Hard X-ray multilayer zone plate with 25-nm outermost zone width

NASA Astrophysics Data System (ADS)

Takano, H.; Sumida, K.; Hirotomo, H.; Koyama, T.; Ichimaru, S.; Ohchi, T.; Takenaka, H.; Kagoshima, Y.

2017-06-01

We have improved the performance of a previously reported multilayer zone plate by reducing its outermost zone width, using the same multilayer materials (MoSi2 and Si) and fabrication technique. The focusing performance was evaluated at the BL24XU of SPring-8 using 20-keV X-rays. The line spread function (LSF) in the focal plane was measured using a dark-field knife-edge scan method, and the point spread function was obtained from the LSF through a tomographic reconstruction principle. The spatial resolution was estimated to be 30 nm, which is in relatively good agreement with the calculated diffraction-limited value of 25 nm, while the measured diffraction efficiency of the +1st order was 24%.

Accretion mode of oceanic ridges governed by axial mechanical strength

NASA Astrophysics Data System (ADS)

Sibrant, A. L. R.; Mittelstaedt, E.; Davaille, A.; Pauchard, L.; Aubertin, A.; Auffray, L.; Pidoux, R.

2018-04-01

Oceanic spreading ridges exhibit structural changes as a function of spreading rate, mantle temperature and the balance of tectonic and magmatic accretion. The role that these or other processes have in governing the overall shape of oceanic ridges is unclear. Here, we use laboratory experiments to simulate ridge spreading in colloidal aqueous dispersions whose rheology evolves from purely viscous to elastic and brittle when placed in contact with a saline water solution. We find that ridge shape becomes increasingly linear with spreading rate until reaching a minimum tortuosity. This behaviour is predicted by the axial failure parameter ΠF, a dimensionless number describing the balance of brittle and plastic failure of axial lithosphere. Slow-spreading, fault-dominated and fast-spreading, fluid intrusion-dominated ridges on Earth and in the laboratory are separated by the same critical ΠF value, suggesting that the axial failure mode governs ridge geometry. Values of ΠF can also be calculated for different mantle temperatures and applied to other planets or the early Earth. For higher mantle temperatures during the Archaean, our results preclude the predicted formation of large tectonic plates at high spreading velocity.

Models of Plumes: Their Flow, Their Geometric Spreading, and Their Mixing with Interplume Flow

NASA Technical Reports Server (NTRS)

Suess, Steven T.

1998-01-01

There are two types of plume flow models: (1) 1D models using ad hoc spreading functions, f(r); (2) MagnetoHydroDynamics (MHD) models. 1D models can be multifluid, time dependent, and incorporate very general descriptions of the energetics. They confirm empirical results that plume flow is slow relative to requirements for high speed wind. But, no published 1 D model incorporates the rapid local spreading at the base (fl(r)) which has an important effect on mass flux. The one published MHD model is isothermal, but confirms that if b=8*pi*p/absolute value(B)2<

Geometrical optical transfer function: is it worth calculating?

PubMed

Díaz, José A; Mahajan, Virendra N

2017-10-01

In this paper, we explore the merit of calculating the geometrical optical transfer function (GOTF) in optical design by comparing the time to calculate it with the time to calculate the diffraction optical transfer function (DOTF). We determine the DOTF by numerical integration of the pupil function autocorrelation (that reduces to an integration of a complex exponential of the aberration difference function), 2D digital autocorrelation of the pupil function, and the Fourier transform (FT) of the point-spread function (PSF); and we determine the GOTF by the FT of the geometrical PSF (that reduces to an integration over the pupil plane of a complex exponential that is a scalar product of the spatial frequency and transverse ray aberration vectors) and the FT of the spot diagram. Our starting point for calculating the DOTF is the wave aberrations of the system in its pupil plane, and the transverse ray aberrations in the image plane for the GOTF. Numerical results for primary aberrations and some typical imaging systems show that the direct numerical integrations are slow, but the GOTF calculation by a FT of the spot diagram is two or even three times slower than the DOTF calculation by an FT of the PSF, depending on the aberration. We conclude that the calculation of GOTF is, at best, an approximation of the DOTF and only for large aberrations; GOTF does not offer any advantage in the optical design process, and hence negates its utility.

A numerical analysis of forces exerted by laminar flow on spreading cells in a parallel plate flow chamber assay.

PubMed

Olivier, L A; Truskey, G A

1993-10-01

Exposure of spreading anchorage-dependent cells to laminar flow is a common technique to measure the strength of cell adhesion. Since cells protrude into the flow stream, the force exerted by the fluid on the cells is a function of cell shape. To assess the relationship between cell shape and the hydrodynamic force on adherent cells, we obtained numerical solutions of the velocity and stress fields around bovine aortic endothelial cells during various stages of spreading and calculated the force required to detach the cells. Morphometric parameters were obtained from light and scanning electron microscopy measurements. Cells were assumed to have a constant volume, but the surface area increased during spreading until the membrane was stretched taut. Two-dimensional models of steady flow were generated using the software packages ANSYS (mesh generation) and FIDAP (problem solution). The validity of the numerical results was tested by comparison with published results for a semicircle in contact with the surface. The drag force and torque were greatest for round cells making initial contact with the surface. During spreading, the drag force and torque declined by factors of 2 and 20, respectively. The calculated forces and moments were used in adhesion models to predict the wall shear stress at which the cells detached. Based upon published values for the bond force and receptor number, round cells should detach at shear stresses between 2.5 and 6 dyn/cm(2), whereas substantially higher stresses are needed to detach spreading and fully spread cells. Results from the simulations indicate that (1) the drag force varies little with cell shape whereas the torque is very sensitive to cell shape, and (2) the increase in the strength of adhesion during spreading is due to increased contact area and receptor densities within the contact area. (c) 1993 John Wiley & Sons, Inc.

Three-Dimensional Ignition and Flame Propagation Above Liquid Fuel Pools: Computational Analysis

NASA Technical Reports Server (NTRS)

Cai, Jinsheng; Sirignano, William A.

2001-01-01

A three-dimensional unsteady reactive Navier-Stokes code is developed to study the ignition and flame spread above liquid fuels initially below the flashpoint temperature. Opposed air flow to the flame spread due to forced and/or natural convection is considered. Pools of finite width and length are studied in air channels of prescribed height and width. Three-dimensional effects of the flame front near the edge of the pool are captured in the computation. The formation of a recirculation zone in the gas phase similar to that found in two-dimensional calculations is also present in the three-dimensional calculations. Both uniform spread and pulsating spread modes are found in the calculated results.

SU-E-T-353: Verification of Water Equivalent Thickness (WET) and Water Equivalent Spreadness (WES) of Proton Beam

DOE Office of Scientific and Technical Information (OSTI.GOV)

Demez, N; Lee, T; Keppel, Cynthia

Purpose: To verify calculated water equivalent thickness (WET) and water equivalent spreadness (WES) in various tissue equivalent media for proton therapy Methods: Water equivalent thicknesses (WET) of tissue equivalent materials have been calculated using the Bragg-Kleeman rule. Lateral spreadness and fluence reduction of proton beams both in those media were calculated using proton loss model (PLM) algorithm. In addition, we calculated lateral spreadness ratios with respect to that in water at the same WET depth and so the WES was defined. The WETs of those media for different proton beam energies were measured using MLIC (Multi-Layered Ionization Chamber). Also, fluencemore » and field sizes in those materials of various thicknesses were measured with ionization chambers and films Results: Calculated WETs are in agreement with measured WETs within 0.5%. We found that water equivalent spreadness (WES) is constant and the fluence and field size measurements verify that fluence can be estimated using the concept of WES. Conclusions: Calculation of WET based on the Bragg-Kleeman rule as well as the constant WES of proton beams for tissue equivalent phantoms can be used to predict fluence and field sizes at the depths of interest both in tissue equivalent media accurately for clinically available protonenergies.« less

Plasma Effects on Fast Pair Beams. II. Reactive versus Kinetic Instability of Parallel Electrostatic Waves

NASA Astrophysics Data System (ADS)

Schlickeiser, R.; Krakau, S.; Supsar, M.

2013-11-01

The interaction of TeV gamma-rays from distant blazars with the extragalactic background light produces relativistic electron-positron pair beams by the photon-photon annihilation process. Using the linear instability analysis in the kinetic limit, which properly accounts for the longitudinal and the small but finite perpendicular momentum spread in the pair momentum distribution function, the growth rate of parallel propagating electrostatic oscillations in the intergalactic medium is calculated. Contrary to the claims of Miniati and Elyiv, we find that neither the longitudinal nor the perpendicular spread in the relativistic pair distribution function significantly affect the electrostatic growth rates. The maximum kinetic growth rate for no perpendicular spread is even about an order of magnitude greater than the corresponding reactive maximum growth rate. The reduction factors in the maximum growth rate due to the finite perpendicular spread in the pair distribution function are tiny and always less than 10-4. We confirm earlier conclusions by Broderick et al. and our group that the created pair beam distribution function is quickly unstable in the unmagnetized intergalactic medium. Therefore, there is no need to require the existence of small intergalactic magnetic fields to scatter the produced pairs, so that the explanation (made by several authors) for the Fermi non-detection of the inverse Compton scattered GeV gamma-rays by a finite deflecting intergalactic magnetic field is not necessary. In particular, the various derived lower bounds for the intergalactic magnetic fields are invalid due to the pair beam instability argument.

Computer program for calculating and plotting fire direction and rate of spread.

Treesearch

James E. Eenigenburg

1987-01-01

Presents an analytical procedure that uses a FORTRAN 77 program to estimate fire direction and rate of spread. The program also calculates the variability of these parameters, both for subsections of the fire and for the fires as a whole. An option in the program allows users with a CALCOMP plotter to obtain a map of the fire with spread vectors.

Variation of Crustal Shear Velocity Structure Along the Eastern Lau Back-Arc Spreading Center Constrained By Seafloor Compliance

NASA Astrophysics Data System (ADS)

Zha, Y.; Webb, S. C.; Dunn, R. A.

2014-12-01

Measurements of seafloor compliance, the deformation under long period (typically 30-300 s) ocean wave forcing, are primarily sensitive to crustal shear velocity structure. We analyze seafloor compliance from data collected from a subset of 50 broadband Ocean Bottom Seismographs (OBS) deployed at the Eastern Lau spreading center (ELSC) from 2009 to 2010. The ELSC is a 400-km-long back-arc spreading center lying closely to the Tonga subduction trench in the southwestern Pacific. Seafloor morphology, crustal seismic structure and lava composition data show rapid variations along the ridge as the ridge migrates away from the volcanic arc front to the north, indicating a decreasing influence of the subducting slab. We calculate seafloor compliance functions by taking the spectral transfer function between the vertical displacement and pressure signal recorded by the 4-component OBSs, which are equipped with differential pressure gauges (DPGs). In the ridge perpendicular direction, compliance amplitude vary by more than an order of magnitude from the ridge crest to older seafloor covered by sediment. Along the spreading ridge, compliance measured from on-axis sites increases southwards, indicative of a decrease in the upper crustal shear velocity possibly due to increasing porosity and a thickening extrusive layer [Jacobs et al., 2007; Dunn et al., 2013]. We apply a Markov Chain Monte Carlo method to invert the compliance functions for crustal shear velocities at various locations along the ELSC.

Evaluation of a Dynamic Load Transfer Function Using Grassland Curing Data

Treesearch

Patricia L. Andrews; Stuart A.J. Anderson; Wendy R. Anderson

2006-01-01

Understanding and calculating fire behaviour in various fuel types is essential for effective fire management, including wildfire suppression and fuels management. Fire spread in grassland fuel is affected by the curing level, the amount of dead fuel expressed as a percentage of the total (live and dead fuel combined). The influence of live fuel is included in various...

Modification of electron beam ion source instability by longitudinal kinetic effects

NASA Astrophysics Data System (ADS)

Krafft, G. A.; Mark, J. W.-K.

1982-07-01

The electron beam ion source (EBIS) was proposed and subsequently realized by Donets. Further development has been done by the Orsay group and by the Berkeley group. Much theoretical work has been done on EBIS and, in particular, Litwin, Vella, and Sessler find that an electrostatic mode of the electron beam-ion system is unstable using a fluid calculation. The present work indicates that the inclusion of a longitudinal velocity spread in the electron beam decreases the instability growth rate, but their conclusions are not significantly modified. Numerically it is shown that substantial linear instability remains, even when sizeable longitudinal velocity spread is included. The principal result of the work is fig. 1; it gives the complex frequency of the mode as a function of σ/ υ0 z, σ being the spread and υ0 z being the average electron axial velocity.

Vectorial point spread function and optical transfer function in oblique plane imaging.

PubMed

Kim, Jeongmin; Li, Tongcang; Wang, Yuan; Zhang, Xiang

2014-05-05

Oblique plane imaging, using remote focusing with a tilted mirror, enables direct two-dimensional (2D) imaging of any inclined plane of interest in three-dimensional (3D) specimens. It can image real-time dynamics of a living sample that changes rapidly or evolves its structure along arbitrary orientations. It also allows direct observations of any tilted target plane in an object of which orientational information is inaccessible during sample preparation. In this work, we study the optical resolution of this innovative wide-field imaging method. Using the vectorial diffraction theory, we formulate the vectorial point spread function (PSF) of direct oblique plane imaging. The anisotropic lateral resolving power caused by light clipping from the tilted mirror is theoretically analyzed for all oblique angles. We show that the 2D PSF in oblique plane imaging is conceptually different from the inclined 2D slice of the 3D PSF in conventional lateral imaging. Vectorial optical transfer function (OTF) of oblique plane imaging is also calculated by the fast Fourier transform (FFT) method to study effects of oblique angles on frequency responses.

The Measurement of the Evaporation Residues Excitation Functions in the Fusion Reactions 144Sm (40Ar,xn) and 166Er(40Ar,xn)

NASA Astrophysics Data System (ADS)

Chernysheva, E. V.; Rodin, A. M.; Belozerov, A. V.; Dmitriev, S. N.; Gulyaev, A. V.; Gulyaeva, A. V.; Itkis, M. G.; Novoselov, A. S.; Oganessian, Yu. Ts.; Salamatin, V. S.; Stepantsov, S. V.; Vedeneev, V. Yu.; Yukhimchuk, S. A.; Krupa, L.; Kliman, J.; Motycak, S.; Sivacek, I.

2015-06-01

The evaporation residues excitation functions for the reactions 40Ar+144Sm→184Hg and 40Ar+166Er→206Rn were measured at the energies below and above the Coulomb barrier (Elab=142-207 MeV) using a mass-separator MASHA. The experimental data were compared with theoretical calculations using a Channel Coupling Model. The influence of experimental beam energy spread on the excitation functions was taking into account. It was found that structure of xn-cross sections correlate strongly with the nuclear structure of colliding nuclei.

Neutron Transmission of Single-crystal Sapphire Filters

NASA Astrophysics Data System (ADS)

Adib, M.; Kilany, M.; Habib, N.; Fathallah, M.

2005-05-01

An additive formula is given that permits the calculation of the nuclear capture, thermal diffuse and Bragg scattering cross-sections as a function of sapphire temperature and crystal parameters. We have developed a computer program that allows calculations of the thermal neutron transmission for the sapphire rhombohedral structure and its equivalent trigonal structure. The calculated total cross-section values and effective attenuation coefficient for single-crystalline sapphire at different temperatures are compared with measured values. Overall agreement is indicated between the formula and experimental data. We discuss the use of sapphire single crystal as a thermal neutron filter in terms of the optimum cystal thickness, mosaic spread, temperature, cutting plane and tuning for efficient transmission of thermal-reactor neutrons.

Effects of rewiring strategies on information spreading in complex dynamic networks

NASA Astrophysics Data System (ADS)

Ally, Abdulla F.; Zhang, Ning

2018-04-01

Recent advances in networks and communication services have attracted much interest to understand information spreading in social networks. Consequently, numerous studies have been devoted to provide effective and accurate models for mimicking information spreading. However, knowledge on how to spread information faster and more widely remains a contentious issue. Yet, most existing works are based on static networks which limit the reality of dynamism of entities that participate in information spreading. Using the SIR epidemic model, this study explores and compares effects of two rewiring models (Fermi-Dirac and Linear functions) on information spreading in scale free and small world networks. Our results show that for all the rewiring strategies, the spreading influence replenishes with time but stabilizes in a steady state at later time-steps. This means that information spreading takes-off during the initial spreading steps, after which the spreading prevalence settles toward its equilibrium, with majority of the population having recovered and thus, no longer affecting the spreading. Meanwhile, rewiring strategy based on Fermi-Dirac distribution function in one way or another impedes the spreading process, however, the structure of the networks mimic the spreading, even with a low spreading rate. The worst case can be when the spreading rate is extremely small. The results emphasize that despite a big role of such networks in mimicking the spreading, the role of the parameters cannot be simply ignored. Apparently, the probability of giant degree neighbors being informed grows much faster with the rewiring strategy of linear function compared to that of Fermi-Dirac distribution function. Clearly, rewiring model based on linear function generates the fastest spreading across the networks. Therefore, if we are interested in speeding up the spreading process in stochastic modeling, linear function may play a pivotal role.

TU-D-209-02: A Backscatter Point Spread Function for Entrance Skin Dose Determination

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vijayan, S; Xiong, Z; Shankar, A

Purpose: To determine the distribution of backscattered radiation to the skin resulting from a non-uniform distribution of primary radiation through convolution with a backscatter point spread function (PSF). Methods: A backscatter PSF is determined using Monte Carlo simulation of a 1 mm primary beam incident on a 30 × 30 cm × 20 cm thick PMMA phantom using EGSnrc software. A primary profile is similarly obtained without the phantom and the difference from the total provides the backscatter profile. This scatter PSF characterizes the backscatter spread for a “point” primary interaction and can be convolved with the entrance primary dosemore » distribution to obtain the total entrance skin dose. The backscatter PSF was integrated into the skin dose tracking system (DTS), a graphical utility for displaying the color-coded skin dose distribution on a 3D graphic of the patient during interventional fluoroscopic procedures. The backscatter convolution method was validated for the non-uniform beam resulting from the use of an ROI attenuator. The ROI attenuator is a copper sheet with about 20% primary transmission (0.7 mm thick) containing a circular aperture; this attenuator is placed in the beam to reduce dose in the periphery while maintaining full dose in the region of interest. The DTS calculated primary plus backscatter distribution is compared to that measured with GafChromic film and that calculated using EGSnrc Monte-Carlo software. Results: The PSF convolution method used in the DTS software was able to account for the spread of backscatter from the ROI region to the region under the attenuator. The skin dose distribution determined using DTS with the ROI attenuator was in good agreement with the distributions measured with Gafchromic film and determined by Monte Carlo simulation Conclusion: The PSF convolution technique provides an accurate alternative for entrance skin dose determination with non-uniform primary x-ray beams. Partial support from NIH Grant R01-EB002873 and Toshiba Medical Systems Corp.« less

PynPoint code for exoplanet imaging

NASA Astrophysics Data System (ADS)

Amara, A.; Quanz, S. P.; Akeret, J.

2015-04-01

We announce the public release of PynPoint, a Python package that we have developed for analysing exoplanet data taken with the angular differential imaging observing technique. In particular, PynPoint is designed to model the point spread function of the central star and to subtract its flux contribution to reveal nearby faint companion planets. The current version of the package does this correction by using a principal component analysis method to build a basis set for modelling the point spread function of the observations. We demonstrate the performance of the package by reanalysing publicly available data on the exoplanet β Pictoris b, which consists of close to 24,000 individual image frames. We show that PynPoint is able to analyse this typical data in roughly 1.5 min on a Mac Pro, when the number of images is reduced by co-adding in sets of 5. The main computational work, the calculation of the Singular-Value-Decomposition, parallelises well as a result of a reliance on the SciPy and NumPy packages. For this calculation the peak memory load is 6 GB, which can be run comfortably on most workstations. A simpler calculation, by co-adding over 50, takes 3 s with a peak memory usage of 600 MB. This can be performed easily on a laptop. In developing the package we have modularised the code so that we will be able to extend functionality in future releases, through the inclusion of more modules, without it affecting the users application programming interface. We distribute the PynPoint package under GPLv3 licence through the central PyPI server, and the documentation is available online (http://pynpoint.ethz.ch).

Invited Article: Refined analysis of synchrotron radiation for NIST's SURF III facility

NASA Astrophysics Data System (ADS)

Shirley, Eric L.; Furst, Mitchell; Arp, Uwe

2018-04-01

We have developed a new method for the exact calculation of synchrotron radiation for the National Institute of Standards and Technology Synchrotron Ultraviolet Radiation Facility, SURF III. Instead of using the Schwinger formula, which is only an approximation, we develop formulae based on Graf's addition theorem for Bessel functions and accurate asymptotic expansions for Hankel functions and Bessel functions. By measuring the radiation intensity profile at two distances from the storage ring, we also confirm an apparent vertical emittance that is consistent with the vertical betatron oscillations that are intentionally introduced to extend beam lifetime by spreading the electron beam spatially. Finally, we determine how much diffraction by beamline apertures enhances the spectral irradiance at an integrating sphere entrance port at the end station. This should eliminate small but treatable components of the uncertainty budget that one should consider when using SURF III or similar synchrotrons as standard, calculable sources of ultraviolet and other radiation.

Improved resolution in practical light microscopy by means of a glass-fiber 2 π-tilting device

NASA Astrophysics Data System (ADS)

Bradl, Joachim; Rinke, Bernd; Schneider, Bernhard; Hausmann, Michael; Cremer, Christoph G.

1996-01-01

The spatial resolution of a conventional light microscope or a confocal laser scanning microscope can be determined by calculating the point spread function for the objective used. Normally, ideal conditions are assumed for these calculations. Such conditions, however, are often not fulfilled in biological applications especially in those cases where biochemical requirements (e.g. buffer conditions) influence the specimen preparation on the microscope slide (i.e. 'practical' light microscopy). It has been shown that the problem of a reduced z- resolution in 3D-microscopy (optical sectioning) can be overcome by a capillary in a 2(pi) - tilting device that allows object rotation into an optimal perspective. The application of the glass capillary instead of a standard slide has an additional influence on the imaging properties of the microscope. Therefore, another 2(pi) -tilting device was developed, using a glass fiber for object fixation and rotation. Such a fiber could be covered by standard cover glasses. To estimate the resolution of this setup, point spread functions were measured under different conditions using fluorescent microspheres of subwavelength dimensions. Results obtained from standard slide setups were compared to the glass fiber setup. These results showed that in practice rotation leads to an overall 3D-resolution improvement.

SU-E-T-439: An Improved Formula of Scatter-To-Primary Ratio for Photon Dose Calculation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhu, T

2014-06-01

Purpose: Scatter-to-primary ratio (SPR) is an important dosimetric quantity that describes the contribution from the scatter photons in an external photon beam. The purpose of this study is to develop an improved analytical formula to describe SPR as a function of circular field size (r) and depth (d) using Monte Carlo (MC) simulation. Methods: MC simulation was performed for Mohan photon spectra (Co-60, 4, 6, 10, 15, 23 MV) using EGSNRC code. Point-spread scatter dose kernels in water are generated. The scatter-to-primary ratio (SPR) is also calculated using MC simulation as a function of field size for circular field sizemore » with radius r and depth d. The doses from forward scatter and backscatter photons are calculated using a convolution of the point-spread scatter dose kernel and by accounting for scatter photons contributing to dose before (z'd) reaching the depth of interest, d, where z' is the location of scatter photons, respectively. The depth dependence of the ratio of the forward scatter and backscatter doses is determined as a function of depth and field size. Results: We are able to improve the existing 3-parameter (a, w, d0) empirical formula for SPR by introducing depth dependence for one of the parameter d0, which becomes 0 for deeper depths. The depth dependence of d0 can be directly calculated as a ratio of backscatter-to-forward scatter doses for otherwise the same field and depth. With the improved empirical formula, we can fit SPR for all megavoltage photon beams to within 2%. Existing 3-parameter formula cannot fit SPR data for Co-60 to better than 3.1%. Conclusion: An improved empirical formula is developed to fit SPR for all megavoltage photon energies to within 2%.« less

Continuous energy adjoint transport for photons in PHITS

NASA Astrophysics Data System (ADS)

Malins, Alex; Machida, Masahiko; Niita, Koji

2017-09-01

Adjoint Monte Carlo can be an effcient algorithm for solving photon transport problems where the size of the tally is relatively small compared to the source. Such problems are typical in environmental radioactivity calculations, where natural or fallout radionuclides spread over a large area contribute to the air dose rate at a particular location. Moreover photon transport with continuous energy representation is vital for accurately calculating radiation protection quantities. Here we describe the incorporation of an adjoint Monte Carlo capability for continuous energy photon transport into the Particle and Heavy Ion Transport code System (PHITS). An adjoint cross section library for photon interactions was developed based on the JENDL- 4.0 library, by adding cross sections for adjoint incoherent scattering and pair production. PHITS reads in the library and implements the adjoint transport algorithm by Hoogenboom. Adjoint pseudo-photons are spawned within the forward tally volume and transported through space. Currently pseudo-photons can undergo coherent and incoherent scattering within the PHITS adjoint function. Photoelectric absorption is treated implicitly. The calculation result is recovered from the pseudo-photon flux calculated over the true source volume. A new adjoint tally function facilitates this conversion. This paper gives an overview of the new function and discusses potential future developments.

Calculation of the static in-flight telescope-detector response by deconvolution applied to point-spread function for the geostationary earth radiation budget experiment.

PubMed

Matthews, Grant

2004-12-01

The Geostationary Earth Radiation Budget (GERB) experiment is a broadband satellite radiometer instrument program intended to resolve remaining uncertainties surrounding the effect of cloud radiative feedback on future climate change. By use of a custom-designed diffraction-aberration telescope model, the GERB detector spatial response is recovered by deconvolution applied to the ground calibration point-spread function (PSF) measurements. An ensemble of randomly generated white-noise test scenes, combined with the measured telescope transfer function results in the effect of noise on the deconvolution being significantly reduced. With the recovered detector response as a base, the same model is applied in construction of the predicted in-flight field-of-view response of each GERB pixel to both short- and long-wave Earth radiance. The results of this study can now be used to simulate and investigate the instantaneous sampling errors incurred by GERB. Also, the developed deconvolution method may be highly applicable in enhancing images or PSF data for any telescope system for which a wave-front error measurement is available.

Comparison of measured and computed Strehl ratios for light propagated through a channel flow of a He N 2 mixing layer at high Reynolds numbers

NASA Astrophysics Data System (ADS)

Gardner, Patrick J.; Roggemann, Michael C.; Welsh, Byron M.; Bowersox, Rodney D.; Luke, Theodore E.

1997-04-01

A lateral shearing interferometer was used to measure the slope of perturbed wave fronts after they propagated through a He N 2 mixing layer in a rectangular channel. Slope measurements were used to reconstruct the phase of the turbulence-corrupted wave front. The random phase fluctuations induced by the mixing layer were captured in a large ensemble of wave-front measurements. Phase structure functions, computed from the reconstructed phase surfaces, were stationary in first increments. A five-thirds power law is shown to fit streamwise and cross-stream slices of the structure function, analogous to the Kolmogorov model for isotropic turbulence, which describes the structure function with a single parameter. Strehl ratios were computed from the phase structure functions and compared with a measured experiment obtained from simultaneous point-spread function measurements. Two additional Strehl ratios were calculated by using classical estimates that assume statistical isotropy throughout the flow. The isotropic models are a reasonable estimate of the optical degradation only within a few centimeters of the initial mixing, where the Reynolds number is low. At higher Reynolds numbers, Strehl ratios calculated from the structure functions match the experiment much better than Strehl ratio calculations that assume isotropic flow.

Extension and applications of switching model: Range theory, multiple scattering model of Goudsmit-Saunderson, and lateral spread treatment of Marwick-Sigmund

NASA Astrophysics Data System (ADS)

Ikegami, Seiji

2017-09-01

The switching model (PSM) developed in the previous paper is extended to obtain an ;extended switching model (ESM). In the ESM, the mixt electronic-and-nuclear energy-loss region, in addition to the electronic and nuclear energy-loss regions in PSM, is taken into account analytically and appropriately. This model is combined with a small-angle multiple scattering range theory considering both nuclear and electronic stopping effects developed by Marwick-Sigmund and Valdes-Arista to formulate a improved range theory. The ESM is also combined with the multiple scattering theory with non-small angle approximation by Goudsmit-Saunderson. Furthermore, we applied ESM to lateral spread model of Marwick-Sigmund. Numerical calculations of the entire distribution functions including one of the mixt region are roughly and approximately possible. However, exact numerical calculation may be impossible. Consequently, several preliminary numerical calculations of the electronic, mixt, and nuclear regions are performed to examine their underlying behavior with respect to the incident energy, the scattering angle, the outgoing projectile intensity, and the target thickness. We show the numerical results not only of PSM and but also of ESM. Both numerical results are shown in the present paper for the first time. Since the theoretical relations are constructed using reduced variables, the calculations are made only on the case of C colliding on C.

Theoretical analysis of the performance of code division multiple access communications over multimode optical fiber channels. Part 1: Transmission and detection

NASA Astrophysics Data System (ADS)

Walker, Ernest L.

1994-05-01

This paper presents results of a theoretical investigation to evaluate the performance of code division multiple access communications over multimode optical fiber channels in an asynchronous, multiuser communication network environment. The system is evaluated using Gold sequences for spectral spreading of the baseband signal from each user employing direct-sequence biphase shift keying and intensity modulation techniques. The transmission channel model employed is a lossless linear system approximation of the field transfer function for the alpha -profile multimode optical fiber. Due to channel model complexity, a correlation receiver model employing a suboptimal receive filter was used in calculating the peak output signal at the ith receiver. In Part 1, the performance measures for the system, i.e., signal-to-noise ratio and bit error probability for the ith receiver, are derived as functions of channel characteristics, spectral spreading, number of active users, and the bit energy to noise (white) spectral density ratio. In Part 2, the overall system performance is evaluated.

Support for the beam focusing hypothesis in the false killer whale.

PubMed

Kloepper, Laura N; Buck, John R; Smith, Adam B; Supin, Alexander Ya; Gaudette, Jason E; Nachtigall, Paul E

2015-08-01

The odontocete sound production system is complex and composed of tissues, air sacs and a fatty melon. Previous studies suggested that the emitted sonar beam might be actively focused, narrowing depending on target distance. In this study, we further tested this beam focusing hypothesis in a false killer whale. Using three linear arrays of hydrophones, we recorded the same emitted click at 2, 4 and 7 m distance and calculated the beamwidth, intensity, center frequency and bandwidth as recorded on each array at every distance. If the whale did not focus her beam, acoustics predicts the intensity would decay with range as a function of spherical spreading and the angular beamwidth would remain constant. On the contrary, our results show that as the distance from the whale to the array increases, the beamwidth is narrower and the received click intensity is higher than that predicted by a spherical spreading function. Each of these measurements is consistent with the animal focusing her beam on a target at a given range. These results support the hypothesis that the false killer whale is 'focusing' its sonar beam, producing a narrower and more intense signal than that predicted by spherical spreading. © 2015. Published by The Company of Biologists Ltd.

LANDSAT-D investigations in snow hydrology

NASA Technical Reports Server (NTRS)

Dozier, J.

1983-01-01

The atmospheric radiative transfer calculation program (ATARD) and its supporting programs (setting up atmospheric profile, making Mie tables and an exponential-sum-fitting table) were completed. More sophisticated treatment of aerosol scattering (including angular phase function or asymmetric factor) and multichannel analysis of results from ATRAD are being developed. Some progress was made on a Monte Carlo program for examining two dimensional effects, specifically a surface boundary condition that varies across a scene. The MONTE program combines ATRAD and the Monte Carlo method together to produce an atmospheric point spread function. Currently the procedure passes monochromatic tests and the results are reasonable.

Characteristics of the retinal images of the eye optical systems with implanted intraocular lenses

NASA Astrophysics Data System (ADS)

Siedlecki, Damian; Zając, Marek; Nowak, Jerzy

2007-04-01

Cataract, or opacity of crystalline lens in the human eye is one of the most frequent reasons of blindness nowadays. Removing the pathologically altered crystalline lens and replacing it with artificial implantable intraocular lens (IOL) is practically the only therapy in this illness. There exist a wide variety of artificial IOL types on the medical market, differing in their material and design (shape). In this paper six exemplary models of IOL's made of PMMA, acrylic and silicone are considered. The retinal image quality is analyzed numerically on the basis of Liou-Brennan eye model with these IOL's inserted. Chromatic aberration as well as polychromatic Point Spread Function and Modulation Transfer Function are calculated as most adequate image quality measures. The calculations made with Zemax TM software show the importance of chromatic aberration correction.

Toward standardized quantitative image quality (IQ) assessment in computed tomography (CT): A comprehensive framework for automated and comparative IQ analysis based on ICRU Report 87.

PubMed

Pahn, Gregor; Skornitzke, Stephan; Schlemmer, Hans-Peter; Kauczor, Hans-Ulrich; Stiller, Wolfram

2016-01-01

Based on the guidelines from "Report 87: Radiation Dose and Image-quality Assessment in Computed Tomography" of the International Commission on Radiation Units and Measurements (ICRU), a software framework for automated quantitative image quality analysis was developed and its usability for a variety of scientific questions demonstrated. The extendable framework currently implements the calculation of the recommended Fourier image quality (IQ) metrics modulation transfer function (MTF) and noise-power spectrum (NPS), and additional IQ quantities such as noise magnitude, CT number accuracy, uniformity across the field-of-view, contrast-to-noise ratio (CNR) and signal-to-noise ratio (SNR) of simulated lesions for a commercially available cone-beam phantom. Sample image data were acquired with different scan and reconstruction settings on CT systems from different manufacturers. Spatial resolution is analyzed in terms of edge-spread function, line-spread-function, and MTF. 3D NPS is calculated according to ICRU Report 87, and condensed to 2D and radially averaged 1D representations. Noise magnitude, CT numbers, and uniformity of these quantities are assessed on large samples of ROIs. Low-contrast resolution (CNR, SNR) is quantitatively evaluated as a function of lesion contrast and diameter. Simultaneous automated processing of several image datasets allows for straightforward comparative assessment. The presented framework enables systematic, reproducible, automated and time-efficient quantitative IQ analysis. Consistent application of the ICRU guidelines facilitates standardization of quantitative assessment not only for routine quality assurance, but for a number of research questions, e.g. the comparison of different scanner models or acquisition protocols, and the evaluation of new technology or reconstruction methods. Copyright © 2015 Associazione Italiana di Fisica Medica. Published by Elsevier Ltd. All rights reserved.

Analysis of the Yule-Nielsen effect with the multiple-path point spread function in a frequency-modulated halftone.

PubMed

Rogers, Geoffrey

2018-06-01

The Yule-Nielsen effect is an influence on halftone color caused by the diffusion of light within the paper upon which the halftone ink is printed. The diffusion can be characterized by a point spread function. In this paper, a point spread function for paper is derived using the multiple-path model of reflection. This model treats the interaction of light with turbid media as a random walk. Using the multiple-path point spread function, a general expression is derived for the average reflectance of light from a frequency-modulated halftone, in which dot size is constant and the number of dots is varied, with the arrangement of dots random. It is also shown that the line spread function derived from the multiple-path model has the form of a Lorentzian function.

Modeling solvation effects in real-space and real-time within density functional approaches

NASA Astrophysics Data System (ADS)

Delgado, Alain; Corni, Stefano; Pittalis, Stefano; Rozzi, Carlo Andrea

2015-10-01

The Polarizable Continuum Model (PCM) can be used in conjunction with Density Functional Theory (DFT) and its time-dependent extension (TDDFT) to simulate the electronic and optical properties of molecules and nanoparticles immersed in a dielectric environment, typically liquid solvents. In this contribution, we develop a methodology to account for solvation effects in real-space (and real-time) (TD)DFT calculations. The boundary elements method is used to calculate the solvent reaction potential in terms of the apparent charges that spread over the van der Waals solute surface. In a real-space representation, this potential may exhibit a Coulomb singularity at grid points that are close to the cavity surface. We propose a simple approach to regularize such singularity by using a set of spherical Gaussian functions to distribute the apparent charges. We have implemented the proposed method in the Octopus code and present results for the solvation free energies and solvatochromic shifts for a representative set of organic molecules in water.

Modeling solvation effects in real-space and real-time within density functional approaches

DOE Office of Scientific and Technical Information (OSTI.GOV)

Delgado, Alain; Centro de Aplicaciones Tecnológicas y Desarrollo Nuclear, Calle 30 # 502, 11300 La Habana; Corni, Stefano

2015-10-14

The Polarizable Continuum Model (PCM) can be used in conjunction with Density Functional Theory (DFT) and its time-dependent extension (TDDFT) to simulate the electronic and optical properties of molecules and nanoparticles immersed in a dielectric environment, typically liquid solvents. In this contribution, we develop a methodology to account for solvation effects in real-space (and real-time) (TD)DFT calculations. The boundary elements method is used to calculate the solvent reaction potential in terms of the apparent charges that spread over the van der Waals solute surface. In a real-space representation, this potential may exhibit a Coulomb singularity at grid points that aremore » close to the cavity surface. We propose a simple approach to regularize such singularity by using a set of spherical Gaussian functions to distribute the apparent charges. We have implemented the proposed method in the OCTOPUS code and present results for the solvation free energies and solvatochromic shifts for a representative set of organic molecules in water.« less

Validity of virial theorem in all-electron mixed basis density functional, Hartree–Fock, and GW calculations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kuwahara, Riichi; Accelrys K. K., Kasumigaseki Tokyu Building 17F, 3-7-1 Kasumigaseki, Chiyoda-ku, Tokyo 100-0013; Tadokoro, Yoichi

In this paper, we calculate kinetic and potential energy contributions to the electronic ground-state total energy of several isolated atoms (He, Be, Ne, Mg, Ar, and Ca) by using the local density approximation (LDA) in density functional theory, the Hartree–Fock approximation (HFA), and the self-consistent GW approximation (GWA). To this end, we have implemented self-consistent HFA and GWA routines in our all-electron mixed basis code, TOMBO. We confirm that virial theorem is fairly well satisfied in all of these approximations, although the resulting eigenvalue of the highest occupied molecular orbital level, i.e., the negative of the ionization potential, is inmore » excellent agreement only in the case of the GWA. We find that the wave function of the lowest unoccupied molecular orbital level of noble gas atoms is a resonating virtual bound state, and that of the GWA spreads wider than that of the LDA and thinner than that of the HFA.« less

Optical comparison of multizone and single-zone photorefractive keratectomy

NASA Astrophysics Data System (ADS)

Gonzalez-Cirre, Xochitl; Manns, Fabrice; Rol, Pascal O.; Parel, Jean-Marie A.

1997-05-01

The purpose is to calculate and compare the point-spread function and the central ablation depth (CAD) of a paraxial eye model after photo-refractive keratectomy (PRK), with single and multizone treatments. A modified Le Grand-El Hage paraxial eye model, with a pupil diameter ranging from 2 to 8 mm was used. Ray-tracing was performed for initial myopia ranging from 1 to 10D; after single zone PRK; after double zone PRK; and after tripe zone PRK. The ray-tracing of a parallel incident beam was calculated by using the paraxial matrix method. At equal CAD, the optical image quality is better after single zone treatments. Multizone treatments do not seem to be advantageous optically.

Tritium permeation model for plasma facing components

NASA Astrophysics Data System (ADS)

Longhurst, G. R.

1992-12-01

This report documents the development of a simplified one-dimensional tritium permeation and retention model. The model makes use of the same physical mechanisms as more sophisticated, time-transient codes such as implantation, recombination, diffusion, trapping and thermal gradient effects. It takes advantage of a number of simplifications and approximations to solve the steady-state problem and then provides interpolating functions to make estimates of intermediate states based on the steady-state solution. The model is developed for solution using commercial spread-sheet software such as Lotus 123. Comparison calculations are provided with the verified and validated TMAP4 transient code with good agreement. Results of calculations for the ITER CDA diverter are also included.

Quantification of uncertainty in first-principles predicted mechanical properties of solids: Application to solid ion conductors

NASA Astrophysics Data System (ADS)

Ahmad, Zeeshan; Viswanathan, Venkatasubramanian

2016-08-01

Computationally-guided material discovery is being increasingly employed using a descriptor-based screening through the calculation of a few properties of interest. A precise understanding of the uncertainty associated with first-principles density functional theory calculated property values is important for the success of descriptor-based screening. The Bayesian error estimation approach has been built in to several recently developed exchange-correlation functionals, which allows an estimate of the uncertainty associated with properties related to the ground state energy, for example, adsorption energies. Here, we propose a robust and computationally efficient method for quantifying uncertainty in mechanical properties, which depend on the derivatives of the energy. The procedure involves calculating energies around the equilibrium cell volume with different strains and fitting the obtained energies to the corresponding energy-strain relationship. At each strain, we use instead of a single energy, an ensemble of energies, giving us an ensemble of fits and thereby, an ensemble of mechanical properties associated with each fit, whose spread can be used to quantify its uncertainty. The generation of ensemble of energies is only a post-processing step involving a perturbation of parameters of the exchange-correlation functional and solving for the energy non-self-consistently. The proposed method is computationally efficient and provides a more robust uncertainty estimate compared to the approach of self-consistent calculations employing several different exchange-correlation functionals. We demonstrate the method by calculating the uncertainty bounds for several materials belonging to different classes and having different structures using the developed method. We show that the calculated uncertainty bounds the property values obtained using three different GGA functionals: PBE, PBEsol, and RPBE. Finally, we apply the approach to calculate the uncertainty associated with the DFT-calculated elastic properties of solid state Li-ion and Na-ion conductors.

Biobeam—Multiplexed wave-optical simulations of light-sheet microscopy

PubMed Central

Weigert, Martin; Bundschuh, Sebastian T.

2018-01-01

Sample-induced image-degradation remains an intricate wave-optical problem in light-sheet microscopy. Here we present biobeam, an open-source software package that enables simulation of operational light-sheet microscopes by combining data from 105–106 multiplexed and GPU-accelerated point-spread-function calculations. The wave-optical nature of these simulations leads to the faithful reproduction of spatially varying aberrations, diffraction artifacts, geometric image distortions, adaptive optics, and emergent wave-optical phenomena, and renders image-formation in light-sheet microscopy computationally tractable. PMID:29652879

Nomographs for estimating surface fire behavior characteristics

Treesearch

Joe H. Scott

2007-01-01

A complete set of nomographs for estimating surface fire rate of spread and flame length for the original 13 and new 40 fire behavior fuel models is presented. The nomographs allow calculation of spread rate and flame length for wind in any direction with respect to slope and allow for nonheading spread directions. Basic instructions for use are included.

Comparison of PSF maxima and minima of multiple annuli coded aperture (MACA) and complementary multiple annuli coded aperture (CMACA) systems

NASA Astrophysics Data System (ADS)

Ratnam, Challa; Lakshmana Rao, Vadlamudi; Lachaa Goud, Sivagouni

2006-10-01

In the present paper, and a series of papers to follow, the Fourier analytical properties of multiple annuli coded aperture (MACA) and complementary multiple annuli coded aperture (CMACA) systems are investigated. First, the transmission function for MACA and CMACA is derived using Fourier methods and, based on the Fresnel-Kirchoff diffraction theory, the formulae for the point spread function are formulated. The PSF maxima and minima are calculated for both the MACA and CMACA systems. The dependence of these properties on the number of zones is studied and reported in this paper.

Moments of click-evoked otoacoustic emissions in human ears: group delay and spread, instantaneous frequency and bandwidth.

PubMed

Keefe, Douglas H

2012-11-01

A click-evoked otoacoustic emission (CEOAE) has group delay and spread as first- and second-order temporal moments varying over frequency, and instantaneous frequency and bandwidth as first- and second-order spectral moments varying over time. Energy-smoothed moments were calculated from a CEOAE database over 0.5-15 kHz bandwidth and 0.25-20 ms duration. Group delay and instantaneous frequency were calculated without phase unwrapping using a coherence synchrony measure that accurately classified ears with hearing loss. CEOAE moment measurements were repeatable in individual ears. Group delays were similar for CEOAEs and stimulus-frequency OAEs. Group spread is a frequency-specific measure of temporal spread in an emission, related to spatial spread across tonotopic generation sites along the cochlea. In normal ears, group delay and spread increased with frequency and decreased with level. A direct measure of cochlear tuning above 4 kHz was analyzed using instantaneous frequency and bandwidth. Synchronized spontaneous OAEs were present in most ears below 4 kHz, and confounded interpretation of moments. In ears with sensorineural hearing loss, group delay and spread varied with audiometric classification and amount of hearing loss; group delay differed between older males and females. CEOAE moments reveal clinically relevant information on cochlear tuning in ears with normal and impaired hearing.

Blurred image restoration using knife-edge function and optimal window Wiener filtering.

PubMed

Wang, Min; Zhou, Shudao; Yan, Wei

2018-01-01

Motion blur in images is usually modeled as the convolution of a point spread function (PSF) and the original image represented as pixel intensities. The knife-edge function can be used to model various types of motion-blurs, and hence it allows for the construction of a PSF and accurate estimation of the degradation function without knowledge of the specific degradation model. This paper addresses the problem of image restoration using a knife-edge function and optimal window Wiener filtering. In the proposed method, we first calculate the motion-blur parameters and construct the optimal window. Then, we use the detected knife-edge function to obtain the system degradation function. Finally, we perform Wiener filtering to obtain the restored image. Experiments show that the restored image has improved resolution and contrast parameters with clear details and no discernible ringing effects.

Blurred image restoration using knife-edge function and optimal window Wiener filtering

PubMed Central

Zhou, Shudao; Yan, Wei

2018-01-01

Motion blur in images is usually modeled as the convolution of a point spread function (PSF) and the original image represented as pixel intensities. The knife-edge function can be used to model various types of motion-blurs, and hence it allows for the construction of a PSF and accurate estimation of the degradation function without knowledge of the specific degradation model. This paper addresses the problem of image restoration using a knife-edge function and optimal window Wiener filtering. In the proposed method, we first calculate the motion-blur parameters and construct the optimal window. Then, we use the detected knife-edge function to obtain the system degradation function. Finally, we perform Wiener filtering to obtain the restored image. Experiments show that the restored image has improved resolution and contrast parameters with clear details and no discernible ringing effects. PMID:29377950

Development of a golden beam data set for the commissioning of a proton double-scattering system in a pencil-beam dose calculation algorithm

DOE Office of Scientific and Technical Information (OSTI.GOV)

Slopsema, R. L., E-mail: rslopsema@floridaproton.org; Flampouri, S.; Yeung, D.

2014-09-15

Purpose: The purpose of this investigation is to determine if a single set of beam data, described by a minimal set of equations and fitting variables, can be used to commission different installations of a proton double-scattering system in a commercial pencil-beam dose calculation algorithm. Methods: The beam model parameters required to commission the pencil-beam dose calculation algorithm (virtual and effective SAD, effective source size, and pristine-peak energy spread) are determined for a commercial double-scattering system. These parameters are measured in a first room and parameterized as function of proton energy and nozzle settings by fitting four analytical equations tomore » the measured data. The combination of these equations and fitting values constitutes the golden beam data (GBD). To determine the variation in dose delivery between installations, the same dosimetric properties are measured in two additional rooms at the same facility, as well as in a single room at another facility. The difference between the room-specific measurements and the GBD is evaluated against tolerances that guarantee the 3D dose distribution in each of the rooms matches the GBD-based dose distribution within clinically reasonable limits. The pencil-beam treatment-planning algorithm is commissioned with the GBD. The three-dimensional dose distribution in water is evaluated in the four treatment rooms and compared to the treatment-planning calculated dose distribution. Results: The virtual and effective SAD measurements fall between 226 and 257 cm. The effective source size varies between 2.4 and 6.2 cm for the large-field options, and 1.0 and 2.0 cm for the small-field options. The pristine-peak energy spread decreases from 1.05% at the lowest range to 0.6% at the highest. The virtual SAD as well as the effective source size can be accurately described by a linear relationship as function of the inverse of the residual energy. An additional linear correction term as function of RM-step thickness is required for accurate parameterization of the effective SAD. The GBD energy spread is given by a linear function of the exponential of the beam energy. Except for a few outliers, the measured parameters match the GBD within the specified tolerances in all of the four rooms investigated. For a SOBP field with a range of 15 g/cm{sup 2} and an air gap of 25 cm, the maximum difference in the 80%–20% lateral penumbra between the GBD-commissioned treatment-planning system and measurements in any of the four rooms is 0.5 mm. Conclusions: The beam model parameters of the double-scattering system can be parameterized with a limited set of equations and parameters. This GBD closely matches the measured dosimetric properties in four different rooms.« less

Regulation of adhesion behavior of murine macrophage using supported lipid membranes displaying tunable mannose domains

NASA Astrophysics Data System (ADS)

Kaindl, T.; Oelke, J.; Pasc, A.; Kaufmann, S.; Konovalov, O. V.; Funari, S. S.; Engel, U.; Wixforth, A.; Tanaka, M.

2010-07-01

Highly uniform, strongly correlated domains of synthetically designed lipids can be incorporated into supported lipid membranes. The systematic characterization of membranes displaying a variety of domains revealed that the equilibrium size of domains significantly depends on the length of fluorocarbon chains, which can be quantitatively interpreted within the framework of an equivalent dipole model. A mono-dispersive, narrow size distribution of the domains enables us to treat the inter-domain correlations as two-dimensional colloidal crystallization and calculate the potentials of mean force. The obtained results demonstrated that both size and inter-domain correlation can precisely be controlled by the molecular structures. By coupling α-D-mannose to lipid head groups, we studied the adhesion behavior of the murine macrophage (J774A.1) on supported membranes. Specific adhesion and spreading of macrophages showed a clear dependence on the density of functional lipids. The obtained results suggest that such synthetic lipid domains can be used as a defined platform to study how cells sense the size and distribution of functional molecules during adhesion and spreading.

Interval Predictor Models with a Formal Characterization of Uncertainty and Reliability

NASA Technical Reports Server (NTRS)

Crespo, Luis G.; Giesy, Daniel P.; Kenny, Sean P.

2014-01-01

This paper develops techniques for constructing empirical predictor models based on observations. By contrast to standard models, which yield a single predicted output at each value of the model's inputs, Interval Predictors Models (IPM) yield an interval into which the unobserved output is predicted to fall. The IPMs proposed prescribe the output as an interval valued function of the model's inputs, render a formal description of both the uncertainty in the model's parameters and of the spread in the predicted output. Uncertainty is prescribed as a hyper-rectangular set in the space of model's parameters. The propagation of this set through the empirical model yields a range of outputs of minimal spread containing all (or, depending on the formulation, most) of the observations. Optimization-based strategies for calculating IPMs and eliminating the effects of outliers are proposed. Outliers are identified by evaluating the extent by which they degrade the tightness of the prediction. This evaluation can be carried out while the IPM is calculated. When the data satisfies mild stochastic assumptions, and the optimization program used for calculating the IPM is convex (or, when its solution coincides with the solution to an auxiliary convex program), the model's reliability (that is, the probability that a future observation would be within the predicted range of outputs) can be bounded rigorously by a non-asymptotic formula.

EPISODIC ACCRETION AT EARLY STAGES OF EVOLUTION OF LOW-MASS STARS AND BROWN DWARFS: A SOLUTION FOR THE OBSERVED LUMINOSITY SPREAD IN H-R DIAGRAMS?

DOE Office of Scientific and Technical Information (OSTI.GOV)

Baraffe, I.; Chabrier, G.; Gallardo, J.

2009-09-01

We present evolutionary models for young low-mass stars and brown dwarfs taking into account episodic phases of accretion at early stages of the evolution, a scenario supported by recent large surveys of embedded protostars. An evolution including short episodes of vigorous accretion followed by longer quiescent phases can explain the observed luminosity spread in H-R diagrams of star-forming regions at ages of a few Myr, for objects ranging from a few Jupiter masses to a few tenths of a solar mass. The gravitational contraction of these accreting objects strongly departs from the standard Hayashi track at constant T{sub eff}. Themore » best agreement with the observed luminosity scatter is obtained if most of the accretion shock energy is radiated away. The obtained luminosity spread at 1 Myr in the H-R diagram is equivalent to what can be misinterpreted as an {approx}10 Myr age spread for non-accreting objects. We also predict a significant spread in radius at a given T{sub eff}, as suggested by recent observations. These calculations bear important consequences for our understanding of star formation and early stages of evolution and on the determination of the initial mass function for young ({<=} a few Myr) clusters. Our results also show that the concept of a stellar birthline for low-mass objects has no valid support.« less

Dynamic Chemically Driven Dewetting, Spreading, and Self-Running of Sessile Droplets on Crystalline Silicon.

PubMed

Arscott, Steve

2016-12-06

A chemically driven dewetting effect is demonstrated using sessile droplets of dilute hydrofluoric acid on chemically oxidized silicon wafers. The dewetting occurs as the thin oxide is slowly etched by the droplet and replaced by a hydrogen-terminated surface; the result of this is a gradual increase in the contact angle of the droplet with time. The time-varying work of adhesion is calculated from the time-varying contact angle; this corresponds to the changing chemical nature of the surface during dewetting and can be modeled by the well-known logistic (sigmoid) function often used for the modeling of restricted growth, in this case, the transition from an oxidized surface to a hydrogen-terminated silicon surface. The observation of the time-varying contact angle allows one to both measure the etch rate of the silicon oxide and estimate the hydrogenation rate as a function of HF concentration and wafer type. In addition to this, at a certain HF concentration, a self-running droplet effect is observed. In contrast, on hydrogen-terminated silicon wafers, a chemically induced spreading effect is observed using sessile droplets of nitric acid. The droplet spreading can also be modeled using a logistical function, where the restricted growth is the transition from hydrogen-terminated to a chemically induced oxidized silicon surface. The chemically driven dewetting and spreading observed here add to the methods available to study dynamic wetting (e.g., the moving three-phase contact line) of sessile droplets on surfaces. By slowing down chemical kinetics of the wetting, one is able to record the changing profile of the sessile droplet with time and gather information concerning the time-varying surface chemistry. The data also indicates a chemical interface hysteresis (CIH) that is compared to contact angle hysteresis (CAH). The approach can also be used to study the chemical etching and deposition behavior of thin films using liquids by monitoring the macroscopic droplet profile and relating this to the time-varying physical and chemical interface phenomena.

Sandia Strehl Calculator Version 1.0

DOE Office of Scientific and Technical Information (OSTI.GOV)

Anthony, Stephen M

The Sandia Strehl Calculator is designed to calculate the Gibson and Lanni point spread function (PSF), Strehl ratio, and ensquared energy, allowing non-design immersion, coverslip, and sample layers. It also uses Abbe number calculations to determine the refractive index at specific wavelengths when given the refractive index at a different wavelength and the dispersion. The primary application of Sandia Strehl Calculator is to determine the theoretical impacts of using an optical microscope beyond its normal design parameters. Examples of non-design microscope usage include: a) using coverslips of non-design material b) coverslips of different thicknesses c) imaging deep into an aqueousmore » sample with an immersion objective d) imaging a sample at 37 degrees. All of these changes can affect the imaging quality, sometimes profoundly, but are at the same time non-design conditions employed not infrequently. Rather than having to experimentally determine whether the changes will result in unacceptable image quality, Sandia Strehl Calculator uses existing optical theory to determine the approximate effect of the change, saving the need to perform experiments.« less

Spreading activation in nonverbal memory networks.

PubMed

Foster, Paul S; Wakefield, Candias; Pryjmak, Scott; Roosa, Katelyn M; Branch, Kaylei K; Drago, Valeria; Harrison, David W; Ruff, Ronald

2017-09-01

Theories of spreading activation primarily involve semantic memory networks. However, the existence of separate verbal and visuospatial memory networks suggests that spreading activation may also occur in visuospatial memory networks. The purpose of the present investigation was to explore this possibility. Specifically, this study sought to create and describe the design frequency corpus and to determine whether this measure of visuospatial spreading activation was related to right hemisphere functioning and spreading activation in verbal memory networks. We used word frequencies taken from the Controlled Oral Word Association Test and design frequencies taken from the Ruff Figural Fluency Test as measures of verbal and visuospatial spreading activation, respectively. Average word and design frequencies were then correlated with measures of left and right cerebral functioning. The results indicated that a significant relationship exists between performance on a test of right posterior functioning (Block Design) and design frequency. A significant negative relationship also exists between spreading activation in semantic memory networks and design frequency. Based on our findings, the hypotheses were supported. Further research will need to be conducted to examine whether spreading activation exists in visuospatial memory networks as well as the parameters that might modulate this spreading activation, such as the influence of neurotransmitters.

Single crystal to polycrystal neutron transmission simulation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dessieux, Luc Lucius; Stoica, Alexandru Dan; Bingham, Philip R.

A collection of routines for calculation of the total cross section that determines the attenuation of neutrons by crystalline solids is presented. The total cross section is calculated semi-empirically as a function of crystal structure, neutron energy, temperature, and crystal orientation. The semi-empirical formula includes the contribution of parasitic Bragg scattering to the total cross section using both the crystal’s mosaic spread value and its orientation with respect to the neutron beam direction as parameters. These routines allow users to enter a distribution of crystal orientations for calculation of total cross sections of user defined powder or pseudo powder distributions,more » which enables simulation of non-uniformities such as texture and strain. In conclusion, the spectra for neutron transmission simulations in the neutron thermal energy range (2 meV–100 meV) are presented for single crystal and polycrystal samples and compared to measurements.« less

Solar wind pickup of ionized Venus exosphere atoms

NASA Technical Reports Server (NTRS)

Curtis, S. A.

1981-01-01

Previous calculations of electrostatic and electromagnetic growth rates for plasma instabilities have neglected the thermal spread of the distribution function of the planetary ions. We consider the effects of finite temperatures for exospheric ions borne in the solar wind. Specifically, growth rates are calculated for electromagnetic instabilities in the low-frequency case for Alfven waves and the intermediate frequency case for whistlers. Also, electrostatic growth rates are calculated for the intermediate frequency regime. From these growth rates, estimates are derived for the pickup times of the planetary ions. The electromagnetic instabilities are shown to produce the most rapid pickup. In the situation where the angle between the local Venus magnetic field and the plasma flow direction is small, the pickup times for both electromagnetic and electrostatic instabilities become very long. A possible consequence of this effect is to produce regions of enhanced planetary ion density in favorable Venus magnetic field-solar wind flow geometries.

Single crystal to polycrystal neutron transmission simulation

DOE PAGES

Dessieux, Luc Lucius; Stoica, Alexandru Dan; Bingham, Philip R.

2018-02-02

A collection of routines for calculation of the total cross section that determines the attenuation of neutrons by crystalline solids is presented. The total cross section is calculated semi-empirically as a function of crystal structure, neutron energy, temperature, and crystal orientation. The semi-empirical formula includes the contribution of parasitic Bragg scattering to the total cross section using both the crystal’s mosaic spread value and its orientation with respect to the neutron beam direction as parameters. These routines allow users to enter a distribution of crystal orientations for calculation of total cross sections of user defined powder or pseudo powder distributions,more » which enables simulation of non-uniformities such as texture and strain. In conclusion, the spectra for neutron transmission simulations in the neutron thermal energy range (2 meV–100 meV) are presented for single crystal and polycrystal samples and compared to measurements.« less

Point spread functions for earthquake source imaging: An interpretation based on seismic interferometry

USGS Publications Warehouse

Nakahara, Hisashi; Haney, Matt

2015-01-01

Recently, various methods have been proposed and applied for earthquake source imaging, and theoretical relationships among the methods have been studied. In this study, we make a follow-up theoretical study to better understand the meanings of earthquake source imaging. For imaging problems, the point spread function (PSF) is used to describe the degree of blurring and degradation in an obtained image of a target object as a response of an imaging system. In this study, we formulate PSFs for earthquake source imaging. By calculating the PSFs, we find that waveform source inversion methods remove the effect of the PSF and are free from artifacts. However, the other source imaging methods are affected by the PSF and suffer from the effect of blurring and degradation due to the restricted distribution of receivers. Consequently, careful treatment of the effect is necessary when using the source imaging methods other than waveform inversions. Moreover, the PSF for source imaging is found to have a link with seismic interferometry with the help of the source-receiver reciprocity of Green’s functions. In particular, the PSF can be related to Green’s function for cases in which receivers are distributed so as to completely surround the sources. Furthermore, the PSF acts as a low-pass filter. Given these considerations, the PSF is quite useful for understanding the physical meaning of earthquake source imaging.

Nano-fabrication of molecular electronic junctions by targeted modification of metal-molecule bonds

NASA Astrophysics Data System (ADS)

Jafri, S. Hassan M.; Löfås, Henrik; Blom, Tobias; Wallner, Andreas; Grigoriev, Anton; Ahuja, Rajeev; Ottosson, Henrik; Leifer, Klaus

2015-09-01

Reproducibility, stability and the coupling between electrical and molecular properties are central challenges in the field of molecular electronics. The field not only needs devices that fulfill these criteria but they also need to be up-scalable to application size. In this work, few-molecule based electronics devices with reproducible electrical characteristics are demonstrated. Our previously reported 5 nm gold nanoparticles (AuNP) coated with ω-triphenylmethyl (trityl) protected 1,8-octanedithiol molecules are trapped in between sub-20 nm gap spacing gold nanoelectrodes forming AuNP-molecule network. When the trityl groups are removed, reproducible devices and stable Au-thiol junctions are established on both ends of the alkane segment. The resistance of more than 50 devices is reduced by orders of magnitude as well as a reduction of the spread in the resistance histogram is observed. By density functional theory calculations the orders of magnitude decrease in resistance can be explained and supported by TEM observations thus indicating that the resistance changes and strongly improved resistance spread are related to the establishment of reproducible and stable metal-molecule bonds. The same experimental sequence is carried out using 1,6-hexanedithiol functionalized AuNPs. The average resistances as a function of molecular length, demonstrated herein, are comparable to the one found in single molecule devices.

Beam energy spread in FERMI@elettra gun and linac induced by intrabeam scattering

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zholents, Alexander A; Zholents, Alexander A; Zolotorev, Max S.

Intrabeam scattering (IBS) of electrons in the pre-cathode area in the electron guns know in the literature as Boersh effect is responsible for a growth of the electron beam energy spread there. Albeit most visible within the electron gun where the electron beam density is large and the energy spread is small, the IBS acts all along the entire electron beam pass through the Linac. In this report we calculate the energy spread induced by IBS in the FERMI@elettra electron gun.

The influence of the directional energy distribution on the nonlinear dispersion relation in a random gravity wave field

NASA Technical Reports Server (NTRS)

Huang, N. E.; Tung, C.-C.

1977-01-01

The influence of the directional distribution of wave energy on the dispersion relation is calculated numerically using various directional wave spectrum models. The results indicate that the dispersion relation varies both as a function of the directional energy distribution and the direction of propagation of the wave component under consideration. Furthermore, both the mean deviation and the random scatter from the linear approximation increase as the energy spreading decreases. Limited observational data are compared with the theoretical results. The agreement is favorable.

Epidemic spread in bipartite network by considering risk awareness

NASA Astrophysics Data System (ADS)

Han, She; Sun, Mei; Ampimah, Benjamin Chris; Han, Dun

2018-02-01

Human awareness plays an important role in the spread of infectious diseases and the control of propagation patterns. Exploring the interplay between human awareness and epidemic spreading is a topic that has been receiving increasing attention. Considering the fact, some well-known diseases only spread between different species we propose a theoretical analysis of the Susceptible-Infected-Susceptible (SIS) epidemic spread from the perspective of bipartite network and risk aversion. Using mean field theory, the epidemic threshold is calculated theoretically. Simulation results are consistent with the proposed analytic model. The results show that, the final infection density is negative linear with the value of individuals' risk awareness. Therefore, the epidemic spread could be effectively suppressed by improving individuals' risk awareness.

Observed Luminosity Spread in Young Clusters and FU Ori Stars: A Unified Picture

NASA Astrophysics Data System (ADS)

Baraffe, I.; Vorobyov, E.; Chabrier, G.

2012-09-01

The idea that non-steady accretion during the embedded phase of protostar evolution can produce the observed luminosity spread in the Herzsprung-Russell diagram (HRD) of young clusters has recently been called into question. Observations of FU Ori, for instance, suggest an expansion of the star during strong accretion events, whereas the luminosity spread implies a contraction of the accreting objects, decreasing their radiating surface. In this paper, we present a global scenario based on calculations coupling episodic accretion histories derived from numerical simulations of collapsing cloud prestellar cores of various masses and subsequent protostar evolution. Our calculations show that, assuming an initial protostar mass Mi ~ 1 M Jup, typical of the second Larson's core, both the luminosity spread in the HRD and the inferred properties of FU Ori events (mass, radius, accretion rate) can be explained by this scenario, providing two conditions. First, there must be some variation within the fraction of accretion energy absorbed by the protostar during the accretion process. Second, the range of this variation should increase with increasing accretion burst intensity and thus with the initial core mass and final star mass. The numerical hydrodynamics simulations of collapsing cloud prestellar cores indeed show that the intensity of the accretion bursts correlates with the mass and initial angular momentum of the prestellar core. Massive prestellar cores with high initial angular momentum are found to produce intense bursts characteristic of FU Ori-like events. Our results thus suggest a link between the burst intensities and the fraction of accretion energy absorbed by the protostar, with some threshold in the accretion rate, of the order of 10-5 M ⊙ yr-1, delimitating the transition from "cold" to "hot" accretion. Such a transition might reflect a change in the accretion geometry with increasing accretion rate, i.e., a transition from magnetospheric or thin-disk to thick-disk accretion, or in the magnetospheric interaction between the star and the disk. Conversely, the luminosity spread can also be explained by a variation of the initial protostar mass within the ~1-5 M Jup range, although it is unclear for now whether such a spread among the second Larson's core can be produced during the prestellar core second collapse. This unified picture confirms the idea that early accretion during protostar and proto-brown dwarf formation/evolution can explain the observed luminosity spread in young clusters without invoking any significant age spread, and that the concept of a well-defined birthline does not apply for low-mass objects. Finally, we examine the impact of accretion on the determination of the initial mass function in young clusters.

Point spread function and depth-invariant focal sweep point spread function for plenoptic camera 2.0.

PubMed

Jin, Xin; Liu, Li; Chen, Yanqin; Dai, Qionghai

2017-05-01

This paper derives a mathematical point spread function (PSF) and a depth-invariant focal sweep point spread function (FSPSF) for plenoptic camera 2.0. Derivation of PSF is based on the Fresnel diffraction equation and image formation analysis of a self-built imaging system which is divided into two sub-systems to reflect the relay imaging properties of plenoptic camera 2.0. The variations in PSF, which are caused by changes of object's depth and sensor position variation, are analyzed. A mathematical model of FSPSF is further derived, which is verified to be depth-invariant. Experiments on the real imaging systems demonstrate the consistency between the proposed PSF and the actual imaging results.

Watching excitons move: the time-dependent transition density matrix

NASA Astrophysics Data System (ADS)

Ullrich, Carsten

2012-02-01

Time-dependent density-functional theory allows one to calculate excitation energies and the associated transition densities in principle exactly. The transition density matrix (TDM) provides additional information on electron-hole localization and coherence of specific excitations of the many-body system. We have extended the TDM concept into the real-time domain in order to visualize the excited-state dynamics in conjugated molecules. The time-dependent TDM is defined as an implicit density functional, and can be approximately obtained from the time-dependent Kohn-Sham orbitals. The quality of this approximation is assessed in simple model systems. A computational scheme for real molecular systems is presented: the time-dependent Kohn-Sham equations are solved with the OCTOPUS code and the time-dependent Kohn-Sham TDM is calculated using a spatial partitioning scheme. The method is applied to show in real time how locally created electron-hole pairs spread out over neighboring conjugated molecular chains. The coupling mechanism, electron-hole coherence, and the possibility of charge separation are discussed.

Noise from Supersonic Coaxial Jets. Part 1; Mean Flow Predictions

NASA Technical Reports Server (NTRS)

Dahl, Milo D.; Morris, Philip J.

1997-01-01

Recent theories for supersonic jet noise have used an instability wave noise generation model to predict radiated noise. This model requires a known mean flow that has typically been described by simple analytic functions for single jet mean flows. The mean flow of supersonic coaxial jets is not described easily in terms of analytic functions. To provide these profiles at all axial locations, a numerical scheme is developed to calculate the mean flow properties of a coaxial jet. The Reynolds-averaged, compressible, parabolic boundary layer equations are solved using a mixing length turbulence model. Empirical correlations are developed to account for the effects of velocity and temperature ratios and Mach number on the shear layer spreading. Both normal velocity profile and inverted velocity profile coaxial jets are considered. The mixing length model is modified in each case to obtain reasonable results when the two stream jet merges into a single fully developed jet. The mean flow calculations show both good qualitative and quantitative agreement with measurements in single and coaxial jet flows.

Rumor spreading model with the different attitudes towards rumors

NASA Astrophysics Data System (ADS)

Hu, Yuhan; Pan, Qiuhui; Hou, Wenbing; He, Mingfeng

2018-07-01

Rumor spreading has a profound influence on people's well-being and social stability. There are many factors influencing rumor spreading. In this paper, we recommended an assumption that among the common mass there are three attitudes towards rumors: to like rumor spreading, to dislike rumor spreading, and to be hesitant (or neutral) to rumor spreading. Based on such an assumption, a Susceptible-Hesitating-Affected-Resistant(SHAR) model is established, which considered individuals' different attitudes towards rumor spreading. We also analyzed the local and global stability of rumor-free equilibrium and rumor-existence equilibrium, calculated the basic reproduction number of our model. With numerical simulations, we illustrated the effect of parameter changes on rumor spreading, analyzing the parameter sensitivity of the model. The results of the theoretical analysis and numerical simulations illustrated the conclusions of this study. People having different attitudes towards rumors may play different roles in the process of rumor spreading. It was surprising to find, in our research, that people who hesitate to spread rumors have a positive effect on the spread of rumors.

Use of a spread sheet to calculate the current-density distribution produced in human and rat models by low-frequency electric fields.

PubMed

Hart, F X

1990-01-01

The current-density distribution produced inside irregularly shaped, homogeneous human and rat models by low-frequency electric fields is obtained by a two-stage finite-difference procedure. In the first stage the model is assumed to be equipotential. Laplace's equation is solved by iteration in the external region to obtain the capacitive-current densities at the model's surface elements. These values then provide the boundary conditions for the second-stage relaxation solution, which yields the internal current-density distribution. Calculations were performed with the Excel spread-sheet program on a Macintosh-II microcomputer. A spread sheet is a two-dimensional array of cells. Each cell of the sheet can represent a square element of space. Equations relating the values of the cells can represent the relationships between the potentials in the corresponding spatial elements. Extension to three dimensions is readily made. Good agreement was obtained with current densities measured on human models with both, one, or no legs grounded and on rat models in four different grounding configurations. The results also compared well with predictions of more sophisticated numerical analyses. Spread sheets can provide an inexpensive and relatively simple means to perform good, approximate dosimetric calculations on irregularly shaped objects.

Ignition, Transition, Flame Spread in Multidimensional Configurations in Microgravity

NASA Technical Reports Server (NTRS)

Kashiwagi, Takashi; Mell, William E.; McGrattan, Kevin B.; Baum, Howard R.; Olson, Sandra L.; Fujita, Osamu; Kikuchi, Masao; Ito, Kenichi

1997-01-01

Ignition of solid fuels by external thermal radiation and subsequent transition to flame spread are processes that not only are of considerable scientific interest but which also have fire safety applications. A material which undergoes a momentary ignition might be tolerable but a material which permits a transition to subsequent flame spread would significantly increase the fire hazard in a spacecraft. Therefore, the limiting condition under which flame cannot spread should be calculated from a model of the transition from ignition instead of by the traditional approach based on limits to a steady flame spread model. However, although the fundamental processes involved in ignition have been suggested there have been no definitive experimental or modeling studies due to the flow motion generated by buoyancy near the heated sample surface. In this study, microgravity experiments which required longer test times such as in air and surface smoldering experiment were conducted in the space shuttle STS-75 flight; shorter experimental tests such as in 35% and 50% oxygen were conducted in the droptower in the Japan Microgravity Center, JAMIC. Their experimental data along with theoretically calculated results from solving numerically the time-dependent Navier-Stokes equations are summarized in this paper.

ISR corrections to associated HZ production at future Higgs factories

NASA Astrophysics Data System (ADS)

Greco, Mario; Montagna, Guido; Nicrosini, Oreste; Piccinini, Fulvio; Volpi, Gabriele

2018-02-01

We evaluate the QED corrections due to initial state radiation (ISR) to associated Higgs boson production in electron-positron (e+e-) annihilation at typical energies of interest for the measurement of the Higgs properties at future e+e- colliders, such as CEPC and FCC-ee. We apply the QED Structure Function approach to the four-fermion production process e+e- →μ+μ- b b bar , including both signal and background contributions. We emphasize the relevance of the ISR corrections particularly near threshold and show that finite third order collinear contributions are mandatory to meet the expected experimental accuracy. We analyze in turn the rôle played by a full four-fermion calculation and beam energy spread in precision calculations for Higgs physics at future e+e- colliders.

Imaging samples in silica aerogel using an experimental point spread function.

PubMed

White, Amanda J; Ebel, Denton S

2015-02-01

Light microscopy is a powerful tool that allows for many types of samples to be examined in a rapid, easy, and nondestructive manner. Subsequent image analysis, however, is compromised by distortion of signal by instrument optics. Deconvolution of images prior to analysis allows for the recovery of lost information by procedures that utilize either a theoretically or experimentally calculated point spread function (PSF). Using a laser scanning confocal microscope (LSCM), we have imaged whole impact tracks of comet particles captured in silica aerogel, a low density, porous SiO2 solid, by the NASA Stardust mission. In order to understand the dynamical interactions between the particles and the aerogel, precise grain location and track volume measurement are required. We report a method for measuring an experimental PSF suitable for three-dimensional deconvolution of imaged particles in aerogel. Using fluorescent beads manufactured into Stardust flight-grade aerogel, we have applied a deconvolution technique standard in the biological sciences to confocal images of whole Stardust tracks. The incorporation of an experimentally measured PSF allows for better quantitative measurements of the size and location of single grains in aerogel and more accurate measurements of track morphology.

Computational Study of Droplet Trains Impacting a Smooth Solid Surface

NASA Astrophysics Data System (ADS)

Markt, David, Jr.; Pathak, Ashish; Raessi, Mehdi; Lee, Seong-Young; Zhao, Emma

2017-11-01

The study of droplet impingement is vital to understanding the fluid dynamics of fuel injection in modern internal combustion engines. One widely accepted model was proposed by Yarin and Weiss (JFM, 1995), developed from experiments of single trains of ethanol droplets impacting a substrate. The model predicts the onset of splashing and the mass ejected upon splashing. In this study, using an in-house 3D multiphase flow solver, the experiments of Yarin and Weiss were computationally simulated. The experimentally observed splashing threshold was captured by the simulations, thus validating the solver's ability to accurately simulate the splashing dynamics. Then, we performed simulations of cases with multiple droplet trains, which have high relevance to dense fuel sprays, where droplets impact within the spreading diameters of their neighboring droplets, leading to changes in splashing dynamics due to interactions of spreading films. For both single and multi-train simulations the amount of splashed mass was calculated as a function of time, allowing a quantitative comparison between the two cases. Furthermore, using a passive scalar the amount of splashed mass per impinging droplet was also calculated. This work is supported by the Department of Energy, Office of Energy Efficiency and Renewable Energy (EERE) and the Department of Defense, Tank and Automotive Research, Development, and Engineering Center (TARDEC), under Award Number DE-EE0007292.

Coordination analysis of players' distribution in football using cross-correlation and vector coding techniques.

PubMed

Moura, Felipe Arruda; van Emmerik, Richard E A; Santana, Juliana Exel; Martins, Luiz Eduardo Barreto; Barros, Ricardo Machado Leite de; Cunha, Sergio Augusto

2016-12-01

The purpose of this study was to investigate the coordination between teams spread during football matches using cross-correlation and vector coding techniques. Using a video-based tracking system, we obtained the trajectories of 257 players during 10 matches. Team spread was calculated as functions of time. For a general coordination description, we calculated the cross-correlation between the signals. Vector coding was used to identify the coordination patterns between teams during offensive sequences that ended in shots on goal or defensive tackles. Cross-correlation showed that opponent teams have a tendency to present in-phase coordination, with a short time lag. During offensive sequences, vector coding results showed that, although in-phase coordination dominated, other patterns were observed. We verified that during the early stages, offensive sequences ending in shots on goal present greater anti-phase and attacking team phase periods, compared to sequences ending in tackles. Results suggest that the attacking team may seek to present a contrary behaviour of its opponent (or may lead the adversary behaviour) in the beginning of the attacking play, regarding to the distribution strategy, to increase the chances of a shot on goal. The techniques allowed detecting the coordination patterns between teams, providing additional information about football dynamics and players' interaction.

Electrostatic energy analyzer measurements of low energy zirconium beam parameters in a plasma sputter-type negative ion source

DOE Office of Scientific and Technical Information (OSTI.GOV)

Malapit, Giovanni M.; Department of Physical Sciences, University of the Philippines Baguio, Baguio City 2600; Mahinay, Christian Lorenz S.

2012-02-15

A plasma sputter-type negative ion source is utilized to produce and detect negative Zr ions with energies between 150 and 450 eV via a retarding potential-type electrostatic energy analyzer. Traditional and modified semi-cylindrical Faraday cups (FC) inside the analyzer are employed to sample negative Zr ions and measure corresponding ion currents. The traditional FC registered indistinct ion current readings which are attributed to backscattering of ions and secondary electron emissions. The modified Faraday cup with biased repeller guard ring, cut out these signal distortions leaving only ringings as issues which are theoretically compensated by fitting a sigmoidal function into themore » data. The mean energy and energy spread are calculated using the ion current versus retarding potential data while the beam width values are determined from the data of the transverse measurement of ion current. The most energetic negative Zr ions yield tighter energy spread at 4.11 eV compared to the least energetic negative Zr ions at 4.79 eV. The smallest calculated beam width is 1.04 cm for the negative Zr ions with the highest mean energy indicating a more focused beam in contrast to the less energetic negative Zr ions due to space charge forces.« less

Calibration of Predictor Models Using Multiple Validation Experiments

NASA Technical Reports Server (NTRS)

Crespo, Luis G.; Kenny, Sean P.; Giesy, Daniel P.

2015-01-01

This paper presents a framework for calibrating computational models using data from several and possibly dissimilar validation experiments. The offset between model predictions and observations, which might be caused by measurement noise, model-form uncertainty, and numerical error, drives the process by which uncertainty in the models parameters is characterized. The resulting description of uncertainty along with the computational model constitute a predictor model. Two types of predictor models are studied: Interval Predictor Models (IPMs) and Random Predictor Models (RPMs). IPMs use sets to characterize uncertainty, whereas RPMs use random vectors. The propagation of a set through a model makes the response an interval valued function of the state, whereas the propagation of a random vector yields a random process. Optimization-based strategies for calculating both types of predictor models are proposed. Whereas the formulations used to calculate IPMs target solutions leading to the interval value function of minimal spread containing all observations, those for RPMs seek to maximize the models' ability to reproduce the distribution of observations. Regarding RPMs, we choose a structure for the random vector (i.e., the assignment of probability to points in the parameter space) solely dependent on the prediction error. As such, the probabilistic description of uncertainty is not a subjective assignment of belief, nor is it expected to asymptotically converge to a fixed value, but instead it casts the model's ability to reproduce the experimental data. This framework enables evaluating the spread and distribution of the predicted response of target applications depending on the same parameters beyond the validation domain.

Evaluation and testing of image quality of the Space Solar Extreme Ultraviolet Telescope

NASA Astrophysics Data System (ADS)

Peng, Jilong; Yi, Zhong; Zhou, Shuhong; Yu, Qian; Hou, Yinlong; Wang, Shanshan

2018-01-01

For the space solar extreme ultraviolet telescope, the star point test can not be performed in the x-ray band (19.5nm band) as there is not light source of bright enough. In this paper, the point spread function of the optical system is calculated to evaluate the imaging performance of the telescope system. Combined with the actual processing surface error, such as small grinding head processing and magnetorheological processing, the optical design software Zemax and data analysis software Matlab are used to directly calculate the system point spread function of the space solar extreme ultraviolet telescope. Matlab codes are programmed to generate the required surface error grid data. These surface error data is loaded to the specified surface of the telescope system by using the communication technique of DDE (Dynamic Data Exchange), which is used to connect Zemax and Matlab. As the different processing methods will lead to surface error with different size, distribution and spatial frequency, the impact of imaging is also different. Therefore, the characteristics of the surface error of different machining methods are studied. Combining with its position in the optical system and simulation its influence on the image quality, it is of great significance to reasonably choose the processing technology. Additionally, we have also analyzed the relationship between the surface error and the image quality evaluation. In order to ensure the final processing of the mirror to meet the requirements of the image quality, we should choose one or several methods to evaluate the surface error according to the different spatial frequency characteristics of the surface error.

wannier90: A tool for obtaining maximally-localised Wannier functions

NASA Astrophysics Data System (ADS)

Mostofi, Arash A.; Yates, Jonathan R.; Lee, Young-Su; Souza, Ivo; Vanderbilt, David; Marzari, Nicola

2008-05-01

We present wannier90, a program for calculating maximally-localised Wannier functions (MLWF) from a set of Bloch energy bands that may or may not be attached to or mixed with other bands. The formalism works by minimising the total spread of the MLWF in real space. This is done in the space of unitary matrices that describe rotations of the Bloch bands at each k-point. As a result, wannier90 is independent of the basis set used in the underlying calculation to obtain the Bloch states. Therefore, it may be interfaced straightforwardly to any electronic structure code. The locality of MLWF can be exploited to compute band-structure, density of states and Fermi surfaces at modest computational cost. Furthermore, wannier90 is able to output MLWF for visualisation and other post-processing purposes. Wannier functions are already used in a wide variety of applications. These include analysis of chemical bonding in real space; calculation of dielectric properties via the modern theory of polarisation; and as an accurate and minimal basis set in the construction of model Hamiltonians for large-scale systems, in linear-scaling quantum Monte Carlo calculations, and for efficient computation of material properties, such as the anomalous Hall coefficient. wannier90 is freely available under the GNU General Public License from http://www.wannier.org/. Program summaryProgram title: wannier90 Catalogue identifier: AEAK_v1_0 Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AEAK_v1_0.html Program obtainable from: CPC Program Library, Queen's University, Belfast, N. Ireland Licensing provisions: Standard CPC licence, http://cpc.cs.qub.ac.uk/licence/licence.html No. of lines in distributed program, including test data, etc.: 556 495 No. of bytes in distributed program, including test data, etc.: 5 709 419 Distribution format: tar.gz Programming language: Fortran 90, perl Computer: any architecture with a Fortran 90 compiler Operating system: Linux, Windows, Solaris, AIX, Tru64 Unix, OSX RAM: 10 MB Word size: 32 or 64 Classification: 7.3 External routines:BLAS ( http://www/netlib.org/blas). LAPACK ( http://www.netlib.org/lapack). Both available under open-source licenses. Nature of problem: Obtaining maximally-localised Wannier functions from a set of Bloch energy bands that may or may not be entangled. Solution method: In the case of entangled bands, the optimally-connected subspace of interest is determined by minimising a functional which measures the subspace dispersion across the Brillouin zone. The maximally-localised Wannier functions within this subspace are obtained by subsequent minimisation of a functional that represents the total spread of the Wannier functions in real space. For the case of isolated energy bands only the second step of the procedure is required. Unusual features: Simple and user-friendly input system. Wannier functions and interpolated band structure output in a variety of file formats for visualisation. Running time: Test cases take 1 minute. References:N. Marzari, D. Vanderbilt, Maximally localized generalized Wannier functions for composite energy bands, Phys. Rev. B 56 (1997) 12847. I. Souza, N. Marzari, D. Vanderbilt, Maximally localized Wannier functions for entangled energy bands, Phys. Rev. B 65 (2001) 035109.

Ghost suppression in image restoration filtering

NASA Technical Reports Server (NTRS)

Riemer, T. E.; Mcgillem, C. D.

1975-01-01

An optimum image restoration filter is described in which provision is made to constrain the spatial extent of the restoration function, the noise level of the filter output and the rate of falloff of the composite system point-spread away from the origin. Experimental results show that sidelobes on the composite system point-spread function produce ghosts in the restored image near discontinuities in intensity level. By redetermining the filter using a penalty function that is zero over the main lobe of the composite point-spread function of the optimum filter and nonzero where the point-spread function departs from a smoothly decaying function in the sidelobe region, a great reduction in sidelobe level is obtained. Almost no loss in resolving power of the composite system results from this procedure. By iteratively carrying out the same procedure even further reductions in sidelobe level are obtained. Examples of original and iterated restoration functions are shown along with their effects on a test image.

New deconvolution method for microscopic images based on the continuous Gaussian radial basis function interpolation model.

PubMed

Chen, Zhaoxue; Chen, Hao

2014-01-01

A deconvolution method based on the Gaussian radial basis function (GRBF) interpolation is proposed. Both the original image and Gaussian point spread function are expressed as the same continuous GRBF model, thus image degradation is simplified as convolution of two continuous Gaussian functions, and image deconvolution is converted to calculate the weighted coefficients of two-dimensional control points. Compared with Wiener filter and Lucy-Richardson algorithm, the GRBF method has an obvious advantage in the quality of restored images. In order to overcome such a defect of long-time computing, the method of graphic processing unit multithreading or increasing space interval of control points is adopted, respectively, to speed up the implementation of GRBF method. The experiments show that based on the continuous GRBF model, the image deconvolution can be efficiently implemented by the method, which also has a considerable reference value for the study of three-dimensional microscopic image deconvolution.

How the government's punishment and individual's sensitivity affect the rumor spreading in online social networks

NASA Astrophysics Data System (ADS)

Li, Dandan; Ma, Jing

2017-03-01

We explore the impact of punishment of governments and sensitivity of individuals on the rumor spreading in this paper. Considering the facts that some rumors that relate to the hot events could be disseminated repeatedly, however, some other rumors will never be disseminated after they have been popular for some time. Therefore, we investigate two types (SIS and SIR) of rumor spreading models in which the punishment of government and sensitivity of individuals are considered. Based on the mean-field method, we have calculated the spreading threshold of SIS and SIR model, respectively. Furthermore, we perform the rumor spreading process in the Facebook and POK social networks, and achieve that there is an excellent agreement between the theoretical and numerical results of spreading threshold. The results indicate that improving the punishment of government and increasing the sensitivity of individuals could control the spreading of rumor effectively.

Chiral three-nucleon forces and the evolution of correlations along the oxygen isotopic chain

NASA Astrophysics Data System (ADS)

Cipollone, A.; Barbieri, C.; Navrátil, P.

2015-07-01

Background: Three-nucleon forces (3NFs) have nontrivial implications on the evolution of correlations at extreme proton-neutron asymmetries. Recent ab initio calculations show that leading-order chiral interactions are crucial to obtain the correct binding energies and neutron driplines along the O, N, and F chains [A. Cipollone, C. Barbieri, and P. Navrátil, Phys. Rev. Lett. 111, 062501 (2013), 10.1103/PhysRevLett.111.062501]. Purpose: Here we discuss the impact of 3NFs along the oxygen chain for other quantities of interest, such has the spectral distribution for attachment and removal of a nucleon, spectroscopic factors, and radii. The objective is to better delineate the general effects of 3NFs on nuclear correlations. Methods: We employ self-consistent Green's function (SCGF) theory which allows a comprehensive calculation of the single-particle spectral function. For the closed subshell isotopes, 14O, 16O, 22O, 24O, and 28O, we perform calculations with the Dyson-ADC(3) method, which is fully nonperturbative and is the state of the art for both nuclear physics and quantum chemistry applications. The remaining open-shell isotopes are studied using the newly developed Gorkov-SCGF formalism up to second order. Results: We produce complete plots for the spectral distributions. The spectroscopic factors for the dominant quasiparticle peaks are found to depend very little on the leading-order (NNLO) chiral 3NFs. The latter have small impact on the calculated matter radii, which, however, are consistently obtained smaller than experiment. Similarly, single-particle spectra tend to be too spread with respect to the experiment. This effect might hinder, to some extent, the onset of correlations and screen the quenching of calculated spectroscopic factors. The most important effect of 3NFs is thus the fine tuning of the energies for the dominant quasiparticle states, which governs the shell evolution and the position of driplines. Conclusions: Although present chiral NNLO 3NFs interactions do reproduce the binding energies correctly in this mass region, the details of the nuclear spectral function remain at odds with the experiment showing too-small radii and a too-spread single-particle spectrum, similar to what has already been pointed out for larger masses. This suggests a lack of repulsion in the present model of N N +3 N interactions, which is mildly apparent already for masses in the A =14 - 28 mass range.

Blind deconvolution post-processing of images corrected by adaptive optics

NASA Astrophysics Data System (ADS)

Christou, Julian C.

1995-08-01

Experience with the adaptive optics system at the Starfire Optical Range has shown that the point spread function is non-uniform and varies both spatially and temporally as well as being object dependent. Because of this, the application of a standard linear and non-linear deconvolution algorithms make it difficult to deconvolve out the point spread function. In this paper we demonstrate the application of a blind deconvolution algorithm to adaptive optics compensated data where a separate point spread function is not needed.

Slow neutron total cross-section, transmission and reflection calculation for poly- and mono-NaCl and PbF2 crystals

NASA Astrophysics Data System (ADS)

Mansy, Muhammad S.; Adib, M.; Habib, N.; Bashter, I. I.; Morcos, H. N.; El-Mesiry, M. S.

2016-10-01

A detailed study about the calculation of total neutron cross-section, transmission and reflection from crystalline materials was performed. The developed computer code is approved to be sufficient for the required calculations, also an excellent agreement has been shown when comparing the code results with the other calculated and measured values. The optimal monochromator and filter parameters were discussed in terms of crystal orientation, mosaic spread, and thickness. Calculations show that 30 cm thick of PbF2 poly-crystal is an excellent cold neutron filter producing neutron wavelengths longer than 0.66 nm needed for the investigation of magnetic structure experiments. While mono-crystal filter PbF2 cut along its (1 1 1), having mosaic spread (η = 0.5°) and thickness 10 cm can only transmit thermal neutrons of the desired wavelengths and suppress epithermal and γ-rays forming unwanted background, when it is cooled to liquid nitrogen temperature. NaCl (2 0 0) and PbF2 (1 1 1) monochromator crystals having mosaic spread (η = 0.5°) and thickness 10 mm shows high neutron reflectivity for neutron wavelengths (λ = 0.114 nm and λ = 0.43 nm) when they used as a thermal and cold neutron monochromators respectively with very low contamination from higher order reflections.

SEIR Model of Rumor Spreading in Online Social Network with Varying Total Population Size

NASA Astrophysics Data System (ADS)

Dong, Suyalatu; Deng, Yan-Bin; Huang, Yong-Chang

2017-10-01

Based on the infectious disease model with disease latency, this paper proposes a new model for the rumor spreading process in online social network. In this paper what we establish an SEIR rumor spreading model to describe the online social network with varying total number of users and user deactivation rate. We calculate the exact equilibrium points and reproduction number for this model. Furthermore, we perform the rumor spreading process in the online social network with increasing population size based on the original real world Facebook network. The simulation results indicate that the SEIR model of rumor spreading in online social network with changing total number of users can accurately reveal the inherent characteristics of rumor spreading process in online social network. Supported by National Natural Science Foundation of China under Grant Nos. 11275017 and 11173028

Optical Imaging and Radiometric Modeling and Simulation

NASA Technical Reports Server (NTRS)

Ha, Kong Q.; Fitzmaurice, Michael W.; Moiser, Gary E.; Howard, Joseph M.; Le, Chi M.

2010-01-01

OPTOOL software is a general-purpose optical systems analysis tool that was developed to offer a solution to problems associated with computational programs written for the James Webb Space Telescope optical system. It integrates existing routines into coherent processes, and provides a structure with reusable capabilities that allow additional processes to be quickly developed and integrated. It has an extensive graphical user interface, which makes the tool more intuitive and friendly. OPTOOL is implemented using MATLAB with a Fourier optics-based approach for point spread function (PSF) calculations. It features parametric and Monte Carlo simulation capabilities, and uses a direct integration calculation to permit high spatial sampling of the PSF. Exit pupil optical path difference (OPD) maps can be generated using combinations of Zernike polynomials or shaped power spectral densities. The graphical user interface allows rapid creation of arbitrary pupil geometries, and entry of all other modeling parameters to support basic imaging and radiometric analyses. OPTOOL provides the capability to generate wavefront-error (WFE) maps for arbitrary grid sizes. These maps are 2D arrays containing digital sampled versions of functions ranging from Zernike polynomials to combination of sinusoidal wave functions in 2D, to functions generated from a spatial frequency power spectral distribution (PSD). It also can generate optical transfer functions (OTFs), which are incorporated into the PSF calculation. The user can specify radiometrics for the target and sky background, and key performance parameters for the instrument s focal plane array (FPA). This radiometric and detector model setup is fairly extensive, and includes parameters such as zodiacal background, thermal emission noise, read noise, and dark current. The setup also includes target spectral energy distribution as a function of wavelength for polychromatic sources, detector pixel size, and the FPA s charge diffusion modulation transfer function (MTF).

Aberration Theory and Design Techniques for Refracting Prism Systems.

NASA Astrophysics Data System (ADS)

Al-Bizri, N.

Available from UMI in association with The British Library. The general case of image formation by optical systems consisting of combinations of ordinary lens components and refracting prisms is studied in detail. Formulae for the sagittal and tangential magnifications, the pupil scale ratios, the image tilt, the positions of (newly defined) principal planes and the equivalent focal lengths have been derived. Formulae for the axial astigmatism, axial transverse chromatic aberration and the focal shift measure of the aberration due to the tilt of the image plane have also been obtained. All of these formulae are equally valid for any optical system which has a single plane of symmetry. The calculation of the wavefront aberration coefficients and of the variance of the aberration for such systems has been treated using the pre-inverted matrix method. In addition formulae for the numerical evaluation of the optical transfer function, the point spread function, the line spread function and the edge response function, have been obtained and programmed. First-order formulae, and a refinement technique, for the design of cemented refracting doublet prisms have been obtained, which ensure that the desired prismatic deviation of the axis is obtained, and that the axial astigmatism and the axial transverse chromatic aberration have stipulated target values. All of the above formulae have been carefully tested by numerical examples, and the design technique has been used to design endoscope objectives which provide small deviations (<10^circ ) of the optical axis.

Topography and tectonics of mid-oceanic ridge axes

NASA Technical Reports Server (NTRS)

Sleep, N. H.; Rosendahl, B. R.

1979-01-01

Numerical fluid dynamic models of mid-oceanic ridge axes were constructed using distributions of material properties constrained by seismic studies and thermal calculations. The calculations indicate that spreading is passive except for forces caused by density differences due to thermal expansion and partial melt. Except for geometric differences due to temperature distribution, one set of mechanical properties can adequately explain central rifts of slow ridges and central peaks of fast ridges. Viscous head loss in the upwelling material dominates at low spreading rates where material ascends through a narrow conduit. Thermal expansion and partial melting dominate at high spreading rates where a wide low viscosity crustal magma chamber is present. The preferred rheology is 10 to the 20th poise for the upwelling lithosphere; less than 5 x 10 to the 17th for the crustal magma chamber and axial intrusion zone at fast ridges, and a yield stress of 200 bars for the lithosphere. The calculation correctly predicts the existence of central peaks at 'hot-spot' ridges, where seismic evidence indicates a large magma chamber.

Velocity Spread Reduction for Axis-encircling Electron Beam Generated by Single Magnetic Cusp

NASA Astrophysics Data System (ADS)

Jeon, S. G.; Baik, C. W.; Kim, D. H.; Park, G. S.; Sato, N.; Yokoo, K.

2001-10-01

Physical characteristics of an annular Pierce-type electron gun are investigated analytically. An annular electron gun is used in conjunction with a non-adiabatic magnetic reversal and an adiabatic compression to produce an axis-encircling electron beam. Velocity spread close to zero is realized with an initial canonical angular momentum spread at the cathode when the beam trajectory does not coincide with the magnetic flux line. Both the analytical calculation and the EGUN code simulation confirm this phenomenon.

Postquench prethermalization in a disordered quantum fluid of light

NASA Astrophysics Data System (ADS)

Larré, Pierre-Élie; Delande, Dominique; Cherroret, Nicolas

2018-04-01

We study the coherence of a disordered and interacting quantum light field after propagation along a nonlinear optical fiber. Disorder is generated by a cross-phase modulation with a randomized auxiliary classical light field, while interactions are induced by self-phase modulation. When penetrating the fiber from free space, the incoming quantum light undergoes a disorder and interaction quench. By calculating the coherence function of the transmitted quantum light, we show that the decoherence induced by the quench spreads in a light-cone fashion in the nonequilibrium many-body quantum system, leaving the latter prethermalize with peculiar features originating from disorder.

Examination of the wind speed limit function in the Rothermel surface fire spread model

Treesearch

Patricia L. Andrews; Miguel G. Cruz; Richard C. Rothermel

2013-01-01

The Rothermel surface fire spread model includes a wind speed limit, above which predicted rate of spread is constant. Complete derivation of the wind limit as a function of reaction intensity is given, along with an alternate result based on a changed assumption. Evidence indicates that both the original and the revised wind limits are too restrictive. Wind limit is...

Segmented Mirror Image Degradation Due to Surface Dust, Alignment and Figure

NASA Technical Reports Server (NTRS)

Schreur, Julian J.

1999-01-01

In 1996 an algorithm was developed to include the effects of surface roughness in the calculation of the point spread function of a telescope mirror. This algorithm has been extended to include the effects of alignment errors and figure errors for the individual elements, and an overall contamination by surface dust. The final algorithm builds an array for a guard-banded pupil function of a mirror that may or may not have a central hole, a central reflecting segment, or an outer ring of segments. The central hole, central reflecting segment, and outer ring may be circular or polygonal, and the outer segments may have trimmed comers. The modeled point spread functions show that x-tilt and y-tilt, or the corresponding R-tilt and theta-tilt for a segment in an outer ring, is readily apparent for maximum wavefront errors of 0.1 lambda. A similar sized piston error is also apparent, but integral wavelength piston errors are not. Severe piston error introduces a focus error of the opposite sign, so piston could be adjusted to compensate for segments with varying focal lengths. Dust affects the image principally by decreasing the Strehl ratio, or peak intensity of the image. For an eight-meter telescope a 25% coverage by dust produced a scattered light intensity of 10(exp -9) of the peak intensity, a level well below detectability.

Nano-fabrication of molecular electronic junctions by targeted modification of metal-molecule bonds

PubMed Central

Jafri, S. Hassan M.; Löfås, Henrik; Blom, Tobias; Wallner, Andreas; Grigoriev, Anton; Ahuja, Rajeev; Ottosson, Henrik; Leifer, Klaus

2015-01-01

Reproducibility, stability and the coupling between electrical and molecular properties are central challenges in the field of molecular electronics. The field not only needs devices that fulfill these criteria but they also need to be up-scalable to application size. In this work, few-molecule based electronics devices with reproducible electrical characteristics are demonstrated. Our previously reported 5 nm gold nanoparticles (AuNP) coated with ω-triphenylmethyl (trityl) protected 1,8-octanedithiol molecules are trapped in between sub-20 nm gap spacing gold nanoelectrodes forming AuNP-molecule network. When the trityl groups are removed, reproducible devices and stable Au-thiol junctions are established on both ends of the alkane segment. The resistance of more than 50 devices is reduced by orders of magnitude as well as a reduction of the spread in the resistance histogram is observed. By density functional theory calculations the orders of magnitude decrease in resistance can be explained and supported by TEM observations thus indicating that the resistance changes and strongly improved resistance spread are related to the establishment of reproducible and stable metal-molecule bonds. The same experimental sequence is carried out using 1,6-hexanedithiol functionalized AuNPs. The average resistances as a function of molecular length, demonstrated herein, are comparable to the one found in single molecule devices. PMID:26395225

[Analysis on the mechanism of acupuncture infrasound energy in treatment of diseases].

PubMed

Wang, Xi-ming

2009-03-01

Infrasound is a sound wave with vibration frequency of less than 20 Hz, characterized by a longer wavelength, weak attenuating and strong penetration power, etc. Since the inherent frequencies of the human body and the organs are within infrasound vibration range, so infrasound has a stronger effect on the human body. The study found that the process of acupuncture at acupoints could be regarded as one containing a forced vibration with damping, and in the acupuncture, a infrasound of 2-15 Hz could be produced, which can easily has a resonance with the human body and the organs. By calculation of the sound pressure and sound strength in acupuncture, it was found that acupuncture infrasound had four characteristics: small total energy, small amplitude, strong voice, and orientation spreading along the meridian line. Because the meridian lines are the good pathway to spread low-frequency sound, acupuncture infrasound energy can successfully pass the meridian lines to reach the focus, penetrate the morbid tissues and improve the functions of tissues or organs.

How to predict the spread and intensity of forest and range fires

Treesearch

Richard C. Rothermel

1983-01-01

This manual documents procedures for estimating the rate of forward spread, intensity, flame length, and size of fires burning in forests and rangelands. Contains instructions for obtaining fuel and weather data, calculating fire behavior, and interpreting the results for application to actual fire problems. This is a companion publication to "

Reformulation of Rothermel's wildland fire behaviour model for heterogeneous fuelbeds.

Treesearch

David V. Sandberg; Cynthia L. Riccardi; Mark D. Schaaf

2007-01-01

Abstract: The Fuel Characteristic Classification System (FCCS) includes equations that calculate energy release and one-dimensional spread rate in quasi-steady-state fires in heterogeneous but spatially uniform wildland fuelbeds, using a reformulation of the widely used Rothermel fire spread model. This reformulation provides an automated means to predict fire behavior...

Upper mantle electrical resistivity structure beneath back-arc spreading centers

NASA Astrophysics Data System (ADS)

Seama, N.; Shibata, Y.; Kimura, M.; Shindo, H.; Matsuno, T.; Nogi, Y.; Okino, K.

2011-12-01

We compare four electrical resistivity structure images of the upper mantle across back-arc spreading centers (Mariana Trough at 18 N and 13 N, and the Eastern Lau at 19.7 S and 21.3 S) to provide geophysical constraints on issues of mantle dynamics beneath the back-arc spreading system related to the subducting slab. The central Mariana Trough at 18 N has the full spreading rate of 25 km/Myr, and shows characteristic slow-spreading features; existence of median valley neovolcanic zone and "Bull's eyes" mantle Bouguer anomaly (MBA) along the axes. On the other hand, the southern Mariana Trough at 13 N shows an EPR type axial relief in morphology and lower MBA than that in the central Mariana Trough (Kitada et al., 2006), suggesting abundance of magma supply, even though the full spreading rate is 35 km/Myr that is categorized as a slow spreading ridge. At the Eastern Lau spreading center, crustal thickness and morphology vary systematically with arc proximity and shows the opposed trends against spreading rate: The full spreading rate increases from 65 km/Myr at 21.3 S to 85 km/Myr at 19.7 S, while the crustal thicknesses decrease together with morphology transitions from shallow peaked volcanic highs to a deeper flat axis (Martinez et al., 2006). Matsuno et al. (2010) provides a resistivity structure image of the upper mantle across the central Mariana subduction system, which contains several key features: There is an uppermost resistive layer with a thickness of 80-100 km beneath the central Mariana Trough, suggesting dry residual from the plate accretion process. But there is no evidence for a conductive feature beneath the back-arc spreading center at 18 N, and this feature is clearly independent from the conductive region beneath the volcanic arc below 60 km depth that reflects melting and hydration driven by water release from the subducting slab. The resultant upper mantle resistivity structure well support that the melt supply is not abundant, resulting in characteristic slow-spreading features at the surface. We have conducted marine magnetotelluric (MT) surveys at the southern Mariana in 2010 and at the Eastern Lau in 2009-2010. We obtained 10 ocean bottom electro-magnetometer (OBEM) data from a 130 km length MT transect across the southern Mariana spreading axis at 13 N, while we obtained 2 OBEM data and 11 ocean bottom magnetometer data from two 160 km length MT transects across the Eastern Lau spreading axes at 19.7 S and 21.3 S. After calculation of MT response functions and their correction for topographic distortion, two-dimensional electrical resistivity structures will be derived using an inversion algorithm. At this meeting, first we will show the resistivity structure images of the upper mantle beneath these spreading axes. Then, these structure images will be compared to identify differences in the mantle dynamics and the melt supply beneath the back-arc spreading system related to the subducting slab.

Experimental investigation of dynamic impact of firearm with suppressor

NASA Astrophysics Data System (ADS)

Kilikevicius, Arturas; Skeivalas, Jonas; Jurevicius, Mindaugas; Turla, Vytautas; Kilikeviciene, Kristina; Bureika, Gintautas; Jakstas, Arunas

2017-09-01

The internal ballistics processes occur in the tube during firearm firing. They cause tremendous vibratory shock forces and robust sounds. The determination of these dynamic parameters is relevant in order to reasonably estimate the firearm ergonomic and noise reduction features. The objective of this study is to improve the reliability of the results of measuring a firearm suppressor's dynamic parameters. The analysis of indicator stability is based on an assessment of dynamic parameters and setting the correlation during experimental research. An examination of the spread of intensity of firearm with suppressor dynamic vibration and an analysis of its signals upon applying the theory of covariance functions are carried out in this paper. The results of measuring the intensity of vibrations in fixed points of a firearm and a shooter have been recorded on a time scale in the form of data arrays (matrices). The estimates of covariance functions between the arrays of digital results in measuring the intensity of firearm vibrations and the estimates of covariance functions of single arrays have been calculated upon changing the quantization interval on the time scale. Software Matlab 7 has been applied in the calculation. Finally, basic conclusions are given.

Assessing the role of spatial correlations during collective cell spreading

PubMed Central

Treloar, Katrina K.; Simpson, Matthew J.; Binder, Benjamin J.; McElwain, D. L. Sean; Baker, Ruth E.

2014-01-01

Spreading cell fronts are essential features of development, repair and disease processes. Many mathematical models used to describe the motion of cell fronts, such as Fisher's equation, invoke a mean–field assumption which implies that there is no spatial structure, such as cell clustering, present. Here, we examine the presence of spatial structure using a combination of in vitro circular barrier assays, discrete random walk simulations and pair correlation functions. In particular, we analyse discrete simulation data using pair correlation functions to show that spatial structure can form in a spreading population of cells either through sufficiently strong cell–to–cell adhesion or sufficiently rapid cell proliferation. We analyse images from a circular barrier assay describing the spreading of a population of MM127 melanoma cells using the same pair correlation functions. Our results indicate that the spreading melanoma cell populations remain very close to spatially uniform, suggesting that the strength of cell–to–cell adhesion and the rate of cell proliferation are both sufficiently small so as not to induce any spatial patterning in the spreading populations. PMID:25026987

Application of Interval Predictor Models to Space Radiation Shielding

NASA Technical Reports Server (NTRS)

Crespo, Luis G.; Kenny, Sean P.; Giesy,Daniel P.; Norman, Ryan B.; Blattnig, Steve R.

2016-01-01

This paper develops techniques for predicting the uncertainty range of an output variable given input-output data. These models are called Interval Predictor Models (IPM) because they yield an interval valued function of the input. This paper develops IPMs having a radial basis structure. This structure enables the formal description of (i) the uncertainty in the models parameters, (ii) the predicted output interval, and (iii) the probability that a future observation would fall in such an interval. In contrast to other metamodeling techniques, this probabilistic certi cate of correctness does not require making any assumptions on the structure of the mechanism from which data are drawn. Optimization-based strategies for calculating IPMs having minimal spread while containing all the data are developed. Constraints for bounding the minimum interval spread over the continuum of inputs, regulating the IPMs variation/oscillation, and centering its spread about a target point, are used to prevent data over tting. Furthermore, we develop an approach for using expert opinion during extrapolation. This metamodeling technique is illustrated using a radiation shielding application for space exploration. In this application, we use IPMs to describe the error incurred in predicting the ux of particles resulting from the interaction between a high-energy incident beam and a target.

On the use of bismuth as a neutron filter

NASA Astrophysics Data System (ADS)

Adib, M.; Kilany, M.

2003-02-01

A formula is given which, for neutron energies in the range 10 -4< E<10 eV, permits calculation of the nuclear capture, thermal diffuse and Bragg scattering cross-sections as a function of bismuth temperature and crystalline form. Computer programs have been developed which allow calculations for the Bi rhombohedral structure in its poly-crystalline form and its equivalent hexagonal close-packed structure. The calculated total neutron cross-sections for poly-crystalline Bi at different temperatures were compared with the measured values. An overall agreement is indicated between the formula fits and experimental data. Agreement was also obtained for values of Bi-single crystals, at room and liquid nitrogen temperatures. A feasibility study for use of Bi in powdered form, as a cold neutron filter, is detailed in terms of the optimum Bi-single crystal thickness, mosaic spread, temperature and cutting plane for efficient transmission of thermal-reactor neutrons, and also for rejection of the accompanying fast neutrons and gamma rays.

Macroscopic elastic properties of textured ZrN-AlN polycrystalline aggregates: From ab initio calculations to grain-scale interactions

NASA Astrophysics Data System (ADS)

Holec, D.; Tasnádi, F.; Wagner, P.; Friák, M.; Neugebauer, J.; Mayrhofer, P. H.; Keckes, J.

2014-11-01

Despite the fast development of computational material modeling, the theoretical description of macroscopic elastic properties of textured polycrystalline aggregates starting from basic principles remains a challenging task. In this study we use a supercell-based approach to obtain the elastic properties of a random solid solution cubic Zr1 -xAlxN system as a function of the metallic sublattice composition and texture descriptors. The employed special quasirandom structures are optimized not only with respect to short-range-order parameters, but also to make the three cubic directions [1 0 0 ] , [0 1 0 ] , and [0 0 1 ] as similar as possible. In this way, only a small spread of elastic constant tensor components is achieved and an optimum trade-off between modeling of chemical disorder and computational limits regarding the supercell size and calculational time is proposed. The single-crystal elastic constants are shown to vary smoothly with composition, yielding x ≈0.5 an alloy constitution with an almost isotropic response. Consequently, polycrystals with this composition are suggested to have Young's modulus independent of the actual microstructure. This is indeed confirmed by explicit calculations of polycrystal elastic properties, both within the isotropic aggregate limit and with fiber textures with various orientations and sharpness. It turns out that for low AlN mole fractions, the spread of the possible Young's modulus data caused by the texture variation can be larger than 100 GPa. Consequently, our discussion of Young's modulus data of cubic Zr1 -xAlxN contains also the evaluation of the texture typical for thin films.

Spreading of correlations in the Falicov-Kimball model

NASA Astrophysics Data System (ADS)

Herrmann, Andreas J.; Antipov, Andrey E.; Werner, Philipp

2018-04-01

We study dynamical properties of the one- and two-dimensional Falicov-Kimball model using lattice Monte Carlo simulations. In particular, we calculate the spreading of charge correlations in the equilibrium model and after an interaction quench. The results show a reduction of the light-cone velocity with interaction strength at low temperature, while the phase velocity increases. At higher temperature, the initial spreading is determined by the Fermi velocity of the noninteracting system and the maximum range of the correlations decreases with increasing interaction strength. Charge order correlations in the disorder potential enhance the range of the correlations. We also use the numerically exact lattice Monte Carlo results to benchmark the accuracy of equilibrium and nonequilibrium dynamical cluster approximation calculations. It is shown that the bias introduced by the mapping to a periodized cluster is substantial, and that from a numerical point of view, it is more efficient to simulate the lattice model directly.

Point-spread imaging for measurement of skin translucency and scattering.

PubMed

Jiang, Zhi-xing; Kaplan, Peter D

2008-08-01

The translucency of skin has long been identified as an important cue for healthy and youthful looking skin. There is currently no universal definition for skin translucency let alone a measurement method. We propose that skin translucency is the light scattering beneath skin surface. We demonstrate the use of polarization gated point spreading imaging for non-invasive, in vivo measurement of the translucency and the reduced scattering coefficient m's of skin. We developed a polarization-gated point-spread imaging system to measure the spread of the incident pencil-thin laser beam on the skin. Skin translucency was calculated as the spread of the laser beam. From the measurement of the shift of the light diffuse center from the light injection point, the reduced scattering coefficient m's of the skin was calculated. We validated the measurement technique with milk as an in vitro model for skin. The measured m's of milk solution was found to be linearly proportional to the milk concentration, in agreement with Beer's law. The calculated translucency decreased as the milk concentration increased or as the reduced scattering coefficient m's increased. It was also found that the translucency decreased as the absorption coefficient of the milk solution increased. The measured translucency of a set of custom made clay tiles correlated well with the consumer perception of the incremental ranking of the translucency. In vivo measurement of skin translucency and the reduced scattering coefficient m's were carried out on several volunteers. The measured reduced scattering coefficient m's was in agreement with those in the literature. The measured skin translucency for different skin ethnicities of Caucasian, North Asian, South Asian and African American were in line with the expectation that skin translucency decreases as the skin color gets darker.

Epidemic spreading in a hierarchical social network.

PubMed

Grabowski, A; Kosiński, R A

2004-09-01

A model of epidemic spreading in a population with a hierarchical structure of interpersonal interactions is described and investigated numerically. The structure of interpersonal connections is based on a scale-free network. Spatial localization of individuals belonging to different social groups, and the mobility of a contemporary community, as well as the effectiveness of different interpersonal interactions, are taken into account. Typical relations characterizing the spreading process, like a range of epidemic and epidemic curves, are discussed. The influence of preventive vaccinations on the spreading process is investigated. The critical value of preventively vaccinated individuals that is sufficient for the suppression of an epidemic is calculated. Our results are compared with solutions of the master equation for the spreading process and good agreement of the character of this process is found.

Dose calculation for electron therapy using an improved LBR method.

PubMed

Gebreamlak, Wondesen T; Tedeschi, David J; Alkhatib, Hassaan A

2013-07-01

To calculate the percentage depth dose (PDD) of any irregularly shaped electron beam using a modified lateral build-up ratio (LBR) method. Percentage depth dose curves were measured using 6, 9, 12, and 15 MeV electron beam energies for applicator cone sizes of 6 × 6, 10 × 10, 14 × 14, and 20 × 20 cm(2). Circular cutouts for each cone were prepared from 2.0 cm diameter to the maximum possible size for each cone. In addition, three irregular cutouts were prepared. The LBR for each circular cutout was calculated from the measured PDD curve using the open field of the 14 × 14 cm(2) cone as the reference field. Using the LBR values and the radius of the circular cutouts, the corresponding lateral spread parameter [σR(z)] of the electron shower was calculated. Unlike the commonly accepted assumption that σR(z) is independent of cutout size, it is shown that its value increases linearly with circular cutout size (R). Using this characteristic of the lateral spread parameter, the PDD curves of irregularly shaped cutouts were calculated. Finally, the calculated PDD curves were compared with measured PDD curves. In this research, it is shown that the lateral spread parameter σR(z) increases with cutout size. For radii of circular cutout sizes up to the equilibrium range of the electron beam, the increase of σR(z) with the cutout size is linear. The percentage difference of the calculated PDD curve from the measured PDD data for irregularly shaped cutouts was under 1.0% in the region between the surface and therapeutic range of the electron beam. Similar results were obtained for four electron beam energies (6, 9, 12, and 15 MeV).

An Overview of FlamMap Fire Modeling Capabilities

Treesearch

Mark A. Finney

2006-01-01

Computerized and manual systems for modeling wildland fire behavior have long been available (Rothermel 1983, Andrews 1986). These systems focus on one-dimensional behaviors and assume the fire geometry is a spreading line-fire (in contrast with point or area-source fires). Models included in these systems were developed to calculate fire spread rate (Rothermel 1972,...

Higher Order Analysis of Turbulent Changes Found in the ELF Range Electric Field Plasma Before Major Earthquakes

NASA Astrophysics Data System (ADS)

Kosciesza, M.; Blecki, J. S.; Parrot, M.

2014-12-01

We report the structure function analysis of changes found in electric field in the ELF range plasma turbulence registered in the ionosphere over epicenter region of major earthquakes with depth less than 40 km that took place during 6.5 years of the scientific mission of the DEMETER satellite. We compare the data for the earthquakes for which we found turbulence with events without any turbulent changes. The structure functions were calculated also for the Polar CUSP region and equatorial spread F region. Basic studies of the turbulent processes were conducted with use of higher order spectra and higher order statistics. The structure function analysis was performed to locate and check if there are intermittent behaviors in the ionospheres plasma over epicenter region of the earthquakes. These registrations are correlated with the plasma parameters measured onboard DEMETER satellite and with geomagnetic indices.

Error analysis of the Golay3 optical imaging system.

PubMed

Wu, Quanying; Fan, Junliu; Wu, Feng; Zhao, Jun; Qian, Lin

2013-05-01

We use aberration theory to derive a generalized pupil function of the Golay3 imaging system when astigmatisms exist in its submirrors. Theoretical analysis and numerical simulation using ZEMAX show that the point spread function (PSF) and the modulation transfer function (MTF) of the Golay3 sparse aperture system have a periodic change when there are piston errors. When the peak-valley value of the wavefront (PV(tilt)) due to the tilt error increases from zero to λ, the PSF and the MTF change significantly, and the change direction is determined by the location of the submirror with the tilt error. When PV(tilt) becomes larger than λ, the PSF and the MTF remain unvaried. We calculate the peaks of the signal-to-noise ratio (PSNR) resulting from the piston and tilt errors according to the Strehl ratio, and show that the PSNR decreases when the errors increase.

Influence of particle size distribution on reflected and transmitted light from clouds.

PubMed

Kattawar, G W; Plass, G N

1968-05-01

The light reflected and transmitted from clouds with various drop size distributions is calculated by a Monte Carlo technique. Six different models are used for the drop size distribution: isotropic, Rayleigh, haze continental, haze maritime, cumulus, and nimbostratus. The scattering function for each model is calculated from the Mie theory. In general, the reflected and transmitted radiances for the isotropic and Rayleigh models tend to be similar, as are those for the various haze and cloud models. The reflected radiance is less for the haze and cloud models than for the isotropic and Rayleigh models/except for an angle of incidence near the horizon when it is larger around the incident beam direction. The transmitted radiance is always much larger for the haze and cloud models near the incident direction; at distant angles it is less for small and moderate optical thicknesses and greater for large optical thicknesses (all comparisons to isotropic and Rayleigh models). The downward flux, cloud albedo, and ean optical path are discussed. The angular spread of the beam as a function of optical thickness is shown for the nimbostratus model.

A spectral analysis of team dynamics and tactics in Brazilian football.

PubMed

Moura, Felipe Arruda; Martins, Luiz Eduardo Barreto; Anido, Ricardo O; Ruffino, Paulo Régis C; Barros, Ricardo M L; Cunha, Sergio Augusto

2013-01-01

The purposes of this study were to characterise the total space covered and the distances between players within teams over ten Brazilian First Division Championship matches. Filmed recordings, combined with a tracking system, were used to obtain the trajectories of the players (n = 277), before and after half-time. The team surface area (the area of the convex hull formed by the positions of the players) and spread (the Frobenius norm of the distance-between-player matrix) were calculated as functions of time. A Fast Fourier Transform (FFT) was applied to each time series. The median frequency was then calculated. The results of the surface area time series median frequencies for the first half (0.63 ± 0.10 cycles · min⁻¹) were significantly greater (P < 0.01) than the second-half values (0.47 ± 0.14 cycles · min⁻¹). Similarly, the spread variable median frequencies for the first half (0.60 ± 0.14 cycles · min⁻¹) were significantly greater (P < 0.01) than the second-half values (0.46 ± 0.16 cycles · min⁻¹). The median frequencies allowed the characterisation of the time series oscillations that represent the speed at which players distribute and then compact their team formation during a match. This analysis can provide insights that allow coaches to better control the team organisation on the pitch.

Spectral and spread-spectral teleportation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Humble, Travis S.

2010-06-15

We report how quantum information encoded into the spectral degree of freedom of a single-photon state may be teleported using a finite spectrally entangled biphoton state. We further demonstrate how the bandwidth of the teleported wave form can be controllably and coherently dilated using a spread-spectral variant of teleportation. We calculate analytical expressions for the fidelities of spectral and spread-spectral teleportation when complex-valued Gaussian states are transferred using a proposed experimental approach. Finally, we discuss the utility of these techniques for integrating broad-bandwidth photonic qubits with narrow-bandwidth receivers in quantum communication systems.

Point spread function modeling and image restoration for cone-beam CT

NASA Astrophysics Data System (ADS)

Zhang, Hua; Huang, Kui-Dong; Shi, Yi-Kai; Xu, Zhe

2015-03-01

X-ray cone-beam computed tomography (CT) has such notable features as high efficiency and precision, and is widely used in the fields of medical imaging and industrial non-destructive testing, but the inherent imaging degradation reduces the quality of CT images. Aimed at the problems of projection image degradation and restoration in cone-beam CT, a point spread function (PSF) modeling method is proposed first. The general PSF model of cone-beam CT is established, and based on it, the PSF under arbitrary scanning conditions can be calculated directly for projection image restoration without the additional measurement, which greatly improved the application convenience of cone-beam CT. Secondly, a projection image restoration algorithm based on pre-filtering and pre-segmentation is proposed, which can make the edge contours in projection images and slice images clearer after restoration, and control the noise in the equivalent level to the original images. Finally, the experiments verified the feasibility and effectiveness of the proposed methods. Supported by National Science and Technology Major Project of the Ministry of Industry and Information Technology of China (2012ZX04007021), Young Scientists Fund of National Natural Science Foundation of China (51105315), Natural Science Basic Research Program of Shaanxi Province of China (2013JM7003) and Northwestern Polytechnical University Foundation for Fundamental Research (JC20120226, 3102014KYJD022)

Distortion correction of echo planar images applying the concept of finite rate of innovation to point spread function mapping (FRIP).

PubMed

Nunes, Rita G; Hajnal, Joseph V

2018-06-01

Point spread function (PSF) mapping enables estimating the displacement fields required for distortion correction of echo planar images. Recently, a highly accelerated approach was introduced for estimating displacements from the phase slope of under-sampled PSF mapping data. Sampling schemes with varying spacing were proposed requiring stepwise phase unwrapping. To avoid unwrapping errors, an alternative approach applying the concept of finite rate of innovation to PSF mapping (FRIP) is introduced, using a pattern search strategy to locate the PSF peak, and the two methods are compared. Fully sampled PSF data was acquired in six subjects at 3.0 T, and distortion maps were estimated after retrospective under-sampling. The two methods were compared for both previously published and newly optimized sampling patterns. Prospectively under-sampled data were also acquired. Shift maps were estimated and deviations relative to the fully sampled reference map were calculated. The best performance was achieved when using FRIP with a previously proposed sampling scheme. The two methods were comparable for the remaining schemes. The displacement field errors tended to be lower as the number of samples or their spacing increased. A robust method for estimating the position of the PSF peak has been introduced.

[Initial studies of the application of the linear signal transfer theory in evaluating diaphanoscopic examinations exemplified by rheumatism diagnosis].

PubMed

Beuthan, J; Cappius, H J; Hielscher, A; Hopf, M; Klose, A; Netz, U

2001-11-01

Rheumatoid arthritis affecting the small joints--in particular the fingers--has advantageous geometry for the transmission of near-infrared (NIR) light. Examination of the optical properties of tissues has revealed that as a result of changes to the capsule and synovial fluid there is a considerable increase in photon scattering already in the early stages of the disease--in particular around 685 nm. This suggests the appropriateness of analysing the photon density profile resulting from punctiform irradiation of the joint. In a first approximation, the point spread function of transmitted photon density is confirmed to be proportional to a Gauss distribution, as suggested by Arridge. In accordance with the linear signal transfer theory, therefore, it is possible to establish a virtual transfer system described by a first-order differential equation. (The tissue optical conditions mu a < mu's and mu a = constant (mu a = absorption coefficient) were assumed). The parameter mu's (= reduced scattering coefficient) was determined by linear approximation of the Gauss distribution to the calculated or measured point spread function. For selected patient data, the mu's was determined in healthy and diseased finger joints (e.g. 10.1 cm-1 and 26.8 cm-1, respectively), and the results were in good agreement with those obtained experimentally.

Flame Spread Along Free Edges of Thermally Thin Samples in Microgravity

NASA Technical Reports Server (NTRS)

Mell, W. E.; Olson, S. L.; Kashiwagi, T.

2000-01-01

The effects of imposed flow velocity on flame spread along open edges of a thermally thin cellulosic sample in microgravity are studied experimentally and theoretically. In this study, the sample is ignited locally at the middle of the 4 cm wide sample and subsequent flame spread reaches both open edges of the sample. The following flame behaviors are observed in the experiments and predicted by the numerical calculation; in order of increased imposed flow velocity: (1) ignition but subsequent flame spread is not attained, (2) flame spreads upstream (opposed mode) without any downstream flame, and (3) the upstream flame and two separate downstream flames traveling along the two open edges (concurrent mode). Generally, the upstream and downstream edge flame spread rates are faster than the central flame spread rate for an imposed flow velocity of up to 5 cm/s. This is due to greater oxygen supply from the outer free stream to the edge flames than the central flames, For the upstream edge flame, the greater oxygen supply results in a flame spread rate that is nearly independent of, or decreases gradually, with the imposed flow velocity. The spread rate of the downstream edge, however, increases significantly with the imposed flow velocity.

Method Of Characterizing An Electrode Binder

DOEpatents

Cocciantelli, Jean-Michel; Coco, Isabelle; Villenave, Jean-Jacques

1999-05-11

In a method of characterizing a polymer binder for cell electrodes in contact with an electrolyte and including a current collector and a paste containing an electrochemically active material and said binder, a spreading coefficient of the binder on the active material is calculated from the measured angle of contact between standard liquids and the active material and the binder, respectively. An interaction energy of the binder with the electrolyte is calculated from the measured angle of contact between the electrolyte and the binder. The binder is selected such that the spreading coefficient is less than zero and the interaction energy is at least 60 mJ/m.sup.2.

Terraced spreading of simple liquids on solid surfaces

NASA Technical Reports Server (NTRS)

Yang, Ju-Xing; Koplik, Joel; Banavar, Jayanth R.

1992-01-01

We have studied the spreading of liquid drops on a solid surface by molecular-dynamics simulations of coexisting three-phase Lennard-Jones systems of liquid, vapor, and solid. We consider both spherically symmetric atoms and diatomic molecules, and a range of interaction strengths. As the attraction between liquid and solid increases we observe a smooth transition in spreading regimes, from partial to complete to terraced wetting. In the terraced case, where distinct monomolecular layers spread with different velocities, the layers are ordered but not solid, with substantial molecular diffusion both within and between layers. The quantitative behavior resembles recent experimental findings, but the detailed dynamics differ. In particular, the layers exhibit an unusual spreading law, where their radii vary in time as R-squared approximately equal to log10t, which disagrees with experiments on polymeric liquids as well as recent calculations.

Reduced Risk of Importing Ebola Virus Disease because of Travel Restrictions in 2014: A Retrospective Epidemiological Modeling Study.

PubMed

Otsuki, Shiori; Nishiura, Hiroshi

An epidemic of Ebola virus disease (EVD) from 2013-16 posed a serious risk of global spread during its early growth phase. A post-epidemic evaluation of the effectiveness of travel restrictions has yet to be conducted. The present study aimed to estimate the effectiveness of travel restrictions in reducing the risk of importation from mid-August to September, 2014, using a simple hazard-based statistical model. The hazard rate was modeled as an inverse function of the effective distance, an excellent predictor of disease spread, which was calculated from the airline transportation network. By analyzing datasets of the date of EVD case importation from the 15th of July to the 15th of September 2014, and assuming that the network structure changed from the 8th of August 2014 because of travel restrictions, parameters that characterized the hazard rate were estimated. The absolute risk reduction and relative risk reductions due to travel restrictions were estimated to be less than 1% and about 20%, respectively, for all models tested. Effectiveness estimates among African countries were greater than those for other countries outside Africa. The travel restrictions were not effective enough to expect the prevention of global spread of Ebola virus disease. It is more efficient to control the spread of disease locally during an early phase of an epidemic than to attempt to control the epidemic at international borders. Capacity building for local containment and coordinated and expedited international cooperation are essential to reduce the risk of global transmission.

Reduced Risk of Importing Ebola Virus Disease because of Travel Restrictions in 2014: A Retrospective Epidemiological Modeling Study

PubMed Central

Otsuki, Shiori

2016-01-01

Background An epidemic of Ebola virus disease (EVD) from 2013–16 posed a serious risk of global spread during its early growth phase. A post-epidemic evaluation of the effectiveness of travel restrictions has yet to be conducted. The present study aimed to estimate the effectiveness of travel restrictions in reducing the risk of importation from mid-August to September, 2014, using a simple hazard-based statistical model. Methodology/Principal Findings The hazard rate was modeled as an inverse function of the effective distance, an excellent predictor of disease spread, which was calculated from the airline transportation network. By analyzing datasets of the date of EVD case importation from the 15th of July to the 15th of September 2014, and assuming that the network structure changed from the 8th of August 2014 because of travel restrictions, parameters that characterized the hazard rate were estimated. The absolute risk reduction and relative risk reductions due to travel restrictions were estimated to be less than 1% and about 20%, respectively, for all models tested. Effectiveness estimates among African countries were greater than those for other countries outside Africa. Conclusions The travel restrictions were not effective enough to expect the prevention of global spread of Ebola virus disease. It is more efficient to control the spread of disease locally during an early phase of an epidemic than to attempt to control the epidemic at international borders. Capacity building for local containment and coordinated and expedited international cooperation are essential to reduce the risk of global transmission. PMID:27657544

Scattering and the Point Spread Function of the New Generation Space Telescope

NASA Technical Reports Server (NTRS)

Schreur, Julian J.

1996-01-01

Preliminary design work on the New Generation Space Telescope (NGST) is currently under way. This telescope is envisioned as a lightweight, deployable Cassegrain reflector with an aperture of 8 meters, and an effective focal length of 80 meters. It is to be folded into a small-diameter package for launch by an Atlas booster, and unfolded in orbit. The primary is to consist of an octagon with a hole at the center, and with eight segments arranged in a flower petal configuration about the octagon. The comers of the petal-shaped segments are to be trimmed so that the package will fit atop the Atlas booster. This mirror, along with its secondary will focus the light from a point source into an image which is spread from a point by diffraction effects, figure errors, and scattering of light from the surface. The distribution of light in the image of a point source is called a point spread function (PSF). The obstruction of the incident light by the secondary mirror and its support structure, the trimmed corners of the petals, and the grooves between the segments all cause the diffraction pattern characterizing an ideal point spread function to be changed, with the trimmed comers causing the rings of the Airy pattern to become broken up, and the linear grooves causing diffraction spikes running radially away from the central spot, or Airy disk. Any figure errors the mirror segments may have, or any errors in aligning the petals with the central octagon will also spread the light out from the ideal point spread function. A point spread function for a mirror the size of the NGST and having an incident wavelength of 900 nm is considered. Most of the light is confined in a circle with a diameter of 0.05 arc seconds. The ring pattern ranges in intensity from 10(exp -2) near the center to 10(exp -6) near the edge of the plotted field, and can be clearly discerned in a log plot of the intensity. The total fraction of the light scattered from this point spread function is called the total integrated scattering (TIS), and the fraction remaining is called the Strehl ratio. The angular distribution of the scattered light is called the angle resolved scattering (ARS), and it shows a strong spike centered on a scattering angle of zero, and a broad , less intense distribution at larger angles. It is this scattered light, and its effect on the point spread function which is the focus of this study.

Spread-spectrum multiple access using wideband noncoherent MFSK

NASA Technical Reports Server (NTRS)

Ha, Tri T.; Pratt, Timothy; Maggenti, Mark A.

1987-01-01

Two spread-spectrum multiple access systems which use wideband M-ary frequency shift keying (FSK) (MFSK) as the primary modulation are presented. A bit error rate performance analysis is presented and system throughput is calculated for sample C band and Ku band satellite systems. Sample link analyses are included to illustrate power and adjacent satellite interference considerations in practical multiple access systems.

Modelling the Wind-Borne Spread of Highly Pathogenic Avian Influenza Virus between Farms

PubMed Central

Ssematimba, Amos; Hagenaars, Thomas J.; de Jong, Mart C. M.

2012-01-01

A quantitative understanding of the spread of contaminated farm dust between locations is a prerequisite for obtaining much-needed insight into one of the possible mechanisms of disease spread between farms. Here, we develop a model to calculate the quantity of contaminated farm-dust particles deposited at various locations downwind of a source farm and apply the model to assess the possible contribution of the wind-borne route to the transmission of Highly Pathogenic Avian Influenza virus (HPAI) during the 2003 epidemic in the Netherlands. The model is obtained from a Gaussian Plume Model by incorporating the dust deposition process, pathogen decay, and a model for the infection process on exposed farms. Using poultry- and avian influenza-specific parameter values we calculate the distance-dependent probability of between-farm transmission by this route. A comparison between the transmission risk pattern predicted by the model and the pattern observed during the 2003 epidemic reveals that the wind-borne route alone is insufficient to explain the observations although it could contribute substantially to the spread over short distance ranges, for example, explaining 24% of the transmission over distances up to 25 km. PMID:22348042

Modelling the wind-borne spread of highly pathogenic avian influenza virus between farms.

PubMed

Ssematimba, Amos; Hagenaars, Thomas J; de Jong, Mart C M

2012-01-01

A quantitative understanding of the spread of contaminated farm dust between locations is a prerequisite for obtaining much-needed insight into one of the possible mechanisms of disease spread between farms. Here, we develop a model to calculate the quantity of contaminated farm-dust particles deposited at various locations downwind of a source farm and apply the model to assess the possible contribution of the wind-borne route to the transmission of Highly Pathogenic Avian Influenza virus (HPAI) during the 2003 epidemic in the Netherlands. The model is obtained from a Gaussian Plume Model by incorporating the dust deposition process, pathogen decay, and a model for the infection process on exposed farms. Using poultry- and avian influenza-specific parameter values we calculate the distance-dependent probability of between-farm transmission by this route. A comparison between the transmission risk pattern predicted by the model and the pattern observed during the 2003 epidemic reveals that the wind-borne route alone is insufficient to explain the observations although it could contribute substantially to the spread over short distance ranges, for example, explaining 24% of the transmission over distances up to 25 km.

Liquid Fuels: Pyrolytic Degradation and Fire Spread Behavior as Influenced by Buoyancy

NASA Technical Reports Server (NTRS)

Ross, Howard D. (Technical Monitor); Yeboah, Yaw D.

2003-01-01

This project was conducted by the Combustion and Emission Control Lab in the Engineering Department at Clark Atlanta University under NASA Grant No. NCC3-707. The work aimed at providing data to supplement the ongoing NASA research activities on flame spread across liquid pools by providing flow visualization and velocity measurements especially in the gas phase and gas-liquid interface. During this investigation, the detailed physics of flame spread across liquid pools was revealed using particle image velocimetry (PIV), 3-dimensional Laser Doppler velocimetry (LDV) and high-speed video imaging system (HSVS). Flow fields (front and side views) of both the liquid and gas phases were visually investigated for the three subflash regimes of flame spread behavior. Some interesting findings obtained from the front and side views on flame spread across butanol pools are presented. PIV results showed the size of the transient vortex in the liquid phase near the flame front varied with the initial pool temperature. The transient vortex ahead of the flame front in the gas phase was, for the first time, clearly observed located just within 0-3 mm above the liquid surface and its size was dependent on the initial pool temperature. We calculated the flow velocity at 1 mm below the liquid surface near the flame front and inferred the generation mechanism of the vortex in the gas phase. Finally, after comparison of the flow velocity of the liquid surface and the flame spread rate, a reasonable explanation to the formation mechanism of the pulsating characteristic was proposed. This explanation is compatible with the previous numerical calculations and deductions.

Correction of dichroic mirror-induced PSF distortion in STED microscopy

NASA Astrophysics Data System (ADS)

Li, Yanghui; Zhou, Hui; Liu, Xiaoyu; Xia, Chengliang; Wang, Le

2018-07-01

Due to its spectral transmission/reflection properties, dichroic mirror (DM) is widely applied in nearly all microscopes to separate and combine beams with diverse wavelengths. However, its potential distortion effects to the point-spread function (PSF) have been ignored to a large extent. Here, we built a mathematical model to quantify these effects. Specifically, we focus on STED microscopy, whose performance is extremely sensitive to the systematic deficiencies. Both excitation and depletion beams are analysed, and the peak intensity and the shape of the effective PSF are calculated accordingly. More importantly, the strategy to compensate the DM-induced PSF distortion is also given in this paper.

Diffraction patterns in Fresnel approximation of periodic objects for a colorimeter of two apertures

NASA Astrophysics Data System (ADS)

Cortes-Reynoso, Jose-German R.; Suarez-Romero, Jose G.; Hurtado-Ramos, Juan B.; Tepichin-Rodriguez, Eduardo; Solorio-Leyva, Juan Carlos

2004-10-01

In this work, we present a study of Fresnel diffraction of periodic structures in an optical system of two apertures. This system of two apertures was used successfully for measuring color in textile samples solving the problems of illumination and directionality that present current commercial equipments. However, the system is sensible to the spatial frequency of the periodic sample"s area enclosed in its optical field of view. The study of Fresnel diffraction allows us to establish criteria for geometrical parameters of measurements in order to assure invariance in angular rotations and spatial positions. In this work, we use the theory of partial coherence to calculate the diffraction through two continuous apertures. In the calculation process, we use the concept of point-spread function of the system for partial coherence, in this way we avoid complicated statistical processes commonly used in the partial coherence theory.

High-speed spectral calibration by complex FIR filter in phase-sensitive optical coherence tomography.

PubMed

Kim, Sangmin; Raphael, Patrick D; Oghalai, John S; Applegate, Brian E

2016-04-01

Swept-laser sources offer a number of advantages for Phase-sensitive Optical Coherence Tomography (PhOCT). However, inter- and intra-sweep variability leads to calibration errors that adversely affect phase sensitivity. While there are several approaches to overcoming this problem, our preferred method is to simply calibrate every sweep of the laser. This approach offers high accuracy and phase stability at the expense of a substantial processing burden. In this approach, the Hilbert phase of the interferogram from a reference interferometer provides the instantaneous wavenumber of the laser, but is computationally expensive. Fortunately, the Hilbert transform may be approximated by a Finite Impulse-Response (FIR) filter. Here we explore the use of several FIR filter based Hilbert transforms for calibration, explicitly considering the impact of filter choice on phase sensitivity and OCT image quality. Our results indicate that the complex FIR filter approach is the most robust and accurate among those considered. It provides similar image quality and slightly better phase sensitivity than the traditional FFT-IFFT based Hilbert transform while consuming fewer resources in an FPGA implementation. We also explored utilizing the Hilbert magnitude of the reference interferogram to calculate an ideal window function for spectral amplitude calibration. The ideal window function is designed to carefully control sidelobes on the axial point spread function. We found that after a simple chromatic correction, calculating the window function using the complex FIR filter and the reference interferometer gave similar results to window functions calculated using a mirror sample and the FFT-IFFT Hilbert transform. Hence, the complex FIR filter can enable accurate and high-speed calibration of the magnitude and phase of spectral interferograms.

High-speed spectral calibration by complex FIR filter in phase-sensitive optical coherence tomography

PubMed Central

Kim, Sangmin; Raphael, Patrick D.; Oghalai, John S.; Applegate, Brian E.

2016-01-01

Swept-laser sources offer a number of advantages for Phase-sensitive Optical Coherence Tomography (PhOCT). However, inter- and intra-sweep variability leads to calibration errors that adversely affect phase sensitivity. While there are several approaches to overcoming this problem, our preferred method is to simply calibrate every sweep of the laser. This approach offers high accuracy and phase stability at the expense of a substantial processing burden. In this approach, the Hilbert phase of the interferogram from a reference interferometer provides the instantaneous wavenumber of the laser, but is computationally expensive. Fortunately, the Hilbert transform may be approximated by a Finite Impulse-Response (FIR) filter. Here we explore the use of several FIR filter based Hilbert transforms for calibration, explicitly considering the impact of filter choice on phase sensitivity and OCT image quality. Our results indicate that the complex FIR filter approach is the most robust and accurate among those considered. It provides similar image quality and slightly better phase sensitivity than the traditional FFT-IFFT based Hilbert transform while consuming fewer resources in an FPGA implementation. We also explored utilizing the Hilbert magnitude of the reference interferogram to calculate an ideal window function for spectral amplitude calibration. The ideal window function is designed to carefully control sidelobes on the axial point spread function. We found that after a simple chromatic correction, calculating the window function using the complex FIR filter and the reference interferometer gave similar results to window functions calculated using a mirror sample and the FFT-IFFT Hilbert transform. Hence, the complex FIR filter can enable accurate and high-speed calibration of the magnitude and phase of spectral interferograms. PMID:27446666

Microgravity flame spread over thick solids in low velocity opposed flow

NASA Astrophysics Data System (ADS)

Wang, Shuangfeng; Zhu, Feng

2016-07-01

Motivated primarily by fire safety of spacecraft, a renewed interest in microgravity flame spread over solid materials has arisen. With few exceptions, however, research on microgravity flame spread has been focused on thermally thin fuels due to the constraint on available test time. In this study, two sets of experiments are conducted to examine the flame spread and extinction behavior over thick PMMA in simulated and actual microgravity environments. The low-gravity flame spread environment is produced by a narrow channel apparatus in normal gravity. Extinction limits using flow velocity and oxygen concentration as coordinates are presented, and flame spread rates are determined as a function of the velocity and oxygen concentration of the gas flow. The microgravity experiments are also performed with varying low-velocity flow and varying ambient oxygen concentration. The important observations include flame behavior and appearance as a function of oxygen concentration and flow velocity, temperature variation in gas and solid phases, and flame spread rate. A comparison between simulated and actual microgravity data is made, and general agreement is found. Based on the experimental observations, mechanisms for flame spread and extinction in low velocity opposed flows are discussed.

On the universality of Marangoni-driven spreading

NASA Astrophysics Data System (ADS)

Visser, Claas; van Capelleveen, Bram; Koldeweij, Robin; Lohse, Detlef

2017-11-01

When two liquids of different surface tensions come into contact, the liquid with lower surface tension spreads over the other. Here we measure the dynamics of this Marangoni-driven spreading in the drop-drop geometry, revealing universal behavior with respect to the control parameters as well as other geometries (such as spreading over a flat interface). The distance L over which the low-surface-tension liquid has covered the high-surface-tension droplet is measured as a function of time t, surface tension difference between the liquids Δσ , and viscosity η, revealing power-law behavior L(t) tα . The exponent α is discussed for the early and late spreading regimes. Spreading inhibition is observed at high viscosity, for which the threshold is discussed. Finally, we show that our results collapse onto a single curve of dimensionless L(t) as a function of dimensionless time, which also captures previous results for different geometries, surface tension modifiers, and miscibility. As this curve spans 7 orders of magnitude, Marangoni-induced spreading can be considered a universal phenomenon for many practically encountered liquid-liquid systems.

Skin dose mapping for non-uniform x-ray fields using a backscatter point spread function

NASA Astrophysics Data System (ADS)

Vijayan, Sarath; Xiong, Zhenyu; Shankar, Alok; Rudin, Stephen; Bednarek, Daniel R.

2017-03-01

Beam shaping devices like ROI attenuators and compensation filters modulate the intensity distribution of the xray beam incident on the patient. This results in a spatial variation of skin dose due to the variation of primary radiation and also a variation in backscattered radiation from the patient. To determine the backscatter component, backscatter point spread functions (PSF) are generated using EGS Monte-Carlo software. For this study, PSF's were determined by simulating a 1 mm beam incident on the lateral surface of an anthropomorphic head phantom and a 20 cm thick PMMA block phantom. The backscatter PSF's for the head phantom and PMMA phantom are curve fit with a Lorentzian function after being normalized to the primary dose intensity (PSFn). PSFn is convolved with the primary dose distribution to generate the scatter dose distribution, which is added to the primary to obtain the total dose distribution. The backscatter convolution technique is incorporated in the dose tracking system (DTS), which tracks skin dose during fluoroscopic procedures and provides a color map of the dose distribution on a 3D patient graphic model. A convolution technique is developed for the backscatter dose determination for the nonuniformly spaced graphic-model surface vertices. A Gafchromic film validation was performed for shaped x-ray beams generated with an ROI attenuator and with two compensation filters inserted into the field. The total dose distribution calculated by the backscatter convolution technique closely agreed with that measured with the film.

Optimum constrained image restoration filters

NASA Technical Reports Server (NTRS)

Riemer, T. E.; Mcgillem, C. D.

1974-01-01

The filter was developed in Hilbert space by minimizing the radius of gyration of the overall or composite system point-spread function subject to constraints on the radius of gyration of the restoration filter point-spread function, the total noise power in the restored image, and the shape of the composite system frequency spectrum. An iterative technique is introduced which alters the shape of the optimum composite system point-spread function, producing a suboptimal restoration filter which suppresses undesirable secondary oscillations. Finally this technique is applied to multispectral scanner data obtained from the Earth Resources Technology Satellite to provide resolution enhancement. An experimental approach to the problems involving estimation of the effective scanner aperture and matching the ERTS data to available restoration functions is presented.

Spreading law of non-Newtonian power-law liquids on a spherical substrate by an energy-balance approach.

PubMed

Iwamatsu, Masao

2017-07-01

The spreading of a cap-shaped spherical droplet of non-Newtonian power-law liquids, both shear-thickening and shear-thinning liquids, that completely wet a spherical substrate is theoretically investigated in the capillary-controlled spreading regime. The crater-shaped droplet model with the wedge-shaped meniscus near the three-phase contact line is used to calculate the viscous dissipation near the contact line. Then the energy balance approach is adopted to derive the equation that governs the evolution of the contact line. The time evolution of the dynamic contact angle θ of a droplet obeys a power law θ∼t^{-α} with the spreading exponent α, which is different from Tanner's law for Newtonian liquids and those for non-Newtonian liquids on a flat substrate. Furthermore, the line-tension dominated spreading, which could be realized on a spherical substrate for late-stage of spreading when the contact angle becomes low and the curvature of the contact line becomes large, is also investigated.

Tetrahydrocannabinol-induced suppression of macrophage spreading and phagocytic activity in vitro.

PubMed

Lopez-Cepero, M; Friedman, M; Klein, T; Friedman, H

1986-06-01

The effects of tetrahydrocannabinol (THC) on several parameters of macrophage function in vitro were assessed. Delta 9 THC added to cultures of normal mouse peritoneal cells in vitro affected the ability of the cells to spread on glass surfaces and also had some effect on their ability to phagocytize yeast. These effects were dose related. A concentration of 20 micrograms of THC almost completely inhibited macrophage spreading, but it also decreased viability and the total number of these cells. Doses of 10 or 5 micrograms of THC also inhibited spreading but had little effect on cell viability or number. A dose of 1.0 microgram of THC had some inhibitory effect on spreading and the lowest dose affecting spreading appeared to be about 0.05 micrograms per culture. Higher doses of THC were necessary to inhibit phagocytosis of yeast particles as determined by direct microscopic examination or use of radiolabeled yeast as the test particles. These results indicate that several readily measured functions of macrophages may be suppressed by THC.

Quickbird Satellite in-orbit Modulation Transfer Function (MTF) Measurement Using Edge, Pulse and Impulse Methods for Summer 2003

NASA Technical Reports Server (NTRS)

Helder, Dennis; Choi, Taeyoung; Rangaswamy, Manjunath

2005-01-01

The spatial characteristics of an imaging system cannot be expressed by a single number or simple statement. However, the Modulation Transfer Function (MTF) is one approach to measure the spatial quality of an imaging system. Basically, MTF is the normalized spatial frequency response of an imaging system. The frequency response of the system can be evaluated by applying an impulse input. The resulting impulse response is termed the Point Spread function (PSF). This function is a measure of the amount of blurring present in the imaging system and is itself a useful measure of spatial quality. An underlying assumption is that the imaging system is linear and shift-independent. The Fourier transform of the PSF is called the Optical Transfer Function (OTF) and the normalized magnitude of the OTF is the MTF. In addition to using an impulse input, a knife-edge in technique has also been used in this project. The sharp edge exercises an imaging system at all spatial frequencies. The profile of an edge response from an imaging system is called an Edge Spread Function (ESF). Differentiation of the ESF results in a one-dimensional version of the Point Spread Function (PSF). Finally, MTF can be calculated through use of Fourier transform of the PSF as stated previously. Every image includes noise in some degree which makes MTF of PSF estimation more difficult. To avoid the noise effects, many MTF estimation approaches use smooth numerical models. Historically, Gaussian models and Fermi functions were applied to reduce the random noise in the output profiles. The pulse-input method was used to measure the MTF of the Landsat Thematic Mapper (TM) using 8th order even functions over the San Mateo Bridge in San Francisco, California. Because the bridge width was smaller than the 30-meter ground sample distance (GSD) of the TM, the Nyquist frequency was located before the first zero-crossing point of the sinc function from the Fourier transformation of the bridge pulse. To avoid the zero-crossing points in the frequency domain from a pulse, the pulse width should be less than the width of two pixels (or 2 GSD's), but the short extent of the pulse results in a poor signal-to-noise ratio. Similarly, for a high-resolution satellite imaging system such as Quickbird, the input pulse width was critical because of the zero crossing points and noise present in the background area. It is important, therefore, that the width of the input pulse be appropriately sized. Finally, the MTF was calculated by taking ratio between Fourier transform of output and Fourier transform of input. Regardless of whether the edge, pulse and impulse target method is used, the orientation of the targets is critical in order to obtain uniformly spaced sub-pixel data points. When the orientation is incorrect, sample data points tend to be located in clusters that result in poor reconstruction of the edge or pulse profiles. Thus, a compromise orientation must be selected so that all spectral bands can be accommodated. This report continues by outlining the objectives in Section 2, procedures followed in Section 3, descriptions of the field campaigns in Section 4, results in Section 5, and a brief summary in Section 6.

Identification of Patient Zero in Static and Temporal Networks: Robustness and Limitations

NASA Astrophysics Data System (ADS)

Antulov-Fantulin, Nino; Lančić, Alen; Šmuc, Tomislav; Štefančić, Hrvoje; Šikić, Mile

2015-06-01

Detection of patient zero can give new insights to epidemiologists about the nature of first transmissions into a population. In this Letter, we study the statistical inference problem of detecting the source of epidemics from a snapshot of spreading on an arbitrary network structure. By using exact analytic calculations and Monte Carlo estimators, we demonstrate the detectability limits for the susceptible-infected-recovered model, which primarily depend on the spreading process characteristics. Finally, we demonstrate the applicability of the approach in a case of a simulated sexually transmitted infection spreading over an empirical temporal network of sexual interactions.

Nanoscale modeling for ultrathin liquid films: Spreading and coupled layering

NASA Astrophysics Data System (ADS)

Phillips, David Michael

The hard disk drive (HDD) industry is currently experiencing a compound annual growth rate of 100% for the areal density. Current production drives have an areal density of 80 Gbit in-2, and drives with an areal density of 100 Gbit in-2 have been recently demonstrated. While much of this growth has been fueled by the development of new read/write heads, some of this gain was achieved by reducing the spacing between the heads and the magnetic media. This in turn reduces the spacing at the head-disk interface (HDI). The HDI in a HDD system consists of a slider, which contains the read/write heads, flying over the disk surface on an air bearing. The current designed separation distance, or fly height, is less than 10 nm. This spacing is expected to reduce to a mere 5 nm within the next few years. With the reduced fly height, intermittent contacts at the HDI become more probable. Only a thin lubricant film of perfluoropolyether (PFPE) and a sputtered carbon overcoat on the disk surface protect the slider and the stored data from mechanical and thermal damage. The PFPE film is quite thin, with a thickness of less than 2 nm or about a monolayer of molecules. During an HDI contact, the PFPE film is considered sacrificial and is often depleted in the contact area. In order to maintain adequate protection for the disk surface, PFPE molecules from the surrounding film must replenish the depleted area. This replenishment ability directly opposes the requirement that the PFPE film must not spin-off of the disk surface due to the disk rotation rate, which is as high as 10,000 RPM in current drives. To balance the PFPE films to sufficiently meet both requirements, HDD manufacturers functionalized the endgroups of the PFPE molecules to allow some portion of the lubricant film to reversibly bond with the disk overcoat. The result is a lubricant film that has a slower replenishment but does not spin-off. The work presented here focuses on the replenishment ability of thin films of liquid PFPE. The experimental analogue of replenishment is the one-dimensional spreading analysis. PFPEs with functional endgroups demonstrated coupled molecular layering and dewetting phenomena during the spreading analysis, while PFPEs with nonfunctional endgroups did not. All of the PFPE thin films spread via a diffusive process and had diffusion coefficients that depended on the local film thickness. A theoretical analysis is presented here for both the governing equation and the disjoining pressure driving force for the PFPE thin film spreading. For PFPEs with non-functional endgroups, a reasonable analysis is performed on the diffusion coefficient for two classes of film: submonolayer and multilayer. The diffusion coefficient of PFPEs with functional endgroups are qualitatively linked to the gradient of the film disjoining pressure. To augment this theory, both lattice-based and off-lattice Monte Carlo simulations are conducted for PFPE film models. The lattice-based model shows the existence of a critical functional endgroup interaction strength. It is also used to study the break-up of molecular layers for a spreading film via a fractal analysis. The off-lattice model is used to calculate the anisotropic pressure tensor for the model PFPE thin film and subsequently the film disjoining pressure. The model also qualitatively analyzes of the self diffusion in the film.

The MELTSPREAD Code for Modeling of Ex-Vessel Core Debris Spreading Behavior, Code Manual – Version3-beta

DOE Office of Scientific and Technical Information (OSTI.GOV)

Farmer, M. T.

MELTSPREAD3 is a transient one-dimensional computer code that has been developed to predict the gravity-driven flow and freezing behavior of molten reactor core materials (corium) in containment geometries. Predictions can be made for corium flowing across surfaces under either dry or wet cavity conditions. The spreading surfaces that can be selected are steel, concrete, a user-specified material (e.g., a ceramic), or an arbitrary combination thereof. The corium can have a wide range of compositions of reactor core materials that includes distinct oxide phases (predominantly Zr, and steel oxides) plus metallic phases (predominantly Zr and steel). The code requires input thatmore » describes the containment geometry, melt “pour” conditions, and cavity atmospheric conditions (i.e., pressure, temperature, and cavity flooding information). For cases in which the cavity contains a preexisting water layer at the time of RPV failure, melt jet breakup and particle bed formation can be calculated mechanistically given the time-dependent melt pour conditions (input data) as well as the heatup and boiloff of water in the melt impingement zone (calculated). For core debris impacting either the containment floor or previously spread material, the code calculates the transient hydrodynamics and heat transfer which determine the spreading and freezing behavior of the melt. The code predicts conditions at the end of the spreading stage, including melt relocation distance, depth and material composition profiles, substrate ablation profile, and wall heatup. Code output can be used as input to other models such as CORQUENCH that evaluate long term core-concrete interaction behavior following the transient spreading stage. MELTSPREAD3 was originally developed to investigate BWR Mark I liner vulnerability, but has been substantially upgraded and applied to other reactor designs (e.g., the EPR), and more recently to the plant accidents at Fukushima Daiichi. The most recent round of improvements that are documented in this report have been specifically implemented to support industry in developing Severe Accident Water Management (SAWM) strategies for Boiling Water Reactors.« less

Identifying and ranking influential spreaders in complex networks by combining a local-degree sum and the clustering coefficient

NASA Astrophysics Data System (ADS)

Li, Mengtian; Zhang, Ruisheng; Hu, Rongjing; Yang, Fan; Yao, Yabing; Yuan, Yongna

2018-03-01

Identifying influential spreaders is a crucial problem that can help authorities to control the spreading process in complex networks. Based on the classical degree centrality (DC), several improved measures have been presented. However, these measures cannot rank spreaders accurately. In this paper, we first calculate the sum of the degrees of the nearest neighbors of a given node, and based on the calculated sum, a novel centrality named clustered local-degree (CLD) is proposed, which combines the sum and the clustering coefficients of nodes to rank spreaders. By assuming that the spreading process in networks follows the susceptible-infectious-recovered (SIR) model, we perform extensive simulations on a series of real networks to compare the performances between the CLD centrality and other six measures. The results show that the CLD centrality has a competitive performance in distinguishing the spreading ability of nodes, and exposes the best performance to identify influential spreaders accurately.

The starting transient of solid propellant rocket motors with high internal gas velocities. Ph.D. Thesis

NASA Technical Reports Server (NTRS)

Peretz, A.; Caveny, L. H.; Kuo, K. K.; Summerfield, M.

1973-01-01

A comprehensive analytical model which considers time and space development of the flow field in solid propellant rocket motors with high volumetric loading density is described. The gas dynamics in the motor chamber is governed by a set of hyperbolic partial differential equations, that are coupled with the ignition and flame spreading events, and with the axial variation of mass addition. The flame spreading rate is calculated by successive heating-to-ignition along the propellant surface. Experimental diagnostic studies have been performed with a rectangular window motor (50 cm grain length, 5 cm burning perimeter and 1 cm hydraulic port diameter), using a controllable head-end gaseous igniter. Tests were conducted with AP composite propellant at port-to-throat area ratios of 2.0, 1.5, 1.2, and 1.06, and head-end pressures from 35 to 70 atm. Calculated pressure transients and flame spreading rates are in very good agreement with those measured in the experimental system.

Dynamics of bid-ask spread return and volatility of the Chinese stock market

NASA Astrophysics Data System (ADS)

Qiu, Tian; Chen, Guang; Zhong, Li-Xin; Wu, Xiao-Run

2012-04-01

The bid-ask spread is taken as an important measure of the financial market liquidity. In this article, we study the dynamics of the spread return and the spread volatility of four liquid stocks in the Chinese stock market, including the memory effect and the multifractal nature. By investigating the autocorrelation function and the Detrended Fluctuation Analysis (DFA), we find that the spread return is the lack of long-range memory, while the spread volatility is long-range time correlated. Besides, the spread volatilities of different stocks present long-range cross-correlations. Moreover, by applying the Multifractal Detrended Fluctuation Analysis (MF-DFA), the spread return is observed to possess a strong multifractality, which is similar to the dynamics of a variety of financial quantities. Different from the spread return, the spread volatility exhibits a weak multifractal nature.

Communication: A combined periodic density functional and incremental wave-function-based approach for the dispersion-accounting time-resolved dynamics of ⁴He nanodroplets on surfaces: ⁴He/graphene.

PubMed

de Lara-Castells, María Pilar; Stoll, Hermann; Civalleri, Bartolomeo; Causà, Mauro; Voloshina, Elena; Mitrushchenkov, Alexander O; Pi, Martí

2014-10-21

In this work we propose a general strategy to calculate accurate He-surface interaction potentials. It extends the dispersionless density functional approach recently developed by Pernal et al. [Phys. Rev. Lett. 103, 263201 (2009)] to adsorbate-surface interactions by including periodic boundary conditions. We also introduce a scheme to parametrize the dispersion interaction by calculating two- and three-body dispersion terms at coupled cluster singles and doubles and perturbative triples (CCSD(T)) level via the method of increments [H. Stoll, J. Chem. Phys. 97, 8449 (1992)]. The performance of the composite approach is tested on (4)He/graphene by determining the energies of the low-lying selective adsorption states, finding an excellent agreement with the best available theoretical data. Second, the capability of the approach to describe dispersionless correlation effects realistically is used to extract dispersion effects in time-dependent density functional simulations on the collision of (4)He droplets with a single graphene sheet. It is found that dispersion effects play a key role in the fast spreading of the (4)He nanodroplet, the evaporation-like process of helium atoms, and the formation of solid-like helium structures. These characteristics are expected to be quite general and highly relevant to explain experimental measurements with the newly developed helium droplet mediated deposition technique.

Properties of rice bran oil-derived functional ingredients

USDA-ARS?s Scientific Manuscript database

Lipid ingredients that demonstrate high stability and positive health profiles without the use of trans-fats are needed in the food supply. Rice bran oil can be fractionated at low temperatures to create a series of spreads that show promise as functional ingredients. A rice bran oil-derived spread ...

SNARE-mediated trafficking of {alpha}{sub 5}{beta}{sub 1} integrin is required for spreading in CHO cells

DOE Office of Scientific and Technical Information (OSTI.GOV)

Skalski, Michael; Coppolino, Marc G.

2005-10-07

In this study, the role of SNARE-mediated membrane traffic in regulating integrin localization was examined and the requirement for SNARE function in cellular spreading was quantitatively assessed. Membrane traffic was inhibited with the VAMP-specific catalytic light chain from tetanus toxin (TeTx-LC), a dominant-negative form (E329Q) of N-ethylmaleimide-sensitive fusion protein (NSF), and brefeldin A (BfA). Inhibition of membrane traffic with either E329Q-NSF or TeTx-LC, but not BfA, significantly inhibited spreading of CHO cells on fibronectin. Spreading was rescued in TeTx-LC-expressing cells by co-transfection with a TeTx-resistant cellubrevin/VAMP3. E329Q-NSF, a general inhibitor of SNARE function, was a more potent inhibitor of cellmore » spreading than TeTx-LC, suggesting that tetanus toxin-insensitive SNAREs contribute to adhesion. It was found that E329Q-NSF prevented trafficking of {alpha}{sub 5}{beta}{sub 1} integrins from a central Rab11-containing compartment to sites of protrusion during cell adhesion, while TeTx-LC delayed this trafficking. These results are consistent with a model of cellular adhesion that implicates SNARE function as an important component of integrin trafficking during the process of cell spreading.« less

Monolayer Adsorption of Ar and Kr on Graphite: Theoretical Isotherms and Spreading Pressures

PubMed

Mulero; Cuadros

1997-02-01

The validity of analytical equations for two-dimensional fluids in the prediction of monolayer adsorption isotherms and spreading pressures of rare gases on graphite is analyzed. The statistical mechanical theory of Steele is used to relate the properties of the adsorbed and two-dimensional fluids. In such theory the model of graphite is a perfectly flat surface, which means that only the first order contribution of the fluid-solid interactions are taken into account. Two analytical equations for two-dimensional Lennard-Jones fluids are used: one proposed by Reddy-O'Shea, based in the fit on pressure and potential energy computer simulated results, and other proposed by Cuadros-Mulero, based in the fit of the Helmholtz free energy calculated from computer simulated results of the radial distribution function. The theoretical results are compared with experimental results of Constabaris et al. (J. Chem. Phys. 37, 915 (1962)) for Ar and of Putnam and Fort (J. Phys. Chem. 79, 459 (1975)) for Kr. Good agreement is found using both equations in both cases.

Morphoregulatory functions of the RNA-binding motif protein 3 in cell spreading, polarity and migration.

PubMed

Pilotte, J; Kiosses, W; Chan, S W; Makarenkova, H P; Dupont-Versteegden, E; Vanderklish, P W

2018-05-09

RNA-binding proteins are emerging as key regulators of transitions in cell morphology. The RNA-binding motif protein 3 (RBM3) is a cold-inducible RNA-binding protein with broadly relevant roles in cellular protection, and putative functions in cancer and development. Several findings suggest that RBM3 has morphoregulatory functions germane to its roles in these contexts. For example, RBM3 helps maintain the morphological integrity of cell protrusions during cell stress and disease. Moreover, it is highly expressed in migrating neurons of the developing brain and in cancer invadopodia, suggesting roles in migration. We here show that RBM3 regulates cell polarity, spreading and migration. RBM3 was present in spreading initiation centers, filopodia and blebs that formed during cell spreading in cell lines and primary myoblasts. Reducing RBM3 triggered exaggerated spreading, increased RhoA expression, and a loss of polarity that was rescued by Rho kinase inhibition and overexpression of CRMP2. High RBM3 expression enhanced the motility of cells migrating by a mesenchymal mode involving extension of long protrusions, whereas RBM3 knockdown slowed migration, greatly reducing the ability of cells to extend protrusions and impairing multiple processes that require directional migration. These data establish novel functions of RBM3 of potential significance to tissue repair, metastasis and development.

On the parametrization of lateral dose profiles in proton radiation therapy.

PubMed

Bellinzona, V E; Ciocca, M; Embriaco, A; Fontana, A; Mairani, A; Mori, M; Parodi, K

2015-07-01

The accurate evaluation of the lateral dose profile is an important issue in the field of proton radiation therapy. The beam spread, due to Multiple Coulomb Scattering (MCS), is described by the Molière's theory. To take into account also the contribution of nuclear interactions, modern Treatment Planning Systems (TPSs) generally approximate the dose profiles by a sum of Gaussian functions. In this paper we have compared different parametrizations for the lateral dose profile of protons in water for therapeutical energies: the goal is to improve the performances of the actual treatment planning. We have simulated typical dose profiles at the CNAO (Centro Nazionale di Adroterapia Oncologica) beamline with the FLUKA code and validated them with data taken at CNAO considering different energies and depths. We then performed best fits of the lateral dose profiles for different functions using ROOT and MINUIT. The accuracy of the best fits was analyzed by evaluating the reduced χ(2), the number of free parameters of the functions and the calculation time. The best results were obtained with the triple Gaussian and double Gaussian Lorentz-Cauchy functions which have 6 parameters, but good results were also obtained with the so called Gauss-Rutherford function which has only 4 parameters. The comparison of the studied functions with accurate and validated Monte Carlo calculations and with experimental data from CNAO lead us to propose an original parametrization, the Gauss-Rutherford function, to describe the lateral dose profiles of proton beams. Copyright © 2015 Associazione Italiana di Fisica Medica. Published by Elsevier Ltd. All rights reserved.

Accurate simulation of backscattering spectra in the presence of sharp resonances

NASA Astrophysics Data System (ADS)

Barradas, N. P.; Alves, E.; Jeynes, C.; Tosaki, M.

2006-06-01

In elastic backscattering spectrometry, the shape of the observed spectrum due to resonances in the nuclear scattering cross-section is influenced by many factors. If the energy spread of the beam before interaction is larger than the resonance width, then a simple convolution with the energy spread on exit and with the detection system resolution will lead to a calculated spectrum with a resonance much sharper than the observed signal. Also, the yield from a thin layer will not be calculated accurately. We have developed an algorithm for the accurate simulation of backscattering spectra in the presence of sharp resonances. Albeit approximate, the algorithm leads to dramatic improvements in the quality and accuracy of the simulations. It is simple to implement and leads to only small increases of the calculation time, being thus suitable for routine data analysis. We show different experimental examples, including samples with roughness and porosity.

Simulation of Non-Uniform Electron Beams in the Gyrotron Electron-Optical System

NASA Astrophysics Data System (ADS)

Louksha, O. I.; Trofimov, P. A.

2018-04-01

New calculated data on the effect of emission inhomogeneities on the quality of the electron beam, which is formed in an electron-optical system of a gyrotron, have been obtained. The calculations were based on emission current density distributions, which were measured for the different cathodes in the gyrotron of Peter the Great St. Petersburg Polytechnic University. A satisfactory agreement between the experimental and calculated data on the influence of emission nonuniformities on the velocity spread of electrons has been shown. The necessity of considering the real distribution of the emission current density over the cathode surface to determine the main parameters of the electron beam—the velocity and energy spreads of the electrons, spatial structure of the beam, and coefficient of reflection of electrons from the magnetic mirror—has been demonstrated. The maximum level of emission inhomogeneities, which are permissible for effective work of gyrotrons, has been discussed.

Characteristics of poly- and mono-crystalline BeO and SiO2 as thermal and cold neutron filters

NASA Astrophysics Data System (ADS)

Adib, M.; Habib, N.; Bashter, I. I.; Morcos, H. N.; El-Mesiry, M. S.; Mansy, M. S.

2015-09-01

A simple model along with a computer code "HEXA-FILTERS" is used to carry out the calculation of the total cross-sections of BeO and SiO2 having poly or mono-crystalline form as a function of neutron wavelength at room (R.T.) and liquid nitrogen (L.N.) temperatures. An overall agreement is indicated between the calculated neutron cross-sections and experimental data. Calculation shows that 25 cm thick of polycrystalline BeO cooled at liquid nitrogen temperature was found to be a good filter for neutron wavelengths longer than 0.46 nm. While, 50 cm of SiO2, with much less transmission, for neutrons with wavelengths longer than 0.85 nm. It was also found that 10 cm of BeO and 15 cm SiO2 thick mono-crystals cut along their (0 0 2) plane, with 0.5° FWHM on mosaic spread and cooled at L.N., are a good thermal neutron filter, with high effect-to-noise ratio.

Attenuation of thermal neutrons by an imperfect single crystal

NASA Astrophysics Data System (ADS)

Naguib, K.; Adib, M.

1996-06-01

A semi-empirical formula is given which allows one to calculate the total thermal cross section of an imperfect single crystal as a function of crystal constants, temperature and neutron energy E, in the energy range between 3 meV and 10 eV. The formula also includes the contribution of the parasitic Bragg scattering to the total cross section that takes into account the crystal mosaic spread value and its orientation with respect to the neutron beam direction. A computer program (ISCANF) was developed to calculate the total attenuation of neutrons using the proposed formula. The ISCANF program was applied to investigate the neutron attenuation through a copper single crystal. The calculated values of the neutron transmission through the imperfect copper single crystal were fitted to the measured ones in the energy range 3 - 40 meV at different crystal orientations. The result of fitting shows that use of the computer program ISCANF allows one to predict the behaviour of the total cross section of an imperfect copper single crystal for the whole energy range.

Emergence of two lamellas during impact of compound droplets

NASA Astrophysics Data System (ADS)

Liu, Dongdong; Tran, Tuan

2018-05-01

A compound droplet consisting of water and silicone oil either spreads or splashes upon impacting a solid surface. We show that the transition from spreading to splashing of this type of compound droplet can be changed by varying the volumetric oil ratio in the droplets. In the spreading regime, we observe a surprising emergence of two lamellas spreading one after the other: the first spreading lamella consists of only oil and the trailing one water. We show that the two lamellas eventually meet, significantly affecting the spreading dynamics. Finally, we quantify the maximum spreading radius and show that it is a function of both the impact velocity and the volumetric oil ratio.

Optimal Design for Hetero-Associative Memory: Hippocampal CA1 Phase Response Curve and Spike-Timing-Dependent Plasticity

PubMed Central

Miyata, Ryota; Ota, Keisuke; Aonishi, Toru

2013-01-01

Recently reported experimental findings suggest that the hippocampal CA1 network stores spatio-temporal spike patterns and retrieves temporally reversed and spread-out patterns. In this paper, we explore the idea that the properties of the neural interactions and the synaptic plasticity rule in the CA1 network enable it to function as a hetero-associative memory recalling such reversed and spread-out spike patterns. In line with Lengyel’s speculation (Lengyel et al., 2005), we firstly derive optimally designed spike-timing-dependent plasticity (STDP) rules that are matched to neural interactions formalized in terms of phase response curves (PRCs) for performing the hetero-associative memory function. By maximizing object functions formulated in terms of mutual information for evaluating memory retrieval performance, we search for STDP window functions that are optimal for retrieval of normal and doubly spread-out patterns under the constraint that the PRCs are those of CA1 pyramidal neurons. The system, which can retrieve normal and doubly spread-out patterns, can also retrieve reversed patterns with the same quality. Finally, we demonstrate that purposely designed STDP window functions qualitatively conform to typical ones found in CA1 pyramidal neurons. PMID:24204822

Radiological detection of extracapsular spread in head and neck squamous cell carcinoma (HNSCC) cervical metastases.

PubMed

Url, C; Schartinger, V H; Riechelmann, H; Glückert, R; Maier, H; Trumpp, M; Widmann, G

2013-10-01

Extracapsular spread of cervical lymph nodes deteriorates the prognosis of patients with head and neck squamous cell carcinoma. Postoperative radiochemotherapy is superior to postoperative radiotherapy alone in patients with histologically proven extracapsular spread. If extracapsular spread can be detected preoperatively, patients may favor primary radiochemotherapy instead of primary surgery plus postoperative radiochemotherapy. Computed tomography (CT) scans of nodal positive head and neck squamous cell carcinoma patients treated between 2008 and 2010 with comprehensive neck dissection as part of first line surgical treatment were retrospectively scanned for extracapsular spread by two blinded radiologists. If a positive lymph node was identified by the pathologist, CT scans were assessed for extracapsular spread retrospectively. CT criteria for Extracapsular spread were apparent fat and soft tissue infiltration or infiltration of sternocleidomastoid muscle, internal jugular vein or carotid artery. Radiologic judgment was compared with histological evidence of extracapsular spread and specificity and sensitivity of CT detection was calculated. Forty-nine patients with histologically proven positive lymph nodes (pN+) were included. Extracapsular spread was histologically proven in 17 cases; the number of all affected lymph nodes was not listed. Radiologist 1 found extracapsular spread in CT scans of 15/49 patients and radiologist 2 in 16/49 patients (Cohen's kappa=0.86; p<0.01). Sensitivity of radiologic extracapsular spread detection was 73% (95% confidential index (CI): 44.0-89.7%) and specificity 91% (75.0-98.0%). Extracapsular spread depicted on computed tomography using strict criteria has high specificity. Copyright © 2013 Elsevier Ireland Ltd. All rights reserved.

Beam-width spreading of vortex beams in free space

NASA Astrophysics Data System (ADS)

Wang, Weiwei; Li, Jinhong; Duan, Meiling

2018-01-01

Based on the extended Huygens-Fresnel principle and the definition of second-order moments of the Wigner distribution function, the analytical expression for the beam-width spreading of Gaussian Schell-model (GSM) vortex beams in free space are derived, and used to study the influence of beam parameters on the beam-width spreading of GSM vortex beams. With the increment of the propagation distance, the beam-width spreading of GSM vortex beams will increase; the bigger the topological charge, spatial correlation length, wavelength and waist width are, the smaller the beam-width spreading is.

Operator Spreading in Random Unitary Circuits

NASA Astrophysics Data System (ADS)

Nahum, Adam; Vijay, Sagar; Haah, Jeongwan

2018-04-01

Random quantum circuits yield minimally structured models for chaotic quantum dynamics, which are able to capture, for example, universal properties of entanglement growth. We provide exact results and coarse-grained models for the spreading of operators by quantum circuits made of Haar-random unitaries. We study both 1 +1 D and higher dimensions and argue that the coarse-grained pictures carry over to operator spreading in generic many-body systems. In 1 +1 D , we demonstrate that the out-of-time-order correlator (OTOC) satisfies a biased diffusion equation, which gives exact results for the spatial profile of the OTOC and determines the butterfly speed vB. We find that in 1 +1 D , the "front" of the OTOC broadens diffusively, with a width scaling in time as t1 /2. We address fluctuations in the OTOC between different realizations of the random circuit, arguing that they are negligible in comparison to the broadening of the front within a realization. Turning to higher dimensions, we show that the averaged OTOC can be understood exactly via a remarkable correspondence with a purely classical droplet growth problem. This implies that the width of the front of the averaged OTOC scales as t1 /3 in 2 +1 D and as t0.240 in 3 +1 D (exponents of the Kardar-Parisi-Zhang universality class). We support our analytic argument with simulations in 2 +1 D . We point out that, in two or higher spatial dimensions, the shape of the spreading operator at late times is affected by underlying lattice symmetries and, in general, is not spherical. However, when full spatial rotational symmetry is present in 2 +1 D , our mapping implies an exact asymptotic form for the OTOC, in terms of the Tracy-Widom distribution. For an alternative perspective on the OTOC in 1 +1 D , we map it to the partition function of an Ising-like statistical mechanics model. As a result of special structure arising from unitarity, this partition function reduces to a random walk calculation which can be performed exactly. We also use this mapping to give exact results for entanglement growth in 1 +1 D circuits.

Practical Weak-lensing Shear Measurement with Metacalibration

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sheldon, Erin S.; Huff, Eric M.

2017-05-20

Metacalibration is a recently introduced method to accurately measure weak gravitational lensing shear using only the available imaging data, without need for prior information about galaxy properties or calibration from simulations. The method involves distorting the image with a small known shear, and calculating the response of a shear estimator to that applied shear. The method was shown to be accurate in moderate-sized simulations with galaxy images that had relatively high signal-to-noise ratios, and without significant selection effects. In this work we introduce a formalism to correct for both shear response and selection biases. We also observe that for imagesmore » with relatively low signal-to-noise ratios, the correlated noise that arises during the metacalibration process results in significant bias, for which we develop a simple empirical correction. To test this formalism, we created large image simulations based on both parametric models and real galaxy images, including tests with realistic point-spread functions. We varied the point-spread function ellipticity at the five-percent level. In each simulation we applied a small few-percent shear to the galaxy images. We introduced additional challenges that arise in real data, such as detection thresholds, stellar contamination, and missing data. We applied cuts on the measured galaxy properties to induce significant selection effects. Using our formalism, we recovered the input shear with an accuracy better than a part in a thousand in all cases.« less

Monte-Carlo simulation of spatial resolution of an image intensifier in a saturation mode

NASA Astrophysics Data System (ADS)

Xie, Yuntao; Wang, Xi; Zhang, Yujun; Sun, Xiaoquan

2018-04-01

In order to investigate the spatial resolution of an image intensifier which is irradiated by high-energy pulsed laser, a three-dimensional electron avalanche model was built and the cascade process of the electrons was numerically simulated. The influence of positive wall charges, due to the failure of replenishing charges extracted from the channel during the avalanche, was considered by calculating its static electric field through particle-in-cell (PIC) method. By tracing the trajectory of electrons throughout the image intensifier, the energy of the electrons at the output of the micro channel plate and the electron distribution at the phosphor screen are numerically calculated. The simulated energy distribution of output electrons are in good agreement with experimental data of previous studies. In addition, the FWHM extensions of the electron spot at phosphor screen as a function of the number of incident electrons are calculated. The results demonstrate that the spot size increases significantly with the increase in the number of incident electrons. Furthermore, we got the MTFs of the image intensifier by Fourier transform of a point spread function at phosphor screen. Comparison between the MTFs in our model and the MTFs by analytic method shows that spatial resolution of the image intensifier decreases significantly as the number of incident electrons increases, and it is particularly obvious when incident electron number greater than 100.

Course for undergraduate students: analysis of the retinal image quality of a human eye model

NASA Astrophysics Data System (ADS)

del Mar Pérez, Maria; Yebra, Ana; Fernández-Oliveras, Alicia; Ghinea, Razvan; Ionescu, Ana M.; Cardona, Juan C.

2014-07-01

In teaching of Vision Physics or Physiological Optics, the knowledge and analysis of the aberration that the human eye presents are of great interest, since this information allows a proper evaluation of the quality of the retinal image. The objective of the present work is that the students acquire the required competencies which will allow them to evaluate the optical quality of the human visual system for emmetropic and ammetropic eye, both with and without the optical compensation. For this purpose, an optical system corresponding to the Navarro-Escudero eye model, which allows calculating and evaluating the aberration of this eye model in different ammetropic conditions, was developed employing the OSLO LT software. The optical quality of the visual system will be assessed through determinations of the third and fifth order aberration coefficients, the impact diagram, wavefront analysis, calculation of the Point Spread Function and the Modulation Transfer Function for ammetropic individuals, with myopia or hyperopia, both with or without the optical compensation. This course is expected to be of great interest for student of Optics and Optometry Sciences, last courses of Physics or medical sciences related with human vision.

Calculation of free turbulent mixing by interaction approach.

NASA Technical Reports Server (NTRS)

Morel, T.; Torda, T. P.

1973-01-01

The applicability of Bradshaw's interaction hypothesis to two-dimensional free shear flows was investigated. According to it, flows with velocity extrema may be considered to consist of several interacting layers. The hypothesis leads to a new expression for the shear stress which removes the usual restriction that shear stress vanishes at the velocity extremum. The approach is based on kinetic energy and the length scale equations. The compressible flow equations are simplified by restriction to low Mach numbers, and the range of their applicability is discussed. The empirical functions of the turbulence model are found here to be correlated with the spreading rate of the shear layer. The analysis demonstrates that the interaction hypothesis is a workable concept.

Electronic transport in disordered chains with saturable nonlinearity

NASA Astrophysics Data System (ADS)

dos Santos, J. L. L.; Nguyen, Ba Phi; de Moura, F. A. B. F.

2015-10-01

In this work we study numerically the dynamics of an initially localized wave packet in one-dimensional disordered chains with saturable nonlinearity. By using the generalized discrete nonlinear Schrödinger equation, we calculate two different physical quantities as a function of time, which are the participation number and the mean square displacement from the excitation site. From detailed numerical analysis, we find that the saturable nonlinearity can promote a sub-diffusive spreading of the wave packet even in the presence of diagonal disorder for a long time. In addition, we also investigate the effect of the saturated nonlinearity for initial times of the electronic evolution thus showing the possibility of mobile breather-like modes.

Evaluation of the image quality of telescopes using the star test

NASA Astrophysics Data System (ADS)

Vazquez y Monteil, Sergio; Salazar Romero, Marcos A.; Gale, David M.

2004-10-01

The Point Spread Function (PSF) or star test is one of the main criteria to be considered in the quality of the image formed by a telescope. In a real system the distribution of irradiance in the image of a point source is given by the PSF, a function which is highly sensitive to aberrations. The PSF of a telescope may be determined by measuring the intensity distribution in the image of a star. Alternatively, if we already know the aberrations present in the optical system, then we may use diffraction theory to calculate the function. In this paper we propose a method for determining the wavefront aberrations from the PSF, using Genetic Algorithms to perform an optimization process starting from the PSF instead of the more traditional method of adjusting an aberration polynomial. We show that this method of phase recuperation is immune to noise-induced errors arising during image aquisition and registration. Some practical results are shown.

Lunar-edge based on-orbit modulation transfer function (MTF) measurement

NASA Astrophysics Data System (ADS)

Cheng, Ying; Yi, Hongwei; Liu, Xinlong

2017-10-01

Modulation transfer function (MTF) is an important parameter for image quality evaluation of on-orbit optical image systems. Various methods have been proposed to determine the MTF of an imaging system which are based on images containing point, pulse and edge features. In this paper, the edge of the moon can be used as a high contrast target to measure on-orbit MTF of image systems based on knife-edge methods. The proposed method is an extension of the ISO 12233 Slanted-edge Spatial Frequency Response test, except that the shape of the edge is a circular arc instead of a straight line. In order to get more accurate edge locations and then obtain a more authentic edge spread function (ESF), we choose circular fitting method based on least square to fit lunar edge in sub-pixel edge detection process. At last, simulation results show that the MTF value at Nyquist frequency calculated using our lunar edge method is reliable and accurate with error less than 2% comparing with theoretical MTF value.

Exploration of material removal rate of srf elliptical cavities as a function of media type and cavity shape on niobium and copper using centrifugal barrel polishing (cbp)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Palczewski, Ari; Ciovati, Gianluigi; Li, Yongming

Centrifugal barrel polishing (cbp) for SRF application is becoming more wide spread as the technique for cavity surface preparation. CBP is now being used in some form at SRF laboratories around the world including in the US, Europe and Asia. Before the process can become as mature as wet chemistry like eletro-polishing (EP) and buffered chemical polishing (BCP) there are many questions which remain unanswered. One of these topics includes the uniformity of removal as a function of cavity shape and material type. In this presentation we show CBP removal rates for various media types on 1.3 GHz TESLA andmore » 1.5 GHz CEBAF large/fine grain niobium cavities, and 1.3GHz low surface field copper cavity. The data will also include calculated RF frequency shift modeling non-uniform removal as a function of cavity position and comparing them with CBP results.« less

Research on Free Electron Lasers

DTIC Science & Technology

1989-01-01

<exp(Aa)vo) >A = exp((YG -o/2) (67) For the exponential distribution function is another example that results from a symmetric angular spread in the...vo = 47 when there is an angular spread. This indicates that the actual peak moves to the right when 00 increases. The last term term decreases the...value of the gain at vo = F7 when either the angular spread ag or energy spread OG increases. 10. SPIE FEL Review Paper During the contracting period

The point-spread function measure of resolution for the 3-D electrical resistivity experiment

NASA Astrophysics Data System (ADS)

Oldenborger, Greg A.; Routh, Partha S.

2009-02-01

The solution appraisal component of the inverse problem involves investigation of the relationship between our estimated model and the actual model. However, full appraisal is difficult for large 3-D problems such as electrical resistivity tomography (ERT). We tackle the appraisal problem for 3-D ERT via the point-spread functions (PSFs) of the linearized resolution matrix. The PSFs represent the impulse response of the inverse solution and quantify our parameter-specific resolving capability. We implement an iterative least-squares solution of the PSF for the ERT experiment, using on-the-fly calculation of the sensitivity via an adjoint integral equation with stored Green's functions and subgrid reduction. For a synthetic example, analysis of individual PSFs demonstrates the truly 3-D character of the resolution. The PSFs for the ERT experiment are Gaussian-like in shape, with directional asymmetry and significant off-diagonal features. Computation of attributes representative of the blurring and localization of the PSF reveal significant spatial dependence of the resolution with some correlation to the electrode infrastructure. Application to a time-lapse ground-water monitoring experiment demonstrates the utility of the PSF for assessing feature discrimination, predicting artefacts and identifying model dependence of resolution. For a judicious selection of model parameters, we analyse the PSFs and their attributes to quantify the case-specific localized resolving capability and its variability over regions of interest. We observe approximate interborehole resolving capability of less than 1-1.5m in the vertical direction and less than 1-2.5m in the horizontal direction. Resolving capability deteriorates significantly outside the electrode infrastructure.

Twelve mortal sins of the turbulence propagation science

NASA Astrophysics Data System (ADS)

Charnotskii, Mikhail

2011-09-01

In this review paper we discuss a series of typical mistakes and omissions that are made by engineers and scientists involved in the theoretical research and modeling of the optical propagation through atmospheric turbulence. We show how the use of the oversimplified Gaussian spectral model of turbulence delivers the completely erroneous results for the beam wander. We address a series of common omissions related to calculations of the average beam intensity: unnecessary use of the approximations when rigorous result is available, invalid application of the RMS beam size to the turbulence-distorted beams, overlooking the simple theoretical result - average beam intensity is a convolution with the turbulent Point Spread Function (PSF). We discuss the meaning and potential dangers of the use of the quadratic structure function for modeling of the turbulent perturbations. We will also address the issues related to the energy conservation principle and reciprocity that have very important consequences for the turbulence propagation, but are frequently overlooked in the current literature. We discuss a series of misconceptions that very common in of the Scintillation Index (SI) calculations. We will clarify the infamous misunderstanding of the Rytov's approximation: vanishing scintillation at the beam focus, and show the correct weak and strong scintillation solutions for the SI at the beam focus. We discuss the flaws of the Fried model of the short-term PSF, and direct to the more accurate PSF model. We will briefly review the propagation of the polarized optical waves through turbulence and discuss the inadequacy of the recently published calculations of the electromagnetic beams calculations. We discuss some common errors in representation of the calculation results for the non-Kolmogorov turbulence.

Study of Permanent Magnet Focusing for Astronomical Camera Tubes

NASA Technical Reports Server (NTRS)

Long, D. C.; Lowrance, J. L.

1975-01-01

A design is developed of a permanent magnet assembly (PMA) useful as the magnetic focusing unit for the 35 and 70 mm (diagonal) format SEC tubes. Detailed PMA designs for both tubes are given, and all data on their magnetic configuration, size, weight, and structure of magnetic shields adequate to screen the camera tube from the earth's magnetic field are presented. A digital computer is used for the PMA design simulations, and the expected operational performance of the PMA is ascertained through the calculation of a series of photoelectron trajectories. A large volume where the magnetic field uniformity is greater than 0.5% appears obtainable, and the point spread function (PSF) and modulation transfer function(MTF) indicate nearly ideal performance. The MTF at 20 cycles per mm exceeds 90%. The weight and volume appear tractable for the large space telescope and ground based application.

Simulation and prediction of the thuringiensin abiotic degradation processes in aqueous solution by a radius basis function neural network model.

PubMed

Zhou, Jingwen; Xu, Zhenghong; Chen, Shouwen

2013-04-01

The thuringiensin abiotic degradation processes in aqueous solution under different conditions, with a pH range of 5.0-9.0 and a temperature range of 10-40°C, were systematically investigated by an exponential decay model and a radius basis function (RBF) neural network model, respectively. The half-lives of thuringiensin calculated by the exponential decay model ranged from 2.72 d to 16.19 d under the different conditions mentioned above. Furthermore, an RBF model with accuracy of 0.1 and SPREAD value 5 was employed to model the degradation processes. The results showed that the model could simulate and predict the degradation processes well. Both the half-lives and the prediction data showed that thuringiensin was an easily degradable antibiotic, which could be an important factor in the evaluation of its safety. Copyright © 2012 Elsevier Ltd. All rights reserved.

Web malware spread modelling and optimal control strategies

NASA Astrophysics Data System (ADS)

Liu, Wanping; Zhong, Shouming

2017-02-01

The popularity of the Web improves the growth of web threats. Formulating mathematical models for accurate prediction of malicious propagation over networks is of great importance. The aim of this paper is to understand the propagation mechanisms of web malware and the impact of human intervention on the spread of malicious hyperlinks. Considering the characteristics of web malware, a new differential epidemic model which extends the traditional SIR model by adding another delitescent compartment is proposed to address the spreading behavior of malicious links over networks. The spreading threshold of the model system is calculated, and the dynamics of the model is theoretically analyzed. Moreover, the optimal control theory is employed to study malware immunization strategies, aiming to keep the total economic loss of security investment and infection loss as low as possible. The existence and uniqueness of the results concerning the optimality system are confirmed. Finally, numerical simulations show that the spread of malware links can be controlled effectively with proper control strategy of specific parameter choice.

Web malware spread modelling and optimal control strategies.

PubMed

Liu, Wanping; Zhong, Shouming

2017-02-10

The popularity of the Web improves the growth of web threats. Formulating mathematical models for accurate prediction of malicious propagation over networks is of great importance. The aim of this paper is to understand the propagation mechanisms of web malware and the impact of human intervention on the spread of malicious hyperlinks. Considering the characteristics of web malware, a new differential epidemic model which extends the traditional SIR model by adding another delitescent compartment is proposed to address the spreading behavior of malicious links over networks. The spreading threshold of the model system is calculated, and the dynamics of the model is theoretically analyzed. Moreover, the optimal control theory is employed to study malware immunization strategies, aiming to keep the total economic loss of security investment and infection loss as low as possible. The existence and uniqueness of the results concerning the optimality system are confirmed. Finally, numerical simulations show that the spread of malware links can be controlled effectively with proper control strategy of specific parameter choice.

Web malware spread modelling and optimal control strategies

PubMed Central

Liu, Wanping; Zhong, Shouming

2017-01-01

The popularity of the Web improves the growth of web threats. Formulating mathematical models for accurate prediction of malicious propagation over networks is of great importance. The aim of this paper is to understand the propagation mechanisms of web malware and the impact of human intervention on the spread of malicious hyperlinks. Considering the characteristics of web malware, a new differential epidemic model which extends the traditional SIR model by adding another delitescent compartment is proposed to address the spreading behavior of malicious links over networks. The spreading threshold of the model system is calculated, and the dynamics of the model is theoretically analyzed. Moreover, the optimal control theory is employed to study malware immunization strategies, aiming to keep the total economic loss of security investment and infection loss as low as possible. The existence and uniqueness of the results concerning the optimality system are confirmed. Finally, numerical simulations show that the spread of malware links can be controlled effectively with proper control strategy of specific parameter choice. PMID:28186203

Code-Time Diversity for Direct Sequence Spread Spectrum Systems

PubMed Central

Hassan, A. Y.

2014-01-01

Time diversity is achieved in direct sequence spread spectrum by receiving different faded delayed copies of the transmitted symbols from different uncorrelated channel paths when the transmission signal bandwidth is greater than the coherence bandwidth of the channel. In this paper, a new time diversity scheme is proposed for spread spectrum systems. It is called code-time diversity. In this new scheme, N spreading codes are used to transmit one data symbol over N successive symbols interval. The diversity order in the proposed scheme equals to the number of the used spreading codes N multiplied by the number of the uncorrelated paths of the channel L. The paper represents the transmitted signal model. Two demodulators structures will be proposed based on the received signal models from Rayleigh flat and frequency selective fading channels. Probability of error in the proposed diversity scheme is also calculated for the same two fading channels. Finally, simulation results are represented and compared with that of maximal ration combiner (MRC) and multiple-input and multiple-output (MIMO) systems. PMID:24982925

A new numerical formulation of gas leakage and spread into a residential space in terms of hazard analysis.

PubMed

Nagaosa, Ryuichi S

2014-04-30

This study proposes a new numerical formulation of the spread of a flammable gas leakage. A new numerical approach has been applied to establish fundamental data for a hazard assessment of flammable gas spread in an enclosed residential space. The approach employs an extended version of a two-compartment concept, and determines the leakage concentration of gas using a mass-balance based formulation. The study also introduces a computational fluid dynamics (CFD) technique for calculating three-dimensional details of the gas spread by resolving all the essential scales of fluid motions without a turbulent model. The present numerical technique promises numerical solutions with fewer uncertainties produced by the model equations while maintaining high accuracy. The study examines the effect of gas density on the concentration profiles of flammable gas spread. It also discusses the effect of gas leakage rate on gas concentration profiles. Copyright © 2014 The Authors. Published by Elsevier B.V. All rights reserved.

Probe measurements of the electron velocity distribution function in beams: Low-voltage beam discharge in helium

NASA Astrophysics Data System (ADS)

Sukhomlinov, V.; Mustafaev, A.; Timofeev, N.

2018-04-01

Previously developed methods based on the single-sided probe technique are altered and applied to measure the anisotropic angular spread and narrow energy distribution functions of charged particle (electron and ion) beams. The conventional method is not suitable for some configurations, such as low-voltage beam discharges, electron beams accelerated in near-wall and near-electrode layers, and vacuum electron beam sources. To determine the range of applicability of the proposed method, simple algebraic relationships between the charged particle energies and their angular distribution are obtained. The method is verified for the case of the collisionless mode of a low-voltage He beam discharge, where the traditional method for finding the electron distribution function with the help of a Legendre polynomial expansion is not applicable. This leads to the development of a physical model of the formation of the electron distribution function in a collisionless low-voltage He beam discharge. The results of a numerical calculation based on Monte Carlo simulations are in good agreement with the experimental data obtained using the new method.

Impact of horizontal and vertical localization scales on microwave sounder SAPHIR radiance assimilation

NASA Astrophysics Data System (ADS)

Krishnamoorthy, C.; Balaji, C.

2016-05-01

In the present study, the effect of horizontal and vertical localization scales on the assimilation of direct SAPHIR radiances is studied. An Artificial Neural Network (ANN) has been used as a surrogate for the forward radiative calculations. The training input dataset for ANN consists of vertical layers of atmospheric pressure, temperature, relative humidity and other hydrometeor profiles with 6 channel Brightness Temperatures (BTs) as output. The best neural network architecture has been arrived at, by a neuron independence study. Since vertical localization of radiance data requires weighting functions, a ANN has been trained for this purpose. The radiances were ingested into the NWP using the Ensemble Kalman Filter (EnKF) technique. The horizontal localization has been taken care of, by using a Gaussian localization function centered around the observed coordinates. Similarly, the vertical localization is accomplished by assuming a function which depends on the weighting function of the channel to be assimilated. The effect of both horizontal and vertical localizations has been studied in terms of ensemble spread in the precipitation. Aditionally, improvements in 24 hr forecast from assimilation are also reported.

Cell-free transmission of human adenovirus by passive mass transfer in cell culture simulated in a computer model.

PubMed

Yakimovich, Artur; Gumpert, Heidi; Burckhardt, Christoph J; Lütschg, Verena A; Jurgeit, Andreas; Sbalzarini, Ivo F; Greber, Urs F

2012-09-01

Viruses spread between cells, tissues, and organisms by cell-free and cell-cell transmissions. Both mechanisms enhance disease development, but it is difficult to distinguish between them. Here, we analyzed the transmission mode of human adenovirus (HAdV) in monolayers of epithelial cells by wet laboratory experimentation and a computer simulation. Using live-cell fluorescence microscopy and replication-competent HAdV2 expressing green fluorescent protein, we found that the spread of infection invariably occurred after cell lysis. It was affected by convection and blocked by neutralizing antibodies but was independent of second-round infections. If cells were overlaid with agarose, convection was blocked and round plaques developed around lytic infected cells. Infected cells that did not lyse did not give rise to plaques, highlighting the importance of cell-free transmission. Key parameters for cell-free virus transmission were the time from infection to lysis, the dose of free viruses determining infection probability, and the diffusion of single HAdV particles in aqueous medium. With these parameters, we developed an in silico model using multiscale hybrid dynamics, cellular automata, and particle strength exchange. This so-called white box model is based on experimentally determined parameters and reproduces viral infection spreading as a function of the local concentration of free viruses. These analyses imply that the extent of lytic infections can be determined by either direct plaque assays or can be predicted by calculations of virus diffusion constants and modeling.

Healthy brain connectivity predicts atrophy progression in non-fluent variant of primary progressive aphasia.

PubMed

Mandelli, Maria Luisa; Vilaplana, Eduard; Brown, Jesse A; Hubbard, H Isabel; Binney, Richard J; Attygalle, Suneth; Santos-Santos, Miguel A; Miller, Zachary A; Pakvasa, Mikhail; Henry, Maya L; Rosen, Howard J; Henry, Roland G; Rabinovici, Gil D; Miller, Bruce L; Seeley, William W; Gorno-Tempini, Maria Luisa

2016-10-01

Neurodegeneration has been hypothesized to follow predetermined large-scale networks through the trans-synaptic spread of toxic proteins from a syndrome-specific epicentre. To date, no longitudinal neuroimaging study has tested this hypothesis in vivo in frontotemporal dementia spectrum disorders. The aim of this study was to demonstrate that longitudinal progression of atrophy in non-fluent/agrammatic variant primary progressive aphasia spreads over time from a syndrome-specific epicentre to additional regions, based on their connectivity to the epicentre in healthy control subjects. The syndrome-specific epicentre of the non-fluent/agrammatic variant of primary progressive aphasia was derived in a group of 10 mildly affected patients (clinical dementia rating equal to 0) using voxel-based morphometry. From this region, the inferior frontal gyrus (pars opercularis), we derived functional and structural connectivity maps in healthy controls (n = 30) using functional magnetic resonance imaging at rest and diffusion-weighted imaging tractography. Graph theory analysis was applied to derive functional network features. Atrophy progression was calculated using voxel-based morphometry longitudinal analysis on 34 non-fluent/agrammatic patients. Correlation analyses were performed to compare volume changes in patients with connectivity measures of the healthy functional and structural speech/language network. The default mode network was used as a control network. From the epicentre, the healthy functional connectivity network included the left supplementary motor area and the prefrontal, inferior parietal and temporal regions, which were connected through the aslant, superior longitudinal and arcuate fasciculi. Longitudinal grey and white matter changes were found in the left language-related regions and in the right inferior frontal gyrus. Functional connectivity strength in the healthy speech/language network, but not in the default network, correlated with longitudinal grey matter changes in the non-fluent/agrammatic variant of primary progressive aphasia. Graph theoretical analysis of the speech/language network showed that regions with shorter functional paths to the epicentre exhibited greater longitudinal atrophy. The network contained three modules, including a left inferior frontal gyrus/supplementary motor area, which was most strongly connected with the epicentre. The aslant tract was the white matter pathway connecting these two regions and showed the most significant correlation between fractional anisotropy and white matter longitudinal atrophy changes. This study showed that the pattern of longitudinal atrophy progression in the non-fluent/agrammatic variant of primary progressive aphasia relates to the strength of connectivity in pre-determined functional and structural large-scale speech production networks. These findings support the hypothesis that the spread of neurodegeneration occurs by following specific anatomical and functional neuronal network architectures. © The Author (2016). Published by Oxford University Press on behalf of the Guarantors of Brain. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Gas Dynamics of a Recessed Nozzle in Its Displacement in the Radial Direction

NASA Astrophysics Data System (ADS)

Volkov, K. N.; Denisikhin, S. V.; Emel'yanov, V. N.

2017-07-01

Numerical simulation of gasdynamic processes accompanying the operation of the recessed nozzle of a solid-propellant rocket motor in its linear displacement is carried out. Reynolds-averaged Navier-Stokes equations closed using the equations of a k-ɛ turbulence model are used for calculations. The calculations are done for different rates of flow of the gas in the main channel and in the over-nozzle gap, and also for different displacements of the nozzle from an axisymmetric position. The asymmetry of geometry gives rise to a complicated spatial flow pattern characterized by the presence of singular points of spreading and by substantially inhomogeneous velocity and pressure distributions. The vortex flow pattern resulting from the linear displacement of the nozzle from an axisymmetric position is compared with the data of experimental visualization. The change in the vortex pattern of the flow and in the position of the singular points as a function of the flow coefficient and the displacement of the nozzle from the symmetry axis is discussed.

Phasor based single-molecule localization microscopy in 3D (pSMLM-3D): An algorithm for MHz localization rates using standard CPUs

NASA Astrophysics Data System (ADS)

Martens, Koen J. A.; Bader, Arjen N.; Baas, Sander; Rieger, Bernd; Hohlbein, Johannes

2018-03-01

We present a fast and model-free 2D and 3D single-molecule localization algorithm that allows more than 3 × 106 localizations per second to be calculated on a standard multi-core central processing unit with localization accuracies in line with the most accurate algorithms currently available. Our algorithm converts the region of interest around a point spread function to two phase vectors (phasors) by calculating the first Fourier coefficients in both the x- and y-direction. The angles of these phasors are used to localize the center of the single fluorescent emitter, and the ratio of the magnitudes of the two phasors is a measure for astigmatism, which can be used to obtain depth information (z-direction). Our approach can be used both as a stand-alone algorithm for maximizing localization speed and as a first estimator for more time consuming iterative algorithms.

PRIMELT3 MEGA.XLSM software for primary magma calculation: Peridotite primary magma MgO contents from the liquidus to the solidus

NASA Astrophysics Data System (ADS)

Herzberg, C.; Asimow, P. D.

2015-02-01

An upgrade of the PRIMELT algorithm for calculating primary magma composition is given together with its implementation in PRIMELT3 MEGA.xlsm software. It supersedes PRIMELT2.xls in correcting minor mistakes in melt fraction and computed Ni content of olivine, it identifies residuum mineralogy, and it provides a thorough analysis of uncertainties in mantle potential temperature and olivine liquidus temperature. The uncertainty analysis was made tractable by the computation of olivine liquidus temperatures as functions of pressure and partial melt MgO content between the liquidus and solidus. We present a computed anhydrous peridotite solidus in T-P space using relations amongst MgO, T and P along the solidus; it compares well with experiments on the solidus. Results of the application of PRIMELT3 to a wide range of basalts shows that the mantle sources of ocean islands and large igneous provinces were hotter than oceanic spreading centers, consistent with earlier studies and expectations of the mantle plume model.

Geodynamics of seafloor spreading extinction: Constraints from the South China Sea

NASA Astrophysics Data System (ADS)

Zhang, X.; Lin, J.; Behn, M. D.

2016-12-01

We investigate magmatism and mantle thermal structure beneath fossil spreading centers in the South China Sea (SCS), focusing on two aspects: (1) mantle thermal structure and melting, and (2) magmatism associated with seamounts. We carried out 3D geodynamic models to study thermal structure beneath the SCS during the process from initiation to cessation of seafloor spreading. Modeling results suggested that the overall mantle temperatures of the East Subbasin were significantly greater than that of the Southwest Subbasin when the seafloor spreading of both subbasins ceased at about 15-16 Ma. However, the differences in thermal structure between the two subbasins were calculated to have decreased with time. Work is in progress to couple geochemical and geophysical constraints with geodynamic modeling to investigate melt generation, fractional crystallization, and melt extraction at the fossil spreading centers in the SCS. Among the seamounts that can be identified on multi-beam bathymetry data, about half of them are located along the fossil spreading centers while the remaining located off axis. This is in contrast to fossil spreading ridges in the West Scotia Sea and Phoenix Ridge, where most seamounts are located off axis. The off-axis seamounts in the SCS also show strong asymmetry about the fossil spreading centers with most seamounts concentrated in the northern flank. Work is in progress to investigate the melting processes associated with seamounts.

A mesoscopic simulation of static and dynamic wetting using many-body dissipative particle dynamics

NASA Astrophysics Data System (ADS)

Ghorbani, Najmeh; Pishevar, Ahmadreza

2018-01-01

A many-body dissipative particle dynamics simulation is applied here to pave the way for investigating the behavior of mesoscale droplets after impact on horizontal solid substrates. First, hydrophobic and hydrophilic substrates are simulated through tuning the solid-liquid interfacial interaction parameters of an innovative conservative force model. The static contact angles are calculated on homogeneous and several patterned surfaces and compared with the predicted values by the Cassie's law in order to verify the model. The results properly evaluate the amount of increase in surface superhydrophobicity as a result of surface patterning. Then drop impact phenomenon is studied by calculating the spreading factor and dimensionless height versus dimensionless time and the comparisons made between the results and the experimental values for three different static contact angles. The results show the capability of the procedure in calculating the amount of maximum spreading factor, which is a significant concept in ink-jet printing and coating process.

Retrograde tracing and toe spreading after experimental autologous nerve transplantation and crush injury of the sciatic nerve: a descriptive methodological study.

PubMed

van Neerven, Sabien Ga; Bozkurt, Ahmet; O'Dey, Dan Mon; Scheffel, Juliane; Boecker, Arne H; Stromps, Jan-Philipp; Dunda, Sebastian; Brook, Gary A; Pallua, Norbert

2012-04-30

Evaluation of functional and structural recovery after peripheral nerve injury is crucial to determine the therapeutic effect of a nerve repair strategy. In the present study, we examined the relationship between the structural evaluation of regeneration by means of retrograde tracing and the functional analysis of toe spreading. Two standardized rat sciatic nerve injury models were used to address this relationship. As such, animals received either a 2 cm sciatic nerve defect (neurotmesis) followed by autologous nerve transplantation (ANT animals) or a crush injury with spontaneous recovery (axonotmesis; CI animals). Functional recovery of toe spreading was observed over an observation period of 84 days. In contrast to CI animals, ANT animals did not reach pre-surgical levels of toe spreading. After the observation period, the lipophilic dye DiI was applied to label sensory and motor neurons in dorsal root ganglia (DRG; sensory neurons) and spinal cord (motor neurons), respectively. No statistical difference in motor or sensory neuron counts could be detected between ANT and CI animals.In the present study we could indicate that there was no direct relationship between functional recovery (toe spreading) measured by SSI and the number of labelled (motor and sensory) neurons evaluated by retrograde tracing. The present findings demonstrate that a multimodal approach with a variety of independent evaluation tools is essential to understand and estimate the therapeutic benefit of a nerve repair strategy.

The addition effect of Tunisian date seed fibers on the quality of chocolate spreads.

PubMed

Bouaziz, Mohamed Ali; Abbes, Fatma; Mokni, Abir; Blecker, Christophe; Attia, Hamadi; Besbes, Souhail

2017-04-01

Novel chocolate spreads were enriched by soluble and insoluble dietary fibers from Tunisian Deglet Nour date seeds at 1, 2, 3, 4, and 5% levels in the conventional chocolate spread. Defatted Deglet Nour date seeds, date seed soluble fiber concentrate (DSSFC) and date seed insoluble fiber concentrate (DSIFC) were characterized by high levels of dietary fibers (80-90%). Chocolate spread enriched with 5% of DSSFC presented the highest oil binding capacity (304.62%) compared to the control (102%). Whatever the DSIFC and DSSFC incorporation levels, no significant difference was recorded between the firmness, chewiness, and adhesiveness of prepared chocolate spreads compared to the control (p < .05). Sensory evaluation revealed that all prepared chocolate spreads enriched by DSIFC and DSSFC were accepted by panelists. These results indicated the value of date seeds as new source of dietary fibers to develop chocolate spread and could also improve health benefits and functional properties. Tunisia is considered to be one of the dates-producing countries. The mean annual yield of date fruits is about 200,000 tons. From this, around 20,000 tons of date seeds could be collected. This by-product of date processing industries could be regarded as an excellent source of dietary fiber with interesting technological functionality and many beneficial effects on human health. Then, date seeds could present a value addition by extraction and use of date seed fiber concentrate in chocolate spread formulation. © 2016 Wiley Periodicals, Inc.

How the growth and freeboard of continents may relate to geometric and kinematic parameters of mid-ocean spreading ridges

USGS Publications Warehouse

Howell, D.G.

1989-01-01

If the volume of continents has been growing since 4 Ga then the area of the ocean basins must have been shrinking. Therefore, by inferring a constant continental freeboard, in addition to constant continental crustal thicknesses and seawater volume, it is possible to calculate the necessary combinations of increased ridge lengths and spreading rates required to displace the seawater in the larger oceans of the past in order to maintain the constant freeboard. A reasonable choice from the various possibilities is that at 4 Ga ago, the ridge length and spreading rates were ca. 2.5 times greater than the averages of these parameters during the past 200 Ma. By 2.5 Ga ago the ridge length and spreading rate decreased to about 1.8 times the recent average and by 1 Ga ago these features became reduced to approximately 1.4 times recent averages. ?? 1989.

Bispectral analysis of equatorial spread F density irregularities

NASA Technical Reports Server (NTRS)

Labelle, J.; Lund, E. J.

1992-01-01

Bispectral analysis has been applied to density irregularities at frequencies 5-30 Hz observed with a sounding rocket launched from Peru in March 1983. Unlike the power spectrum, the bispectrum contains statistical information about the phase relations between the Fourier components which make up the waveform. In the case of spread F data from 475 km the 5-30 Hz portion of the spectrum displays overall enhanced bicoherence relative to that of the background instrumental noise and to that expected due to statistical considerations, implying that the observed f exp -2.5 power law spectrum has a significant non-Gaussian component. This is consistent with previous qualitative analyses. The bicoherence has also been calculated for simulated equatorial spread F density irregularities in approximately the same wavelength regime, and the resulting bispectrum has some features in common with that of the rocket data. The implications of this analysis for equatorial spread F are discussed, and some future investigations are suggested.

Jet Spreading Increase by Passive Control and Associated Performance Penalty

NASA Technical Reports Server (NTRS)

Zaman, K. B. M. Q.

1999-01-01

This paper reviews the effects of 'screech', 'asymmetric nozzle shaping', 'tabs' and 'overexpansion' on the spreading of free jets. Corresponding thrust penalty for the tabs and overexpanded condition are also evaluated. The asymmetric shapes include rectangular ones with varying aspect ratio. Tabs investigated are triangular shaped 'delta-tabs' placed at the exit of a convergent circular nozzle. The effect of overexpansion is examined with circular convergent-divergent (C-D) nozzles. Tabs and overexpansion are found to yield the largest increase in jet spreading. Each, however, involves a performance penalty, i.e., a loss in thrust coefficient. Variation of the size of four delta-tabs show that there exists an optimum size for which the gain in jet spreading is the maximum per unit loss in thrust coefficient. With the C-D nozzles, the minimum in thrust coefficient is expected near the beginning of the overexpanded regime based on idealized flow calculations. The maximum increase in jet spreading, however, is found to occur at higher pressure ratios well into the overexpanded regime. The optimum benefit with the overexpanded flow, in terms of gain in spreading for unit penalty, is found to be comparable to the optimum tab case.

The specific features of pollution spread in the northwest Pacific Ocean

NASA Astrophysics Data System (ADS)

Dianskii, N. A.; Gusev, A. V.; Fomin, V. V.

2012-04-01

We present two calculations of pollutant dispersal in the Pacific Ocean: (1) during possible ship-wrecks in the process of spent nuclear fuel transportation from Petropavlovsk-Kamchatsky and (2) pollutant spread from the Japanese coast after the Fukushima-1 nuclear disaster on March 11, 2011. The circulation was calculated using a σ model of ocean hydrothermodynamics developed at the Institute of Numerical Mathematics (INM), Russian Academy of Sciences (RAS); it is adapted to cover the Pacific Ocean basin from the equator to the Bering Strait with a high (1/8)° spatial resolution and it is capable of reproducing the mesoscale ocean variations. The pollutant dispersal in the case of possible shipwrecks was estimated for currents characteristic for a statistically average year with atmospheric forcing in accordance with the so-called normal CORE year data. The pollution spread from the Fukushima-1 nuclear power plant (NPP) was estimated by calculating the circulation with the real atmospheric forcing in accordance with the NCEP analysis data obtained from the Hydrometeorological Centre of Russia. It is noteworthy that a simplified assimilation of the observed sea surface temperature (SST) was performed. In both cases the currents were calculated simultaneously with the transport calculation of the pollutant as a passive admixture, which corresponds to a real-time calculation of pollutant transport. A map analysis of pollution dispersal shows that the horizontal transport is substantially more intense in the upper ocean layers than in deep ones. Therefore, like in the North branch of Kuroshio, pollutants can be delivered to the deep layers not through deep-water horizontal transport, but rather as a result of vertical downwelling from the already contaminated upper layers. However, the complex three-dimensional structure of the horizontal and vertical transport may lead to reverse situations. A calculation of pollution transport from the Fukushima-1 NPP showed that radioactive pollution would propagate eastward and not present the danger for Russian territory. Moreover, even for an exaggerated scenario of pollution emission, the background pollution level will be exceeded only in a narrow region within 50 km of the Japanese coast.

Improved spatial resolution of luminescence images acquired with a silicon line scanning camera

NASA Astrophysics Data System (ADS)

Teal, Anthony; Mitchell, Bernhard; Juhl, Mattias K.

2018-04-01

Luminescence imaging is currently being used to provide spatially resolved defect in high volume silicon solar cell production. One option to obtain the high throughput required for on the fly detection is the use a silicon line scan cameras. However, when using a silicon based camera, the spatial resolution is reduced as a result of the weakly absorbed light scattering within the camera's chip. This paper address this issue by applying deconvolution from a measured point spread function. This paper extends the methods for determining the point spread function of a silicon area camera to a line scan camera with charge transfer. The improvement in resolution is quantified in the Fourier domain and in spatial domain on an image of a multicrystalline silicon brick. It is found that light spreading beyond the active sensor area is significant in line scan sensors, but can be corrected for through normalization of the point spread function. The application of this method improves the raw data, allowing effective detection of the spatial resolution of defects in manufacturing.

Characteristics of Solar Energetic Ions as a Function of Longitude

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cohen, C. M. S.; Mewaldt, R. A.; Mason, G. M., E-mail: cohen@srl.caltech.edu

Since the 2006 launch of STEREO , multi-spacecraft studies have yielded several surprising results regarding the spread of solar energetic particles (SEPs) within the inner heliosphere. We have investigated the role of energy and ridigity, using ACE and STEREO 10 MeV n{sup −1} oxygen data to identify 41 large SEP events observed by two or three spacecraft. We calculated fluence spectra from ∼0.1 to >10 MeV n{sup −1} for H, He, O, and Fe for each event at the observing spacecraft (including SOHO and GOES ). The particle fluences at 0.3, 1, and 10 MeV n{sup −1} were examined asmore » a function of the distance between the associated solar flare longitude and the spacecraft magnetic footpoints at the Sun to determine the longitudinal spread of particles and study how the distribution centers and widths depend on energy and charge-to-mass (Q/M) for the first time. On average, the three-spacecraft event distributions were centered at 22 ± 4° west of the flare site and were 43 ± 1° wide, though there was substantial variability, while the fit to the aggregate of the two-spacecraft event fluences yielded significantly wider distributions at 0.3 and 1 MeV n{sup −1}. The widths derived from both the three- and two-spacecraft events show an energy dependence with distributions narrowing with increasing energy, consistent with lower energy ions experiencing more field line co-rotation, or being accelerated over a larger portion of the CME-driven shock or for longer times as the shock expands. Surprisingly, no clear evidence was found for a Q/M dependence to the widths or centers suggesting that rigidity-related processes are not the dominant means of spreading particles in longitude.« less

On-Orbit Lunar Modulation Transfer Function Measurements for the Moderate Resolution Imaging Spectroradiometer

NASA Technical Reports Server (NTRS)

Choi, Taeyong; Xiong, Xiaoxiong; Wang, Zhipeng

2013-01-01

Spatial quality of an imaging sensor can be estimated by evaluating its modulation transfer function (MTF) from many different sources such as a sharp edge, a pulse target, or bar patterns with different spatial frequencies. These well-defined targets are frequently used for prelaunch laboratory tests, providing very reliable and accurate MTF measurements. A laboratory-quality edge input source was included in the spatial-mode operation of the Spectroradiometric Calibration Assembly (SRCA), which is one of the onboard calibrators of the Moderate Resolution Imaging Spectroradiometer (MODIS). Since not all imaging satellites have such an instrument, SRCA MTF estimations can be used as a reference for an on-orbit lunar MTF algorithm and results. In this paper, the prelaunch spatial quality characterization process from the Integrated Alignment Collimator and SRCA is briefly discussed. Based on prelaunch MTF calibration using the SRCA, a lunar MTF algorithm is developed and applied to the lifetime on-orbit Terra and Aqua MODIS lunar collections. In each lunar collection, multiple scan-directionMoon-to-background transition profiles are aligned by the subpixel edge locations from a parametric Fermi function fit. Corresponding accumulated edge profiles are filtered and interpolated to obtain the edge spread function (ESF). The MTF is calculated by applying a Fourier transformation on the line spread function through a simple differentiation of the ESF. The lifetime lunar MTF results are analyzed and filtered by a relationship with the Sun-Earth-MODIS angle. Finally, the filtered lunarMTF values are compared to the SRCA MTF results. This comparison provides the level of accuracy for on-orbit MTF estimations validated through prelaunch SRCA measurements. The lunar MTF values had larger uncertainty than the SRCA MTF results; however, the ratio mean of lunarMTF fit and SRCA MTF values is within 2% in the 250- and 500-m bands. Based on the MTF measurement uncertainty range, the suggested lunar MTF algorithm can be applied to any on-orbit imaging sensor with lunar calibration capability.

Studies of EGRET sources with a novel image restoration technique

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tajima, Hiroyasu; Cohen-Tanugi, Johann; Kamae, Tuneyoshi

2007-07-12

We have developed an image restoration technique based on the Richardson-Lucy algorithm optimized for GLAST-LAT image analysis. Our algorithm is original since it utilizes the PSF (point spread function) that is calculated for each event. This is critical for EGRET and GLAST-LAT image analysis since the PSF depends on the energy and angle of incident gamma-rays and varies by more than one order of magnitude. EGRET and GLAST-LAT image analysis also faces Poisson noise due to low photon statistics. Our technique incorporates wavelet filtering to minimize noise effects. We present studies of EGRET sources using this novel image restoration techniquemore » for possible identification of extended gamma-ray sources.« less

CCD centroiding analysis for Nano-JASMINE observation data

NASA Astrophysics Data System (ADS)

Niwa, Yoshito; Yano, Taihei; Araki, Hiroshi; Gouda, Naoteru; Kobayashi, Yukiyasu; Yamada, Yoshiyuki; Tazawa, Seiichi; Hanada, Hideo

2010-07-01

Nano-JASMINE is a very small satellite mission for global space astrometry with milli-arcsecond accuracy, which will be launched in 2011. In this mission, centroids of stars in CCD image frames are estimated with sub-pixel accuracy. In order to realize such a high precision centroiding an algorithm utilizing a least square method is employed. One of the advantages is that centroids can be calculated without explicit assumption of the point spread functions of stars. CCD centroiding experiment has been performed to investigate whether this data analysis is available, and centroids of artificial star images on a CCD are determined with a precision of less than 0.001 pixel. This result indicates parallaxes of stars within 300 pc from Sun can be observed in Nano-JASMINE.

An interferometer for high-resolution optical surveillance from geostationary orbit - space system study

NASA Astrophysics Data System (ADS)

Bonino, L.; Bresciani, F.; Piasini, G.; Flebus, C.; Lecat, J.-H.; Roose, S.; Pisani, M.; Cabral, A.; Rebordão, J.; Proença, C.; Costal, J.; Lima, P. U.; Musso, F.

2017-11-01

This paper describes the study of an interferometric instrument for the high-resolution surveillance of the Earth from geostationary orbit (GEO) performed for the EUCLID CEPA 9 RTP 9.9 "High Resolution Optical Satellite Sensor" project of the WEAO Research Cell. It is an in-depth description of a part of the activities described in. The instrument design, both optical and mechanical, is described; tradeoffs have been done for different restoration methods, based on an image generated using calculated point spread functions (PSF's) for the complete FOV. Co-phasing concept for the optical interferometer has been defined together with the optical metrology needed. Design and simulation of the overall instrument control system was carried out.

The energy distribution of very heavy cosmic ray nuclei within the penumbra at Palestine, Texas

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mathiesen, O.; Larsson, L.; Andersson, R.

1975-09-01

The low-energy end of the rigidity spectrum of cosmic ray nuclei with atomic numbers 7greater than or equal to18, recorded in a balloon flight conducted from Palestine, Texas, has been compared with a corresponding theoretical spectrum based on the computations by Shea and Smart. The two distributions are found to be in qualitative agreement with each other. The spread in apparent particle charge, caused by the theoretical distribution of particle velocity at Palestine, has been calculated for detectors with different response functions. The resulting structure of the predicted charge spectrum of iron group nuclei is found to be in goodmore » agreement with corresponding experimental data.« less

Quantum diffusion of H/D on Ni(111)—A partially adiabatic centroid MD study

NASA Astrophysics Data System (ADS)

Hopkinson, A. R.; Probert, M. I. J.

2018-03-01

We present the results of a theoretical study of H/D diffusion on a Ni(111) surface at a range of temperatures, from 250 K to 75 K. The diffusion is studied using both classical molecular dynamics and the partially adiabatic centroid molecular dynamics method. The calculations are performed with the hydrogen (or deuterium) moving in 3D across a static nickel surface using a novel Fourier interpolated potential energy surface which has been parameterized to density functional theory calculations. The results of the classical simulations are that the calculated diffusion coefficients are far too small and with too large a variation with temperature compared with experiment. By contrast, the quantum simulations are in much better agreement with experiment and show that quantum effects in the diffusion of hydrogen are significant at all temperatures studied. There is also a crossover to a quantum-dominated diffusive regime for temperatures below ˜150 K for hydrogen and ˜85 K for deuterium. The quantum diffusion coefficients are found to accurately reproduce the spread in values with temperature, but with an absolute value that is a little high compared with experiment.

Market Mobilities/Immobilities: Mutation, Path-Dependency, and the Spread of Charter School Policies in the United States

ERIC Educational Resources Information Center

Cohen, Dan

2017-01-01

Over the past 25 years charter school policies have spread through the United States at a rapid pace. However, despite this rapid growth these policies have spread unevenly across the country with important variations in how charter school systems function in each state. Drawing on case studies in Michigan and Oregon, this article argues that…

Homology geoinformation modeling of the threat of avian influenza occuring in a region

NASA Astrophysics Data System (ADS)

Myasnikova, S. I.

2008-03-01

This paper addresses the problem of modeling the likely foci of Avian Influenza emergence and spread. The factors contributing to the emergence and spread of the virus are identified. The connection of the factors with invariant structure (landscape map) is determined, and the complex (homotopic) coefficient is calculated, which takes into account the geographical inhomogeneity of the factors, and of the model conditions. The computer-aided mapping and geoinformation modeling procedures are used to assess the situation.

Commonly Asked Questions about Children and Heart Disease

MedlinePlus

... heart is a pump with a built-in electrical system. Normally, electricity starts in the upper chamber and spreads to ... function. Heart block occurs when the spread of electricity from the upper chambers (atria) to the lower ...

Impact of the Equation of State in Models for Surfactant Spreading Experiments

NASA Astrophysics Data System (ADS)

Levy, Rachel

2014-11-01

Pulmonary surfactant spreading models often rely on an equation of state relating surfactant concentration to surface tension. Mathematically, these models have been analyzed with simple functional relationships. However, to model an experiment with a given fluid and surfactant, a physically meaningful equation of state can be derived from experimentally obtained isotherms. We discuss the comparison between model and experiment for NBD-PC lipid (surfactant) spreading on glycerol for an empirically-determined equation of state, and compare those results to simulations with traditionally employed functional forms. In particular we compare the timescales by tracking the leading edge of surfactant, the central fluid height and dynamics of the Marangoni ridge. We consider both outward spreading of a disk-shaped region of surfactant and the hole-closure problem in which a disk-shaped surfactant-free region self-heals. Support from NSF-DMS-FRG 0968154, RCSA-CCS-19788, and HHMI.

Anatomy and histochemistry of spread-wing posture in birds. I. Wing drying posture in the double-crested cormorant, Phalacrocorax auritus.

PubMed

Meyers, Ron A

1997-07-01

Spread-wing postures of birds often have been studied with respect to the function of behavior, but ignored with regard to the mechanism by which the birds accomplish posture. The double-crested cormorant, Phalacrocorax auritus, was used as a model for this study of spread-wing posture. Those muscles capable of positioning and maintaining the wing in extension and protraction were assayed histochemically for the presence of slow (postural) muscle fibers. Within the forelimb of Phalacrocorax, Mm. coracobrachialis cranialis, pectoralis thoracicus (cranial portion), deltoideus minor, triceps scapularis, and extensor metacarpi radialis pars dorsalis and ventralis were found to contain populations of slow-twitch or slow-tonic muscle fibers. These slow fibers in the above muscles are considered to function during spread-wing posture in this species. J Morphol 233:67-76, 1997. © 1997 Wiley-Liss, Inc. Copyright © 1997 Wiley-Liss, Inc.

Identifying multiple influential spreaders based on generalized closeness centrality

NASA Astrophysics Data System (ADS)

Liu, Huan-Li; Ma, Chuang; Xiang, Bing-Bing; Tang, Ming; Zhang, Hai-Feng

2018-02-01

To maximize the spreading influence of multiple spreaders in complex networks, one important fact cannot be ignored: the multiple spreaders should be dispersively distributed in networks, which can effectively reduce the redundance of information spreading. For this purpose, we define a generalized closeness centrality (GCC) index by generalizing the closeness centrality index to a set of nodes. The problem converts to how to identify multiple spreaders such that an objective function has the minimal value. By comparing with the K-means clustering algorithm, we find that the optimization problem is very similar to the problem of minimizing the objective function in the K-means method. Therefore, how to find multiple nodes with the highest GCC value can be approximately solved by the K-means method. Two typical transmission dynamics-epidemic spreading process and rumor spreading process are implemented in real networks to verify the good performance of our proposed method.

Practical Weak-lensing Shear Measurement with Metacalibration

DOE PAGES

Sheldon, Erin S.; Huff, Eric M.

2017-05-19

We report that metacalibration is a recently introduced method to accurately measure weak gravitational lensing shear using only the available imaging data, without need for prior information about galaxy properties or calibration from simulations. The method involves distorting the image with a small known shear, and calculating the response of a shear estimator to that applied shear. The method was shown to be accurate in moderate-sized simulations with galaxy images that had relatively high signal-to-noise ratios, and without significant selection effects. In this work we introduce a formalism to correct for both shear response and selection biases. We also observemore » that for images with relatively low signal-to-noise ratios, the correlated noise that arises during the metacalibration process results in significant bias, for which we develop a simple empirical correction. To test this formalism, we created large image simulations based on both parametric models and real galaxy images, including tests with realistic point-spread functions. We varied the point-spread function ellipticity at the five-percent level. In each simulation we applied a small few-percent shear to the galaxy images. We introduced additional challenges that arise in real data, such as detection thresholds, stellar contamination, and missing data. We applied cuts on the measured galaxy properties to induce significant selection effects. Finally, using our formalism, we recovered the input shear with an accuracy better than a part in a thousand in all cases.« less

Experimental Investigation of the Performance of Image Registration and De-aliasing Algorithms

DTIC Science & Technology

2009-09-01

spread function In the literature these types of algorithms are sometimes hcluded under the broad umbrella of superresolution . However, in the current...We use one of these patterns to visually demonstrate successful de-aliasing 15. SUBJECT TERMS Image de-aliasing Superresolution Microscanning Image...undersampled point spread function. In the literature these types of algorithms are sometimes included under the broad umbrella of superresolution . However, in

Improved axial point spread function in a two-frequency laser scanning confocal fluorescence microscope

NASA Astrophysics Data System (ADS)

Wu, Jheng-Syong; Chung, Yung-Chin; Chien, Jun-Jei; Chou, Chien

2018-01-01

A two-frequency laser scanning confocal fluorescence microscope (TF-LSCFM) based on intensity modulated fluorescence signal detection was proposed. The specimen-induced spherical aberration and scattering effect were suppressed intrinsically, and high image contrast was presented due to heterodyne interference. An improved axial point spread function in a TF-LSCFM compared with a conventional laser scanning confocal fluorescence microscope was demonstrated and discussed.

The role of ITO resistivity on current spreading and leakage in InGaN/GaN light emitting diodes

NASA Astrophysics Data System (ADS)

Sheremet, V.; Genç, M.; Elçi, M.; Sheremet, N.; Aydınlı, A.; Altuntaş, I.; Ding, K.; Avrutin, V.; Özgür, Ü.; Morkoç, H.

2017-11-01

The effect of a transparent ITO current spreading layer on electrical and light output properties of blue InGaN/GaN light emitting diodes (LEDs) is discussed. When finite conductivity of ITO is taken into account, unlike in previous models, the topology of LED die and contacts are shown to significantly affect current spreading and light output characteristics in top emitting devices. We propose an approach for calculating the current transfer length describing current spreading. We show that an inter-digitated electrode configuration with distance between the contact pad and the edge of p-n junction equal to transfer length in the current spreading ITO layer allows one to increase the optical area of LED chip, as compared to the physical area of the die, light output power, and therefore, the LED efficiency for a given current density. A detailed study of unpassivated LEDs also shows that current transfer lengths longer than the distance between the contact pad and the edge of p-n junction leads to increasing surface leakage that can only be remedied with proper passivation.

Generations of spreading basins and stages of breakdown of Wegener's Pangea in the geodynamic evolution of the Arctic Ocean

NASA Astrophysics Data System (ADS)

Shipilov, E. V.

2008-03-01

Chronological succession in the formation of spreading basins is considered in the context of reconstruction of breakdown of Wegener’s Pangea and the development of the geodynamic system of the Arctic Ocean. This study made it possible to indentify three temporally and spatially isolated generations of spreading basins: Late Jurassic-Early Cretaceous, Late Cretaceous-Early Cenozoic, and Cenozoic. The first generation is determined by the formation, evolution, and extinction of the spreading center in the Canada Basin as a tectonic element of the Amerasia Basin. The second generation is connected to the development of the Labrador-Baffin-Makarov spreading branch that ceased to function in the Eocene. The third generation pertains to the formation of the spreading system of interrelated ultraslow Mohna, Knipovich, and Gakkel mid-ocean ridges that has functioned until now in the Norwegian-Greenland and Eurasia basins. The interpretation of the available geological and geophysical data shows that after the formation of the Canada Basin, the Arctic region escaped the geodynamic influence of the Paleopacific, characterized by spreading, subduction, formation of backarc basins, collision-related processes, etc. The origination of the Makarov Basin marks the onset of the oceanic regime characteristic of the North Atlantic (intercontinental rifting, slow and ultraslow spreading, separation of continental blocks (microcontinents), extinction of spreading centers of primary basins, spreading jumps, formation of young spreading ridges and centers, etc., are typical) along with retention of northward propagation of spreading systems both from the Pacific and Atlantic sides. The aforesaid indicates that the Arctic Ocean is in fact a hybrid basin or, in other words, a composite heterogeneous ocean in respect to its architectonics. The Arctic Ocean was formed as a result of spatial juxtaposition of two geodynamic systems different in age and geodynamic style: the Paleopacific system of the Canada Basin that finished its evolution in the Late Cretaceous and the North Atlantic system of the Makarov and Eurasia basins that came to take the place of the Paleopacific system. In contrast to traditional views, it has been suggested that asymmetry of the northern Norwegian-Greenland Basin is explained by two-stage development of this Atlantic segment with formation of primary and secondary spreading centers. The secondary spreading center of the Knipovich Ridge started to evolve approximately at the Oligocene-Miocene transition. This process resulted in the breaking off of the Hovgard continental block from the Barents Sea margin. Thus, the breakdown of Wegener’s Pangea and its Laurasian fragments with the formation of young spreading basins was a staged process that developed nearly from opposite sides. Before the Late Cretaceous (the first stage), the Pangea broke down from the side of Paleopacific to form the Canada Basin, an element of the Amerasia Basin (first phase of ocean formation). Since the Late Cretaceous, destructive pulses came from the side of the North Atlantic and resulted in the separation of Greenland from North America and the development of the Labrador-Baffin-Makarov spreading system (second phase of ocean formation). The Cenozoic was marked by the development of the second spreading branch and the formation of the Norwegian-Greenland and Eurasia oceanic basins (third phase of ocean formation). Spreading centers of this branch are functioning currently but at an extremely low rate.

Proper Analytic Point Spread Function for Lateral Modulation

NASA Astrophysics Data System (ADS)

Chikayoshi Sumi,; Kunio Shimizu,; Norihiko Matsui,

2010-07-01

For ultrasonic lateral modulation for the imaging and measurement of tissue motion, better envelope shapes of the point spread function (PSF) than of a parabolic function are searched for within analytic functions or windows on the basis of the knowledge of the ideal shape of PSF previously obtained, i.e., having a large full width at half maximum and short feet. Through simulation of displacement vector measurement, better shapes are determined. As a better shape, a new window is obtained from a Turkey window by changing Hanning windows by power functions with an order larger than the second order. The order of measurement accuracies obtained is as follows, the new window > rectangular window > power function with a higher order > parabolic function > Akaike window.

Modeling the propagation of mobile malware on complex networks

NASA Astrophysics Data System (ADS)

Liu, Wanping; Liu, Chao; Yang, Zheng; Liu, Xiaoyang; Zhang, Yihao; Wei, Zuxue

2016-08-01

In this paper, the spreading behavior of malware across mobile devices is addressed. By introducing complex networks to model mobile networks, which follows the power-law degree distribution, a novel epidemic model for mobile malware propagation is proposed. The spreading threshold that guarantees the dynamics of the model is calculated. Theoretically, the asymptotic stability of the malware-free equilibrium is confirmed when the threshold is below the unity, and the global stability is further proved under some sufficient conditions. The influences of different model parameters as well as the network topology on malware propagation are also analyzed. Our theoretical studies and numerical simulations show that networks with higher heterogeneity conduce to the diffusion of malware, and complex networks with lower power-law exponents benefit malware spreading.

Fat composition of vegetable oil spreads and margarines in the USA in 2013: a national marketplace analysis

PubMed Central

Garsetti, Marcella; Balentine, Douglas A.; Zock, Peter L.; Blom, Wendy A.M.; Wanders, Anne J.

2016-01-01

Abstract Worldwide, the fat composition of spreads and margarines (“spreads”) has significantly changed over the past decades. Data on fat composition of US spreads are limited and outdated. This paper compares the fat composition of spreads sold in 2013 to that sold in 2002 in the USA. The fat composition of 37 spreads representing >80% of the US market sales volume was determined by standard analytical methods. Sales volume weighted averages were calculated. In 2013, a 14 g serving of spread contained on average 7.1 g fat and 0.2 g trans-fatty acids and provided 22% and 15% of the daily amounts recommended for male adults in North America of omega-3 α-linolenic acid and omega-6 linoleic acid, respectively. Our analysis of the ingredient list on the food label showed that 86% of spreads did not contain partially hydrogenated vegetable oils (PHVO) in 2013. From 2002 to 2013, based on a 14 g serving, total fat and trans-fatty acid content of spreads decreased on average by 2.2 g and 1.5 g, respectively. In the same period, the overall fat composition improved as reflected by a decrease of solid fat (from 39% to 30% of total-fatty acids), and an increase of unsaturated fat (from 61% to 70% of total-fatty acids). The majority of US spreads no longer contains PHVO and can contribute to meeting dietary recommendations by providing unsaturated fat. PMID:27046021

Heterogeneous incidence and propagation of spreading depolarizations

PubMed Central

Kaufmann, Dan; Theriot, Jeremy J; Zyuzin, Jekaterina; Service, C Austin; Chang, Joshua C; Tang, Y Tanye; Bogdanov, Vladimir B; Multon, Sylvie; Schoenen, Jean; Ju, Y Sungtaek

2016-01-01

Spreading depolarizations are implicated in a diverse set of neurologic diseases. They are unusual forms of nervous system activity in that they propagate very slowly and approximately concentrically, apparently not respecting the anatomic, synaptic, functional, or vascular architecture of the brain. However, there is evidence that spreading depolarizations are not truly concentric, isotropic, or homogeneous, either in space or in time. Here we present evidence from KCl-induced spreading depolarizations, in mouse and rat, in vivo and in vitro, showing the great variability that these depolarizations can exhibit. This variability can help inform the mechanistic understanding of spreading depolarizations, and it has implications for their phenomenology in neurologic disease. PMID:27562866

FAK Is Required for Schwann Cell Spreading on Immature Basal Lamina to Coordinate the Radial Sorting of Peripheral Axons with Myelination

PubMed Central

Grove, Matthew

2014-01-01

Without Focal Adhesion Kinase (FAK), developing murine Schwann cells (SCs) proliferate poorly, sort axons inefficiently, and cannot myelinate peripheral nerves. Here we show that FAK is required for the development of SCs when their basal lamina (BL) is fragmentary, but not when it is mature in vivo. Mutant SCs fail to spread on fragmentary BL during development in vivo, and this is phenocopied by SCs lacking functional FAK on low laminin (LN) in vitro. Furthermore, SCs without functional FAK initiate differentiation prematurely, both in vivo and in vitro. In contrast to their behavior on high levels of LN, SCs lacking functional FAK grown on low LN display reduced spreading, proliferation, and indicators of contractility (i.e., stress fibers, arcs, and focal adhesions) and are primed to differentiate. Growth of SCs lacking functional FAK on increasing LN concentrations in vitro revealed that differentiation is not regulated by G1 arrest but rather by cell spreading and the level of contractile actomyosin. The importance of FAK as a critical regulator of the specific response of developing SCs to fragmentary BL was supported by the ability of adult FAK mutant SCs to remyelinate demyelinated adult nerves on mature BL in vivo. We conclude that FAK promotes the spreading and actomyosin contractility of immature SCs on fragmentary BL, thus maintaining their proliferation, and preventing differentiation until they reach high density, thereby promoting radial sorting. Hence, FAK has a critical role in the response of SCs to limiting BL by promoting proliferation and preventing premature SC differentiation. PMID:25274820

The relationship between the retinal image quality and the refractive index of defects arising in IOL: numerical analysis

NASA Astrophysics Data System (ADS)

Geniusz, Malwina

2017-09-01

The best treatment for cataract patients, which allows to restore clear vision is implanting an artificial intraocular lens (IOL). The image quality of the lens has a significant impact on the quality of patient's vision. After a long exposure the implant to aqueous environment some defects appear in the artificial lenses. The defects generated in the IOL have different refractive indices. For example, glistening phenomenon is based on light scattering on the oval microvacuoles filled with an aqueous humor which refractive index value is about 1.34. Calcium deposits are another example of lens defects and they can be characterized by the refractive index 1.63. In the presented studies it was calculated how the difference between the refractive indices of the defect and the refractive index of the lens material affects the quality of image. The OpticStudio Professional program (from Radiant Zemax, LLC) was used for the construction of the numerical model of the eye with IOL and to calculate the characteristics of the retinal image. Retinal image quality was described in such characteristics as Point Spread Function (PSF) and the Optical Transfer Function with amplitude and phase. The results show a strong correlation between the refractive indices difference and retinal image quality.

String-theoretic breakdown of effective field theory near black hole horizons

NASA Astrophysics Data System (ADS)

Dodelson, Matthew; Silverstein, Eva

2017-09-01

We investigate the validity of the equivalence principle near horizons in string theory, analyzing the breakdown of effective field theory caused by longitudinal string spreading effects. An experiment is set up where a detector is thrown into a black hole a long time after an early infalling string. Light cone gauge calculations, taken at face value, indicate a detectable level of root-mean-square longitudinal spreading of the initial string as measured by the late infaller. This results from the large relative boost between the string and detector in the near-horizon region, which develops automatically despite their modest initial energies outside the black hole and the weak curvature in the geometry. We subject this scenario to basic consistency checks, using these to obtain a relatively conservative criterion for its detectability. In a companion paper, we exhibit longitudinal nonlocality in well-defined gauge-invariant S-matrix calculations, obtaining results consistent with the predicted spreading albeit not in a direct analog of the black hole process. We discuss applications of this effect to the firewall paradox, and estimate the time and distance scales it predicts for new physics near black hole and cosmological horizons.

In vivo Three-Dimensional Superresolution Fluorescence Tracking using a Double-Helix Point Spread Function

PubMed Central

Lew, Matthew D.; Thompson, Michael A.; Badieirostami, Majid; Moerner, W. E.

2010-01-01

The point spread function (PSF) of a widefield fluorescence microscope is not suitable for three-dimensional super-resolution imaging. We characterize the localization precision of a unique method for 3D superresolution imaging featuring a double-helix point spread function (DH-PSF). The DH-PSF is designed to have two lobes that rotate about their midpoint in any transverse plane as a function of the axial position of the emitter. In effect, the PSF appears as a double helix in three dimensions. By comparing the Cramer-Rao bound of the DH-PSF with the standard PSF as a function of the axial position, we show that the DH-PSF has a higher and more uniform localization precision than the standard PSF throughout a 2 μm depth of field. Comparisons between the DH-PSF and other methods for 3D super-resolution are briefly discussed. We also illustrate the applicability of the DH-PSF for imaging weak emitters in biological systems by tracking the movement of quantum dots in glycerol and in live cells. PMID:20563317

Resolution improvement by nonconfocal theta microscopy.

PubMed

Lindek, S; Stelzer, E H

1999-11-01

We present a novel scanning fluorescence microscopy technique, nonconfocal theta microscopy (NCTM), that provides almost isotropic resolution. In NCTM, multiphoton absorption from two orthogonal illumination directions is used to induce fluorescence emission. Therefore the point-spread function of the microscope is described by the product of illumination point-spread functions with reduced spatial overlap, which provides the resolution improvement and the more isotropic observation volume. We discuss the technical details of this new method.

Tracking perturbations in Boolean networks with spectral methods

NASA Astrophysics Data System (ADS)

Kesseli, Juha; Rämö, Pauli; Yli-Harja, Olli

2005-08-01

In this paper we present a method for predicting the spread of perturbations in Boolean networks. The method is applicable to networks that have no regular topology. The prediction of perturbations can be performed easily by using a presented result which enables the efficient computation of the required iterative formulas. This result is based on abstract Fourier transform of the functions in the network. In this paper the method is applied to show the spread of perturbations in networks containing a distribution of functions found from biological data. The advances in the study of the spread of perturbations can directly be applied to enable ways of quantifying chaos in Boolean networks. Derrida plots over an arbitrary number of time steps can be computed and thus distributions of functions compared with each other with respect to the amount of order they create in random networks.

Improved surface-wave retrieval from ambient seismic noise by multi-dimensional deconvolution

NASA Astrophysics Data System (ADS)

Wapenaar, Kees; Ruigrok, Elmer; van der Neut, Joost; Draganov, Deyan

2011-01-01

The methodology of surface-wave retrieval from ambient seismic noise by crosscorrelation relies on the assumption that the noise field is equipartitioned. Deviations from equipartitioning degrade the accuracy of the retrieved surface-wave Green's function. A point-spread function, derived from the same ambient noise field, quantifies the smearing in space and time of the virtual source of the Green's function. By multidimensionally deconvolving the retrieved Green's function by the point-spread function, the virtual source becomes better focussed in space and time and hence the accuracy of the retrieved surface-wave Green's function may improve significantly. We illustrate this at the hand of a numerical example and discuss the advantages and limitations of this new methodology.

Age Spreads and the Temperature Dependence of Age Estimates in Upper Sco

NASA Astrophysics Data System (ADS)

Fang, Qiliang; Herczeg, Gregory J.; Rizzuto, Aaron

2017-06-01

Past estimates for the age of the Upper Sco Association are typically 11–13 Myr for intermediate-mass stars and 4–5 Myr for low-mass stars. In this study, we simulate populations of young stars to investigate whether this apparent dependence of estimated age on spectral type may be explained by the star formation history of the association. Solar and intermediate mass stars begin their pre-main sequence evolution on the Hayashi track, with fully convective interiors and cool photospheres. Intermediate-mass stars quickly heat up and transition onto the radiative Henyey track. As a consequence, for clusters in which star formation occurs on a timescale similar to that of the transition from a convective to a radiative interior, discrepancies in ages will arise when ages are calculated as a function of temperature instead of mass. Simple simulations of a cluster with constant star formation over several Myr may explain about half of the difference in inferred ages versus photospheric temperature; speculative constructions that consist of a constant star formation followed by a large supernova-driven burst could fully explain the differences, including those between F and G stars where evolutionary tracks may be more accurate. The age spreads of low-mass stars predicted from these prescriptions for star formation are consistent with the observed luminosity spread of Upper Sco. The conclusion that a lengthy star formation history will yield a temperature dependence in ages is expected from the basic physics of pre-main sequence evolution, and is qualitatively robust to the large uncertainties in pre-main sequence evolutionary models.

Fundamental studies of bloodstain formation and characteristics.

PubMed

Adam, Craig D

2012-06-10

A detailed understanding of blood droplet impact dynamics and stain formation is an essential prerequisite to the interpretation of both individual bloodstains and spatter patterns. The current literature on theoretical models for the spreading and splashing of liquid drops on surfaces relevant to the forensic context of bloodstain formation has been reviewed. These models have been evaluated for a paper substrate using experimental data obtained as function of droplet size, impact velocity and angle. It is shown that for perpendicular impact there are fairly simple mathematical models for the spreading diameter and the number of scallops or spines formed around the stain though these have quite limited ranges of validity in their basic form. In particular, predictions for the diameter are best for small droplets impacting at high velocity and the number of spines saturates for higher impact velocities. In the case of spreading, a modification to the energy conservation model is found to provide excellent agreement with experimental stain diameters across a wide range of impact velocities. For non-perpendicular impact, the width of stains is found to depend principally on the normal component of impact velocity and may be predicted by an appropriate modification to the expression for the perpendicular case. Limitations in the calculation of impact angle from the stain aspect ratio are identified and a theoretical basis for the prediction of spines around an elliptical stain is proposed. Some key issues for future research are identified which include a systematic, quantitative study of the effect of surface properties on bloodstain formation. Copyright © 2011 Elsevier Ireland Ltd. All rights reserved.

Imaging characteristics of Zernike and annular polynomial aberrations.

PubMed

Mahajan, Virendra N; Díaz, José Antonio

2013-04-01

The general equations for the point-spread function (PSF) and optical transfer function (OTF) are given for any pupil shape, and they are applied to optical imaging systems with circular and annular pupils. The symmetry properties of the PSF, the real and imaginary parts of the OTF, and the modulation transfer function (MTF) of a system with a circular pupil aberrated by a Zernike circle polynomial aberration are derived. The interferograms and PSFs are illustrated for some typical polynomial aberrations with a sigma value of one wave, and 3D PSFs and MTFs are shown for 0.1 wave. The Strehl ratio is also calculated for polynomial aberrations with a sigma value of 0.1 wave, and shown to be well estimated from the sigma value. The numerical results are compared with the corresponding results in the literature. Because of the same angular dependence of the corresponding annular and circle polynomial aberrations, the symmetry properties of systems with annular pupils aberrated by an annular polynomial aberration are the same as those for a circular pupil aberrated by a corresponding circle polynomial aberration. They are also illustrated with numerical examples.

Blind deconvolution of astronomical images with band limitation determined by optical system parameters

NASA Astrophysics Data System (ADS)

Luo, L.; Fan, M.; Shen, M. Z.

2007-07-01

Atmospheric turbulence greatly limits the spatial resolution of astronomical images acquired by the large ground-based telescope. The record image obtained from telescope was thought as a convolution result of the object function and the point spread function. The statistic relationship of the images measured data, the estimated object and point spread function was in accord with the Bayes conditional probability distribution, and the maximum-likelihood formulation was found. A blind deconvolution approach based on the maximum-likelihood estimation technique with real optical band limitation constraint is presented for removing the effect of atmospheric turbulence on this class images through the minimization of the convolution error function by use of the conjugation gradient optimization algorithm. As a result, the object function and the point spread function could be estimated from a few record images at the same time by the blind deconvolution algorithm. According to the principle of Fourier optics, the relationship between the telescope optical system parameters and the image band constraint in the frequency domain was formulated during the image processing transformation between the spatial domain and the frequency domain. The convergence of the algorithm was increased by use of having the estimated function variable (also is the object function and the point spread function) nonnegative and the point-spread function band limited. Avoiding Fourier transform frequency components beyond the cut off frequency lost during the image processing transformation when the size of the sampled image data, image spatial domain and frequency domain were the same respectively, the detector element (e.g. a pixels in the CCD) should be less than the quarter of the diffraction speckle diameter of the telescope for acquiring the images on the focal plane. The proposed method can easily be applied to the case of wide field-view turbulent-degraded images restoration because of no using the object support constraint in the algorithm. The performance validity of the method is examined by the computer simulation and the restoration of the real Alpha Psc astronomical image data. The results suggest that the blind deconvolution with the real optical band constraint can remove the effect of the atmospheric turbulence on the observed images and the spatial resolution of the object image can arrive at or exceed the diffraction-limited level.

Estimation of liquefaction-induced lateral spread from numerical modeling and its application

NASA Astrophysics Data System (ADS)

Meng, Xianhong

A noncoupled numerical procedure was developed using a scheme of pore water generation that causes shear modulus degradation and shear strength degradation resulting from earthquake cyclic motion. The designed Fast Lagrangian Analysis of Continua (FLAC) model procedure was tested using the liquefaction-induced lateral spread and ground response for Wildlife and Kobe sites. Sixteen well-documented case histories of lateral spread were reviewed and modeled using the modeling procedure. The dynamic residual strength ratios were back-calculated by matching the predicted displacement with the measured lateral spread, or with the displacement predicted by the Yound et al. model. Statistical analysis on the modeling results and soil properties show that most significant parameters governing the residual strength of the liquefied soil are the SPT blow count, fine content and soil particle size of the lateral spread layer. A regression equation was developed to express the residual strength values with these soil properties. Overall, this research demonstrated that a calibrated numerical model can predict the first order effectiveness of liquefaction-induced lateral spread using relatively simple parameters obtained from routine geotechnical investigation. In addition, the model can be used to plan a soil improvement program for cases where liquefaction remediation is needed. This allows the model to be used for design purposes at bridge approaches structured on liquefiable materials.

Prediction of Three-Dimensional Downward Flame Spread Characteristics over Poly(methyl methacrylate) Slabs in Different Pressure Environments.

PubMed

Zhao, Kun; Zhou, Xiao-Dong; Liu, Xue-Qiang; Lu, Lei; Wu, Zhi-Bo; Peng, Fei; Ju, Xiao-Yu; Yang, Li-Zhong

2016-11-22

The present study is aimed at predicting downward flame spread characteristics over poly(methyl methacrylate) (PMMA) with different sample dimensions in different pressure environments. Three-dimensional (3-D) downward flame spread experiments on free PMMA slabs were conducted at five locations with different altitudes, which provide different pressures. Pressure effects on the flame spread rate, profile of pyrolysis front and flame height were analyzed at all altitudes. The flame spread rate in the steady-state stage was calculated based on the balance on the fuel surface and fuel properties. Results show that flame spread rate increases exponentially with pressure, and the exponent of pressure further shows an increasing trend with the thickness of the sample. The angle of the pyrolysis front emerged on sample residue in the width direction, which indicates a steady-burning stage, varies clearly with sample thicknesses and ambient pressures. A global non-dimensional equation was proposed to predict the variation tendency of the angle of the pyrolysis front with pressure and was found to fit well with the measured results. In addition, the dependence of average flame height on mass burning rate, sample dimension and pressure was proposed based on laminar diffusion flame theory. The fitted exponent of experimental data is 1.11, which is close to the theoretical value.

Research on the middle-of-receiver-spread assumption of the MASW method

USGS Publications Warehouse

Luo, Y.; Xia, J.; Liu, J.; Xu, Y.; Liu, Q.

2009-01-01

The multichannel analysis of surface wave (MASW) method has been effectively used to determine near-surface shear- (S-) wave velocity. Estimating the S-wave velocity profile from Rayleigh-wave measurements is straightforward. A three-step process is required to obtain S-wave velocity profiles: acquisition of a multiple number of multichannel records along a linear survey line by use of the roll-along mode, extraction of dispersion curves of Rayleigh waves, and inversion of dispersion curves for an S-wave velocity profile for each shot gather. A pseudo-2D S-wave velocity section can be generated by aligning 1D S-wave velocity models. In this process, it is very important to understand where the inverted 1D S-wave velocity profile should be located: the midpoint of each spread (a middle-of-receiver-spread assumption) or somewhere between the source and the last receiver. In other words, the extracted dispersion curve is determined by the geophysical structure within the geophone spread or strongly affected by the source geophysical structure. In this paper, dispersion curves of synthetic datasets and a real-world example are calculated by fixing the receiver spread and changing the source location. Results demonstrate that the dispersion curves are mainly determined by structures within a receiver spread. ?? 2008 Elsevier Ltd. All rights reserved.

Toe spreading ability in men with chronic pelvic pain syndrome

PubMed Central

Yilmaz, Ugur; Rothman, Ivan; Ciol, Marcia A; Yang, Claire C; Berger, Richard E

2005-01-01

Background We examined toe-spreading ability in subjects with chronic pelvic pain syndrome (CPPS) to test the hypothesis that subjects with CPPS could have deficiencies in lower extremity functions innervated by sacral spinal roots. Methods Seventy two subjects with CPPS and 98 volunteer controls were examined as part of a larger study on CPPS. All the subjects underwent a detailed urologic and neurological examination including a toe-spreading examination with a quantitative scoring system. We compared the groups in terms of ability of toe-spreading as either "complete" (all toes spreading) or "incomplete" (at least one interdigital space not spreading) and also by comparing the number of interdigital spaces. For CPPS subjects only, we also analyzed the variation of the National Institutes of Health Chronic Prostatitis Symptom Index (NIH-CPSI) scales by toe-spreading categories. Results CPPS subjects were less often able to spread all toes than subjects without CPPS (p = 0.005). None of the NIH-CPSI sub-scales (pain, urinary symptoms, and quality of life), nor the total score showed an association with toe spreading ability. Conclusion We found toe spreading to be diminished in subjects with CPPS. We hypothesize that incomplete toe spreading in subjects with CPPS may be related to subtle deficits involving the most caudal part of the spinal segments. PMID:15949041

Many-particle effects in adsorbed magnetic atoms with easy-axis anisotropy: the case of Fe on the CuN/Cu(100) surface

NASA Astrophysics Data System (ADS)

Žitko, R.; Pruschke, Th

2010-06-01

We study the effects of the exchange interaction between an adsorbed magnetic atom with easy-axis magnetic anisotropy and the conduction-band electrons from the substrate. We model the system using an anisotropic Kondo model and we compute the impurity spectral function, which is related to the differential conductance (dI/dV) spectra measured using a scanning tunneling microscope. To make contact with the known experimental results for iron atoms on the CuN/Cu(100) surface (Hirjibehedin et al 2007 Science 317 1199), we calculated the spectral functions in the presence of an external magnetic field of varying strength applied along all three spatial directions. It is possible to establish an upper bound on the coupling constant J: in the range of the magnetic fields for which the experimental results are currently known (up to 7 T), the low-energy features in the calculated spectra agree well with the measured dI/dV spectra if the exchange coupling constant J is at most half as large as that for cobalt atoms on the same surface. We show that for an even higher magnetic field (between 8 and 9 T) applied along the 'hollow direction', the impurity energy states cross, giving rise to a Kondo effect which takes the form of a zero-bias resonance. The coupling strength J could be determined experimentally by performing tunneling spectroscopy in this range of magnetic fields. On the technical side, the paper introduces an approach for calculating the expectation values of global spin operators and all the components of the impurity magnetic susceptibility tensor (including the out-of-diagonal ones) in numerical renormalization group (NRG) calculations with no spin symmetry. An appendix contains a density functional theory (DFT) study of the Co and Fe adsorbates on the CuN/Cu(100) surface: we compare magnetic moments, as well as orbital energies, occupancies, centers and spreads, by calculating the maximally localized Wannier orbitals of the adsorbates.

Study on the Filament Yarns Spreading Techniques and Assessment Methods of the Electronic Fiberglass Fabric

NASA Astrophysics Data System (ADS)

Wang, Xi; Chen, Shouhui; Zheng, Tianyong; Ning, Xiangchun; Dai, Yifei

2018-03-01

The filament yarns spreading techniques of electronic fiberglass fabric were developed in the past few years in order to meet the requirements of the development of electronic industry. Copper clad laminate (CCL) requires that the warp and weft yarns of the fabric could be spread out of apart and formed flat. The penetration performance of resin could be improved due to the filament yarns spreading techniques of electronic fiberglass fabric, the same as peeling strength of CCL and drilling performance of printed circuit board (PCB). This paper shows the filament yarns spreading techniques of electronic fiberglass fabric from several aspects, such as methods and functions, also with the assessment methods of their effects.

Polynomial Expressions for Estimating Elastic Constants From the Resonance of Circular Plates

NASA Technical Reports Server (NTRS)

Salem, Jonathan A.; Singh, Abhishek

2005-01-01

Two approaches were taken to make convenient spread sheet calculations of elastic constants from resonance data and the tables in ASTM C1259 and E1876: polynomials were fit to the tables; and an automated spread sheet interpolation routine was generated. To compare the approaches, the resonant frequencies of circular plates made of glass, hardened maraging steel, alpha silicon carbide, silicon nitride, tungsten carbide, tape cast NiO-YSZ, and zinc selenide were measured. The elastic constants, as calculated via the polynomials and linear interpolation of the tabular data in ASTM C1259 and E1876, were found comparable for engineering purposes, with the differences typically being less than 0.5 percent. Calculation of additional v values at t/R between 0 and 0.2 would allow better curve fits. This is not necessary for common engineering purposes, however, it might benefit the testing of emerging thin structures such as fuel cell electrolytes, gas conversion membranes, and coatings when Poisson s ratio is less than 0.15 and high precision is needed.

Determination of the resolution of a digital system for panoramic radiography based on CCD technology.

PubMed

Mastoris, Mihalis; Li, Gang; Welander, Ulf; McDavid, W D

2004-03-01

To determine Line Spread Functions (LSFs) and Modulation Transfer Functions (MTFs) for a digital system for panoramic radiography: the Dimax I (Planmeca Oy, Helsinki, Finland) based on Charge-Coupled Device (CCD) technology. A test object was specially designed having a gold foil positioned vertically. Images of the gold foil created edge functions that were used to determine LSFs and MTFs. The design of the test object made it possible to move the gold foil forward and backward relative to the central plane of the image layer by means of a micrometer screw. The experiment was carried out for different object depths in 5 different regions: the anterior, the canine, the premolar, the molar, and the TMJ regions. LSFs and MTFs were calculated using specially designed software. The results are presented graphically. LSFs and MTFs for the central plane were essentially the same for all regions. The MTFs for different object depths in the 5 investigated regions exhibited typical characteristics of MTFs for panoramic radiography with the exception for the functions for the molar region. The present findings indicate that the resolution of the Dimax I CCD system is comparable to that of film-based panoramic radiography.

CROSS-DISCIPLINARY PHYSICS AND RELATED AREAS OF SCIENCE AND TECHNOLOGY: Message Spreading and Forget Remember Mechanism on a Scale-Free Network

NASA Astrophysics Data System (ADS)

Li, Wei; Gu, Jiao; Cai, Xu

2008-06-01

We study message spreading on a scale-free network, by introducing a novel forget-remember mechanism. Message, a general term which can refer to email, news, rumor or disease, etc, can be forgotten and remembered by its holder. The way the message is forgotten and remembered is governed by the forget and remember function, F and R, respectively. Both F and R are functions of history time t concerning individual's previous states, namely being active (with message) or inactive (without message). Our systematic simulations show at the low transmission rate whether or not the spreading can be efficient is primarily determined by the corresponding parameters for F and R.

Determination of localization accuracy based on experimentally acquired image sets: applications to single molecule microscopy

PubMed Central

Tahmasbi, Amir; Ward, E. Sally; Ober, Raimund J.

2015-01-01

Fluorescence microscopy is a photon-limited imaging modality that allows the study of subcellular objects and processes with high specificity. The best possible accuracy (standard deviation) with which an object of interest can be localized when imaged using a fluorescence microscope is typically calculated using the Cramér-Rao lower bound, that is, the inverse of the Fisher information. However, the current approach for the calculation of the best possible localization accuracy relies on an analytical expression for the image of the object. This can pose practical challenges since it is often difficult to find appropriate analytical models for the images of general objects. In this study, we instead develop an approach that directly uses an experimentally collected image set to calculate the best possible localization accuracy for a general subcellular object. In this approach, we fit splines, i.e. smoothly connected piecewise polynomials, to the experimentally collected image set to provide a continuous model of the object, which can then be used for the calculation of the best possible localization accuracy. Due to its practical importance, we investigate in detail the application of the proposed approach in single molecule fluorescence microscopy. In this case, the object of interest is a point source and, therefore, the acquired image set pertains to an experimental point spread function. PMID:25837101

Asymptotic Spreading Rate of Initially Compressible Jets-Experiment and Analysis

NASA Technical Reports Server (NTRS)

Zaman, K. B. M. Q.

1998-01-01

Experimental results for the spreading and centerline velocity decay rates for round, compressible jets, from a convergent and a convergent-divergent nozzle, are presented. The spreading rate is determined from the variation of streamwise mass flux obtained from Pitot probe surveys. Results for the far asymptotic region show that both spreading and centerline velocity decay rates, when nondimensionalized by parameters at the nozzle exit, decrease with increasing "jet Mach number" M(sub j). Dimensional analysis with the assumption of momentum conservation, together with compressible flow calculations for the conditions at the nozzle exit, predict this Mach number dependence well. The analysis also demonstrates that an increase in the "potential core length" of the jet occurring with increasing M(sub j), a commonly observed trend, is largely accounted for simply by the variations in the density and static pressure at the nozzle exit. The effect of decreasing mixing efficiency with increasing compressibility is inferred to contribute only partially to the latter trend.

Age of the Scan Basin (Scotia Sea)

NASA Astrophysics Data System (ADS)

Schreider, Al. A.; Schreider, A. A.; Galindo-Zaldivar, J.; Maldonado, A.; Sazhneva, A. E.; Evsenko, E. I.

2017-03-01

Integrated geological and geophysical analysis of the anomalous magnetic field along with the previously unpublished profiles of Spanish expeditions onboard the R/V Hesperides and international databases of geomagnetic data processed in the context of the global tectonics concepts made it possible to identify paleomagnetic anomalies C11-C15 and compile the first map of the bottom geochronology of the Scan Basin. Unlike in earlier known publications, the paleoaxis of spreading does extend northeast, but approximately at an angle of 345°. According to calculations, spreading began 35.294‒35.706 Ma ago during chron C15r, and the spreading paleoaxis was abandoned 29.527‒29.970 Ma ago during chron C11n.2n. Thus, the destruction of the American-Antarctic bridge in the region joining the Bruce and Discovery banks with formation of oceanic crust in the Scan Basin started about 36 Ma ago. Regular spreading of the bottom has been continuing for about 6 Ma at a average rate close to 1.8 cm/year.

Mechanics of gravitational spreading of steep-sided ridges («sackung»)

USGS Publications Warehouse

Savage, W.Z.; Varnes, D.J.

1987-01-01

Large-scale gravitational spreading of steep-sided ridges characterized by linear fissures, trenches, and uphill-facing scarps high on the sides and tops of ridges are known worldwide. Such spreading, termed sackung, is commonly attributed to pervasive plastic deformation of a rock mass, and is here analyzed as such. Beginning with a previously developed exact elastic solution for gravity-induced stresses in a symmetric ridge, stresses calculated from the exact solution are used in the Coulomb failure criterion to determine the extent of ridge failure under self-weight. Finally, when the regions of failure are established, a plastic flow solution is applied to predict the location of and sense of movement on upward-facing scarps near ridge crests and other features common in sackung. ?? 1987 International Assocaition of Engineering Geology.

Age-associated reduction of cellular spreading/mechanical force up-regulates matrix metalloproteinase-1 expression and collagen fibril fragmentation via c-Jun/AP-1 in human dermal fibroblasts.

PubMed

Qin, Zhaoping; Voorhees, John J; Fisher, Gary J; Quan, Taihao

2014-12-01

The dermal compartment of human skin is largely composed of dense collagen-rich fibrils, which provide structural and mechanical support. Skin dermal fibroblasts, the major collagen-producing cells, are interact with collagen fibrils to maintain cell spreading and mechanical force for function. A characteristic feature of aged human skin is fragmentation of collagen fibrils, which is initiated by matrix metalloproteinase 1 (MMP-1). Fragmentation impairs fibroblast attachment and thereby reduces spreading. Here, we investigated the relationship among fibroblast spreading, mechanical force, MMP-1 expression, and collagen fibril fragmentation. Reduced fibroblast spreading due to cytoskeletal disruption was associated with reduced cellular mechanical force, as determined by atomic force microscopy. These reductions substantially induced MMP-1 expression, which led to collagen fibril fragmentation and disorganization in three-dimensional collagen lattices. Constraining fibroblast size by culturing on slides coated with collagen micropatterns also significantly induced MMP-1 expression. Reduced spreading/mechanical force induced transcription factor c-Jun and its binding to a canonical AP-1 binding site in the MMP-1 proximal promoter. Blocking c-Jun function with dominant negative mutant c-Jun significantly reduced induction of MMP-1 expression in response to reduced spreading/mechanical force. Furthermore, restoration of fibroblast spreading/mechanical force led to decline of c-Jun and MMP-1 levels and eliminated collagen fibril fragmentation and disorganization. These data reveal a novel mechanism by which alteration of fibroblast shape/mechanical force regulates c-Jun/AP-1-dependent expression of MMP-1 and consequent collagen fibril fragmentation. This mechanism provides a foundation for understanding the cellular and molecular basis of age-related collagen fragmentation in human skin. © 2014 The Authors. Aging Cell published by the Anatomical Society and John Wiley & Sons Ltd.

Use of a priori statistics to minimize acquisition time for RFI immune spread spectrum systems

NASA Technical Reports Server (NTRS)

Holmes, J. K.; Woo, K. T.

1978-01-01

The optimum acquisition sweep strategy was determined for a PN code despreader when the a priori probability density function was not uniform. A psuedo noise spread spectrum system was considered which could be utilized in the DSN to combat radio frequency interference. In a sample case, when the a priori probability density function was Gaussian, the acquisition time was reduced by about 41% compared to a uniform sweep approach.

Spatial and spectral imaging of point-spread functions using a spatial light modulator

NASA Astrophysics Data System (ADS)

Munagavalasa, Sravan; Schroeder, Bryce; Hua, Xuanwen; Jia, Shu

2017-12-01

We develop a point-spread function (PSF) engineering approach to imaging the spatial and spectral information of molecular emissions using a spatial light modulator (SLM). We show that a dispersive grating pattern imposed upon the emission reveals spectral information. We also propose a deconvolution model that allows the decoupling of the spectral and 3D spatial information in engineered PSFs. The work is readily applicable to single-molecule measurements and fluorescent microscopy.

Image Processing Research

DTIC Science & Technology

1975-09-30

systems a linear model results in an object f being mappad into an image _ by a point spread function matrix H. Thus with noise j +Hf +n (1) The simplest... linear models for imaging systems are given by space invariant point spread functions (SIPSF) in which case H is block circulant. If the linear model is...Ij,...,k-IM1 is a set of two dimensional indices each distinct and prior to k. Modeling Procedare: To derive the linear predictor (block LP of figure

Flexible high speed CODEC

NASA Technical Reports Server (NTRS)

Wernlund, James V.

1993-01-01

HARRIS, under contract with NASA Lewis, has developed a hard decision BCH (Bose-Chaudhuri-Hocquenghem) triple error correcting block CODEC ASIC, that can be used in either a bursted or continuous mode. the ASIC contains both encoder and decoder functions, programmable lock thresholds, and PSK related functions. The CODEC provides up to 4 dB of coding gain for data rates up to 300 Mbps. The overhead is selectable from 7/8 to 15/16 resulting in minimal band spreading, for a given BER. Many of the internal calculations are brought out enabling the CODEC to be incorporated in more complex designs. The ASIC has been tested in BPSK, QPSK and 16-ary PSK link simulators and found to perform to within 0.1 dB of theory for BER's of 10(exp -2) to 10(exp -9). The ASIC itself, being a hard decision CODEC, is not limited to PSK modulation formats. Unlike most hard decision CODEC's, the HARRIS CODEC doesn't upgrade BER performance significantly at high BER's but rather becomes transparent.

Optimization of the performance of a tandem microchannel plate detector as a function of interplate spacing and voltage

NASA Technical Reports Server (NTRS)

Rogers, D.; Malina, R. F.

1982-01-01

The effect of varying the size of the gap voltage and spacing on the performance of a tandem pair of microchannel plates (MCP) is investigated. Results show that increasing the voltage in the gap increases the gain of the pair and also produces a narrower Gaussian pulse-height distribution, although beyond a critical voltage the gain of the channel plate pair is found to plateau. A model is developed which explains the nonlinear gain behavior of individual microchannels and the behavior of the electron cloud emitted from the first MCP as it spreads out between the two MCPs and hits the surface of the second. The model calculates the plateau voltage as a function of the gap size, the gain of each MCP, and the diameter of the channels, and is found to show good agreement with the observed results. It is concluded that interplate gaps of up to several millimeters can be accommodated without a significant degradation in pulse-height distribution.

Development of MPS Method for Analyzing Melt Spreading Behavior and MCCI in Severe Accidents

NASA Astrophysics Data System (ADS)

Yamaji, Akifumi; Li, Xin

2016-08-01

Spreading of molten core (corium) on reactor containment vessel floor and molten corium-concrete interaction (MCCI) are important phenomena in the late phase of a severe accident for assessment of the containment integrity and managing the severe accident. The severe accident research at Waseda University has been advancing to show that simulations with moving particle semi-implicit (MPS) method (one of the particle methods) can greatly improve the analytical capability and mechanical understanding of the melt behavior in severe accidents. MPS models have been developed and verified regarding calculations of radiation and thermal field, solid-liquid phase transition, buoyancy, and temperature dependency of viscosity to simulate phenomena, such as spreading of corium, ablation of concrete by the corium, crust formation and cooling of the corium by top flooding. Validations have been conducted against experiments such as FARO L26S, ECOKATS-V1, Theofanous, and SPREAD for spreading, SURC-2, SURC-4, SWISS-1, and SWISS-2 for MCCI. These validations cover melt spreading behaviors and MCCI by mixture of molten oxides (including prototypic UO2-ZrO2), metals, and water. Generally, the analytical results show good agreement with the experiment with respect to the leading edge of spreading melt and ablation front history of concrete. The MPS results indicate that crust formation may play important roles in melt spreading and MCCI. There is a need to develop a code for two dimensional MCCI experiment simulation with MPS method as future study, which will be able to simulate anisotropic ablation of concrete.

The measurement of energy consumption by exercise bikes

NASA Astrophysics Data System (ADS)

Jwo, Ching-Song; Chien, Chao-Chun; Jeng, Lung-Yue

2006-11-01

This paper is intended as an investigation is that to measure the amount of energy consumption can be consumed by riding bikes and also could recycle the consuming energy during exercising. Exercisers ride the bicycle inputting the driving force through a compressor of refrigeration system, which can circulate the refrigerant in the system and calculate the calorific capacity from the spread of the condenser. In addition, we can make up chiller water in the evaporator. Experiments were performed to prove the hypotheses. Therefore, this experiment has designed the sports goods which reach the purpose of doing exercise, measuring accurately the consuming calorific capacity and having the function of making chiller water. After exercising, you can drink the water producing during exercise and apply on the system of air conditioner, which attains two objectives.

First and second sound in cylindrically trapped gases.

PubMed

Bertaina, G; Pitaevskii, L; Stringari, S

2010-10-08

We investigate the propagation of density and temperature waves in a cylindrically trapped gas with radial harmonic confinement. Starting from two-fluid hydrodynamic theory we derive effective 1D equations for the chemical potential and the temperature which explicitly account for the effects of viscosity and thermal conductivity. Differently from quantum fluids confined by rigid walls, the harmonic confinement allows for the propagation of both first and second sound in the long wavelength limit. We provide quantitative predictions for the two sound velocities of a superfluid Fermi gas at unitarity. For shorter wavelengths we discover a new surprising class of excitations continuously spread over a finite interval of frequencies. This results in a nondissipative damping in the response function which is analytically calculated in the limiting case of a classical ideal gas.

Expected performances of a Laue lens made with bent crystals

NASA Astrophysics Data System (ADS)

Virgilli, Enrico; Valsan, Vineeth; Frontera, Filippo; Caroli, Ezio; Liccardo, Vincenzo; Stephen, John Buchan

2017-10-01

In the context of the Laue project devoted to build a Laue lens prototype for focusing celestial hard x-/soft gamma-rays, a Laue lens made of bent crystal tiles, with 20-m focal length, is simulated. The focusing energy passband is assumed to be 90 to 600 keV. The distortion of the image produced by the lens on the focal plane, due to effects of crystal tile misalignment and radial distortion of the crystal curvature, is investigated. The corresponding effective area of the lens, its point spread function, and sensitivity are calculated and compared with those exhibited by a nominal Laue lens with no misalignment and/or distortion. Such analysis is crucial to estimate the optical properties of a real lens, in which the investigated shortcomings could be present.

Toward a generalized theory of epidemic awareness in social networks

NASA Astrophysics Data System (ADS)

Wu, Qingchu; Zhu, Wenfang

We discuss the dynamics of a susceptible-infected-susceptible (SIS) model with local awareness in networks. Individual awareness to the infectious disease is characterized by a general function of epidemic information in its neighborhood. We build a high-accuracy approximate equation governing the spreading dynamics and derive an approximate epidemic threshold above which the epidemic spreads over the whole network. Our results extend the previous work and show that the epidemic threshold is dependent on the awareness function in terms of one infectious neighbor. Interestingly, when a pow-law awareness function is chosen, the epidemic threshold can emerge in infinite networks.

Propagation of a Free Flame in a Turbulent Gas Stream

NASA Technical Reports Server (NTRS)

Mickelsen, William R; Ernstein, Norman E

1956-01-01

Effective flame speeds of free turbulent flames were measured by photographic, ionization-gap, and photomultiplier-tube methods, and were found to have a statistical distribution attributed to the nature of the turbulent field. The effective turbulent flame speeds for the free flame were less than those previously measured for flames stabilized on nozzle burners, Bunsen burners, and bluff bodies. The statistical spread of the effective turbulent flame speeds was markedly wider in the lean and rich fuel-air-ratio regions, which might be attributed to the greater sensitivity of laminar flame speed to flame temperature in those regions. Values calculated from the turbulent free-flame-speed analysis proposed by Tucker apparently form upper limits for the statistical spread of free-flame-speed data. Hot-wire anemometer measurements of the longitudinal velocity fluctuation intensity and longitudinal correlation coefficient were made and were employed in the comparison of data and in the theoretical calculation of turbulent flame speed.

Uniform heating of materials into the warm dense matter regime with laser-driven quasimonoenergetic ion beams

DOE PAGES

Bang, W.; Albright, B. J.; Bradley, P. A.; ...

2015-12-01

In a recent experiment at the Trident laser facility, a laser-driven beam of quasimonoenergetic aluminum ions was used to heat solid gold and diamond foils isochorically to 5.5 and 1.7 eV, respectively. Here theoretical calculations are presented that suggest the gold and diamond were heated uniformly by these laser-driven ion beams. According to calculations and SESAME equation-of-state tables, laser-driven aluminum ion beams achievable at Trident, with a finite energy spread of ΔE/E~20%, are expected to heat the targets more uniformly than a beam of 140-MeV aluminum ions with zero energy spread. As a result, the robustness of the expected heatingmore » uniformity relative to the changes in the incident ion energy spectra is evaluated, and expected plasma temperatures of various target materials achievable with the current experimental platform are presented.« less

Butterfly velocities for holographic theories of general spacetimes

DOE PAGES

Nomura, Yasunori; Salzetta, Nico

2017-10-01

The butterfly velocity characterizes the spread of correlations in a quantum system. Recent work has provided a method of calculating the butterfly velocity of a class of boundary operators using holographic duality. Utilizing this and a presumed extension of the canonical holographic correspondence of AdS/CFT, we investigate the butterfly velocities of operators with bulk duals living in general spacetimes. We analyze some ubiquitous issues in calculating butterfly velocities using the bulk effective theory, and then extend the previously proposed method to include operators in entanglement shadows. Here in this paper, we explicitly compute butterfly velocities for bulk local operators inmore » the holographic theory of flat Friedmann-Robertson-Walker spacetimes and find a universal scaling behavior for the spread of operators in the boundary theory, independent of dimension and fluid components. This result may suggest that a Lifshitz field theory with z = 4 is the appropriate holographic dual for these spacetimes.« less

Uniform heating of materials into the warm dense matter regime with laser-driven quasimonoenergetic ion beams

NASA Astrophysics Data System (ADS)

Bang, W.; Albright, B. J.; Bradley, P. A.; Vold, E. L.; Boettger, J. C.; Fernández, J. C.

2015-12-01

In a recent experiment at the Trident laser facility, a laser-driven beam of quasimonoenergetic aluminum ions was used to heat solid gold and diamond foils isochorically to 5.5 and 1.7 eV, respectively. Here theoretical calculations are presented that suggest the gold and diamond were heated uniformly by these laser-driven ion beams. According to calculations and SESAME equation-of-state tables, laser-driven aluminum ion beams achievable at Trident, with a finite energy spread of ΔE /E ˜20 %, are expected to heat the targets more uniformly than a beam of 140-MeV aluminum ions with zero energy spread. The robustness of the expected heating uniformity relative to the changes in the incident ion energy spectra is evaluated, and expected plasma temperatures of various target materials achievable with the current experimental platform are presented.

Three-dimensional analysis of alveolar bone resorption by image processing of 3-D dental CT images

NASA Astrophysics Data System (ADS)

Nagao, Jiro; Kitasaka, Takayuki; Mori, Kensaku; Suenaga, Yasuhito; Yamada, Shohzoh; Naitoh, Munetaka

2006-03-01

We have developed a novel system that provides total support for assessment of alveolar bone resorption, caused by periodontitis, based on three-dimensional (3-D) dental CT images. In spite of the difficulty in perceiving the complex 3-D shape of resorption, dentists assessing resorption location and severity have been relying on two-dimensional radiography and probing, which merely provides one-dimensional information (depth) about resorption shape. However, there has been little work on assisting assessment of the disease by 3-D image processing and visualization techniques. This work provides quantitative evaluation results and figures for our system that measures the three-dimensional shape and spread of resorption. It has the following functions: (1) measures the depth of resorption by virtually simulating probing in the 3-D CT images, taking advantage of image processing of not suffering obstruction by teeth on the inter-proximal sides and much smaller measurement intervals than the conventional examination; (2) visualizes the disposition of the depth by movies and graphs; (3) produces a quantitative index and intuitive visual representation of the spread of resorption in the inter-radicular region in terms of area; and (4) calculates the volume of resorption as another severity index in the inter-radicular region and the region outside it. Experimental results in two cases of 3-D dental CT images and a comparison of the results with the clinical examination results and experts' measurements of the corresponding patients confirmed that the proposed system gives satisfying results, including 0.1 to 0.6mm of resorption measurement (probing) error and fairly intuitive presentation of measurement and calculation results.

Rumor spreading in online social networks by considering the bipolar social reinforcement

NASA Astrophysics Data System (ADS)

Ma, Jing; Li, Dandan; Tian, Zihao

2016-04-01

Considering the bipolar social reinforcement which includes positive and negative effects, in this paper we explore the rumor spreading dynamics in online social networks. By means of the generation function and cavity method developed from statistical physics of disordered system, the rumor spreading threshold can be theoretically drawn. Simulation results indicate that decreasing the positive reinforcement factor or increasing the negative reinforcement factor can suppress the rumor spreading effectively. By analyzing the topological properties of the real world social network, we find that the nodes with lower degree usually have smaller weight. However, the nodes with lower degree may have larger k-shell. In order to curb rumor spreading, some control strategies that are based on the nodes' degree, k-shell and weight are presented. By comparison, we show that controlling those nodes that have larger degree or weight are two effective strategies to prevent the rumor spreading.

The spreading time in SIS epidemics on networks

NASA Astrophysics Data System (ADS)

He, Zhidong; Van Mieghem, Piet

2018-03-01

In a Susceptible-Infected-Susceptible (SIS) process, we investigate the spreading time Tm, which is the time when the number of infected nodes in the metastable state is first reached, starting from the outbreak of the epidemics. We observe that the spreading time Tm resembles a lognormal-like distribution, though with different deep tails, both for the Markovian and the non-Markovian infection process, which implies that the spreading time can be very long with a relatively high probability. In addition, we show that a stronger virus, with a higher effective infection rate τ or an earlier timing of the infection attempts, does not always lead to a shorter average spreading time E [Tm ] . We numerically demonstrate that the average spreading time E [Tm ] in the complete graph and the star graph scales logarithmically as a function of the network size N for a fixed fraction of infected nodes in the metastable state.

Spreading of Neutrophils: From Activation to Migration

PubMed Central

Sengupta, Kheya; Aranda-Espinoza, Helim; Smith, Lee; Janmey, Paul; Hammer, Daniel

2006-01-01

Neutrophils rely on rapid changes in morphology to ward off invaders. Time-resolved dynamics of spreading human neutrophils after activation by the chemoattractant fMLF (formyl methionyl leucyl phenylalanine) was observed by RICM (reflection interference contrast microscopy). An image-processing algorithm was developed to identify the changes in the overall cell shape and the zones of close contact with the substrate. We show that in the case of neutrophils, cell spreading immediately after exposure of fMLF is anisotropic and directional. The dependence of spreading area, A, of the cell as a function of time, t, shows several distinct regimes, each of which can be fitted as power laws (A ∼ tb). The different spreading regimes correspond to distinct values of the exponent b and are related to the adhesion state of the cell. Treatment with cytochalasin-B eliminated the anisotropy in the spreading. PMID:17012330

A practical implementation of wave front construction for 3-D isotropic media

NASA Astrophysics Data System (ADS)

Chambers, K.; Kendall, J.-M.

2008-06-01

Wave front construction (WFC) methods are a useful tool for tracking wave fronts and are a natural extension to standard ray shooting methods. Here we describe and implement a simple WFC method that is used to interpolate wavefield properties throughout a 3-D heterogeneous medium. Our approach differs from previous 3-D WFC procedures primarily in the use of a ray interpolation scheme, based on approximating the wave front as a `locally spherical' surface and a `first arrival mode', which reduces computation times, where only first arrivals are required. Both of these features have previously been included in 2-D WFC algorithms; however, until now they have not been extended to 3-D systems. The wave front interpolation scheme allows for rays to be traced from a nearly arbitrary distribution of take-off angles, and the calculation of derivatives with respect to take-off angles is not required for wave front interpolation. However, in regions of steep velocity gradient, the locally spherical approximation is not valid, and it is necessary to backpropagate rays to a sufficiently homogenous region before interpolation of the new ray. Our WFC technique is illustrated using a realistic velocity model, based on a North Sea oil reservoir. We examine wavefield quantities such as traveltimes, ray angles, source take-off angles and geometrical spreading factors, all of which are interpolated on to a regular grid. We compare geometrical spreading factors calculated using two methods: using the ray Jacobian and by taking the ratio of a triangular area of wave front to the corresponding solid angle at the source. The results show that care must be taken when using ray Jacobians to calculate geometrical spreading factors, as the poles of the source coordinate system produce unreliable values, which can be spread over a large area, as only a few initial rays are traced in WFC. We also show that the use of the first arrival mode can reduce computation time by ~65 per cent, with the accuracy of the interpolated traveltimes, ray angles and source take-off angles largely unchanged. However, the first arrival mode does lead to inaccuracies in interpolated angles near caustic surfaces, as well as small variations in geometrical spreading factors for ray tubes that have passed through caustic surfaces.

Toward 3D Printing of Medical Implants: Reduced Lateral Droplet Spreading of Silicone Rubber under Intense IR Curing.

PubMed

Stieghorst, Jan; Majaura, Daniel; Wevering, Hendrik; Doll, Theodor

2016-03-01

The direct fabrication of silicone-rubber-based individually shaped active neural implants requires high-speed-curing systems in order to prevent extensive spreading of the viscous silicone rubber materials during vulcanization. Therefore, an infrared-laser-based test setup was developed to cure the silicone rubber materials rapidly and to evaluate the resulting spreading in relation to its initial viscosity, the absorbed infrared radiation, and the surface tensions of the fabrication bed's material. Different low-adhesion materials (polyimide, Parylene-C, polytetrafluoroethylene, and fluorinated ethylenepropylene) were used as bed materials to reduce the spreading of the silicone rubber materials by means of their well-known weak surface tensions. Further, O2-plasma treatment was performed on the bed materials to reduce the surface tensions. To calculate the absorbed radiation, the emittance of the laser was measured, and the absorptances of the materials were investigated with Fourier transform infrared spectroscopy in attenuated total reflection mode. A minimum silicone rubber spreading of 3.24% was achieved after 2 s curing time, indicating the potential usability of the presented high-speed-curing process for the direct fabrication of thermal-curing silicone rubbers.

Quantifying the effect of air gap, depth, and range shifter thickness on TPS dosimetric accuracy in superficial PBS proton therapy.

PubMed

Shirey, Robert J; Wu, Hsinshun Terry

2018-01-01

This study quantifies the dosimetric accuracy of a commercial treatment planning system as functions of treatment depth, air gap, and range shifter thickness for superficial pencil beam scanning proton therapy treatments. The RayStation 6 pencil beam and Monte Carlo dose engines were each used to calculate the dose distributions for a single treatment plan with varying range shifter air gaps. Central axis dose values extracted from each of the calculated plans were compared to dose values measured with a calibrated PTW Markus chamber at various depths in RW3 solid water. Dose was measured at 12 depths, ranging from the surface to 5 cm, for each of the 18 different air gaps, which ranged from 0.5 to 28 cm. TPS dosimetric accuracy, defined as the ratio of calculated dose relative to the measured dose, was plotted as functions of depth and air gap for the pencil beam and Monte Carlo dose algorithms. The accuracy of the TPS pencil beam dose algorithm was found to be clinically unacceptable at depths shallower than 3 cm with air gaps wider than 10 cm, and increased range shifter thickness only added to the dosimetric inaccuracy of the pencil beam algorithm. Each configuration calculated with Monte Carlo was determined to be clinically acceptable. Further comparisons of the Monte Carlo dose algorithm to the measured spread-out Bragg Peaks of multiple fields used during machine commissioning verified the dosimetric accuracy of Monte Carlo in a variety of beam energies and field sizes. Discrepancies between measured and TPS calculated dose values can mainly be attributed to the ability (or lack thereof) of the TPS pencil beam dose algorithm to properly model secondary proton scatter generated in the range shifter. © 2017 The Authors. Journal of Applied Clinical Medical Physics published by Wiley Periodicals, Inc. on behalf of American Association of Physicists in Medicine.

Actualizing Flexible National Security Space Systems

DTIC Science & Technology

2011-01-01

single launch vehicle is a decision unique to small satellites that adds an extra dimension to the launch risk calculation. While bundling...following a launch failure. The ability to bundle multiple payloads on a single launch vehicle is a decision unique to small satellites that adds an extra ... dimension to the launch risk calculation. While bundling multiple small satellites on a single launch vehicle spreads the initial launch cost across

Differential Dynamics of Platelet Contact and Spreading

PubMed Central

Lee, Dooyoung; Fong, Karen P.; King, Michael R.; Brass, Lawrence F.; Hammer, Daniel A.

2012-01-01

Platelet spreading is critical for hemostatic plug formation and thrombosis. However, the detailed dynamics of platelet spreading as a function of receptor-ligand adhesive interactions has not been thoroughly investigated. Using reflection interference contrast microscopy, we found that both adhesive interactions and PAR4 activation affect the dynamics of platelet membrane contact formation during spreading. The initial growth of close contact area during spreading was controlled by the combination of different immobilized ligands or PAR4 activation on fibrinogen, whereas the growth of the total area of spreading was independent of adhesion type and PAR4 signaling. We found that filopodia extend to their maximal length and then contract over time; and that filopodial protrusion and expansion were affected by PAR4 signaling. Upon PAR4 activation, the integrin αIIbβ3 mediated close contact to fibrinogen substrata and led to the formation of ringlike patterns in the platelet contact zone. A systematic study of platelet spreading of GPVI-, α2-, or β3-deficient platelets on collagen or fibrinogen suggests the integrin α2 is indispensable for spreading on collagen. The platelet collagen receptors GPVI and α2 regulate integrin αIIbβ3-mediated platelet spreading on fibrinogen. This work elucidates quantitatively how receptor-ligand adhesion and biochemical signals synergistically control platelet spreading. PMID:22325269

Dynamical consequences of compositional and thermal density stratification beneath spreading centers

NASA Technical Reports Server (NTRS)

Sotin, C.; Parmentier, E. M.

1989-01-01

Dynamical consequences of compositional buoyancy and the combined effects of compositional and thermal buoyancy on mantle flow and crustal production are explored. The results show that for a low enough mantle viscosity, buoyant upwelling can significantly enhance the crustal thickness relative to that which would be produced by plate spreading alone, while for a mantle viscosity of 10 to the 22nd Pa s, upwelling due to plate spreading is dominant and crustal thickness is predicted to be a function of spreading rate. The results indicate that thermal and compositional density variations result in opposing buoyancy forces that can cause time-dependent upwelling.

Enclosure fire hazard analysis using relative energy release criteria. [burning rate and combustion control

NASA Technical Reports Server (NTRS)

Coulbert, C. D.

1978-01-01

A method for predicting the probable course of fire development in an enclosure is presented. This fire modeling approach uses a graphic plot of five fire development constraints, the relative energy release criteria (RERC), to bound the heat release rates in an enclosure as a function of time. The five RERC are flame spread rate, fuel surface area, ventilation, enclosure volume, and total fuel load. They may be calculated versus time based on the specified or empirical conditions describing the specific enclosure, the fuel type and load, and the ventilation. The calculation of these five criteria, using the common basis of energy release rates versus time, provides a unifying framework for the utilization of available experimental data from all phases of fire development. The plot of these criteria reveals the probable fire development envelope and indicates which fire constraint will be controlling during a criteria time period. Examples of RERC application to fire characterization and control and to hazard analysis are presented along with recommendations for the further development of the concept.

Threshold-free method for three-dimensional segmentation of organelles

NASA Astrophysics Data System (ADS)

Chan, Yee-Hung M.; Marshall, Wallace F.

2012-03-01

An ongoing challenge in the field of cell biology is to how to quantify the size and shape of organelles within cells. Automated image analysis methods often utilize thresholding for segmentation, but the calculated surface of objects depends sensitively on the exact threshold value chosen, and this problem is generally worse at the upper and lower zboundaries because of the anisotropy of the point spread function. We present here a threshold-independent method for extracting the three-dimensional surface of vacuoles in budding yeast whose limiting membranes are labeled with a fluorescent fusion protein. These organelles typically exist as a clustered set of 1-10 sphere-like compartments. Vacuole compartments and center points are identified manually within z-stacks taken using a spinning disk confocal microscope. A set of rays is defined originating from each center point and radiating outwards in random directions. Intensity profiles are calculated at coordinates along these rays, and intensity maxima are taken as the points the rays cross the limiting membrane of the vacuole. These points are then fit with a weighted sum of basis functions to define the surface of the vacuole, and then parameters such as volume and surface area are calculated. This method is able to determine the volume and surface area of spherical beads (0.96 to 2 micron diameter) with less than 10% error, and validation using model convolution methods produce similar results. Thus, this method provides an accurate, automated method for measuring the size and morphology of organelles and can be generalized to measure cells and other objects on biologically relevant length-scales.

On entanglement spreading from holography

DOE PAGES

Mezei, Márk

2017-05-11

A global quench is an interesting setting where we can study thermalization of subsystems in a pure state. We investigate entanglement entropy (EE) growth in global quenches in holographic field theories and relate some of its aspects to quantities characterizing chaos. More specifically we obtain four key results: 1. We prove holographic bounds on the entanglement velocity vE and the butterfly effect speed vB that arises in the study of chaos. 2. We obtain the EE as a function of time for large spherical entangling surfaces analytically. We show that the EE is insensitive to the details of the initialmore » state or quench protocol. 3. In a thermofield double state we determine analytically the two-sided mutual information between two large concentric spheres separated in time. 4. We derive a bound on the rate of growth of EE for arbitrary shapes, and develop an expansion for EE at early times. In a companion paper, these results are put in the broader context of EE growth in chaotic systems: we relate EE growth to the chaotic spreading of operators, derive bounds on EE at a given time, and compare the holographic results to spin chain numerics and toy models. In this paper, we perform holographic calculations that provide the basis of arguments presented in that paper.« less

Rapid cooling rates at an active mid-ocean ridge from zircon thermochronology

USGS Publications Warehouse

Schmitt, Axel K.; Perfit, Michael R.; Rubin, Kenneth H.; Stockli, Daniel F.; Smith, Matthew C.; Cotsonika, Laurie A.; Zellmer, Georg F.; Ridley, W. Ian

2011-01-01

Oceanic spreading ridges are Earth's most productive crust generating environment, but mechanisms and rates of crustal accretion and heat loss are debated. Existing observations on cooling rates are ambiguous regarding the prevalence of conductive vs. convective cooling of lower oceanic crust. Here, we report the discovery and dating of zircon in mid-ocean ridge dacite lavas that constrain magmatic differentiation and cooling rates at an active spreading center. Dacitic lavas erupted on the southern Cleft segment of the Juan de Fuca ridge, an intermediate-rate spreading center, near the intersection with the Blanco transform fault. Their U–Th zircon crystallization ages (29.3-4.6+4.8 ka; 1δ standard error s.e.) overlap with the (U–Th)/He zircon eruption age (32.7 ± 1.6 ka) within uncertainty. Based on similar 238U-230Th disequilibria between southern Cleft dacite glass separates and young mid-ocean ridge basalt (MORB) erupted nearby, differentiation must have occurred rapidly, within ~ 10–20 ka at most. Ti-in-zircon thermometry indicates crystallization at 850–900 °C and pressures > 70–150 MPa are calculated from H2O solubility models. These time-temperature constraints translate into a magma cooling rate of ~ 2 × 10-2 °C/a. This rate is at least one order-of-magnitude faster than those calculated for zircon-bearing plutonic rocks from slow spreading ridges. Such short intervals for differentiation and cooling can only be resolved through uranium-series (238U–230Th) decay in young lavas, and are best explained by dissipating heat convectively at high crustal permeability.

Robust location and spread measures for nonparametric probability density function estimation.

PubMed

López-Rubio, Ezequiel

2009-10-01

Robustness against outliers is a desirable property of any unsupervised learning scheme. In particular, probability density estimators benefit from incorporating this feature. A possible strategy to achieve this goal is to substitute the sample mean and the sample covariance matrix by more robust location and spread estimators. Here we use the L1-median to develop a nonparametric probability density function (PDF) estimator. We prove its most relevant properties, and we show its performance in density estimation and classification applications.

Thematic Mapper Protoflight Model Line Spread Function

NASA Technical Reports Server (NTRS)

Schueler, C.

1984-01-01

The Thematic Mapper (TM) Protoflight Model Spatial Line Spread Function (LSF) was not measured before launch. Therefore, methodology are developed to characterize LSF with protoflight model optics and electronics measurements that were made before launch. Direct prelaunch LSF measurements that were made from the flight model TM verified the protoflight TM LSF simulation. Results for two selected protoflight TM channels are presented here. It is shown that LSF data for the other ninety-four channels could be generated in the same fashion.

Pupil engineering for a confocal reflectance line-scanning microscope

NASA Astrophysics Data System (ADS)

Patel, Yogesh G.; Rajadhyaksha, Milind; DiMarzio, Charles A.

2011-03-01

Confocal reflectance microscopy may enable screening and diagnosis of skin cancers noninvasively and in real-time, as an adjunct to biopsy and pathology. Current confocal point-scanning systems are large, complex, and expensive. A confocal line-scanning microscope, utilizing a of linear array detector can be simpler, smaller, less expensive, and may accelerate the translation of confocal microscopy in clinical and surgical dermatology. A line scanner may be implemented with a divided-pupil, half used for transmission and half for detection, or with a full-pupil using a beamsplitter. The premise is that a confocal line-scanner with either a divided-pupil or a full-pupil will provide high resolution and optical sectioning that would be competitive to that of the standard confocal point-scanner. We have developed a confocal line-scanner that combines both divided-pupil and full-pupil configurations. This combined-pupil prototype is being evaluated to determine the advantages and limitations of each configuration for imaging skin, and comparison of performance to that of commercially available standard confocal point-scanning microscopes. With the combined configuration, experimental evaluation of line spread functions (LSFs), contrast, signal-to-noise ratio, and imaging performance is in progress under identical optical and skin conditions. Experimental comparisons between divided-pupil and full-pupil LSFs will be used to determine imaging performance. Both results will be compared to theoretical calculations using our previously reported Fourier analysis model and to the confocal point spread function (PSF). These results may lead to a simpler class of confocal reflectance scanning microscopes for clinical and surgical dermatology.

The requirements for herpes simplex virus type 1 cell-cell spread via nectin-1 parallel those for virus entry.

PubMed

Even, Deborah L; Henley, Allison M; Geraghty, Robert J

2006-08-01

Herpes simplex virus type 1 (HSV-1) spreads from an infected cell to an uninfected cell by virus entry, virus-induced cell fusion, and cell-cell spread. The three forms of virus spread require the viral proteins gB, gD, and gH-gL, as well as a cellular gD receptor. The mutual requirement for the fusion glycoproteins and gD receptor suggests that virus entry, cell fusion, and cell-cell spread occur by a similar mechanism. The goals of this study were to examine the role of the nectin-1alpha transmembrane domain and cytoplasmic tail in cell-cell spread and to obtain a better understanding of the receptor-dependent events occurring at the plasma membrane during cell-cell spread. We determined that an intact nectin-1alpha V-like domain was required for cell-cell spread, while a membrane-spanning domain and cytoplasmic tail were not. Chimeric forms of nectin-1 that were non-functional for virus entry did not mediate cell-cell spread regardless of whether they could mediate cell fusion. Also, cell-cell spread of syncytial isolates was dependent upon nectin-1alpha expression and occurred through a nectin-1-dependent mechanism. Taken together, our results indicate that nectin-1-dependent events occurring at the plasma membrane during cell-cell spread were equivalent to those for virus entry.

40 CFR Appendix A to Part 197 - Calculation of Annual Committed Effective Dose Equivalent

Code of Federal Regulations, 2011 CFR

2011-07-01

... resulting from irradiation of the tissue or organ to the total risk when the whole body is irradiated... internal irradiation from incorporated radionuclides, the total absorbed dose will be spread out in time...

40 CFR Appendix A to Part 197 - Calculation of Annual Committed Effective Dose Equivalent

Code of Federal Regulations, 2012 CFR

2012-07-01

... resulting from irradiation of the tissue or organ to the total risk when the whole body is irradiated... internal irradiation from incorporated radionuclides, the total absorbed dose will be spread out in time...

40 CFR Appendix A to Part 197 - Calculation of Annual Committed Effective Dose Equivalent

Code of Federal Regulations, 2014 CFR

2014-07-01

... resulting from irradiation of the tissue or organ to the total risk when the whole body is irradiated... internal irradiation from incorporated radionuclides, the total absorbed dose will be spread out in time...

40 CFR Appendix A to Part 197 - Calculation of Annual Committed Effective Dose Equivalent

Code of Federal Regulations, 2013 CFR

2013-07-01

... resulting from irradiation of the tissue or organ to the total risk when the whole body is irradiated... internal irradiation from incorporated radionuclides, the total absorbed dose will be spread out in time...

40 CFR Appendix A to Part 197 - Calculation of Annual Committed Effective Dose Equivalent

Code of Federal Regulations, 2010 CFR

2010-07-01

... resulting from irradiation of the tissue or organ to the total risk when the whole body is irradiated... internal irradiation from incorporated radionuclides, the total absorbed dose will be spread out in time...

Evaluation of the amperex 56 TVP photomultiplier. [characteristics: photoelectron time spread, anode pulse amplitude and photocathode sensing area

NASA Technical Reports Server (NTRS)

Lo, C. C.; Leskovar, B.

1976-01-01

Characteristics were measured for the Amperex 56 TVP 42 mm-diameter photomultiplier. Some typical photomultiplier characteristics-such as gain, dark current, transit and rise times-are compared with data provided. Photomultiplier characteristics generally not available such as the single photoelectron time spread, the relative collection efficiency, the relative anode pulse amplitude as a function of the voltage between the photocathode and focusing electrode, and the position of the photocathode sensing area were measured and are discussed for two 56 TVP's. The single photoelectron time spread, the relative collection efficiency, and the transit time difference as a function of the voltage between photocathode and focusing electrode were also measured and are discussed, particularly with respect to the optimization of photomultiplier operating conditions for timing applications.

Detecting Near-Earth Objects Using Cross-Correlation with a Point Spread Function

DTIC Science & Technology

2009-03-01

greater than .001 seconds [Goodman, 2000]. Cross-Correlation Cross-Correlation measures the strength and direction of the linear relationship between...real(ifft2(fftshift(otf_long)))); %normalize point spread funtion 55 if (Corner == 1) psf_source = makeshift(psf*source_img(ccd_x/2,ccd_y/2

Crustal accretion along the global mid-ocean ridge system based on basaltic glass and olivine-hosted melt inclusion compositions

NASA Astrophysics Data System (ADS)

Wanless, V. D.; Behn, M. D.

2015-12-01

The depth and distribution of crystallization at mid-ocean ridges controls the overall architecture of the oceanic crust, influences hydrothermal circulation, and determines geothermal gradients in the crust and uppermost mantle. Despite this, there is no overall consensus on how crystallization is distributed within the crust/upper mantle or how this varies with spreading rate. Here, we examine crustal accretion at mid-ocean ridges by combining crystallization pressures calculated from major element barometers on mid-ocean ridge basalt (MORB) glasses with vapor-saturation pressures from melt inclusions to produce a detailed map of crystallization depths and distributions along the global ridge system. We calculate pressures of crystallization from >11,500 MORB glasses from the global ridge system using two established major element barometers (1,2). Additionally, we use vapor-saturation pressures from >400 olivine-hosted melt inclusions from five ridges with variable spreading rates to constrain pressures and distributions of crystallization along the global ridge system. We show that (i) crystallization depths from MORB glasses increase and become less focused with decreasing spreading rate, (ii) maximum glass pressures are greater than the maximum melt inclusion pressure, which indicates that the melt inclusions do not record the deepest crystallization at mid-ocean ridges, and (iii) crystallization occurs in the lower crust/upper mantle at all ridges, indicating accretion is distributed throughout the crust at all spreading rates, including those with a steady-state magma lens. Finally, we suggest that the remarkably similar maximum vapor-saturation pressures (~ 3000 bars) in melt inclusion from all spreading rates reflects the CO2 content of the depleted upper mantle feeding the global mid-ocean ridge system. (1) Michael, P. & W. Cornell (1998), Journal of Geophysical Research, 103(B8), 18325-18356; (2) Herzberg, C. (2004), Journal of Petrology, 45(12), 2389.

Experimental assessment and analysis of super-resolution in fluorescence microscopy based on multiple-point spread function fitting of spectrally demultiplexed images

NASA Astrophysics Data System (ADS)

Nishimura, Takahiro; Kimura, Hitoshi; Ogura, Yusuke; Tanida, Jun

2018-06-01

This paper presents an experimental assessment and analysis of super-resolution microscopy based on multiple-point spread function fitting of spectrally demultiplexed images using a designed DNA structure as a test target. For the purpose, a DNA structure was designed to have binding sites at a certain interval that is smaller than the diffraction limit. The structure was labeled with several types of quantum dots (QDs) to acquire their spatial information as spectrally encoded images. The obtained images are analyzed with a point spread function multifitting algorithm to determine the QD locations that indicate the binding site positions. The experimental results show that the labeled locations can be observed beyond the diffraction-limited resolution using three-colored fluorescence images that were obtained with a confocal fluorescence microscope. Numerical simulations show that labeling with eight types of QDs enables the positions aligned at 27.2-nm pitches on the DNA structure to be resolved with high accuracy.

Biphasic regulation of polymorphonuclear leukocyte spreading by polyphenolic compounds with pyrogallol moieties.

PubMed

Kori, Soichiro; Namiki, Hideo; Suzuki, Kingo

2009-09-01

Green tea polyphenols have been reported to have anti-inflammatory activities, although the molecular mechanisms responsible for this effect remain unclear. In the present study, we examined the effect of green tea extract and a variety of polyphenolic compounds on spreading of peripheral blood polymorphonuclear leukocytes (PMNs) over fibrinogen-coated surfaces. Green tea extract exerted a biphasic effect on PMN spreading; it induced or suppressed spreading at low and high concentrations, respectively. We also found that pyrogallol-bearing compounds have spreading induction activity. Among the compounds tested, tannic acid (TA) had the strongest activity; the concentrations required for induction of maximal spreading were 2 microM for TA, 200 microM for (-)-epigallocatechin gallate, and 2000 microM for the other active compounds. Furthermore, TA was the only compound showing a biphasic effect similar to that of green tea extract; TA at 20 or 200 microM suppressed spreading. The spreading-stimulatory signal was still latent during PMN exposure to TA at concentrations that inhibited spreading, because the pre-exposed PMNs underwent spreading when plated after removal of free TA by centrifugation. The spreading-inhibitory effect of TA at high concentrations overcame the induction of spreading by other stimuli, including phorbol 12-myristate 13-acetate, hydrogen peroxide, denatured fibrinogen surfaces, and naked plastic surfaces. These results suggest that TA as well as green tea extract is bi-functional, having pro-inflammatory and anti-inflammatory effects at low and high concentrations, respectively. Pharmacological use of TA may thus provide new strategies aimed at regulation of PMN spreading for control of inflammation.

Heat Transfer to a Thin Solid Combustible in Flame Spreading at Microgravity

NASA Technical Reports Server (NTRS)

Bhattacharjee, S.; Altenkirch, R. A.; Olson, S. L.; Sotos, R. G.

1991-01-01

The heat transfer rate to a thin solid combustible from an attached diffusion flame, spreading across the surface of the combustible in a quiescent, microgravity environment, was determined from measurements made in the drop tower facility at NASA-Lewis Research Center. With first-order Arrhenius pyrolysis kinetics, the solid-phase mass and energy equations along with the measured spread rate and surface temperature profiles were used to calculate the net heat flux to the surface. Results of the measurements are compared to the numerical solution of the complete set of coupled differential equations that describes the temperature, species, and velocity fields in the gas and solid phases. The theory and experiment agree on the major qualitative features of the heat transfer. Some fundamental differences are attributed to the neglect of radiation in the theoretical model.

GENERAL: Epidemic spreading on networks with vaccination

NASA Astrophysics Data System (ADS)

Shi, Hong-Jing; Duan, Zhi-Sheng; Chen, Guan-Rong; Li, Rong

2009-08-01

In this paper, a new susceptible-infected-susceptible (SIS) model on complex networks with imperfect vaccination is proposed. Two types of epidemic spreading patterns (the recovered individuals have or have not immunity) on scale-free networks are discussed. Both theoretical and numerical analyses are presented. The epidemic thresholds related to the vaccination rate, the vaccination-invalid rate and the vaccination success rate on scale-free networks are demonstrated, showing different results from the reported observations. This reveals that whether or not the epidemic can spread over a network under vaccination control is determined not only by the network structure but also by the medicine's effective duration. Moreover, for a given infective rate, the proportion of individuals to vaccinate can be calculated theoretically for the case that the recovered nodes have immunity. Finally, simulated results are presented to show how to control the disease prevalence.

Lateral Spread of Orientation Selectivity in V1 is Controlled by Intracortical Cooperativity

PubMed Central

Chavane, Frédéric; Sharon, Dahlia; Jancke, Dirk; Marre, Olivier; Frégnac, Yves; Grinvald, Amiram

2011-01-01

Neurons in the primary visual cortex receive subliminal information originating from the periphery of their receptive fields (RF) through a variety of cortical connections. In the cat primary visual cortex, long-range horizontal axons have been reported to preferentially bind to distant columns of similar orientation preferences, whereas feedback connections from higher visual areas provide a more diverse functional input. To understand the role of these lateral interactions, it is crucial to characterize their effective functional connectivity and tuning properties. However, the overall functional impact of cortical lateral connections, whatever their anatomical origin, is unknown since it has never been directly characterized. Using direct measurements of postsynaptic integration in cat areas 17 and 18, we performed multi-scale assessments of the functional impact of visually driven lateral networks. Voltage-sensitive dye imaging showed that local oriented stimuli evoke an orientation-selective activity that remains confined to the cortical feedforward imprint of the stimulus. Beyond a distance of one hypercolumn, the lateral spread of cortical activity gradually lost its orientation preference approximated as an exponential with a space constant of about 1 mm. Intracellular recordings showed that this loss of orientation selectivity arises from the diversity of converging synaptic input patterns originating from outside the classical RF. In contrast, when the stimulus size was increased, we observed orientation-selective spread of activation beyond the feedforward imprint. We conclude that stimulus-induced cooperativity enhances the long-range orientation-selective spread. PMID:21629708

Red Hot: Determining the Physical Properties of Lava Lake Skin

NASA Astrophysics Data System (ADS)

Ford, C.; Lev, E.

2015-12-01

Lava lakes are the surface expression of conduits that bring magma to the mouth of a volcano from deep within the earth. Time-lapse footage from a thermal imaging camera at Halema'uma'u lake at Kilauea volcano, Hawaii was used to investigate the cooling rate of the lava lake's surface. The data was then combined with an analytical model of lava flow cooling to constrain the porosity of the lava lake skin. The data was processed to account for the influence that the camera's position relative to the lake had on the image geometry and the recorded temperature values. We examined lake cooling in two separate scenarios: First, we calculated the cooling rate of the skin immediately after large gas bubbles burst at the lake's surface. Second, the temperature of the skin was measured as a function of distance from molten spreading centers (cracks) on the surface, and then converted to cooling as a function of the skin's age using the local lake surface velocity. The resulting cooling time-series were compared against cooling curves produced by a model that simulates lava flow cooling based on a myriad of physical factors. We performed quantitative data analysis to determine the approximate porosity of the lava lake skin. Preliminary comparisons reveal that the calculated cooling rates most closely correspond to the cooling curves that were produced with a lava porosity value of at least 80%.

Ground-based adaptive optics coronagraphic performance under closed-loop predictive control

NASA Astrophysics Data System (ADS)

Males, Jared R.; Guyon, Olivier

2018-01-01

The discovery of the exoplanet Proxima b highlights the potential for the coming generation of giant segmented mirror telescopes (GSMTs) to characterize terrestrial-potentially habitable-planets orbiting nearby stars with direct imaging. This will require continued development and implementation of optimized adaptive optics systems feeding coronagraphs on the GSMTs. Such development should proceed with an understanding of the fundamental limits imposed by atmospheric turbulence. Here, we seek to address this question with a semianalytic framework for calculating the postcoronagraph contrast in a closed-loop adaptive optics system. We do this starting with the temporal power spectra of the Fourier basis calculated assuming frozen flow turbulence, and then apply closed-loop transfer functions. We include the benefits of a simple predictive controller, which we show could provide over a factor of 1400 gain in raw point spread function contrast at 1 λ/D on bright stars, and more than a factor of 30 gain on an I=7.5 mag star such as Proxima. More sophisticated predictive control can be expected to improve this even further. Assuming a photon-noise limited observing technique such as high-dispersion coronagraphy, these gains in raw contrast will decrease integration times by the same large factors. Predictive control of atmospheric turbulence should therefore be seen as one of the key technologies that will enable ground-based telescopes to characterize terrestrial planets.

Measurement of the muon neutrino inclusive charged-current cross section in the energy range of 1-3 GeV with the T2K INGRID detector

NASA Astrophysics Data System (ADS)

Abe, K.; Andreopoulos, C.; Antonova, M.; Aoki, S.; Ariga, A.; Assylbekov, S.; Autiero, D.; Barbi, M.; Barker, G. J.; Barr, G.; Bartet-Friburg, P.; Batkiewicz, M.; Bay, F.; Berardi, V.; Berkman, S.; Bhadra, S.; Blondel, A.; Bolognesi, S.; Bordoni, S.; Boyd, S. B.; Brailsford, D.; Bravar, A.; Bronner, C.; Calland, R. G.; Cao, S.; Caravaca Rodríguez, J.; Cartwright, S. L.; Castillo, R.; Catanesi, M. G.; Cervera, A.; Cherdack, D.; Chikuma, N.; Christodoulou, G.; Clifton, A.; Coleman, J.; Collazuol, G.; Cremonesi, L.; Dabrowska, A.; De Rosa, G.; Dealtry, T.; Dennis, S. R.; Densham, C.; Dewhurst, D.; Di Lodovico, F.; Di Luise, S.; Dolan, S.; Drapier, O.; Duffy, K.; Dumarchez, J.; Dytman, S.; Dziewiecki, M.; Emery-Schrenk, S.; Ereditato, A.; Feusels, T.; Finch, A. J.; Fiorentini, G. A.; Friend, M.; Fujii, Y.; Fukuda, D.; Fukuda, Y.; Furmanski, A. P.; Galymov, V.; Garcia, A.; Giffin, S.; Giganti, C.; Gilje, K.; Gonin, M.; Grant, N.; Hadley, D. R.; Haegel, L.; Haigh, M. D.; Hamilton, P.; Hansen, D.; Hara, T.; Hartz, M.; Hasegawa, T.; Hastings, N. C.; Hayashino, T.; Hayato, Y.; Helmer, R. L.; Hierholzer, M.; Hillairet, A.; Himmel, A.; Hiraki, T.; Hirota, S.; Holeczek, J.; Horikawa, S.; Hosomi, F.; Huang, K.; Ichikawa, A. K.; Ieki, K.; Ikeda, M.; Imber, J.; Insler, J.; Intonti, R. A.; Irvine, T. J.; Ishida, T.; Ishii, T.; Iwai, E.; Iwamoto, K.; Izmaylov, A.; Jacob, A.; Jamieson, B.; Jiang, M.; Johnson, S.; Jo, J. H.; Jonsson, P.; Jung, C. K.; Kabirnezhad, M.; Kaboth, A. C.; Kajita, T.; Kakuno, H.; Kameda, J.; Karlen, D.; Karpikov, I.; Katori, T.; Kearns, E.; Khabibullin, M.; Khotjantsev, A.; Kielczewska, D.; Kikawa, T.; Kim, H.; Kim, J.; King, S.; Kisiel, J.; Kobayashi, T.; Koch, L.; Koga, T.; Konaka, A.; Kondo, K.; Kopylov, A.; Kormos, L. L.; Korzenev, A.; Koshio, Y.; Kropp, W.; Kudenko, Y.; Kurjata, R.; Kutter, T.; Lagoda, J.; Lamont, I.; Larkin, E.; Laveder, M.; Lawe, M.; Lazos, M.; Lindner, T.; Liptak, Z. J.; Litchfield, R. P.; Longhin, A.; Lopez, J. P.; Ludovici, L.; Lu, X.; Magaletti, L.; Mahn, K.; Malek, M.; Manly, S.; Marino, A. D.; Marteau, J.; Martin, J. F.; Martins, P.; Martynenko, S.; Maruyama, T.; Matveev, V.; Mavrokoridis, K.; Ma, W. Y.; Mazzucato, E.; McCarthy, M.; McCauley, N.; McFarland, K. S.; McGrew, C.; Mefodiev, A.; Mezzetto, M.; Mijakowski, P.; Miller, C. A.; Minamino, A.; Mineev, O.; Mine, S.; Missert, A.; Miura, M.; Moriyama, S.; Mueller, Th. A.; Murphy, S.; Myslik, J.; Nakadaira, T.; Nakahata, M.; Nakamura, K. G.; Nakamura, K.; Nakamura, K. D.; Nakayama, S.; Nakaya, T.; Nakayoshi, K.; Nantais, C.; Nielsen, C.; Nirkko, M.; Nishikawa, K.; Nishimura, Y.; Nowak, J.; O'Keeffe, H. M.; Ohta, R.; Okumura, K.; Okusawa, T.; Oryszczak, W.; Oser, S. M.; Ovsyannikova, T.; Owen, R. A.; Oyama, Y.; Palladino, V.; Palomino, J. L.; Paolone, V.; Payne, D.; Perkin, J. D.; Petrov, Y.; Pickard, L.; Pickering, L.; Pinzon Guerra, E. S.; Pistillo, C.; Popov, B.; Posiadala-Zezula, M.; Poutissou, J.-M.; Poutissou, R.; Przewlocki, P.; Quilain, B.; Radicioni, E.; Ratoff, P. N.; Ravonel, M.; Rayner, M. A. M.; Redij, A.; Reinherz-Aronis, E.; Riccio, C.; Rojas, P.; Rondio, E.; Roth, S.; Rubbia, A.; Rychter, A.; Sacco, R.; Sakashita, K.; Sánchez, F.; Sato, F.; Scantamburlo, E.; Scholberg, K.; Schoppmann, S.; Schwehr, J. D.; Scott, M.; Seiya, Y.; Sekiguchi, T.; Sekiya, H.; Sgalaberna, D.; Shah, R.; Shaikhiev, A.; Shaker, F.; Shaw, D.; Shiozawa, M.; Shirahige, T.; Short, S.; Smy, M.; Sobczyk, J. T.; Sorel, M.; Southwell, L.; Stamoulis, P.; Steinmann, J.; Stewart, T.; Suda, Y.; Suvorov, S.; Suzuki, A.; Suzuki, K.; Suzuki, S. Y.; Suzuki, Y.; Tacik, R.; Tada, M.; Takahashi, S.; Takeda, A.; Takeuchi, Y.; Tanaka, H. K.; Tanaka, H. A.; Terhorst, D.; Terri, R.; Thompson, L. F.; Tobayama, S.; Toki, W.; Tomura, T.; Touramanis, C.; Tsukamoto, T.; Tzanov, M.; Uchida, Y.; Vacheret, A.; Vagins, M.; Vallari, Z.; Vasseur, G.; Wachala, T.; Wakamatsu, K.; Walter, C. W.; Wark, D.; Warzycha, W.; Wascko, M. O.; Weber, A.; Wendell, R.; Wilkes, R. J.; Wilking, M. J.; Wilkinson, C.; Wilson, J. R.; Wilson, R. J.; Yamada, Y.; Yamamoto, K.; Yamamoto, M.; Yanagisawa, C.; Yano, T.; Yen, S.; Yershov, N.; Yokoyama, M.; Yoo, J.; Yoshida, K.; Yuan, T.; Yu, M.; Zalewska, A.; Zalipska, J.; Zambelli, L.; Zaremba, K.; Ziembicki, M.; Zimmerman, E. D.; Zito, M.; Żmuda, J.; T2K Collaboration

2016-04-01

We report a measurement of the νμ-nucleus inclusive charged-current cross section (=σc c ) on iron using data from the INGRID detector exposed to the J-PARC neutrino beam. The detector consists of 14 modules in total, which are spread over a range of off-axis angles from 0° to 1.1°. The variation in the neutrino energy spectrum as a function of the off-axis angle, combined with event topology information, is used to calculate this cross section as a function of neutrino energy. The cross section is measured to be σc c(1.1 GeV )=1.10 ±0.15 (1 0-38 cm2/nucleon) , σc c(2.0 GeV )=2.07 ±0.27 (1 0-38 cm2/nucleon) , and σc c(3.3 GeV )=2.29 ±0.45 (1 0-38 cm2/nucleon), at energies of 1.1, 2.0, and 3.3 GeV, respectively. These results are consistent with the cross section calculated by the neutrino interaction generators currently used by T2K. More importantly, the method described here opens up a new way to determine the energy dependence of neutrino-nucleus cross sections.

Epidemic spreading on interconnected networks.

PubMed

Saumell-Mendiola, Anna; Serrano, M Ángeles; Boguñá, Marián

2012-08-01

Many real networks are not isolated from each other but form networks of networks, often interrelated in nontrivial ways. Here, we analyze an epidemic spreading process taking place on top of two interconnected complex networks. We develop a heterogeneous mean-field approach that allows us to calculate the conditions for the emergence of an endemic state. Interestingly, a global endemic state may arise in the coupled system even though the epidemics is not able to propagate on each network separately and even when the number of coupling connections is small. Our analytic results are successfully confronted against large-scale numerical simulations.

Epidemic spreading on interconnected networks

NASA Astrophysics Data System (ADS)

Saumell-Mendiola, Anna; Serrano, M. Ángeles; Boguñá, Marián

2012-08-01

Many real networks are not isolated from each other but form networks of networks, often interrelated in nontrivial ways. Here, we analyze an epidemic spreading process taking place on top of two interconnected complex networks. We develop a heterogeneous mean-field approach that allows us to calculate the conditions for the emergence of an endemic state. Interestingly, a global endemic state may arise in the coupled system even though the epidemics is not able to propagate on each network separately and even when the number of coupling connections is small. Our analytic results are successfully confronted against large-scale numerical simulations.

An application of synthetic seismicity in earthquake statistics - The Middle America Trench

NASA Technical Reports Server (NTRS)

Ward, Steven N.

1992-01-01

The way in which seismicity calculations which are based on the concept of fault segmentation incorporate the physics of faulting through static dislocation theory can improve earthquake recurrence statistics and hone the probabilities of hazard is shown. For the Middle America Trench, the spread parameters of the best-fitting lognormal or Weibull distributions (about 0.75) are much larger than the 0.21 intrinsic spread proposed in the Nishenko Buland (1987) hypothesis. Stress interaction between fault segments disrupts time or slip predictability and causes earthquake recurrence to be far more aperiodic than has been suggested.

Sampling Based Influence Maximization on Linear Threshold Model

NASA Astrophysics Data System (ADS)

Jia, Su; Chen, Ling

2018-04-01

A sampling based influence maximization on linear threshold (LT) model method is presented. The method samples the routes in the possible worlds in the social networks, and uses Chernoff bound to estimate the number of samples so that the error can be constrained within a given bound. Then the active possibilities of the routes in the possible worlds are calculated, and are used to compute the influence spread of each node in the network. Our experimental results show that our method can effectively select appropriate seed nodes set that spreads larger influence than other similar methods.

Rapid simulation of spatial epidemics: a spectral method.

PubMed

Brand, Samuel P C; Tildesley, Michael J; Keeling, Matthew J

2015-04-07

Spatial structure and hence the spatial position of host populations plays a vital role in the spread of infection. In the majority of situations, it is only possible to predict the spatial spread of infection using simulation models, which can be computationally demanding especially for large population sizes. Here we develop an approximation method that vastly reduces this computational burden. We assume that the transmission rates between individuals or sub-populations are determined by a spatial transmission kernel. This kernel is assumed to be isotropic, such that the transmission rate is simply a function of the distance between susceptible and infectious individuals; as such this provides the ideal mechanism for modelling localised transmission in a spatial environment. We show that the spatial force of infection acting on all susceptibles can be represented as a spatial convolution between the transmission kernel and a spatially extended 'image' of the infection state. This representation allows the rapid calculation of stochastic rates of infection using fast-Fourier transform (FFT) routines, which greatly improves the computational efficiency of spatial simulations. We demonstrate the efficiency and accuracy of this fast spectral rate recalculation (FSR) method with two examples: an idealised scenario simulating an SIR-type epidemic outbreak amongst N habitats distributed across a two-dimensional plane; the spread of infection between US cattle farms, illustrating that the FSR method makes continental-scale outbreak forecasting feasible with desktop processing power. The latter model demonstrates which areas of the US are at consistently high risk for cattle-infections, although predictions of epidemic size are highly dependent on assumptions about the tail of the transmission kernel. Copyright © 2015 Elsevier Ltd. All rights reserved.

SU-D-BRC-01: An Automatic Beam Model Commissioning Method for Monte Carlo Simulations in Pencil-Beam Scanning Proton Therapy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Qin, N; Shen, C; Tian, Z

Purpose: Monte Carlo (MC) simulation is typically regarded as the most accurate dose calculation method for proton therapy. Yet for real clinical cases, the overall accuracy also depends on that of the MC beam model. Commissioning a beam model to faithfully represent a real beam requires finely tuning a set of model parameters, which could be tedious given the large number of pencil beams to commmission. This abstract reports an automatic beam-model commissioning method for pencil-beam scanning proton therapy via an optimization approach. Methods: We modeled a real pencil beam with energy and spatial spread following Gaussian distributions. Mean energy,more » and energy and spatial spread are model parameters. To commission against a real beam, we first performed MC simulations to calculate dose distributions of a set of ideal (monoenergetic, zero-size) pencil beams. Dose distribution for a real pencil beam is hence linear superposition of doses for those ideal pencil beams with weights in the Gaussian form. We formulated the commissioning task as an optimization problem, such that the calculated central axis depth dose and lateral profiles at several depths match corresponding measurements. An iterative algorithm combining conjugate gradient method and parameter fitting was employed to solve the optimization problem. We validated our method in simulation studies. Results: We calculated dose distributions for three real pencil beams with nominal energies 83, 147 and 199 MeV using realistic beam parameters. These data were regarded as measurements and used for commission. After commissioning, average difference in energy and beam spread between determined values and ground truth were 4.6% and 0.2%. With the commissioned model, we recomputed dose. Mean dose differences from measurements were 0.64%, 0.20% and 0.25%. Conclusion: The developed automatic MC beam-model commissioning method for pencil-beam scanning proton therapy can determine beam model parameters with satisfactory accuracy.« less

On the estimation of spread rate for a biological population

Treesearch

Jim Clark; Lajos Horváth; Mark Lewis

2001-01-01

We propose a nonparametric estimator for the rate of spread of an introduced population. We prove that the limit distribution of the estimator is normal or stable, depending on the behavior of the moment generating function. We show that resampling methods can also be used to approximate the distribution of the estimators.

Detector Sampling of Optical/IR Spectra: How Many Pixels per FWHM?

NASA Astrophysics Data System (ADS)

Robertson, J. Gordon

2017-08-01

Most optical and IR spectra are now acquired using detectors with finite-width pixels in a square array. Each pixel records the received intensity integrated over its own area, and pixels are separated by the array pitch. This paper examines the effects of such pixellation, using computed simulations to illustrate the effects which most concern the astronomer end-user. It is shown that coarse sampling increases the random noise errors in wavelength by typically 10-20 % at 2 pixels per Full Width at Half Maximum, but with wide variation depending on the functional form of the instrumental Line Spread Function (i.e. the instrumental response to a monochromatic input) and on the pixel phase. If line widths are determined, they are even more strongly affected at low sampling frequencies. However, the noise in fitted peak amplitudes is minimally affected by pixellation, with increases less than about 5%. Pixellation has a substantial but complex effect on the ability to see a relative minimum between two closely spaced peaks (or relative maximum between two absorption lines). The consistent scale of resolving power presented by Robertson to overcome the inadequacy of the Full Width at Half Maximum as a resolution measure is here extended to cover pixellated spectra. The systematic bias errors in wavelength introduced by pixellation, independent of signal/noise ratio, are examined. While they may be negligible for smooth well-sampled symmetric Line Spread Functions, they are very sensitive to asymmetry and high spatial frequency sub-structure. The Modulation Transfer Function for sampled data is shown to give a useful indication of the extent of improperly sampled signal in an Line Spread Function. The common maxim that 2 pixels per Full Width at Half Maximum is the Nyquist limit is incorrect and most Line Spread Functions will exhibit some aliasing at this sample frequency. While 2 pixels per Full Width at Half Maximum is nevertheless often an acceptable minimum for moderate signal/noise work, it is preferable to carry out simulations for any actual or proposed Line Spread Function to find the effects of various sampling frequencies. Where spectrograph end-users have a choice of sampling frequencies, through on-chip binning and/or spectrograph configurations, it is desirable that the instrument user manual should include an examination of the effects of the various choices.

Diffusion in Colocation Contact Networks: The Impact of Nodal Spatiotemporal Dynamics.

PubMed

Thomas, Bryce; Jurdak, Raja; Zhao, Kun; Atkinson, Ian

2016-01-01

Temporal contact networks are studied to understand dynamic spreading phenomena such as communicable diseases or information dissemination. To establish how spatiotemporal dynamics of nodes impact spreading potential in colocation contact networks, we propose "inducement-shuffling" null models which break one or more correlations between times, locations and nodes. By reconfiguring the time and/or location of each node's presence in the network, these models induce alternative sets of colocation events giving rise to contact networks with varying spreading potential. This enables second-order causal reasoning about how correlations in nodes' spatiotemporal preferences not only lead to a given contact network but ultimately influence the network's spreading potential. We find the correlation between nodes and times to be the greatest impediment to spreading, while the correlation between times and locations slightly catalyzes spreading. Under each of the presented null models we measure both the number of contacts and infection prevalence as a function of time, with the surprising finding that the two have no direct causality.

Magnetic Anomaly Lineations in the Gulf of Aden

NASA Astrophysics Data System (ADS)

Noguchi, Y.; Nakanishi, M.; Tamaki, K.; Fujimoto, H.; Huchon, P.; Leroy, S. D.; Styles, P.

2014-12-01

We present the magnetic anomaly lineations in the Gulf of Aden. The Gulf of Aden has slow spreading ridges between the Arabia Plate and Somalia Plate. The Arabian plate moves away from Somalia Plate in an NE direction, at a rate of about 2 cm/yr. Previous works indicates that seafloor spreading started about 20 Ma in the eastern part of the Gulf of Aden and propagated westward. The spreading axis has a E-W trend west of 46 E and that east of 46 E has a N60 W trend. We examined magnetic data acquired in the cruises by R/V L'Atalante in 1995, R/V Hakuho-maru from 2000 to 2001, R/V Maurice Ewing in 2001, and Shackleton in 1975 and 1979. We also used data obtained from National Geophysical Data Center, NOAA. We calculated magnetic anomalies using the latest Internation Geomagnetic Reference Field. Elongated negative magnetic anomalies, which amplitude are more than 500 nT, observed over the spreading centers. Most of the elongated anomalies are parallel with the spreading centers. The elongated magnetic anomalies west of 46 30'E have an E-W trend around the spreading centers. Several discontinuities in the magnetic anomaly contour map illustrate the position of the fracture zones concealed by sediments. We identified magnetic lineations from 43 E to 52 E. Most of magnetic lineations west and east of 46 30'E have N-E and N60-65 W strikes, respectively. The oldest lineations are C3r (5.48~5.74 Ma) between 43 10'E and 44 E and C5Ar (12.4~12.7 Ma) east of 44 E. Our identification of magnetic anomaly lineations indicates a symmetric seafloor spreading with a spreading rate of about 1.0 cm/yr, although Leroy et al. (2004) showed an asymmetric seafloor spreading of the Sheba Ridge, east of our study area. The kinematics of the Arabia plate changed about 5 Ma, but our results did not show any coeval change in spreading rates of the spreading system in the Gulf of Aden.

Modeling mountain pine beetle habitat suitability within Sequoia National Park

NASA Astrophysics Data System (ADS)

Nguyen, Andrew

Understanding significant changes in climate and their effects on timber resources can help forest managers make better decisions regarding the preservation of natural resources and land management. These changes may to alter natural ecosystems dependent on historical and current climate conditions. Increasing mountain pine beetle (MBP) outbreaks within the southern Sierra Nevada are the result of these alterations. This study better understands MPB behavior within Sequoia National Park (SNP) and model its current and future habitat distribution. Variables contributing to MPB spread are vegetation stress, soil moisture, temperature, precipitation, disturbance, and presence of Ponderosa (Pinus ponderosa) and Lodgepole (Pinus contorta) pine trees. These variables were obtained using various modeled, insitu, and remotely sensed sources. The generalized additive model (GAM) was used to calculate the statistical significance of each variable contributing to MPB spread and also created maps identifying habitat suitability. Results indicate vegetation stress and forest disturbance to be variables most indicative of MPB spread. Additionally, the model was able to detect habitat suitability of MPB with a 45% accuracy concluding that a geospatial driven modeling approach can be used to delineate potential MPB spread within SNP.

Dynamic deformation image de-blurring and image processing for digital imaging correlation measurement

NASA Astrophysics Data System (ADS)

Guo, X.; Li, Y.; Suo, T.; Liu, H.; Zhang, C.

2017-11-01

This paper proposes a method for de-blurring of images captured in the dynamic deformation of materials. De-blurring is achieved based on the dynamic-based approach, which is used to estimate the Point Spread Function (PSF) during the camera exposure window. The deconvolution process involving iterative matrix calculations of pixels, is then performed on the GPU to decrease the time cost. Compared to the Gauss method and the Lucy-Richardson method, it has the best result of the image restoration. The proposed method has been evaluated by using the Hopkinson bar loading system. In comparison to the blurry image, the proposed method has successfully restored the image. It is also demonstrated from image processing applications that the de-blurring method can improve the accuracy and the stability of the digital imaging correlation measurement.

Entropy and complexity analysis of hydrogenic Rydberg atoms

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lopez-Rosa, S.; Departamento de Fisica Aplicada II, Universidad de Sevilla, 41012-Sevilla; Toranzo, I. V.

The internal disorder of hydrogenic Rydberg atoms as contained in their position and momentum probability densities is examined by means of the following information-theoretic spreading quantities: the radial and logarithmic expectation values, the Shannon entropy, and the Fisher information. As well, the complexity measures of Cramer-Rao, Fisher-Shannon, and Lopez Ruiz-Mancini-Calvet types are investigated in both reciprocal spaces. The leading term of these quantities is rigorously calculated by use of the asymptotic properties of the concomitant entropic functionals of the Laguerre and Gegenbauer orthogonal polynomials which control the wavefunctions of the Rydberg states in both position and momentum spaces. The associatedmore » generalized Heisenberg-like, logarithmic and entropic uncertainty relations are also given. Finally, application to linear (l= 0), circular (l=n- 1), and quasicircular (l=n- 2) states is explicitly done.« less

Expansion Potentials for Exact Far-from-Equilibrium Spreading of Particles and Energy

DOE PAGES

Vasseur, Romain; Karrasch, Christoph; Moore, Joel E.

2015-12-01

We report that the rates at which energy and particle densities move to equalize arbitrarily large temperature and chemical potential differences in an isolated quantum system have an emergent thermodynamical description whenever energy or particle current commutes with the Hamiltonian. Concrete examples include the energy current in the 1D spinless fermion model with nearest-neighbor interactions (XXZ spin chain), energy current in Lorentz-invariant theories or particle current in interacting Bose gases in arbitrary dimension. Even far from equilibrium, these rates are controlled by state functions, which we call "expansion potentials", expressed as integrals of equilibrium Drude weights. This relation between nonequilibriummore » quantities and linear response implies non-equilibrium Maxwell relations for the Drude weights. Lastly, we verify our results via DMRG calculations for the XXZ chain.« less

Artificial testing targets with controllable blur for adaptive optics microscopes

NASA Astrophysics Data System (ADS)

Hattori, Masayuki; Tamada, Yosuke; Murata, Takashi; Oya, Shin; Hasebe, Mitsuyasu; Hayano, Yutaka; Kamei, Yasuhiro

2017-08-01

This letter proposes a method of configuring a testing target to evaluate the performance of adaptive optics microscopes. In this method, a testing slide with fluorescent beads is used to simultaneously determine the point spread function and the field of view. The point spread function is reproduced to simulate actual biological samples by etching a microstructure on the cover glass. The fabrication process is simplified to facilitate an onsite preparation. The artificial tissue consists of solid materials and silicone oil and is stable for use in repetitive experiments.

Identifying influential spreaders in complex networks through local effective spreading paths

NASA Astrophysics Data System (ADS)

Wang, Xiaojie; Zhang, Xue; Yi, Dongyun; Zhao, Chengli

2017-05-01

How to effectively identify a set of influential spreaders in complex networks is of great theoretical and practical value, which can help to inhibit the rapid spread of epidemics, promote the sales of products by word-of-mouth advertising, and so on. A naive strategy is to select the top ranked nodes as identified by some centrality indices, and other strategies are mainly based on greedy methods and heuristic methods. However, most of those approaches did not concern the connections between nodes. Usually, the distances between the selected spreaders are very close, leading to a serious overlapping of their influence. As a consequence, the global influence of the spreaders in networks will be greatly reduced, which largely restricts the performance of those methods. In this paper, a simple and efficient method is proposed to identify a set of discrete yet influential spreaders. By analyzing the spreading paths in the network, we present the concept of effective spreading paths and measure the influence of nodes via expectation calculation. The numerical analysis in undirected and directed networks all show that our proposed method outperforms many other centrality-based and heuristic benchmarks, especially in large-scale networks. Besides, experimental results on different spreading models and parameters demonstrates the stability and wide applicability of our method.

Imaging performance of annular apertures. IV - Apodization and point spread functions. V - Total and partial energy integral functions

NASA Technical Reports Server (NTRS)

Tschunko, H. F. A.

1983-01-01

Reference is made to a study by Tschunko (1979) in which it was discussed how apodization modifies the modulation transfer function for various central obstruction ratios. It is shown here how apodization, together with the central obstruction ratio, modifies the point spread function, which is the basic element for the comparison of imaging performance and for the derivation of energy integrals and other functions. At high apodization levels and lower central obstruction (less than 0.1), new extended radial zones are formed in the outer part of the central ring groups. These transmutation of the image functions are of more than theoretical interest, especially if the irradiance levels in the outer ring zones are to be compared to the background irradiance levels. Attention is then given to the energy distribution in point images generated by annular apertures apodized by various transmission functions. The total energy functions are derived; partial energy integrals are determined; and background irradiance functions are discussed.

Modelling of air flow supply in a room at variable regime by using both K - E and spalart - allmaras turbulent model

NASA Astrophysics Data System (ADS)

Korbut, Vadim; Voznyak, Orest; Sukholova, Iryna; Myroniuk, Khrystyna

2017-12-01

The abstract is to The article is devoted to the decision of actual task of air distribution efficiency increasing with the help of swirl and spread air jets to provide normative parameters of air in the production apartments. The mathematical model of air supply with swirl and spread air jets in that type of apartments is improved. It is shown that for reachin of air distribution maximal efficiency it is necessary to supply air by air jets, that intensively extinct before entering into a working area. Simulation of air flow performed with the help of CFD FLUENT (Ansys FLUENT). Calculations of the equation by using one-parameter model of turbulence Spalart-Allmaras are presented. The graphical and the analytical dependences on the basis of the conducted experimental researches, which can be used in subsequent engineering calculations, are shown out. Dynamic parameters of air flow that is created due to swirl and spread air jets at their leakage at variable regime and creation of dynamic microclimate in a room has been determined. Results of experimental investigations of air supply into the room by air distribution device which creates swirl air jets for creation more intensive turbulization air flow in the room are presented. Obtained results of these investigations give possibility to realize engineer calculations of air distribution with swirl air jets. The results of theoretical researches of favourable influence of dynamic microclimate to the man are presented. When using dynamic microclimate, it's possible to decrease conditioning and ventilation system expenses. Human organism reacts favourably on short lasting deviations from the rationed parameters of air environment.

Dynamics of epidemic spreading with vaccination: Impact of social pressure and engagement

NASA Astrophysics Data System (ADS)

Pires, Marcelo A.; Crokidakis, Nuno

2017-02-01

In this work we consider a model of epidemic spreading coupled with an opinion dynamics in a fully-connected population. Regarding the opinion dynamics, the individuals may be in two distinct states, namely in favor or against a vaccination campaign. Individuals against the vaccination follow a standard SIS model, whereas the pro-vaccine individuals can also be in a third compartment, namely Vaccinated. In addition, the opinions change according to the majority-rule dynamics in groups with three individuals. We also consider that the vaccine can give permanent or temporary immunization to the individuals. By means of analytical calculations and computer simulations, we show that the opinion dynamics can drastically affect the disease propagation, and that the engagement of the pro-vaccine individuals can be crucial for stopping the epidemic spreading. The full numerical code for simulating the model is available from the authors' webpage.

Vibrational Properties of Bulk Boric Acid 2A and 3T Polymorphs and Their Two-Dimensional Layers: Measurements and Density Functional Theory Calculations.

PubMed

Bezerra da Silva, M; Santos, R C R; Freire, P T C; Caetano, E W S; Freire, V N

2018-02-08

Boric acid (H 3 BO 3 ) is being used effectively nowadays in traps/baits for the management of Aedes aegypti L. and Aedes albopictus Skuse species of mosquitoes, which are the main spreading vectors worldwide for diseases such as malaria, dengue, and zika. Previously, we published results on the structural, electronic, and optical properties of its molecular triclinic H 3 BO 3 -2A and trigonal H 3 BO 3 -3T polymorphs within the framework of density functional theory (DFT). Because of the renewed importance of these materials, the focus of this work is on the vibrational properties of the bulk boric acid 2A and 3T polymorphs. We measured the infrared and Raman spectra of the former, which was accompanied and interpreted through state-of-the-art DFT calculations, supplemented by computations regarding the H 3 BO 3 molecule and two-dimensional layers based on the bulk structures. We identify/assign their normal modes and find vibrational signatures for each polymorph as well as in- and out-of-plane motions and molecular vibrations, unveiling a nice agreement between the DFT level of theory employed and our improved spectroscopic measurements in the wavenumber ranges of 400-2000 cm -1 (infrared) and 0-1500 cm -1 (Raman). We show that a dispersion-corrected DFT functional within the generalized gradient approximation (GGA) can be very accurate in describing the vibrational properties of the boric acid polymorphs. Besides, several issues left open/not clearly resolved in previously published works on the vibrational mode assignments of the bulk and 2D sheets of boric acid are explained satisfactorily. Finally, phonon dispersions and associated densities of states were also evaluated for each polymorph along with their temperature-dependent DFT-calculated entropy, enthalpy, free energy, heat capacity, and Debye temperature. In particular, our DFT calculations suggest a possible way to differentiate the 2A and 3T boric acid polymorphs through Raman spectroscopy and heat capacity measurements.

Visual attention spreads broadly but selects information locally.

PubMed

Shioiri, Satoshi; Honjyo, Hajime; Kashiwase, Yoshiyuki; Matsumiya, Kazumichi; Kuriki, Ichiro

2016-10-19

Visual attention spreads over a range around the focus as the spotlight metaphor describes. Spatial spread of attentional enhancement and local selection/inhibition are crucial factors determining the profile of the spatial attention. Enhancement and ignorance/suppression are opposite effects of attention, and appeared to be mutually exclusive. Yet, no unified view of the factors has been provided despite their necessity for understanding the functions of spatial attention. This report provides electroencephalographic and behavioral evidence for the attentional spread at an early stage and selection/inhibition at a later stage of visual processing. Steady state visual evoked potential showed broad spatial tuning whereas the P3 component of the event related potential showed local selection or inhibition of the adjacent areas. Based on these results, we propose a two-stage model of spatial attention with broad spread at an early stage and local selection at a later stage.

Numerical simulations of fire spread in a Pinus pinaster needles fuel bed

NASA Astrophysics Data System (ADS)

Menage, D.; Chetehouna, K.; Mell, W.

2012-11-01

The main aim of this paper is to extend the cases of WFDS model validation by comparing its predictions to literature data on a ground fire spreading in a Pinus pinaster needles fuel bed. This comparison is based on the experimental results of Mendes-Lopes and co-workers. This study is performed using the same domain as in the experiments (3.0m×1.2m×0.9m) with a mesh of 49,280 cells. We investigate the influence of wind (varied between 0 and 2 m/s) and moisture content (10 and 18%) on the rate of spread. The WFDS rate of spread is determined using a cross-correlation function of ground temperature profiles. The simulated rate of spread, as well as temperature, compared favourably to experimental values and show the WFDS model capacity to predict ground fires in Pinus Pinaster fuel beds.

Creating buzz: the neural correlates of effective message propagation.

PubMed

Falk, Emily B; Morelli, Sylvia A; Welborn, B Locke; Dambacher, Karl; Lieberman, Matthew D

2013-07-01

Social interaction promotes the spread of values, attitudes, and behaviors. Here, we report on neural responses to ideas that are destined to spread. We scanned message communicators using functional MRI during their initial exposure to the to-be-communicated ideas. These message communicators then had the opportunity to spread the messages and their corresponding subjective evaluations to message recipients outside the scanner. Successful ideas were associated with neural responses in the communicators' mentalizing systems and reward systems when they first heard the messages, prior to spreading them. Similarly, individuals more able to spread their own views to others produced greater mentalizing-system activity during initial encoding. Unlike prior social-influence studies that focused on the individuals being influenced, this investigation focused on the brains of influencers. Successful social influence is reliably associated with an influencer-to-be's state of mind when first encoding ideas.

The role of roadsides in plant invasions: a demographic approach.

PubMed

Christen, Douglas; Matlack, Glenn

2006-04-01

Non-native plant species are common along roadsides, but presence does not necessarily indicate spread along the road axis. Roadsides may serve merely as habitat for a species spreading independently of roads. The potential conduit function of roads depends on the habitat specificity of the spreading species, its dispersal range relative to the spacing of roads in the landscape, and the relative importance of long- and short-range dispersal. We describe a demographic model of the road x species interaction and suggest methods of assessing conduit function in the field based on the model results. A species limited to roadside habitat will be constrained to spread along the road axis unless its long-range dispersal is sufficient to carry it across the intervening unfavorable area to another road. It will propagate along a road corridor at a rate determined by the scale of short-range dispersal. Effective management of an invasion requires distinguishing between the habitat and conduit functions, a distinction difficult to make with only snapshot data. Invasions can be reconstructed by several methods, but none is totally satisfactory. We suggest comparing stem distributions on transects parallel and perpendicular to the road axis, and beside the road, and away from it, with an idealized Gaussian curve. Such comparisons would allow discrimination between pattern determined by habitat suitability and pattern reflecting random and facilitated dispersal.

A fuzzy rumor spreading model based on transmission capacity

NASA Astrophysics Data System (ADS)

Zhang, Yi; Xu, Jiuping; Wu, Yue

This paper proposes a rumor spreading model that considers three main factors: the event importance, event ambiguity, and the publics critical sense, each of which are defined by decision makers using linguistic descriptions and then transformed into triangular fuzzy numbers. To calculate the resultant force of these three factors, the transmission capacity and a new parameter category with fuzzy variables are determined. A rumor spreading model is then proposed which has fuzzy parameters rather than the fixed parameters in traditional models. As the proposed model considers the comprehensive factors affecting rumors from three aspects rather than examining special factors from a particular aspect. The proposed rumor spreading model is tested using different parameters for several different conditions on BA networks and three special cases are simulated. The simulation results for all three cases suggested that events of low importance, those that are only clarifying facts, and those that are strongly critical do not result in rumors. Therefore, the model assessment results were proven to be in agreement with reality. Parameters for the model were then determined and applied to an analysis of the 7.23 Yong-Wen line major transportation accident (YWMTA). When the simulated data were compared with the real data from this accident, the results demonstrated that the interval for the rumor spreading key point in the model was accurate, and that the key point for the YWMTA rumor spread fell into the range estimated by the model.

Analysis of flame spread over multicomponent combustibles

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ohtani, H.; Sato, J.

1985-01-01

A theoretical model of volatile component diffusion in the condensed phase is carried out in order to form a basis for predicting the flame spread rate in thermally thick multicomponent combustibles in a non-fluid condensed phase. The fuels could be, e.g., crude oil, heavy oil, or light oil. Mass transfer occurs only by diffusion so the gas phase volatile concentration at the surface is estimated from the condensed phase volatile concentration and the surface temperature, which increases close to the leading flame edge. The flame spread rate is assumed steady. The velocity of the flame spread is shown to bemore » a function of the initial condensed phase temperature and the temperature at the leading flame edge.« less

Prediction of ISO 9705 Room/Corner Test Results. Volume 1

DTIC Science & Technology

1999-11-01

spread rates depend on the flame length , so that it is not a unique function of the material being burned. The flame spread model developed by Mowrer and...height is expressed as: = kf (5) xp -X16 16I The parameter, kf is a correlating factor used to define the flame length . Cleary and Quintiere (1991

The spread of invasive species and infectious disease as drivers of ecosystem change.

Treesearch

Todd A. Crowl; Thomas O. Crist; Robert R. Parmenter; Gary Belovsky; Ariel E. Lugo

2008-01-01

Invasive species, disease vectors, and pathogens affect biodiversity, ecosystem function and services, and human health. Climate change, land use, and transport vectors interact in complex ways to determine the spread of native and non-native invasive species, pathogens, and their effects on ecosystem dynamics. Early detection and in-depth understanding of invasive...

An Exactly Solvable Model for the Spread of Disease

ERIC Educational Resources Information Center

Mickens, Ronald E.

2012-01-01

We present a new SIR epidemiological model whose exact analytical solution can be calculated. In this model, unlike previous models, the infective population becomes zero at a finite time. Remarkably, these results can be derived from only an elementary knowledge of differential equations.

Synthesis, XRD single crystal structure analysis, vibrational spectral analysis, molecular dynamics and molecular docking studies of 2-(3-methoxy-4-hydroxyphenyl) benzothiazole

NASA Astrophysics Data System (ADS)

Sarau Devi, A.; Aswathy, V. V.; Sheena Mary, Y.; Yohannan Panicker, C.; Armaković, Stevan; Armaković, Sanja J.; Ravindran, Reena; Van Alsenoy, C.

2017-11-01

The vibrational spectra and corresponding vibrational assignments of 2-(3-methoxy-4-hydroxyphenyl)benzothiazole is reported. Single crystal XRD data of the title compound is reported and the orientation of methoxy group is cis to nitrogen atom of the thiazole ring. The phenyl ring breathing modes of the title compound are assigned at 1042 and 731 cm-1 theoretically. The charge transfer within the molecule is studied using frontier molecular orbital analysis. The chemical reactivity descriptors are calculated theoretically. The NMR spectral data predicted theoretically are in good agreement with the experimental data. The strong negative region spread over the phenyl rings, nitrogen atom and oxygen atom of the hydroxyl group in the MEP plot is due to the immense conjugative and hyper conjugative resonance charge delocalization of π-electrons. Molecule sites prone to electrophilic attacks have been determined by analysis of ALIE surfaces, while Fukui functions provided further insight into the local reactivity properties of title molecule. Autoxidation properties have been investigated by calculation of bond dissociation energies (BDEs) of hydrogen abstraction, while BDEs of the rest of the single acyclic bonds were valuable for the further investigation of degradation properties. Calculation of radial distribution functions was performed in order to determine which atoms of the title molecule have pronounced interactions with water molecules. The title compound forms a stable complex with aryl hydrocarbon receptor and can be a lead compound for developing new anti-tumor drug. Antimicrobial properties of the title compound was screened against one bacterial culture Escherchia coli and four fungal cultures viz., Aspergillus niger, Pencillum chrysogenum, Saccharomyces cerevisiae and Rhyzopus stolonifer.

SU-G-IeP3-08: Image Reconstruction for Scanning Imaging System Based On Shape-Modulated Point Spreading Function

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Ruixing; Yang, LV; Xu, Kele

Purpose: Deconvolution is a widely used tool in the field of image reconstruction algorithm when the linear imaging system has been blurred by the imperfect system transfer function. However, due to the nature of Gaussian-liked distribution for point spread function (PSF), the components with coherent high frequency in the image are hard to restored in most of the previous scanning imaging system, even the relatively accurate PSF is acquired. We propose a novel method for deconvolution of images which are obtained by using shape-modulated PSF. Methods: We use two different types of PSF - Gaussian shape and donut shape -more » to convolute the original image in order to simulate the process of scanning imaging. By employing deconvolution of the two images with corresponding given priors, the image quality of the deblurred images are compared. Then we find the critical size of the donut shape compared with the Gaussian shape which has similar deconvolution results. Through calculation of tightened focusing process using radially polarized beam, such size of donut is achievable under same conditions. Results: The effects of different relative size of donut and Gaussian shapes are investigated. When the full width at half maximum (FWHM) ratio of donut and Gaussian shape is set about 1.83, similar resolution results are obtained through our deconvolution method. Decreasing the size of donut will favor the deconvolution method. A mask with both amplitude and phase modulation is used to create a donut-shaped PSF compared with the non-modulated Gaussian PSF. Donut with size smaller than our critical value is obtained. Conclusion: The utility of donutshaped PSF are proved useful and achievable in the imaging and deconvolution processing, which is expected to have potential practical applications in high resolution imaging for biological samples.« less

Effect of plasma spray processing variations on particle melting and splat spreading of hydroxylapatite and alumina

NASA Astrophysics Data System (ADS)

Yankee, S. J.; Pletka, B. J.

1993-09-01

Splats of hydroxylapatite (HA) and alumina were obtained via plasma spraying using systematically varied combinations of plasma velocity and temperature, which were achieved by altering the primary plasma gas flow rate and plasma gas composition. Particle size was also varied in the case of alumina. Splat spreading was quantified via computer- aided image analysis as a function of processing variations. A comparison of the predicted splat dimensions from a model developed by Madejski with experimental observations of HA and alumina splats was performed. The model tended to underestimate the HA splat sizes, suggesting that evaporation of smaller particles occurred under the chosen experimental conditions, and to overestimate the observed alumina splat dimensions. Based on this latter result and on the surface appearance of the substrates, incomplete melting appeared to take place in all but the smaller alumina particles. Analysis of the spreading data as a function of the processing variations indicated that the particle size as well as the plasma temperature and velocity influenced the extent of particle melting. Based on these data and other considerations, a physical model was developed that described the degree of particle melting in terms of material and processing parameters. The physical model correctly predicted the relative splat spreading behavior of HA and alumina, assuming that spreading was directly linked to the extent of particle melting.

Epidemic spreading between two coupled subpopulations with inner structures

NASA Astrophysics Data System (ADS)

Ruan, Zhongyuan; Tang, Ming; Gu, Changgui; Xu, Jinshan

2017-10-01

The structure of underlying contact network and the mobility of agents are two decisive factors for epidemic spreading in reality. Here, we study a model consisting of two coupled subpopulations with intra-structures that emphasizes both the contact structure and the recurrent mobility pattern of individuals simultaneously. We show that the coupling of the two subpopulations (via interconnections between them and round trips of individuals) makes the epidemic threshold in each subnetwork to be the same. Moreover, we find that the interconnection probability between two subpopulations and the travel rate are important factors for spreading dynamics. In particular, as a function of interconnection probability, the epidemic threshold in each subpopulation decreases monotonously, which enhances the risks of an epidemic. While the epidemic threshold displays a non-monotonic variation as travel rate increases. Moreover, the asymptotic infected density as a function of travel rate in each subpopulation behaves differently depending on the interconnection probability.

Myopic astigmatism correction: comparison of a Toric Implantable Collamer Lens and a bioptics technique by an adaptive optics visual simulator.

PubMed

Pérez-Vives, Cari; Domínguez-Vicent, Alberto; Madrid-Costa, David; Ferrer-Blasco, Teresa; Montés-Micó, Robert

2013-03-01

To compare the optical and visual quality of a simulated Toric Implantable Collamer Lens (TICL) and a bioptics technique to treat high myopic astigmatism. An adaptive optics visual simulator was used to simulate the vision after TICL implantation and a bioptics procedure from the wavefront aberration pattern for moderate and high-myopic astigmatism. Visual acuity (VA) at different contrasts and contrast sensitivity (CS) at 10, 20 and 25 cycles degree(-1) were measured for 3 and 5-mm pupils. Modulation Transfer Function (MTF) and Point Spread Function (PSF) were calculated for a 5-mm pupil. At a 3-mm pupil we only found statistically significant differences in VA between the two simulated surgeries at low-contrast for moderate- and high-myopic astigmatism (p < 0.05). Statistically significant differences were found in CS at 3-mm pupil between both procedures at the highest spatial frequency for moderate-myopic astigmatism and at all frequencies for high-myopic astigmatism (p < 0.05). At a 5-mm pupil we found statistically significant differences in VA and CS between both simulated surgeries at all contrasts and frequencies evaluated for both groups (p < 0.05). In all cases VA and CS were better with the TICL than with the bioptics technique. MTFs for the bioptics technique were worse than those computed for the TICL. The TICL showed less spread out of the PSF than the bioptics procedure. Simulated TICL and bioptics procedures provided good optical and visual quality, although TICL implantation provided slightly better outcomes than the bioptics procedure, especially when the pupil diameter was increased. Ophthalmic & Physiological Optics © 2013 The College of Optometrists.

Magnetoacoustic tomography with magnetic induction for high-resolution bioimepedance imaging through vector source reconstruction under the static field of MRI magnet.

PubMed

Mariappan, Leo; Hu, Gang; He, Bin

2014-02-01

Magnetoacoustic tomography with magnetic induction (MAT-MI) is an imaging modality to reconstruct the electrical conductivity of biological tissue based on the acoustic measurements of Lorentz force induced tissue vibration. This study presents the feasibility of the authors' new MAT-MI system and vector source imaging algorithm to perform a complete reconstruction of the conductivity distribution of real biological tissues with ultrasound spatial resolution. In the present study, using ultrasound beamformation, imaging point spread functions are designed to reconstruct the induced vector source in the object which is used to estimate the object conductivity distribution. Both numerical studies and phantom experiments are performed to demonstrate the merits of the proposed method. Also, through the numerical simulations, the full width half maximum of the imaging point spread function is calculated to estimate of the spatial resolution. The tissue phantom experiments are performed with a MAT-MI imaging system in the static field of a 9.4 T magnetic resonance imaging magnet. The image reconstruction through vector beamformation in the numerical and experimental studies gives a reliable estimate of the conductivity distribution in the object with a ∼ 1.5 mm spatial resolution corresponding to the imaging system frequency of 500 kHz ultrasound. In addition, the experiment results suggest that MAT-MI under high static magnetic field environment is able to reconstruct images of tissue-mimicking gel phantoms and real tissue samples with reliable conductivity contrast. The results demonstrate that MAT-MI is able to image the electrical conductivity properties of biological tissues with better than 2 mm spatial resolution at 500 kHz, and the imaging with MAT-MI under a high static magnetic field environment is able to provide improved imaging contrast for biological tissue conductivity reconstruction.

Monte Carlo investigation of backscatter point spread function for x-ray imaging examinations

NASA Astrophysics Data System (ADS)

Xiong, Zhenyu; Vijayan, Sarath; Rudin, Stephen; Bednarek, Daniel R.

2017-03-01

X-ray imaging examinations, especially complex interventions, may result in relatively high doses to the patient's skin inducing skin injuries. A method was developed to determine the skin-dose distribution for non-uniform x-ray beams by convolving the backscatter point-spread-function (PSF) with the primary-dose distribution to generate the backscatter distribution that, when added to the primary dose, gives the total-dose distribution. This technique was incorporated in the dose-tracking system (DTS), which provides a real-time color-coded 3D-mapping of skin dose during fluoroscopic procedures. The aim of this work is to investigate the variation of the backscatter PSF with different parameters. A backscatter PSF of a 1-mm x-ray beam was generated by EGSnrc Monte-Carlo code for different x-ray beam energies, different soft-tissue thickness above bone, different bone thickness and different entrance-beam angles, as well as for different locations on the SK-150 anthropomorphic head phantom. The results show a reduction of the peak scatter to primary dose ratio of 48% when X-ray beam voltage is increased from 40 keV to 120 keV. The backscatter dose was reduced when bone was beneath the soft tissue layer and this reduction increased with thinner soft tissue and thicker bone layers. The backscatter factor increased about 21% as the angle of incidence of the beam with the entrance surface decreased from 90° (perpendicular) to 30°. The backscatter PSF differed for different locations on the SK-150 phantom by up to 15%. The results of this study can be used to improve the accuracy of dose calculation when using PSF convolution in the DTS.

A Hybrid Ground-Motion Prediction Equation for Earthquakes in Western Alberta

NASA Astrophysics Data System (ADS)

Spriggs, N.; Yenier, E.; Law, A.; Moores, A. O.

2015-12-01

Estimation of ground-motion amplitudes that may be produced by future earthquakes constitutes the foundation of seismic hazard assessment and earthquake-resistant structural design. This is typically done by using a prediction equation that quantifies amplitudes as a function of key seismological variables such as magnitude, distance and site condition. In this study, we develop a hybrid empirical prediction equation for earthquakes in western Alberta, where evaluation of seismic hazard associated with induced seismicity is of particular interest. We use peak ground motions and response spectra from recorded seismic events to model the regional source and attenuation attributes. The available empirical data is limited in the magnitude range of engineering interest (M>4). Therefore, we combine empirical data with a simulation-based model in order to obtain seismologically informed predictions for moderate-to-large magnitude events. The methodology is two-fold. First, we investigate the shape of geometrical spreading in Alberta. We supplement the seismic data with ground motions obtained from mining/quarry blasts, in order to gain insights into the regional attenuation over a wide distance range. A comparison of ground-motion amplitudes for earthquakes and mining/quarry blasts show that both event types decay at similar rates with distance and demonstrate a significant Moho-bounce effect. In the second stage, we calibrate the source and attenuation parameters of a simulation-based prediction equation to match the available amplitude data from seismic events. We model the geometrical spreading using a trilinear function with attenuation rates obtained from the first stage, and calculate coefficients of anelastic attenuation and site amplification via regression analysis. This provides a hybrid ground-motion prediction equation that is calibrated for observed motions in western Alberta and is applicable to moderate-to-large magnitude events.

Dispersal of the Pearl River plume over continental shelf in summer

NASA Astrophysics Data System (ADS)

Chen, Zhaoyun; Gong, Wenping; Cai, Huayang; Chen, Yunzhen; Zhang, Heng

2017-07-01

Satellite images of turbidity were used to study the climatological, monthly, and typical snapshot distributions of the Pearl River plume over the shelf in summer from 2003 to 2016. These images show that the plume spreads offshore over the eastern shelf and is trapped near the coast over the western shelf. Eastward extension of the plume retreats from June to August. Monthly spatial variations of the plume are characterized by eastward spreading, westward spreading, or both. Time series of monthly plume area was quantified by applying the K-mean clustering method to identify the turbid plume water. Decomposition of the 14-year monthly turbidity data by the empirical orthogonal function (EOF) analysis isolated the 1st mode in both the eastward and westward spreading pattern as the time series closely related to the Pearl River discharge, and the 2nd mode with out-of-phase turbidity anomalies over the eastern and western shelves that is associated with the prevailing wind direction. Eight typical plume types were detected from the satellite snapshots. They are characterized by coastal jet, eastward offshore spreading, westward spreading, bidirectional spreading, bulge, isolated patch, offshore branch, and offshore filaments, respectively. Their possible mechanisms are discussed.

Energy spectrum control for modulated proton beams.

PubMed

Hsi, Wen C; Moyers, Michael F; Nichiporov, Dmitri; Anferov, Vladimir; Wolanski, Mark; Allgower, Chris E; Farr, Jonathan B; Mascia, Anthony E; Schreuder, Andries N

2009-06-01

In proton therapy delivered with range modulated beams, the energy spectrum of protons entering the delivery nozzle can affect the dose uniformity within the target region and the dose gradient around its periphery. For a cyclotron with a fixed extraction energy, a rangeshifter is used to change the energy but this produces increasing energy spreads for decreasing energies. This study investigated the magnitude of the effects of different energy spreads on dose uniformity and distal edge dose gradient and determined the limits for controlling the incident spectrum. A multilayer Faraday cup (MLFC) was calibrated against depth dose curves measured in water for nonmodulated beams with various incident spectra. Depth dose curves were measured in a water phantom and in a multilayer ionization chamber detector for modulated beams using different incident energy spreads. Some nozzle entrance energy spectra can produce unacceptable dose nonuniformities of up to +/-21% over the modulated region. For modulated beams and small beam ranges, the width of the distal penumbra can vary by a factor of 2.5. When the energy spread was controlled within the defined limits, the dose nonuniformity was less than +/-3%. To facilitate understanding of the results, the data were compared to the measured and Monte Carlo calculated data from a variable extraction energy synchrotron which has a narrow spectrum for all energies. Dose uniformity is only maintained within prescription limits when the energy spread is controlled. At low energies, a large spread can be beneficial for extending the energy range at which a single range modulator device can be used. An MLFC can be used as part of a feedback to provide specified energy spreads for different energies.

MTF evaluation of in-line phase contrast imaging system

NASA Astrophysics Data System (ADS)

Sun, Xiaoran; Gao, Feng; Zhao, Huijuan; Zhang, Limin; Li, Jiao; Zhou, Zhongxing

2017-02-01

X-ray phase contrast imaging (XPCI) is a novel method that exploits the phase shift for the incident X-ray to form an image. Various XPCI methods have been proposed, among which, in-line phase contrast imaging (IL-PCI) is regarded as one of the most promising clinical methods. The contrast of the interface is enhanced due to the introduction of the boundary fringes in XPCI, thus it is generally used to evaluate the image quality of XPCI. But the contrast is a comprehensive index and it does not reflect the information of image quality in the frequency range. The modulation transfer function (MTF), which is the Fourier transform of the system point spread function, is recognized as the metric to characterize the spatial response of conventional X-ray imaging system. In this work, MTF is introduced into the image quality evaluation of the IL-PCI system. Numerous simulations based on Fresnel - Kirchhoff diffraction theory are performed with varying system settings and the corresponding MTFs were calculated for comparison. The results show that MTF can provide more comprehensive information of image quality comparing to contrast in IL-PCI.

Optical effects of the cranium in trans-cranial in vivo two photon laser scanning microscopy in mice

NASA Astrophysics Data System (ADS)

Helm, P. Johannes; Ottersen, Ole P.; Nase, Gabriele

2007-02-01

The combination of multi photon laser scanning microscopy with transgenic techniques has set the stage for in vivo studies of long term dynamics of the central nervous system in mice. Brain structures located within 100μm to 200μm below the brain surface can be observed minimum-invasively during the post-adolescent life of the animal. However, even when selecting the most appropriate microscope optics available for the purpose, trans-cranial observation is compromised by the aberrations induced by the cranium and the tissue interposed between the cranium and the actual focus. It still is an un-resolved task to calculate these aberrational effects or to, at least, estimate quantitatively the distortions they induce onto the recorded images. Here, we report about measurements of the reflection, the absorption, and the effects on the objective point spread function of the mouse cranium as a function of the thickness of the cranium, the locus of trans-cranial observation and the wavelength. There is experimental evidence for pronounced Second Harmonic Generation (SHG) effects.

Investigation of the 9B nucleus and its cluster-nucleon correlations

NASA Astrophysics Data System (ADS)

Zhao, Qing; Ren, Zhongzhou; Lyu, Mengjiao; Horiuchi, Hisashi; Funaki, Yasuro; Röpke, Gerd; Schuck, Peter; Tohsaki, Akihiro; Xu, Chang; Yamada, Taiichi; Zhou, Bo

2018-05-01

In order to study the correlations between clusters and nucleons in light nuclei, we formulate a new superposed Tohsaki-Horiuchi-Schuck-Röpke (THSR) wave function which describes both spatially large spreading and cluster-correlated dynamics of valence nucleons. Using this new THSR wave function, the binding energy of 9B is significantly improved in comparison with our previous studies. We calculate the excited states of 9B and obtain an energy spectrum of 9B which is consistent with the experimental results. This includes the prediction of the first 1 /2+ excited state of 9B which is not yet fixed experimentally. We study the proton dynamics in 9B and find that the cluster-proton correlation plays an essential role for the proton dynamics in the ground state of 9B. Furthermore, we discuss the density distribution of the valence proton with special attention to its tail structure. Finally, the resonance nature of excited states of 9B is illustrated comparing root-mean-square radii between the ground and excited states.

dbWGFP: a database and web server of human whole-genome single nucleotide variants and their functional predictions.

PubMed

Wu, Jiaxin; Wu, Mengmeng; Li, Lianshuo; Liu, Zhuo; Zeng, Wanwen; Jiang, Rui

2016-01-01

The recent advancement of the next generation sequencing technology has enabled the fast and low-cost detection of all genetic variants spreading across the entire human genome, making the application of whole-genome sequencing a tendency in the study of disease-causing genetic variants. Nevertheless, there still lacks a repository that collects predictions of functionally damaging effects of human genetic variants, though it has been well recognized that such predictions play a central role in the analysis of whole-genome sequencing data. To fill this gap, we developed a database named dbWGFP (a database and web server of human whole-genome single nucleotide variants and their functional predictions) that contains functional predictions and annotations of nearly 8.58 billion possible human whole-genome single nucleotide variants. Specifically, this database integrates 48 functional predictions calculated by 17 popular computational methods and 44 valuable annotations obtained from various data sources. Standalone software, user-friendly query services and free downloads of this database are available at http://bioinfo.au.tsinghua.edu.cn/dbwgfp. dbWGFP provides a valuable resource for the analysis of whole-genome sequencing, exome sequencing and SNP array data, thereby complementing existing data sources and computational resources in deciphering genetic bases of human inherited diseases. © The Author(s) 2016. Published by Oxford University Press.

A Simplified Algorithm for Statistical Investigation of Damage Spreading

NASA Astrophysics Data System (ADS)

Gecow, Andrzej

2009-04-01

On the way to simulating adaptive evolution of complex system describing a living object or human developed project, a fitness should be defined on node states or network external outputs. Feedbacks lead to circular attractors of these states or outputs which make it difficult to define a fitness. The main statistical effects of adaptive condition are the result of small change tendency and to appear, they only need a statistically correct size of damage initiated by evolutionary change of system. This observation allows to cut loops of feedbacks and in effect to obtain a particular statistically correct state instead of a long circular attractor which in the quenched model is expected for chaotic network with feedback. Defining fitness on such states is simple. We calculate only damaged nodes and only once. Such an algorithm is optimal for investigation of damage spreading i.e. statistical connections of structural parameters of initial change with the size of effected damage. It is a reversed-annealed method—function and states (signals) may be randomly substituted but connections are important and are preserved. The small damages important for adaptive evolution are correctly depicted in comparison to Derrida annealed approximation which expects equilibrium levels for large networks. The algorithm indicates these levels correctly. The relevant program in Pascal, which executes the algorithm for a wide range of parameters, can be obtained from the author.

Slit Function Measurement of An Imaging Spectrograph Using Fourier Transform Techniques

NASA Technical Reports Server (NTRS)

Park, Hongwoo; Swimyard, Bruce; Jakobsen, Peter; Moseley, Harvey; Greenhouse, Matthew

2004-01-01

Knowledge of a spectrograph slit function is necessary to interpret the unresolved lines in an observed spectrum. A theoretical slit function can be calculated from the sizes of the entrance slit, the detector aperture when it functions as an exit slit, the dispersion characteristic of the disperser, and the point spread function of the spectrograph. A measured slit function is preferred to the theoretical one for the correct interpretation of the spectral data. In a scanning spectrometer with a single exit slit, the slit function is easily measured. In a fixed grating/or disperser spectrograph, illuminating the entrance slit with a near monochromatic light from a pre-monochrmator or a tunable laser and varying the wavelength of the incident light can measure the slit function. Even though the latter technique had been used successfully for the slit function measurements, it had been very laborious and it would be prohibitive to an imaging spectrograph or a multi-object spectrograph that has a large field of view. We explore an alternative technique that is manageable for the measurements. In the proposed technique, the imaging spectrograph is used as a detector of a Fourier transform spectrometer. This method can be applied not only to an IR spectrograph but also has a potential to a visible/UV spectrograph including a wedge filter spectrograph. This technique will require a blackbody source of known temperature and a bolometer to characterize the interferometer part of the Fourier Transform spectrometer. This pa?er will describe the alternative slit function measurement technique using a Fourier transform spectrometer.

Three-dimensional seismic depth migration

NASA Astrophysics Data System (ADS)

Zhou, Hongbo

1998-12-01

One-pass 3-D modeling and migration for poststack seismic data may be implemented by replacing the traditional 45sp° one-way wave equation (a third-order partial differential equation) with a pair of second and first order partial differential equations. Except for an extra correction term, the resulting second order equation has a form similar to Claerbout's 15sp° one-way wave equation, which is known to have a nearly circular horizontal impulse response. In this approach, there is no need to compensate for splitting errors. Numerical tests on synthetic data show that this algorithm has the desirable attributes of being second-order in accuracy and economical to solve. A modification of the Crank-Nicholson implementation maintains stability. Absorbing boundary conditions play an important role in one-way wave extrapolations by reducing reflections at grid edges. Clayton and Engquist's 2-D absorbing boundary conditions for one-way wave extrapolation by depth-stepping in the frequency domain are extended to 3-D using paraxial approximations of the scalar wave equation. Internal consistency is retained by incorporating the interior extrapolation equation with the absorbing boundary conditions. Numerical schemes are designed to make the proposed absorbing boundary conditions both mathematically correct and efficient with negligible extra cost. Synthetic examples illustrate the effectiveness of the algorithm for extrapolation with the 3-D 45sp° one-way wave equation. Frequency-space domain Butterworth and Chebyshev dip filters are implemented. By regrouping the product terms in the filter transfer function into summations, a cascaded (serial) Butterworth dip filter can be made parallel. A parallel Chebyshev dip filter can be similarly obtained, and has the same form as the Butterworth filter; but has different coeffcients. One of the advantages of the Chebyshev filter is that it has a sharper transition zone than that of Butterworth filter of the same order. Both filters are incorporated into 3-D one-way frequency-space depth migration for evanescent energy removal and for phase compensation of splitting errors; a single filter achieves both goals. Synthetic examples illustrate the behavior of the parallel filters. For a given order of filter, the cost of the Butterworth and Chebyshev filters is the same. A Chebyshev filter is more effective for phase compensation than the Butterworth filter of the same order, at the expense of some wavenumber-dependent amplitude ripples. An analytical formula for geometrical spreading is derived for a horizontally layered transversely isotropic medium with a vertical symmetry axis. Under this expression, geometrical spreading can be determined only by the anisotropic parameters in the first layer, the traveltime derivatives, and source-receiver offset. An explicit, numerically feasible expression for geometrical spreading can be further obtained by considering some of the special cases of transverse isotropy, such as weak anisotropy or elliptic anisotropy. Therefore, with the techniques of non-hyerbolic moveout for transverse isotropic media, geometrical spreading can be calculated by using picked traveltimes of primary P-wave reflections without having to know the actual parameters in the deeper subsurface; no ray tracing is needed. Synthetic examples verify the algorithm and show that it is numerically feasible for calculation of geometrical spreading.

Advanced Optimal Extraction for the Spitzer/IRS

NASA Astrophysics Data System (ADS)

Lebouteiller, V.; Bernard-Salas, J.; Sloan, G. C.; Barry, D. J.

2010-02-01

We present new advances in the spectral extraction of pointlike sources adapted to the Infrared Spectrograph (IRS) on board the Spitzer Space Telescope. For the first time, we created a supersampled point-spread function of the low-resolution modules. We describe how to use the point-spread function to perform optimal extraction of a single source and of multiple sources within the slit. We also examine the case of the optimal extraction of one or several sources with a complex background. The new algorithms are gathered in a plug-in called AdOpt which is part of the SMART data analysis software.

Subdiffraction incoherent optical imaging via spatial-mode demultiplexing: Semiclassical treatment

NASA Astrophysics Data System (ADS)

Tsang, Mankei

2018-02-01

I present a semiclassical analysis of a spatial-mode demultiplexing (SPADE) measurement scheme for far-field incoherent optical imaging under the effects of diffraction and photon shot noise. Building on previous results that assume two point sources or the Gaussian point-spread function, I generalize SPADE for a larger class of point-spread functions and evaluate its errors in estimating the moments of an arbitrary subdiffraction object. Compared with the limits to direct imaging set by the Cramér-Rao bounds, the results show that SPADE can offer far superior accuracy in estimating second- and higher-order moments.

HF propagation factors affecting the design and operation of real time, channel evaluation, adaptive systems

NASA Astrophysics Data System (ADS)

Aarons, J.; Grossi, M. D.

1982-08-01

To develop and operate an adaptive system, propagation factors of the ionospheric medium must be given to the designer. The operation of the system must change as a function of multipath spread, Doppler spread, path losses, channel correlation functions, etc. In addition, NATO mid-latitude HF transmission and transauroral paths require varying system operation, which must fully utilize automatic path diversity across transauroral paths. Current research and literature are reviewed to estimate the extent of the available technical information. Additional investigations to allow designers to orient new systems on realistic models of these parameters are suggested.

Resequencing of the Phytophthora ramorum genome to characterize genetic variation and population dynamics of the invasive pathogen

Treesearch

Jennifer Yuzon; David M. Rizzo; Mathu Malar C; Sucheta Tripathy; Takao Kasuga

2017-01-01

Phytophthora ramorum has spread and diversified throughout California’s northwestern coast since its introduction in the 1990s. Tracking the spread of P. ramorum and the functional response of the pathogen to the environment is of particular interest to managing the epidemic. Using genetic tools such as microsatellite...

Epidemiological modeling of invasion in heterogeneous landscapes: Spread of sudden oak death in California (1990-2030)

Treesearch

R.K. Meentemeyer; N.J. Cunniffe; A.R. Cook; J.A.N. Filipe; R.D. Hunter; D.M. Rizzo; C.A. Gilligan

2011-01-01

The spread of emerging infectious diseases (EIDs) in natural environments poses substantial risks to biodiversity and ecosystem function. As EIDs and their impacts grow, landscape- to regional-scale models of disease dynamics are increasingly needed for quantitative prediction of epidemic outcomes and design of practicable strategies for control. Here we use spatio-...

Discrete Radon transform has an exact, fast inverse and generalizes to operations other than sums along lines

PubMed Central

Press, William H.

2006-01-01

Götz, Druckmüller, and, independently, Brady have defined a discrete Radon transform (DRT) that sums an image's pixel values along a set of aptly chosen discrete lines, complete in slope and intercept. The transform is fast, O(N2log N) for an N × N image; it uses only addition, not multiplication or interpolation, and it admits a fast, exact algorithm for the adjoint operation, namely backprojection. This paper shows that the transform additionally has a fast, exact (although iterative) inverse. The inverse reproduces to machine accuracy the pixel-by-pixel values of the original image from its DRT, without artifacts or a finite point-spread function. Fourier or fast Fourier transform methods are not used. The inverse can also be calculated from sampled sinograms and is well conditioned in the presence of noise. Also introduced are generalizations of the DRT that combine pixel values along lines by operations other than addition. For example, there is a fast transform that calculates median values along all discrete lines and is able to detect linear features at low signal-to-noise ratios in the presence of pointlike clutter features of arbitrarily large amplitude. PMID:17159155

Discrete Radon transform has an exact, fast inverse and generalizes to operations other than sums along lines.

PubMed

Press, William H

2006-12-19

Götz, Druckmüller, and, independently, Brady have defined a discrete Radon transform (DRT) that sums an image's pixel values along a set of aptly chosen discrete lines, complete in slope and intercept. The transform is fast, O(N2log N) for an N x N image; it uses only addition, not multiplication or interpolation, and it admits a fast, exact algorithm for the adjoint operation, namely backprojection. This paper shows that the transform additionally has a fast, exact (although iterative) inverse. The inverse reproduces to machine accuracy the pixel-by-pixel values of the original image from its DRT, without artifacts or a finite point-spread function. Fourier or fast Fourier transform methods are not used. The inverse can also be calculated from sampled sinograms and is well conditioned in the presence of noise. Also introduced are generalizations of the DRT that combine pixel values along lines by operations other than addition. For example, there is a fast transform that calculates median values along all discrete lines and is able to detect linear features at low signal-to-noise ratios in the presence of pointlike clutter features of arbitrarily large amplitude.

Transmitter and receiver antenna gain analysis for laser radar and communication systems

NASA Technical Reports Server (NTRS)

Klein, B. J.; Degnan, J. J.

1973-01-01

A comprehensive and fairly self-contained study of centrally obscured optical transmitting and receiving antennas is presented and is intended for use by the laser radar and communication systems designer. The material is presented in a format which allows the rapid and accurate evaluation of antenna gain. The Fresnel approximation to scalar wave theory is reviewed and the antenna analysis proceeds in terms of the power gain. Conventional range equations may then be used to calculate the power budget. The transmitter calculations, resulting in near and far field antenna gain patterns, assumes the antenna is illuminated by a laser operating in the fundamental cavity mode. A simple equation is derived for matching the incident source distribution to a general antenna configuration for maximum on-axis gain. An interpretation of the resultant gain curves allows a number of auxiliary design curves to be drawn which display the losses in antenna gain due to pointing errors and the cone angle of the outgoing beam as a function of antenna size and central obscuration. The use of telescope defocusing as an approach to spreading the beam for target acquisition is compared to some alternate methods.

Calculating complete and exact Pareto front for multiobjective optimization: a new deterministic approach for discrete problems.

PubMed

Hu, Xiao-Bing; Wang, Ming; Di Paolo, Ezequiel

2013-06-01

Searching the Pareto front for multiobjective optimization problems usually involves the use of a population-based search algorithm or of a deterministic method with a set of different single aggregate objective functions. The results are, in fact, only approximations of the real Pareto front. In this paper, we propose a new deterministic approach capable of fully determining the real Pareto front for those discrete problems for which it is possible to construct optimization algorithms to find the k best solutions to each of the single-objective problems. To this end, two theoretical conditions are given to guarantee the finding of the actual Pareto front rather than its approximation. Then, a general methodology for designing a deterministic search procedure is proposed. A case study is conducted, where by following the general methodology, a ripple-spreading algorithm is designed to calculate the complete exact Pareto front for multiobjective route optimization. When compared with traditional Pareto front search methods, the obvious advantage of the proposed approach is its unique capability of finding the complete Pareto front. This is illustrated by the simulation results in terms of both solution quality and computational efficiency.

Spread of Epidemic on Complex Networks Under Voluntary Vaccination Mechanism

NASA Astrophysics Data System (ADS)

Xue, Shengjun; Ruan, Feng; Yin, Chuanyang; Zhang, Haifeng; Wang, Binghong

Under the assumption that the decision of vaccination is a voluntary behavior, in this paper, we use two forms of risk functions to characterize how susceptible individuals estimate the perceived risk of infection. One is uniform case, where each susceptible individual estimates the perceived risk of infection only based on the density of infection at each time step, so the risk function is only a function of the density of infection; another is preferential case, where each susceptible individual estimates the perceived risk of infection not only based on the density of infection but only related to its own activities/immediate neighbors (in network terminology, the activity or the number of immediate neighbors is the degree of node), so the risk function is a function of the density of infection and the degree of individuals. By investigating two different ways of estimating the risk of infection for susceptible individuals on complex network, we find that, for the preferential case, the spread of epidemic can be effectively controlled; yet, for the uniform case, voluntary vaccination mechanism is almost invalid in controlling the spread of epidemic on networks. Furthermore, given the temporality of some vaccines, the waves of epidemic for two cases are also different. Therefore, our work insight that the way of estimating the perceived risk of infection determines the decision on vaccination options, and then determines the success or failure of control strategy.

Human land use promotes the abundance and diversity of exotic species on caribbean islands.

PubMed

Jesse, Wendy A M; Behm, Jocelyn E; Helmus, Matthew R; Ellers, Jacintha

2018-05-31

Human land use causes major changes in species abundance and composition, yet native and exotic species can exhibit different responses to land use change. Native populations generally decline in human-impacted habitats while exotic species often benefit. In this study, we assessed the effects of human land use on exotic and native reptile diversity, including functional diversity, which relates to the range of habitat use strategies in biotic communities. We surveyed 114 reptile communities from localities that varied in habitat structure and human impact level on two Caribbean islands, and calculated species richness, overall abundance and evenness for every plot. Functional diversity indices were calculated using published trait data, which enabled us to detect signs of trait filtering associated with impacted habitats. Our results show that environmental variation among sampling plots was explained by two PCA ordination axes related to habitat structure (i.e. forest or non-forest) and human impact level (i.e. addition of man-made constructions such as roads and buildings). Several diversity indices were significantly correlated with the two PCA axes, but exotic and native species showed opposing responses. Native species reached the highest abundance in forests, while exotic species were absent in this habitat. Human impact was associated with an increase in exotic abundance and species richness, while native species showed no significant associations. Functional diversity was highest in non-forested environments on both islands, and further increased on St. Martin with the establishment of functionally unique exotic species in non-forested habitat. Habitat structure, rather than human impact, proved to be an important agent for environmental filtering of traits, causing divergent functional trait values across forested and non-forested environments. Our results illustrate the importance of considering various elements of land use when studying its impact on species diversity and the establishment and spread of exotic species. This article is protected by copyright. All rights reserved. This article is protected by copyright. All rights reserved.

Correcting bulk in-plane motion artifacts in MRI using the point spread function.

PubMed

Lin, Wei; Wehrli, Felix W; Song, Hee Kwon

2005-09-01

A technique is proposed for correcting both translational and rotational motion artifacts in magnetic resonance imaging without the need to collect additional navigator data or to perform intensive postprocessing. The method is based on measuring the point spread function (PSF) by attaching one or two point-sized markers to the main imaging object. Following the isolation of a PSF marker from the acquired image, translational motion could be corrected directly from the modulation transfer function, without the need to determine the object's positions during the scan, although the shifts could be extracted if desired. Rotation is detected by analyzing the relative displacements of two such markers. The technique was evaluated with simulations, phantom and in vivo experiments.

Effects of interleukin-1ß on cortical spreading depolarization and cerebral vasculature

PubMed Central

Eitner, Annett; Leuchtweis, Johannes; Bauer, Reinhard; Lehmenkühler, Alfred; Schaible, Hans-Georg

2016-01-01

During brain damage and ischemia, the cytokine interleukin-1ß is rapidly upregulated due to activation of inflammasomes. We studied whether interleukin-1ß influences cortical spreading depolarization, and whether lipopolysaccharide, often used for microglial stimulation, influences cortical spreading depolarizations. In anaesthetized rats, cortical spreading depolarizations were elicited by microinjection of KCl. Interleukin-1ß, the IL-1 receptor 1 antagonist, the GABAA receptor blocker bicuculline, and lipopolysaccharide were administered either alone or combined (interleukin-1ß + IL-1 receptor 1 antagonist; interleukin-1ß + bicuculline; lipopolysaccharide + IL-1 receptor 1 antagonist) into a local cortical treatment area. Using microelectrodes, cortical spreading depolarizations were recorded in a non-treatment and in the treatment area. Plasma extravasation in cortical grey matter was assessed with Evans blue. Local application of interleukin-1ß reduced cortical spreading depolarization amplitudes in the treatment area, but not at a high dose. This reduction was prevented by IL-1 receptor 1 antagonist and by bicuculline. However, interleukin-1ß induced pronounced plasma extravasation independently on cortical spreading depolarizations. Application of lipopolysaccharide reduced cortical spreading depolarization amplitudes but prolonged their duration; EEG activity was still present. These effects were also blocked by IL-1 receptor 1 antagonist. Interleukin-1ß evokes changes of neuronal activity and of vascular functions. Thus, although the reduction of cortical spreading depolarization amplitudes at lower doses of interleukin-1ß may reduce deleterious effects of cortical spreading depolarizations, the sum of interleukin-1ß effects on excitability and on the vasculature rather promote brain damaging mechanisms. PMID:27037093

Event ambiguity fuels the effective spread of rumors

NASA Astrophysics Data System (ADS)

Xu, Jiuping; Zhang, Yi

2015-08-01

In this paper, a new rumor spreading model which quantifies a specific rumor spreading feature is proposed. The specific feature focused on is the important role the event ambiguity plays in the rumor spreading process. To study the impact of this event ambiguity on the spread of rumors, the probability p(t) that an individual becomes a rumor spreader from an initially unaware person at time t is built. p(t) reflects the extent of event ambiguity, and a parameter c of p(t) is used to measure the speed at which the event moves from ambiguity to confirmation. At the same time, a principle is given to decide on the correct value for parameter c A rumor spreading model is then developed with this function added as a parameter to the traditional model. Then, several rumor spreading model simulations are conducted with different values for c on both regular networks and ER random networks. The simulation results indicate that a rumor spreads faster and more broadly when c is smaller. This shows that if events are ambiguous over a longer time, rumor spreading appears to be more effective, and is influenced more significantly by parameter c in a random network than in a regular network. We then determine parameters of this model through data fitting of the missing Malaysian plane, and apply this model to an analysis of the missing Malaysian plane. The simulation results demonstrate that the most critical time for authorities to control rumor spreading is in the early stages of a critical event.

CaMKII-dependent endoplasmic reticulum fission by whisker stimulation and during cortical spreading depolarization.

PubMed

Kucharz, Krzysztof; Lauritzen, Martin

2018-04-01

Cortical spreading depolarization waves, the cause underlying migraine aura, are also the markers and mechanism of pathology in the acutely injured human brain. Propagation of spreading depolarization wave uniquely depends on the interaction between presynaptic and postsynaptic glutamate N-methyl-d-aspartate receptors (NMDARs). In the normally perfused brain, even a single wave causes a massive depolarization of neurons and glia, which results in transient loss of neuronal function and depression of the ongoing electrocorticographic activity. Endoplasmic reticulum is the cellular organelle of particular importance for modulation of neurotransmission. Neuronal endoplasmic reticulum structure is assumed to be persistently continuous in neurons, but is rapidly lost within 1 to 2 min of global cerebral ischaemia, i.e. the organelle disintegrates by fission. This phenomenon appears to be timed with the cardiac arrest-induced cortical spreading depolarizations, rather than ensuing cell death. To what extent NMDAR-dependent processes may trigger neuronal endoplasmic reticulum fission and whether fission is reversible in the normally perfused brain is unknown. We used two-photon microscopy to examine neuronal endoplasmic reticulum structural dynamics during whisker stimulation and cortical spreading depolarizations in vivo. Somatosensory stimulation triggered loss of endoplasmic reticulum continuity, a likely outcome of constriction and fission, in dendritic spines within less than 10 s of stimulation, which was spontaneously reversible and recovery to normal took 5 min. The endoplasmic reticulum fission was inhibited by blockade of NMDAR and Ca2+/calmodulin-dependent protein kinase II (CaMKII) activated downstream of the NMDARs, whereas inhibition of guanosine triphosphate hydrolases hindered regain of endoplasmic reticulum continuity, i.e. fusion. In contrast to somatosensory stimulation, endoplasmic reticulum fission during spreading depolarization was widespread and present in dendrites and spines, and was preceded by dramatic rise in intracellular Ca2+. The endoplasmic reticulum fission during spreading depolarization was more persistent, as 1 h after the depolarization cortical neurons still exhibited loss of endoplasmic reticulum continuity. Notably, endoplasmic reticulum fission was accompanied with loss of electrocorticographic activity, whereas subsequent regain of synaptic function paralleled the organelle fusion. Furthermore, blocking CaMKII activity partly rescued endoplasmic reticulum fission and markedly shortened the recovery time of brain spontaneous activity. Thus, prevention of endoplasmic reticulum fission with CaMKII inhibitors may be a novel strategy to rescue brain function in patients with migraine and a promising therapeutic avenue in the acutely injured brain.

Controls on melting at spreading ridges from correlated abyssal peridotite - mid-ocean ridge basalt compositions

NASA Astrophysics Data System (ADS)

Regelous, Marcel; Weinzierl, Christoph G.; Haase, Karsten M.

2016-09-01

Variations in the volume and major element composition of basalt erupted along the global mid-ocean ridge system have been attributed to differences in mantle potential temperature, mantle composition, or plate spreading rate and lithosphere thickness. Abyssal peridotites, the residues of mantle melting beneath mid-ocean ridges, provide additional information on the melting process, which could be used to test these hypotheses. We compiled a global database of abyssal peridotite compositions averaged over the same ridge segments defined by Gale et al. (2013). In addition, we calculated the distance of each ridge segment to the nearest hotspots. We show that Cr# in spinel in abyssal peridotites is negatively correlated with Na90 in basalts from the same ridge segments on a global scale. Ridge segments that erupt basalts apparently produced by larger degrees of mantle melting are thus underlain by peridotites from which large amounts of melt have been extracted. We find that near-ridge hotspots have a more widespread influence on mid-ocean ridge basalt (MORB) composition and ridge depth than previously thought. However, when these hotspot-influenced ridge segments are excluded, the remaining segments show clear relationships between MORB composition, peridotite composition, and ridge depth with spreading rate. Very slow-spreading ridges (<20 mm/yr) are deeper, erupt basalts with higher Na90, Al90, K90/Ti90, and lower Fe90, Ca90/Al90, and expose peridotites with lower Cr# than intermediate and fast-spreading ridges. We show that away from hotspots, the spreading-rate dependence of the maximum degree of mantle melting inferred from Cr# in peridotites (FM) and the bulk degree of melting inferred from Na90 in basalts (FB) from the same ridge segments is unlikely to be due to variations in mantle composition. Nor can the effects of dynamic mantle upwelling or incomplete melt extraction at low spreading rates satisfactorily explain the observed compositions of abyssal peridotites and MORB from very slow-spreading ridges. Instead, the distinctive compositions of abyssal peridotites and MORB from very slow-spreading ridges could result from the presence of a thick lithospheric lid, leading to a lower average degree of melting, and a higher contribution to melting from more fertile mantle lithologies. Alternatively, spreading rate influences the thermal structure of the upper mantle such that the mantle beneath very slow-spreading ridges is cooler.

7 CFR 407.16 - Group risk plan for soybean.

Code of Federal Regulations, 2012 CFR

2012-01-01

... calculate indemnities. Planted acreage. Land in which the soybean seed has been placed by a machine... properly prepared for the planting method and production practice. Land on which seed is initially spread... accepted application; (b) Properly planted and reported by the acreage reporting date; (c) Planted with the...

7 CFR 407.17 - Group risk plan for wheat.

Code of Federal Regulations, 2011 CFR

2011-01-01

... calculate indemnities. Planted acreage. Land in which the wheat seed has been planted by a machine... properly prepared for the planting method and production practice. Land on which seed is initially spread... accepted application; (b) Properly planted and reported by the acreage reporting date; (c) Planted with the...

7 CFR 407.16 - Group risk plan for soybean.

Code of Federal Regulations, 2011 CFR

2011-01-01

... calculate indemnities. Planted acreage. Land in which the soybean seed has been placed by a machine... properly prepared for the planting method and production practice. Land on which seed is initially spread... accepted application; (b) Properly planted and reported by the acreage reporting date; (c) Planted with the...

7 CFR 407.17 - Group risk plan for wheat.

Code of Federal Regulations, 2012 CFR

2012-01-01

... calculate indemnities. Planted acreage. Land in which the wheat seed has been planted by a machine... properly prepared for the planting method and production practice. Land on which seed is initially spread... accepted application; (b) Properly planted and reported by the acreage reporting date; (c) Planted with the...

Continuing Care Retirement Communities: An Analysis of Financial Viability and Health Care Coverage.

ERIC Educational Resources Information Center

Ruchlin, Hirsch S.

1988-01-01

Calculated financial ratios for 109 Continuing Care Retirement Communities (CCRCs). Noted problems with regard to asset productivity, profitability, and equity levels. Found that a risk-spreading charge structure for financing health care needs appeared to exist among CCRCs providing a full-care contract. (Author/ABL)

Effects of variability of X-ray binaries on the X-ray luminosity functions of Milky Way

NASA Astrophysics Data System (ADS)

Islam, Nazma; Paul, Biswajit

2016-08-01

The X-ray luminosity functions of galaxies have become a useful tool for population studies of X-ray binaries in them. The availability of long term light-curves of X-ray binaries with the All Sky X-ray Monitors opens up the possibility of constructing X-ray luminosity functions, by also including the intensity variation effects of the galactic X-ray binaries. We have constructed multiple realizations of the X-ray luminosity functions (XLFs) of Milky Way, using the long term light-curves of sources obtained in the 2-10 keV energy band with the RXTE-ASM. The observed spread seen in the value of slope of both HMXB and LMXB XLFs are due to inclusion of variable luminosities of X-ray binaries in construction of these XLFs as well as finite sample effects. XLFs constructed for galactic HMXBs in the luminosity range 1036-1039 erg/sec is described by a power-law model with a mean power-law index of -0.48 and a spread due to variability of HMXBs as 0.19. XLFs constructed for galactic LMXBs in the luminosity range 1036-1039 erg/sec has a shape of cut-off power-law with mean power-law index of -0.31 and a spread due to variability of LMXBs as 0.07.

Immunization of Epidemics in Multiplex Networks

PubMed Central

Zhao, Dawei; Wang, Lianhai; Li, Shudong; Wang, Zhen; Wang, Lin; Gao, Bo

2014-01-01

Up to now, immunization of disease propagation has attracted great attention in both theoretical and experimental researches. However, vast majority of existing achievements are limited to the simple assumption of single layer networked population, which seems obviously inconsistent with recent development of complex network theory: each node could possess multiple roles in different topology connections. Inspired by this fact, we here propose the immunization strategies on multiplex networks, including multiplex node-based random (targeted) immunization and layer node-based random (targeted) immunization. With the theory of generating function, theoretical analysis is developed to calculate the immunization threshold, which is regarded as the most critical index for the effectiveness of addressed immunization strategies. Interestingly, both types of random immunization strategies show more efficiency in controlling disease spreading on multiplex Erdös-Rényi (ER) random networks; while targeted immunization strategies provide better protection on multiplex scale-free (SF) networks. PMID:25401755

Immunization of epidemics in multiplex networks.

PubMed

Zhao, Dawei; Wang, Lianhai; Li, Shudong; Wang, Zhen; Wang, Lin; Gao, Bo

2014-01-01

Up to now, immunization of disease propagation has attracted great attention in both theoretical and experimental researches. However, vast majority of existing achievements are limited to the simple assumption of single layer networked population, which seems obviously inconsistent with recent development of complex network theory: each node could possess multiple roles in different topology connections. Inspired by this fact, we here propose the immunization strategies on multiplex networks, including multiplex node-based random (targeted) immunization and layer node-based random (targeted) immunization. With the theory of generating function, theoretical analysis is developed to calculate the immunization threshold, which is regarded as the most critical index for the effectiveness of addressed immunization strategies. Interestingly, both types of random immunization strategies show more efficiency in controlling disease spreading on multiplex Erdös-Rényi (ER) random networks; while targeted immunization strategies provide better protection on multiplex scale-free (SF) networks.

Closed loop adaptive optics for microscopy without a wavefront sensor.

PubMed

Kner, Peter; Winoto, Lukman; Agard, David A; Sedat, John W

2010-02-24

A three-dimensional wide-field image of a small fluorescent bead contains more than enough information to accurately calculate the wavefront in the microscope objective back pupil plane using the phase retrieval technique. The phase-retrieved wavefront can then be used to set a deformable mirror to correct the point-spread function (PSF) of the microscope without the use of a wavefront sensor. This technique will be useful for aligning the deformable mirror in a widefield microscope with adaptive optics and could potentially be used to correct aberrations in samples where small fluorescent beads or other point sources are used as reference beacons. Another advantage is the high resolution of the retrieved wavefont as compared with current Shack-Hartmann wavefront sensors. Here we demonstrate effective correction of the PSF in 3 iterations. Starting from a severely aberrated system, we achieve a Strehl ratio of 0.78 and a greater than 10-fold increase in maximum intensity.

Secondary gamma-ray production in a coded aperture mask

NASA Technical Reports Server (NTRS)

Owens, A.; Frye, G. M., Jr.; Hall, C. J.; Jenkins, T. L.; Pendleton, G. N.; Carter, J. N.; Ramsden, D.; Agrinier, B.; Bonfand, E.; Gouiffes, C.

1985-01-01

The application of the coded aperture mask to high energy gamma-ray astronomy will provide the capability of locating a cosmic gamma-ray point source with a precision of a few arc-minutes above 20 MeV. Recent tests using a mask in conjunction with drift chamber detectors have shown that the expected point spread function is achieved over an acceptance cone of 25 deg. A telescope employing this technique differs from a conventional telescope only in that the presence of the mask modifies the radiation field in the vicinity of the detection plane. In addition to reducing the primary photon flux incident on the detector by absorption in the mask elements, the mask will also be a secondary radiator of gamma-rays. The various background components in a CAMTRAC (Coded Aperture Mask Track Chamber) telescope are considered. Monte-Carlo calculations are compared with recent measurements obtained using a prototype instrument in a tagged photon beam line.

Obtaining the phase in the star test using genetic algorithms

NASA Astrophysics Data System (ADS)

Salazar Romero, Marcos A.; Vazquez-Montiel, Sergio; Cornejo-Rodriguez, Alejandro

2004-10-01

The star test is conceptually perhaps the most basic and simplest of all methods of testing image-forming optical systems, the irradiance distribution at the image of a point source (such as a star) is give for the Point Spread Function, PSF. The PSF is very sensitive to aberrations. One way to quantify the PSF is measuring the irradiance distribution on the image of the source point. On the other hand, if we know the aberrations introduced by the optical systems and utilizing the diffraction theory then we can calculate the PSF. In this work we propose a method in order to find the wavefront aberrations starting from the PSF, transforming the problem of fitting a polynomial of aberrations in a problem of optimization using Genetic Algorithm. Also, we show that this method is immune to the noise introduced in the register or recording of the image. Results of these methods are shown.

Interocular high-order corneal wavefront aberration symmetry

NASA Astrophysics Data System (ADS)

Lombardo, Marco; Lombardo, Giuseppe; Serrao, Sebastiano

2006-04-01

The interocular symmetry of the high-order corneal wavefront aberration (WA) in a population of myopic eyes was analyzed before and after photorefractive keratectomy (PRK). The preoperative and one-year postoperative corneal aberration data (from third to seventh Zernike orders) for 4- and 7-mm pupils from right and left eyes were averaged after correcting for the effects of enantiomorphism to test for mirror symmetry. Also, the mean corneal point-spread function (PSF) for right and left eyes was calculated. Preoperatively, a moderate and high degree of correlation in the high-order corneal WA between eyes was found for 4- and 7-mm pupils, respectively. Myopic PRK did not significantly change the interocular symmetry of corneal high-order aberrations. No discernible differences in the orientation PSF between eyes were observed one year after surgery in comparison with the preoperative state over the two analyzed pupils.

Data Reduction and Image Reconstruction Techniques for Non-redundant Masking

NASA Astrophysics Data System (ADS)

Sallum, S.; Eisner, J.

2017-11-01

The technique of non-redundant masking (NRM) transforms a conventional telescope into an interferometric array. In practice, this provides a much better constrained point-spread function than a filled aperture and thus higher resolution than traditional imaging methods. Here, we describe an NRM data reduction pipeline. We discuss strategies for NRM observations regarding dithering patterns and calibrator selection. We describe relevant image calibrations and use example Large Binocular Telescope data sets to show their effects on the scatter in the Fourier measurements. We also describe the various ways to calculate Fourier quantities, and discuss different calibration strategies. We present the results of image reconstructions from simulated observations where we adjust prior images, weighting schemes, and error bar estimation. We compare two imaging algorithms and discuss implications for reconstructing images from real observations. Finally, we explore how the current state of the art compares to next-generation Extremely Large Telescopes.

Hyperspectral optical imaging of two different species of lepidoptera

PubMed Central

2011-01-01

In this article, we report a hyperspectral optical imaging application for measurement of the reflectance spectra of photonic structures that produce structural colors with high spatial resolution. The measurement of the spectral reflectance function is exemplified in the butterfly wings of two different species of Lepidoptera: the blue iridescence reflected by the nymphalid Morpho didius and the green iridescence of the papilionid Papilio palinurus. Color coordinates from reflectance spectra were calculated taking into account human spectral sensitivity. For each butterfly wing, the observed color is described by a characteristic color map in the chromaticity diagram and spreads over a limited volume in the color space. The results suggest that variability in the reflectance spectra is correlated with different random arrangements in the spatial distribution of the scales that cover the wing membranes. Hyperspectral optical imaging opens new ways for the non-invasive study and classification of different forms of irregularity in structural colors. PMID:21711872

Quantification of pulmonary vessel diameter in low-dose CT images

NASA Astrophysics Data System (ADS)

Rudyanto, Rina D.; Ortiz de Solórzano, Carlos; Muñoz-Barrutia, Arrate

2015-03-01

Accurate quantification of vessel diameter in low-dose Computer Tomography (CT) images is important to study pulmonary diseases, in particular for the diagnosis of vascular diseases and the characterization of morphological vascular remodeling in Chronic Obstructive Pulmonary Disease (COPD). In this study, we objectively compare several vessel diameter estimation methods using a physical phantom. Five solid tubes of differing diameters (from 0.898 to 3.980 mm) were embedded in foam, simulating vessels in the lungs. To measure the diameters, we first extracted the vessels using either of two approaches: vessel enhancement using multi-scale Hessian matrix computation, or explicitly segmenting them using intensity threshold. We implemented six methods to quantify the diameter: three estimating diameter as a function of scale used to calculate the Hessian matrix; two calculating equivalent diameter from the crosssection area obtained by thresholding the intensity and vesselness response, respectively; and finally, estimating the diameter of the object using the Full Width Half Maximum (FWHM). We find that the accuracy of frequently used methods estimating vessel diameter from the multi-scale vesselness filter depends on the range and the number of scales used. Moreover, these methods still yield a significant error margin on the challenging estimation of the smallest diameter (on the order or below the size of the CT point spread function). Obviously, the performance of the thresholding-based methods depends on the value of the threshold. Finally, we observe that a simple adaptive thresholding approach can achieve a robust and accurate estimation of the smallest vessels diameter.

MAPS of Cancer

NASA Technical Reports Server (NTRS)

Gray, Lincoln

1998-01-01

Our goal was to produce an interactive visualization from a mathematical model that successfully predicts metastases from head and neck cancer. We met this goal early in the project. The visualization is available for the public to view. Our work appears to fill a need for more information about this deadly disease. The idea of this project was to make an easily interpretable visualization based on what we call "functional maps" of disease. A functional map is a graphic summary of medical data, where distances between parts of the body are determined by the probability of disease, not by anatomical distances. Functional maps often beat little resemblance to anatomical maps, but they can be used to predict the spread of disease. The idea of modeling the spread of disease in an abstract multidimensional space is difficult for many people. Our goal was to make the important predictions easy to see. NASA must face this problem frequently: how to help laypersons and professionals see important trends in abstract, complex data. We took advantage of concepts perfected in NASA's graphics libraries. As an analogy, consider a functional map of early America. Suppose we choose travel times, rather than miles, as our measures of inter-city distances. For Abraham Lincoln, travel times would have been the more meaningful measure of separation between cities. In such a map New Orleans would be close to Memphis because of the Mississippi River. St. Louis would be close to Portland because of the Oregon Trail. Oklahoma City would be far from Little Rock because of the Cheyenne. Such a map would look puzzling to those of us who have always seen physical maps, but the functional map would be more useful in predicting the probabilities of inter-site transit. Continuing the analogy, we could predict the spread of social diseases such as gambling along the rivers and cattle rustling along the trails. We could simply print the functional map of America, but it would be more interesting to show meaningful patterns of dispersal. We had previously published the functional map of the head and neck, but it was difficult to explain to either patients or surgeons because that view of our body did not resemble anatomy. This discrepancy between functional and physical maps is just a mathematical restatement of the well-known fact that some diseases, such as head and neck cancer, spread in complex patterns, not always to the next nearest site. We had discovered that a computer could re-arrange anatomy so that this particular disease spreads to the next nearest site. The functional map explains over 95% of the metastases in 1400 patients. In a sense, we had graphed what our body "looks like" to a tumor. The tumor readily travels between adjacent areas in the functional map. The functional map is a succinct visual display of trends that are not easily appreciated in tables of probabilities.

Validation of the physical and RBE-weighted dose estimator based on PHITS coupled with a microdosimetric kinetic model for proton therapy.

PubMed

Takada, Kenta; Sato, Tatsuhiko; Kumada, Hiroaki; Koketsu, Junichi; Takei, Hideyuki; Sakurai, Hideyuki; Sakae, Takeji

2018-01-01

The microdosimetric kinetic model (MKM) is widely used for estimating relative biological effectiveness (RBE)-weighted doses for various radiotherapies because it can determine the surviving fraction of irradiated cells based on only the lineal energy distribution, and it is independent of the radiation type and ion species. However, the applicability of the method to proton therapy has not yet been investigated thoroughly. In this study, we validated the RBE-weighted dose calculated by the MKM in tandem with the Monte Carlo code PHITS for proton therapy by considering the complete simulation geometry of the clinical proton beam line. The physical dose, lineal energy distribution, and RBE-weighted dose for a 155 MeV mono-energetic and spread-out Bragg peak (SOBP) beam of 60 mm width were evaluated. In estimating the physical dose, the calculated depth dose distribution by irradiating the mono-energetic beam using PHITS was consistent with the data measured by a diode detector. A maximum difference of 3.1% in the depth distribution was observed for the SOBP beam. In the RBE-weighted dose validation, the calculated lineal energy distributions generally agreed well with the published measurement data. The calculated and measured RBE-weighted doses were in excellent agreement, except at the Bragg peak region of the mono-energetic beam, where the calculation overestimated the measured data by ~15%. This research has provided a computational microdosimetric approach based on a combination of PHITS and MKM for typical clinical proton beams. The developed RBE-estimator function has potential application in the treatment planning system for various radiotherapies. © The Author 2017. Published by Oxford University Press on behalf of The Japan Radiation Research Society and Japanese Society for Radiation Oncology.

Validation of the physical and RBE-weighted dose estimator based on PHITS coupled with a microdosimetric kinetic model for proton therapy

PubMed Central

Sato, Tatsuhiko; Kumada, Hiroaki; Koketsu, Junichi; Takei, Hideyuki; Sakurai, Hideyuki; Sakae, Takeji

2018-01-01

Abstract The microdosimetric kinetic model (MKM) is widely used for estimating relative biological effectiveness (RBE)-weighted doses for various radiotherapies because it can determine the surviving fraction of irradiated cells based on only the lineal energy distribution, and it is independent of the radiation type and ion species. However, the applicability of the method to proton therapy has not yet been investigated thoroughly. In this study, we validated the RBE-weighted dose calculated by the MKM in tandem with the Monte Carlo code PHITS for proton therapy by considering the complete simulation geometry of the clinical proton beam line. The physical dose, lineal energy distribution, and RBE-weighted dose for a 155 MeV mono-energetic and spread-out Bragg peak (SOBP) beam of 60 mm width were evaluated. In estimating the physical dose, the calculated depth dose distribution by irradiating the mono-energetic beam using PHITS was consistent with the data measured by a diode detector. A maximum difference of 3.1% in the depth distribution was observed for the SOBP beam. In the RBE-weighted dose validation, the calculated lineal energy distributions generally agreed well with the published measurement data. The calculated and measured RBE-weighted doses were in excellent agreement, except at the Bragg peak region of the mono-energetic beam, where the calculation overestimated the measured data by ~15%. This research has provided a computational microdosimetric approach based on a combination of PHITS and MKM for typical clinical proton beams. The developed RBE-estimator function has potential application in the treatment planning system for various radiotherapies. PMID:29087492

New Synthesis of Ocean Crust Velocity Structure From Two-Dimensional Profiles

NASA Astrophysics Data System (ADS)

Christeson, G. L.; Goff, J.; Carlson, R. L.; Reece, R.

2017-12-01

The velocity structure of typical oceanic crust consists of Layer 2, where velocities increase rapidly with depth from seafloor, and Layer 3, which is thicker and has a lower velocity gradient. Previous syntheses have found no correlation of velocity structure with spreading rate, even though we know that magmatic processes differ between slow-spreading and fast-spreading crust. We present a new synthesis of ocean crust velocity structure, compiling observations from two-dimensional studies in the Atlantic, Pacific, and Indian ocean basins. The Layer 2/3 boundary was picked from each publication at a change in gradient either on velocity-depth functions or contour plots (with at least 0.5 km/s contour interval), or from the appropriate layer boundary for layered models. We picked multiple locations at each seismic refraction profile if warranted by model variability. Preliminary results show statistically significant differences in average Layer 2 and Layer 3 thicknesses between slow-spreading and superfast-spreading crust, with Layer 2 thinner and Layer 3 thicker for the higher spreading rate crust. The thickness changes are about equivalent, resulting in no change in mean crustal thickness. The Layer 2/3 boundary is often interpreted as the top of the gabbros; however, a comparison with mapped magma lens depths at the ridge axis shows that the boundary is typically deeper than average axial melt lens depth at superfast-spreading crust, and shallower at intermediate-spreading crust.

Tyrosine phosphorylated c-Cbl regulates platelet functional responses mediated by outside-in signaling

PubMed Central

Buitrago, Lorena; Langdon, Wallace Y.

2011-01-01

c-Cbl protein functions as an E3 ligase and scaffolding protein, where 3 residues, Y700, Y731, and Y774, upon phosphorylation, have been shown to initiate several signaling cascades. In this study, we investigated the role of these phospho-tyrosine residues in the platelet functional responses after integrin engagement. We observed that c-Cbl Y700, Y731 and Y774 undergo phosphorylation upon platelet adhesion to immobilized fibrinogen, which was inhibited in the presence of PP2, a pan-src family kinase (SFK) inhibitor, suggesting that c-Cbl is phosphorylated downstream of SFKs. However, OXSI-2, a Syk inhibitor, significantly reduced c-Cbl phosphorylation at residues Y774 and Y700, without affecting Y731 phosphorylation. Interestingly, PP2 inhibited both platelet-spreading on fibrinogen as well as clot retraction, whereas OXSI-2 blocked only platelet-spreading, suggesting a differential role of these tyrosine residues. The physiologic role of c-Cbl and Y731 was studied using platelets from c-Cbl KO and c-CblYF/YF knock-in mice. c-Cbl KO and c-CblYF/YF platelets had a significantly reduced spreading over immobilized fibrinogen. Furthermore, clot retraction with c-Cbl KO and c-CblYF/YF platelets was drastically delayed. These results indicate that c-Cbl and particularly its phosphorylated residue Y731 plays an important role in platelet outside-in signaling contributing to platelet-spreading and clot retraction. PMID:21967979

Effects of lower limb neurodynamic mobilization on intraneural fluid dispersion of the fourth lumbar nerve root: an unembalmed cadaveric investigation

PubMed Central

Gilbert, Kerry K.; Smith, Michael P.; Sobczak, Stéphane; James, C. Roger; Sizer, Phillip S.; Brismée, Jean-Michel

2015-01-01

Objectives Manual and physical therapists incorporate neurodynamic mobilisation (NDM) to improve function and decrease pain. Little is known about the mechanisms by which these interventions affect neural tissue. The objective of this research was to assess the effects of repetitive straight leg raise (SLR) NDM on the fluid dynamics within the fourth lumbar nerve root in unembalmed cadavers. Methods A biomimetic solution (Toluidine Blue Stock 1% and Plasma) was injected intraneurally, deep to the epineurium, into the L4 nerve roots of seven unembalmed cadavers. The initial dye spread was allowed to stabilise and measured with a digital calliper. Once the initial longitudinal dye spread stabilised, an intervention strategy (repetitive SLR) was applied incorporating NDMs (stretch/relax cycles) at a rate of 30 repetitions per minute for 5 minutes. Post-intervention calliper measurements of the longitudinal dye spread were measured. Results The mean experimental posttest longitudinal dye spread measurement (1.1 ± 0.9 mm) was significantly greater (P = 0.02) than the initial stabilised pretest longitudinal dye spread measurement. Increases ranged from 0.0 to 2.6 mm and represented an average of 7.9% and up to an 18.1% increase in longitudinal dye spread. Discussion Passive NDM in the form of repetitive SLR induced a significant increase in longitudinal fluid dispersion in the L4 nerve root of human cadaveric specimen. Lower limb NDM may be beneficial in promoting nerve function by limiting or altering intraneural fluid accumulation within the nerve root, thus preventing the adverse effects of intraneural oedema. PMID:26955255

Prognostic effect of isolated paraaortic nodal spread in endometrial cancer.

PubMed

Türkmen, Osman; Başaran, Derman; Karalok, Alper; Cömert Kimyon, Günsu; Taşçı, Tolga; Üreyen, Işın; Tulunay, Gökhan; Turan, Taner

2018-03-28

To evaluate the prognostic effect of isolated paraaortic lymph node metastasis in endometrial cancer (EC). This retrospective study included patients with FIGO 2009 stage IIIC2 disease due to isolated paraaortic lymph node metastasis (LNM). Patients with sarcomatous histology, synchronous gynecologic cancers and patients with concurrent pelvic lymph node metastases or patients that have intraabdominal tumor spread were excluded. Kaplan-Meier method was used for calculation of progression free survival (PFS) and overall survival. 1614 patients were operated for EC during study period.961 patients underwent lymph node dissection and 25 (2.6%) were found to have isolated LNM in paraaortic region and these constituted the study cohort.20 (80%) patients had endometrioid EC. Median number of retrieved lymph nodes from pelvic region and paraaortic region was 21.5 (range; 5-41) and 34.5 (range; 1-65), respectively. Median number of metastatic paraaortic nodes was 1 (range; 1-32).The median follow-up time was 15 months (range 5-94). 7 (28%) patients recurred after a median of 20 months (range, 3-99) from initial surgery. 3 patients recurred only in pelvis, one patient had upper abdominal spread and 3 had isolated extraabdominal recurrence.İnvolvement of uterine serosa, positive peritoneal cytology and presence of adnexal metastasis were significantly associated with diminished PFS (p<0.05). The presence of serosal involvement or adnexal involvement is as important as gross peritoneal spread and is related with poor survival in patients with isolated paraaortic nodal spread in EC. Chemotherapy should be the mainstay of treatment in this patient cohort which may eradicate systemic tumor spread.

A Parallel Product-Convolution approach for representing the depth varying Point Spread Functions in 3D widefield microscopy based on principal component analysis.

PubMed

Arigovindan, Muthuvel; Shaevitz, Joshua; McGowan, John; Sedat, John W; Agard, David A

2010-03-29

We address the problem of computational representation of image formation in 3D widefield fluorescence microscopy with depth varying spherical aberrations. We first represent 3D depth-dependent point spread functions (PSFs) as a weighted sum of basis functions that are obtained by principal component analysis (PCA) of experimental data. This representation is then used to derive an approximating structure that compactly expresses the depth variant response as a sum of few depth invariant convolutions pre-multiplied by a set of 1D depth functions, where the convolving functions are the PCA-derived basis functions. The model offers an efficient and convenient trade-off between complexity and accuracy. For a given number of approximating PSFs, the proposed method results in a much better accuracy than the strata based approximation scheme that is currently used in the literature. In addition to yielding better accuracy, the proposed methods automatically eliminate the noise in the measured PSFs.

Social Distancing Strategies against Disease Spreading

NASA Astrophysics Data System (ADS)

Valdez, L. D.; Buono, C.; Macri, P. A.; Braunstein, L. A.

2013-12-01

The recurrent infectious diseases and their increasing impact on the society has promoted the study of strategies to slow down the epidemic spreading. In this review we outline the applications of percolation theory to describe strategies against epidemic spreading on complex networks. We give a general outlook of the relation between link percolation and the susceptible-infected-recovered model, and introduce the node void percolation process to describe the dilution of the network composed by healthy individual, i.e., the network that sustain the functionality of a society. Then, we survey two strategies: the quenched disorder strategy where an heterogeneous distribution of contact intensities is induced in society, and the intermittent social distancing strategy where health individuals are persuaded to avoid contact with their neighbors for intermittent periods of time. Using percolation tools, we show that both strategies may halt the epidemic spreading. Finally, we discuss the role of the transmissibility, i.e., the effective probability to transmit a disease, on the performance of the strategies to slow down the epidemic spreading.

Local variations in spatial synchrony of influenza epidemics.

PubMed

Stark, James H; Cummings, Derek A T; Ermentrout, Bard; Ostroff, Stephen; Sharma, Ravi; Stebbins, Samuel; Burke, Donald S; Wisniewski, Stephen R

2012-01-01

Understanding the mechanism of influenza spread across multiple geographic scales is not complete. While the mechanism of dissemination across regions and states of the United States has been described, understanding the determinants of dissemination between counties has not been elucidated. The paucity of high resolution spatial-temporal influenza incidence data to evaluate disease structure is often not available. We report on the underlying relationship between the spread of influenza and human movement between counties of one state. Significant synchrony in the timing of epidemics exists across the entire state and decay with distance (regional correlation=62%). Synchrony as a function of population size display evidence of hierarchical spread with more synchronized epidemics occurring among the most populated counties. A gravity model describing movement between two populations is a stronger predictor of influenza spread than adult movement to and from workplaces suggesting that non-routine and leisure travel drive local epidemics. These findings highlight the complex nature of influenza spread across multiple geographic scales.

Local Variations in Spatial Synchrony of Influenza Epidemics

PubMed Central

Stark, James H.; Cummings, Derek A. T.; Ermentrout, Bard; Ostroff, Stephen; Sharma, Ravi; Stebbins, Samuel; Burke, Donald S.; Wisniewski, Stephen R.

2012-01-01

Background Understanding the mechanism of influenza spread across multiple geographic scales is not complete. While the mechanism of dissemination across regions and states of the United States has been described, understanding the determinants of dissemination between counties has not been elucidated. The paucity of high resolution spatial-temporal influenza incidence data to evaluate disease structure is often not available. Methodology and Findings We report on the underlying relationship between the spread of influenza and human movement between counties of one state. Significant synchrony in the timing of epidemics exists across the entire state and decay with distance (regional correlation = 62%). Synchrony as a function of population size display evidence of hierarchical spread with more synchronized epidemics occurring among the most populated counties. A gravity model describing movement between two populations is a stronger predictor of influenza spread than adult movement to and from workplaces suggesting that non-routine and leisure travel drive local epidemics. Conclusions These findings highlight the complex nature of influenza spread across multiple geographic scales. PMID:22916274

Lower crustal hydrothermal circulation at slow-spreading ridges: evidence from chlorine in Arctic and South Atlantic basalt glasses and melt inclusions

NASA Astrophysics Data System (ADS)

van der Zwan, Froukje M.; Devey, Colin W.; Hansteen, Thor H.; Almeev, Renat R.; Augustin, Nico; Frische, Matthias; Haase, Karsten M.; Basaham, Ali; Snow, Jonathan E.

2017-12-01

Hydrothermal circulation at slow-spreading ridges is important for cooling the newly formed lithosphere, but the depth to which it occurs is uncertain. Magmas which stagnate and partially crystallize during their rise from the mantle provide a means to constrain the depth of circulation because assimilation of hydrothermal fluids or hydrothermally altered country rock will raise their chlorine (Cl) contents. Here we present Cl concentrations in combination with chemical thermobarometry data on glassy basaltic rocks and melt inclusions from the Southern Mid-Atlantic Ridge (SMAR; 3 cm year-1 full spreading rate) and the Gakkel Ridge (max. 1.5 cm year-1 full spreading rate) in order to define the depth and extent of chlorine contamination. Basaltic glasses show Cl-contents ranging from ca. 50-430 ppm and ca. 40-700 ppm for the SMAR and Gakkel Ridge, respectively, whereas SMAR melt inclusions contain between 20 and 460 ppm Cl. Compared to elements of similar mantle incompatibility (e.g. K, Nb), Cl-excess (Cl/Nb or Cl/K higher than normal mantle values) of up to 250 ppm in glasses and melt inclusions are found in 75% of the samples from both ridges. Cl-excess is interpreted to indicate assimilation of hydrothermal brines (as opposed to bulk altered rock or seawater) based on the large range of Cl/K ratios in samples showing a limited spread in H2O contents. Resorption and disequilibrium textures of olivine, plagioclase and clinopyroxene phenocrysts and an abundance of xenocrysts and gabbroic fragments in the SMAR lavas suggest multiple generations of crystallization and assimilation of hydrothermally altered rocks that contain these brines. Calculated pressures of last equilibration based on the major element compositions of melts cannot provide reliable estimates of the depths at which this crystallization/assimilation occurred as the assimilation negates the assumption of crystallization under equilibrium conditions implicit in such calculations. Clinopyroxene-melt thermobarometry on rare clinopyroxene phenocrysts present in the SMAR magmas yield lower crustal crystallization/assimilation depths (10-13 km in the segment containing clinopyroxene). The Cl-excesses in SMAR melt inclusions indicate that assimilation occurred before crystallization, while also homogeneous Cl in melts from Gakkel Ridge indicate Cl addition during magma chamber processes. Combined, these observations imply that hydrothermal circulation reaches the lower crust at slow-spreading ridges, and thereby promotes cooling of the lower crust. The generally lower Cl-excess at slow-spreading ridges (compared to fast-spreading ridges) is probably related to them having few if any permanent magma chambers. Magmas therefore do not fractionate as extensively in the crust, providing less heat for assimilation (on average, slow-spreading ridge magmas have higher Mg#), and hydrothermal systems are ephemeral, leading to lower total degrees of crustal alteration and more variation in the amount of Cl contamination. Hydrothermal plumes and vent fields have samples in close vicinity that display Cl-excess, mostly of > 25 ppm, which thus can aid as a guide for the exploration of (active or extinct) hydrothermal vent fields on the axis.

Convective Ignition of Propellant Cylinders in a Developing Cross-Flow Field.

DTIC Science & Technology

1980-09-01

Ignition. .. ...... ..... 69 (ii) Polymer Ignition .. ....... ....... 72 F . Flame Spreading and Blow -off Phenomena .. ...... 72 G. Ignition and Flame...polymeric fuel binder for mechanical integrity. It also includes solid additives (like aluminum) and various catalysts and plasticizing agents . Ballistic...placed on distinguishing the ignition sites and the flame spreading (and blow off) tendencies as functions of the external flow velocity pressure and

Transformation Theory, Accelerating Frames, and Two Simple Problems

ERIC Educational Resources Information Center

Schmid, G. Bruno

1977-01-01

Presents an operator which transforms quantum functions to solve problems of the stationary state wave functions for a particle and the motion and spreading of a Gaussian wave packet in uniform gravitational fields. (SL)

Coupling effects on turning points of infectious diseases epidemics in scale-free networks.

PubMed

Kim, Kiseong; Lee, Sangyeon; Lee, Doheon; Lee, Kwang Hyung

2017-05-31

Pandemic is a typical spreading phenomenon that can be observed in the human society and is dependent on the structure of the social network. The Susceptible-Infective-Recovered (SIR) model describes spreading phenomena using two spreading factors; contagiousness (β) and recovery rate (γ). Some network models are trying to reflect the social network, but the real structure is difficult to uncover. We have developed a spreading phenomenon simulator that can input the epidemic parameters and network parameters and performed the experiment of disease propagation. The simulation result was analyzed to construct a new marker VRTP distribution. We also induced the VRTP formula for three of the network mathematical models. We suggest new marker VRTP (value of recovered on turning point) to describe the coupling between the SIR spreading and the Scale-free (SF) network and observe the aspects of the coupling effects with the various of spreading and network parameters. We also derive the analytic formulation of VRTP in the fully mixed model, the configuration model, and the degree-based model respectively in the mathematical function form for the insights on the relationship between experimental simulation and theoretical consideration. We discover the coupling effect between SIR spreading and SF network through devising novel marker VRTP which reflects the shifting effect and relates to entropy.

Identifying the starting point of a spreading process in complex networks.

PubMed

Comin, Cesar Henrique; Costa, Luciano da Fontoura

2011-11-01

When dealing with the dissemination of epidemics, one important question that can be asked is the location where the contamination began. In this paper, we analyze three spreading schemes and propose and validate an effective methodology for the identification of the source nodes. The method is based on the calculation of the centrality of the nodes on the sampled network, expressed here by degree, betweenness, closeness, and eigenvector centrality. We show that the source node tends to have the highest measurement values. The potential of the methodology is illustrated with respect to three theoretical complex network models as well as a real-world network, the email network of the University Rovira i Virgili.

Experimental comparison of various techniques for spot size measurement of high-energy X-ray

NASA Astrophysics Data System (ADS)

Wang, Yi; Li, Qin; Chen, Nan; Cheng, Jin-Ming; Li, Cheng-Gang; Li, Hong; Long, Quan-Hong; Shi, Jin-Shui; Deng, Jian-Jun

2016-08-01

In flash-radiography experiments, the quality of the acquired image strongly depends on the focal size of the X-ray source spot. A variety of techniques based on imaging of the pinhole, the slit and the rollbar are adopted to measure the focal spot size of the Dragon-I linear induction accelerator. The image of the pinhole provides a two-dimensional distribution of the X-ray spot, while those of the slit and the rollbar give a line-spread distribution and an edge-spread distribution, respectively. The spot size characterized by the full-width at half-maximum and that characterized by the LANL definition are calculated for comparison.

Research on the Additional Secondary Phase Factor for Automatic Identification System Signals Transmitted over a Rough Sea Surface

PubMed Central

Zhang, Shufang; Sun, Xiaowen

2018-01-01

This paper investigates the Additional Secondary Phase Factor (ASF) characteristics of Automatic Identification System (AIS) signals spreading over a rough sea surface. According to the change of the ASFs for AIS signals in different signal form, the influences of the different propagation conditions on the ASFs are analyzed. The expression, numerical calculation, and simulation analysis of the ASFs of AIS signal are performed in the rough sea surface. The results contribute to the high-accuracy propagation delay measurement of AIS signals spreading over the rough sea surface as, well as providing a reference for reliable communication link design in marine engineering for Very High Frequency (VHF) signals. PMID:29462995

The Specific Features of Pollution Transport in the Northwest Pacific Ocean

NASA Astrophysics Data System (ADS)

Diansky, Nikolay; Fomin, Vladimir; Gusev, Anatoly

2013-04-01

Two calculations of pollutant dispersal in the Northwest Pacific Ocean are presented: (1) during possible shipwrecks in the process of spent nuclear fuel transportation from Petropavlovsk-Kamchatsky and (2) pollutant spread from the Japanese coast after the Fukushima 1 nuclear disaster on March 11, 2011. The circulation was simulated using a σ - coordinate ocean model INMOM (Institute of Numerical Mathematics Ocean Model) developed at the INM RAS. The INMOM is based on the primitive equations using the spherical σ - coordinate system with a free ocean surface. The INMOM was realized for the Pacific Ocean basin from the equator to the Bering Strait with a high 1/8° spatial resolution for reproducing the mesoscale ocean variability. The pollutant dispersal in the case of possible shipwrecks was estimated for currents for a statistically average year with atmospheric forcing from Common Ocean-ice Reference Experiments (CORE) for normal year data. The pollution spread from the Fukushima 1 nuclear power plant (NPP) was estimated for currents calculated with the real atmospheric forcing in accordance with the NCEP GFS (0.5 degree grid). The simulation period of pollutant dispersal from Fukushima 1 was 17 days: from March 11 to 28, 2011. The results of numerical simulation show that pollutant dispersal from the Fukushima 1 spread eastward according to the Kuroshio. Moreover, exceeding of natural background radiation level was simulated in the narrow region of the Japanese coast with width of less than 50 km.

Stochastic analysis of epidemics on adaptive time varying networks

NASA Astrophysics Data System (ADS)

Kotnis, Bhushan; Kuri, Joy

2013-06-01

Many studies investigating the effect of human social connectivity structures (networks) and human behavioral adaptations on the spread of infectious diseases have assumed either a static connectivity structure or a network which adapts itself in response to the epidemic (adaptive networks). However, human social connections are inherently dynamic or time varying. Furthermore, the spread of many infectious diseases occur on a time scale comparable to the time scale of the evolving network structure. Here we aim to quantify the effect of human behavioral adaptations on the spread of asymptomatic infectious diseases on time varying networks. We perform a full stochastic analysis using a continuous time Markov chain approach for calculating the outbreak probability, mean epidemic duration, epidemic reemergence probability, etc. Additionally, we use mean-field theory for calculating epidemic thresholds. Theoretical predictions are verified using extensive simulations. Our studies have uncovered the existence of an “adaptive threshold,” i.e., when the ratio of susceptibility (or infectivity) rate to recovery rate is below the threshold value, adaptive behavior can prevent the epidemic. However, if it is above the threshold, no amount of behavioral adaptations can prevent the epidemic. Our analyses suggest that the interaction patterns of the infected population play a major role in sustaining the epidemic. Our results have implications on epidemic containment policies, as awareness campaigns and human behavioral responses can be effective only if the interaction levels of the infected populace are kept in check.

Partitioning of the degradation space for OCR training

NASA Astrophysics Data System (ADS)

Barney Smith, Elisa H.; Andersen, Tim

2006-01-01

Generally speaking optical character recognition algorithms tend to perform better when presented with homogeneous data. This paper studies a method that is designed to increase the homogeneity of training data, based on an understanding of the types of degradations that occur during the printing and scanning process, and how these degradations affect the homogeneity of the data. While it has been shown that dividing the degradation space by edge spread improves recognition accuracy over dividing the degradation space by threshold or point spread function width alone, the challenge is in deciding how many partitions and at what value of edge spread the divisions should be made. Clustering of different types of character features, fonts, sizes, resolutions and noise levels shows that edge spread is indeed shown to be a strong indicator of the homogeneity of character data clusters.

Cannibalism amplifies the spread of vertically transmitted pathogens.

PubMed

Sadeh, Asaf; Rosenheim, Jay A

2016-08-01

Cannibalism is a widespread behavior. Abundant empirical evidence demonstrates that cannibals incur a risk of contracting pathogenic infections when they consume infected conspecifics. However, current theory suggests that cannibalism generally impedes disease spread, because each victim is usually consumed by a single cannibal, such that cannibalism does not function as a spreading process. Consequently, cannibalism cannot be the only mode of transmission of most parasites. We develop simple, but general epidemiological models to analyze the interaction of cannibalism and vertical transmission. We show that cannibalism increases the prevalence of vertically transmitted pathogens whenever the host population density is not solely regulated by cannibalism. This mechanism, combined with additional, recently published, theoretical mechanisms, presents a strong case for the role of cannibalism in the spread of infectious diseases across a wide range of parasite-host systems. © 2016 by the Ecological Society of America.

Buoyancy effects on smoldering combustion

NASA Technical Reports Server (NTRS)

Dosanjh, S.; Peterson, J.; Fernandez-Pello, A. C.; Pagni, P. J.

1985-01-01

The effect of buoyancy on the rate of spread of a concurrent smolder reaction through a porous combustible material is investigated theoretically and experimentally. In the experiments, buoyant forces are controlled by varying the density difference, and the smolder rate spread through porous alpha cellulose (0.83 void fraction) is measured as a function of the ambient air pressure. The smolder velocity is found to increase with the ambient pressure; extinction occurs when the buoyancy forces cannot overcome the drag forces, indicating that diffusion by itself cannot support the spread of a smolder reaction. Theoretical predictions are found to be in good qualitative agreement with the experimental results.

An agent-based computational model for tuberculosis spreading on age-structured populations

NASA Astrophysics Data System (ADS)

Graciani Rodrigues, C. C.; Espíndola, Aquino L.; Penna, T. J. P.

2015-06-01

In this work we present an agent-based computational model to study the spreading of the tuberculosis (TB) disease on age-structured populations. The model proposed is a merge of two previous models: an agent-based computational model for the spreading of tuberculosis and a bit-string model for biological aging. The combination of TB with the population aging, reproduces the coexistence of health states, as seen in real populations. In addition, the universal exponential behavior of mortalities curves is still preserved. Finally, the population distribution as function of age shows the prevalence of TB mostly in elders, for high efficacy treatments.

Quantitative Infrared Image Analysis Of Simultaneous Upstream and Downstream Microgravity Flame Spread over Thermally-Thin Cellulose in Low Speed Forced Flow

NASA Technical Reports Server (NTRS)

Olson, S. L.; Lee, J. R.; Fujita, O.; Kikuchi, M.; Kashiwagi, T.

2013-01-01

The effect of low velocity forced flow on microgravity flame spread is examined using quantitative analysis of infrared video imaging. The objective of the quantitative analysis is to provide insight into the mechanisms of flame spread in microgravity where the flame is able to spread from a central location on the fuel surface, rather than from an edge. Surface view calibrated infrared images of ignition and flame spread over a thin cellulose fuel were obtained along with a color video of the surface view and color images of the edge view using 35 mm color film at 2 Hz. The cellulose fuel samples were mounted in the center of a 12 cm wide by 16 cm tall flow duct and were ignited in microgravity using a straight hot wire across the center of the 7.5 cm wide by 14 cm long samples. Four cases, at 1 atm. 35%O2 in N2, at forced flows from 2 cm/s to 20 cm/s are presented here. This flow range captures flame spread from strictly upstream spread at low flows, to predominantly downstream spread at high flow. Surface temperature profiles are evaluated as a function of time, and temperature gradients for upstream and downstream flame spread are measured. Flame spread rates from IR image data are compared to visible image spread rate data. IR blackbody temperatures are compared to surface thermocouple readings to evaluate the effective emissivity of the pyrolyzing surface. Preheat lengths and pyrolysis lengths are evaluated both upstream and downstream of the central ignition point. A surface energy balance estimates the net heat flux from the flame to the fuel surface along the length of the fuel. Surface radiative loss and gas-phase radiation from soot are measured relative to the net heat feedback from the flame. At high surface heat loss relative to heat feedback, the downstream flame spread does not occur.

Modeling the state dependent impulse control for computer virus propagation under media coverage

NASA Astrophysics Data System (ADS)

Liang, Xiyin; Pei, Yongzhen; Lv, Yunfei

2018-02-01

A state dependent impulsive control model is proposed to model the spread of computer virus incorporating media coverage. By the successor function, the sufficient conditions for the existence and uniqueness of order-1 periodic solution are presented first. Secondly, for two classes of periodic solutions, the geometric property of successor function and the analogue of the Poincaré criterion are employed to obtain the stability results. These results show that the number of the infective computers is under the threshold all the time. Finally, the theoretic and numerical analysis show that media coverage can delay the spread of computer virus.

Characterisation of a resolution enhancing image inversion interferometer.

PubMed

Wicker, Kai; Sindbert, Simon; Heintzmann, Rainer

2009-08-31

Image inversion interferometers have the potential to significantly enhance the lateral resolution and light efficiency of scanning fluorescence microscopes. Self-interference of a point source's coherent point spread function with its inverted copy leads to a reduction in the integrated signal for off-axis sources compared to sources on the inversion axis. This can be used to enhance the resolution in a confocal laser scanning microscope. We present a simple image inversion interferometer relying solely on reflections off planar surfaces. Measurements of the detection point spread function for several types of light sources confirm the predicted performance and suggest its usability for scanning confocal fluorescence microscopy.

Advanced S-Band studies using the TDRSS communications satellite

NASA Technical Reports Server (NTRS)

Jenkins, Jeffrey D.; Osborne, William P.; Fan, Yiping

1994-01-01

This report will describe the design, implementation, and results of a propagation experiment which used TDRSS to transmit spread signals at S-Band to an instrumented mobile receiver. The results consist of fade measurements and distribution functions in 21 environments across the Continental United States (CONUS). From these distribution functions, some idea may be gained about what system designers should expect for excess path loss in many mobile environments. Some of these results may be compared against similar measurements made with narrowband beacon measurements. Such comparisons provide insight into what gains the spread signaling system may or may not have in multipath and shadowing environments.

Characterisation of chicken TES and its role in cell spreading and motility.

PubMed

Griffith, Elen; Coutts, Amanda S; Black, Donald M

2004-03-01

Previously we identified TES as a candidate tumour suppressor gene that is located at human chromosome 7q31.1. More recently, we and others have shown TES to encode a novel LIM domain protein that localises to focal adhesions. Here, we present the cloning and functional analysis of the chicken orthologue of TES, cTES. The TES proteins are highly conserved between chicken and human, showing 89% identity at the amino acid level. We show that the cTES protein localised at focal adhesions, actin stress fibres, and sites of cell-cell contact, and GST-cTES can pull-down zyxin and actin. To investigate a functional role for cTES, we looked at the effect of its overexpression on cell spreading and cell motility. Cells overexpressing cTES showed increased cell spreading on fibronectin, and decreased cell motility, compared to RCAS vector transfected control cells. The data from our studies with cTES support our previous findings with human TES and further implicate TES as a member of a complex of proteins that function together to regulate cell adhesion and additionally demonstrate a role for TES in cell motility. Copyright 2004 Wiley-Liss, Inc.

Optical aberration correction for simple lenses via sparse representation

NASA Astrophysics Data System (ADS)

Cui, Jinlin; Huang, Wei

2018-04-01

Simple lenses with spherical surfaces are lightweight, inexpensive, highly flexible, and can be easily processed. However, they suffer from optical aberrations that lead to limitations in high-quality photography. In this study, we propose a set of computational photography techniques based on sparse signal representation to remove optical aberrations, thereby allowing the recovery of images captured through a single-lens camera. The primary advantage of the proposed method is that many prior point spread functions calibrated at different depths are successfully used for restoring visual images in a short time, which can be generally applied to nonblind deconvolution methods for solving the problem of the excessive processing time caused by the number of point spread functions. The optical software CODE V is applied for examining the reliability of the proposed method by simulation. The simulation results reveal that the suggested method outperforms the traditional methods. Moreover, the performance of a single-lens camera is significantly enhanced both qualitatively and perceptually. Particularly, the prior information obtained by CODE V can be used for processing the real images of a single-lens camera, which provides an alternative approach to conveniently and accurately obtain point spread functions of single-lens cameras.

Pseudorandom binary injection of levitons for electron quantum optics

NASA Astrophysics Data System (ADS)

Glattli, D. C.; Roulleau, P.

2018-03-01

The recent realization of single-electron sources lets us envision performing electron quantum optics experiments, where electrons can be viewed as flying qubits propagating in a ballistic conductor. To date, all electron sources operate in a periodic electron injection mode, leading to energy spectrum singularities in various physical observables which sometimes hide the bare nature of physical effects. To go beyond this, we propose a spread-spectrum approach where electron flying qubits are injected in a nonperiodic manner following a pseudorandom binary bit pattern. Extending the Floquet scattering theory approach from periodic to spread-spectrum drive, the shot noise of pseudorandom binary sequences of single-electron injection can be calculated for leviton and nonleviton sources. Our new approach allows us to disentangle the physics of the manipulated excitations from that of the injection protocol. In particular, the spread-spectrum approach is shown to provide better knowledge of electronic Hong-Ou-Mandel correlations and to clarify the nature of the pulse train coherence and the role of the dynamical orthogonality catastrophe for noninteger charge injection.

The point-spread function of fiber-coupled area detectors

PubMed Central

Holton, James M.; Nielsen, Chris; Frankel, Kenneth A.

2012-01-01

The point-spread function (PSF) of a fiber-optic taper-coupled CCD area detector was measured over five decades of intensity using a 20 µm X-ray beam and ∼2000-fold averaging. The ‘tails’ of the PSF clearly revealed that it is neither Gaussian nor Lorentzian, but instead resembles the solid angle subtended by a pixel at a point source of light held a small distance (∼27 µm) above the pixel plane. This converges to an inverse cube law far from the beam impact point. Further analysis revealed that the tails are dominated by the fiber-optic taper, with negligible contribution from the phosphor, suggesting that the PSF of all fiber-coupled CCD-type detectors is best described as a Moffat function. PMID:23093762

Modelling indirect interactions during failure spreading in a project activity network.

PubMed

Ellinas, Christos

2018-03-12

Spreading broadly refers to the notion of an entity propagating throughout a networked system via its interacting components. Evidence of its ubiquity and severity can be seen in a range of phenomena, from disease epidemics to financial systemic risk. In order to understand the dynamics of these critical phenomena, computational models map the probability of propagation as a function of direct exposure, typically in the form of pairwise interactions between components. By doing so, the important role of indirect interactions remains unexplored. In response, we develop a simple model that accounts for the effect of both direct and subsequent exposure, which we deploy in the novel context of failure propagation within a real-world engineering project. We show that subsequent exposure has a significant effect in key aspects, including the: (a) final spreading event size, (b) propagation rate, and (c) spreading event structure. In addition, we demonstrate the existence of 'hidden influentials' in large-scale spreading events, and evaluate the role of direct and subsequent exposure in their emergence. Given the evidence of the importance of subsequent exposure, our findings offer new insight on particular aspects that need to be included when modelling network dynamics in general, and spreading processes specifically.

Spreading dynamics of forget-remember mechanism

NASA Astrophysics Data System (ADS)

Deng, Shengfeng; Li, Wei

2017-04-01

We study extensively the forget-remember mechanism (FRM) for message spreading, originally introduced in Eur. Phys. J. B 62, 247 (2008), 10.1140/epjb/e2008-00139-4. The freedom of specifying forget-remember functions governing the FRM can enrich the spreading dynamics to a very large extent. The master equation is derived for describing the FRM dynamics. By applying the mean field techniques, we have shown how the steady states can be reached under certain conditions, which agrees well with the Monte Carlo simulations. The distributions of forget and remember times can be explicitly given when the forget-remember functions take linear or exponential forms, which might shed some light on understanding the temporal nature of diseases like flu. For time-dependent FRM there is an epidemic threshold related to the FRM parameters. We have proven that the mean field critical transmissibility for the SIS model and the critical transmissibility for the SIR model are the lower and the the upper bounds of the critical transmissibility for the FRM model, respectively.

In-flight calibration of the Hitomi Soft X-ray Spectrometer. (2) Point spread function

NASA Astrophysics Data System (ADS)

Maeda, Yoshitomo; Sato, Toshiki; Hayashi, Takayuki; Iizuka, Ryo; Angelini, Lorella; Asai, Ryota; Furuzawa, Akihiro; Kelley, Richard; Koyama, Shu; Kurashima, Sho; Ishida, Manabu; Mori, Hideyuki; Nakaniwa, Nozomi; Okajima, Takashi; Serlemitsos, Peter J.; Tsujimoto, Masahiro; Yaqoob, Tahir

2018-03-01

We present results of inflight calibration of the point spread function of the Soft X-ray Telescope that focuses X-rays onto the pixel array of the Soft X-ray Spectrometer system. We make a full array image of a point-like source by extracting a pulsed component of the Crab nebula emission. Within the limited statistics afforded by an exposure time of only 6.9 ks and limited knowledge of the systematic uncertainties, we find that the raytracing model of 1 {^'.} 2 half-power-diameter is consistent with an image of the observed event distributions across pixels. The ratio between the Crab pulsar image and the raytracing shows scatter from pixel to pixel that is 40% or less in all except one pixel. The pixel-to-pixel ratio has a spread of 20%, on average, for the 15 edge pixels, with an averaged statistical error of 17% (1 σ). In the central 16 pixels, the corresponding ratio is 15% with an error of 6%.

Long term spatial and temporal trends in frost day indices in Kansas, USA

USDA-ARS?s Scientific Manuscript database

Frost day indices such as number of frost days (nFDs), frost free days (nFFDs), last spring freeze (LSF), first fall freeze (FFF), and growing-season length (GSL), were calculated using daily minimum air temperature (Tmin) values from 23 centennial weather stations spread across Kansas during four t...

Predicting wildfire behavior in black spruce forests in Alaska.

Treesearch

Rodney A. Norum

1982-01-01

The current fire behavior system, when properly adjusted, accurately predicts forward rate of spread and flame length of wildfires in black spruce (Picea mariana (Mill.) B.S.P.) forests in Alaska. After fire behavior was observed and quantified, adjustment factors were calculated and assigned to the selected fuel models to correct the outputs to...

Lévy processes on a generalized fractal comb

NASA Astrophysics Data System (ADS)

Sandev, Trifce; Iomin, Alexander; Méndez, Vicenç

2016-09-01

Comb geometry, constituted of a backbone and fingers, is one of the most simple paradigm of a two-dimensional structure, where anomalous diffusion can be realized in the framework of Markov processes. However, the intrinsic properties of the structure can destroy this Markovian transport. These effects can be described by the memory and spatial kernels. In particular, the fractal structure of the fingers, which is controlled by the spatial kernel in both the real and the Fourier spaces, leads to the Lévy processes (Lévy flights) and superdiffusion. This generalization of the fractional diffusion is described by the Riesz space fractional derivative. In the framework of this generalized fractal comb model, Lévy processes are considered, and exact solutions for the probability distribution functions are obtained in terms of the Fox H-function for a variety of the memory kernels, and the rate of the superdiffusive spreading is studied by calculating the fractional moments. For a special form of the memory kernels, we also observed a competition between long rests and long jumps. Finally, we considered the fractal structure of the fingers controlled by a Weierstrass function, which leads to the power-law kernel in the Fourier space. This is a special case, when the second moment exists for superdiffusion in this competition between long rests and long jumps.

Multilayer thin-film phantoms for axial contrast transfer function measurement in optical coherence tomography.

PubMed

Agrawal, Anant; Chen, Chao-Wei; Baxi, Jigesh; Chen, Yu; Pfefer, T Joshua

2013-07-01

In optical coherence tomography (OCT), axial resolution is one of the most critical parameters impacting image quality. It is commonly measured by determining the point spread function (PSF) based on a specular surface reflection. The contrast transfer function (CTF) provides more insights into an imaging system's resolving characteristics and can be readily generated in a system-independent manner, without consideration for image pixel size. In this study, we developed a test method for determination of CTF based on multi-layer, thin-film phantoms, evaluated using spectral- and time-domain OCT platforms with different axial resolution values. Phantoms representing six spatial frequencies were fabricated and imaged. The fabrication process involved spin coating silicone films with precise thicknesses in the 8-40 μm range. Alternating layers were doped with a specified concentration of scattering particles. Validation of layer optical properties and thicknesses were achieved with spectrophotometry and stylus profilometry, respectively. OCT B-scans were used to calculate CTFs and results were compared with convetional PSF measurements based on specular reflections. Testing of these phantoms indicated that our approach can provide direct access to axial resolution characteristics highly relevant to image quality. Furthermore, tissue phantoms based on our thin-film fabrication approach may have a wide range of additional applications in optical imaging and spectroscopy.

Behavior of the Position-Spread Tensor in Diatomic Systems.

PubMed

Brea, Oriana; El Khatib, Muammar; Angeli, Celestino; Bendazzoli, Gian Luigi; Evangelisti, Stefano; Leininger, Thierry

2013-12-10

The behavior of the Position-Spread Tensor (Λ) in a series of light diatomic molecules (either neutral or negative ions) is investigated at a Full Configuration Interaction level. This tensor, which is the second moment cumulant of the total position operator, is invariant with respect to molecular translations, while its trace is also rotationally invariant. Moreover, the tensor is additive in the case of noninteracting subsystems and can be seen as an intrinsic property of a molecule. In the present work, it is shown that the longitudinal component of the tensor, Λ∥, which is small for internuclear distances close to the equilibrium, tends to grow if the bond is stretched. A maximum is reached in the region of the bond breaking, then Λ∥ decreases and converges toward the isolated-atom value. The degenerate transversal components, Λ⊥, on the other hand, usually have a monotonic growth toward the atomic value. The Position Spread is extremely sensitive to reorganization of the molecular wave function, and it becomes larger in the case of an increase of the electron mobility, as illustrated by the neutral-ionic avoided crossing in LiF. For these reasons, the Position Spread can be an extremely useful property that characterizes the nature of the wave function in a molecular system.

Endomembrane-associated RSD-3 is important for RNAi induced by extracellular silencing RNA in both somatic and germ cells of Caenorhabditis elegans

PubMed Central

Imae, Rieko; Dejima, Katsufumi; Kage-Nakadai, Eriko; Arai, Hiroyuki; Mitani, Shohei

2016-01-01

RNA silencing signals in C. elegans spread among cells, leading to RNAi throughout the body. During systemic spread of RNAi, membrane trafficking is thought to play important roles. Here, we show that RNAi Spreading Defective-3 (rsd-3), which encodes a homolog of epsinR, a conserved ENTH (epsin N-terminal homology) domain protein, generally participates in cellular uptake of silencing RNA. RSD-3 is previously thought to be involved in systemic RNAi only in germ cells, but we isolated several deletion alleles of rsd-3, and found that these mutants are defective in the spread of silencing RNA not only into germ cells but also into somatic cells. RSD-3 is ubiquitously expressed, and intracellularly localized to the trans-Golgi network (TGN) and endosomes. Tissue-specific rescue experiments indicate that RSD-3 is required for importing silencing RNA into cells rather than exporting from cells. Structure/function analysis showed that the ENTH domain alone is sufficient, and membrane association of the ENTH domain is required, for RSD-3 function in systemic RNAi. Our results suggest that endomembrane trafficking through the TGN and endosomes generally plays an important role in cellular uptake of silencing RNA. PMID:27306325

Endomembrane-associated RSD-3 is important for RNAi induced by extracellular silencing RNA in both somatic and germ cells of Caenorhabditis elegans.

PubMed

Imae, Rieko; Dejima, Katsufumi; Kage-Nakadai, Eriko; Arai, Hiroyuki; Mitani, Shohei

2016-06-16

RNA silencing signals in C. elegans spread among cells, leading to RNAi throughout the body. During systemic spread of RNAi, membrane trafficking is thought to play important roles. Here, we show that RNAi Spreading Defective-3 (rsd-3), which encodes a homolog of epsinR, a conserved ENTH (epsin N-terminal homology) domain protein, generally participates in cellular uptake of silencing RNA. RSD-3 is previously thought to be involved in systemic RNAi only in germ cells, but we isolated several deletion alleles of rsd-3, and found that these mutants are defective in the spread of silencing RNA not only into germ cells but also into somatic cells. RSD-3 is ubiquitously expressed, and intracellularly localized to the trans-Golgi network (TGN) and endosomes. Tissue-specific rescue experiments indicate that RSD-3 is required for importing silencing RNA into cells rather than exporting from cells. Structure/function analysis showed that the ENTH domain alone is sufficient, and membrane association of the ENTH domain is required, for RSD-3 function in systemic RNAi. Our results suggest that endomembrane trafficking through the TGN and endosomes generally plays an important role in cellular uptake of silencing RNA.

On a thermal analysis of a second stripper for rare isotope accelerator.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Momozaki, Y.; Nolen, J.; Nuclear Engineering Division

2008-08-04

This memo summarizes simple calculations and results of the thermal analysis on the second stripper to be used in the driver linac of Rare Isotope Accelerator (RIA). Both liquid (Sodium) and solid (Titanium and Vanadium) stripper concepts were considered. These calculations were intended to provide basic information to evaluate the feasibility of liquid (thick film) and solid (rotating wheel) second strippers. Nuclear physics calculations to estimate the volumetric heat generation in the stripper material were performed by 'LISE for Excel'. In the thermal calculations, the strippers were modeled as a thin 2D plate with uniform heat generation within the beammore » spot. Then, temperature distributions were computed by assuming that the heat spreads conductively in the plate in radial direction without radiative heat losses to surroundings.« less

Revised East-West Antarctic plate motions since the Middle Eocene

NASA Astrophysics Data System (ADS)

Granot, R.; Cande, S. C.; Stock, J.; Damaske, D.

2010-12-01

The middle Cenozoic (43-26 Ma) rifting between East and West Antarctica is defined by an episode of ultraslow seafloor spreading in the Adare Basin, located off northwestern Ross Sea. The absence of fracture zones and the lack of sufficient well-located magnetic anomaly picks have resulted in a poorly constrained kinematic model (Cande et al., 2000). Here we utilize the results from a dense aeromagnetic survey (Damaske et al., 2007) collected as part of GANOVEX IX 2005/06 campaign to re-evaluate the kinematics of the West Antarctic rift system since the Middle Eocene. We identify marine magnetic anomalies (anomalies 12o, 13o, 16y, and 18o) along a total of 25,000 km of the GPS navigated magnetic profiles. The continuation of these anomalies into the Northern Basin has allowed us to use the entire N-S length of this dataset in our calculations. A distinct curvature in the orientation of the spreading axis provides a strong constraint on our calculated kinematic models. The results from two- (East-West Antarctica) and three- (Australia-East Antarctica-West Antarctica) plate solutions agree well and create a cluster of rotation axes located south of the rift system, near the South Pole. These solutions reveal that spreading rate and direction, and therefore motion between East and West Antarctica, were steady between the Middle Eocene and Early Oligocene. Our kinematic solutions confirm the results of Davey and De Santis (2005) that the Victoria Land Basin has accommodated ~95 km of extension since the Middle Eocene. This magnetic pattern also provides valuable constraints on the post-spreading deformation of the Adare Basin (Granot et al., 2010). The Adare Basin has accommodated very little extension since the Late Oligocene (<7 km), but motion has probably increased southward. The details of this younger phase of motion are still crudely constrained.

Static network analysis of a pork supply chain in Northern Germany-Characterisation of the potential spread of infectious diseases via animal movements.

PubMed

Büttner, Kathrin; Krieter, Joachim; Traulsen, Arne; Traulsen, Imke

2013-07-01

Transport of live animals is a major risk factor in the spread of infectious diseases between holdings. The present study analysed the pork supply chain of a producer community in Northern Germany. The structure of trade networks can be characterised by carrying out a network analysis. To identify holdings with a central position in this directed network of pig production, several parameters describing these properties were measured (in-degree, out-degree, ingoing and outgoing infection chain, betweenness centrality and ingoing and outgoing closeness centrality). To obtain the importance of the different holding types (multiplier, farrowing farms, finishing farms and farrow-to-finishing farms) within the pyramidal structure of the pork supply chain, centrality parameters were calculated for the entire network as well as for the individual holding types. Using these centrality parameters, two types of holdings could be identified. In the network studied, finishing and farrow-to-finishing farms were more likely to be infected due to the high number of ingoing trade contacts. Due to the high number of outgoing trade contacts multipliers and farrowing farms had an increased risk to spread a disease to other holdings. However, the results of the centrality parameters degree and infection chain were not always consistent, such that the indirect trade contacts should be taken into consideration to understand the real importance of a holding in spreading or contracting an infection. Furthermore, all calculated parameters showed a highly right-skewed distribution. Networks with such a degree distribution are considered to be highly resistant concerning the random removal of nodes. But by strategic removal of the most central holdings, e.g. by trade restrictions or selective vaccination or culling, the network structure can be changed efficiently and thus decompose into fragments. Such a fragmentation of the trade networks is of particular importance from an epidemiological perspective. Copyright © 2013 Elsevier B.V. All rights reserved.

Channeling at the base of the lithosphere during the lateral flow of plume material beneath flow line hot spots

NASA Astrophysics Data System (ADS)

Sleep, Norman H.

2008-08-01

Chains of volcanic edifices lie along flow lines between plume-fed hot spots and the thin lithosphere at ridge axes. Discovery and Euterpe/Musicians Seamounts are two examples. An attractive hypothesis is that buoyant plume material flows along the base of the lithosphere perpendicular to isochrons. The plume material may conceivably flow in a broad front or flow within channels convectively eroded into the base to the lithosphere. A necessary but not sufficient condition for convective channeling is that the expected stagnant-lid heat flow for the maximum temperature of the plume material is comparable to the half-space surface heat flow of the oceanic lithosphere. Two-dimensional and three-dimensional numerical calculations confirm this inference. A second criterion for significant convective erosion is that it needs to occur before the plume material thins by lateral spreading. Scaling relationships indicate spreading and convection are closely related. Mathematically, the Nusselt number (ratio of convective to conductive heat flow in the plume material) scales with the flux (volume per time per length of flow front) of the plume material. A blob of unconfined plume material thus spreads before the lithosphere thins much and evolves to a slowly spreading and slowly convecting warm region in equilibrium with conduction into the base of the overlying lithosphere. Three-dimensional calculations illustrate this long-lasting (and hence observable) state of plume material away from its plume source. A different flow domain occurs around a stationary hot plume that continuously supplies hot material. The plume convectively erodes the overlying lithosphere, trapping the plume material near its orifice. The region of lithosphere underlain by plume material grows toward the ridge axis and laterally by convective thinning of the lithosphere at its edges. The hottest plume material channels along flow lines. Geologically, the regions of lithosphere underlain by either warm or hot plume material are likely to extend laterally away from the volcanic edifices whether or not channeling occurs.

Bone Density Development of the Temporal Bone Assessed by Computed Tomography.

PubMed

Takahashi, Kuniyuki; Morita, Yuka; Ohshima, Shinsuke; Izumi, Shuji; Kubota, Yamato; Horii, Arata

2017-12-01

The temporal bone shows regional differences in bone development. The spreading pattern of acute mastoiditis shows age-related differences. In infants, it spreads laterally and causes retroauricular swelling, whereas in older children, it tends to spread medially and causes intracranial complications. We hypothesized that bone maturation may influence the spreading pattern of acute mastoiditis. Eighty participants with normal hearing, aged 3 months to 42 years, participated in this study. Computed tomography (CT) values (Hounsfield unit [HU]) in various regions of the temporal bone, such as the otic capsule (OC), lateral surface of the mastoid cavity (LS), posterior cranial fossa (PCF), and middle cranial fossa (MCF), were measured as markers of bone density. Bone density development curves, wherein CT values were plotted against age, were created for each region. The age at which the CT value exceeded 1000 HU, which is used as an indicator of bone maturation, was calculated from the development curves and compared between the regions. The OC showed mature bone at birth, whereas the LS, PCF, and MCF showed rapid maturation in early childhood. However, there were significant regional differences in the ages of maturation: 1.7, 3.9, and 10.8 years for the LS, PCF, and MCF, respectively. To our knowledge, this is the first report to show regional differences in the maturation of temporal bone, which could partly account for the differences in the spreading pattern of acute mastoiditis in individuals of different ages.

Measurement of nanoscale molten polymer droplet spreading using atomic force microscopy

NASA Astrophysics Data System (ADS)

Soleymaniha, Mohammadreza; Felts, Jonathan R.

2018-03-01

We present a technique for measuring molten polymer spreading dynamics with nanometer scale spatial resolution at elevated temperatures using atomic force microscopy (AFM). The experimental setup is used to measure the spreading dynamics of polystyrene droplets with 2 μm diameters at 115-175 °C on sapphire, silicon oxide, and mica. Custom image processing algorithms determine the droplet height, radius, volume, and contact angle of each AFM image over time to calculate the droplet spreading dynamics. The contact angle evolution follows a power law with time with experimentally determined values of -0.29 ± 0.01, -0.08 ± 0.02, and -0.21 ± 0.01 for sapphire, silicon oxide, and mica, respectively. The non-zero steady state contact angles result in a slower evolution of contact angle with time consistent with theories combining molecular kinetic and hydrodynamic models. Monitoring the cantilever phase provides additional information about the local mechanics of the droplet surface. We observe local crystallinity on the molten droplet surface, where crystalline structures appear to nucleate at the contact line and migrate toward the top of the droplet. Increasing the temperature from 115 °C to 175 °C reduced surface crystallinity from 35% to 12%, consistent with increasingly energetically favorable amorphous phase as the temperature approaches the melting temperature. This platform provides a way to measure spreading dynamics of extremely small volumes of heterogeneously complex fluids not possible through other means.

Lithospheric structure of the South China Sea and adjacent regions: Results from potential field modelling

NASA Astrophysics Data System (ADS)

Chen, Ming; Fang, Jian; Cui, Ronghua

2018-02-01

This work aims to investigate the crustal and lithospheric mantle thickness of the South China Sea (SCS) and adjacent regions. The crust-mantle interface, average crustal density, and lithospheric mantle base are calculated from free-air gravity anomaly and topographic data using an iterative inversion method. We construct a three-dimensional lithospheric model with different hierarchical layers. The satellite-derived gravity is used to invert the average crustal density and Moho (crust-mantle interface) undulations. The average crustal density and LAB (lithosphere-asthenosphere boundary) depths are further adjusted by topographic data under the assumption of local isostasy. The average difference in Moho depths between this study and the seismic measurement results is <1.5 km. The results show that in oceanic regions, the Moho depths are 7.5-30 km and the LAB depths are 65-120 km. The lithospheric thickness of the SCS basin and the adjacent regions increases from the sea basin to the continental margin with a large gradient in the ocean-continent transition zones. The Moho depths of conjugate plots during the opening of SCS, Zhongsha Islands and Reed Bank, reveal the asymmetric spreading pattern of SCS seafloor spreading. The lithospheric thinning pattern indicate two different spreading directions during seafloor spreading, which changed from N-S to NW-SE after the southward transition of the spreading axis. The lithosphere of the SCS basin and adjacent regions indicate that the SCS basin is a young basin with a stable interior lithosphere.

Saltstone SDU6 Modeling Study

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lee, Si Y.; Hyun, Sinjae

2013-01-10

A new disposal unit, designated as Saltstone Disposal Unit 6 (SDU6), is being designed for support of site accelerated closure goals and salt waste projections identified in the new Liquid Waste System Plan. The unit is a cylindrical disposal cell of 375 ft in diameter and 43 ft in height, and it has a minimum 30 million gallons of capacity. SRNL was requested to evaluate the impact of an increased grout placement height on the flow patterns radially spread on the floor and to determine whether grout quality is impacted by the height. The primary goals of the work aremore » to develop the baseline Computational Fluid Dynamics (CFD) model and to perform the evaluations for the flow patterns of grout material in SDU6 as a function of elevation of grout discharge port and grout rheology. Two transient grout models have been developed by taking a three-dimensional multiphase CFD approach to estimate the domain size of the grout materials radially spread on the facility floor and to perform the sensitivity analysis with respect to the baseline design and operating conditions such as elevation height of the discharge port and fresh grout properties. For the CFD modeling calculations, air-grout Volume of Fluid (VOF) method combined with Bingham plastic and time-dependent grout models were used for examining the impact of fluid spread performance for the initial baseline configurations and to evaluate the impact of grout pouring height on grout quality. The grout quality was estimated in terms of the air volume fraction for the grout layer formed on the SDU6 floor, resulting in the change of grout density. The study results should be considered as preliminary scoping analyses since benchmarking analysis is not included in this task scope. Transient analyses with the Bingham plastic model were performed with the FLUENTTM code on the high performance parallel computing platform in SRNL. The analysis coupled with a transient grout aging model was performed by using ANSYS-CFX code in the parallel computing platform in Mercer University. Recommended operational guidance was developed assuming that local shear rates and flow patterns related to radial spread along the SDU floor can be used as a measure of grout performance and spatial dispersion affected by the grout height and viscosity. The 5 ft height baseline results show that when the 150 gpm grout flow with a 5 Pa yield stress and a 60 cp viscosity is poured down through a 3 inch discharge port, the grout is spread radially up to about 64 ft distance from the pouring center after 2 hours' pouring time. The air volume fraction of the grout layer is about 29% at 5 minutes' transient time, and it is reduced by about 9% in 2 hours' pouring time, resulting in the grout density consisting of about 80% grout and 20% air volume fractions. The sensitivity results show that when the discharge port is located at a higher position, a larger amount of air is trapped inside the layer formed below the discharge port at the early transient time of less than 30 minutes because of the higher impinging momentum of the grout flow on the floor, resulting in the formation of less smooth layer. The results clearly indicate that the radial spread for the 43 ft discharge port is about 10% faster than that of the 5 ft discharge port for the early transient period of 5 minutes. However, for the pouring time longer than half an hour, the discharge port height does not affect the radial distance spread on the disposal floor. When grout quality is related to grout volume fraction, the grout volume fraction for the 43 ft discharge port has lower volume fraction than the 5 ft discharge port for the transient period of the first 5 minutes. However, for the pouring time longer than half an hour, the discharge port height does not affect the grout volume fraction for the layer accumulated on the disposal floor. A modified Bingham plastic model coupled with time-dependent viscosity behavior was developed for conducting the initial scoping calculations to assess the impact of fluid residence time on radial spreading and basic flow patterns. The results for the transient viscosity model show that when grout material becomes more viscous, the thickness of the grout layer accumulated on the floor becomes higher, but the radial distance spread on the horizontal floor becomes smaller. The early transient results for the grout density with about 32% air volume fractions are in reasonable agreement with those of the idealized Bingham plastic model. It is recommended that the current models developed here be benchmarked against the experimental results for critical applications of the modeling results.« less

Non-cell autonomous cell death caused by transmission of Huntingtin aggregates in Drosophila.

PubMed

Babcock, Daniel T; Ganetzky, Barry

2015-01-01

Recent evidence indicates that protein aggregates can spread between neurons in several neurodegenerative diseases but much remains unknown regarding the underlying mechanisms responsible for this spreading and its role in disease progression. We recently demonstrated that mutant Huntingtin aggregates spread between cells within the Drosophila brain resulting in non-cell autonomous loss of a pair of large neurons in the posterior protocerebrum. However, the full extent of neuronal loss throughout the brain was not determined. Here we examine the effects of driving expression of mutant Huntingtin in Olfactory Receptor Neurons (ORNs) by using a marker for cleaved caspase activity to monitor neuronal apoptosis as a function of age. We find widespread caspase activity in various brain regions over time, demonstrating that non-cell autonomous damage is widespread. Improved understanding of which neurons are most vulnerable and why should be useful in developing treatment strategies for neurodegenerative diseases that involve transcellular spreading of aggregates.

Common cold outbreaks: A network theory approach

NASA Astrophysics Data System (ADS)

Vishkaie, Faranak Rajabi; Bakouie, Fatemeh; Gharibzadeh, Shahriar

2014-11-01

In this study, at first we evaluated the network structure in social encounters by which respiratory diseases can spread. We considered common-cold and recorded a sample of human population and actual encounters between them. Our results show that the database structure presents a great value of clustering. In the second step, we evaluated dynamics of disease spread with SIR model by assigning a function to each node of the structural network. The rate of disease spread in networks was observed to be inversely correlated with characteristic path length. Therefore, the shortcuts have a significant role in increasing spread rate. We conclude that the dynamics of social encounters' network stands between the random and the lattice in network spectrum. Although in this study we considered the period of common-cold disease for network dynamics, it seems that similar approaches may be useful for other airborne diseases such as SARS.

An in vivo evaluation of the antiseizure activity and acute neurotoxicity of agmatine.

PubMed

Bence, Aimee K; Worthen, David R; Stables, James P; Crooks, Peter A

2003-02-01

Agmatine, an endogenous cationic amine, exerts a wide range of biological effects, including modulation of glutamate-activated N-methyl-D-aspartate (NMDA) receptor function in the central nervous system (CNS). Since glutamate and the NMDA receptor have been implicated in the initiation and spread of seizure activity, the capacity of agmatine to inhibit seizure spread was evaluated in vivo. Orally administered agmatine (30 mg/kg) protected against maximal electroshock seizure (MES)-induced seizure spread in rats as rapidly as 15 min and for as long as 6 h after administration. Inhibition of MES-induced seizure spread was also observed when agmatine was administered intraperitoneally. Agmatine's antiseizure activity did not appear to be dose-dependent. An in vivo neurotoxicity screen indicated that agmatine was devoid of any acute neurological toxicity at the doses tested. These preliminary data suggest that agmatine has promising anticonvulsant activity.

Graphene interlayer for current spreading enhancement by engineering of barrier height in GaN-based light-emitting diodes.

PubMed

Min, Jung-Hong; Son, Myungwoo; Bae, Si-Young; Lee, Jun-Yeob; Yun, Joosun; Maeng, Min-Jae; Kwon, Dae-Gyeon; Park, Yongsup; Shim, Jong-In; Ham, Moon-Ho; Lee, Dong-Seon

2014-06-30

Pristine graphene and a graphene interlayer inserted between indium tin oxide (ITO) and p-GaN have been analyzed and compared with ITO, which is a typical current spreading layer in lateral GaN LEDs. Beyond a certain current injection, the pristine graphene current spreading layer (CSL) malfunctioned due to Joule heat that originated from the high sheet resistance and low work function of the CSL. However, by combining the graphene and the ITO to improve the sheet resistance, it was found to be possible to solve the malfunctioning phenomenon. Moreover, the light output power of an LED with a graphene interlayer was stronger than that of an LED using ITO or graphene CSL. We were able to identify that the improvement originated from the enhanced current spreading by inspecting the contact and conducting the simulation.

Spread of activation and deactivation in the brain: does age matter?

PubMed Central

Gordon, Brian A.; Tse, Chun-Yu; Gratton, Gabriele; Fabiani, Monica

2014-01-01

Cross-sectional aging functional MRI results are sometimes difficult to interpret, as standard measures of activation and deactivation may confound variations in signal amplitude and spread, which however, may be differentially affected by age-related changes in various anatomical and physiological factors. To disentangle these two types of measures, here we propose a novel method to obtain independent estimates of the peak amplitude and spread of the BOLD signal in areas activated (task-positive) and deactivated (task-negative) by a Sternberg task, in 14 younger and 28 older adults. The peak measures indicated that, compared to younger adults, older adults had increased activation of the task-positive network, but similar levels of deactivation in the task-negative network. Measures of signal spread revealed that older adults had an increased spread of activation in task-positive areas, but a starkly reduced spread of deactivation in task-negative areas. These effects were consistent across regions within each network. Further, there was greater variability in the anatomical localization of peak points in older adults, leading to reduced cross-subject overlap. These results reveal factors that may confound the interpretation of studies of aging. Additionally, spread measures may be linked to local connectivity phenomena and could be particularly useful to analyze age-related deactivation patterns, complementing the results obtained with standard peak and region of interest analyses. PMID:25360115

A novel function of WAVE in lamellipodia: WAVE1 is required for stabilization of lamellipodial protrusions during cell spreading.

PubMed

Yamazaki, Daisuke; Fujiwara, Takashi; Suetsugu, Shiro; Takenawa, Tadaomi

2005-05-01

When a cell spreads and moves, reorganization of the actin cytoskeleton pushes the cell membrane, and the resulting membrane protrusions create new points of contact with the substrate and generate the locomotive force. Membrane extension and adhesion to a substrate must be tightly coordinated for effective cell movement, but little is known about the mechanisms underlying these processes. WAVEs are critical regulators of Rac-induced actin reorganization. WAVE2 is essential for formation of lamellipodial structures at the cell periphery stimulated by growth factors, but it is thought that WAVE1 is dispensable for such processes in mouse embryonic fibroblasts (MEFs). Here we show a novel function of WAVE in lamellipodial protrusions during cell spreading. During spreading on fibronectin (FN), MEFs with knockouts (KOs) of WAVE1 and WAVE2 showed different membrane dynamics, suggesting that these molecules have distinct roles in lamellipodium formation. Formation of lamellipodial structures on FN was inhibited in WAVE2 KO MEFs. In contrast, WAVE1 is not essential for extension of lamellipodial protrusions but is required for stabilization of such structures. WAVE1-deficiency decreased the density of actin filaments and increased the speed of membrane extension, causing deformation of focal complex at the tip of spreading edges. Thus, at the tip of the lamellipodial protrusion, WAVE2 generates the membrane protrusive structures containing actin filaments, and modification by WAVE1 stabilizes these structures through cell-substrate adhesion. Coordination of WAVE1 and WAVE2 activities appears to be necessary for formation of proper actin structures in stable lamellipodia.

a Study of the AGB in Local Group Bulge Populations

NASA Astrophysics Data System (ADS)

Rich, R.

1994-01-01

We propose to survey the bolometric luminosities, colors, and space distribution of the most luminous asymptotic giant branch (AGB) stars in the bulges of M31, M32, and M33. We seek to discover whether the bulges of these galaxies are relatively young, of order 10 Gyr rather than 15 Gyr. We will use WFPC2 and the R, I, and F1042M (1 micron) filters. Knowing that F1042M falls on the first continuum point of M giants, we have shown that we can use 1.04 micron fluxes to reliably calculate bolometric magnitudes for these very red stars. Color information from R and I will permit (1) comparison with Galactic bulge M giants, (2) an estimate of the spread of abundance and (3) increase the accuracy of the bolometric magnitudes. Frames with the damaged HST show signs of resolution to within 3" of the M31 nucleus; Red images with the aberrated HST show a red star cluster associated with the nucleus. Ground-based studies of M32 find an intermediate-age population from spectroscopy and infrared photometry. The repaired HST should resolve stars close to the nuclei of these galaxies. We will measure bolometric luminosity functions to determine if the populations are intermediate age, and attempt to measure the abundance range for stars near the nuclei of these galaxies. If metals have been lost due to winds, theory predicts that we should see a substantial spread of abundances even near the nucleus.

Channel fading for mobile satellite communications using spread spectrum signaling and TDRSS

NASA Technical Reports Server (NTRS)

Jenkins, Jeffrey D.; Fan, Yiping; Osborne, William P.

1995-01-01

This paper will present some preliminary results from a propagation experiment which employed NASA's TDRSS and an 8 MHz chip rate spread spectrum signal. Channel fade statistics were measured and analyzed in 21 representative geographical locations covering urban/suburban, open plain, and forested areas. Cumulative distribution Functions (CDF's) of 12 individual locations are presented and classified based on location. Representative CDF's from each of these three types of terrain are summarized. These results are discussed, and the fade depths exceeded 10 percent of the time in three types of environments are tabulated. The spread spectrum fade statistics for tree-lined roads are compared with the Empirical Roadside Shadowing Model.

Reanalysis of the start of the UK 1967 to 1968 foot-and-mouth disease epidemic to calculate airborne transmission probabilities.

PubMed

Sanson, R L; Gloster, J; Burgin, L

2011-09-24

The aims of this study were to statistically reassess the likelihood that windborne spread of foot-and-mouth disease (FMD) virus (FMDV) occurred at the start of the UK 1967 to 1968 FMD epidemic at Oswestry, Shropshire, and to derive dose-response probability of infection curves for farms exposed to airborne FMDV. To enable this, data on all farms present in 1967 in the parishes near Oswestry were assembled. Cases were infected premises whose date of appearance of first clinical signs was within 14 days of the depopulation of the index farm. Logistic regression was used to evaluate the association between infection status and distance and direction from the index farm. The UK Met Office's NAME atmospheric dispersion model (ADM) was used to generate plumes for each day that FMDV was excreted from the index farm based on actual historical weather records from October 1967. Daily airborne FMDV exposure rates for all farms in the study area were calculated using a geographical information system. Probit analyses were used to calculate dose-response probability of infection curves to FMDV, using relative exposure rates on case and control farms. Both the logistic regression and probit analyses gave strong statistical support to the hypothesis that airborne spread occurred. There was some evidence that incubation period was inversely proportional to the exposure rate.

Impact of uneven sample morphology on mass resolving power in linear MALDI-TOF mass spectrometry: A comprehensive theoretical investigation.

PubMed

Cai, Yi-Hong; Wang, Yi-Sheng

2018-04-01

This work discusses the correlation between the mass resolving power of matrix-assisted laser desorption/ionization time-of-flight mass analyzers and extraction condition with an uneven sample morphology. Previous theoretical calculations show that the optimum extraction condition for flat samples involves an ideal ion source design and extraction delay. A general expression of spectral feature takes into account ion initial velocity, and extraction delay is derived in the current study. The new expression extends the comprehensive calculation to uneven sample surfaces and above 90% Maxell-Boltzmann initial velocity distribution of ions to account for imperfect ionization condition. Calculation shows that the impact of uneven sample surface or initial spatial spread of ions is negligible when the extraction delay is away from the ideal value. When the extraction delay approaches the optimum value, the flight-time topology shows a characteristic curve shape, and the time-domain mass spectral feature broadens with an increase in initial spatial spread of ions. For protonated 2,5-dihydroxybenzoic acid, the mass resolving power obtained from a sample of 3-μm surface roughness is approximately 3.3 times lower than that of flat samples. For ions of m/z 3000 coexpanded with 2,5-dihydroxybenzoic acid, the mass resolving power in the 3-μm surface roughness case only reduces roughly 7%. Comprehensive calculations also show that the mass resolving power of lighter ions is more sensitive to the accuracy of the extraction delay than heavier ions. Copyright © 2018 John Wiley & Sons, Ltd.

Turing-like structures in a functional model of cortical spreading depression

NASA Astrophysics Data System (ADS)

Verisokin, A. Yu.; Verveyko, D. V.; Postnov, D. E.

2017-12-01

Cortical spreading depression (CSD) along with migraine waves and spreading depolarization events with stroke or injures are the front-line examples of extreme physiological behaviors of the brain cortex which manifest themselves via the onset and spreading of localized areas of neuronal hyperactivity followed by their depression. While much is known about the physiological pathways involved, the dynamical mechanisms of the formation and evolution of complex spatiotemporal patterns during CSD are still poorly understood, in spite of the number of modeling studies that have been already performed. Recently we have proposed a relatively simple mathematical model of cortical spreading depression which counts the effects of neurovascular coupling and cerebral blood flow redistribution during CSD. In the present study, we address the main dynamical consequences of newly included pathways, namely, the changes in the formation and propagation speed of the CSD front and the pattern formation features in two dimensions. Our most notable finding is that the combination of vascular-mediated spatial coupling with local regulatory mechanisms results in the formation of stationary Turing-like patterns during a CSD event.

Measurement of the point spread function and effective area of the Solar-A Soft X-ray Telescope mirror

NASA Technical Reports Server (NTRS)

Lemen, J. R.; Claflin, E. S.; Brown, W. A.; Bruner, M. E.; Catura, R. C.

1989-01-01

A grazing incidence solar X-ray telescope, Soft X-ray Telescope (SXT), will be flown on the Solar-A satellite in 1991. Measurements have been conducted to determine the focal length, Point Spread Function (PSF), and effective area of the SXT mirror. The measurements were made with pinholes, knife edges, a CCD, and a proportional counter. The results show the 1/r character of the PSF, and indicate a half power diameter of 4.9 arcsec and an effective area of 1.33 sq cm at 13.3 A (0.93 keV). The mirror was found to provide a high contrast image with very little X-ray scattering.

[Economic impact of external laboratory test].

PubMed

Takura, Tomoyuki

2006-11-01

The realities of the spread and the aim of the introduction, and an economical influence of an external laboratory tests were researched. As a result, 90% or more the ratio to have consigned the external whole became clear. But it is preferable to correspond about inspection item of about 70% in own facilities because of the characteristic of the medical institution and the inspection item. Moreover, when correct the unbridgeable gulf of characteristic of the realities of spread of present external laboratory tests inspection and the ranging of ideal external laboratory tests inspection that specialist thinks about, the needed medical payment was thought that the investment of about 50 billion yen a year was necessary to expand the inspection in own facilities, by calculated based on the stochastic model.

Simulation of emittance dilution in electron storage ring from Compton backscattering

NASA Astrophysics Data System (ADS)

Blumberg, L. N.; Blum, E.

A Monte-Carlo simulation of Compton backscattered kappa(sub L) = 3.2-micron photons from an IR-FEL on 75-MeV electrons in a storage ring yields an RMS electron energy spread of delta(sub E) = 11.9-keV for a sample of 10(exp 7) single scattering events. Electrons are sampled from a beam of natural energy spread sigma(sub E) = 5.6-keV and damped transverse angle spreads sigma(sub x)(prime) = .041-mrad and sigma(sub y)(prime) = .052-mrad (100%) coupling, scaled from the 200-MeV BNL XLS compact storage ring. The Compton-scattered x-rays are generated from an integral of the CM Klein-Nishina cross-section transformed to the lab. A tracking calculation has also been performed in 6-dimensional phase space. Initial electron coordinates are selected randomly from a Gaussian distribution of RMS spreads sigma(sub xo) = .102-mm, sigma(sub x(prime)o) = .041-mrad, sigma(sub yo) = .018-mm, sigma(sub y(prime)o) = .052-mrad, sigma(sub (phi)o) = 22-mrad and sigma(sub Eo) = 6-keV. A sample of 10000 electrons were each following for 40000 turns around the ring through an RF cavity of f(sub RF) = 211.54-MHz and peak voltage V(sub m)=300-keV. Preliminary results indicate that the resulting energy distribution is quite broad with an RMS width of delta(sub E) = 124-keV. The transverse widths are only slightly increased from their original values, i.e. delta(sub x) = .106-mm and delta(sub x)(prime) = .043 mrad. The scaled energy spread of delta(sub E) approximately = 360-keV for approximately 350,000 turns desired in a 10-msec x-ray angiography exposure is well within the RF bucket used here; even V(sub m) less than 50-kV is adequate. Further, the electron energy spread adds a negligible RMS x-ray energy spread of delta(sub Ex) = .32-keV. The electron energy damping time of tau(sub E) = 379-msec at 75-MeV in an XLS-type ring allows for damping this induced spread and top-off of the ring between heart cycles.

Potential corridors and barriers for plague spread in Central Asia.

PubMed

Wilschut, Liesbeth I; Addink, Elisabeth A; Heesterbeek, Hans; Heier, Lise; Laudisoit, Anne; Begon, Mike; Davis, Stephen; Dubyanskiy, Vladimir M; Burdelov, Leonid A; de Jong, Steven M

2013-10-31

Plague (Yersinia pestis infection) is a vector-borne disease which caused millions of human deaths in the Middle Ages. The hosts of plague are mostly rodents, and the disease is spread by the fleas that feed on them. Currently, the disease still circulates amongst sylvatic rodent populations all over the world, including great gerbil (Rhombomys opimus) populations in Central Asia. Great gerbils are social desert rodents that live in family groups in burrows, which are visible on satellite images. In great gerbil populations an abundance threshold exists, above which plague can spread causing epizootics. The spatial distribution of the host species is thought to influence the plague dynamics, such as the direction of plague spread, however no detailed analysis exists on the possible functional or structural corridors and barriers that are present in this population and landscape. This study aims to fill that gap. Three 20 by 20 km areas with known great gerbil burrow distributions were used to analyse the spatial distribution of the burrows. Object-based image analysis was used to map the landscape at several scales, and was linked to the burrow maps. A novel object-based method was developed - the mean neighbour absolute burrow density difference (MNABDD) - to identify the optimal scale and evaluate the efficacy of using landscape objects as opposed to square cells. Multiple regression using raster maps was used to identify the landscape-ecological variables that explain burrow density best. Functional corridors and barriers were mapped using burrow density thresholds. Cumulative resistance of the burrow distribution to potential disease spread was evaluated using cost distance analysis. A 46-year plague surveillance dataset was used to evaluate whether plague spread was radially symmetric. The burrow distribution was found to be non-random and negatively correlated with Greenness, especially in the floodplain areas. Corridors and barriers showed a mostly NWSE alignment, suggesting easier spreading along this axis. This was confirmed by the analysis of the plague data. Plague spread had a predominantly NWSE direction, which is likely due to the NWSE alignment of corridors and barriers in the burrow distribution and the landscape. This finding may improve predictions of plague in the future and emphasizes the importance of including landscape analysis in wildlife disease studies.

Potential corridors and barriers for plague spread in central Asia

PubMed Central

2013-01-01

Background Plague (Yersinia pestis infection) is a vector-borne disease which caused millions of human deaths in the Middle Ages. The hosts of plague are mostly rodents, and the disease is spread by the fleas that feed on them. Currently, the disease still circulates amongst sylvatic rodent populations all over the world, including great gerbil (Rhombomys opimus) populations in Central Asia. Great gerbils are social desert rodents that live in family groups in burrows, which are visible on satellite images. In great gerbil populations an abundance threshold exists, above which plague can spread causing epizootics. The spatial distribution of the host species is thought to influence the plague dynamics, such as the direction of plague spread, however no detailed analysis exists on the possible functional or structural corridors and barriers that are present in this population and landscape. This study aims to fill that gap. Methods Three 20 by 20 km areas with known great gerbil burrow distributions were used to analyse the spatial distribution of the burrows. Object-based image analysis was used to map the landscape at several scales, and was linked to the burrow maps. A novel object-based method was developed – the mean neighbour absolute burrow density difference (MNABDD) – to identify the optimal scale and evaluate the efficacy of using landscape objects as opposed to square cells. Multiple regression using raster maps was used to identify the landscape-ecological variables that explain burrow density best. Functional corridors and barriers were mapped using burrow density thresholds. Cumulative resistance of the burrow distribution to potential disease spread was evaluated using cost distance analysis. A 46-year plague surveillance dataset was used to evaluate whether plague spread was radially symmetric. Results The burrow distribution was found to be non-random and negatively correlated with Greenness, especially in the floodplain areas. Corridors and barriers showed a mostly NWSE alignment, suggesting easier spreading along this axis. This was confirmed by the analysis of the plague data. Conclusions Plague spread had a predominantly NWSE direction, which is likely due to the NWSE alignment of corridors and barriers in the burrow distribution and the landscape. This finding may improve predictions of plague in the future and emphasizes the importance of including landscape analysis in wildlife disease studies. PMID:24171709

Contributions to the theory of the spreading of a free jet issuing from a nozzle

NASA Technical Reports Server (NTRS)

Szablewski, W

1951-01-01

For the flow field of a free jet leaving a nozzle of circular cross section in a medium with a straight uniform flow field, approximate formulas are presented for the calculation of the velocity distribution and the dimensions of the core region. The agreement with measured results is satisfactory.

Costs and Benefits of Electronic Fetal Monitoring: A Review of the Literature. NCHSR Research Report Series.

ERIC Educational Resources Information Center

Banta, H. David; Thacker, Stephen B.

This report focuses on electronic fetal monitoring (EFM)--a technology that was developed during the 1960s and has rapidly spread into use in clinical obstetrics. The report includes a review of the extensive published literature on EFM and related subjects. It also contains original calculations concerning the technique's specificity and…

Thermochemical properties of flame gases from fine wildland fuels

Treesearch

Frank A. Albini

1979-01-01

Describes a theoretical model for calculating thermochemical properties of the gaseous fuel that burns in the free flame at the edge of a spreading fire in fine forest fuels. Predicted properties are the heat of combustion, stoichiometric air/fuel mass ratio, mass-averaged temperature, and mass fraction of unburned fuel in the gas mixture emitted from the flame-...

A Wigner-based ray-tracing method for imaging simulations

NASA Astrophysics Data System (ADS)

Mout, B. M.; Wick, M.; Bociort, F.; Urbach, H. P.

2015-09-01

The Wigner Distribution Function (WDF) forms an alternative representation of the optical field. It can be a valuable tool for understanding and classifying optical systems. Furthermore, it possesses properties that make it suitable for optical simulations: both the intensity and the angular spectrum can be easily obtained from the WDF and the WDF remains constant along the paths of paraxial geometrical rays. In this study we use these properties by implementing a numerical Wigner-Based Ray-Tracing method (WBRT) to simulate diffraction effects at apertures in free-space and in imaging systems. Both paraxial and non-paraxial systems are considered and the results are compared with numerical implementations of the Rayleigh-Sommerfeld and Fresnel diffraction integrals to investigate the limits of the applicability of this approach. The results of the different methods are in good agreement when simulating free-space diffraction or calculating point spread functions (PSFs) for aberration-free imaging systems, even at numerical apertures exceeding the paraxial regime. For imaging systems with aberrations, the PSFs of WBRT diverge from the results using diffraction integrals. For larger aberrations WBRT predicts negative intensities, suggesting that this model is unable to deal with aberrations.

Adsorption of TNT, DNAN, NTO, FOX7 and NQ onto Cellulose, Chitin and Cellulose Triacetate. Insights from Density Functional Theory Calculations

NASA Astrophysics Data System (ADS)

Todde, Guido; Jha, Sanjiv; Subramanian, Gopinath; Shukla, Manoj

Insensitive munitions (IM) like DNAN (2,4-dinitroanisole), NTO (3-nitro-1,2,4-triazol-5-one), NQ (nitroguanidine) and FOX7 (1,1-diamino-2,2-dinitroethene) reduce the risk of accidental explosions due to shock and high temperature exposure. These compounds are used as replacement for TNT (2,4,6-trinitromethylbenzene) and RDX (1,3,5-hexahydro-1,3,5-trinitro-1,3,5-triazine). Unfortunately they are more soluble than TNT or RDX, hence they can easily spread in the environment and get dissolved by precipitation. Due to the abundance of cellulosic biomass in the environment it is important to investigate the adsorption of these new contaminants onto cellulose and cellulose derivative surfaces. Using Density Functional Theory methods we have studied the adsorption of TNT, DNAN, NTO, NQ and FOX7 onto cellulose I α and I β, chitin and cellulose triacetate. The solvent effect on the adsorption was also investigated. Our results show how all contaminants are adsorbed onto chitin and cellulose I α. FOX7 is very weakly absorbed onto cellulose I β which is mainly found in wood and ramie fibers.

Correspondence of electroencephalography and near-infrared spectroscopy sensitivities to the cerebral cortex using a high-density layout

PubMed Central

Giacometti, Paolo; Diamond, Solomon G.

2014-01-01

Abstract. This study investigates the correspondence of the cortical sensitivity of electroencephalography (EEG) and near-infrared spectroscopy (NIRS). EEG forward model sensitivity to the cerebral cortex was calculated for 329 EEG electrodes following the 10-5 EEG positioning system using a segmented structural magnetic resonance imaging scan of a human subject. NIRS forward model sensitivity was calculated for the same subject using 156 NIRS source-detector pairs selected from 32 source and 32 detector optodes positioned on the scalp using a subset of the 10-5 EEG positioning system. Sensitivity correlations between colocalized NIRS source-detector pair groups and EEG channels yielded R=0.46±0.08. Groups of NIRS source-detector pairs with maximum correlations to EEG electrode sensitivities are tabulated. The mean correlation between the point spread functions for EEG and NIRS regions of interest (ROI) was R=0.43±0.07. Spherical ROIs with radii of 26 mm yielded the maximum correlation between EEG and NIRS averaged across all cortical mesh nodes. These sensitivity correlations between EEG and NIRS should be taken into account when designing multimodal studies of neurovascular coupling and when using NIRS as a statistical prior for EEG source localization. PMID:25558462

Current status of genome editing in vector mosquitoes: A review.

PubMed

Reegan, Appadurai Daniel; Ceasar, Stanislaus Antony; Paulraj, Michael Gabriel; Ignacimuthu, Savarimuthu; Al-Dhabi, Naif Abdullah

2017-01-16

Mosquitoes pose a major threat to human health as they spread many deadly diseases like malaria, dengue, chikungunya, filariasis, Japanese encephalitis and Zika. Identification and use of novel molecular tools are essential to combat the spread of vector borne diseases. Genome editing tools have been used for the precise alterations of the gene of interest for producing the desirable trait in mosquitoes. Deletion of functional genes or insertion of toxic genes in vector mosquitoes will produce either knock-out or knock-in mutants that will check the spread of vector-borne diseases. Presently, three types of genome editing tools viz., zinc finger nuclease (ZFN), transcription activator-like effector nucleases (TALEN) and clustered regulatory interspaced short palindromic repeats (CRISPR) and CRISPR associated protein 9 (Cas9) are widely used for the editing of the genomes of diverse organisms. These tools are also applied in vector mosquitoes to control the spread of vector-borne diseases. A few studies have been carried out on genome editing to control the diseases spread by vector mosquitoes and more studies need to be performed with the utilization of more recently invented tools like CRISPR/Cas9 to combat the spread of deadly diseases by vector mosquitoes. The high specificity and flexibility of CRISPR/Cas9 system may offer possibilities for novel genome editing for the control of important diseases spread by vector mosquitoes. In this review, we present the current status of genome editing research on vector mosquitoes and also discuss the future applications of vector mosquito genome editing to control the spread of vectorborne diseases.

Tobacco mosaic virus Movement Protein Enhances the Spread of RNA Silencing

PubMed Central

Vogler, Hannes; Kwon, Myoung-Ok; Dang, Vy; Sambade, Adrian; Fasler, Monika; Ashby, Jamie; Heinlein, Manfred

2008-01-01

Eukaryotic cells restrain the activity of foreign genetic elements, including viruses, through RNA silencing. Although viruses encode suppressors of silencing to support their propagation, viruses may also exploit silencing to regulate host gene expression or to control the level of their accumulation and thus to reduce damage to the host. RNA silencing in plants propagates from cell to cell and systemically via a sequence-specific signal. Since the signal spreads between cells through plasmodesmata like the viruses themselves, virus-encoded plasmodesmata-manipulating movement proteins (MP) may have a central role in compatible virus:host interactions by suppressing or enhancing the spread of the signal. Here, we have addressed the propagation of GFP silencing in the presence and absence of MP and MP mutants. We show that the protein enhances the spread of silencing. Small RNA analysis indicates that MP does not enhance the silencing pathway but rather enhances the transport of the signal through plasmodesmata. The ability to enhance the spread of silencing is maintained by certain MP mutants that can move between cells but which have defects in subcellular localization and do not support the spread of viral RNA. Using MP expressing and non-expressing virus mutants with a disabled silencing suppressing function, we provide evidence indicating that viral MP contributes to anti-viral silencing during infection. Our results suggest a role of MP in controlling virus propagation in the infected host by supporting the spread of silencing signal. This activity of MP involves only a subset of its properties implicated in the spread of viral RNA. PMID:18389061

Uncertainty in Wildfire Behavior

NASA Astrophysics Data System (ADS)

Finney, M.; Cohen, J. D.

2013-12-01

The challenge of predicting or modeling fire behavior is well recognized by scientists and managers who attempt predictions of fire spread rate or growth. At the scale of the spreading fire, the uncertainty in winds, moisture, fuel structure, and fire location make accurate predictions difficult, and the non-linear response of fire spread to these conditions means that average behavior is poorly represented by average environmental parameters. Even more difficult are estimations of threshold behaviors (e.g. spread/no-spread, crown fire initiation, ember generation and spotting) because the fire responds as a step-function to small changes in one or more environmental variables, translating to dynamical feedbacks and unpredictability. Recent research shows that ignition of fuel particles, itself a threshold phenomenon, depends on flame contact which is absolutely not steady or uniform. Recent studies of flame structure in both spreading and stationary fires reveals that much of the non-steadiness of the flames as they contact fuel particles results from buoyant instabilities that produce quasi-periodic flame structures. With fuel particle ignition produced by time-varying heating and short-range flame contact, future improvements in fire behavior modeling will likely require statistical approaches to deal with the uncertainty at all scales, including the level of heat transfer, the fuel arrangement, and weather.

Quantifying fluctuations in market liquidity: analysis of the bid-ask spread.

PubMed

Plerou, Vasiliki; Gopikrishnan, Parameswaran; Stanley, H Eugene

2005-04-01

Quantifying the statistical features of the bid-ask spread offers the possibility of understanding some aspects of market liquidity. Using quote data for the 116 most frequently traded stocks on the New York Stock Exchange over the two-year period 1994-1995, we analyze the fluctuations of the average bid-ask spread S over a time interval deltat. We find that S is characterized by a distribution that decays as a power law P[S>x] approximately x(-zeta(S) ), with an exponent zeta(S) approximately = 3 for all 116 stocks analyzed. Our analysis of the autocorrelation function of S shows long-range power-law correlations, (S(t)S(t + tau)) approximately tau(-mu(s)), similar to those previously found for the volatility. We next examine the relationship between the bid-ask spread and the volume Q, and find that S approximately ln Q; we find that a similar logarithmic relationship holds between the transaction-level bid-ask spread and the trade size. We then study the relationship between S and other indicators of market liquidity such as the frequency of trades N and the frequency of quote updates U, and find S approximately ln N and S approximately ln U. Lastly, we show that the bid-ask spread and the volatility are also related logarithmically.

Assessing the Impact of Analytical Error on Perceived Disease Severity.

PubMed

Kroll, Martin H; Garber, Carl C; Bi, Caixia; Suffin, Stephen C

2015-10-01

The perception of the severity of disease from laboratory results assumes that the results are free of analytical error; however, analytical error creates a spread of results into a band and thus a range of perceived disease severity. To assess the impact of analytical errors by calculating the change in perceived disease severity, represented by the hazard ratio, using non-high-density lipoprotein (nonHDL) cholesterol as an example. We transformed nonHDL values into ranges using the assumed total allowable errors for total cholesterol (9%) and high-density lipoprotein cholesterol (13%). Using a previously determined relationship between the hazard ratio and nonHDL, we calculated a range of hazard ratios for specified nonHDL concentrations affected by analytical error. Analytical error, within allowable limits, created a band of values of nonHDL, with a width spanning 30 to 70 mg/dL (0.78-1.81 mmol/L), depending on the cholesterol and high-density lipoprotein cholesterol concentrations. Hazard ratios ranged from 1.0 to 2.9, a 16% to 50% error. Increased bias widens this range and decreased bias narrows it. Error-transformed results produce a spread of values that straddle the various cutoffs for nonHDL. The range of the hazard ratio obscures the meaning of results, because the spread of ratios at different cutoffs overlap. The magnitude of the perceived hazard ratio error exceeds that for the allowable analytical error, and significantly impacts the perceived cardiovascular disease risk. Evaluating the error in the perceived severity (eg, hazard ratio) provides a new way to assess the impact of analytical error.

Generation of a pseudo-2D shear-wave velocity section by inversion of a series of 1D dispersion curves

USGS Publications Warehouse

Luo, Y.; Xia, J.; Liu, J.; Xu, Y.; Liu, Q.

2008-01-01

Multichannel Analysis of Surface Waves utilizes a multichannel recording system to estimate near-surface shear (S)-wave velocities from high-frequency Rayleigh waves. A pseudo-2D S-wave velocity (vS) section is constructed by aligning 1D models at the midpoint of each receiver spread and using a spatial interpolation scheme. The horizontal resolution of the section is therefore most influenced by the receiver spread length and the source interval. The receiver spread length sets the theoretical lower limit and any vS structure with its lateral dimension smaller than this length will not be properly resolved in the final vS section. A source interval smaller than the spread length will not improve the horizontal resolution because spatial smearing has already been introduced by the receiver spread. In this paper, we first analyze the horizontal resolution of a pair of synthetic traces. Resolution analysis shows that (1) a pair of traces with a smaller receiver spacing achieves higher horizontal resolution of inverted S-wave velocities but results in a larger relative error; (2) the relative error of the phase velocity at a high frequency is smaller than at a low frequency; and (3) a relative error of the inverted S-wave velocity is affected by the signal-to-noise ratio of data. These results provide us with a guideline to balance the trade-off between receiver spacing (horizontal resolution) and accuracy of the inverted S-wave velocity. We then present a scheme to generate a pseudo-2D S-wave velocity section with high horizontal resolution using multichannel records by inverting high-frequency surface-wave dispersion curves calculated through cross-correlation combined with a phase-shift scanning method. This method chooses only a pair of consecutive traces within a shot gather to calculate a dispersion curve. We finally invert surface-wave dispersion curves of synthetic and real-world data. Inversion results of both synthetic and real-world data demonstrate that inverting high-frequency surface-wave dispersion curves - by a pair of traces through cross-correlation with phase-shift scanning method and with the damped least-square method and the singular-value decomposition technique - can feasibly achieve a reliable pseudo-2D S-wave velocity section with relatively high horizontal resolution. ?? 2008 Elsevier B.V. All rights reserved.

Identification and functional characterization of a novel locust peptide belonging to the family of insect growth blocking peptides.

PubMed

Duressa, Tewodros Firdissa; Boonen, Kurt; Hayakawa, Yoichi; Huybrechts, Roger

2015-12-01

Growth blocking peptides (GBPs) are recognized as insect cytokines that take part in multifaceted functions including immune system activation and growth retardation. The peptides induce hemocyte spreading in vitro, which is considered as the initial step in hemocyte activation against infection in many insect species. Therefore, in this study, we carried out a series of in vitro bioassay driven fractionations of Locusta migratoria hemolymph combined with mass spectrometry to identify locust hemocyte activation factors belonging to the family of insect GBPs. We identified the locust hemocyte spreading peptide (locust GBP) as a 28-mer peptide encoded at the C-terminus of a 64 amino acid long precursor polypeptide. As demonstrated by QRT-PCR, the gene encoding the locust GBP precursor (proGBP) was expressed in large quantities in diverse locust tissues including fat body, endocrine glands, central nervous system, reproductive tissues and flight muscles. In contrary, hemocytes, gut tissues and Malpighian tubules displayed little expression of the proGBP transcript. The bioactive peptide induces transient depletion of hemocytes in vivo and when injected in last instar nymphs it extends the larval growth phase and postpones adult molting. In addition, we identified a functional homologous hemocyte spreading peptide in Schistocerca gregaria. Copyright © 2015 Elsevier Inc. All rights reserved.

Effect of masking phase-only holograms on the quality of reconstructed images.

PubMed

Deng, Yuanbo; Chu, Daping

2016-04-20

A phase-only hologram modulates the phase of the incident light and diffracts it efficiently with low energy loss because of the minimum absorption. Much research attention has been focused on how to generate phase-only holograms, and little work has been done to understand the effect and limitation of their partial implementation, possibly due to physical defects and constraints, in particular as in the practical situations where a phase-only hologram is confined or needs to be sliced or tiled. The present study simulates the effect of masking phase-only holograms on the quality of reconstructed images in three different scenarios with different filling factors, filling positions, and illumination intensity profiles. Quantitative analysis confirms that the width of the image point spread function becomes wider and the image quality decreases, as expected, when the filling factor decreases, and the image quality remains the same for different filling positions as well. The width of the image point spread function as derived from different filling factors shows a consistent behavior to that as measured directly from the reconstructed image, especially as the filling factor becomes small. Finally, mask profiles of different shapes and intensity distributions are shown to have more complicated effects on the image point spread function, which in turn affects the quality and textures of the reconstructed image.

Lateral spread affects nitrogen leaching from urine patches.

PubMed

Cichota, Rogerio; Vogeler, Iris; Snow, Val; Shepherd, Mark; McAuliffe, Russell; Welten, Brendon

2018-09-01

Nitrate leaching from urine deposited by grazing animals is a critical constraint for sustainable dairy farming in New Zealand. While considerable progress has been made to understand the fate of nitrogen (N) under urine patches, little consideration has been given to the spread of urinary N beyond the wetted area. In this study, we modelled the lateral spread of nitrogen from the wetted area of a urine patch to the soil outside the patch using a combination of two process-based models (HYDRUS and APSIM). The simulations provided insights on the extent and temporal pattern for the redistribution of N in the soil following a urine deposition and enabled investigating the effect of lateral spread of urinary N on plant growth and N leaching. The APSIM simulation, using an implementation of a dispersion-diffusion function, was tested against experimental data from a field experiment conducted in spring on a well-drained soil. Depending on the geometry considered for the dispersion-diffusion function (plate or cylindrical) the area-averaged N leaching decreased by 8 and 37% compared with simulations without lateral N spread; this was due to additional N uptake from pasture on the edge area. A sensitivity analysis showed that area-averaged pasture growth was not greatly affected by the value of the dispersion factor used in the model, whereas N leaching was very sensitive. Thus, the need to account for the edge effect may depend on the objective of the simulations. The modelling results also showed that considering lateral spread of urinary N was sufficient to describe the experimental data, but plant root uptake across urine patch zones may still be relevant in other conditions. Although further work is needed for improving accuracy, the simulated and experimental results demonstrate that accounting for the edge effect is important for determining N leaching from urine-affected areas. Copyright © 2018 Elsevier B.V. All rights reserved.

New approach to the retrieval of AOD and its uncertainty from MISR observations over dark water

NASA Astrophysics Data System (ADS)

Witek, Marcin L.; Garay, Michael J.; Diner, David J.; Bull, Michael A.; Seidel, Felix C.

2018-01-01

A new method for retrieving aerosol optical depth (AOD) and its uncertainty from Multi-angle Imaging SpectroRadiometer (MISR) observations over dark water is outlined. MISR's aerosol retrieval algorithm calculates cost functions between observed and pre-simulated radiances for a range of AODs (from 0.0 to 3.0) and a prescribed set of aerosol mixtures. The previous version 22 (V22) operational algorithm considered only the AOD that minimized the cost function for each aerosol mixture and then used a combination of these values to compute the final, best estimate AOD and associated uncertainty. The new approach considers the entire range of cost functions associated with each aerosol mixture. The uncertainty of the reported AOD depends on a combination of (a) the absolute values of the cost functions for each aerosol mixture, (b) the widths of the cost function distributions as a function of AOD, and (c) the spread of the cost function distributions among the ensemble of mixtures. A key benefit of the new approach is that, unlike the V22 algorithm, it does not rely on empirical thresholds imposed on the cost function to determine the success or failure of a particular mixture. Furthermore, a new aerosol retrieval confidence index (ARCI) is established that can be used to screen high-AOD retrieval blunders caused by cloud contamination or other factors. Requiring ARCI ≥ 0.15 as a condition for retrieval success is supported through statistical analysis and outperforms the thresholds used in the V22 algorithm. The described changes to the MISR dark water algorithm will become operational in the new MISR aerosol product (V23), planned for release in 2017.

New Approach to the Retrieval of AOD and its Uncertainty from MISR Observations Over Dark Water

NASA Astrophysics Data System (ADS)

Witek, M. L.; Garay, M. J.; Diner, D. J.; Bull, M. A.; Seidel, F.

2017-12-01

A new method for retrieving aerosol optical depth (AOD) and its uncertainty from Multi-angle Imaging SpectroRadiometer (MISR) observations over dark water is outlined. MISR's aerosol retrieval algorithm calculates cost functions between observed and pre-simulated radiances for a range of AODs (from 0.0 to 3.0) and a prescribed set of aerosol mixtures. The previous Version 22 (V22) operational algorithm considered only the AOD that minimized the cost function for each aerosol mixture, then used a combination of these values to compute the final, "best estimate" AOD and associated uncertainty. The new approach considers the entire range of cost functions associated with each aerosol mixture. The uncertainty of the reported AOD depends on a combination of a) the absolute values of the cost functions for each aerosol mixture, b) the widths of the cost function distributions as a function of AOD, and c) the spread of the cost function distributions among the ensemble of mixtures. A key benefit of the new approach is that, unlike the V22 algorithm, it does not rely on arbitrary thresholds imposed on the cost function to determine the success or failure of a particular mixture. Furthermore, a new Aerosol Retrieval Confidence Index (ARCI) is established that can be used to screen high-AOD retrieval blunders caused by cloud contamination or other factors. Requiring ARCI≥0.15 as a condition for retrieval success is supported through statistical analysis and outperforms the thresholds used in the V22 algorithm. The described changes to the MISR dark water algorithm will become operational in the new MISR aerosol product (V23), planned for release in 2017.

Modeling super-resolution SERS using a T-matrix method to elucidate molecule-nanoparticle coupling and the origins of localization errors

NASA Astrophysics Data System (ADS)

Heaps, Charles W.; Schatz, George C.

2017-06-01

A computational method to model diffraction-limited images from super-resolution surface-enhanced Raman scattering microscopy is introduced. Despite significant experimental progress in plasmon-based super-resolution imaging, theoretical predictions of the diffraction limited images remain a challenge. The method is used to calculate localization errors and image intensities for a single spherical gold nanoparticle-molecule system. The light scattering is calculated using a modification of generalized Mie (T-matrix) theory with a point dipole source and diffraction limited images are calculated using vectorial diffraction theory. The calculation produces the multipole expansion for each emitter and the coherent superposition of all fields. Imaging the constituent fields in addition to the total field provides new insight into the strong coupling between the molecule and the nanoparticle. Regardless of whether the molecular dipole moment is oriented parallel or perpendicular to the nanoparticle surface, the anisotropic excitation distorts the center of the nanoparticle as measured by the point spread function by approximately fifty percent of the particle radius toward to the molecule. Inspection of the nanoparticle multipoles reveals that distortion arises from a weak quadrupole resonance interfering with the dipole field in the nanoparticle. When the nanoparticle-molecule fields are in-phase, the distorted nanoparticle field dominates the observed image. When out-of-phase, the nanoparticle and molecule are of comparable intensity and interference between the two emitters dominates the observed image. The method is also applied to different wavelengths and particle radii. At off-resonant wavelengths, the method predicts images closer to the molecule not because of relative intensities but because of greater distortion in the nanoparticle. The method is a promising approach to improving the understanding of plasmon-enhanced super-resolution experiments.

A Method for Assessing Material Flammability for Micro-Gravity Environments

NASA Technical Reports Server (NTRS)

Steinhaus, T.; Olenick, S. M.; Sifuentes, A.; Long, R. T.; Torero, J. L.

1999-01-01

On a spacecraft, one of the greatest fears during a mission is the outbreak of a fire. Since spacecraft are enclosed spaces and depend highly on technical electronics, a small fire could cause a large amount of damage. NASA uses upward flame spread as a "worst case scenario" evaluation for materials and the Heat and Visible Smoke Release Rates Test to assess the damage potential of a fire. Details of these tests and the protocols followed are provided by the "Flammability, Odor, Offgassing, and Compatibility Requirements and Test Procedures for Materials in Environments that Support Combustion" document. As pointed by Ohlemiller and Villa, the upward flame spread test does not address the effect of external radiation on ignition and spread. External radiation, as that coming from an overheated electrical component, is a plausible fire scenario in a space facility and could result in a reversal of the flammability rankings derived from the upward flame spread test. The "Upward Flame Propagation Test" has been the subject of strong criticism in the last few years. In many cases, theoretical exercises and experimental results have demonstrated the possibility of a reversal in the material flammability rankings from normal to micro-gravity. Furthermore, the need to incorporate information on the effects of external radiation and opposed flame spread when ranking materials based on their potential to burn in micro-gravity has been emphasized. Experiments conducted in a 2.2 second drop tower with an ethane burner in an air cross flow have emphasized that burning at the trailing edge is deterred in micro-gravity due to the decreased oxygen transport. For very low air flow velocities (U<0.005 m/s) the flame envelopes the burner and a slight increase in velocity results in extinction of the trailing edge (U>0.01 m/s). Only for U>0.l m/s extinction is observed at the leading edge (blow-off). Three dimensional numerical calculations performed for thin cellulose centrally ignited with an axisymmetric source have shown that under the presence of a forced flow slower than 0.035 m/s flames spreads only opposing the flow. Extinction is observed at the trailing edge with no concurrent propagation. Experiments conducted by the same authors at the JAMIC 10 second drop tower verified these calculations. Reducing the oxygen supply to the flame also results in a decrease of the Damk6hler number which might lead to extinction. Greyson et al. and Ferkul conducted experiments in micro-gravity (5 second drop tower) with thin paper and observed that at very low flow velocities concurrent flame spread will stop propagating and the flame will reduce in size and extinguish. They noted that quenching differs significantly from blow-off in that the upstream leading edge will remain anchored to the burn out edge.

Claustrum of the short-tailed fruit bat, Carollia perspicillata: Alignment of cellular orientation and functional connectivity.

PubMed

Orman, Rena; Kollmar, Richard; Stewart, Mark

2017-04-15

The claustrum is a gray-matter structure that underlies neocortex and reciprocates connections with cortical and subcortical targets. In lower mammals, the claustrum is directly adjacent to neocortex, making the definition of claustral boundaries challenging. Latexin, an endogenous inhibitor of metallocarboxypeptidases, localizes to claustral cells, enabling a clear delineation of claustrum. Given its proportionately large claustrum, we hypothesized that the short-tailed fruit bat, Carollia perspicillata, can be a useful model for claustral structure-function relations. We used latexin immunohistochemistry to identify claustral boundaries and intrinsic structure and multielectrode recordings from brain slices to explore intrinsic excitatory connectivity of the claustrum. Carollia's claustrum contains cells whose intrinsic connectivity and alignment permit the generation of spontaneous, synchronous population events and mirror their pattern of spread in disinhibited brain slices over millimeters. Carollia shows cellular alignment and spontaneous population-activity spread along both horizontal and dorsoventral axes. Carollia claustrum possesses intrinsic excitatory connectivity sufficient to: 1) generate single, spontaneous, synchronized burst discharges, 2) support activity spread along axes where claustral cells are aligned, and 3), because of multiple axes for cell alignment, support activity spread along both rostrocaudal and dorsoventral axes. The smaller event sizes in bat claustrum compared with rat claustrum are consistent with events occurring in population subsets rather than the full claustral cell population. The overall size of claustrum, its pronounced vascularity, and its more complex intrinsic connectivity than rat suggest that the bat is an animal model for claustral structure and function that will permit unique access to claustrum's processing capabilities. J. Comp. Neurol. 525:1459-1474, 2017. © 2016 Wiley Periodicals, Inc. © 2016 Wiley Periodicals, Inc.

Amoxicillin effects on functional microbial community and spread of antibiotic resistance genes in amoxicillin manufacture wastewater treatment system.

PubMed

Meng, Lingwei; Li, Xiangkun; Wang, Xinran; Ma, Kaili; Liu, Gaige; Zhang, Jie

2017-11-01

This study aimed to reveal how amoxicillin (AMX) affected the microbial community and the spread mechanism of antibiotic resistance genes (ARGs) in the AMX manufacture wastewater treatment system. For this purpose, a 1.47 L expanded granular sludge bed (EGSB) reactor was designed and run for 241days treating artificial AMX manufacture wastewater. 454 pyrosequencing was applied to analyze functional microorganisms in the system. The antibiotic genes OXA- 1 , OXA -2 , OXA -10 , TEM -1 , CTX-M -1 , class I integrons (intI1) and 16S rRNA genes were also examined in sludge samples. The results showed that the genera Ignavibacterium, Phocoenobacter, Spirochaeta, Aminobacterium and Cloacibacillus contributed to the degradation of different organic compounds (such as various sugars and amines). And the relative quantification of each β-lactam resistance gene in the study was changed with the increasing of AMX concentration. Furthermore the vertical gene transfer was the main driver for the spread of ARGs rather than horizontal transfer pathways in the system. Copyright © 2017. Published by Elsevier B.V.

Scrambling and thermalization in a diffusive quantum many-body system

DOE PAGES

Bohrdt, A.; Mendl, C. B.; Endres, M.; ...

2017-06-02

Out-of-time ordered (OTO) correlation functions describe scrambling of information in correlated quantum matter. They are of particular interest in incoherent quantum systems lacking well defined quasi-particles. Thus far, it is largely elusive how OTO correlators spread in incoherent systems with diffusive transport governed by a few globally conserved quantities. Here, we study the dynamical response of such a system using high-performance matrix-product-operator techniques. Specifically, we consider the non-integrable, one-dimensional Bose–Hubbard model in the incoherent high-temperature regime. Our system exhibits diffusive dynamics in time-ordered correlators of globally conserved quantities, whereas OTO correlators display a ballistic, light-cone spreading of quantum information. Themore » slowest process in the global thermalization of the system is thus diffusive, yet information spreading is not inhibited by such slow dynamics. We furthermore develop an experimentally feasible protocol to overcome some challenges faced by existing proposals and to probe time-ordered and OTO correlation functions. As a result, our study opens new avenues for both the theoretical and experimental exploration of thermalization and information scrambling dynamics.« less

Scrambling and thermalization in a diffusive quantum many-body system

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bohrdt, A.; Mendl, C. B.; Endres, M.

Out-of-time ordered (OTO) correlation functions describe scrambling of information in correlated quantum matter. They are of particular interest in incoherent quantum systems lacking well defined quasi-particles. Thus far, it is largely elusive how OTO correlators spread in incoherent systems with diffusive transport governed by a few globally conserved quantities. Here, we study the dynamical response of such a system using high-performance matrix-product-operator techniques. Specifically, we consider the non-integrable, one-dimensional Bose–Hubbard model in the incoherent high-temperature regime. Our system exhibits diffusive dynamics in time-ordered correlators of globally conserved quantities, whereas OTO correlators display a ballistic, light-cone spreading of quantum information. Themore » slowest process in the global thermalization of the system is thus diffusive, yet information spreading is not inhibited by such slow dynamics. We furthermore develop an experimentally feasible protocol to overcome some challenges faced by existing proposals and to probe time-ordered and OTO correlation functions. As a result, our study opens new avenues for both the theoretical and experimental exploration of thermalization and information scrambling dynamics.« less

Design of Capillary Flows with Spatially Graded Porous Films

NASA Astrophysics Data System (ADS)

Joung, Young Soo; Figliuzzi, Bruno Michel; Buie, Cullen

2013-11-01

We have developed a new capillary tube model, consisting of multi-layered capillary tubes oriented in the direction of flow, to predict capillary speeds on spatially graded porous films. Capillary flows through thin porous media have been widely utilized for small size liquid transport systems. However, for most media it is challenging to realize arbitrary shapes and spatially functionalized micro-structures with variable flow properties. Therefore, conventional media can only be used for capillary flows obeying Washburn's equation and the modifications thereof. Given this background, we recently developed a method called breakdown anodization (BDA) to produce highly wetting porous films. The resulting surfaces show nearly zero contact angles and fast water spreading speed. Furthermore, capillary pressure and spreading diffusivity can be expressed as functions of capillary height when customized electric fields are used in BDA. From the capillary tube model, we derived a general capillary flow equation of motion in terms of capillary pressure and spreading diffusivity. The theoretical model shows good agreement with experimental capillary flows. The study will provide novel design methodologies for paper-based microfluidic devices.

Microgravity Flame Spread in Exploration Atmospheres: Pressure, Oxygen, and Velocity Effects on Opposed and Concurrent Flame Spread

NASA Technical Reports Server (NTRS)

Olson, Sandra L.; Ruff, Gary A.; Fletcher, J. Miller

2008-01-01

Microgravity tests of flammability and flame spread were performed in a low-speed flow tunnel to simulate spacecraft ventilation flows. Three thin fuels were tested for flammability (Ultem 1000 (General Electric Company), 10 mil film, Nomex (Dupont) HT90-40, and Mylar G (Dupont) and one fuel for flame spread testing (Kimwipes (Kimberly-Clark Worldwide, Inc.). The 1g Upward Limiting Oxygen Index (ULOI) and 1g Maximum Oxygen Concentration (MOC) are found to be greater than those in 0g, by up to 4% oxygen mole fraction, meaning that the fuels burned in 0g at lower oxygen concentrations than they did using the NASA Standard 6001 Test 1 protocol. Flame spread tests with Kimwipes were used to develop correlations that capture the effects of flow velocity, oxygen concentration, and pressure on flame spread rate. These correlations were used to determine that over virtually the entire range of spacecraft atmospheres and flow conditions, the opposed spread is faster, especially for normoxic atmospheres. The correlations were also compared with 1g MOC for various materials as a function of pressure and oxygen. The lines of constant opposed flow agreed best with the 1g MOC trends, which indicates that Test 1 limits are essentially dictated by the critical heat flux for ignition. Further evaluation of these and other materials is continuing to better understand the 0g flammability of materials and its effect on the oxygen margin of safety.

PSD-95 uncoupling from NMDA receptors by Tat- N-dimer ameliorates neuronal depolarization in cortical spreading depression.

PubMed

Kucharz, Krzysztof; Søndergaard Rasmussen, Ida; Bach, Anders; Strømgaard, Kristian; Lauritzen, Martin

2017-05-01

Cortical spreading depression is associated with activation of NMDA receptors, which interact with the postsynaptic density protein 95 (PSD-95) that binds to nitric oxide synthase (nNOS). Here, we tested whether inhibition of the nNOS/PSD-95/NMDA receptor complex formation by anti-ischemic compound, UCCB01-144 (Tat- N-dimer) ameliorates the persistent effects of cortical spreading depression on cortical function. Using in vivo two-photon microscopy in somatosensory cortex in mice, we show that fluorescently labelled Tat- N-dimer readily crosses blood-brain barrier and accumulates in nerve cells during the first hour after i.v. injection. The Tat- N-dimer suppressed stimulation-evoked synaptic activity by 2-20%, while cortical blood flow and cerebral oxygen metabolic (CMRO 2 ) responses were preserved. During cortical spreading depression, the Tat- N-dimer reduced the average amplitude of the negative shift in direct current potential by 33% (4.1 mV). Furthermore, the compound diminished the average depression of spontaneous electrocorticographic activity by 11% during first 40 min of post-cortical spreading depression recovery, but did not mitigate the suppressing effect of cortical spreading depression on cortical blood flow and CMRO 2 . We suggest that uncoupling of PSD-95 from NMDA receptors reduces overall neuronal excitability and the amplitude of the spreading depolarization wave. These findings may be of interest for understanding the neuroprotective effects of the nNOS/PSD-95 uncoupling in stroke.

Spreading properties of cosmetic emollients: Use of synthetic skin surface to elucidate structural effect.

PubMed

Douguet, Marine; Picard, Céline; Savary, Géraldine; Merlaud, Fabien; Loubat-Bouleuc, Nathalie; Grisel, Michel

2017-06-01

The study focuses on the impact of structural and physicochemical properties of emollients on their spreadability. Fifty-three emollients, among which esters, silicones, vegetable and mineral oils, have been characterized. Their viscosity, surface tension, density and spreadability have been measured. Vitro-skin ® , an artificial skin substitute, was used as an artificial porous substrate to measure spreadability. Two different methods have been selected to characterize spreadability, namely contact angle and spreading value. Dynamic contact angle measurements showed that emollient spreadability is first governed by spontaneous spreading and that, in a second phase, absorption and migration into the porous substrate becomes the driver of the extension of the spreading area. Statistical analysis of physicochemical and spreading value data revealed that viscosity has a major impact on the spreading behavior of emollients whatever their chemical type. A special emphasis was placed on the ester family in which chemical diversity is very wide. The results highlighted a difference between "high viscosity esters" for which viscosity is the main factor impacting spreadability and "low viscosity esters" for which structural variations (mono/diester, saturated/unsaturated chain, linear/branched chain) have to be considered in addition to viscosity. Linear regressions were used to express spreading value as a function of viscosity for each of the four emollient families tested (esters, silicones, vegetable and mineral oils). These regressions allowed the development of reliable predictive models as a powerful tool for formulators to forecast spreadability of emollients. Copyright © 2017 Elsevier B.V. All rights reserved.

Assessing Biosecurity Risks for the Introduction and Spread of Diseases Among Commercial Sheep Properties in New South Wales, Australia, Using Foot-and-Mouth Disease as a Case Study.

PubMed

Fountain, Jake; Woodgate, Robert; Rast, Luzia; Hernández-Jover, Marta

2018-01-01

Sheep production systems are a major industry in Australia, with a gross value of roughly $4.66 billion; 87.3% of which is attributable to export markets. Exotic diseases such as foot-and-mouth disease (FMD) are a potential threat to the viability of Australia's export market. Previous outbreaks of FMD in developed countries, and challenges in the management of onshore biosecurity, signify the importance of on-farm biosecurity in controlling disease transmission. This study aims to investigate the risk of disease introduction and spread among New South Wales (NSW) sheep properties using FMD as a case study and draw recommendation for the industry. Exposure and partial consequence assessments, using scenario trees and Monte Carlo stochastic modeling, were conducted to identify pathways of introduction and spread and calculate the probabilities of these pathways occurring. Input parameters were estimated from the data obtained during qualitative interviews with producers and scientific literature. According to the reported practices of sheep producers and assuming each pathway was carrying the FMD virus, the exposure assessment estimates the median (5-95%) probability of FMD exposure of sheep on a naive property to be 0.619 (0.541-0.698), 0.151 (0.085-0.239), 0.235 (0.153-0.324), and 0.710 (0.619-0.791) for introduction through new stock, wildlife, carriers (humans, dogs, and vehicles), and neighbors, respectively. The spread assessment estimated the median probability of FMD spreading from an infected sheep property to neighboring enterprises to be 0.603 (0.504-0.698). A similar probability was estimated for spread via wildlife (0.523; 0.404-0.638); and a lower spread probability was estimated for carriers (0.315; 0.171-0.527), sheep movement (0.285; 0.161-0.462), and dead stock (0.168; 0.070-0.312). The sensitivity analysis revealed that the introduction of an FMD-infected sheep was more influential for exposure via new stock than isolation practices. Sharing adjacent boundaries was found to be the most influential factor for exposure and spread between neighboring enterprises, and to a lesser extent, hygiene practices were found to have the most influence on exposure and spread through carriers. To minimize the potential risk of FMD introduction and spread between sheep properties, maintenance of boundary fences, identification of infected animals before introduction to the property, and hygiene and disinfection practices should be improved.

Assessing Biosecurity Risks for the Introduction and Spread of Diseases Among Commercial Sheep Properties in New South Wales, Australia, Using Foot-and-Mouth Disease as a Case Study

PubMed Central

Fountain, Jake; Woodgate, Robert; Rast, Luzia; Hernández-Jover, Marta

2018-01-01

Sheep production systems are a major industry in Australia, with a gross value of roughly $4.66 billion; 87.3% of which is attributable to export markets. Exotic diseases such as foot-and-mouth disease (FMD) are a potential threat to the viability of Australia’s export market. Previous outbreaks of FMD in developed countries, and challenges in the management of onshore biosecurity, signify the importance of on-farm biosecurity in controlling disease transmission. This study aims to investigate the risk of disease introduction and spread among New South Wales (NSW) sheep properties using FMD as a case study and draw recommendation for the industry. Exposure and partial consequence assessments, using scenario trees and Monte Carlo stochastic modeling, were conducted to identify pathways of introduction and spread and calculate the probabilities of these pathways occurring. Input parameters were estimated from the data obtained during qualitative interviews with producers and scientific literature. According to the reported practices of sheep producers and assuming each pathway was carrying the FMD virus, the exposure assessment estimates the median (5–95%) probability of FMD exposure of sheep on a naive property to be 0.619 (0.541–0.698), 0.151 (0.085–0.239), 0.235 (0.153–0.324), and 0.710 (0.619–0.791) for introduction through new stock, wildlife, carriers (humans, dogs, and vehicles), and neighbors, respectively. The spread assessment estimated the median probability of FMD spreading from an infected sheep property to neighboring enterprises to be 0.603 (0.504–0.698). A similar probability was estimated for spread via wildlife (0.523; 0.404–0.638); and a lower spread probability was estimated for carriers (0.315; 0.171–0.527), sheep movement (0.285; 0.161–0.462), and dead stock (0.168; 0.070–0.312). The sensitivity analysis revealed that the introduction of an FMD-infected sheep was more influential for exposure via new stock than isolation practices. Sharing adjacent boundaries was found to be the most influential factor for exposure and spread between neighboring enterprises, and to a lesser extent, hygiene practices were found to have the most influence on exposure and spread through carriers. To minimize the potential risk of FMD introduction and spread between sheep properties, maintenance of boundary fences, identification of infected animals before introduction to the property, and hygiene and disinfection practices should be improved. PMID:29755989

Measuring the effect of fuel treatments on forest carbon using landscape risk analysis

NASA Astrophysics Data System (ADS)

Ager, A. A.; Finney, M. A.; McMahan, A.; Cathcart, J.

2010-12-01

Wildfire simulation modelling was used to examine whether fuel reduction treatments can potentially reduce future wildfire emissions and provide carbon benefits. In contrast to previous reports, the current study modelled landscape scale effects of fuel treatments on fire spread and intensity, and used a probabilistic framework to quantify wildfire effects on carbon pools to account for stochastic wildfire occurrence. The study area was a 68 474 ha watershed located on the Fremont-Winema National Forest in southeastern Oregon, USA. Fuel reduction treatments were simulated on 10% of the watershed (19% of federal forestland). We simulated 30 000 wildfires with random ignition locations under both treated and untreated landscapes to estimate the change in burn probability by flame length class resulting from the treatments. Carbon loss functions were then calculated with the Forest Vegetation Simulator for each stand in the study area to quantify change in carbon as a function of flame length. We then calculated the expected change in carbon from a random ignition and wildfire as the sum of the product of the carbon loss and the burn probabilities by flame length class. The expected carbon difference between the non-treatment and treatment scenarios was then calculated to quantify the effect of fuel treatments. Overall, the results show that the carbon loss from implementing fuel reduction treatments exceeded the expected carbon benefit associated with lowered burn probabilities and reduced fire severity on the treated landscape. Thus, fuel management activities resulted in an expected net loss of carbon immediately after treatment. However, the findings represent a point in time estimate (wildfire immediately after treatments), and a temporal analysis with a probabilistic framework used here is needed to model carbon dynamics over the life cycle of the fuel treatments. Of particular importance is the long-term balance between emissions from the decay of dead trees killed by fire and carbon sequestration by forest regeneration following wildfire.

The effect of a low-fat spread with added plant sterols on vascular function markers: results of the Investigating Vascular Function Effects of Plant Sterols (INVEST) study12345

PubMed Central

Ras, Rouyanne T; Fuchs, Dagmar; Koppenol, Wieneke P; Garczarek, Ursula; Greyling, Arno; Keicher, Christian; Verhoeven, Carole; Bouzamondo, Hakim; Wagner, Frank; Trautwein, Elke A

2015-01-01

Background: Plant sterols (PSs) lower LDL cholesterol, an established risk factor for coronary artery disease (CAD). No direct evidence is available supporting a reduced risk of CAD for foods with added PSs. Endothelial dysfunction is seen as an early indicator of atherosclerotic damage. Objectives: This study was primarily designed to investigate the effect of a low-fat spread with added PSs on brachial artery endothelial function as measured by flow-mediated dilation (FMD). Second, effects on arterial stiffness, blood pressure, serum lipids, and plasma PS concentrations were investigated. We hypothesized that PSs would not worsen FMD but would rather modestly improve FMD. Design: This study had a double-blind, randomized, placebo-controlled, parallel design. After a 4-wk run-in period, 240 hypercholesterolemic but otherwise healthy men and women consumed 20 g/d of low-fat spread without (control) or with added PSs (3 g/d) during 12 wk. Pre- and postintervention, vascular function measurements and blood sampling were performed. Results: In total, 232 participants completed the study period. For the primary endpoint FMD, 199 participants were included in the statistical analysis. PS intake did not affect FMD (+0.01 percentage points; 95% CI: −0.73, 0.75) compared with control. Measures of arterial stiffness (pulse wave velocity and augmentation index) and blood pressure were also not significantly changed compared with control. After PS intervention, LDL cholesterol significantly decreased on average by 0.26 mmol/L (95% CI: −0.40, −0.12) or 6.7% compared with control. Plasma sitosterol and campesterol concentrations significantly increased in the PS group up to on average 11.5 μmol/L and 13.9 μmol/L (expressed as geometric means), respectively. Conclusions: The intake of a low-fat spread with added PSs neither improved nor worsened FMD or other vascular function markers in hypercholesterolemic men and women. As expected, serum LDL cholesterol decreased, whereas plasma PSs increased after PS intake. This study was registered at clinicaltrials.gov as NCT01803178. PMID:25809853

Platelet impedance adhesiometry: A novel technique for the measurement of platelet adhesion and spreading.

PubMed

Polgár, L; Soós, P; Lajkó, E; Láng, O; Merkely, B; Kőhidai, L

2018-06-01

Thrombogenesis plays an important role in today's morbidity and mortality. Antithrombotics are among the most frequently prescribed drugs. Thorough knowledge of platelet function is needed for optimal clinical care. Platelet adhesion is a separate subprocess of platelet thrombus formation; still, no well-standardized technique for the isolated measurement of platelet adhesion exists. Impedimetry is one of the most reliable, state-of-art techniques to analyze cell adhesion, proliferation, viability, and cytotoxicity. We propose impedimetry as a feasible novel method for the isolated measurement of 2 significant platelet functions: adhesion and spreading. Laboratory reference platelet agonists (epinephrine, ADP, and collagen) were applied to characterize platelet functions by impedimetry using the xCELLigence SP system. Platelet samples were obtained from 20 healthy patients under no drug therapy. Standard laboratory parameters and clinical patient history were also analyzed. Epinephrine and ADP increased platelet adhesion in a concentration-dependent manner, while collagen tended to have a negative effect. Serum sodium and calcium levels and age had a negative correlation with platelet adhesion induced by epinephrine and ADP, while increased immunoreactivity connected with allergic diseases was associated with increased platelet adhesion induced by epinephrine and ADP. ADP increased platelet spreading in a concentration-dependent manner. Impedimetry proved to be a useful and sensitive method for the qualitative and quantitated measurement of platelet adhesion, even differentiating between subgroups of a healthy population. This novel technique is offered as an important method in the further investigation of platelet function. © 2018 John Wiley & Sons Ltd.

Summary of the U.S. Geological Survey National Field Quality Assurance Program from 1979 through 1997

USGS Publications Warehouse

Stanley, D.L.; Boozer, T.M.; Schroder, L.J.

1998-01-01

Since the inception of the U.S. Geological Survey National Field Quality Assurance Program, over 85,000 proficiency samples have been analyzed by water-quality analysts. This includes more than 10,000 alkalinity samples, more than 15,000 pH samples, and more than 16,000 specific conductance samples, which were analyzed from 1990 through 1997, and a total of more than 43,000 proficiency samples analyzed from 1979 through 1989. The analyte values were evaluated to determine the fourth-spread, a measure of the width of the middle half of the data, and the F-pseudosigma, a robust replacement for the standard deviation, for each of the different measurement ranges. The result of the statistical evaluation showed that the vast majority of reference sample measurements made by water-quality analysts were within acceptable ranges. From 1990 to 1997, the measurement of pH had the highest level of acceptable results, 98.4 percent, followed by specific conductance with 95.2 percent acceptable results, and alkalinity with 88.6 percent acceptable results. The statistical summary of pH indicates the calculated fourth-spread values for the entire tested range is +0.06 pH units. For specific conductance, the magnitude of the fourth-spread increases as the magnitude of the specific conductance ranges increases. The average relative fourth-spread percent for all reported specific conductance values is +1.8 percent. From 1990 through 1997, the evaluation of the results for alkalinity measurement for the average fourth-spread was determined to be + 3.3 milligrams per liter as calcium carbonate.

Possibilities to use tank-mix adjuvants for better fungicide spreading on triticale ears.

PubMed

Ryckaert, Bert; Spanoghe, Pieter; Heremans, Betty; Haesaert, Geert; Steurbaut, Walter

2008-09-10

Tank-mix adjuvants can increase the overall performance of plant protection products. Their most important ways of action are the improved retention, spreading, wetting, and penetration of the pesticide on the target and the reduction of fine droplets. In this paper, deposition and spreading of the systemic fungicide propiconazole on triticale ears were quantified. A better deposition and spreading of fungicide on the ear may be a possible help for the Fusarium problem in triticale, wheat, and other cereals. Triticale ears were applied with propiconazole in combination with 11 different tank-mix adjuvants. Vegetable oil, alcohol ethoxylates, lactate ester, trisiloxanes, and an amphoteric molecule were included in this experiment. When no tank-mix adjuvant was used, the lower part of the ear was reached five times less by the propiconazole spray than the upper part of the ear. When the tank-mix adjuvant was combined with the propiconazole formulation, an increase in residue on both the upper and the lower part of the ear was observed. A higher residue on the upper half of the ear means a better deposition, while a higher residue on the lower part of the ear is related to a better downward spreading over the grains and the needles of the ear. The combination of those two observations makes it interesting to use tank-mix adjuvants for the prevention of mycotoxin-producing Fusarium species. The advantages are emphasized even more when cost effectiveness was calculated. The use of a proper tank-mix adjuvant can result in 40% lower cost per application per hectare.

Numerical Model of Flame Spread Over Solids in Microgravity: A Supplementary Tool for Designing a Space Experiment

NASA Technical Reports Server (NTRS)

Shih, Hsin-Yi; Tien, James S.; Ferkul, Paul (Technical Monitor)

2001-01-01

The recently developed numerical model of concurrent-flow flame spread over thin solids has been used as a simulation tool to help the designs of a space experiment. The two-dimensional and three-dimensional, steady form of the compressible Navier-Stokes equations with chemical reactions are solved. With the coupled multi-dimensional solver of the radiative heat transfer, the model is capable of answering a number of questions regarding the experiment concept and the hardware designs. In this paper, the capabilities of the numerical model are demonstrated by providing the guidance for several experimental designing issues. The test matrix and operating conditions of the experiment are estimated through the modeling results. The three-dimensional calculations are made to simulate the flame-spreading experiment with realistic hardware configuration. The computed detailed flame structures provide the insight to the data collection. In addition, the heating load and the requirements of the product exhaust cleanup for the flow tunnel are estimated with the model. We anticipate that using this simulation tool will enable a more efficient and successful space experiment to be conducted.

Spreading Resistance on Thin Film Contacts

NASA Astrophysics Data System (ADS)

Zhang, Peng; Lau, Y. Y.; Hung, D.; Gilgenbach, R. M.

2012-10-01

Electrical contact [1] is important to wire-array z-pinches, metal-insulator-vacuum junctions, and high power microwave sources, etc. Contact problems account for 40 percent of all electrical failures, from small scale consumer electronics to large scale defense and aerospace systems. The crowding of the current lines at contacts leads to enhanced localized heating, a measure of which is the spreading resistance (Rs). For a microscopic area of contact (the ``a-spot'' [1]) on a thin film, we calculate Rs in both Cartesian and cylindrical geometries [2]. In the limit of small film thickness, h, the normalized thin film spreading resistance converges to the finite values, 2.77 for the Cartesian case and 0.28 for the cylindrical case. These same finite limits are found to be applicable to the a-spot between bulk solids in the high frequency limit if the skin depth is identified with h. Extension to a general a-spot geometry is proposed [2]. [4pt] [1] R. Holm, Electric Contacts, 4th ed., Springer (1967). [0pt] [2] P. Zhang et al., IEEE Trans. Electron Devices 59, 1936 (2012).

A numerical solution of the problem of crown forest fire initiation and spread

NASA Astrophysics Data System (ADS)

Marzaeva, S. I.; Galtseva, O. V.

2018-05-01

Mathematical model of forest fire was based on an analysis of known experimental data and using concept and methods from reactive media mechanics. The study takes in to account the mutual interaction of the forest fires and three-dimensional atmosphere flows. The research is done by means of mathematical modeling of physical processes. It is based on numerical solution of Reynolds equations for chemical components and equations of energy conservation for gaseous and condensed phases. It is assumed that the forest during a forest fire can be modeled as a two-temperature multiphase non-deformable porous reactive medium. A discrete analog for the system of equations was obtained by means of the control volume method. The developed model of forest fire initiation and spreading would make it possible to obtain a detailed picture of the variation in the velocity, temperature and chemical species concentration fields with time. Mathematical model and the result of the calculation give an opportunity to evaluate critical conditions of the forest fire initiation and spread which allows applying the given model for of means for preventing fires.

Multisensor surveillance data augmentation and prediction with optical multipath signal processing

NASA Astrophysics Data System (ADS)

Bush, G. T., III

1980-12-01

The spatial characteristics of an oil spill on the high seas are examined in the interest of determining whether linear-shift-invariant data processing implemented on an optical computer would be a useful tool in analyzing spill behavior. Simulations were performed on a digital computer using data obtained from a 25,000 gallon spill of soy bean oil in the open ocean. Marked changes occurred in the observed spatial frequencies when the oil spill was encountered. An optical detector may readily be developed to sound an alarm automatically when this happens. The average extent of oil spread between sequential observations was quantified by a simulation of non-holographic optical computation. Because a zero crossover was available in this computation, it may be possible to construct a system to measure automatically the amount of spread. Oil images were subjected to deconvolutional filtering to reveal the force field which acted upon the oil to cause spreading. Some features of spill-size prediction were observed. Calculations based on two sequential photos produced an image which exhibited characteristics of the third photo in that sequence.

Identifying the most influential spreaders in complex networks by an Extended Local K-Shell Sum

NASA Astrophysics Data System (ADS)

Yang, Fan; Zhang, Ruisheng; Yang, Zhao; Hu, Rongjing; Li, Mengtian; Yuan, Yongna; Li, Keqin

Identifying influential spreaders is crucial for developing strategies to control the spreading process on complex networks. Following the well-known K-Shell (KS) decomposition, several improved measures are proposed. However, these measures cannot identify the most influential spreaders accurately. In this paper, we define a Local K-Shell Sum (LKSS) by calculating the sum of the K-Shell indices of the neighbors within 2-hops of a given node. Based on the LKSS, we propose an Extended Local K-Shell Sum (ELKSS) centrality to rank spreaders. The ELKSS is defined as the sum of the LKSS of the nearest neighbors of a given node. By assuming that the spreading process on networks follows the Susceptible-Infectious-Recovered (SIR) model, we perform extensive simulations on a series of real networks to compare the performance between the ELKSS centrality and other six measures. The results show that the ELKSS centrality has a better performance than the six measures to distinguish the spreading ability of nodes and to identify the most influential spreaders accurately.

Vibrissal touch sensing in the harbor seal (Phoca vitulina): how do seals judge size?

PubMed

Grant, Robyn; Wieskotten, Sven; Wengst, Nina; Prescott, Tony; Dehnhardt, Guido

2013-06-01

"Whisker specialists" such as rats, shrews, and seals actively employ their whiskers to explore their environments and extract object properties such as size, shape, and texture. It has been suggested that whiskers could be used to discriminate between different sized objects in one of two ways: (i) to use whisker positions, such as angular position, spread or amplitude to approximate size; or (ii) to calculate the number of whiskers that contact an object. This study describes in detail how two adult harbor seals use their whiskers to differentiate between three sizes of disk. The seals judged size very fast, taking <400 ms. In addition, they oriented their smaller, most rostral, ventral whiskers to the disks, so that more whiskers contacted the surface, complying to a maximal contact sensing strategy. Data from this study supports the suggestion that it is the number of whisker contacts that predict disk size, rather than how the whiskers are positioned (angular position), the degree to which they are moved (amplitude) or how spread out they are (angular spread).

Graphene as current spreading layer on AlGaInP light emitting diodes

NASA Astrophysics Data System (ADS)

Guo, Xia; Feng, Yajie; Liu, Qiaoli; Hu, Anqi; He, Xiaoying; Hu, Zonghai

2018-05-01

Due to high transmittance and high mobility, graphene is one of the promising candidates for a current spreading layer, which is crucial to light emitting diode (LED) performance. In this paper, improved AlGaInP LED performance was reported after graphene was applied on the GaP surface. Due to its lowered work function difference than with the GaN material, the electrical properties remain the same without additional voltage bias. The light output power is enhanced by about 40% under the current injection of 5 mA at room temperature, which was confirmed by the light emission profile analysis in this study. Such results indicate that raphene is a promising candidate as a current spreading layer under low current injection.

Spread spectrum mobile communication experiment using ETS-V satellite

NASA Technical Reports Server (NTRS)

Ikegami, Tetsushi; Suzuki, Ryutaro; Kadowaki, Naoto; Taira, Shinichi; Sato, Nobuyasu

1990-01-01

The spread spectrum technique is attractive for application to mobile satellite communications, because of its random access capability, immunity to inter-system interference, and robustness to overloading. A novel direct sequence spread spectrum communication equipment is developed for land mobile satellite applications. The equipment is developed based on a matched filter technique to improve the initial acquisition performance. The data rate is 2.4 kilobits per sec. and the PN clock rate is 2.4552 mega-Hz. This equipment also has a function of measuring the multipath delay profile of land mobile satellite channel, making use of a correlation property of a PN code. This paper gives an outline of the equipment and the field test results with ETS-V satellite.

Selective binding and lateral clustering of α5β1 and αvβ3 integrins: Unraveling the spatial requirements for cell spreading and focal adhesion assembly

PubMed Central

Schaufler, Viktoria; Czichos-Medda, Helmi; Hirschfeld-Warnecken, Vera; Neubauer, Stefanie; Rechenmacher, Florian; Medda, Rebecca; Kessler, Horst; Geiger, Benjamin; Spatz, Joachim P.; Cavalcanti-Adam, E. Ada

2016-01-01

ABSTRACT Coordination of the specific functions of α5β1 and αvβ3 integrins is crucial for the precise regulation of cell adhesion, spreading and migration, yet the contribution of differential integrin-specific crosstalk to these processes remains unclear. To determine the specific functions of αvβ3 and α5β1 integrins, we used nanoarrays of gold particles presenting immobilized, integrin-selective peptidomimetic ligands. Integrin binding to the peptidomimetics is highly selective, and cells can spread on both ligands. However, spreading is faster and the projected cell area is greater on α5β1 ligand; both depend on ligand spacing. Quantitative analysis of adhesion plaques shows that focal adhesion size is increased in cells adhering to αvβ3 ligand at 30 and 60 nm spacings. Analysis of αvβ3 and α5β1 integrin clusters indicates that fibrillar adhesions are more prominent in cells adhering to α5β1 ligand, while clusters are mostly localized at the cell margins in cells adhering to αvβ3 ligand. αvβ3 integrin clusters are more pronounced on αvβ3 ligand, though they can also be detected in cells adhering to α5β1 ligand. Furthermore, α5β1 integrin clusters are present in cells adhering to α5β1 ligand, and often colocalize with αvβ3 clusters. Taken together, these findings indicate that the activation of αvβ3 integrin by ligand binding is dispensable for initial adhesion and spreading, but essential to formation of stable focal adhesions. PMID:27003228

Numerically bridging lamellipodial and filopodial activity during cell spreading reveals a potentially novel trigger of focal adhesion maturation.

PubMed

Loosli, Y; Vianay, B; Luginbuehl, R; Snedeker, J G

2012-05-01

We present a novel approach to modeling cell spreading, and use it to reveal a potentially central mechanism regulating focal adhesion maturation in various cell phenotypes. Actin bundles that span neighboring focal complexes at the lamellipodium-lamellum interface were assumed to be loaded by intracellular forces in proportion to bundle length. We hypothesized that the length of an actin bundle (with the corresponding accumulated force at its adhesions) may thus regulate adhesion maturation to ensure cell mechanical stability and morphological integrity. We developed a model to test this hypothesis, implementing a "top-down" approach to simplify certain cellular processes while explicitly incorporating complexity of other key subcellular mechanisms. Filopodial and lamellipodial activities were treated as modular processes with functional spatiotemporal interactions coordinated by rules regarding focal adhesion turnover and actin bundle dynamics. This theoretical framework was able to robustly predict temporal evolution of cell area and cytoskeletal organization as reported from a wide range of cell spreading experiments using micropatterned substrates. We conclude that a geometric/temporal modeling framework can capture the key functional aspects of the rapid spreading phase and resultant cytoskeletal complexity. Hence the model is used to reveal mechanistic insight into basic cell behavior essential for spreading. It demonstrates that actin bundles spanning nascent focal adhesions such that they are aligned to the leading edge may accumulate centripetal endogenous forces along their length, and could thus trigger focal adhesion maturation in a force-length dependent fashion. We suggest that this mechanism could be a central "integrating" factor that effectively coordinates force-mediated adhesion maturation at the lamellipodium-lamellum interface.

A simple method for correcting spatially resolved solar intensity oscillation observations for variations in scattered light

NASA Technical Reports Server (NTRS)

Jefferies, S. M.; Duvall, T. L., Jr.

1991-01-01

A measurement of the intensity distribution in an image of the solar disk will be corrupted by a spatial redistribution of the light that is caused by the earth's atmosphere and the observing instrument. A simple correction method is introduced here that is applicable for solar p-mode intensity observations obtained over a period of time in which there is a significant change in the scattering component of the point spread function. The method circumvents the problems incurred with an accurate determination of the spatial point spread function and its subsequent deconvolution from the observations. The method only corrects the spherical harmonic coefficients that represent the spatial frequencies present in the image and does not correct the image itself.

Spatial and spectral simulation of LANDSAT images of agricultural areas

NASA Technical Reports Server (NTRS)

Pont, W. F., Jr. (Principal Investigator)

1982-01-01

A LANDSAT scene simulation capability was developed to study the effects of small fields and misregistration on LANDSAT-based crop proportion estimation procedures. The simulation employs a pattern of ground polygons each with a crop ID, planting date, and scale factor. Historical greenness/brightness crop development profiles generate the mean signal values for each polygon. Historical within-field covariances add texture to pixels in each polygon. The planting dates and scale factors create between-field/within-crop variation. Between field and crop variation is achieved by the above and crop profile differences. The LANDSAT point spread function is used to add correlation between nearby pixels. The next effect of the point spread function is to blur the image. Mixed pixels and misregistration are also simulated.

Objective assessment of image quality. IV. Application to adaptive optics

PubMed Central

Barrett, Harrison H.; Myers, Kyle J.; Devaney, Nicholas; Dainty, Christopher

2008-01-01

The methodology of objective assessment, which defines image quality in terms of the performance of specific observers on specific tasks of interest, is extended to temporal sequences of images with random point spread functions and applied to adaptive imaging in astronomy. The tasks considered include both detection and estimation, and the observers are the optimal linear discriminant (Hotelling observer) and the optimal linear estimator (Wiener). A general theory of first- and second-order spatiotemporal statistics in adaptive optics is developed. It is shown that the covariance matrix can be rigorously decomposed into three terms representing the effect of measurement noise, random point spread function, and random nature of the astronomical scene. Figures of merit are developed, and computational methods are discussed. PMID:17106464

Magnetoacoustic tomography with magnetic induction for high-resolution bioimepedance imaging through vector source reconstruction under the static field of MRI magnet

PubMed Central

Mariappan, Leo; Hu, Gang; He, Bin

2014-01-01

Purpose: Magnetoacoustic tomography with magnetic induction (MAT-MI) is an imaging modality to reconstruct the electrical conductivity of biological tissue based on the acoustic measurements of Lorentz force induced tissue vibration. This study presents the feasibility of the authors' new MAT-MI system and vector source imaging algorithm to perform a complete reconstruction of the conductivity distribution of real biological tissues with ultrasound spatial resolution. Methods: In the present study, using ultrasound beamformation, imaging point spread functions are designed to reconstruct the induced vector source in the object which is used to estimate the object conductivity distribution. Both numerical studies and phantom experiments are performed to demonstrate the merits of the proposed method. Also, through the numerical simulations, the full width half maximum of the imaging point spread function is calculated to estimate of the spatial resolution. The tissue phantom experiments are performed with a MAT-MI imaging system in the static field of a 9.4 T magnetic resonance imaging magnet. Results: The image reconstruction through vector beamformation in the numerical and experimental studies gives a reliable estimate of the conductivity distribution in the object with a ∼1.5 mm spatial resolution corresponding to the imaging system frequency of 500 kHz ultrasound. In addition, the experiment results suggest that MAT-MI under high static magnetic field environment is able to reconstruct images of tissue-mimicking gel phantoms and real tissue samples with reliable conductivity contrast. Conclusions: The results demonstrate that MAT-MI is able to image the electrical conductivity properties of biological tissues with better than 2 mm spatial resolution at 500 kHz, and the imaging with MAT-MI under a high static magnetic field environment is able to provide improved imaging contrast for biological tissue conductivity reconstruction. PMID:24506649

Effect of fault roughness on aftershock distribution and post co-seismic strain accumulation.

NASA Astrophysics Data System (ADS)

Aslam, K.; Daub, E. G.

2017-12-01

We perform physics-based simulations of earthquake rupture propagation on geometrically complex strike-slip faults. We consider many different realization of the fault roughness and obtain heterogeneous stress fields by performing dynamic rupture simulation of large earthquakes. We calculate the Coulomb failure function (CFF) for all these realizations so that we can quantify zones of stress increase/shadows surrounding the main fault and compare our results to seismic catalogs. To do this comparison, we use relocated earthquake catalogs from Northern and Southern California. We specify the range of fault roughness parameters based on past observational studies. The Hurst exponent (H) varies in range from 0.5 to 1 and RMS height to wavelength ratio ( RMS deviation of a fault profile from planarity) has values between 10-2 to 10-3. For any realization of fault roughness, the Probability density function (PDF) values relative to the mean CFF change show a wider spread near the fault and this spread squeezes into a narrow band as we move away from fault. For lower value of RMS ratio ( 10-3), we see bigger zones of stress change near the hypocenter and for higher value of RMS ratio ( 10-2), we see alternate zones of stress increase/decrease surrounding the fault to have comparable lengths. We also couple short-term dynamic rupture simulation with long-term tectonic modelling. We do this by giving the stress output from one of the dynamic rupture simulation (of a single realization of fault roughness) to long term tectonic model (LTM) as initial condition and then run LTM over duration of seismic cycle. This short term and long term coupling enables us to understand how heterogeneous stresses due to fault geometry influence the dynamics of strain accumulation in the post-seismic and inter-seismic phase of seismic cycle.

Deep-ocean basalts: inert gas content and uncertainties in age dating.

PubMed

Noble, C S; Naughton, J J

1968-10-11

The radiogenic argon and helium contents of three basalts erupted into the deep ocean from an active volcano (Kilauea) have been measured. Ages calculated from these measurements increase with sample depth up to 22 million years for lavas deduced to be recent. Caution is urged in applying dates from deep-ocean basalts in studies on ocean-floor spreading.

HRR Upgrade to mass loss calorimeter and modified Schlyter test for FR Wood

Treesearch

Mark A. Dietenberger; Charles R. Boardman

2013-01-01

Enhanced Heat Release Rate (HRR) methodology has been extended to the Mass Loss Calorimeter (MLC) and the Modified Schlyter flame spread test to evaluate fire retardant effectiveness used on wood based materials. Modifications to MLC include installation of thermopile on the chimney walls to correct systematic errors to the sensible HRR calculations to account for...

How to generate and interpret fire characteristics charts for surface and crown fire behavior

Treesearch

Patricia L. Andrews; Faith Ann Heinsch; Luke Schelvan

2011-01-01

A fire characteristics chart is a graph that presents primary related fire behavior characteristics-rate of spread, flame length, fireline intensity, and heat per unit area. It helps communicate and interpret modeled or observed fire behavior. The Fire Characteristics Chart computer program plots either observed fire behavior or values that have been calculated by...

Measurements of the energy distribution of a high brightness rubidium ion beam.

PubMed

Ten Haaf, G; Wouters, S H W; Nijhof, D F J; Mutsaers, P H A; Vredenbregt, E J D

2018-07-01

The energy distribution of a high brightness rubidium ion beam, which is intended to be used as the source for a focused ion beam instrument, is measured with a retarding field analyzer. The ions are created from a laser-cooled and compressed atomic beam by two-step photoionization in which the ionization laser power is enhanced in a build-up cavity. Particle tracing simulations are performed to ensure the analyzer is able to resolve the distribution. The lowest achieved full width 50% energy spread is (0.205 ± 0.006) eV, which is measured at a beam current of 9 pA. The energy spread originates from the variation in the ionization position of the ions which are created inside an extraction electric field. This extraction field is essential to limit disorder-induced heating which can decrease the ion beam brightness. The ionization position distribution is limited by a tightly focused excitation laser beam. Energy distributions are measured for various ionization and excitation laser intensities and compared with calculations based on numerical solutions of the optical Bloch equations including ionization. A good agreement is found between measurements and calculations. Copyright © 2018 Elsevier B.V. All rights reserved.

Some aspects of large-scale travelling ionospheric disturbances

NASA Astrophysics Data System (ADS)

Bowman, G. G.

1992-06-01

On two occasions the speeds and directions of travel of large-scale traveling ionospheric disturbances (LS-TIDs) following geomagnetic substorm onsets, have been calculated for the propagation of these disturbances in both hemispheres of the earth. N(h) analyses have been used to produce height change profiles at a fixed frequency from which time shifts between stations (used for the speed and direction-of-travel values) have been calculated. Fixed-frequency phase path measurements at Bribie Island for two events reveal wavetrains with periodicities around 17 min associated with these disturbances. Another event recorded a periodicity of 19 min. Also, for two of the events additional periodicities around 30 min were found. These wavetrains along with the macroscale height changes and electron density depletions associated with these LS-TIDs are essentially the same as the ionospheric structure changes observed during the passage of night-time medium-scale traveling ionospheric disturbances (MS-TIDs). However, unlike these MS-TIDs, the LS-TIDs are generally not associated with the recording of spread-F on ionograms. Possible reasons for this difference are discussed as well as the special conditions which probably prevail on the few occasions when spread-F is associated with LS-TIDs.

Spot Radiative Ignition and Subsequent Three Dimensional Flame Spread Over Thin Cellulose Fuels

NASA Technical Reports Server (NTRS)

Olson, Sandra L.; Kashiwagi, T.; Kikuchi, M.; Fujita, O.; Ito, K.

1999-01-01

Spontaneous radiative ignition and transition to flame spread over thin cellulose fuel samples was studied aboard the USMP-3 STS-75 Space Shuttle mission, and in three test series in the 10 second Japan Microgravity Center (JAMIC). A focused beam from a tungsten/halogen lamp was used to ignite the center of the fuel sample while an external air flow was varied from 0 to 10 cm/s. Non-piloted radiative ignition of the paper was found to occur more easily in microgravity than in normal gravity. Ignition of the sample was achieved under all conditions studied (shuttle cabin air, 21%-50% O2 in JAMIC), with transition to flame spread occurring for all but the lowest oxygen and flow conditions. While radiative ignition in a quiescent atmosphere was achieved, the flame quickly extinguished in air. The ignition delay time was proportional to the gas-phase mixing time, which is estimated using the inverse flow rate. The ignition delay was a much stronger function of flow at lower oxygen concentrations. After ignition, the flame initially spread only upstream, in a fan-shaped pattern. The fan angle increased with increasing external flow and oxygen concentration from zero angle (tunneling flame spread) at the limiting 0.5 cm/s external air flow, to 90 degrees (semicircular flame spread) for external flows at and above 5 cm/s, and higher oxygen concentrations. The fan angle was shown to be directly related to the limiting air flow velocity. Despite the convective heating from the upstream flame, the downstream flame was inhibited due to the 'oxygen shadow' of the upstream flame for the air flow conditions studied. Downstream flame spread rates in air, measured after upstream flame spread was complete and extinguished, were slower than upstream flame spread rates at the same flow. The quench regime for the transition to flame spread was skewed toward the downstream, due to the augmenting role of diffusion for opposed flow flame spread, versus the canceling effect of diffusion at very low cocurrent flows.

Closed loop adaptive optics for microscopy without a wavefront sensor

PubMed Central

Kner, Peter; Winoto, Lukman; Agard, David A.; Sedat, John W.

2013-01-01

A three-dimensional wide-field image of a small fluorescent bead contains more than enough information to accurately calculate the wavefront in the microscope objective back pupil plane using the phase retrieval technique. The phase-retrieved wavefront can then be used to set a deformable mirror to correct the point-spread function (PSF) of the microscope without the use of a wavefront sensor. This technique will be useful for aligning the deformable mirror in a widefield microscope with adaptive optics and could potentially be used to correct aberrations in samples where small fluorescent beads or other point sources are used as reference beacons. Another advantage is the high resolution of the retrieved wavefont as compared with current Shack-Hartmann wavefront sensors. Here we demonstrate effective correction of the PSF in 3 iterations. Starting from a severely aberrated system, we achieve a Strehl ratio of 0.78 and a greater than 10-fold increase in maximum intensity. PMID:24392198