, Daejeon (Korea, Republic of); Aimo, I. [Dipartimento di Fisica dell' Università and Sezione INFN, Turin (Italy); Sezione INFN, Turin (Italy); Politecnico di Torino, Turin (Italy); Ajaz, M. [COMSATS Institute of Information Technology (CIIT), Islamabad (Pakistan); Akindinov, A. [Institute for Theoretical and Experimental Physics, Moscow (Russian Federation); Aleksandrov, D. [Russian Research Centre Kurchatov Institute, Moscow (Russian Federation); Alessandro, B. [Sezione INFN, Turin (Italy); and others

    2013-11-04

    We present the first wide-range measurement of the charged-particle pseudorapidity density distribution, for different centralities (the 0–5%, 5–10%, 10–20%, and 20–30% most central events) in Pb–Pb collisions at √(s{sub NN})=2.76 TeV at the LHC. The measurement is performed using the full coverage of the ALICE detectors, −5.0<η<5.5, and employing a special analysis technique based on collisions arising from LHC ‘satellite’ bunches. We present the pseudorapidity density as a function of the number of participating nucleons as well as an extrapolation to the total number of produced charged particles (N{sub ch}=17165±772 for the 0–5% most central collisions). From the measured dN{sub ch}/dη distribution we derive the rapidity density distribution, dN{sub ch}/dy, under simple assumptions. The rapidity density distribution is found to be significantly wider than the predictions of the Landau model. We assess the validity of longitudinal scaling by comparing to lower energy results from RHIC. Finally the mechanisms of the underlying particle production are discussed based on a comparison with various theoretical models.

  8. MODTOHAFSD — A GUI based JAVA code for gravity analysis of strike limited sedimentary basins by means of growing bodies with exponential density contrast-depth variation: A space domain approach

    Science.gov (United States)

    Chakravarthi, V.; Sastry, S. Rajeswara; Ramamma, B.

    2013-07-01

    Based on the principles of modeling and inversion, two interpretation methods are developed in the space domain along with a GUI based JAVA code, MODTOHAFSD, to analyze the gravity anomalies of strike limited sedimentary basins using a prescribed exponential density contrast-depth function. A stack of vertical prisms all having equal widths, but each one possesses its own limited strike length and thickness, describes the structure of a sedimentary basin above the basement complex. The thicknesses of prisms represent the depths to the basement and are the unknown parameters to be estimated from the observed gravity anomalies. Forward modeling is realized in the space domain using a combination of analytical and numerical approaches. The algorithm estimates the initial depths of a sedimentary basin and improves them, iteratively, based on the differences between the observed and modeled gravity anomalies within the specified convergence criteria. The present code, works on Model-View-Controller (MVC) pattern, reads the Bouguer gravity anomalies, constructs/modifies regional gravity background in an interactive approach, estimates residual gravity anomalies and performs automatic modeling or inversion based on user specification for basement topography. Besides generating output in both ASCII and graphical forms, the code displays (i) the changes in the depth structure, (ii) nature of fit between the observed and modeled gravity anomalies, (iii) changes in misfit, and (iv) variation of density contrast with iteration in animated forms. The code is used to analyze both synthetic and real field gravity anomalies. The proposed technique yielded information that is consistent with the assumed parameters in case of synthetic structure and with available drilling depths in case of field example. The advantage of the code is that it can be used to analyze the gravity anomalies of sedimentary basins even when the profile along which the interpretation is intended fails to

  9. Density-dependent regulation of brook trout population dynamics along a core-periphery distribution gradient in a central Appalachian watershed.

    Directory of Open Access Journals (Sweden)

    Brock M Huntsman

    Full Text Available Spatial population models predict strong density-dependence and relatively stable population dynamics near the core of a species' distribution with increasing variance and importance of density-independent processes operating towards the population periphery. Using a 10-year data set and an information-theoretic approach, we tested a series of candidate models considering density-dependent and density-independent controls on brook trout population dynamics across a core-periphery distribution gradient within a central Appalachian watershed. We sampled seven sub-populations with study sites ranging in drainage area from 1.3-60 km(2 and long-term average densities ranging from 0.335-0.006 trout/m. Modeled response variables included per capita population growth rate of young-of-the-year, adult, and total brook trout. We also quantified a stock-recruitment relationship for the headwater population and coefficients of variability in mean trout density for all sub-populations over time. Density-dependent regulation was prevalent throughout the study area regardless of stream size. However, density-independent temperature models carried substantial weight and likely reflect the effect of year-to-year variability in water temperature on trout dispersal between cold tributaries and warm main stems. Estimated adult carrying capacities decreased exponentially with increasing stream size from 0.24 trout/m in headwaters to 0.005 trout/m in the main stem. Finally, temporal variance in brook trout population size was lowest in the high-density headwater population, tended to peak in mid-sized streams and declined slightly in the largest streams with the lowest densities. Our results provide support for the hypothesis that local density-dependent processes have a strong control on brook trout dynamics across the entire distribution gradient. However, the mechanisms of regulation likely shift from competition for limited food and space in headwater streams to

  10. A DETERMINATION OF THE FLUX DENSITY IN CORE OF DISTRIBUTION TRANSFORMERS, WHAT BUILT WITH THE COMMON USING OF GRAIN AND NON GRAIN ORIENTED MAGNETIC STEELS

    Directory of Open Access Journals (Sweden)

    I.V. Pentegov

    2015-12-01

    Full Text Available Purpose. The development of calculation method to determinate the flux densities in different parts of the magnetic cores of distribution transformers, what built from different types magnetic steel (mixed core. Methodology. The method is based on the scientific positions of Theoretical Electrical Engineering – the theory of the electromagnetic field in nonlinear mediums to determine the distribution of magnetic flux in mixed core of transformer, what are using different types of steel what have the different magnetic properties. Results. The developed method gives possible to make calculation of the flux density and influence of skin effect in different parts of the magnetic cores of distribution transformer, where are used mix of grain oriented (GO and non grain oriented (NGO steels. Was determinate the general basic conditions for the calculation of flux density in the laminations from grain and non grain oriented steels of the magnetic core: the strength of magnetic field for the laminations of particular part of mixed core is the same; the sum of the magnetic fluxes in GO and NGO steels in particular part of mixed core is equal with the designed magnetic flux in this part of mixed core. Discover, the magnetic flux in mixed core of the transformer has specific distribution between magnetic steels. The flux density is higher in laminations from GO steel and smaller in laminations from the NGO steel. That is happened because for magnetic flux is easier pass through laminations from GO steel, what has better magnetic conductance than laminations from NGO steel. Originality. The common using of different types of magnetic steels in cores for distribution transformers gives possibility to make design of transformer with low level of no load losses, high efficiency and with optimal cost. Practical value. The determination of the flux density in different parts of magnetic core with GO and NGO steels gives possibility make accurate calculation of

  11. Sowing Density