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Sample records for density gradient technique

  1. Processing of semen by density gradient centrifugation selects spermatozoa with longer telomeres for assisted reproduction techniques.

    Science.gov (United States)

    Yang, Qingling; Zhang, Nan; Zhao, Feifei; Zhao, Wanli; Dai, Shanjun; Liu, Jinhao; Bukhari, Ihtisham; Xin, Hang; Niu, Wenbing; Sun, Yingpu

    2015-07-01

    The ends of eukaryotic chromosomes contain specialized chromatin structures called telomeres, the length of which plays a key role in early human embryonic development. Although the effect of sperm preparation techniques on major sperm characteristics, such as concentration, motility and morphology have been previously documented, the possible status of telomere length and its relation with sperm preparation techniques is not well-known for humans. The aim of this study was to investigate the role of density gradient centrifugation in the selection of spermatozoa with longer telomeres for use in assisted reproduction techniques in 105 samples before and after sperm processing. After density gradient centrifugation, the average telomere length of the sperm was significantly longer (6.51 ± 2.54 versus 5.16 ± 2.29, P average motile sperm rate was significantly higher (77.9 ± 11.8 versus 44.6 ± 11.2, P average DNA fragmentation rate was significantly lower (11.1 ± 5.9 versus 25.9 ± 12.9, P sperm count (rs = 0.58; P sperm with longer telomeres. Copyright © 2015 Reproductive Healthcare Ltd. Published by Elsevier Ltd. All rights reserved.

  2. A novel technique for real-time estimation of edge pedestal density gradients via reflectometer time delay data

    Energy Technology Data Exchange (ETDEWEB)

    Zeng, L., E-mail: zeng@fusion.gat.com; Doyle, E. J.; Rhodes, T. L.; Wang, G.; Sung, C.; Peebles, W. A. [Physics and Astronomy Department, University of California, Los Angeles, California 90095 (United States); Bobrek, M. [Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831-6006 (United States)

    2016-11-15

    A new model-based technique for fast estimation of the pedestal electron density gradient has been developed. The technique uses ordinary mode polarization profile reflectometer time delay data and does not require direct profile inversion. Because of its simple data processing, the technique can be readily implemented via a Field-Programmable Gate Array, so as to provide a real-time density gradient estimate, suitable for use in plasma control systems such as envisioned for ITER, and possibly for DIII-D and Experimental Advanced Superconducting Tokamak. The method is based on a simple edge plasma model with a linear pedestal density gradient and low scrape-off-layer density. By measuring reflectometer time delays for three adjacent frequencies, the pedestal density gradient can be estimated analytically via the new approach. Using existing DIII-D profile reflectometer data, the estimated density gradients obtained from the new technique are found to be in good agreement with the actual density gradients for a number of dynamic DIII-D plasma conditions.

  3. Multi-Dimensional Quantum Effect Simulation Using a Density-Gradient Model and Script-Level Programming Techniques

    Science.gov (United States)

    Rafferty, Connor S.; Biegel, Bryan A.; Yu, Zhi-Ping; Ancona, Mario G.; Bude, J.; Dutton, Robert W.; Saini, Subhash (Technical Monitor)

    1998-01-01

    A density-gradient (DG) model is used to calculate quantum-mechanical corrections to classical carrier transport in MOS (Metal Oxide Semiconductor) inversion/accumulation layers. The model is compared to measured data and to a fully self-consistent coupled Schrodinger and Poisson equation (SCSP) solver. Good agreement is demonstrated for MOS capacitors with gate oxide as thin as 21 A. It is then applied to study carrier distribution in ultra short MOSFETs (Metal Oxide Semiconductor Field Effect Transistor) with surface roughness. This work represents the first implementation of the DG formulation on multidimensional unstructured meshes. It was enabled by a powerful scripting approach which provides an easy-to-use and flexible framework for solving the fourth-order PDEs (Partial Differential Equation) of the DG model.

  4. Density gradient multilayered polymerization (DGMP): a novel technique for creating multi-compartment, customizable scaffolds for tissue engineering.

    Science.gov (United States)

    Joshi-Barr, Shivanjali; Karpiak, Jerome V; Ner, Yogesh; Wen, Jessica H; Engler, Adam J; Almutairi, Adah

    2013-02-12

    Complex tissue culture matrices, in which types and concentrations of biological stimuli (e.g. growth factors, inhibitors, or small molecules) or matrix structure (e.g. composition, concentration, or stiffness of the matrix) vary over space, would enable a wide range of investigations concerning how these variables affect cell differentiation, migration, and other phenomena. The major challenge in creating layered matrices is maintaining the structural integrity of layer interfaces without diffusion of individual components from each layer. Current methodologies to achieve this include photopatterning, lithography, sequential functionalization5, freeze drying, microfluidics, or centrifugation, many of which require sophisticated instrumentation and technical skills. Others rely on sequential attachment of individual layers, which may lead to delamination of layers. DGMP overcomes these issues by using an inert density modifier such as iodixanol to create layers of varying densities. Since the density modifier can be mixed with any prepolymer or bioactive molecule, DGMP allows each scaffold layer to be customized. Simply varying the concentration of the density modifier prevents mixing of adjacent layers while they remain aqueous. Subsequent single step polymerization gives rise to a structurally continuous multilayered scaffold, in which each layer has distinct chemical and mechanical properties. The density modifier can be easily removed with sufficient rinsing without perturbation of the individual layers or their components. This technique is therefore well suited for creating hydrogels of various sizes, shapes, and materials. A protocol for fabricating a 2D-polyethylene glycol (PEG) gel, in which alternating layers incorporate RGDS-350, is outlined below. We use PEG because it is biocompatible and inert. RGDS, a cell adhesion peptide, is used to demonstrate spatial restriction of a biological cue, and the conjugation of a fluorophore (Alexa Fluor 350) enables

  5. Combining Step Gradients and Linear Gradients in Density.

    Science.gov (United States)

    Kumar, Ashok A; Walz, Jenna A; Gonidec, Mathieu; Mace, Charles R; Whitesides, George M

    2015-06-16

    Combining aqueous multiphase systems (AMPS) and magnetic levitation (MagLev) provides a method to produce hybrid gradients in apparent density. AMPS—solutions of different polymers, salts, or surfactants that spontaneously separate into immiscible but predominantly aqueous phases—offer thermodynamically stable steps in density that can be tuned by the concentration of solutes. MagLev—the levitation of diamagnetic objects in a paramagnetic fluid within a magnetic field gradient—can be arranged to provide a near-linear gradient in effective density where the height of a levitating object above the surface of the magnet corresponds to its density; the strength of the gradient in effective density can be tuned by the choice of paramagnetic salt and its concentrations and by the strength and gradient in the magnetic field. Including paramagnetic salts (e.g., MnSO4 or MnCl2) in AMPS, and placing them in a magnetic field gradient, enables their use as media for MagLev. The potential to create large steps in density with AMPS allows separations of objects across a range of densities. The gradients produced by MagLev provide resolution over a continuous range of densities. By combining these approaches, mixtures of objects with large differences in density can be separated and analyzed simultaneously. Using MagLev to add an effective gradient in density also enables tuning the range of densities captured at an interface of an AMPS by simply changing the position of the container in the magnetic field. Further, by creating AMPS in which phases have different concentrations of paramagnetic ions, the phases can provide different resolutions in density. These results suggest that combining steps in density with gradients in density can enable new classes of separations based on density.

  6. Microinstabilities in weak density gradient tokamak systems

    International Nuclear Information System (INIS)

    Tang, W.M.; Rewoldt, G.; Chen, L.

    1986-04-01

    A prominent characteristic of auxiliary-heated tokamak discharges which exhibit improved (''H-mode type'') confinement properties is that their density profiles tend to be much flatter over most of the plasma radius. Depsite this favorable trend, it is emphasized here that, even in the limit of zero density gradient, low-frequency microinstabilities can persist due to the nonzero temperature gradient

  7. The effect of density gradients on hydrometers

    Science.gov (United States)

    Heinonen, Martti; Sillanpää, Sampo

    2003-05-01

    Hydrometers are simple but effective instruments for measuring the density of liquids. In this work, we studied the effect of non-uniform density of liquid on a hydrometer reading. The effect induced by vertical temperature gradients was investigated theoretically and experimentally. A method for compensating for the effect mathematically was developed and tested with experimental data obtained with the MIKES hydrometer calibration system. In the tests, the method was found reliable. However, the reliability depends on the available information on the hydrometer dimensions and density gradients.

  8. Clinical efficacy of a combination of Percoll continuous density gradient and swim-up techniques for semen processing in HIV-1 serodiscordant couples

    Directory of Open Access Journals (Sweden)

    Osamu Inoue

    2017-01-01

    Full Text Available To evaluate the clinical efficacy of a procedure comprising a combination of Percoll continuous density gradient and modified swim-up techniques for the removal of human immunodeficiency virus type 1 (HIV-1 from the semen of HIV-1 infected males, a total of 129 couples with an HIV-1 positive male partner and an HIV-1 negative female partner (serodiscordant couples who were treated at Keio University Hospital between January 2002 and April 2012 were examined. A total of 183 ejaculates from 129 HIV-1 infected males were processed. After swim-up, we successfully collected motile sperms at a recovery rate as high as 100.0% in cases of normozoospermia (126/126 ejaculates, oligozoospermia (6/6, and asthenozoospermia (36/36. The recovery rate of oligoasthenozoospermia was 86.7% (13/15. In processed semen only four ejaculates (4/181:2.2% showed viral nucleotide sequences consistent with those in the blood of the infected males. After using these sperms, no horizontal infections of the female patients and no vertical infections of the newborns were observed. Furthermore, no obvious adverse effects were observed in the offspring. This protocol allowed us to collect HIV-1 negative motile sperms at a high rate, even in male factor cases. We concluded that our protocol is clinically effective both for decreasing HIV-1 infections and for yielding a healthy child.

  9. EFFECTIVENESS OF DOUBLE WASH SWIM-UP VERSUS DOUBLE DENSITY GRADIENT SWIM-UP TECHNIQUE OF SPERM PREPARATION IN IN VITRO FERTILISATION

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    Srinivas Sangisapu

    2017-10-01

    Full Text Available BACKGROUND Recovery of optimum number of good quality of spermatozoa is an important component of In Vitro Fertilisation (IVF. This is achieved by sperm preparation methods involving separation and recovery of capacitated sperms. Double Wash Swim-up (DWSU and Double Density Gradient Swim-up (DDGSU are two most accepted methods. Cochrane systematic review (2007 finds no clear benefit of one method over the other in Intrauterine Insemination (IUI. Systematic review on effectiveness of these preparations in IVF is lacking. Effectiveness is generally assessed in terms recovery rates of the sperms. Capability of successful fertilisation of good quality oocytes should ideally be the functional endpoint for evaluating effectiveness of sperm preparation methods. The aim of the study is to1. Compare the successful fertilisation rates of oocytes inseminated by semen preparation of Double Wash Swim-up (DWSU vis-a-vis by Double Density Gradient Swim-up (DDGSU method. 2. Evaluate the effectiveness of fertilisation of oocytes by Double Wash Swim-up method (DWSU vis-a-vis Double Density Gradient Swim-up (DDGSU method. MATERIALS AND METHODS A retrospective cohort study was conducted on infertile couples undergoing IVF from June 2014 to June 2017 at an ART Centre of a tertiary care hospital. The male partners were normozoospermic and female partners were normoresponsive to controlled ovarian stimulation and oocyte retrieval. RESULTS 70 male partners were subjected to double wash swim-up and 64 underwent double density gradient swim-up preparation. 1296 good quality oocytes were retrieved in their respective female partners. 452 (61% out of 742 oocytes were successfully fertilised after insemination by semen prepared by DWSU method. 378 (68% oocytes out of 554 were fertilised by insemination with semen prepared by DDGSU method. There seems to be strong association (RR=1.12 of fertilisation success with oocytes exposed to semen prepared by Double Density Gradient

  10. EFFECTIVENESS OF DOUBLE WASH SWIM-UP VERSUS DOUBLE DENSITY GRADIENT SWIM-UP TECHNIQUE OF SPERM PREPARATION IN IN VITRO FERTILISATION

    OpenAIRE

    Srinivas Sangisapu; Sandeep Karunakaran; Ashok Kumar Pillai

    2017-01-01

    BACKGROUND Recovery of optimum number of good quality of spermatozoa is an important component of In Vitro Fertilisation (IVF). This is achieved by sperm preparation methods involving separation and recovery of capacitated sperms. Double Wash Swim-up (DWSU) and Double Density Gradient Swim-up (DDGSU) are two most accepted methods. Cochrane systematic review (2007) finds no clear benefit of one method over the other in Intrauterine Insemination (IUI). Systematic review on effective...

  11. Effect of Crustal Density Structures on GOCE Gravity Gradient Observables

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    Robert Tenzer Pavel Novák

    2013-01-01

    Full Text Available We investigate the gravity gradient components corrected for major known anomalous density structures within the Earth¡¦s crust. Heterogeneous mantle density structures are disregarded. The gravimetric forward modeling technique is utilized to compute the gravity gradients based on methods for a spherical harmonic analysis and synthesis of a gravity field. The Earth¡¦s gravity gradient components are generated using the global geopotential model GOCO-03s. The topographic and stripping gravity corrections due to the density contrasts of the ocean and ice are computed from the global topographic/bathymetric model DTM2006.0 (which also includes the ice-thickness dataset. The discrete data of sediments and crust layers taken from the CRUST2.0 global crustal model are then used to apply the additional stripping corrections for sediments and remaining anomalous crustal density structures. All computations are realized globally on a one arc-deg geographical grid at a mean satellite elevation of 255 km. The global map of the consolidated crust-stripped gravity gradients reveals distinctive features which are attributed to global tectonics, lithospheric plate configuration, lithosphere structure and mantle dynamics (e.g., glacial isostatic adjustment, mantle convection. The Moho signature, which is the most pronounced signal in these refined gravity gradients, is superimposed over a weaker gravity signal of the lithospheric mantle. An interpretational quality of the computed (refined gravity gradient components is mainly limited by a low accuracy and resolution of the CRUST2.0 sediment and crustal layer data and unmodeled mantle structures.

  12. Density Gradient Stabilization of Electron Temperature Gradient Driven Turbulence in a Spherical Tokamak

    International Nuclear Information System (INIS)

    Ren, Y.; Kaye, S.M.; Mazzucato, E.; Guttenfelder, W.; Bell, R.E.; Domier, C.W.; LeBlanc, B.P.; Lee, K.C.; Luhmann, N.C. Jr.; Smith, D.R.; Yuh, H.

    2011-01-01

    In this letter we report the first clear experimental observation of density gradient stabilization of electron temperature gradient driven turbulence in a fusion plasma. It is observed that longer wavelength modes, k (perpendicular) ρ s ∼< 10, are most stabilized by density gradient, and the stabilization is accompanied by about a factor of two decrease in the plasma effective thermal diffusivity.

  13. Density gradients in the solar plasma observed by interplanetary scintillation

    International Nuclear Information System (INIS)

    Gapper, G.R.; Hewish, A.

    1981-01-01

    A new technique is described which overcomes the limitation set by Fresnel filtering in previous IPS studies of the small-scale density irregularities in the solar plasma. Phase gradients introduced by irregularities larger than the Fresnel limit cause transverse displacements of the small-scale scintillation pattern. In the presence of the solar wind, such refraction effects may be revealed by simultaneous measurements of intensity scintillation at two radio frequencies. Observations show that the structure corresponding to temporal frequencies approximately 0.02 Hz is in agreement with an extrapolation of the Kolmogorov spectrum derived from spacecraft data at lower frequencies. (author)

  14. A density gradient theory based method for surface tension calculations

    DEFF Research Database (Denmark)

    Liang, Xiaodong; Michelsen, Michael Locht; Kontogeorgis, Georgios

    2016-01-01

    The density gradient theory has been becoming a widely used framework for calculating surface tension, within which the same equation of state is used for the interface and bulk phases, because it is a theoretically sound, consistent and computationally affordable approach. Based on the observation...... that the optimal density path from the geometric mean density gradient theory passes the saddle point of the tangent plane distance to the bulk phases, we propose to estimate surface tension with an approximate density path profile that goes through this saddle point. The linear density gradient theory, which...... assumes linearly distributed densities between the two bulk phases, has also been investigated. Numerical problems do not occur with these density path profiles. These two approximation methods together with the full density gradient theory have been used to calculate the surface tension of various...

  15. Destabilization of drift waves due to nonuniform density gradient

    International Nuclear Information System (INIS)

    Hirose, A.; Ishihara, O.

    1985-01-01

    It is shown that the conventional mode differential equation for low frequency electrostatic waves in a tokamak does not contain full ion dynamics. Both electrons and ions contribute to the ballooning term, which is subject to finite ion Larmor radius effects. Also, both fluid ion approximation and kinetic ion model yield the same correction. Reexamined are the density gradient universal mode and ion temperature gradient instability employing the lowest order Pearlstein-Berk type radial eigenfunctions. No unstable, bounded, energy outgoing eigenfunctions have been found. In particular, a large ion temperature gradient (eta/sub i/) tends to further stabilize the temperature gradient driven mode

  16. Density gradients in ceramic pellets measured by computed tomography

    International Nuclear Information System (INIS)

    Sawicka, B.D.; Palmer, B.J.F.

    1986-07-01

    Density gradients are of fundamental importance in ceramic processing and computed tomography (CT) can provide accurate measurements of density profiles in sintered and unsintered ceramic parts. As a demonstration of this potential, the density gradients in an unsintered pellet pressed from an alumina powder were measured by CT scanning. To detect such small density gradients, the CT images must have good density resolution and be free from beam-hardening effects. This was achieved by measuring high-contrast (low-noise) images with the use of an Ir-192 isotopic source. A beam-hardening correction was applied. The resulting images are discussed relative to the transmission of forces through the powder mass during the pelletizing process

  17. Virus purification by CsCl density gradient using general centrifugation.

    Science.gov (United States)

    Nasukawa, Tadahiro; Uchiyama, Jumpei; Taharaguchi, Satoshi; Ota, Sumire; Ujihara, Takako; Matsuzaki, Shigenobu; Murakami, Hironobu; Mizukami, Keijirou; Sakaguchi, Masahiro

    2017-11-01

    Virus purification by cesium chloride (CsCl) density gradient, which generally requires an expensive ultracentrifuge, is an essential technique in virology. Here, we optimized virus purification by CsCl density gradient using general centrifugation (40,000 × g, 2 h, 4 °C), which showed almost the same purification ability as conventional CsCl density gradient ultracentrifugation (100,000 × g, 1 h, 4 °C) using phages S13' and φEF24C. Moreover, adenovirus strain JM1/1 was also successfully purified by this method. We suggest that general centrifugation can become a less costly alternative to ultracentrifugation for virus purification by CsCl densiy gradient and will thus encourage research in virology.

  18. Graph approach to the gradient expansion of density functionals

    International Nuclear Information System (INIS)

    Kozlowski, P.M.; Nalewajski, R.F.

    1986-01-01

    A graph representation of terms in the gradient expansion of the kinetic energy density functional is presented. They briefly discuss the implications of the virial theorem for the graph structure and relations between possible graphs at a given order of expansion

  19. Is the temperature gradient or the derivative of the density gradient responsible for drift solitons?

    International Nuclear Information System (INIS)

    Salat, A.

    1990-01-01

    In conventional drift wave theory the density gradient κ n =d lnn/dχ determines the linear phase velocity, and the (electron) temperature gradient κ T =d lnT/dχ gives rise to a nonlinear term which leads to the existence of soliton-type solutions and solitary waves. LAKHIN, MIKHAILOVSKI and ONISHCHENKO, Phys. Lett. A 119, 348 (1987) and Plasma Phys. and Contr. Fus. 30, 457 (1988), recently claimed that it is not κ T but essentially the derivative of the density gradient, dκ n /dχ, that is relevant. This claim is refuted by means of an expansion scheme in ε=eΦ/T≤1, where Φ is the drift wave potential. (orig.)

  20. Spectroscopic analysis of the density and temperature gradients in the laser-heated gas jet

    International Nuclear Information System (INIS)

    Matthews, D.L.; Lee, R.W.; Auerbach, J.M.

    1981-01-01

    We have performed an analysis of the x-ray spectra produced by a 1.0TW, lambda/sub L/-0.53μm laser-irradiated gas jet. Plasmas produced by ionization of neon, argon and N 2 + SF 6 gases were included in those measurements. Plasma electron density and temperature gradients were obtained by comparison of measured spectra with those produced by computer modeling. Density gradients were also obtained using laser interferometry. The limitations of this technique for plasma diagnosis will be discussed

  1. Preparation of synaptic plasma membrane and postsynaptic density proteins using a discontinuous sucrose gradient.

    Science.gov (United States)

    Bermejo, Marie Kristel; Milenkovic, Marija; Salahpour, Ali; Ramsey, Amy J

    2014-09-03

    Neuronal subcellular fractionation techniques allow the quantification of proteins that are trafficked to and from the synapse. As originally described in the late 1960's, proteins associated with the synaptic plasma membrane can be isolated by ultracentrifugation on a sucrose density gradient. Once synaptic membranes are isolated, the macromolecular complex known as the post-synaptic density can be subsequently isolated due to its detergent insolubility. The techniques used to isolate synaptic plasma membranes and post-synaptic density proteins remain essentially the same after 40 years, and are widely used in current neuroscience research. This article details the fractionation of proteins associated with the synaptic plasma membrane and post-synaptic density using a discontinuous sucrose gradient. Resulting protein preparations are suitable for western blotting or 2D DIGE analysis.

  2. The causal relation between turbulent particle flux and density gradient

    Energy Technology Data Exchange (ETDEWEB)

    Milligen, B. Ph. van; Martín de Aguilera, A.; Hidalgo, C. [CIEMAT - Laboratorio Nacional de Fusión, Avda. Complutense 40, 28040 Madrid (Spain); Carreras, B. A. [BACV Solutions, 110 Mohawk Road, Oak Ridge, Tennessee 37830 (United States); García, L.; Nicolau, J. H. [Universidad Carlos III, 28911 Leganés, Madrid (Spain)

    2016-07-15

    A technique for detecting the causal relationship between fluctuating signals is used to investigate the relation between flux and gradient in fusion plasmas. Both a resistive pressure gradient driven turbulence model and experimental Langmuir probe data from the TJ-II stellarator are studied. It is found that the maximum influence occurs at a finite time lag (non-instantaneous response) and that quasi-periodicities exist. Furthermore, the model results show very long range radial influences, extending over most of the investigated regions, possibly related to coupling effects associated with plasma self-organization. These results clearly show that transport in fusion plasmas is not local and instantaneous, as is sometimes assumed.

  3. Gradient-based stochastic estimation of the density matrix

    Science.gov (United States)

    Wang, Zhentao; Chern, Gia-Wei; Batista, Cristian D.; Barros, Kipton

    2018-03-01

    Fast estimation of the single-particle density matrix is key to many applications in quantum chemistry and condensed matter physics. The best numerical methods leverage the fact that the density matrix elements f(H)ij decay rapidly with distance rij between orbitals. This decay is usually exponential. However, for the special case of metals at zero temperature, algebraic decay of the density matrix appears and poses a significant numerical challenge. We introduce a gradient-based probing method to estimate all local density matrix elements at a computational cost that scales linearly with system size. For zero-temperature metals, the stochastic error scales like S-(d+2)/2d, where d is the dimension and S is a prefactor to the computational cost. The convergence becomes exponential if the system is at finite temperature or is insulating.

  4. Interacting Eigenmodes of a plasma diode with a density gradient

    International Nuclear Information System (INIS)

    Loefgren, T.; Gunell, H.

    1997-08-01

    The formation of narrow high frequency electric field spikes in plasma density gradients is investigated using one-dimensional particle in cell simulations. It is found that the shape of the plasma density gradient is very important for the spike formation. The spike appears also in simulations with immobile ions showing that a coupling to the ion motion, as for example in wave interactions, is not necessary for the formation of HF spikes. However, the HF spike influences the ion motion, and ion waves are seen in the simulations. It has been found, in experiments and simulations, that the electron velocity distribution function deviates from the Maxwellian distribution. Dispersion relations are calculated using realistic distribution functions. The spike can be seen as a coupled system of two Eigenmodes of a plasma diode fed by the beam-plasma interaction. Based on a simplified fluid description of such Eigenmodes, explanations for the localization of the spike, spatially and in frequency, are given. The density amplitude is comparable with the DC density level close to the cathode. Space charge limits of waves in this region seem to determine the amplitude of the spike through the Poisson's equation

  5. Density gradient effect on waveguide launching of lower hybrid waves

    International Nuclear Information System (INIS)

    Fichet, M.; Fidone, I.

    1981-01-01

    An extensive numerical investigation of the waveguide-plasma coupling, in the lower hybrid range of frequencies, is presented. The role of a sharp density gradient at the plasma edge is investigated. It is found that, in the case of a very sharp gradient, the accessibility condition |nsub(parallel)|>nsub(c)=(1-ω 2 /ωsub(i)ωsub(e))sup(-1/2) is violated and an appreciable fraction of the total energy is launched in the range |nsub(parallel)|< nsub(c). The case of one, two and four waveguides is considered, and it is found that the general pattern of the energy spectrum is very similar for the three antennas. (author)

  6. Correcting the error in neutron moisture probe measurements caused by a water density gradient

    International Nuclear Information System (INIS)

    Wilson, D.J.

    1988-01-01

    If a neutron probe lies in or near a water density gradient, the probe may register a water density different to that at the measuring point. The effect of a thin stratum of soil containing an excess or depletion of water at various distances from a probe in an otherwise homogeneous system has been calculated, producing an 'importance' curve. The effect of these strata can be integrated over the soil region in close proximity to the probe resulting in the net effect of the presence of a water density gradient. In practice, the probe is scanned through the point of interest and the count rate at that point is corrected for the influence of the water density on each side of it. An example shows that the technique can reduce an error of 10 per cent to about 2 per cent

  7. Mineral density volume gradients in normal and diseased human tissues.

    Directory of Open Access Journals (Sweden)

    Sabra I Djomehri

    Full Text Available Clinical computed tomography provides a single mineral density (MD value for heterogeneous calcified tissues containing early and late stage pathologic formations. The novel aspect of this study is that, it extends current quantitative methods of mapping mineral density gradients to three dimensions, discretizes early and late mineralized stages, identifies elemental distribution in discretized volumes, and correlates measured MD with respective calcium (Ca to phosphorus (P and Ca to zinc (Zn elemental ratios. To accomplish this, MD variations identified using polychromatic radiation from a high resolution micro-computed tomography (micro-CT benchtop unit were correlated with elemental mapping obtained from a microprobe X-ray fluorescence (XRF using synchrotron monochromatic radiation. Digital segmentation of tomograms from normal and diseased tissues (N=5 per group; 40-60 year old males contained significant mineral density variations (enamel: 2820-3095 mg/cc, bone: 570-1415 mg/cc, cementum: 1240-1340 mg/cc, dentin: 1480-1590 mg/cc, cementum affected by periodontitis: 1100-1220 mg/cc, hypomineralized carious dentin: 345-1450 mg/cc, hypermineralized carious dentin: 1815-2740 mg/cc, and dental calculus: 1290-1770 mg/cc. A plausible linear correlation between segmented MD volumes and elemental ratios within these volumes was established, and Ca/P ratios for dentin (1.49, hypomineralized dentin (0.32-0.46, cementum (1.51, and bone (1.68 were observed. Furthermore, varying Ca/Zn ratios were distinguished in adapted compared to normal tissues, such as in bone (855-2765 and in cementum (595-990, highlighting Zn as an influential element in prompting observed adaptive properties. Hence, results provide insights on mineral density gradients with elemental concentrations and elemental footprints that in turn could aid in elucidating mechanistic processes for pathologic formations.

  8. Mineral Density Volume Gradients in Normal and Diseased Human Tissues

    Science.gov (United States)

    Djomehri, Sabra I.; Candell, Susan; Case, Thomas; Browning, Alyssa; Marshall, Grayson W.; Yun, Wenbing; Lau, S. H.; Webb, Samuel; Ho, Sunita P.

    2015-01-01

    Clinical computed tomography provides a single mineral density (MD) value for heterogeneous calcified tissues containing early and late stage pathologic formations. The novel aspect of this study is that, it extends current quantitative methods of mapping mineral density gradients to three dimensions, discretizes early and late mineralized stages, identifies elemental distribution in discretized volumes, and correlates measured MD with respective calcium (Ca) to phosphorus (P) and Ca to zinc (Zn) elemental ratios. To accomplish this, MD variations identified using polychromatic radiation from a high resolution micro-computed tomography (micro-CT) benchtop unit were correlated with elemental mapping obtained from a microprobe X-ray fluorescence (XRF) using synchrotron monochromatic radiation. Digital segmentation of tomograms from normal and diseased tissues (N=5 per group; 40-60 year old males) contained significant mineral density variations (enamel: 2820-3095mg/cc, bone: 570-1415mg/cc, cementum: 1240-1340mg/cc, dentin: 1480-1590mg/cc, cementum affected by periodontitis: 1100-1220mg/cc, hypomineralized carious dentin: 345-1450mg/cc, hypermineralized carious dentin: 1815-2740mg/cc, and dental calculus: 1290-1770mg/cc). A plausible linear correlation between segmented MD volumes and elemental ratios within these volumes was established, and Ca/P ratios for dentin (1.49), hypomineralized dentin (0.32-0.46), cementum (1.51), and bone (1.68) were observed. Furthermore, varying Ca/Zn ratios were distinguished in adapted compared to normal tissues, such as in bone (855-2765) and in cementum (595-990), highlighting Zn as an influential element in prompting observed adaptive properties. Hence, results provide insights on mineral density gradients with elemental concentrations and elemental footprints that in turn could aid in elucidating mechanistic processes for pathologic formations. PMID:25856386

  9. Probability density function method for variable-density pressure-gradient-driven turbulence and mixing

    International Nuclear Information System (INIS)

    Bakosi, Jozsef; Ristorcelli, Raymond J.

    2010-01-01

    Probability density function (PDF) methods are extended to variable-density pressure-gradient-driven turbulence. We apply the new method to compute the joint PDF of density and velocity in a non-premixed binary mixture of different-density molecularly mixing fluids under gravity. The full time-evolution of the joint PDF is captured in the highly non-equilibrium flow: starting from a quiescent state, transitioning to fully developed turbulence and finally dissipated by molecular diffusion. High-Atwood-number effects (as distinguished from the Boussinesq case) are accounted for: both hydrodynamic turbulence and material mixing are treated at arbitrary density ratios, with the specific volume, mass flux and all their correlations in closed form. An extension of the generalized Langevin model, originally developed for the Lagrangian fluid particle velocity in constant-density shear-driven turbulence, is constructed for variable-density pressure-gradient-driven flows. The persistent small-scale anisotropy, a fundamentally 'non-Kolmogorovian' feature of flows under external acceleration forces, is captured by a tensorial diffusion term based on the external body force. The material mixing model for the fluid density, an active scalar, is developed based on the beta distribution. The beta-PDF is shown to be capable of capturing the mixing asymmetry and that it can accurately represent the density through transition, in fully developed turbulence and in the decay process. The joint model for hydrodynamics and active material mixing yields a time-accurate evolution of the turbulent kinetic energy and Reynolds stress anisotropy without resorting to gradient diffusion hypotheses, and represents the mixing state by the density PDF itself, eliminating the need for dubious mixing measures. Direct numerical simulations of the homogeneous Rayleigh-Taylor instability are used for model validation.

  10. 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.

  11. Microfluidic Adaptation of Density-Gradient Centrifugation for Isolation of Particles and Cells

    Directory of Open Access Journals (Sweden)

    Yuxi Sun

    2017-08-01

    Full Text Available Density-gradient centrifugation is a label-free approach that has been extensively used for cell separations. Though elegant, this process is time-consuming (>30 min, subjects cells to high levels of stress (>350 g and relies on user skill to enable fractionation of cells that layer as a narrow band between the density-gradient medium and platelet-rich plasma. We hypothesized that microfluidic adaptation of this technique could transform this process into a rapid fractionation approach where samples are separated in a continuous fashion while being exposed to lower levels of stress (<100 g for shorter durations of time (<3 min. To demonstrate proof-of-concept, we designed a microfluidic density-gradient centrifugation device and constructed a setup to introduce samples and medium like Ficoll in a continuous, pump-less fashion where cells and particles can be exposed to centrifugal force and separated via different outlets. Proof-of-concept studies using binary mixtures of low-density polystyrene beads (1.02 g/cm3 and high-density silicon dioxide beads (2.2 g/cm3 with Ficoll–Paque (1.06 g/cm3 show that separation is indeed feasible with >99% separation efficiency suggesting that this approach can be further adapted for separation of cells.

  12. Weighted graph based ordering techniques for preconditioned conjugate gradient methods

    Science.gov (United States)

    Clift, Simon S.; Tang, Wei-Pai

    1994-01-01

    We describe the basis of a matrix ordering heuristic for improving the incomplete factorization used in preconditioned conjugate gradient techniques applied to anisotropic PDE's. Several new matrix ordering techniques, derived from well-known algorithms in combinatorial graph theory, which attempt to implement this heuristic, are described. These ordering techniques are tested against a number of matrices arising from linear anisotropic PDE's, and compared with other matrix ordering techniques. A variation of RCM is shown to generally improve the quality of incomplete factorization preconditioners.

  13. The low thermal gradient CZ technique as a way of growing of dislocation-free germanium crystals

    Science.gov (United States)

    Moskovskih, V. A.; Kasimkin, P. V.; Shlegel, V. N.; Vasiliev, Y. V.; Gridchin, V. A.; Podkopaev, O. I.

    2014-09-01

    This paper considers the possibility of growth of dislocation-free germanium single crystals. This is achieved by reducing the temperature gradients at the level of 1 K/cm and lower. Single germanium crystals 45-48 mm in diameter with a dislocation density of 102 cm-2 were grown by a Low Thermal Gradient Czochralski technique (LTG CZ).

  14. Gram-scale fractionation of nanodiamonds by density gradient ultracentrifugation

    KAUST Repository

    Peng, Wei

    2013-01-01

    Size is a defining characteristic of nanoparticles; it influences their optical and electronic properties as well as their interactions with molecules and macromolecules. Producing nanoparticles with narrow size distributions remains one of the main challenges to their utilization. At this time, the number of practical approaches to optimize the size distribution of nanoparticles in many interesting materials systems, including diamond nanocrystals, remains limited. Diamond nanocrystals synthesized by detonation protocols-so-called detonation nanodiamonds (DNDs)-are promising systems for drug delivery, photonics, and composites. DNDs are composed of primary particles with diameters mainly <10 nm and their aggregates (ca. 10-500 nm). Here, we introduce a large-scale approach to rate-zonal density gradient ultracentrifugation to obtain monodispersed fractions of nanoparticles in high yields. We use this method to fractionate a highly concentrated and stable aqueous solution of DNDs and to investigate the size distribution of various fractions by dynamic light scattering, analytical ultracentrifugation, transmission electron microscopy and powder X-ray diffraction. This fractionation method enabled us to separate gram-scale amounts of DNDs into several size ranges within a relatively short period of time. In addition, the high product yields obtained for each fraction allowed us to apply the fractionation method iteratively to a particular size range of particles and to collect various fractions of highly monodispersed primary particles. Our method paves the way for in-depth studies of the physical and optical properties, growth, and aggregation mechanism of DNDs. Applications requiring DNDs with specific particle or aggregate sizes are now within reach. © 2013 The Royal Society of Chemistry.

  15. Modelling CO2-Brine Interfacial Tension using Density Gradient Theory

    KAUST Repository

    Ruslan, Mohd Fuad Anwari Che

    2018-03-01

    Knowledge regarding carbon dioxide (CO2)-brine interfacial tension (IFT) is important for petroleum industry and Carbon Capture and Storage (CCS) strategies. In petroleum industry, CO2-brine IFT is especially importance for CO2 – based enhanced oil recovery strategy as it affects phase behavior and fluid transport in porous media. CCS which involves storing CO2 in geological storage sites also requires understanding regarding CO2-brine IFT as this parameter affects CO2 quantity that could be securely stored in the storage site. Several methods have been used to compute CO2-brine interfacial tension. One of the methods employed is by using Density Gradient Theory (DGT) approach. In DGT model, IFT is computed based on the component density distribution across the interface. However, current model is only applicable for modelling low to medium ionic strength solution. This limitation is due to the model only considers the increase of IFT due to the changes of bulk phases properties and does not account for ion distribution at interface. In this study, a new modelling strategy to compute CO2-brine IFT based on DGT was proposed. In the proposed model, ion distribution across interface was accounted for by separating the interface to two sections. The saddle point of tangent plane distance where ( ) was defined as the boundary separating the two sections of the interface. Electrolyte is assumed to be present only in the second section which is connected to the bulk liquid phase side. Numerical simulations were performed using the proposed approach for single and mixed salt solutions for three salts (NaCl, KCl, and CaCl2), for temperature (298 K to 443 K), pressure (2 MPa to 70 MPa), and ionic strength (0.085 mol·kg-1 to 15 mol·kg-1). The simulation result shows that the tuned model was able to predict with good accuracy CO2-brine IFT for all studied cases. Comparison with current DGT model showed that the proposed approach yields better match with the experiment data

  16. TIGER: Development of Thermal Gradient Compensation Algorithms and Techniques

    Science.gov (United States)

    Hereford, James; Parker, Peter A.; Rhew, Ray D.

    2004-01-01

    In a wind tunnel facility, the direct measurement of forces and moments induced on the model are performed by a force measurement balance. The measurement balance is a precision-machined device that has strain gages at strategic locations to measure the strain (i.e., deformations) due to applied forces and moments. The strain gages convert the strain (and hence the applied force) to an electrical voltage that is measured by external instruments. To address the problem of thermal gradients on the force measurement balance NASA-LaRC has initiated a research program called TIGER - Thermally-Induced Gradients Effects Research. The ultimate goals of the TIGER program are to: (a) understand the physics of the thermally-induced strain and its subsequent impact on load measurements and (b) develop a robust thermal gradient compensation technique. This paper will discuss the impact of thermal gradients on force measurement balances, specific aspects of the TIGER program (the design of a special-purpose balance, data acquisition and data analysis challenges), and give an overall summary.

  17. The disparate impact of the ion temperature gradient and the density gradient on edge transport and the low-high transition in tokamaks

    International Nuclear Information System (INIS)

    Kleva, Robert G.; Guzdar, Parvez N.

    2009-01-01

    Steepening of the ion temperature gradient in nonlinear fluid simulations of the edge region of a tokamak plasma causes a rapid degradation in confinement. As the density gradient steepens, there is a continuous improvement in confinement analogous to the low (L) to high (H) transition observed in tokamaks. In contrast, as the ion temperature gradient steepens, there is a rapid increase in the particle and energy fluxes and no L-H transition. For a given pressure gradient, confinement always improves when more of the pressure gradient arises from the density gradient, and less of the pressure gradient arises from the ion temperature gradient.

  18. Quantitation of structural distortion with gradient-echo imaging techniques

    International Nuclear Information System (INIS)

    Tien, R.D.; Schwaighofer, B.W.; Hesselink, J.R.; Chu, P.K.

    1990-01-01

    This paper determines the structural distortion and measurement error associated with fast MR imaging of the spinal neural foramina. Dry skeletal specimens and a thin cadaveric sagittal section through the neural foramina were placed in a water bath. MR images were obtained with a 1.5-T unit in different planes and with various pulse sequences. The size and shape of each neural foramen were carefully measured on the images and on the skeletal specimens. Gradient-echo (GRE) techniques (gradient recalled acquisition in a steady state, MPGR, three-dimensional volume acquisition) resulted in structural distortion in up to 10% on the fresh skeleton and 30% of the dry skeleton specimens when a small TE was used (the foramina appear narrower on the images)

  19. General approach for solving the density gradient theory in the interfacial tension calculations

    DEFF Research Database (Denmark)

    Liang, Xiaodong; Michelsen, Michael Locht

    2017-01-01

    Within the framework of the density gradient theory, the interfacial tension can be calculated by finding the density profiles that minimize an integral of two terms over the system of infinite width. It is found that the two integrands exhibit a constant difference along the interface for a finite...... property evaluations compared to other methods. The performance of the algorithm with recommended parameters is analyzed for various systems, and the efficiency is further compared with the geometric-mean density gradient theory, which only needs to solve nonlinear algebraic equations. The results show...... that the algorithm is only 5-10 times less efficient than solving the geometric-mean density gradient theory....

  20. Stabilization of electron-scale turbulence by electron density gradient in national spherical torus experiment

    Energy Technology Data Exchange (ETDEWEB)

    Ruiz Ruiz, J.; White, A. E. [MIT-Plasma Science and Fusion Center, Cambridge, Massachusetts 02139 (United States); Ren, Y.; Guttenfelder, W.; Kaye, S. M.; Leblanc, B. P.; Mazzucato, E. [Princeton Plasma Physics Laboratory, Princeton, New Jersey 08543 (United States); Lee, K. C. [National Fusion Research Institute, Daejeon (Korea, Republic of); Domier, C. W. [University of California at Davis, Davis, California 95616 (United States); Smith, D. R. [University of Wisconsin-Madison, Madison, Wisconsin 53706 (United States); Yuh, H. [Nova Photonics, Inc., Princeton, New Jersey 08540 (United States)

    2015-12-15

    Theory and experiments have shown that electron temperature gradient (ETG) turbulence on the electron gyro-scale, k{sub ⊥}ρ{sub e} ≲ 1, can be responsible for anomalous electron thermal transport in NSTX. Electron scale (high-k) turbulence is diagnosed in NSTX with a high-k microwave scattering system [D. R. Smith et al., Rev. Sci. Instrum. 79, 123501 (2008)]. Here we report on stabilization effects of the electron density gradient on electron-scale density fluctuations in a set of neutral beam injection heated H-mode plasmas. We found that the absence of high-k density fluctuations from measurements is correlated with large equilibrium density gradient, which is shown to be consistent with linear stabilization of ETG modes due to the density gradient using the analytical ETG linear threshold in F. Jenko et al. [Phys. Plasmas 8, 4096 (2001)] and linear gyrokinetic simulations with GS2 [M. Kotschenreuther et al., Comput. Phys. Commun. 88, 128 (1995)]. We also found that the observed power of electron-scale turbulence (when it exists) is anti-correlated with the equilibrium density gradient, suggesting density gradient as a nonlinear stabilizing mechanism. Higher density gradients give rise to lower values of the plasma frame frequency, calculated based on the Doppler shift of the measured density fluctuations. Linear gyrokinetic simulations show that higher values of the electron density gradient reduce the value of the real frequency, in agreement with experimental observation. Nonlinear electron-scale gyrokinetic simulations show that high electron density gradient reduces electron heat flux and stiffness, and increases the ETG nonlinear threshold, consistent with experimental observations.

  1. Conjugate-gradient optimization method for orbital-free density functional calculations.

    Science.gov (United States)

    Jiang, Hong; Yang, Weitao

    2004-08-01

    Orbital-free density functional theory as an extension of traditional Thomas-Fermi theory has attracted a lot of interest in the past decade because of developments in both more accurate kinetic energy functionals and highly efficient numerical methodology. In this paper, we developed a conjugate-gradient method for the numerical solution of spin-dependent extended Thomas-Fermi equation by incorporating techniques previously used in Kohn-Sham calculations. The key ingredient of the method is an approximate line-search scheme and a collective treatment of two spin densities in the case of spin-dependent extended Thomas-Fermi problem. Test calculations for a quartic two-dimensional quantum dot system and a three-dimensional sodium cluster Na216 with a local pseudopotential demonstrate that the method is accurate and efficient. (c) 2004 American Institute of Physics.

  2. BMP4 density gradient in disk-shaped confinement

    Science.gov (United States)

    Bozorgui, Behnaz; Teimouri, Hamid; Kolomeisky, Anatoly B.

    We present a quantitative model that explains the scaling of BMP4 gradients during gastrulation and the recent experimental observation that geometric confinement of human embryonic stem cells is sufficient to recapitulate much of germ layer patterning. Based on a assumption that BMP4 diffusion rate is much smaller than the diffusion rate of it's inhibitor molecules, our results confirm that the length-scale which defines germ layer territories does not depend on system size.

  3. Depth perception: cuttlefish (Sepia officinalis) respond to visual texture density gradients.

    Science.gov (United States)

    Josef, Noam; Mann, Ofri; Sykes, António V; Fiorito, Graziano; Reis, João; Maccusker, Steven; Shashar, Nadav

    2014-11-01

    Studies concerning the perceptual processes of animals are not only interesting, but are fundamental to the understanding of other developments in information processing among non-humans. Carefully used visual illusions have been proven to be an informative tool for understanding visual perception. In this behavioral study, we demonstrate that cuttlefish are responsive to visual cues involving texture gradients. Specifically, 12 out of 14 animals avoided swimming over a solid surface with a gradient picture that to humans resembles an illusionary crevasse, while only 5 out of 14 avoided a non-illusionary texture. Since texture gradients are well-known cues for depth perception in vertebrates, we suggest that these cephalopods were responding to the depth illusion created by the texture density gradient. Density gradients and relative densities are key features in distance perception in vertebrates. Our results suggest that they are fundamental features of vision in general, appearing also in cephalopods.

  4. Semiautomated system for the production and analysis of sucrose density gradients

    International Nuclear Information System (INIS)

    Lange, C.S.; Liberman, D.F.

    1974-01-01

    A semiautomated system in DNA damage studies permitting considerable accuracy, speed, and reproducibility in the making and fractionation of sucrose density gradients is described. The system consists of a modified Beckman gradient forming device that makes six gradients simultaneously and delivers them into six 12.5 ml polyallomer centrifuge tubes in such a manner that new material is continuously added to the meniscus of the gradient. The gradients are fractionated three at a time and up to 100 fractions per gradient can be collected automatically directly into scintillation vials with a choice of drop counting or time mode with rinse and automatic addition of scintillation fluid to each vial. The system can process up to six gradients per hour but centrifugation time is usually the limiting factor. With neutral sucrose gradients, sharp, reproducible, monodisperse peaks containing up to 100 percent of the gradient radioactivity are usually obtained but a smaller monodisperse peak containing as little as 3.5 percent of the gradient radioactivity can be detected under conditions where some pairs of molecules might tangle or dimerize. The resolution and reproducibility of this system when used with neutral sucrose gradients is at least the equal if not superior to that commonly claimed for alkaline sucrose gradients. (U.S.)

  5. Noninvasive prenatal diagnosis. Use of density gradient centrifugation, magnetically activated cell sorting and in situ hybridization

    DEFF Research Database (Denmark)

    Campagnoli, C; Multhaupt, H A; Ludomirski, A

    1997-01-01

    OBJECTIVE: To develop a noninvasive method suitable for clinical prenatal diagnosis. STUDY DESIGN: Fetal nucleated erythrocytes were separated from peripheral blood of 17 healthy pregnant women using small magnetically activated cell sorting columns (MiniMACS) following density gradient centrifug...

  6. Purification of Sarcocystis neurona sporocysts from opossum (Didelphis virginiana) using potassium bromide discontinuous density gradient centrifugation.

    Science.gov (United States)

    Elsheikha, Hany M; Murphy, Alice J; Fitzgerald, Scott D; Mansfield, Linda S; Massey, Jeffrey P; Saeed, Mahdi A

    2003-06-01

    This report describes a new, inexpensive procedure for the rapid and efficient purification of Sarcocystis neurona sporocysts from opossum small intestine. S. neurona sporocysts were purified using a discontinuous potassium bromide density gradient. The procedure provides a source of sporocyst wall and sporozoites required for reliable biochemical characterization and for immunological studies directed at characterizing antigens responsible for immunological responses by the host. The examined isolates were identified as S. neurona using random amplified polymorphic DNA primers and restriction endonuclease digestion assays. This method allows the collection of large numbers of highly purified S. neurona sporocysts without loss of sporocyst viability as indicated by propidium iodide permeability and cell culture infectivity assays. In addition, this technique might also be used for sporocyst purification of other Sarcocystis spp.

  7. Analytic solutions for Rayleigh-Taylor growth rates in smooth density gradients

    International Nuclear Information System (INIS)

    Munro, D.H.

    1988-01-01

    The growth rate of perturbations on the shell of a laser fusion target can be estimated as √gk , where g is the shell acceleration and k is the transverse wave number of the perturbation. This formula overestimates the growth rate, and should be modified for the effects of density gradients and/or ablation of the unstable interface. The density-gradient effect is explored here analytically. With the use of variational calculus to explore all possible density profiles, the growth rate is shown to exceed √gk/(1+kL) , where L is a typical density-gradient scale length. Density profiles actually exhibiting this minimum growth rate are found

  8. Semi-local machine-learned kinetic energy density functional with third-order gradients of electron density

    Science.gov (United States)

    Seino, Junji; Kageyama, Ryo; Fujinami, Mikito; Ikabata, Yasuhiro; Nakai, Hiromi

    2018-06-01

    A semi-local kinetic energy density functional (KEDF) was constructed based on machine learning (ML). The present scheme adopts electron densities and their gradients up to third-order as the explanatory variables for ML and the Kohn-Sham (KS) kinetic energy density as the response variable in atoms and molecules. Numerical assessments of the present scheme were performed in atomic and molecular systems, including first- and second-period elements. The results of 37 conventional KEDFs with explicit formulae were also compared with those of the ML KEDF with an implicit formula. The inclusion of the higher order gradients reduces the deviation of the total kinetic energies from the KS calculations in a stepwise manner. Furthermore, our scheme with the third-order gradient resulted in the closest kinetic energies to the KS calculations out of the presented functionals.

  9. Vitality of oligozoospermic semen samples is improved by both swim-up and density gradient centrifugation before cryopreservation.

    Science.gov (United States)

    Counsel, Madeleine; Bellinge, Rhys; Burton, Peter

    2004-05-01

    To ascertain whether washing sperm from oligozoospermic and normozoospermic samples before cryopreservation improves post-thaw vitality. Normozoospermic (n = 18) and oligozoospermic (n = 16) samples were divided into three aliquots. The first aliquot remained untreated and the second and third aliquots were subjected to the swim-up and discontinuous density gradient sperm washing techniques respectively. Vitality staining was performed, samples mixed with cryopreservation media and frozen. Spermatozoa were thawed, stained, and vitality quantified and expressed as the percentage of live spermatozoa present. Post-thaw vitality in untreated aliquots from normozoospermic samples (24.9% +/- 2.3; mean +/- SEM) was significantly higher (unpaired t-tests; P vitality was significantly higher after swim-up in normozoospermic samples (35.6% +/- 2.1; P vitality in oligozoospermic (22.4% +/- 1.0; P vitality in cryopreserved oligozoospermic samples was improved by both the swim-up and density gradient centrifugation washing techniques prior to freezing.

  10. Engineering zonal cartilage through bioprinting collagen type II hydrogel constructs with biomimetic chondrocyte density gradient.

    Science.gov (United States)

    Ren, Xiang; Wang, Fuyou; Chen, Cheng; Gong, Xiaoyuan; Yin, Li; Yang, Liu

    2016-07-20

    Cartilage tissue engineering is a promising approach for repairing and regenerating cartilage tissue. To date, attempts have been made to construct zonal cartilage that mimics the cartilaginous matrix in different zones. However, little attention has been paid to the chondrocyte density gradient within the articular cartilage. We hypothesized that the chondrocyte density gradient plays an important role in forming the zonal distribution of extracellular matrix (ECM). In this study, collagen type II hydrogel/chondrocyte constructs were fabricated using a bioprinter. Three groups were created according to the total cell seeding density in collagen type II pre-gel: Group A, 2 × 10(7) cells/mL; Group B, 1 × 10(7) cells/mL; and Group C, 0.5 × 10(7) cells/mL. Each group included two types of construct: one with a biomimetic chondrocyte density gradient and the other with a single cell density. The constructs were cultured in vitro and harvested at 0, 1, 2, and 3 weeks for cell viability testing, reverse-transcription quantitative PCR (RT-qPCR), biochemical assays, and histological analysis. We found that total ECM production was positively correlated with the total cell density in the early culture stage, that the cell density gradient distribution resulted in a gradient distribution of ECM, and that the chondrocytes' biosynthetic ability was affected by both the total cell density and the cell distribution pattern. Our results suggested that zonal engineered cartilage could be fabricated by bioprinting collagen type II hydrogel constructs with a biomimetic cell density gradient. Both the total cell density and the cell distribution pattern should be optimized to achieve synergistic biological effects.

  11. Space charge profiles in low density polyethylene samples containing a permittivity/conductivity gradient

    DEFF Research Database (Denmark)

    Bambery, K.R.; Fleming, R.J.; Holbøll, Joachim

    2001-01-01

    .5×107 V m-1. Current density was also measured as a function of temperature and field. Space charge due exclusively to the temperature gradient was detected, with density of order 0.01 C m-3. The activation energy associated with the transport of electrons through the bulk was calculated as 0.09 e...

  12. The impact of edge gradients in the pressure, density, ion temperature, and electron temperature on edge-localized modes

    International Nuclear Information System (INIS)

    Kleva, Robert G.; Guzdar, Parvez N.

    2011-01-01

    The magnitude of the energy and particle fluxes in simulations of edge-localized modes (ELMs) is determined by the edge gradients in the pressure, density, ion temperature, and electron temperature. The total edge pressure gradient is the dominant influence on ELMs by far. An increase (decrease) of merely 2% in the pressure gradient results in an increase (decrease) of more than a factor of ten in the size of the ELM bursts. At a fixed pressure gradient, the size of the ELM bursts decreases as the density gradient increases, while the size of the bursts increases as the electron temperature gradient or, especially, the ion temperature gradient increases.

  13. Crystalline phases by an improved gradient expansion technique

    Science.gov (United States)

    Carignano, S.; Mannarelli, M.; Anzuini, F.; Benhar, O.

    2018-02-01

    We develop an innovative technique for studying inhomogeneous phases with a spontaneous broken symmetry. The method relies on the knowledge of the exact form of the free energy in the homogeneous phase and on a specific gradient expansion of the order parameter. We apply this method to quark matter at vanishing temperature and large chemical potential, which is expected to be relevant for astrophysical considerations. The method is remarkably reliable and fast as compared to performing the full numerical diagonalization of the quark Hamiltonian in momentum space and is designed to improve the standard Ginzburg-Landau expansion close to the phase transition points. For definiteness, we focus on inhomogeneous chiral symmetry breaking, accurately reproducing known results for one-dimensional and two-dimensional modulations and examining novel crystalline structures, as well. Consistently with previous results, we find that the energetically favored modulation is the so-called one-dimensional real-kink crystal. We propose a qualitative description of the pairing mechanism to motivate this result.

  14. Reflection and absorption of ion-acoustic waves in a plasma density gradient

    International Nuclear Information System (INIS)

    Ishihara, O.

    1977-01-01

    Plasma is characterized by electrical quasineutrality and the collective behavior. There exists a longitudinal low-frequency wave called an ion-acoustic wave in a plasma. One problem in the experimental study of ion-acoustic waves has been that sometimes they are observed to be reflected from discharge tube walls, and sometimes to be absorbed. Theoretical computation reveals that a velocity gradient produced by a density gradient plays a significant role in the reflection. The velocity gradient produces the subsonic-supersonic transition and long wavelength waves are reflected before reaching the transition while short wavelength waves penetrate over the transition and are absorbed in the supersonic flow plasma

  15. OptiPrep? Density Gradient Solutions for Macromolecules and Macromolecular Complexes

    Directory of Open Access Journals (Sweden)

    John Graham

    2002-01-01

    Full Text Available Any density gradient for the isolation of mammalian cells should ideally only expose the sedimenting particles to an increasing concentration of the gradient solute. Thus they will experience only an increasing density and viscosity, other parameters such as osmolality, pH, ionic strength and the concentration of important additives (such as EDTA or divalent cations should remain as close to constant as possible. This Protocol Article describes the strategies for the dilution of OptiPrep™ in order to prepare such solutions for mammalian cells.

  16. Numerical Study on Density Gradient Carbon-Carbon Composite for Vertical Launching System

    Science.gov (United States)

    Yoon, Jin-Young; Kim, Chun-Gon; Lim, Juhwan

    2018-04-01

    This study presents new carbon-carbon (C/C) composite that has a density gradient within single material, and estimates its heat conduction performance by a numerical method. To address the high heat conduction of a high-density C/C, which can cause adhesion separation in the steel structures of vertical launching systems, density gradient carbon-carbon (DGCC) composite is proposed due to its exhibiting low thermal conductivity as well as excellent ablative resistance. DGCC is manufactured by hybridizing two different carbonization processes into a single carbon preform. One part exhibits a low density using phenolic resin carbonization to reduce heat conduction, and the other exhibits a high density using thermal gradient-chemical vapor infiltration for excellent ablative resistance. Numerical analysis for DGCC is performed with a heat conduction problem, and internal temperature distributions are estimated by the forward finite difference method. Material properties of the transition density layer, which is inevitably formed during DGCC manufacturing, are assumed to a combination of two density layers for numerical analysis. By comparing numerical results with experimental data, we validate that DGCC exhibits a low thermal conductivity, and it can serve as highly effective ablative material for vertical launching systems.

  17. Density gradient in SiO 2 films on silicon as revealed by positron annihilation spectroscopy

    Science.gov (United States)

    Revesz, A. G.; Anwand, W.; Brauer, G.; Hughes, H. L.; Skorupa, W.

    2002-06-01

    Positron annihilation spectroscopy of thermally grown and deposited SiO 2 films on silicon shows in a non-destructive manner that these films have a gradient in their density. The gradient is most pronounced for the oxide grown in dry oxygen. Oxidation in water-containing ambient results in an oxide with reduced gradient, similarly to the gradient in the deposited oxide. These observations are in accordance with earlier optical and other studies using stepwise etching or a set of samples of varying thickness. The effective oxygen charge, which is very likely one of the reasons for the difference in the W parameters of silica glass and quartz crystal, could be even higher at some localized configurations in the SiO 2 films resulting in increased positron trapping.

  18. Measurement of the temperature of density maximum of water solutions using a convective flow technique

    OpenAIRE

    Cawley, M.F.; McGlynn, D.; Mooney, P.A.

    2006-01-01

    A technique is described which yields an accurate measurement of the temperature of density maximum of fluids which exhibit such anomalous behaviour. The method relies on the detection of changes in convective flow in a rectangular cavity containing the test fluid.The normal single-cell convection which occurs in the presence of a horizontal temperature gradient changes to a double cell configuration in the vicinity of the density maximum, and this transition manifests itself in changes in th...

  19. Vertical density gradient in the eastern North Atlantic during the last 30,000 years

    Energy Technology Data Exchange (ETDEWEB)

    Rogerson, M.; Ramirez, J. [University of Hull, Geography Department, Hull (United Kingdom); Bigg, G.R. [University of Sheffield, Department of Geography, Sheffield (United Kingdom); Rohling, E.J. [University of Southampton, National Oceanography Centre, School of Ocean and Earth Science, Southampton (United Kingdom)

    2012-08-15

    Past changes in the density and momentum structure of oceanic circulation are an important aspect of changes in the Atlantic Meridional Overturning Circulation and consequently climate. However, very little is known about past changes in the vertical density structure of the ocean, even very extensively studied systems such as the North Atlantic. Here we exploit the physical controls on the settling depth of the dense Mediterranean water plume derived from the Strait of Gibraltar to obtain the first robust, observations-based, probabilistic reconstruction of the vertical density gradient in the eastern North Atlantic during the last 30,000 years. We find that this gradient was weakened by more than 50%, relative to the present, during the last Glacial Maximum, and that changes in general are associated with reductions in AMOC intensity. However, we find only a small change during Heinrich Event 1 relative to the Last Glacial Maximum, despite strong evidence that overturning was substantially altered. This implies that millennial-scale changes may not be reflected in vertical density structure of the ocean, which may be limited to responses on an ocean-overturning timescale or longer. Regardless, our novel reconstruction of Atlantic density structure can be used as the basis for a dynamical measure for validation of model-based AMOC reconstructions. In addition, our general approach is transferrable to other marginal sea outflow plumes, to provide estimates of oceanic vertical density gradients in other locations. (orig.)

  20. Pitfalls of using the geometric-mean combining rule in the density gradient theory

    DEFF Research Database (Denmark)

    Liang, Xiaodong; Michelsen, Michael Locht; Kontogeorgis, Georgios

    2016-01-01

    It is popular and attractive to model the interfacial tension using the density gradient theory with the geometric-mean combining rule, in which the same equation of state is used for the interface and bulk phases. The computational efficiency is the most important advantage of this theory. In th...

  1. Critical temperature gradient and critical current density in thin films of a type I superconductor

    Energy Technology Data Exchange (ETDEWEB)

    Heubener, R P

    1968-12-16

    Measurements of the critical temperature gradient and the critical current density in superconducting lead films in a transverse magnetic field indicate that the critical current flows predominantly along the surface of the films and that the critical surface currents contribute only very little to the Lorentz force on a fluxoid.

  2. Modified method for labeling human platelets with indium-111 oxine using albumin density-gradient separation

    International Nuclear Information System (INIS)

    Bunting, R.W.; Callahan, R.J.; Finkelstein, S.; Lees, R.S.; Strauss, H.W.

    1982-01-01

    When labeling platelets with indium-111 oxine, albumin density-gradient separation minimizes the time spent to resuspend those platelets that have been centrifuged against a hard surface. Labeling efficiency or platelet viability, as measured by platelet survival or aggregation with adenosine diphosphate, are not adversely affected

  3. Enrichment of unlabeled human Langerhans cells from epidermal cell suspensions by discontinuous density gradient centrifugation

    NARCIS (Netherlands)

    Teunissen, M. B.; Wormmeester, J.; Kapsenberg, M. L.; Bos, J. D.

    1988-01-01

    In this report we introduce an alternative procedure for enrichment of human epidermal Langerhans cells (LC) from epidermal cell suspensions of normal skin. By means of discontinuous Ficoll-Metrizoate density gradient centrifugation, a fraction containing high numbers of viable, more than 80% pure

  4. Properties of ion temperature gradient and trapped electron modes in tokamak plasmas with inverted density profiles

    Science.gov (United States)

    Du, Huarong; Jhang, Hogun; Hahm, T. S.; Dong, J. Q.; Wang, Z. X.

    2017-12-01

    We perform a numerical study of linear stability of the ion temperature gradient (ITG) mode and the trapped electron mode (TEM) in tokamak plasmas with inverted density profiles. A local gyrokinetic integral equation is applied for this study. From comprehensive parametric scans, we obtain stability diagrams for ITG modes and TEMs in terms of density and temperature gradient scale lengths. The results show that, for the inverted density profile, there exists a normalized threshold temperature gradient above which the ITG mode and the TEM are either separately or simultaneously unstable. The instability threshold of the TEM for the inverted density profile is substantially different from that for normal and flat density profiles. In addition, deviations are found on the ITG threshold from an early analytic theory in sheared slab geometry with the adiabatic electron response [T. S. Hahm and W. M. Tang, Phys. Fluids B 1, 1185 (1989)]. A possible implication of this work on particle transport in pellet fueled tokamak plasmas is discussed.

  5. Empirical gradient threshold technique for automated segmentation across image modalities and cell lines.

    Science.gov (United States)

    Chalfoun, J; Majurski, M; Peskin, A; Breen, C; Bajcsy, P; Brady, M

    2015-10-01

    New microscopy technologies are enabling image acquisition of terabyte-sized data sets consisting of hundreds of thousands of images. In order to retrieve and analyze the biological information in these large data sets, segmentation is needed to detect the regions containing cells or cell colonies. Our work with hundreds of large images (each 21,000×21,000 pixels) requires a segmentation method that: (1) yields high segmentation accuracy, (2) is applicable to multiple cell lines with various densities of cells and cell colonies, and several imaging modalities, (3) can process large data sets in a timely manner, (4) has a low memory footprint and (5) has a small number of user-set parameters that do not require adjustment during the segmentation of large image sets. None of the currently available segmentation methods meet all these requirements. Segmentation based on image gradient thresholding is fast and has a low memory footprint. However, existing techniques that automate the selection of the gradient image threshold do not work across image modalities, multiple cell lines, and a wide range of foreground/background densities (requirement 2) and all failed the requirement for robust parameters that do not require re-adjustment with time (requirement 5). We present a novel and empirically derived image gradient threshold selection method for separating foreground and background pixels in an image that meets all the requirements listed above. We quantify the difference between our approach and existing ones in terms of accuracy, execution speed, memory usage and number of adjustable parameters on a reference data set. This reference data set consists of 501 validation images with manually determined segmentations and image sizes ranging from 0.36 Megapixels to 850 Megapixels. It includes four different cell lines and two image modalities: phase contrast and fluorescent. Our new technique, called Empirical Gradient Threshold (EGT), is derived from this reference

  6. High frequency electric field spikes formed by electron beam-plasma interaction in plasma density gradients

    International Nuclear Information System (INIS)

    Gunell, H.; Loefgren, T.

    1997-02-01

    In the electron beam-plasma interaction at an electric double layer the beam density is much higher than in the classical beam-plasma experiments. The wave propagation takes place along the density gradient, that is present at the high potential side of the double layer. Such a case is studied experimentally by injecting the electron beam from a plane cathode, without any grids suppressing the gradient, and by particle simulations. The high frequency field concentrates in a sharp 'spike' with a half width of the order of one wavelength. The spike is found to be a standing wave surrounded by regions dominated by propagating waves. It forms at a position where its frequency is close to the local plasma frequency. The spike forms also when the electric field is well below the threshold for modulational instability, and long before a density cavity is formed in the simulations. Particle simulations reveal that, at the spike, there is a backward travelling wave that, when it is strongly damped, accelerates electrons back towards the cathode. In a simulation of a homogeneous plasma without the density gradient no spike is seen, and the wave is purely travelling instead of standing. 9 refs

  7. Electric field spikes formed by electron beam endash plasma interaction in plasma density gradients

    International Nuclear Information System (INIS)

    Gunell, H.; Loefgren, T.

    1997-01-01

    In the electron beam endash plasma interaction at an electric double layer the beam density is much higher than in the classical beam endash plasma experiments. The wave propagation takes place along the density gradient that is present at the high potential side of the double layer. Such a case is studied experimentally by injecting the electron beam from a plane cathode, without any grids suppressing the gradient, and by particle simulations. The high frequency field concentrates in a sharp open-quotes spikeclose quotes with a half width of the order of one wavelength. The spike is found to be a standing wave surrounded by regions dominated by propagating waves. It forms at a position where its frequency is close to the local plasma frequency. The spike forms also when the electric field is well below the threshold for modulational instability, and long before a density cavity is formed in the simulations. Particle simulations reveal that, at the spike, there is a backward traveling wave that, when it is strongly damped, accelerates electrons back towards the cathode. In a simulation of a homogeneous plasma without the density gradient no spike is seen, and the wave is purely travelling instead of standing. copyright 1997 American Institute of Physics

  8. A rapid and robust gradient measurement technique using dynamic single-point imaging.

    Science.gov (United States)

    Jang, Hyungseok; McMillan, Alan B

    2017-09-01

    We propose a new gradient measurement technique based on dynamic single-point imaging (SPI), which allows simple, rapid, and robust measurement of k-space trajectory. To enable gradient measurement, we utilize the variable field-of-view (FOV) property of dynamic SPI, which is dependent on gradient shape. First, one-dimensional (1D) dynamic SPI data are acquired from a targeted gradient axis, and then relative FOV scaling factors between 1D images or k-spaces at varying encoding times are found. These relative scaling factors are the relative k-space position that can be used for image reconstruction. The gradient measurement technique also can be used to estimate the gradient impulse response function for reproducible gradient estimation as a linear time invariant system. The proposed measurement technique was used to improve reconstructed image quality in 3D ultrashort echo, 2D spiral, and multi-echo bipolar gradient-echo imaging. In multi-echo bipolar gradient-echo imaging, measurement of the k-space trajectory allowed the use of a ramp-sampled trajectory for improved acquisition speed (approximately 30%) and more accurate quantitative fat and water separation in a phantom. The proposed dynamic SPI-based method allows fast k-space trajectory measurement with a simple implementation and no additional hardware for improved image quality. Magn Reson Med 78:950-962, 2017. © 2016 International Society for Magnetic Resonance in Medicine. © 2016 International Society for Magnetic Resonance in Medicine.

  9. Analytic calculations of hyper-Raman spectra from density functional theory hyperpolarizability gradients

    Energy Technology Data Exchange (ETDEWEB)

    Ringholm, Magnus; Ruud, Kenneth [Centre for Theoretical and Computational Chemistry, Department of Chemistry, University of Tromsø – The Arctic University of Norway, 9037 Tromsø (Norway); Bast, Radovan [Theoretical Chemistry and Biology, School of Biotechnology, Royal Institute of Technology, AlbaNova University Center, S-10691 Stockholm (Sweden); PDC Center for High Performance Computing, Royal Institute of Technology, S-10044 Stockholm (Sweden); Oggioni, Luca [Centre for Theoretical and Computational Chemistry, Department of Chemistry, University of Tromsø – The Arctic University of Norway, 9037 Tromsø (Norway); Department of Physics G. Occhialini, University of Milano Bicocca, Piazza della scienza 3, 20126 Milan (Italy); Ekström, Ulf [Centre for Theoretical and Computational Chemistry, Department of Chemistry, University of Oslo, P.O. Box 1033 Blindern, 0315 Oslo (Norway)

    2014-10-07

    We present the first analytic calculations of the geometrical gradients of the first hyperpolarizability tensors at the density-functional theory (DFT) level. We use the analytically calculated hyperpolarizability gradients to explore the importance of electron correlation effects, as described by DFT, on hyper-Raman spectra. In particular, we calculate the hyper-Raman spectra of the all-trans and 11-cis isomers of retinal at the Hartree-Fock (HF) and density-functional levels of theory, also allowing us to explore the sensitivity of the hyper-Raman spectra on the geometrical characteristics of these structurally related molecules. We show that the HF results, using B3LYP-calculated vibrational frequencies and force fields, reproduce the experimental data for all-trans-retinal well, and that electron correlation effects are of minor importance for the hyper-Raman intensities.

  10. Effects of bunch density gradient in high-gain free-electron lasers

    International Nuclear Information System (INIS)

    Huang, Z.; Kim, K.-J.

    1999-01-01

    The authors investigate effects of the bunch density gradient in self-amplified spontaneous emission (SASE), including the role of coherent spontaneous emission (CSE) in the evolution of the free-electron laser (FEL) process. In the exponential gain regime, the authors solve the coupled Maxwell-Vlasov equations and extend the linear theory to a bunched beam with energy spread. A time-dependent, nonlinear simulation algorithm is used to study the CSE effect and the nonlinear evolution of the radiation pulse

  11. Isolation of human salivary extracellular vesicles by iodixanol density gradient ultracentrifugation and their characterizations

    Directory of Open Access Journals (Sweden)

    Kazuya Iwai

    2016-05-01

    Full Text Available Diagnostic methods that focus on the extracellular vesicles (EVs present in saliva have been attracting great attention because of their non-invasiveness. EVs contain biomolecules such as proteins, messenger RNA (mRNA and microRNA (miRNA, which originate from cells that release EVs, making them an ideal source for liquid biopsy. Although there have been many reports on density-based fractionation of EVs from blood and urine, the number of reports on EVs from saliva has been limited, most probably because of the difficulties in separating EVs from viscous saliva using density gradient centrifugation. This article establishes a protocol for the isolation of EVs from human saliva using density gradient centrifugation. The fractionated salivary EVs were characterized by atomic force microscopy, western blot and reverse transcription polymerase chain reaction. The results indicate that salivary EVs have a smaller diameter (47.8±12.3 nm and higher density (1.11 g/ml than EVs isolated from conditioned cell media (74.0±23.5 nm and 1.06 g/ml, respectively. Additionally, to improve the throughput of density-based fractionation of EVs, the original protocol was further modified by using a fixed angle rotor instead of a swinging rotor. It was also confirmed that several miRNAs were expressed strongly in the EV-marker-expressing fractions.

  12. Subsystem density functional theory with meta-generalized gradient approximation exchange-correlation functionals.

    Science.gov (United States)

    Śmiga, Szymon; Fabiano, Eduardo; Laricchia, Savio; Constantin, Lucian A; Della Sala, Fabio

    2015-04-21

    We analyze the methodology and the performance of subsystem density functional theory (DFT) with meta-generalized gradient approximation (meta-GGA) exchange-correlation functionals for non-bonded molecular systems. Meta-GGA functionals depend on the Kohn-Sham kinetic energy density (KED), which is not known as an explicit functional of the density. Therefore, they cannot be directly applied in subsystem DFT calculations. We propose a Laplacian-level approximation to the KED which overcomes this limitation and provides a simple and accurate way to apply meta-GGA exchange-correlation functionals in subsystem DFT calculations. The so obtained density and energy errors, with respect to the corresponding supermolecular calculations, are comparable with conventional approaches, depending almost exclusively on the approximations in the non-additive kinetic embedding term. An embedding energy error decomposition explains the accuracy of our method.

  13. Travelling waves of density for a fourth-gradient model of fluids

    Science.gov (United States)

    Gouin, Henri; Saccomandi, Giuseppe

    2016-09-01

    In mean-field theory, the non-local state of fluid molecules can be taken into account using a statistical method. The molecular model combined with a density expansion in Taylor series of the fourth order yields an internal energy value relevant to the fourth-gradient model, and the equation of isothermal motions takes then density's spatial derivatives into account for waves travelling in both liquid and vapour phases. At equilibrium, the equation of the density profile across interfaces is more precise than the Cahn and Hilliard equation, and near the fluid's critical point, the density profile verifies an Extended Fisher-Kolmogorov equation, allowing kinks, which converges towards the Cahn-Hillard equation when approaching the critical point. Nonetheless, we also get pulse waves oscillating and generating critical opalescence.

  14. Infrared technique for measuring steam density

    International Nuclear Information System (INIS)

    Snyder, S.C.; Baker, A.G.

    1982-01-01

    A prototype infrared steam densitometer using a two-wavelength, dual-beam technique was developed. Tests were performed on dry steam flows with this technique, which uses two narrow bandwidths of infrared light in the region of 0.9 to 3.0 μm. One wavelength is absorbed by steam, while the other is not. The latter wavelength is used to account for nonabsorptive light losses. In addition to the beam that traverses the steam flow, a reference beam that does not traverse the flow allows the light source to be monitored. The theory of the device is presented, along with a description of the components and of the system's operation. Test results are also presented

  15. Current Density Functional Theory Using Meta-Generalized Gradient Exchange-Correlation Functionals.

    Science.gov (United States)

    Furness, James W; Verbeke, Joachim; Tellgren, Erik I; Stopkowicz, Stella; Ekström, Ulf; Helgaker, Trygve; Teale, Andrew M

    2015-09-08

    We present the self-consistent implementation of current-dependent (hybrid) meta-generalized gradient approximation (mGGA) density functionals using London atomic orbitals. A previously proposed generalized kinetic energy density is utilized to implement mGGAs in the framework of Kohn-Sham current density functional theory (KS-CDFT). A unique feature of the nonperturbative implementation of these functionals is the ability to seamlessly explore a wide range of magnetic fields up to 1 au (∼235 kT) in strength. CDFT functionals based on the TPSS and B98 forms are investigated, and their performance is assessed by comparison with accurate coupled-cluster singles, doubles, and perturbative triples (CCSD(T)) data. In the weak field regime, magnetic properties such as magnetizabilities and nuclear magnetic resonance shielding constants show modest but systematic improvements over generalized gradient approximations (GGA). However, in the strong field regime, the mGGA-based forms lead to a significantly improved description of the recently proposed perpendicular paramagnetic bonding mechanism, comparing well with CCSD(T) data. In contrast to functionals based on the vorticity, these forms are found to be numerically stable, and their accuracy at high field suggests that the extension of mGGAs to CDFT via the generalized kinetic energy density should provide a useful starting point for further development of CDFT approximations.

  16. Medicinal Plants Density Along an Altitudinal Gradient in and Around Ayubia National Park

    International Nuclear Information System (INIS)

    Tariq, A.; Adnan, M.; Begum, S.

    2016-01-01

    Medicinal plants are an essential source of livelihood for many rural populations and are currently facing several threats of extinction in temperate Himalaya, such as excessive grazing and collection along altitudinal gradients. The present study was designed to investigate the species density of medicinal plants at different mid-altitude levels (2200, 2300, 2400, and 2500 m above the sea level (a.s.l.) between two forest-use types and to examine the possible association between medicinal plant densities and forest-stand structural variables along the altitudinal gradient. Factorial design analysis of variance showed that the densities of all medicinal plants differed significantly between the forest-use types (p<0.00) and elevation (p<0.00). Moreover, a significant interaction (p<0.04) was also observed between the forest-use types and elevation. In the old-growth forest, density of medicinal plants was 290/40 m/sup 2/ at the higher altitude (2500 m a.s.l.), approximately 1.5-fold less than the 475/40 m/sup 2/ density observed at lower altitude (2200 m a.s.l.). However, in derived woodland, density of medicinal plants at higher altitude was approximately 4-fold less than that at the lower altitude. At these altitudinal levels, medicinal plants densities, such as Valeriana jatamansi, were significantly higher under old-growth forest compared to derived woodland, where they were almost nonexistent. A rapid vulnerability assessment has also shown that Valeriana jatamansi and Viola canescens were highly vulnerable species. Litter cover was the influential variable that was most likely related to medicinal plant density. In conclusion, abundance of medicinal plants decreased along mid-altitude levels in both of the forest-use types. However, this decrease was extremely marked in the derived woodland, and this decline may be due to human activity. Hence, these factors must be considered in future studies to suggest protective measures that can be applied along

  17. Application of interferometry and Faraday rotation techniques for density measurements on ITER

    International Nuclear Information System (INIS)

    Snider, R.T.; Carlstrom, T.N.; Ma, C.H.; Peebles, W.A.

    1995-01-01

    There is a need for real time, reliable density measurement for density control, compatible with the restricted access and radiation environment on ITER. Line average density measurements using microwave or laser interferometry techniques have proven to be robust and reliable for density control on contemporary tokamaks. In ITER, the large path length, high density and density gradients, limit the wavelength of a probing beam to shorter then about 50 microm due to refraction effects. In this paper the authors consider the design of short wavelength vibration compensated interferometers and Faraday rotation techniques for density measurements on ITER. These techniques allow operation of the diagnostics without a prohibitively large vibration isolated structure and permits the optics to be mounted directly on the radial port plugs on ITER. A beam path designed for 10.6 microm (CO2 laser) with a tangential path through the plasma allows both an interferometer and a Faraday rotation measurement of the line average density with good density resolution while avoiding refraction problems. Plasma effects on the probing beams and design tradeoffs will be discussed along with radiation and long pulse issues. A proposed layout of the diagnostic for ITER will be present

  18. Plasma membrane temperature gradients and multiple cell permeabilization induced by low peak power density femtosecond lasers

    Directory of Open Access Journals (Sweden)

    Allen L. Garner

    2016-03-01

    Full Text Available Calculations indicate that selectively heating the extracellular media induces membrane temperature gradients that combine with electric fields and a temperature-induced reduction in the electropermeabilization threshold to potentially facilitate exogenous molecular delivery. Experiments by a wide-field, pulsed femtosecond laser with peak power density far below typical single cell optical delivery systems confirmed this hypothesis. Operating this laser in continuous wave mode at the same average power permeabilized many fewer cells, suggesting that bulk heating alone is insufficient and temperature gradients are crucial for permeabilization. This work suggests promising opportunities for a high throughput, low cost, contactless method for laser mediated exogenous molecule delivery without the complex optics of typical single cell optoinjection, for potential integration into microscope imaging and microfluidic systems.

  19. Nonlinear theory of trapped electron temperature gradient driven turbulence in flat density H-mode plasmas

    International Nuclear Information System (INIS)

    Hahm, T.S.

    1990-12-01

    Ion temperature gradient turbulence based transport models have difficulties reconciling the recent DIII-D H-mode results where the density profile is flat, but χ e > χ i in the core region. In this work, a nonlinear theory is developed for recently discovered ion temperature gradient trapped electron modes propagating in the electron diamagnetic direction. This instability is predicted to be linearly unstable for L Ti /R approx-lt κ θ ρ s approx-lt (L Ti /R) 1/4 . They are also found to be strongly dispersive even at these long wavelengths, thereby suggesting the importance of the wave-particle-wave interactions in the nonlinear saturation phase. The fluctuation spectrum and anomalous fluxes are calculated. In accordance with the trends observed in DIII-D, the predicted electron thermal diffusivity can be larger than the ion thermal diffusivity. 17 refs., 3 figs

  20. Chemical bond as a test of density-gradient expansions for kinetic and exchange energies

    International Nuclear Information System (INIS)

    Perdew, J.P.; Levy, M.; Painter, G.S.; Wei, S.; Lagowski, J.B.

    1988-01-01

    Errors in kinetic and exchange contributions to the molecular bonding energy are assessed for approximate density functionals by reference to near-exact Hartree-Fock values. From the molecular calculations of Allan et al. and of Lee and Ghosh, it is demonstrated that the density-gradient expansion does not accurately describe the noninteracting kinetic contribution to the bonding energy, even when this expansion is carried to fourth order and applied in its spin-density-functional form to accurate Hartree-Fock densities. In a related study, it is demonstrated that the overbinding of molecules such as N 2 and F 2 , which occurs in the local-spin-density (LSD) approximation for the exchange-correlation energy, is not attributable to errors in the self-consistent LSD densities. Contrary to expectations based upon the Gunnarsson-Jones nodality argument, it is found that the LSD approximation for the exchange energy can seriously overbind a molecule even when bonding does not create additional nodes in the occupied valence orbitals. LSD and exact values for the exchange contribution to the bonding energy are displayed and discussed for several molecules

  1. Measurement of hepatic venous pressure gradient revisited: Catheter wedge vs balloon wedge techniques

    Directory of Open Access Journals (Sweden)

    S Timothy Chelliah

    2011-01-01

    Full Text Available Aims: To evaluate the accuracy of measurement of hepatic venous pressure gradient by catheter wedge as compared to balloon wedge (the gold standard. Materials and Methods: Forty-five patients having a clinical diagnosis of intrahepatic portal hypertension were subjected to the two different types of pressure measurements (catheter wedge and balloon wedge during transjugular liver biopsy under fluoroscopic guidance. Statistical Analysis: Spearman′s rank correlation coefficient, Bland-Altman plot for agreement, and single measure intraclass correlation were used for analysis of data. Results: There was a close correlation between the results obtained by both the techniques, with highly significant concordance (P < 0.0001. Hepatic venous pressure gradients as measured by the catheter wedge technique were either equal to or less than those obtained by the balloon wedge technique. Conclusions: The difference in hepatic venous pressure gradients measured by the two techniques is insignificant.

  2. Isolating peripheral lymphocytes by density gradient centrifugation and magnetic cell sorting.

    Science.gov (United States)

    Brosseron, Frederic; Marcus, Katrin; May, Caroline

    2015-01-01

    Combining density gradient centrifugation with magnetic cell sorting provides a powerful tool to isolate blood cells with high reproducibility, yield, and purity. It also allows for subsequent separation of multiple cell types, resulting in the possibility to analyze different purified fractions from one donor's sample. The centrifugation step divides whole blood into peripheral blood mononuclear cells (PBMC), erythrocytes, and platelet-rich plasma. In the following, lymphocyte subtypes can be consecutively isolated from the PBMC fraction. This chapter describes enrichment of erythrocytes, CD14-positive monocytes and CD3-positive T lymphocytes. Alternatively, other cell types can be targeted by using magnetic beads specific for the desired subpopulation.

  3. A single-gradient junction technique to replace multiple-junction shifts for craniospinal irradiation treatment

    International Nuclear Information System (INIS)

    Hadley, Austin; Ding, George X.

    2014-01-01

    Craniospinal irradiation (CSI) requires abutting fields at the cervical spine. Junction shifts are conventionally used to prevent setup error–induced overdosage/underdosage from occurring at the same location. This study compared the dosimetric differences at the cranial-spinal junction between a single-gradient junction technique and conventional multiple-junction shifts and evaluated the effect of setup errors on the dose distributions between both techniques for a treatment course and single fraction. Conventionally, 2 lateral brain fields and a posterior spine field(s) are used for CSI with weekly 1-cm junction shifts. We retrospectively replanned 4 CSI patients using a single-gradient junction between the lateral brain fields and the posterior spine field. The fields were extended to allow a minimum 3-cm field overlap. The dose gradient at the junction was achieved using dose painting and intensity-modulated radiation therapy planning. The effect of positioning setup errors on the dose distributions for both techniques was simulated by applying shifts of ± 3 and 5 mm. The resulting cervical spine doses across the field junction for both techniques were calculated and compared. Dose profiles were obtained for both a single fraction and entire treatment course to include the effects of the conventional weekly junction shifts. Compared with the conventional technique, the gradient-dose technique resulted in higher dose uniformity and conformity to the target volumes, lower organ at risk (OAR) mean and maximum doses, and diminished hot spots from systematic positioning errors over the course of treatment. Single-fraction hot and cold spots were improved for the gradient-dose technique. The single-gradient junction technique provides improved conformity, dose uniformity, diminished hot spots, lower OAR mean and maximum dose, and one plan for the entire treatment course, which reduces the potential human error associated with conventional 4-shifted plans

  4. Les écoulements par RMN à gradient pulsé Pulsed Gradient Nmr Techniques for Studying Flows

    Directory of Open Access Journals (Sweden)

    Lebon L.

    2006-12-01

    Full Text Available Nous présentons ici les techniques de RMN à gradient pulsé qui permettent d'étudier les écoulements multiphasiques en canalisation ou en milieu poreux. Les principaux avantages sont de pouvoir travailler sur des milieux non transparents et d'accéder à des échelles de longueurs faibles. On montre qu'il est possible d'obtenir des informations locales sur l'écoulement, telles que le profil de vitesse et ses fluctuations dans les écoulements diphasiques, ou les cartes de distribution des probabilités de déplacement dans des échantillons poreux hétérogènes. Pulsed gradient NMR techniques are presented here. They allow the study of multiphase flow in pipes as well as porous media. The main advantages are the possibilities of studying non transparent media at small length scales. We show that it is possible to obtain local information on the fluid flow, such as velocity profiles in two phase systems, or maps of distribution of displacement probabilities in heterogeneous porous media.

  5. Method and means for a spatial and temporal probe for laser-generated plumes based on density gradients

    Science.gov (United States)

    Yeung, E.S.; Chen, G.

    1990-05-01

    A method and means are disclosed for a spatial and temporal probe for laser generated plumes based on density gradients includes generation of a plume of vaporized material from a surface by an energy source. The probe laser beam is positioned so that the plume passes through the probe laser beam. Movement of the probe laser beam caused by refraction from the density gradient of the plume is monitored. Spatial and temporal information, correlated to one another, is then derived. 15 figs.

  6. Effects of population density and chemical environment on the behavior of Escherichia coli in shallow temperature gradients

    International Nuclear Information System (INIS)

    Demir, Mahmut; Yoney, Anna; Salman, Hanna; Douarche, Carine; Libchaber, Albert

    2011-01-01

    In shallow temperature gradients, changes in temperature that bacteria experience occur over long time scales. Therefore, slow processes such as adaptation, metabolism, chemical secretion and even gene expression become important. Since these are cellular processes, the cell density is an important parameter that affects the bacteria's response. We find that there are four density regimes with distinct behaviors. At low cell density, bacteria do not cause changes in their chemical environment; however, their response to the temperature gradient is strongly influenced by it. In the intermediate cell-density regime, the consumption of nutrients becomes significant and induces a gradient of nutrients opposing the temperature gradient due to higher consumption rate at the high temperature. This causes the bacteria to drift toward low temperature. In the high cell-density regime, interactions among bacteria due to secretion of an attractant lead to a strong local accumulation of bacteria. This together with the gradient of nutrients, resulted from the differential consumption rate, creates a fast propagating pulse of bacterial density. These observations are a result of classical nonlinear population dynamics. At extremely high cell density, a change in the physiological state of the bacteria is observed. The bacteria, at the individual level, become cold seeking. This appears initially as a result of a change in the methylation level of the two most abundant sensing receptors, Tsr and Tar. It is further enforced at an even higher cell density by a change in the expression level of these receptors. (perspective)

  7. Fabrication of a wettability-gradient surface on copper by screen-printing techniques

    International Nuclear Information System (INIS)

    Huang, Ding-Jun; Leu, Tzong-Shyng

    2015-01-01

    In this study, a screen-printing technique is utilized to fabricate a wettability-gradient surface on a copper substrate. The pattern definitions on the copper surface were freely fabricated to define the regions with different wettabilities, for which the printing definition technique was developed as an alternative to the existing costly photolithography techniques. This fabrication process using screen printing in tandem with chemical modification methods can easily realize an excellent wettability-gradient surface with superhydrophobicity and superhydrophilicity. Surface analyses were performed to characterize conditions in some fabrication steps. A water droplet movement sequence is provided to clearly demonstrate the droplet-driving effectiveness of the fabricated gradient surface. The droplet-driving efficiency offers a promising solution for condensation heat transfer applications in the foreseeable future. (paper)

  8. Linking Soil Physical Parameters Along a Density Gradient in a Loess-Soil Long-Term Experiment

    DEFF Research Database (Denmark)

    Eden, Marie; Møldrup, Per; Schjønning, Per

    2012-01-01

    It is important to understand the impact of texture and organic carbon (OC) on soil structure development. Only few studies investigated this for silt-dominated soils. In this study, soil physical properties were determined on samples from a controlled experiment (Static Fertilization Experiment...... hydraulic conductivity. The management resulted in a distinct gradient in OC. A bulk density gradient developed from differences in amount of clay not complexed with OC. This gradient in bulk density mainly affected content of pores larger than 3 [mu]m. The air-connected porosity measured by a pycnometer...

  9. The use of singular value gradients and optimization techniques to design robust controllers for multiloop systems

    Science.gov (United States)

    Newsom, J. R.; Mukhopadhyay, V.

    1983-01-01

    A method for designing robust feedback controllers for multiloop systems is presented. Robustness is characterized in terms of the minimum singular value of the system return difference matrix at the plant input. Analytical gradients of the singular values with respect to design variables in the controller are derived. A cumulative measure of the singular values and their gradients with respect to the design variables is used with a numerical optimization technique to increase the system's robustness. Both unconstrained and constrained optimization techniques are evaluated. Numerical results are presented for a two output drone flight control system.

  10. Study of Streamers in Gradient Density Air: Table Top Modeling of Red Sprites

    Science.gov (United States)

    Opaits, D. F.; Shneider, M. N.; Howard, P. J.; Miles, R. B.; Milikh, G. M.

    2009-12-01

    Sprites and blue jets develop in the upper atmosphere where ambient density changes drastically over their lengths. Theoretical analysis of Red Sprites [1] and Blue Jets [2,3] are based on the streamer tip parameters’ functional dependence on a local gas density N(h). At the moment there is a lack of experimental data for streamer propagation in a non-uniform ambient gas density. Small scale experiments in controllable conditions are important for validation of analytical models as well as numerical simulations, which can be used for the investigation of real scale plasma phenomena that develop above thunderclouds. Controllable, non-uniform gas density can be achieved in laboratory conditions in super sonic nozzles, fast centrifuges or gas filled tubes with a non-uniform temperature distribution along the axis. The latter approach was used in the present work. A quartz tube, approximately one foot in length, was filled with air at different pressures. A density gradient was created by heating up the top of the tube while keeping the bottom at room temperature. The discharge was initiated by applying a high voltage pulse to a pin electrode at the top of the tube while a flat electrode was grounded at the bottom. Similar to Red Sprites, the streamer propagates downwards into a region of higher density and stops before reaching the lower electrode while the top electrode remains under high potential. This work will present results of streamer propagation at different pressures and voltages. Measurements of current-voltage characteristics as well as integral images will be presented. 1. Y. P.Raizer, G. M. Milikh, M. N. Shneider, and S. V. Novakovski (1998), J. Phys. D: Appl. Phys. 31, 3255-3264. 2. Y. P.Raizer, G. M. Milikh, and M. N. Shneider (2006), Geophys. Res. Lett., 33, L23801 3. Y .P.Raizer, G. M. Milikh, and M. N. Shneider (2007), J. Atmos. & Solat-Terr. Phys, 69, 925-938

  11. Techniques for Ultra-high Magnetic Field Gradient NMR Diffusion Measurements

    Science.gov (United States)

    Sigmund, Eric E.; Mitrovic, Vesna F.; Calder, Edward S.; Will Thomas, G.; Halperin, William P.; Reyes, Arneil P.; Kuhns, Philip L.; Moulton, William G.

    2001-03-01

    We report on development and application of techniques for ultraslow diffusion coefficient measurements through nuclear magnetic resonance (NMR) in high magnetic field gradients. We have performed NMR experiments in a steady fringe field gradient of 175 T/m from a 23 T resistive Bitter magnet, as well as in a gradient of 42 T/m from an 8 T superconducting magnet. New techniques to provide optimum sensitivity in these experiments are described. To eliminate parasitic effects of the temporal instability of the resistive magnet, we have introduced a passive filter: a highly conductive cryogen-cooled inductive shield. We show experimental demonstration of such a shield’s effect on NMR performed in the Bitter magnet. For enhanced efficiency, we have employed “frequency jumping” in our spectrometer system. Application of these methods has made possible measurements of diffusion coefficients as low as 10-10 cm^2/s, probing motion on a 250 nm length scale.

  12. Sea surface density gradients in the Nordic Seas during the Holocene as revealed by paired microfossil and isotope proxies

    DEFF Research Database (Denmark)

    Van Nieuwenhove, Nicolas; Hillaire-Marcel, Claude; Bauch, Henning A.

    2016-01-01

    We attempt to assess the Holocene surface-subsurface seawater density gradient on millennial time-scale based on the reconstruction of potential density (σθ) by combining data from dinoflagellate cyst assemblages and planktic foraminiferal (Neogloboquadrina pachyderma (s)) stable oxygen isotopes (δ...

  13. Effects of density gradients and fluctuations at the plasma edge on ECEI measurements at ASDEX Upgrade

    Science.gov (United States)

    Vanovac, B.; Wolfrum, E.; Denk, S. S.; Mink, F.; Laggner, F. M.; Birkenmeier, G.; Willensdorfer, M.; Viezzer, E.; Hoelzl, M.; Freethy, S. J.; Dunne, M. G.; Lessig, A.; Luhmann, N. C., Jr.; the ASDEX Upgrade Team; the EUROfusion MST1 Team

    2018-04-01

    Electron cyclotron emission imaging (ECEI) provides measurements of electron temperature (T e ) and its fluctuations (δT e ). However, when measuring at the plasma edge, in the steep gradient region, radiation transport effects must be taken into account. It is shown that due to these effects, the scrape-off layer region is not accessible to the ECEI measurements in steady state conditions and that the signal is dominated by the shine-through emission. Transient effects, such as filaments, can change the radiation transport locally, but cannot be distinguished from the shine-through. Local density measurements are essential for the correct interpretation of the electron cyclotron emission, since the density fluctuations influence the temperature measurements at the plasma edge. As an example, a low frequency 8 kHz mode, which causes 10%-15% fluctuations in the signal level of the ECEI, is analysed. The same mode has been measured with the lithium beam emission spectroscopy density diagnostic, and is very well correlated in time with high frequency magnetic fluctuations. With radiation transport modelling of the electron cyclotron radiation in the ECEI geometry, it is shown that the density contributes significantly to the radiation temperature (T rad) and the experimental observations have shown the amplitude modulation in both density and temperature measurements. The poloidal velocity of the low frequency mode measured by the ECEI is 3 km s-1. The calculated velocity of the high frequency mode measured with the magnetic pick-up coils is about 25 km s-1. Velocities are compared with the E × B background flow velocity and possible explanations for the origin of the low frequency mode are discussed.

  14. New resin gel for uranium determination by diffusive gradient in thin films technique

    Czech Academy of Sciences Publication Activity Database

    Gregušová, Michaela; Dočekal, Bohumil

    2011-01-01

    Roč. 684, 1-2 (2011), s. 142-146 ISSN 0003-2670 R&D Projects: GA ČR GAP503/10/2002 Institutional research plan: CEZ:AV0Z40310501 Keywords : diffusive gradient in thin film technique * 8-hydroxyquinoline resin gel * uranium determination Subject RIV: CB - Analytical Chemistry, Separation Impact factor: 4.555, year: 2011

  15. Effect of stable-density stratification on counter gradient flux of a homogeneous shear flow

    Energy Technology Data Exchange (ETDEWEB)

    Lida, Oaki; Nagano, Yasutaka [Nagoya Institute of Technology, Gokiso-cho, Showa-ku, Nagoya (Japan). Department of Mechanical Engineering

    2007-01-15

    We performed direct numerical simulations of homogeneous shear flow under stable-density stratification to study the buoyancy effects on the heat and momentum transfer. These numerical data were compared with those of a turbulent channel flow to investigate the similarity between the near-wall turbulence and the homogeneous shear flow. We also investigated the generation mechanism of the persistent CGFs (counter gradient fluxes) appearing at the higher wavenumbers of the cospectrum, and lasting over a long time without oscillation. Spatially, the persistent CGFs are associated with the longitudinal vortical structure, which is elongated in the streamwise direction and typically observed in both homogeneous shear flow and near-wall turbulence. The CGFs appear at both the top and bottom of this longitudinal vortical structure, and expand horizontally with an increase in the Richardson number. It was found that the production and turbulent-diffusion terms are responsible for the distribution of the Reynolds shear stress including the persistent CGFs. The buoyancy term, combined with the swirling motion of the vortex, contributes to expand the persistent CGF regions and decrease the down gradient fluxes. (author)

  16. Resistance scaling for composite fermions in the presence of a density gradient

    International Nuclear Information System (INIS)

    Stormer, H. L.; Tsui, Daniel Chee; Pan, Wei; West, Ken W.; Baldwin, K. W.; Pfeiffer, Loren N.

    2006-01-01

    The magnetoresistance, R xx , at even-denominator fractional fillings, of an ultra high quality two-dimensional electron system at T ∼ 35 mK is observed to be strictly linear in magnetic field, B. While at 35 mK R xx is dominated by the integer and fractional quantum Hall states, at T ≅ 1.2 K an almost perfect linear relationship between R xx and B emerges over the whole magnetic field range except for spikes at the integer quantum Hall states. This linear R xx cannot be understood within the Composite Fermion model, but can be explained through the existence of a density gradient in our sample

  17. Density gradient instabilities in a neutron inhomogeneous guiding-centre plasma

    International Nuclear Information System (INIS)

    Shoucri, M.M.; Gagne, R.R.J.

    1977-01-01

    The guiding-centre equations for a plasma of cold ions and thermal electrons admit neutral and non-neutral inhomogeneous equilibrium solutions, and the linear stability of these solutions has been recently investigated numerically by Shoucri and Knorr (1975). With arbitrary density profiles, numerical techniques appear to be the only practical way to study the linear stability of the inhomogeneous equilibrium solutions for the guiding centre plasma. However, analytical methods can be applied to some simple types of density profiles. The purpose of the present note is to present some analytical results on the linear instabilities of an inhomogeneous neutral guiding centre plasma. (U.K.)

  18. Role of Density Gradient Driven Trapped Electron Modes in the H-Mode Inner Core with Electron Heating

    Science.gov (United States)

    Ernst, D.

    2015-11-01

    We present new experiments and nonlinear gyrokinetic simulations showing that density gradient driven TEM (DGTEM) turbulence dominates the inner core of H-Mode plasmas during strong electron heating. Thus α-heating may degrade inner core confinement in H-Mode plasmas with moderate density peaking. These DIII-D low torque quiescent H-mode experiments were designed to study DGTEM turbulence. Gyrokinetic simulations using GYRO (and GENE) closely match not only particle, energy, and momentum fluxes, but also density fluctuation spectra, with and without ECH. Adding 3.4 MW ECH doubles Te /Ti from 0.5 to 1.0, which halves the linear TEM critical density gradient, locally flattening the density profile. Density fluctuations from Doppler backscattering (DBS) intensify near ρ = 0.3 during ECH, displaying a band of coherent fluctuations with adjacent toroidal mode numbers. GYRO closely reproduces the DBS spectrum and its change in shape and intensity with ECH, identifying these as coherent TEMs. Prior to ECH, parallel flow shear lowers the effective nonlinear DGTEM critical density gradient 50%, but is negligible during ECH, when transport displays extreme stiffness in the density gradient. GS2 predictions show the DGTEM can be suppressed, to avoid degradation with electron heating, by broadening the current density profile to attain q0 >qmin > 1 . A related experiment in the same regime varied the electron temperature gradient in the outer half-radius (ρ ~ 0 . 65) using ECH, revealing spatially coherent 2D mode structures in the Te fluctuations measured by ECE imaging. Fourier analysis with modulated ECH finds a threshold in Te profile stiffness. Supported by the US DOE under DE-FC02-08ER54966 and DE-FC02-04ER54698.

  19. Self-diffusion measurements in heterogeneous systems using NMR pulsed field gradient technique

    International Nuclear Information System (INIS)

    Heink, W.; Kaerger, J.; Walter, A.

    1978-01-01

    The experimental pecularities of the NMR pulsed field gradient technique are critical surveyed in its application to zeolite adsorbate adsorbent systems. After a presentation of the different transport parameters accessible by this technique, the consequences of the existence of inner field gradients being inherent to heterogeneous systems are analyzed. Experimental conditions and consequences of an application of pulsed field gradients of high intensity which are necessary for the measurement of small intracrystalline self-diffusion coefficients, are discussed. Gradient pulses of 0.15 Tcm -1 with pulse widths of 2 ms maximum and relative deviations of less than 0.01 per mille can be realized. Since for a number of adsorbate adsorbent systems a distinct dependence of the intracrystalline self-diffusion coeffcients on adsorbate concentration is observed, determination of zeolite pore fiiling factor is of considerable importance for the interpretation of the diffusivities obtained. It is demonstrated that also this information can be obtained by NMR technique in a straightforward way with a mean error of less than 5 to 10 %. Applying this new method and using an optimum experimental device as described, pore filling factor dependences of the self-diffusion coefficients of alkanes in NaX zeolites can be followed over more than two orders of magnitude. (author)

  20. Dimmable electronic ballasts by variable power density modulation technique

    Science.gov (United States)

    Borekci, Selim; Kesler, Selami

    2014-11-01

    Dimming can be accomplished commonly by switching frequency and pulse density modulation techniques and a variable inductor. In this study, a variable power density modulation (VPDM) control technique is proposed for dimming applications. A fluorescent lamp is operated in several states to meet the desired lamp power in a modulation period. The proposed technique has the same advantages of magnetic dimming topologies have. In addition, a unique and flexible control technique can be achieved. A prototype dimmable electronic ballast is built and experiments related to it have been conducted. As a result, a 36WT8 fluorescent lamp can be driven for a desired lamp power from several alternatives without modulating the switching frequency.

  1. Analytic energy gradients for the coupled-cluster singles and doubles method with the density-fitting approximation

    International Nuclear Information System (INIS)

    Bozkaya, Uğur; Sherrill, C. David

    2016-01-01

    An efficient implementation is presented for analytic gradients of the coupled-cluster singles and doubles (CCSD) method with the density-fitting approximation, denoted DF-CCSD. Frozen core terms are also included. When applied to a set of alkanes, the DF-CCSD analytic gradients are significantly accelerated compared to conventional CCSD for larger molecules. The efficiency of our DF-CCSD algorithm arises from the acceleration of several different terms, which are designated as the “gradient terms”: computation of particle density matrices (PDMs), generalized Fock-matrix (GFM), solution of the Z-vector equation, formation of the relaxed PDMs and GFM, back-transformation of PDMs and GFM to the atomic orbital (AO) basis, and evaluation of gradients in the AO basis. For the largest member of the alkane set (C 10 H 22 ), the computational times for the gradient terms (with the cc-pVTZ basis set) are 2582.6 (CCSD) and 310.7 (DF-CCSD) min, respectively, a speed up of more than 8-folds. For gradient related terms, the DF approach avoids the usage of four-index electron repulsion integrals. Based on our previous study [U. Bozkaya, J. Chem. Phys. 141, 124108 (2014)], our formalism completely avoids construction or storage of the 4-index two-particle density matrix (TPDM), using instead 2- and 3-index TPDMs. The DF approach introduces negligible errors for equilibrium bond lengths and harmonic vibrational frequencies.

  2. Detection of human DNA polymorphisms with a simplified denaturing gradient gel electrophoresis technique

    International Nuclear Information System (INIS)

    Noll, W.W.; Collins, M.

    1987-01-01

    Single base pair differences between otherwise identical DNA molecules can result in altered melting behavior detectable by denaturing gradient gel electrophoresis. The authors have developed a simplified procedure for using denaturing gradient gel electrophoresis to detect base pair changes in genomic DNA. Genomic DNA is digested with restriction enzymes and hybridized in solution to labeled single-stranded probe DNA. The excess probe is then hybridized to complementary phage M13 template DNA, and the reaction mixture is electrophoresed on a denaturing gradient gel. Only the genomic DNA probe hybrids migrate into the gel. Differences in hybrid mobility on the gel indicate base pair changes in the genomic DNA. They have used this technique to identify two polymorphic sites within a 1.2-kilobase region of human chromosome 20. This approach should greatly facilitate the identification of DNA polymorphisms useful for gene linkage studies and the diagnosis of genetic diseases

  3. Assessment of plasma impedance probe for measuring electron density and collision frequency in a plasma with spatial and temporal gradients

    International Nuclear Information System (INIS)

    Hopkins, Mark A.; King, Lyon B.

    2014-01-01

    Numerical simulations and experimental measurements were combined to determine the ability of a plasma impedance probe (PIP) to measure plasma density and electron collision frequency in a plasma containing spatial gradients as well as time-varying oscillations in the plasma density. A PIP is sensitive to collision frequency through the width of the parallel resonance in the Re[Z]-vs.-frequency characteristic, while also being sensitive to electron density through the zero-crossing of the Im[Z]-vs.-frequency characteristic at parallel resonance. Simulations of the probe characteristic in a linear plasma gradient indicated that the broadening of Re[Z] due to the spatial gradient obscured the broadening due to electron collision frequency, preventing a quantitative measurement of the absolute collision frequency for gradients considered in this study. Simulation results also showed that the PIP is sensitive to relative changes in electron collision frequency in a spatial density gradient, but a second broadening effect due to time-varying oscillations made collision frequency measurements impossible. The time-varying oscillations had the effect of causing multiple zero-crossings in Im[Z] at parallel resonance. Results of experiments and simulations indicated that the lowest-frequency zero-crossing represented the lowest plasma density in the oscillations and the highest-frequency zero-crossing represented the highest plasma density in the oscillations, thus the PIP probe was found to be an effective tool to measure both the average plasma density as well as the maximum and minimum densities due to temporal oscillations

  4. An Experiment Using Sucrose Density Gradients in the Undergraduate Biochemistry Laboratory.

    Science.gov (United States)

    Turchi, Sandra L.; Weiss, Monica

    1988-01-01

    Describes an experiment to be performed in an undergraduate biochemistry laboratory that is based on a gradient centrifugation system employing a simple bench top centrifuge, a freezer, and frozen surcose gradient solution to separate macromolecules and subcellular components. (CW)

  5. Preconditioned conjugate gradient technique for the analysis of symmetric anisotropic structures

    Science.gov (United States)

    Noor, Ahmed K.; Peters, Jeanne M.

    1987-01-01

    An efficient preconditioned conjugate gradient (PCG) technique and a computational procedure are presented for the analysis of symmetric anisotropic structures. The technique is based on selecting the preconditioning matrix as the orthotropic part of the global stiffness matrix of the structure, with all the nonorthotropic terms set equal to zero. This particular choice of the preconditioning matrix results in reducing the size of the analysis model of the anisotropic structure to that of the corresponding orthotropic structure. The similarities between the proposed PCG technique and a reduction technique previously presented by the authors are identified and exploited to generate from the PCG technique direct measures for the sensitivity of the different response quantities to the nonorthotropic (anisotropic) material coefficients of the structure. The effectiveness of the PCG technique is demonstrated by means of a numerical example of an anisotropic cylindrical panel.

  6. Electromagnetic considerations for RF current density imaging [MRI technique].

    Science.gov (United States)

    Scott, G C; Joy, M G; Armstrong, R L; Henkelman, R M

    1995-01-01

    Radio frequency current density imaging (RF-CDI) is a recent MRI technique that can image a Larmor frequency current density component parallel to B(0). Because the feasibility of the technique was demonstrated only for homogeneous media, the authors' goal here is to clarify the electromagnetic assumptions and field theory to allow imaging RF currents in heterogeneous media. The complete RF field and current density imaging problem is posed. General solutions are given for measuring lab frame magnetic fields from the rotating frame magnetic field measurements. For the general case of elliptically polarized fields, in which current and magnetic field components are not in phase, one can obtain a modified single rotation approximation. Sufficient information exists to image the amplitude and phase of the RF current density parallel to B(0) if the partial derivative in the B(0) direction of the RF magnetic field (amplitude and phase) parallel to B(0) is much smaller than the corresponding current density component. The heterogeneous extension was verified by imaging conduction and displacement currents in a phantom containing saline and pure water compartments. Finally, the issues required to image eddy currents are presented. Eddy currents within a sample will distort both the transmitter coil reference system, and create measurable rotating frame magnetic fields. However, a three-dimensional electro-magnetic analysis will be required to determine how the reference system distortion affects computed eddy current images.

  7. Radar observations of density gradients, electric fields, and plasma irregularities near polar cap patches in the context of the gradient-drift instability

    Science.gov (United States)

    Lamarche, Leslie J.; Makarevich, Roman A.

    2017-03-01

    We present observations of plasma density gradients, electric fields, and small-scale plasma irregularities near a polar cap patch made by the Super Dual Auroral Radar Network radar at Rankin Inlet (RKN) and the northern face of Resolute Bay Incoherent Scatter Radar (RISR-N). RKN echo power and occurrence are analyzed in the context of gradient-drift instability (GDI) theory, with a particular focus on the previously uninvestigated 2-D dependencies on wave propagation, electric field, and gradient vectors, with the latter two quantities evaluated directly from RISR-N measurements. It is shown that higher gradient and electric field components along the wave vector generally lead to the higher observed echo occurrence, which is consistent with the expected higher GDI growth rate, but the relationship with echo power is far less straightforward. The RKN echo power increases monotonically as the predicted linear growth rate approaches zero from negative values but does not continue this trend into positive growth rate values, in contrast with GDI predictions. The observed greater consistency of echo occurrence with GDI predictions suggests that GDI operating in the linear regime can control basic plasma structuring, but measured echo strength may be affected by other processes and factors, such as multistep or nonlinear processes or a shear-driven instability.

  8. Identification techniques for phenomenological models of hysteresis based on the conjugate gradient method

    International Nuclear Information System (INIS)

    Andrei, Petru; Oniciuc, Liviu; Stancu, Alexandru; Stoleriu, Laurentiu

    2007-01-01

    An identification technique for the parameters of phenomenological models of hysteresis is presented. The basic idea of our technique is to set up a system of equations for the parameters of the model as a function of known quantities on the major or minor hysteresis loops (e.g. coercive force, susceptibilities at various points, remanence), or other magnetization curves. This system of equations can be either over or underspecified and is solved by using the conjugate gradient method. Numerical results related to the identification of parameters in the Energetic, Jiles-Atherton, and Preisach models are presented

  9. EUROMECH colloquium 377. Stability and control of shear flows with strong temperature or density gradients. Book of abstracts

    International Nuclear Information System (INIS)

    1998-10-01

    The topics discussed comprise the onset of instability in heated free jets and jets with density gradients, flow past heated/cooled boundaries, atmospheric shear flow, and mathematical modeling of laminar-turbulent transition phenomena. Three contributions have been input to INIS. (P.A.)

  10. Changes in home range sizes and population densities of carnivore species along the natural to urban habitat gradient

    Czech Academy of Sciences Publication Activity Database

    Šálek, Martin; Drahníková, L.; Tkadlec, Emil

    2015-01-01

    Roč. 45, č. 1 (2015), s. 1-14 ISSN 0305-1838 Institutional support: RVO:68081766 Keywords : Carnivores * home range size * natural–urban gradient * population density * review Subject RIV: EG - Zoology Impact factor: 4.116, year: 2015

  11. The effect of shear flow and the density gradient on the Weibel instability growth rate in the dense plasma

    Science.gov (United States)

    Amininasab, S.; Sadighi-Bonabi, R.; Khodadadi Azadboni, F.

    2018-02-01

    Shear stress effect has been often neglected in calculation of the Weibel instability growth rate in laser-plasma interactions. In the present work, the role of the shear stress in the Weibel instability growth rate in the dense plasma with density gradient is explored. By increasing the density gradient, the shear stress threshold is increasing and the range of the propagation angles of growing modes is limited. Therefore, by increasing steps of the density gradient plasma near the relativistic electron beam-emitting region, the Weibel instability occurs at a higher stress flow. Calculations show that the minimum value of the stress rate threshold for linear polarization is greater than that of circular polarization. The Wiebel instability growth rate for linear polarization is 18.3 times circular polarization. One sees that for increasing stress and density gradient effects, there are smaller maximal growth rates for the range of the propagation angles of growing modes /π 2 propagation angles of growing modes /π 2 < θ m i n < π and /3 π 2 < θ m i n < 2 π in circular polarized plasma.

  12. A comparison of density functional theory and coupled cluster methods for the calculation of electric dipole polarizability gradients of methane

    DEFF Research Database (Denmark)

    Paidarová, Ivana; Sauer, Stephan P. A.

    2012-01-01

    We have compared the performance of density functional theory (DFT) using five different exchange-correlation functionals with four coupled cluster theory based wave function methods in the calculation of geometrical derivatives of the polarizability tensor of methane. The polarizability gradient...

  13. Development of density and moisture gauge by nuclear techniques

    International Nuclear Information System (INIS)

    Mangelaviraj, V.; Karasuddhi, P.; Banchornthevakal, V.; Punyachaiya, S.

    1981-08-01

    A combined soil moisture/density gauge using nuclear technique was developed. Simultaneous density and moisture measurements can take place by means of gamma and neutron sources which are attached to the moisture probe. Backscattered gamma radiation giving information on density is detected by a G.M. counter while slow neutron radiation containing moisture information is detected by a boron-lined proportional counter. The instrument makes use of a 30 mCi americium 241-beryllium neutron source and a 10 mCi cesium 137 gamma source. The instrument was calibrated using soil and sand filled in a 200 litre-barrel in laboratory and field work which was carried out to check the correctness of the calibration curves. (author)

  14. Ultrasonic Technique for Density Measurement of Liquids in Extreme Conditions

    Directory of Open Access Journals (Sweden)

    Rymantas Kazys

    2015-08-01

    Full Text Available An ultrasonic technique, invariant to temperature changes, for a density measurement of different liquids under in situ extreme conditions is presented. The influence of geometry and material parameters of the measurement system (transducer, waveguide, matching layer on measurement accuracy and reliability is analyzed theoretically along with experimental results. The proposed method is based on measurement of the amplitude of the ultrasonic wave, reflected from the interface of the solid/liquid medium under investigation. In order to enhance sensitivity, the use of a quarter wavelength acoustic matching layer is proposed. Therefore, the sensitivity of the measurement system increases significantly. Density measurements quite often must be performed in extreme conditions at high temperature (up to 220 °C and high pressure. In this case, metal waveguides between piezoelectric transducer and the measured liquid are used in order to protect the conventional transducer from the influence of high temperature and to avoid depolarization. The presented ultrasonic density measurement technique is suitable for density measurement in different materials, including liquids and polymer melts in extreme conditions. A new calibration algorithm was proposed. The metrological evaluation of the measurement method was performed. The expanded measurement uncertainty Uρ = 7.4 × 10−3 g/cm3 (1%.

  15. Ultrasonic Technique for Density Measurement of Liquids in Extreme Conditions

    Science.gov (United States)

    Kazys, Rymantas; Sliteris, Reimondas; Rekuviene, Regina; Zukauskas, Egidijus; Mazeika, Liudas

    2015-01-01

    An ultrasonic technique, invariant to temperature changes, for a density measurement of different liquids under in situ extreme conditions is presented. The influence of geometry and material parameters of the measurement system (transducer, waveguide, matching layer) on measurement accuracy and reliability is analyzed theoretically along with experimental results. The proposed method is based on measurement of the amplitude of the ultrasonic wave, reflected from the interface of the solid/liquid medium under investigation. In order to enhance sensitivity, the use of a quarter wavelength acoustic matching layer is proposed. Therefore, the sensitivity of the measurement system increases significantly. Density measurements quite often must be performed in extreme conditions at high temperature (up to 220 °C) and high pressure. In this case, metal waveguides between piezoelectric transducer and the measured liquid are used in order to protect the conventional transducer from the influence of high temperature and to avoid depolarization. The presented ultrasonic density measurement technique is suitable for density measurement in different materials, including liquids and polymer melts in extreme conditions. A new calibration algorithm was proposed. The metrological evaluation of the measurement method was performed. The expanded measurement uncertainty Uρ = 7.4 × 10−3 g/cm3 (1%). PMID:26262619

  16. Ultrasonic Technique for Density Measurement of Liquids in Extreme Conditions.

    Science.gov (United States)

    Kazys, Rymantas; Sliteris, Reimondas; Rekuviene, Regina; Zukauskas, Egidijus; Mazeika, Liudas

    2015-08-07

    An ultrasonic technique, invariant to temperature changes, for a density measurement of different liquids under in situ extreme conditions is presented. The influence of geometry and material parameters of the measurement system (transducer, waveguide, matching layer) on measurement accuracy and reliability is analyzed theoretically along with experimental results. The proposed method is based on measurement of the amplitude of the ultrasonic wave, reflected from the interface of the solid/liquid medium under investigation. In order to enhance sensitivity, the use of a quarter wavelength acoustic matching layer is proposed. Therefore, the sensitivity of the measurement system increases significantly. Density measurements quite often must be performed in extreme conditions at high temperature (up to 220 °C) and high pressure. In this case, metal waveguides between piezoelectric transducer and the measured liquid are used in order to protect the conventional transducer from the influence of high temperature and to avoid depolarization. The presented ultrasonic density measurement technique is suitable for density measurement in different materials, including liquids and polymer melts in extreme conditions. A new calibration algorithm was proposed. The metrological evaluation of the measurement method was performed. The expanded measurement uncertainty Uρ = 7.4 × 10(-3) g/cm(3) (1%).

  17. Synchrotron X-ray measurement techniques for thermal barrier coated cylindrical samples under thermal gradients

    Energy Technology Data Exchange (ETDEWEB)

    Siddiqui, Sanna F.; Knipe, Kevin; Manero, Albert; Raghavan, Seetha [Department of Mechanical and Aerospace Engineering, University of Central Florida, Orlando, Florida 32816 (United States); Meid, Carla; Wischek, Janine; Bartsch, Marion [German Aerospace Center (DLR), Institute of Materials Research, 51147 Cologne (Germany); Okasinski, John; Almer, Jonathan [X-Ray Science Division, Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois 60439 (United States); Karlsson, Anette M. [Cleveland State University, 2121 Euclid Avenue, Cleveland, Ohio 44115 (United States)

    2013-08-15

    Measurement techniques to obtain accurate in situ synchrotron strain measurements of thermal barrier coating systems (TBCs) applied to hollow cylindrical specimens are presented in this work. The Electron Beam Physical Vapor Deposition coated specimens with internal cooling were designed to achieve realistic temperature gradients over the TBC coated material such as that occurring in the turbine blades of aeroengines. Effects of the circular cross section on the x-ray diffraction (XRD) measurements in the various layers, including the thermally grown oxide, are investigated using high-energy synchrotron x-rays. Multiple approaches for beam penetration including collection, tangential, and normal to the layers, along with variations in collection parameters are compared for their ability to attain high-resolution XRD data from the internal layers. This study displays the ability to monitor in situ, the response of the internal layers within the TBC, while implementing a thermal gradient across the thickness of the coated sample. The thermal setup maintained coating surface temperatures in the range of operating conditions, while monitoring the substrate cooling, for a controlled thermal gradient. Through variation in measurement location and beam parameters, sufficient intensities are obtained from the internal layers which can be used for depth resolved strain measurements. Results are used to establish the various techniques for obtaining XRD measurements through multi-layered coating systems and their outcomes will pave the way towards goals in achieving realistic in situ testing of these coatings.

  18. Improving Rydberg Excitations within Time-Dependent Density Functional Theory with Generalized Gradient Approximations: The Exchange-Enhancement-for-Large-Gradient Scheme.

    Science.gov (United States)

    Li, Shaohong L; Truhlar, Donald G

    2015-07-14

    Time-dependent density functional theory (TDDFT) with conventional local and hybrid functionals such as the local and hybrid generalized gradient approximations (GGA) seriously underestimates the excitation energies of Rydberg states, which limits its usefulness for applications such as spectroscopy and photochemistry. We present here a scheme that modifies the exchange-enhancement factor to improve GGA functionals for Rydberg excitations within the TDDFT framework while retaining their accuracy for valence excitations and for the thermochemical energetics calculated by ground-state density functional theory. The scheme is applied to a popular hybrid GGA functional and tested on data sets of valence and Rydberg excitations and atomization energies, and the results are encouraging. The scheme is simple and flexible. It can be used to correct existing functionals, and it can also be used as a strategy for the development of new functionals.

  19. Frequency-domain beamformers using conjugate gradient techniques for speech enhancement.

    Science.gov (United States)

    Zhao, Shengkui; Jones, Douglas L; Khoo, Suiyang; Man, Zhihong

    2014-09-01

    A multiple-iteration constrained conjugate gradient (MICCG) algorithm and a single-iteration constrained conjugate gradient (SICCG) algorithm are proposed to realize the widely used frequency-domain minimum-variance-distortionless-response (MVDR) beamformers and the resulting algorithms are applied to speech enhancement. The algorithms are derived based on the Lagrange method and the conjugate gradient techniques. The implementations of the algorithms avoid any form of explicit or implicit autocorrelation matrix inversion. Theoretical analysis establishes formal convergence of the algorithms. Specifically, the MICCG algorithm is developed based on a block adaptation approach and it generates a finite sequence of estimates that converge to the MVDR solution. For limited data records, the estimates of the MICCG algorithm are better than the conventional estimators and equivalent to the auxiliary vector algorithms. The SICCG algorithm is developed based on a continuous adaptation approach with a sample-by-sample updating procedure and the estimates asymptotically converge to the MVDR solution. An illustrative example using synthetic data from a uniform linear array is studied and an evaluation on real data recorded by an acoustic vector sensor array is demonstrated. Performance of the MICCG algorithm and the SICCG algorithm are compared with the state-of-the-art approaches.

  20. Visualization techniques for spatial probability density function data

    Directory of Open Access Journals (Sweden)

    Udeepta D Bordoloi

    2006-01-01

    Full Text Available Novel visualization methods are presented for spatial probability density function data. These are spatial datasets, where each pixel is a random variable, and has multiple samples which are the results of experiments on that random variable. We use clustering as a means to reduce the information contained in these datasets; and present two different ways of interpreting and clustering the data. The clustering methods are used on two datasets, and the results are discussed with the help of visualization techniques designed for the spatial probability data.

  1. Lithosphere density structure beneath the eastern margin of the Tibetan Plateau and its surrounding areas derived from GOCE gradients data

    Directory of Open Access Journals (Sweden)

    Honglei Li

    2017-05-01

    Full Text Available A three-dimensional density model of the crust and uppermost mantle is determined by the inversion of a set of GOCE gravity and gradients residual anomalies beneath the eastern margin of the Tibetan Plateau and its surrounding areas. In our work, we choose five independent gravity gradients (Txx, Tzz, Txy, Txz, Tyz to perform density inversion. Objective function is given based on Tikhonov regularization theory. Seismic S-wave velocities play the role of initial constraint for the inversion based on a relationship between density and S-wave velocity. Damped Least Square method is used during the inversion. The final density results offer some insights into understanding the underlying geodynamic processes: (1 Low densities in the margin of the Tibet, along with low wave velocity and resistivity results, yield conversions from soft and weak Tibet to the hard and rigid cratons. (2The lowest densities are found in the boundary of the plateau, instead of the whole Tibet indicates that the effects of extrusion stress environment in the margin affect the changes of the substance there. The substances and environments conditioning for the earthquake preparations and strong deformation in this transitional zone. (3 Evident low-D anomaly in the upper and middle crust in the Lasha terrane and Songpan-Ganzi terrane illustrated the eastward sub-ducted of southeastern Tibet, which could be accounts for the frequent volcano and earthquakes there.

  2. Density gradient effects in weakly nonlinear ablative Rayleigh-Taylor instability

    International Nuclear Information System (INIS)

    Wang, L. F.; Ye, W. H.; He, X. T.

    2012-01-01

    In this research, density gradient effects (i.e., finite thickness of ablation front effects) in ablative Rayleigh-Taylor instability (ARTI), in the presence of preheating within the weakly nonlinear regime, are investigated numerically. We analyze the weak, medium, and strong ablation surfaces which have different isodensity contours, respectively, to study the influences of finite thickness of ablation front on the weakly nonlinear behaviors of ARTI. Linear growth rates, generation coefficients of the second and the third harmonics, and coefficients of the third-order feedback to the fundamental mode are obtained. It is found that the linear growth rate which has a remarkable maximum, is reduced, especially when the perturbation wavelength λ is short and a cut-off perturbation wavelength λ c appears when the perturbation wavelength λ is sufficiently short, where no higher harmonics exists when λ c . The phenomenon of third-order positive feedback to the fundamental mode near the λ c [J. Sanz et al., Phys. Rev. Lett. 89, 195002 (2002); J. Garnier et al., Phys. Rev. Lett. 90, 185003 (2003); J. Garnier and L. Masse, Phys. Plasmas 12, 062707 (2005)] is confirmed in numerical simulations, and the physical mechanism of the third-order positive feedback is qualitatively discussed. Moreover, it is found that generations and growths of the second and the third harmonics are stabilized (suppressed and reduced) by the ablation effect. Meanwhile, the third-order negative feedback to the fundamental mode is also reduced by the ablation effect, and hence, the linear saturation amplitude (typically ∼0.2λ in our simulations) is increased significantly and therefore exceeds the classical prediction 0.1λ, especially for the strong ablation surface with a small perturbation wavelength. Overall, the ablation effect stabilizes the ARTI in the weakly nonlinear regime. Numerical results obtained are in general agreement with the recent weakly nonlinear theories and simulations

  3. Monotonous and oscillation instability of mechanical equilibrium of isothermal three-components mixture with zero-gradient density

    International Nuclear Information System (INIS)

    Zhavrin, Yu.I.; Kosov, V.N.; Kul'zhanov, D.U.; Karataev, K.K.

    2000-01-01

    Presence of two types of instabilities of mechanical equilibrium of a mixture experimentally is shown at an isothermal diffusion of multicomponent system with zero gradient of density/ Theoretically is proved, that partial Rayleigh numbers R 1 , R 2 having different signs, there are two areas with monotonous (R 1 2 < by 0) instability. The experimental data confirm presence of these areas and satisfactory are described by the represented theory. (author)

  4. A forward model and conjugate gradient inversion technique for low-frequency ultrasonic imaging.

    Science.gov (United States)

    van Dongen, Koen W A; Wright, William M D

    2006-10-01

    Emerging methods of hyperthermia cancer treatment require noninvasive temperature monitoring, and ultrasonic techniques show promise in this regard. Various tomographic algorithms are available that reconstruct sound speed or contrast profiles, which can be related to temperature distribution. The requirement of a high enough frequency for adequate spatial resolution and a low enough frequency for adequate tissue penetration is a difficult compromise. In this study, the feasibility of using low frequency ultrasound for imaging and temperature monitoring was investigated. The transient probing wave field had a bandwidth spanning the frequency range 2.5-320.5 kHz. The results from a forward model which computed the propagation and scattering of low-frequency acoustic pressure and velocity wave fields were used to compare three imaging methods formulated within the Born approximation, representing two main types of reconstruction. The first uses Fourier techniques to reconstruct sound-speed profiles from projection or Radon data based on optical ray theory, seen as an asymptotical limit for comparison. The second uses backpropagation and conjugate gradient inversion methods based on acoustical wave theory. The results show that the accuracy in localization was 2.5 mm or better when using low frequencies and the conjugate gradient inversion scheme, which could be used for temperature monitoring.

  5. Application of GelGreen™ in Cesium Chloride Density Gradients for DNA-Stable Isotope Probing Experiments.

    Directory of Open Access Journals (Sweden)

    Jingfeng Gao

    Full Text Available In this study, GelGreen™ was investigated as a replacement for SYBR® Safe to stain DNA in cesium chloride (CsCl density gradients for DNA-stable isotope probing (SIP experiments. Using environmental DNA, the usage of GelGreen™ was optimized for sensitivity compared to SYBR® Safe, its optimal concentration, detection limit for environmental DNA and its application in environmental DNA-SIP assay. Results showed that GelGreen™ was more sensitive than SYBR® Safe, while the optimal dosage (15X concentration needed was approximately one-third of SYBR® Safe, suggesting that its sensitivity was three times more superior than SYBR® Safe. At these optimal parameters, the detection limit of GelGreen™-stained environmental DNA was as low as 0.2 μg, but the usage of 0.5 μg environmental DNA was recommended to produce a more consistent DNA band. In addition, a modified needle extraction procedure was developed to withdraw DNA effectively by fractionating CsCl density gradients into four or five fractions. The successful application of GelGreen™ staining with 13C-labeled DNA from enriched activated sludge suggests that this stain was an excellent alternative of SYBR® Safe in CsCl density gradients for DNA-SIP assays.

  6. Metals pollution tracing in the sewerage network using the diffusive gradients in thin films technique.

    Science.gov (United States)

    Thomas, P

    2009-01-01

    Diffusive Gradients in Thin-films (DGT) is a quantitative, passive monitoring technique that can be used to measure concentrations of trace species in situ in solutions. Its potential for tracing metals pollution in the sewer system has been investigated by placing the DGT devices into sewage pumping stations and into manholes, to measure the concentration of certain metals in the catchment of a sewage treatment works with a known metals problem. In addition the methodology and procedure of using the DGT technique in sewers was investigated. Parameters such as temperature and pH were measured to ensure they were within the limits required by the DGT devices, and the optimum deployment time was examined. It was found that although the results given by the DGT technique could not be considered to be fully quantitative, they could be used to identify locations that were showing an excess concentration of metals, and hence trace pollution back to its source. The DGT technique is 'user friendly' and requires no complicated equipment for deployment or collection, and minimal training for use. It is thought that this is the first time that the DGT technique has been used in situ in sewers for metals pollution tracing.

  7. Thermocapillary migration of liquid droplets in a temperature gradient in a density matched system

    Science.gov (United States)

    Rashidnia, N.; Balasubramaniam, R.

    1991-01-01

    An experimental investigation of thermocapillary flow in droplets of a vegetable oil (partially hydrogenated soybean oil) immersed in silicone oil was conducted in a test cell with a heated top wall and a cooled bottom wall. The liquids are nearly immiscible and have equal densities at a temperature below the room temperature, thus providing a simulation of low-gravity conditions by reducing the buoyancy forces. The interfacial tension between the two oils was measured in the temperature range 20 to 50 C using a capillary tube and (d sigma)/(d T) was determined to be negative. Droplets ranging in sizes from 3 mm to 1 cm diameter were injected into the silicone oil. The vertical temperature profile in the bulk liquid (silicone oil) produces temperature variations along the interface which induce variations in the interfacial tension. The flow inside the droplet driven by the resulting interfacial shear stresses was observed using a laser light-sheet flow visualization technique. The flow direction is consistent with the sign of (d sigma)/(d T). The observed maximum surface velocities are compared to the theoretical predictions of Young et al. (1959).

  8. Development of gradient-corrected exchange-correlation functionals in the density functional theory; Developpement de fonctionnelles corrigees du gradient en theorie de la fonctionnelle de la densite

    Energy Technology Data Exchange (ETDEWEB)

    Lembarki, A.

    1994-12-01

    In this work, we have developed some gradient-corrected exchange-correlation functionals. This study is in keeping with the density functional theory (DFT) formalism. In the first part of this memory, a description of Hartree-Fock (HF), post-HF and density functional theories is given. The second part is devoted the study the different approximations of DFT exchange-correlation functionals which have been proposed in the last years. In particular, we have underlined the approximations used for the construction of these functionals. The third part of this memory consists in the development of new gradient-corrected functionals. In this study, we have established a new relation between exchange energy, correlation energy and kinetic energy. We have deduced two new possible forms of exchange or correlation functionals, respectively. In the fourth part, we have studied the exchange potential, for which the actual formulation does not satisfy some theoretical conditions, such as the asymptotic behavior -1/r. Our contribution lies in the development of an exchange potential with a correct asymptotic -1/r behavior for large values of r. In this chapter, we have proposed a model which permits the obtention of the exchange energy from the exchange potential, using the virial theorem. The fifth part of this memory is devoted the application of these different functionals to simple systems (H{sub 2}O, CO, N{sub 2}O, H{sub 3}{sup +} and H{sub 5}{sup +}) in order to characterize the performance of DFT calculations in regards to those obtained with post-HF methods. (author). 215 refs., 8 figs., 28 tabs.

  9. A modified gradient approach for the growth of low-density InAs quantum dot molecules by molecular beam epitaxy

    Science.gov (United States)

    Sharma, Nandlal; Reuter, Dirk

    2017-11-01

    Two vertically stacked quantum dots that are electronically coupled, so called quantum dot molecules, are of great interest for the realization of solid state building blocks for quantum communication networks. We present a modified gradient approach to realize InAs quantum dot molecules with a low areal density so that single quantum dot molecules can be optically addressed. The individual quantum dot layers were prepared by solid source molecular beam epitaxy depositing InAs on GaAs(100). The bottom quantum dot layer has been grown without substrate rotation resulting in an In-gradient across the surface, which translated into a density gradient with low quantum dot density in a certain region of the wafer. For the top quantum dot layer, separated from the bottom quantum dot layer by a 6 nm thick GaAs barrier, various InAs amounts were deposited without an In-gradient. In spite of the absence of an In-gradient, a pronounced density gradient is observed for the top quantum dots. Even for an In-amount slightly below the critical thickness for a single dot layer, a density gradient in the top quantum dot layer, which seems to reproduce the density gradient in the bottom layer, is observed. For more or less In, respectively, deviations from this behavior occur. We suggest that the obvious influence of the bottom quantum dot layer on the growth of the top quantum dots is due to the strain field induced by the buried dots.

  10. Crust-mantle density distribution in the eastern Qinghai-Tibet Plateau revealed by satellite-derived gravity gradients

    Science.gov (United States)

    LI, Honglei; Fang, Jian; Braitenberg, Carla; Wang, Xinsheng

    2015-04-01

    As the highest, largest and most active plateau on Earth, the Qinghai-Tibet Plateau has a complex crust-mantle structure, especially in its eastern part. In response to the subduction of the lithospheric mantle of the Indian plate, large-scale crustal motion occurs in this area. Despite the many previous studies, geodynamic processes at depth remain unclear. Knowledge of crust and upper mantle density distribution allows a better definition of the deeper geological structure and thus provides critically needed information for understanding of the underlying geodynamic processes. With an unprecedented precision of 1-2 mGal and a spatial resolution better than 100 km, GOCE (Gravity field and steady-state Ocean Circulation Explorer) mission products can be used to constrain the crust-mantle density distribution. Here we used GOCE gravitational gradients at an altitude of 10km after reducing the effects of terrain, sediment thickness variations, and Moho undulations to image the density structures of eastern Tibet up to 200 km depths. We inverted the residual satellite gravitational gradients using a least square approach. The initial density model for the inversion is based on seismic velocities from the tomography. The model is composed of rectangular blocks, having a uniform density, with widths of about 100 km and variable thickness and depths. The thickness of the rectangular cells changes from10 to 60km in accordance with the seismic model. Our results reveal some large-scale, structurally controlled density variations at depths. The lithospheric root defined by higher-density contrast features from southwest to northeast, with shallowing in the central part: base of lithosphere reaches a depth of180 km, less than 100km, and 200 km underneath the Lhasa, Songpan-Ganzi, and Ordos crustal blocks, respectively. However, these depth values only represent a first-order parameterization because they depend on model discretization inherited from the original seismic

  11. Effects of density gradients and fluctuations at the plasma edge on ECEI measurements at ASDEX Upgrade

    NARCIS (Netherlands)

    Vanovac, B.; Wolfrum, E.; Denk, S. S.; Mink, F.; Laggner, F. M.; Birkenmeier, G.; Willensdorfer, M.; Viezzer, E.; Hoelzl, M.; Freethy, S. J.; Dunne, M. G.; Lessig, A.; Luhmann, N. C.; ASDEX Upgrade team,; EUROfusion MST1 Team,

    2018-01-01

    Electron cyclotron emission imaging (ECEI) provides measurements of electron temperature (T-e) and its fluctuations (delta T-e). However, when measuring at the plasma edge, in the steep gradient region, radiation transport effects must be taken into account. It is shown that due to these effects,

  12. Compensation of spatial system response in SPECT with conjugate gradient reconstruction technique

    International Nuclear Information System (INIS)

    Formiconi, A.R.; Pupi, A.; Passeri, A.

    1989-01-01

    A procedure for determination of the system matrix in single photon emission tomography (SPECT) is described which use a conjugate gradient reconstruction technique to take into account the variable system resolution of a camera equipped with parallel-hole collimators. The procedure involves acquisition of system line spread functions (LSF) in the region occupied by the object studied. Those data are used to generate a set of weighting factors based on the assumption that the LSFs of the collimated camera are of Gaussian shape with full width at half maximum (FWHM) linearly dependent on source depth in the span of image space. Factors are stored on a disc file for subsequent use in reconstruction. Afterwards reconstruction is performed using the conjugate gradient method with the system matrix modified by incorporation of these precalculated factors to take into account variable geometrical system response. The set of weighting factors is regenerated whenever acquisition conditions are changed (collimator, radius of rotation) with an ultra high resolution (UHR) collimator 2000 weighting factors need to be calculated. (author)

  13. Density gradient localization of vanadate- and NO-3-sensitive ATPase from sterile cultures of Spirodela polyrrhiza (L. Schleiden

    Directory of Open Access Journals (Sweden)

    Józef Buczek

    2014-01-01

    Full Text Available The present work deals with the separation and some characteristics of ATPase activities bound with plant membanes prepared from sterile cultures of Spirodela polyrrhiza. The membrane-bound ATPases were separated on sucrose gradients and distinguished by membrane density and sensitivity to several inhibitors. The results showed that N0-3-sensitive ATPase activity associated with the tonoplast was localized at a sucrose density between 1.095-1.117 g•cm-3. The vanadate-sensitive ATPase activity bound with the plasma membrane showed a density between 1.127-1.151 g•cm-3. Both ATPases were insensitive to azide and oligomycin and were separable from markers for mitochondria.

  14. The effect of swim-up and gradient sperm preparation techniques on deoxyribonucleic acid (DNA) fragmentation in subfertile patients.

    Science.gov (United States)

    Oguz, Yuksel; Guler, Ismail; Erdem, Ahmet; Mutlu, Mehmet Firat; Gumuslu, Seyhan; Oktem, Mesut; Bozkurt, Nuray; Erdem, Mehmet

    2018-03-23

    To compare the effect of two different sperm preparation techniques, including swim-up and gradient methods on sperm deoxyribonucleic acid (DNA) fragmentation status of semen samples from unexplained and mild male factor subfertile patients undergoing intrauterine insemination (IUI). A prospective randomized study was conducted in 65 subfertile patients, including 34 unexplained and 31 male factor infertility to compare basal and post-procedure DNA fragmentation rates in swim-up and gradient techniques. Sperm DNA fragmentation rates were evaluated by a sperm chromatin dispersion (SCD) test in two portions of each sample of semen that was prepared with either swim-up or gradient techniques. Sperm motility and morphology were also assessed based on WHO 2010 criteria. Swim-up but not gradient method yielded a statistically significant reduction in the DNA fragmented sperm rate after preparation as compared to basal rates, in the semen samples of both unexplained (41.85 ± 22.04 vs. 28.58 ± 21.93, p gradient) and mild male factor (46.61 ± 19.38 vs. 30.32 ± 18.20, p gradient) subgroups. Swim-up method significantly reduces sperm DNA fragmentation rates and may have some prognostic value on intrauterine insemination in patients with decreased sperm DNA integrity.

  15. Scanning tunnelling microscope imaging of nanoscale electron density gradients on the surface of GaAs

    International Nuclear Information System (INIS)

    Hamilton, B; Jacobs, J; Missous, M

    2003-01-01

    This paper is concerned with the scanning tunnelling microscope tunnelling conditions needed to produce constant current images dominated either by surface topology or by electronic effects. A model experimental structure was produced by cleaving a GaAs multiδ-doped layer in UHV and so projecting a spatially varying electron gas density onto the (110) surface. This cross sectional electron density varies on a nanometre scale in the [100] growth direction. The electronic structure and tunnelling properties of this system were modelled, and the tunnelling conditions favouring sensitivity to the surface electron gas density determined

  16. Reservoir longitudinal gradient promotes ordered losses on diversity and density of Ephemeroptera community

    Directory of Open Access Journals (Sweden)

    S. M. Melo

    2018-02-01

    Full Text Available Abstract Reservoir operations alter, eliminate or restrain the natural hydrologic cycles. Biotic community has become subject to these non-cyclic events, responding by reducing the species diversity. Ephemeroptera species present distinct responses to environmental deterioration such that poses this assemblage between the most useful groups in biomonitoring programs. We hypothesized an alteration in beta diversity at the longitudinal species gradient, which will be influenced mainly by species losses between zones. Changes in temporal beta diversity is also expected, but the main drivers of such alterations will be the species turnover between the sampling period. Ephemeroptera community was monitored in nine sampling points from Itaipu Reservoir, where were installed three sets of substrates composed by a float and 2 wooden substrates. We took biological samples in triplicates monthly, from June-01 to August-02. Our initial hypothesis was partially supported and with significant variations only for spatial approach, between the Reservoir zones. The generated ordering from Non-Metric Dimensional Scale – NMDS - corroborated with spatial analyzes, with the formation of two groups along the gradient zonation of the reservoir. The temporal ordination showed no clear pattern. As expected, the contribution to beta diversity was different for our two approaches, such that the loss of species was more important along the spatial gradient and despite of no significant result, the species replacement was more important among months. The spatial results lead us to infer that differences in limnological characteristics between zones are important for determining differences in Ephemeroptera composition and can reflect the dependency degree of the species in relation to the lentic and sometimes-lotic conditions, mainly in the riverine zone of reservoirs. On the other hand, the absence of a temporal pattern can be result of chaotic variations in the

  17. Imaging of the brain using the fast-spin-echo and gradient-spin-echo techniques

    International Nuclear Information System (INIS)

    Umek, W.; Ba-Ssalamah, A.; Prokesch, R.; Mallek, R.; Heimberger, K.; Hittmair, K.

    1998-01-01

    The aim of our study was to compare gradient-spin-echo (GRASE) to fast-spin-echo (FSE) sequences for fast T2-weighted MR imaging of the brain. Thirty-one patients with high-signal-intensity lesions on T2-weighted images were examined on a 1.5-T MR system. The FSE and GRASE sequences with identical sequence parameters were obtained and compared side by side. Image assessment criteria included lesion conspicuity, contrast between different types of normal tissue, and image artifacts. In addition, signal-to-noise, contrast-to-noise, and contrast ratios and were determined. The FSE technique demonstrated more lesions than GRASE and with generally better conspicuity. Smaller lesions in particular were better demonstrated on FSE because of lower image noise and slightly weaker image artifacts. Gray-white differentiation was better on FSE. Ferritin and hemosiderin depositions appeared darker on GRASE, which resulted in better contrast. Fatty tissue was less bright on GRASE. With current standard hardware equipment, the FSE technique seems preferable to GRASE for fast T2-weighted routine MR imaging of the brain. For the assessment of hemosiderin or ferritin depositions, GRASE might be considered. (orig.)

  18. Acceptable solutions obtained by unfolding noisy data with a conjugate gradient technique

    International Nuclear Information System (INIS)

    Lang, D.W.

    1976-01-01

    A linear resolution function in a physical measurement leads to data values and standard deviations at, say, N points. It is noted that the associated resolution functions may require that a number n of particular linear combinations of the data values be each not significantly different from zero. One is left with at most N-n parameters to evaluate. If the resolution functions are reasonably behaved, one can show that one sensible way to describe the underlying spectrum treats it as a linear combination of the given resolution functions and includes all the significant information from the data. An iterative search for the best component available to minimize the chi-square of the next fit to the data leads to a conjugate gradient technique. Programs based on the technique have been successfully used to obtain neutron spectra as a function of energy; in raw data from a pulse height analysis of proton recoils in a proportional counter, and where the raw data are time of flight spectra from a time dependent pulse of known form. It is planned to incorporate these, together with working programs respectively for photonuclear analysis and to explore the impurity concentration profile in a surface, into a single ''work-bench'' type program. A suitably difficult model unfolding problem has been developed and used to show the strengths and weaknesses of a number of other methods that have been used for unfolding

  19. Adjustment technique without explicit formation of normal equations /conjugate gradient method/

    Science.gov (United States)

    Saxena, N. K.

    1974-01-01

    For a simultaneous adjustment of a large geodetic triangulation system, a semiiterative technique is modified and used successfully. In this semiiterative technique, known as the conjugate gradient (CG) method, original observation equations are used, and thus the explicit formation of normal equations is avoided, 'huge' computer storage space being saved in the case of triangulation systems. This method is suitable even for very poorly conditioned systems where solution is obtained only after more iterations. A detailed study of the CG method for its application to large geodetic triangulation systems was done that also considered constraint equations with observation equations. It was programmed and tested on systems as small as two unknowns and three equations up to those as large as 804 unknowns and 1397 equations. When real data (573 unknowns, 965 equations) from a 1858-km-long triangulation system were used, a solution vector accurate to four decimal places was obtained in 2.96 min after 1171 iterations (i.e., 2.0 times the number of unknowns).

  20. Fast-electron self-collimation in a plasma density gradient

    International Nuclear Information System (INIS)

    Yang, X. H.; Borghesi, M.; Robinson, A. P. L.

    2012-01-01

    A theoretical and numerical study of fast electron transport in solid and compressed fast ignition relevant targets is presented. The principal aim of the study is to assess how localized increases in the target density (e.g., by engineering of the density profile) can enhance magnetic field generation and thus pinching of the fast electron beam through reducing the rate of temperature rise. The extent to which this might benefit fast ignition is discussed.

  1. Droplet and bubble nucleation modeled by density gradient theory – cubic equation of state versus saft model

    Directory of Open Access Journals (Sweden)

    Hrubý Jan

    2012-04-01

    Full Text Available The study presents some preliminary results of the density gradient theory (GT combined with two different equations of state (EoS: the classical cubic equation by van der Waals and a recent approach based on the statistical associating fluid theory (SAFT, namely its perturbed-chain (PC modification. The results showed that the cubic EoS predicted for a given surface tension the density profile with a noticeable defect. Bulk densities predicted by the cubic EoS differed as much as by 100 % from the reference data. On the other hand, the PC-SAFT EoS provided accurate results for density profile and both bulk densities in the large range of temperatures. It has been shown that PC-SAFT is a promising tool for accurate modeling of nucleation using the GT. Besides the basic case of a planar phase interface, the spherical interface was analyzed to model a critical cluster occurring either for nucleation of droplets (condensation or bubbles (boiling, cavitation. However, the general solution for the spherical interface will require some more attention due to its numerical difficulty.

  2. Threatened species richness along a Himalayan elevational gradient: quantifying the influences of human population density, range size, and geometric constraints.

    Science.gov (United States)

    Paudel, Prakash Kumar; Sipos, Jan; Brodie, Jedediah F

    2018-02-07

    A crucial step in conserving biodiversity is to identify the distributions of threatened species and the factors associated with species threat status. In the biodiversity hotspot of the Himalaya, very little is known about which locations harbour the highest diversity of threatened species and whether diversity of such species is related to area, mid-domain effects (MDE), range size, or human density. In this study, we assessed the drivers of variation in richness of threatened birds, mammals, reptiles, actinopterygii, and amphibians along an elevational gradient in Nepal Himalaya. Although geometric constraints (MDE), species range size, and human population density were significantly related to threatened species richness, the interaction between range size and human population density was of greater importance. Threatened species richness was positively associated with human population density and negatively associated with range size. In areas with high richness of threatened species, species ranges tend to be small. The preponderance of species at risk of extinction at low elevations in the subtropical biodiversity hotspot could be due to the double impact of smaller range sizes and higher human density.

  3. Thermodynamic, energy efficiency, and power density analysis of reverse electrodialysis power generation with natural salinity gradients.

    Science.gov (United States)

    Yip, Ngai Yin; Vermaas, David A; Nijmeijer, Kitty; Elimelech, Menachem

    2014-05-06

    Reverse electrodialysis (RED) can harness the Gibbs free energy of mixing when fresh river water flows into the sea for sustainable power generation. In this study, we carry out a thermodynamic and energy efficiency analysis of RED power generation, and assess the membrane power density. First, we present a reversible thermodynamic model for RED and verify that the theoretical maximum extractable work in a reversible RED process is identical to the Gibbs free energy of mixing. Work extraction in an irreversible process with maximized power density using a constant-resistance load is then examined to assess the energy conversion efficiency and power density. With equal volumes of seawater and river water, energy conversion efficiency of ∼ 33-44% can be obtained in RED, while the rest is lost through dissipation in the internal resistance of the ion-exchange membrane stack. We show that imperfections in the selectivity of typical ion exchange membranes (namely, co-ion transport, osmosis, and electro-osmosis) can detrimentally lower efficiency by up to 26%, with co-ion leakage being the dominant effect. Further inspection of the power density profile during RED revealed inherent ineffectiveness toward the end of the process. By judicious early discontinuation of the controlled mixing process, the overall power density performance can be considerably enhanced by up to 7-fold, without significant compromise to the energy efficiency. Additionally, membrane resistance was found to be an important factor in determining the power densities attainable. Lastly, the performance of an RED stack was examined for different membrane conductivities and intermembrane distances simulating high performance membranes and stack design. By thoughtful selection of the operating parameters, an efficiency of ∼ 37% and an overall gross power density of 3.5 W/m(2) represent the maximum performance that can potentially be achieved in a seawater-river water RED system with low

  4. Relaxation of a steep density gradient in a simple fluid: Comparison between atomistic and continuum modeling

    International Nuclear Information System (INIS)

    Pourali, Meisam; Maghari, Ali; Meloni, Simone; Magaletti, Francesco; Casciola, Carlo Massimo; Ciccotti, Giovanni

    2014-01-01

    We compare dynamical nonequilibrium molecular dynamics and continuum simulations of the dynamics of relaxation of a fluid system characterized by a non-uniform density profile. Results match quite well as long as the lengthscale of density nonuniformities are greater than the molecular scale (∼10 times the molecular size). In presence of molecular scale features some of the continuum fields (e.g., density and momentum) are in good agreement with atomistic counterparts, but are smoother. On the contrary, other fields, such as the temperature field, present very large difference with respect to reference (atomistic) ones. This is due to the limited accuracy of some of the empirical relations used in continuum models, the equation of state of the fluid in the present example

  5. Evaluation of the impact of density gradient centrifugation on fetal cell loss during enrichment from maternal peripheral blood.

    Science.gov (United States)

    Emad, Ahmed; Drouin, Régen

    2014-09-01

    Physical separation by density gradient centrifugation (DGC) is usually used as an initial step of multistep enrichment protocols for purification of fetal cells (FCs) from maternal blood. Many protocols were designed but no single approach was efficient enough to provide noninvasive prenatal diagnosis. Procedures and methods were difficult to compare because of the nonuniformity of protocols among different groups. Recovery of FCs is jeopardized by their loss during the process of enrichment. Any loss of FCs must be minimized because of the multiplicative effect of each step of the enrichment process. The main objective of this study was to evaluate FC loss caused by DGC. Fetal cells were quantified in peripheral blood samples obtained from both euploid and aneuploid pregnancies before and after enrichment by buoyant DGC using Histopaque 1.119 g/mL. Density gradient centrifugation results in major loss of 60% to 80% of rare FCs, which may further complicate subsequent enrichment procedures. Eliminating aggressive manipulations can significantly minimize FC loss. Data obtained raise questions about the appropriateness of the DGC step for the enrichment of rare FCs and argues for the use of the alternative nonaggressive version of the procedure presented here or prioritizing other methods of enrichments. © 2014 John Wiley & Sons, Ltd.

  6. Automatic pellet density checking machine using vision technique

    International Nuclear Information System (INIS)

    Kumar, Suman; Raju, Y.S.; Raj Kumar, J.V.; Sairam, S.; Sheela; Hemantha Rao, G.V.S.

    2012-01-01

    Uranium di-oxide powder prepared through chemical process is converted to green pellets through the powder metallurgy route of precompaction and final compaction operations. These green pellets are kept in a molybdenum boat, which consists of a molybdenum base and a shroud. The boats are passed through the high temperature sintering furnaces to achieve required density of pellets. At present MIL standard 105 E is followed for measuring density of sintered pellets in the boat. As per AQL 2.5 of MIL standard, five pellets are collected from each boat, which contains approximately 800 nos of pellets. The densities of these collected pellets are measured. If anyone pellet density is less than the required value, the entire boat of pellets are rejected and sent back for dissolution for further processing. An Automatic Pellet Density Checking Machine (APDCM) was developed to salvage the acceptable density pellets from the rejected boat of pellets

  7. Damping-Growth Transition for Ion-Acoustic Waves in a Density Gradient

    DEFF Research Database (Denmark)

    D'Angelo, N.; Michelsen, Poul; Pécseli, Hans

    1975-01-01

    A damping-growth transition for ion-acoustic waves propagating in a nonuniform plasma (e-folding length for the density ln) is observed at a wavelength λ∼2πln. This result supports calculations performed in connection with the problem of heating of the solar corona by ion-acoustic waves generated...

  8. Thermodynamic, energy efficiency, and power density analysis of reverse electrodialysis power generation with natural salinity gradients

    NARCIS (Netherlands)

    Yip, N.Y.; Vermaas, D.A.; Nijmeijer, K.; Elimelech, M.

    2014-01-01

    Reverse electrodialysis (RED) can harness the Gibbs free energy of mixing when fresh river water flows into the sea for sustainable power generation. In this study, we carry out a thermodynamic and energy efficiency analysis of RED power generation, and assess the membrane power density. First, we

  9. Numerical Studies of Electron Acceleration Behind Self-Modulating Proton Beam in Plasma with a Density Gradient

    CERN Document Server

    Petrenko, A.; Sosedkin, A.

    2016-01-01

    Presently available high-energy proton beams in circular accelerators carry enough momentum to accelerate high-intensity electron and positron beams to the TeV energy scale over several hundred meters of the plasma with a density of about 1e15 1/cm^3. However, the plasma wavelength at this density is 100-1000 times shorter than the typical longitudinal size of the high-energy proton beam. Therefore the self-modulation instability (SMI) of a long (~10 cm) proton beam in the plasma should be used to create the train of micro-bunches which would then drive the plasma wake resonantly. Changing the plasma density profile offers a simple way to control the development of the SMI and the acceleration of particles during this process. We present simulations of the possible use of a plasma density gradient as a way to control the acceleration of the electron beam during the development of the SMI of a 400 GeV proton beam in a 10 m long plasma. This work is done in the context of the AWAKE project --- the proof-of-prin...

  10. Adsorption combined with superconducting high gradient magnetic separation technique used for removal of arsenic and antimony.

    Science.gov (United States)

    Qi, Zenglu; Joshi, Tista Prasai; Liu, Ruiping; Li, Yiran; Liu, Huijuan; Qu, Jiuhui

    2018-02-05

    Manganese iron oxide (MnFe 2 O 4 ), an excellent arsenic(As)/antimony(Sb) removal adsorbent, is greatly restricted for the solid-liquid separation. Through the application of superconducting high gradient magnetic separation (HGMS) technique, we herein constructed a facility for the in situ solid-liquid separation of micro-sized MnFe 2 O 4 adsorbent in As/Sb removal process. To the relative low initial concentration 50.0μgL -1 , MnFe 2 O 4 material sorbent can still decrease As or Sb below US EPA's drinking water standard limit. The separation of MnFe 2 O 4 was mainly relied on the flow rate and the amount of steel wools in the HGMS system. At a flow rate 1Lmin -1 and 5% steel wools filling rate, the removal efficacies of As and Sb in natural water with the system were achieved to be 94.6% and 76.8%, respectively. At the meantime, nearly 100% micro-sized MnFe 2 O 4 solid in the continuous field was readily to be separated via HGMS system. In a combination with the experiment results and finite element simulation, the separation was seemed to be independent on the magnetic field intensity, and the maximum separation capacities in various conditions were well predicted using the Thomas model (R 2 =0.87-0.99). Copyright © 2017 Elsevier B.V. All rights reserved.

  11. Evaluation of renal function with dynamic MRI-T2-weighted gradient echo technique

    International Nuclear Information System (INIS)

    Kato, Katsuya

    1995-01-01

    To evaluate the usefulness of dynamic MRI of kidneys in healthy volunteers and patients with different 24-hour creatinine clearance (Ccr) levels, a dynamic study that employed the T2 weighted gradient echo technique (FLASH: TR/TE=34/25 msec, flip angle= 20 degrees) with single images during breathhold was performed on 10 healthy volunteers and 35 patients, all examined for the Ccr and suspected of having renal parenchymal disease after a phantom study. T1-weighted and dynamic MR imagings were obtained with a 1.5T imager. I analyzed the time-intensity curve of renal cortex and medulla, and defined a cortex decreased ratio (CDR) and medulla decreased ratio (MDR) in comparison with the Ccr. The cortico-medullary difference ratio (CMDR) of T1WI was also compared with the Ccr. The parameters of the T2 dynamic MRI study (CDR, MDR) better correlated with the Ccr than CMDR. Renal function can be quantitatively evaluated with the T2 dynamic MRI and there is a possibility that we can qualitatively evaluate the renal dysfunction and estimate its cause. (author)

  12. New resin gel for uranium determination by diffusive gradient in thin films technique

    International Nuclear Information System (INIS)

    Gregusova, Michaela; Docekal, Bohumil

    2011-01-01

    A new resin gel based on Spheron-Oxin chelating ion-exchanger with anchored 8-hydroxyquinoline functional groups was tested for application in diffusive gradient in thin film technique (DGT) for determination of uranium. Selectivity of uranium uptake from model carbonate loaded solutions of natural water was studied under laboratory conditions and compared with selectivity of the conventional Chelex 100 based resin gel. The affinity of Spheron-Oxin functional groups enables determination of the overall uranium concentration in water containing carbonates up to the concentration level of 10 2 mg L -1 . The effect of uranium binding to the polyacrylamide (APA) and agarose diffusive gels (AGE) was also studied. Uranium is probably bound in both gels by a weak interaction with traces of acrylic acid groups in the structure of APA gel and with pyruvic and sulfonic acid groups in the AGE gel. These sorption effects can be eliminated to the negligible level by prolonged deployment of DGT probes or by disassembling probes after the 1-2 days post-sampling period that is sufficient for release of uranium from diffusive gel and its sorption in resin gel.

  13. New resin gel for uranium determination by diffusive gradient in thin films technique

    Energy Technology Data Exchange (ETDEWEB)

    Gregusova, Michaela, E-mail: gregusova@iach.cz [Institute of Analytical Chemistry, Academy of Sciences of the Czech Republic v.v.i., Veveri 97, 602 00 Brno (Czech Republic); Docekal, Bohumil [Institute of Analytical Chemistry, Academy of Sciences of the Czech Republic v.v.i., Veveri 97, 602 00 Brno (Czech Republic)

    2011-01-17

    A new resin gel based on Spheron-Oxin chelating ion-exchanger with anchored 8-hydroxyquinoline functional groups was tested for application in diffusive gradient in thin film technique (DGT) for determination of uranium. Selectivity of uranium uptake from model carbonate loaded solutions of natural water was studied under laboratory conditions and compared with selectivity of the conventional Chelex 100 based resin gel. The affinity of Spheron-Oxin functional groups enables determination of the overall uranium concentration in water containing carbonates up to the concentration level of 10{sup 2} mg L{sup -1}. The effect of uranium binding to the polyacrylamide (APA) and agarose diffusive gels (AGE) was also studied. Uranium is probably bound in both gels by a weak interaction with traces of acrylic acid groups in the structure of APA gel and with pyruvic and sulfonic acid groups in the AGE gel. These sorption effects can be eliminated to the negligible level by prolonged deployment of DGT probes or by disassembling probes after the 1-2 days post-sampling period that is sufficient for release of uranium from diffusive gel and its sorption in resin gel.

  14. Alternative sample-introduction technique to avoid breakthrough in gradient-elution liquid chromatography of polymers

    NARCIS (Netherlands)

    Reingruber, E.; Bedani, F.; Buchberger, W.; Schoenmakers, P.

    2010-01-01

    Gradient-elution liquid chromatography (GELC) is a powerful tool for the characterization of synthetic polymers. However, gradient-elution chromatograms often suffer from breakthrough phenomena. Breakthrough can be averted by using a sample solvent as weak as the mobile phase. However, this approach

  15. Species-specific gradients of juvenile fish density and size in pelagic areas of temperate reservoirs

    Czech Academy of Sciences Publication Activity Database

    Jůza, Tomáš; Ricard, Daniel; Blabolil, Petr; Čech, Martin; Draštík, Vladislav; Frouzová, Jaroslava; Muška, Milan; Peterka, Jiří; Prchalová, Marie; Říha, Milan; Sajdlová, Zuzana; Šmejkal, Marek; Tušer, Michal; Vašek, Mojmír; Vejřík, Lukáš; Kubečka, Jan

    2015-01-01

    Roč. 762, č. 1 (2015), s. 169-181 ISSN 0018-8158 R&D Projects: GA MŠk(CZ) EE2.3.20.0204; GA MŠk(CZ) EE2.3.30.0032; GA MŠk(CZ) 7F14316 Institutional support: RVO:60077344 Keywords : trawling * juvenile density * horizontal distribution * vertical distribution * tributary area Subject RIV: EH - Ecology, Behaviour Impact factor: 2.051, year: 2015

  16. Autoradiography and density gradient separation of technetium-99m-Exametazime (HMPAO) labelled leucocytes reveals selectivity for eosinophils

    Energy Technology Data Exchange (ETDEWEB)

    Puncher, M.R.B. [Biological Lab., Univ. of Kent, Canterbury (United Kingdom); Blower, P.J. [Nuclear Medicine Dept., Kent and Canterbury Hospital (United Kingdom)

    1994-11-01

    Technetium-99m-Exametazime (HMPAO) is widely used for radiolabelling leucocytes for localization of infection. The subcellular distribution of radionuclide in the labelled cells and the distribution of radioactivity among the leucocyte population are incompletely understood. Frozen section autoradiography was used to determine quantitatively the distribution of {sup 99m}Tc in leucocytes labelled with {sup 99m}Tc-Exametazime. Sections of rapidly frozen suspensions of labelled leucocytes in plasma were autoradiographed on Ilford K2 emulsion and stained with haematoxylin and eosin. Neutrophils, eosinophils and mononuclear cells were separated by Percoll density gradient centrifugation. Cell nuclei were isolated by a rapid cell-breakage and fractionation method. In a typical experiment mean grain densities [grains/100 {mu}m{sup 2} (ESD)] over cells were: eosinophils 31.2 (18.4), neutrophils 3.5 (3.5), mononuclear cells 4.2 (5.1). Mean grain numbers per cell (ESD) were: eosinophils 13 (6.8), neutrophils 1.3 (1.3), mononuclear cells 1.1 (1.3). These findings were confirmed by separation of labelled leucocytes on discontinuous density gradients. In four separation experiments, the mean activity-per-cell ratio for eosinophils to neutrophils was 10.1 (4.8):1, and for eosinophils to mononuclear cells, 14.1 (6.7):1. The subcellular distribution of the label was investigated using image analysis of autoradiographs and cell fractionation. This revealed no selectivity for nuclear or extranuclear compartments. It may be concluded that {sup 99m}Tc-Exametazime has strong selectivity for eosinophils over other leucocytes but no selectivity for nuclear/cytoplasmic compartments. (orig.)

  17. Weak turbulence theory of ion temperature gradient modes for inverted density plasmas

    International Nuclear Information System (INIS)

    Hahm, T.S.; Tang, W.M.

    1989-09-01

    Typical profiles measured in H-mode (''high confinement'') discharges from tokamaks such as JET and DIII-D suggest that the ion temperature gradient instability threshold parameter η i (≡dlnT i /dlnn i ) could be negative in many cases. Previous linear theoretical calculations have established the onset conditions for these negative η i -modes and the fact that their growth rate is much smaller than their real frequency over a wide range of negative η i values. This has motivated the present nonlinear weak turbulence analysis to assess the relevance of such instabilities for confinement in H-mode plasmas. The nonlinear eigenmode equation indicates that the 3-wave coupling to shorter wavelength modes is the dominant nonlinear saturation mechanism. It is found that both the saturation level for these fluctuations and the magnitude of the associated ion thermal diffusivity are considerably smaller than the strong turbulence mixing length type estimates for the more conventional positive-η i -instabilities. 19 refs., 3 figs

  18. Study of early laser-induced plasma dynamics: Transient electron density gradients via Thomson scattering and Stark Broadening, and the implications on laser-induced breakdown spectroscopy measurements

    International Nuclear Information System (INIS)

    Diwakar, P.K.; Hahn, D.W.

    2008-01-01

    To further develop laser-induced breakdown spectroscopy (LIBS) as an analytical technique, it is necessary to better understand the fundamental processes and mechanisms taking place during the plasma evolution. This paper addresses the very early plasma dynamics (first 100 ns) using direct plasma imaging, light scattering, and transmission measurements from a synchronized 532-nm probe laser pulse. During the first 50 ns following breakdown, significant Thomson scattering was observed while the probe laser interacted with the laser-induced plasma. The Thomson scattering was observed to peak 15-25 ns following plasma initiation and then decay rapidly, thereby revealing the highly transient nature of the free electron density and plasma equilibrium immediately following breakdown. Such an intense free electron density gradient is suggestive of a non-equilibrium, free electron wave generated by the initial breakdown and growth processes. Additional probe beam transmission measurements and electron density measurements via Stark broadening of the 500.1-nm nitrogen ion line corroborate the Thomson scattering observations. In concert, the data support the finding of a highly transient plasma that deviates from local thermodynamic equilibrium (LTE) conditions during the first tens of nanoseconds of plasma lifetime. The implications of this early plasma transient behavior are discussed in the context of plasma-analyte interactions and the role on LIBS measurements

  19. Rapid and automated processing of bone marrow grafts without Ficoll density gradient for transplantation of cryopreserved autologous or ABO-incompatible allogeneic bone marrow.

    Science.gov (United States)

    Schanz, U; Gmür, J

    1992-12-01

    The growing number of BMTs has increased interest in safe and standardized in vitro bone marrow processing techniques. We describe our experience with a rapid automated method for the isolation of mononuclear cells (MNC) from large volumes of bone marrow using a Fenwal CS-3000 cell separator without employing density gradient materials. Forty bone marrow harvests with a mean volume of 1650 +/- 307 ml were processed. A mean of 75 +/- 34% (50 percentile range 54-94%) of the original MNCs were recovered in a volume of 200 ml with only 4 +/- 2% of the starting red blood cells (RBC). Removal of granulocytes, immature myeloid precursors and platelets proved to be sufficient to permit safe cryopreservation and successful autologous BMT (n = 25). Allogeneic BMT (n = 14, including three major ABO-incompatible) could be performed without additional manipulation. In both groups of patients timely and stable engraftment comparable to historical controls receiving Ficoll gradient processed autologous (n = 17) or unprocessed allogeneic BMT (n = 54) was observed. Moreover, 70 +/- 14% of the RBC could be recovered from the grafts. They were used for autologous RBC support of donors, rendering unnecessary autologous blood pre-donations.

  20. Ion temperature gradient driven transport in a density modification experiment on the TFTR tokamak

    International Nuclear Information System (INIS)

    Horton, W.; Lindberg, D.; Kim, J.Y.; Dong, J.Q.; Hammett, G.W.; Scott, S.D.; Zarnstorff, M.C.; Hamaguchi, S.

    1991-07-01

    TFTR profiles from a supershot density-modification experiment are analyzed for their local and ballooning stability to toroidal η i -modes in order to understand the initially puzzling results showing no increase in X i when a pellet is used to produce an abrupt and large increase in the η i parameter. The local stability analysis assumes that k parallel = 1/qR and ignores the effects of shear, but makes no assumption on the magnitude of k parallel v ti /ω. The ballooning stability analysis determines a self-consistent linear spectrum of k parallel's including the effect of shear and toroidicity, but it expands in k parallel v ti /ω ≤ 1, which is a marginal assumption for this experiment. Nevertheless, the two approaches agree well and show that the mixing length estimate of the transport rate does not change appreciably during the density-modification and has a value close to or less than the observed X i , in contrast to most previous theories which predicted X i 's which were over an order-of-magnitude too large. However, we are still unable to explain the observed increase X i (r) with minor radius by adding the effects of the finite beta drift - MHD mode coupling, the slab-like mode, or the trapped electron response. The experimental tracking 0.2 e /X i i and trapped-electron driving mechanisms are operating. 4 refs., 5 figs., 5 tabs

  1. Determination of moisture content gradient in wood by gamma-ray attenuation technique

    International Nuclear Information System (INIS)

    Aguiar, O.; Barros Ferraz, E.S. de

    1981-01-01

    A new methodology for determining water content gradients in wood was developed. It was based on the low energy gamma ray attenuation. Two equations were proposed for determining wood water content, below and above the fiber saturation point. A series of measurents of moisture content gradients in wood samples of Pinus oocarpa was made, during drying in an environment with controlled relative humidity and temperature. The water cntent gradients determination was quick, non-destructive and presented sensitivity and accuracy in moisture content range from 9% to 150%. Aspects of the application of this methodology in water diffusion and flow studies in wood are discussed. (Author) [pt

  2. Influence of thermal gradient on gas turbine combustor wall using impingement/effusion cooling techniques: CHT CFD predictions

    Directory of Open Access Journals (Sweden)

    A. M. El-jummah

    2017-04-01

    Full Text Available Internal wall heat transfer relevant to impingement/effusion cooling techniques was investigated using conjugate heat transfer (CHT computational fluid dynamics (CFD with ANSYS Fluent and ICEM commercial software. This work concentrates on the development of CHT CFD design procedures that are applicable to combustor wall and turbine blade heat transfer optimisation in gas turbine (GT. It specifically modelled and compares two configuration which are specifically relevant to the impingement and effusion holes density n (m-2 and is the ratio of the hole pitch X2. The configurations investigated are equal and unequal impingement and effusion holes density n (m-2, respectively, whereby in each case the variation in the number of cooling holes were carried out. The ratio of impingement and effusion number of holes/m2 (or hole density n, investigated were impingement/effusion: 4306/4306 and 1076/4306, respectively. The geometries were for impingement wall, hole pitch X to diameter D, X/D ratio of ~ 11 but different number of holes N for both n geometries, at a constant offset effusion wall, hole X/D of 4.7 of the same N for both the two configurations. The model geometries have a constant impingement gap of 8 mm with both impingement and effusion walls at 6.35 mm thick Nimonic - 75 material and were computed for varied air mass flux G from 0.1 - 0.94 kg/sm2. Symmetrical applications were employed in modelling each of the geometry, whereby for the impingement hole, only quarter of one hole was modelled, while for the effusion side the holes were either quarter or half modelled. The two n geometries were computed with k - ɛ turbulence model using standard wall functions, which also applies to all G. The predicted locally surface X2 (or hole square area average heat transfer coefficient (HTC h values compared with with previously published experimental data showed good agreement. The reduced internal gap flow recirculation with reduced heat transfer to

  3. Mapping axonal density and average diameter using non-monotonic time-dependent gradient-echo MRI

    DEFF Research Database (Denmark)

    Nunes, Daniel; Cruz, Tomás L; Jespersen, Sune N

    2017-01-01

    available in the clinic, or extremely long acquisition schemes to extract information from parameter-intensive models. In this study, we suggest that simple and time-efficient multi-gradient-echo (MGE) MRI can be used to extract the axon density from susceptibility-driven non-monotonic decay in the time...... the quantitative results are compared against ground-truth histology, they seem to reflect the axonal fraction (though with a bias, as evident from Bland-Altman analysis). As well, the extra-axonal fraction can be estimated. The results suggest that our model is oversimplified, yet at the same time evidencing......-dependent signal. We show, both theoretically and with simulations, that a non-monotonic signal decay will occur for multi-compartmental microstructures – such as axons and extra-axonal spaces, which we here used in a simple model for the microstructure – and that, for axons parallel to the main magnetic field...

  4. Impact of Ficoll density gradient centrifugation on major and trace element concentrations in erythrocytes and blood plasma.

    Science.gov (United States)

    Lu, Ying; Ahmed, Sultan; Harari, Florencia; Vahter, Marie

    2015-01-01

    Ficoll density gradient centrifugation is widely used to separate cellular components of human blood. We evaluated the suitability to use erythrocytes and blood plasma obtained from Ficoll centrifugation for assessment of elemental concentrations. We determined 22 elements (from Li to U) in erythrocytes and blood plasma separated by direct or Ficoll density gradient centrifugation, using inductively coupled plasma mass spectrometry. Compared with erythrocytes and blood plasma separated by direct centrifugation, those separated by Ficoll had highly elevated iodine and Ba concentration, due to the contamination from the Ficoll-Paque medium, and about twice as high concentrations of Sr and Mo in erythrocytes. On the other hand, the concentrations of Ca in erythrocytes and plasma were markedly reduced by the Ficoll separation, to some extent also Li, Co, Cu, and U. The reduced concentrations were probably due to EDTA, a chelator present in the Ficoll medium. Arsenic concentrations seemed to be lowered by Ficoll, probably in a species-specific manner. The concentrations of Mg, P, S, K, Fe, Zn, Se, Rb, and Cs were not affected in the erythrocytes, but decreased in plasma. Concentrations of Mn, Cd, and Pb were not affected in erythrocytes, but in plasma affected by EDTA and/or pre-analytical contamination. Ficoll separation changed the concentrations of Li, Ca, Co, Cu, As, Mo, I, Ba, and U in erythrocytes and blood plasma, Sr in erythrocytes, and Mg, P, S, K, Fe, Zn, Se, Rb and Cs in blood plasma, to an extent that will invalidate evaluation of deficiencies or excess intakes. Copyright © 2014 Elsevier GmbH. All rights reserved.

  5. Stabilization of the Rayleigh-Taylor instability by convection and thermal conduction in smooth density gradient: WKB analysis

    International Nuclear Information System (INIS)

    Bud'ko, A.B.; Liberman, M.A.; Bondarenko, E.A.

    1992-01-01

    Since development of the RT modes in the ablatively accelerated plasma of laser targets imposes crucial limitations on symmetry of spherical implosions and hence on energy cumulation, it has been the subject of intensive numerical and analytical analysis in the recent years, particularly in the context of inertial confinement fusion. Recent thin-foil ablative-acceleration experiments as well as the results of 2D numerical simulations demonstrated substantial reduction of the instability growth rates compared with the classical theory predictions up to the total stabilization in the short-wavelength limit. The numerical results indicated that the main stabilization mechanism is convection. To derive the scaling laws for the RT growth rates and cut-off wavenumbers in the wide range of flow parameters, analytical solutions attract special interest. The analytical approach based on the discontinuity model was developed to analyze the reduction of the RT growth rates by the plasma convective flow and the thermal conductivity effects. The following major problem arises in the discontinuity approximation, which leaves the solution undetermined: the number of the boundary conditions on the perturbed ablation surface is not sufficient to derive the dispersion equation. One needs additional boundary conditions not associated with the conservation laws on the discontinuity surface to close the system of linearized equations for small perturbations. The stabilization effect of highly structured hydrodynamic profiles was studied by Mikaelian and Munro for a stationary plasma. Nevertheless, no reasonable analytical model was constructed taking into account the combined convective, thermal conductivity and density gradient reduction of the RT growth rates. In this report we develop the analytical approach based on the WKB approximation to analyze the stabilization of the RT modes in plasma with smooth density and velocity gradients. (author) 9 refs., 1 fig

  6. Detection of human DNA polymorphisms with a simplified denaturing gradient gel electrophoresis technique.

    OpenAIRE

    Noll, W W; Collins, M

    1987-01-01

    Single base pair differences between otherwise identical DNA molecules can result in altered melting behavior detectable by denaturing gradient gel electrophoresis. We have developed a simplified procedure for using denaturing gradient gel electrophoresis to detect base pair changes in genomic DNA. Genomic DNA is digested with restriction enzymes and hybridized in solution to labeled single-stranded probe DNA. The excess probe is then hybridized to complementary phage M13 template DNA, and th...

  7. Arbitrary magnetic field gradient waveform correction using an impulse response based pre-equalization technique.

    Science.gov (United States)

    Goora, Frédéric G; Colpitts, Bruce G; Balcom, Bruce J

    2014-01-01

    The time-varying magnetic fields used in magnetic resonance applications result in the induction of eddy currents on conductive structures in the vicinity of both the sample under investigation and the gradient coils. These eddy currents typically result in undesired degradations of image quality for MRI applications. Their ubiquitous nature has resulted in the development of various approaches to characterize and minimize their impact on image quality. This paper outlines a method that utilizes the magnetic field gradient waveform monitor method to directly measure the temporal evolution of the magnetic field gradient from a step-like input function and extracts the system impulse response. With the basic assumption that the gradient system is sufficiently linear and time invariant to permit system theory analysis, the impulse response is used to determine a pre-equalized (optimized) input waveform that provides a desired gradient response at the output of the system. An algorithm has been developed that calculates a pre-equalized waveform that may be accurately reproduced by the amplifier (is physically realizable) and accounts for system limitations including system bandwidth, amplifier slew rate capabilities, and noise inherent in the initial measurement. Significant improvements in magnetic field gradient waveform fidelity after pre-equalization have been realized and are summarized. Copyright © 2013 Elsevier Inc. All rights reserved.

  8. The control of plasma density profile in Tore Supra. Comparison of different fueling techniques

    International Nuclear Information System (INIS)

    Commaux, N.

    2007-09-01

    The behaviour of a reactor-class plasma when fuelled using the existing techniques (gas puffing, supersonic molecular beam injection and pellet injection) is still very difficult to foresee. The present work has been initiated on Tore Supra in order to extrapolate the consequences of the different fuelling systems on ITER. Two main topics have been studied: the comparison of the plasma behaviour when fuelled using the different techniques at high Greenwald density fractions and the study of the homogenization following a pellet injection (main fuelling technique for ITER burning plasmas). The experiments at high Greenwald density fractions performed on Tore Supra showed that the plasma behaviour is very dependent on the fuelling method. The plasma energy confinement is following the scaling laws determined at low density when fuelled using pellet injection. which is better than for gas puffing and SMBI. both inducing a significant confinement loss. This behaviour is nor related to a transport modification: the ratio between effective diffusion and convection is similar to the pellet case. The difference between these shots is related only to the position of the matter source (at the edge for gas and close to the center for pellets). The study concerning the homogenization phenomena following a pellet injection aims mainly to study the ∇B-drift effect that expels the mater deposited by a pellet toward the low field side. A new phenomenon. which appears to be particularly important for the ∇B-drift during low field side injections. was then discovered: the influence of magnetic surfaces with an integer-valued safety factor (q). When the mater drifting toward low field side crosses an integer q surface. it experiences an important braking effect which stops the drift motion. It implies that the pellet material is mainly deposited on the last integer q surface crossed by the pellet during its injection. This study allows also to determine that the

  9. Costs of coexistence along a gradient of competitor densities: an experiment with arvicoline rodents.

    Science.gov (United States)

    Eccard, Jana A; Ylönen, Hannu

    2007-01-01

    1. Costs of coexistence for species with indirect resource competition usually increase monotonically with competitor numbers. Very little is known though about the shape of the cost function for species with direct interference competition. 2. Here we report the results of an experiment with two vole species in artificial coexistence in large enclosures, where density of the dominant competitor species (Microtus agrestis) was manipulated. Experimental populations of the subordinate vole species (Clethrionomys glareolus) were composed of same aged individuals to study distribution of costs of coexistence with a dominant species within an age-cohort. 3. Survival and space use decreased gradually with increasing field vole numbers. Thus, responses to interference competition in our system appeared to be similar as expected from resource competition. The total number of breeders was stable. Reproductive characteristics such as the timing of breeding, and the litter size were not affected. In the single species enclosures a proportion of surviving individuals were not able to establish a breeding territory against stronger conspecifics. Under competition with heterospecifics such nonbreeders suffered high mortality, whereas the breeders survived. 4. Combined interference of dominant conspecifics and heterospecifics probably increased the frequency of aggressive interactions, social stress and mortality for the weaker individuals within a homogeneous age cohort of the subordinate competitor population. 5. Our results suggest, that in open systems where bank voles are outcompeted over the breeding season by faster reproducing field voles, animals able to establish a territory may be able to withstand competitor pressure, while nonbreeding bank vole individuals are forced to emigrate to suboptimal forest habitats.

  10. Technique for fabrication of gradual standards of radiographic image blachening density

    International Nuclear Information System (INIS)

    Borovin, I.V.; Kondina, M.A.

    1987-01-01

    The technique of fabrication of gradual standards of blackening density for industrial radiography by contact printing from a negative is described. The technique is designed for possibilities of industrial laboratoriesof radiation defectoscopy possessing no special-purpose sensitometric equipment

  11. An oscillating extracellular voltage gradient reduces the density and influences the orientation of astrocytes in injured mammalian spinal cord.

    Science.gov (United States)

    Moriarty, L J; Borgens, R B

    2001-01-01

    We have studied the cellular basis for recovery from acute spinal cord injury induced by applied electric fields. We have emphasized this recovery is due to the regeneration of spinal axons around and through the lesion, and have begun to evaluate the contribution of other cells to the recovery process. We have imposed a voltage gradient of about 320 microV/mm across puncture wounds to the adult rat spinal cord in order to study the accumulation and orientation of GFAP+ astrocytes within and adjacent to the lesion. This electric field was imposed by a miniaturized electronic implant designed to alternate the polarity of the field every 15 minutes. Astrocytes are known to undergo hyperplastic transformation within injured mammalian cords forming a major component of the scar that forms in response to injury. We have made three observations using a new computer based morphometry technique: First, we note a slight shift in the orientation of astrocytes parallel to the long axis of the spinal cord towards an imaginary reference perpendicular to this axis by approximately 10 degrees--but only in undamaged white matter near the lesion. Second, the relative number of astrocytes was markedly, and statistically significantly, reduced within electrically--treated spinal cords, particularly in the lesion. Third, the imposed voltage gradient statistically reduced the numbers of astrocytes possessing oriented cell processes within the injury site compared to adjacent undamaged regions of spinal cord.

  12. Forest biomass density across large climate gradients in northern South America is related to water availability but not with temperature.

    Science.gov (United States)

    Álvarez-Dávila, Esteban; Cayuela, Luis; González-Caro, Sebastián; Aldana, Ana M; Stevenson, Pablo R; Phillips, Oliver; Cogollo, Álvaro; Peñuela, Maria C; von Hildebrand, Patricio; Jiménez, Eliana; Melo, Omar; Londoño-Vega, Ana Catalina; Mendoza, Irina; Velásquez, Oswaldo; Fernández, Fernando; Serna, Marcela; Velázquez-Rua, Cesar; Benítez, Doris; Rey-Benayas, José M

    2017-01-01

    Understanding and predicting the likely response of ecosystems to climate change are crucial challenges for ecology and for conservation biology. Nowhere is this challenge greater than in the tropics as these forests store more than half the total atmospheric carbon stock in their biomass. Biomass is determined by the balance between biomass inputs (i.e., growth) and outputs (mortality). We can expect therefore that conditions that favor high growth rates, such as abundant water supply, warmth, and nutrient-rich soils will tend to correlate with high biomass stocks. Our main objective is to describe the patterns of above ground biomass (AGB) stocks across major tropical forests across climatic gradients in Northwestern South America. We gathered data from 200 plots across the region, at elevations ranging between 0 to 3400 m. We estimated AGB based on allometric equations and values for stem density, basal area, and wood density weighted by basal area at the plot-level. We used two groups of climatic variables, namely mean annual temperature and actual evapotranspiration as surrogates of environmental energy, and annual precipitation, precipitation seasonality, and water availability as surrogates of water availability. We found that AGB is more closely related to water availability variables than to energy variables. In northwest South America, water availability influences carbon stocks principally by determining stand structure, i.e. basal area. When water deficits increase in tropical forests we can expect negative impact on biomass and hence carbon storage.

  13. A Magnetic Resonance Measurement Technique for Rapidly Switched Gradient Magnetic Fields in a Magnetic Resonance Tomograph

    Directory of Open Access Journals (Sweden)

    K. Bartušek

    2003-01-01

    Full Text Available This paper describes a method for measuring of the gradient magnetic field in Nuclear Magnetic Resonance (NMR tomography, which is one of the modern medical diagnostic methods. A very important prerequisite for high quality imaging is a gradient magnetic field in the instrument with exactly defined properties. Nuclear magnetic resonance enables us to measure the pulse gradient magnetic field characteristics with high accuracy. These interesting precise methods were designed, realised, and tested at the Institute of Scientific Instruments (ISI of the Academy of Sciences of the Czech Republic. The first of them was the Instantaneous Frequency (IF method, which was developed into the Instantaneous Frequency of Spin Echo (IFSE and the Instantaneous Frequency of Spin Echo Series (IFSES methods. The above named methods are described in this paper and their a comparison is also presented.

  14. Bone marrow-derived cells for cardiovascular cell therapy: an optimized GMP method based on low-density gradient improves cell purity and function.

    Science.gov (United States)

    Radrizzani, Marina; Lo Cicero, Viviana; Soncin, Sabrina; Bolis, Sara; Sürder, Daniel; Torre, Tiziano; Siclari, Francesco; Moccetti, Tiziano; Vassalli, Giuseppe; Turchetto, Lucia

    2014-09-27

    Cardiovascular cell therapy represents a promising field, with several approaches currently being tested. The advanced therapy medicinal product (ATMP) for the ongoing METHOD clinical study ("Bone marrow derived cell therapy in the stable phase of chronic ischemic heart disease") consists of fresh mononuclear cells (MNC) isolated from autologous bone marrow (BM) through density gradient centrifugation on standard Ficoll-Paque. Cells are tested for safety (sterility, endotoxin), identity/potency (cell count, CD45/CD34/CD133, viability) and purity (contaminant granulocytes and platelets). BM-MNC were isolated by density gradient centrifugation on Ficoll-Paque. The following process parameters were optimized throughout the study: gradient medium density; gradient centrifugation speed and duration; washing conditions. A new manufacturing method was set up, based on gradient centrifugation on low density Ficoll-Paque, followed by 2 washing steps, of which the second one at low speed. It led to significantly higher removal of contaminant granulocytes and platelets, improving product purity; the frequencies of CD34+ cells, CD133+ cells and functional hematopoietic and mesenchymal precursors were significantly increased. The methodological optimization described here resulted in a significant improvement of ATMP quality, a crucial issue to clinical applications in cardiovascular cell therapy.

  15. Endothelial cell density after deep anterior lamellar keratoplasty (Melles technique)

    NARCIS (Netherlands)

    van Dooren, Bart T. H.; Mulder, Paul G. H.; Nieuwendaal, Carla P.; Beekhuis, W. Houdijn; Melles, Gerrit R. J.

    2004-01-01

    To measure the recipient endothelial cell loss after the Melles technique for deep anterior lamellar keratoplasty. In 21 eyes of 21 patients, a deep anterior lamellar keratoplasty procedure was performed. Before surgery and at 6, 12, and 24 months after surgery, specular microscopy was performed to

  16. Endothelial cell density after deep anterior lamellar keratoplasty (Melles technique)

    NARCIS (Netherlands)

    Van Dooren, BTH; Mulder, PGH; Nieuwendaal, CP; Beekhuis, WH; Melles, GRJ

    PURPOSE: To measure the recipient endothelial cell loss after the Melles technique for deep anterior lamellar keratoplasty. METHODS: In 21 eyes of 21 patients, a deep anterior lamellar keratoplasty procedure was performed. Before surgery and at 6, 12, and 24 months after surgery, specular microscopy

  17. Density determination of langmuir-blodgett monolayer films using x-ray reflectivity technique

    International Nuclear Information System (INIS)

    Damar Yoga Kusuma

    2015-01-01

    Monolayer deposition by Langmuir-Blodgett technique produces monolayer films that are uniform with controllable thickness down to nanometer scale. To evaluate the quality of the monolayer deposition, X-ray reflectivity technique are employed to monitor the monolayers density. Langmuir-Blodgett monolayer with good coverage and uniformity results in film density close to its macroscopic film counterpart whereas films with presence of air gaps shows lower density compared to its macroscopic film counterpart. (author)

  18. Assessment of swim-up and discontinuous density gradient in sperm sex preselection for bovine embryo production

    Directory of Open Access Journals (Sweden)

    A.C Lucio

    2012-06-01

    Full Text Available The purpose of this work was to associate the modified swim-up method with centrifugation in density gradient for the separation of X-bearing spermatozoa. Sperm viability and integrity were evaluated through the Trypan Blue/Giemsa staining method. Quality control of centrifuged spermatozoa was performed in in vitro produced embryos. The results were validated by the sex ratio of in vitro produced embryos using PCR by Y- specific sequences present in bovine male genomic DNA. After determining genetic sex of in vitro produced embryos, the results showed difference (P<0.05 in deviation of sex ratio when comparing the control group (45.2% females with the other spermatozoa selection procedures (60.6% females (P<0.05. The sperm selection methods are capable of selecting X-bearing spermatozoa without compromising the spermatozoa fertility (cleavage and blastocyst rates, 70% and 26%, respectively and were considered relevant methods to be introduced in bovine in vitro produced embryo programs.

  19. Space Electron Density Gradient Studies using a 3D Embedded Reconfigurable Sounder and ESA/NASA CLUSTER Mission

    Science.gov (United States)

    Dekoulis, George

    2016-07-01

    This paper provides a direct comparison between data captured by a new embedded reconfigurable digital sounder, different ground-based ionospheric sounders spread around Europe and the ESA/NASA CLUSTER mission. The CLUSTER mission consists of four identical space probes flying in a formation that allows measurements of the electron density gradient in the local magnetic field. Both the ground-based and the spacecraft instrumentations assist in studying the motion, geometry and boundaries of the plasmasphere. The comparison results are in accordance to each other. Some slight deviations among the captured data were expected from the beginning of this investigation. These small discrepancies are reasonable and seriatim analyzed. The results of this research are significant, since the level of the plasma's ionization, which is related to the solar activity, dominates the propagation of electromagnetic waves through it. Similarly, unusually high solar activity presents serious hazards to orbiting satellites, spaceborne instrumentation, satellite communications and infrastructure located on the Earth's surface. Long-term collaborative study of the data is required to continue, in order to identify and determine the enhanced risk in advance. This would allow scientists to propose an immediate cure.

  20. A density gradient of VAPG peptides on a cell-resisting surface achieves selective adhesion and directional migration of smooth muscle cells over fibroblasts.

    Science.gov (United States)

    Yu, Shan; Zuo, Xingang; Shen, Tao; Duan, Yiyuan; Mao, Zhengwei; Gao, Changyou

    2018-05-01

    Selective adhesion and migration of smooth muscle cells (SMCs) over fibroblasts (FIBs) is required to prevent adventitia fibrosis in vascular regeneration. In this study, a uniform cell-resisting layer of poly(ethylene glycol) (PEG) with a density gradient of azide groups was generated on a substrate by immobilizing two kinds of PEG molecules in a gradient manner. A density gradient of alkynyl-functionalized Val-Ala-Pro-Gly (VAPG) peptides was then prepared on the PEG layer via click chemistry. The VAPG density gradient was characterized by fluorescence imaging, revealing the gradual enhancement of the fluorescent intensity along the substrate direction. The adhesion and mobility of SMCs were selectively enhanced on the VAPG density gradient, leading to directional migration toward the higher peptide density (up to 84%). In contrast, the adhesion and mobility of FIBs were significantly weakened. The net displacement of SMCs also significantly increased compared with that on tissue culture polystyrene (TCPS) and that of FIBs on the gradient. The mitogen-activated protein kinase (MAPK) signaling pathways related to cell migration were studied, showing higher expressions of functional proteins from SMCs on the VAPG-modified surface in a density-dependent manner. For the first time the selective adhesion and directional migration of SMCs over FIBs was achieved by an elaborative design of a gradient surface, leading to a new insight in design of novel vascular regenerative materials. Selective cell adhesion and migration guided by regenerative biomaterials are extremely important for the regeneration of targeted tissues, which can avoid the drawbacks of incorrect and uncontrolled responses of tissue cells to implants. For example, selectivity of smooth muscle cells (SMCs) over fibroblasts (FIBs) is required to prevent adventitia fibrosis in vascular regeneration. Herein we prepare a uniform cell-repelling layer, on which SMCs-selective Val-Ala-Pro-Gly (VAPG) peptides

  1. Cultivo de células mesenquimais do sangue de cordão umbilical com e sem uso do gradiente de densidade Ficoll-Paque Blood mesenchymal stem cell culture from the umbilical cord with and without Ficoll-Paque density gradient method

    Directory of Open Access Journals (Sweden)

    Rosa Sayoko Kawasaki-Oyama

    2008-03-01

    Ficoll-Paque gradient density method (d=1.077g/ml. METHODS: Ten samples of the umbilical cord blood obtained from full-term deliveries were submitted to two different procedures of mesenchymal stem cell culture: a Method without the Ficoll-Paque density gradient, which concentrates all nucleated cells; b Method with the Ficoll-Paque density gradient, which selects only low-density mononuclear cells. Cells were initially plated into 25 cm² cultures flasks at a density of 1x10(7 nucleated cells/cm² and 1x10(6 mononuclear cells/cm². RESULTS: It was obtained 2-13x10(7 (median = 2.35x10(7 nucleated cells/cm² by the method without the Ficoll-Paque gradient density, and 3.7-15.7x10(6 (median = 7.2x10(6 mononuclear cells/cm² by the method with the Ficoll-Paque gradient density. In all cultures adherent cells were observed 24 hours after being cultured. Cells presented fibroblastoid and epithelioid morphology. In most of the cultures, cell proliferation occurred in the first week, but after the second week only some cultures - derived from the method without the Ficoll-Paque gradient density - maintained the growth rate reaching confluence. Those cultures were submitted to trypsinization with 0.25% trypsin/EDTA solution and cultured for two to three months. CONCLUSION: In the samples analyzed, cell separation and mesenchymal stem cell culture techniques from human umbilical cord blood by the method without the Ficoll-Paque density gradient was more efficient than the method with the Ficoll-Paque density gradient.

  2. X-ray radiographic technique for measuring density uniformity of silica aerogel

    International Nuclear Information System (INIS)

    Tabata, Makoto; Hatakeyama, Yoshikiyo; Adachi, Ichiro; Morita, Takeshi; Nishikawa, Keiko

    2013-01-01

    This paper proposes a new X-ray radiographic technique for measuring density uniformity of silica aerogels used as radiator in proximity-focusing ring-imaging Cherenkov detectors. To obtain high performance in a large-area detector, a key characteristic of radiator is the density (i.e. refractive index) uniformity of an individual aerogel monolith. At a refractive index of n=1.05, our requirement for the refractive index uniformity in the transverse plane direction of an aerogel tile is |δ(n−1)/(n−1)|<4% in a focusing dual layer radiator (with different refractive indices) scheme. We applied the radiographic technique to evaluate the density uniformity of our original aerogels from a trial production and that of Panasonic products (SP-50) as a reference, and to confirm they have sufficient density uniformity within ±1% along the transverse plane direction. The measurement results show that the proposed technique can quantitatively estimate the density uniformity of aerogels.

  3. Influence of plasma density and plasma sheath dynamics on the ion implantation by plasma immersion technique

    OpenAIRE

    Ensinger, Wolfgang

    1996-01-01

    Influence of plasma density and plasma sheath dynamics on the ion implantation by plasma immersion technique / B. Rauschenbach ... - In: Nuclear instruments and methods in physics research. B. 113. 1996. S. 266-269

  4. Evaluation of techniques for determining the density of fine woody debris

    Science.gov (United States)

    Becky Fasth; Mark E. Harmon; Christopher W. Woodall; Jay. Sexton

    2010-01-01

    Evaluated various techniques for determining the density (i.e., bulk density) of fine woody debris during forest inventory activities. It was found that only experts in dead wood inventory may be able to identify fine woody debris stages of decay. Suggests various future research directions such as...

  5. A new technique for MR elastography of the supraspinatus muscle: A gradient-echo type multi-echo sequence.

    Science.gov (United States)

    Ito, Daiki; Numano, Tomokazu; Mizuhara, Kazuyuki; Takamoto, Koichi; Onishi, Takaaki; Nishijo, Hisao

    2016-10-01

    Magnetic resonance elastography (MRE) can measure tissue stiffness quantitatively and noninvasively. Supraspinatus muscle injury is a significant problem among throwing athletes. The purpose of this study was to develop an MRE technique for application to the supraspinatus muscle by using a conventional magnetic resonance imaging (MRI). MRE acquisitions were performed with a gradient-echo type multi-echo MR sequence at 100Hz pneumatic vibration. A custom-designed vibration pad was used as a pneumatic transducer in order to adapt to individual shoulder shapes. In a gradient-echo type multi-echo MR sequence, without motion encoding gradient (MEG) that synchronizes with vibrations, bipolar readout gradient lobes achieved a similar function to MEG (MEG-like effect). In other words, a dedicated MRE sequence (built-in MEG) is not always necessary for MRE. In this study, 7 healthy volunteers underwent MRE. We investigated the effects of direction of the MEG-like effect and selected imaging planes on the patterns of wave propagation (wave image). The results indicated that wave images showed clear wave propagation on a condition that the direction of the MEG-like effect was nearly perpendicular to the long axis of the supraspinatus muscle, and that the imaging plane was superior to the proximal supraspinatus muscle. This limited condition might be ascribed to specific features of fibers in the supraspinatus muscle and wave reflection from the boundaries of the supraspinous fossa. The mean stiffness of the supraspinatus muscle was 10.6±3.17kPa. Our results demonstrated that using MRE, our method can be applied to the supraspinatus muscle by using conventional MRI. Copyright © 2016 Elsevier Inc. All rights reserved.

  6. An analysis of the gradient-induced electric fields and current densities in human models when situated in a hybrid MRI-LINAC system

    International Nuclear Information System (INIS)

    Liu, Limei; Trakic, Adnan; Sanchez-Lopez, Hector; Liu, Feng; Crozier, Stuart

    2014-01-01

    MRI-LINAC is a new image-guided radiotherapy treatment system that combines magnetic resonance imaging (MRI) with a linear accelerator (LINAC) in a single unit. One drawback is that the pulsing of the split gradient coils of the system induces an electric field and currents in the patient which need to be predicted and evaluated for patient safety. In this novel numerical study the in situ electric fields and associated current densities were evaluated inside tissue-accurate male and female human voxel models when a number of different split-geometry gradient coils were operated. The body models were located in the MRI-LINAC system along the axial and radial directions in three different body positions. Each model had a region of interest (ROI) suitable for image-guided radiotherapy. The simulation results show that the amplitudes and distributions of the field and current density induced by different split x-gradient coils were similar with one another in the ROI of the body model, but varied outside of the region. The fields and current densities induced by a split classic coil with the surface unconnected showed the largest deviation from those given by the conventional non-split coils. Another finding indicated that the distributions of the peak current densities varied when the body position, orientation or gender changed, while the peak electric fields mainly occurred in the skin and fat tissues. (paper)

  7. Novel Application of Density Estimation Techniques in Muon Ionization Cooling Experiment

    Energy Technology Data Exchange (ETDEWEB)

    Mohayai, Tanaz Angelina [IIT, Chicago; Snopok, Pavel [IIT, Chicago; Neuffer, David [Fermilab; Rogers, Chris [Rutherford

    2017-10-12

    The international Muon Ionization Cooling Experiment (MICE) aims to demonstrate muon beam ionization cooling for the first time and constitutes a key part of the R&D towards a future neutrino factory or muon collider. Beam cooling reduces the size of the phase space volume occupied by the beam. Non-parametric density estimation techniques allow very precise calculation of the muon beam phase-space density and its increase as a result of cooling. These density estimation techniques are investigated in this paper and applied in order to estimate the reduction in muon beam size in MICE under various conditions.

  8. Methylmercury speciation in the dissolved phase of a stratified lake using the diffusive gradient in thin film technique

    Energy Technology Data Exchange (ETDEWEB)

    Clarisse, Olivier [Trent University, Department of Chemistry, 1600 West Bank Drive, Peterborough, Ontario K9J 7B8 (Canada)], E-mail: olivier.clarisse@umoncton.ca; Foucher, Delphine; Hintelmann, Holger [Trent University, Department of Chemistry, 1600 West Bank Drive, Peterborough, Ontario K9J 7B8 (Canada)

    2009-03-15

    The diffusive gradient in thin film (DGT) technique was successfully used to monitor methylmercury (MeHg) speciation in the dissolved phase of a stratified boreal lake, Lake 658 of the Experimental Lakes Area (ELA) in Ontario, Canada. Water samples were conventionally analysed for MeHg, sulfides, and dissolved organic matter (DOM). MeHg accumulated by DGT devices was compared to MeHg concentration measured conventionally in water samples to establish MeHg speciation. In the epilimnion, MeHg was almost entirely bound to DOM. In the top of the hypolimnion an additional labile fraction was identified, and at the bottom of the lake a significant fraction of MeHg was potentially associated to colloidal material. As part of the METAALICUS project, isotope enriched inorganic mercury was applied to Lake 658 and its watershed for several years to establish the relationship between atmospheric Hg deposition and Hg in fish. Little or no difference in MeHg speciation in the dissolved phase was detected between ambient and spike MeHg. - Methylmercury speciation was determined in the dissolved phase of a stratified lake using the diffusive gradient in thin film technique.

  9. Methylmercury speciation in the dissolved phase of a stratified lake using the diffusive gradient in thin film technique

    International Nuclear Information System (INIS)

    Clarisse, Olivier; Foucher, Delphine; Hintelmann, Holger

    2009-01-01

    The diffusive gradient in thin film (DGT) technique was successfully used to monitor methylmercury (MeHg) speciation in the dissolved phase of a stratified boreal lake, Lake 658 of the Experimental Lakes Area (ELA) in Ontario, Canada. Water samples were conventionally analysed for MeHg, sulfides, and dissolved organic matter (DOM). MeHg accumulated by DGT devices was compared to MeHg concentration measured conventionally in water samples to establish MeHg speciation. In the epilimnion, MeHg was almost entirely bound to DOM. In the top of the hypolimnion an additional labile fraction was identified, and at the bottom of the lake a significant fraction of MeHg was potentially associated to colloidal material. As part of the METAALICUS project, isotope enriched inorganic mercury was applied to Lake 658 and its watershed for several years to establish the relationship between atmospheric Hg deposition and Hg in fish. Little or no difference in MeHg speciation in the dissolved phase was detected between ambient and spike MeHg. - Methylmercury speciation was determined in the dissolved phase of a stratified lake using the diffusive gradient in thin film technique

  10. Measurement of the temperature Gradient in air using Talbot effect and Moire technique

    International Nuclear Information System (INIS)

    Tavassoly, M.T.; Rasouli, S.

    2000-01-01

    In this paper we have exploited the self-imaging or Talbot effect and Moire technique to measure the temperature distribution in the air enclosed between two paral led plates of different temperatures. This study shows that for the plates width of 60 cm a change of 1 d egC in 1 cm can be easily detected

  11. Characterization of urban particulate matter by diffusive gradients in thin film technique

    Czech Academy of Sciences Publication Activity Database

    Dufka, Michaela; Dočekal, Bohumil

    (2018), s. 1-8, č. článku 9698710. ISSN 2090-8865 R&D Projects: GA ČR GAP503/10/2002 Institutional support: RVO:68081715 Keywords : thin film technique * urban particulate matter * particulate air pollution Subject RIV: CB - Analytical Chemistry , Separation OBOR OECD: Analytical chemistry Impact factor: 1.801, year: 2016

  12. Layout-Driven Post-Placement Techniques for Temperature Reduction and Thermal Gradient Minimization

    DEFF Research Database (Denmark)

    Liu, Wei; Calimera, Andrea; Macii, Alberto

    2013-01-01

    With the continuing scaling of CMOS technology, on-chip temperature and thermal-induced variations have become a major design concern. To effectively limit the high temperature in a chip equipped with a cost-effective cooling system, thermal specific approaches, besides low power techniques, are ...

  13. Characterization of urban particulate matter by diffusive gradients in thin film technique

    Czech Academy of Sciences Publication Activity Database

    Dufka, Michaela; Dočekal, Bohumil

    (2018), s. 1-8, č. článku 9698710. ISSN 2090-8865 R&D Projects: GA ČR GAP503/10/2002 Institutional support: RVO:68081715 Keywords : thin film technique * urban particulate matter * particulate air pollution Subject RIV: CB - Analytical Chemistry, Separation OBOR OECD: Analytical chemistry Impact factor: 1.801, year: 2016

  14. Influence of velocity gradient on optimisation of the aggregation process and physical properties of formed aggregates. Part 1. Inline high density suspension (IHDS) aggregation process

    Czech Academy of Sciences Publication Activity Database

    Polášek, Pavel

    2011-01-01

    Roč. 59, č. 2 (2011), s. 107-117 ISSN 0042-790X R&D Projects: GA ČR GA103/07/1016 Institutional research plan: CEZ:AV0Z20600510 Keywords : flocculation optimum * inline high density suspension (IHDS) formation process * properties of aggregates * intensity of agitation * velocity gradient G Subject RIV: BK - Fluid Dynamics Impact factor: 0.340, year: 2011

  15. A Breast Cell Atlas: Organelle analysis of the MDA-MB-231 cell line by density-gradient fractionation using isotopic marking and label-free analysis

    Directory of Open Access Journals (Sweden)

    Marianne Sandin

    2015-09-01

    Full Text Available Protein translocation between organelles in the cell is an important process that regulates many cellular functions. However, organelles can rarely be isolated to purity so several methods have been developed to analyse the fractions obtained by density gradient centrifugation. We present an analysis of the distribution of proteins amongst organelles in the human breast cell line, MDA-MB-231 using two approaches: an isotopic labelling and a label-free approach.

  16. Derivation of the threshold condition for the ion temperature gradient mode with an inverted density profile from a simple physics picture

    Science.gov (United States)

    Jhang, Hogun

    2018-05-01

    We show that the threshold condition for the toroidal ion temperature gradient (ITG) mode with an inverted density profile can be derived from a simple physics argument. The key in this picture is that the density inversion reduces the ion compression due to the ITG mode and the electron drift motion mitigates the poloidal potential build-up. This condition reproduces the same result that has been reported from a linear gyrokinetic calculation [T. S. Hahm and W. M. Tang, Phys. Fluids B 1, 1185 (1989)]. The destabilizing role of trapped electrons in toroidal geometry is easily captured in this picture.

  17. Analytic energy gradients for orbital-optimized MP3 and MP2.5 with the density-fitting approximation: An efficient implementation.

    Science.gov (United States)

    Bozkaya, Uğur

    2018-03-15

    Efficient implementations of analytic gradients for the orbital-optimized MP3 and MP2.5 and their standard versions with the density-fitting approximation, which are denoted as DF-MP3, DF-MP2.5, DF-OMP3, and DF-OMP2.5, are presented. The DF-MP3, DF-MP2.5, DF-OMP3, and DF-OMP2.5 methods are applied to a set of alkanes and noncovalent interaction complexes to compare the computational cost with the conventional MP3, MP2.5, OMP3, and OMP2.5. Our results demonstrate that density-fitted perturbation theory (DF-MP) methods considered substantially reduce the computational cost compared to conventional MP methods. The efficiency of our DF-MP methods arise from the reduced input/output (I/O) time and the acceleration of gradient related terms, such as computations of particle density and generalized Fock matrices (PDMs and GFM), solution of the Z-vector equation, back-transformations of PDMs and GFM, and evaluation of analytic gradients in the atomic orbital basis. Further, application results show that errors introduced by the DF approach are negligible. Mean absolute errors for bond lengths of a molecular set, with the cc-pCVQZ basis set, is 0.0001-0.0002 Å. © 2017 Wiley Periodicals, Inc. © 2017 Wiley Periodicals, Inc.

  18. High energy X-ray diffraction study of a dental ceramics–titanium functional gradient material prepared by field assisted sintering technique

    International Nuclear Information System (INIS)

    Witte, K.; Bodnar, W.; Schell, N.; Lang, H.; Burkel, E.

    2014-01-01

    A functional gradient material with eleven layers composed of a dental ceramics and titanium was successfully consolidated using field assisted sintering technique in a two-step sintering process. High energy X-ray diffraction studies on the gradient were performed at High Energy Material Science beamline at Desy in Hamburg. Phase composition, crystal unit edges and lattice mismatch along the gradient were determined applying Rietveld refinement procedure. Phase analysis revealed that the main crystalline phase present in the gradient is α-Ti. Crystallinity increases stepwisely along the gradient with a decreasing increment between every next layer, following rather the weight fraction of titanium. The crystal unit edge a of titanium remains approximately constant with a value of 2.9686(1) Å, while c is reduced with increasing amount of titanium. In the layer with pure titanium the crystal unit edge c is constant with a value of 4.7174(2) Å. The lattice mismatch leading to an internal stress was calculated over the whole gradient. It was found that the maximal internal stress in titanium embedded in the studied gradient is significantly smaller than its yield strength, which implies that the structure of titanium along the whole gradient is mechanically stable. - Highlights: • High energy XRD studies of dental ceramics–Ti gradient material consolidated by FAST. • Phase composition, crystallinity and lattice parameters are determined. • Crystallinity increases stepwisely along the gradient following weight fraction of Ti. • Lattice mismatch leading to internal stress is calculated over the whole gradient. • Internal stress in α-Ti embedded in the gradient is smaller than its yield strength

  19. Capitalizing Resolving Power of Density Gradient Ultracentrifugation by Freezing and Precisely Slicing Centrifuged Solution: Enabling Identification of Complex Proteins from Mitochondria by Matrix Assisted Laser Desorption/Ionization Time-of-Flight Mass Spectrometry

    Directory of Open Access Journals (Sweden)

    Haiqing Yu

    2016-01-01

    Full Text Available Density gradient centrifugation is widely utilized for various high purity sample preparations, and density gradient ultracentrifugation (DGU is often used for more resolution-demanding purification of organelles and protein complexes. Accurately locating different isopycnic layers and precisely extracting solutions from these layers play a critical role in achieving high-resolution DGU separations. In this technique note, we develop a DGU procedure by freezing the solution rapidly (but gently after centrifugation to fix the resolved layers and by slicing the frozen solution to fractionate the sample. Because the thickness of each slice can be controlled to be as thin as 10 micrometers, we retain virtually all the resolution produced by DGU. To demonstrate the effectiveness of this method, we fractionate complex V from HeLa mitochondria using a conventional technique and this freezing-slicing (F-S method. The comparison indicates that our F-S method can reduce complex V layer thicknesses by ~40%. After fractionation, we analyze complex V proteins directly on a matrix assisted laser desorption/ionization, time-of-flight mass spectrometer. Twelve out of fifteen subunits of complex V are positively identified. Our method provides a practical protocol to identify proteins from complexes, which is useful to investigate biomolecular complexes and pathways in various conditions and cell types.

  20. Technique of Critical Current Density Measurement of Bulk Superconductor with Linear Extrapolation Method

    International Nuclear Information System (INIS)

    Adi, Wisnu Ari; Sukirman, Engkir; Winatapura, Didin S.

    2000-01-01

    Technique of critical current density measurement (Jc) of HTc bulk ceramic superconductor has been performed by using linear extrapolation with four-point probes method. The measurement of critical current density HTc bulk ceramic superconductor usually causes damage in contact resistance. In order to decrease this damage factor, we introduce extrapolation method. The extrapolating data show that the critical current density Jc for YBCO (123) and BSCCO (2212) at 77 K are 10,85(6) Amp.cm - 2 and 14,46(6) Amp.cm - 2, respectively. This technique is easier, simpler, and the use of the current flow is low, so it will not damage the contact resistance of the sample. We expect that the method can give a better solution for bulk superconductor application. Key words. : superconductor, critical temperature, and critical current density

  1. A Compton scattering technique to determine wood density and locating defects in it

    International Nuclear Information System (INIS)

    Tondon, Akash; Sandhu, B. S.; Singh, Bhajan; Singh, Mohinder

    2015-01-01

    A Compton scattering technique is presented to determine density and void location in the given wooden samples. The technique uses a well collimated gamma ray beam from 137 Cs along with the NaI(Tl) scintillation detector. First, a linear relationship is established between Compton scattered intensity and known density of chemical compounds, and then density of the wood is determined from this linear relation. In another experiment, the ability of penetration of gamma rays is explored to detect voids in wooden (low Z) sample. The sudden reduction in the Compton scattered intensities agrees well with the position and size of voids in the wooden sample. It is concluded that wood density and the voids of size ∼ 4 mm and more can be detected easily by this method

  2. Study of homogeneous bubble nucleation in liquid carbon dioxide by a hybrid approach combining molecular dynamics simulation and density gradient theory.

    Science.gov (United States)

    Langenbach, K; Heilig, M; Horsch, M; Hasse, H

    2018-03-28

    A new method for predicting homogeneous bubble nucleation rates of pure compounds from vapor-liquid equilibrium (VLE) data is presented. It combines molecular dynamics simulation on the one side with density gradient theory using an equation of state (EOS) on the other. The new method is applied here to predict bubble nucleation rates in metastable liquid carbon dioxide (CO 2 ). The molecular model of CO 2 is taken from previous work of our group. PC-SAFT is used as an EOS. The consistency between the molecular model and the EOS is achieved by adjusting the PC-SAFT parameters to VLE data obtained from the molecular model. The influence parameter of density gradient theory is fitted to the surface tension of the molecular model. Massively parallel molecular dynamics simulations are performed close to the spinodal to compute bubble nucleation rates. From these simulations, the kinetic prefactor of the hybrid nucleation theory is estimated, whereas the nucleation barrier is calculated from density gradient theory. This enables the extrapolation of molecular simulation data to the whole metastable range including technically relevant densities. The results are tested against available experimental data and found to be in good agreement. The new method does not suffer from typical deficiencies of classical nucleation theory concerning the thermodynamic barrier at the spinodal and the bubble size dependence of surface tension, which is typically neglected in classical nucleation theory. In addition, the density in the center of critical bubbles and their surface tension is determined as a function of their radius. The usual linear Tolman correction to the capillarity approximation is found to be invalid.

  3. Study of homogeneous bubble nucleation in liquid carbon dioxide by a hybrid approach combining molecular dynamics simulation and density gradient theory

    Science.gov (United States)

    Langenbach, K.; Heilig, M.; Horsch, M.; Hasse, H.

    2018-03-01

    A new method for predicting homogeneous bubble nucleation rates of pure compounds from vapor-liquid equilibrium (VLE) data is presented. It combines molecular dynamics simulation on the one side with density gradient theory using an equation of state (EOS) on the other. The new method is applied here to predict bubble nucleation rates in metastable liquid carbon dioxide (CO2). The molecular model of CO2 is taken from previous work of our group. PC-SAFT is used as an EOS. The consistency between the molecular model and the EOS is achieved by adjusting the PC-SAFT parameters to VLE data obtained from the molecular model. The influence parameter of density gradient theory is fitted to the surface tension of the molecular model. Massively parallel molecular dynamics simulations are performed close to the spinodal to compute bubble nucleation rates. From these simulations, the kinetic prefactor of the hybrid nucleation theory is estimated, whereas the nucleation barrier is calculated from density gradient theory. This enables the extrapolation of molecular simulation data to the whole metastable range including technically relevant densities. The results are tested against available experimental data and found to be in good agreement. The new method does not suffer from typical deficiencies of classical nucleation theory concerning the thermodynamic barrier at the spinodal and the bubble size dependence of surface tension, which is typically neglected in classical nucleation theory. In addition, the density in the center of critical bubbles and their surface tension is determined as a function of their radius. The usual linear Tolman correction to the capillarity approximation is found to be invalid.

  4. Emerging Techniques in Stratified Designs and Continuous Gradients for Tissue Engineering of Interfaces

    Science.gov (United States)

    Dormer, Nathan H.; Berkland, Cory J.; Detamore, Michael S.

    2013-01-01

    Interfacial tissue engineering is an emerging branch of regenerative medicine, where engineers are faced with developing methods for the repair of one or many functional tissue systems simultaneously. Early and recent solutions for complex tissue formation have utilized stratified designs, where scaffold formulations are segregated into two or more layers, with discrete changes in physical or chemical properties, mimicking a corresponding number of interfacing tissue types. This method has brought forth promising results, along with a myriad of regenerative techniques. The latest designs, however, are employing “continuous gradients” in properties, where there is no discrete segregation between scaffold layers. This review compares the methods and applications of recent stratified approaches to emerging continuously graded methods. PMID:20411333

  5. Study on the technique for precision measurement of density of SiO_2 foam shells

    International Nuclear Information System (INIS)

    Ma Xiaojun; Gao Dangzhong; Meng Jie

    2013-01-01

    The measuring method based on vertical scanning interference and combined with the relation between refraction index and density of SiO_2 foam shells is introduced, and the relation is analyzed according to formulas of Lorentz-Lorenz and Gladstone-Dale. The experimental result and measuring uncertainty evaluation indicate that the precision measurement of density of low density SiO_2 foam shells can be realized by using the vertical scanning interference technique and combining with Gladstone and Dale analysis method, and the measuring uncertainty is about 5%. (authors)

  6. The Mellin transform technique for the extraction of the gluon density

    International Nuclear Information System (INIS)

    Graudenz, D.

    1995-06-01

    A new method is presented to determine the gluon density in the proton from jet production in deeply inelastic scattering. By using the technique of Mellin transforms not only for the solution of the scale evolution equation of the parton densities but also for the evaluation of scattering cross sections, the gluon density can be extracted in next-to-leading order QCD. The method described in this paper is, however, more general, and can be used in situations where a repeated fast numerical evaluation of scattering cross sections for varying parton distribution functions is required. (orig.)

  7. Measurements of low density, high velocity flow by electron beam fluorescence technique

    International Nuclear Information System (INIS)

    Soga, Takeo; Takanishi, Masaya; Yasuhara, Michiru

    1981-01-01

    A low density chamber with an electron gun system was made for the measurements of low density, high velocity (high Mach number) flow. This apparatus is a continuous running facility. The number density and the rotational temperature in the underexpanding free jet of nitrogen were measured along the axis of the jet by the electron beam fluorescence technique. The measurements were carried out from the vicinity of the exit of the jet to far downstream of the first Mach disk. Rotational nonequilibrium phenomena were observed in the hypersonic flow field as well as in the shock wave (Mach disk). (author)

  8. Radioisotope labeling technique for vapor density measurements of volatile inorganic species

    International Nuclear Information System (INIS)

    Peterson, E.J.; Caird, J.A.; Hessler, J.P.; Hoekstra, H.R.; Williams, C.W.

    1979-01-01

    A new method for complexed metal ion vapor density measurement involving labeling the metal ions of interest with a radioactive isotope is described. The isotope chosen in the present work is unstable and leads to emission of a characteristic γ ray. Thus the γ-counting rate was related to the number density of complexed metal ions in the vapor phase. This technique is applicable to the study of any volatile inorganic species, but in the present study has been used to measure vapor densities of complex species in the TbCl 3 -AlCl 3 system by using tracer 160 Tb. 4 figures, 2 tables

  9. High density of tree-cavities and snags in tropical dry forest of western Mexico raises questions for a latitudinal gradient.

    Directory of Open Access Journals (Sweden)

    Leopoldo Vázquez

    Full Text Available It has been suggested that a latitudinal gradient exists of a low density of snags and high density of naturally-formed tree-cavities in tropical vs. temperate forests, though few cavities may have characteristics suitable for nesting by birds. We determined snag and cavity density, characteristics, and suitability for birds in a tropical dry forest biome of western Mexico, and evaluated whether our data fits the trend of snag and cavity density typically found in tropical moist and wet forests. We established five 0.25-ha transects to survey and measure tree-cavities and snags in each of three vegetation types of deciduous, semi-deciduous, and mono-dominant Piranhea mexicana forest, comprising a total of 3.75 ha. We found a high density of 77 cavities/ha, with 37 cavities suitable for birds/ha, where density, and characteristics of cavities varied significantly among vegetation types. Lowest abundance of cavities occurred in deciduous forest, and these were in smaller trees, at a lower height, and with a narrower entrance diameter. Only 8.6% of cavities were excavated by woodpeckers, and only 11% of cavities were occupied, mainly by arthropods, though 52% of all cavities were unsuitable for birds. We also found a high density of 56 snags/ha, with greatest density in deciduous forest (70 snags/ha, though these were of significantly smaller diameter, and snags of larger diameter were more likely to contain cavities. The Chamela-Cuixmala tropical dry forest had the highest density of snags recorded for any tropical or temperate forest, and while snag density was significantly correlated with mean snag dbh, neither latitude nor mean dbh predicted snag density in ten forest sites. The high spatial aggregation of snag and cavity resources in tropical dry forest may limit their availability, particularly for large-bodied cavity adopters, and highlights the importance of habitat heterogeneity in providing resources for primary and secondary cavity-nesters.

  10. High density of tree-cavities and snags in tropical dry forest of western Mexico raises questions for a latitudinal gradient.

    Science.gov (United States)

    Vázquez, Leopoldo; Renton, Katherine

    2015-01-01

    It has been suggested that a latitudinal gradient exists of a low density of snags and high density of naturally-formed tree-cavities in tropical vs. temperate forests, though few cavities may have characteristics suitable for nesting by birds. We determined snag and cavity density, characteristics, and suitability for birds in a tropical dry forest biome of western Mexico, and evaluated whether our data fits the trend of snag and cavity density typically found in tropical moist and wet forests. We established five 0.25-ha transects to survey and measure tree-cavities and snags in each of three vegetation types of deciduous, semi-deciduous, and mono-dominant Piranhea mexicana forest, comprising a total of 3.75 ha. We found a high density of 77 cavities/ha, with 37 cavities suitable for birds/ha, where density, and characteristics of cavities varied significantly among vegetation types. Lowest abundance of cavities occurred in deciduous forest, and these were in smaller trees, at a lower height, and with a narrower entrance diameter. Only 8.6% of cavities were excavated by woodpeckers, and only 11% of cavities were occupied, mainly by arthropods, though 52% of all cavities were unsuitable for birds. We also found a high density of 56 snags/ha, with greatest density in deciduous forest (70 snags/ha), though these were of significantly smaller diameter, and snags of larger diameter were more likely to contain cavities. The Chamela-Cuixmala tropical dry forest had the highest density of snags recorded for any tropical or temperate forest, and while snag density was significantly correlated with mean snag dbh, neither latitude nor mean dbh predicted snag density in ten forest sites. The high spatial aggregation of snag and cavity resources in tropical dry forest may limit their availability, particularly for large-bodied cavity adopters, and highlights the importance of habitat heterogeneity in providing resources for primary and secondary cavity-nesters.

  11. Measurement of density and humidity of soils using radioactive techniques and its application in civil work

    International Nuclear Information System (INIS)

    Obando, E.; Torres, J.E.; Moreno, N.J.

    1987-01-01

    The purpose of this article is to inform about the applications of radioactive techniques related with the measurement of humidity and density of soils. After a brief introduction which describes the basic equipment the main advantages and applications in relation with the conventional methods in engineering, agriculture and industry, it gives a description of the theory related with the basis of these techniques, such as transmission and detection

  12. Measurement of deuterium density profiles in the H-mode steep gradient region using charge exchange recombination spectroscopy on DIII-D.

    Science.gov (United States)

    Haskey, S R; Grierson, B A; Burrell, K H; Chrystal, C; Groebner, R J; Kaplan, D H; Pablant, N A; Stagner, L

    2016-11-01

    Recent completion of a thirty two channel main-ion (deuterium) charge exchange recombination spectroscopy (CER) diagnostic on the DIII-D tokamak [J. L. Luxon, Nucl. Fusion 42, 614 (2002)] enables detailed comparisons between impurity and main-ion temperature, density, and toroidal rotation. In a H-mode DIII-D discharge, these new measurement capabilities are used to provide the deuterium density profile, demonstrate the importance of profile alignment between Thomson scattering and CER diagnostics, and aid in determining the electron temperature at the separatrix. Sixteen sightlines cover the core of the plasma and another sixteen are densely packed towards the plasma edge, providing high resolution measurements across the pedestal and steep gradient region in H-mode plasmas. Extracting useful physical quantities such as deuterium density is challenging due to multiple photoemission processes. These challenges are overcome using a detailed fitting model and by forward modeling the photoemission using the FIDASIM code, which implements a comprehensive collisional radiative model.

  13. Pancreatin-EDTA treatment affects buoyancy of cells in Cohn fraction V protein density gradients without residual effect on cell size.

    Science.gov (United States)

    Sheridan, J W; Simmons, R J

    1983-12-01

    The buoyancy of suspension-grown Mastocytoma P815 X-2 cells in albumin-rich Cohn fraction V protein (CFVP) density gradients was found to be affected by prior incubation of the cells in pancreatin-EDTA salt solution. Whereas in pH 5.2 CFVP, pancreatin-EDTA treated cells behaved as if of reduced density when compared with the control 'undigested' group, in pH 7.3 CFVP they behaved as if of increased density. By contrast, pancreatin-EDTA treatment had no effect on the buoyancy of mastocytoma cells in polyvinylpyrrolidone-coated colloidal silica (PVP-CS, Percoll T.M.) density gradients of either pH 5.2 or pH 7.3. As cell size determinations failed to reveal alterations in cell size either as a direct result of pancreatin-EDTA treatment or as a combined consequence of such treatment and exposure to CFVP either with or without centrifugation, a mechanism involving a change in cell density other than during the centrifugation process itself seems unlikely. Binding studies employing 125I-CFVP, although indicating that CFVP bound to cells at 4 degrees, failed to reveal a pancreatin-EDTA treatment-related difference in the avidity of this binding. Although the mechanism of the pancreatin-EDTA-induced buoyancy shift in CFVP remains obscure, the absence of such an effect in PVP-CS suggests that the latter cell separation solution may more accurately be used to determine cell density.

  14. Prediction of mercury bioavailability to common carp (Cyprinus carpio L.) using the diffusive gradient in thin film technique.

    Science.gov (United States)

    Pelcová, Pavlína; Vičarová, Petra; Ridošková, Andrea; Dočekalová, Hana; Kopp, Radovan; Mareš, Jan; Poštulková, Eva

    2017-11-01

    The mercury bioaccumulation by common carp (Cyprinus carpio L.) tissues (gills, skin, eyes, scales, muscle, brain, kidneys, liver, and spleen) and the capability of the diffusive gradient in thin film (DGT) technique to predict bioavailability of mercury for individual carp's tissues were evaluated. Carp and DGT units were exposed to increasing concentrations of mercury (Hg 2+ : 0 μg L -1 , 0.5 μg L -1 , 1.5 μg L -1 and 3.0 μg L -1 ) in fish tanks for 14 days. In the uncontaminated fish group, the highest mercury concentration was determined in the muscle tissues and, in fish groups exposed to mercury, the highest mercury concentration was determined in the detoxification (kidneys) and input (gills) organs. A strong and positive correlation between the rate of mercury uptake by the DGT technique and the rate of mercury accumulation by fish tissues (gills, skin, scales, and eyes) was observed. Copyright © 2017 Elsevier Ltd. All rights reserved.

  15. Reduced density gradient as a novel approach for estimating QSAR descriptors, and its application to 1, 4-dihydropyridine derivatives with potential antihypertensive effects.

    Science.gov (United States)

    Jardínez, Christiaan; Vela, Alberto; Cruz-Borbolla, Julián; Alvarez-Mendez, Rodrigo J; Alvarado-Rodríguez, José G

    2016-12-01

    The relationship between the chemical structure and biological activity (log IC 50 ) of 40 derivatives of 1,4-dihydropyridines (DHPs) was studied using density functional theory (DFT) and multiple linear regression analysis methods. With the aim of improving the quantitative structure-activity relationship (QSAR) model, the reduced density gradient s( r) of the optimized equilibrium geometries was used as a descriptor to include weak non-covalent interactions. The QSAR model highlights the correlation between the log IC 50 with highest molecular orbital energy (E HOMO ), molecular volume (V), partition coefficient (log P), non-covalent interactions NCI(H4-G) and the dual descriptor [Δf(r)]. The model yielded values of R 2 =79.57 and Q 2 =69.67 that were validated with the next four internal analytical validations DK=0.076, DQ=-0.006, R P =0.056, and R N =0.000, and the external validation Q 2 boot =64.26. The QSAR model found can be used to estimate biological activity with high reliability in new compounds based on a DHP series. Graphical abstract The good correlation between the log IC 50 with the NCI (H4-G) estimated by the reduced density gradient approach of the DHP derivatives.

  16. Evaluation results on the effectiveness of the corrosion protection system for underground pipelines, using the DC-voltage gradient technique

    Energy Technology Data Exchange (ETDEWEB)

    Ribeiro, Antonio Carlos [Petroquimica Uniao S.A., Santo Andre, SP (Brazil)

    2003-07-01

    A pipeline of diameter 6'' with 17.694 km of extension was evaluated how much to the integrity of its external covering and the effectiveness of the system of cathodic protection, using the method DC-Voltage Gradient. The Cathodic Protection in this pipeline is made by seven rectifiers. The gotten data indicate that the potential pipe-ground registered in some check points to the long one of the pipeline is extremely negative, what has led to a super protection of the pipeline for the CP. This if explains for the great proximity between the anodes and the pipeline. For km had been identified 917 failures with a mean density of 50,1 per Km. Beyond the analysis of the data, this work includes conclusions and recommendations detailed for the repairs of the covering of the pipeline and for improvement of the effectiveness of the CP. One sends regards to a combination of repairs in the covering and reevaluation of the CP, in way to improve the protection level and to assure the reduction of the risk of external corrosion. (author)

  17. Evaluation results on the effectiveness of the corrosion protection system for underground pipelines, using the DC-voltage gradient technique

    Energy Technology Data Exchange (ETDEWEB)

    Ribeiro, Antonio Carlos [Petroquimica Uniao S.A., Santo Andre, SP (Brazil)

    2003-07-01

    A pipeline of diameter 6'' with 17.694 km of extension was evaluated how much to the integrity of its external covering and the effectiveness of the system of cathodic protection, using the method DC-Voltage Gradient. The Cathodic Protection in this pipeline is made by seven rectifiers. The gotten data indicate that the potential pipe-ground registered in some check points to the long one of the pipeline is extremely negative, what has led to a super protection of the pipeline for the CP. This if explains for the great proximity between the anodes and the pipeline. For km had been identified 917 failures with a mean density of 50,1 per Km. Beyond the analysis of the data, this work includes conclusions and recommendations detailed for the repairs of the covering of the pipeline and for improvement of the effectiveness of the CP. One sends regards to a combination of repairs in the covering and reevaluation of the CP, in way to improve the protection level and to assure the reduction of the risk of external corrosion. (author)

  18. Schlieren technique applied to the arc temperature measurement in a high energy density cutting torch

    International Nuclear Information System (INIS)

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

    2010-01-01

    Plasma temperature and radial density profiles of the plasma species in a high energy density cutting arc have been obtained by using a quantitative schlieren technique. A Z-type two-mirror schlieren system was used in this research. Due to its great sensibility such technique allows measuring plasma composition and temperature from the arc axis to the surrounding medium by processing the gray-level contrast values of digital schlieren images recorded at the observation plane for a given position of a transverse knife located at the exit focal plane of the system. The technique has provided a good visualization of the plasma flow emerging from the nozzle and its interactions with the surrounding medium and the anode. The obtained temperature values are in good agreement with those values previously obtained by the authors on the same torch using Langmuir probes.

  19. Methodology for attainment of density and effective atomic number through dual energy technique using microtomographic images

    International Nuclear Information System (INIS)

    Alves, H.; Lima, I.; Lopes, R.T.

    2014-01-01

    Dual energy technique for computerized microtomography shows itself as a promising method for identification of mineralogy on geological samples of heterogeneous composition. It can also assist with differentiating very similar objects regarding the attenuation coefficient, which are usually not separable during image processing and analysis of microtomographic data. Therefore, the development of a feasible and applicable methodology of dual energy in the analysis of microtomographic images was sought. - Highlights: • Dual energy technique is promising for identification of distribution of minerals. • A feasible methodology of dual energy in analysis of tomographic images was sought. • The dual energy technique is efficient for density and atomic number identification. • Simulation showed that the proposed methodology agrees with theoretical data. • Nondestructive characterization of distribution of density and chemical composition

  20. Derivation of general analytic gradient expressions for density-fitted post-Hartree-Fock methods: An efficient implementation for the density-fitted second-order Møller–Plesset perturbation theory

    Energy Technology Data Exchange (ETDEWEB)

    Bozkaya, Uğur, E-mail: ugur.bozkaya@atauni.edu.tr [Department of Chemistry, Atatürk University, Erzurum 25240, Turkey and Department of Chemistry, Middle East Technical University, Ankara 06800 (Turkey)

    2014-09-28

    General analytic gradient expressions (with the frozen-core approximation) are presented for density-fitted post-HF methods. An efficient implementation of frozen-core analytic gradients for the second-order Møller–Plesset perturbation theory (MP2) with the density-fitting (DF) approximation (applying to both reference and correlation energies), which is denoted as DF-MP2, is reported. The DF-MP2 method is applied to a set of alkanes, conjugated dienes, and noncovalent interaction complexes to compare the computational cost of single point analytic gradients with MP2 with the resolution of the identity approach (RI-MP2) [F. Weigend and M. Häser, Theor. Chem. Acc. 97, 331 (1997); R. A. Distasio, R. P. Steele, Y. M. Rhee, Y. Shao, and M. Head-Gordon, J. Comput. Chem. 28, 839 (2007)]. In the RI-MP2 method, the DF approach is used only for the correlation energy. Our results demonstrate that the DF-MP2 method substantially accelerate the RI-MP2 method for analytic gradient computations due to the reduced input/output (I/O) time. Because in the DF-MP2 method the DF approach is used for both reference and correlation energies, the storage of 4-index electron repulsion integrals (ERIs) are avoided, 3-index ERI tensors are employed instead. Further, as in case of integrals, our gradient equation is completely avoid construction or storage of the 4-index two-particle density matrix (TPDM), instead we use 2- and 3-index TPDMs. Hence, the I/O bottleneck of a gradient computation is significantly overcome. Therefore, the cost of the generalized-Fock matrix (GFM), TPDM, solution of Z-vector equations, the back transformation of TPDM, and integral derivatives are substantially reduced when the DF approach is used for the entire energy expression. Further application results show that the DF approach introduce negligible errors for closed-shell reaction energies and equilibrium bond lengths.

  1. Convergent sum of gradient expansion of the kinetic-energy density functional up to the sixth order term using Padé approximant

    Science.gov (United States)

    Sergeev, A.; Alharbi, F. H.; Jovanovic, R.; Kais, S.

    2016-04-01

    The gradient expansion of the kinetic energy density functional, when applied to atoms or finite systems, usually grossly overestimates the energy in the fourth order and generally diverges in the sixth order. We avoid the divergence of the integral by replacing the asymptotic series including the sixth order term in the integrand by a rational function. Padé approximants show moderate improvements in accuracy in comparison with partial sums of the series. The results are discussed for atoms and Hooke’s law model for two-electron atoms.

  2. Comparison of Conjugate Gradient Density Matrix Search and Chebyshev Expansion Methods for Avoiding Diagonalization in Large-Scale Electronic Structure Calculations

    Science.gov (United States)

    Bates, Kevin R.; Daniels, Andrew D.; Scuseria, Gustavo E.

    1998-01-01

    We report a comparison of two linear-scaling methods which avoid the diagonalization bottleneck of traditional electronic structure algorithms. The Chebyshev expansion method (CEM) is implemented for carbon tight-binding calculations of large systems and its memory and timing requirements compared to those of our previously implemented conjugate gradient density matrix search (CG-DMS). Benchmark calculations are carried out on icosahedral fullerenes from C60 to C8640 and the linear scaling memory and CPU requirements of the CEM demonstrated. We show that the CPU requisites of the CEM and CG-DMS are similar for calculations with comparable accuracy.

  3. On the estimation of the current density in space plasmas: Multi- versus single-point techniques

    Science.gov (United States)

    Perri, Silvia; Valentini, Francesco; Sorriso-Valvo, Luca; Reda, Antonio; Malara, Francesco

    2017-06-01

    Thanks to multi-spacecraft mission, it has recently been possible to directly estimate the current density in space plasmas, by using magnetic field time series from four satellites flying in a quasi perfect tetrahedron configuration. The technique developed, commonly called ;curlometer; permits a good estimation of the current density when the magnetic field time series vary linearly in space. This approximation is generally valid for small spacecraft separation. The recent space missions Cluster and Magnetospheric Multiscale (MMS) have provided high resolution measurements with inter-spacecraft separation up to 100 km and 10 km, respectively. The former scale corresponds to the proton gyroradius/ion skin depth in ;typical; solar wind conditions, while the latter to sub-proton scale. However, some works have highlighted an underestimation of the current density via the curlometer technique with respect to the current computed directly from the velocity distribution functions, measured at sub-proton scales resolution with MMS. In this paper we explore the limit of the curlometer technique studying synthetic data sets associated to a cluster of four artificial satellites allowed to fly in a static turbulent field, spanning a wide range of relative separation. This study tries to address the relative importance of measuring plasma moments at very high resolution from a single spacecraft with respect to the multi-spacecraft missions in the current density evaluation.

  4. Desvio da proporção de sexo e da integridade do DNA dos espermatozóides bovinos centrifugados em gradientes de densidade contínuos Alteration of sex ratio and DNA integrity of bovine sperm centrifuged in continuous density gradients

    Directory of Open Access Journals (Sweden)

    Alberto Lopes Gusmão

    2010-03-01

    Full Text Available O objetivo, neste trabalho, foi verificar o desvio da proporção de sexo e a presença de fragmentação do DNA, pela técnica de TUNEL (“In situ terminal deoxinucleotidyl transferase mediated dUTP nick end labeling assay”, em espermatozoides bovinos centrifugados em gradientes de densidade de Percoll ou OptiPrep durante a separação espermática. Doses de sêmen de touros foram descongeladas, e cerca de 40 milhões de espermatozoides foram depositados sobre cada gradiente de densidade compostos por Percoll ou OptiPrep com três camadas entre 1.110g/mL e 1.123g/mL, em tubos de 15mL, em que permaneceram por 24h a 4°C antes da deposição dos espermatozoides. Os tubos foram centrifugados a 500xg por 15min a 22°C. Os sobrenadantes foram aspirados, e os sedimentos, recuperados para verificação da fragmentação do DNA pela técnica de TUNEL. Obteve-se um desvio dos embriões produzidos in vitro para fêmeas no gradiente de Percoll (62% de fêmeas, em relação aos grupos OptiPrep e Controle (47,1 e 48,7% de fêmeas, respectivamente. Não foi detectada fragmentação do DNA dos espermatozoides nas amostras centrifugadas, tanto no gradiente de Percoll quanto de OptiPrep. Dessa forma, foi possível realizar a sexagem espermática, com uma maior porcentagem de espermatozoides X do que o grupo controle, por meio de metodologia mais simples e sem provocar danos ao DNA dos espermatozoides.The objective of the present study was to verify the sex ratio and presence of DNA fragmentation by TUNEL technique (In situ terminal deoxinucleotidyl transferase mediated dUTP nick end labeling assay in bovine spermatozoa centrifuged in density gradients of Percoll or OptiPrep during the sperm separation. Approximately 40 million of frozen/thawed bovine spermatozoa were deposited on each density gradient composed of Percoll or OptiPrep with three layers ranging from 1.110g/mL to 1.123g/mL in polystyrene tubes of 15mL. The tubes were kept at 4°C for 24h before

  5. A one-step separation of human serum high density lipoproteins 2 and 3 by rate-zonal density gradient ultracentrifugation in a swinging bucket rotor

    NARCIS (Netherlands)

    Groot, P.H.E.; Scheek, L.M.; Havekes, L.; Noort, W.L. van; Hooft, F.M. van 't

    1982-01-01

    A method was developed for the separation of the high density lipoprotein subclasses HDL2 and HDL3 from human serum. Six serum samples are fractionated in a single-step ultracentrifugal procedure using the Beckman (SW-40) swinging bucket rotor. The method is based on a difference in flotation rate

  6. Development and evaluation of a diffusive gradients in a thin film technique for measuring ammonium in freshwaters

    DEFF Research Database (Denmark)

    Huang, Jianyin; Bennett, William W.; Welsh, David T.

    2016-01-01

    A new diffusive gradients in a thin film (DGT) technique, using Microlite PrCH cation exchange resin, was developed and evaluated for measuring NH4-N in freshwaters. Microlite PrCH had high uptake (>92.5%) and elution efficiencies (87.2% using 2 mol L-1 NaCl). Mass vs. time validation experiments...... over 24 h demonstrated excellent linearity (R2 ≥ 0.996). PrCH-DGT binding layers had an extremely high intrinsic binding capacity for NH4-N (~3000 μg). NH4-N uptake was quantitative over pH ranges 3.5-8.5 and ionic strength (up to 0.012 mol L-1 as NaCl) typical of freshwater systems. Several cations...... (Na+, K+, Ca2+ and Mg2+) were found to compete with NH4-N for uptake by PrCH-DGT, but NH4-N uptake was quantitative over concentration ranges typical of freshwater (up to 0.012 mol L-1 Na+, 0.006 mol L-1 K+, 0.003 mol L-1 Ca2+ and 0.004 mol L-1 Mg2+). Effective diffusion coefficients determined from...

  7. Renormalization techniques applied to the study of density of states in disordered systems

    International Nuclear Information System (INIS)

    Ramirez Ibanez, J.

    1985-01-01

    A general scheme for real space renormalization of formal scattering theory is presented and applied to the calculation of density of states (DOS) in some finite width systems. This technique is extended in a self-consistent way, to the treatment of disordered and partially ordered chains. Numerical results of moments and DOS are presented in comparison with previous calculations. In addition, a self-consistent theory for the magnetic order problem in a Hubbard chain is derived and a parametric transition is observed. Properties of localization of the electronic states in disordered chains are studied through various decimation averaging techniques and using numerical simulations. (author) [pt

  8. Novel technique of making thin target foil of high density material via rolling method

    Science.gov (United States)

    Gupta, C. K.; Rohilla, Aman; Singh, R. P.; Singh, Gurjot; Chamoli, S. K.

    2018-05-01

    The conventional rolling method fails to yield good quality thin foils of thicknesses less than 2 mg/cm2 for high density materials with Z ≥ 70 (e.g. gold, lead). A special and improved technique has been developed to obtain such low thickness good quality gold foils by rolling method. Using this technique thin gold foils of thickness in the range of 0.850-2.5 mg/cm2 were obtained in the present work. By making use of alcohol during rolling, foils of thickness 1 mg/cm2 can be obtained in shorter time with less effort.

  9. Comparative validation using quantitative real-time PCR (qPCR and conventional PCR of bovine semen centrifuged in continuous density gradient

    Directory of Open Access Journals (Sweden)

    M.V. Resende

    2011-06-01

    Full Text Available The objective of the present study was to determine the sperm enrichment with X-bearing spermatozoa, after one centrifugation in a Percoll or OptiPrep continuous density gradient, using quantitative real-time polymerase chain reaction (qPCR of sperm DNA and resultant in vitro-produced bovine embryos by PCR. Frozen/thawed sperm was layered on density gradients and the tubes were centrifuged. Supernatants were gently aspirated and the sperm recovered from the bottom of the tubes. Cleavage and blastocyst rates were determined through in vitro production of embryos and PCR was performed to identify the embryos' genetic sex. A difference in blastocyst rate was found in the Percoll treatment compared to OptiPrep (P<0.05. The percentage of female embryos in the Percoll and OptiPrep groups was 62.0% and 47.1%, respectively. These results were confirmed by qPCR of spermatozoa DNA and underestimation was seen only in the Percoll group. It was possible to sexing sperm using simple approach.

  10. Error Analysis of a Fractional Time-Stepping Technique for Incompressible Flows with Variable Density

    KAUST Repository

    Guermond, J.-L.; Salgado, Abner J.

    2011-01-01

    In this paper we analyze the convergence properties of a new fractional time-stepping technique for the solution of the variable density incompressible Navier-Stokes equations. The main feature of this method is that, contrary to other existing algorithms, the pressure is determined by just solving one Poisson equation per time step. First-order error estimates are proved, and stability of a formally second-order variant of the method is established. © 2011 Society for Industrial and Applied Mathematics.

  11. 3D-Laser-Scanning Technique Applied to Bulk Density Measurements of Apollo Lunar Samples

    Science.gov (United States)

    Macke, R. J.; Kent, J. J.; Kiefer, W. S.; Britt, D. T.

    2015-01-01

    In order to better interpret gravimetric data from orbiters such as GRAIL and LRO to understand the subsurface composition and structure of the lunar crust, it is import to have a reliable database of the density and porosity of lunar materials. To this end, we have been surveying these physical properties in both lunar meteorites and Apollo lunar samples. To measure porosity, both grain density and bulk density are required. For bulk density, our group has historically utilized sub-mm bead immersion techniques extensively, though several factors have made this technique problematic for our work with Apollo samples. Samples allocated for measurement are often smaller than optimal for the technique, leading to large error bars. Also, for some samples we were required to use pure alumina beads instead of our usual glass beads. The alumina beads were subject to undesirable static effects, producing unreliable results. Other investigators have tested the use of 3d laser scanners on meteorites for measuring bulk volumes. Early work, though promising, was plagued with difficulties including poor response on dark or reflective surfaces, difficulty reproducing sharp edges, and large processing time for producing shape models. Due to progress in technology, however, laser scanners have improved considerably in recent years. We tested this technique on 27 lunar samples in the Apollo collection using a scanner at NASA Johnson Space Center. We found it to be reliable and more precise than beads, with the added benefit that it involves no direct contact with the sample, enabling the study of particularly friable samples for which bead immersion is not possible

  12. Renormalization-group decimation technique for spectra, wave-functions and density of states

    International Nuclear Information System (INIS)

    Wiecko, C.; Roman, E.

    1983-09-01

    The Renormalization Group decimation technique is very useful for problems described by 1-d nearest neighbour tight-binding model with or without translational invariance. We show how spectra, wave-functions and density of states can be calculated with little numerical work from the renormalized coefficients upon iteration. The results of this new procedure are verified using the model of Soukoulis and Economou. (author)

  13. UF6 Density and Mass Flow Measurements for Enrichment Plants using Acoustic Techniques

    Energy Technology Data Exchange (ETDEWEB)

    Good, Morris S.; Smith, Leon E.; Warren, Glen A.; Jones, Anthony M.; Ramuhalli, Pradeep; Roy, Surajit; Moran, Traci L.; Denslow, Kayte M.; Longoni, Gianluca

    2017-09-01

    A key enabling capability for enrichment plant safeguards being considered by the International Atomic Energy Agency (IAEA) is high-accuracy, noninvasive, unattended measurement of UF6 gas density and mass flow rate. Acoustic techniques are currently used to noninvasively monitor gas flow in industrial applications; however, the operating pressures at gaseous centrifuge enrichment plants (GCEPs) are roughly two orders magnitude below the capabilities of commercial instrumentation. Pacific Northwest National Laboratory is refining acoustic techniques for estimating density and mass flow rate of UF6 gas in scenarios typical of GCEPs, with the goal of achieving 1% measurement accuracy. Proof-of-concept laboratory measurements using a surrogate gas for UF6 have demonstrated signatures sensitive to gas density at low operating pressures such as 10–50 Torr, which were observed over the background acoustic interference. Current efforts involve developing a test bed for conducting acoustic measurements on flowing SF6 gas at representative flow rates and pressures to ascertain the viability of conducting gas flow measurements under these conditions. Density and flow measurements will be conducted to support the evaluation. If successful, the approach could enable an unattended, noninvasive approach to measure mass flow in unit header pipes of GCEPs.

  14. A Noncontact Measurement Technique for the Density and Thermal Expansion Coefficient of Solid and Liquid Materials

    Science.gov (United States)

    Chung, Sang K.; Thiessen, David B.; Rhim, Won-Kyu

    1996-01-01

    A noncontact measurement technique for the density and the thermal expansion refractory materials in their molten as well as solid phases is presented. This technique is based on the video image processing of a levitated sample. Experiments were performed using the high-temperature electrostatic levitator (HTESL) at the Jet Propulsion Laboratory in which 2-3 mm diameter samples can be levitated, melted, and radiatively cooled in a vacuum. Due to the axisymmetric nature of the molten samples when levitated in the HTESL, a rather simple digital image analysis can be employed to accurately measure the volumetric change as a function of temperature. Density and the thermal expansion coefficient measurements were made on a pure nickel sample to test the accuracy of the technique in the temperature range of 1045-1565 C. The result for the liquid phase density can be expressed by p = 8.848 + (6.730 x 10(exp -4)) x T (degC) g/cu cm within 0.8% accuracy, and the corresponding thermal expansion coefficient can be expressed by Beta=(9.419 x 10(exp -5)) - (7.165 x 10(exp -9) x T (degC)/K within 0.2% accuracy.

  15. Different elution modes and field programming in gravitational field-flow fractionation: Field programming using density and viscosity gradients

    Czech Academy of Sciences Publication Activity Database

    Plocková, Jana; Chmelík, Josef

    2006-01-01

    Roč. 1118, č. 2 (2006), s. 253-260 ISSN 0021-9673 R&D Projects: GA MZe QD1005 Institutional research plan: CEZ:AV0Z40310501 Keywords : gravitational field flow fractionation * focusing elution mode * carrier liquid density Subject RIV: CB - Analytical Chemistry, Separation Impact factor: 3.554, year: 2006

  16. Simultaneous multipoint measurements of density gradients and temperature in a flame. Progress report, July 1, 1982-January 31, 1983

    International Nuclear Information System (INIS)

    Chang, R.K.; Chu, B.T.; Long, M.B.

    1983-02-01

    An account is given of recent progress in the development of nonintrusive optical diagnostic techniques and the application of these techniques to turbulent combustion systems. The primary focus of the work over the past year has been in: (1) the use of a broadband rotational CARS technique for the measurement of temperature in flames, and (2) the use of spontaneous Raman scattering to simultaneously map out the fuel gas concentration in a turbulent diffusion flame at 2500 points in a plane intersecting the flow. A summary of new results in each of these areas is given

  17. Tracing salmon-derived nutrients and contaminants in freshwater food webs across a pronounced spawner density gradient.

    Science.gov (United States)

    Gregory-Eaves, Irene; Demers, J Marc J; Kimpe, Lynda; Krümmel, Eva M; Macdonald, Robie W; Finney, Bruce P; Blais, Jules M

    2007-06-01

    Many have demonstrated that anadromous Pacific salmon are significant vectors of nutrients from the ocean to freshwaters. Recently. however, it has been recognized that salmon spawners also input significant quantities of contaminants. The objectives of this paper are to delineate the extent to which salmon-derived nutrients are integrated into the freshwater food web using delta(15)N and delta(13)C and to assess the influence of the salmon pathway in the accumulation of contaminants in rainbow trout (Oncorhynchus mykiss). We found that the delta(15)N and delta(13)C of food web components were related positively and significantly to sockeye salmon (Oncorhynchus nerka) spawner density. Contaminant concentrations in rainbow trout also positively and significantly were related to sockeye salmon spawner density. These data suggest that the anadromous salmon nutrient and contaminant pathways are related and significantly impact the contaminant burden of resident fish.

  18. 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.

  19. The application of full spectrum gamma-gamma techniques to density/photoelectric cross section logging

    International Nuclear Information System (INIS)

    Minette, D.C.; Hubner, B.G.; Koudelka, J.C.; Schmidt, M.

    1986-01-01

    The Compensated Z-Densilog instrument is a new full spectrum gamma-gamma logging instrument, measuring the density and photoelectric cross section (Pe) of the formation. This instrument represents an advancement over present instruments in that the observed gamma spectrum is sent to the surface as a full 256-channel spectrum instead of count rates in a few energy gates. This advancement is made possible by the use of high speed digital electronics which are protected from the high temperatures observed downhole by custom-built flasks. In this paper, the new advanced electronics are considered in some detail. This consideration includes a comparison of full spectrum data acquisition with the multiple discriminator window technique, which is the foundation of the ''few gate'' method. Both of these methods are critiqued based upon electronic stability and the information obtained. The full spectrum provided by high speed electronics facilitates a much more sophisticated data analysis. This data analysis, based on phenomenological model of the instrument (Minette, 1984), includes real time compensation for changes in detector gain and crystal resolution. It also includes a ''four-dimensional'' rib-spine plot, which separates the compensation for mudcake density from the compensation for the Pe of the formation and the mudcake. Also included in the software are real time error minimization and real time decision-making techniques. These techniques maximize the sensitivity of the instrument to the density and Pe of the formation and minimize error due to statistical fluctuations. Gain and resolution compensation completes the data analysis. This compensation virtually eliminates density and Pe errors caused by changing gain and resolution

  20. Cell Seeding Densities in Autologous Chondrocyte Implantation Techniques for Cartilage Repair.

    Science.gov (United States)

    Foldager, Casper Bindzus; Gomoll, Andreas H; Lind, Martin; Spector, Myron

    2012-04-01

    Cartilage repair techniques have been among the most intensively investigated treatments in orthopedics for the past decade, and several different treatment modalities are currently available. Despite the extensive research effort within this field, the generation of hyaline cartilage remains a considerable challenge. There are many parameters attendant to each of the cartilage repair techniques that can affect the amount and types of reparative tissue generated in the cartilage defect, and some of the most fundamental of these parameters have yet to be fully investigated. For procedures in which in vitro-cultured autologous chondrocytes are implanted under a periosteal or synthetic membrane cover, or seeded onto a porous membrane or scaffold, little is known about how the number of cells affects the clinical outcome. Few published clinical studies address the cell seeding density that was employed. The principal objective of this review is to provide an overview of the cell seeding densities used in cell-based treatments currently available in the clinic for cartilage repair. Select preclinical studies that have informed the use of specific cell seeding densities in the clinic are also discussed.

  1. Intensity Modulated Proton Therapy for Craniospinal Irradiation: Organ-at-Risk Exposure and a Low-Gradient Junctioning Technique

    International Nuclear Information System (INIS)

    Stoker, Joshua B.; Grant, Jonathan; Zhu, X. Ronald; Pidikiti, Rajesh; Mahajan, Anita; Grosshans, David R.

    2014-01-01

    Purpose: To compare field junction robustness and sparing of organs at risk (OARs) during craniospinal irradiation (CSI) using intensity modulated proton therapy (IMPT) to conventional passively scattered proton therapy (PSPT). Methods and Materials: Ten patients, 5 adult and 5 pediatric patients, previously treated with PSPT-based CSI were selected for comparison. Anterior oblique cranial fields, using a superior couch rotation, and posterior spinal fields were used for IMPT planning. To facilitate low-gradient field junctioning along the spine, the inverse-planning IMPT technique was divided into 3 stages. Dose indices describing target coverage and normal tissue dose, in silico error modeling, and film dosimetry were used to assess plan quality. Results: Field junction robustness along the spine was improved using the staged IMPT planning technique, reducing the worst case impact of a 4-mm setup error from 25% in PSPT to <5% of prescription dose. This was verified by film dosimetry for clinical delivery. Exclusive of thyroid dose in adult patients, IMPT plans demonstrated sparing of organs at risk as good or better than PSPT. Coverage of the cribriform plate for pediatric (V95% [percentage of volume of the target receiving at least 95% of the prescribed dose]; 87 ± 11 vs 92 ± 7) and adult (V95%; 94 ± 7 vs 100 ± 1) patients and the clinical target in pediatric (V95%; 98 ± 2 vs 100 ± 1) and adult (V95%; 100 ± 1 vs 100 ± 1) patients for PSPT and IMPT plans, respectively, were comparable or improved. For adult patients, IMPT target dose inhomogeneity was increased, as determined by heterogeneity index (HI) and inhomogeneity coefficient (IC). IMPT lowered maximum spinal cord dose, improved spinal dose homogeneity, and reduced exposure to other OARs. Conclusions: IMPT has the potential to improve CSI plan quality and the homogeneity of intrafractional dose at match lines. The IMPT approach developed may also simplify treatments and reduce

  2. Irradiance gradients

    International Nuclear Information System (INIS)

    Ward, G.J.; Heckbert, P.S.; Technische Hogeschool Delft

    1992-04-01

    A new method for improving the accuracy of a diffuse interreflection calculation is introduced in a ray tracing context. The information from a hemispherical sampling of the luminous environment is interpreted in a new way to predict the change in irradiance as a function of position and surface orientation. The additional computation involved is modest and the benefit is substantial. An improved interpolation of irradiance resulting from the gradient calculation produces smoother, more accurate renderings. This result is achieved through better utilization of ray samples rather than additional samples or alternate sampling strategies. Thus, the technique is applicable to a variety of global illumination algorithms that use hemicubes or Monte Carlo sampling techniques

  3. A Centrifugal Microfluidic Platform That Separates Whole Blood Samples into Multiple Removable Fractions Due to Several Discrete but Continuous Density Gradient Sections

    Science.gov (United States)

    Moen, Scott T.; Hatcher, Christopher L.; Singh, Anup K.

    2016-01-01

    We present a miniaturized centrifugal platform that uses density centrifugation for separation and analysis of biological components in small volume samples (~5 μL). We demonstrate the ability to enrich leukocytes for on-disk visualization via microscopy, as well as recovery of viable cells from each of the gradient partitions. In addition, we simplified the traditional Modified Wright-Giemsa staining by decreasing the time, volume, and expertise involved in the procedure. From a whole blood sample, we were able to extract 95.15% of leukocytes while excluding 99.8% of red blood cells. This platform has great potential in both medical diagnostics and research applications as it offers a simpler, automated, and inexpensive method for biological sample separation, analysis, and downstream culturing. PMID:27054764

  4. Forward calculation of gravity and its gradient using polyhedral representation of density interfaces: an application of spherical or ellipsoidal topographic gravity effect

    Science.gov (United States)

    Zhang, Yi; Chen, Chao

    2018-02-01

    A density interface modeling method using polyhedral representation is proposed to construct 3-D models of spherical or ellipsoidal interfaces such as the terrain surface of the Earth and applied to forward calculating gravity effect of topography and bathymetry for regional or global applications. The method utilizes triangular facets to fit undulation of the target interface. The model maintains almost equal accuracy and resolution at different locations of the globe. Meanwhile, the exterior gravitational field of the model, including its gravity and gravity gradients, is obtained simultaneously using analytic solutions. Additionally, considering the effect of distant relief, an adaptive computation process is introduced to reduce the computational burden. Then features and errors of the method are analyzed. Subsequently, the method is applied to an area for the ellipsoidal Bouguer shell correction as an example and the result is compared to existing methods, which shows our method provides high accuracy and great computational efficiency. Suggestions for further developments and conclusions are drawn at last.

  5. Density-Gradient Mediated Band Extraction of Leukocytes from Whole Blood Using Centrifugo-Pneumatic Siphon Valving on Centrifugal Microfluidic Discs

    Science.gov (United States)

    Kearney, Sinéad M.; Kilcawley, Niamh A.; Early, Philip L.; Glynn, Macdara T.; Ducrée, Jens

    2016-01-01

    Here we present retrieval of Peripheral Blood Mononuclear Cells by density-gradient medium based centrifugation for subsequent analysis of the leukocytes on an integrated microfluidic “Lab-on-a-Disc” cartridge. Isolation of white blood cells constitutes a critical sample preparation step for many bioassays. Centrifugo-pneumatic siphon valves are particularly suited for blood processing as they function without need of surface treatment and are ‘low-pass’, i.e., holding at high centrifugation speeds and opening upon reduction of the spin rate. Both ‘hydrostatically’ and ‘hydrodynamically’ triggered centrifugo-pneumatic siphon valving schemes are presented. Firstly, the geometry of the pneumatic chamber of hydrostatically primed centrifugo-pneumatic siphon valves is optimised to enable smooth and uniform layering of blood on top of the density-gradient medium; this feature proves to be key for efficient Peripheral Blood Mononuclear Cell extraction. A theoretical analysis of hydrostatically primed valves is also presented which determines the optimum priming pressure for the individual valves. Next, ‘dual siphon’ configurations for both hydrostatically and hydrodynamically primed centrifugo-pneumatic siphon valves are introduced; here plasma and Peripheral Blood Mononuclear Cells are extracted through a distinct siphon valve. This work represents a first step towards enabling on disc multi-parameter analysis. Finally, the efficiency of Peripheral Blood Mononuclear Cells extraction in these structures is characterised using a simplified design. A microfluidic mechanism, which we termed phase switching, is identified which affects the efficiency of Peripheral Blood Mononuclear Cell extraction. PMID:27167376

  6. Efficient enrichment of hepatic cancer stem-like cells from a primary rat HCC model via a density gradient centrifugation-centered method.

    Directory of Open Access Journals (Sweden)

    Wei-hui Liu

    Full Text Available BACKGROUND: Because few definitive markers are available for hepatic cancer stem cells (HCSCs, based on physical rather than immunochemical properties, we applied a novel method to enrich HCSCs. METHODOLOGY: After hepatic tumor cells (HTCs were first isolated from diethylinitrosamine-induced F344 rat HCC model using percoll discontinuous gradient centrifugation (PDGC and purified via differential trypsinization and differential attachment (DTDA, they were separated into four fractions using percoll continuous gradient centrifugation (PCGC and sequentially designated as fractions I-IV (FI-IV. Morphological characteristics, mRNA and protein levels of stem cell markers, proliferative abilities, induced differentiation, in vitro migratory capacities, in vitro chemo-resistant capacities, and in vivo malignant capacities were determined for the cells of each fraction. FINDINGS: As the density of cells increased, 22.18%, 11.62%, 4.73% and 61.47% of primary cultured HTCs were segregated in FI-FIV, respectively. The cells from FIII (density between 1.041 and 1.062 g/ml displayed a higher nuclear-cytoplasmic ratio and fewer organelles and expressed higher levels of stem cell markers (AFP, EpCAM and CD133 than cells from other fractions (P<0.01. Additionally, in vitro, the cells from FIII showed a greater capacity to self-renew, differentiate into mature HTCs, transit across membranes, close scratches, and carry resistance to chemotherapy than did cells from any other fraction; in vivo, injection of only 1×10(4 cells from FIII could generate tumors not only in subcutaneous tissue but also in the livers of nude mice. CONCLUSIONS: Through our novel method, HCSC-like cells were successfully enriched in FIII. This study will greatly contribute to two important areas of biological interest: CSC isolation and HCC therapy.

  7. Development of nonintrusive, scatter-independent techniques for measurement of liquid density inside dense sprays

    Science.gov (United States)

    Hartfield, Roy

    1994-01-01

    A nonintrusive optical technique for measuring the liquid density in sprays used to simulate LOX injector flows is under development. This manuscript is a report on work toward that development which is currently in progress. The technique is a scatter-independent, absorption-based approach which depends on the numerical inversion of a collection of absorption profiles. For the case in which visible radiation passes through liquid-gas interfaces so numerous in sprays, substantial reductions and alterations in the signal result from scattering even in the absence of absorption. To avoid these problems, X-Rays will be used as the absorbed radiation. The experimental process is simulated by integrating the absorption spectrum for a known distribution, adding instrument noise to this 'measurement', creating a projection from the 'measurement', filtering the projection, inverting the projection, and comparing the results with the original prescribed distribution.

  8. Remote sensing and spatial statistical techniques for modelling Ommatissus lybicus (Hemiptera: Tropiduchidae) habitat and population densities.

    Science.gov (United States)

    Al-Kindi, Khalifa M; Kwan, Paul; R Andrew, Nigel; Welch, Mitchell

    2017-01-01

    In order to understand the distribution and prevalence of Ommatissus lybicus (Hemiptera: Tropiduchidae) as well as analyse their current biographical patterns and predict their future spread, comprehensive and detailed information on the environmental, climatic, and agricultural practices are essential. The spatial analytical techniques such as Remote Sensing and Spatial Statistics Tools, can help detect and model spatial links and correlations between the presence, absence and density of O. lybicus in response to climatic, environmental, and human factors. The main objective of this paper is to review remote sensing and relevant analytical techniques that can be applied in mapping and modelling the habitat and population density of O. lybicus . An exhaustive search of related literature revealed that there are very limited studies linking location-based infestation levels of pests like the O. lybicus with climatic, environmental, and human practice related variables. This review also highlights the accumulated knowledge and addresses the gaps in this area of research. Furthermore, it makes recommendations for future studies, and gives suggestions on monitoring and surveillance methods in designing both local and regional level integrated pest management strategies of palm tree and other affected cultivated crops.

  9. Remote sensing and spatial statistical techniques for modelling Ommatissus lybicus (Hemiptera: Tropiduchidae habitat and population densities

    Directory of Open Access Journals (Sweden)

    Khalifa M. Al-Kindi

    2017-08-01

    Full Text Available In order to understand the distribution and prevalence of Ommatissus lybicus (Hemiptera: Tropiduchidae as well as analyse their current biographical patterns and predict their future spread, comprehensive and detailed information on the environmental, climatic, and agricultural practices are essential. The spatial analytical techniques such as Remote Sensing and Spatial Statistics Tools, can help detect and model spatial links and correlations between the presence, absence and density of O. lybicus in response to climatic, environmental, and human factors. The main objective of this paper is to review remote sensing and relevant analytical techniques that can be applied in mapping and modelling the habitat and population density of O. lybicus. An exhaustive search of related literature revealed that there are very limited studies linking location-based infestation levels of pests like the O. lybicus with climatic, environmental, and human practice related variables. This review also highlights the accumulated knowledge and addresses the gaps in this area of research. Furthermore, it makes recommendations for future studies, and gives suggestions on monitoring and surveillance methods in designing both local and regional level integrated pest management strategies of palm tree and other affected cultivated crops.

  10. Alpha particle density and energy distributions in tandem mirrors using Monte-Carlo techniques

    International Nuclear Information System (INIS)

    Kerns, J.A.

    1986-05-01

    We have simulated the alpha thermalization process using a Monte-Carlo technique, in which the alpha guiding center is followed between simulated collisions and Spitzer's collision model is used for the alpha-plasma interaction. Monte-Carlo techniques are used to determine the alpha radial birth position, the alpha particle position at a collision, and the angle scatter and dispersion at a collision. The plasma is modeled as a hot reacting core, surrounded by a cold halo plasma (T approx.50 eV). Alpha orbits that intersect the halo lose 90% of their energy to the halo electrons because of the halo drag, which is ten times greater than the drag in the core. The uneven drag across the alpha orbit also produces an outward, radial, guiding center drift. This drag drift is dependent on the plasma density and temperature radial profiles. We have modeled these profiles and have specifically studied a single-scale-length model, in which the density scale length (r/sub pD/) equals the temperature scale length (r/sub pT/), and a two-scale-length model, in which r/sub pD//r/sub pT/ = 1.1

  11. Fat-suppressed three-dimensional fast spoiled gradient-recalled echo imaging: a modified FS 3D SPGR technique for assessment of patellofemoral joint chondromalacia.

    Science.gov (United States)

    Wang, S F; Cheng, H C; Chang, C Y

    1999-01-01

    Fast fat-suppressed (FS) three-dimensional (3D) spoiled gradient-recalled echo (SPGR) imaging of 64 articular cartilage regions in 16 patellofemoral joints was evaluated to assess its feasibility in diagnosing patellofemoral chondromalacia. It demonstrated good correlation with arthroscopic reports and took about half of the examination time that FS 3D SPGR did. This modified, faster technique has the potential to diagnose patellofemoral chondromalacia with shorter examination time than FS 3D SPGR did.

  12. Nonlinear electronic excitations in crystalline solids using meta-generalized gradient approximation and hybrid functional in time-dependent density functional theory

    Energy Technology Data Exchange (ETDEWEB)

    Sato, Shunsuke A. [Graduate School of Pure and Applied Sciences, University of Tsukuba, Tsukuba 305-8571 (Japan); Taniguchi, Yasutaka [Center for Computational Science, University of Tsukuba, Tsukuba 305-8571 (Japan); Department of Medical and General Sciences, Nihon Institute of Medical Science, 1276 Shimogawara, Moroyama-Machi, Iruma-Gun, Saitama 350-0435 (Japan); Shinohara, Yasushi [Max Planck Institute of Microstructure Physics, 06120 Halle (Germany); Yabana, Kazuhiro [Graduate School of Pure and Applied Sciences, University of Tsukuba, Tsukuba 305-8571 (Japan); Center for Computational Science, University of Tsukuba, Tsukuba 305-8571 (Japan)

    2015-12-14

    We develop methods to calculate electron dynamics in crystalline solids in real-time time-dependent density functional theory employing exchange-correlation potentials which reproduce band gap energies of dielectrics; a meta-generalized gradient approximation was proposed by Tran and Blaha [Phys. Rev. Lett. 102, 226401 (2009)] (TBm-BJ) and a hybrid functional was proposed by Heyd, Scuseria, and Ernzerhof [J. Chem. Phys. 118, 8207 (2003)] (HSE). In time evolution calculations employing the TB-mBJ potential, we have found it necessary to adopt the predictor-corrector step for a stable time evolution. We have developed a method to evaluate electronic excitation energy without referring to the energy functional which is unknown for the TB-mBJ potential. For the HSE functional, we have developed a method for the operation of the Fock-like term in Fourier space to facilitate efficient use of massive parallel computers equipped with graphic processing units. We compare electronic excitations in silicon and germanium induced by femtosecond laser pulses using the TB-mBJ, HSE, and a simple local density approximation (LDA). At low laser intensities, electronic excitations are found to be sensitive to the band gap energy: they are close to each other using TB-mBJ and HSE and are much smaller in LDA. At high laser intensities close to the damage threshold, electronic excitation energies do not differ much among the three cases.

  13. A Simple Density with Distance Based Initial Seed Selection Technique for K Means Algorithm

    Directory of Open Access Journals (Sweden)

    Sajidha Syed Azimuddin

    2017-01-01

    Full Text Available Open issues with respect to K means algorithm are identifying the number of clusters, initial seed concept selection, clustering tendency, handling empty clusters, identifying outliers etc. In this paper we propose a novel and a simple technique considering both density and distance of the concepts in a dataset to identify initial seed concepts for clustering. Many authors have proposed different techniques to identify initial seed concepts; but our method ensures that the initial seed concepts are chosen from different clusters that are to be generated by the clustering solution. The hallmark of our algorithm is that it is a single pass algorithm that does not require any extra parameters to be estimated. Further, our seed concepts are one among the actual concepts and not the mean of representative concepts as is the case in many other algorithms. We have implemented our proposed algorithm and compared the results with the interval based technique of Fouad Khan. We see that our method outperforms the interval based method. We have also compared our method with the original random K means and K Means++ algorithms.

  14. Consolidation of titanium matrix composites to maximum density by different hot pressing techniques

    International Nuclear Information System (INIS)

    Montealegre Melendez, I.; Neubauer, E.; Danninger, H.

    2010-01-01

    In this present work, TiMMCs were manufactured through conventional and inductive hot pressing techniques. The starting materials were two titanium based powders as metal matrices, and two types of reinforcements, carbon nanofibres and nano-micro-boron particles. After several manufacturing runs with varying parameters, especially, optimized hot pressing parameters, the titanium compacts were characterized. Density and hardness measurements, chemical analyses and microstructural studies were conducted. The two objectives of this work were achieved. On one hand the influence, in the properties of TiMMCs, of the starting materials as matrix powder and reinforcements was determined. Higher content of impurities from the starting materials affected the hardness and the microstructure of the composites, independently of the manufacturing process. On another hand, the study of variations of the manufacturing process as temperature of consolidation and soaking time was reported. Higher densification was obtained at higher consolidation temperature; however, reaction between the matrix and the carbonaceous reinforcement was detected.

  15. Performance evaluation of drip-fertigated cotton grown under different plant densities using nuclear techniques

    International Nuclear Information System (INIS)

    Janat, M.; Kalhout, A.

    2007-04-01

    Field experiment was conducted over two growing seasons to assess different planting densities of cotton variety Aleppo 118 (71.000, 57.000, 48.000, 41.000, 33.500 plants /ha), and two irrigation systems; one irrigation line per one planting row and one irrigation line per two planting rows. Nitrogen fertilizer (120 kg N/ha) as Urea (46% N) was injected through the irrigation system in six equally split applications. A labeled area (1.0 m 2 ) was established for the labeled sub plots and labeled Urea was applied to the labeled sub plots in the same manner as for unlabeled N fertilizer. Irrigation scheduling was accomplished using the direct method of neutron scattering technique. Irrigation was determined when the soil moisture content in the active root depth reached almost 80% of the field capacity. The amount of water applied for one line / one row were 6738 and 9149 m 3 /ha, whereas, for one line/two rows were 7489 and 12653 m 3 / ha for the two growing seasons 2004 and 2005 respectively. The objectives of the experiment were to evaluate the effect of different planting densities and two irrigation system on cotton yield, lint properties, dry matter yield, N-uptake, chlorophyll content and leaf area. The experimental design was randomized block design with 6 replications for each irrigation method. Results revealed that no significant differences between all different plant densities were recorded for all growth parameters tested in this study such as seed cotton yield, dry matter yield, lint properties, chlorophyll content and leaf area.(author)

  16. Comparison of volatility function technique for risk-neutral densities estimation

    Science.gov (United States)

    Bahaludin, Hafizah; Abdullah, Mimi Hafizah

    2017-08-01

    Volatility function technique by using interpolation approach plays an important role in extracting the risk-neutral density (RND) of options. The aim of this study is to compare the performances of two interpolation approaches namely smoothing spline and fourth order polynomial in extracting the RND. The implied volatility of options with respect to strike prices/delta are interpolated to obtain a well behaved density. The statistical analysis and forecast accuracy are tested using moments of distribution. The difference between the first moment of distribution and the price of underlying asset at maturity is used as an input to analyze forecast accuracy. RNDs are extracted from the Dow Jones Industrial Average (DJIA) index options with a one month constant maturity for the period from January 2011 until December 2015. The empirical results suggest that the estimation of RND using a fourth order polynomial is more appropriate to be used compared to a smoothing spline in which the fourth order polynomial gives the lowest mean square error (MSE). The results can be used to help market participants capture market expectations of the future developments of the underlying asset.

  17. Measurement techniques for AGR circulators in a full-density rig

    International Nuclear Information System (INIS)

    Watson, I.; Wilson, R.R.

    1977-01-01

    Safety and reliability are the most important factors of a nuclear power plant. This applies in particular to the circulators used to drive the high-density CO 2 around the reactor core and boiler circuits. Under operating conditions, very high sound-pressure levels are generated which could excite components and cause possible fatigue failures. Failures of this type were experienced on the original axial blowers for the Hinkley 'A' Magnox reactor and, following this, a stringent test plan was specified for the AGR circulators. The present paper describes some of the techniques used to measure strain, sound and vibration on circulators in a full-density rig. This rig reproduces the actual reactor working conditions of 300 0 C and 4.1 MN m -2 with gas velocities up to 120 m s -1 . Under these conditions sound-pressure levels of up to 172 dB are generated. This programme of circulator testing has continued for the past 10 years. During this period many obstacles and difficulties were encountered. Some of these problems, together with the solutions found, are discussed. (author)

  18. Applications of Low Density Flow Techniques and Catalytic Recombination at the Johnson Space Center

    Science.gov (United States)

    Scott, Carl D.

    2000-01-01

    The talk presents a brief background on defInitions of catalysis and effects associated with chemically nonequilibrium and low-density flows of aerospace interest. Applications of catalytic recombination on surfaces in dissociated flow are given, including aero heating on reentry spacecraft thermal protection surfaces and reflection of plume flow on pressure distributions associated with the space station. Examples include aero heating predictions for the X-38 test vehicle, the inlet of a proposed gas-sampling probe used in high enthalpy test facilities, and a parabolic body at angle of attack. The effect of accommodation coefficients on thruster induced pressure distributions is also included. Examples of tools used include simple aero heating formulas based on boundary layer solutions, an engineering approximation that uses axisymmetric viscous shock layer flow to simulate full three dimensional flow, full computational fluid dynamics, and direct simulation Monte-Carlo calculations. Methods of determining catalytic recombination rates in arc jet flow are discus ed. An area of catalysis not fully understood is the formation of single-wall carbon nanotubes (SWNT) with gas phase or nano-size metal particles. The Johnson Space Center is making SWNTs using both a laser ablation technique and an electric arc vaporization technique.

  19. Calorific value of Prosopis africana and Balanites aegyptiaca wood: Relationships with tree growth, wood density and rainfall gradients in the West African Sahel

    Energy Technology Data Exchange (ETDEWEB)

    Montes, Carmen Sotelo; Weber, John C. [World Agroforestry Centre (ICRAF), Sahel Office, B.P. E 5118 Bamako (Mali); Silva, Dimas Agostinho da; Bolzon de Muniz, Graciela Ines [Universidade Federal do Parana (UFPR), Av. Lothario Meissner, 900, CEP.: 80270-170-Curitiba (Brazil); Garcia, Rosilei A. [Universidade Federal Rural do Rio de Janeiro (UFRRJ), Instituto de Florestas, Departamento de Produtos Florestais, BR 465, km 07, 23890-000, Seropedica, Rio de Janeiro (Brazil)

    2011-01-15

    Prosopis africana and Balanites aegyptiaca are native tree species in the West African Sahel and provide wood for fuel, construction and other essential products. A provenance/progeny test of each species was established at one relatively dry site in Niger, and evaluated at 13 years. Gross calorific value of the wood was determined for a random sample of trees in each test: gross CV and CVm{sup 3} = gross calorific value in MJ kg{sup -1} and MJ m{sup -3}, respectively. The major objectives were to determine if gross CV was positively correlated with wood density and tree growth, and if gross CV and/or CVm{sup 3} varied with rainfall gradients in the sample region. Provenances were grouped into a drier and more humid zone, and correlations were computed among all trees and separately in each zone. Results indicated that gross CV was not significantly correlated with density in either species. Gross CV was positively correlated with growth of P. africana (but not B. aegyptiaca) only in the drier zone. Gross CVm{sup 3} was positively correlated with growth of both species, and the correlations were stronger in the drier zone. Multiple regressions with provenance latitude, longitude and elevation indicated that provenance means for gross CV increased, in general, from the drier to the more humid zones. Regressions with gross CVm{sup 3} were not significant. Results are compared with earlier research reports from the provenance/progeny tests and with other tropical hardwood species; and practical implications are presented for tree improvement and conservation programs in the region. (author)

  20. [A thermodynamic study on bovine spermatozoa by microcalorimetry after Percoll density-gradient centrifugation - experimental probe of its utility in andrology].

    Science.gov (United States)

    Fischer, C; Scherfer-Brähler, V; Müller-Schlösser, F; Schröder-Printzen, I; Weidner, W

    2007-05-01

    Microcalorimetric measurements can be used for recording exothermic or endothermic summation effects of a great variety of biological processes. The aim of the present study was to examine the usefullness of the microcalorimetry method to characterise the biological activity of spermatozoa. The heat flow of bovine fresh sperm as well as cryosperm samples were measured after Percoll density-gradient centrifugation in a 4-channel microcalorimeter. Various calibration times, volumes of samples and sperm concentrations were tested and analysed. Sperm concentration was recorded by a computer-assisted, computer-aided software system method (CASA). Using a calibration time of 15 minutes, the heat signal of the fresh and cryosperm samples showed a characteristic peak after 39.5 min and 38.1 min (mean), respectively, with a significant correlation to sample volume and sperm concentration (p < 0.05). For obtaining the best results, a sample volume of 1 ml and a sperm concentration of more than 50 x 10 (6)/mL was used. With microcalorimetric measurements the biological activity of spermatozoa could be recorded for reproducible results, thus opening the way to an automatised ejaculate analysis in the future. More investigations are necessary to correlate microcalorimetric parameters with semen function.

  1. Zinc phthalocyanine thin film and chemical analyte interaction studies by density functional theory and vibrational techniques

    International Nuclear Information System (INIS)

    Saini, G S S; Singh, Sukhwinder; Kumar, Ranjan; Tripathi, S K; Kaur, Sarvpreet; Sathe, Vasant

    2009-01-01

    Thin films of zinc phthalocyanine have been deposited on KBr and glass substrates by the thermal evaporation method and characterized by the x-ray diffraction, optical, infrared and Raman techniques. The observed x-ray diffraction and infrared absorption spectra of as-deposited thin films suggest the presence of an α crystalline phase. Infrared and Raman spectra of thin films after exposure to vapours of ammonia and methanol have also been recorded. Shifts in the position of some IR and Raman bands in the spectra of exposed films have been observed. Some bands also show changes in their intensity on exposure. Increased charge on the phthalocyanine ring and out-of-plane distortion of the core due to interaction between zinc phthalocyanine and vapour molecules involving the fifth coordination site of the central metal ion may be responsible for the band shifts. Changes in the intensity of bands are interpreted in terms of the lowering of molecular symmetry from D 4h to C 4v due to doming of the core. Molecular parameters and Mulliken atomic charges of zinc phthalocyanine and its complexes with methanol and ammonia have been calculated from density functional theory. The binding energy of the complexes have also been calculated. Calculated values of the energy for different complexes suggest that axially coordinated vapour molecules form the most stable complex. Calculated Mulliken atomic charges show net charge transfer from vapour molecules to the phthalocyanine ring for the most stable complex.

  2. Rev1, Rev3, or Rev7 siRNA Abolishes Ultraviolet Light-Induced Translesion Replication in HeLa Cells: A Comprehensive Study Using Alkaline Sucrose Density Gradient Sedimentation

    Directory of Open Access Journals (Sweden)

    Jun Takezawa

    2010-01-01

    Full Text Available When a replicative DNA polymerase stalls upon encountering a lesion on the template strand, it is relieved by other low-processivity polymerase(s, which insert nucleotide(s opposite the lesion, extend by a few nucleotides, and dissociate from the 3′-OH. The replicative polymerase then resumes DNA synthesis. This process, termed translesion replication (TLS or replicative bypass, may involve at least five different polymerases in mammals, although the participating polymerases and their roles have not been entirely characterized. Using siRNAs originally designed and an alkaline sucrose density gradient sedimentation technique, we verified the involvement of several polymerases in ultraviolet (UV light-induced TLS in HeLa cells. First, siRNAs to Rev3 or Rev7 largely abolished UV-TLS, suggesting that these 2 gene products, which comprise Polζ, play a main role in mutagenic TLS. Second, Rev1-targeted siRNA also abrogated UV-TLS, indicating that Rev1 is also indispensable to mutagenic TLS. Third, Polη-targeted siRNA also prevented TLS to a greater extent than our expectations. Forth, although siRNA to Polι had no detectable effect, that to Polκ delayed UV-TLS. To our knowledge, this is the first study reporting apparent evidence for the participation of Polκ in UV-TLS.

  3. Skin-Friction Measurements in An Incompressible Pressure-Gradient Turbulent Boundary Layer. Review of Techniques and Results

    National Research Council Canada - National Science Library

    Kornilov, V

    2002-01-01

    .... However, to define this value accurately, one should have a clear conception of the possibilities and efficiency of application of one or another technique for a special case of body flow around...

  4. Comparison of dynamic dual spin-echo and fast-gradient-echo techniques in the evaluation of cardiac diseases

    International Nuclear Information System (INIS)

    Pettigrew, R.I.; Eisner, R.L.; Groen, J.P.; Baron, M.G.

    1987-01-01

    To determine the relative roles of a dynamic spin-echo method and a fast acquisition with multiphase excitations (FAME) technique, ten patients with myocardial infarction (MI), five with myocardial masses, and five healthy patients were studied with both methods. The dynamic dual-spin-echo (DSE) technique allows acquisition of each of seven sections at 14 cardiac phases in 20 minutes. Wall motion abnormalities were seen equally well with both techniques, but FAME usually required a shorter study time (10 minutes). DSE, however, was superior for evaluating cardiac masses and provided superior wall blood contrast. Thus, these techniques are complementary, and both are now a routine part of the authors' study of cardiac patients

  5. Sperm quality after swim up and density gradient centrifugation sperm preparation with supplementation of alpha lipoic acid (ALA): A preliminary study

    Science.gov (United States)

    Lestari, Silvia W.; Lestari, Sarah H.; Pujianto, Dwi A.

    2018-02-01

    Intra uterine insemination (IUI) as one of the treatment for infertility, persists low success rate. A factor that contributes to the unsuccessful of IUI is sperm preparation, performed through Swim-up (SU) and Density Gradient Centrifugation (DGC) methods. Furthermore, studies have shown that Alpha Lipoic Acid (ALA) is a potent antioxidant that could enhance the sperm motility and protect the DNA integrity of the sperm [1]. This study is aimed to re-evaluate the efficiency of the DGC and SU methods in selecting sperm before being transferred for IUI by the supplementation of ALA based on the sperm DNA integrity. Semen samples were obtained from 13 men from partners of women who are infertile (normozoospermia) and underwent IUI. Semen analysis based on the guideline of World Health Organization (WHO) 2010 was performed to measure the sperm motility and velocity, before and after sperm preparation. Then, samples were incubated with Alpha Lipoic Acid (ALA) in 0.625 mg (ALA 1), 1.25 mg (ALA 2) and 2.5 mg (ALA 3). The Sperm Chromatin Dispersion (SCD) test was performed to evaluate the sperm DNA Fragmentation Index (DFI). The percentage of motile sperm was higher in prepared sperm (post-DGC and post-SU) than in whole semen. Furthermore, the percentage of motile sperm was higher in post-DGC compared to post-SU. The level of DFI after the supplementation of ALA was decreased in prepared sperm compared to the whole semen. ALA was proved capable to select the better sperm quality with decreased sperm DNA fragmentation of prepared sperm in the all of DFI category.

  6. Effects of gradient encoding and number of signal averages on fractional anisotropy and fiber density index in vivo at 1.5 tesla.

    Science.gov (United States)

    Widjaja, E; Mahmoodabadi, S Z; Rea, D; Moineddin, R; Vidarsson, L; Nilsson, D

    2009-01-01

    Tensor estimation can be improved by increasing the number of gradient directions (NGD) or increasing the number of signal averages (NSA), but at a cost of increased scan time. To evaluate the effects of NGD and NSA on fractional anisotropy (FA) and fiber density index (FDI) in vivo. Ten healthy adults were scanned on a 1.5T system using nine different diffusion tensor sequences. Combinations of 7 NGD, 15 NGD, and 25 NGD with 1 NSA, 2 NSA, and 3 NSA were used, with scan times varying from 2 to 18 min. Regions of interest (ROIs) were placed in the internal capsules, middle cerebellar peduncles, and splenium of the corpus callosum, and FA and FDI were calculated. Analysis of variance was used to assess whether there was a difference in FA and FDI of different combinations of NGD and NSA. There was no significant difference in FA of different combinations of NGD and NSA of the ROIs (P>0.005). There was a significant difference in FDI between 7 NGD/1 NSA and 25 NGD/3 NSA in all three ROIs (PNSA, 25 NGD/1 NSA, and 25 NGD/2 NSA and 25 NGD/3 NSA in all ROIs (P>0.005). We have not found any significant difference in FA with varying NGD and NSA in vivo in areas with relatively high anisotropy. However, lower NGD resulted in reduced FDI in vivo. With larger NGD, NSA has less influence on FDI. The optimal sequence among the nine sequences tested with the shortest scan time was 25 NGD/1 NSA.

  7. New diffusive gradients in a thin film technique for measuring inorganic arsenic and selenium(IV) using a titanium dioxide based adsorbent

    DEFF Research Database (Denmark)

    Bennett, William W.; Teasdale, Peter R.; Panther, Jared G.

    2010-01-01

    A new diffusive gradients in a thin film (DGT) technique, using a titanium dioxide based adsorbent (Metsorb), has been developed and evaluated for the determination of dissolved inorganic arsenic and selenium. AsIII, AsV, and SeIV were found to be quantitatively accumulated by the adsorbent (uptake...... measurement of inorganic arsenic. Reproducibility of the technique in field deployments was good (relative standard deviation arsenic and 0.05 μg L-1 for SeIV. The results of this study confirmed that DGT with Metsorb was a reliable...... and robust method for the measurement of inorganic arsenic and the selective measurement of SeIV within useful limits of accuracy....

  8. Application of the denaturing gradient gel electrophoresis (DGGE) technique as an efficient diagnostic tool for ciliate communities in soil.

    Science.gov (United States)

    Jousset, Alexandre; Lara, Enrique; Nikolausz, Marcell; Harms, Hauke; Chatzinotas, Antonis

    2010-02-01

    Ciliates (or Ciliophora) are ubiquitous organisms which can be widely used as bioindicators in ecosystems exposed to anthropogenic and industrial influences. The evaluation of the environmental impact on soil ciliate communities with methods relying on morphology-based identification may be hampered by the large number of samples usually required for a statistically supported, reliable conclusion. Cultivation-independent molecular-biological diagnostic tools are a promising alternative to greatly simplify and accelerate such studies. In this present work a ciliate-specific fingerprint method based on the amplification of a phylogenetic marker gene (i.e. the 18S ribosomal RNA gene) with subsequent analysis by denaturing gradient gel electrophoresis (DGGE) was developed and used to monitor community shifts in a polycyclic aromatic hydrocarbon (PAH) polluted soil. The semi-nested approach generated ciliate-specific amplification products from all soil samples and allowed to distinguish community profiles from a PAH-polluted and a non-polluted control soil. Subsequent sequence analysis of excised bands provided evidence that polluted soil samples are dominated by organisms belonging to the class Colpodea. The general DGGE approach presented in this study might thus in principle serve as a fast and reproducible diagnostic tool, complementing and facilitating future ecological and ecotoxicological monitoring of ciliates in polluted habitats. Copyright 2009 Elsevier B.V. All rights reserved.

  9. Determination of bone mineral density in the third lumbar vertebral body using photon absorptiometry techniques

    International Nuclear Information System (INIS)

    Swanpalmer, Janos; Kullenberg, Ragnar; Hansson, Tommy

    1998-01-01

    Dual-photon absorptiometry and triple-energy X-ray absorptiometry were used to investigate the total bone mineral content and density as well as the trabecular bone mineral density in the third lumbar vertebral body. Both anteroposterior (AP) and lateral (LAT) measurements were performed. By combining the two projections it was found that the mean trabecular bone mineral density for all 202 subjects included in the study was 52% (SD±20%) of the total bone mineral density in the third lumbar vertebral body. The mean trabecular bone mineral density as a fraction of the total vertebral body bone mineral density decreased as a function of age. The relative annual change in this fraction differed between males and females. It was also found that neither trabecular nor total bone mineral density differed significantly between male and female subjects aged 25-35 years, and bone mineral density (BMD), expressed in g/cm 3 , showed no correlation to subject height, body weight or body mass index (BMI). Male and female individuals showed different rates of change of trabecular bone mineral density with age

  10. Diffusive gradient in thin films technique for assessment of cadmium and copper bioaccessibility to radish (Raphanus sativus)

    Czech Academy of Sciences Publication Activity Database

    Dočekalová, H.; Škarpa, P.; Dočekal, Bohumil

    2015-01-01

    Roč. 134, March (2015), s. 153-157 ISSN 0039-9140 R&D Projects: GA ČR GAP503/10/2002 Institutional support: RVO:68081715 Keywords : radish * cadmium * copper * DGT technique * bioaccesibility Subject RIV: CB - Analytical Chemistry, Separation Impact factor: 4.035, year: 2015

  11. SU-E-T-470: Importance of HU-Mass Density Calibration Technique in Proton Pencil Beam Dose Calculation

    Energy Technology Data Exchange (ETDEWEB)

    Penfold, S; Miller, A [University of Adelaide, Adelaide, SA (Australia)

    2015-06-15

    Purpose: Stoichiometric calibration of Hounsfield Units (HUs) for conversion to proton relative stopping powers (RStPs) is vital for accurate dose calculation in proton therapy. However proton dose distributions are not only dependent on RStP, but also on relative scattering power (RScP) of patient tissues. RScP is approximated from material density but a stoichiometric calibration of HU-density tables is commonly neglected. The purpose of this work was to quantify the difference in calculated dose of a commercial TPS when using HU-density tables based on tissue substitute materials and stoichiometric calibrated ICRU tissues. Methods: Two HU-density calibration tables were generated based on scans of the CIRS electron density phantom. The first table was based directly on measured HU and manufacturer quoted density of tissue substitute materials. The second was based on the same CT scan of the CIRS phantom followed by a stoichiometric calibration of ICRU44 tissue materials. The research version of Pinnacle{sup 3} proton therapy was used to compute dose in a patient CT data set utilizing both HU-density tables. Results: The two HU-density tables showed significant differences for bone tissues; the difference increasing with increasing HU. Differences in density calibration table translated to a difference in calculated RScP of −2.5% for ICRU skeletal muscle and 9.2% for ICRU femur. Dose-volume histogram analysis of a parallel opposed proton therapy prostate plan showed that the difference in calculated dose was negligible when using the two different HU-density calibration tables. Conclusion: The impact of HU-density calibration technique on proton therapy dose calculation was assessed. While differences were found in the calculated RScP of bony tissues, the difference in dose distribution for realistic treatment scenarios was found to be insignificant.

  12. Thermal expansion and density measurements of molten and solid materials at high temperatures by the gamma attenuation technique

    International Nuclear Information System (INIS)

    Drotning, W.D.

    1979-05-01

    An apparatus is described for the measurement of the density and thermal expansion of molten materials to 3200 0 K using the gamma attenuation technique. The precision of the experimental technique was analytically examined for both absolute and relative density determinations. Three analytical expressions used to reduce data for liquid density determinations were evaluated for their precision. Each allows use of a different set of input data parameters, which can be chosen based on experimental considerations. Using experimentally reasonable values for the precision of the parameters yields a similar resultant density precision from the three methods, on the order of 0.2%. The analytical method for measurements of the linear thermal expansion of solids by the gamma method is also described. To demonstrate the use of the technique on reasonably well-characterized systems, data are presented for (1) the density and thermal expansion of molten tin, lead, and aluminum to 1300 0 K, (2) the thermal expansion of solid aluminum to the melting point, and (3) the thermal expansion of a low melting point glass through the transition temperature and melting region. The data agree very well with published results using other methods where such published data exist

  13. Parallel-beam correlation technique for measuring density fluctuations in plasmas with strong magnetic shear

    International Nuclear Information System (INIS)

    Jacobson, A.R.

    1981-04-01

    A laser diagnostic scheme is described which facilitates localization of density fluctuations along the line of sight. The method exploits both the generally observed anisotropy of density fluctuations in low-beta plasmas, as well as the twisting of the magnetic field which occurs across the minor diameter of reversed-field pinches, spheromaks, etc. Both interferometric and schlieren variations are discussed

  14. A technique to circumvent lower density water trapping by tide-wells

    Digital Repository Service at National Institute of Oceanography (India)

    Joseph, A.; VijayKumar, K.; Desa, E.S.; Desa, E.; Peshwe, V.B.

    A 3-year study of water density differences inside and outside of a conventional tide-well indicated that the average water density within the well is consistently lower than the external ambient waters. The tide-well at Goa is situated at the mouth...

  15. Investigation of orientation gradients around a hard Laves particle in a warm-rolled Fe3Al-based alloy using a 3D EBSD-FIB technique

    International Nuclear Information System (INIS)

    Konrad, J.; Zaefferer, S.; Raabe, D.

    2006-01-01

    We present a study of the microstructure around a hard Laves particle in a warm-rolled intermetallic Fe 3 Al-based alloy. The experiments are conducted using a system for three-dimensional orientation microscopy (3D electron backscattering diffraction, EBSD). The approach is realized by a combination of a focused ion beam (FIB) unit for serial sectioning with high-resolution field emission scanning electron microscopy with EBSD. We observe the formation of steep 3D orientation gradients in the Fe 3 Al matrix around the rigid precipitate which entail in part particle-stimulated nucleation events in the immediate vicinity of the particle. The orientation gradients assume a characteristic pattern around the particle in the transverse plane while revealing an elongated tubular morphology in the rolling direction. However, they do not reveal a characteristic common rotation axis. Recovered areas in the matrix appear both in the transverse and rolling directions around the particle. The work demonstrates that the new 3D EBSD-FIB technique provides a new level of microstructure information that cannot be achieved by conventional 2D-EBSD analysis

  16. Modeling relaxation length and density of acacia mangium wood using gamma - ray attenuation technique

    International Nuclear Information System (INIS)

    Tamer A Tabet; Fauziah Abdul Aziz

    2009-01-01

    Wood density measurement is related to the several factors that influence wood quality. In this paper, density, relaxation length and half-thickness value of eight ages, 3, 5, 7, 10, 11, 13 and 15 year-old of Acacia mangium wood were determined using gamma radiation from 137 Cs source. Results show that Acacia mangium tree of age 3 year has the highest relaxation length of 83.33 cm and least density of 0.43 gcm -3 , while the tree of age 15 year has the least Relaxation length of 28.56 cm and highest density of 0.76 gcm -3 . Results also show that the 3 year-old Acacia mangium wood has the highest half thickness value of 57.75 cm and 15 year-old tree has the least half thickness value of 19.85 cm. Two mathematical models have been developed for the prediction of density, variation with relaxation length and half-thickness value of different age of tree. A good agreement (greater than 85% in most cases) was observed between the measured values and predicted ones. Very good linear correlation was found between measured density and the age of tree (R2 = 0.824), and between estimated density and Acacia mangium tree age (R2 = 0.952). (Author)

  17. Sperm Na+, K+-ATPase and Ca2+-ATPase activity: A preliminary study of comparison of swim up and density gradient centrifugation methods for sperm preparation

    Science.gov (United States)

    Lestari, Silvia W.; Larasati, Manggiasih D.; Asmarinah, Mansur, Indra G.

    2018-02-01

    As one of the treatment for infertility, the success rate of Intrauterine Insemination (IUI) is still relatively low. Several sperm preparation methods, swim-up (SU) and the density-gradient centrifugation (DGC) are frequently used to select for better sperm quality which also contribute to IUI failure. Sperm selection methods mainly separate the motile from the immotile sperm, eliminating the seminal plasma. The sperm motility involves the structure and function of sperm membrane in maintaining the balance of ion transport system which is regulated by the Na+, K+-ATPase, and Ca2+-ATPase enzymes. This study aims to re-evaluate the efficiency of these methods in selecting for sperm before being used for IUI and based the evaluation on sperm Na+,K+-ATPase and Ca2+-ATPase activities. Fourteen infertile men from couples who underwent IUI were involved in this study. The SU and DGC methods were used for the sperm preparation. Semen analysis was performed based on the reference value of World Health Organization (WHO) 2010. After isolating the membrane fraction of sperms, the Na+, K+-ATPase activity was defined as the difference in the released inorganic phosphate (Pi) with and without the existence of 10 mM ouabain in the reaction, while the Ca2+-ATPase was determined as the difference in Pi contents with and without the existence of 55 µm CaCl2. The prepared sperm demonstrated a higher percentage of motile sperm compared to sperm from the whole semen. Additionally, the percentage of motile sperm of post-DGC showed higher result than the sperm from post-SU. The velocity of sperm showed similar pattern with the percentage of motile sperm, in which the velocity of prepared sperm was higher than the sperm from whole semen. Furthermore, the sperm velocity of post-DGC was higher compared to the sperm from post-SU. The Na+, K+-ATPase activity of prepared sperm was higher compared to whole semen, whereas Na+, K+-ATPase activity in the post DGC was higher than post SU. The Ca2

  18. 3D CT cerebral angiography technique using a 320-detector machine with a time–density curve and low contrast medium volume: Comparison with fixed time delay technique

    International Nuclear Information System (INIS)

    Das, K.; Biswas, S.; Roughley, S.; Bhojak, M.; Niven, S.

    2014-01-01

    Aim: To describe a cerebral computed tomography angiography (CTA) technique using a 320-detector CT machine and a small contrast medium volume (35 ml, 15 ml for test bolus). Also, to compare the quality of these images with that of the images acquired using a larger contrast medium volume (90 or 120 ml) and a fixed time delay (FTD) of 18 s using a 16-detector CT machine. Materials and methods: Cerebral CTA images were acquired using a 320-detector machine by synchronizing the scanning time with the time of peak enhancement as determined from the time–density curve (TDC) using a test bolus dose. The quality of CTA images acquired using this technique was compared with that obtained using a FTD of 18 s (by 16-detector CT), retrospectively. Average densities in four different intracranial arteries, overall opacification of arteries, and the degree of venous contamination were graded and compared. Results: Thirty-eight patients were scanned using the TDC technique and 40 patients using the FTD technique. The arterial densities achieved by the TDC technique were higher (significant for supraclinoid and basilar arteries, p < 0.05). The proportion of images deemed as having “good” arterial opacification was 95% for TDC and 90% for FTD. The degree of venous contamination was significantly higher in images produced by the FTD technique (p < 0.001%). Conclusion: Good diagnostic quality CTA images with significant reduction of venous contamination can be achieved with a low contrast medium dose using a 320-detector machine by coupling the time of data acquisition with the time of peak enhancement

  19. Stantardization problems in radioisotopic techniques for measuring rock density and humidity

    International Nuclear Information System (INIS)

    Golubin, O.V.; Pavlov, L.S.

    1977-01-01

    A description of the main technical characteristics is given of radioisotope densimeters and hydrometers taken as a base for the State Standard design for field radioisotope instruments for measuring density and moisture of the soil and rocks

  20. Thermal and optical properties of polycrystalline CdS thin films deposited by the gradient recrystallization and growth (GREG) technique using photoacoustic methods

    International Nuclear Information System (INIS)

    Albor-Aguilera, M.L.; Gonzalez-Trujillo, M.A.; Cruz-Orea, A.; Tufino-Velazquez, M.

    2009-01-01

    In this work we report the study of the thermal and optical properties of polycrystalline CdS thin films deposited by the gradient recrystallization and growth technique. CdS films were grown on pyrex glass substrates. These studies were carried out using an open photoacoustic cell made out of an electret microphone. From X-ray diffraction, atomic force microscope and photoluminescence measurements we observed polycrystalline CdS films with good morphology and crystalline quality. We obtained a thermal diffusivity coefficient of our samples with values ranging from 3.15 to 3.89 x 10 -2 cm 2 /s. For comparison, we measured a value of 1.0 x 10 -2 cm 2 /s for the thermal diffusivity coefficient of a CdS single crystal. We measured an energy gap value of 2.42 eV for our samples by using a photoacoustic spectroscopy system

  1. Sodium magnetic resonance imaging. Development of a 3D radial acquisition technique with optimized k-space sampling density and high SNR-efficiency

    International Nuclear Information System (INIS)

    Nagel, Armin Michael

    2009-01-01

    A 3D radial k-space acquisition technique with homogenous distribution of the sampling density (DA-3D-RAD) is presented. This technique enables short echo times (TE 23 Na-MRI, and provides a high SNR-efficiency. The gradients of the DA-3D-RAD-sequence are designed such that the average sampling density in each spherical shell of k-space is constant. The DA-3D-RAD-sequence provides 34% more SNR than a conventional 3D radial sequence (3D-RAD) if T 2 * -decay is neglected. This SNR-gain is enhanced if T 2 * -decay is present, so a 1.5 to 1.8 fold higher SNR is measured in brain tissue with the DA-3D-RAD-sequence. Simulations and experimental measurements show that the DA-3D-RAD sequence yields a better resolution in the presence of T 2 * -decay and less image artefacts when B 0 -inhomogeneities exist. Using the developed sequence, T 1 -, T 2 * - and Inversion-Recovery- 23 Na-image contrasts were acquired for several organs and 23 Na-relaxation times were measured (brain tissue: T 1 =29.0±0.3 ms; T 2s * ∼4 ms; T 2l * ∼31 ms; cerebrospinal fluid: T 1 =58.1±0.6 ms; T 2 * =55±3 ms (B 0 =3 T)). T 1 - und T 2 * -relaxation times of cerebrospinal fluid are independent of the selected magnetic field strength (B0 = 3T/7 T), whereas the relaxation times of brain tissue increase with field strength. Furthermore, 23 Na-signals of oedemata were suppressed in patients and thus signals from different tissue compartments were selectively measured. (orig.)

  2. Uranium aqueous speciation in the vicinity of the former uranium mining sites using the diffusive gradients in thin films and ultrafiltration techniques.

    Science.gov (United States)

    Drozdzak, Jagoda; Leermakers, Martine; Gao, Yue; Elskens, Marc; Phrommavanh, Vannapha; Descostes, Michael

    2016-03-24

    The performance of the Diffusive Gradients in Thin films (DGT) technique with Chelex(®)-100, Metsorb™ and Diphonix(®) as binding phases was evaluated in the vicinity of the former uranium mining sites of Chardon and L'Ecarpière (Loire-Atlantique department in western France). This is the first time that the DGT technique with three different binding agents was employed for the aqueous U determination in the context of uranium mining environments. The fractionation and speciation of uranium were investigated using a multi-methodological approach using filtration (0.45 μm, 0.2 μm), ultrafiltration (500 kDa, 100 kDa and 10 kDa) coupled to geochemical speciation modelling (PhreeQC) and the DGT technique. The ultrafiltration data showed that at each sampling point uranium was present mostly in the 10 kDa truly dissolved fraction and the geochemical modelling speciation calculations indicated that U speciation was markedly predominated by CaUO2(CO3)3(2-). In natural waters, no significant difference was observed in terms of U uptake between Chelex(®)-100 and Metsorb™, while similar or inferior U uptake was observed on Diphonix(®) resin. In turn, at mining influenced sampling spots, the U accumulation on DGT-Diphonix(®) was higher than on DGT-Chelex(®)-100 and DGT-Metsorb™, probably because their performance was disturbed by the extreme composition of the mining waters. The use of Diphonix(®) resin leads to a significant advance in the application and development of the DGT technique for determination of U in mining influenced environments. This investigation demonstrated that such multi-technique approach provides a better picture of U speciation and enables to assess more accurately the potentially bioavailable U pool. Copyright © 2016 Elsevier B.V. All rights reserved.

  3. Uranium aqueous speciation in the vicinity of the former uranium mining sites using the diffusive gradients in thin films and ultrafiltration techniques

    Energy Technology Data Exchange (ETDEWEB)

    Drozdzak, Jagoda, E-mail: jdrozdza@vub.ac.be [Analytical, Environmental and Geochemistry (AMGC), Vrije Universiteit Brussels (VUB), Pleinlaan 2, 1050 Brussels (Belgium); Leermakers, Martine; Gao, Yue; Elskens, Marc [Analytical, Environmental and Geochemistry (AMGC), Vrije Universiteit Brussels (VUB), Pleinlaan 2, 1050 Brussels (Belgium); Phrommavanh, Vannapha; Descostes, Michael [AREVA Mines – R& D Dpt., Tour AREVA, 1 Place Jean Millier, 92084 Paris La Défense (France)

    2016-03-24

    The performance of the Diffusive Gradients in Thin films (DGT) technique with Chelex{sup ®}-100, Metsorb™ and Diphonix{sup ®} as binding phases was evaluated in the vicinity of the former uranium mining sites of Chardon and L'Ecarpière (Loire-Atlantique department in western France). This is the first time that the DGT technique with three different binding agents was employed for the aqueous U determination in the context of uranium mining environments. The fractionation and speciation of uranium were investigated using a multi-methodological approach using filtration (0.45 μm, 0.2 μm), ultrafiltration (500 kDa, 100 kDa and 10 kDa) coupled to geochemical speciation modelling (PhreeQC) and the DGT technique. The ultrafiltration data showed that at each sampling point uranium was present mostly in the 10 kDa truly dissolved fraction and the geochemical modelling speciation calculations indicated that U speciation was markedly predominated by CaUO{sub 2}(CO{sub 3}){sub 3}{sup 2−}. In natural waters, no significant difference was observed in terms of U uptake between Chelex{sup ®}-100 and Metsorb™, while similar or inferior U uptake was observed on Diphonix{sup ®} resin. In turn, at mining influenced sampling spots, the U accumulation on DGT-Diphonix{sup ®} was higher than on DGT-Chelex{sup ®}-100 and DGT-Metsorb™, probably because their performance was disturbed by the extreme composition of the mining waters. The use of Diphonix{sup ®} resin leads to a significant advance in the application and development of the DGT technique for determination of U in mining influenced environments. This investigation demonstrated that such multi-technique approach provides a better picture of U speciation and enables to assess more accurately the potentially bioavailable U pool. - Highlights: • The applicability of the DGT technique in the vicinity of former uranium mining sites was evaluated. • The binding selectivity order of the binding phase is

  4. Novel analysis technique for measuring edge density fluctuation profiles with reflectometry in the Large Helical Device

    Science.gov (United States)

    Creely, A. J.; Ida, K.; Yoshinuma, M.; Tokuzawa, T.; Tsujimura, T.; Akiyama, T.; Sakamoto, R.; Emoto, M.; Tanaka, K.; Michael, C. A.

    2017-07-01

    A new method for measuring density fluctuation profiles near the edge of plasmas in the Large Helical Device (LHD) has been developed utilizing reflectometry combined with pellet-induced fast density scans. Reflectometer cutoff location was calculated by proportionally scaling the cutoff location calculated with fast far infrared laser interferometer (FIR) density profiles to match the slower time resolution results of the ray-tracing code LHD-GAUSS. Plasma velocity profile peaks generated with this reflectometer mapping were checked against velocity measurements made with charge exchange spectroscopy (CXS) and were found to agree within experimental uncertainty once diagnostic differences were accounted for. Measured density fluctuation profiles were found to peak strongly near the edge of the plasma, as is the case in most tokamaks. These measurements can be used in the future to inform inversion methods of phase contrast imaging (PCI) measurements. This result was confirmed with both a fixed frequency reflectometer and calibrated data from a multi-frequency comb reflectometer, and this method was applied successfully to a series of discharges. The full width at half maximum of the turbulence layer near the edge of the plasma was found to be only 1.5-3 cm on a series of LHD discharges, less than 5% of the normalized minor radius.

  5. Density-controllable nonvolatile memory devices having metal nanocrystals through chemical synthesis and assembled by spin-coating technique

    International Nuclear Information System (INIS)

    Wang Guangli; Chen Yubin; Shi Yi; Pu Lin; Pan Lijia; Zhang Rong; Zheng Youdou

    2010-01-01

    A novel two-step method is employed, for the first time, to fabricate nonvolatile memory devices that have metal nanocrystals. First, size-averaged Au nanocrystals are synthesized chemically; second, they are assembled into memory devices by a spin-coating technique at room temperature. This attractive approach makes it possible to tailor the diameter and control the density of nanocrystals individually. In addition, processes at room temperature prevent Au diffusion, which is a main concern for the application of metal nanocrystal-based memory. The experimental results, both the morphology characterization and the electrical measurements, reveal that there is an optimum density of nanocrystal monolayer to balance between long data retention and a large hysteresis memory window. At the same time, density-controllable devices could also feed the preferential emphasis on either memory window or retention time. All these facts confirm the advantages and novelty of our two-step method. (semiconductor devices)

  6. Differences in below-ground bud bank density and composition along a climatic gradient in the temperate steppe of northern China

    Czech Academy of Sciences Publication Activity Database

    Qian, J.; Wang, Z.; Klimešová, Jitka; Lü, X.; Kuang, W.; Liu, Z.; Han, X.

    2017-01-01

    Roč. 120, č. 5 (2017), s. 755-764 ISSN 0305-7364 R&D Projects: GA ČR GB14-36079G Institutional support: RVO:67985939 Keywords : Bud Bank * Precipitation gradient * Stepic vegetation Subject RIV: EH - Ecology, Behaviour OBOR OECD: Ecology Impact factor: 4.041, year: 2016

  7. Mercury Distribution in the Deûle River (Northern France) Measured by the Diffusive Gradients in Thin Films Technique and Conventional Methods.

    Science.gov (United States)

    Diviš, Pavel; Kadlecová, Milada; Ouddane, Baghdad

    2016-05-01

    The distribution of mercury in surface water and in sediment from Deûle River in Northern France was studied by application of conventional sampling methods and by diffusive gradients in thin films technique (DGT). Concentration of total dissolved mercury in surface water was 20.8 ± 0.8 ng l(-1). The particulate mercury concentration was 6.2 ± 0.6 µg g(-1). The particulate mercury was accumulated in sediment (9.9 ± 2.3 mg kg(-1)), and it was transformed by methylating bacteria to methylmercury, mainly in the first 2-cm layer of the sediment. Total dissolved concentration of mercury in sediment pore water obtained by application of centrifugation extraction was 17.6 ± 4.1 ng l(-1), and it was comparable with total dissolved pore water mercury concentration measured by DGT probe containing Duolite GT-73 resin gel (18.2 ± 4.3 ng l(-1)), taking the sediment heterogeneity and different principles of the applied methods into account. By application of two DGT probes with different resin gels specific for mercury, it was found that approximately 30% of total dissolved mercury in sediment pore water was present in labile forms easy available for biota. The resolution of mercury DGT depth profiles was 0.5 cm, which allows, unlike conventional techniques, to study the connection of the geochemical cycle of mercury with geochemical cycles of iron and manganese.

  8. Differentiation between grade 3 and grade 4 articular cartilage defects of the knee: Fat-suppressed proton density-weighted versus fat-suppressed three-dimensional gradient-echo MRI

    Energy Technology Data Exchange (ETDEWEB)

    Lee, So Yeon; Jee, Won-Hee; Kim, Sun Ki (Dept. of Radiology, Seoul St Mary' s Hospital, Catholic Univ. of Korea, Seoul (Korea)), e-mail: whjee@catholic.ac.kr; Koh, In-Jun (Dept. of Joint Reconstruction Center, Seoul National Univ. Bundang Hospital, Seoul (Korea)); Kim, Jung-Man (Dept. of Orthopedic Surgery, Seoul St Mary' s Hospital, Catholic Univ. of Korea, Seoul (Korea))

    2010-05-15

    Background: Fat-suppressed (FS) proton density (PD)-weighted magnetic resonance imaging (MRI) and FS three-dimensional (3D) gradient-echo imaging such as spoiled gradient-recalled (SPGR) sequence have been established as accurate methods for detecting articular cartilage defects. Purpose: To retrospectively compare the diagnostic efficacy between FS PD-weighted and FS 3D gradient-echo MRI for differentiating between grade 3 and grade 4 cartilage defects of the knee with arthroscopy as the standard of reference. Material and Methods: Twenty-one patients who had grade 3 or 4 cartilage defects in medial femoral condyle at arthroscopy and knee MRI were included in this study: grade 3, >50% cartilage defects; grade 4, full thickness cartilage defects exposed to the bone. Sagittal FS PD-weighted MR images and FS 3D gradient-echo images with 1.5 T MR images were independently graded for the cartilage abnormalities of medial femoral condyle by two musculoskeletal radiologists. Statistical analysis was performed by Fisher's exact test. Inter-observer agreement in grading of cartilage was assessed using ? coefficients. Results: Arthroscopy revealed grade 3 defects in 17 patients and grade 4 defects in 4 patients in medial femoral condyles. For FS 3D gradient-echo images grade 3 defects were graded as grade 3 (n=15) and grade 4 (n=2), and all grade 4 defects (n=4) were correctly graded. However, for FS PD-weighted MR images all grade 3 defects were misinterpreted as grade 1 (n=1) and grade 4 (n=16), whereas all grade 4 defects (n=4) were correctly graded. FS 3D gradient-echo MRI could differentiate grade 3 from grade 4 defects (P=0.003), whereas FS PD-weighted imaging could not (P=1.0). Inter-observer agreement was substantial (?=0.70) for grading of cartilage using FS PD-weighted imaging, whereas it was moderate (?=0.46) using FS 3D gradient-echo imaging. Conclusion: FS 3D gradient-echo MRI is more helpful for differentiating between grade 3 and grade 4 cartilage

  9. Prediction of Five Softwood Paper Properties from its Density using Support Vector Machine Regression Techniques

    Directory of Open Access Journals (Sweden)

    Esperanza García-Gonzalo

    2016-01-01

    Full Text Available Predicting paper properties based on a limited number of measured variables can be an important tool for the industry. Mathematical models were developed to predict mechanical and optical properties from the corresponding paper density for some softwood papers using support vector machine regression with the Radial Basis Function Kernel. A dataset of different properties of paper handsheets produced from pulps of pine (Pinus pinaster and P. sylvestris and cypress species (Cupressus lusitanica, C. sempervirens, and C. arizonica beaten at 1000, 4000, and 7000 revolutions was used. The results show that it is possible to obtain good models (with high coefficient of determination with two variables: the numerical variable density and the categorical variable species.

  10. Complex Langevin simulation of QCD at finite density and low temperature using the deformation technique

    Science.gov (United States)

    Nagata, Keitro; Nishimura, Jun; Shimasaki, Shinji

    2018-03-01

    We study QCD at finite density and low temperature by using the complex Langevin method. We employ the gauge cooling to control the unitarity norm and intro-duce a deformation parameter in the Dirac operator to avoid the singular-drift problem. The reliability of the obtained results are judged by the probability distribution of the magnitude of the drift term. By making extrapolations with respect to the deformation parameter using only the reliable results, we obtain results for the original system. We perform simulations on a 43 × 8 lattice and show that our method works well even in the region where the reweighing method fails due to the severe sign problem. As a result we observe a delayed onset of the baryon number density as compared with the phase-quenched model, which is a clear sign of the Silver Blaze phenomenon.

  11. Comparison of automated ribosomal intergenic spacer analysis (ARISA) and denaturing gradient gel electrophoresis (DGGE) techniques for analysing the influence of diet on ruminal bacterial diversity.

    Science.gov (United States)

    Saro, Cristina; Molina-Alcaide, Eduarda; Abecia, Leticia; Ranilla, María José; Carro, María Dolores

    2018-04-01

    The objective of this study was to compare the automated ribosomal intergenic spacer analysis (ARISA) and the denaturing gradient gel electrophoresis (DGGE) techniques for analysing the effects of diet on diversity in bacterial pellets isolated from the liquid (liquid-associated bacteria (LAB)) and solid (solid-associated bacteria (SAB)) phase of the rumen. The four experimental diets contained forage to concentrate ratios of 70:30 or 30:70 and had either alfalfa hay or grass hay as forage. Four rumen-fistulated animals (two sheep and two goats) received the diets in a Latin square design. Bacterial pellets (LAB and SAB) were isolated at 2 h post-feeding for DNA extraction and analysed by ARISA and DGGE. The number of peaks in individual samples ranged from 48 to 99 for LAB and from 41 to 95 for SAB with ARISA, and values of DGGE-bands ranged from 27 to 50 for LAB and from 18 to 45 for SAB. The LAB samples from high concentrate-fed animals tended (p forage-fed animals with ARISA, but no differences were identified with DGGE. The SAB samples from high concentrate-fed animals had lower (p forage diets with ARISA, but only a trend was noticed for these parameters with DGGE (p forage type on LAB diversity was detected by any technique. In this study, ARISA detected some changes in ruminal bacterial communities that were not detected by DGGE, and therefore ARISA was considered more appropriate for assessing bacterial diversity of ruminal bacterial pellets. The results highlight the impact of the fingerprinting technique used to draw conclusions on dietary factors affecting bacterial diversity in ruminal bacterial pellets.

  12. Amorphous and liquid samples structure and density measurements at high pressure - high temperature using diffraction and imaging techniques

    Science.gov (United States)

    Guignot, N.; King, A.; Clark, A. N.; Perrillat, J. P.; Boulard, E.; Morard, G.; Deslandes, J. P.; Itié, J. P.; Ritter, X.; Sanchez-Valle, C.

    2016-12-01

    Determination of the density and structure of liquids such as iron alloys, silicates and carbonates is a key to understand deep Earth structure and dynamics. X-ray diffraction provided by large synchrotron facilities gives excellent results as long as the signal scattered from the sample can be isolated from its environment. Different techniques already exist; we present here the implementation and the first results given by the combined angle- and energy-dispersive structural analysis and refinement (CAESAR) technique introduced by Wang et al. in 2004, that has never been used in this context. It has several advantages in the study of liquids: 1/ the standard energy-dispersive technique (EDX), fast and compatible with large multi-anvil presses frames, is used for fast analysis free of signal pollution from the sample environment 2/ some limitations of the EDX technique (homogeneity of the sample, low resolution) are irrelevant in the case of liquid signals, others (wrong intensities, escape peaks artifacts, background subtraction) are solved by the CAESAR technique 3/ high Q data (up to 15 A-1 and more) can be obtained in a few hours (usually less than 2). We present here the facilities available on the PSICHE beamline (SOLEIL synchrotron, France) and a few results obtained using a Paris-Edinburgh (PE) press and a 1200 tons load capacity multi-anvil press with a (100) DIA compression module. X-ray microtomography, used in conjunction with a PE press featuring rotating anvils (RotoPEc, Philippe et al., 2013) is also very effective, by simply measuring the 3D volume of glass or liquid spheres at HPHT, thus providing density. This can be done in conjunction with the CAESAR technique and we illustrate this point. Finally, absorption profiles can be obtained via imaging techniques, providing another independent way to measure the density of these materials. References Y. Wang et al., A new technique for angle-dispersive powder diffraction using an energy

  13. Wood formation from the base to the crown in Pinus radiata: gradients of tracheid wall thickness, wood density, radial growth rate and gene expression

    Science.gov (United States)

    Sheree Cato; Lisa McMillan; Lloyd Donaldson; Thomas Richardson; Craig Echt; Richard Gardner

    2006-01-01

    Wood formation was investigated at five heights along the bole for two unrelated trees of Pinus radiataBoth trees showed clear gradients in wood properties from the base to the crown. Cambial cells at the base of the tree were dividing 3.3-fold slower than those at the crown, while the average thickness of cell walls in wood was highest at the base....

  14. Advantageous use of SSA technique to observe effects of thickness, antioxidant and oxygen in gamma irradiated low density polyethylene

    Energy Technology Data Exchange (ETDEWEB)

    Perez, C.J., E-mail: cjperez@fi.mdp.edu.ar [Research Institute of Material Science and Technology (INTEMA), National Research Council (CONICET), Engineering Faculty, Mar del Plata University, Av. J.B. Justo 4302, 7600 Mar del Plata (Argentina); Failla, M.D. [Planta Piloto de Ingenieria Quimica-PLAPIQUI (UNS-CONICET), Camino ' La Carrindanga' Km 7, 8000 Bahia Blanca (Argentina); Carella, J.M. [Research Institute of Material Science and Technology (INTEMA), National Research Council (CONICET), Engineering Faculty, Mar del Plata University, Av. J.B. Justo 4302, 7600 Mar del Plata (Argentina)

    2012-06-20

    Highlights: Black-Right-Pointing-Pointer Information from successive self-nucleation and annealing technique is analyzed. Black-Right-Pointing-Pointer Oxygen and antioxidants reduce crosslinking efficiency by reaction with free radicals. Black-Right-Pointing-Pointer Recognizable differences are obtained in samples irradiated at different atmospheres. - Abstract: Information obtained from successive self-nucleation and annealing (SSA) technique is analyzed, paying special attention to the observable effects of samples thickness and antioxidant and oxygen concentrations. Molecular structure changes for low density polyethylene (LDPE) samples, irradiated under three different atmospheres for doses between 33 and 222 kGy were analyzed, with emphasis on the changes of longer polymethylene crystallizable lengths. Antioxidant and oxygen concentrations were varied for samples of different thickness to study the effects on degradation. The changes in the molecular structure were followed simultaneously by SSA and Infrared spectroscopy (FTIR) via carbonyl group concentration. Preliminary quantifications of the SSA technique sensitivity are also advanced.

  15. A simple microwave technique for plasma density measurement using frequency modulation

    International Nuclear Information System (INIS)

    Bora, D.; Jayakumar, R.; Vijayashankar, M.K.

    1984-01-01

    A simple method of determining the phase variation unambiguously during microwave interferometric measurement is described. The frequency of the Klystron source is modulated with the help of staircase voltage pulse. The height of each stair is adjusted such that the corresponding phase shift in the test branch with an additional path length is 90 0 . Signals, proportional to cosine and sine of the phase shift due to plasma, can be generated in the same channel and plasma density information can be inferred. The microwave hardware remains the same as in conventional interferometry and the cost of such a scheme is low. (author)

  16. A comparative study on full diagonalization of Hessian matrix and Gradient-only technique to trace out reaction path in doped noble gas clusters using stochastic optimization

    International Nuclear Information System (INIS)

    Biring, Shyamal Kumar; Chaudhury, Pinaki

    2012-01-01

    Highlights: ► Estimation of critical points in Noble-gas clusters. ► Evaluation of first order saddle point or transition states. ► Construction of reaction path for structural change in clusters. ► Use of Monte-Carlo Simulated Annealing to study structural changes. - Abstract: This paper proposes Simulated Annealing based search to locate critical points in mixed noble gas clusters where Ne and Xe are individually doped in Ar-clusters. Using Lennard–Jones (LJ) atomic interaction we try to explore the search process of transformation through Minimum Energy Path (MEP) from one minimum energy geometry to another via first order saddle point on the potential energy surface of the clusters. Here we compare the results based on diagonalization of the full Hessian all through the search and quasi-gradient only technique to search saddle points and construction of reaction path (RP) for three sizes of doped Ar-clusters, (Ar) 19 Ne/Xe,(Ar) 24 Ne/Xe and (Ar) 29 Ne/Xe.

  17. Development and application of the diffusive gradients in thin films technique for the measurement of total dissolved inorganic arsenic in waters

    International Nuclear Information System (INIS)

    Panther, Jared G.; Stillwell, Kathryn P.; Powell, Kipton J.; Downard, Alison J.

    2008-01-01

    The diffusive gradients in thin films (DGT) technique, utilizing an iron-hydroxide adsorbent, has been investigated for the in situ accumulation of total dissolved inorganic As in natural waters. Diffusion coefficients of the inorganic As V and As III species in the polyacrylamide gel were measured using a diffusion cell and DGT devices and a variety of factors that may affect the adsorption of the As species to the iron-hydroxide adsorbent, or the diffusion of the individual As species, were investigated. Under conditions commonly encountered in environmental samples, solution pH and the presence of anions, cations, fulvic acid, Fe III -fulvic acid complexes and colloidal iron-hydroxide were demonstrated not to affect uptake of dissolved As. To evaluate DGT as a method for accumulation and pre-concentration of total dissolved inorganic As in natural waters, DGT was applied to two well waters and a river water that was spiked with As. For each sample, the concentration obtained with use of DGT followed by measurement by hydride generation atomic absorption spectrometry with a Pd modifier (HG-AAS) was compared with the concentration of As measured directly by HG-AAS. The results confirmed that DGT is a reliable method for pre-concentration of total dissolved As

  18. Development and application of the diffusive gradients in thin films technique for the measurement of total dissolved inorganic arsenic in waters

    Energy Technology Data Exchange (ETDEWEB)

    Panther, Jared G.; Stillwell, Kathryn P.; Powell, Kipton J. [Chemistry Department, University of Canterbury, Private Bag 4800, Christchurch (New Zealand); Downard, Alison J. [Chemistry Department, University of Canterbury, Private Bag 4800, Christchurch (New Zealand)], E-mail: alison.downard@canterbury.ac.nz

    2008-08-01

    The diffusive gradients in thin films (DGT) technique, utilizing an iron-hydroxide adsorbent, has been investigated for the in situ accumulation of total dissolved inorganic As in natural waters. Diffusion coefficients of the inorganic As{sup V} and As{sup III} species in the polyacrylamide gel were measured using a diffusion cell and DGT devices and a variety of factors that may affect the adsorption of the As species to the iron-hydroxide adsorbent, or the diffusion of the individual As species, were investigated. Under conditions commonly encountered in environmental samples, solution pH and the presence of anions, cations, fulvic acid, Fe{sup III}-fulvic acid complexes and colloidal iron-hydroxide were demonstrated not to affect uptake of dissolved As. To evaluate DGT as a method for accumulation and pre-concentration of total dissolved inorganic As in natural waters, DGT was applied to two well waters and a river water that was spiked with As. For each sample, the concentration obtained with use of DGT followed by measurement by hydride generation atomic absorption spectrometry with a Pd modifier (HG-AAS) was compared with the concentration of As measured directly by HG-AAS. The results confirmed that DGT is a reliable method for pre-concentration of total dissolved As.

  19. Combining frozen-density embedding with the conductor-like screening model using Lagrangian techniques for response properties.

    Science.gov (United States)

    Schieschke, Nils; Di Remigio, Roberto; Frediani, Luca; Heuser, Johannes; Höfener, Sebastian

    2017-07-15

    We present the explicit derivation of an approach to the multiscale description of molecules in complex environments that combines frozen-density embedding (FDE) with continuum solvation models, in particular the conductor-like screening model (COSMO). FDE provides an explicit atomistic description of molecule-environment interactions at reduced computational cost, while the outer continuum layer accounts for the effect of long-range isotropic electrostatic interactions. Our treatment is based on a variational Lagrangian framework, enabling rigorous derivations of ground- and excited-state response properties. As an example of the flexibility of the theoretical framework, we derive and discuss FDE + COSMO analytical molecular gradients for excited states within the Tamm-Dancoff approximation (TDA) and for ground states within second-order Møller-Plesset perturbation theory (MP2) and a second-order approximate coupled cluster with singles and doubles (CC2). It is shown how this method can be used to describe vertical electronic excitation (VEE) energies and Stokes shifts for uracil in water and carbostyril in dimethyl sulfoxide (DMSO), respectively. In addition, VEEs for some simplified protein models are computed, illustrating the performance of this method when applied to larger systems. The interaction terms between the FDE subsystem densities and the continuum can influence excitation energies up to 0.3 eV and, thus, cannot be neglected for general applications. We find that the net influence of the continuum in presence of the first FDE shell on the excitation energy amounts to about 0.05 eV for the cases investigated. The present work is an important step toward rigorously derived ab initio multilayer and multiscale modeling approaches. © 2017 Wiley Periodicals, Inc. © 2017 Wiley Periodicals, Inc.

  20. Surface Tension of Binary Mixtures Including Polar Components Modeled by the Density Gradient Theory Combined with the PC-SAFT Equation of State

    Czech Academy of Sciences Publication Activity Database

    Vinš, Václav; Planková, Barbora; Hrubý, Jan

    2013-01-01

    Roč. 34, č. 5 (2013), s. 792-812 ISSN 0195-928X R&D Projects: GA AV ČR IAA200760905; GA ČR(CZ) GPP101/11/P046; GA ČR GA101/09/1633 Institutional research plan: CEZ:AV0Z20760514 Institutional support: RVO:61388998 Keywords : chemical polarity * gradient theory * surface tension Subject RIV: BJ - Thermodynamics Impact factor: 0.623, year: 2013 http://www.springerlink.com/openurl.asp?genre=article&id=doi:10.1007/s10765-012-1207-z

  1. Modelling risk of tick exposure in southern Scandinavia using machine learning techniques, satellite imagery, and human population density maps

    DEFF Research Database (Denmark)

    Kjær, Lene Jung; Korslund, L.; Kjelland, V.

    30 sites (forests and meadows) in each of Denmark, southern Norway and south-eastern Sweden. At each site we measured presence/absence of ticks, and used the data obtained along with environmental satellite images to run Boosted Regression Tree machine learning algorithms to predict overall spatial...... and Sweden), areas with high population densities tend to overlap with these zones.Machine learning techniques allow us to predict for larger areas without having to perform extensive sampling all over the region in question, and we were able to produce models and maps with high predictive value. The results...

  2. A model for the electrical double layer combining integral equation techniques with quantum density functional theory

    International Nuclear Information System (INIS)

    Luque, N.B.; Woelki, S.; Henderson, D.; Schmickler, W.

    2011-01-01

    Highlights: · We augment a double-layer model based on integral equations by calculating the interaction parameters with the electrode from quantum density functional theory · Explicit model calculations for Ag(1 1 1) in aqueous solutions give at least qualitatively good results for the particle profiles · Ours is the only method which allows the calculation of capacity-charge characteristics. · We obtain reasonable values for the Helmholtz (inner-layer) capacity. - Abstract: We have complemented the singlet reference interaction site model for the electric double layer by quantum chemical calculations for the interaction of ions and solvents with an electrode. Specific calculations have been performed for an aqueous solution of NaCl in contact with a Ag(1 1 1) electrode. The particle profiles near the electrode show the specific adsorption of Cl - ions, but not of Na + , and are at least in qualitative agreement with those obtained by molecular dynamics. Including the electronic response of the silver surface into the model results in reasonable capacity-charge characteristics.

  3. Density, temperature, and potential fluctuation measurements by the swept Langmuir probe technique in Wendelstein 7-AS

    International Nuclear Information System (INIS)

    Giannone, L.; Balbin, R.; Niedermeyer, H.; Endler, M.; Herre, G.; Hidalgo, C.; Rudyj, A.; Theimer, G.; Verplanke, P.

    1994-01-01

    In the Wendelstein 7-AS stellarator (W7-AS) [Plasma Phys. Controlled Fusion 33, 1591 (1991)], current-voltage characteristics of the Langmuir probe at sweep frequencies in the range 400 kHz to 1 MHz were measured and it was found that the mean and fluctuation values of the ion saturation current, floating potential, and electron temperature were independent of the sweep frequency. A radial scan in the vicinity of the velocity shear layer was performed. The simultaneous sweeping of 3 probe tips showed a statistically significant spatial coherence of the fluctuations in the poloidal direction and a decrease in spatial coherence of the fluctuations with increasing tip separation could be demonstrated. The observation of a change in the propagation direction of fluctuations as the shear layer was crossed and a calculation of the transport spectrum show that the swept probe method is capable of reproducing known results. Apparent temperature fluctuations, due to variations of density and potential during a sweep, are shown by simulations to be only of importance at frequencies above half the Nyquist frequency

  4. Development of liquid film thickness measurement technique by high-density multipoint electrodes method

    International Nuclear Information System (INIS)

    Arai, Takahiro; Furuya, Masahiro; Kanai, Taizo

    2010-01-01

    High-density multipoint electrode method was developed to measure a liquid film thickness transient on a curved surface. The devised method allows us to measure spatial distribution of liquid film with its conductance between electrodes. The sensor was designed and fabricated as a multilayer print circuit board, where electrode pairs were distributed in reticular pattern with narrow interval. In order to measure a lot of electrode pairs at a high sampling rate, signal-processing method used by the wire mesh sensor measurement system was applied. An electrochemical impedance spectrometry concludes that the sampling rate of 1000 slices/s is feasible without signal distortion by electric double layer. The method was validated with two experimental campaigns: (1) a droplet impingement on a flat film and (2) a jet impingement on a rod-shape sensor surface. In the former experiment, a water droplet having 4 mm in diameter impinged onto the 1 mm thick film layer. A visual observation study with high-speed video camera shows after the liquid impingement, the water layer thinning process was clearly demonstrated with the sensor. For the latter experiment, the flexible circuit board was bended to form a cylindrical shape to measure water film on a simulated fuel rod in bundle geometry. A water jet having 3 mm in diameter impinged onto the rod-shape sensor surface. The process of wetting area enlargement on the rod surface was demonstrated in the same manner that the video-frames showed. (author)

  5. Radiation technique in density and strength testing of coniferous structural timber

    International Nuclear Information System (INIS)

    Dzbenski, W.; Krzosek, S.

    1998-01-01

    The control process of intermediate and final wood products manufacturing is more and more frequently assisted by flow detectors. In radiation devices cesium isotope 137 Cs is replaced by less harmful americium 241 Am. Americium 241 Am was used in the measuring device made in The Academy of Mining and Metallurgy in Cracow. The device was applied in Warsaw Agricultural University (SGGW) in research on Polish structural timber. Negative influence of anatomical defects (knots, compression wood, resinasis, slope of grain, decay) was estimated by gammascopy method. Botanical species (pine, spruce), position in a stem (sapwood, heartwood), anatomical direction (radial, tangential) and moisture content were taken into account. The method of determination a critical place in timber were density is the lowest value (what is an obligatory criterion of stress graded structural timber according to EN standards) was developed. The practical implementation of the method can be reached when sawmills producing structural timber (especially for export) will be more interested in using miniaturized isotope densitometers. (author)

  6. FPGA based phase detection technique for electron density measurement in SST-1 tokamak

    International Nuclear Information System (INIS)

    Pramila; Mandaliya, Hitesh; Rajpal, Rachana; Kaur, Rajwinder

    2016-01-01

    A multi-channel signal-conditioning and phase-detection concept is implemented in the prototype design using the high-precision OPAMP, high-speed comparators, high Q filters, high-density FPGA (Field Programmable Gate array), 10 MHz parallel-multiplying DACs (Digital to Analog Converter), etc. The complete digital-logic for the phase-detection is implemented inside the logic cells of FPGA using VHDL code, with high speed 100 MHz clock generated from Digital Clock Manager (DCM), which is used to measure the time elapsed between zero crossings of the two signals coming from reference and probe paths of the diagnostics. The logic is implemented to measure either leading or lagging phase and also to accumulate the total phase difference throughout the shot duration with the maximum value of accumulated phase of 5760 (16 cycles × 360°) degree and a resolution of 3.6 °. A precision high speed and high bandwidth (80 MHz) operational amplifiers are used as the front end-electronics component for conditioning the high-frequency (1 MHz) and low amplitude signal (μV). The hardware detail, implementation concept in FPGA and testing results will be presented in the paper.

  7. Equivalent Energy Density concept: A preliminary reexamination of a technique for equating thermal loads

    International Nuclear Information System (INIS)

    Ryder, E.E.

    1992-08-01

    Historical and projected inventories of spent fuel from commercial light-water nuclear reactors exhibit diverse decay characteristics and ages. This report summarizes a preliminary reexamination of a method for determining equivalent thermal loads for the range of spent fuel expected at a potential underground repository. The method, known at the Equivalent Energy Density (EED) concept, bases its equivalence criteria on the assumption that a given waste will produce worst-case thermomechanical effects equal to worst-case thermomechanical effects produced by a baseline waste, provided that the thermal energy deposited in the host rock over a specified deposition period is the same for both waste descriptions. To test this assumption, temperature histories at representative locations within the host rock were calculated using layouts defined by the EED concept and four deposition periods (20, 50, 100, and 300 years). It was found that the peak temperatures at near-field locations were best matched by the shorter deposition periods of 20 and 50 years. However, due to the sensitivity of the near-field environment to short-term canister-to-canister interactions, caution,should be used when choosing a near-field deposition period. At the location chosen to represent the far-field, a 300-year deposition period provided reasonable correspondence of peak temperature responses for all waste descriptions examined

  8. FPGA based phase detection technique for electron density measurement in SST-1 tokamak

    Energy Technology Data Exchange (ETDEWEB)

    Pramila, E-mail: pramila@ipr.res.in; Mandaliya, Hitesh; Rajpal, Rachana; Kaur, Rajwinder

    2016-11-15

    A multi-channel signal-conditioning and phase-detection concept is implemented in the prototype design using the high-precision OPAMP, high-speed comparators, high Q filters, high-density FPGA (Field Programmable Gate array), 10 MHz parallel-multiplying DACs (Digital to Analog Converter), etc. The complete digital-logic for the phase-detection is implemented inside the logic cells of FPGA using VHDL code, with high speed 100 MHz clock generated from Digital Clock Manager (DCM), which is used to measure the time elapsed between zero crossings of the two signals coming from reference and probe paths of the diagnostics. The logic is implemented to measure either leading or lagging phase and also to accumulate the total phase difference throughout the shot duration with the maximum value of accumulated phase of 5760 (16 cycles × 360°) degree and a resolution of 3.6 °. A precision high speed and high bandwidth (80 MHz) operational amplifiers are used as the front end-electronics component for conditioning the high-frequency (1 MHz) and low amplitude signal (μV). The hardware detail, implementation concept in FPGA and testing results will be presented in the paper.

  9. [Significance of bone mineral density and modern cementing technique for in vitro cement penetration in total shoulder arthroplasty].

    Science.gov (United States)

    Pape, G; Raiss, P; Kleinschmidt, K; Schuld, C; Mohr, G; Loew, M; Rickert, M

    2010-12-01

    Loosening of the glenoid component is one of the major causes of failure in total shoulder arthroplasty. Possible risk factors for loosening of cemented components include an eccentric loading, poor bone quality, inadequate cementing technique and insufficient cement penetration. The application of a modern cementing technique has become an established procedure in total hip arthroplasty. The goal of modern cementing techniques in general is to improve the cement-penetration into the cancellous bone. Modern cementing techniques include the cement vacuum-mixing technique, retrograde filling of the cement under pressurisation and the use of a pulsatile lavage system. The main purpose of this study was to analyse cement penetration into the glenoid bone by using modern cement techniques and to investigate the relationship between the bone mineral density (BMD) and the cement penetration. Furthermore we measured the temperature at the glenoid surface before and after jet-lavage of different patients during total shoulder arthroplasty. It is known that the surrounding temperature of the bone has an effect on the polymerisation of the cement. Data from this experiment provide the temperature setting for the in-vitro study. The glenoid surface temperature was measured in 10 patients with a hand-held non-contact temperature measurement device. The bone mineral density was measured by DEXA. Eight paired cadaver scapulae were allocated (n = 16). Each pair comprised two scapulae from one donor (matched-pair design). Two different glenoid components were used, one with pegs and the other with a keel. The glenoids for the in-vitro study were prepared with the bone compaction technique by the same surgeon in all cases. Pulsatile lavage was used to clean the glenoid of blood and bone fragments. Low viscosity bone cement was applied retrogradely into the glenoid by using a syringe. A constant pressure was applied with a modified force sensor impactor. Micro-computed tomography

  10. Influence of Heartwood on Wood Density and Pulp Properties Explained by Machine Learning Techniques

    Directory of Open Access Journals (Sweden)

    Carla Iglesias

    2017-01-01

    Full Text Available The aim of this work is to develop a tool to predict some pulp properties e.g., pulp yield, Kappa number, ISO brightness (ISO 2470:2008, fiber length and fiber width, using the sapwood and heartwood proportion in the raw-material. For this purpose, Acacia melanoxylon trees were collected from four sites in Portugal. Percentage of sapwood and heartwood, area and the stem eccentricity (in N-S and E-W directions were measured on transversal stem sections of A. melanoxylon R. Br. The relative position of the samples with respect to the total tree height was also considered as an input variable. Different configurations were tested until the maximum correlation coefficient was achieved. A classical mathematical technique (multiple linear regression and machine learning methods (classification and regression trees, multi-layer perceptron and support vector machines were tested. Classification and regression trees (CART was the most accurate model for the prediction of pulp ISO brightness (R = 0.85. The other parameters could be predicted with fair results (R = 0.64–0.75 by CART. Hence, the proportion of heartwood and sapwood is a relevant parameter for pulping and pulp properties, and should be taken as a quality trait when assessing a pulpwood resource.

  11. Gradient Boosting Machines, A Tutorial

    Directory of Open Access Journals (Sweden)

    Alexey eNatekin

    2013-12-01

    Full Text Available Gradient boosting machines are a family of powerful machine-learning techniques that have shown considerable success in a wide range of practical applications. They are highly customizable to the particular needs of the application, like being learned with respect to different loss functions. This article gives a tutorial introduction into the methodology of gradient boosting methods. A theoretical information is complemented with many descriptive examples and illustrations which cover all the stages of the gradient boosting model design. Considerations on handling the model complexity are discussed. A set of practical examples of gradient boosting applications are presented and comprehensively analyzed.

  12. Determination of mercury species by the diffusive gradient in thin film technique and liquid chromatography – atomic fluorescence spectrometry after microwave extraction

    Energy Technology Data Exchange (ETDEWEB)

    Pelcová, Pavlína, E-mail: pavlina.pelcova@mendelu.cz; Dočekalová, Hana, E-mail: hana.docekalova@mendelu.cz; Kleckerová, Andrea, E-mail: andrea.kleckerova@mendelu.cz

    2015-03-25

    Highlights: • DGT–MAE–LC–CV-AFS method was developed for determination of four mercury species. • The microwave extraction was used for isolation of mercury species from resin gels. • Optimized DGT–MAE–LC–CV-AFS method provides low detection limits (13–38 ng L{sup −1}). • The diffusion coefficients of four mercury species were simultaneously determined. - Abstract: A diffusive gradient in thin films technique (DGT) was combined with liquid chromatography (LC) and cold vapor atomic fluorescence spectrometry (CV-AFS) for the simultaneous quantification of four mercury species (Hg{sup 2+}, CH{sub 3}Hg{sup +}, C{sub 2}H{sub 5}Hg{sup +}, and C{sub 6}H{sub 5}Hg{sup +}). After diffusion through an agarose diffusive layer, the mercury species were accumulated in resin gels containing thiol-functionalized ion-exchange resins (Duolite GT73, and Ambersep GT74). A microwave-assisted extraction (MAE) in the presence of 6 M HCl and 5 M HCl (55 °C, 15 min) was used for isolation of mercury species from Ambersep and Duolite resin gels, respectively. The extraction efficiency was higher than 95.0% (RSD 3.5%). The mercury species were separated with a mobile phase containing 6.2% methanol + 0.05% 2-mercaptoethanol + 0.02 M ammonium acetate with a stepwise increase of methanol content up to 80% in the 16th min on a Zorbax C18 reverse phase column. The LODs of DGT–MAE–LC–CV-AFS method were 38 ng L{sup −1} for CH{sub 3}Hg{sup +}, 13 ng L{sup −1} for Hg{sup 2+}, 34 ng L{sup −1} for C{sub 2}H{sub 5}Hg{sup +} and 30 ng L{sup −1} for C{sub 6}H{sub 5}Hg{sup +} for 24 h DGT accumulation at 25 °C.

  13. Application of gradient-corrected density functional theory to the structures and thermochemistries of ScF3, TiF4, VF5, and CrF6

    International Nuclear Information System (INIS)

    Russo, T.V.; Martin, R.L.; Jeffrey Hay, P.

    1995-01-01

    Density functional theory (DFT) and Hartree--Fock (HF) calculations are reported for the family of transition metal fluorides ScF 3 , TiF 4 , VF 5 , and CrF 6 . Both HF and the local-density approximation (LDA) yield excellent agreement with experimental bond lengths, while the B-LYP gradient-corrected density functional gives bond lengths 0.04-0.05 A too long. An investigation of various combinations of exchange and correlation functionals shows that, for this series, the origin of this behavior lies in the Becke exchange functional. Much improved bond distances are found using the hybrid HF/DFT functional advocated by Becke. This approximation also leads to much improved thermochemistries. The LDA overestimates average bond energies in this series by 30-40 kcal/mol, whereas the B-LYP functional overbinds by only ∼8-12 kcal/mol, and the hybrid HF/DFT method overbinds by only ∼2 kcal/mol. The hybrid method predicts the octahedral isomer of CrF 6 to be more stable than the trigonal prismatic form by 14 kcal/mol. Comparison of theoretical vibrational frequencies with experiment supports the assignment of an octahedral geometry

  14. Pancreatic islet isolation by mechanical-enzymatic separation, stationary collagenase digestion and dextran discontinuous density gradient purification: experimental study in dogs Isolamento das ilhotas pancreáticas pela separação mecânica-enzimática digestão estacionária com colagenase e purificação com gradiente de densidade descontínua de dextran: estudo experimental em cães

    Directory of Open Access Journals (Sweden)

    Jaques Waisberg

    2002-04-01

    Full Text Available The prospects for allotransplantation of pancreatic islets in man depend on the development of methods that provide sufficient quantities of pancreatic islets from a single donor, which are capable, when transplanted, of achieve the normalization of carbohydrate metabolism. Objective: Evaluate the efficacy of the isolation of Langerhans islets from dogs, by means of mechanical-enzymatic separation technique with stationary digestion using collagenase, and purification with a discontinuous dextran density gradient. Methods: The counting of islet numbers and evaluation of their sizes was accomplished by staining with diphenylthiocarbazone and using stereoscopic microscopes equipped with eyepiece reticule for the measurement of average diameters of stained islets. Results: The results disclosed that the average number of islets isolated was 81032.20 ± 24736.79 and the average number of islets isolated per kg of body weight was 6938.70 ± 1392.43. The average number of islets isolated per kg of body weight showed significant correlation with body weight and weight of the pancreas resected. Conclusion: The number of islets isolated, of a single donor, by mechanical-enzymatic separation, stationary collagenase digestion and discontinuous dextran density gradient purification can be sufficient to success of pancreatic islets transplant in dogs.A perspectiva do alotransplante de ilhotas pancreáticas no homem está na dependência do desenvolvimento de métodos que propiciem quantidades suficientes de ilhotas pancreáticas, originadas de doador único, capazes de, quando transplantadas, levarem à normalização do metabolismo dos hidratos de carbono. Objetivo: Avaliar, em cães, a eficácia do isolamento das ilhotas de Langerhans por meio da técnica de separação mecânica-enzimática, digestão estacionária com colagenase e purificação pelo gradiente de densidade descontínua de dextran. Métodos: A contagem do número e avaliação do tamanho

  15. Density characterization of radiochromic film through source axis distance (SAD) technique in linac with slab phantom for radiotherapy applications

    Science.gov (United States)

    Hariani, Yousida; Haris, Bambang

    2017-05-01

    Characterization of radiochromic film density is accomplished through Source Axis Distance (SAD) technique in a slab phantom Linac with various depths and breadths of field. Type of the film used is gafchromic RTQA2. The dose of radiation exposure of the film may cause changes in the film density. This research aims to determine the relation between the density and the dose depth through the characteristic of curves to identify the depth of the dose and particular breadth of the field as a reference for the dose of radiotherapy patients. The result shows that the higher the dose is absorbed, the darker the film will be, yet the lower the density is obtained. The dose depth is determined by measuring the amount of dose received at various depths and breadths of field using film that is placed on the slab phantom with 6 MV linac radiation and dose of 300 cGy. The variation of the depth at 1.5 cm; 4 cm; 6 cm; 8 cm; 10 cm, the field size at 4 × 4 cm2, and the dose depth at 359.7 cGy; 315.3 cGy; 281.4 cGy; 241.2 cGy; 220.5 cGy were settled. The field size 6 × 6 cm2 takes the dose depth 354.6 cGy; 314.1 cGy; 282.6 cGy; 244.5 cGy; 224.7 cGy. The field size 8 × 8 cm2 takes the dose depth 351.6 cGy; 313 cGy; 283.8 cGy; 247.2 cGy; 228 cGy. The field size 10 × 10 cm2 takes the dose depth 348.9 cGy; 342.6 cGy; 248.4 cGy; 249.6 cGy; 231 cGy.

  16. Density characterization of radiochromic film through source axis distance (SAD) technique in linac with slab phantom for radiotherapy applications

    International Nuclear Information System (INIS)

    Hariani, Yousida; Haris, Bambang

    2017-01-01

    Characterization of radiochromic film density is accomplished through Source Axis Distance (SAD) technique in a slab phantom Linac with various depths and breadths of field. Type of the film used is gafchromic RTQA2. The dose of radiation exposure of the film may cause changes in the film density. This research aims to determine the relation between the density and the dose depth through the characteristic of curves to identify the depth of the dose and particular breadth of the field as a reference for the dose of radiotherapy patients. The result shows that the higher the dose is absorbed, the darker the film will be, yet the lower the density is obtained. The dose depth is determined by measuring the amount of dose received at various depths and breadths of field using film that is placed on the slab phantom with 6 MV linac radiation and dose of 300 cGy. The variation of the depth at 1.5 cm; 4 cm; 6 cm; 8 cm; 10 cm, the field size at 4 × 4 cm 2 , and the dose depth at 359.7 cGy; 315.3 cGy; 281.4 cGy; 241.2 cGy; 220.5 cGy were settled. The field size 6 × 6 cm 2 takes the dose depth 354.6 cGy; 314.1 cGy; 282.6 cGy; 244.5 cGy; 224.7 cGy. The field size 8 × 8 cm 2 takes the dose depth 351.6 cGy; 313 cGy; 283.8 cGy; 247.2 cGy; 228 cGy. The field size 10 × 10 cm 2 takes the dose depth 348.9 cGy; 342.6 cGy; 248.4 cGy; 249.6 cGy; 231 cGy. (paper)

  17. Using soft computing techniques to predict corrected air permeability using Thomeer parameters, air porosity and grain density

    Science.gov (United States)

    Nooruddin, Hasan A.; Anifowose, Fatai; Abdulraheem, Abdulazeez

    2014-03-01

    Soft computing techniques are recently becoming very popular in the oil industry. A number of computational intelligence-based predictive methods have been widely applied in the industry with high prediction capabilities. Some of the popular methods include feed-forward neural networks, radial basis function network, generalized regression neural network, functional networks, support vector regression and adaptive network fuzzy inference system. A comparative study among most popular soft computing techniques is presented using a large dataset published in literature describing multimodal pore systems in the Arab D formation. The inputs to the models are air porosity, grain density, and Thomeer parameters obtained using mercury injection capillary pressure profiles. Corrected air permeability is the target variable. Applying developed permeability models in recent reservoir characterization workflow ensures consistency between micro and macro scale information represented mainly by Thomeer parameters and absolute permeability. The dataset was divided into two parts with 80% of data used for training and 20% for testing. The target permeability variable was transformed to the logarithmic scale as a pre-processing step and to show better correlations with the input variables. Statistical and graphical analysis of the results including permeability cross-plots and detailed error measures were created. In general, the comparative study showed very close results among the developed models. The feed-forward neural network permeability model showed the lowest average relative error, average absolute relative error, standard deviations of error and root means squares making it the best model for such problems. Adaptive network fuzzy inference system also showed very good results.

  18. Formation of large-scale structures with sharp density gradient through Rayleigh-Taylor growth in a two-dimensional slab under the two-fluid and finite Larmor radius effects

    International Nuclear Information System (INIS)

    Goto, R.; Hatori, T.; Miura, H.; Ito, A.; Sato, M.

    2015-01-01

    Two-fluid and the finite Larmor effects on linear and nonlinear growth of the Rayleigh-Taylor instability in a two-dimensional slab are studied numerically with special attention to high-wave-number dynamics and nonlinear structure formation at a low β-value. The two effects stabilize the unstable high wave number modes for a certain range of the β-value. In nonlinear simulations, the absence of the high wave number modes in the linear stage leads to the formation of the density field structure much larger than that in the single-fluid magnetohydrodynamic simulation, together with a sharp density gradient as well as a large velocity difference. The formation of the sharp velocity difference leads to a subsequent Kelvin-Helmholtz-type instability only when both the two-fluid and finite Larmor radius terms are incorporated, whereas it is not observed otherwise. It is shown that the emergence of the secondary instability can modify the outline of the turbulent structures associated with the primary Rayleigh-Taylor instability

  19. A pseudo-discrete algebraic reconstruction technique (PDART) prior image-based suppression of high density artifacts in computed tomography

    Energy Technology Data Exchange (ETDEWEB)

    Pua, Rizza; Park, Miran; Wi, Sunhee; Cho, Seungryong, E-mail: scho@kaist.ac.kr

    2016-12-21

    We propose a hybrid metal artifact reduction (MAR) approach for computed tomography (CT) that is computationally more efficient than a fully iterative reconstruction method, but at the same time achieves superior image quality to the interpolation-based in-painting techniques. Our proposed MAR method, an image-based artifact subtraction approach, utilizes an intermediate prior image reconstructed via PDART to recover the background information underlying the high density objects. For comparison, prior images generated by total-variation minimization (TVM) algorithm, as a realization of fully iterative approach, were also utilized as intermediate images. From the simulation and real experimental results, it has been shown that PDART drastically accelerates the reconstruction to an acceptable quality of prior images. Incorporating PDART-reconstructed prior images in the proposed MAR scheme achieved higher quality images than those by a conventional in-painting method. Furthermore, the results were comparable to the fully iterative MAR that uses high-quality TVM prior images. - Highlights: • An accelerated reconstruction method, PDART, is proposed for exterior problems. • With a few iterations, soft prior image was reconstructed from the exterior data. • PDART framework has enabled an efficient hybrid metal artifact reduction in CT.

  20. Electron Density Measurement on JUICE Mission by Mutual Impedance Technique: MIME Instrument as a Part of RPWI Consortium

    Science.gov (United States)

    Rauch, J. L.; Henri, P.; Wahlund, J. E.; Le Duff, O.; Sene, O.; Colin, F.; Lagoutte, D.; Gilet, N.; Ahlen, L.; Bergman, J.; Gill, R.; Puccio, W.

    2017-09-01

    Mutual Impedance MEasurements (MIME) instrument is a part of the Radio Wave Plasma Investigation (RPWI) consortium which has been selected by European Space Agency (ESA) on the nest planetary mission JJUpiter ICy moons Exploer (JUICE) for a launch in 2022. The goals are to explore Jupiter and its potentially habitable icy moons and to study its plasma environment. Impedance probes, which are well known in geophysical prospection, in particular for ground permittivity investigations, have been successfully transposed to space plasmas diagnostic. Transmitting and receiving electrodes are used for measuring on open circuit the dynamic impedance of the system at several fixed frequencies over a range that includes characteristic frequencies of the ambient plasma. The measurements are then interpreted using a suitable theory and the values of plasma parameters, such as the electron density and possibly the temperature of the plasma can be deduced. To show how powerful this technique is, results obtained in the Earth's plasmasphere by the mutual impedance probe onboard ROSETTA are presented as example. MIME instrument proposal is then described and its ability to make valuable measurements in the Jupiter space environment and in particular around Europe, Callisto and Ganymede is investigated..

  1. Reliability of a two-wavelength autofluorescence technique by Heidelberg Spectralis to measure macular pigment optical density in Asian subjects.

    Science.gov (United States)

    Obana, Akira; Gellermann, Werner; Gohto, Yuko; Seto, Takahiko; Sasano, Hiroyuki; Tanito, Masaki; Okazaki, Shigetoshi

    2018-03-01

    This study evaluates the accuracy of an objective two-wavelength fundus autofluorescence technique for the purpose of measuring the macular pigment optical density (MPOD) in Asian pigmented eyes. Potential differences between MPOD values obtained via autofluorescence technique and subjective heterochromatic photometry (HFP) were examined. Inter-examiner reproducibility between three examiners and test-retest reliability over five time points were also explored. Subjects were 27 healthy Japanese volunteers aged 24 to 58 (mean ± standard deviation, 40.2 ± 9.0) years. An MPOD module of the Spectralis MultiColor instrument configuration (Spectralis-MP) was used for the autofluorescence technique, and a Macular Metrics Densitometer (MM) was used for HFP. The mean MPOD values at 0.25° and 0.5° eccentricities using the Spectralis-MP were 0.51 ± 0.12 and 0.48 ± 0.13, respectively. In comparison, the MM based values were 0.72 ± 0.23 and 0.61 ± 0.25, respectively. High correlations between the Spectralis-MP and MM instrument were found (Pearson's correlation coefficients of 0.73 and 0.87 at 0.25° and 0.5° eccentricities, respectively), but there was a systematic bias: the MPOD values by MM method were significantly higher than those by Spectralis-MP at 0.25° eccentricity. High inter-examiner reproducibility and test-retest reliability were found for MM measurements at 0.5° eccentricity, but not at 0.25°. The Spectralis-MP showed less inter-examiner and test-retest variability than the MM instrument at 0.25° and 0.5° eccentricities. We conclude that the Spectralis-MP, given its high agreement with the HFP method and due to its higher reproducibility and reliability, is well suited for clinical measurements of MPOD levels in Asian pigmented eyes. Copyright © 2018. Published by Elsevier Ltd.

  2. In-phase and out-of-phase gradient-echo imaging in abdominal studies: intra-individual comparison of three different techniques

    International Nuclear Information System (INIS)

    Ramalho, Miguel; Heredia, Vasco; Campos, Rafael O. P. de; Azevedo, Rafael M.; Semelka, Richard C.; Dale, Brian M.

    2012-01-01

    Background: T1-weighted gradient-echo in-phase and out-of-phase imaging is an essential component of comprehensive abdominal MR exams. It is useful for the study of fat-containing lesions and to identify various disease states related to the presence of fat in the liver. Purpose: To compare three T1-weighted in-phase and out-of-phase (IP/OP) gradient-echo imaging sequences in an intra-individual fashion, and to determine whether advantages exist for each of these sequences for various patient types. Material and Methods: One hundred and eighteen consecutive subjects (74 men, 44 women; mean age 53.9 ± 13.8 years) who had MRI examinations containing all three different IP/OP sequences (two-dimensional spoiled gradient-echo [2D-GRE], three-dimensional gradient-echo [3D-GRE], and magnetization-prepared gradient-recall echo [MP-GRE]) were included. Two different reviewers independently and blindly qualitatively evaluated IP/OP sequences to determine image quality, extent of artifacts, lesion detectability and conspicuity, and subjective grading of liver steatosis for the various sequences. Quantitative analysis was also performed. Qualitative and quantitative data were subjected to statistical analysis. Results: Respiratory ghosting, parallel imaging, and truncation artifacts as well as shading and blurring were more pronounced with 3D-GRE IP/OP imaging. Overall image quality was higher with 2D-GRE (P < 0.05). Detectability of low-fluid content lesions was lower with IP/OP MP-GRE sequences. MP-GRE sequences had the lowest SNRs (P < 0.001). Liver-to-spleen and liver-to-lesion CNRs were significantly lower with 3D-GRE and MP-GR, respectively (P < 0.001). Fat liver indexes showed strongly positive correlation between all sequences. Conclusion: Currently, 2D-GRE remains the best approach for clinical IP/OP imaging. The good image quality of MP-GRE sequences acquired in a free-breathing manner should recommend its use in patients unable to suspend breathing

  3. In-phase and out-of-phase gradient-echo imaging in abdominal studies: intra-individual comparison of three different techniques

    Energy Technology Data Exchange (ETDEWEB)

    Ramalho, Miguel; Heredia, Vasco; Campos, Rafael O. P. de; Azevedo, Rafael M.; Semelka, Richard C. (Dept. of Radiology, Univ. of North Carolina at Chapel Hill (United States)); Dale, Brian M. (Siemens Medical Systems, Morrisville (United States)), email: richsem@med.unc.edu

    2012-05-15

    Background: T1-weighted gradient-echo in-phase and out-of-phase imaging is an essential component of comprehensive abdominal MR exams. It is useful for the study of fat-containing lesions and to identify various disease states related to the presence of fat in the liver. Purpose: To compare three T1-weighted in-phase and out-of-phase (IP/OP) gradient-echo imaging sequences in an intra-individual fashion, and to determine whether advantages exist for each of these sequences for various patient types. Material and Methods: One hundred and eighteen consecutive subjects (74 men, 44 women; mean age 53.9 +- 13.8 years) who had MRI examinations containing all three different IP/OP sequences (two-dimensional spoiled gradient-echo [2D-GRE], three-dimensional gradient-echo [3D-GRE], and magnetization-prepared gradient-recall echo [MP-GRE]) were included. Two different reviewers independently and blindly qualitatively evaluated IP/OP sequences to determine image quality, extent of artifacts, lesion detectability and conspicuity, and subjective grading of liver steatosis for the various sequences. Quantitative analysis was also performed. Qualitative and quantitative data were subjected to statistical analysis. Results: Respiratory ghosting, parallel imaging, and truncation artifacts as well as shading and blurring were more pronounced with 3D-GRE IP/OP imaging. Overall image quality was higher with 2D-GRE (P < 0.05). Detectability of low-fluid content lesions was lower with IP/OP MP-GRE sequences. MP-GRE sequences had the lowest SNRs (P < 0.001). Liver-to-spleen and liver-to-lesion CNRs were significantly lower with 3D-GRE and MP-GR, respectively (P < 0.001). Fat liver indexes showed strongly positive correlation between all sequences. Conclusion: Currently, 2D-GRE remains the best approach for clinical IP/OP imaging. The good image quality of MP-GRE sequences acquired in a free-breathing manner should recommend its use in patients unable to suspend breathing

  4. A theory of gradient analysis

    NARCIS (Netherlands)

    Braak, ter C.J.F.

    1988-01-01

    The theory of gradient analysis is presented in this chapter, in which the heuristic techniques are integrated with regression, calibration, ordination and constrained ordination as distinct, well-defined statistical problems. The various techniques used for each type of problem are classified into

  5. CO{sub 2} laser diagnostics for measurements of the plasma density profile and plasma density fluctuations on LHD

    Energy Technology Data Exchange (ETDEWEB)

    Vyacheslavov, L.N. [Budker Institute of Nuclear Physics, Novosibirsk (Russian Federation); Tanaka, K.; Kawahata, K. [National Inst. for Fusion Science, Toki, Gifu (Japan)

    2001-04-01

    A CO{sub 2} laser based diagnostics complimentary to the existing FIR interferometer is proposed. It combines interferometry for plasma density profile measurement under conditions of large density gradients, and both imaging and scattering techniques for observation of plasma fluctuations. Two-colour interferometer with a slablike probe beam and a single multichannel linear detector array provide observation of plasma density profile and density fluctuations at two locations along the probe beam. Basic characteristics of the diagnostics are considered as well as some effects that include dispersion and are critical for two colour imaging technique. The results of the bench-top experiments with the prototype of the interferometer are presented. (author)

  6. CO2 laser diagnostics for measurements of the plasma density profile and plasma density fluctuations on LHD

    International Nuclear Information System (INIS)

    Vyacheslavov, L.N.; Tanaka, K.; Kawahata, K.

    2001-04-01

    A CO 2 laser based diagnostics complimentary to the existing FIR interferometer is proposed. It combines interferometry for plasma density profile measurement under conditions of large density gradients, and both imaging and scattering techniques for observation of plasma fluctuations. Two-colour interferometer with a slablike probe beam and a single multichannel linear detector array provide observation of plasma density profile and density fluctuations at two locations along the probe beam. Basic characteristics of the diagnostics are considered as well as some effects that include dispersion and are critical for two colour imaging technique. The results of the bench-top experiments with the prototype of the interferometer are presented. (author)

  7. Utilization of combined remote sensing techniques to detect environmental variables influencing malaria vector densities in rural West Africa

    Directory of Open Access Journals (Sweden)

    Dambach Peter

    2012-03-01

    Full Text Available Abstract Introduction The use of remote sensing has found its way into the field of epidemiology within the last decades. With the increased sensor resolution of recent and future satellites new possibilities emerge for high resolution risk modeling and risk mapping. Methods A SPOT 5 satellite image, taken during the rainy season 2009 was used for calculating indices by combining the image's spectral bands. Besides the widely used Normalized Difference Vegetation Index (NDVI other indices were tested for significant correlation against field observations. Multiple steps, including the detection of surface water, its breeding appropriateness for Anopheles and modeling of vector imagines abundance, were performed. Data collection on larvae, adult vectors and geographic parameters in the field, was amended by using remote sensing techniques to gather data on altitude (Digital Elevation Model = DEM, precipitation (Tropical Rainfall Measurement Mission = TRMM, land surface temperatures (LST. Results The DEM derived altitude as well as indices calculations combining the satellite's spectral bands (NDTI = Normalized Difference Turbidity Index, NDWI Mac Feeters = Normalized Difference Water Index turned out to be reliable indicators for surface water in the local geographic setting. While Anopheles larvae abundance in habitats is driven by multiple, interconnected factors - amongst which the NDVI - and precipitation events, the presence of vector imagines was found to be correlated negatively to remotely sensed LST and positively to the cumulated amount of rainfall in the preceding 15 days and to the Normalized Difference Pond Index (NDPI within the 500 m buffer zone around capture points. Conclusions Remotely sensed geographical and meteorological factors, including precipitations, temperature, as well as vegetation, humidity and land cover indicators could be used as explanatory variables for surface water presence, larval development and imagines

  8. Modeling the effects of the vertical temperature gradient in the furnace in an edge-defined film-fed growth technique

    International Nuclear Information System (INIS)

    Epure, S.; Braescu, L.; Balint, St.

    2006-01-01

    In this paper, the mathematical model for the growth of cylindrical bars described elsewhere is considered. Using MathCAD 11 Enterprise Edition and mathematical tools, the asymptotically stable steady-states (r*, h*) of the nonlinear system of differential equations which governs the evolution of the bar radius r=r(t) and the meniscus height h=h(t), for different values of the pulling rate v, the melt temperature T 0 at the meniscus basis and the vertical temperature gradient k in the furnace, respectively, are found. For a given k, the range of the stable growth regions in the (v, T 0 ) plane (i.e. those couples (v, T 0 ) for which (r*, h*) has physical sense) are determined. The effects of the changes of the vertical temperature gradient k are investigated and it is shown that if v and T 0 are constant, and k increases, then the bar radius r increases and the meniscus height h decreases. Numerical results are given for the silicon bar grown in an edge-defined film-fed growth (E.F.G.) system with a die radius r 0e =20(cmx10 -2 )

  9. Influence of the surgical technique and surface roughness on the primary stability of an implant in artificial bone with a density equivalent to maxillary bone: a laboratory study.

    NARCIS (Netherlands)

    Tabassum, A.; Meijer, G.J.; Wolke, J.G.C.; Jansen, J.A.

    2009-01-01

    OBJECTIVE: The aim of this biomechanical study was to assess the effect of surgical technique and surface roughness on primary implant stability in low-density bone. MATERIAL AND METHODS: Eighty screw-shaped (Biocomp) implants with machined or etched surface topography were inserted into a

  10. Sea-to-air flux of dimethyl sulfide in the South and North Pacific Ocean as measured by proton transfer reaction-mass spectrometry coupled with the gradient flux technique

    Science.gov (United States)

    Omori, Yuko; Tanimoto, Hiroshi; Inomata, Satoshi; Ikeda, Kohei; Iwata, Toru; Kameyama, Sohiko; Uematsu, Mitsuo; Gamo, Toshitaka; Ogawa, Hiroshi; Furuya, Ken

    2017-07-01

    Exchange of dimethyl sulfide (DMS) between the surface ocean and the lower atmosphere was examined by using proton transfer reaction-mass spectrometry coupled with the gradient flux (PTR-MS/GF) system. We deployed the PTR-MS/GF system and observed vertical gradients of atmospheric DMS just above the sea surface in the subtropical and transitional South Pacific Ocean and the subarctic North Pacific Ocean. In total, we obtained 370 in situ profiles, and of these we used 46 data sets to calculate the sea-to-air flux of DMS. The DMS flux determined was in the range from 1.9 to 31 μmol m-2 d-1 and increased with wind speed and biological activity, in reasonable accordance with previous observations in the open ocean. The gas transfer velocity of DMS derived from the PTR-MS/GF measurements was similar to either that of DMS determined by the eddy covariance technique or that of insoluble gases derived from the dual tracer experiments, depending on the observation sites located in different geographic regions. When atmospheric conditions were strongly stable during the daytime in the subtropical ocean, the PTR-MS/GF observations captured a daytime versus nighttime difference in DMS mixing ratios in the surface air overlying the ocean surface. The difference was mainly due to the sea-to-air DMS emissions and stable atmospheric conditions, thus affecting the gradient of DMS. This indicates that the DMS gradient is strongly controlled by diurnal variations in the vertical structure of the lower atmosphere above the ocean surface.

  11. Effective porosity and density of carbonate rocks (Maynardville Limestone and Copper Ridge Dolomite) within Bear Creek Valley on the Oak Ridge Reservation based on modern petrophysical techniques

    International Nuclear Information System (INIS)

    Dorsch, J.

    1997-02-01

    The purpose of this study is to provide quantitative data on effective porosity of carbonate rock from the Maynardville Limestone and Copper Ridge Dolomite within Bear Creek Valley based on modern petrophysical techniques. The data will be useful for groundwater-flow and contaminant-flow modeling in the vicinity of the Y-12 Plant on the Oak Ridge Reservation (ORR). Furthermore, the data provides needed information on the amount of interconnected pore space potentially available for operation of matrix diffusion as a transport process within the fractured carbonate rock. A second aspect of this study is to compare effective porosity data based on modern petrophysical techniques to effective porosity data determined earlier by Goldstrand et al. (1995) with a different technique. An added bonus of the study is quantitative data on the bulk density and grain density of dolostone and limestone of the Maynardville Limestone and Copper Ridge Dolomite which might find use for geophysical modeling on the ORR

  12. Determination of peak bone mass density and composition in low income urban residents of metro Manila using isotope techniques

    International Nuclear Information System (INIS)

    Lim-Abrahan, M.A.

    2000-01-01

    The work described in this paper is a continuation of the first phase of the study, which is the determination of the peak bone mass density among residents of Metro Manila using dual energy x-ray absorptiometry. However, it also aims to correlate sex, body mass index, nutritional factors, physical activity and lifestyle to peak bone mass and thus attempts to explain any discrepancies in peak bone mass density to that seen in other countries

  13. Determination of photocarrier density under continuous photoirradiation using spectroscopic techniques as applied to polymer: Fullerene blend films

    Energy Technology Data Exchange (ETDEWEB)

    Kanemoto, Katsuichi, E-mail: kkane@sci.osaka-cu.ac.jp; Nakatani, Hitomi; Domoto, Shinya [Department of Physics, Osaka City University, 3-3-138 Sugimoto, Sumiyoshi-ku, Osaka 558-8585 (Japan)

    2014-10-28

    We propose a method to determine the density of photocarrier under continuous photoirradiation in conjugated polymers using spectroscopic signals obtained by photoinduced absorption (PIA) measurements. The bleaching signals in the PIA measurements of polymer films and the steady-state absorption signals of oxidized polymer solution are employed to determine the photocarrier density. The method is applied to photocarriers of poly (3-hexylthiophene) (P3HT) in a blended film consisting of P3HT and [6,6]-phenyl C61 butyric acid methyl ester (PCBM). The photocarrier density under continuous photoirradiation of 580 mW/cm{sup 2} is determined to be 3.5 × 10{sup 16 }cm{sup −3}. Using a trend of the carrier density increasing in proportion to the square root of photo-excitation intensity, we provide a general formula to estimate the photocarrier density under simulated 1 sun solar irradiation for the P3HT: PCBM film of an arbitrary thickness. We emphasize that the method proposed in this study enables an estimate of carrier density without measuring a current and can be applied to films with no electrodes as well as to devices.

  14. 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.)

  15. A Diffusive Gradient-in-Thin-Film Technique for Evaluation of the Bioavailability of Cd in Soil Contaminated with Cd and Pb

    Directory of Open Access Journals (Sweden)

    Peifang Wang

    2016-06-01

    Full Text Available Management of heavy metal contamination requires accurate information about the distribution of bioavailable fractions, and about exchange between the solid and solution phases. In this study, we employed diffusive gradients in thin-films (DGT and traditional chemical extraction methods (soil solution, HOAc, EDTA, CaCl2, and NaOAc to determine the Cd bioavailability in Cd-contaminated soil with the addition of Pb. Two typical terrestrial species (wheat, Bainong AK58; maize, Zhengdan 958 were selected as the accumulation plants. The results showed that the added Pb may enhance the efficiency of Cd phytoextraction which is indicated by the increasing concentration of Cd accumulating in the plant tissues. The DGT-measured Cd concentrations and all the selected traditional extractants measured Cd concentrations all increased with increasing concentration of the addition Pb which were similar to the change trends of the accumulated Cd concentrations in plant tissues. Moreover, the Pearson regression coefficients between the different indicators obtained Cd concentrations and plants uptake Cd concentrations were further indicated significant correlations (p < 0.01. However, the values of Pearson regression coefficients showed the merits of DGT, CaCl2, and Csol over the other three methods. Consequently, the in situ measurement of DGT and the ex situ traditional methods could all reflect the inhibition effects between Cd and Pb. Due to the feature of dynamic measurements of DGT, it could be a robust tool to predict Cd bioavaiability in complex contaminated soil.

  16. A Diffusive Gradient-in-Thin-Film Technique for Evaluation of the Bioavailability of Cd in Soil Contaminated with Cd and Pb

    Science.gov (United States)

    Wang, Peifang; Wang, Teng; Yao, Yu; Wang, Chao; Liu, Cui; Yuan, Ye

    2016-01-01

    Management of heavy metal contamination requires accurate information about the distribution of bioavailable fractions, and about exchange between the solid and solution phases. In this study, we employed diffusive gradients in thin-films (DGT) and traditional chemical extraction methods (soil solution, HOAc, EDTA, CaCl2, and NaOAc) to determine the Cd bioavailability in Cd-contaminated soil with the addition of Pb. Two typical terrestrial species (wheat, Bainong AK58; maize, Zhengdan 958) were selected as the accumulation plants. The results showed that the added Pb may enhance the efficiency of Cd phytoextraction which is indicated by the increasing concentration of Cd accumulating in the plant tissues. The DGT-measured Cd concentrations and all the selected traditional extractants measured Cd concentrations all increased with increasing concentration of the addition Pb which were similar to the change trends of the accumulated Cd concentrations in plant tissues. Moreover, the Pearson regression coefficients between the different indicators obtained Cd concentrations and plants uptake Cd concentrations were further indicated significant correlations (p < 0.01). However, the values of Pearson regression coefficients showed the merits of DGT, CaCl2, and Csol over the other three methods. Consequently, the in situ measurement of DGT and the ex situ traditional methods could all reflect the inhibition effects between Cd and Pb. Due to the feature of dynamic measurements of DGT, it could be a robust tool to predict Cd bioavaiability in complex contaminated soil. PMID:27271644

  17. Selective sampling and measurement of Cr (VI) in water with polyquaternary ammonium salt as a binding agent in diffusive gradients in thin-films technique.

    Science.gov (United States)

    Chen, Hong; Zhang, Yang-Yang; Zhong, Ke-Li; Guo, Lian-Wen; Gu, Jia-Li; Bo, Le; Zhang, Meng-Han; Li, Jian-Rong

    2014-04-30

    A diffusive gradients in thin films (DGT) device with polyquaternary ammonium salt (PQAS) as a novel binding agent (PQAS DGT) combined with graphite furnace atomic absorption spectrometry (GFAAS) was developed for the selective sampling and measurement of Cr (VI) in water. The performance of PQAS DGT was independent of pH 3-12 and ionic strength from 1 × 10(-3) to 1 molL(-1). DGT validation experiments showed that Cr (VI) was measured accurately as well as selectively by PQAS DGT, whereas Cr (III) was not determined quantitatively. Compared with diphenylcarbazide spectrophotometric method (DPC), the measurement of Cr (VI) with PQAS DGT was agreement with that of DPC method in the industrial wastewater. PQAS-DGT device had been successfully deployed in local freshwater. The concentrations of Cr (VI) determined by PQAS DGT coupled with GFAAS in Nuer River, Ling River and North Lake were 0.73 ± 0.09 μg L(-1), 0.50 ± 0.07 μg L(-1) and 0.61 ± 0.07 μg L(-1), respectively. The results indicate that PQAS DGT device can be used for the selective sampling and measurement Cr (VI) in water and its detection limit is lower than that of DPC method. Copyright © 2014 Elsevier B.V. All rights reserved.

  18. Measurement of dissolved reactive phosphorus in water with polyquaternary ammonium salt as a binding agent in diffusive gradients in thin-films technique.

    Science.gov (United States)

    Chen, Hong; Zhang, Meng-Han; Gu, Jia-Li; Zhao, Gang; Zhang, Yu; Li, Jian-Rong

    2014-12-17

    Diffusive gradients in thin-films (DGT) sampler with a polyquaternary ammonium salt (PQAS) aqueous solution as a binding phase and a dialysis membrane as a diffusive phase (PQAS DGT) was developed for the measurement of dissolved reactive phosphorus (DRP) in water. The performance of PQAS DGT was not dependent upon pH 3-10 and ionic strength from 1 × 10(-4) to 1 mol L(-1). The effective binding capacity of PQAS DGT containing 2.0 mL of 0.050 mol L(-1) PQAS solution was estimated as 9.9 μg cm(-2). The measurement of DRP in a synthetic solution by PQAS DGT over a 48 h deployment period demonstrated high consistency with the concentration of DRP in the synthetic solution measured directly by the ammonium molybdate spectrophotometric method. Field deployments of PQAS DGT samplers allowed for accurate measurement of the DRP concentration in situ. The advantages of PQAS DGT include no requirement of the elution steps and direct concentration measurements of the binding phase.

  19. Imaging the Buried Chicxulub Crater with Gravity Gradients and Cenotes

    Science.gov (United States)

    Hildebrand, A. R.; Pilkington, M.; Halpenny, J. F.; Ortiz-Aleman, C.; Chavez, R. E.; Urrutia-Fucugauchi, J.; Connors, M.; Graniel-Castro, E.; Camara-Zi, A.; Vasquez, J.

    1995-09-01

    Differing interpretations of the Bouguer gravity anomaly over the Chicxulub crater, Yucatan Peninsula, Mexico, have yielded diameter estimates of 170 to 320 km. Knowing the crater's size is necessary to quantify the lethal perturbations to the Cretaceous environment associated with its formation. The crater's size (and internal structure) is revealed by the horizontal gradient of the Bouguer gravity anomaly over the structure, and by mapping the karst features of the Yucatan region. To improve our resolution of the crater's gravity signature we collected additional gravity measurements primarily along radial profiles, but also to fill in previously unsurveyed areas. Horizontal gradient analysis of Bouguer gravity data objectively highlights the lateral density contrasts of the impact lithologies and suppresses regional anomalies which may obscure the gravity signature of the Chicxulub crater lithologies. This gradient technique yields a striking circular structure with at least 6 concentric gradient features between 25 and 85 km radius. These features are most distinct in the southwest probably because of denser sampling of the gravity field. Our detailed profiles detected an additional feature and steeper gradients (up to 5 mGal/km) than the original survey. We interpret the outer four gradient maxima to represent concentric faults in the crater's zone of slumping as is also revealed by seismic reflection data. The inner two probably represent the margin of the central uplift and the peak ring and or collapsed transient cavity. Radial gradients in the SW quadrant over the inferred ~40 km-diameter central uplift (4) may represent structural "puckering" as revealed at eroded terrestrial craters. Gradient features related to regional gravity highs and lows are visible outside the crater, but no concentric gradient features are apparent at distances > 90 km radius. The marginal gradient features may be modelled by slump faults as observed in large complex craters on

  20. The control of plasma density profile in Tore Supra. Comparison of different fueling techniques; Controle du profil de densite dans le plasma de Tore Supra. Comparaison de differentes methodes d'alimentation en particules

    Energy Technology Data Exchange (ETDEWEB)

    Commaux, N

    2007-09-15

    The behaviour of a reactor-class plasma when fuelled using the existing techniques (gas puffing, supersonic molecular beam injection and pellet injection) is still very difficult to foresee. The present work has been initiated on Tore Supra in order to extrapolate the consequences of the different fuelling systems on ITER. Two main topics have been studied: the comparison of the plasma behaviour when fuelled using the different techniques at high Greenwald density fractions and the study of the homogenization following a pellet injection (main fuelling technique for ITER burning plasmas). The experiments at high Greenwald density fractions performed on Tore Supra showed that the plasma behaviour is very dependent on the fuelling method. The plasma energy confinement is following the scaling laws determined at low density when fuelled using pellet injection. which is better than for gas puffing and SMBI. both inducing a significant confinement loss. This behaviour is nor related to a transport modification: the ratio between effective diffusion and convection is similar to the pellet case. The difference between these shots is related only to the position of the matter source (at the edge for gas and close to the center for pellets). The study concerning the homogenization phenomena following a pellet injection aims mainly to study the {nabla}B-drift effect that expels the mater deposited by a pellet toward the low field side. A new phenomenon. which appears to be particularly important for the {nabla}B-drift during low field side injections. was then discovered: the influence of magnetic surfaces with an integer-valued safety factor (q). When the mater drifting toward low field side crosses an integer q surface. it experiences an important braking effect which stops the drift motion. It implies that the pellet material is mainly deposited on the last integer q surface crossed by the pellet during its injection. This study allows also to determine that the {nabla

  1. Selective sampling and measurement of Cr (VI) in water with polyquaternary ammonium salt as a binding agent in diffusive gradients in thin-films technique

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Hong, E-mail: redastar@163.com [College of Chemistry, Chemical Engineering and Food Safety, Bohai University (China); Research Institute of Food Science, Bohai University (China); Food Safety Key Lab of Liaoning Province, Jinzhou 121013 (China); Zhang, Yang-Yang; Zhong, Ke-Li; Guo, Lian-Wen [College of Chemistry, Chemical Engineering and Food Safety, Bohai University (China); Research Institute of Food Science, Bohai University (China); Food Safety Key Lab of Liaoning Province, Jinzhou 121013 (China); Gu, Jia-Li [College of Chemistry, Chemical Engineering and Food Safety, Bohai University (China); Bo, Le; Zhang, Meng-Han [College of Chemistry, Chemical Engineering and Food Safety, Bohai University (China); Research Institute of Food Science, Bohai University (China); Food Safety Key Lab of Liaoning Province, Jinzhou 121013 (China); Li, Jian-Rong, E-mail: lijianrong@zjgsu.edu.cn [College of Chemistry, Chemical Engineering and Food Safety, Bohai University (China); Research Institute of Food Science, Bohai University (China); Food Safety Key Lab of Liaoning Province, Jinzhou 121013 (China)

    2014-04-01

    Graphical abstract: - Highlights: • We develop a new DGT device for in situ sampling Cr (VI) in water. • Polyquaternary ammonium salt (PQAS) was used as binding agent of DGT device. • Cr (VI) can be accumulated in the PQAS binding phase whereas Cr (III) cannot. • The DGT performance was independent of pH 3–12 and ionic strength 1 × 10{sup −3}–1 mol L{sup −1}. - Abstract: A diffusive gradients in thin films (DGT) device with polyquaternary ammonium salt (PQAS) as a novel binding agent (PQAS DGT) combined with graphite furnace atomic absorption spectrometry (GFAAS) was developed for the selective sampling and measurement of Cr (VI) in water. The performance of PQAS DGT was independent of pH 3–12 and ionic strength from 1 × 10{sup −3} to 1 mol L{sup −1}. DGT validation experiments showed that Cr (VI) was measured accurately as well as selectively by PQAS DGT, whereas Cr (III) was not determined quantitatively. Compared with diphenylcarbazide spectrophotometric method (DPC), the measurement of Cr (VI) with PQAS DGT was agreement with that of DPC method in the industrial wastewater. PQAS-DGT device had been successfully deployed in local freshwater. The concentrations of Cr (VI) determined by PQAS DGT coupled with GFAAS in Nuer River, Ling River and North Lake were 0.73 ± 0.09 μg L{sup −1}, 0.50 ± 0.07 μg L{sup −1} and 0.61 ± 0.07 μg L{sup −1}, respectively. The results indicate that PQAS DGT device can be used for the selective sampling and measurement Cr (VI) in water and its detection limit is lower than that of DPC method.

  2. Selective sampling and measurement of Cr (VI) in water with polyquaternary ammonium salt as a binding agent in diffusive gradients in thin-films technique

    International Nuclear Information System (INIS)

    Chen, Hong; Zhang, Yang-Yang; Zhong, Ke-Li; Guo, Lian-Wen; Gu, Jia-Li; Bo, Le; Zhang, Meng-Han; Li, Jian-Rong

    2014-01-01

    Graphical abstract: - Highlights: • We develop a new DGT device for in situ sampling Cr (VI) in water. • Polyquaternary ammonium salt (PQAS) was used as binding agent of DGT device. • Cr (VI) can be accumulated in the PQAS binding phase whereas Cr (III) cannot. • The DGT performance was independent of pH 3–12 and ionic strength 1 × 10 −3 –1 mol L −1 . - Abstract: A diffusive gradients in thin films (DGT) device with polyquaternary ammonium salt (PQAS) as a novel binding agent (PQAS DGT) combined with graphite furnace atomic absorption spectrometry (GFAAS) was developed for the selective sampling and measurement of Cr (VI) in water. The performance of PQAS DGT was independent of pH 3–12 and ionic strength from 1 × 10 −3 to 1 mol L −1 . DGT validation experiments showed that Cr (VI) was measured accurately as well as selectively by PQAS DGT, whereas Cr (III) was not determined quantitatively. Compared with diphenylcarbazide spectrophotometric method (DPC), the measurement of Cr (VI) with PQAS DGT was agreement with that of DPC method in the industrial wastewater. PQAS-DGT device had been successfully deployed in local freshwater. The concentrations of Cr (VI) determined by PQAS DGT coupled with GFAAS in Nuer River, Ling River and North Lake were 0.73 ± 0.09 μg L −1 , 0.50 ± 0.07 μg L −1 and 0.61 ± 0.07 μg L −1 , respectively. The results indicate that PQAS DGT device can be used for the selective sampling and measurement Cr (VI) in water and its detection limit is lower than that of DPC method

  3. Application of nuclear techniques to the measurement of rock density and transport of solid particles suspended in rivers

    International Nuclear Information System (INIS)

    Seddiki, A.

    1984-10-01

    In order to better understand hydron phenomens in semi-arid regions characterized by torrential rains, we measured solid particles suspended to dums and in rivers. We also determined the density profile of a drilling and density of saline solutions. We designed an automatic nuclear gauge used for measuring the concentration of particles suspended to rivers. The installation, calibration and operations of a LABEN gauge were done in BENI SLIMANE on the 27th and 28th of February, 1984. The first results we obtained were received on the 24th of April, 1984

  4. MR imaging of articular cartilage : comparison of magnetization transfer contrast and fat-suppression in multiplanar and 3D gradient-echo, spin-echo, turbo spin-echo techniques

    International Nuclear Information System (INIS)

    Lee, Young Joon; Joo, Eun Young; Eun, Choong Ki

    1999-01-01

    The purpose of this study was to evaluate the effects of magnetization transfer contrast(MTC) and fat-suppression(FS) in variable spin-echo and gradient-echo sequences for articular cartilage imaging and to determine the optimal pulse sequences. Using variable 7-pulse sequences, the knees of 15 pigs were imaged Axial images were obtained using proton density and T2-weighted spin-echo (PDWSE and T2WSE), turbo spin-echo (TSE), multiplanar gradient-echo (MPGR), and 3D steady-state gradient-echo (3DGRE) sequences, and the same pulse sequences were then repeated using MTC. Also T1-weighted spin-echo(T1WSE) and 3D spoiled gradient-echo(3DSPGR) images of knees were also acquired, and the procedure was repeated using FS. For each knee, a total of 14 axial images were acquired, and using a 6-band scoring system, the visibility of and the visibilities of the the articular cartilage was analyzed. The visual effect of MTC and FS was scored using a 4-band scale. For each image, the signal intensities of articular cartilage, subchondral bone, muscles, and saline were measured, and signal-to-noise ratios(SNR) and contrast-to-noise ratios(CNR) were also calculated. Visibility of the cartilage was best when 3DSPGR and T1WSE sequences were used. MTC imaging increased the negative contrast between cartilage and saline, but FS imaging provided more positive contrast. CNR between cartilage and saline was highest when using TSE with FS(-351.1±15.3), though CNR between cartilage and bone then fell to -14.7±10.8. In MTC imaging using MPGR showed the greatest increase of negative contrast between cartilage and saline(CNR change=-74.7); the next highest was when 3DGRE was used(CNR change=-34.3). CNR between cartilage and bone was highest with MPGR(161.9±17.7), but with MTC, the greatest CNR decrease(-81.8) was observed. The greatest CNR increase between cartilage and bone was noted in T1WSE with FS. In all scans, FS provided a cartilage-only positive contrast image, though the absolute

  5. Quantitative assessment of breast density from mammograms

    International Nuclear Information System (INIS)

    Jamal, N.; Ng, K.H.

    2004-01-01

    Full text: It is known that breast density is increasingly used as a risk factor for breast cancer. This study was undertaken to develop and validate a semi-automated computer technique for the quantitative assessment of breast density from digitised mammograms. A computer technique had been developed using MATLAB (Version 6.1) based GUI applications. This semi-automated image analysis tool consists of gradient correction, segmentation of breast region from background, segmentation of fibroglandular and adipose region within the breast area and calculation of breast density. The density is defined as the percentage of fibroglandular tissue area divided by the total breast area in the mammogram. This technique was clinically validated with 122 normal mammograms; these were subjectively evaluated and classified according to the five parenchyma patterns of the Tabar's scheme (Class I- V) by a consultant radiologist. There was a statistical significant correlation between the computer technique and subjective classification (r 2 = 0.84, p<0.05). 71.3% of subjective classification was correctly classified using the computer technique. We had developed a computer technique for the quantitative assessment of breast density and validated its accuracy for computerized classification based on Tabar's scheme. This quantitative tool is useful for the evaluation of a large dataset of mammograms to predict breast cancer risk based on density. Furthermore it has the potential to provide an early marker for success or failure in chemoprevention studies such as hormonal replacement therapy. Copyright (2004) Australasian College of Physical Scientists and Engineers in Medicine

  6. Design for coordinated measurements of Faraday rotation and line-of-sight electron density using heterodyne techniques

    International Nuclear Information System (INIS)

    Jacobson, A.R.

    1977-07-01

    This report proposes a device which can overcome certain of the compromises of conventional Faraday rotation methods and at the same time measure the optical phase as well as the polarization. This would be useful for unfolding the Faraday rotation signal using the line-of-sight density along exactly the same path. Preliminary design parameters using a CO 2 laser are presented

  7. Using Apparent Density of Paper from Hardwood Kraft Pulps to Predict Sheet Properties, based on Unsupervised Classification and Multivariable Regression Techniques

    Directory of Open Access Journals (Sweden)

    Ofélia Anjos

    2015-07-01

    Full Text Available Paper properties determine the product application potential and depend on the raw material, pulping conditions, and pulp refining. The aim of this study was to construct mathematical models that predict quantitative relations between the paper density and various mechanical and optical properties of the paper. A dataset of properties of paper handsheets produced with pulps of Acacia dealbata, Acacia melanoxylon, and Eucalyptus globulus beaten at 500, 2500, and 4500 revolutions was used. Unsupervised classification techniques were combined to assess the need to perform separated prediction models for each species, and multivariable regression techniques were used to establish such prediction models. It was possible to develop models with a high goodness of fit using paper density as the independent variable (or predictor for all variables except tear index and zero-span tensile strength, both dry and wet.

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

    International Nuclear Information System (INIS)

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

    2011-01-01

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

  9. Graded/Gradient Porous Biomaterials

    Directory of Open Access Journals (Sweden)

    Xigeng Miao

    2009-12-01

    Full Text Available Biomaterials include bioceramics, biometals, biopolymers and biocomposites and they play important roles in the replacement and regeneration of human tissues. However, dense bioceramics and dense biometals pose the problem of stress shielding due to their high Young’s moduli compared to those of bones. On the other hand, porous biomaterials exhibit the potential of bone ingrowth, which will depend on porous parameters such as pore size, pore interconnectivity, and porosity. Unfortunately, a highly porous biomaterial results in poor mechanical properties. To optimise the mechanical and the biological properties, porous biomaterials with graded/gradient porosity, pores size, and/or composition have been developed. Graded/gradient porous biomaterials have many advantages over graded/gradient dense biomaterials and uniform or homogenous porous biomaterials. The internal pore surfaces of graded/gradient porous biomaterials can be modified with organic, inorganic, or biological coatings and the internal pores themselves can also be filled with biocompatible and biodegradable materials or living cells. However, graded/gradient porous biomaterials are generally more difficult to fabricate than uniform or homogenous porous biomaterials. With the development of cost-effective processing techniques, graded/gradient porous biomaterials can find wide applications in bone defect filling, implant fixation, bone replacement, drug delivery, and tissue engineering.

  10. Effect of cell density on adipogenic differentiation of mesenchymal stem cells

    International Nuclear Information System (INIS)

    Lu, Hongxu; Guo, Likun; Wozniak, Michal J.; Kawazoe, Naoki; Tateishi, Tetsuya; Zhang, Xingdong; Chen, Guoping

    2009-01-01

    The effect of cell density on the adipogenic differentiation of human bone marrow-derived mesenchymal stem cells (MSCs) was investigated by using a patterning technique to induce the formation of a cell density gradient on a micropatterned surface. The adipogenic differentiation of MSCs at a density gradient from 5 x 10 3 to 3 x 10 4 cells/cm 2 was examined. Lipid vacuoles were observed at all cell densities after 1-3 weeks of culture in adipogenic differentiation medium although the lipid vacuoles were scarce at the low cell density and abundant at the high cell density. Real-time RT-PCR analysis showed that adipogenesis marker genes encoding peroxisome proliferator-activated receptor γ2 (PPARγ2), lipoprotein lipase (LPL), and fatty acid binding protein-4 (FABP4) were detected in the MSCs cultured at all cell densities. The results suggest that there was no apparent effect of cell density on the adipogenic differentiation of human MSCs.

  11. A systematic determination of diffusion coefficients of trace elements in open and restricted diffusive layers used by the diffusive gradients in a thin film technique

    DEFF Research Database (Denmark)

    Shiva, Amir Houshang; Teasdale, Peter R.; Bennett, William W.

    2015-01-01

    A systematic comparison of the diffusion coefficients of cations (Al, Cd, Co, Cu, Mn, Ni, Pb, Zn) and oxyanions (Al, As, Mo, Sb, V, W) in open (ODL) and restricted (RDL) diffusive layers used by the DGT technique was undertaken. Diffusion coefficients were measured using both the diffusion cell...... concentrations required with the Dcell measurements. This is the first time that D values have been reported for several oxyanions using RDL. Except for Al at pH 8.30 with ODL, all DDGT measurements were retarded relative to diffusion coefficients in water (DW) for both diffusive hydrogels. Diffusion in RDL...

  12. Comparison of several measure-correlate-predict models using support vector regression techniques to estimate wind power densities. A case study

    International Nuclear Information System (INIS)

    Díaz, Santiago; Carta, José A.; Matías, José M.

    2017-01-01

    Highlights: • Eight measure-correlate-predict (MCP) models used to estimate the wind power densities (WPDs) at a target site are compared. • Support vector regressions are used as the main prediction techniques in the proposed MCPs. • The most precise MCP uses two sub-models which predict wind speed and air density in an unlinked manner. • The most precise model allows to construct a bivariable (wind speed and air density) WPD probability density function. • MCP models trained to minimise wind speed prediction error do not minimise WPD prediction error. - Abstract: The long-term annual mean wind power density (WPD) is an important indicator of wind as a power source which is usually included in regional wind resource maps as useful prior information to identify potentially attractive sites for the installation of wind projects. In this paper, a comparison is made of eight proposed Measure-Correlate-Predict (MCP) models to estimate the WPDs at a target site. Seven of these models use the Support Vector Regression (SVR) and the eighth the Multiple Linear Regression (MLR) technique, which serves as a basis to compare the performance of the other models. In addition, a wrapper technique with 10-fold cross-validation has been used to select the optimal set of input features for the SVR and MLR models. Some of the eight models were trained to directly estimate the mean hourly WPDs at a target site. Others, however, were firstly trained to estimate the parameters on which the WPD depends (i.e. wind speed and air density) and then, using these parameters, the target site mean hourly WPDs. The explanatory features considered are different combinations of the mean hourly wind speeds, wind directions and air densities recorded in 2014 at ten weather stations in the Canary Archipelago (Spain). The conclusions that can be drawn from the study undertaken include the argument that the most accurate method for the long-term estimation of WPDs requires the execution of a

  13. An Inexpensive Digital Gradient Controller for HPLC.

    Science.gov (United States)

    Brady, James E.; Carr, Peter W.

    1983-01-01

    Use of gradient elution techniques in high performance liquid chromatography (HPLC) is often essential for direct separation of complex mixtures. Since most commercial controllers have features that are of marginal value for instructional purposes, a low-cost controller capable of illustrating essential features of gradient elution was developed.…

  14. Effects of forest road amelioration techniques on soil bulk density, surface runoff, sediment transport, soil moisture and seedling growth

    Science.gov (United States)

    Randy K. Kolka; Mathew F. Smidt

    2004-01-01

    Although numerous methods have been used to retire roads, new technologies have evolved that can potentially ameliorate soil damage, lessen ,the generation of nonpoint source pollution and increase tree productivity on forest roads. In this study we investigated the effects of three forest road amelioration techniques, subsoiling, recontouring and traditional...

  15. Determination of peak bone mass density and composition in low-income urban residents of metro Manila using isotope techniques

    International Nuclear Information System (INIS)

    Lim-Abrahan, M.A.V.; Guanzon, L.V.V.; De Guzman, A.M.; Villaruel, C.M.; Santos, F.

    1996-01-01

    Filipinos are predisposed to osteoporosis because of inadequate calcium in their diet early on in life, confounded by malnutrition, susceptibility to infectious diseases and their generally small body frame. And yet the problem of osteoporosis has not been properly addressed. The incidence of osteoporosis is not known since oftentimes it is established only once complications have set in. It is believed that osteoporosis poses a public health concern but its extent is not realized at present because of lack of local epidemiological data. This study aims to determine the bone mass density as a function of age among 210 screened and healthy volunteers coming from urban poor communities of Metro Manila over a 3-year period. A LUNAR DPX-L bone densitometry for dual X-ray photon absorptiometry will be used, with measurements taken on the spine and femur. It also aims to correlate factors such as nutritional intake, physical activity, lifestyle, sex and body mass index with that of bone mass density. Blood and urine samples will be obtained for biochemistry and hormonal radioimmunoassay examination. Statistical analysis will be done to com are differences within the group and to determine rate of bone loss as a function of age and sex. Plans for future research include the determination of trace element content in cortical bone and tooth samples from healthy living subjects. (author)

  16. Lung density

    DEFF Research Database (Denmark)

    Garnett, E S; Webber, C E; Coates, G

    1977-01-01

    The density of a defined volume of the human lung can be measured in vivo by a new noninvasive technique. A beam of gamma-rays is directed at the lung and, by measuring the scattered gamma-rays, lung density is calculated. The density in the lower lobe of the right lung in normal man during quiet...... breathing in the sitting position ranged from 0.25 to 0.37 g.cm-3. Subnormal values were found in patients with emphsema. In patients with pulmonary congestion and edema, lung density values ranged from 0.33 to 0.93 g.cm-3. The lung density measurement correlated well with the findings in chest radiographs...... but the lung density values were more sensitive indices. This was particularly evident in serial observations of individual patients....

  17. The gradient flow running coupling with twisted boundary conditions

    International Nuclear Information System (INIS)

    Ramos, Alberto

    2014-09-01

    We study the gradient flow for Yang-Mills theories with twisted boundary conditions. The perturbative behavior of the energy density left angle E(t) right angle is used to define a running coupling at a scale given by the linear size of the finite volume box. We compute the non-perturbative running of the pure gauge SU(2) coupling constant and conclude that the technique is well suited for further applications due to the relatively mild cutoff effects of the step scaling function and the high numerical precision that can be achieved in lattice simulations. We also comment on the inclusion of matter fields.

  18. Sensitivity of 3D gradient recalled echo susceptibility-weighted imaging technique compared to computed tomography angiography for detection of middle cerebral artery thrombus in acute stroke

    Directory of Open Access Journals (Sweden)

    Amit Agarwal

    2014-11-01

    Full Text Available We aimed at comparing the sensitivity of magnetic resonance (MR susceptibility-weighted imaging (SWI with computed tomography angiography (CTA in the detection of middle cerebral artery (MCA thrombus in acute stroke. Seventy-nine patients with acute MCA stroke was selected using our search engine software; only the ones showing restricted diffusion in the MCA territory on diffusion-weighted images were included. We finally selected 35 patients who had done both MRI (including SWI and CTA. Twenty random subjects with completely normal MRI (including SWI exam were selected as control. Two neuroradiologists (blinded to the presence or absence of stroke reviewed the SW images and then compared the findings with CT angiogram (in patients with stroke. The number of MCA segments showing thrombus in each patient was tabulated to estimate the thrombus burden. Thrombus was detected on SWI in one or more MCA segments in 30 out of 35 patients, on the first review. Of the 30, SWI showed thrombus in more than one MCA segments in 7 patients. CTA depicted branch occlusion in 31 cases. Thrombus was seen on both SWI and CTA in 28 patients. Thrombus was noted in two patients on SWI only, with no corresponding abnormality seen on CTA. Two patients with acute MCA showed no vascular occlusion or thrombus on either CTA or SWI. Only two case of false-positive thrombus was reported in normal control subjects. Susceptibility-weighted images had sensitivity and specificity of 86% and 90% respectively, with positive predictive value 94%. Sensitivity was 86% for SWI, compared with 89% for CTA, and this difference was statistically insignificant (P>0.05. Of all the positive cases on CTA (31 corresponding thrombus was seen on SWI in 90% of subjects (28 of 31. Susceptibility-weighted imaging has high sensitivity for detection of thrombus in acute MCA stroke. Moreover, SWI is a powerful technique for estimation of thrombus burden, which can be challenging on CTA.

  19. Differentiation between simple cyst and hepatic hemangioma utilizing T2-weighted magnetic resonance imaging with gradient-echo (b-FFE) technique

    International Nuclear Information System (INIS)

    Burim, Carolina Valente; D'Ippolito, Giuseppe; Pecci Neto, Luiz; Torlai, Fabiola Goda; Tiferes, Dario Ariel

    2008-01-01

    Objective: to establish the role of MRI T2-weighted sequences in the differentiation between simple cysts and hepatic hemangiomas. Materials and methods: a double-blinded, prospective, observational, cross sectional study evaluated 52 patients with 91 hepatic lesions (34 simple cysts and 57 hemangiomas) submitted to abdominal magnetic resonance imaging. The combined analysis of all sequences was considered as the golden-standard. TSE sequences with long echo trains and b-FFE sequences were subjectively analyzed by two independent observers for differentiating cysts from hemangiomas. The kappa test (κ) was utilized in the analysis of the methods accuracy and inter- and intra-observer agreement (p * ). Results: cysts and hemangiomas dimensions ranged respectively between 0.5 and 6.5 cm (mean 1.89 cm), and 0.8 and 11 cm (mean = 2.62 cm). The analysis of the sequences with long-TE and the golden-standard demonstrated a non-statistically significant agreement (k: 0.00-0.10). The agreement between the evaluation of the b-FFE sequence and the golden-standard ranged from substantial (κ: 0.62-0.71) to almost perfect (κ: 0.86) for both observers. The inter- and intra-observer agreement for the b-FFE sequence ranged from substantial (κ: 0.62-0.70) to almost perfect (κ: 0.85-0.91). Conclusion: T2-weighted images acquired with the b-FFE technique present a high accuracy and reproducibility in the differentiation between cysts and hepatic hemangiomas. (author)

  20. Development of the fabrication of ultra-low density ploy (4-methyl-1-pentene) (PMP) foams by thermal induced phase-inversion technique

    International Nuclear Information System (INIS)

    Zhang Lin; Wang Chaoyang; Luo Xuan; Du Kai; Tu Haiyan; Fan Hong; Luo Qing; Yuan Guanghui; Huang Lizhen

    2003-01-01

    By thermally induced phase-inversion technique, ploy (4-methyl-1-pentene) (PMP) foams are successfully prepared; the density and pore size are 3-80 mg/cm 3 and 1-20 μm respectively. Durene/naphthalene (60/40) is confirmed as the suitable solvent/nonsolvent binary system. The PMP's thermal properties are characterized by TG-DSC system. It is found that the foams thermal properties depend on the density. The thermal analysis method is utilized to measure the gelation of PMP in the binary solvent/nonsolvent system. The range of gelation temperature is preliminarily determined. The influence of mixture system composition and the cooling rate during the making of foams is discussed. TG-DSC is applied to determine the thermal properties of low-density PMP foams prepared in the laboratory. And the effect of density change on the thermal stability of foams are studied. The thermal analysis data play a great role in improving the foam quality. (authors)

  1. Measurement of the relative power density distribution of the IPEN/MB-01 reactor, using a fuel rod gamma scanning technique

    International Nuclear Information System (INIS)

    Carneiro, Alvaro Luiz Guimaraes

    1996-01-01

    This work presents a measurement methodology for determination of radial and axial relative power density distribution of the IPEN/MB-01 Reactor core by means of the fuel rod gamma scanning. The methodology is based on the proportionality between gamma activity emitted by the radioactive decay of the fission products and power density. The scanning technique consists of counting gamma radiation above 0,6 MeV along the active area of the fuel rod, getting a distribution profile. The experimental results will be used as a benchmark for qualification and to establish possible deviations for the calculational methodology currently used at IPEN. The comparison of the calculated and measured results showed good agreement. (author)

  2. Rapid Gradient-Echo Imaging

    Science.gov (United States)

    Hargreaves, Brian

    2012-01-01

    Gradient echo sequences are widely used in magnetic resonance imaging (MRI) for numerous applications ranging from angiography to perfusion to functional MRI. Compared with spin-echo techniques, the very short repetition times of gradient-echo methods enable very rapid 2D and 3D imaging, but also lead to complicated “steady states.” Signal and contrast behavior can be described graphically and mathematically, and depends strongly on the type of spoiling: fully balanced (no spoiling), gradient spoiling, or RF-spoiling. These spoiling options trade off between high signal and pure T1 contrast while the flip angle also affects image contrast in all cases, both of which can be demonstrated theoretically and in image examples. As with spin-echo sequences, magnetization preparation can be added to gradient-echo sequences to alter image contrast. Gradient echo sequences are widely used for numerous applications such as 3D perfusion imaging, functional MRI, cardiac imaging and MR angiography. PMID:23097185

  3. SEPARATION OF X-BEARING BOVINE SPERM BY CENTRIFUGATION IN CONTINUOUS PERCOLL AND OPTIPREP DENSITY GRADIENT: EFFECT IN SPERM VIABILITY AND IN VITRO EMBRYO PRODUCTION SEPARAÇÃO DE ESPERMATOZOIDES PORTADORES DO CROMOSSOMO X BOVINO POR CENTRIFUGAÇÃO EM GRADIENTE DE DENSIDADE CONTÍNUO DE PERCOLL E OPTIPREP: EFEITO SOBRE A VIABILIDADE ESPERMÁTICA E NA PRODUÇÃO IN VITRO DE EMBRIÕES

    Directory of Open Access Journals (Sweden)

    Aline Costa Lucio

    2009-07-01

    Full Text Available

    The aim of this study was to separate X-bearing bovine sperm by continuous Percoll and OptiPrep density gradients and to validate the sexing of resultant in vitro produced embryos by Polimerase Chain Reaction (PCR. Frozen/thawed sperm was layered on density gradients which were previously prepared in polystyrene tubes, 24 h before procedures and maintained at 4 °C. The tubes were centrifuged at 500 x g for 15 min at 22 °C. Supernatants were gently aspirated and the sperm recovered from the bottom of the tubes. Viability and integrity of sperm were evaluated by Trypan Blue/Giemsa stain. Cleavage and blastocyst rates were determined by in vitro production of embryos and PCR was performed for identification of the embryos’ genetic sex. No damage in viability and acrossomal integrity and in cleavage and blastocyst rates was found in the Percoll and OptiPrep treatment compared to the non-centrifuged group (P>0.05. The percentage of female embryos in the Percoll and OptiPrep group was 63.0 and 47.6%, respectively. The female embryos in control group were 48.7%. A sexual deviation in the Percoll density gradient was achieved without reduction of sperm viability and in vitro production rates.

    KEY WORDS: Bovine, centrifugation, in vitro production of embryos, PCR, X-bearing sperm.

    O objetivo deste estudo foi separar espermatozoides bovinos portadores do cromossomo X pela centrifugação em gradiente de densidade contínuo de Percoll e OptiPrep, e validar a sexagem pela reação em cadeia da polimerase (PCR, dos embriões produzidos in vitro. Para a sexagem, espermatozoides descongelados foram depositados nos gradientes de densidade, previamente preparados, em tubos de poliestireno, 24 horas antes da sexagem e mantidos a 4°C. Centrifugou-se a 500 x g por quinze minutos a 22°C. Os sobrenadantes foram aspirados, e os espermatozoides recuperados do

  4. Eigenvector of gravity gradient tensor for estimating fault dips considering fault type

    Science.gov (United States)

    Kusumoto, Shigekazu

    2017-12-01

    The dips of boundaries in faults and caldera walls play an important role in understanding their formation mechanisms. The fault dip is a particularly important parameter in numerical simulations for hazard map creation as the fault dip affects estimations of the area of disaster occurrence. In this study, I introduce a technique for estimating the fault dip using the eigenvector of the observed or calculated gravity gradient tensor on a profile and investigating its properties through numerical simulations. From numerical simulations, it was found that the maximum eigenvector of the tensor points to the high-density causative body, and the dip of the maximum eigenvector closely follows the dip of the normal fault. It was also found that the minimum eigenvector of the tensor points to the low-density causative body and that the dip of the minimum eigenvector closely follows the dip of the reverse fault. It was shown that the eigenvector of the gravity gradient tensor for estimating fault dips is determined by fault type. As an application of this technique, I estimated the dip of the Kurehayama Fault located in Toyama, Japan, and obtained a result that corresponded to conventional fault dip estimations by geology and geomorphology. Because the gravity gradient tensor is required for this analysis, I present a technique that estimates the gravity gradient tensor from the gravity anomaly on a profile.

  5. Heat generation during implant placement in low-density bone: effect of surgical technique, insertion torque and implant macro design.

    Science.gov (United States)

    Marković, Aleksa; Mišić, Tijana; Miličić, Biljana; Calvo-Guirado, Jose Luis; Aleksić, Zoran; Ðinić, Ana

    2013-07-01

    The study aimed to investigate the effect of surgical technique, implant macrodesign and insertion torque on bone temperature changes during implant placement. In the in vitro study, 144 self-tapping (blueSKY(®) 4 × 10 mm; Bredent) and 144 non-self-tapping (Standard implant(®) 4.1 × 10 mm; Straumann) were placed in osteotomies prepared in pig ribs by lateral bone condensing or bone drilling techniques. The maximum insertion torque values of 30, 35 and 40 Ncm were used. Real-time bone temperature measurement during implant placement was performed by three thermocouples positioned vertically, in tripod configuration around every osteotomy, at a distance of 5 mm from it and at depths of 1, 5 and 10 mm. Data were analysed using Kruskal-Wallis, Mann-Whitney U-tests and Regression analysis. Significant predictor of bone temperature at the osteotomy depth of 1 mm was insertion torque (P = 0.003) and at the depth of 10-mm implant macrodesign (P = 0.029), while no significant predictor at depth of 5 mm was identified (P > 0.05). Higher insertion torque values as well as non-self-tapping implant macrodesign were related to higher temperatures. Implant placement in sites prepared by bone drilling induced significantly higher temperature increase (P = 0.021) compared with bone condensing sites at the depth of 5 mm, while no significant difference was recorded at other depths. Compared with 30 Ncm, insertion torque values of 35 and 40 Ncm produced significantly higher temperature increase (P = 0.005; P = 0.003, respectively) at the depth of 1 mm. There was no significant difference in temperature change induced by 35 and 40 Ncm, neither by implant macrodesign at all investigated depths (P > 0.05). Placement of self-tapping implants with low insertion torque into sites prepared by lateral bone condensing technique might be advantageous in terms of thermal effect on bone. © 2012 John Wiley & Sons A/S.

  6. An x-ray backlit Talbot-Lau deflectometer for high-energy-density electron density diagnostics

    Science.gov (United States)

    Valdivia, M. P.; Stutman, D.; Stoeckl, C.; Theobald, W.; Mileham, C.; Begishev, I. A.; Bromage, J.; Regan, S. P.

    2016-02-01

    X-ray phase-contrast techniques can measure electron density gradients in high-energy-density plasmas through refraction induced phase shifts. An 8 keV Talbot-Lau interferometer consisting of free standing ultrathin gratings was deployed at an ultra-short, high-intensity laser system using K-shell emission from a 1-30 J, 8 ps laser pulse focused on thin Cu foil targets. Grating survival was demonstrated for 30 J, 8 ps laser pulses. The first x-ray deflectometry images obtained under laser backlighting showed up to 25% image contrast and thus enabled detection of electron areal density gradients with a maximum value of 8.1 ± 0.5 × 1023 cm-3 in a low-Z millimeter sized sample. An electron density profile was obtained from refraction measurements with an error of x-ray source-size, similar to conventional radiography.

  7. "Cuts in Action": A High-Density EEG Study Investigating the Neural Correlates of Different Editing Techniques in Film.

    Science.gov (United States)

    Heimann, Katrin S; Uithol, Sebo; Calbi, Marta; Umiltà, Maria A; Guerra, Michele; Gallese, Vittorio

    2017-08-01

    In spite of their striking differences with real-life perception, films are perceived and understood without effort. Cognitive film theory attributes this to the system of continuity editing, a system of editing guidelines outlining the effect of different cuts and edits on spectators. A major principle in this framework is the 180° rule, a rule recommendation that, to avoid spectators' attention to the editing, two edited shots of the same event or action should not be filmed from angles differing in a way that expectations of spatial continuity are strongly violated. In the present study, we used high-density EEG to explore the neural underpinnings of this rule. In particular, our analysis shows that cuts and edits in general elicit early ERP component indicating the registration of syntactic violations as known from language, music, and action processing. However, continuity edits and cuts-across the line differ from each other regarding later components likely to be indicating the differences in spatial remapping as well as in the degree of conscious awareness of one's own perception. Interestingly, a time-frequency analysis of the occipital alpha rhythm did not support the hypothesis that such differences in processing routes are mainly linked to visual attention. On the contrary, our study found specific modulations of the central mu rhythm ERD as an indicator of sensorimotor activity, suggesting that sensorimotor networks might play an important role. We think that these findings shed new light on current discussions about the role of attention and embodied perception in film perception and should be considered when explaining spectators' different experience of different kinds of cuts. Copyright © 2016 Cognitive Science Society, Inc.

  8. Denaturing gradient gel electrophoresis

    International Nuclear Information System (INIS)

    Kocherginskaya, S.A.; Cann, I.K.O.; Mackie, R.I.

    2005-01-01

    It is worthwhile considering that only some 30 species make up the bulk of the bacterial population in human faeces at any one time based on the classical cultivation-based approach. The situation in the rumen is similar. Thus, it is practical to focus on specific groups of interest within the complex community. These may be the predominant or the most active species, specific physiological groups or readily identifiable (genetic) clusters of phylogenetically related organisms. Several 16S rDNA fingerprinting techniques can be invaluable for selecting and monitoring sequences or phylogenetic groups of interest and are described below. Over the past few decades, considerable attention was focussed on the identification of pure cultures of microbes on the basis of genetic polymorphisms of DNA encoding rRNA such as ribotyping, amplified fragment length polymorphism and randomly amplified polymorphic DNA. However, many of these methods require prior cultivation and are less suitable for use in analysis of complex mixed populations although important in describing cultivated microbial diversity in molecular terms. Much less attention was given to molecular characterization of complex communities. In particular, research into diversity and community structure over time has been revolutionized by the advent of molecular fingerprinting techniques for complex communities. Denaturing or temperature gradient gel electrophoresis (DGGE/TGGE) methods have been successfully applied to the analysis of human, pig, cattle, dog and rodent intestinal populations

  9. Magnetoelectric Transverse Gradient Sensor with High Detection Sensitivity and Low Gradient Noise

    OpenAIRE

    Zhang, Mingji; Or, Siu Wing

    2017-01-01

    We report, theoretically and experimentally, the realization of a high detection performance in a novel magnetoelectric (ME) transverse gradient sensor based on the large ME effect and the magnetic field gradient (MFG) technique in a pair of magnetically-biased, electrically-shielded, and mechanically-enclosed ME composites having a transverse orientation and an axial separation. The output voltage of the gradient sensor is directly obtained from the transverse MFG-induced difference in ME vo...

  10. A analytical comparison of different estimators for the density distribution of the catalyst in a experimental riser by a gammametric technique

    International Nuclear Information System (INIS)

    Lima, Emerson Alexandre de Oliveira; Dantas Carlos C.; Melo, Silvio de Barros; Santos, Valdemir Alexandre dos

    2005-01-01

    In this paper, we solve the following questions: what will be the estimate of the r = r (x, y, z) function format? Which method would describe the density distribution function more precisely? Which is the best estimator? Also, once the ρ=ρ(x, y, z) format and the approximation technique is defined, comes the experimental arrangement and pass length configuration, which are the next problems to be solved. Finding the best parameter estimation for the ρ=ρ(x, y, z) function according to the C pass lengths and their spatial configuration. The latter is required to define the ρ=ρ(x, y, z) function resolution and the mechanical scanning movements of the arrangement. Such definitions will be implemented for an automate arrangement, by a computational program, to further development of the reconstruction of catalyst density distribution on experimental risers.. The precision evaluation was finally compared to the arrangement geometry that yields the best pass length spatial configuration. The results are shown in graphics for the two known density distributions. As a conclusion, the parameters for an automate arrangement design, are given under the required precision for the catalyst distribution reconstruction. (author)

  11. Tubing-Electrospinning: A One-Step Process for Fabricating Fibrous Matrices with Spatial, Chemical, and Mechanical Gradients.

    Science.gov (United States)

    Kim, Jung-Suk; Im, Byung Gee; Jin, Gyuhyung; Jang, Jae-Hyung

    2016-08-31

    Guiding newly generated tissues in a gradient pattern, thereby precisely mimicking inherent tissue morphology and subsequently arranging the intimate networks between adjacent tissues, is essential to raise the technical levels of tissue engineering and facilitate its transition into the clinic. In this study, a straightforward electrospinning method (the tubing-electrospinning technique) was developed to create fibrous matrices readily with diverse gradient patterns and to induce patterned cellular responses. Gradient fibrous matrices can be produced simply by installing a series of polymer-containing lengths of tubing into an electrospinning circuit and sequentially processing polymers without a time lag. The loading of polymer samples with different characteristics, including concentration, wettability, and mechanical properties, into the tubing system enabled unique features in fibrous matrices, such as longitudinal gradients in fiber density, surface properties, and mechanical stiffness. The resulting fibrous gradients were shown to arrange cellular migration and residence in a gradient manner, thereby offering efficient cues to mediate patterned tissue formation. The one-step process using tubing-electrospinning apparatus can be used without significant modifications regardless of the type of fibrous gradient. Hence, the tubing-electrospinning system can serve as a platform that can be readily used by a wide-range of users to induce patterned tissue formation in a gradient manner, which will ultimately improve the functionality of tissue engineering scaffolds.

  12. Ion temperature gradient instability

    International Nuclear Information System (INIS)

    1989-01-01

    Anomalous ion thermal conductivity remains an open physics issue for the present generation of high temperature Tokamaks. It is generally believed to be due to Ion Temperature Gradient Instability (η i mode). However, it has been difficult, if not impossible to identify this instability and study the anomalous transport due to it, directly. Therefore the production and identification of the mode is pursued in the simpler and experimentally convenient configuration of the Columbia Linear Machine (CLM). CLM is a steady state machine which already has all the appropriate parameters, except η i . This parameter is being increased to the appropriate value of the order of 1 by 'feathering' a tungsten screen located between the plasma source and the experimental cell to flatten the density profile and appropriate redesign of heating antennas to steepen the ion temperature profile. Once the instability is produced and identified, a thorough study of the characteristics of the mode can be done via a wide range of variation of all the critical parameters: η i , parallel wavelength, etc

  13. A substrate independent approach for generation of surface gradients

    Energy Technology Data Exchange (ETDEWEB)

    Goreham, Renee V. [Mawson Institute, University of South Australia, Mawson Lakes 5095 (Australia); Mierczynska, Agnieszka; Pierce, Madelene [Ian Wark Research Institute, University of South Australia, Mawson Lakes 5095 (Australia); Short, Robert D.; Taheri, Shima; Bachhuka, Akash; Cavallaro, Alex; Smith, Louise E. [Mawson Institute, University of South Australia, Mawson Lakes 5095 (Australia); Vasilev, Krasimir, E-mail: krasimir.vasilev@unisa.edu.au [Mawson Institute, University of South Australia, Mawson Lakes 5095 (Australia)

    2013-01-01

    Recently, surface gradients have attracted significant interest for various research and technological applications. In this paper, we report a facile and versatile method for generating surface gradients of immobilized nanoparticles, nanotopography and ligands that is independent from the substrate material. The method consists of first depositing a functional polymer layer on a substrate and subsequent time controlled immersion of this functionalized substrate in solution gold nanoparticles (AuNPs), silver nanoparticles (AgNPs) or poly (styrenesulfonate) (PSS). Chemical characterization by X-ray Photoelectron Spectroscopy (XPS) and morphological analysis by Atomic Force Microscopy (AFM) show that the density of nanoparticles and the concentration of PSS across the surface increases in a gradient manner. As expected, time of immersion determines the concentration of surface bound species. We also demonstrate the generation of surface gradients of pure nanotopography. This is achieved by depositing a 5 nm thick plasma polymer layer on top of the number density gradient of nanoparticles to achieve a homogeneous surface chemistry. The surface independent approach for generation of surface gradients presented in this paper may open opportunities for a wider use of surface gradient in research and in various technologies. - Highlights: ► We present a substrate independent approach for generation of surface gradients. ► We demonstrate well-defined density gradients of gold and silver nanoparticles. ► We provide an example of pure surface nanotopography gradients. ► We demonstrate concentration gradients of bound ligands.

  14. A substrate independent approach for generation of surface gradients

    International Nuclear Information System (INIS)

    Goreham, Renee V.; Mierczynska, Agnieszka; Pierce, Madelene; Short, Robert D.; Taheri, Shima; Bachhuka, Akash; Cavallaro, Alex; Smith, Louise E.; Vasilev, Krasimir

    2013-01-01

    Recently, surface gradients have attracted significant interest for various research and technological applications. In this paper, we report a facile and versatile method for generating surface gradients of immobilized nanoparticles, nanotopography and ligands that is independent from the substrate material. The method consists of first depositing a functional polymer layer on a substrate and subsequent time controlled immersion of this functionalized substrate in solution gold nanoparticles (AuNPs), silver nanoparticles (AgNPs) or poly (styrenesulfonate) (PSS). Chemical characterization by X-ray Photoelectron Spectroscopy (XPS) and morphological analysis by Atomic Force Microscopy (AFM) show that the density of nanoparticles and the concentration of PSS across the surface increases in a gradient manner. As expected, time of immersion determines the concentration of surface bound species. We also demonstrate the generation of surface gradients of pure nanotopography. This is achieved by depositing a 5 nm thick plasma polymer layer on top of the number density gradient of nanoparticles to achieve a homogeneous surface chemistry. The surface independent approach for generation of surface gradients presented in this paper may open opportunities for a wider use of surface gradient in research and in various technologies. - Highlights: ► We present a substrate independent approach for generation of surface gradients. ► We demonstrate well-defined density gradients of gold and silver nanoparticles. ► We provide an example of pure surface nanotopography gradients. ► We demonstrate concentration gradients of bound ligands

  15. Experimental estimation of fluctuating velocity and scalar gradients in turbulence

    Energy Technology Data Exchange (ETDEWEB)

    Hearst, R.J.; Lavoie, P. [University of Toronto, Institute for Aerospace Studies, Toronto, ON (Canada); Buxton, O.R.H. [The University of Texas at Austin, Center for Aeromechanics Research, Austin, TX (United States); Ganapathisubramani, B. [University of Southampton, Aerodynamics and Flight Mechanics Research Group, Southampton (United Kingdom)

    2012-10-15

    The effect of numerical differentiation is investigated in the context of evaluating fluctuating velocity and scalar quantities in turbulent flows. In particular, 2-point forward-difference and 3-, 5-, 7-, and 9-point centred-difference schemes are investigated. The spectral technique introduced by Wyngaard (in J Sci Instr 1(2):1105-1108, 1968) for homogeneous turbulence is used to quantify the effects of the schemes. Numerical differentiation is shown to attenuate gradient spectra over a range of wavenumbers. The spectral attenuation, which varies with the order of the scheme, results in a reduction in the measured mean-squared gradients. High-order schemes (e.g. 7- or 9-point) are shown to significantly decrease the attenuation at all wavenumbers and as a result produce more accurate gradients. Hot-wire measurements and direct numerical simulations of decaying homogeneous, isotropic turbulence are found to be in good agreement with the predictions of the analysis, which suggests that high-order schemes can be used to improve empirical gradient estimates. The shape of the probability density functions is also found to be sensitive to the choice of numerical differentiation scheme. The effect of numerical differentiation is also discussed with respect to particle image velocimetry (PIV) measurements of a nominally two-dimensional planar mixing layer. It is found that the relatively low signal-to-noise ratio inherent in typical PIV measurements necessitates the use of low-order schemes to prevent excessive noise amplification, which increases with the order of the scheme. The results of the present work demonstrate that high-order numerical differentiation schemes can be employed to more accurately resolve gradients measured at a given resolution provided the measurements have an adequate signal-to-noise ratio. (orig.)

  16. Aluminum and gallium nuclei as microscopic probes for pulsed electron-nuclear double resonance diagnostics of electric-field gradient and spin density in garnet ceramics doped with paramagnetic ions

    Science.gov (United States)

    Uspenskaya, Yu. A.; Mamin, G. V.; Babunts, R. A.; Badalyan, A. G.; Edinach, E. V.; Asatryan, H. R.; Romanov, N. G.; Orlinskii, S. B.; Khanin, V. M.; Wieczorek, H.; Ronda, C.; Baranov, P. G.

    2018-03-01

    The presence of aluminum and gallium isotopes with large nuclear magnetic and quadrupole moments in the nearest environment of impurity ions Mn2+ and Ce3+ in garnets made it possible to use hyperfine and quadrupole interactions with these ions to determine the spatial distribution of the unpaired electron and the gradient of the electric field at the sites of aluminum and gallium in the garnet lattice. High-frequency (94 GHz) electron spin echo detected electron paramagnetic resonance and electron-nuclear double resonance measurements have been performed. Large difference in the electric field gradient and quadrupole splitting at octahedral and tetrahedral sites allowed identifying the positions of aluminum and gallium ions in the garnet lattice and proving that gallium first fills tetrahedral positions in mixed aluminum-gallium garnets. This should be taken into account in the development of garnet-based scintillators and lasers. It is shown that the electric field gradient at aluminum nuclei near Mn2+ possessing an excess negative charge in the garnet lattice is ca. 2.5 times larger than on aluminum nuclei near Ce3+.

  17. $L_{0}$ Gradient Projection.

    Science.gov (United States)

    Ono, Shunsuke

    2017-04-01

    Minimizing L 0 gradient, the number of the non-zero gradients of an image, together with a quadratic data-fidelity to an input image has been recognized as a powerful edge-preserving filtering method. However, the L 0 gradient minimization has an inherent difficulty: a user-given parameter controlling the degree of flatness does not have a physical meaning since the parameter just balances the relative importance of the L 0 gradient term to the quadratic data-fidelity term. As a result, the setting of the parameter is a troublesome work in the L 0 gradient minimization. To circumvent the difficulty, we propose a new edge-preserving filtering method with a novel use of the L 0 gradient. Our method is formulated as the minimization of the quadratic data-fidelity subject to the hard constraint that the L 0 gradient is less than a user-given parameter α . This strategy is much more intuitive than the L 0 gradient minimization because the parameter α has a clear meaning: the L 0 gradient value of the output image itself, so that one can directly impose a desired degree of flatness by α . We also provide an efficient algorithm based on the so-called alternating direction method of multipliers for computing an approximate solution of the nonconvex problem, where we decompose it into two subproblems and derive closed-form solutions to them. The advantages of our method are demonstrated through extensive experiments.

  18. Density Distributions of Cyclotrimethylenetrinitramines (RDX)

    International Nuclear Information System (INIS)

    Hoffman, D M

    2002-01-01

    As part of the US Army Foreign Comparative Testing (FCT) program the density distributions of six samples of class 1 RDX were measured using the density gradient technique. This technique was used in an attempt to distinguish between RDX crystallized by a French manufacturer (designated insensitive or IRDX) from RDX manufactured at Holston Army Ammunition Plant (HAAP), the current source of RDX for Department of Defense (DoD). Two samples from different lots of French IRDX had an average density of 1.7958 ± 0.0008 g/cc. The theoretical density of a perfect RDX crystal is 1.806 g/cc. This yields 99.43% of the theoretical maximum density (TMD). For two HAAP RDX lots the average density was 1.786 ± 0.002 g/cc, only 98.89% TMD. Several other techniques were used for preliminary characterization of one lot of French IRDX and two lot of HAAP RDX. Light scattering, SEM and polarized optical microscopy (POM) showed that SNPE and Holston RDX had the appropriate particle size distribution for Class 1 RDX. High performance liquid chromatography showed quantities of HMX in HAAP RDX. French IRDX also showed a 1.1 C higher melting point compared to HAAP RDX in the differential scanning calorimetry (DSC) consistent with no melting point depression due to the HMX contaminant. A second part of the program involved characterization of Holston RDX recrystallized using the French process. After reprocessing the average density of the Holston RDX was increased to 1.7907 g/cc. Apparently HMX in RDX can act as a nucleating agent in the French RDX recrystallization process. The French IRDX contained no HMX, which is assumed to account for its higher density and narrower density distribution. Reprocessing of RDX from Holston improved the average density compared to the original Holston RDX, but the resulting HIRDX was not as dense as the original French IRDX. Recrystallized Holston IRDX crystals were much larger (3-500 (micro)m or more) then either the original class 1 HAAP RDX or French

  19. Dual fuel gradients in uranium silicide plates

    Energy Technology Data Exchange (ETDEWEB)

    Pace, B.W. [Babock and Wilcox, Lynchburg, VA (United States)

    1997-08-01

    Babcock & Wilcox has been able to achieve dual gradient plates with good repeatability in small lots of U{sub 3}Si{sub 2} plates. Improvements in homogeneity and other processing parameters and techniques have allowed the development of contoured fuel within the cladding. The most difficult obstacles to overcome have been the ability to evaluate the bidirectional fuel loadings in comparison to the perfect loading model and the different methods of instilling the gradients in the early compact stage. The overriding conclusion is that to control the contour of the fuel, a known relationship between the compact, the frames and final core gradient must exist. Therefore, further development in the creation and control of dual gradients in fuel plates will involve arriving at a plausible gradient requirement and building the correct model between the compact configuration and the final contoured loading requirements.

  20. Deep inspiration breath-hold technique for lung tumors: the potential value of target immobilization and reduced lung density in dose escalation

    International Nuclear Information System (INIS)

    Hanley, J.; Debois, M.M.; Raben, A.; Mageras, G.S.; Lutz, W.R.; Mychalczak, B.; Schwartz, L.H.; Gloeggler, P.J.; Leibel, S.A.; Fuks, Z.; Kutcher, G.J.

    1996-01-01

    Purpose/Objective: Lung tumors are subject to movement due to respiratory motion. Conventionally, a margin is applied to the clinical target volume (CTV) to account for this and other treatment uncertainties. The purpose of this study is to evaluate the dosimetric benefits of a deep inspiration breath-hold (DIBH) technique which has two distinct features - deep inspiration which reduces lung density and breath-hold which immobilizes lung tumors. Both properties can potentially reduce the mass of normal lung tissue in the high dose region, thus improving the possibility of dose escalation. Methods and Materials: To study the efficacy of the DIBH technique, CT scans are acquired for each patient under 4 respiration conditions: free-breathing; DIBH; shallow inspiration breath-hold; shallow expiration breath-hold. The free-breathing and DIBH scans are used to generate treatment plans for comparison of standard and DIBH techniques, while the shallow inspiration and expiration scans provide information on the maximum extent of tumor motion under free-breathing conditions. To acquire the breath-hold scans, the patients are brought to reproducible respiration levels using spirometry and slow vital capacity maneuvers. For the treatment plan comparison free-breathing and DIBH planning target volumes (PTVs) are constructed consisting of the CTV plus a margin for setup error and lung tumor motion. For both plans the margin for setup error is the same while the margin for lung tumor motion differs. The margin for organ motion in free-breathing is determined by the maximum tumor excursions in the shallow inspiration and expiration CT scans. For the DIBH, tumor motion is reduced to the extent to which DIBH can be maintained and the margin for any residual tumor motion is determined from repeat fluoroscopic movies, acquired with the patient monitored using spirometry. Three-dimensional treatment plans, generated using apertures based on the free-breathing and DIBH PTVs, are

  1. Three gradients and the perception of flat and curved surfaces.

    Science.gov (United States)

    Cutting, J E; Millard, R T

    1984-06-01

    Researchers of visual perception have long been interested in the perceived slant of a surface and in the gradients that purportedly specify it. Slant is the angle between the line of sight and the tangent to the planar surface at any point, also called the surface normal. Gradients are the sources of information that grade, or change, with visual angle as one looks from one's feet upward to the horizon. The present article explores three gradients--perspective, compression, and density--and the phenomenal impression of flat and curved surfaces. The perspective gradient is measured at right angles to the axis of tilt at any point in the optic array; that is, when looking down a hallway at the tiles of a floor receding in the distance, perspective is measured by the x-axis width of each tile projected on the image plane orthogonal to the line of sight. The compression gradient is the ratio of y/x axis measures on the projected plane. The density gradient is measured by the number of tiles per unit solid visual angle. For flat surfaces and many others, perspective and compression gradients decrease with distance, and the density gradient increases. We discuss the manner in which these gradients change for various types of surfaces. Each gradient is founded on a different assumption about textures on the surfaces around us. In Experiment 1, viewers assessed the three-dimensional character of projections of flat and curved surfaces receding in the distance. They made pairwise judgments of preference and of dissimilarity among eight stimuli in each of four sets. The presence of each gradient was manipulated orthogonally such that each stimulus had zero, one, two, or three gradients appropriate for either a flat surface or a curved surface. Judgments were made were made for surfaces with both regularly shaped and irregularly shaped textures scattered on them. All viewer assessment were then scaled in one dimension. Multiple correlation and regression on the scale values

  2. Generalized Gradient Approximation Made Simple

    International Nuclear Information System (INIS)

    Perdew, J.P.; Burke, K.; Ernzerhof, M.

    1996-01-01

    Generalized gradient approximations (GGA close-quote s) for the exchange-correlation energy improve upon the local spin density (LSD) description of atoms, molecules, and solids. We present a simple derivation of a simple GGA, in which all parameters (other than those in LSD) are fundamental constants. Only general features of the detailed construction underlying the Perdew-Wang 1991 (PW91) GGA are invoked. Improvements over PW91 include an accurate description of the linear response of the uniform electron gas, correct behavior under uniform scaling, and a smoother potential. copyright 1996 The American Physical Society

  3. Measurement of gradient magnetic field temporal characteristics

    International Nuclear Information System (INIS)

    Bartusek, K.; Jflek, B.

    1994-01-01

    We describe a technique of measuring the time dependence and field distortions of magnetic fields due to eddy currents (EC) produced by time-dependent magnetic field gradients. The EC measuring technique makes use of a large volume sample and selective RF excitation pulses and free induction decay (FID) (or a spin or gradient echo) to measure the out-of-phase component of the FID, which is proportional to γδB, i.e. the amount the signal is off resonance. The measuring technique is sensitive, easy to implement and interpret, and used for determining pre-emphasis compensation parameters

  4. Evaluation of mandibular bone mineral density using the dual-energy X-ray absorptiometry technique in edentulous subjects living in an endemic fluorosis region.

    Science.gov (United States)

    Buyukkaplan, U S; Guldag, M U

    2012-07-01

    Fluoride is one of the biological trace elements with a strong affinity for osseous, cartilaginous and dental tissue. The dental and skeletal effects of high fluoride intake have already been studied in the literature, but little is known about the effects of high fluoride intake on edentulous mandibles. The purpose of this study was to evaluate the effects of high fluoride intake on mandibular bone mineral density (BMD) measured by the dual-energy X-ray absorptiometry (DXA) technique in edentulous individuals with systemic fluorosis. 32 people who were living in an endemic fluorosis area since birth and 31 people who were living in a non-endemic fluorosis area since birth (control group) participated in this study. Systemic fluorosis was diagnosed in the patients using the sialic acid (NANA)/glycosaminoglycan (GAG) ratio. The BMDs of the mandibles were determined by the DXA technique. The serum NANA/GAG ratios in the fluorosis group were significantly lower than those in the control group (p structures of the stomatognathic system.

  5. A PD-SOI based DTI-LOCOS combined cross isolation technique for minimizing TID radiation induced leakage in high density memory

    International Nuclear Information System (INIS)

    Qiao Fengying; Pan Liyang; Wu Dong; Liu Lifang; Xu Jun

    2014-01-01

    In order to minimize leakage current increase under total ionizing dose (TID) radiation in high density memory circuits, a new isolation technique, combining deep trench isolation (DTI) between the wells, local oxidation of silicon (LOCOS) isolation between the devices within the well, and a P-diffused area in order to limit leakage at the isolation edge is implemented in partly-depleted silicon-on-insulator (PD-SOI) technology. This radiation hardening technique can minimize the layout area by more than 60%, and allows flexible placement of the body contact. Radiation hardened transistors and 256 Kb flash memory chips are designed and fabricated in a 0.6 μm PD-SOI process. Experiments show that no obvious increase in leakage current is observed for single transistors under 1 Mrad(Si) radiation, and that the 256 Kb memory chip still functions well after a TID of 100 krad(Si), with only 50% increase of the active power consumption in read mode. (semiconductor devices)

  6. Quantification of Liver Proton-Density Fat Fraction in an 7.1 Tesla preclinical MR Systems: Impact of the Fitting Technique

    Science.gov (United States)

    Mahlke, C; Hernando, D; Jahn, C; Cigliano, A; Ittermann, T; Mössler, A; Kromrey, ML; Domaska, G; Reeder, SB; Kühn, JP

    2016-01-01

    Purpose To investigate the feasibility of estimating the proton-density fat fraction (PDFF) using a 7.1 Tesla magnetic resonance imaging (MRI) system and to compare the accuracy of liver fat quantification using different fitting approaches. Materials and Methods Fourteen leptin-deficient ob/ob mice and eight intact controls were examined in a 7.1 Tesla animal scanner using a 3-dimensional six-echo chemical shift-encoded pulse sequence. Confounder-corrected PDFF was calculated using magnitude (magnitude data alone) and combined fitting (complex and magnitude data). Differences between fitting techniques were compared using Bland-Altman analysis. In addition, PDFFs derived with both reconstructions were correlated with histopathological fat content and triglyceride mass fraction using linear regression analysis. Results The PDFFs determined with use of both reconstructions correlated very strongly (r=0.91). However, small mean bias between reconstructions demonstrated divergent results (3.9%; CI 2.7%-5.1%). For both reconstructions, there was linear correlation with histopathology (combined fitting: r=0.61; magnitude fitting: r=0.64) and triglyceride content (combined fitting: r=0.79; magnitude fitting: r=0.70). Conclusion Liver fat quantification using the PDFF derived from MRI performed at 7.1 Tesla is feasible. PDFF has strong correlations with histopathologically determined fat and with triglyceride content. However, small differences between PDFF reconstruction techniques may impair the robustness and reliability of the biomarker at 7.1 Tesla. PMID:27197806

  7. Coreless Concept for High Gradient Induction Cell

    International Nuclear Information System (INIS)

    Krasnykh, Anatoly

    2008-01-01

    An induction linac cell for a high gradient is discussed. The proposed solid state coreless approach for the induction linac topology (SLIM(reg s ign)) is based on nanosecond mode operation. This mode may have an acceleration gradient comparable with gradients of rf- accelerator structures. The discussed induction system has the high electric efficiency. The key elements are a solid state semiconductor switch and a high electric density dielectric with a thin section length. The energy in the induction system is storied in the magnetic field. The nanosecond current break-up produces the high voltage. The induced voltage is used for acceleration. This manner of an operation allows the use of low voltage elements in the booster part and achieves a high accelerating gradient. The proposed topology was tested in POP (proof of principle) experiments

  8. Geometry optimization of molecules within an LCGTO local-density functional approach

    International Nuclear Information System (INIS)

    Mintmire, J.W.

    1990-01-01

    We describe our implementation of geometry optimization techniques within the linear combination of Gaussian-type orbitals (LCGTO) approach to local-density functional theory. The algorithm for geometry optimization is based on the evaluation of the gradient of the total energy with respect to internal coordinates within the local-density functional scheme. We present optimization results for a range of small molecules which serve as test cases for our approach

  9. Predator Presence and Vegetation Density Affect Capture Rates and Detectability of Litoria aurea Tadpoles: Wide-Ranging Implications for a Common Survey Technique.

    Directory of Open Access Journals (Sweden)

    Madeleine R Sanders

    Full Text Available Trapping is a common sampling technique used to estimate fundamental population metrics of animal species such as abundance, survival and distribution. However, capture success for any trapping method can be heavily influenced by individuals' behavioural plasticity, which in turn affects the accuracy of any population estimates derived from the data. Funnel trapping is one of the most common methods for sampling aquatic vertebrates, although, apart from fish studies, almost nothing is known about the effects of behavioural plasticity on trapping success. We used a full factorial experiment to investigate the effects that two common environmental parameters (predator presence and vegetation density have on the trapping success of tadpoles. We estimated that the odds of tadpoles being captured in traps was 4.3 times higher when predators were absent compared to present and 2.1 times higher when vegetation density was high compared to low, using odds ratios based on fitted model means. The odds of tadpoles being detected in traps were also 2.9 times higher in predator-free environments. These results indicate that common environmental factors can trigger behavioural plasticity in tadpoles that biases trapping success. We issue a warning to researchers and surveyors that trapping biases may be commonplace when conducting surveys such as these, and urge caution in interpreting data without consideration of important environmental factors present in the study system. Left unconsidered, trapping biases in capture success have the potential to lead to incorrect interpretations of data sets, and misdirection of limited resources for managing species.

  10. Large-scale symmetry-adapted perturbation theory computations via density fitting and Laplace transformation techniques: investigating the fundamental forces of DNA-intercalator interactions.

    Science.gov (United States)

    Hohenstein, Edward G; Parrish, Robert M; Sherrill, C David; Turney, Justin M; Schaefer, Henry F

    2011-11-07

    Symmetry-adapted perturbation theory (SAPT) provides a means of probing the fundamental nature of intermolecular interactions. Low-orders of SAPT (here, SAPT0) are especially attractive since they provide qualitative (sometimes quantitative) results while remaining tractable for large systems. The application of density fitting and Laplace transformation techniques to SAPT0 can significantly reduce the expense associated with these computations and make even larger systems accessible. We present new factorizations of the SAPT0 equations with density-fitted two-electron integrals and the first application of Laplace transformations of energy denominators to SAPT. The improved scalability of the DF-SAPT0 implementation allows it to be applied to systems with more than 200 atoms and 2800 basis functions. The Laplace-transformed energy denominators are compared to analogous partial Cholesky decompositions of the energy denominator tensor. Application of our new DF-SAPT0 program to the intercalation of DNA by proflavine has allowed us to determine the nature of the proflavine-DNA interaction. Overall, the proflavine-DNA interaction contains important contributions from both electrostatics and dispersion. The energetics of the intercalator interaction are are dominated by the stacking interactions (two-thirds of the total), but contain important contributions from the intercalator-backbone interactions. It is hypothesized that the geometry of the complex will be determined by the interactions of the intercalator with the backbone, because by shifting toward one side of the backbone, the intercalator can form two long hydrogen-bonding type interactions. The long-range interactions between the intercalator and the next-nearest base pairs appear to be negligible, justifying the use of truncated DNA models in computational studies of intercalation interaction energies.

  11. Validation of a motion-robust 2D sequential technique for quantification of hepatic proton density fat fraction during free breathing.

    Science.gov (United States)

    Pooler, B Dustin; Hernando, Diego; Ruby, Jeannine A; Ishii, Hiroshi; Shimakawa, Ann; Reeder, Scott B

    2018-04-17

    Current chemical-shift-encoded (CSE) MRI techniques for measuring hepatic proton density fat fraction (PDFF) are sensitive to motion artifacts. Initial validation of a motion-robust 2D-sequential CSE-MRI technique for quantification of hepatic PDFF. Phantom study and prospective in vivo cohort. Fifty adult patients (27 women, 23 men, mean age 57.2 years). 3D, 2D-interleaved, and 2D-sequential CSE-MRI acquisitions at 1.5T. Three CSE-MRI techniques (3D, 2D-interleaved, 2D-sequential) were performed in a PDFF phantom and in vivo. Reference standards were 3D CSE-MRI PDFF measurements for the phantom study and single-voxel MR spectroscopy hepatic PDFF measurements (MRS-PDFF) in vivo. In vivo hepatic MRI-PDFF measurements were performed during a single breath-hold (BH) and free breathing (FB), and were repeated by a second reader for the FB 2D-sequential sequence to assess interreader variability. Correlation plots to validate the 2D-sequential CSE-MRI against the phantom and in vivo reference standards. Bland-Altman analysis of FB versus BH CSE-MRI acquisitions to evaluate robustness to motion. Bland-Altman analysis to assess interreader variability. Phantom 2D-sequential CSE-MRI PDFF measurements demonstrated excellent agreement and correlation (R 2 > 0.99) with 3D CSE-MRI. In vivo, the mean (±SD) hepatic PDFF was 8.8 ± 8.7% (range 0.6-28.5%). Compared with BH acquisitions, FB hepatic PDFF measurements demonstrated bias of +0.15% for 2D-sequential compared with + 0.53% for 3D and +0.94% for 2D-interleaved. 95% limits of agreement (LOA) were narrower for 2D-sequential (±0.99%), compared with 3D (±3.72%) and 2D-interleaved (±3.10%). All CSE-MRI techniques had excellent correlation with MRS (R 2 > 0.97). The FB 2D-sequential acquisition demonstrated little interreader variability, with mean bias of +0.07% and 95% LOA of ± 1.53%. This motion-robust 2D-sequential CSE-MRI can accurately measure hepatic PDFF during free breathing in a patient population with

  12. Cell orientation gradients on an inverse opal substrate.

    Science.gov (United States)

    Lu, Jie; Zou, Xin; Zhao, Ze; Mu, Zhongde; Zhao, Yuanjin; Gu, Zhongze

    2015-05-20

    The generation of cell gradients is critical for understanding many biological systems and realizing the unique functionality of many implanted biomaterials. However, most previous work can only control the gradient of cell density and this has no effect on the gradient of cell orientation, which has an important role in regulating the functions of many connecting tissues. Here, we report on a simple stretched inverse opal substrate for establishing desired cell orientation gradients. It was demonstrated that tendon fibroblasts on the stretched inverse opal gradient showed a corresponding alignment along with the elongation gradient of the substrate. This "random-to-aligned" cell gradient reproduces the insertion part of many connecting tissues, and thus, will have important applications in tissue engineering.

  13. Travelling gradient thermocouple calibration

    International Nuclear Information System (INIS)

    Broomfield, G.H.

    1975-01-01

    A short discussion of the origins of the thermocouple EMF is used to re-introduce the idea that the Peltier and Thompson effects are indistinguishable from one another. Thermocouples may be viewed as devices which generate an EMF at junctions or as integrators of EMF's developed in thermal gradients. The thermal gradient view is considered the more appropriate, because of its better accord with theory and behaviour, the correct approach to calibration, and investigation of service effects is immediately obvious. Inhomogeneities arise in thermocouples during manufacture and in service. The results of travelling gradient measurements are used to show that such effects are revealed with a resolution which depends on the length of the gradient although they may be masked during simple immersion calibration. Proposed tests on thermocouples irradiated in a nuclear reactor are discussed

  14. Quaternion Gradient and Hessian

    OpenAIRE

    Xu, Dongpo; Mandic, Danilo P.

    2014-01-01

    The optimization of real scalar functions of quaternion variables, such as the mean square error or array output power, underpins many practical applications. Solutions typically require the calculation of the gradient and Hessian. However, real functions of quaternion variables are essentially nonanalytic, which are prohibitive to the development of quaternion-valued learning systems. To address this issue, we propose new definitions of quaternion gradient and Hessian, based on the novel gen...

  15. Gradient Alloy for Optical Packaging

    Data.gov (United States)

    National Aeronautics and Space Administration — Advances in additive manufacturing, such as Laser Engineered Net Shaping (LENS), enables the fabrication of compositionally gradient microstructures, i.e. gradient...

  16. Measurements of labile Cd, Cu, Ni, Pb, and Zn levels at a northeastern Brazilian coastal area under the influence of oil production with diffusive gradients in thin films technique (DGT).

    Science.gov (United States)

    de Souza, João M; Menegário, Amauri A; de Araújo Júnior, Marcus A G; Francioni, Eleine

    2014-12-01

    In this work, the ability of the diffusive gradients in thin films technique (DGT) was evaluated for monitoring the concentrations, and estimating the availability, of metals at a northeastern Brazilian coastal area under the influence of oil production. Three sites with an average distance between 0m (EM-1), 100 m (EM-2), and 1,000 m (EM-3) of a submarine outfall-I (Guamaré-RN, Brazil) and another site (GA-1) with an average distance of 12,000 m east of Outfall I, near the city of Galinhos, were studied. DGT units were deployed at the same sites in three campaigns from July, 2010 to June, 2011. Effects on the accuracy of analytical results regarding the deployment time, gel porosity, and thickness were evaluated. There was no difference between the measurements obtained with two sets of DGT devices, those assembled with open or restrictive pore gel, respectively, showing that organic metallic species are not present near the submarine outlet. After 21 day deployments in a region (near Submarine Outfall I) that receives produced waters that have been treated, there was evidence of biofilm formation on DGT membranes. However, it was demonstrated that the biofilm interference with DGT measurements was negligible. Data found in this work show that total concentrations of Cd, Cu, Pb, Ni, and Zn in seawater samples collected at sites GA-1 and EM-1 in two campaigns were below 0.33, 1.67, 0.47, 0.70, 2.86 ng mL(-1) respectively. For the first time, labile levels of Cd, Cu, Pb, Ni, and Zn in an area under the influence of oil production were determined. DGT measurements allowed the verification of the effects of temporal variation on levels of Zn and Ni. There were no effects of spatial variations on levels of Cd, Cu, Ni, Pb, and Zn at the four studied sites, suggesting no contamination of these metals at the northeastern Brazilian coastal area investigated in this work. Copyright © 2014. Published by Elsevier B.V.

  17. Full charge-density scheme with a kinetic-energy correction: Application to ground-state properties of the 4d metals

    DEFF Research Database (Denmark)

    Vitos, Levente; Kollár, J.; Skriver, Hans Lomholt

    1997-01-01

    defined within nonoverlapping, space-filling Wigner-Seitz cells; the exchange-correlation energy is evaluated by means of the local-density approximation or the generalized gradient approximation applied to the complete charge-density; and the ASA kinetic energy is corrected for the nonspherically...... symmetric charge density by a gradient expansion. The technique retains most of the simplicity and the computational efficiency of the LMTO-ASA method, and calculations of atomic volumes and elastic constants of the 4d elements show that it has the accuracy of full-potential methods....

  18. High Gradient Accelerator Research

    International Nuclear Information System (INIS)

    Temkin, Richard

    2016-01-01

    The goal of the MIT program of research on high gradient acceleration is the development of advanced acceleration concepts that lead to a practical and affordable next generation linear collider at the TeV energy level. Other applications, which are more near-term, include accelerators for materials processing; medicine; defense; mining; security; and inspection. The specific goals of the MIT program are: • Pioneering theoretical research on advanced structures for high gradient acceleration, including photonic structures and metamaterial structures; evaluation of the wakefields in these advanced structures • Experimental research to demonstrate the properties of advanced structures both in low-power microwave cold test and high-power, high-gradient test at megawatt power levels • Experimental research on microwave breakdown at high gradient including studies of breakdown phenomena induced by RF electric fields and RF magnetic fields; development of new diagnostics of the breakdown process • Theoretical research on the physics and engineering features of RF vacuum breakdown • Maintaining and improving the Haimson / MIT 17 GHz accelerator, the highest frequency operational accelerator in the world, a unique facility for accelerator research • Providing the Haimson / MIT 17 GHz accelerator facility as a facility for outside users • Active participation in the US DOE program of High Gradient Collaboration, including joint work with SLAC and with Los Alamos National Laboratory; participation of MIT students in research at the national laboratories • Training the next generation of Ph. D. students in the field of accelerator physics.

  19. Collisional transport in a plasma with steep gradients

    International Nuclear Information System (INIS)

    Wang, W.; Okamoto, M.; Nakajima, N.; Murakami, S.

    1999-06-01

    The validity is given to the newly proposed two δf method for neoclassical transport calculation, which can be solve the drift kinetic equation considering effects of steep plasma gradients, large radial electric field, finite banana width, and an orbit topology near the axis. The new method is applied to the study of ion transport with steep plasma gradients. It is found that the ion thermal diffusivity decreases as the scale length of density gradient decreases, while the ion particle flux due to ion-ion self collisions increases with increasing gradient. (author)

  20. The Number Density Evolution of Extreme Emission Line Galaxies in 3D-HST: Results from a Novel Automated Line Search Technique for Slitless Spectroscopy

    Science.gov (United States)

    Maseda, Michael V.; van der Wel, Arjen; Rix, Hans-Walter; Momcheva, Ivelina; Brammer, Gabriel B.; Franx, Marijn; Lundgren, Britt F.; Skelton, Rosalind E.; Whitaker, Katherine E.

    2018-02-01

    The multiplexing capability of slitless spectroscopy is a powerful asset in creating large spectroscopic data sets, but issues such as spectral confusion make the interpretation of the data challenging. Here we present a new method to search for emission lines in the slitless spectroscopic data from the 3D-HST survey utilizing the Wide-Field Camera 3 on board the Hubble Space Telescope. Using a novel statistical technique, we can detect compact (extended) emission lines at 90% completeness down to fluxes of 1.5(3.0)× {10}-17 {erg} {{{s}}}-1 {{cm}}-2, close to the noise level of the grism exposures, for objects detected in the deep ancillary photometric data. Unlike previous methods, the Bayesian nature allows for probabilistic line identifications, namely redshift estimates, based on secondary emission line detections and/or photometric redshift priors. As a first application, we measure the comoving number density of Extreme Emission Line Galaxies (restframe [O III] λ5007 equivalent widths in excess of 500 Å). We find that these galaxies are nearly 10× more common above z ∼ 1.5 than at z ≲ 0.5. With upcoming large grism surveys such as Euclid and WFIRST, as well as grisms featured prominently on the NIRISS and NIRCam instruments on the James Webb Space Telescope, methods like the one presented here will be crucial for constructing emission line redshift catalogs in an automated and well-understood manner. This work is based on observations taken by the 3D-HST Treasury Program and the CANDELS Multi-Cycle Treasury Program with the NASA/ESA HST, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS5-26555.

  1. Uniform gradient expansions

    CERN Document Server

    Giovannini, Massimo

    2015-01-01

    Cosmological singularities are often discussed by means of a gradient expansion that can also describe, during a quasi-de Sitter phase, the progressive suppression of curvature inhomogeneities. While the inflationary event horizon is being formed the two mentioned regimes coexist and a uniform expansion can be conceived and applied to the evolution of spatial gradients across the protoinflationary boundary. It is argued that conventional arguments addressing the preinflationary initial conditions are necessary but generally not sufficient to guarantee a homogeneous onset of the conventional inflationary stage.

  2. High gradient superconducting quadrupoles

    International Nuclear Information System (INIS)

    Lundy, R.A.; Brown, B.C.; Carson, J.A.; Fisk, H.E.; Hanft, R.H.; Mantsch, P.M.; McInturff, A.D.; Remsbottom, R.H.

    1987-07-01

    Prototype superconducting quadrupoles with a 5 cm aperture and gradient of 16 kG/cm have been built and tested as candidate magnets for the final focus at SLC. The magnets are made from NbTi Tevatron style cable with 10 inner and 14 outer turns per quadrant. Quench performance and multipole data are presented. Design and data for a low current, high gradient quadrupole, similar in cross section but wound with a cable consisting of five insulated conductors are also discussed

  3. Impact of the Z potential technique on reducing the sperm DNA fragmentation index, fertilization rate and embryo development.

    Science.gov (United States)

    Duarte, Carlos; Núñez, Víctor; Wong, Yat; Vivar, Carlos; Benites, Elder; Rodriguez, Urso; Vergara, Carlos; Ponce, Jorge

    2017-12-01

    In assisted reproduction procedures, we need to develop and enhance new protocols to optimize sperm selection. The aim of this study is to evaluate the ability of the Z potential technique to select sperm with intact DNA in non-normospermic patients and evaluate the impact of this selection on embryonic development. We analyzed a total of 174 human seminal samples with at least one altered parameter. We measured basal, post density gradients, and post density gradients + Z potential DNA fragmentation index. To evaluate the impact of this technique on embryo development, 54 cases were selected. The embryo development parameters evaluated were fertilization rate, cleavage rate, top quality embryos at the third day and blastocysts rate. We found significant differences in the study groups when we compared the sperm fragmentation index by adding the Z potential technique to density gradient selection vs. density gradients alone. Furthermore, there was no significant difference in the embryo development parameters between the low sperm fragmentation index group vs. the moderate and high sperm fragmentation index groups, when selecting sperms with this new technique. The Z potential technique is a very useful tool for sperm selection; it significantly reduces the DNA fragmentation index and improves the parameters of embryo development. This technique could be considered routine for its simplicity and low cost.

  4. Pressure gradient turbulent transport and collisionless reconnection

    International Nuclear Information System (INIS)

    Connor, J.W.

    1993-01-01

    The scale invariance technique is employed to discuss pressure gradient driven turbulent transport when an Ohm's law with electron inertia, rather than resistivity, is relevant. An expression for thermal diffusivity which has many features appropriate to L-mode transport in tokamaks, is seen to have greater generality than indicated by their particular calculation. The results of applying the technique to a more appropriate collisionless Ohm's law are discussed. (Author)

  5. Application of several physical techniques in the total analysis of a canine urinary calculus.

    Science.gov (United States)

    Rodgers, A L; Mezzabotta, M; Mulder, K J; Nassimbeni, L R

    1981-06-01

    A single calculus from the bladder of a Beagle bitch has been analyzed by a multiple technique approach employing x-ray diffraction, infrared spectroscopy, scanning electron microscopy, x-ray fluorescence spectrometry, atomic absorption spectrophotometry and density gradient fractionation. The qualitative and quantitative data obtained showed excellent agreement, lending confidence to such an approach for the evaluation and understanding of stone disease.

  6. Manipulating the Gradient

    Science.gov (United States)

    Gaze, Eric C.

    2005-01-01

    We introduce a cooperative learning, group lab for a Calculus III course to facilitate comprehension of the gradient vector and directional derivative concepts. The lab is a hands-on experience allowing students to manipulate a tangent plane and empirically measure the effect of partial derivatives on the direction of optimal ascent. (Contains 7…

  7. Hybridization analysis of P2 phage and of a defective prophage of Escherichia Coli B by the density gradient centrifugation method; Analyse de l'hybridation du phage P2 et d'un prophage defectifs d'Escherichia Coli B, par la methode de centrifugation en gradient de densite

    Energy Technology Data Exchange (ETDEWEB)

    Cohen, Denise [Commissariat a l' energie atomique et aux energies alternatives - CEA, C. E. N. de Saclay, Service de Biologie (France)

    1960-07-01

    The P2 Hydis phage produced by P2 phage multiplication in E. coli B shows a higher density than its P2 parent. This density increase is the same for all P2 Hydis coming from a huge number of distinct hybridizations. It is closed to 0.002 g.cm{sup -3}. Reprint of a paper published in Comptes rendus des seances de l'Academie des Sciences, t. 250, p. 946-948, sitting of 1 February 1960 [French] Le phage P2 Hydis, produit lors de la multiplication du phage P2 dans E. Coli B, presente une densite superieure a celle de son parent P2. Cette augmentation de densite est la meme pour tous les P2 Hydis issus d'un grand nombre d'hybridations distinctes. Elle est voisine de 0,002 g.cm{sup -3}. Reproduction d'un article publie dans les Comptes rendus des seances de l'Academie des Sciences, t. 250, p. 946-948, seance du 1er fevrier 1960.

  8. A comparison of conventional maximum intensity projection with a new depth-specific topographic mapping technique in the CT analysis of proximal tibial subchondral bone density

    International Nuclear Information System (INIS)

    Johnston, James D.; Kontulainen, Saija A.; Masri, Bassam A.; Wilson, David R.

    2010-01-01

    The objective was to identify subchondral bone density differences between normal and osteoarthritic (OA) proximal tibiae using computed tomography osteoabsorptiometry (CT-OAM) and computed tomography topographic mapping of subchondral density (CT-TOMASD). Sixteen intact cadaver knees from ten donors (8 male:2 female; mean age:77.8, SD:7.4 years) were categorized as normal (n = 10) or OA (n = 6) based upon CT reconstructions. CT-OAM assessed maximum subchondral bone mineral density (BMD). CT-TOMASD assessed average subchondral BMD across three layers (0-2.5, 2.5-5 and 5-10 mm) measured in relation to depth from the subchondral surface. Regional analyses of CT-OAM and CT-TOMASD included: medial BMD, lateral BMD, and average BMD of a 10-mm diameter area that searched each medial and lateral plateau for the highest ''focal'' density present within each knee. Compared with normal knees, both CT-OAM and CT-TOMASD demonstrated an average of 17% greater whole medial compartment density in OA knees (p 0.05). CT-TOMASD focal region analyses revealed an average of 24% greater density in the 0- to 2.5-mm layer (p = 0.003) and 36% greater density in the 2.5- to 5-mm layer (p = 0.034) in OA knees. Both CT-OAM and TOMASD identified higher medial compartment density in OA tibiae compared with normal tibiae. In addition, CT-TOMASD indicated greater focal density differences between normal and OA knees with increased depth from the subchondral surface. Depth-specific density analyses may help identify and quantify small changes in subchondral BMD associated with OA disease onset and progression. (orig.)

  9. NIF optics phase gradient specfication

    International Nuclear Information System (INIS)

    Williams, W.; Auerbach, J.; Hunt, J.; Lawson, L.; Manes, K.; Orth, C.; Sacks, R.; Trenholme, J.; Wegner, P.

    1997-01-01

    A root-mean-square (rms) phase gradient specification seems to allow a good connection between the NIP optics quality and focal spot requirements. Measurements on Beamlet optics individually, and as a chain, indicate they meet the assumptions necessary to use this specification, and that they have a typical rms phase gradient of ∼80 angstrom/cm. This may be sufficient for NIP to meet the proposed Stockpile Stewardship Management Program (SSMP) requirements of 80% of a high- power beam within a 200-250 micron diameter spot. Uncertainties include, especially, the scale length of the optics phase noise, the ability of the adaptive optic to correct against pump-induced distortions and optics noise, and the possibility of finding mitigation techniques against whole-beam self-focusing (e.g. a pre- correction optic). Further work is needed in these areas to better determine the NIF specifications. This memo is a written summary of a presentation on this topic given by W. Williams 24 April 1997 to NIP and LS ampersand T personnel

  10. Adaptive Regularization of Neural Networks Using Conjugate Gradient

    DEFF Research Database (Denmark)

    Goutte, Cyril; Larsen, Jan

    1998-01-01

    Andersen et al. (1997) and Larsen et al. (1996, 1997) suggested a regularization scheme which iteratively adapts regularization parameters by minimizing validation error using simple gradient descent. In this contribution we present an improved algorithm based on the conjugate gradient technique........ Numerical experiments with feedforward neural networks successfully demonstrate improved generalization ability and lower computational cost...

  11. Joining of Tungsten Armor Using Functional Gradients

    International Nuclear Information System (INIS)

    John Scott O'Dell

    2006-01-01

    The joining of low thermal expansion armor materials such as tungsten to high thermal expansion heat sink materials has been a major problem in plasma facing component (PFC) development. Conventional planar bonding techniques have been unable to withstand the high thermal induced stresses resulting from fabrication and high heat flux testing. During this investigation, innovative functional gradient joints produced using vacuum plasma spray forming techniques have been developed for joining tungsten armor to copper alloy heat sinks. A model was developed to select the optimum gradient architecture. Based on the modeling effort, a 2mm copper rich gradient was selected. Vacuum plasma pray parameters and procedures were then developed to produce the functional gradient joint. Using these techniques, dual cooling channel, medium scale mockups (32mm wide x 400mm length) were produced with vacuum plasma spray formed tungsten armor. The thickness of the tungsten armor was up to 5mm thick. No evidence of debonding at the interface between the heat sink and the vacuum plasma sprayed material was observed.

  12. Magnetoelectric Transverse Gradient Sensor with High Detection Sensitivity and Low Gradient Noise.

    Science.gov (United States)

    Zhang, Mingji; Or, Siu Wing

    2017-10-25

    We report, theoretically and experimentally, the realization of a high detection performance in a novel magnetoelectric (ME) transverse gradient sensor based on the large ME effect and the magnetic field gradient (MFG) technique in a pair of magnetically-biased, electrically-shielded, and mechanically-enclosed ME composites having a transverse orientation and an axial separation. The output voltage of the gradient sensor is directly obtained from the transverse MFG-induced difference in ME voltage between the two ME composites and is calibrated against transverse MFGs to give a high detection sensitivity of 0.4-30.6 V/(T/m), a strong common-mode magnetic field noise rejection rate of gradient noise of 0.16-620 nT/m/ Hz in a broad frequency range of 1 Hz-170 kHz under a small baseline of 35 mm. An analysis of experimental gradient noise spectra obtained in a magnetically-unshielded laboratory environment reveals the domination of the pink (1/ f ) noise, dielectric loss noise, and power-frequency noise below 3 kHz, in addition to the circuit noise above 3 kHz, in the gradient sensor. The high detection performance, together with the added merit of passive and direct ME conversion by the large ME effect in the ME composites, makes the gradient sensor suitable for the passive, direct, and broadband detection of transverse MFGs.

  13. Bigravity from gradient expansion

    International Nuclear Information System (INIS)

    Yamashita, Yasuho; Tanaka, Takahiro

    2016-01-01

    We discuss how the ghost-free bigravity coupled with a single scalar field can be derived from a braneworld setup. We consider DGP two-brane model without radion stabilization. The bulk configuration is solved for given boundary metrics, and it is substituted back into the action to obtain the effective four-dimensional action. In order to obtain the ghost-free bigravity, we consider the gradient expansion in which the brane separation is supposed to be sufficiently small so that two boundary metrics are almost identical. The obtained effective theory is shown to be ghost free as expected, however, the interaction between two gravitons takes the Fierz-Pauli form at the leading order of the gradient expansion, even though we do not use the approximation of linear perturbation. We also find that the radion remains as a scalar field in the four-dimensional effective theory, but its coupling to the metrics is non-trivial.

  14. Signal restoration for NMR imaging using time-dependent gradients

    International Nuclear Information System (INIS)

    Frahm, J.; Haenicke, W.

    1984-01-01

    NMR imaging experiments that employ linear but time-dependent gradients for encoding spatial information in the time-domain signals result in distorted images when treated with conventional image reconstruction techniques. It is shown here that the phase and amplitude distortions can be entirely removed if the timeshape of the gradient is known. The method proposed is of great theoretical and experimental simplicity. It consists of a retransformation of the measured time-domain signal and corresponds to synchronisation of the signal sampling with the time-development of the gradient field strength. The procedure complements other treatments of periodically oscillating gradients in NMR imaging. (author)

  15. Gradient-Index Optics

    Science.gov (United States)

    2010-03-31

    nonimaging design capabilities to incorporate 1. REPORT DATE (DD-MM-YYYY) 4. TITLE AND SUBTITLE 12-04-2011 13. SUPPLEMENTARY NOTES The views, opinions...Box 12211 Research Triangle Park, NC 27709-2211 15. SUBJECT TERMS Imaging Optics, Nonimaging Optics, Gradient Index Optics, Camera, Concentrator...imaging and nonimaging design capabilities to incorporate manufacturable GRIN lenses can provide imaging lens systems that are compact and

  16. Near-surface temperature gradient in a coastal upwelling regime

    Science.gov (United States)

    Maske, H.; Ochoa, J.; Almeda-Jauregui, C. O.; Ruiz-de la Torre, M. C.; Cruz-López, R.; Villegas-Mendoza, J. R.

    2014-08-01

    In oceanography, a near homogeneous mixed layer extending from the surface to a seasonal thermocline is a common conceptual basis in physics, chemistry, and biology. In a coastal upwelling region 3 km off the coast in the Mexican Pacific, we measured vertical density gradients with a free-rising CTD and temperature gradients with thermographs at 1, 3, and 5 m depths logging every 5 min during more than a year. No significant salinity gradient was observed down to 10 m depth, and the CTD temperature and density gradients showed no pronounced discontinuity that would suggest a near-surface mixed layer. Thermographs generally logged decreasing temperature with depth with gradients higher than 0.2 K m-1 more than half of the time in the summer between 1 and 3 m, 3 and 5 m and in the winter between 1 and 3 m. Some negative temperature gradients were present and gradients were generally highly variable in time with high peaks lasting fractions of hours to hours. These temporal changes were too rapid to be explained by local heating or cooling. The pattern of positive and negative peaks might be explained by vertical stacks of water layers of different temperatures and different horizontal drift vectors. The observed near-surface gradient has implications for turbulent wind energy transfer, vertical exchange of dissolved and particulate water constituents, the interpretation of remotely sensed SST, and horizontal wind-induced transport.

  17. Inversion gradients for acoustic VTI wavefield tomography

    KAUST Repository

    Li, Vladimir; Wang, Hui; Tsvankin, Ilya; Dí az, Esteban; Alkhalifah, Tariq Ali

    2017-01-01

    Wavefield tomography can handle complex subsurface geology better than ray-based techniques and, ultimately, provide a higher resolution. Here, we implement forward and adjoint wavefield extrapolation for VTI (transversely isotropic with a vertical symmetry axis) media using a generalized pseudospectral operator based on a separable approximation for the P-wave dispersion relation. This operator is employed to derive the gradients of the differential semblance optimization (DSO) and modified image-power objective functions. We also obtain the gradient expressions for a data-domain objective function that can more easily incorporate borehole information necessary for stable VTI velocity analysis. These gradients are similar to the ones obtained with a space-time finite-difference (FD) scheme for a system of coupled wave equations but the pseudospectral method is not hampered by the imprint of the shear-wave artifact. Numerical examples also show the potential advantages of the modified image-power objective function in estimating the anellipticity parameter η.

  18. Gradient pattern analysis applied to galaxy morphology

    Science.gov (United States)

    Rosa, R. R.; de Carvalho, R. R.; Sautter, R. A.; Barchi, P. H.; Stalder, D. H.; Moura, T. C.; Rembold, S. B.; Morell, D. R. F.; Ferreira, N. C.

    2018-06-01

    Gradient pattern analysis (GPA) is a well-established technique for measuring gradient bilateral asymmetries of a square numerical lattice. This paper introduces an improved version of GPA designed for galaxy morphometry. We show the performance of the new method on a selected sample of 54 896 objects from the SDSS-DR7 in common with Galaxy Zoo 1 catalogue. The results suggest that the second gradient moment, G2, has the potential to dramatically improve over more conventional morphometric parameters. It separates early- from late-type galaxies better (˜ 90 per cent) than the CAS system (C˜ 79 per cent, A˜ 50 per cent, S˜ 43 per cent) and a benchmark test shows that it is applicable to hundreds of thousands of galaxies using typical processing systems.

  19. Nonlinear conjugate gradient methods in micromagnetics

    Directory of Open Access Journals (Sweden)

    J. Fischbacher

    2017-04-01

    Full Text Available Conjugate gradient methods for energy minimization in micromagnetics are compared. The comparison of analytic results with numerical simulation shows that standard conjugate gradient method may fail to produce correct results. A method that restricts the step length in the line search is introduced, in order to avoid this problem. When the step length in the line search is controlled, conjugate gradient techniques are a fast and reliable way to compute the hysteresis properties of permanent magnets. The method is applied to investigate demagnetizing effects in NdFe12 based permanent magnets. The reduction of the coercive field by demagnetizing effects is μ0ΔH = 1.4 T at 450 K.

  20. Inversion gradients for acoustic VTI wavefield tomography

    KAUST Repository

    Li, Vladimir

    2017-03-21

    Wavefield tomography can handle complex subsurface geology better than ray-based techniques and, ultimately, provide a higher resolution. Here, we implement forward and adjoint wavefield extrapolation for VTI (transversely isotropic with a vertical symmetry axis) media using a generalized pseudospectral operator based on a separable approximation for the P-wave dispersion relation. This operator is employed to derive the gradients of the differential semblance optimization (DSO) and modified image-power objective functions. We also obtain the gradient expressions for a data-domain objective function that can more easily incorporate borehole information necessary for stable VTI velocity analysis. These gradients are similar to the ones obtained with a space-time finite-difference (FD) scheme for a system of coupled wave equations but the pseudospectral method is not hampered by the imprint of the shear-wave artifact. Numerical examples also show the potential advantages of the modified image-power objective function in estimating the anellipticity parameter η.

  1. Densities of carbon foils

    International Nuclear Information System (INIS)

    Stoner, J.O. Jr.

    1991-01-01

    The densities of arc-evaporated carbon target foils have been measured by several methods. The density depends upon the method used to measure it; for the same surface density, values obtained by different measurement techniques may differ by fifty percent or more. The most reliable density measurements are by flotation, yielding a density of 2.01±0.03 g cm -3 , and interferometric step height with the surface density known from auxiliary measurements, yielding a density of 2.61±0.4 g cm -3 . The difference between these density values mayy be due in part to the compressive stresses that carbon films have while still on their substrates, uncertainties in the optical calibration of surface densities of carbon foils, and systematic errors in step-height measurements. Mechanical thickness measurements by micrometer caliper are unreliable due to nonplanarity of these foils. (orig.)

  2. Bacterial pleomorphism and competition in a relative humidity gradient

    NARCIS (Netherlands)

    de Goffau, Marcus C.; Yang, Xiaomei; van Dijl, Jan Maarten; Harmsen, Hermie J. M.

    The response of different bacterial species to reduced water availability was studied using a simple relative humidity gradient technique. Interestingly, distinct differences in morphology and growth patterns were observed between populations of the same species growing at different relative

  3. Abnormal distribution of low-latitude ionospheric electron density during November 2004 superstorm as reconstructed by 3-D CT technique from IGS and LEO/GPS observations

    Science.gov (United States)

    Xiao, R.; Ma, S.; Xu, J.; Xiong, C.; Yan, W.; Luhr, H.; Jakowski, N.

    2010-12-01

    Using time-dependent 3-D tomography method, the electron density distributions in the mid- and low-latitude ionosphere are reconstructed from GPS observations of joint ground-based IGS network and onboard CHAMP/GRACE satellites during November 2004 super-storm. For LEO satellite-based GPS receiving, both the occultation TEC data and that along the radio propagation paths above the LEO are used. The electron density images versus latitude/altitude/longitude are reconstructed for different sectors of America/Asia/Europe and produced every hour. The reconstructed electron densities are validated by satellite in situ measurements of CHAMP Langmuir probe and GRACE Ka-band SST (low-low satellite-to-satellite tracking) derived electron density averaged between the two satellites, as well as by CIT simulations. It reveals some very interesting storm-time structures of Ne distributions, such as top-hat-like F2-3 double layer and column-like enhanced electron densities (CEED). The double layer structure appeared over a large latitude range from about -30 degree to 20 degree along East-Asian/Australia longitudes before local noon, looking like one additional smaller EIA structure standing above the usual one of EIA. It is consistent with the F-3 layer observed by ionosonde at an Australian low-latitude station. The CEED are found just 1-2 hours before the minimum of Dst and in the longitudinal sector about 157 E. They extend from the topside ionosphere toward plasmasphere, reaching at least about 2000 km as high. Their footprints stand on the two peaks of the EIA. This CEED is also seen in the image of 30.4 nm He ++ radiation by IMAGE, showing a narrow channel of enhanced density extending from afternoon ionosphere to plasmsphere westward. The forming mechanism of CEED and its relationship with SED and plasmaspheric plumes are worthy of further study. Acknowledgement: This work is supported by NSFC (No.40674078).

  4. Tripolar vortex formation in dense quantum plasma with ion-temperature-gradients

    Science.gov (United States)

    Qamar, Anisa; Ata-ur-Rahman, Mirza, Arshad M.

    2012-05-01

    We have derived system of nonlinear equations governing the dynamics of low-frequency electrostatic toroidal ion-temperature-gradient mode for dense quantum magnetoplasma. For some specific profiles of the equilibrium density, temperature, and ion velocity gradients, the nonlinear equations admit a stationary solution in the form of a tripolar vortex. These results are relevant to understand nonlinear structure formation in dense quantum plasmas in the presence of equilibrium ion-temperature and density gradients.

  5. Tripolar vortex formation in dense quantum plasma with ion-temperature-gradients

    Energy Technology Data Exchange (ETDEWEB)

    Qamar, Anisa; Ata-ur-Rahman [Institute of Physics and Electronics, University of Peshawar, Khyber Pakhtoon Khwa 25000 (Pakistan); National Center for Physics Shahdrah Valley Road, Islamabad 44000 (Pakistan); Mirza, Arshad M. [Theoretical Plasma Physics Group, Physics Department, Quaid-i-Azam University, Islamabad 45320 (Pakistan)

    2012-05-15

    We have derived system of nonlinear equations governing the dynamics of low-frequency electrostatic toroidal ion-temperature-gradient mode for dense quantum magnetoplasma. For some specific profiles of the equilibrium density, temperature, and ion velocity gradients, the nonlinear equations admit a stationary solution in the form of a tripolar vortex. These results are relevant to understand nonlinear structure formation in dense quantum plasmas in the presence of equilibrium ion-temperature and density gradients.

  6. Tripolar vortex formation in dense quantum plasma with ion-temperature-gradients

    International Nuclear Information System (INIS)

    Qamar, Anisa; Ata-ur-Rahman; Mirza, Arshad M.

    2012-01-01

    We have derived system of nonlinear equations governing the dynamics of low-frequency electrostatic toroidal ion-temperature-gradient mode for dense quantum magnetoplasma. For some specific profiles of the equilibrium density, temperature, and ion velocity gradients, the nonlinear equations admit a stationary solution in the form of a tripolar vortex. These results are relevant to understand nonlinear structure formation in dense quantum plasmas in the presence of equilibrium ion-temperature and density gradients.

  7. A novel method to create high density stratification with matching refractive index for optical flow investigations

    Science.gov (United States)

    Krohn, Benedikt; Manera, Annalisa; Petrov, Victor

    2018-04-01

    Turbulent mixing in stratified environments represents a challenging task in experimental turbulence research, especially when large density gradients are desired. When optical measurement techniques like particle image velocimetry (PIV) are applied to stratified liquids, it is common practice to combine two aqueous solutions with different density but equal refractive index, to suppress particle image deflections. While refractive image matching (RIM) has been developed in the late 1970s, the achieved limit of 4% density ratio was not rivalled up to day. In the present work, we report a methodology, based on the behavior of excess properties and their change in a multicomponent system while mixing, that allows RIM for solutions with higher density differences. The methodology is then successfully demonstrated using a ternary combination of water, isopropanol and glycerol, for which RIM in presence of a density ratio of 8.6% has been achieved. Qualitative PIV results of a turbulent buoyant jet with 8.6% density ratio are shown.

  8. In-situ plasma processing to increase the accelerating gradients of superconducting radio-frequency cavities

    Science.gov (United States)

    Doleans, M.; Tyagi, P. V.; Afanador, R.; McMahan, C. J.; Ball, J. A.; Barnhart, D. L.; Blokland, W.; Crofford, M. T.; Degraff, B. D.; Gold, S. W.; Hannah, B. S.; Howell, M. P.; Kim, S.-H.; Lee, S.-W.; Mammosser, J.; Neustadt, T. S.; Saunders, J. W.; Stewart, S.; Strong, W. H.; Vandygriff, D. J.; Vandygriff, D. M.

    2016-03-01

    A new in-situ plasma processing technique is being developed at the Spallation Neutron Source (SNS) to improve the performance of the cavities in operation. The technique utilizes a low-density reactive oxygen plasma at room temperature to remove top surface hydrocarbons. The plasma processing technique increases the work function of the cavity surface and reduces the overall amount of vacuum and electron activity during cavity operation; in particular it increases the field emission onset, which enables cavity operation at higher accelerating gradients. Experimental evidence also suggests that the SEY of the Nb surface decreases after plasma processing which helps mitigating multipacting issues. In this article, the main developments and results from the plasma processing R&D are presented and experimental results for in-situ plasma processing of dressed cavities in the SNS horizontal test apparatus are discussed.

  9. Wetting of flat gradient surfaces.

    Science.gov (United States)

    Bormashenko, Edward

    2018-04-01

    Gradient, chemically modified, flat surfaces enable directed transport of droplets. Calculation of apparent contact angles inherent for gradient surfaces is challenging even for atomically flat ones. Wetting of gradient, flat solid surfaces is treated within the variational approach, under which the contact line is free to move along the substrate. Transversality conditions of the variational problem give rise to the generalized Young equation valid for gradient solid surfaces. The apparent (equilibrium) contact angle of a droplet, placed on a gradient surface depends on the radius of the contact line and the values of derivatives of interfacial tensions. The linear approximation of the problem is considered. It is demonstrated that the contact angle hysteresis is inevitable on gradient surfaces. Electrowetting of gradient surfaces is discussed. Copyright © 2018 Elsevier Inc. All rights reserved.

  10. Refined discrete and empirical horizontal gradients in VLBI analysis

    Science.gov (United States)

    Landskron, Daniel; Böhm, Johannes

    2018-02-01

    Missing or incorrect consideration of azimuthal asymmetry of troposphere delays is a considerable error source in space geodetic techniques such as Global Navigation Satellite Systems (GNSS) or Very Long Baseline Interferometry (VLBI). So-called horizontal troposphere gradients are generally utilized for modeling such azimuthal variations and are particularly required for observations at low elevation angles. Apart from estimating the gradients within the data analysis, which has become common practice in space geodetic techniques, there is also the possibility to determine the gradients beforehand from different data sources than the actual observations. Using ray-tracing through Numerical Weather Models (NWMs), we determined discrete gradient values referred to as GRAD for VLBI observations, based on the standard gradient model by Chen and Herring (J Geophys Res 102(B9):20489-20502, 1997. https://doi.org/10.1029/97JB01739) and also for new, higher-order gradient models. These gradients are produced on the same data basis as the Vienna Mapping Functions 3 (VMF3) (Landskron and Böhm in J Geod, 2017.https://doi.org/10.1007/s00190-017-1066-2), so they can also be regarded as the VMF3 gradients as they are fully consistent with each other. From VLBI analyses of the Vienna VLBI and Satellite Software (VieVS), it becomes evident that baseline length repeatabilities (BLRs) are improved on average by 5% when using a priori gradients GRAD instead of estimating the gradients. The reason for this improvement is that the gradient estimation yields poor results for VLBI sessions with a small number of observations, while the GRAD a priori gradients are unaffected from this. We also developed a new empirical gradient model applicable for any time and location on Earth, which is included in the Global Pressure and Temperature 3 (GPT3) model. Although being able to describe only the systematic component of azimuthal asymmetry and no short-term variations at all, even these

  11. Comparison of a new GIS-based technique and a manual method for determining sinkhole density: An example from Illinois' sinkhole plain

    Science.gov (United States)

    Angel, J.C.; Nelson, D.O.; Panno, S.V.

    2004-01-01

    A new Geographic Information System (GIS) method was developed as an alternative to the hand-counting of sinkholes on topographic maps for density and distribution studies. Sinkhole counts were prepared by hand and compared to those generated from USGS DLG data using ArcView 3.2 and the ArcInfo Workstation component of ArcGIS 8.1 software. The study area for this investigation, chosen for its great density of sinkholes, included the 42 public land survey sections that reside entirely within the Renault Quadrangle in southwestern Illinois. Differences between the sinkhole counts derived from the two methods for the Renault Quadrangle study area were negligible. Although the initial development and refinement of the GIS method required considerably more time than counting sinkholes by hand, the flexibility of the GIS method is expected to provide significant long-term benefits and time savings when mapping larger areas and expanding research efforts. ?? 2004 by The National Speleological Society.

  12. Experimental investigation of fast electron transport in solid density matter: Recent results from a new technique of X-ray energy-encoded 2D imaging

    Czech Academy of Sciences Publication Activity Database

    Labate, L.; Förster, E.; Giulietti, A.; Giulietti, D.; Höfer, S.; Kämpfer, T.; Köster, P.; Kozlová, Michaela; Levato, T.; Lötzsch, R.; Lübecke, A.; Mocek, Tomáš; Polan, Jiří; Rus, Bedřich; Uschmann, I.; Zamponi, F.; Gizzi, L.A.

    2009-01-01

    Roč. 27, č. 4 (2009), s. 643-649 ISSN 0263-0346 R&D Projects: GA MŠk(CZ) 7E09092 EU Projects: European Commission(XE) 12843 - TUIXS Institutional research plan: CEZ:AV0Z10100523 Keywords : anisotropic Bremsstrahlung * fast electron diagnostics * fast electron transport * high-density matter * relativistic electrons Subject RIV: BH - Optics, Masers, Lasers Impact factor: 4.420, year: 2008

  13. Modelling CO2-Brine Interfacial Tension using Density Gradient Theory

    KAUST Repository

    Ruslan, Mohd Fuad Anwari Che

    2018-01-01

    In this study, a new modelling strategy to compute CO2-brine IFT based on DGT was proposed. In the proposed model, ion distribution across interface was accounted for by separating the interface to two sections

  14. Gram-scale fractionation of nanodiamonds by density gradient ultracentrifugation.

    Science.gov (United States)

    Peng, Wei; Mahfouz, Remi; Pan, Jun; Hou, Yuanfang; Beaujuge, Pierre M; Bakr, Osman M

    2013-06-07

    Size is a defining characteristic of nanoparticles; it influences their optical and electronic properties as well as their interactions with molecules and macromolecules. Producing nanoparticles with narrow size distributions remains one of the main challenges to their utilization. At this time, the number of practical approaches to optimize the size distribution of nanoparticles in many interesting materials systems, including diamond nanocrystals, remains limited. Diamond nanocrystals synthesized by detonation protocols - so-called detonation nanodiamonds (DNDs) - are promising systems for drug delivery, photonics, and composites. DNDs are composed of primary particles with diameters mainly Applications requiring DNDs with specific particle or aggregate sizes are now within reach.

  15. Gram-scale fractionation of nanodiamonds by density gradient ultracentrifugation

    KAUST Repository

    Peng, Wei; Mahfouz, Remi; Pan, Jun; Hou, Yuanfang; Beaujuge, Pierre; Bakr, Osman

    2013-01-01

    challenges to their utilization. At this time, the number of practical approaches to optimize the size distribution of nanoparticles in many interesting materials systems, including diamond nanocrystals, remains limited. Diamond nanocrystals synthesized

  16. Spiral Gradient Coil Design for Use in Cylindrical MRI Systems.

    Science.gov (United States)

    Wang, Yaohui; Xin, Xuegang; Liu, Feng; Crozier, Stuart

    2018-04-01

    In magnetic resonance imaging, the stream function based method is commonly used in the design of gradient coils. However, this method can be prone to errors associated with the discretization of continuous current density and wire connections. In this paper, we propose a novel gradient coil design scheme that works directly in the wire space, avoiding the system errors that may appear in the stream function approaches. Specifically, the gradient coil pattern is described with dedicated spiral functions adjusted to allow the coil to produce the required field gradients in the imaging area, minimal stray field, and other engineering terms. The performance of a designed spiral gradient coil was compared with its stream-function counterpart. The numerical evaluation shows that when compared with the conventional solution, the inductance and resistance was reduced by 20.9 and 10.5%, respectively. The overall coil performance (evaluated by the figure of merit (FoM)) was improved up to 26.5% for the x -gradient coil design; for the z-gradient coil design, the inductance and resistance were reduced by 15.1 and 6.7% respectively, and the FoM was increased by 17.7%. In addition, by directly controlling the wire distributions, the spiral gradient coil design was much sparser than conventional coils.

  17. Ponderomotive force effects on temperature-gradient-driven instabilities

    International Nuclear Information System (INIS)

    Sundaram, A.K.; Hershkowitz, N.

    1992-01-01

    The modification of temperature-gradient-driven instabilities due to the presence of nonuniform radio-frequency fields near the ion cyclotron frequency is investigated in the linear regime. Employing the fluid theory, it is shown that the induced field line compression caused by ion cyclotron range of frequencies (ICRF) fields makes the net parallel compressibility positive, and thus provides a stabilizing influence on the ion-temperature-gradient-driven mode for an appropriately tailored profile of radio-frequency (rf) pressure. Concomitantly, the radial ponderomotive force generates an additional contribution via coupling between the perturbed fluid motion and the equilibrium ponderomotive force and this effect plays the role of dissipation to enhance or decrease the growth of temperature-gradient-driven modes depending upon the sign of rf pressure gradients. For decreased growth of temperature-gradient-driven instabilities, the plasma density gradients and rf pressure gradients must have opposite signs while enhancement in growth arises when both gradients have the same sign. Finally, the kinetic effects associated with these modes are briefly discussed

  18. Color Gradient in the King Type Globular Cluster NGC 7089

    Directory of Open Access Journals (Sweden)

    Young-Jong Sohn

    1999-12-01

    Full Text Available We use BV CCD images to investigate the reality of the color gradient within a King type globular cluster NGC 7089. Surface photometry shows that there is a strong radial color gradient in the central region of the cluster in the sense of bluer center with the amplitude of -0.39 +/- 0.07 mag/arcsec2 in (B - V. In the outer region of the cluster, however, the radial color gradient shows a reverse case, i.e., redder toward the center. (B - V color profile which was derived from resolved stars in VGC 7089 field also shows a significant color gradient in the central region of the clusters, indicating that lights from the combination of red giant stars and blue horizontal branch stars cause the radial color gradient. Color gradient of the outer region of NGC 7089 may be due to the unresolved background of the cluster. Similar color gradients in the central area of clusters have been previously observed exserved exclusively in highly concentrated systems classified as post core collapse clusters. We caution, however, to confirm the reality of the color gradient from resolved stars, we need more accurate imaging data of the cluster with exceptional seeing condition because the effect of completeness correlates with local density of stars.

  19. Testing joint inversion techniques of gravity data and cosmic ray muon flux at a well-characterized site for use in the detection of subsurface density structures beneath volcanoes.

    Science.gov (United States)

    Cosburn, K.; Roy, M.; Rowe, C. A.; Guardincerri, E.

    2017-12-01

    Obtaining accurate static and time-dependent shallow subsurface density structure beneath volcanic, hydrogeologic, and tectonic targets can help illuminate active processes of fluid flow and magma transport. A limitation of using surface gravity measurements for such imaging is that these observations are vastly underdetermined and non-unique. In order to hone in on a more accurate solution, other data sets are needed to provide constraints, typically seismic or borehole observations. The spatial resolution of these techniques, however, is relatively poor, and a novel solution to this problem in recent years has been to use attenuation of the cosmic ray muon flux, which provides an independent constraint on density. In this study we present a joint inversion of gravity and cosmic ray muon flux observations to infer the density structure of a target rock volume at a well-characterized site near Los Alamos, New Mexico, USA. We investigate the shallow structure of a mesa formed by the Quaternary ash-flow tuffs on the Pajarito Plateau, flanking the Jemez volcano in New Mexico. Gravity measurements were made using a Lacoste and Romberg D meter on the surface of the mesa and inside a tunnel beneath the mesa. Muon flux measurements were also made at the mesa surface and at various points within the same tunnel using a muon detector having an acceptance region of 45 degrees from the vertical and a track resolution of several milliradians. We expect the combination of muon and gravity data to provide us with enhanced resolution as well as the ability to sense deeper structures in our region of interest. We use Bayesian joint inversion techniques on the gravity-muon dataset to test these ideas, building upon previous work using gravity inversion alone to resolve density structure in our study area. Both the regional geology and geometry of our study area is well-known and we assess the inferred density structure from our gravity-muon joint inversion within this known

  20. An automated technique for most-probable-number (MPN) analysis of densities of phagotrophic protists with lux-AB labelled bacteria as growth medium

    DEFF Research Database (Denmark)

    Ekelund, Flemming; Christensen, Søren; Rønn, Regin

    1999-01-01

    An automated modification of the most-probable-number (MPN) technique has been developed for enumeration of phagotrophic protozoa. The method is based on detection of prey depletion in micro titre plates rather than on presence of protozoa. A transconjugant Pseudomonas fluorescens DR54 labelled w...

  1. Gradient computation for VTI acoustic wavefield tomography

    KAUST Repository

    Li, Vladimir

    2016-09-06

    Wavefield tomography can handle complex subsurface geology better than ray-based techniques and, ultimately, provide a higher resolution. Here, we implement forward and adjoint wavefield extrapolation for VTI (transversely isotropic with a vertical symmetry axis) media using a pseudospectral operator that employes a separable approximation of the P-wave dispersion relation. This operator is employed to derive the gradients of the differential semblance optimization (DSO) and modified stack-power objective functions. We also obtain the gradient expressions for the data-domain objective function, which can incorporate borehole information necessary for stable VTI velocity analysis. These gradients are compared to the ones obtained with a space-time finite-difference (FD) scheme for a system of coupled wave equations. Whereas the kernels computed with the two wave-equation operators are similar, the pseudospectral method is not hampered by the imprint of the shear-wave artifact. Numerical examples also show that the modified stack-power objective function produces cleaner gradients than the more conventional DSO operator.

  2. Observation of Enhanced Hole Extraction in Br Concentration Gradient Perovskite Materials.

    Science.gov (United States)

    Kim, Min-Cheol; Kim, Byeong Jo; Son, Dae-Yong; Park, Nam-Gyu; Jung, Hyun Suk; Choi, Mansoo

    2016-09-14

    Enhancing hole extraction inside the perovskite layer is the key factor for boosting photovoltaic performance. Realization of halide concentration gradient perovskite materials has been expected to exhibit rapid hole extraction due to the precise bandgap tuning. Moreover, a formation of Br-rich region on the tri-iodide perovskite layer is expected to enhance moisture stability without a loss of current density. However, conventional synthetic techniques of perovskite materials such as the solution process have not achieved the realization of halide concentration gradient perovskite materials. In this report, we demonstrate the fabrication of Br concentration gradient mixed halide perovskite materials using a novel and facile halide conversion method based on vaporized hydrobromic acid. Accelerated hole extraction and enhanced lifetime due to Br gradient was verified by observing photoluminescence properties. Through the combination of secondary ion mass spectroscopy and transmission electron microscopy with energy-dispersive X-ray spectroscopy analysis, the diffusion behavior of Br ions in perovskite materials was investigated. The Br-gradient was found to be eventually converted into a homogeneous mixed halide layer after undergoing an intermixing process. Br-substituted perovskite solar cells exhibited a power conversion efficiency of 18.94% due to an increase in open circuit voltage from 1.08 to 1.11 V and an advance in fill-factor from 0.71 to 0.74. Long-term stability was also dramatically enhanced after the conversion process, i.e., the power conversion efficiency of the post-treated device has remained over 97% of the initial value under high humid conditions (40-90%) without any encapsulation for 4 weeks.

  3. Direct comparison of photoluminescence lifetime and defect densities in ZnO epilayers studied by time-resolved photoluminescence and slow positron annihilation techniques

    Energy Technology Data Exchange (ETDEWEB)

    Koida, T. [Institute of Applied Physics and Graduate School of Pure and Applied Sciences, University of Tsukuba, Tsukuba 305-8573 (Japan); NICP, ERATO, Japan Science and Technology Agency (JST), Chiyoda 102-0071 (Japan); Uedono, A. [Institute of Applied Physics and Graduate School of Pure and Applied Sciences, University of Tsukuba, Tsukuba 305-8573 (Japan); Tsukazaki, A. [Institute for Materials Research, Tohoku University, Sendai 980-8755 (Japan); Sota, T. [Department of Electrical, Engineering and Bioscience, Waseda University, Shinjuku 169-8555 (Japan); Kawasaki, M. [Institute for Materials Research, Tohoku University, Sendai 980-8755 (Japan); Combinatorial Materials Exploration and Technology (COMET), Tsukuba 305-0044 (Japan); Chichibu, S.F. [NICP, ERATO, Japan Science and Technology Agency (JST), Chiyoda 102-0071 (Japan); Photodynamics Research Center, RIKEN, Sendai 980-0868 (Japan)

    2004-09-01

    The roles of point defects and defect complexes governing nonradiative processes in ZnO epilayers were studied using time-resolved photoluminescence (PL) and slow positron annihilation measurements. The density or size of Zn vacancies (V{sub Zn}) decreased and the nonradiative PL lifetime ({tau}{sub nr}) increased with higher growth temperature for epilayers grown on a ScAlMgO{sub 4} substrate. Accordingly, the steady-state free excitonic PL intensity increased with increase in {tau}{sub nr} at room temperature. The use of a homoepitaxial substrate further decreased the V{sub Zn} concentration. However, no perfect relation between {tau}{sub nr} and the density or size of V{sub Zn} or other positron scattering centers was found. The results indicated that nonradiative recombination processes are governed not solely by single point defects, but by certain defect species introduced by the presence of V{sub Zn} such as vacancy complexes. (copyright 2004 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  4. HG2006 Workshop on High-Gradient Radio Frequency

    CERN Multimedia

    2006-01-01

    Meeting to be held at CERN on 25-27 September 2006 in Room 40/S2-B01 (Building 40). The objective of the workshop is to bring the high-gradient RF community together to present and discuss recent theoretical and experimental developments. Significant progress has recently been made in understanding the basic physics of rf breakdown and developing techniques for achieving higher gradients. This workshop should contribute to maintaining these efforts and to promoting contacts and collaboration. The scientific programme will be organized in half day sessions dedicated to: High-gradient rf experimental results Theory and computation High-gradient technology, materials and processing Specialized experiments on related high-gradient or high-power phenomenon like dc discharge and pulsed surface heating Reports from collaborations and projects. Each session will consist of selected presentations followed by a dedicated discussion. Information about the meeting and participant registration is available at http...

  5. On the solution of the Hartree-Fock-Bogoliubov equations by the conjugate gradient method

    International Nuclear Information System (INIS)

    Egido, J.L.; Robledo, L.M.

    1995-01-01

    The conjugate gradient method is formulated in the Hilbert space for density and non-density dependent Hamiltonians. We apply it to the solution of the Hartree-Fock-Bogoliubov equations with constraints. As a numerical application we show calculations with the finite range density dependent Gogny force. The number of iterations required to reach convergence is reduced by a factor of three to four as compared with the standard gradient method. (orig.)

  6. Gradient waveform synthesis for magnetic propulsion using MRI gradient coils

    International Nuclear Information System (INIS)

    Han, B H; Lee, S Y; Park, S

    2008-01-01

    Navigating an untethered micro device in a living subject is of great interest for both diagnostic and therapeutic applications. Magnetic propulsion of an untethered device carrying a magnetic core in it is one of the promising methods to navigate the device. MRI gradients coils are thought to be suitable for navigating the device since they are capable of magnetic propulsion in any direction while providing magnetic resonance images. For precise navigation of the device, especially in the peripheral region of the gradient coils, the concomitant gradient fields, as well as the linear gradient fields in the main magnetic field direction, should be considered in driving the gradient coils. For simple gradient coil configurations, the Maxwell coil in the z-direction and the Golay coil in the x- and y-directions, we have calculated the magnetic force fields, which are not necessarily the same as the conventional linear gradient fields of MRI. Using the calculated magnetic force fields, we have synthesized gradient waveforms to navigate the device along a desired path

  7. Temperature Gradients on the Cell Wall in the Critical Viscosity Experiment

    Science.gov (United States)

    Berg, Robert F.; Moldover, Michael R.

    1993-01-01

    Because of the diverging susceptibility delta rho/delta Tau near the liquid-vapor critical point, temperature gradients must be kept small to maintain adequate sample homogeneity. In our Science Requirements Document we paid particular attention to radial density gradients caused by equilibration of the xenon sample. Axial density gradients were addressed through the requirement that the cell's copper wall have a gradient less than 22 microK/m. This report re-examines the cell wall's temperature distribution in more detail by estimating all known significant contributions to temperature differences on the cell's wall.

  8. Turbo-Proton Echo Planar Spectroscopic Imaging (t-PEPSI) MR technique in the detection of diffuse axonal damage in brain injury. Comparison with Gradient-Recalled Echo (GRE) sequence.

    Science.gov (United States)

    Giugni, E; Sabatini, U; Hagberg, G E; Formisano, R; Castriota-Scanderbeg, A

    2005-01-01

    Diffuse axonal injury (DAI) is a common type of primary neuronal injury in patients with severe traumatic brain injury, and is frequently accompanied by tissue tear haemorrhage. The T2*-weighted gradient-recalled echo (GRE) sequences are more sensitive than T2-weighted spin-echo images for detection of haemorrhage. This study was undertaken to determine whether turbo-PEPSI, an extremely fast multi-echo-planar-imaging sequence, can be used as an alternative to the GRE sequence for detection of DAI. Nineteen patients (mean age 24,5 year) with severe traumatic brain injury (TBI), occurred at least 3 months earlier, underwent a brain MRI study on a 1.5-Tesla scanner. A qualitative evaluation of the turbo-PEPSI sequences was performed by identifying the optimal echo time and in-plane resolution. The number and size of DAI lesions, as well as the signal intensity contrast ratio (SI CR), were computed for each set of GRE and turbo-PEPSI images, and divided according to their anatomic location into lobar and/or deep brain. There was no significant difference between GRE and turbo-PEPSI sequences in the total number of DAI lesions detected (283 vs 225 lesions, respectively). The GRE sequence identified a greater number of hypointense lesions in the temporal lobe compared to the t-PEPSI sequence (72 vs 35, pPEPSI than for the GRE sequence (pPEPSI sequence can be used as an alternative to the GRE to assess brain DAI in severe TBI patients, especially if uncooperative and medically unstable.

  9. Theory of resistivity-gradient-driven turbulence

    International Nuclear Information System (INIS)

    Garcia, L.; Carreras, B.A.; Diamond, P.H.; Callen, J.D.

    1984-10-01

    A theory of the nonlinear evolution and saturation of resistivity-driven turbulence, which evolves from linear rippling instabilities, is presented. The nonlinear saturation mechanism is identified both analytically and numerically. Saturation occurs when the turbulent diffusion of the resistivity is large enough so that dissipation due to parallel electron thermal conduction balances the nonlinearly modified resistivity gradient driving term. The levels of potential, resistivity, and density fluctuations at saturation are calculated. A combination of computational modeling and analytic treatment is used in this investigation

  10. Theory of neoclassical resistivity-gradient-driven turbulence

    International Nuclear Information System (INIS)

    Kwon, O.J.; Diamond, P.H.; Hahm, T.S.

    1988-12-01

    It is shown that rippling instabilities can tap the density gradient expansion free energy source through the density dependence of the neoclassical resistivity. Linear analyses show that the region where neoclassical rippling modes are significantly excited extends from the edge of the plasma to the region where ν/sub *e/ ≤ 1. Since these modes are non-dispersive, diamagnetic effects are negligible in comparison to the nonlinear decorrelation rate at saturation. Thus, the relevant regime is the 'strong turbulence' regime. The turbulent radial diffusivities of the temperature and the density are obtained as eigenvalues of the renormalized eigenmode equations at steady state. The density gradient acts to enhance the level of turbulence, compared to that driven by the temperature gradient alone. The saturated turbulent state is characterized by: current decoupling, the breakdown of Boltzmann relation, a radial mode scale of density fluctuations exceeding that of temperature fluctuations, implying that density diffusivity exceeds temperature diffusivity, and that density fluctuation levels exceed temperature fluctuation levels. Magnetic fluctuation levels are negligible. 29 refs., 1 fig

  11. A molecular dynamics investigation of the surface tension of water nanodroplets and a new technique for local pressure determination through density correlation

    Science.gov (United States)

    Leong, Kai-Yang; Wang, Feng

    2018-04-01

    The surface tension of nanoscale droplets of water was studied with molecular dynamics simulations using the BLYPSP-4F water potential. The internal pressure of the droplet was measured using an empirical correlation between the pressure and density, established through a series of bulk simulations performed at pressures from 1 to 1000 bars. Such a procedure allows for reliable determination of internal pressure without the need to calculate the local virial. The surface tension, estimated with the Young-Laplace relation, shows good agreement with the Tolman equation with a Tolman length of -0.48 Å. The interface of a liquid water droplet is shown to be around 1.1-1.3 nm thick depending on radii. The fairly thick interface region puts a lower limit on the size of droplets that still have a bulk-like interior.

  12. Road density

    Data.gov (United States)

    U.S. Environmental Protection Agency — Road density is generally highly correlated with amount of developed land cover. High road densities usually indicate high levels of ecological disturbance. More...

  13. Variational approach to coarse-graining of generalized gradient flows

    NARCIS (Netherlands)

    Duong, M.H.; Lamacz, A.; Peletier, M.A.; Sharma, U.

    2017-01-01

    In this paper we present a variational technique that handles coarse-graining and passing to a limit in a unified manner. The technique is based on a duality structure, which is present in many gradient flows and other variational evolutions, and which often arises from a large-deviations principle.

  14. A technique for determining fast and thermal neutron flux densities in intense high-energy (8-30 MeV) photon fields

    International Nuclear Information System (INIS)

    Price, K.W.; Holeman, G.R.; Nath, R.

    1978-01-01

    A technique for measuring fast and thermal neutron fluxes in intense high-energy photon fields has been developed. Samples of phorphorous pentoxide are exposed to a mixed photon-neutron field. The irradiated samples are then dissolved in distilled water and their activation products are counted in a liquid scintillation spectrometer at 95-97% efficiency. The radioactive decay characteristics of the samples are then analyzed to determine fast and thermal neutron fluxes. Sensitivity of this neutron detector to high energy photons has been measured and found to be small. (author)

  15. Characterization of gradient control systems

    NARCIS (Netherlands)

    Cortés, Jorge; van der Schaft, Arjan; Crouch, Peter E.

    2005-01-01

    Given a general nonlinear affine control system with outputs and a torsion-free affine connection defined on its state space, we investigate the gradient realization problem: we give necessary and sufficient conditions under which the control system can be written as a gradient control system

  16. Characterization of Gradient Control Systems

    NARCIS (Netherlands)

    Cortés, Jorge; Schaft, Arjan van der; Crouch, Peter E.

    2005-01-01

    Given a general nonlinear affine control system with outputs and a torsion-free affine connection defined on its state space, we investigate the gradient realization problem: we give necessary and sufficient conditions under which the control system can be written as a gradient control system

  17. Sobolev gradients and differential equations

    CERN Document Server

    Neuberger, J W

    2010-01-01

    A Sobolev gradient of a real-valued functional on a Hilbert space is a gradient of that functional taken relative to an underlying Sobolev norm. This book shows how descent methods using such gradients allow a unified treatment of a wide variety of problems in differential equations. For discrete versions of partial differential equations, corresponding Sobolev gradients are seen to be vastly more efficient than ordinary gradients. In fact, descent methods with these gradients generally scale linearly with the number of grid points, in sharp contrast with the use of ordinary gradients. Aside from the first edition of this work, this is the only known account of Sobolev gradients in book form. Most of the applications in this book have emerged since the first edition was published some twelve years ago. What remains of the first edition has been extensively revised. There are a number of plots of results from calculations and a sample MatLab code is included for a simple problem. Those working through a fair p...

  18. Electric field gradients in metals

    International Nuclear Information System (INIS)

    Schatz, G.

    1979-01-01

    A review of the recent works on electric field gradient in metals is given. The main emphasis is put on the temperature dependence of the electric field gradient in nonmagnetic metals. Some methods of investigation of this effect using nuclear probes are described. One of them is nuclear accoustic resonance method. (S.B.)

  19. Rainbow refractometry on particles with radial refractive index gradients

    Energy Technology Data Exchange (ETDEWEB)

    Saengkaew, Sawitree [CNRS/Universite et INSA de Rouen, UMR 6614/CORIA, BP12, 76 800, Saint Etienne du Rouvray CEDEX (France); Chulalongkorn University, Center of Excellence in Particle Technology, Faculty of Engineering, Bangkok (Thailand); Charinpanitkul, Tawatchai; Vanisri, Hathaichanok; Tanthapanichakoon, Wiwut [Chulalongkorn University, Center of Excellence in Particle Technology, Faculty of Engineering, Bangkok (Thailand); Biscos, Yves; Garcia, Nicolas; Lavergne, Gerard [ONERA/DMAE, Toulouse (France); Mees, Loic; Gouesbet, Gerard; Grehan, Gerard [CNRS/Universite et INSA de Rouen, UMR 6614/CORIA, BP12, 76 800, Saint Etienne du Rouvray CEDEX (France)

    2007-10-15

    The rainbow refractrometry, under its different configurations (classical and global), is an attractive technique to extract information from droplets in evaporation such as diameter and temperature. Recently a new processing strategy has been developed which increases dramatically the size and refractive index measurements accuracy for homogeneous droplets. Nevertheless, for mono component as well as for multicomponent droplets, the presence of temperature and/or of concentration gradients induce the presence of a gradient of refractive index which affects the interpretation of the recorded signals. In this publication, the effect of radial gradient on rainbow measurements with a high accuracy never reached previously is quantified. (orig.)

  20. Superconducting niobium cavities with high gradients

    International Nuclear Information System (INIS)

    Kneisel, P.; Saito, K.

    1992-01-01

    Present accelerator projects making use of superconducting cavity technology are constructed with design accelerating gradients E acc ranging between 5 MV/m and 8 MV/m and Q-values of several 10 9 . Future plans for upgrades of existing accelerators or for linear colliders call for gradients greater than 15 MV/m corresponding to peak surface electric fields above 30 MV/m. These demands challenge state-of-the-art production technology and require improvements in processing and handling of these cavities to overcome the major performance limitation of field emission loading. This paper reports on efforts to improve the performance of cavities made from niobium from different suppliers by using improved cleaning techniques after processing and ultrahigh vacuum annealing at temperatures of 1400 C. In single cell L-band cavities peak surface electric fields as high as 50 MV/m have been measured without significant field emission loading. (Author) 8 refs., fig

  1. Continuous gradient temperature Raman spectroscopy of oleic and linoleic acids from -100 to 50°C

    Science.gov (United States)

    Gradient Temperature Raman spectroscopy (GTRS) applies the temperature gradients utilized in differential scanning calorimetry (DSC) to Raman spectroscopy, providing a straightforward technique to identify molecular rearrangements that occur near and at phase transitions. Herein we apply GTRS and DS...

  2. The geomagnetic field gradient tensor

    DEFF Research Database (Denmark)

    Kotsiaros, Stavros; Olsen, Nils

    2012-01-01

    We develop the general mathematical basis for space magnetic gradiometry in spherical coordinates. The magnetic gradient tensor is a second rank tensor consisting of 3 × 3 = 9 spatial derivatives. Since the geomagnetic field vector B is always solenoidal (∇ · B = 0) there are only eight independent...... tensor elements. Furthermore, in current free regions the magnetic gradient tensor becomes symmetric, further reducing the number of independent elements to five. In that case B is a Laplacian potential field and the gradient tensor can be expressed in series of spherical harmonics. We present properties...... of the magnetic gradient tensor and provide explicit expressions of its elements in terms of spherical harmonics. Finally we discuss the benefit of using gradient measurements for exploring the Earth’s magnetic field from space, in particular the advantage of the various tensor elements for a better determination...

  3. The determination of partial current densities for the corrosion of valve metals and alloys with the aid of combined radioanalytical and electrochemical techniques

    International Nuclear Information System (INIS)

    Marx, G.; Bestanpouri, A.; Droste, R.; Erben, W.; Schoenemann, W.; Wegen, D.

    1986-01-01

    Valve metals and stainless steel were investigated under practical conditions in order to evaluate their applicability from a corrosion viewpoint in nuclear technology. A new technique based upon the combined application of neutron activation analysis and normal electrochemical procedures, was developed which allowed the amount of material directly dissolved as a result of corrosion to be distinguished from that fraction forming the oxide passivation layer. Not only isotopic but also non-isotopic radionuclides were successfully employed in these studies. It was shown by potentiodynamic and potentiostatic measurements that any metal removal due to corrosion could be neglected for Hf, Ti and Ta under anodic Purex conditions. A plutonium content of up to 2.2 g l -1 even stabilized the oxide layer towards corrosion by forming mixed oxides of Hf and Pu. The influence of F - ions on the stability of the oxide layer was systematically investigated and techniques were evolved for masking these corroding anions. A particular advantage of the new radioisotopic method is its applicability for the determination of the selective corrosion of stainless steel whereby the corrosion of the various metal components may be followed with the aid of specific radionuclides. Experiments have shown that corrosion rates calculated from these radiochemical measurements were in accordance with those evaluated from various Huey-tests. (orig.) [de

  4. Two-dimensional imaging of edge plasma electron density and temperature by the passive helium emission ratio technique in TJ-II

    International Nuclear Information System (INIS)

    De la Cal, E; Guasp, J

    2011-01-01

    An intensified visible camera looks tangentially at a poloidal limiter where helium recycles, acting as a wide neutral source, and the atomic line emission due to plasma excitation becomes strongly localized there. It includes a bifurcated coherent bundle, each end with a different interference filter to select helium atomic lines, so that two simultaneous filtered images are captured in one single frame. The object of the proposed technique is to apply the well-known helium-beam line-ratio technique to obtain from selected filtered images the two-dimensional (2D) edge plasma n e and T e . The code EIRENE was used to demonstrate that the helium emission from recycling neutrals dominates the emission for the lines of view passing close above the limiter. Since these chords are nearly parallel to magnetic field lines in the emission region, the images can be approximated to poloidal cuts of the plasma emission within the tolerances discussed in the paper. The absolute radial profiles of T e and n e obtained with the method presented here were checked in the TJ-II stellarator to be in relatively good agreement with other diagnostics within a wide range of plasma parameters for both ECRH and NBI plasmas. The method is finally used to get 2D images of edge plasma T e and n e .

  5. On combined gravity gradient components modelling for applied geophysics

    International Nuclear Information System (INIS)

    Veryaskin, Alexey; McRae, Wayne

    2008-01-01

    Gravity gradiometry research and development has intensified in recent years to the extent that technologies providing a resolution of about 1 eotvos per 1 second average shall likely soon be available for multiple critical applications such as natural resources exploration, oil reservoir monitoring and defence establishment. Much of the content of this paper was composed a decade ago, and only minor modifications were required for the conclusions to be just as applicable today. In this paper we demonstrate how gravity gradient data can be modelled, and show some examples of how gravity gradient data can be combined in order to extract valuable information. In particular, this study demonstrates the importance of two gravity gradient components, Txz and Tyz, which, when processed together, can provide more information on subsurface density contrasts than that derived solely from the vertical gravity gradient (Tzz)

  6. Theory of ion-temperature-gradient-driven turbulence in tokamaks

    International Nuclear Information System (INIS)

    Lee, G.S.; Diamond, P.H.

    1986-01-01

    An analytic theory of ion-temperature-gradient-driven turbulence in tokamaks is presented. Energy-conserving, renormalized spectrum equations are derived and solved in order to obtain the spectra of stationary ion-temperature-gradient-driven turbulence. Corrections to mixing-length estimates are calculated explicitly. The resulting anomalous ion thermal diffusivity chi/sub i/ = 0.4[(π/2)ln(1 + eta/sub i/)] 2 [(1 + eta/sub i/)/tau] 2 rho/sub s/ 2 c/sub s//L/sub s/ is derived and is found to be consistent with experimentally-deduced thermal diffusivities. The associated electron thermal diffusivity and particle and heat-pinch velocities are also calculated. The effect of impurity gradients on saturated ion-temperature-gradient-driven turbulence is discussed and a related explanation of density profile steepening during Z-mode operation is proposed. 35 refs., 4 figs

  7. A novel technique to measure interface trap density in a GaAs MOS capacitor using time-varying magnetic fields

    Energy Technology Data Exchange (ETDEWEB)

    Choudhury, Aditya N. Roy, E-mail: aditya@physics.iisc.ernet.in; Venkataraman, V. [Dept. of Physics, Indian Institute of Science, Bangalore – 560012 (India)

    2016-05-23

    Interface trap density (D{sub it}) in a GaAs metal-oxide-semiconductor (MOS) capacitor can be measured electrically by measuring its impedance, i.e. by exciting it with a small signal voltage source and measuring the resulting current through the circuit. We propose a new method of measuring D{sub it} where the MOS capacitor is subjected to a (time-varying) magnetic field instead, which produces an effect equivalent to a (time-varying) voltage drop across the sample. This happens because the electron chemical potential of GaAs changes with a change in an externally applied magnetic field (unlike that of the gate metal); this is not the voltage induced by Faraday’s law of electromagnetic induction. So, by measuring the current through the MOS, D{sub it} can be found similarly. Energy band diagrams and equivalent circuits of a MOS capacitor are drawn in the presence of a magnetic field, and analyzed. The way in which a magnetic field affects a MOS structure is shown to be fundamentally different compared to an electrical voltage source.

  8. Characterization of a texture gradient in tantalum plate

    International Nuclear Information System (INIS)

    Wright, S.I.; Gray, G.T. III.

    1994-01-01

    Clark et al. have shown that significant texture gradients can be produced in rolled tantalum plate and that the strength of the gradient is dependent on the processing path. Texture gradients are often ignored because they are time consuming to characterize and add significant complexity to materials modeling. The variation in texture through the thickness of rolled materials is most commonly measured by sectioning samples to different depths through the thickness of the plate and then measuring the texture from these section planes by X-ray diffraction. A new technique based on automatic indexing of electron backscatter diffraction patterns in the scanning electron microscope enables spatially specific orientations to be measured in a practical manner. This technique allows spatial variations in texture to be measured directly enabling gradients in texture to be investigated in more detail than previously possible. This data can be used directly in coupled finite-element/polycrystal-plasticity models to simulate the effects of variations in texture on the plastic behavior of polycrystals. This work examines the variation in texture through the thickness of a tantalum plate and its resultant effect on the compressive deformation of samples prepared from the plate. The characterization of the texture gradient using the automatic point-by-point measurement technique mentioned above is described in detail. The effect of the gradient on the plastic response of through-thickness compression tests is also discussed

  9. Sodium magnetic resonance imaging. Development of a 3D radial acquisition technique with optimized k-space sampling density and high SNR-efficiency; Natrium-Magnetresonanztomographie. Entwicklung einer 3D radialen Messtechnik mit optimierter k-Raum-Abtastdichte und hoher SNR-Effizienz

    Energy Technology Data Exchange (ETDEWEB)

    Nagel, Armin Michael

    2009-04-01

    A 3D radial k-space acquisition technique with homogenous distribution of the sampling density (DA-3D-RAD) is presented. This technique enables short echo times (TE<0.5 ms), that are necessary for {sup 23}Na-MRI, and provides a high SNR-efficiency. The gradients of the DA-3D-RAD-sequence are designed such that the average sampling density in each spherical shell of k-space is constant. The DA-3D-RAD-sequence provides 34% more SNR than a conventional 3D radial sequence (3D-RAD) if T{sub 2}{sup *}-decay is neglected. This SNR-gain is enhanced if T{sub 2}{sup *}-decay is present, so a 1.5 to 1.8 fold higher SNR is measured in brain tissue with the DA-3D-RAD-sequence. Simulations and experimental measurements show that the DA-3D-RAD sequence yields a better resolution in the presence of T{sub 2}{sup *}-decay and less image artefacts when B{sub 0}-inhomogeneities exist. Using the developed sequence, T{sub 1}-, T{sub 2}{sup *}- and Inversion-Recovery-{sup 23}Na-image contrasts were acquired for several organs and {sup 23}Na-relaxation times were measured (brain tissue: T{sub 1}=29.0{+-}0.3 ms; T{sub 2s}{sup *}{approx}4 ms; T{sub 2l}{sup *}{approx}31 ms; cerebrospinal fluid: T{sub 1}=58.1{+-}0.6 ms; T{sub 2}{sup *}=55{+-}3 ms (B{sub 0}=3 T)). T{sub 1}- und T{sub 2}{sup *}-relaxation times of cerebrospinal fluid are independent of the selected magnetic field strength (B0 = 3T/7 T), whereas the relaxation times of brain tissue increase with field strength. Furthermore, {sup 23}Na-signals of oedemata were suppressed in patients and thus signals from different tissue compartments were selectively measured. (orig.)

  10. Evaluation of Over-The-Row Harvester Damage in a Super-High-Density Olive Orchard Using On-Board Sensing Techniques

    Directory of Open Access Journals (Sweden)

    Manuel Pérez-Ruiz

    2018-04-01

    Full Text Available New super-high-density (SHD olive orchards designed for mechanical harvesting using over-the-row harvesters are becoming increasingly common around the world. Some studies regarding olive SHD harvesting have focused on the effective removal of the olive fruits; however, the energy applied to the canopy by the harvesting machine that can result in fruit damage, structural damage or extra stress on the trees has been little studied. Using conventional analyses, this study investigates the effects of different nominal speeds and beating frequencies on the removal efficiency and the potential for fruit damage, and it uses remote sensing to determine changes in the plant structures of two varieties of olive trees (‘Manzanilla Cacereña’ and ‘Manzanilla de Sevilla’ planted in SHD orchards harvested by an over-the-row harvester. ‘Manzanilla de Sevilla’ fruit was the least tolerant to damage, and for this variety, harvesting at the highest nominal speed led to the greatest percentage of fruits with cuts. Different vibration patterns were applied to the olive trees and were evaluated using triaxial accelerometers. The use of two light detection and ranging (LiDAR sensing devices allowed us to evaluate structural changes in the studied olive trees. Before- and after-harvest measurements revealed significant differences in the LiDAR data analysis, particularly at the highest nominal speed. The results of this work show that the operating conditions of the harvester are key to minimising fruit damage and that a rapid estimate of the damage produced by an over-the-row harvester with contactless sensing could provide useful information for automatically adjusting the machine parameters in individual olive groves in the future.

  11. Data analysis techniques, differential cross sections, and spin density matrix elements for the reaction γp →ϕp

    Science.gov (United States)

    Dey, B.; Meyer, C. A.; Bellis, M.; Williams, M.; Adhikari, K. P.; Adikaram, D.; Aghasyan, M.; Amaryan, M. J.; Anderson, M. D.; Anefalos Pereira, S.; Ball, J.; Baltzell, N. A.; Battaglieri, M.; Bedlinskiy, I.; Biselli, A. S.; Bono, J.; Boiarinov, S.; Briscoe, W. J.; Brooks, W. K.; Burkert, V. D.; Carman, D. S.; Celentano, A.; Chandavar, S.; Colaneri, L.; Cole, P. L.; Contalbrigo, M.; Cortes, O.; Crede, V.; D'Angelo, A.; Dashyan, N.; De Vita, R.; De Sanctis, E.; Deur, A.; Djalali, C.; Doughty, D.; Dugger, M.; Dupre, R.; El Alaoui, A.; El Fassi, L.; Elouadrhiri, L.; Fedotov, G.; Fegan, S.; Fleming, J. A.; Garçon, M.; Gevorgyan, N.; Ghandilyan, Y.; Gilfoyle, G. P.; Giovanetti, K. L.; Girod, F. X.; Glazier, D. I.; Goetz, J. T.; Gothe, R. W.; Griffioen, K. A.; Guidal, M.; Hafidi, K.; Hanretty, C.; Harrison, N.; Hattawy, M.; Hicks, K.; Ho, D.; Holtrop, M.; Hyde, C. E.; Ilieva, Y.; Ireland, D. G.; Ishkhanov, B. S.; Jenkins, D.; Jo, H. S.; Joo, K.; Keller, D.; Khandaker, M.; Kim, A.; Kim, W.; Klein, A.; Klein, F. J.; Koirala, S.; Kubarovsky, V.; Kuhn, S. E.; Kuleshov, S. V.; Lenisa, P.; Livingston, K.; Lu, H.; MacGregor, I. J. D.; Markov, N.; Mayer, M.; McCracken, M. E.; McKinnon, B.; Mineeva, T.; Mirazita, M.; Mokeev, V.; Montgomery, R. A.; Moriya, K.; Moutarde, H.; Munevar, E.; Munoz Camacho, C.; Nadel-Turonski, P.; Niccolai, S.; Niculescu, G.; Niculescu, I.; Osipenko, M.; Pappalardo, L. L.; Paremuzyan, R.; Park, K.; Pasyuk, E.; Peng, P.; Phillips, J. J.; Pisano, S.; Pogorelko, O.; Pozdniakov, S.; Price, J. W.; Procureur, S.; Protopopescu, D.; Puckett, A. J. R.; Rimal, D.; Ripani, M.; Ritchie, B. G.; Rizzo, A.; Rossi, P.; Roy, P.; Sabatié, F.; Saini, M. S.; Schott, D.; Schumacher, R. A.; Seder, E.; Senderovich, I.; Sharabian, Y. G.; Simonyan, A.; Smith, E. S.; Sober, D. I.; Sokhan, D.; Stepanyan, S. S.; Stoler, P.; Strakovsky, I. I.; Strauch, S.; Sytnik, V.; Taiuti, M.; Tang, W.; Tkachenko, S.; Ungaro, M.; Vernarsky, B.; Vlassov, A. V.; Voskanyan, H.; Voutier, E.; Walford, N. K.; Watts, D. P.; Zachariou, N.; Zana, L.; Zhang, J.; Zhao, Z. W.; Zonta, I.; CLAS Collaboration

    2014-05-01

    High-statistics measurements of differential cross sections and spin density matrix elements for the reaction γp →ϕp have been made using the CLAS detector at Jefferson Lab. We cover center-of-mass energies (√s ) from 1.97 to 2.84 GeV, with an extensive coverage in the ϕ production angle. The high statistics of the data sample made it necessary to carefully account for the interplay between the ϕ natural lineshape and effects of the detector resolution, that are found to be comparable in magnitude. We study both the charged- (ϕ →K+K-) and neutral- (ϕ →KS0KL0) KK ¯ decay modes of the ϕ. Further, for the charged mode, we differentiate between the cases where the final K- track is directly detected or its momentum reconstructed as the total missing momentum in the event. The two charged-mode topologies and the neutral-mode have different resolutions and are calibrated against each other. Extensive usage is made of kinematic fitting to improve the reconstructed ϕ mass resolution. Our final results are reported in 10- and mostly 30-MeV-wide √s bins for the charged- and the neutral-modes, respectively. Possible effects from K+Λ* channels with pKK ¯ final states are discussed. These present results constitute the most precise and extensive ϕ photoproduction measurements to date and in conjunction with the ω photoproduction results recently published by CLAS, will greatly improve our understanding of low energy vector meson photoproduction.

  12. Earthworm communities along an elevation gradient in Northeastern Puerto Rico.

    Science.gov (United States)

    Grizelle Gonzalez; Emerita Garcia; Veronica Cruz; Sonia Borges; Marcela Zalamea; Maria M. Rivera

    2007-01-01

    In this study, we describe earthworm communities along an elevation gradient of eight forest types in Northeastern Puerto Rico, and determine whether their abundance, biomass and/or diversity is related to climatic, soil physical/chemical and/or biotic characteristics. We found that the density, biomass, and diversity of worms varied significantly among forest types....

  13. MODIFIED ARMIJO RULE ON GRADIENT DESCENT AND CONJUGATE GRADIENT

    Directory of Open Access Journals (Sweden)

    ZURAIDAH FITRIAH

    2017-10-01

    Full Text Available Armijo rule is an inexact line search method to determine step size in some descent method to solve unconstrained local optimization. Modified Armijo was introduced to increase the numerical performance of several descent algorithms that applying this method. The basic difference of Armijo and its modified are in existence of a parameter and estimating the parameter that is updated in every iteration. This article is comparing numerical solution and time of computation of gradient descent and conjugate gradient hybrid Gilbert-Nocedal (CGHGN that applying modified Armijo rule. From program implementation in Matlab 6, it's known that gradient descent was applying modified Armijo more effectively than CGHGN from one side: iteration needed to reach some norm of the gradient  (input by the user. The amount of iteration was representing how long the step size of each algorithm in each iteration. In another side, time of computation has the same conclusion.

  14. Edge gradient and safety factor effects on electrostatic turbulent transport in tokamaks

    International Nuclear Information System (INIS)

    Tan, Ing Hwie.

    1992-05-01

    Electrostatic turbulence and transport measurements are performed on the Tokapole-II tokamak at the University of Wisconsin-Madison, as the safety-factor and the edge equilibrium gradients and varied substantially. Tokapole-II is a poloidal divertor tokamak capable of operating at a wide range of safety factors due to its unique magnetic limiter configuration. It also has retractable material limiters in a large scrape-off region, which permits the study of edge boundary conditions like density and temperature gradients. The turbulence is independent of safety factor, but strongly sensitive to the local density gradient, which itself depends upon the limiter configuration. When a material limiter is inserted in a high discharge, the density gradient is increased locally together with a local increase of the turbulence. On the other hand, limiter insertion in low discharges did not increase the density gradient as much and the turbulence properties are unchanged with respect to the magnetic limiter case. It is conducted then, that electrostatic turbulence is caused by the density gradient. Although the electrostatic fluctuation driven transport is enhanced in the large density gradient case, it is in all cases to small to explain the observed energy confinement times. To explore instabilities with small wavelengths, a 0.5 mm diameter shperical Langmuir probe was constructed, and its power compared with the power measured by larger cylindrical probes

  15. Resonant transducers for solid-state plasma density modulation

    Energy Technology Data Exchange (ETDEWEB)

    Hallock, Gary A., E-mail: hallock@ece.utexas.edu [The University of Texas at Austin, Austin, Texas 78701 (United States); Meier, Mark A., E-mail: mark.a.meier@exxonmobil.com [ExxonMobil Upstream Research Company, Houston, Texas 77389 (United States)

    2016-04-15

    We have developed transducers capable of modulating the plasma density and plasma density gradients in indium antimonide. These transducers make use of piezoelectric drivers to excite acoustic pressure resonance at 3λ/2, generating large amplitude standing waves and plasma density modulations. The plasma density has been directly measured using a laser diagnostic. A layered media model shows good agreement with the experimental measurements.

  16. Block-conjugate-gradient method

    International Nuclear Information System (INIS)

    McCarthy, J.F.

    1989-01-01

    It is shown that by using the block-conjugate-gradient method several, say s, columns of the inverse Kogut-Susskind fermion matrix can be found simultaneously, in less time than it would take to run the standard conjugate-gradient algorithm s times. The method improves in efficiency relative to the standard conjugate-gradient algorithm as the fermion mass is decreased and as the value of the coupling is pushed to its limit before the finite-size effects become important. Thus it is potentially useful for measuring propagators in large lattice-gauge-theory calculations of the particle spectrum

  17. All Hazard Hotspots/Population Density

    Indian Academy of Sciences (India)

    This map shows hotspots of humanitarian risk for floods, cyclones, and drought overlaying a population density gradient. Blue areas with striped overlay represent areas of high population density that are also risk hotspots. These are at higher risk of future population displacement as a result of climate hazards.

  18. Long-term culture of rat hippocampal neurons at low density in serum-free medium: combination of the sandwich culture technique with the three-dimensional nanofibrous hydrogel PuraMatrix.

    Science.gov (United States)

    Kaneko, Ai; Sankai, Yoshiyuki

    2014-01-01

    The primary culture of neuronal cells plays an important role in neuroscience. There has long been a need for methods enabling the long-term culture of primary neurons at low density, in defined serum-free medium. However, the lower the cell density, the more difficult it is to maintain the cells in culture. Therefore, we aimed to develop a method for long-term culture of neurons at low density, in serum-free medium, without the need for a glial feeder layer. Here, we describe the work leading to our determination of a protocol for long-term (>2 months) primary culture of rat hippocampal neurons in serum-free medium at the low density of 3×10(4) cells/mL (8.9×10(3) cells/cm2) without a glial feeder layer. Neurons were cultured on a three-dimensional nanofibrous hydrogel, PuraMatrix, and sandwiched under a coverslip to reproduce the in vivo environment, including the three-dimensional extracellular matrix, low-oxygen conditions, and exposure to concentrated paracrine factors. We examined the effects of varying PuraMatrix concentrations, the timing and presence or absence of a coverslip, the timing of neuronal isolation from embryos, cell density at plating, medium components, and changing the medium or not on parameters such as developmental pattern, cell viability, neuronal ratio, and neurite length. Using our method of combining the sandwich culture technique with PuraMatrix in Neurobasal medium/B27/L-glutamine for primary neuron culture, we achieved longer neurites (≥3,000 µm), greater cell viability (≥30%) for 2 months, and uniform culture across the wells. We also achieved an average neuronal ratio of 97%, showing a nearly pure culture of neurons without astrocytes. Our method is considerably better than techniques for the primary culture of neurons, and eliminates the need for a glial feeder layer. It also exhibits continued support for axonal elongation and synaptic activity for long periods (>6 weeks).

  19. Long-term culture of rat hippocampal neurons at low density in serum-free medium: combination of the sandwich culture technique with the three-dimensional nanofibrous hydrogel PuraMatrix.

    Directory of Open Access Journals (Sweden)

    Ai Kaneko

    Full Text Available The primary culture of neuronal cells plays an important role in neuroscience. There has long been a need for methods enabling the long-term culture of primary neurons at low density, in defined serum-free medium. However, the lower the cell density, the more difficult it is to maintain the cells in culture. Therefore, we aimed to develop a method for long-term culture of neurons at low density, in serum-free medium, without the need for a glial feeder layer. Here, we describe the work leading to our determination of a protocol for long-term (>2 months primary culture of rat hippocampal neurons in serum-free medium at the low density of 3×10(4 cells/mL (8.9×10(3 cells/cm2 without a glial feeder layer. Neurons were cultured on a three-dimensional nanofibrous hydrogel, PuraMatrix, and sandwiched under a coverslip to reproduce the in vivo environment, including the three-dimensional extracellular matrix, low-oxygen conditions, and exposure to concentrated paracrine factors. We examined the effects of varying PuraMatrix concentrations, the timing and presence or absence of a coverslip, the timing of neuronal isolation from embryos, cell density at plating, medium components, and changing the medium or not on parameters such as developmental pattern, cell viability, neuronal ratio, and neurite length. Using our method of combining the sandwich culture technique with PuraMatrix in Neurobasal medium/B27/L-glutamine for primary neuron culture, we achieved longer neurites (≥3,000 µm, greater cell viability (≥30% for 2 months, and uniform culture across the wells. We also achieved an average neuronal ratio of 97%, showing a nearly pure culture of neurons without astrocytes. Our method is considerably better than techniques for the primary culture of neurons, and eliminates the need for a glial feeder layer. It also exhibits continued support for axonal elongation and synaptic activity for long periods (>6 weeks.

  20. Thermoelectric properties of high electron concentration materials under large temperature gradients

    International Nuclear Information System (INIS)

    Bulat, L.P.; Stefansky, V.A.

    1994-01-01

    Theoretical methods of investigating of transport properties in solids under large temperature gradients are grounded. The nonlinear and non-local expressions for current density and heat flow are obtained with degenerated of current carriers gas. A number of new effects with large temperature gradients have been tested. Use of large temperature gradients leads to the increasing of the thermoelectric figure of merit. copyright 1995 American Institute of Physics

  1. Insectivorous Birds and Environmental Factors Across an Edge-Interior Gradient in Tropical Rainforest of Malaysia

    OpenAIRE

    Abdullah B. Mohd; Mohamed Zakaria; Hossein Varasteh Moradi; Ebil Yusof

    2009-01-01

    The study objectives were to test: (1) the effects of the edge-interior gradient on understorey insectivorous bird abundance, density and diversity; (2) effects of environmental variables along an edge-interior gradient at population level (i.e., on each sub-guilds and species abundance); (3) possible effects of environmental structure along an edge-interior gradient at community level (i.e., species richness, diversity and total abundance). Fifteen hundred and four birds belonging to ...

  2. The effect of water uptake gradient in membrane electrode assembly on fuel cell performance

    Energy Technology Data Exchange (ETDEWEB)

    Fujita, H., E-mail: hajime.phy@gmail.co [Research Institute for Science Engineering, Waseda University, 103, R.J.Shillman Hall, 3-14-9, Okubo, Shinjuku, Tokyo 169-0072 (Japan); Shiraki, F.; Oshima, Y.; Tatsumi, T.; Yoshikawa, T.; Sasaki, T. [Research Institute for Science Engineering, Waseda University, 103, R.J.Shillman Hall, 3-14-9, Okubo, Shinjuku, Tokyo 169-0072 (Japan); Oshima, A. [Institute for Scientific and Industrial Research, Osaka University, 8-1 Mihogaoka, Ibaraki, Osaka 567-0047 (Japan); Washio, M. [Research Institute for Science Engineering, Waseda University, 103, R.J.Shillman Hall, 3-14-9, Okubo, Shinjuku, Tokyo 169-0072 (Japan)

    2011-02-15

    Novel proton exchange membranes (PEMs) with functionally gradient ionic sites were fabricated utilizing low energy electron beam (EB) irradiations. The low energy electron beam irradiation to polymer membranes possessed the property of gradient energy deposition in the membrane thickness direction. In the process of EB grafting of styrene onto base films, selective ranges of the gradient energy deposition were used. Micro FT-IR spectra showed that the simulated energy deposition of EB irradiation to base polymer membranes in the thickness direction corresponded to the amount of styrene grafted onto EB-irradiated films. After sulfonation, a functionally gradient ionic site PEM (gradient-PEM) was prepared, corresponding to EB depth-dose profile. The functionally gradients of ionic sites in the gradient-PEM and flat-PEM were evaluated with XPS and SEM-EDX. The results of XPS and SEM-EDX suggest that the prepared gradient-PEM had a gradient sulfonated acid groups. In addition, the polarization performance of MEA based on gradient-PEM was improved in high current density. It was thought that water uptake gradient could have a function to prevent flooding in the MEA during FC operation. Thus, the functionally gradient-PEMs could be a promising solution to manage the water behavior in MEA.

  3. Diffusiophoresis in one-dimensional solute gradients

    Energy Technology Data Exchange (ETDEWEB)

    Ault, Jesse T. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Warren, Patrick B. [Unilever R& D Port Sunlight, Bebington (United Kingdom); Shin, Sangwoo [Univ. of Hawaii at Manoa, Honolulu, HI (United States); Stone, Howard A. [Princeton Univ., Princeton, NJ (United States)

    2017-11-06

    Here, the diffusiophoretic motion of suspended colloidal particles under one-dimensional solute gradients is solved using numerical and analytical techniques. Similarity solutions are developed for the injection and withdrawal dynamics of particles into semi-infinite pores. Furthermore, a method of characteristics formulation of the diffusion-free particle transport model is presented and integrated to realize particle trajectories. Analytical solutions are presented for the limit of small particle diffusiophoretic mobility Γp relative to the solute diffusivity Ds for particle motions in both semi-infinite and finite domains. Results confirm the build up of local maxima and minima in the propagating particle front dynamics. The method of characteristics is shown to successfully predict particle motions and the position of the particle front, although it fails to accurately predict suspended particle concentrations in the vicinity of sharp gradients, such as at the particle front peak seen in some injection cases, where particle diffusion inevitably plays an important role. Results inform the design of applications in which the use of applied solute gradients can greatly enhance particle injection into and withdrawal from pores.

  4. Diffusiophoresis in one-dimensional solute gradients

    International Nuclear Information System (INIS)

    Ault, Jesse T.; Warren, Patrick B.; Shin, Sangwoo; Stone, Howard A.

    2017-01-01

    Here, the diffusiophoretic motion of suspended colloidal particles under one-dimensional solute gradients is solved using numerical and analytical techniques. Similarity solutions are developed for the injection and withdrawal dynamics of particles into semi-infinite pores. Furthermore, a method of characteristics formulation of the diffusion-free particle transport model is presented and integrated to realize particle trajectories. Analytical solutions are presented for the limit of small particle diffusiophoretic mobility Γ p relative to the solute diffusivity D s for particle motions in both semi-infinite and finite domains. Results confirm the build up of local maxima and minima in the propagating particle front dynamics. The method of characteristics is shown to successfully predict particle motions and the position of the particle front, although it fails to accurately predict suspended particle concentrations in the vicinity of sharp gradients, such as at the particle front peak seen in some injection cases, where particle diffusion inevitably plays an important role. Results inform the design of applications in which the use of applied solute gradients can greatly enhance particle injection into and withdrawal from pores.

  5. Spatial gradient tuning in metamaterials

    Science.gov (United States)

    Driscoll, Tom; Goldflam, Michael; Jokerst, Nan; Basov, Dimitri; Smith, David

    2011-03-01

    Gradient Index (GRIN) metamaterials have been used to create devices inspired by, but often surpassing the potential of, conventional GRIN optics. The unit-cell nature of metamaterials presents the opportunity to exert much greater control over spatial gradients than is possible in natural materials. This is true not only during the design phase but also offers the potential for real-time reconfiguration of the metamaterial gradient. This ability fits nicely into the picture of transformation-optics, in which spatial gradients can enable an impressive suite of innovative devices. We discuss methods to exert control over metamaterial response, focusing on our recent demonstrations using Vanadium Dioxide. We give special attention to role of memristance and mem-capacitance observed in Vanadium Dioxide, which simplify the demands of stimuli and addressing, as well as intersecting metamaterials with the field of memory-materials.

  6. Low-gradient aortic stenosis.

    Science.gov (United States)

    Clavel, Marie-Annick; Magne, Julien; Pibarot, Philippe

    2016-09-07

    An important proportion of patients with aortic stenosis (AS) have a 'low-gradient' AS, i.e. a small aortic valve area (AVA gradient (gradient discrepancy raises uncertainty about the actual stenosis severity and thus about the indication for aortic valve replacement (AVR) if the patient has symptoms and/or left ventricular (LV) systolic dysfunction. The most frequent cause of low-gradient (LG) AS is the presence of a low LV outflow state, which may occur with reduced left ventricular ejection fraction (LVEF), i.e. classical low-flow, low-gradient (LF-LG), or preserved LVEF, i.e. paradoxical LF-LG. Furthermore, a substantial proportion of patients with AS may have a normal-flow, low-gradient (NF-LG) AS: i.e. a small AVA-low-gradient combination but with a normal flow. One of the most important clinical challenges in these three categories of patients with LG AS (classical LF-LG, paradoxical LF-LG, and NF-LG) is to differentiate a true-severe AS that generally benefits from AVR vs. a pseudo-severe AS that should be managed conservatively. A low-dose dobutamine stress echocardiography may be used for this purpose in patients with classical LF-LG AS, whereas aortic valve calcium scoring by multi-detector computed tomography is the preferred modality in those with paradoxical LF-LG or NF-LG AS. Although patients with LF-LG severe AS have worse outcomes than those with high-gradient AS following AVR, they nonetheless display an important survival benefit with this intervention. Some studies suggest that transcatheter AVR may be superior to surgical AVR in patients with LF-LG AS. Published on behalf of the European Society of Cardiology. All rights reserved. © The Author 2016. For permissions please email: journals.permissions@oup.com.

  7. The evolving approach to the evaluation of low-gradient aortic stenosis.

    Science.gov (United States)

    Cutting, William B; Bavry, Anthony A

    2018-04-07

    Severe aortic stenosis (AS) is typically identified by a low valve area (≤1.0 cm 2 ) and high mean gradient (≥40 mm Hg). A subset of patients are found to have a less than severe mean gradient (gradient AS (stage D2) or normal ejection fraction with low-gradient AS (stage D3). Determining the true severity of disease within these categories has proved difficult. In this review we illustrate both traditional and novel techniques that can be used for further valvular assessment. We also propose a simple algorithm that can be used to evaluate low-gradient AS. Published by Elsevier Inc.

  8. Study of the possibility of growing germanium single crystals under low temperature gradients

    Science.gov (United States)

    Moskovskih, V. A.; Kasimkin, P. V.; Shlegel, V. N.; Vasiliev, Y. V.; Gridchin, V. A.; Podkopaev, O. I.; Zhdankov, V. N.

    2014-03-01

    The possibility of growing germanium single crystals under low temperature gradients in order to produce a dislocation-free material has been studied. Germanium crystals with a dislocation density of about 100-200 cm-2 have been grown in a system with a weight control of crystal growth at maximum axial gradients of about 1.5 K/cm.

  9. Dose gradient curve: A new tool for evaluating dose gradient.

    Science.gov (United States)

    Sung, KiHoon; Choi, Young Eun

    2018-01-01

    Stereotactic radiotherapy, which delivers an ablative high radiation dose to a target volume for maximum local tumor control, requires a rapid dose fall-off outside the target volume to prevent extensive damage to nearby normal tissue. Currently, there is no tool to comprehensively evaluate the dose gradient near the target volume. We propose the dose gradient curve (DGC) as a new tool to evaluate the quality of a treatment plan with respect to the dose fall-off characteristics. The average distance between two isodose surfaces was represented by the dose gradient index (DGI) estimated by a simple equation using the volume and surface area of isodose levels. The surface area was calculated by mesh generation and surface triangulation. The DGC was defined as a plot of the DGI of each dose interval as a function of the dose. Two types of DGCs, differential and cumulative, were generated. The performance of the DGC was evaluated using stereotactic radiosurgery plans for virtual targets. Over the range of dose distributions, the dose gradient of each dose interval was well-characterized by the DGC in an easily understandable graph format. Significant changes in the DGC were observed reflecting the differences in planning situations and various prescription doses. The DGC is a rational method for visualizing the dose gradient as the average distance between two isodose surfaces; the shorter the distance, the steeper the dose gradient. By combining the DGC with the dose-volume histogram (DVH) in a single plot, the DGC can be utilized to evaluate not only the dose gradient but also the target coverage in routine clinical practice.

  10. Strain gradient crystal plasticity: A continuum mechanics approach to modeling micro-structural evolution

    DEFF Research Database (Denmark)

    El-Naaman, Salim Abdallah; Nielsen, Kim Lau; Niordson, Christian Frithiof

    2015-01-01

    In agreement with dislocation theory, recent experiments show, both quantitatively and qualitatively, how geometrically necessary dislocations (GNDs) distribute in dislocation wall and cell structures. Hence, GND density fields are highly localized with large gradients and discontinuities occurring...

  11. Xenon ventilation CT using dual-source and dual-energy technique in children with bronchiolitis obliterans: correlation of xenon and CT density values with pulmonary function test results

    International Nuclear Information System (INIS)

    Goo, Hyun Woo; Yang, Dong Hyun; Seo, Joon Beom; Chae, Eun Jin; Lee, Jeongjin; Hong, Soo-Jong; Yu, Jinho; Kim, Byoung-Ju; Krauss, Bernhard

    2010-01-01

    Xenon ventilation CT using dual-source and dual-energy technique is a recently introduced, promising functional lung imaging method. To expand its clinical applications evidence of additional diagnostic value of xenon ventilation CT over conventional chest CT is required. To evaluate the usefulness of xenon ventilation CT using dual-source and dual-energy technique in children with bronchiolitis obliterans (BO). Seventeen children (age 7-18 years; 11 boys) with BO underwent xenon ventilation CT using dual-source and dual-energy technique. Xenon and CT density values were measured in normal and hyperlucent lung regions on CT and were compared between the two regions. Volumes of hyperlucent regions and ventilation defects were calculated with thresholds determined by visual and histogram-based analysis. Indexed volumes of hyperlucent lung regions and ventilation defects were correlated with pulmonary function test results. Effective doses of xenon CT were calculated. Xenon (14.6 ± 6.4 HU vs 26.1 ± 6.5 HU; P 25-75 , (γ = -0.68-0.88, P ≤ 0.002). Volume percentages of xenon ventilation defects (35.0 ± 16.4%)] were not significantly different from those of hyperlucent lung regions (38.2 ± 18.6%). However, mismatches between the volume percentages were variable up to 21.4-33.3%. Mean effective dose of xenon CT was 1.9 ± 0.5 mSv. In addition to high-resolution anatomic information, xenon ventilation CT using dual-source and dual-energy technique demonstrates impaired regional ventilation and its heterogeneity accurately in children with BO without additional radiation exposure. (orig.)

  12. Treatment of Layered Structures Using a Semilocal meta-GGA Density Functional

    DEFF Research Database (Denmark)

    Madsen, Georg; Ferrighi, Lara; Hammer, Bjørk

    2010-01-01

    Density functional theory calculations on solids consisting of covalently bonded layers held together by dispersive interactions are presented. Utilizing the kinetic energy density in addition to the density and its gradients gives the meta-generalized gradient approximation (MGGA) M06-L enough...

  13. The influence of ALN-Al gradient material gradient index on ballistic performance

    International Nuclear Information System (INIS)

    Wang Youcong; Liu Qiwen; Li Yao; Shen Qiang

    2013-01-01

    Ballistic performance of the gradient material is superior to laminated material, and gradient materials have different gradient types. Using ls-dyna to simulate the ballistic performance of ALN-AL gradient target plates which contain three gradient index (b = 1, b = 0.5, b = 2). Through Hopkinson bar numerical simulation to the target plate materials, we obtained the reflection stress wave and transmission stress wave state of gradient material to get the best gradient index. The internal stress state of gradient material is simulated by amplification processing of the target plate model. When the gradient index b is equal to 1, the gradient target plate is best of all.

  14. Measurement of loose powder density

    International Nuclear Information System (INIS)

    Akhtar, S.; Ali, A.; Haider, A.; Farooque, M.

    2011-01-01

    Powder metallurgy is a conventional technique for making engineering articles from powders. Main objective is to produce final products with the highest possible uniform density, which depends on the initial loose powder characteristics. Producing, handling, characterizing and compacting materials in loose powder form are part of the manufacturing processes. Density of loose metallic or ceramic powder is an important parameter for die design. Loose powder density is required for calculating the exact mass of powder to fill the die cavity for producing intended green density of the powder compact. To fulfill this requirement of powder metallurgical processing, a loose powder density meter as per ASTM standards is designed and fabricated for measurement of density. The density of free flowing metallic powders can be determined using Hall flow meter funnel and density cup of 25 cm/sup 3/ volume. Density of metal powders like cobalt, manganese, spherical bronze and pure iron is measured and results are obtained with 99.9% accuracy. (author)

  15. Salinity Gradient Energy from Expansion and Contraction of Poly(allylamine hydrochloride) Hydrogels.

    Science.gov (United States)

    Bui, Tri Quang; Cao, Vinh Duy; Do, Nu Bich Duyen; Christoffersen, Trine Eker; Wang, Wei; Kjøniksen, Anna-Lena

    2018-06-22

    Salinity gradients exhibit a great potential for production of renewable energy. Several techniques such as pressure-retarded osmosis and reverse electrodialysis have been employed to extract this energy. Unfortunately, these techniques are restricted by the high costs of membranes and problems with membrane fouling. However, the expansion and contraction of hydrogels can be a new and cheaper way to harvest energy from salinity gradients since the hydrogels swell in freshwater and shrink in saltwater. We have examined the effect of cross-linker concentration and different external loads on the energy recovered for this type of energy-producing systems. Poly(allylamine hydrochloride) hydrogels were cross-linked with glutaraldehyde to produce hydrogels with excellent expansion and contraction properties. Increasing the cross-linker concentration markedly improved the energy that could be recovered from the hydrogels, especially at high external loads. A swollen hydrogel of 60 g could recover more than 1800 mJ when utilizing a high cross-linker concentration, and the maximum amount of energy produced per gram of polymer was 3.4 J/g. Although more energy is recovered at high cross-linking densities, the maximum amount of energy produced per gram of polymer is highest at an intermediate cross-linking concentration. Energy recovery was reduced when the salt concentration was increased for the low-concentration saline solution. The results illustrate that hydrogels are promising for salinity gradient energy recovery, and that optimizing the systems significantly increases the amount of energy that can be recovered.

  16. Optimal Design of Gradient Materials and Bi-Level Optimization of Topology Using Targets (BOTT)

    Science.gov (United States)

    Garland, Anthony

    The objective of this research is to understand the fundamental relationships necessary to develop a method to optimize both the topology and the internal gradient material distribution of a single object while meeting constraints and conflicting objectives. Functionally gradient material (FGM) objects possess continuous varying material properties throughout the object, and they allow an engineer to tailor individual regions of an object to have specific mechanical properties by locally modifying the internal material composition. A variety of techniques exists for topology optimization, and several methods exist for FGM optimization, but combining the two together is difficult. Understanding the relationship between topology and material gradient optimization enables the selection of an appropriate model and the development of algorithms, which allow engineers to design high-performance parts that better meet design objectives than optimized homogeneous material objects. For this research effort, topology optimization means finding the optimal connected structure with an optimal shape. FGM optimization means finding the optimal macroscopic material properties within an object. Tailoring the material constitutive matrix as a function of position results in gradient properties. Once, the target macroscopic properties are known, a mesostructure or a particular material nanostructure can be found which gives the target material properties at each macroscopic point. This research demonstrates that topology and gradient materials can both be optimized together for a single part. The algorithms use a discretized model of the domain and gradient based optimization algorithms. In addition, when considering two conflicting objectives the algorithms in this research generate clear 'features' within a single part. This tailoring of material properties within different areas of a single part (automated design of 'features') using computational design tools is a novel benefit

  17. Low Bone Density

    Science.gov (United States)

    ... Density Exam/Testing › Low Bone Density Low Bone Density Low bone density is when your bone density ... people with normal bone density. Detecting Low Bone Density A bone density test will determine whether you ...

  18. Characterization of low density carbon foams by x-ray computed tomography (CT) and ion microtomography (IMF)

    International Nuclear Information System (INIS)

    Moddeman, W.E.; Kramer, D.P.; Firsich, D.W.; Trainer, P.D.; Yancy, R.N.; Weirup, D.L.; Logan, C.M.; Pontau, A.E.; Antolak, A.J.; Morse, D.H.

    1990-01-01

    Two NDT techniques were used to characterize low-density, microcellular, carbon foams fabricated from a salt replica process. In this paper the two techniques are x-ray computed tomography (CT) and ion microtomography (IMT); data are presented on carbon foams that contain high-density regions. The data show that densities which differ by 3 ) materials. The data reveal that the carbon foams produced by this replica process have small density variations; the density being ∼30% greater at the outer edges than when compared to the interior of the foam. In addition, the density gradient is found to be rather sharp, that is the density drops-off rapidly from the outer edges to a uniform one in the interior of the foam. This edge build-up in carbon density was explained in terms of polymer concentrating on the foam exterior during drying which immediately followed a polymer infusion processing step. Supporting analytical data from other techniques show the foam material to be >88.8% carbon

  19. CRISS power spectral density

    International Nuclear Information System (INIS)

    Vaeth, W.

    1979-04-01

    The correlation of signal components at different frequencies like higher harmonics cannot be detected by a normal power spectral density measurement, since this technique correlates only components at the same frequency. This paper describes a special method for measuring the correlation of two signal components at different frequencies: the CRISS power spectral density. From this new function in frequency analysis, the correlation of two components can be determined quantitatively either they stem from one signal or from two diverse signals. The principle of the method, suitable for the higher harmonics of a signal as well as for any other frequency combinations is shown for the digital frequency analysis technique. Two examples of CRISS power spectral densities demonstrates the operation of the new method. (orig.) [de

  20. High current density ion beam measurement techniques

    International Nuclear Information System (INIS)

    Ko, W.C.; Sawatzky, E.

    1976-01-01

    High ion beam current measurements are difficult due to the presence of the secondary particles and beam neutralization. For long Faraday cages, true current can be obtained only by negative bias on the target and by summing the cage wall and target currents; otherwise, the beam will be greatly distorted. For short Faraday cages, a combination of small magnetic field and the negative target bias results in correct beam current. Either component alone does not give true current