Stray Light Analysis

NASA Technical Reports Server (NTRS)

1997-01-01

Based on a Small Business Innovation Research contract from the Jet Propulsion Laboratory, TracePro is state-of-the-art interactive software created by Lambda Research Corporation to detect stray light in optical systems. An image can be ruined by incidental light in an optical system. To maintain image excellence from an optical system, stray light must be detected and eliminated. TracePro accounts for absorption, specular reflection and refraction, scattering and aperture diffraction of light. Output from the software consists of spatial irradiance plots and angular radiance plots. Results can be viewed as contour maps or as ray histories in tabular form. TracePro is adept at modeling solids such as lenses, baffles, light pipes, integrating spheres, non-imaging concentrators, and complete illumination systems. The firm's customer base includes Lockheed Martin, Samsung Electronics and other manufacturing, optical, aerospace, and educational companies worldwide.

Computer program for optical systems ray tracing

NASA Technical Reports Server (NTRS)

Ferguson, T. J.; Konn, H.

1967-01-01

Program traces rays of light through optical systems consisting of up to 65 different optical surfaces and computes the aberrations. For design purposes, paraxial tracings with astigmation and third order tracings are provided.

Evaluation of simulation alternatives for the brute-force ray-tracing approach used in backlight design

NASA Astrophysics Data System (ADS)

Desnijder, Karel; Hanselaer, Peter; Meuret, Youri

2016-04-01

A key requirement to obtain a uniform luminance for a side-lit LED backlight is the optimised spatial pattern of structures on the light guide that extract the light. The generation of such a scatter pattern is usually performed by applying an iterative approach. In each iteration, the luminance distribution of the backlight with a particular scatter pattern is analysed. This is typically performed with a brute-force ray-tracing algorithm, although this approach results in a time-consuming optimisation process. In this study, the Adding-Doubling method is explored as an alternative way for evaluating the luminance of a backlight. Due to the similarities between light propagating in a backlight with extraction structures and light scattering in a cloud of light scatterers, the Adding-Doubling method which is used to model the latter could also be used to model the light distribution in a backlight. The backlight problem is translated to a form upon which the Adding-Doubling method is directly applicable. The calculated luminance for a simple uniform extraction pattern with the Adding-Doubling method matches the luminance generated by a commercial raytracer very well. Although successful, no clear computational advantage over ray tracers is realised. However, the dynamics of light propagation in a light guide as used the Adding-Doubling method, also allow to enhance the efficiency of brute-force ray-tracing algorithms. The performance of this enhanced ray-tracing approach for the simulation of backlights is also evaluated against a typical brute-force ray-tracing approach.

Examining the Effects of Chromatic Aberration, Object Distance, and Eye Shape on Image-Formation in the Mirror-Based Eyes of the Bay Scallop Argopecten irradians.

PubMed

Speiser, Daniel I; Gagnon, Yakir Luc; Chhetri, Raghav K; Oldenburg, Amy L; Johnsen, Sönke

2016-11-01

The eyes of scallops form images using a concave spherical mirror and contain two separate retinas, one layered on top of the other. Behavioral and electrophysiological studies indicate that the images formed by these eyes have angular resolutions of about 2°. Based on previous ray-tracing models, it has been thought that the more distal of the two retinas lies near the focal point of the mirror and that the proximal retina, positioned closer to the mirror at the back of the eye, receives light that is out-of-focus. Here, we propose three mechanisms through which both retinas may receive focused light: (1) chromatic aberration produced by the lens may cause the focal points for longer and shorter wavelengths to fall near the distal and proximal retinas, respectively; (2) focused light from near and far objects may fall on the distal and proximal retinas, respectively; and (3) the eyes of scallops may be dynamic structures that change shape to determine which retina receives focused light. To test our hypotheses, we used optical coherence tomography (OCT), a method of near-infrared optical depth-ranging, to acquire virtual cross-sections of live, intact eyes from the bay scallop Argopecten irradians Next, we used a custom-built ray-tracing model to estimate the qualities of the images that fall on an eye's distal and proximal retinas as functions of the wavelengths of light entering the eye (400-700 nm), object distances (0.01-1 m), and the overall shape of the eye. When we assume 550 nm wavelength light and object distances greater than 0.01 m, our model predicts that the angular resolutions of the distal and proximal retinas are 2° and 7°, respectively. Our model also predicts that neither chromatic aberration nor differences in object distance lead to focused light falling on the distal and proximal retinas simultaneously. However, if scallops can manipulate the shapes of their eyes, perhaps through muscle contractions, we speculate that they may be able to influence the qualities of the images that fall on their proximal retinas and-to a lesser extent-those that fall on their distal retinas as well. © The Author 2016. Published by Oxford University Press on behalf of the Society for Integrative and Comparative Biology.

Examining the Effects of Chromatic Aberration, Object Distance, and Eye Shape on Image-Formation in the Mirror-Based Eyes of the Bay Scallop Argopecten irradians

PubMed Central

Speiser, Daniel I.; Gagnon, Yakir Luc; Chhetri, Raghav K.; Oldenburg, Amy L.; Johnsen, Sönke

2016-01-01

The eyes of scallops form images using a concave spherical mirror and contain two separate retinas, one layered on top of the other. Behavioral and electrophysiological studies indicate that the images formed by these eyes have angular resolutions of about 2°. Based on previous ray-tracing models, it has been thought that the more distal of the two retinas lies near the focal point of the mirror and that the proximal retina, positioned closer to the mirror at the back of the eye, receives light that is out-of-focus. Here, we propose three mechanisms through which both retinas may receive focused light: (1) chromatic aberration produced by the lens may cause the focal points for longer and shorter wavelengths to fall near the distal and proximal retinas, respectively; (2) focused light from near and far objects may fall on the distal and proximal retinas, respectively; and (3) the eyes of scallops may be dynamic structures that change shape to determine which retina receives focused light. To test our hypotheses, we used optical coherence tomography (OCT), a method of near-infrared optical depth-ranging, to acquire virtual cross-sections of live, intact eyes from the bay scallop Argopecten irradians. Next, we used a custom-built ray-tracing model to estimate the qualities of the images that fall on an eye’s distal and proximal retinas as functions of the wavelengths of light entering the eye (400–700 nm), object distances (0.01–1 m), and the overall shape of the eye. When we assume 550 nm wavelength light and object distances greater than 0.01 m, our model predicts that the angular resolutions of the distal and proximal retinas are 2° and 7°, respectively. Our model also predicts that neither chromatic aberration nor differences in object distance lead to focused light falling on the distal and proximal retinas simultaneously. However, if scallops can manipulate the shapes of their eyes, perhaps through muscle contractions, we speculate that they may be able to influence the qualities of the images that fall on their proximal retinas and—to a lesser extent—those that fall on their distal retinas as well. PMID:27549200

Effect of Surface Reflectivity Variations On Uv-visible Limb Scattering Measurements of The Atmosphere

NASA Astrophysics Data System (ADS)

Oikarinen, L.

Solar UV and visible radiation scattered at the limb of the Earth's atmosphere is used for measuring density profiles of atmosperic trace gases. For example, the OSIRIS instrument on Odin and SCIAMACHY on Envisat use this technique. A limb-viewing instrument does not see Earth's surface or tropospheric clouds directly. However, in- direct light reflected from the surface or low altitude clouds can make up tens of per cents of the signal. Furthermore, the surface area that contributes to limb intensity ex- tends over 1000 km along the instrument line-of-sight and 200 km across it. Over this area surface reflectivity can vary from almost 0% to 100%. Inaccurate modelling of reflected intensity is a potential source of error in the trace gas retrieval. Generally, radiative transfer models used for analysing limb measure- ments have to assume that the surface has a constant albedo. We have used a three- dimensional Monte Carlo radiative transfer model to study the effects of surface vari- ation to limb radiance. Based on the simulations, we have developed an approximate method for averaging surface albedo for limb scattering measurements with the help of a simple single scattering radiative transfer model.

Searching for biological traces on different materials using a forensic light source and infrared photography.

PubMed

Sterzik, V; Panzer, S; Apfelbacher, M; Bohnert, M

2016-05-01

Because biological traces often play an important role in the investigation process of criminal acts, their detection is essential. As they are not always visible to the human eye, tools like a forensic light source or infrared photography can be used. The intention of the study presented was to give advice how to visualize biological traces best. Which wavelengths and/or filters give the best results for different traces on different fabrics of different colors? Therefore, blood (undiluted and diluted), semen, urine, saliva, and perspiration have been examined on 29 different materials.

Polyarnye siyaniya sistemy avroral'nogo ovala kak kosmoloficheskij obraz drevnej mifologii %t The northern light of the auroral oval system as a cosmological concept of the archaic mythology

NASA Astrophysics Data System (ADS)

Alekseeva, L. M.

Since archaic epochs people attentively observe the sky. They used to associate the sky phenomena with gods, heroes, spirits, etc. People interpreted the regularities in the motion of celestial objects in terms of their mythological model of the Universe. These observations and interpretations were first steps of the archaeoastronomy. Many remarkable features are inherent in the patterns of northern lights of the auroral oval system. Their manifestations are fairly regular. Did the ancients observe and some how classify these northern light phenomena? If yes, with which mythological personages were they associated? When were studies of the polar lights initiated? The present work is an attempt to answer these questions. We shall see that the ancient people assumed the spirit-world to be situated on the North. If so, it should manifest itself in spectacular polar aurorae. The specifically northern mythic cosmology formed the basis for Slavic fairy tales (theme of the Serpent and Serpent Fighter) and folk-beliefs. Other inhabitants of snowy latitudes should also manifest similar views. Studying the mythological reflections of typical auroral phenomena, it is possible to trace up long-standing ideological trends from the late glaciation epoch to the present time. Our results can help geophysicists in studying paleoauroral phenomena.

Asymptotic Solutions for Optical Properties of Large Particles with Strong Absorption

NASA Technical Reports Server (NTRS)

Yang, Ping; Gao, Bo-Cai; Baum, Bryan A.; Hu, Yong X.; Wiscombe, Warren J.; Mishchenko, Michael I.; Winker, Dave M.; Nasiri, Shaima L.; Einaudi, Franco (Technical Monitor)

2000-01-01

For scattering calculations involving nonspherical particles such as ice crystals, we show that the transverse wave condition is not applicable to the refracted electromagnetic wave in the context of geometric optics when absorption is involved. Either the TM wave condition (i.e., where the magnetic field of the refracted wave is transverse with respect to the wave direction) or the TE wave condition (i.e., where the electric field is transverse with respect to the propagating direction of the wave) may be assumed for the refracted wave in an absorbing medium to locally satisfy the electromagnetic boundary condition in the ray tracing calculation. The wave mode assumed for the refracted wave affects both the reflection and refraction coefficients. As a result, a nonunique solution for these coefficients is derived from the electromagnetic boundary condition. In this study we have identified the appropriate solution for the Fresnel reflection/refraction coefficients in light scattering calculation based on the ray tracing technique. We present the 3 x 2 refraction or transmission matrix that completely accounts for the inhomogeneity of the refracted wave in an absorbing medium. Using the Fresnel coefficients for an absorbing medium, we derive an asymptotic solution in an analytical format for the scattering properties of a general polyhedral particle. Numerical results are presented for hexagonal plates and columns with both preferred and random orientations. The asymptotic theory can produce reasonable accuracy in the phase function calculations in the infrared window region (wavelengths near 10 micron) if the particle size (in diameter) is on the order of 40 micron or larger. However, since strong absorption is assumed in the computation of the single-scattering albedo in the asymptotic theory, the single scattering albedo does not change with variation of the particle size. As a result, the asymptotic theory can lead to substantial errors in the computation of single-scattering albedo for small and moderate particle sizes. However, from comparison of the asymptotic results with the FDTD solution, it is expected that a convergence between the FDTD results and the asymptotic theory results can be reached when the particle size approaches 200 micron. We show that the phase function at side-scattering and backscattering angles is insensitive to particle shape if the random orientation condition is assumed. However, if preferred orientations are assumed for particles, the phase function has a strong dependence on scattering azimuthal angle. The single-scattering albedo also shows very strong dependence on the inclination angle of incident radiation with respect to the rotating axis for the preferred particle orientations.

THE PANCHROMATIC HUBBLE ANDROMEDA TREASURY. II. TRACING THE INNER M31 HALO WITH BLUE HORIZONTAL BRANCH STARS

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

Williams, Benjamin F.; Dalcanton, Julianne J.; Gilbert, Karoline M.

We attempt to constrain the shape of M31's inner stellar halo by tracing the surface density of blue horizontal branch (BHB) stars at galactocentric distances ranging from 2 kpc to 35 kpc. Our measurements make use of resolved stellar photometry from a section of the Panchromatic Hubble Andromeda Treasury survey, supplemented by several archival Hubble Space Telescope observations. We find that the ratio of BHB to red giant stars is relatively constant outside of 10 kpc, suggesting that the BHB is as reliable a tracer of the halo population as the red giant branch. In the inner halo, we domore » not expect BHB stars to be produced by the high-metallicity bulge and disk, making BHB stars a good candidate to be a reliable tracer of the stellar halo to much smaller galactocentric distances. If we assume a power-law profile r {sup -{alpha}} for the two-dimensional (2D) projected surface density BHB distribution, we obtain a high-quality fit with a 2D power-law index of {alpha} = 2.6{sup +0.3} {sub -0.2} outside of 3 kpc, which flattens to {alpha} < 1.2 inside of 3 kpc. This slope is consistent with previous measurements but is anchored to a radial baseline that extends much farther inward. Finally, assuming azimuthal symmetry and a constant mass-to-light ratio, the best-fitting profile yields a total halo stellar mass of 2.1{sup +1.7} {sub -0.4} Multiplication-Sign 10{sup 9} M {sub Sun }. These properties are comparable with both simulations of stellar halo formation by satellite disruption alone and simulations that include some in situ formation of halo stars.« less

The coherence length of the peculiar velocity field in the universe and the large-scale galaxy correlation data

NASA Technical Reports Server (NTRS)

Kashlinsky, A.

1992-01-01

This study presents a method for obtaining the true rms peculiar flow in the universe on scales up to 100-120/h Mpc using APM data as an input assuming only that peculiar motions are caused by peculiar gravity. The comparison to the local (Great Attractor) flow is expected to give clear information on the density parameter, Omega, and the local bias parameter, b. The observed peculiar flows in the Great Attractor region are found to be in better agreement with the open (Omega = 0.1) universe in which light traces mass (b = 1) than with a flat (Omega = 1) universe unless the bias parameter is unrealistically large (b is not less than 4). Constraints on Omega from a comparison of the APM and PV samples are discussed.

Logistics of community smallpox control through contact tracing and ring vaccination: a stochastic network model.

PubMed

Porco, Travis C; Holbrook, Karen A; Fernyak, Susan E; Portnoy, Diane L; Reiter, Randy; Aragón, Tomás J

2004-08-06

Previous smallpox ring vaccination models based on contact tracing over a network suggest that ring vaccination would be effective, but have not explicitly included response logistics and limited numbers of vaccinators. We developed a continuous-time stochastic simulation of smallpox transmission, including network structure, post-exposure vaccination, vaccination of contacts of contacts, limited response capacity, heterogeneity in symptoms and infectiousness, vaccination prior to the discontinuation of routine vaccination, more rapid diagnosis due to public awareness, surveillance of asymptomatic contacts, and isolation of cases. We found that even in cases of very rapidly spreading smallpox, ring vaccination (when coupled with surveillance) is sufficient in most cases to eliminate smallpox quickly, assuming that 95% of household contacts are traced, 80% of workplace or social contacts are traced, and no casual contacts are traced, and that in most cases the ability to trace 1-5 individuals per day per index case is sufficient. If smallpox is assumed to be transmitted very quickly to contacts, it may at times escape containment by ring vaccination, but could be controlled in these circumstances by mass vaccination. Small introductions of smallpox are likely to be easily contained by ring vaccination, provided contact tracing is feasible. Uncertainties in the nature of bioterrorist smallpox (infectiousness, vaccine efficacy) support continued planning for ring vaccination as well as mass vaccination. If initiated, ring vaccination should be conducted without delays in vaccination, should include contacts of contacts (whenever there is sufficient capacity) and should be accompanied by increased public awareness and surveillance.

Testing light-traces-mass in Hubble Frontier Fields Cluster MACS-J0416.1-2403

DOE PAGES

Sebesta, Kevin; Williams, Liliya L. R.; Mohammed, Irshad; ...

2016-06-17

Here, we reconstruct the projected mass distribution of a massive merging Hubble Frontier Fields cluster MACSJ0416 using the genetic algorithm based free-form technique called Grale. The reconstructions are constrained by 149 lensed images identified by Jauzac et al. using HFF data. No information about cluster galaxies or light is used, which makes our reconstruction unique in this regard. Using visual inspection of the maps, as well as galaxy-mass correlation functions we conclude that overall light does follow mass. Furthermore, the fact that brighter galaxies are more strongly clustered with mass is an important confirmation of the standard biasing scenario inmore » galaxy clusters. On the smallest scales, approximately less than a few arcseconds, the resolution afforded by 149 images is still not sufficient to confirm or rule out galaxy-mass offsets of the kind observed in ACO 3827. We also compare the mass maps of MACSJ0416 obtained by three different groups: Grale, and two parametric Lenstool reconstructions from the CATS and Sharon/Johnson teams. Overall, the three agree well; one interesting discrepancy between Grale and Lenstool galaxy-mass correlation functions occurs on scales of tens of kpc and may suggest that cluster galaxies are more biased tracers of mass than parametric methods generally assume.« less

Testing light-traces-mass in Hubble Frontier Fields Cluster MACS-J0416.1-2403

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

Sebesta, Kevin; Williams, Liliya L. R.; Mohammed, Irshad

Here, we reconstruct the projected mass distribution of a massive merging Hubble Frontier Fields cluster MACSJ0416 using the genetic algorithm based free-form technique called Grale. The reconstructions are constrained by 149 lensed images identified by Jauzac et al. using HFF data. No information about cluster galaxies or light is used, which makes our reconstruction unique in this regard. Using visual inspection of the maps, as well as galaxy-mass correlation functions we conclude that overall light does follow mass. Furthermore, the fact that brighter galaxies are more strongly clustered with mass is an important confirmation of the standard biasing scenario inmore » galaxy clusters. On the smallest scales, approximately less than a few arcseconds, the resolution afforded by 149 images is still not sufficient to confirm or rule out galaxy-mass offsets of the kind observed in ACO 3827. We also compare the mass maps of MACSJ0416 obtained by three different groups: Grale, and two parametric Lenstool reconstructions from the CATS and Sharon/Johnson teams. Overall, the three agree well; one interesting discrepancy between Grale and Lenstool galaxy-mass correlation functions occurs on scales of tens of kpc and may suggest that cluster galaxies are more biased tracers of mass than parametric methods generally assume.« less

National Ignition Facility main laser stray light analysis and control

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

English, R E; Miller, J L; Peterson, G

1998-06-26

Stray light analysis has been carried out for the main laser section of the National Ignition Facility main laser section using a comprehensive non-sequential ray trace model supplemented with additional ray trace and diffraction propagation modeling. This paper describes the analysis and control methodology, gives examples of ghost paths and required tilted lenses, baffles, absorbers, and beam dumps, and discusses analysis of stray light "pencil beams" in the system.

Response of Southern Ocean Phytoplankton Communities to Trace Metal (including Iron) and Light Availability

NASA Astrophysics Data System (ADS)

Fietz, S.; Roychoudhury, A. N.; Thomalla, S.; Mtshali, T. N.; Philibert, R.; Van Horsten, N.; Loock, J. C.; Cloete, R.

2016-02-01

Phytoplankton primary productivity depends on macro- and micronutrient availability and in turn plays a key role in the marine biogeochemical cycles. The role of iron in regulating phytoplankton primary production and thus biogeochemical cycles in the Southern Ocean has been widely recognized; however, it also became obvious that iron is not the sole factor limiting primary production in the Southern Ocean and that light, for instance, might aggravate or relief trace nutrient limitation. We conducted a suite of ship-board incubation experiments in austral summer 2013/14, 2014/15 and winter 2015 to shed light on the complex interplay between trace metal and light limitation. We observed a strong difference in acclimation and photophysiological response depending on the environmental conditions of the in-situ communities prior to the experiment. The differences in acclimation and photophysiological responses resulted in different growth and macronutrient uptake rates. Revisited stations did, however, not always show the same responses. At at least one station we will link the incubation experiments to the in-situ vertical profiles of trace metals, macronutrients and primary productivity.

Ray-tracing analysis of intraocular lens power in situ.

PubMed

Olsen, Thomas; Funding, Mikkel

2012-04-01

To describe a method for back-solving the power of an intraocular lens (IOL) in situ based on laser biometry and ray-tracing analysis of the pseudophakic eye. University Eye Clinic, Aarhus Hospital, Aarhus, Denmark. Evaluation of diagnostic test or technology. This study comprised pseudophakic eyes with an IOL power ranging from -2.00 to +36.00 diopters (D). Preoperatively, the corneal radius was measured with conventional autokeratometry and the axial length (AL) with optical biometry. After surgery, the position of the IOL was recorded using laser interferometry. Based on the postoperative refraction and the biometric measurements, a ray-tracing analysis was performed back-solving for the power of the IOL in situ. The analysis was performed assuming pupil diameters from 0.0 to 8.0 mm with and without correction for the Stiles-Crawford effect. The study evaluated 767 pseudophakic eyes (583 patients). Assuming a 3.0 mm pupil, the mean prediction error between the labeled and the calculated IOL power (± 1 standard deviation [SD]) was -0.26 D ± 0.65 (SD) (range -2.4 to +1.8 D). The prediction error showed no bias with IOL power or with AL. The calculated IOL power depended on the assumed pupil size and the Stiles-Crawford effect. However, the latter had a modulatory effect on the prediction error for large pupil diameters (>5.0 mm) only. The optics of the pseudophakic eye can be accurately described using exact ray tracing and modern biometric techniques. Copyright © 2012 ASCRS and ESCRS. Published by Elsevier Inc. All rights reserved.

Simulation of photons from plasmas for the applications to display devices

NASA Astrophysics Data System (ADS)

Lee, Hae June; Yoon, Hyun Jin; Lee, Jae Koo

2007-07-01

Numerical modeling of the photon transport of the ultraviolet (UV) and the visible lights are presented for plasma based display devices. The transport of UV lights which undergo resonance trapping by ground state atoms is solved by using the Holstein equation. After the UV lights are transformed to visible lights at the phosphor surfaces, the visible lights experience complicated traces inside the cell and finally are emitted toward the viewing window after having some power loss within the cell. A three-dimensional ray trace of the visible lights is calculated with a radiosity model. These simulations for the photons strengthen plasma discharge modeling for the application to display devices.

Laser Light Scattering by Shock Waves

NASA Technical Reports Server (NTRS)

Panda, J.; Adamovsky, G.

1995-01-01

Scattering of coherent light as it propagates parallel to a shock wave, formed in front of a bluff cylindrical body placed in a supersonic stream, is studied experimentally and numerically. Two incident optical fields are considered. First, a large diameter collimated beam is allowed to pass through the shock containing flow. The light intensity distribution in the resultant shadowgraph image, measured by a low light CCD camera, shows well-defined fringes upstream and downstream of the shadow cast by the shock. In the second situation, a narrow laser beam is brought to a grazing incidence on the shock and the scattered light, which appears as a diverging sheet from the point of interaction, is visualized and measured on a screen placed normal to the laser path. Experiments are conducted on shocks formed at various free-stream Mach numbers, M, and total pressures, P(sub 0). It is found that the widths of the shock shadows in a shadowgraph image become independent of M and P(sub 0) when plotted against the jump in the refractive index, (Delta)n, created across the shock. The total scattered light measured from the narrow laser beam and shock interaction also follows the same trend. In the numerical part of the study, the shock is assumed to be a 'phase object', which introduces phase difference between the upstream and downstream propagating parts of the light disturbances. For a given shape and (Delta)n of the bow shock the phase and amplitude modulations are first calculated by ray tracing. The wave front is then propagated to the screen using the Fresnet diffraction equation. The calculated intensity distribution, for both of the incident optical fields, shows good agreement with the experimental data.

Modeling Geometric Arrangements of TiO2-Based Catalyst Substrates and Isotropic Light Sources to Enhance the Efficiency of a Photocatalystic Oxidation (PCO) Reactor

NASA Technical Reports Server (NTRS)

Richards, Jeffrey T.; Levine, Lanfang H.; Husk, Geoffrey K.

2011-01-01

The closed confined environments of the ISS, as well as in future spacecraft for exploration beyond LEO, provide many challenges to crew health. One such challenge is the availability of a robust, energy efficient, and re-generable air revitalization system that controls trace volatile organic contaminants (VOCs) to levels below a specified spacecraft maximum allowable concentration (SMAC). Photocatalytic oxidation (PCO), which is capable of mineralizing VOCs at room temperature and of accommodating a high volumetric flow, is being evaluated as an alternative trace contaminant control technology. In an architecture of a combined air and water management system, placing a PCO unit before a condensing heat exchanger for humidity control will greatly reduce the organic load into the humidity condensate loop ofthe water processing assembly (WPA) thereby enhancing the life cycle economics ofthe WPA. This targeted application dictates a single pass efficiency of greater than 90% for polar VOCs. Although this target was met in laboratory bench-scaled reactors, no commercial or SBIR-developed prototype PCO units examined to date have achieved this goal. Furthermore, the formation of partial oxidation products (e.g., acetaldehyde) was not eliminated. It is known that single pass efficiency and partial oxidation are strongly dependent upon the contact time and catalyst illumination, hence the requirement for an efficient reactor design. The objective of this study is to maximize the apparent contact time and illuminated catalyst surface area at a given reactor volume and volumetric flow. In this study, a Ti02-based photocatalyst is assumed to be immobilized on porous substrate panels and illumination derived from linear isotropic light sources. Mathematical modeling using computational fluid dynamics (CFD) analyses were performed to investigate the effect of: 1) the geometry and configuration of catalyst-coated substrate panels, 2) porosity of the supporting substrate, and 3) varying the light source and spacing on contact time and illuminated catalyst area.

Miniature Tunable Laser Spectrometer for Detection of a Trace Gas

NASA Technical Reports Server (NTRS)

Christensen, Lance E. (Inventor)

2017-01-01

An open-path laser spectrometer (OPLS) for measuring a concentration of a trace gas, the OPLS including an open-path multi-pass analysis region including a first mirror, a second mirror at a distance and orientation from the first mirror, and a support structure for locating the mirrors, a laser coupled to the analysis region and configured to emit light of a wavelength range and to enable a plurality of reflections of the emitted light between the mirrors, a detector coupled to the analysis region and configured to detect a portion of the emitted light impinging on the detector and to generate a corresponding signal, and an electronic system coupled to the laser and the detector, and configured to adjust the wavelength range of the emitted light from the laser based on the generated signal, and to measure the concentration of the trace gas based on the generated signal.

Cosmic background radiation anisotropies in universes dominated by nonbaryonic dark matter

NASA Technical Reports Server (NTRS)

Bond, J. R.; Efstathiou, G.

1984-01-01

Detailed calculations of the temperature fluctuations in the cosmic background radiation for universes dominated by massive collisionless relics of the big bang are presented. An initially adiabatic constant curvature perturbation spectrum is assumed. In models with cold dark matter, the simplest hypothesis - that galaxies follow the mass distribution leads to small-scale anisotropies which exceed current observational limits if omega is less than 0.2 h to the -4/3. Since low values of omega are indicated by dynamical studies of galaxy clustering, cold particle models in which light traces mass are probably incorrect. Reheating of the pregalactic medium is unlikely to modify this conclusion. In cold particle or neutrino-dominated universes with omega = 1, presented predictions for small-scale and quadrupole anisotropies are below current limits. In all cases, the small-scale fluctuations are predicted to be about 10 percent linearly polarized.

Gravitational Lensing: Einstein's unfinished symphony

NASA Astrophysics Data System (ADS)

Treu, Tommaso; Ellis, Richard S.

2015-01-01

Gravitational lensing - the deflection of light rays by gravitating matter - has become a major tool in the armoury of the modern cosmologist. Proposed nearly a hundred years ago as a key feature of Einstein's theory of general relativity, we trace the historical development since its verification at a solar eclipse in 1919. Einstein was apparently cautious about its practical utility and the subject lay dormant observationally for nearly 60 years. Nonetheless there has been rapid progress over the past twenty years. The technique allows astronomers to chart the distribution of dark matter on large and small scales thereby testing predictions of the standard cosmological model which assumes dark matter comprises a massive weakly-interacting particle. By measuring the distances and tracing the growth of dark matter structure over cosmic time, gravitational lensing also holds great promise in determining whether the dark energy, postulated to explain the accelerated cosmic expansion, is a vacuum energy density or a failure of general relativity on large scales. We illustrate the wide range of applications which harness the power of gravitational lensing, from searches for the earliest galaxies magnified by massive clusters to those for extrasolar planets which temporarily brighten a background star. We summarise the future prospects with dedicated ground and space-based facilities designed to exploit this remarkable physical phenomenon.

Canopy polarized BRDF simulation based on non-stationary Monte Carlo 3-D vector RT modeling

NASA Astrophysics Data System (ADS)

Kallel, Abdelaziz; Gastellu-Etchegorry, Jean Philippe

2017-03-01

Vector radiative transfer (VRT) has been largely used to simulate polarized reflectance of atmosphere and ocean. However it is still not properly used to describe vegetation cover polarized reflectance. In this study, we try to propose a 3-D VRT model based on a modified Monte Carlo (MC) forward ray tracing simulation to analyze vegetation canopy reflectance. Two kinds of leaf scattering are taken into account: (i) Lambertian diffuse reflectance and transmittance and (ii) specular reflection. A new method to estimate the condition on leaf orientation to produce reflection is proposed, and its probability to occur, Pl,max, is computed. It is then shown that Pl,max is low, but when reflection happens, the corresponding radiance Stokes vector, Io, is very high. Such a phenomenon dramatically increases the MC variance and yields to an irregular reflectance distribution function. For better regularization, we propose a non-stationary MC approach that simulates reflection for each sunny leaf assuming that its orientation is randomly chosen according to its angular distribution. It is shown in this case that the average canopy reflection is proportional to Pl,max ·Io which produces a smooth distribution. Two experiments are conducted: (i) assuming leaf light polarization is only due to the Fresnel reflection and (ii) the general polarization case. In the former experiment, our results confirm that in the forward direction, canopy polarizes horizontally light. In addition, they show that in inclined forward direction, diagonal polarization can be observed. In the latter experiment, polarization is produced in all orientations. It is particularly pointed out that specular polarization explains just a part of the forward polarization. Diffuse scattering polarizes light horizontally and vertically in forward and backward directions, respectively. Weak circular polarization signal is also observed near the backscattering direction. Finally, validation of the non-polarized reflectance using the ROMC tool is done, and our model shows good agreement with the ROMC reference.

Comparison between ray-tracing and physical optics for the computation of light absorption in capillaries--the influence of diffraction and interference.

PubMed

Qin, Yuan; Michalowski, Andreas; Weber, Rudolf; Yang, Sen; Graf, Thomas; Ni, Xiaowu

2012-11-19

Ray-tracing is the commonly used technique to calculate the absorption of light in laser deep-penetration welding or drilling. Since new lasers with high brilliance enable small capillaries with high aspect ratios, diffraction might become important. To examine the applicability of the ray-tracing method, we studied the total absorptance and the absorbed intensity of polarized beams in several capillary geometries. The ray-tracing results are compared with more sophisticated simulations based on physical optics. The comparison shows that the simple ray-tracing is applicable to calculate the total absorptance in triangular grooves and in conical capillaries but not in rectangular grooves. To calculate the distribution of the absorbed intensity ray-tracing fails due to the neglected interference, diffraction, and the effects of beam propagation in the capillaries with sub-wavelength diameter. If diffraction is avoided e.g. with beams smaller than the entrance pupil of the capillary or with very shallow capillaries, the distribution of the absorbed intensity calculated by ray-tracing corresponds to the local average of the interference pattern found by physical optics.

Light ray tracing through a leaf cross section

NASA Technical Reports Server (NTRS)

Kumar, R.; Silva, L. F.

1973-01-01

A light ray, incident at about 5 deg to the normal, is geometrically plotted through the drawing of the cross section of a soybean leaf using Fresnel's equations and Snell's law. The optical mediums of the leaf considered for ray tracing are: air, cell sap, chloroplast, and cell wall. The ray is also drawn through the same leaf cross section with cell wall and air as the only optical mediums. The values of the reflection and transmission found from the ray tracing tests agree closely with the experimental results obtained using a Beckman Dk-2A Spectroreflector.

Ray trace visualization of negative refraction of light in two-dimensional air-bridged silicon photonic crystal slabs at 1.55 microm.

PubMed

Gan, Lin; Liu, Ya-Zhao; Li, Jiang-Yan; Zhang, Ze-Bo; Zhang, Dao-Zhong; Li, Zhi-Yuan

2009-06-08

We demonstrate design, fabrication, and ray trace observation of negative refraction of near-infrared light in a two-dimensional square lattice of air holes etched into an air-bridged silicon slab. Special surface morphologies are designed to reduce the impedance mismatch when light refracts from a homogeneous silicon slab into the photonic crystal slab. We clearly observed negative refraction of infrared light for TE-like modes in a broad wavelength range by using scanning near-field optical microscopy technology. The experimental results are in good agreement with finite-difference time-domain simulations. The results indicate the designed photonic crystal structure can serve as polarization beam splitter.

Effects of Water Depth, Seasonal Exposure, and Substrate Orientation on Microbial Bioerosion in the Ionian Sea (Eastern Mediterranean)

PubMed Central

Färber, Claudia; Wisshak, Max; Pyko, Ines; Bellou, Nikoleta; Freiwald, André

2015-01-01

The effects of water depth, seasonal exposure, and substrate orientation on microbioerosion were studied by means of a settlement experiment deployed in 15, 50, 100, and 250 m water depth south-west of the Peloponnese Peninsula (Greece). At each depth, an experimental platform was exposed for a summer period, a winter period, and about an entire year. On the up- and down-facing side of each platform, substrates were fixed to document the succession of bioerosion traces, and to measure variations in bioerosion and accretion rates. In total, 29 different bioerosion traces were recorded revealing a dominance of microborings produced by phototrophic and organotrophic microendoliths, complemented by few macroborings, attachment scars, and grazing traces. The highest bioerosion activity was recorded in 15 m up-facing substrates in the shallow euphotic zone, largely driven by phototrophic cyanobacteria. Towards the chlorophyte-dominated deep euphotic to dysphotic zones and the organotroph-dominated aphotic zone the intensity of bioerosion and the diversity of bioerosion traces strongly decreased. During summer the activity of phototrophs was higher than during winter, which was likely stimulated by enhanced light availability due to more hours of daylight and increased irradiance angles. Stable water column stratification and a resulting nutrient depletion in shallow water led to lower turbidity levels and caused a shift in the photic zonation that was reflected by more phototrophs being active at greater depth. With respect to the subordinate bioerosion activity of organotrophs, fluctuations in temperature and the trophic regime were assumed to be the main seasonal controls. The observed patterns in overall bioeroder distribution and abundance were mirrored by the calculated carbonate budget with bioerosion rates exceeding carbonate accretion rates in shallow water and distinctly higher bioerosion rates at all depths during summer. These findings highlight the relevance of bioerosion and accretion for the carbonate budget of the Ionian Sea. PMID:25893244

Ray tracing simulation of aero-optical effect using multiple gradient index layer

NASA Astrophysics Data System (ADS)

Yang, Seul Ki; Seong, Sehyun; Ryu, Dongok; Kim, Sug-Whan; Kwon, Hyeuknam; Jin, Sang-Hun; Jeong, Ho; Kong, Hyun Bae; Lim, Jae Wan; Choi, Jong Hwa

2016-10-01

We present a new ray tracing simulation of aero-optical effect through anisotropic inhomogeneous media as supersonic flow field surrounds a projectile. The new method uses multiple gradient-index (GRIN) layers for construction of the anisotropic inhomogeneous media and ray tracing simulation. The cone-shaped projectile studied has 19° semi-vertical angle; a sapphire window is parallel to the cone angle; and an optical system of the projectile was assumed via paraxial optics and infrared image detector. The condition for the steady-state solver conducted through computational fluid dynamics (CFD) included Mach numbers 4 and 6 in speed, 25 km altitude, and 0° angle of attack (AoA). The grid refractive index of the flow field via CFD analysis and Gladstone-Dale relation was discretized into equally spaced layers which are parallel with the projectile's window. Each layer was modeled as a form of 2D polynomial by fitting the refractive index distribution. The light source of ray set generated 3,228 rays for varying line of sight (LOS) from 10° to 40°. Ray tracing simulation adopted the Snell's law in 3D to compute the paths of skew rays in the GRIN layers. The results show that optical path difference (OPD) and boresight error (BSE) decreases exponentially as LOS increases. The variation of refractive index decreases, as the speed of flow field increases the OPD and its rate of decay at Mach number 6 in speed has somewhat larger value than at Mach number 4 in speed. Compared with the ray equation method, at Mach number 4 and 10° LOS, the new method shows good agreement, generated 0.33% of relative root-mean-square (RMS) OPD difference and 0.22% of relative BSE difference. Moreover, the simulation time of the new method was more than 20,000 times faster than the conventional ray equation method. The technical detail of the new method and simulation is presented with results and implication.

The SAMI Galaxy Survey: gas streaming and dynamical M/L in rotationally supported systems

NASA Astrophysics Data System (ADS)

Cecil, G.; Fogarty, L. M. R.; Richards, S.; Bland-Hawthorn, J.; Lange, R.; Moffett, A.; Catinella, B.; Cortese, L.; Ho, I.-T.; Taylor, E. N.; Bryant, J. J.; Allen, J. T.; Sweet, S. M.; Croom, S. M.; Driver, S. P.; Goodwin, M.; Kelvin, L.; Green, A. W.; Konstantopoulos, I. S.; Owers, M. S.; Lawrence, J. S.; Lorente, N. P. F.

2016-02-01

Line-of-sight velocities of gas and stars can constrain dark matter (DM) within rotationally supported galaxies if they trace circular orbits extensively. Photometric asymmetries may signify non-circular motions, requiring spectra with dense spatial coverage. Our integral-field spectroscopy of 178 galaxies spanned the mass range of the Sydney-AAO Multi-object integral field spectrograph (SAMI) Galaxy Survey. We derived circular speed curves (CSCs) of gas and stars from non-parametric fits out to r ˜ 2re. For 12/14 with measured H I profiles, ionized gas and H I maximum velocities agreed. We fitted mass-follows-light models to 163 galaxies by approximating the radial light profile as nested, very flattened mass homeoids viewed as a Sérsic form. Fitting broad-band spectral energy distributions to Sloan Digital Sky Survey images gave median stellar mass/light 1.7 assuming a Kroupa initial mass function (IMF) versus 2.6 dynamically. Two-thirds of the dynamical mass/light measures were consistent with star+remnant IMFs. One-fifth required upscaled starlight to fit, hence comparable mass of unobserved baryons and/or DM distributed like starlight across the SAMI aperture that came to dominate motions as the starlight CSCs declined rapidly. The rest had mass distributed differently from light. Subtracting fits of Sérsic radial profiles to 13 VIKING Z-band images revealed residual weak bars. Near the bar major axis, we assessed m = 2 streaming velocities, and found deviations usually <30 km s-1 from the CSC; three showed no deviation. Thus, asymmetries rarely influenced the CSC despite colocated shock-indicating, emission-line flux ratios in more than 2/3 of our sample.

Distance measurement based on light field geometry and ray tracing.

PubMed

Chen, Yanqin; Jin, Xin; Dai, Qionghai

2017-01-09

In this paper, we propose a geometric optical model to measure the distances of object planes in a light field image. The proposed geometric optical model is composed of two sub-models based on ray tracing: object space model and image space model. The two theoretic sub-models are derived on account of on-axis point light sources. In object space model, light rays propagate into the main lens and refract inside it following the refraction theorem. In image space model, light rays exit from emission positions on the main lens and subsequently impinge on the image sensor with different imaging diameters. The relationships between imaging diameters of objects and their corresponding emission positions on the main lens are investigated through utilizing refocusing and similar triangle principle. By combining the two sub-models together and tracing light rays back to the object space, the relationships between objects' imaging diameters and corresponding distances of object planes are figured out. The performance of the proposed geometric optical model is compared with existing approaches using different configurations of hand-held plenoptic 1.0 cameras and real experiments are conducted using a preliminary imaging system. Results demonstrate that the proposed model can outperform existing approaches in terms of accuracy and exhibits good performance at general imaging range.

Outlines of a multiple trace theory of temporal preparation.

PubMed

Los, Sander A; Kruijne, Wouter; Meeter, Martijn

2014-01-01

We outline a new multiple trace theory of temporal preparation (MTP), which accounts for behavior in reaction time (RT) tasks in which the participant is presented with a warning stimulus (S1) followed by a target stimulus (S2) that requires a speeded response. The theory assumes that during the foreperiod (FP; the S1-S2 interval) inhibition is applied to prevent premature response, while a wave of activation occurs upon the presentation of S2. On each trial, these actions are stored in a separate memory trace, which, jointly with earlier formed memory traces, starts contributing to preparation on subsequent trials. We show that MTP accounts for classic effects in temporal preparation, including mean RT-FP functions observed under a variety of FP distributions and asymmetric sequential effects. We discuss the advantages of MTP over other accounts of these effects (trace-conditioning and hazard-based explanations) and suggest a critical experiment to empirically distinguish among them.

Thermal Characterization of the Air Force Institute of Technology Solar Simulation Thermal Vacuum Chamber

DTIC Science & Technology

2014-03-27

mass and surface area, Equation 12 demonstrates an energy balance for the material, assuming the rest of the surfaces of the material are isothermal...radiation in order to dissipate heat from 18 the spacecraft [8]. As discussed in the system thermal energy balance defined previously, emission of IR... energy balance calculations will be utilized. The Monte Carlo/Ray Trace Radiation Method The Monte Carlo/Ray Trace method is utilized in order to

Applications of Blue Light-curing Acrylic Resin to Forensic Sample Preparation and Microtomy.

PubMed

Groves, Ethan; Palenik, Christopher S

2016-03-01

This study discusses the results of an evaluation of a one-part blue light-curing acrylic resin for embedding trace evidence prior to the preparation of thin sections with a microtome. Through a comparison to several epoxy resins, the physical properties relevant to both trace evidence examination and analytical microscopy in general, including as viscosity, clarity, color, hardness, and cure speed, were explored. Finally, thin sections from paint samples embedded in this acrylic resin were evaluated to determine if, through smearing or impregnation, the resin contributed to the infrared spectra. The results of this study show that blue light-curing acrylic resins provide the desired properties of an embedding medium, generate high-quality thin sections, and can significantly simplify the preparation of paint chips, fibers and a multitude of other types of microscopic samples in the forensic trace evidence laboratory. © 2015 American Academy of Forensic Sciences.

Geochemical modeling of low melt-fraction anatexis in a peraluminous system: The Pena Negra complex (central Spain)

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

Bea, F.

1991-07-01

A study was made of the chemical fractionation associated with four cases of anatectic segregation of low melt-fraction cordieritic granites from migmatized meta-greywackes. The aims of the study were to (1) reveal the fractionation patterns of major and trace elements, (2) compare the major element chemistry of leucogranites and the quantitative behavior of source minerals during anatexis - inferred by mass-balance adjustment - with available experimental data for peraluminous systems, and (3) discuss the behavior of trace elements in crustal melting by comparing the chemically determined composition of leucogranites with the results of three fractionation models. Two of these assumemore » a perfect diffusive behavior of trace elements within residual solids, but they use a different set of distribution coefficients. The third assumes a perfect nondiffusive behavior. In relation to their source rocks, the leucogranites are strongly depleted in Li, Transition Elements, and Light Rare Earth Elements, but enriched in K{sub 2}O, SiO{sub 2}, and Ba. Mass balance analysis using the Anatexis Mixing Model shows that the chemistry of cordierite leucogranites is compatible with its having originated by closed-system, water-undersaturated anatexis on previously migmatized meta-greywackes, leaving a residue enriched in cordierite plus biotite and exhausted in K-feldspar. Biotite melts congruently unless important amounts of sillimanite were also present in the source. Compared with experimental metals obtained from sources with the same chemical composition but with a different femic mineralogy (biotite + sillimanite, instead of cordierite + biotite), the Pena Negra leucogranites are richer in K{sub 2}O and MgO with a lower Fe/(Fe + Mg) ratio. The differences in magnesium are believed to result from the changes in the mineral assemblage of the source rocks.« less

Investigating Planetesimal Evolution by Experiments with Fe-Ni Metallic Melts: Light Element Composition Effects on Trace Element Partitioning Behavior

NASA Astrophysics Data System (ADS)

Chabot, N. L.

2017-12-01

As planetesimals were heated up in the early Solar System, the formation of Fe-Ni metallic melts was a common occurrence. During planetesimal differentiation, the denser Fe-Ni metallic melts separated from the less dense silicate components, though some meteorites suggest that their parent bodies only experienced partial differentiation. If the Fe-Ni metallic melts did form a central metallic core, the core eventually crystallized to a solid, some of which we sample as iron meteorites. In all of these planetesimal evolution processes, the composition of the Fe-Ni metallic melt influenced the process and the resulting trace element chemical signatures. In particular, the metallic melt's "light element" composition, those elements present in the metallic melt in a significant concentration but with lower atomic masses than Fe, can strongly affect trace element partitioning. Experimental studies have provided critical data to determine the effects of light elements in Fe-Ni metallic melts on trace element partitioning behavior. Here I focus on combining numerous experimental results to identify trace elements that provide unique insight into constraining the light element composition of early Solar System Fe-Ni metallic melts. Experimental studies have been conducted at 1 atm in a variety of Fe-Ni systems to investigate the effects of light elements on trace element partitioning behavior. A frequent experimental examination of the effects of light elements in metallic systems involves producing run products with coexisting solid metal and liquid metal phases. Such solid-metal-liquid-metal experiments have been conducted in the Fe-Ni binary system as well as Fe-Ni systems with S, P, and C. Experiments with O-bearing or Si-bearing Fe-Ni metallic melts do not lend themselves to experiments with coexisting solid metal and liquid metal phases, due to the phase diagrams of these elements, but experiments with two immiscible Fe-Ni metallic melts have provided insight into the qualitative effects of O and Si relative to the well-determined effects of S. Together, these experimental studies provide a robust dataset to identify key elements that are predicted to produce distinct chemical signatures as a function of different Fe-Ni metallic melt compositions during planetesimal evolution processes.

Light pollution offshore: Zenithal sky glow measurements in the mediterranean coastal waters

NASA Astrophysics Data System (ADS)

Ges, Xavier; Bará, Salvador; García-Gil, Manuel; Zamorano, Jaime; Ribas, Salvador J.; Masana, Eduard

2018-05-01

Light pollution is a worldwide phenomenon whose consequences for the natural environment and the human health are being intensively studied nowadays. Most published studies address issues related to light pollution inland. Coastal waters, however, are spaces of high environmental interest, due to their biodiversity richness and their economical significance. The elevated population density in coastal regions is accompanied by correspondingly large emissions of artificial light at night, whose role as an environmental stressor is increasingly being recognized. Characterizing the light pollution levels in coastal waters is a necessary step for protecting these areas. At the same time, the marine surface environment provides a stage free from obstacles for measuring the dependence of the skyglow on the distance to the light polluting sources, and validating (or rejecting) atmospheric light propagation models. In this work we present a proof-of-concept of a gimbal measurement system that can be used for zenithal skyglow measurements on board both small boats and large vessels under actual navigation conditions. We report the results obtained in the summer of 2016 along two measurement routes in the Mediterranean waters offshore Barcelona, travelling 9 and 31.7 km away from the coast. The atmospheric conditions in both routes were different from the ones assumed for the calculation of recently published models of the anthropogenic sky brightness. They were closer in the first route, whose results approach better the theoretical predictions. The results obtained in the second route, conducted under a clearer atmosphere, showed systematic differences that can be traced back to two expected phenomena, which are a consequence of the smaller aerosol content: the reduction of the anthropogenic sky glow at short distances from the sources, and the slower decay rate of brightness with distance, which gives rise to a relative excess of brightness at large distances from the coastline.

Fluorescence tomography using synchrotron radiation at the NSLS

NASA Astrophysics Data System (ADS)

Boisseau, P.; Grodzins, L.

1987-03-01

Fluorescence tomography utilizing focussed, tunable, monoenergetic X-rays from synchrotron light sources hold the promise of a non-invasive analytic tool for studying trace elements in specimens, particularly biological, at spatial resolutions of the order of micrometers. This note reports an early test at the National Synchrotron Light Source at Brookhaven National Laboratories in which fluorescence tomographic scans were successfully made of trace elements of iron and titanium in NBS standard glass and in a bee.

The application of UV LEDs for differential optical absorption spectroscopy

NASA Astrophysics Data System (ADS)

Geiko, Pavel P.; Smirnov, Sergey S.; Samokhvalov, Ignatii V.

2018-04-01

Modern UV LEDs represent a potentially very advantageous alternative to thermal light sources, in particular xenon arc lamps, which are the most common light sources in trace gas-analyzers. So, the light-emitting diodes are very attractive for use of as light sources for Long Path Differential Optical Absorption Spectroscopy (DOAS) measurements of trace gases in the open atmosphere. Recent developments in fibre-coupling telescope technology and the availability of ultraviolet light emitting diodes have now allowed us to construct a portable, long path DOAS instrument for use at remote locations and specifically for measuring degassing from active volcanic systems. First of all, we are talking about the measurement of sulphur dioxide, carbon disulphide and, oxides of chlorine and bromine. The parallel measurements of sulfur dioxide using a certified gas analyzer, were conducted and showed good correlation.

Divided multimodal attention sensory trace and context coding strategies in spatially congruent auditory and visual presentation.

PubMed

Kristjánsson, Tómas; Thorvaldsson, Tómas Páll; Kristjánsson, Arni

2014-01-01

Previous research involving both unimodal and multimodal studies suggests that single-response change detection is a capacity-free process while a discriminatory up or down identification is capacity-limited. The trace/context model assumes that this reflects different memory strategies rather than inherent differences between identification and detection. To perform such tasks, one of two strategies is used, a sensory trace or a context coding strategy, and if one is blocked, people will automatically use the other. A drawback to most preceding studies is that stimuli are presented at separate locations, creating the possibility of a spatial confound, which invites alternative interpretations of the results. We describe a series of experiments, investigating divided multimodal attention, without the spatial confound. The results challenge the trace/context model. Our critical experiment involved a gap before a change in volume and brightness, which according to the trace/context model blocks the sensory trace strategy, simultaneously with a roaming pedestal, which should block the context coding strategy. The results clearly show that people can use strategies other than sensory trace and context coding in the tasks and conditions of these experiments, necessitating changes to the trace/context model.

Relational Associative Learning Induces Cross-Modal Plasticity in Early Visual Cortex

PubMed Central

Headley, Drew B.; Weinberger, Norman M.

2015-01-01

Neurobiological theories of memory posit that the neocortex is a storage site of declarative memories, a hallmark of which is the association of two arbitrary neutral stimuli. Early sensory cortices, once assumed uninvolved in memory storage, recently have been implicated in associations between neutral stimuli and reward or punishment. We asked whether links between neutral stimuli also could be formed in early visual or auditory cortices. Rats were presented with a tone paired with a light using a sensory preconditioning paradigm that enabled later evaluation of successful association. Subjects that acquired this association developed enhanced sound evoked potentials in their primary and secondary visual cortices. Laminar recordings localized this potential to cortical Layers 5 and 6. A similar pattern of activation was elicited by microstimulation of primary auditory cortex in the same subjects, consistent with a cortico-cortical substrate of association. Thus, early sensory cortex has the capability to form neutral stimulus associations. This plasticity may constitute a declarative memory trace between sensory cortices. PMID:24275832

The effects of atmospheric refraction on the accuracy of laser ranging systems

NASA Technical Reports Server (NTRS)

Zanter, D. L.; Gardner, C. S.; Rao, N. N.

1976-01-01

Correction formulas derived by Saastamoinen and Marini, and the ray traces through the refractivity profiles all assume a spherically symmetric refractivity profile. The errors introduced by this assumption were investigated by ray tracing through three-dimensional profiles. The results of this investigation indicate that the difference between ray traces through the spherically symmetric and three-dimensional profiles is approximately three centimeters at 10 deg and decreases to less than one half of a centimeter at 80 deg. If the accuracy desired in future laser ranging systems is less than a few centimeters, Saastamoinen and Marini's formulas must be altered to account for the fact that the refractivity profile is not spherically symmetric.

The repair of low dose UV light-induced damage to human skin DNA in condition of trace amount Mg 2+

NASA Astrophysics Data System (ADS)

Gao, Fang; Guo, Zhouyi; Zheng, Changchun; Wang, Rui; Liu, Zhiming; Meng, Pei; Zhai, Juan

2008-12-01

Ultraviolet light-induced damage to human skin DNA was widely investigated. The primary mechanism of this damage contributed to form cyclobutane pyrimidine dimmers (CPDs). Although the distribution of UV light-induced CPDs within a defined sequence is similar, the damage in cellular environment which shields the nuclear DNA was higher than that in organism in apparent dose. So we use low UVB light as main study agent. Low dose UV-irradiated HDF-a cells (Human Dermal Fibroblasts-adult cells) which is weaker than epidermic cells were cultured with DMEM at different trace amount of Mg2+ (0mmol/L , 0.1mmol/L , 0.2mmol/L, 0.4mmol/L, 0.8mmol/L, 1.2mmol/L) free-serum DMEM and the repair of DNA strands injured were observed. Treat these cells with DNA strand breaks detection, photoproducts detection and the repair of photoproducts detection. Then quantitate the role of trace amount Mg2+ in repair of UV light-induced damage to human skin. The experiment results indicated that epidermic cells have capability of resistance to UV-radiation at a certain extent. And Mg2+ can regulate the UV-induced damage repair and relative vitality. It can offer a rationale and experiment data to relieve UV light-induced skin disease.

A preliminary study on ice shape tracing with a laser light sheet

NASA Technical Reports Server (NTRS)

Mercer, Carolyn R.; Vargas, Mario; Oldenburg, John R.

1993-01-01

Preliminary work towards the development of an automated method of measuring the shape of ice forming on an airfoil during wind tunnel tests has been completed. A thin sheet of light illuminated the front surfaces of rime, glaze, and mixed ice shapes and a solid-state camera recorded images of each. A maximum intensity algorithm extracted the profiles of the ice shapes and the results were compared to hand tracings. Very good general agreement was found in each case.

CosApps: Simulate gravitational lensing through ray tracing and shear calculation

NASA Astrophysics Data System (ADS)

Coss, David

2017-12-01

Cosmology Applications (CosApps) provides tools to simulate gravitational lensing using two different techniques, ray tracing and shear calculation. The tool ray_trace_ellipse calculates deflection angles on a grid for light passing a deflecting mass distribution. Using MPI, ray_trace_ellipse may calculate deflection in parallel across network connected computers, such as cluster. The program physcalc calculates the gravitational lensing shear using the relationship of convergence and shear, described by a set of coupled partial differential equations.

Optics: Light, Color, and Their Uses. An Educator's Guide with Activities in Science and Mathematics.

ERIC Educational Resources Information Center

National Aeronautics and Space Administration, Huntsville, AL. George C. Marshall Space Flight Center.

This educator's guide from discusses optics, light, color and their uses. Activities include: (1) "Reflection of Light with a Plane (Flat) Mirror--Trace a Star"; (2) "Reflection of Light with Two Plane Mirrors--Double Mirrors Placed at a 90-Degree Angle"; (3) "Reflection of Light with Two Plane Mirrors--Double Mirrors Placed at a Number of…

Light propagation in the averaged universe

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

Bagheri, Samae; Schwarz, Dominik J., E-mail: s_bagheri@physik.uni-bielefeld.de, E-mail: dschwarz@physik.uni-bielefeld.de

Cosmic structures determine how light propagates through the Universe and consequently must be taken into account in the interpretation of observations. In the standard cosmological model at the largest scales, such structures are either ignored or treated as small perturbations to an isotropic and homogeneous Universe. This isotropic and homogeneous model is commonly assumed to emerge from some averaging process at the largest scales. We assume that there exists an averaging procedure that preserves the causal structure of space-time. Based on that assumption, we study the effects of averaging the geometry of space-time and derive an averaged version of themore » null geodesic equation of motion. For the averaged geometry we then assume a flat Friedmann-Lemaître (FL) model and find that light propagation in this averaged FL model is not given by null geodesics of that model, but rather by a modified light propagation equation that contains an effective Hubble expansion rate, which differs from the Hubble rate of the averaged space-time.« less

Illuminating Systems: Edison and Electrical Incandescence.

ERIC Educational Resources Information Center

Sanford, Greg

1989-01-01

Traces the life and inventions of Thomas A. Edison up to the invention of electrical incandescent lighting in 1881. Focuses on the process that Edison followed in developing incandescent lighting, including financial aspects, other competitors in the field, and the eventual establishment of the Edison Electric Light Companies. (RW)

Light-field camera-based 3D volumetric particle image velocimetry with dense ray tracing reconstruction technique

NASA Astrophysics Data System (ADS)

Shi, Shengxian; Ding, Junfei; New, T. H.; Soria, Julio

2017-07-01

This paper presents a dense ray tracing reconstruction technique for a single light-field camera-based particle image velocimetry. The new approach pre-determines the location of a particle through inverse dense ray tracing and reconstructs the voxel value using multiplicative algebraic reconstruction technique (MART). Simulation studies were undertaken to identify the effects of iteration number, relaxation factor, particle density, voxel-pixel ratio and the effect of the velocity gradient on the performance of the proposed dense ray tracing-based MART method (DRT-MART). The results demonstrate that the DRT-MART method achieves higher reconstruction resolution at significantly better computational efficiency than the MART method (4-50 times faster). Both DRT-MART and MART approaches were applied to measure the velocity field of a low speed jet flow which revealed that for the same computational cost, the DRT-MART method accurately resolves the jet velocity field with improved precision, especially for the velocity component along the depth direction.

Simultaneous cryo X-ray ptychographic and fluorescence microscopy of green algae

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

Deng, Junjing; Vine, David J.; Chen, Si

Trace metals play important roles in normal and in disease-causing biological functions. X-ray fluorescence microscopy reveals trace elements with no dependence on binding affinities (unlike with visible light fluorophores) and with improved sensitivity relative to electron probes. However, X-ray fluorescence is not very sensitive for showing the light elements that comprise the majority of cellular material. Here we show that X-ray ptychography can be combined with fluorescence to image both cellular structure and trace element distribution in frozen-hydrated cells at cryogenic temperatures, with high structural and chemical fidelity. Ptychographic reconstruction algorithms deliver phase and absorption contrast images at a resolutionmore » beyond that of the illuminating lens or beam size. Using 5.2-keV X-rays, we have obtained sub-30-nm resolution structural images and ~90-nm-resolution fluorescence images of several elements in frozen-hydrated green algae. Finally, this combined approach offers a way to study the role of trace elements in their structural context.« less

Simultaneous cryo X-ray ptychographic and fluorescence microscopy of green algae

DOE PAGES

Deng, Junjing; Vine, David J.; Chen, Si; ...

2015-02-24

Trace metals play important roles in normal and in disease-causing biological functions. X-ray fluorescence microscopy reveals trace elements with no dependence on binding affinities (unlike with visible light fluorophores) and with improved sensitivity relative to electron probes. However, X-ray fluorescence is not very sensitive for showing the light elements that comprise the majority of cellular material. Here we show that X-ray ptychography can be combined with fluorescence to image both cellular structure and trace element distribution in frozen-hydrated cells at cryogenic temperatures, with high structural and chemical fidelity. Ptychographic reconstruction algorithms deliver phase and absorption contrast images at a resolutionmore » beyond that of the illuminating lens or beam size. Using 5.2-keV X-rays, we have obtained sub-30-nm resolution structural images and ~90-nm-resolution fluorescence images of several elements in frozen-hydrated green algae. Finally, this combined approach offers a way to study the role of trace elements in their structural context.« less

Simultaneous cryo X-ray ptychographic and fluorescence microscopy of green algae

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

Deng, Junjing; Vine, David J.; Chen, Si

Trace metals play important roles in normal and in disease-causing biological functions. X-ray fluorescence microscopy reveals trace elements with no dependence on binding affinities (unlike with visible light fluorophores) and with improved sensitivity relative to electron probes. However, X-ray fluorescence is not very sensitive for showing the light elements that comprise the majority of cellular material. Here we show that X-ray ptychography can be combined with fluorescence to image both cellular structure and trace element distribution in frozen-hydrated cells at cryogenic temperatures, with high structural and chemical fidelity. Ptychographic reconstruction algorithms deliver phase and absorption contrast images at a resolutionmore » beyond that of the illuminating lens or beam size. Using 5.2-keV X-rays, we have obtained sub-30-nm resolution structural images and similar to 90-nm-resolution fluorescence images of several elements in frozen-hydrated green algae. This combined approach offers a way to study the role of trace elements in their structural context.« less

Vertex shading of the three-dimensional model based on ray-tracing algorithm

NASA Astrophysics Data System (ADS)

Hu, Xiaoming; Sang, Xinzhu; Xing, Shujun; Yan, Binbin; Wang, Kuiru; Dou, Wenhua; Xiao, Liquan

2016-10-01

Ray Tracing Algorithm is one of the research hotspots in Photorealistic Graphics. It is an important light and shadow technology in many industries with the three-dimensional (3D) structure, such as aerospace, game, video and so on. Unlike the traditional method of pixel shading based on ray tracing, a novel ray tracing algorithm is presented to color and render vertices of the 3D model directly. Rendering results are related to the degree of subdivision of the 3D model. A good light and shade effect is achieved by realizing the quad-tree data structure to get adaptive subdivision of a triangle according to the brightness difference of its vertices. The uniform grid algorithm is adopted to improve the rendering efficiency. Besides, the rendering time is independent of the screen resolution. In theory, as long as the subdivision of a model is adequate, cool effects as the same as the way of pixel shading will be obtained. Our practical application can be compromised between the efficiency and the effectiveness.

The influence of leaf anatomy on the internal light environment and photosynthetic electron transport rate: exploration with a new leaf ray tracing model

PubMed Central

Xiao, Yi; Tholen, Danny; Zhu, Xin-Guang

2016-01-01

Leaf photosynthesis is determined by biochemical properties and anatomical features. Here we developed a three-dimensional leaf model that can be used to evaluate the internal light environment of a leaf and its implications for whole-leaf electron transport rates (J). This model includes (i) the basic components of a leaf, such as the epidermis, palisade and spongy tissues, as well as the physical dimensions and arrangements of cell walls, vacuoles and chloroplasts; and (ii) an efficient forward ray-tracing algorithm, predicting the internal light environment for light of wavelengths between 400 and 2500nm. We studied the influence of leaf anatomy and ambient light on internal light conditions and J. The results show that (i) different chloroplasts can experience drastically different light conditions, even when they are located at the same distance from the leaf surface; (ii) bundle sheath extensions, which are strips of parenchyma, collenchyma or sclerenchyma cells connecting the vascular bundles with the epidermis, can influence photosynthetic light-use efficiency of leaves; and (iii) chloroplast positioning can also influence the light-use efficiency of leaves. Mechanisms underlying leaf internal light heterogeneity and implications of the heterogeneity for photoprotection and for the convexity of the light response curves are discussed. PMID:27702991

False memory for orthographically versus semantically similar words in adolescents with dyslexia: a fuzzy-trace theory perspective.

PubMed

Obidziński, Michał; Nieznański, Marek

2017-10-01

The presented research was conducted in order to investigate the connections between developmental dyslexia and the functioning of verbatim and gist memory traces-assumed in the fuzzy-trace theory. The participants were 71 high school students (33 with dyslexia and 38 without learning difficulties). The modified procedure and multinomial model of Stahl and Klauer (simplified conjoint recognition model) was used to collect and analyze data. Results showed statistically significant differences in four of the model parameters: (a) the probability of verbatim trace recollection upon presentation of orthographically similar stimulus was higher in the control than dyslexia group, (b) the probability of verbatim trace recollection upon presentation of semantically similar stimulus was higher in the control than dyslexia group, (c) the probability of gist trace retrieval upon presentation of semantically similar stimulus was higher in the dyslexia than control group, and (d) the probability of gist trace retrieval upon target stimulus presentation (in the semantic condition) was higher in the control than dyslexia group. The obtained results suggest differences of memory functioning in terms of verbatim and gist trace retrieval between people with and without dyslexia on specific, elementary cognitive processes postulated by the fuzzy-trace theory. These can indicate new approaches in the education of persons with developmental dyslexia, focused on specific impairments and the strengths of their memory functioning.

Regional Application of an Ecosystem Production Model for Studies of Biogeochemistry in the...

NASA Technical Reports Server (NTRS)

Potter, C. S.; Klooster, S.; Brooks, V.; Peterson, David L. (Technical Monitor)

1997-01-01

The degree to which primary production, soil carbon, and trace gas fluxes in tropical forests of the Amazon are limited by moisture availability and other environmental factors was examined using an ecosystem modeling application for the country of Brazil. A regional geographic information system (GIS) serves as the data source of climate drivers, satellite images, land cover, and soil properties for input to the NASA Ames-CASA (Carnegie-Ames-Stanford Approach) model over a 8-km grid resolution. Simulation results supports the hypothesis that net primary production (NPP) is limited by cloud interception of solar radiation over the humid northwestern portion of the region. Peak annual rates for NPP of nearly 1.4 kg C m-2yr -1are localized in the seasonally dry eastern Amazon in areas that we assume are primarily deep-rooted evergreen forest cover. Regional effects of forest conversion on NPP and soil carbon content are indicated in the model results, especially in seasonally dry areas. Comparison of model flux predictions along selected eco-climatic transects reveal moisture, soil, and land use controls on gradients of ecosystem production and soil trace gas emissions (CO2, N2O, and NO). These results are used to formulate a series of research hypotheses for testing in the next phase of regional modeling, which includes recalibration of the light-use efficiency term in CASA using field measurements of NPP, and refinements of vegetation index and soil property (texture and potential rooting depth) maps for the region.

Isothermal absorption of soluble gases by atmospheric nanoaerosols

NASA Astrophysics Data System (ADS)

Elperin, T.; Fominykh, A.; Krasovitov, B.; Lushnikov, A.

2013-01-01

We investigate mass transfer during the isothermal absorption of atmospheric trace soluble gases by a single droplet whose size is comparable to the molecular mean free path in air at normal conditions. It is assumed that the trace reactant diffuses to the droplet surface and then reacts with the substances inside the droplet according to the first-order rate law. Our analysis applies a flux-matching theory of transport processes in gases and assumes constant thermophysical properties of the gases and liquids. We derive an integral equation of Volterra type for the transient molecular flux density to a liquid droplet and solve it numerically. Numerical calculations are performed for absorption of sulfur dioxide (SO2), dinitrogen trioxide (N2O3), and chlorine (Cl2) by liquid nanoaerosols accompanied by chemical dissociation reaction. It is shown that during gas absorption by nanoaerosols, the kinetic effects play a significant role, and neglecting kinetic effects leads to a significant overestimation of the soluble gas flux into a droplet during the entire period of gas absorption.

Isothermal absorption of soluble gases by atmospheric nanoaerosols.

PubMed

Elperin, T; Fominykh, A; Krasovitov, B; Lushnikov, A

2013-01-01

We investigate mass transfer during the isothermal absorption of atmospheric trace soluble gases by a single droplet whose size is comparable to the molecular mean free path in air at normal conditions. It is assumed that the trace reactant diffuses to the droplet surface and then reacts with the substances inside the droplet according to the first-order rate law. Our analysis applies a flux-matching theory of transport processes in gases and assumes constant thermophysical properties of the gases and liquids. We derive an integral equation of Volterra type for the transient molecular flux density to a liquid droplet and solve it numerically. Numerical calculations are performed for absorption of sulfur dioxide (SO(2)), dinitrogen trioxide (N(2)O(3)), and chlorine (Cl(2)) by liquid nanoaerosols accompanied by chemical dissociation reaction. It is shown that during gas absorption by nanoaerosols, the kinetic effects play a significant role, and neglecting kinetic effects leads to a significant overestimation of the soluble gas flux into a droplet during the entire period of gas absorption.

A fiber optic sensor with a metal organic framework as a sensing material for trace levels of water in industrial gases.

PubMed

Ohira, Shin-Ichi; Miki, Yusuke; Matsuzaki, Toru; Nakamura, Nao; Sato, Yu-ki; Hirose, Yasuo; Toda, Kei

2015-07-30

Industrial gases such as nitrogen, oxygen, argon, and helium are easily contaminated with water during production, transfer and use, because there is a high volume fraction of water in the atmosphere (approximately 1.2% estimated with the average annual atmospheric temperature and relative humidity). Even trace water (<1 parts per million by volume (ppmv) of H2O, dew point < -76 °C) in the industrial gases can cause quality problems in the process such as production of semiconductors. Therefore, it is important to monitor and to control trace water levels in industrial gases at each supplying step, and especially during their use. In the present study, a fiber optic gas sensor was investigated for monitoring trace water levels in industrial gases. The sensor consists of a film containing a metal organic framework (MOF). MOFs are made of metals coordinated to organic ligands, and have mesoscale pores that adsorb gas molecules. When the MOF, copper benzene-1,3,5-tricarboxylate (Cu-BTC), was used as a sensing material, we investigated the color of Cu-BTC with water adsorption changed both in depth and tone. Cu-BTC crystals appeared deep blue in dry gases, and then changed to light blue in wet gases. An optical gas sensor with the Cu-BTC film was developed using a light emitting diode as the light source and a photodiode as the light intensity detector. The sensor showed a reversible response to trace water, did not require heating to remove the adsorbed water molecules. The sample gas flow rate did not affect the sensitivity. The obtained limit of detection was 40 parts per billion by volume (ppbv). The response time for sample gas containing 2.5 ppmvH2O was 23 s. The standard deviation obtained for daily analysis of 1.0 ppmvH2O standard gas over 20 days was 9%. Furthermore, the type of industrial gas did not affect the sensitivity. These properties mean the sensor will be applicable to trace water detection in various industrial gases. Copyright © 2015 Elsevier B.V. All rights reserved.

EXHAUST EMISSION PATTERNS FROM TWO LIGHT-DUTY DIESEL AUTOMOBILES

EPA Science Inventory

Particulate and gaseous emissions from two light-duty diesel automobiles were examined over six operating cycles. Particulate characterizations included mass emission rate, soluble organic content, and trace element content determinations. The particulate matter was sampled using...

Design of optical transmitting antenna with enhance performance in visible light communication

NASA Astrophysics Data System (ADS)

Kuang, Dang; Wang, Jianping; Lu, Huimin

2016-10-01

An optical transmitting antenna for visible light communication(VLC) is designed in this work, in which the antenna is positioned before the light-emitting diodes (LED) source to change the lighting distribution, in order to achieve uniform received power effect. The method to design antenna is introduced into physical optical lens principle. According to the energy conservation law and Snell law, the antenna is designed via establishing energy mapping between the luminous flux emitted by a LED source with Lambertian distribution and the target plane. The coordinates of the antenna model are obtained under matrix laboratory (MATLAB). The antenna model entity is generated through three dimensional (3D) composition software AutoCAD with the coordinates of antenna. Ray-tracing software Tracepro is used to trace the ray which through antenna, and validate the irradiance maps. The uniformity of illumination and received power of the designed VLC is improved from approximately 35% to over 83%.

Design of differential optical absorption spectroscopy long-path telescopes based on fiber optics.

PubMed

Merten, André; Tschritter, Jens; Platt, Ulrich

2011-02-10

We present a new design principle of telescopes for use in the spectral investigation of the atmosphere and the detection of atmospheric trace gases with the long-path differential optical absorption spectroscopy (DOAS) technique. A combination of emitting and receiving fibers in a single bundle replaces the commonly used coaxial-Newton-type combination of receiving and transmitting telescope. This very simplified setup offers a higher light throughput and simpler adjustment and allows smaller instruments, which are easier to handle and more portable. The higher transmittance was verified by ray-tracing calculations, which result in a theoretical factor threefold improvement in signal intensity compared with the old setup. In practice, due to the easier alignment and higher stability, up to factor of 10 higher signal intensities were found. In addition, the use of a fiber optic light source provides a better spectral characterization of the light source, which results in a lower detection limit for trace gases studied with this instrument. This new design will greatly enhance the usability and the range of applications of active DOAS instruments.

Are non-linearity effects of absorption important for MAX-DOAS observations?

NASA Astrophysics Data System (ADS)

Pukite, Janis; Wang, Yang; Wagner, Thomas

2017-04-01

For scattered light observations the absorption optical depth depends non-linearly on the trace gas concentrations if their absorption is strong. This is the case because the Beer-Lambert law is generally not applicable for scattered light measurements due to many (i.e. more than one) light paths contributing to the measurement. While in many cases a linear approximation can be made, for scenarios with strong absorption non-linear effects cannot always be neglected. This is especially the case for observation geometries with spatially extended and diffuse light paths, especially in satellite limb geometry but also for nadir measurements as well. Fortunately the effects of non-linear effects can be quantified by means of expanding the radiative transfer equation in a Taylor series with respect to the trace gas absorption coefficients. Herewith if necessary (1) the higher order absorption structures can be described as separate fit parameters in the DOAS fit and (2) the algorithm constraints of retrievals of VCDs and profiles can be improved by considering higher order sensitivity parameters. In this study we investigate the contribution of the higher order absorption structures for MAX-DOAS observation geometry for different atmospheric and ground properties (cloud and aerosol effects, trace gas amount, albedo) and geometry (different Sun and viewing angles).

Observations of Rotating Sunspots from TRACE

NASA Astrophysics Data System (ADS)

Brown, D. S.; Nightingale, R. W.; Alexander, D.; Schrijver, C. J.; Metcalf, T. R.; Shine, R. A.; Title, A. M.; Wolfson, C. J.

2003-09-01

Recent observations from TRACE in the photospheric white-light channel have shown sunspots that rotate up to 200° about their umbral centre over a period of 3 5 days. The corresponding loops in the coronal fan are often seen to twist and can erupt as flares. In an ongoing study, seven cases of rotating sunspots have been identified, two of which can be associated with sigmoid structures appearing in Yohkoh/SXT and six with events seen by GOES. This paper analyzes the rotation rates of the sunspots using TRACE white-light data. Observations from AR 9114 are presented in detail in the main text and a summary of the results for the remaining six sunspots is presented in Appendixes A F. Discussion of the key results, particularly common features, are presented, as well as possible mechanisms for sunspot rotation.

Real time ray tracing based on shader

NASA Astrophysics Data System (ADS)

Gui, JiangHeng; Li, Min

2017-07-01

Ray tracing is a rendering algorithm for generating an image through tracing lights into an image plane, it can simulate complicate optical phenomenon like refraction, depth of field and motion blur. Compared with rasterization, ray tracing can achieve more realistic rendering result, however with greater computational cost, simple scene rendering can consume tons of time. With the GPU's performance improvement and the advent of programmable rendering pipeline, complicated algorithm can also be implemented directly on shader. So, this paper proposes a new method that implement ray tracing directly on fragment shader, mainly include: surface intersection, importance sampling and progressive rendering. With the help of GPU's powerful throughput capability, it can implement real time rendering of simple scene.

Analytical approximations to the Hotelling trace for digital x-ray detectors

NASA Astrophysics Data System (ADS)

Clarkson, Eric; Pineda, Angel R.; Barrett, Harrison H.

2001-06-01

The Hotelling trace is the signal-to-noise ratio for the ideal linear observer in a detection task. We provide an analytical approximation for this figure of merit when the signal is known exactly and the background is generated by a stationary random process, and the imaging system is an ideal digital x-ray detector. This approximation is based on assuming that the detector is infinite in extent. We test this approximation for finite-size detectors by comparing it to exact calculations using matrix inversion of the data covariance matrix. After verifying the validity of the approximation under a variety of circumstances, we use it to generate plots of the Hotelling trace as a function of pairs of parameters of the system, the signal and the background.

The influence of leaf anatomy on the internal light environment and photosynthetic electron transport rate: exploration with a new leaf ray tracing model.

PubMed

Xiao, Yi; Tholen, Danny; Zhu, Xin-Guang

2016-11-01

Leaf photosynthesis is determined by biochemical properties and anatomical features. Here we developed a three-dimensional leaf model that can be used to evaluate the internal light environment of a leaf and its implications for whole-leaf electron transport rates (J). This model includes (i) the basic components of a leaf, such as the epidermis, palisade and spongy tissues, as well as the physical dimensions and arrangements of cell walls, vacuoles and chloroplasts; and (ii) an efficient forward ray-tracing algorithm, predicting the internal light environment for light of wavelengths between 400 and 2500nm. We studied the influence of leaf anatomy and ambient light on internal light conditions and J The results show that (i) different chloroplasts can experience drastically different light conditions, even when they are located at the same distance from the leaf surface; (ii) bundle sheath extensions, which are strips of parenchyma, collenchyma or sclerenchyma cells connecting the vascular bundles with the epidermis, can influence photosynthetic light-use efficiency of leaves; and (iii) chloroplast positioning can also influence the light-use efficiency of leaves. Mechanisms underlying leaf internal light heterogeneity and implications of the heterogeneity for photoprotection and for the convexity of the light response curves are discussed. © The Author 2016. Published by Oxford University Press on behalf of the Society for Experimental Biology.

Cultures-of-Use and Morphologies of Communicative Action

ERIC Educational Resources Information Center

Thorne, Steven L.

2016-01-01

In this article I revisit the cultures-of-use conceptual framework--that technologies, as forms and processes comprising human culture, mediate and assume variable meanings, values, and conventionalized functions for different communities (Thorne, 2003). I trace the antecedent arc of investigation and serendipitous encounters that led to the 2003…

The Accumulation Of Radium And Other Radionuclides In Drinking Water Distribution Systems

EPA Science Inventory

The tendency for iron solid surfaces to adsorb trace contaminants such as arsenic is well known and has become the basis for several drinking water treatment approaches. It is reasonable to assume that iron-based solids, such as corrosion deposits present in drinking water distr...

The New School

ERIC Educational Resources Information Center

Kennedy, David

2018-01-01

This paper traces the changing status of the school as a counter culture in the anthropological and historical literature, in particular from the moment when compulsory mass schooling assumed the function of ideological state apparatus in the post-revolutionary 19th century West. It then focuses attention on what may be called the New School,…

Reflectance model of a plant leaf

NASA Technical Reports Server (NTRS)

Kumar, R.; Silva, L.

1973-01-01

A light ray, incident at 5 deg to the normal, is geometrically plotted through the drawing of the cross section of a soybean leaf using Fresnel's Equations and Snell's Law. The optical mediums of the leaf considered for ray tracing are: air, cell sap, chloroplast, and cell wall. The above ray is also drawn through the same leaf cross section considering cell wall and air as the only optical mediums. The values of the reflection and transmission found from ray tracing agree closely with the experimental results obtained using a Beckman DK-2A Spectroreflectometer. Similarly a light ray, incident at about 60 deg to the normal, is drawn through the palisade cells of a soybean leaf to illustrate the pathway of light, incident at an oblique angle, through the palisade cells.

Research on illumination uniformity of high-power LED array light source

NASA Astrophysics Data System (ADS)

Yu, Xiaolong; Wei, Xueye; Zhang, Ou; Zhang, Xinwei

2018-06-01

Uniform illumination is one of the most important problem that must be solved in the application of high-power LED array. A numerical optimization algorithm, is applied to obtain the best LED array typesetting so that the light intensity of the target surface is evenly distributed. An evaluation function is set up through the standard deviation of the illuminance function, then the particle swarm optimization algorithm is utilized to optimize different arrays. Furthermore, the light intensity distribution is obtained by optical ray tracing method. Finally, a hybrid array is designed and the optical ray tracing method is applied to simulate the array. The simulation results, which is consistent with the traditional theoretical calculation, show that the algorithm introduced in this paper is reasonable and effective.

Shape Recognition in Infancy: Visual Integration of Sequential Information.

ERIC Educational Resources Information Center

Rose, Susan A

1988-01-01

Investigated infants' integration of visual information across space and time. In four experiments, infants aged 12 months and 6 months viewed objects after watching light trace similar and dissimilar shapes. Infants looked longer at novel shapes, although six-month-olds did not recognize figures taking more than 10 seconds to trace. One-year-old…

Effect of parameters in moving average method for event detection enhancement using phase sensitive OTDR

NASA Astrophysics Data System (ADS)

Kwon, Yong-Seok; Naeem, Khurram; Jeon, Min Yong; Kwon, Il-bum

2017-04-01

We analyze the relations of parameters in moving average method to enhance the event detectability of phase sensitive optical time domain reflectometer (OTDR). If the external events have unique frequency of vibration, then the control parameters of moving average method should be optimized in order to detect these events efficiently. A phase sensitive OTDR was implemented by a pulsed light source, which is composed of a laser diode, a semiconductor optical amplifier, an erbium-doped fiber amplifier, a fiber Bragg grating filter, and a light receiving part, which has a photo-detector and high speed data acquisition system. The moving average method is operated with the control parameters: total number of raw traces, M, number of averaged traces, N, and step size of moving, n. The raw traces are obtained by the phase sensitive OTDR with sound signals generated by a speaker. Using these trace data, the relation of the control parameters is analyzed. In the result, if the event signal has one frequency, then the optimal values of N, n are existed to detect the event efficiently.

The influence of carbon, sulfur, and silicon on trace element partitioning in iron alloys

NASA Astrophysics Data System (ADS)

Han, J.; Van Orman, J. A.; Crispin, K. L.; Ash, R. D.

2014-12-01

Non-metallic light elements are important constituents of planetary cores and have a strong influence on the partitioning behavior of trace elements. Planetary cores may contain a wide range of non-metallic light elements, including H, N, S, P, Si, and C. Under highly reducing conditions, such as those that are thought to have pertained during the formation of Mercury's core, Si and C, in addition to sulfur, may be particularly important constituents. Each of these elements may strongly effect and have a different impact on the partitioning behavior of trace elements but their combined effects on trace element partitioning have not been quantified. We investigated the partitioning behavior of more than 25 siderophile trace elements within the Fe-S-C-Si system with varying concentrations of C, S, and Si. The experiments were performed under pressures varying from 1 atm to 2 GPa and temperatures ranging from 1200˚C to 1450˚C. All experiments produced immiscible liquids, one enriched in Si and C, and the other predominantly FeS. We found some highly siderophile elements including Os, Ru, Ir, and Re are much more enriched in Fe-Si-C phase than in Fe-S phase, whereas other trace elements like V, Co, Ag, Hf, and Pb are enriched in S-rich phase. However, not all the trace elements enriched in Fe-Si-C phase are repelled by sulfur. Elements like Re and Ru could have different partitioning trends if sulfur concentration in S-rich phase rises. The partitioning behavior of these trace elements could enhance our understanding of the differentiation of Mercury's core under oxygen-poor conditions.

The Role of Multiple Neuromodulators in Reinforcement Learning That Is Based on Competition between Eligibility Traces.

PubMed

Huertas, Marco A; Schwettmann, Sarah E; Shouval, Harel Z

2016-01-01

The ability to maximize reward and avoid punishment is essential for animal survival. Reinforcement learning (RL) refers to the algorithms used by biological or artificial systems to learn how to maximize reward or avoid negative outcomes based on past experiences. While RL is also important in machine learning, the types of mechanistic constraints encountered by biological machinery might be different than those for artificial systems. Two major problems encountered by RL are how to relate a stimulus with a reinforcing signal that is delayed in time (temporal credit assignment), and how to stop learning once the target behaviors are attained (stopping rule). To address the first problem synaptic eligibility traces were introduced, bridging the temporal gap between a stimulus and its reward. Although, these were mere theoretical constructs, recent experiments have provided evidence of their existence. These experiments also reveal that the presence of specific neuromodulators converts the traces into changes in synaptic efficacy. A mechanistic implementation of the stopping rule usually assumes the inhibition of the reward nucleus; however, recent experimental results have shown that learning terminates at the appropriate network state even in setups where the reward nucleus cannot be inhibited. In an effort to describe a learning rule that solves the temporal credit assignment problem and implements a biologically plausible stopping rule, we proposed a model based on two separate synaptic eligibility traces, one for long-term potentiation (LTP) and one for long-term depression (LTD), each obeying different dynamics and having different effective magnitudes. The model has been shown to successfully generate stable learning in recurrent networks. Although, the model assumes the presence of a single neuromodulator, evidence indicates that there are different neuromodulators for expressing the different traces. What could be the role of different neuromodulators for expressing the LTP and LTD traces? Here we expand on our previous model to include several neuromodulators, and illustrate through various examples how different these contribute to learning reward-timing within a wide set of training paradigms and propose further roles that multiple neuromodulators can play in encoding additional information of the rewarding signal.

Fiber-optic voltage sensor with cladded fiber and evanescent wave variation detection

DOEpatents

Wood, Charles B.

1992-01-01

A fiber optic voltage sensor is described which includes a source of light, a reference fiber for receiving a known percentage of the light and an electrostrictive element having terminals across which is applied, a voltage to be measured. The electrostrictive element is responsive to the applied voltage to assume an altered physical state. A measuring fiber also receives a known percentage of light from the light source and is secured about the electrostrictive element. The measuring fiber is provided with a cladding and exhibits an evanescent wave in the cladding. The measuring fiber has a known length which is altered when the electrostrictive element assumes its altered physical state. A differential sensor is provided which senses the intensity of light in both the reference fiber and the measuring fiber and provides an output indicative of the difference between the intensities.

Fiber-optic voltage sensor with cladded fiber and evanescent wave variation detection

DOEpatents

Wood, C.B.

1992-12-15

A fiber optic voltage sensor is described which includes a source of light, a reference fiber for receiving a known percentage of the light and an electrostrictive element having terminals across which is applied, a voltage to be measured. The electrostrictive element is responsive to the applied voltage to assume an altered physical state. A measuring fiber also receives a known percentage of light from the light source and is secured about the electrostrictive element. The measuring fiber is provided with a cladding and exhibits an evanescent wave in the cladding. The measuring fiber has a known length which is altered when the electrostrictive element assumes its altered physical state. A differential sensor is provided which senses the intensity of light in both the reference fiber and the measuring fiber and provides an output indicative of the difference between the intensities. 3 figs.

Unpolarized infrared emissivity with shadow from anisotropic rough sea surfaces with non-Gaussian statistics.

PubMed

Bourlier, Christophe

2005-07-10

The emissivity of two-dimensional anisotropic rough sea surfaces with non-Gaussian statistics is investigated. The emissivity derivation is of importance for retrieval of the sea-surface temperature or equivalent temperature of a rough sea surface by infrared thermal imaging. The well-known Cox-Munk slope probability-density function, considered non-Gaussian, is used for the emissivity derivation, in which the skewness and the kurtosis (related to the third- and fourth-order statistics, respectively) are included. The shadowing effect, which is significant for grazing angles, is also taken into account. The geometric optics approximation is assumed to be valid, which means that the rough surface is modeled as a collection of facets reflecting locally the light in the specular direction. In addition, multiple reflections are ignored. Numerical results of the emissivity are presented for Gaussian and non-Gaussian statistics, for moderate wind speeds, for near-infrared wavelengths, for emission angles ranging from 0 degrees (nadir) to 90 degrees (horizon), and according to the wind direction. In addition, the emissivity is compared with both measurements and a Monte Carlo ray-tracing method.

Light reflection models for computer graphics.

PubMed

Greenberg, D P

1989-04-14

During the past 20 years, computer graphic techniques for simulating the reflection of light have progressed so that today images of photorealistic quality can be produced. Early algorithms considered direct lighting only, but global illumination phenomena with indirect lighting, surface interreflections, and shadows can now be modeled with ray tracing, radiosity, and Monte Carlo simulations. This article describes the historical development of computer graphic algorithms for light reflection and pictorially illustrates what will be commonly available in the near future.

DeepNeuron: an open deep learning toolbox for neuron tracing.

PubMed

Zhou, Zhi; Kuo, Hsien-Chi; Peng, Hanchuan; Long, Fuhui

2018-06-06

Reconstructing three-dimensional (3D) morphology of neurons is essential for understanding brain structures and functions. Over the past decades, a number of neuron tracing tools including manual, semiautomatic, and fully automatic approaches have been developed to extract and analyze 3D neuronal structures. Nevertheless, most of them were developed based on coding certain rules to extract and connect structural components of a neuron, showing limited performance on complicated neuron morphology. Recently, deep learning outperforms many other machine learning methods in a wide range of image analysis and computer vision tasks. Here we developed a new Open Source toolbox, DeepNeuron, which uses deep learning networks to learn features and rules from data and trace neuron morphology in light microscopy images. DeepNeuron provides a family of modules to solve basic yet challenging problems in neuron tracing. These problems include but not limited to: (1) detecting neuron signal under different image conditions, (2) connecting neuronal signals into tree(s), (3) pruning and refining tree morphology, (4) quantifying the quality of morphology, and (5) classifying dendrites and axons in real time. We have tested DeepNeuron using light microscopy images including bright-field and confocal images of human and mouse brain, on which DeepNeuron demonstrates robustness and accuracy in neuron tracing.

Impact of impurities on zonal flow driven by trapped electron mode turbulence

NASA Astrophysics Data System (ADS)

Guo, Weixin; Wang, Lu; Zhuang, Ge

2017-12-01

The impact of impurities on the generation of zonal flow (ZF) driven by collisonless trapped electron mode turbulence in deuterium (D)-tritium (T) plasmas is investigated. An expression for ZF growth rate with impurities is derived by balancing the ZF potential shielded by polarization effects and the ZF modulated radial turbulent current. Then, it is shown that the maximum normalized ZF growth rate is reduced by the presence of fully ionized non-trace light impurities with relatively flat density profile, and slightly reduced by highly ionized trace tungsten, while the maximum normalized ZF growth rate can be enhanced by fully ionized non-trace light impurities with relatively steep density profile. In particular, the effects of high temperature helium from D-T reaction on ZF depend on the temperature ratio between electrons and high temperature helium. The possible relevance of our findings to recent experimental results and future burning plasmas is also discussed.

Generalized Processing Tree Models: Jointly Modeling Discrete and Continuous Variables.

PubMed

Heck, Daniel W; Erdfelder, Edgar; Kieslich, Pascal J

2018-05-24

Multinomial processing tree models assume that discrete cognitive states determine observed response frequencies. Generalized processing tree (GPT) models extend this conceptual framework to continuous variables such as response times, process-tracing measures, or neurophysiological variables. GPT models assume finite-mixture distributions, with weights determined by a processing tree structure, and continuous components modeled by parameterized distributions such as Gaussians with separate or shared parameters across states. We discuss identifiability, parameter estimation, model testing, a modeling syntax, and the improved precision of GPT estimates. Finally, a GPT version of the feature comparison model of semantic categorization is applied to computer-mouse trajectories.

Estimation of Whole Plant Photosynthetic Rate of Irwin Mango under Artificial and Natural Lights Using a Three-Dimensional Plant Model and Ray-Tracing.

PubMed

Jung, Dae Ho; Lee, Joon Woo; Kang, Woo Hyun; Hwang, In Ha; Son, Jung Eek

2018-01-04

Photosynthesis is an important physiological response for determination of CO₂ fertilization in greenhouses and estimation of crop growth. In order to estimate the whole plant photosynthetic rate, it is necessary to investigate how light interception by crops changes with environmental and morphological factors. The objectives of this study were to analyze plant light interception using a three-dimensional (3D) plant model and ray-tracing, determine the spatial distribution of the photosynthetic rate, and estimate the whole plant photosynthetic rate of Irwin mango ( Mangifera indica L. cv. Irwin) grown in greenhouses. In the case of mangoes, it is difficult to measure actual light interception at the canopy level due to their vase shape. A two-year-old Irwin mango tree was used to measure the whole plant photosynthetic rate. Light interception and whole plant photosynthetic rate were measured under artificial and natural light conditions using a closed chamber (1 × 1 × 2 m). A 3D plant model was constructed and ray-tracing simulation was conducted for calculating the photosynthetic rate with a two-variable leaf photosynthetic rate model of the plant. Under artificial light, the estimated photosynthetic rate increased from 2.0 to 2.9 μmolCO₂·m -2 ·s -1 with increasing CO₂ concentration. On the other hand, under natural light, the photosynthetic rate increased from 0.2 μmolCO₂·m -2 ·s -1 at 06:00 to a maximum of 7.3 μmolCO₂·m -2 ·s -1 at 09:00, then gradually decreased to -1.0 μmolCO₂·m -2 ·s -1 at 18:00. In validation, simulation results showed good agreement with measured results with R ² = 0.79 and RMSE = 0.263. The results suggest that this method could accurately estimate the whole plant photosynthetic rate and be useful for pruning and adequate CO₂ fertilization.

Nitrogen dioxide observations from the Geostationary Trace gas and Aerosol Sensor Optimization (GeoTASO) airborne instrument: Retrieval algorithm and measurements during DISCOVER-AQ Texas 2013

EPA Science Inventory

The Geostationary Trace gas and Aerosol Sensor Optimization (GeoTASO) airborne instrument is a test bed for upcoming air quality satellite instruments that will measure backscattered ultraviolet, visible and near-infrared light from geostationary orbit. GeoTASO flew on the NASA F...

Leave No Trace! Land Ethics [and] Tread Lightly! On Public and Private Land. A National Land Use Ethics Program.

ERIC Educational Resources Information Center

Forest Service (USDA), Washington, DC.

This document consists of two brochures that provide land ethics guidelines for outdoor recreationists. The brochures provide techniques that visitors can use to help reduce evidence of their presence in the back country, designated "Wilderness" areas. The first brochure, titled "Leave no Trace! Land Ethics," provides…

Tracing WR wind structures by using the orbiting companion in the 29d WC8d + O8-9IV binary CV Ser

NASA Astrophysics Data System (ADS)

David-Uraz, Alexandre; Moffat, Anthony F. J.; Chené, André Nicolas; Lange, Nicholas

2011-01-01

We have obtained continuous, high-precision, broadband visible photometry from the MOST satellite of CV Ser over more than a full orbit in order to link the small-scale light-curve variations to extinction due to wind structures in the WR component, thus permitting us to trace these structures. The light-curve presented unexpected characteristics, in particular eclipses with a varying depth. Parallel optical spectroscopy from the Mont Megantic Observatory and Dominion Astrophysical Observatory was obtained to refine the orbital and wind-collision parameters, as well as to reveal line emission from clumps.

Bacterial Identification Using Light Scattering Measurements: a Preliminary Report

NASA Technical Reports Server (NTRS)

Wilkins, J. R.

1971-01-01

The light scattering properties of single bacterial cells were examined as a possible means of identification. Three species were studied with streptococcus faecalis exhibiting a unique pattern; the light-scattering traces for staphylococcus aureus and escherichia coli were quite similar although differences existed. Based on preliminary investigations, the light scattering approach appeared promising with additional research needed to include a wide variety of bacterial species, computer capability to handle and analyze data, and expansion of light scattering theory to include bacterial cells.

Single-cell computational analysis of light harvesting in a flat-panel photo-bioreactor.

PubMed

Loomba, Varun; Huber, Gregor; von Lieres, Eric

2018-01-01

Flat-panel photo-bioreactors (PBRs) are customarily applied for investigating growth of microalgae. Optimal design and operation of such reactors is still a challenge due to complex non-linear combinations of various impact factors, particularly hydrodynamics, light irradiation, and cell metabolism. A detailed analysis of single-cell light reception can lead to novel insights into the complex interactions of light exposure and algae movement in the reactor. The combined impacts of hydrodynamics and light irradiation on algae cultivation in a flat-panel PBR were studied by tracing the light exposure of individual cells over time. Hydrodynamics and turbulent mixing in this air-sparged bioreactor were simulated using the Eulerian approach for the liquid phase and a slip model for the gas phase velocity profiles. The liquid velocity was then used for tracing single cells and their light exposure, using light intensity profiles obtained from solving the radiative transfer equation at different wavelengths. The residence times of algae cells in defined dark and light zones of the PBR were statistically analyzed for different algal concentrations and sparging rates. The results indicate poor mixing caused by the reactor design which can be only partially improved by increased sparging rates. The results provide important information for optimizing algal biomass productivity by improving bioreactor design and operation and can further be utilized for an in-depth analysis of algal growth by using advanced models of cell metabolism.

Time-Related Decay or Interference-Based Forgetting in Working Memory?

ERIC Educational Resources Information Center

Portrat, Sophie; Barrouillet, Pierre; Camos, Valerie

2008-01-01

The time-based resource-sharing model of working memory assumes that memory traces suffer from a time-related decay when attention is occupied by concurrent activities. Using complex continuous span tasks in which temporal parameters are carefully controlled, P. Barrouillet, S. Bernardin, S. Portrat, E. Vergauwe, & V. Camos (2007) recently…

Desirable Difficulty and Other Predictors of Effective Item Orderings

ERIC Educational Resources Information Center

Tang, Steven; Gogel, Hannah; McBride, Elizabeth; Pardos, Zachary A.

2015-01-01

Online adaptive tutoring systems are increasingly being used in classrooms as a way to provide guided learning for students. Such tutors have the potential to provide tailored feedback based on specific student needs and misunderstandings. Bayesian knowledge tracing (BKT) is used to model student knowledge when knowledge is assumed to be changing…

Working Memory Span Development: A Time-Based Resource-Sharing Model Account

ERIC Educational Resources Information Center

Barrouillet, Pierre; Gavens, Nathalie; Vergauwe, Evie; Gaillard, Vinciane; Camos, Valerie

2009-01-01

The time-based resource-sharing model (P. Barrouillet, S. Bernardin, & V. Camos, 2004) assumes that during complex working memory span tasks, attention is frequently and surreptitiously switched from processing to reactivate decaying memory traces before their complete loss. Three experiments involving children from 5 to 14 years of age…

The Impact on Individualizing Student Models on Necessary Practice Opportunities

ERIC Educational Resources Information Center

Lee, Jung In; Brunskill, Emma

2012-01-01

When modeling student learning, tutors that use the Knowledge Tracing framework often assume that all students have the same set of model parameters. We find that when fitting parameters to individual students, there is significant variation among the individual's parameters. We examine if this variation is important in terms of instructional…

Can Thematic Roles Leave Traces of Their Places?

ERIC Educational Resources Information Center

Chang, Franklin; Bock, Kathryn; Goldberg, Adele E.

2003-01-01

An important question in the study of language production is the nature of the semantic information that speakers use to create syntactic structures. A common answer to this question assumes that thematic roles help to mediate the mapping from messages to syntax. However, research using structural priming has suggested that the construction of…

Multi-wavelength analysis of Ellerman Bomb Light Curves

NASA Astrophysics Data System (ADS)

Herlender, M.; Berlicki, A.

We present the results of a multi-wavelength photometric analysis of Ellerman Bomb (EB) observations obtained from the Dutch Open Telescope. In our data we have found 6 EBs located in the super-penumbra of the main spot in the active region NOAA 10781. We present light curves of EB observed in the Hα line centre and wing +0.7 Å, in the Ca II H line centre and wing~+2.35 Å, in the G-band and in the TRACE 1600 Å filter. We have shown that EBs were visible in the G-band and moreover, there was a good correlation between the light curves in the G-band and in the Hα line wings. We also found quasi-periodic oscillations of EBs brightness in the G-band, CaII H line and TRACE 1600 Å filter.

Don't Forget the Reflector.

ERIC Educational Resources Information Center

Morton, N.

1991-01-01

Various modes of reflection are classified and practical examples of devices, such as cat's eyes, are discussed. Typical light rays are traced through several systems, providing exercises with varying degrees of difficulty. Corner-cube retroreflectors, glass spheres, reflecting luminaries, light concentrators, parabolic reflectors, and off-set and…

Lighting for Our Schools.

ERIC Educational Resources Information Center

Rankin, John C.

In this speech, the author traces the history of lighting in schools, discusses the variables affecting the amount of illuminance needed, and provides a table of illuminances recommended for Ontario schools. Other factors that affect vision--glare, veiling reflection, color, and brightness balance--are outlined. Planners are admonished to…

Through-transmission laser welding of glass fibre composite: Experimental light scattering identification

NASA Astrophysics Data System (ADS)

Cosson, Benoit; Asséko, André Chateau Akué; Dauphin, Myriam

2018-05-01

The purpose of this paper is to develop a cost-effective, efficient and quick to implement experimental optical method in order to predict the optical properties (extinction coefficient) of semi-transparent polymer composites. The extinction coefficient takes into account the effects due to the absorption and the scattering phenomena in a semi-transparent component during the laser processes, i.e. TTLW (through-transmission laser welding). The present method used a laser as light source and a reflex camera equipped with a macro lens as a measurement device and is based on the light transmission measurement through different thickness samples. The interaction between the incident laser beam and the semi-transparent composite is exanimated. The results are presented for the case of a semi-transparent composite reinforced with the unidirectional glass fiber (UD). A numerical method, ray tracing, is used to validate the experimental results. The ray tracing method is appropriate to characterize the light-scattering phenomenon in semi-transparent materials.

Evaluation of light extraction efficiency for the light-emitting diodes based on the transfer matrix formalism and ray-tracing method

NASA Astrophysics Data System (ADS)

Pingbo, An; Li, Wang; Hongxi, Lu; Zhiguo, Yu; Lei, Liu; Xin, Xi; Lixia, Zhao; Junxi, Wang; Jinmin, Li

2016-06-01

The internal quantum efficiency (IQE) of the light-emitting diodes can be calculated by the ratio of the external quantum efficiency (EQE) and the light extraction efficiency (LEE). The EQE can be measured experimentally, but the LEE is difficult to calculate due to the complicated LED structures. In this work, a model was established to calculate the LEE by combining the transfer matrix formalism and an in-plane ray tracing method. With the calculated LEE, the IQE was determined and made a good agreement with that obtained by the ABC model and temperature-dependent photoluminescence method. The proposed method makes the determination of the IQE more practical and conventional. Project supported by the National Natural Science Foundation of China (Nos.11574306, 61334009), the China International Science and Technology Cooperation Program (No. 2014DFG62280), and the National High Technology Program of China (No. 2015AA03A101).

HUBBLE IDENTIFIES SOURCE OF ULTRAVIOLET LIGHT IN AN OLD GALAXY

NASA Technical Reports Server (NTRS)

2002-01-01

Hubble Space Telescope's exquisite resolution has allowed astronomers to resolve, for the first time, hot blue stars deep inside an elliptical galaxy. The swarm of nearly 8,000 blue stars resembles a blizzard of snowflakes near the core (lower right) of the neighboring galaxy M32, located 2.5 million light-years away in the constellation Andromeda. Hubble confirms that the ultraviolet light comes from a population of extremely hot helium-burning stars at a late stage in their lives. Unlike the Sun, which burns hydrogen into helium, these old stars exhausted their central hydrogen long ago, and now burn helium into heavier elements. The observations, taken in October 1998, were made with the camera mode of the Space Telescope Imaging Spectrograph (STIS) in ultraviolet light. The STIS field of view is only a small portion of the entire galaxy, which is 20 times wider on the sky. For reference, the full moon is 70 times wider than the STIS field-of-view. The bright center of the galaxy was placed on the right side of the image, allowing fainter stars to be seen on the left side of the image. These results are to be published in the March 1, 2000 issue of The Astrophysical Journal. Thirty years ago, the first ultraviolet observations of elliptical galaxies showed that they were surprisingly bright when viewed in ultraviolet light. Before those pioneering UV observations, old groups of stars were assumed to be relatively cool and thus extremely faint in the ultraviolet. Over the years since the initial discovery of this unexpected ultraviolet light, indirect evidence has accumulated that it originates in a population of old, but hot, helium-burning stars. Now Hubble provides the first direct visual evidence. Nearby elliptical galaxies are thought to be relatively simple galaxies comprised of old stars. Because they are among the brightest objects in the Universe, this simplicity makes them useful for tracing the evolution of stars and galaxies. Credits: NASA and Thomas M. Brown, Charles W. Bowers, Randy A. Kimble, Allen V. Sweigart (NASA Goddard Space Flight Center) and Henry C. Ferguson (Space Telescope Science Institute).

Limits on the power-law mass and luminosity density profiles of elliptical galaxies from gravitational lensing systems

NASA Astrophysics Data System (ADS)

Cao, Shuo; Biesiada, Marek; Yao, Meng; Zhu, Zong-Hong

2016-09-01

We use 118 strong gravitational lenses observed by the SLACS, BOSS emission-line lens survey (BELLS), LSD and SL2S surveys to constrain the total mass profile and the profile of luminosity density of stars (light tracers) in elliptical galaxies up to redshift z ˜ 1. Assuming power-law density profiles for the total mass density, ρ = ρ0(r/r0)-α, and luminosity density, ν = ν0(r/r0)-δ, we investigate the power-law index and its first derivative with respect to the redshift. Using Monte Carlo simulations of the posterior likelihood taking the Planck's best-fitting cosmology as a prior, we find γ = 2.132 ± 0.055 with a mild trend ∂γ/∂zl = -0.067 ± 0.119 when α = δ = γ, suggesting that the total density profile of massive galaxies could have become slightly steeper over cosmic time. Furthermore, similar analyses performed on sub-samples defined by different lens redshifts and velocity dispersions indicate the need of treating low-, intermediate- and high-mass galaxies separately. Allowing δ to be a free parameter, we obtain α = 2.070 ± 0.031, ∂α/∂zl = -0.121 ± 0.078 and δ = 2.710 ± 0.143. The model in which mass traces light is rejected at >95 per cent confidence, and our analysis robustly indicates the presence of dark matter in the form of a mass component that is differently spatially extended than the light. In this case, intermediate-mass elliptical galaxies (200 km s-1 <σap ≤ 300 km s-1) show the best consistency with the singular isothermal sphere as an effective model of galactic lenses.

New ALMA Images of the HD 32297 and HD 61005 Debris Disks

NASA Astrophysics Data System (ADS)

MacGregor, Meredith Ann; Weinberger, Alycia; Wilner, David; Hughes, A. Meredith; debes, John Henry; Redfield, Seth; Donaldson, Jessica; Nesvold, Erika; Schneider, Glenn; Currie, Thayne; Roberge, Aki; Rodriguez, David

2018-01-01

HD 61005 (G-type star, “The Moth") and HD 32297 (A-type star) host two of the most iconic debris disks. Scattered light images show that both disks are nearly edge-on with dramatic swept-back wings of dust. Previous studies have proposed a range of mechanisms to explain this distinctive morphology including interactions with the interstellar medium, secular perturbations of grains by low-density, neutral interstellar gas, and gravitational interactions with an inclined, eccentric companion. We present new observations from the Atacama Large Millimeter/submillimeter Array (ALMA) at 1.3 mm that provide the highest resolution images at millimeter wavelengths to date of both systems. Observations at millimeter wavelengths are especially critical to our understanding of the physical mechanisms shaping the structure of these disks, since the large grains that dominate emission at these wavelengths are less affected by stellar radiation and winds and more reliably trace the underlying planetesimal distribution. We fit models directly to the observed visibilities within a Markov Chain Monte Carlo (MCMC) framework to characterize the continuum emission and place constraints on the structure of these unique debris disks. Our new ALMA images reveal that despite differences in spectral type, both systems are best described by a two-component structure with (1) a parent body belt, and (2) an outer halo aligned with the scattered light disk. Such halos have typically been assumed to be composed of small grains visible in scattered light, so these images are some of the first observational evidence that larger grains may also populate extended halos. In addition, we detect significant 12CO gas emission from HD 32297, and determine a robust upper limit for HD 61005.

Trace organic solutes in closed-loop forward osmosis applications: influence of membrane fouling and modeling of solute build-up.

PubMed

D'Haese, Arnout; Le-Clech, Pierre; Van Nevel, Sam; Verbeken, Kim; Cornelissen, Emile R; Khan, Stuart J; Verliefde, Arne R D

2013-09-15

In this study, trace organics transport in closed-loop forward osmosis (FO) systems was assessed. The FO systems considered, consisted of an FO unit and a nanofiltration (NF) or reverse osmosis (RO) unit, with the draw solution circulating between both units. The rejection of trace organics by FO, NF and RO was tested. It was found that the rejection rates of FO were generally comparable with NF and lower than RO rejection rates. To assess the influence of fouling in FO on trace organics rejection, FO membranes were fouled with sodium alginate, bovine serum albumin or by biofilm growth, after which trace organics rejection was tested. A negative influence of fouling on FO rejection was found which was limited in most cases, while it was significant for some compounds such as paracetamol and naproxen, indicating specific compound-foulant interactions. The transport mechanism of trace organics in FO was tested, in order to differentiate between diffusive and convective transport. The concentration of trace organics in the final product water and the build-up of trace organics in the draw solution were modeled assuming the draw solution was reconcentrated by NF/RO and taking into account different transport mechanisms for the FO membrane and different rejection rates by NF/RO. Modeling results showed that if the FO rejection rate is lower than the RO rejection rate (as is the case for most compounds tested), the added value of the FO-RO cycle compared to RO only at steady-state was small for diffusively and negative for convectively transported trace organics. Modeling also showed that trace organics accumulate in the draw solution. Copyright © 2013 Elsevier Ltd. All rights reserved.

Dielectric constant of atomic fluids with variable polarizability

PubMed Central

Alder, B. J.; Beers, J. C.; Strauss, H. L.; Weis, J. J.

1980-01-01

The Clausius-Mossotti function for the dielectric constant is expanded in terms of single atom and pair polarizabilities, leading to contributions that depend on both the trace and the anisotropy of the pair-polarizability tensor. The short-range contribution of the anisotropic part to the pair polarizabilities has previously been obtained empirically from light scattering experiments, whereas the trace contribution is now empirically determined by comparison to dielectric experiments. For helium, the short-range trace part agrees well with electronic structure calculations, whereas for argon qualitative agreement is achieved. PMID:16592830

Dielectric constant of atomic fluids with variable polarizability.

PubMed

Alder, B J; Beers, J C; Strauss, H L; Weis, J J

1980-06-01

The Clausius-Mossotti function for the dielectric constant is expanded in terms of single atom and pair polarizabilities, leading to contributions that depend on both the trace and the anisotropy of the pair-polarizability tensor. The short-range contribution of the anisotropic part to the pair polarizabilities has previously been obtained empirically from light scattering experiments, whereas the trace contribution is now empirically determined by comparison to dielectric experiments. For helium, the short-range trace part agrees well with electronic structure calculations, whereas for argon qualitative agreement is achieved.

Optimization of light source parameters in the photodynamic therapy of heterogeneous prostate

NASA Astrophysics Data System (ADS)

Li, Jun; Altschuler, Martin D.; Hahn, Stephen M.; Zhu, Timothy C.

2008-08-01

The three-dimensional (3D) heterogeneous distributions of optical properties in a patient prostate can now be measured in vivo. Such data can be used to obtain a more accurate light-fluence kernel. (For specified sources and points, the kernel gives the fluence delivered to a point by a source of unit strength.) In turn, the kernel can be used to solve the inverse problem that determines the source strengths needed to deliver a prescribed photodynamic therapy (PDT) dose (or light-fluence) distribution within the prostate (assuming uniform drug concentration). We have developed and tested computational procedures to use the new heterogeneous data to optimize delivered light-fluence. New problems arise, however, in quickly obtaining an accurate kernel following the insertion of interstitial light sources and data acquisition. (1) The light-fluence kernel must be calculated in 3D and separately for each light source, which increases kernel size. (2) An accurate kernel for light scattering in a heterogeneous medium requires ray tracing and volume partitioning, thus significant calculation time. To address these problems, two different kernels were examined and compared for speed of creation and accuracy of dose. Kernels derived more quickly involve simpler algorithms. Our goal is to achieve optimal dose planning with patient-specific heterogeneous optical data applied through accurate kernels, all within clinical times. The optimization process is restricted to accepting the given (interstitially inserted) sources, and determining the best source strengths with which to obtain a prescribed dose. The Cimmino feasibility algorithm is used for this purpose. The dose distribution and source weights obtained for each kernel are analyzed. In clinical use, optimization will also be performed prior to source insertion to obtain initial source positions, source lengths and source weights, but with the assumption of homogeneous optical properties. For this reason, we compare the results from heterogeneous optical data with those obtained from average homogeneous optical properties. The optimized treatment plans are also compared with the reference clinical plan, defined as the plan with sources of equal strength, distributed regularly in space, which delivers a mean value of prescribed fluence at detector locations within the treatment region. The study suggests that comprehensive optimization of source parameters (i.e. strengths, lengths and locations) is feasible, thus allowing acceptable dose coverage in a heterogeneous prostate PDT within the time constraints of the PDT procedure.

Geochemical Impacts of Carbon Dioxide, Brine, Trace Metal and Organic Leakage into an Unconfined, Oxidizing Limestone Aquifer

DOE PAGES

Bacon, Diana H.; Dai, Zhenxue; Zheng, Liange

2014-12-31

An important risk at CO2 storage sites is the potential for groundwater quality impacts. As part of a system to assess the potential for these impacts a geochemical scaling function has been developed, based on a detailed reactive transport model of CO2 and brine leakage into an unconfined, oxidizing carbonate aquifer. Stochastic simulations varying a number of geochemical parameters were used to generate a response surface predicting the volume of aquifer that would be impacted with respect to regulated contaminants. The brine was assumed to contain several trace metals and organic contaminants. Aquifer pH and TDS were influenced by CO2more » leakage, while trace metal concentrations were most influenced by the brine concentrations rather than adsorption or desorption on calcite. Organic plume sizes were found to be strongly influenced by biodegradation.« less

Nonimaging light concentration using total internal reflection films.

PubMed

Ouellette, G; Waltham, C E; Drees, R M; Poon, A; Schubank, R; Whitehead, L A

1992-05-01

We present a method of fabricating nonimaging light concentrators from total internal reflection film. A prototype has been made and tested and found to operate in agreement with predictions of ray-tracing codes. The performance of the prototype is comparable with that of concentrators made from specular reflecting materials.

Modeling the light-induced electric potential difference (ΔΨ), the pH difference (ΔpH) and the proton motive force across the thylakoid membrane in C3 leaves.

PubMed

Lyu, Hui; Lazár, Dušan

2017-01-21

A model was constructed which includes electron transport (linear and cyclic and Mehler type reaction) coupled to proton translocation, counter ion movement, ATP synthesis, and Calvin-Benson cycle. The focus is on modeling of the light-induced total electric potential difference (ΔΨ) which in this model originates from the bulk phase electric potential difference (ΔΨ b ), the localized electric potential difference (ΔΨ c ), as well as the surface electric potential difference (ΔΨ s ). The measured dual wavelength transmittance signal (ΔA515-560nm, electrochromic shift) was used as a proxy for experimental ΔΨ. The predictions for theoretical ΔΨ vary with assumed contribution of ΔΨ s , which might imply that the measured ΔA515-560nm trace on a long time scale reflects the interplay of the ΔΨ components. Simulations also show that partitioning of proton motive force (pmf) to ΔΨ b and ΔpH components is sensitive to the stoichiometric ratio of H + /ATP, energy barrier for ATP synthesis, ionic strength, buffer capacity and light intensity. Our model shows that high buffer capacity promotes the establishment of ΔΨ b , while the formation of pH i minimum is not 'dissipated' but 'postponed' until it reaches the same level as that for low buffer capacity. Under physiologically optimal conditions, the output of the model shows that at steady state in light, the ΔpH component is the main contributor to pmf to drive ATP synthesis while a low ΔΨ b persists energizing the membrane. Our model predicts 11mV as the resting electric potential difference across the thylakoid membrane in dark. We suggest that the model presented in this work can be integrated as a module into a more comprehensive model of oxygenic photosynthesis. Copyright © 2016 Elsevier Ltd. All rights reserved.

Time Constraints and Resource Sharing in Adults' Working Memory Spans

ERIC Educational Resources Information Center

Barrouillet, Pierre; Bernardin, Sophie; Camos, Valerie

2004-01-01

This article presents a new model that accounts for working memory spans in adults, the time-based resource-sharing model. The model assumes that both components (i.e., processing and maintenance) of the main working memory tasks require attention and that memory traces decay as soon as attention is switched away. Because memory retrievals are…

20 Years of Autonomy and Technology: How Far Have We Come and Where to Next?

ERIC Educational Resources Information Center

Reinders, Hayo; White, Cynthia

2016-01-01

Learner autonomy has become an assumed goal of language education in many parts of the world. In the 20 years since the launch of "Language Learning & Technology," the relationship among computer-assisted language learning research and practice and autonomy has become both more complex and more promising. This article traces how the…

The Origins of Classroom Deliberation: Democratic Education in the Shadow of Totalitarianism, 1938-1960

ERIC Educational Resources Information Center

Fallace, Thomas D.

2016-01-01

Many theorists of democratic education assume that the idea of having students deliberate about social issues in the classroom can be traced directly to the student-centered and reform-oriented ideals of interwar educational theorists such as John Dewey and Harold Rugg. However, in this intellectual history, Thomas D. Fallace argues that classroom…

Calcineurin Inhibition Blocks Within-, but Not Between-Session Fear Extinction in Mice

ERIC Educational Resources Information Center

Almeida-Corrêa, Suellen; Moulin, Thiago C.; Carneiro, Clarissa F. D.; Gonçalves, Marina M. C.; Junqueira, Lara S.; Amaral, Olavo B.

2015-01-01

Memory extinction involves the formation of a new associative memory that inhibits a previously conditioned association. Nonetheless, it could also depend on weakening of the original memory trace if extinction is assumed to have multiple components. The phosphatase calcineurin (CaN) has been described as being involved in extinction but not in…

Light propagation through black-hole lattices

NASA Astrophysics Data System (ADS)

Bentivegna, Eloisa; Korzyński, Mikołaj; Hinder, Ian; Gerlicher, Daniel

2017-03-01

The apparent properties of distant objects encode information about the way the light they emit propagates to an observer, and therefore about the curvature of the underlying spacetime. Measuring the relationship between the redshift z and the luminosity distance DL of a standard candle, for example, yields information on the Universe's matter content. In practice, however, in order to decode this information the observer needs to make an assumption about the functional form of the DL(z) relation; in other words, a cosmological model needs to be assumed. In this work, we use numerical-relativity simulations, equipped with a new ray-tracing module, to numerically obtain this relation for a few black-hole-lattice cosmologies and compare it to the well-known Friedmann-Lema{ȋtre-Robertson-Walker case, as well as to other relevant cosmologies and to the Empty-Beam Approximation. We find that the latter provides the best estimate of the luminosity distance and formulate a simple argument to account for this agreement. We also find that a Friedmann-Lema{ȋtre-Robertson-Walker model can reproduce this observable exactly, as long as a time-dependent cosmological constant is included in the fit. Finally, the dependence of these results on the lattice mass-to-spacing ratio μ is discussed: we discover that, unlike the expansion rate, the DL(z) relation in a black-hole lattice does not tend to that measured in the corresponding continuum spacetime as 0μ → .

Light propagation through black-hole lattices

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

Bentivegna, Eloisa; Korzyński, Mikołaj; Hinder, Ian

The apparent properties of distant objects encode information about the way the light they emit propagates to an observer, and therefore about the curvature of the underlying spacetime. Measuring the relationship between the redshift z and the luminosity distance D {sub L} of a standard candle, for example, yields information on the Universe's matter content. In practice, however, in order to decode this information the observer needs to make an assumption about the functional form of the D {sub L}( z ) relation; in other words, a cosmological model needs to be assumed. In this work, we use numerical-relativity simulations,more » equipped with a new ray-tracing module, to numerically obtain this relation for a few black-hole-lattice cosmologies and compare it to the well-known Friedmann-Lema(ȋtre-Robertson-Walker case, as well as to other relevant cosmologies and to the Empty-Beam Approximation. We find that the latter provides the best estimate of the luminosity distance and formulate a simple argument to account for this agreement. We also find that a Friedmann-Lema(ȋtre-Robertson-Walker model can reproduce this observable exactly, as long as a time-dependent cosmological constant is included in the fit. Finally, the dependence of these results on the lattice mass-to-spacing ratio μ is discussed: we discover that, unlike the expansion rate, the D {sub L}( z ) relation in a black-hole lattice does not tend to that measured in the corresponding continuum spacetime as 0μ → .« less

Derivatives of Black Knight Technology

NASA Astrophysics Data System (ADS)

Hill, N.; Wright, D.

This paper traces the line of descent from Black Knight to Black Arrow, and at the same time looks at various proposed projects, both civil and military, which were to be Black Knight derivatives, but which for one reason or another never saw the light of day. Research in this area is rather akin to anthropological work, tracing fossils from Homo erectus (Black Knight) to Homo sapiens (Black Arrow), knowing that a lot of the fossils found will not be on the direct line of descent, but represent branches that became extinct. This article attempts to cover designs, which, although they never made it to hardware, are none the less interesting technically, or shine light on the evolution of design philosophy.

Adult stem cell lineage tracing and deep tissue imaging

PubMed Central

Fink, Juergen; Andersson-Rolf, Amanda; Koo, Bon-Kyoung

2015-01-01

Lineage tracing is a widely used method for understanding cellular dynamics in multicellular organisms during processes such as development, adult tissue maintenance, injury repair and tumorigenesis. Advances in tracing or tracking methods, from light microscopy-based live cell tracking to fluorescent label-tracing with two-photon microscopy, together with emerging tissue clearing strategies and intravital imaging approaches have enabled scientists to decipher adult stem and progenitor cell properties in various tissues and in a wide variety of biological processes. Although technical advances have enabled time-controlled genetic labeling and simultaneous live imaging, a number of obstacles still need to be overcome. In this review, we aim to provide an in-depth description of the traditional use of lineage tracing as well as current strategies and upcoming new methods of labeling and imaging. [BMB Reports 2015; 48(12): 655-667] PMID:26634741

Advances in Current Rating Techniques for Flexible Printed Circuits

NASA Technical Reports Server (NTRS)

Hayes, Ron

2014-01-01

Twist Capsule Assemblies are power transfer devices commonly used in spacecraft mechanisms that require electrical signals to be passed across a rotating interface. Flexible printed circuits (flex tapes, see Figure 2) are used to carry the electrical signals in these devices. Determining the current rating for a given trace (conductor) size can be challenging. Because of the thermal conditions present in this environment the most appropriate approach is to assume that the only means by which heat is removed from the trace is thru the conductor itself, so that when the flex tape is long the temperature rise in the trace can be extreme. While this technique represents a worst-case thermal situation that yields conservative current ratings, this conservatism may lead to overly cautious designs when not all traces are used at their full rated capacity. A better understanding of how individual traces behave when they are not all in use is the goal of this research. In the testing done in support of this paper, a representative flex tape used for a flight Solar Array Drive Assembly (SADA) application was tested by energizing individual traces (conductors in the tape) in a vacuum chamber and the temperatures of the tape measured using both fine-gauge thermocouples and infrared thermographic imaging. We find that traditional derating schemes used for bundles of wires do not apply for the configuration tested. We also determine that single active traces located in the center of a flex tape operate at lower temperatures than those on the outside edges.

Light sensors for objective light measurement in ambulatory polysomnography.

PubMed

Schembri, Rachel; Spong, Jo; Peters, Allison; Rochford, Peter; Wilksch, Philip; O'Donoghue, Fergal J; Greenwood, Kenneth M; Barnes, Maree; Kennedy, Gerard A; Berlowitz, David J

2017-01-01

Ambulatory polysomnography (PSG) does not commonly include an objective measure of light to determine the time of lights off (Loff), and thus cannot be used to calculate important indices such as sleep onset latency and sleep efficiency. This study examined the technical specifications and appropriateness of a prototype light sensor (LS) for use in ambulatory Compumedics Somte PSG.Two studies were conducted. The first examined the light measurement characteristics of the LS when used with a portable PSG device, specifically recording trace range, linearity, sensitivity, and stability. This involved the LS being exposed to varying incandescent and fluorescent light levels in a light controlled room. Secondly, the LS was trialled in 24 home and 12 hospital ambulatory PSGs to investigate whether light levels in home and hospital settings were within the recording range of the LS, and to quantify the typical light intensity reduction at the time of Loff. A preliminary exploration of clinical utility was also conducted. Linearity between LS voltage and lux was demonstrated, and the LS trace was stable over 14 hours of recording. The observed maximum voltage output of the LS/PSG device was 250 mV, corresponding to a maximum recording range of 350 lux and 523 lux for incandescent and fluorescent light respectively. At the time of Loff, light levels were within the recording range of the LS, and on average dropped by 72 lux (9-245) in the home and 76 lux (4-348) in the hospital setting. Results suggest that clinical utility was greatest in hospital settings where patients are less mobile. The LS was a simple and effective objective marker of light level in portable PSG, which can be used to identify Loff in ambulatory PSG. This allows measurement of additional sleep indices and support with clinical decisions.

The Nature of Light: II. A Historical Survey from the Planck Era and Implications for Budding Physicists

ERIC Educational Resources Information Center

Oon, Pey Tee; Subramaniam, R.

2009-01-01

Following on from our previous article (Oon and Subramaniam 2009 "Phys. Educ." 44 384-91), here we trace ideas on the history of light from the Planck era to modern times. In particular, the seminal contributions of Planck, Einstein and de Broglie are highlighted. Some lesser known facets of the nature of light are also emphasized. It is stressed…

Improving LED CCT uniformity using micropatterned films optimized by combining ray tracing and FDTD methods.

PubMed

Ding, Xinrui; Li, Jiasheng; Chen, Qiu; Tang, Yong; Li, Zongtao; Yu, Binhai

2015-02-09

Although the light-emitting diode (LED) has revolutionized lighting, the non-uniformity of its correlated color temperature (CCT) still remains a major concern. In this context, to improve the light distribution performance of remote phosphor LED lamps, we employ a micropatterned array (MPA) optical film fabricated using a low-cost molding process. The parameters of the MPA, including different installation configurations, positioning, and diameters, are optimized by combining the finite-difference time-domain and ray-tracing methods. Results show that the sample with the upward-facing convex-cone MPA film that has a diameter of half of that of the remote phosphor glass, and is tightly affixed to the inward surface of the remote phosphor glass renders a superior light distribution performance. When compared with the case in which no MPA film is used, the deviation of the CCT distribution decreases from 1033 K to 223 K, and the corresponding output power of the sample is an acceptable level of 85.6%. We perform experiments to verify our simulation results, and the two sets of results exhibit a close agreement. We believe that our approach can be used to optimize MPA films for various lighting applications.

The dopamine D1 receptor agonist SKF81297 has dose-related effects on locomotor activity but is without effect in a CER trace conditioning procedure conducted with two versus four trials.

PubMed

Pezze, M A; Marshall, H J; Cassaday, H J

2016-08-01

In an appetitively motivated procedure, we have previously reported that systemic treatment with the dopamine (DA) D1 receptor agonist SKF81297 (0.4 and 0.8 mg/kg) depressed acquisition at a 2 s inter-stimulus-interval (ISI), suitable to detect trace conditioning impairment. However since DA is involved in reinforcement processes, the generality of effects across appetitively- and aversively-motivated trace conditioning procedures cannot be assumed. The present study tested the effects of SKF81297 (0.4 and 0.8 mg/kg) in an established conditioned emotional response (CER) procedure. Trace-dependent conditioning was clearly shown in two experiments: while conditioning was relatively strong at a 3-s ISI, it was attenuated at a 30-s ISI. This was shown after two (Experiment 1) or four (Experiment 2) conditioning trials conducted in - as far as possible - the same CER procedure. Contrary to prediction, in neither experiment was there any indication that trace conditioning was attenuated by treatment with 0.4 or 0.8 mg/kg SKF81297. In the same rats, locomotor activity was significantly enhanced at the 0.8 mg/kg dose of SKF81297. These results suggest that procedural details of the trace conditioning variant in use are an important determinant of the profile of dopaminergic modulation.

Novel ray tracing method for stray light suppression from ocean remote sensing measurements.

PubMed

Oh, Eunsong; Hong, Jinsuk; Kim, Sug-Whan; Park, Young-Je; Cho, Seong-Ick

2016-05-16

We developed a new integrated ray tracing (IRT) technique to analyze the stray light effect in remotely sensed images. Images acquired with the Geostationary Ocean Color Imager show a radiance level discrepancy at the slot boundary, which is suspected to be a stray light effect. To determine its cause, we developed and adjusted a novel in-orbit stray light analysis method, which consists of three simulated phases (source, target, and instrument). Each phase simulation was performed in a way that used ray information generated from the Sun and reaching the instrument detector plane efficiently. This simulation scheme enabled the construction of the real environment from the remote sensing data, with a focus on realistic phenomena. In the results, even in a cloud-free environment, a background stray light pattern was identified at the bottom of each slot. Variations in the stray light effect and its pattern according to bright target movement were simulated, with a maximum stray light ratio of 8.5841% in band 2 images. To verify the proposed method and simulation results, we compared the results with the real acquired remotely sensed image. In addition, after correcting for abnormal phenomena in specific cases, we confirmed that the stray light ratio decreased from 2.38% to 1.02% in a band 6 case, and from 1.09% to 0.35% in a band 8 case. IRT-based stray light analysis enabled clear determination of the stray light path and candidates in in-orbit circumstances, and the correction process aided recovery of the radiometric discrepancy.

Viewer Makes Radioactivity "Visible"

NASA Technical Reports Server (NTRS)

Yin, L. I.

1983-01-01

Battery operated viewer demonstrates feasibility of generating threedimensional visible light simulations of objects that emit X-ray or gamma rays. Ray paths are traced for two pinhold positions to show location of reconstructed image. Images formed by pinholes are converted to intensified visible-light images. Applications range from radioactivity contamination surveys to monitoring radioisotope absorption in tumors.

The polarization of light in coastal and open oceans: Reflection and transmission by the air-sea interface and application for the retrieval of water optical properties

NASA Astrophysics Data System (ADS)

Foster, Robert

For decades, traditional remote sensing retrieval methods that rely solely on the spectral intensity of the water-leaving light have provided indicators of aquatic ecosystem health. With the increasing demand for new water quality indicators and improved accuracy of existing ones, the limits of traditional remote sensing approaches are becoming apparent. Use of the additional information intrinsic to the polarization state of light is therefore receiving more attention. One of the major challenges inherent in any above-surface determination of the water-leaving radiance, scalar or vector, is the removal of extraneous light which has not interacted with the water body and is therefore not useful for remote sensing of the water itself. Due in-part to the lack of a proven alternative, existing polarimeter installations have thus far assumed that such light was reflected by a flat sea surface, which can lead to large inaccuracies in the water-leaving polarization signal. This dissertation rigorously determines the full Mueller matrices for both surface-reflected skylight and upwardly transmitted light by a wind-driven ocean surface. A Monte Carlo code models the surface in 3D and performs polarized ray-tracing, while a vector radiative transfer (VRT) simulation generates polarized light distributions from which the initial Stokes vector for each ray is inferred. Matrices are computed for the observable range of surface wind speeds, viewing and solar geometries, and atmospheric aerosol loads. Radiometer field-of-view effects are also assessed. Validation of the results is achieved using comprehensive VRT simulations of the atmosphere-ocean system based on several oceanographic research cruises and specially designed polarimeters developed by the City College of New York: one submerged beneath the surface and one mounted on a research vessel. When available, additional comparisons are made at 9 km altitude with the NASA Research Scanning Polarimeter (RSP). Excellent agreement is achieved between all instrumentation, demonstrating the accuracy of the modeling approach and validating the computed Mueller matrices. Further, the results are used to demonstrate the feasibility for polarimetric retrieval of the total attenuation coefficient for Case II waters, a feat which is not possible using scalar remote sensing methods.

Tracing contacts of TB patients in Malaysia: costs and practicality.

PubMed

Atif, Muhammad; Sulaiman, Syed Azhar Syed; Shafie, Asrul Akmal; Ali, Irfhan; Asif, Muhammad

2012-01-01

Tuberculin skin testing (TST) and chest X-ray are the conventional methods used for tracing suspected tuberculosis (TB) patients. The purpose of the study was to calculate the cost incurred by Penang General Hospital on performing one contact tracing procedure using an activity based costing approach. Contact tracing records (including the demographic profile of contacts and outcome of the contact tracing procedure) from March 2010 until February 2011 were retrospectively obtained from the TB contact tracing record book. The human resource cost was calculated by multiplying the mean time spent (in minutes) by employees doing a specific activity by their per-minute salaries. The costs of consumables, Purified Protein Derivative vials and clinical equipment were obtained from the procurement section of the Pharmacy and Radiology Departments. The cost of the building was calculated by multiplying the area of space used by the facility with the unit cost of the public building department. Straight-line deprecation with a discount rate of 3% was assumed for the calculation of equivalent annual costs for the building and machines. Out of 1024 contact tracing procedures, TST was positive (≥10 mm) in 38 suspects. However, chemoprophylaxis was started in none. Yield of contact tracing (active tuberculosis) was as low as 0.5%. The total unit cost of chest X-ray and TST was MYR 9.23 (2.90 USD) & MYR 11.80 (USD 3.70), respectively. The total cost incurred on a single contact tracing procedure was MYR 21.03 (USD 6.60). Our findings suggest that the yield of contact tracing was very low which may be attributed to an inappropriate prioritization process. TST may be replaced with more accurate and specific methods (interferon gamma release assay) in highly prioritized contacts; or TST-positive contacts should be administered 6H therapy (provided that the chest radiography excludes TB) in accordance with standard protocols. The unit cost of contact tracing can be significantly reduced if radiological examination is done only in TST or IRGA positive contacts.

Oil and gas exploration system and method for detecting trace amounts of hydrocarbon gases in the atmosphere

DOEpatents

Wamsley, Paula R.; Weimer, Carl S.; Nelson, Loren D.; O'Brien, Martin J.

2003-01-01

An oil and gas exploration system and method for land and airborne operations, the system and method used for locating subsurface hydrocarbon deposits based upon a remote detection of trace amounts of gases in the atmosphere. The detection of one or more target gases in the atmosphere is used to indicate a possible subsurface oil and gas deposit. By mapping a plurality of gas targets over a selected survey area, the survey area can be analyzed for measurable concentration anomalies. The anomalies are interpreted along with other exploration data to evaluate the value of an underground deposit. The system includes a differential absorption lidar (DIAL) system with a spectroscopic grade laser light and a light detector. The laser light is continuously tunable in a mid-infrared range, 2 to 5 micrometers, for choosing appropriate wavelengths to measure different gases and avoid absorption bands of interference gases. The laser light has sufficient optical energy to measure atmospheric concentrations of a gas over a path as long as a mile and greater. The detection of the gas is based on optical absorption measurements at specific wavelengths in the open atmosphere. Light that is detected using the light detector contains an absorption signature acquired as the light travels through the atmosphere from the laser source and back to the light detector. The absorption signature of each gas is processed and then analyzed to determine if a potential anomaly exists.

"Once-Upon-A-Time" Reconsidered: The Developmental Dialectic between Function and Form. Technical Report No. 36.

ERIC Educational Resources Information Center

Dyson, Anne Haas

A case study traces the evolution of "once-upon-a-time" in a child's classroom story writing, drawing upon data collected in a three-year study of writing development in an urban magnet school. The subject, Mitzi, is observed from kindergarten through second grade. The study assumes that stories are cultural discourse forms that serve…

Neural Evidence for a Distinction between Short-Term Memory and the Focus of Attention

ERIC Educational Resources Information Center

Lewis-Peacock, Jarrod A.; Drysdale, Andrew T.; Oberauer, Klaus; Postle, Bradley R.

2012-01-01

It is widely assumed that the short-term retention of information is accomplished via maintenance of an active neural trace. However, we demonstrate that memory can be preserved across a brief delay despite the apparent loss of sustained representations. Delay period activity may, in fact, reflect the focus of attention, rather than STM. We…

Coding of Stimuli by Animals: Retrospection, Prospection, Episodic Memory and Future Planning

ERIC Educational Resources Information Center

Zentall, Thomas R.

2010-01-01

When animals code stimuli for later retrieval they can either code them in terms of the stimulus presented (as a retrospective memory) or in terms of the response or outcome anticipated (as a prospective memory). Although retrospective memory is typically assumed (as in the form of a memory trace), evidence of prospective coding has been found…

In Search of an Audience: "Kid Creole and the Coconuts."

ERIC Educational Resources Information Center

Aiex, Nola Kortner

The hybrid music of the group "Kid Creole and the Coconuts" shows traces of every popular music style that has aroused New York City during the past 40 years--big band swing, Latin dance music, calypso, reggae, disco, funk, soul, rock, and movie pop. The fictitious characters the members of the band assume on stage, together with their…

Tracing Sustainability: Education for Sustainable Development in the Lower Secondary Geography Curricula of Germany, Romania, and Mexico

ERIC Educational Resources Information Center

Bagoly-Simó, Péter

2014-01-01

Over the last two decades Education for Sustainable Development (ESD) has received increasing attention. Due to the close affinity that geography as a school subject shares with both theoretical constructs and methodologies of ESD, geography has assumed a key position in the implementation of ESD in formal education. Still, little attention has so…

Effects of dopamine D1 modulation of the anterior cingulate cortex in a fear conditioning procedure

PubMed Central

Pezze, M.A.; Marshall, H.J.; Domonkos, A.; Cassaday, H.J.

2016-01-01

The anterior cingulate cortex (AC) component of the medial prefrontal cortex (mPFC) has been implicated in attention and working memory as measured by trace conditioning. Since dopamine (DA) is a key modulator of mPFC function, the present study evaluated the role of DA receptor agents in rat AC, using trace fear conditioning. A conditioned stimulus (CS, noise) was followed by an unconditioned stimulus (US, shock) with or without a 10 s trace interval interposed between these events in a between-subjects design. Conditioned suppression of drinking was assessed in response to presentation of the CS or an experimental background stimulus (flashing lights, previously presented for the duration of the conditioning session). The selective D1 agonist SKF81297 (0.05 μg/side) or D1 antagonist SCH23390 (0.5 μg/side) was administered by intra-cerebral microinfusion directly into AC. It was predicted that either of these manipulations should be sufficient to impair trace (but not delay) conditioning. Counter to expectation, there was no effect of DA D1 modulation on trace conditioning as measured by suppression to the noise CS. However, rats infused with SKF81297 acquired stronger conditioned suppression to the experimental background stimulus than those infused with SCH23390 or saline. Thus, the DA D1 agonist SKF81297 increased conditioned suppression to the contextual background light stimulus but was otherwise without effect on fear conditioning. PMID:26343307

Mobile Platforms for Continuous Spatial Measurements of Urban Trace Gases and Criteria Pollutants

NASA Astrophysics Data System (ADS)

Fasoli, B.; Mitchell, L.; Bares, R.; Crosman, E.; Bush, S. E.; Horel, J.; Lin, J. C.; Bowling, D. R.; Ehleringer, J. R.

2015-12-01

Surface-based observations of atmospheric trace gases and criteria pollutants provide critical data on how emissions and pollutant concentrations vary over time. However, traditional stationary measurement sites only quantify concentrations at a single point in space, limiting our ability to understand spatial patterns. Using trace gas instrumentation capable of making continuous high-frequency (~1s) measurements, we have developed mobile platforms to complement stationary observation sites in order to better constrain the heterogeneity and complexities of urban emissions. These compact trace gas and criteria pollutant measurement systems are capable of precisely measuring CO2, CH4 PM2.5, O3, NOx, and several meteorological parameters on TRAX, Salt Lake City's light-rail system, and in a van-based mobile laboratory. Using case study observations, we discuss mobile measurement methodologies and the practical applications of mobile trace gas sampling platforms.

Stratospheric H2O and HNO3 profiles derived from solar occultation measurements

NASA Technical Reports Server (NTRS)

Fischer, H.; Fergg, F.; Rabus, D.; Burkert, P.

1985-01-01

Compact two-channel radiometers for solar occultation experiments have been constructed in order to measure stratospheric trace gases. The instruments can be used as filter- or correlation-type radiometers, depending on the trace gas under investigation. Within the LIMS correlative measurement program, balloon flights were performed with a payload of up to four of these two-channel radiometers. From the filter-type measurements, profiles of the trace gases H2O and HNO3 are inferred for the height region between the tropopause and the balloon float level. The data evaluation also includes a comprehensive analysis of the error sources and their effect on the accuracy of the trace gas profiles. The derived H2O and HNO3 profiles are assessed against the observations of other authors and are discussed in the light of the trace gas distributions calcualted from photochemical models.

Cooperative Vehicular Traffic Monitoring in Realistic Low Penetration Scenarios: The COLOMBO Experience

PubMed Central

Caselli, Federico; Corradi, Antonio

2018-01-01

The relevance of effective and efficient solutions for vehicle traffic surveillance is widely recognized in order to enable advanced strategies for traffic management, e.g., based on dynamically adaptive and decentralized traffic light management. However, most related solutions in the literature, based on the powerful enabler of cooperative vehicular communications, assume the complete penetration rate of connectivity/communication technologies (and willingness to participate in the collaborative surveillance service) over the targeted vehicle population, thus making them not applicable nowadays. The paper originally proposes an innovative solution for cooperative traffic surveillance based on vehicular communications capable of: (i) working with low penetration rates of the proposed technology and (ii) of collecting a large set of monitoring data about vehicle mobility in targeted areas of interest. The paper presents insights and lessons learnt from the design and implementation work of the proposed solution. Moreover, it reports extensive performance evaluation results collected on realistic simulation scenarios based on the usage of iTETRIS with real traces of vehicular traffic of the city of Bologna. The reported results show the capability of our proposal to consistently estimate the real vehicular traffic even with low penetration rates of our solution (only 10%). PMID:29522427

LENSED: a code for the forward reconstruction of lenses and sources from strong lensing observations

NASA Astrophysics Data System (ADS)

Tessore, Nicolas; Bellagamba, Fabio; Metcalf, R. Benton

2016-12-01

Robust modelling of strong lensing systems is fundamental to exploit the information they contain about the distribution of matter in galaxies and clusters. In this work, we present LENSED, a new code which performs forward parametric modelling of strong lenses. LENSED takes advantage of a massively parallel ray-tracing kernel to perform the necessary calculations on a modern graphics processing unit (GPU). This makes the precise rendering of the background lensed sources much faster, and allows the simultaneous optimization of tens of parameters for the selected model. With a single run, the code is able to obtain the full posterior probability distribution for the lens light, the mass distribution and the background source at the same time. LENSED is first tested on mock images which reproduce realistic space-based observations of lensing systems. In this way, we show that it is able to recover unbiased estimates of the lens parameters, even when the sources do not follow exactly the assumed model. Then, we apply it to a subsample of the Sloan Lens ACS Survey lenses, in order to demonstrate its use on real data. The results generally agree with the literature, and highlight the flexibility and robustness of the algorithm.

Hard X-Ray Footprint Source Sized

NASA Technical Reports Server (NTRS)

Dennis, Brian R.; Kontar, E. P.

2010-01-01

RHESSI has detected compact hard (25 - 100 keV) X-ray sources that are <4 arcseconds (FWHM) in extent for certain flares (Dennis and Pernak (2009). These sources are believed to be at magnetic loop footpoints that are known from observations at other wavelengths to be very small. Flare ribbons seen in the W with TRACE, for example, are approx. 1 arcsecond in width, and white light flares show structure at the approx. 1 arcsecond level. However, Kontar and Jeffrey (2010) have shown that the measured extent should be >6 arcseconds, even if the X-ray emitting thick-target source is point-like. This is because of the strong albedo contribution in the measured energy range for a source located at the expected altitude of 1 Mm near the top of the chromosphere. This discrepancy between observations and model predictions may indicate that the source altitude is significantly lower than assumed or that the RHESSI image reconstruction procedures are not sensitive to the more diffuse albedo patch in the presence of a strong compact source. Results will be presented exploring the latter possibility using the Pixon image reconstruction procedure and other methods based on visibilities.

ANAIS: Status and prospects

NASA Astrophysics Data System (ADS)

Amaré, J.; Cebrián, S.; Cuesta, C.; García, E.; Ginestra, C.; Martínez, M.; Oliván, M. A.; Ortigoza, Y.; Ortiz de Solórzano, A.; Pobes, C.; Puimedón, J.; Sarsa, M. L.; Villar, J. A.; Villar, P.

2016-04-01

ANAIS (Annual modulation with NAI Scintillators) experiment aims to look for dark matter annual modulation with 250 kg of ultra-pure NaI(Tl) scintillators at the Canfranc Underground Laboratory (LSC), in order to confirm the DAMA/LIBRA positive signal in a model-independent way. The detector will consists in an array of close-packed single modules, each of them coupled to two high efficiency Hamamatsu photomultipliers. Two 12.5 kg each NaI(Tl) crystals provided by Alpha Spectra are currently taking data at the LSC. These modules have shown an outstanding light collection efficiency (12-16 phe/keV), about the double of that from DAMA/LIBRA phase 1 detectors, which could enable reducing the energy threshold down to 1 keVee. ANAIS crystal radiopurity goals are fulfilled for 232Th and 238U chains, assuming equilibrium, and in the case of 40K, present crystals activity (although not at the required 20 ppb level) could be acceptable. However, a 210Pb contamination out-of-equilibrium has been identified and its origin traced back, so we expect it will be avoided in next prototypes. Finally, current status and prospects of the experiment considering several exposure and background scenarios are presented.

A Historical Review of Diachrony and Semantic Dimensions of Trace in Neurosciences and Lacanian Psychoanalysis

PubMed Central

Escobar, Carolina; Ansermet, François; Magistretti, Pierre J.

2017-01-01

Experience leaves a trace in the nervous system through plasticity. However, the exact meaning of the mnesic trace is poorly defined in current literature. This article provides a historical review of the term trace in neuroscience and psychoanalysis literature, to highlight two relevant aspects: the diachronic and the semantic dimensions. There has been a general interest in diachrony, or a form of evolution of the trace, but its indissociable semantic dimension remains partially disregarded. Although frequently implied, the diachronic and semantic dimensions of the trace are rarely clearly articulated. We situate this discussion into the classical opposition of syntax, or rules of inscription of the trace in the nervous system, and semantics, or the content of the trace, which takes into consideration the attempt of the human being to build coherence. A general observation is that the study of the term trace follows trends of the thought of the given epoch. This historical analysis also reveals the decay of the idea that the trace is reliable to the experience. From the articulation between neurosciences and psychoanalysis in a historical perspective, this review shows that the trend is to consider trace as a production of the subject, resulting in a permanent rewriting in an attempt to give meaning to the experience. This trend is becoming increasingly evident in light of recent research in neurosciences and psychoanalysis. PMID:28690553

Light dependence of carboxylation capacity for C3 photosynthesis models

USDA-ARS?s Scientific Manuscript database

Photosynthesis at high light is often modelled by assuming limitation by the maximum capacity of Rubisco carboxylation at low carbon dioxide concentrations, by electron transport capacity at higher concentrations, and sometimes by triose-phosphate utilization rate at the highest concentrations. Pho...

The applicability of physical optics in the millimetre and sub-millimetre spectral region. Part I: The ray tracing with diffraction on facets method

NASA Astrophysics Data System (ADS)

Baran, A. J.; Hesse, Evelyn; Sourdeval, Odran

2017-03-01

Future satellite missions, from 2022 onwards, will obtain near-global measurements of cirrus at microwave and sub-millimetre frequencies. To realise the potential of these observations, fast and accurate light-scattering methods are required to calculate scattered millimetre and sub-millimetre intensities from complex ice crystals. Here, the applicability of the ray tracing with diffraction on facets method (RTDF) in predicting the bulk scalar optical properties and phase functions of randomly oriented hexagonal ice columns and hexagonal ice aggregates at millimetre frequencies is investigated. The applicability of RTDF is shown to be acceptable down to size parameters of about 18, between the frequencies of 243 and 874 GHz. It is demonstrated that RTDF is generally well within about 10% of T-matrix solutions obtained for the scalar optical properties assuming hexagonal ice columns. Moreover, on replacing electromagnetic scalar optical property solutions obtained for the hexagonal ice aggregate with the RTDF counterparts at size parameter values of about 18 or greater, the bulk scalar optical properties can be calculated to generally well within ±5% of an electromagnetic-based database. The RTDF-derived bulk scalar optical properties result in brightness temperature errors to generally within about ±4 K at 874 GHz. Differing microphysics assumptions can easily exceed such errors. Similar findings are found for the bulk scattering phase functions. This finding is owing to the scattering solutions being dominated by the processes of diffraction and reflection, both being well described by RTDF. The impact of centimetre-sized complex ice crystals on interpreting cirrus polarisation measurements at sub-millimetre frequencies is discussed.

MULTI-STRAND CORONAL LOOP MODEL AND FILTER-RATIO ANALYSIS

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

Bourouaine, Sofiane; Marsch, Eckart, E-mail: bourouaine@mps.mpg.d

2010-01-10

We model a coronal loop as a bundle of seven separate strands or filaments. Each of the loop strands used in this model can independently be heated (near their left footpoints) by Alfven/ion-cyclotron waves via wave-particle interactions. The Alfven waves are assumed to penetrate the strands from their footpoints, at which we consider different wave energy inputs. As a result, the loop strands can have different heating profiles, and the differential heating can lead to a varying cross-field temperature in the total coronal loop. The simulation of Transition Region and Coronal Explorer (TRACE) observations by means of this loop modelmore » implies two uniform temperatures along the loop length, one inferred from the 171:195 filter ratio and the other from the 171:284 ratio. The reproduced flat temperature profiles are consistent with those inferred from the observed extreme-ultraviolet coronal loops. According to our model, the flat temperature profile is a consequence of the coronal loop consisting of filaments, which have different temperatures but almost similar emission measures in the cross-field direction. Furthermore, when we assume certain errors in the simulated loop emissions (e.g., due to photometric uncertainties in the TRACE filters) and use the triple-filter analysis, our simulated loop conditions become consistent with those of an isothermal plasma. This implies that the use of TRACE or EUV Imaging Telescope triple filters for observation of a warm coronal loop may not help in determining whether the cross-field isothermal assumption is satisfied or not.« less

Environmental assessment of incinerator residue utilisation.

PubMed

Toller, S; Kärrman, E; Gustafsson, J P; Magnusson, Y

2009-07-01

Incineration ashes may be treated either as a waste to be dumped in landfill, or as a resource that is suitable for re-use. In order to choose the best management scenario, knowledge is needed on the potential environmental impact that may be expected, including not only local, but also regional and global impact. In this study, A life cycle assessment (LCA) based approach was outlined for environmental assessment of incinerator residue utilisation, in which leaching of trace elements as well as other emissions to air and water and the use of resources were regarded as constituting the potential environmental impact from the system studied. Case studies were performed for two selected ash types, bottom ash from municipal solid waste incineration (MSWI) and wood fly ash. The MSWI bottom ash was assumed to be suitable for road construction or as drainage material in landfill, whereas the wood fly ash was assumed to be suitable for road construction or as a nutrient resource to be recycled on forest land after biofuel harvesting. Different types of potential environmental impact predominated in the activities of the system and the use of natural resources and the trace element leaching were identified as being relatively important for the scenarios compared. The scenarios differed in use of resources and energy, whereas there is a potential for trace element leaching regardless of how the material is managed. Utilising MSWI bottom ash in road construction and recycling of wood ash on forest land saved more natural resources and energy than when these materials were managed according to the other scenarios investigated, including dumping in landfill.

Digital micromirror devices in Raman trace detection of explosives

NASA Astrophysics Data System (ADS)

Glimtoft, Martin; Svanqvist, Mattias; Ågren, Matilda; Nordberg, Markus; Östmark, Henric

2016-05-01

Imaging Raman spectroscopy based on tunable filters is an established technique for detecting single explosives particles at stand-off distances. However, large light losses are inherent in the design due to sequential imaging at different wavelengths, leading to effective transmission often well below 1 %. The use of digital micromirror devices (DMD) and compressive sensing (CS) in imaging Raman explosives trace detection can improve light throughput and add significant flexibility compared to existing systems. DMDs are based on mature microelectronics technology, and are compact, scalable, and can be customized for specific tasks, including new functions not available with current technologies. This paper has been focusing on investigating how a DMD can be used when applying CS-based imaging Raman spectroscopy on stand-off explosives trace detection, and evaluating the performance in terms of light throughput, image reconstruction ability and potential detection limits. This type of setup also gives the possibility to combine imaging Raman with non-spatially resolved fluorescence suppression techniques, such as Kerr gating. The system used consists of a 2nd harmonics Nd:YAG laser for sample excitation, collection optics, DMD, CMOScamera and a spectrometer with ICCD camera for signal gating and detection. Initial results for compressive sensing imaging Raman shows a stable reconstruction procedure even at low signals and in presence of interfering background signal. It is also shown to give increased effective light transmission without sacrificing molecular specificity or area coverage compared to filter based imaging Raman. At the same time it adds flexibility so the setup can be customized for new functionality.

Common Rules of Engagement for the Armies of the United States and Australia: A Proposal Stranded on the Moral High Ground

DTIC Science & Technology

1995-04-01

management has between management " "big picture" and employees *Assume subordinates *Assume subordinates have less to contri - share equal bute to...engagement have assumed international importance in light of recent comments by military leaders urging common ROE among allies.3 In 1994, the Commander...of the United States and Australia creating a common set of standing ROE. It will guide the reader through a five -step analysis of influential factors

Some Informal Thoughts on Relativity and Limitations on Interstellar Travel

DTIC Science & Technology

1990-12-01

velocities, as quantified by the following: Consider a device made up of a light source, a light detector, and a mirror in the following relationship (after...the source and detector are close enough together so that the value of the cosine of the angle of incidence on the mirror can be taken to be 1, a light ...34 observer will see the light pulse trace a diagonal path with length 2 z4 + (vAt/2)2 at a speed (by Postulate 2) of c. The duration of a transit measured

The distribution of the scattered laser light in laser-plate-target coupling

NASA Astrophysics Data System (ADS)

Xiao-bo, Nie; Tie-qiang, Chang; Dong-xian, Lai; Shen-ye, Liu; Zhi-jian, Zheng

1997-04-01

Theoretical and experimental studies of the angular distributions of scattered laser light in laser-Au-plate-target coupling are reported. A simple model that describes three-dimensional plasmas and scattered laser light is presented. The approximate shape of critical density surface has been given and the three-dimensional laser ray tracing is applied in the model. The theoretical results of the model are consistent with the experimental data for the scattered laser light in the polar angle range of 25° to 145° from the laser beam.

Project W-320, 241-C-106 sluicing electrical calculations, Volume 2

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

Bailey, J.W.

1998-08-07

This supporting document has been prepared to make the FDNW calculations for Project W-320, readily retrievable. These calculations are required: To determine the power requirements needed to power electrical heat tracing segments contained within three manufactured insulated tubing assemblies; To verify thermal adequacy of tubing assembly selection by others; To size the heat tracing feeder and branch circuit conductors and conduits; To size protective circuit breaker and fuses; and To accomplish thermal design for two electrical heat tracing segments: One at C-106 tank riser 7 (CCTV) and one at the exhaust hatchway (condensate drain). Contents include: C-Farm electrical heat tracing;more » Cable ampacity, lighting, conduit fill and voltage drop; and Control circuit sizing and voltage drop analysis for the seismic shutdown system.« less

Foveal light exposure is increased at the time of removal of silicone oil with the potential for phototoxicity.

PubMed

Dogramaci, Mahmut; Williams, Katie; Lee, Ed; Williamson, Tom H

2013-01-01

There is sudden and dramatic visual function deterioration in 1-10 % of eyes filled with silicone oil at the time of removal of silicon oil. Transmission of high-energy blue light is increased in eyes filled with silicone oil. We sought to identify if increased foveal light exposure is a potential factor in the pathophysiology of the visual loss at the time of removal of silicone oil. A graphic ray tracing computer program and laboratory models were used to determine the effect of the intraocular silicone oil bubble size on the foveal illuminance at the time of removal of silicone oil under direct microscope light. The graphic ray tracing computer program revealed a range of optical vignetting effects created by different sizes of silicone oil bubble within the vitreous cavity giving rise to an uneven macular illumination. The laboratory model was used to quantify the variation of illuminance at the foveal region with different sizes of silicone oil bubble with in the vitreous cavity at the time of removal of silicon oil under direct microscope light. To substantiate the hypothesis of the light toxicity during removal of silicone oil, The outcome of oil removal procedures performed under direct microscope illumination in compared to those performed under blocked illumination. The computer program showed that the optical vignetting effect at the macula was dependent on the size of the intraocular silicone oil bubble. The laboratory eye model showed that the foveal illuminance followed a bell-shaped curve with 70 % greater illuminance demonstrated at with 50-60 % silicone oil fill. The clinical data identified five eyes with unexplained vision loss out of 114 eyes that had the procedure performed under direct microscope illumination compared to none out of 78 eyes that had the procedure under blocked illumination. Foveal light exposure, and therefore the potential for phototoxicity, is transiently increased at the time of removal of silicone oil. This is due to uneven macular illumination resulting from the optical vignetting effect of different silicone oil bubble sizes. The increase in foveal light exposure may be significant when the procedure is performed under bright operating microscope light on already stressed photoreceptors of an eye filled with silicon oil. We advocate the use of precautions, such as central shadow filter on the operating microscope light source to reduce foveal light exposure and the risk of phototoxicity at the time of removal of silicone oil. The graphic ray tracing computer program used in this study shows promise in eye modeling for future studies.

Spectral line shapes of collision-induced light scattering (CILS) and collision-induced absorption (CIA) using isotropic intermolecular potential for H2-Ar

NASA Astrophysics Data System (ADS)

El-Kader, M. S. A.; Godet, J.-L.; El-Sadek, A. A.; Maroulis, G.

2017-10-01

Quantum mechanical line shapes of collision-induced light scattering at room temperature (295 K) and collision-induced absorption at T = 195 K are computed for gaseous mixtures of molecular hydrogen and argon using theoretical values for pair-polarisability trace and anisotropy and induced dipole moments as input. Comparison with other theoretical spectra of isotropic and anisotropic light scattering and measured spectra of absorption shows satisfactory agreement, for which the uncertainty in measurement of its spectral moments is seen to be large. Ab initio models of the trace and anisotropy polarisability which reproduce the recent spectra of scattering are given. Empirical model of the dipole moment which reproduce the experimental spectra and the first three spectral moments more closely than the fundamental theory are also given. Good agreement between computed and/or experimental line shapes of both absorption and scattering is obtained when the potential model which is constructed from the transport and thermo-physical properties is used.

Correction of the spectral calibration of the Joint European Torus core light detecting and ranging Thomson scattering diagnostic using ray tracing

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

Hawke, J.; Scannell, R.; Maslov, M.

2013-10-15

This work isolated the cause of the observed discrepancy between the electron temperature (T{sub e}) measurements before and after the JET Core LIDAR Thomson Scattering (TS) diagnostic was upgraded. In the upgrade process, stray light filters positioned just before the detectors were removed from the system. Modelling showed that the shift imposed on the stray light filters transmission functions due to the variations in the incidence angles of the collected photons impacted plasma measurements. To correct for this identified source of error, correction factors were developed using ray tracing models for the calibration and operational states of the diagnostic. Themore » application of these correction factors resulted in an increase in the observed T{sub e}, resulting in the partial if not complete removal of the observed discrepancy in the measured T{sub e} between the JET core LIDAR TS diagnostic, High Resolution Thomson Scattering, and the Electron Cyclotron Emission diagnostics.« less

New light field camera based on physical based rendering tracing

NASA Astrophysics Data System (ADS)

Chung, Ming-Han; Chang, Shan-Ching; Lee, Chih-Kung

2014-03-01

Even though light field technology was first invented more than 50 years ago, it did not gain popularity due to the limitation imposed by the computation technology. With the rapid advancement of computer technology over the last decade, the limitation has been uplifted and the light field technology quickly returns to the spotlight of the research stage. In this paper, PBRT (Physical Based Rendering Tracing) was introduced to overcome the limitation of using traditional optical simulation approach to study the light field camera technology. More specifically, traditional optical simulation approach can only present light energy distribution but typically lack the capability to present the pictures in realistic scenes. By using PBRT, which was developed to create virtual scenes, 4D light field information was obtained to conduct initial data analysis and calculation. This PBRT approach was also used to explore the light field data calculation potential in creating realistic photos. Furthermore, we integrated the optical experimental measurement results with PBRT in order to place the real measurement results into the virtually created scenes. In other words, our approach provided us with a way to establish a link of virtual scene with the real measurement results. Several images developed based on the above-mentioned approaches were analyzed and discussed to verify the pros and cons of the newly developed PBRT based light field camera technology. It will be shown that this newly developed light field camera approach can circumvent the loss of spatial resolution associated with adopting a micro-lens array in front of the image sensors. Detailed operational constraint, performance metrics, computation resources needed, etc. associated with this newly developed light field camera technique were presented in detail.

Development of Optical Parametric Amplifier for Lidar Measurements of Trace Gases on Earth and Mars

NASA Technical Reports Server (NTRS)

Numata, Kenji; Riris, Haris; Li, Steve; Wu, Stewart; Kawa, Stephen R.; Krainak, Michael; Abshire, James

2011-01-01

Trace gases in planetary atmospheres offer important clues as to the origins of the planet's hydrology, geology. atmosphere. and potential for biology. Wc report on the development effort of a nanosecond-pulsed optical parametric amplifier (OPA) for remote trace gas measurements for Mars and Earth. The OP A output light is single frequency with high spectral purity and is widely tunable both at 1600 nm and 3300 nm with an optical-optical conversion efficiency of approximately 40%. We demonstrated open-path atmospheric measurements ofCH4 (3291 nm and 1651 nm). CO2 (1573 nm), H20 (1652 nm) with this laser source.

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

Lee, Gregory L.; Arnold, Dorian; LeGendre, Matthew

STAT is a light weight debugging tool that gathers and merges stack traces from all of the processes in a parallel application. STAT uses the MRNet tree based overlay network to broadcast commands from the tool front-end to the STAT daemons and for the front-end to gather the traces from the STAT daemons. As the traces propagate through the MRNet network tree, they are merged across all tasks to form a similar function call patterns and to delineate a small set of equivalence classes. A representative task from each of these classes can then be fed into a full featuremore » debugger like TolalView for root cause analysis.« less

The effects of dorsal bundle lesions on serial and trace conditioning.

PubMed

Tsaltas, E; Preston, G C; Gray, J A

1983-12-01

The performance of rats with neurotoxic lesions of the dorsal ascending noradrenergic bundle (DB) was compared with that of sham-operated control animals under two behavioural conditions. Animals with DB lesions were slower than controls to acquire a classically-conditioned emotional response (conditioned suppression) with a trace interval interposed between the clicker conditioned stimulus (CS) and the shock reinforcer. However, if the latter half of the trace interval was filled by a second stimulus, a light, the DB-lesioned animals acquired conditioned suppression to the clicker faster than did controls under the same conditions. These results are discussed in terms of the attentional theory of DB function.

Resolving the potential mantle reservoirs that influence volcanism in the West Antarctic Rift System

NASA Astrophysics Data System (ADS)

Maletic, E. L.; Darrah, T.

2017-12-01

Lithospheric extension and magmatism are key characteristics of active continental rift zones and are often associated with long-lasting alkaline magmatic provinces. In these settings, a relationship between lithospheric extension and mantle plumes is often assumed for the forces leading to rift evolution and the existence of a plume is commonly inferred, but typically only extension is supported by geological evidence. A prime example of long-lasting magmatism associated with an extensive area of continental rifting is the West Antarctic Rift System (WARS), a 2000 km long zone of ongoing extension within the Antarctic plate. The WARS consists of high alkaline silica-undersaturated igneous rocks with enrichments in light rare earth elements (LREEs). The majority of previous geochemical work on WARS volcanism has focused on bulk classification, modal mineralogy, major element composition, trace element chemistry, and radiogenic isotopes (e.g., Sr, Nd, and Pb isotopes), but very few studies have evaluated volatile composition of volcanics from this region. Previous explanations for WARS volcanism have hypothesized a plume beneath Marie Byrd Land, decompression melting of a fossilized plume head, decompression melting of a stratified mantle source, and mixing of recycled oceanic crust with one or more enriched mantle sources from the deep mantle, though researchers are yet to reach a consensus. Unlike trace elements and radiogenic isotopes which can be recycled between the crust and mantle and which are commonly controlled by degrees of partial melting and prior melt differentiation, noble gases are present in low concentrations and chemically inert, allowing them to serve as reliable tracers of volatile sources and subsurface processes. Here, we present preliminary noble gas isotope (e.g., 3He/4He, CO2/3He, CH4/3He, 40Ar/36Ar, 40Ar*/4He) data for a suite of lava samples from across the WARS. By coupling major and trace element chemistry with noble gas elemental and isotopic composition and other volatiles from a suite of volcanic rocks in the WARS, we can better constrain a magmatic source and provide geological evidence that could support or oppose the existence of a mantle plume, HIMU plume, or deconvolve mantle-lithosphere interactions.

Geochemistry and petrogenesis of a peralkaline granite complex from the Midian Mountains, Saudi Arabia

NASA Astrophysics Data System (ADS)

Harris, N. B. W.; Marriner, G. F.

1980-10-01

A zoned intrusion with a biotite granodiorite core and arfvedsonite granite rim represents the source magma for an albitised granite plug near its eastern margin and radioactive siliceous veins along its western margin. A study of selected REE and trace elements of samples from this complex reveals that the albitised granite plug has at least a tenfold enrichment in Zr, Hf, Nb, Ta, Y, Th, U and Sr, and a greatly enhanced heavy/light REE ratio compared with the peralkaline granite. The siliceous veins have even stronger enrichment of these trace elements, but a heavy/light REE ratio and negative eu anomaly similar to the peralkaline granite. It is suggested that the veins were formed from acidic volatile activity and the plug from a combination of highly fractionated magma and co-existing alkaline volatile phase. The granodiorite core intrudes the peralkaline granite and has similar trace element geochemistry. The peralkaline granite is probably derived from the partial melting of the lower crust in the presence of halide-rich volatiles, and the granodiorite from further partial melting under volatile-free conditions.

Earthquake Rupture Forecast of M>= 6 for the Corinth Rift System

NASA Astrophysics Data System (ADS)

Scotti, O.; Boiselet, A.; Lyon-Caen, H.; Albini, P.; Bernard, P.; Briole, P.; Ford, M.; Lambotte, S.; Matrullo, E.; Rovida, A.; Satriano, C.

2014-12-01

Fourteen years of multidisciplinary observations and data collection in the Western Corinth Rift (WCR) near-fault observatory have been recently synthesized (Boiselet, Ph.D. 2014) for the purpose of providing earthquake rupture forecasts (ERF) of M>=6 in WCR. The main contribution of this work consisted in paving the road towards the development of a "community-based" fault model reflecting the level of knowledge gathered thus far by the WCR working group. The most relevant available data used for this exercise are: - onshore/offshore fault traces, based on geological and high-resolution seismics, revealing a complex network of E-W striking, ~10 km long fault segments; microseismicity recorded by a dense network ( > 60000 events; 1.5=5 19th century events and a few paleoseismological investigations, allowing to consider time-dependent ERF. B-value estimates are found to be catalogue-dependent (WCR, homogenized NOA+Thessaloniki, SHARE), which may call for a potential break in scaling relationship. Furthermore, observed discrepancies between seismicity rates assumed for the modeled faults and those expected from GPS deformation rates call for the presence of aseismic deformation. Uncertainty in the ERF resulting from the lack of precise knowledge concerning both, fault geometries and seismic slip rates, is quantified through a logic tree exploration. Median and precentile predictions are then compared to ERF assuming a uniform seismicity rate in the WCR region. The issues raised by this work will be discussed in the light of seismic hazard assessment.

Conversion of Ozone-Depleting Substances (ODS) to Useful Products: Design of a Process for Conversion of Halons 1211 and 1301 to HFCS. Part A

DTIC Science & Technology

2003-06-01

on Climate Change regulations in which carbon dioxide is used as reference with a GWP of 1. Halon 1211 has a net 100-year global warming potential... Carbon ” as % of Feed 773 0.35 0.20 0.06 0.16 trace 0.04 trace 0.05 0.02 tarce nd nd nd nd 0.01 0.7 823 0.82 0.60 0.28 0.49 0.02 0.01 0.01 0.07 0.02...preheating prior to entering the reactor. 5. All missing mass is assumed to be carbon 12, for the purpose of completing the mass balance. 6. The apparent

Sleep on your memory traces: How sleep effects can be explained by Act-In, a functional memory model.

PubMed

Cherdieu, Mélaine; Versace, Rémy; Rey, Amandine E; Vallet, Guillaume T; Mazza, Stéphanie

2018-06-01

Numerous studies have explored the effect of sleep on memory. It is well known that a period of sleep, compared to a similar period of wakefulness, protects memories from interference, improves performance, and might also reorganize memory traces in a way that encourages creativity and rule extraction. It is assumed that these benefits come from the reactivation of brain networks, mainly involving the hippocampal structure, as well as from their synchronization with neocortical networks during sleep, thereby underpinning sleep-dependent memory consolidation and reorganization. However, this memory reorganization is difficult to explain within classical memory models. The present paper aims to describe whether the influence of sleep on memory could be explained using a multiple trace memory model that is consistent with the concept of embodied cognition: the Act-In (activation-integration) memory model. We propose an original approach to the results observed in sleep research on the basis of two simple mechanisms, namely activation and integration. Copyright © 2017 Elsevier Ltd. All rights reserved.

10 CFR 434.520 - Speculative buildings.

Code of Federal Regulations, 2014 CFR

2014-01-01

... assumed lighting power allowance. 520.5 HVAC Systems and Equipment. If the HVAC system is not completely... construction of future HVAC systems and equipment. These assumptions shall be documented so that future HVAC... calculate the Design Energy Consumption must be documented so that the future installed lighting systems may...

10 CFR 434.520 - Speculative buildings.

Code of Federal Regulations, 2010 CFR

2010-01-01

... assumed lighting power allowance. 520.5HVAC Systems and Equipment. If the HVAC system is not completely... construction of future HVAC systems and equipment. These assumptions shall be documented so that future HVAC... calculate the Design Energy Consumption must be documented so that the future installed lighting systems may...

10 CFR 434.520 - Speculative buildings.

Code of Federal Regulations, 2011 CFR

2011-01-01

... assumed lighting power allowance. 520.5HVAC Systems and Equipment. If the HVAC system is not completely... construction of future HVAC systems and equipment. These assumptions shall be documented so that future HVAC... calculate the Design Energy Consumption must be documented so that the future installed lighting systems may...

10 CFR 434.520 - Speculative buildings.

Code of Federal Regulations, 2013 CFR

2013-01-01

... assumed lighting power allowance. 520.5HVAC Systems and Equipment. If the HVAC system is not completely... construction of future HVAC systems and equipment. These assumptions shall be documented so that future HVAC... calculate the Design Energy Consumption must be documented so that the future installed lighting systems may...

10 CFR 434.520 - Speculative buildings.

Code of Federal Regulations, 2012 CFR

2012-01-01

... assumed lighting power allowance. 520.5HVAC Systems and Equipment. If the HVAC system is not completely... construction of future HVAC systems and equipment. These assumptions shall be documented so that future HVAC... calculate the Design Energy Consumption must be documented so that the future installed lighting systems may...

Dungeons, Gratings, and Black Rooms: A Defense of Double-Anchoring Theory and a Reply to Howe et al. (2007)

ERIC Educational Resources Information Center

Bressan, Paola

2007-01-01

Replies to comments mad by Howe et al. on the current author's original article. The double-anchoring theory of lightness (P. Bressan, 2006b) assumes that any given region belongs to a set of frameworks, created by Gestalt grouping principles, and receives a provisional lightness within each of them; the region's final lightness is a weighted…

Trace element diffusion and kinetic fractionation in wet rhyolitic melt

NASA Astrophysics Data System (ADS)

Holycross, Megan E.; Watson, E. Bruce

2018-07-01

Piston-cylinder experiments were run to determine the chemical diffusivities of 21 trace elements (Sc, V, Y, Zr, Nb, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Yb, Lu, Hf, Th and U) in hydrous rhyolitic melts at 1 GPa pressure and temperatures from 850 to 1250 °C. Diffusion couple glasses were doped with trace elements in low concentrations to characterize the diffusivities of all cations in a single experiment. Laser ablation ICP-MS was used to evaluate the trace element concentration gradients that developed in the silicate glasses. All calculated diffusion coefficients correspond to the temperature dependence D = D0exp(-Ea/RT). Rhyolite liquids contained either ∼4.1 wt% or ∼6.2 wt% dissolved H2O; separate Arrhenius relationships are produced for each melt composition. Trace element diffusivities in the melt with 6.2 wt% H2O are roughly two times higher than those in the less hydrous melt. Calculated trace element diffusion coefficients cover nearly two orders of magnitude at a given temperature. The high field strength elements are the slowest diffusers, followed by the transition metals and heavy rare earth elements. The light rare earth elements have the fastest diffusion rates in hydrous rhyolitic melt. The measured diffusion coefficients range down to values sufficiently low to preclude diffusive homogenization over geochemically realistic time scales in some cases. The substantial differences in the diffusivities of individual cations may result in fractionated trace element signatures in rhyolite melt pockets. A simple model is used to explore the potential for kinetic fractionation of REE during growth of an apatite crystal in a diffusive boundary layer locally saturated in P2O5. The faster-diffusing light REE are more efficiently transported away from the crystal interface than the slower-moving heavy REE. Diffusion effects will enrich the melt boundary layer in slow-moving HREE relative to the faster LREE. The kinetic fractionation of REE in the melt growth medium will result in a precipitated apatite crystal with a disequilibrium trace element composition.

Opportunities and challenges for 3D printing of solid-state lighting systems

NASA Astrophysics Data System (ADS)

Narendran, Nadarajah; Perera, Indika U.; Mou, Xi; Thotagamuwa, Dinusha R.

2017-09-01

Low energy use and reduced maintenance have made the LED, a solid-state light (SSL) source, the preferred technology for many lighting applications. With the explosion of products in the marketplace and subsequent price erosion, manufacturers are looking for lower cost materials and manufacturing methods. 3-D printing, also known as additive manufacturing, could be a potential solution. Recently, manufacturers in the automotive, aerospace, and medical industries have embraced 3-D printing for manufacturing parts and systems. This could pave the way for the lighting industry to produce lower cost, custom lighting systems that are 3-D printed on-site to achieve on-time and on-demand manufacturing. One unique aspect of LED fixture manufacturing is that it requires thermo-mechanical, electrical, and optical components. The goal of our investigation was to understand if current 3-D printing technologies and materials can be used to manufacture functional thermo-mechanical, electrical, and optical components for SSL fixtures. We printed heat sink components and electrical traces using an FFF-type 3-D printer with different filaments. The results showed that the printed heat sinks achieved higher thermal conductivity values compared to components made with plastic materials. For electrical traces, graphene-infused PLA showed low resistivity but it is much higher than bulk copper resistivity. For optics, SLA-printed optical components showed that print resolution, print orientation, and postprocessing affect light transmission and light scatter properties. Overall, 3-D printing offers an opportunity for mass customization of SSL fixtures and changing architectural lighting practice, but several challenges in terms of process and materials still have to be overcome.

The extended Beer-Lambert theory for ray tracing modeling of LED chip-scaled packaging application with multiple luminescence materials

NASA Astrophysics Data System (ADS)

Yuan, Cadmus C. A.

2015-12-01

Optical ray tracing modeling applied Beer-Lambert method in the single luminescence material system to model the white light pattern from blue LED light source. This paper extends such algorithm to a mixed multiple luminescence material system by introducing the equivalent excitation and emission spectrum of individual luminescence materials. The quantum efficiency numbers of individual material and self-absorption of the multiple luminescence material system are considered as well. By this combination, researchers are able to model the luminescence characteristics of LED chip-scaled packaging (CSP), which provides simple process steps and the freedom of the luminescence material geometrical dimension. The method will be first validated by the experimental results. Afterward, a further parametric investigation has been then conducted.

Laser absorption of carbon fiber reinforced polymer with randomly distributed carbon fibers

NASA Astrophysics Data System (ADS)

Hu, Jun; Xu, Hebing; Li, Chao

2018-03-01

Laser processing of carbon fiber reinforced polymer (CFRP) is a non-traditional machining method which has many prospective applications. The laser absorption characteristics of CFRP are analyzed in this paper. A ray tracing model describing the interaction of the laser spot with CFRP is established. The material model contains randomly distributed carbon fibers which are generated using an improved carbon fiber placement method. It was found that CFRP has good laser absorption due to multiple reflections of the light rays in the material’s microstructure. The randomly distributed carbon fibers make the absorptivity of the light rays change randomly in the laser spot. Meanwhile, the average absorptivity fluctuation is obvious during movement of the laser. The experimental measurements agree well with the values predicted by the ray tracing model.

Laser Heterodyne Radiometer for Sensitive Detection of CO2 and CH4

NASA Technical Reports Server (NTRS)

Wilson, Emily L.; Miller, J. Houston

2011-01-01

We propose to develop an inexpensive, miniaturized, passive laser heterodyne radiometer (LHR) using commercially available telecommunications laser components to measure two significant carbon cycle gases in the atmospheric column: carbon dioxide (CO2) and methane (CH4). This instrument would operate in tandem with the passive aerosol sensor currently used in AERONET (an established network of more than 450 ground aerosol monitoring instruments worldwide). Because aerosols induce a radiative effect that influences terrestrial carbon exchange, simultaneous detection of aerosols with these key carbon cycle gases offers a uniquely comprehensive measurement approach that supports the Decadal Survey. Laser heterodyne radiometry is a technique for detecting weak signals that was adapted from radio receiver technology. In a radio receiver, a weak input signal from a radio antenna is mixed with a stronger local oscillator signal. The mixed signal (beat note, or intermediate frequency) has a frequency equal to the difference between the input signal and the local oscillator. The intermediate frequency is amplified and sent to a detector that extracts the audio from the signal. In a laser heterodyne radiometer, the weak input signal is light that has undergone absorption by a trace gas. The local oscillator is a laser at a near-by frequency - in this case a low-cost distributed feedback (DFB) telecommunications laser. These two light waves are superimposed in either a beamsplitter or in a fiber coupler (as is the case in this design). The signals are mixed in the detector, and the RF beat frequency is extracted. Changes in concentration of the trace gas are realized through analyzing changes in the beat frequency amplitude. A schematic of the progression of the LHR development project is shown in the figure below. At the center (within the dashed line), light from the local oscillator is superimposed upon light that has undergone absorption by a trace gas, in a single mode fiber coupler. Superimposed light is mixed in a fast photoreceiver, and the beat signal is analyzed for changes in absorption. The left portion of the figure depicts a progression of light sources that pass through the trace gas, increasing in complexity in the downward direction. On the right side of the figure, RF signal processing progresses from a commercially available spectrum analyzer to a RF receiver, and finally to an RF filter bank to deconvolute portions of the beat frequency more heavily weighted for different altitudes.

Quantifying substructures in Hubble Frontier Field clusters: comparison with ΛCDM simulations

DOE PAGES

Mohammed, Irshad; Saha, Prasenjit; Williams, Liliya L. R.; ...

2016-04-13

The Hubble Frontier Fields (HFF) are six clusters of galaxies, all showing indications of recent mergers, which have recently been observed for lensed images. As such they are the natural laboratories to study the merging history of galaxy clusters. In this work, we explore the 2D power spectrum of the mass distributionmore » $$P_{\\rm M}(k)$$ as a measure of substructure. We compare $$P_{\\rm M}(k)$$ of these clusters (obtained using strong gravitational lensing) to that of $$\\Lambda$$CDM simulated clusters of similar mass. In order to compute lensing $$P_{\\rm M}(k)$$, we produced free-form lensing mass reconstructions of HFF clusters, without any light traces mass (LTM) assumption. Moreover, the inferred power at small scales tends to be larger if (i)~the cluster is at lower redshift, and/or (ii)~there are deeper observations and hence more lensed images. In contrast, lens reconstructions assuming LTM show higher power at small scales even with fewer lensed images; it appears the small scale power in the LTM reconstructions is dominated by light information, rather than the lensing data. The average lensing derived $$P_{\\rm M}(k)$$ shows lower power at small scales as compared to that of simulated clusters at redshift zero, both dark-matter only and hydrodynamical. The possible reasons are: (i)~the available strong lensing data are limited in their effective spatial resolution on the mass distribution, (ii)~HFF clusters have yet to build the small scale power they would have at $$z\\sim 0$$, or (iii)~simulations are somehow overestimating the small scale power.« less

Reconstruction of cluster masses using particle based lensing

NASA Astrophysics Data System (ADS)

Deb, Sanghamitra

Clusters of galaxies are among the richest astrophysical data systems, but to truly understand these systems, we need a detailed study of the relationship between observables and the underlying cluster dark matter distribution. Gravitational lensing is the most direct probe of dark matter, but many mass reconstruction techniques assume that cluster light traces mass, or combine different lensing signals in an ad hoc way. In this talk, we will describe "Particle Based Lensing" (PBL), a new method for cluster mass reconstruction, that avoids many of the pitfalls of previous techniques. PBL optimally combines lensing information of varying signal-to-noise, and makes no assumptions about the relationship between mass and light. We will describe mass reconstructions in three very different, but very illuminating cluster systems: the "Bullet Cluster" (lE 0657-56), A901/902 and A1689. The "Bullet Cluster" is a system of merging clusters made famous by the first unambiguous lensing detection of dark matter. A901/902 is a multi-cluster system with four peaks, and provides an ideal laboratory for studying cluster interaction. We are particularly interested in measuring and correlating the dark matter clump ellipticities. A1689 is one of the richest clusters known, and has significant substructure at the core. It is also my first exercise in optimally combining weak and strong gravitational lensing in a cluster reconstruction. We find that the dark matter distribution is significantly clumpier than indicated by X-ray maps of the gas. We conclude by discussing various potential applications of PBL to existing and future data.

Study of optical techniques for the Ames unitary wind tunnels. Part 2: Light sheet and vapor screen

NASA Technical Reports Server (NTRS)

Lee, George

1992-01-01

Light sheet and vapor screen methods have been studied with particular emphasis on those systems that have been used in large transonic and supersonic wind tunnels. The various fluids and solids used as tracers or light scatters and the methods for tracing generation have been studied. Light sources from high intensity lamps and various lasers have been surveyed. Light sheet generation and projection methods were considered. Detectors and location of detectors were briefly studied. A vapor screen system and a technique for location injection of tracers for the NASA Ames 9 by 7 foot Supersonic Wind Tunnel were proposed.

Simulating polarized light scattering in terrestrial snow based on bicontinuous random medium and Monte Carlo ray tracing

NASA Astrophysics Data System (ADS)

Xiong, Chuan; Shi, Jiancheng

2014-01-01

To date, the light scattering models of snow consider very little about the real snow microstructures. The ideal spherical or other single shaped particle assumptions in previous snow light scattering models can cause error in light scattering modeling of snow and further cause errors in remote sensing inversion algorithms. This paper tries to build up a snow polarized reflectance model based on bicontinuous medium, with which the real snow microstructure is considered. The accurate specific surface area of bicontinuous medium can be analytically derived. The polarized Monte Carlo ray tracing technique is applied to the computer generated bicontinuous medium. With proper algorithms, the snow surface albedo, bidirectional reflectance distribution function (BRDF) and polarized BRDF can be simulated. The validation of model predicted spectral albedo and bidirectional reflectance factor (BRF) using experiment data shows good results. The relationship between snow surface albedo and snow specific surface area (SSA) were predicted, and this relationship can be used for future improvement of snow specific surface area (SSA) inversion algorithms. The model predicted polarized reflectance is validated and proved accurate, which can be further applied in polarized remote sensing.

Fiducial marker for correlating images

DOEpatents

Miller, Lisa Marie [Rocky Point, NY; Smith, Randy J [Wading River, NY; Warren, John B [Port Jefferson, NY; Elliott, Donald [Hampton Bays, NY

2011-06-21

The invention relates to a fiducial marker having a marking grid that is used to correlate and view images produced by different imaging modalities or different imaging and viewing modalities. More specifically, the invention relates to the fiducial marking grid that has a grid pattern for producing either a viewing image and/or a first analytical image that can be overlaid with at least one other second analytical image in order to view a light path or to image different imaging modalities. Depending on the analysis, the grid pattern has a single layer of a certain thickness or at least two layers of certain thicknesses. In either case, the grid pattern is imageable by each imaging or viewing modality used in the analysis. Further, when viewing a light path, the light path of the analytical modality cannot be visualized by viewing modality (e.g., a light microscope objective). By correlating these images, the ability to analyze a thin sample that is, for example, biological in nature but yet contains trace metal ions is enhanced. Specifically, it is desired to analyze both the organic matter of the biological sample and the trace metal ions contained within the biological sample without adding or using extrinsic labels or stains.

Anti-glare LED lamps with adjustable illumination light field.

PubMed

Chen, Yung-Sheng; Lin, Chung-Yi; Yeh, Chun-Ming; Kuo, Chie-Tong; Hsu, Chih-Wei; Wang, Hsiang-Chen

2014-03-10

We introduce a type of LED light-gauge steel frame lamp with an adjustable illumination light field that does not require a diffusion plate. Base on the Monte Carlo ray tracing method, this lamp has a good glare rating (GR) of 17.5 at 3050 lm. Compared with the traditional LED light-gauge steel frame lamp (without diffusion plate), the new type has low GR. The adjustability of the illumination light field could improve the zebra effect caused by the inadequate illumination light field of the lamp. Meanwhile, we adopt the retinal image analysis to discuss the influence of GR on vision. High GR could reflect stray light on the retinal image, which will reduce vision clarity and hasten the feeling of eye fatigue.

Modeling of laser interactions with composite materials

DOE PAGES

Rubenchik, Alexander M.; Boley, Charles D.

2013-05-07

In this study, we develop models of laser interactions with composite materials consisting of fibers embedded within a matrix. A ray-trace model is shown to determine the absorptivity, absorption depth, and optical power enhancement within the material, as well as the angular distribution of the reflected light. We also develop a macroscopic model, which provides physical insight and overall results. We show that the parameters in this model can be determined from the ray trace model.

Heterogeneous photocatalytic oxidation of atmospheric trace contaminants

NASA Technical Reports Server (NTRS)

Ollis, David F.

1994-01-01

Research was conducted on: (1) design and construction of a continuous flow photoreactor to study oxidation of trace atmospheric contaminants; (2) kinetics of acetone oxidation including adsorption equilibrium, variation of oxidatiin rate with acetone concentration and water, and variation of rate and apparent quantum yield with light intensity, and (3) kinetics of butanol oxidation, including rate variations; and (4) kinetics of catalyst deactivation including deactivation rate, influence of dark conditions, and photocatalytic regeneration in alcohol-free air.

Novel laser induced photoacoustic spectroscopy for instantaneous trace detection of explosive materials.

PubMed

El-Sharkawy, Yasser H; Elbasuney, Sherif

2017-08-01

Laser photoacoustic spectroscopy (LPAS) is an attractive technology in terms of simplicity, ruggedness, and overall sensitivity; it detects the time dependent heat generated (thermo-elastic effect) in the target via interaction with pulsed optical radiation. This study reports on novel LPAS technique that offers instant and standoff detection capabilities of trace explosives. Over the current study, light is generated using pulsed Q-switched Nd:YAG laser; the generated photoacoustic response in stimulated explosive material offers signature values that depend on the optical, thermal, and acoustical properties. The generated acoustic waves were captured using piezoelectric transducer as well as novel customized optical sensor with remotely laser interferometer probe. A digital signal processing algorithm was employed to identify explosive material signatures via calculation of characteristic optical properties (absorption coefficient), sound velocity, and frequency response of the generated photoacoustic signal. Customized LPAS technique was employed for instantaneous trace detection of three main different high explosive materials including TNT, RDX, and HMX. The main outcome of this study is that the novel customized optical sensor signals were validated with traditional piezoelectric transducer. Furthermore, the customized optical sensor offered standoff detection capabilities (10cm), fast response, high sensitivity, and enhanced signal to noise ratio. This manuscript shaded the light on the instant detection of trace explosive materials from significant standoffs using novel customized LPAS technique. Copyright © 2017 Elsevier B.V. All rights reserved.

Representativeness of laboratory sampling procedures for the analysis of trace metals in soil.

PubMed

Dubé, Jean-Sébastien; Boudreault, Jean-Philippe; Bost, Régis; Sona, Mirela; Duhaime, François; Éthier, Yannic

2015-08-01

This study was conducted to assess the representativeness of laboratory sampling protocols for purposes of trace metal analysis in soil. Five laboratory protocols were compared, including conventional grab sampling, to assess the influence of sectorial splitting, sieving, and grinding on measured trace metal concentrations and their variability. It was concluded that grinding was the most important factor in controlling the variability of trace metal concentrations. Grinding increased the reproducibility of sample mass reduction by rotary sectorial splitting by up to two orders of magnitude. Combined with rotary sectorial splitting, grinding increased the reproducibility of trace metal concentrations by almost three orders of magnitude compared to grab sampling. Moreover, results showed that if grinding is used as part of a mass reduction protocol by sectorial splitting, the effect of sieving on reproducibility became insignificant. Gy's sampling theory and practice was also used to analyze the aforementioned sampling protocols. While the theoretical relative variances calculated for each sampling protocol qualitatively agreed with the experimental variances, their quantitative agreement was very poor. It was assumed that the parameters used in the calculation of theoretical sampling variances may not correctly estimate the constitutional heterogeneity of soils or soil-like materials. Finally, the results have highlighted the pitfalls of grab sampling, namely, the fact that it does not exert control over incorrect sampling errors and that it is strongly affected by distribution heterogeneity.

Light-induced pH change and its application to solid phase extraction of trace heavy metals by high-magnetization Fe3O4@SiO2@TiO2 nanoparticles followed by inductively coupled plasma mass spectrometry detection.

PubMed

Zhang, Nan; Peng, Hanyong; Hu, Bin

2012-05-30

We report here the preparation of high-magnetization Fe(3)O(4)@SiO(2)@TiO(2) nanoparticles for solid phase extraction of trace amounts of Cd(II), Cr(III), Mn(II) and Cu(II) from environmental waters. The prepared nanoparticles were characterized by scanning electron micrograph (SEM) and transmission electron microscopy (TEM). The high-magnetization nanoparticles carrying the target metals could be easily and fast separated from the aqueous solution simply by applying an external magnetic field while no filtration or centrifugation was necessary. A light-induced hydroxide ion emitter, molecular malachite green carbinol base (MGCB) was applied to adjust pH value of solution for quantitative adsorption instead of the conventional used buffer. In the presence of UV light, MGCB gives out OH(-) ions, and this leads to an increase in the pH value without the aid of buffer solution. Using high-magnetization Fe(3)O(4)@SiO(2)@TiO(2) nanoparticles as the extraction material and the light-induced MGCB for pH adjustment, we developed an efficient and convenient two-step method for separation/preconcentration trace amounts of Cd(II), Cr(III), Mn(II) and Cu(II) in environmental water samples followed by inductively coupled plasma mass spectrometry (ICP-MS) detection. The parameters affecting the extraction such as MGCB concentration, exposal time, sample volume, eluent condition, and interfering ions have been investigated in detail. Under the optimized conditions, the limits of detection for Cd(II), Cr(III), Mn(II) and Cu(II) were 4.0, 2.6, 1.6 and 2.3 ng L(-1), respectively, and the relative standard deviations (RSDs, c=1 μg L(-1), n=7) were 3.6%, 4.5%, 4.0 and 4.1%, respectively. The proposed method has been validated using certified reference materials, and it has been successfully applied in the determination of trace Cd(II), Cr(III), Mn(II) and Cu(II) in environmental water samples. Copyright © 2012 Elsevier B.V. All rights reserved.

Dietary trace amine-dependent vasoconstriction in porcine coronary artery

PubMed Central

Herbert, A A; Kidd, E J; Broadley, K J

2008-01-01

Background and purpose: The dietary trace amines tyramine and β-phenylethylamine (β-PEA) can increase blood pressure. However, the mechanisms involved in the vascular effect of trace amines have not been fully established. The purpose of this study was to evaluate whether trace amine-dependent vasoconstriction was brought about by tyramine and β-PEA acting as indirect sympathomimetic agents, as previously assumed, or whether trace amine-dependent vasoconstriction could be mediated by recently discovered trace amine-associated (TAA) receptors. Experimental approach: The responses to p-tyramine and β-PEA were investigated in vitro in rings of the left anterior descending coronary arteries of pigs. Key results: p-Tyramine induced a concentration-dependent (0.1–3 mM) vasoconstriction. The maximum response and pD2 value for p-tyramine was unaffected by endothelium removal or pre-treatment with antagonists for adrenoceptors, histamine, dopamine or 5-HT receptors. β-PEA also produced a concentration-dependent (0.3–10 mM) vasoconstriction which was unaffected by endothelium removal, β-adrenoceptor or 5-HT receptor antagonists. A substantial, but reduced, response to β-PEA was obtained in the presence of prazosin (α1-adrenoceptor antagonist), haloperidol (D2/D3 dopamine receptor antagonist) or mepyramine (H1 histamine receptor antagonist). The pD2 value for β-PEA was unaffected by any of the antagonists tested. Conclusions and implications: Vasoconstriction induced by p-tyramine does not involve an indirect sympathomimetic effect, although vasoconstriction caused by β-PEA may occur, in part, by this mechanism. We therefore propose that trace amine-dependent vasoconstriction is mediated by phenylethylamine-specific receptors, which are closely related to or identical to TAA receptors. These receptors could provide a target for new antihypertensive therapies. PMID:18604230

Sampling strategy and analysis of trace element concentrations by inductively coupled plasma mass spectrometry on medieval human bones--the concept of chemical life history.

PubMed

Skytte, Lilian; Rasmussen, Kaare Lund

2013-07-30

Medieval human bones have the potential to reveal diet, mobility and treatment of diseases in the past. During the last two decades trace element chemistry has been used extensively in archaeometric investigations revealing such data. Many studies have reported the trace element inventory in only one sample from each skeleton - usually from the femur or a tooth. It cannot a priori be assumed that all bones or teeth in a skeleton will have the same trace element concentrations. Six different bone and teeth samples from each individual were carefully decontaminated by mechanical means. Following dissolution of ca. 20 mg sample in nitric acid and hydrogen peroxide the assays were performed using inductively coupled plasma mass spectrometry (ICPMS) with quadropole detection. We describe the precise sampling technique as well as the analytical methods and parameters used for the ICPMS analysis. The places of sampling in the human skeleton did exhibit varying trace element concentrations. Although the samples are contaminated by Fe, Mn and Al from the surrounding soil where the bones have been residing for more than 500 years, other trace elements are intact within the bones. It is shown that the elemental ratios Sr/Ca and Ba/Ca can be used as indicators of provenance. The differences in trace element concentrations can be interpreted as indications of varying diet and provenance as a function of time in the life of the individual - a concept which can be termed chemical life history. A few examples of the results of such analyses are shown, which contains information about provenance and diagenesis. Copyright © 2013 John Wiley & Sons, Ltd.

Cloud Computing Trace Characterization and Synthetic Workload Generation

DTIC Science & Technology

2013-03-01

measurements [44]. Olio is primarily for learning Web 2.0 technologies, evaluating the three implementations (PHP, Java EE, and RubyOnRails (ROR...Add Event 17 Olio is well documented, but assumes prerequisite knowledge with setup and operation of apache web servers and MySQL databases. Olio...Faban supports numerous servers such as Apache httpd, Sun Java System Web, Portal and Mail Servers, Oracle RDBMS, memcached, and others [18]. Perhaps

Determination of the chemical properties of residues retained in individual cloud droplets by XRF microprobe at SPring-8

NASA Astrophysics Data System (ADS)

Ma, C.-J.; Tohno, S.; Kasahara, M.; Hayakawa, S.

2004-06-01

To determine the chemical properties of residue retained in individual cloud droplets is primarily important for the understanding of rainout mechanism and aerosol modification in droplet. The sampling of individual cloud droplets were carried out on the summit of Mt. Taiko located in Tango peninsula, Kyoto prefecture, during Asian dust storm event in March of 2002. XRF microprobe system equipped at SPring-8, BL-37XU was applied to the subsequent quantification analysis of ultra trace elements in residues of individual cloud droplets. It was possible to form the replicas of separated individual cloud droplets on the thin collodion film. The two dimensional XRF maps for the residues in individual cloud droplets were clearly drawn by scanning of micro-beam. Also, XRF spectra of trace elements in residues were well resolved. From the XRF spectra for individual residues, the chemical mixed state of residues could be assumed. The chemical forms of Fe (Fe +++) and Zn (Zn +) could be clearly characterized by their K-edge micro-XANES spectra. By comparison of Z/Si mass ratios of residues in cloud droplets and those of the original sands collected in desert areas in China, the aging of ambient dust particles and their in cloud modification were indirectly assumed.

The Envelope Kinematics and a Possible Disk around the Class 0 Protostar within BHR7

NASA Astrophysics Data System (ADS)

Tobin, John J.; Bos, Steven P.; Dunham, Michael M.; Bourke, Tyler L.; van der Marel, Nienke

2018-04-01

We present a characterization of the protostar embedded within the BHR7 dark cloud, based on both photometric measurements from the near-infrared to millimeter and interferometric continuum and molecular line observations at millimeter wavelengths. We find that this protostar is a Class 0 system, the youngest class of protostars, measuring its bolometric temperature to be 50.5 K, with a bolometric luminosity of 9.3 L ⊙. The near-infrared and Spitzer imaging show a prominent dark lane from dust extinction separating clear bipolar outflow cavities. Observations of 13CO (J=2\\to 1), C18O (J=2\\to 1), and other molecular lines with the Submillimeter Array (SMA) exhibit a clear rotation signature on scales <1300 au. The rotation can be traced to an inner radius of ∼170 au and the rotation curve is consistent with an R ‑1 profile, implying that angular momentum is being conserved. Observations of the 1.3 mm dust continuum with the SMA reveal a resolved continuum source, extended in the direction of the dark lane, orthogonal to the outflow. The deconvolved size of the continuum indicates a radius of ∼100 au for the continuum source at the assumed distance of 400 pc. The visibility amplitude profile of the continuum emission cannot be reproduced by an envelope alone and needs a compact component. Thus, we posit that the resolved continuum source could be tracing a Keplerian disk in this very young system. If we assume that the continuum radius traces a Keplerian disk (R ∼ 120 au) the observed rotation profile is consistent with a protostar mass of 1.0 M ⊙.

A Novel Method of Recording Motion

ERIC Educational Resources Information Center

Ben-Shalom, Amir; Gluck, Paul

2013-01-01

By attaching LEDs and lasers to moving objects, and shining their light on photochromic surfaces below them, we can display traces of many motions of interest in introductory physics courses and science museums.

A novel method of recording motion

NASA Astrophysics Data System (ADS)

Ben-Shalom, Amir; Gluck, Paul

2013-05-01

By attaching LEDs and lasers to moving objects, and shining their light on photochromic surfaces below them, we can display traces of many motions of interest in introductory physics courses and science museums.

Remembering over the short-term: the case against the standard model.

PubMed

Nairne, James S

2002-01-01

Psychologists often assume that short-term storage is synonymous with activation, a mnemonic property that keeps information in an immediately accessible form. Permanent knowledge is activated, as a result of on-line cognitive processing, and an activity trace is established "in" short-term (or working) memory. Activation is assumed to decay spontaneously with the passage of time, so a refreshing process-rehearsal-is needed to maintain availability. Most of the phenomena of immediate retention, such as capacity limitations and word length effects, are assumed to arise from trade-offs between rehearsal and decay. This "standard model" of how we remember over the short-term still enjoys considerable popularity, although recent research questions most of its main assumptions. In this chapter I review the recent research and identify the empirical and conceptual problems that plague traditional conceptions of short-term memory. Increasingly, researchers are recognizing that short-term retention is cue driven, much like long-term memory, and that neither rehearsal nor decay is likely to explain the particulars of short-term forgetting.

A 3D radiative transfer model based on lidar data and its application on hydrological and ecosystem modeling

NASA Astrophysics Data System (ADS)

Li, W.; Su, Y.; Harmon, T. C.; Guo, Q.

2013-12-01

Light Detection and Ranging (lidar) is an optical remote sensing technology that measures properties of scattered light to find range and/or other information of a distant object. Due to its ability to generate 3-dimensional data with high spatial resolution and accuracy, lidar technology is being increasingly used in ecology, geography, geology, geomorphology, seismology, remote sensing, and atmospheric physics. In this study we construct a 3-dimentional (3D) radiative transfer model (RTM) using lidar data to simulate the spatial distribution of solar radiation (direct and diffuse) on the surface of water and mountain forests. The model includes three sub-models: a light model simulating the light source, a sensor model simulating the camera, and a scene model simulating the landscape. We use ground-based and airborne lidar data to characterize the 3D structure of the study area, and generate a detailed 3D scene model. The interactions between light and object are simulated using the Monte Carlo Ray Tracing (MCRT) method. A large number of rays are generated from the light source. For each individual ray, the full traveling path is traced until it is absorbed or escapes from the scene boundary. By locating the sensor at different positions and directions, we can simulate the spatial distribution of solar energy at the ground, vegetation and water surfaces. These outputs can then be incorporated into meteorological drivers for hydrologic and energy balance models to improve our understanding of hydrologic processes and ecosystem functions.

Solid State Research

DTIC Science & Technology

1998-05-15

2 Bioaerosol fluorescence sensor concept. 2 1-3 Bioaerosol fluorescence sensor detection geometry: (a) signal collection (side view... wavelength light, (b) Strength of output signal along vertical line trace indicated by arrow in (a). 37 5-2 Brick wall pattern revealed by chemical...etchant. 38 5-3 (a) Flat-field illumination of improved laser-annealed CCD at -90°C with 410-nm wavelength light, (b) Strength of output signal along

Generation of Olympic logo with freeform lens array

NASA Astrophysics Data System (ADS)

Liu, Chengkun; Huang, Qilu; Qiu, Yishen; Chen, Weijuan; Liao, Tingdi

2017-10-01

In this paper, the Olympic rings pattern is generated by using freeform lens array and illumination light source array. Based on nonimaging optics, the freeform lens array is designed for point light source, which can generate the focused pattern of annular light spot. In order to obtain the Olympic logo pattern of five rings, the array with five freeform lenses is used. By adjusting the emission angle of each light source, the annular spot is obtained at different positions of the target plane and the Olympic rings logo is formed. We used the shading plate on the surface of the freeform lens to reduce the local light intensity so that the light spot overall irradiance distribution is more uniform. We designed a freeform lens with aperture of 26.2mm, focal length of 2000mm and the diameter of a single annual spot is 400mm. We modeled freeform lens and simulated by optical software TracePro. The ray tracing results show that the Olympic rings with uniform illumination can be obtained on the target plane with the optical efficiency up to 85.7%. At the same time, this paper also studies the effects of the target plane defocusing on the spot pattern. Simulations show that when the distance of the receiving surface to the focal plane varies within 300mm, a reasonable uniform and small distorted light spot pattern can be obtained. Compared with the traditional projection method, our method of design has the advantages of high optical efficiency, low cost and the pattern is clear and uniform.

Surface-enhanced Raman detection of CW agents in water using gold sol gel substrates

NASA Astrophysics Data System (ADS)

Premasiri, W. Ranjith; Clarke, Richard H.; Womble, M. Edward

2002-02-01

The development of a water analysis system capable of detecting both inanimate trace chemical contaminants and viable microbial contaminants has long been a project of interest to our group. The capability of detecting both chemical and biological agent sources in a single device configuration would clearly add to the value of such a product. In the present work, we describe results with chemical warfare agents from our efforts to produce a Raman system for the detection of both chemical and biological warfare agents in water. We utilize laser Raman light scattering and employ Surface Enhanced Raman Spectroscopy (SERS)on solid state gold sol-gel detectors combined with fiber optic collection of the enhanced light signal in the sampling system to augment the normally low intensity Raman Scattering signal from trace materials.

Stable Isotope Measurements of Carbon Dioxide, Methane, and Hydrogen Sulfide Gas Using Frequency Modulation Spectroscopy

NASA Astrophysics Data System (ADS)

Nowak-Lovato, K.

2014-12-01

Seepage from enhanced oil recovery, carbon storage, and natural gas sites can emit trace gases such as carbon dioxide, methane, and hydrogen sulfide. Trace gas emission at these locations demonstrate unique light stable isotope signatures that provide information to enable source identification of the material. Light stable isotope detection through surface monitoring, offers the ability to distinguish between trace gases emitted from sources such as, biological (fertilizers and wastes), mineral (coal or seams), or liquid organic systems (oil and gas reservoirs). To make light stable isotope measurements, we employ the ultra-sensitive technique, frequency modulation spectroscopy (FMS). FMS is an absorption technique with sensitivity enhancements approximately 100-1000x more than standard absorption spectroscopy with the advantage of providing stable isotope signature information. We have developed an integrated in situ (point source) system that measures carbon dioxide, methane and hydrogen sulfide with isotopic resolution and enhanced sensitivity. The in situ instrument involves the continuous collection of air and records the stable isotope ratio for the gas being detected. We have included in-line flask collection points to obtain gas samples for validation of isotopic concentrations using our in-house isotope ratio mass spectroscopy (IRMS). We present calibration curves for each species addressed above to demonstrate the sensitivity and accuracy of the system. We also show field deployment data demonstrating the capabilities of the system in making live dynamic measurements from an active source.

40 CFR 51.356 - Vehicle coverage.

Code of Federal Regulations, 2012 CFR

2012-07-01

... 40 Protection of Environment 2 2012-07-01 2012-07-01 false Vehicle coverage. 51.356 Section 51.356....356 Vehicle coverage. The performance standard for enhanced I/M programs assumes coverage of all 1968 and later model year light duty vehicles and light duty trucks up to 8,500 pounds GVWR, and includes...

40 CFR 51.356 - Vehicle coverage.

Code of Federal Regulations, 2013 CFR

2013-07-01

... 40 Protection of Environment 2 2013-07-01 2013-07-01 false Vehicle coverage. 51.356 Section 51.356....356 Vehicle coverage. The performance standard for enhanced I/M programs assumes coverage of all 1968 and later model year light duty vehicles and light duty trucks up to 8,500 pounds GVWR, and includes...

40 CFR 51.356 - Vehicle coverage.

Code of Federal Regulations, 2011 CFR

2011-07-01

... 40 Protection of Environment 2 2011-07-01 2011-07-01 false Vehicle coverage. 51.356 Section 51.356....356 Vehicle coverage. The performance standard for enhanced I/M programs assumes coverage of all 1968 and later model year light duty vehicles and light duty trucks up to 8,500 pounds GVWR, and includes...

40 CFR 51.356 - Vehicle coverage.

Code of Federal Regulations, 2014 CFR

2014-07-01

... 40 Protection of Environment 2 2014-07-01 2014-07-01 false Vehicle coverage. 51.356 Section 51.356....356 Vehicle coverage. The performance standard for enhanced I/M programs assumes coverage of all 1968 and later model year light duty vehicles and light duty trucks up to 8,500 pounds GVWR, and includes...

40 CFR 51.356 - Vehicle coverage.

Code of Federal Regulations, 2010 CFR

2010-07-01

... 40 Protection of Environment 2 2010-07-01 2010-07-01 false Vehicle coverage. 51.356 Section 51.356....356 Vehicle coverage. The performance standard for enhanced I/M programs assumes coverage of all 1968 and later model year light duty vehicles and light duty trucks up to 8,500 pounds GVWR, and includes...

77 FR 38705 - Draft Specification for Airport Light Bases, Transformer Housings, Junction Boxes, and...

Federal Register 2010, 2011, 2012, 2013, 2014

2012-06-28

..., Transformer Housings, Junction Boxes, and Accessories Airport Design'' Advisory Circular, AC 150/5345-42G. The... necessary to carry out this subchapter and regulations to be assumed by the sponsor. Uniform design... A307-A) per Engineering Brief (EB) 83, In-Pavement Light Fixture Bolts is introduced where applicable...

[Trace elements in serum of malnourished and well-nourished children living in Lubumbashi and Kawama].

PubMed

Musimwa, Aimée Mudekereza; Kanteng, Gray Wakamb; Kitoko, Hermann Tamubango; Luboya, Oscar Numbi

2016-01-01

The role of trace metals elements in human nutrition can no longer be ignored. Deficiency caused by inadequate dietary intake, secondary deficiencies often under - estimated, and iatrogenic deficiencies lead to pathologies such as infections and others. For this reason their dosages are particularly important to assess disease severity and to facilitate early treatment or improve patient's diet. The aim of this study was to determine trace elements profile in blood (copper, selenium, zinc, iron, chromium, cobalt, etc.) among malnourished and well-nourished children in a mining community in Lubumbashi. Three hundred eleven cases have been collected, 182 malnourished children and 129 well-nourished children in a cross-sectional descriptive study conducted from July 2013 to December 2014. Exhaustive sampling was performed. Metal determination in serum was performed using Inductively Coupled Plasma Spectroscopy (ICP-OES/MS) in the laboratory at Congolese Control Office in Lubumbashi. Essential trace elements (copper, zinc, selenium and iron) were found at very low concentrations in both the malnourished and well-nourished children. Arsenic, cadmium, magnesium and manganese concentrations were normal compared with reference values in well-nourished children Antimony, chromium, lead and cobalt levels were high in both the malnourished and well-nourished children. Nickel level was normal malnourished and well-nourished children. Magnesium, manganese were found in very low levels in malnourished children. Both the malnourished and well-nourished children suffer from deficiencies of essential trace elements associated with trace metals elements This allows to assume that essential micronutrients deficiency promotes the absorption of heavy metals.

Raman Laser Spectrometer internal Optical Head current status: opto-mechanical redesign to minimize the excitation laser trace

NASA Astrophysics Data System (ADS)

Sanz, Miguel; Ramos, Gonzalo; Moral, Andoni; Pérez, Carlos; Belenguer, Tomás; del Rosario Canchal, María; Zuluaga, Pablo; Rodriguez, Jose Antonio; Santiago, Amaia; Rull, Fernando; Instituto Nacional de Técnica Aeroespacial (INTA); Ingeniería de Sistemas para la Defesa de España S.A. (ISDEFE)

2016-10-01

Raman Laser Spectrometer (RLS) is the Pasteur Payload instruments of the ExoMars mission, within the ESA's Aurora Exploration Programme, that will perform for the first time in an out planetary mission Raman spectroscopy. RLS is composed by SPU (Spectrometer Unit), iOH (Internal Optical Head), and ICEU (Instrument Control and Excitation Unit). iOH focuses the excitation laser on the samples (excitation path), and collects the Raman emission from the sample (collection path, composed on collimation system and filtering system). The original design presented a high laser trace reaching to the detector, and although a certain level of laser trace was required for calibration purposes, the high level degrades the Signal to Noise Ratio confounding some Raman peaks.The investigation revealing that the laser trace was not properly filtered as well as the iOH opto-mechanical redesign are reported on. After the study of the Long Pass Filters Optical Density (OD) as a function of the filtering stage to the detector distance, a new set of filters (Notch filters) was decided to be evaluated. Finally, and in order to minimize the laser trace, a new collection path design (mainly consisting on that the collimation and filtering stages are now separated in two barrels, and on the kind of filters to be used) was required. Distance between filters and collimation stage first lens was increased, increasing the OD. With this new design and using two Notch filters, the laser trace was reduced to assumable values, as can be observed in the functional test comparison also reported on this paper.

Color appearance for photorealistic image synthesis

NASA Astrophysics Data System (ADS)

Marini, Daniele; Rizzi, Alessandro; Rossi, Maurizio

2000-12-01

Photorealistic Image Synthesis is a relevant research and application field in computer graphics, whose aim is to produce synthetic images that are undistinguishable from real ones. Photorealism is based upon accurate computational models of light material interaction, that allow us to compute the spectral intensity light field of a geometrically described scene. The fundamental methods are ray tracing and radiosity. While radiosity allows us to compute the diffuse component of the emitted and reflected light, applying ray tracing in a two pass solution we can also cope with non diffuse properties of the model surfaces. Both methods can be implemented to generate an accurate photometric distribution of light of the simulated environment. A still open problem is the visualization phase, whose purpose is to display the final result of the simulated mode on a monitor screen or on a printed paper. The tone reproduction problem consists of finding the best solution to compress the extended dynamic range of the computed light field into the limited range of the displayable colors. Recently some scholars have addressed this problem considering the perception stage of image formation, so including a model of the human visual system in the visualization process. In this paper we present a working hypothesis to solve the tone reproduction problem of synthetic image generation, integrating Retinex perception model into the photo realistic image synthesis context.

Monte Carlo ray-tracing simulations of luminescent solar concentrators for building integrated photovoltaics

NASA Astrophysics Data System (ADS)

Leow, Shin Woei; Corrado, Carley; Osborn, Melissa; Carter, Sue A.

2013-09-01

Luminescent solar concentrators (LSCs) have the ability to receive light from a wide range of angles, concentrating the captured light onto small photo active areas. This enables greater incorporation of LSCs into building designs as windows, skylights and wall claddings in addition to rooftop installations of current solar panels. Using relatively cheap luminescent dyes and acrylic waveguides to effect light concentration onto lesser photovoltaic (PV) cells, there is potential for this technology to approach grid price parity. We employ a panel design in which the front facing PV cells collect both direct and concentrated light ensuring a gain factor greater than one. This also allows for flexibility in determining the placement and percentage coverage of PV cells during the design process to balance reabsorption losses against the power output and level of light concentration desired. To aid in design optimization, a Monte-Carlo ray tracing program was developed to study the transport of photons and loss mechanisms in LSC panels. The program imports measured absorption/emission spectra and transmission coefficients as simulation parameters with interactions of photons in the panel determined by comparing calculated probabilities with random number generators. LSC panels with multiple dyes or layers can also be simulated. Analysis of the results reveals optimal panel dimensions and PV cell layouts for maximum power output for a given dye concentration, absorbtion/emission spectrum and quantum efficiency.

1831: the map that launched the idea of global health.

PubMed

Koch, Tom

2014-08-01

Today we take for granted the idea of global health, of disease as an international event. Increasingly, we assume as well that the international spread of disease can be traced to human travel patterns as well as to recurring environmental conditions. Perversely, the idea of ‘global health’ and its inverse, global disease, owes little to the three-dimensional imaging of the planet and almost everything to the two-dimensional plane of the map. Here the idea of global disease is traced from its beginnings in the 18th century to its 19th-century introduction in maps of the first cholera pandemic. This global perspective, and the responsibilities it promoted among civil officials, can be seen in modern studies of cancer, influenza and other conditions with both environmental foundations and international presence.

Light Regimes Shape Utilization of Extracellular Organic C and N in a Cyanobacterial Biofilm

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

Stuart, Rhona K.; Mayali, Xavier; Boaro, Amy A.

2016-06-28

Although it is becoming clear that many microbial primary producers can also play a role as organic consumers, we know very little about the metabolic regulation of photoautotroph organic matter consumption. Cyanobacteria in phototrophic biofilms can reuse extracellular organic carbon, but the metabolic drivers of extracellular processes are surprisingly complex. We investigated the metabolic foundations of organic matter reuse by comparing exoproteome composition and incorporation of 13C-labeled and 15N-labeled cyanobacterial extracellular organic matter (EOM) in a unicyanobacterial biofilm incubated using different light regimes. In the light and the dark, cyanobacterial direct organic C assimilation accounted for 32% and 43%, respectively,more » of all organic C assimilation in the community. Under photosynthesis conditions, we measured increased excretion of extracellular polymeric substances (EPS) and proteins involved in micronutrient transport, suggesting that requirements for micronutrients may drive EOM assimilation during daylight hours. This interpretation was supported by photosynthesis inhibition experiments, in which cyanobacteria incorporated N-rich EOM-derived material. In contrast, under dark, C-starved conditions, cyanobacteria incorporated C-rich EOM-derived organic matter, decreased excretion of EPS, and showed an increased abundance of degradative exoproteins, demonstrating the use of the extracellular domain for C storage. Sequence-structure modeling of one of these exoproteins predicted a specific hydrolytic activity that was subsequently detected, confirming increased EOM degradation in the dark. Associated heterotrophic bacteria increased in abundance and upregulated transport proteins under dark relative to light conditions. Taken together, our results indicate that biofilm cyanobacteria are successful competitors for organic C and N and that cyanobacterial nutrient and energy requirements control the use of EOM. IMPORTANCECyanobacteria are globally distributed primary producers, and the fate of their fixed C influences microbial biogeochemical cycling. This fate is complicated by cyanobacterial degradation and assimilation of organic matter, but because cyanobacteria are assumed to be poor competitors for organic matter consumption, regulation of this process is not well tested. In mats and biofilms, this is especially relevant because cyanobacteria produce an extensive organic extracellular matrix, providing the community with a rich source of nutrients. Light is a well-known regulator of cyanobacterial metabolism, so we characterized the effects of light availability on the incorporation of organic matter. Using stable isotope tracing at the single-cell level, we quantified photoautotroph assimilation under different metabolic conditions and integrated the results with proteomics to elucidate metabolic status. We found that cyanobacteria effectively compete for organic matter in the light and the dark and that nutrient requirements and community interactions contribute to cycling of extracellular organic matter.« less

Micro-PIXE analysis of trace element concentrations of natural rubies from different locations in Myanmar

NASA Astrophysics Data System (ADS)

Sanchez, J. L.; Osipowicz, T.; Tang, S. M.; Tay, T. S.; Win, T. T.

1997-07-01

The trace element concentrations found in geological samples can shed light on the formation process. In the case of gemstones, which might be of artificial or natural origin, there is also considerable interest in the development of methods that provide identification of the origin of a sample. For rubies, trace element concentrations present in natural samples were shown previously to be significant indicators of the region of origin [S.M. Tang et al., Appl. Spectr. 42 (1988) 44, and 43 (1989) 219]. Here we report the results of micro-PIXE analyses of trace element (Ti, V, Cr, Fe, Cu and Ga) concentrations of a large set ( n = 130) of natural rough rubies from nine locations in Myanmar (Burma). The resulting concentrations are subjected to statistical analysis. Six of the nine groups form clusters when the data base is evaluated using tree clustering and principal component analysis.

Optical analysis of down-conversion OLEDs

NASA Astrophysics Data System (ADS)

Krummacher, Benjamin; Klein, Markus; von Malm, Norwin; Winnacker, Albrecht

2008-02-01

Phosphor down-conversion of blue organic light-emitting diodes (OLEDs) is one approach to generate white light, which offers the possibility of easy color tuning, a simple device architecture and color stability over lifetime. In this article previous work on down-conversion devices in the field of organic solid state lighting is briefly reviewed. Further, bottom emitting down-conversion OLEDs are studied from an optical point of view. Therefore the physical processes occurring in the down-conversion layer are translated into a model which is implemented in a ray tracing simulation. By comparing its predictions to experimental results the model is confirmed. For the experiments a blue-emitting polymer OLED (PLED) panel optically coupled to a series of down-conversion layers is used. Based on results obtained from ray tracing simulation some of the implications of the model for the performance of down-conversion OLEDs are discussed. In particular it is analysed how the effective reflectance of the underlying blue OLED and the particle size distribution of the phosphor powder embedded in the matrix of the down-conversion layer influence extraction efficiency.

Spatiotemporal Patterns of Urban Trace Gases and Pollutants Observed with a Light Rail Vehicle Platform in Salt Lake City, UT

NASA Astrophysics Data System (ADS)

Mitchell, L.; Crosman, E.; Fasoli, B.; Leclair-Marzolf, L.; Jacques, A.; Horel, J.; Lin, J. C.; Bowling, D. R.; Ehleringer, J. R.

2015-12-01

Urban environments are characterized by both spatial complexity and temporal variability, each of which present challenges for measurement strategies aimed at constraining estimates of greenhouse gas emissions and air quality. To address these challenges we initiated a project in December 2014 to measure trace species (CO2, CH4, O3, and Particulate Matter) by way of a Utah Transit Authority (UTA) light rail vehicle whose route traverses the Salt Lake Valley in Utah on an hourly basis, retracing the same route through commercial, residential, suburban, and rural typologies. Light rail vehicles present advantages as a measurement platform, including the absence of in-situ fossil fuel emissions, repeated transects across a urban region that provides both spatial and temporal information, and relatively low operating costs. We present initial results from the first year of operations including the spatiotemporal patterns of greenhouse gases and pollutants across Salt Lake City, UT with an emphasis on criteria pollutants, identification of sources, and future applications of this measurement platform.

Analytical approach of laser beam propagation in the hollow polygonal light pipe.

PubMed

Zhu, Guangzhi; Zhu, Xiao; Zhu, Changhong

2013-08-10

An analytical method of researching the light distribution properties on the output end of a hollow n-sided polygonal light pipe and a light source with a Gaussian distribution is developed. The mirror transformation matrices and a special algorithm of removing void virtual images are created to acquire the location and direction vector of each effective virtual image on the entrance plane. The analytical method is demonstrated by Monte Carlo ray tracing. At the same time, four typical cases are discussed. The analytical results indicate that the uniformity of light distribution varies with the structural and optical parameters of the hollow n-sided polygonal light pipe and light source with a Gaussian distribution. The analytical approach will be useful to design and choose the hollow n-sided polygonal light pipe, especially for high-power laser beam homogenization techniques.

Illuminating the circadian clock in monarch butterfly migration.

PubMed

Froy, Oren; Gotter, Anthony L; Casselman, Amy L; Reppert, Steven M

2003-05-23

Migratory monarch butterflies use a time-compensated Sun compass to navigate to their overwintering grounds in Mexico. Here, we report that constant light, which disrupts circadian clock function at both the behavioral and molecular levels in monarchs, also disrupts the time-compensated component of flight navigation. We further show that ultraviolet light is important for flight navigation but is not required for photic entrainment of circadian rhythms. Tracing these distinct light-input pathways into the brain should aid our understanding of the clock-compass mechanisms necessary for successful migration.

The Pasamonte unequilibrated eucrite: Pyroxene REE systematic and major-, minor-, and trace-element zoning. [Abstract only

NASA Technical Reports Server (NTRS)

Pun, A.; Papike, J. J.

1994-01-01

We are evaluating the trace-element concentrations in the pyroxenes of Pasamonte. Pasamonte is a characteristic member of the main group eucrites, and has recently been redescribed as a polymict eucrite. Our Pasamonte sample contained eucritic clasts with textures ranging from subophitic to moderately coarse-grained. This study concentrates on pyroxenes from an unequilibrated, coarse-grained eucrite clast. Major-, minor-, and trace-element analyses were measured for zoned pyroxenes in the eucritic clast of Pasamonte. The major- and minor-element zoning traverses were measured using the JEOL 733 electron probe with an Oxford-Link imaging/analysis system. Complemenatry trace elements were then measured for the core and rim of each of the grains by SIMS. The trace elements analyzed consisted of eight REE, Sr, Y, and Zr. These analyses were performed on a Cameca 4f ion probe. The results of the CI chondrite normalized (average CI trace-element analyses for several grains and the major- and minor-element zoning patterns from a single pyroxene grain are given. The Eu abundance in the cores of the pyroxenes represents the detection limit and therefore the (-Eu) anomaly is a minimum. Major- and minor-element patterns are typical for igneous zoning. Pyroxene cores are Mg enriched, whereas the rims are enriched in Fe and Ca. Also, Ti and Mn are found to increase, while Cr and Al generally decrease in core-to-rim traverses. The cores of the pyroxenes are more depleted in the Rare Earth Elements (REE) than the rims. Using the minor- and trace-element concentrations of bulk Pasamonte and the minor- and trace-element concentrations from the cores of the pyroxenes in Pasamonte measured in this study, we calculated partition coefficients between pyroxene and melt. This calculation assumes that bulk Pasamonte is representative of a melt composition.

Robust Requirements Tracing via Internet Search Technology: Improving an IV and V Technique. Phase 2

NASA Technical Reports Server (NTRS)

Hayes, Jane; Dekhtyar, Alex

2004-01-01

There are three major objectives to this phase of the work. (1) Improvement of Information Retrieval (IR) methods for Independent Verification and Validation (IV&V) requirements tracing. Information Retrieval methods are typically developed for very large (order of millions - tens of millions and more documents) document collections and therefore, most successfully used methods somewhat sacrifice precision and recall in order to achieve efficiency. At the same time typical IR systems treat all user queries as independent of each other and assume that relevance of documents to queries is subjective for each user. The IV&V requirements tracing problem has a much smaller data set to operate on, even for large software development projects; the set of queries is predetermined by the high-level specification document and individual requirements considered as query input to IR methods are not necessarily independent from each other. Namely, knowledge about the links for one requirement may be helpful in determining the links of another requirement. Finally, while the final decision on the exact form of the traceability matrix still belongs to the IV&V analyst, his/her decisions are much less arbitrary than those of an Internet search engine user. All this suggests that the information available to us in the framework of the IV&V tracing problem can be successfully leveraged to enhance standard IR techniques, which in turn would lead to increased recall and precision. We developed several new methods during Phase II; (2) IV&V requirements tracing IR toolkit. Based on the methods developed in Phase I and their improvements developed in Phase II, we built a toolkit of IR methods for IV&V requirements tracing. The toolkit has been integrated, at the data level, with SAIC's SuperTracePlus (STP) tool; (3) Toolkit testing. We tested the methods included in the IV&V requirements tracing IR toolkit on a number of projects.

Interpreting ambiguous 'trace' results in Schistosoma mansoni CCA Tests: Estimating sensitivity and specificity of ambiguous results with no gold standard.

PubMed

Clements, Michelle N; Donnelly, Christl A; Fenwick, Alan; Kabatereine, Narcis B; Knowles, Sarah C L; Meité, Aboulaye; N'Goran, Eliézer K; Nalule, Yolisa; Nogaro, Sarah; Phillips, Anna E; Tukahebwa, Edridah Muheki; Fleming, Fiona M

2017-12-01

The development of new diagnostics is an important tool in the fight against disease. Latent Class Analysis (LCA) is used to estimate the sensitivity and specificity of tests in the absence of a gold standard. The main field diagnostic for Schistosoma mansoni infection, Kato-Katz (KK), is not very sensitive at low infection intensities. A point-of-care circulating cathodic antigen (CCA) test has been shown to be more sensitive than KK. However, CCA can return an ambiguous 'trace' result between 'positive' and 'negative', and much debate has focused on interpretation of traces results. We show how LCA can be extended to include ambiguous trace results and analyse S. mansoni studies from both Côte d'Ivoire (CdI) and Uganda. We compare the diagnostic performance of KK and CCA and the observed results by each test to the estimated infection prevalence in the population. Prevalence by KK was higher in CdI (13.4%) than in Uganda (6.1%), but prevalence by CCA was similar between countries, both when trace was assumed to be negative (CCAtn: 11.7% in CdI and 9.7% in Uganda) and positive (CCAtp: 20.1% in CdI and 22.5% in Uganda). The estimated sensitivity of CCA was more consistent between countries than the estimated sensitivity of KK, and estimated infection prevalence did not significantly differ between CdI (20.5%) and Uganda (19.1%). The prevalence by CCA with trace as positive did not differ significantly from estimates of infection prevalence in either country, whereas both KK and CCA with trace as negative significantly underestimated infection prevalence in both countries. Incorporation of ambiguous results into an LCA enables the effect of different treatment thresholds to be directly assessed and is applicable in many fields. Our results showed that CCA with trace as positive most accurately estimated infection prevalence.

New Directions in Software Quality Assurance Automation

DTIC Science & Technology

2009-06-01

generation process. 4.1 Parameterized Safety Analysis We can do a qualitative analysis as well and ask questions like “ what has contributed to this...the probability of interception p1 in the previous example, we can determine what impact those parameters have on the probability of hazardous...assumed that the AEG is traversed top-down and left-to-right and only once to produce a particular event trace Randomized decisions about what

Reverse radiance: a fast accurate method for determining luminance

NASA Astrophysics Data System (ADS)

Moore, Kenneth E.; Rykowski, Ronald F.; Gangadhara, Sanjay

2012-10-01

Reverse ray tracing from a region of interest backward to the source has long been proposed as an efficient method of determining luminous flux. The idea is to trace rays only from where the final flux needs to be known back to the source, rather than tracing in the forward direction from the source outward to see where the light goes. Once the reverse ray reaches the source, the radiance the equivalent forward ray would have represented is determined and the resulting flux computed. Although reverse ray tracing is conceptually simple, the method critically depends upon an accurate source model in both the near and far field. An overly simplified source model, such as an ideal Lambertian surface substantially detracts from the accuracy and thus benefit of the method. This paper will introduce an improved method of reverse ray tracing that we call Reverse Radiance that avoids assumptions about the source properties. The new method uses measured data from a Source Imaging Goniometer (SIG) that simultaneously measures near and far field luminous data. Incorporating this data into a fast reverse ray tracing integration method yields fast, accurate data for a wide variety of illumination problems.

United Arab Emirates (UAE): regional and global dimensions

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

Al-Nabeh, N.A.

1984-01-01

The study traces the background and development of the United Arab Emirates as a federal entity in an essentially tribal culture. It also identifies and discusses the political dynamics that form the vital region in which the Union has emerged, the function played by major regional individuals in this emergence, and the importance of this part of the Middle East in the conception of foreign policy makers of the super powers. The issues of the regional economic policies resulted in formation of the Gulf Cooperation Council (GCC) in 1981 among six Arab Gulf countries: Bahrain, Kuwait, Oman, Qatar, Saudi Arabia,more » and the United Arab Emirates. Formation of the GCC was an essential step toward the comprehensive economic development of the region. One of the conclusions is that the attainment of socio-economic and political development is not a necessary condition for the emergence of a federal structure among highly authoritarian and formalistic political systems. The emergence of the UAE took place mainly as a consequence of the conception by pertinent political elites of the inability of the emirates to individually assume the responsibilities of statehood in a highly complicated world, and in light of the poor material and human resources each commanded after over a century of dependence on a foreign power.« less

TIM, a ray-tracing program for METATOY research and its dissemination

NASA Astrophysics Data System (ADS)

Lambert, Dean; Hamilton, Alasdair C.; Constable, George; Snehanshu, Harsh; Talati, Sharvil; Courtial, Johannes

2012-03-01

TIM (The Interactive METATOY) is a ray-tracing program specifically tailored towards our research in METATOYs, which are optical components that appear to be able to create wave-optically forbidden light-ray fields. For this reason, TIM possesses features not found in other ray-tracing programs. TIM can either be used interactively or by modifying the openly available source code; in both cases, it can easily be run as an applet embedded in a web page. Here we describe the basic structure of TIM's source code and how to extend it, and we give examples of how we have used TIM in our own research. Program summaryProgram title: TIM Catalogue identifier: AEKY_v1_0 Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AEKY_v1_0.html Program obtainable from: CPC Program Library, Queen's University, Belfast, N. Ireland Licensing provisions: GNU General Public License No. of lines in distributed program, including test data, etc.: 124 478 No. of bytes in distributed program, including test data, etc.: 4 120 052 Distribution format: tar.gz Programming language: Java Computer: Any computer capable of running the Java Virtual Machine (JVM) 1.6 Operating system: Any; developed under Mac OS X Version 10.6 RAM: Typically 145 MB (interactive version running under Mac OS X Version 10.6) Classification: 14, 18 External routines: JAMA [1] (source code included) Nature of problem: Visualisation of scenes that include scene objects that create wave-optically forbidden light-ray fields. Solution method: Ray tracing. Unusual features: Specifically designed to visualise wave-optically forbidden light-ray fields; can visualise ray trajectories; can visualise geometric optic transformations; can create anaglyphs (for viewing with coloured "3D glasses") and random-dot autostereograms of the scene; integrable into web pages. Running time: Problem-dependent; typically seconds for a simple scene.

Three-dimensional plant architecture and sunlit-shaded patterns: a stochastic model of light dynamics in canopies.

PubMed

Retkute, Renata; Townsend, Alexandra J; Murchie, Erik H; Jensen, Oliver E; Preston, Simon P

2018-05-25

Diurnal changes in solar position and intensity combined with the structural complexity of plant architecture result in highly variable and dynamic light patterns within the plant canopy. This affects productivity through the complex ways that photosynthesis responds to changes in light intensity. Current methods to characterize light dynamics, such as ray-tracing, are able to produce data with excellent spatio-temporal resolution but are computationally intensive and the resulting data are complex and high-dimensional. This necessitates development of more economical models for summarizing the data and for simulating realistic light patterns over the course of a day. High-resolution reconstructions of field-grown plants are assembled in various configurations to form canopies, and a forward ray-tracing algorithm is applied to the canopies to compute light dynamics at high (1 min) temporal resolution. From the ray-tracer output, the sunlit or shaded state for each patch on the plants is determined, and these data are used to develop a novel stochastic model for the sunlit-shaded patterns. The model is designed to be straightforward to fit to data using maximum likelihood estimation, and fast to simulate from. For a wide range of contrasting 3-D canopies, the stochastic model is able to summarize, and replicate in simulations, key features of the light dynamics. When light patterns simulated from the stochastic model are used as input to a model of photoinhibition, the predicted reduction in carbon gain is similar to that from calculations based on the (extremely costly) ray-tracer data. The model provides a way to summarize highly complex data in a small number of parameters, and a cost-effective way to simulate realistic light patterns. Simulations from the model will be particularly useful for feeding into larger-scale photosynthesis models for calculating how light dynamics affects the photosynthetic productivity of canopies.

Image analysis using reflected light: an underutilized tool for interpreting magnetic fabrics

NASA Astrophysics Data System (ADS)

Waters-Tormey, C. L.; Liner, T.; Miller, B.; Kelso, P. R.

2010-12-01

Grain shape fabric analysis is one of the most common tools used to compare magnetic fabric and handsample scale rock fabric. Usually, this image analysis uses photomicrographs taken under plane or polarized light, which may be problematic if there are several dominant magnetic carriers (e.g., magnetite and pyrrhotite). The method developed for this study uses reflected light photomicrographs, and is effective in assessing the relative contribution of different phases to the opaque mineral shape-preferred orientation (SPO). Mosaics of high-resolution photomicrographs are first assembled and processed in Adobe Photoshop®. The Adobe Illustrator® “Live Trace” tool, whose settings can be optimized for reflected light images, completes initial automatic grain tracing and phase separation. Checking and re-classification of phases using reflected light properties and trace editing occurs manually. Phase identification is confirmed by microprobe or quantitative EDS, after which grain traces are easily reclassified as needed. Traces are imported into SPO2003 (Launeau and Robin, 2005) for SPO analysis. The combination of image resolution and magnification used here includes grains down to 10 microns. This work is part of an ongoing study examining fabric development across strain gradients in the granulite facies Capricorn ridge shear zone exposed in the Mt. Hay block of central Australia (Waters-Tormey et al., 2009). Strain marker shape fabrics, mesoscale structures, and strain localization adjacent to major lithologic boundaries all indicate that the deformation involved flattening, but that components of the deformation have been partitioned into different lithological domains. Thin sections were taken from the two gabbroic map units which volumetrically dominate the shear zone (northern and southern) using samples with similar outcrop fabric intensity. Prior thermomagnetic analyses indicate these units contain magnetite ± titanomagnetite ± ilmenite ± pyrrhotite. When all opaque minerals are combined into one SPO in the northern unit, they define a triaxial (plane) shape fabric, wheras AMS and AARM T values, the orientation distribution of AMS and AARM axes, and shape fabrics defined by other strain markers (pyroxene grains, biotite grains, felsic grain aggregates in outcrop) indicate overall oblate shape fabrics. Magnetite, ilmenite and sulfides were identified in reflected light in all three samples. Magnetite ± ilmenite are dominant (1-2%; 300-1500 sample sizes) with sulfides <1% (16-223 grains). Backscatter images and EDS were used to improve magnetite and ilmenite classification, and isolate pyrrhotite from sulfide complexes. Shape axes of individual and clustered opaque grains are overall well-aligned in all three samples. However, ilmenite shape axis ratios are 2-3 times that of magnetite and pyrrhotite. Separating opaque phase shape fabrics in these samples therefore better characterizes SPO intensity and grain fabric type for comparison with AMS and AARM results.

An integrated theory of attention and decision making in visual signal detection.

PubMed

Smith, Philip L; Ratcliff, Roger

2009-04-01

The simplest attentional task, detecting a cued stimulus in an otherwise empty visual field, produces complex patterns of performance. Attentional cues interact with backward masks and with spatial uncertainty, and there is a dissociation in the effects of these variables on accuracy and on response time. A computational theory of performance in this task is described. The theory links visual encoding, masking, spatial attention, visual short-term memory (VSTM), and perceptual decision making in an integrated dynamic framework. The theory assumes that decisions are made by a diffusion process driven by a neurally plausible, shunting VSTM. The VSTM trace encodes the transient outputs of early visual filters in a durable form that is preserved for the time needed to make a decision. Attention increases the efficiency of VSTM encoding, either by increasing the rate of trace formation or by reducing the delay before trace formation begins. The theory provides a detailed, quantitative account of attentional effects in spatial cuing tasks at the level of response accuracy and the response time distributions. (c) 2009 APA, all rights reserved

Explorabook: A Kids' Science Museum in a Book.

ERIC Educational Resources Information Center

Cassidy, John

This book is written for people who tend to sit toward the back of the classroom during scientific lectures. It assumes that students remember nothing of what happened in their science classes. The book is divided into seven sections: (1) Magnetism; (2) Bending Light Waves; (3) Bacterial Stories; (4) Light Wave Craziness; (5) Homemade Science; (6)…

Verification of the Uncertainty Principle by Using Diffraction of Light Waves

ERIC Educational Resources Information Center

Nikolic, D.; Nesic, Lj

2011-01-01

We described a simple idea for experimental verification of the uncertainty principle for light waves. We used a single-slit diffraction of a laser beam for measuring the angular width of zero-order diffraction maximum and obtained the corresponding wave number uncertainty. We will assume that the uncertainty in position is the slit width. For the…

Geochemical characteristics of the La Réunion mantle plume source inferred from olivine-hosted melt inclusions from the adventive cones of Piton de la Fournaise volcano (La Réunion Island)

NASA Astrophysics Data System (ADS)

Valer, Marina; Schiano, Pierre; Bachèlery, Patrick

2017-09-01

Major and trace element compositions were obtained for bulk rocks and melt inclusions hosted in olivine crystals (Fo > 85) from the adventive cones of the Piton de La Fournaise volcano (La Réunion Island). Ratios of highly incompatible trace elements for these magmas are used to identify the nature of the La Réunion mantle plume source. Although adventive cone lavas display unusual major element compositions compared to the historical lavas of the volcano (e.g., lower CaO/Al2O3), trace element data suggest that the magmas emitted by the adventive cones originate from a common chemical source. This source may correspond to either a homogeneous mixed source of different mantle components or a near-primitive less-differentiated mantle source. The melt inclusions display ratios of highly incompatible elements (e.g., Th/La, Nb/La) which are similar to primitive mantle values, and lower Nb/U ratios compared to most oceanic basalts. These results and previous isotopic and trace element data suggest that La Réunion plume samples a source which is intermediate between a primitive-like mantle domain and a slightly depleted one almost unaffected by the recycling processes. This source could have originated from early depletion of the primitive mantle. Assuming a depletion 4.45 Gyr ago, 10% melting of this slightly depleted source could explain the enriched trace element concentrations of the melt inclusions.

Tracing source pollution in soils using cadmium and lead isotopes.

PubMed

Cloquet, C; Carignan, J; Libourel, G; Sterckeman, T; Perdrix, E

2006-04-15

Tracing the source of heavy metals in the environment is of key importance for our understanding of their pollution and natural cycles in the surface Earth reservoirs. Up to now, most exclusively Pb isotopes were used to effectively trace metal pollution sources in the environment. Here we report systematic variations of Cd isotope ratios measured in polluted topsoils surrounding a Pb-Zn refinery plant in northern France. Fractionated Cd was measured in soil samples surrounding the refinery, and this fractionation can be attributed to the refining processes. Despite the Cd isotopic ratios being precisely measured, the obtained uncertainties are still large compared to the total isotopic variation. Nevertheless, for the first time, Cd isotopically fractionated by industrial processes may be traced in the environment. On the same samples, Pb isotope systematics suggested that materials actually used by the refinery were not the major source of Pb in soils, probably because refined ore origins changed over the 100 years of operation. On the other hand, Cd isotopes and concentrations measured in topsoils allowed identification of three main origins (industrial dust and slag and agriculture), assuming that all Cd ores are not fractionated, as suggested by terrestrial rocks so far analyzed, and calculation of their relative contributions for each sampling point. Understanding that this refinery context was an ideal situation for such a study, our results lead to the possibility of tracing sources of anthropogenic Cd and better constrain mixing processes, fluxes, transport, and phasing out of industrial input in nature.

Indications of photochemical histories of Pacific air masses from measurements of atmospheric trace species at Point Arena, California

NASA Technical Reports Server (NTRS)

Parrish, D. D.; Hahn, C. J.; Williams, E. J.; Norton, R. B.; Fehsenfeld, F. C.; Singh, H. B.; Shetter, J. D.; Gandrud, B. W.; Ridley, B. A.

1992-01-01

Measurements were made of a suite of photochemically active trace species (including light hydrocarbons, ozone, peroxyacetyl nitrate, HNO3, NO3(-), NO(x), and NO(y)) in marine air collected during a 10-day period in April and May 1985 at Point Arena (California), a coastal inflow site. It was found that the mixing ratios of the alkanes, ozone, peroxyacetyl nitrate, and HNO3 correlated with variations in the origins of calculated air parcel trajectories and with variations in the ratios of the light alkanes. The highest levels of alkanes and the photochemical products were found in parcels that had been rapidly transported across the North Pacific Ocean from near the 600-mbar level above the east Asian coast. It is suggested that production over the continents, transport to the marine areas, and parallel removal processes account for much of the observed correlation.

Gamma ray spectroscopy employing divalent europium-doped alkaline earth halides and digital readout for accurate histogramming

DOEpatents

Cherepy, Nerine Jane; Payne, Stephen Anthony; Drury, Owen B; Sturm, Benjamin W

2014-11-11

A scintillator radiation detector system according to one embodiment includes a scintillator; and a processing device for processing pulse traces corresponding to light pulses from the scintillator, wherein pulse digitization is used to improve energy resolution of the system. A scintillator radiation detector system according to another embodiment includes a processing device for fitting digitized scintillation waveforms to an algorithm based on identifying rise and decay times and performing a direct integration of fit parameters. A method according to yet another embodiment includes processing pulse traces corresponding to light pulses from a scintillator, wherein pulse digitization is used to improve energy resolution of the system. A method in a further embodiment includes fitting digitized scintillation waveforms to an algorithm based on identifying rise and decay times; and performing a direct integration of fit parameters. Additional systems and methods are also presented.

Reduction of intensity variations on a photovoltaic array with compound parabolic concentrators

NASA Technical Reports Server (NTRS)

Greenman, P.; Ogallagher, J.; Winston, R.; Costogue, E.

1979-01-01

The reduction of nonuniformities in the intensity distribution of light focused on a photovoltaic array by a compound parabolic concentrator is investigated. The introduction of small distortions into the surfaces of the reflector in order to diffuse the incident collimated light to fill the angular acceptance of the concentrator is calculated by means of ray tracing to decrease the irradiance nonuniformity at the cost of a lowered effective concentration of the concentrator. Measurements of the intensity distribution on a scale test model in terrestrial sunlight with corrugated aluminized mylar reflectors are shown to be in good agreement with the ray tracing results. A two-stage concentrator consisting of a focusing primary and a nonimaging secondary is also shown to result in a fairly uniform intensity distribution except in the case of a 4-deg incidence angle, which may be corrected by the introduction of distortions into one or both concentration stages.

How pigeons discriminate the relative frequency of events.

PubMed

Keen, R; Machado, A

1999-09-01

This study examined how pigeons discriminate the relative frequencies of events when the events occur serially. In a discrete-trials procedure, 6 pigeons were shown one light nf times and then another nl times. Next, they received food for choosing the light that had occurred the least number of times during the sample. At issue were (a) how the discrimination was related to two variables, the difference between the frequencies of the two lights, D = nf - nl, and the total number of lights in the sample, T = nf + nl; and (b) whether a simple mathematical model of the discrimination process could account for the data. In contrast with models that assume that pigeons count the stimulus lights, engage in mental arithmetic on numerons, or remember the number of stimuli, the present model assumed only that the influence of a sample stimulus on choice increases linearly when the stimulus is presented, but decays exponentially when the stimulus is absent. The results showed that, overall, the pigeons discriminated the relative frequencies well. Their accuracy always increased with the absolute value of the difference D and, for D > 0, it decreased with T. Performance also showed clear recency, primacy, and contextual effects. The model accounted well for the major trends in the data.

Towards a Compositional SPIN

NASA Technical Reports Server (NTRS)

Pasareanu, Corina S.; Giannakopoulou, Dimitra

2006-01-01

This paper discusses our initial experience with introducing automated assume-guarantee verification based on learning in the SPIN tool. We believe that compositional verification techniques such as assume-guarantee reasoning could complement the state-reduction techniques that SPIN already supports, thus increasing the size of systems that SPIN can handle. We present a "light-weight" approach to evaluating the benefits of learning-based assume-guarantee reasoning in the context of SPIN: we turn our previous implementation of learning for the LTSA tool into a main program that externally invokes SPIN to provide the model checking-related answers. Despite its performance overheads (which mandate a future implementation within SPIN itself), this approach provides accurate information about the savings in memory. We have experimented with several versions of learning-based assume guarantee reasoning, including a novel heuristic introduced here for generating component assumptions when their environment is unavailable. We illustrate the benefits of learning-based assume-guarantee reasoning in SPIN through the example of a resource arbiter for a spacecraft. Keywords: assume-guarantee reasoning, model checking, learning.

Light interaction in sapphire/MgF2/Al triple-layer omnidirectional reflectors in AlGaN-based near ultraviolet light-emitting diodes

PubMed Central

Lee, Keon Hwa; Moon, Yong-Tae; Song, June-O; Kwak, Joon Seop

2015-01-01

This study examined systematically the mechanism of light interaction in the sapphire/MgF2/Al triple-layer omnidirectional reflectors (ODR) and its effects on the light output power in near ultraviolet light emitting diodes (NUV-LEDs) with the ODR. The light output power of NUV-LEDs with the triple-layer ODR structure increased with decreasing surface roughness of the sapphire backside in the ODR. Theoretical modeling of the roughened surface suggests that the dependence of the reflectance of the triple-layer ODR structure on the surface roughness can be attributed mainly to light absorption by the Al nano-structures and the trapping of scattered light in the MgF2 layer. Furthermore, the ray tracing simulation based upon the theoretical modeling showed good agreement with the measured reflectance of the ODR structure in diffuse mode. PMID:26010378

Light interaction in sapphire/MgF2/Al triple-layer omnidirectional reflectors in AlGaN-based near ultraviolet light-emitting diodes.

PubMed

Lee, Keon Hwa; Moon, Yong-Tae; Song, June-O; Kwak, Joon Seop

2015-05-26

This study examined systematically the mechanism of light interaction in the sapphire/MgF2/Al triple-layer omnidirectional reflectors (ODR) and its effects on the light output power in near ultraviolet light emitting diodes (NUV-LEDs) with the ODR. The light output power of NUV-LEDs with the triple-layer ODR structure increased with decreasing surface roughness of the sapphire backside in the ODR. Theoretical modeling of the roughened surface suggests that the dependence of the reflectance of the triple-layer ODR structure on the surface roughness can be attributed mainly to light absorption by the Al nano-structures and the trapping of scattered light in the MgF2 layer. Furthermore, the ray tracing simulation based upon the theoretical modeling showed good agreement with the measured reflectance of the ODR structure in diffuse mode.

Multi-Wavelength Measurement of Soot Optical Properties: Influence of Non-Absorbing Coatings

NASA Astrophysics Data System (ADS)

Freedman, Andrew; Renbaum-Wollf, Lindsay; Forestieri, Sara; Lambe, Andrew; Cappa, Christopher; Davidovits, Paul; Onasch, Timothy

2015-04-01

Soot, a product of incomplete combustion, plays an important role in the earth's climate system through the absorption and scattering of solar radiation. Important in quantifying the direct radiative impacts of soot in climate models, and specifically of black carbon (BC), is the assumed BC refractive index and shape-dependent interaction of light with BC particles. The latter assumption carries significant uncertainty because BC particles are fractal-like, being agglomerates of smaller (20-40 nm) spherules, yet many optical models such as Mie theory in particular, typically assume a spherical particle morphology. It remains unclear under what conditions this is an acceptable assumption. To investigate the ability of various optical models to reproduce observed BC optical properties, we obtained measurements of light absorption, scattering and extinction coefficients and thus single scattering albedo (SSA) of size-resolved soot particles. Measurements were made on denuded soot particles produced using both methane and ethylene as fuels. In addition, these soot particles were coated with dioctyl sebacate or sulfuric acid and the enhancement in the apparent mass absorption coefficient determined. Extinction and absorption were measured using a dual cavity ringdown photoacoustic spectrometer (CRD-PAS) at 405 nm and 532 nm. Scattering and extinction were measured using a CAPS PMssa single scattering albedo monitor (Aerodyne) at 630 nm. Soot particle mass was quantified using a centrifugal particle mass analyzer (CPMA, Cambustion), mobility size with a scanning mobility particle sizer (SMPS, TSI) and soot concentration with a CPC (Brechtel). The results will be interpreted in light of both Mie theory which assumes spherical and uniform particles and Rayleigh-Debye-Gans (RDG) theory, which assumes that the absorption properties of soot are dictated by the individual spherules. For denuded soot, effective refractive indices will be determined.

Origin of invasive Florida frogs traced to Cuba

PubMed Central

Heinicke, Matthew P.; Diaz, Luis M.; Hedges, S. Blair

2011-01-01

Two of the earliest examples of successful invasive amphibians are the greenhouse frog (Eleutherodactylus planirostris) and the Cuban treefrog (Osteopilus septentrionalis) in Florida. Although both are generally assumed to be recent introductions, they are widespread on Caribbean islands and also have been proposed as natural colonizers. We obtained nucleotide sequence data for both species and their closest relatives in their native and introduced ranges. Phylogenetic analyses trace the origin of E. planirostris to a small area in western Cuba, while O. septentrionalis is derived from at least two Cuban sources, one probably a remote peninsula in western Cuba. The tropical-to-temperate invasion began with colonization of the Florida Keys followed by human-mediated dispersal within peninsular Florida. The subtropical Keys may have served as an adaptive stepping stone for the successful invasion of the North American continent. PMID:21270024

Estimation of Curve Tracing Time in Supercapacitor based PV Characterization

NASA Astrophysics Data System (ADS)

Basu Pal, Sudipta; Das Bhattacharya, Konika; Mukherjee, Dipankar; Paul, Debkalyan

2017-08-01

Smooth and noise-free characterisation of photovoltaic (PV) generators have been revisited with renewed interest in view of large size PV arrays making inroads into the urban sector of major developing countries. Such practice has recently been observed to be confronted by the use of a suitable data acquisition system and also the lack of a supporting theoretical analysis to justify the accuracy of curve tracing. However, the use of a selected bank of supercapacitors can mitigate the said problems to a large extent. Assuming a piecewise linear analysis of the V-I characteristics of a PV generator, an accurate analysis of curve plotting time has been possible. The analysis has been extended to consider the effect of equivalent series resistance of the supercapacitor leading to increased accuracy (90-95%) of curve plotting times.

Magnetospheric ray tracing studies. [Jupiter's decametric radiation

NASA Technical Reports Server (NTRS)

Six, N. F.

1982-01-01

Using a model of Jupiter's magnetized plasma environment, radiation raypaths were calculated with a three-dimension ray tracing program. It is assumed that energetic particles produce the emission in the planet's auroral zone at frequencies just above the electron gyrofrequencies. This radiation is generated in narrow sheets defined by the angle of a ray with respect to the magnetic field line. By specifying the source position: latitude, longitude, and radial distance from the planet, signatures in the spectrum of frequency versus time seen by Voyager 1 and 2 were duplicated. The frequency range and the curvature of the decametric arcs in these dynamic spectra are the result of the geometry of the radiation sheets (imposed by the plasma and by the B-field) and illumination of Voyager 1 and 2 as the rotating magnetosphere mimics a pulsar.

Trace metals, melanin-based pigmentation and their interaction influence immune parameters in feral pigeons (Columba livia).

PubMed

Chatelain, M; Gasparini, J; Frantz, A

2016-04-01

Understanding the effects of trace metals emitted by anthropogenic activities on wildlife is of great concern in urban ecology; yet, information on how they affect individuals, populations, communities and ecosystems remains scarce. In particular, trace metals may impact survival by altering the immune system response to parasites. Plumage melanin is assumed to influence the effects of trace metals on immunity owing to its ability to bind metal ions in feathers and its synthesis being coded by a pleiotropic gene. We thus hypothesized that trace metal exposure would interact with plumage colouration in shaping immune response. We experimentally investigated the interactive effect between exposure to an environmentally relevant range of zinc and/or lead and melanin-based plumage colouration on components of the immune system in feral pigeons (Columba livia). We found that zinc increased anti-keyhole limpet hemocyanin (KLH) IgY primary response maintenance, buffered the negative effect of lead on anti-KLH IgY secondary response maintenance and tended to increase T-cell mediated phytohaemagglutinin (PHA) skin response. Lead decreased the peak of the anti-KLH IgY secondary response. In addition, pheomelanic pigeons exhibited a higher secondary anti-KLH IgY response than did eumelanic ones. Finally, T-cell mediated PHA skin response decreased with increasing plumage eumelanin level of birds exposed to lead. Neither treatments nor plumage colouration correlated with endoparasite intensity. Overall, our study points out the effects of trace metals on some parameters of birds' immunity, independently from other confounding urbanization factors, and underlines the need to investigate their impacts on other life history traits and their consequences in the ecology and evolution of host-parasite interactions.

Testing Dissipative Magnetosphere Model Light Curves and Spectra with Fermi Pulsars

NASA Technical Reports Server (NTRS)

Brambilla, Gabriele; Kalapotharakos, Constantinos; Harding, Alice K.; Kazanas, Demosthenes

2015-01-01

We explore the emission properties of a dissipative pulsar magnetosphere model introduced by Kalapotharakos et al. comparing its high-energy light curves and spectra, due to curvature radiation, with data collected by the Fermi LAT. The magnetosphere structure is assumed to be near the force-free solution. The accelerating electric field, inside the light cylinder (LC), is assumed to be negligible, while outside the LC it rescales with a finite conductivity (sigma). In our approach we calculate the corresponding high-energy emission by integrating the trajectories of test particles that originate from the stellar surface, taking into account both the accelerating electric field components and the radiation reaction forces. First, we explore the parameter space assuming different value sets for the stellar magnetic field, stellar period, and conductivity. We show that the general properties of the model are in a good agreement with observed emission characteristics of young gamma-ray pulsars, including features of the phase-resolved spectra. Second, we find model parameters that fit each pulsar belonging to a group of eight bright pulsars that have a published phase-resolved spectrum. The sigma values that best describe each of the pulsars in this group show an increase with the spin-down rate (E? ) and a decrease with the pulsar age, expected if pair cascades are providing the magnetospheric conductivity. Finally, we explore the limits of our analysis and suggest future directions for improving such models.

Horizontal supergranule-scale motions inferred from TRACE ultraviolet observations of the chromosphere

NASA Astrophysics Data System (ADS)

Tian, H.; Potts, H. E.; Marsch, E.; Attie, R.; He, J.-S.

2010-09-01

Aims: We study horizontal supergranule-scale motions revealed by TRACE observation of the chromospheric emission, and investigate the coupling between the chromosphere and the underlying photosphere. Methods: A highly efficient feature-tracking technique called balltracking has been applied for the first time to the image sequences obtained by TRACE (transition region and coronal explorer) in the passband of white light and the three ultraviolet passbands centered at 1700 Å, 1600 Å, and 1550 Å. The resulting velocity fields have been spatially smoothed and temporally averaged in order to reveal horizontal supergranule-scale motions that may exist at the emission heights of these passbands. Results: We find indeed a high correlation between the horizontal velocities derived in the white-light and ultraviolet passbands. The horizontal velocities derived from the chromospheric and photospheric emission are comparable in magnitude. Conclusions: The horizontal motions derived in the UV passbands might indicate the existence of a supergranule-scale magneto-convection in the chromosphere, which may shed new light on the study of mass and energy supply to the corona and solar wind at the height of the chromosphere. However, it is also possible that the apparent motions reflect the chromospheric brightness evolution as produced by acoustic shocks which might be modulated by the photospheric granular motions in their excitation process, or advected partly by the supergranule-scale flow towards the network while propagating upward from the photosphere. To reach a firm conclusion, it is necessary to investigate the role of granular motions in the excitation of shocks through numerical modeling, and future high-cadence chromospheric magnetograms must be scrutinized.

Learn on the Fly: Quiescent Routing in Wireless Sensor Networks

DTIC Science & Technology

2005-02-01

quality solely based on data traf- fic without employing beacons. Using a realistic sensor network traffic trace and an 802.11b testbed of 195 Stargates ...testbed of 195 Stargates [1] with 802.11b radios. For instance, we investigate the validity of geographic uniformity which is assumed in literature [19...Figure 1), we deploy 29 Stargates in a straight line, with a 45-meter separation between any two consecutive Stargates . The Stargates run Linux with

Predicting and Managing Lighting and Visibility for Human Operations in Space

NASA Technical Reports Server (NTRS)

Maida, James C.; Peacock, Brian

2003-01-01

Lighting is critical to human visual performance. On earth this problem is well understood and solutions are well defined and executed. Because the sun rises and sets on average every 45 minutes during Earth orbit, humans working in space must cope with extremely dynamic lighting conditions varying from very low light conditions to severe glare and contrast conditions. For critical operations, it is essential that lighting conditions be predictable and manageable. Mission planners need to detelmine whether low-light video cameras are required or whether additional luminaires, or lamps, need to be flown . Crew and flight directors need to have up to date daylight orbit time lines showing the best and worst viewing conditions for sunlight and shadowing. Where applicable and possible, lighting conditions need to be part of crew training. In addition, it is desirable to optimize the quantity and quality of light because of the potential impacts on crew safety, delivery costs, electrical power and equipment maintainability for both exterior and interior conditions. Addressing these issues, an illumination modeling system has been developed in the Space Human Factors Laboratory at ASA Johnson Space Center. The system is the integration of a physically based ray-tracing package ("Radiance"), developed at the Lawrence Berkeley Laboratories, a human factors oriented geometric modeling system developed by NASA and an extensive database of humans and their work environments. Measured and published data has been collected for exterior and interior surface reflectivity; luminaire beam spread distribution, color and intensity and video camera light sensitivity and has been associated with their corresponding geometric models. Selecting an eye-point and one or more light sources, including sun and earthshine, a snapshot of the light energy reaching the surfaces or reaching the eye point is computed. This energy map is then used to extract the required information needed for useful predictions. Using a validated, comprehensive illumination model integrated with empirically derived data, predictions of lighting and viewing conditions have been successfully used for Shuttle and Space Station planning and assembly operations. It has successfully balanced the needs for adequate human performance with the utili zation of resources. Keywords: Modeling, ray tracing, luminaires, refl ectivity, luminance, illuminance.

MERCURY EMISSIONS FROM BRAKE WEAR ASSOCIATED WITH ON-ROAD VEHICLES

EPA Science Inventory

This paper will focus on brake wear emissions of mercury and trace metals collected from 16 in-use light-duty vehicles (14 gasoline and 2 diesel) on a chassis dynamometer over the course of urban drive cycles.

Age-related adaptive responses of mitochondria of the retinal pigment epithelium to the everyday blue LED lighting.

PubMed

Serezhnikova, N B; Pogodina, L S; Lipina, T V; Trofimova, N N; Gurieva, T S; Zak, P P

2017-07-01

The effect of everyday blue light (λ = 440-460 nm) on mitochondria of the retinal pigment epithelium of different age groups of Japanese quail was studied using electron microscopy, morphometric methods, and biochemical analysis. We have found a significant increase in the number of mitochondria, including those modified, mainly in young birds. In addition, cell metabolic activity increased in response to blue lighting. These changes are assumed to reflect an adaptive response of mitochondria aimed at neutralizing the phototoxic effect of blue light caused by accumulation of lipofuscin granules.

Relative Reality: the Movie

NASA Astrophysics Data System (ADS)

Onley, David; Steinberg, Gary

2004-04-01

The consequences of the Special Theory of Relativity are explored in a virtual world in which the speed of light is only 10 m/s. Ray tracing software and other visualization tools, modified to allow for the finite speed of light, are employed to create a video that brings to life a journey through this imaginary world. The aberation of light, the Doppler effect, the altered perception of time and power of incoming radiation are explored in separate segments of this 35 min video. Several of the effects observed are new and quite unexpected. A commentary and animated explanations help keep the viewer from losing all perspective.

Visible-Light Responsive Catalysts Using Quantum Dot-Modified TiO2 for Air and Water Purification

NASA Technical Reports Server (NTRS)

Coutts, Janelle L.; Hintze, Paul E.; Clausen, Christian A.; Richards, Jeffrey T.

2014-01-01

Photocatalysis, the oxidation or reduction of contaminants by light-activated catalysts, utilizing titanium dioxide (TiO2) as the catalytic substrate has been widely studied for trace contaminant control in both air and water applications. The interest in this process is due primarily to its low energy consumption and capacity for catalyst regeneration. Titanium dioxide requires ultraviolet light for activation due to its relatively large band gap energy of 3.2 eV. Traditionally, Hg-vapor fluorescent light sources are used in PCO reactors; however, the use of mercury precludes the use of this PCO technology in a spaceflight environment due to concerns over crew Hg exposure.

Active learning of neuron morphology for accurate automated tracing of neurites

PubMed Central

Gala, Rohan; Chapeton, Julio; Jitesh, Jayant; Bhavsar, Chintan; Stepanyants, Armen

2014-01-01

Automating the process of neurite tracing from light microscopy stacks of images is essential for large-scale or high-throughput quantitative studies of neural circuits. While the general layout of labeled neurites can be captured by many automated tracing algorithms, it is often not possible to differentiate reliably between the processes belonging to different cells. The reason is that some neurites in the stack may appear broken due to imperfect labeling, while others may appear fused due to the limited resolution of optical microscopy. Trained neuroanatomists routinely resolve such topological ambiguities during manual tracing tasks by combining information about distances between branches, branch orientations, intensities, calibers, tortuosities, colors, as well as the presence of spines or boutons. Likewise, to evaluate different topological scenarios automatically, we developed a machine learning approach that combines many of the above mentioned features. A specifically designed confidence measure was used to actively train the algorithm during user-assisted tracing procedure. Active learning significantly reduces the training time and makes it possible to obtain less than 1% generalization error rates by providing few training examples. To evaluate the overall performance of the algorithm a number of image stacks were reconstructed automatically, as well as manually by several trained users, making it possible to compare the automated traces to the baseline inter-user variability. Several geometrical and topological features of the traces were selected for the comparisons. These features include the total trace length, the total numbers of branch and terminal points, the affinity of corresponding traces, and the distances between corresponding branch and terminal points. Our results show that when the density of labeled neurites is sufficiently low, automated traces are not significantly different from manual reconstructions obtained by trained users. PMID:24904306

Polarized reflectance and transmittance properties of windblown sea surfaces.

PubMed

Mobley, Curtis D

2015-05-20

Generation of random sea surfaces using wave variance spectra and Fourier transforms is formulated in a way that guarantees conservation of wave energy and fully resolves wave height and slope variances. Monte Carlo polarized ray tracing, which accounts for multiple scattering between light rays and wave facets, is used to compute effective Mueller matrices for reflection and transmission of air- or water-incident polarized radiance. Irradiance reflectances computed using a Rayleigh sky radiance distribution, sea surfaces generated with Cox-Munk statistics, and unpolarized ray tracing differ by 10%-18% compared with values computed using elevation- and slope-resolving surfaces and polarized ray tracing. Radiance reflectance factors, as used to estimate water-leaving radiance from measured upwelling and sky radiances, are shown to depend on sky polarization, and improved values are given.

Efficient calculation of luminance variation of a luminaire that uses LED light sources

NASA Astrophysics Data System (ADS)

Goldstein, Peter

2007-09-01

Many luminaires have an array of LEDs that illuminate a lenslet-array diffuser in order to create the appearance of a single, extended source with a smooth luminance distribution. Designing such a system is challenging because luminance calculations for a lenslet array generally involve tracing millions of rays per LED, which is computationally intensive and time-consuming. This paper presents a technique for calculating an on-axis luminance distribution by tracing only one ray per LED per lenslet. A multiple-LED system is simulated with this method, and with Monte Carlo ray-tracing software for comparison. Accuracy improves, and computation time decreases by at least five orders of magnitude with this technique, which has applications in LED-based signage, displays, and general illumination.

Spectropolarimetric Imaging Observations

NASA Astrophysics Data System (ADS)

Bradley, Christine Lavella

The capability to map anthropogenic aerosol quantities and properties over land can provide significant insights for climate and environmental studies on global and regional scales. One of the primary challenges in aerosol information monitoring is separating two signals measured by downward-viewing airborne or spaceborne instruments: the light scattered from the aerosols and light reflected from the Earth's surface. In order to study the aerosols independently, the surface signal needs to be subtracted out from the measurements. Some observational modalities, such as multispectral and multiangle, do not provide enough information to uniquely define the Earth's directional reflectance properties for this task due to the high magnitude and inhomogeneity of albedo for land surface types. Polarization, however, can provide additional information to define surface reflection. To improve upon current measurement capabilities of aerosols over urban areas, Jet Propulsion Laboratory developed the Multiangle SpectroPolarimetric Imager (MSPI) that can accurately measure the Degree of Linear Polarization to 0.5%. In particular, data acquired by the ground-based prototype, GroundMSPI, is used for directional reflectance studies of outdoor surfaces in this dissertation. This work expands upon an existing model, the microfacet model, to characterize the polarized bidirectional reflectance distribution function (pBRDF) of surfaces and validate an assumption, the Spectral Invariance Hypothesis, on the surface pBRDF that is used in aerosol retrieval algorithms. The microfacet model is commonly used to represent the pBRDF of Earth's surface types, such as ocean and land. It represents a roughened surface comprised of randomly oriented facets that specularly reflect incoming light into the upward hemisphere. The analytic form of the pBRDF for this model assumes only a single reflection of light from the microfaceted surface. If the incoming illumination is unpolarized, as it is with natural light from the Sun, the reflected light is linearly polarized perpendicular to the plane that contains the illumination and view directions, the scattering plane. However, previous work has shown that manmade objects, such as asphalt and brick, show a polarization signature that differs from the single reflection microfacet model. Using the polarization ray-tracing (PRT) program POLARIS-M, a numerical calculation for the pBRDF is made for a roughened surface to account for multiple reflections that light can experience between microfacets. Results from this numerical PRT method shows rays that experience two or more reflections with the microfacet surface can be polarized at an orientation that differs from the analytical single reflection microfacet model. This PRT method is compared against GroundMSPI data of manmade surfaces. An assumption made regarding the pBRDF for this microfacet model is verified with GroundMSPI data of urban areas. This is known as the Spectral Invariance Hypothesis and asserts that the magnitude and shape of the polarized bidirectional reflectance factor (pBRF) is the same for all wavelengths. This simplifies the microfacet model by assuming some surface parameters such as the index of refraction are spectrally neutral. GroundMSPI acquires the pBRF for five prominent region types, asphalt, brick, cement, dirt, and grass, for day-long measurements on clear sky conditions. Over the course of each day, changing solar position in the sky provides a large range of scattering angles for this study. The pBRF is measured for the three polarimetric wavelengths of GroundMSPI, 470, 660, and 865nm, and the best fit slope of the spectral correlation is reported. This investigation shows agreement to the Spectral Invariance Hypothesis within 10% for all region types excluding grass. Grass measurements show a large mean deviation of 31.1%. This motivated an angle of linear polarization (AoLP) analysis of cotton crops to isolate single reflection cases, or specular reflections, from multiple scattering cases of light in vegetation. Results from this AoLP method show that specular reflections off the top surface of leaves follow the Spectral Invariance Hypothesis.

Trace: a high-throughput tomographic reconstruction engine for large-scale datasets

DOE PAGES

Bicer, Tekin; Gursoy, Doga; Andrade, Vincent De; ...

2017-01-28

Here, synchrotron light source and detector technologies enable scientists to perform advanced experiments. These scientific instruments and experiments produce data at such scale and complexity that large-scale computation is required to unleash their full power. One of the widely used data acquisition technique at light sources is Computed Tomography, which can generate tens of GB/s depending on x-ray range. A large-scale tomographic dataset, such as mouse brain, may require hours of computation time with a medium size workstation. In this paper, we present Trace, a data-intensive computing middleware we developed for implementation and parallelization of iterative tomographic reconstruction algorithms. Tracemore » provides fine-grained reconstruction of tomography datasets using both (thread level) shared memory and (process level) distributed memory parallelization. Trace utilizes a special data structure called replicated reconstruction object to maximize application performance. We also present the optimizations we have done on the replicated reconstruction objects and evaluate them using a shale and a mouse brain sinogram. Our experimental evaluations show that the applied optimizations and parallelization techniques can provide 158x speedup (using 32 compute nodes) over single core configuration, which decreases the reconstruction time of a sinogram (with 4501 projections and 22400 detector resolution) from 12.5 hours to less than 5 minutes per iteration.« less

Trace: a high-throughput tomographic reconstruction engine for large-scale datasets

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

Bicer, Tekin; Gursoy, Doga; Andrade, Vincent De

Here, synchrotron light source and detector technologies enable scientists to perform advanced experiments. These scientific instruments and experiments produce data at such scale and complexity that large-scale computation is required to unleash their full power. One of the widely used data acquisition technique at light sources is Computed Tomography, which can generate tens of GB/s depending on x-ray range. A large-scale tomographic dataset, such as mouse brain, may require hours of computation time with a medium size workstation. In this paper, we present Trace, a data-intensive computing middleware we developed for implementation and parallelization of iterative tomographic reconstruction algorithms. Tracemore » provides fine-grained reconstruction of tomography datasets using both (thread level) shared memory and (process level) distributed memory parallelization. Trace utilizes a special data structure called replicated reconstruction object to maximize application performance. We also present the optimizations we have done on the replicated reconstruction objects and evaluate them using a shale and a mouse brain sinogram. Our experimental evaluations show that the applied optimizations and parallelization techniques can provide 158x speedup (using 32 compute nodes) over single core configuration, which decreases the reconstruction time of a sinogram (with 4501 projections and 22400 detector resolution) from 12.5 hours to less than 5 minutes per iteration.« less

Effects of human-induced alteration of groundwater flow on concentrations of naturally-occurring trace elements at water-supply wells

USGS Publications Warehouse

Ayotte, J.D.; Szabo, Z.; Focazio, M.J.; Eberts, S.M.

2011-01-01

The effects of human-induced alteration of groundwater flow patterns on concentrations of naturally-occurring trace elements were examined in five hydrologically distinct aquifer systems in the USA. Although naturally occurring, these trace elements can exceed concentrations that are considered harmful to human health. The results show that pumping-induced hydraulic gradient changes and artificial connection of aquifers by well screens can mix chemically distinct groundwater. Chemical reactions between these mixed groundwaters and solid aquifer materials can result in the mobilization of trace elements such as U, As and Ra, with subsequent transport to water-supply wells. For example, in the High Plains aquifer near York, Nebraska, mixing of shallow, oxygenated, lower-pH water from an unconfined aquifer with deeper, confined, anoxic, higher-pH water is facilitated by wells screened across both aquifers. The resulting higher-O2, lower-pH mixed groundwater facilitated the mobilization of U from solid aquifer materials, and dissolved U concentrations were observed to increase significantly in nearby supply wells. Similar instances of trace element mobilization due to human-induced mixing of groundwaters were documented in: (1) the Floridan aquifer system near Tampa, Florida (As and U), (2) Paleozoic sedimentary aquifers in eastern Wisconsin (As), (3) the basin-fill aquifer underlying the California Central Valley near Modesto (U), and (4) Coastal Plain aquifers of New Jersey (Ra). Adverse water-quality impacts attributed to human activities are commonly assumed to be related solely to the release of the various anthropogenic contaminants to the environment. The results show that human activities including various land uses, well drilling, and pumping rates and volumes can adversely impact the quality of water in supply wells, when associated with naturally-occurring trace elements in aquifer materials. This occurs by causing subtle but significant changes in geochemistry and associated trace element mobilization as well as enhancing advective transport processes.

Redox Conditions on Small Bodies

NASA Technical Reports Server (NTRS)

Jones, J. H.

2004-01-01

The Eucrite Parent Body (4 Vesta). The eucrites are basalts that contain approx. 18 wt% FeO and contain trace metal. The eucrites are very depleted in siderophile elements, so it appears that the source regions of these basalts once equilibrated with Fe-Ni metal. Therefore, it is of interest to ask what fo2 is required to precipitate metal from a liquid of eucrite composition. Or in other words, what f02 did eucrites form under? This fo2 has been determined experimentally by and was found to be IW-1. Therefore, eucrites formed at about IW-1. In addition, it is interesting to note that assuming X(sub feo) = alpha(sub FeO) allows calculation of eucrite fo2 (assuming equilibrium with Fe metal). This calculation yields the same result as the experiments to within approx. 0.25 log units, reinforcing this result.

Disrupting neural activity related to awake-state sharp wave-ripple complexes prevents hippocampal learning.

PubMed

Nokia, Miriam S; Mikkonen, Jarno E; Penttonen, Markku; Wikgren, Jan

2012-01-01

Oscillations in hippocampal local-field potentials (LFPs) reflect the crucial involvement of the hippocampus in memory trace formation: theta (4-8 Hz) oscillations and ripples (~200 Hz) occurring during sharp waves are thought to mediate encoding and consolidation, respectively. During sharp wave-ripple complexes (SPW-Rs), hippocampal cell firing closely follows the pattern that took place during the initial experience, most likely reflecting replay of that event. Disrupting hippocampal ripples using electrical stimulation either during training in awake animals or during sleep after training retards spatial learning. Here, adult rabbits were trained in trace eyeblink conditioning, a hippocampus-dependent associative learning task. A bright light was presented to the animals during the inter-trial interval (ITI), when awake, either during SPW-Rs or irrespective of their neural state. Learning was particularly poor when the light was presented following SPW-Rs. While the light did not disrupt the ripple itself, it elicited a theta-band oscillation, a state that does not usually coincide with SPW-Rs. Thus, it seems that consolidation depends on neuronal activity within and beyond the hippocampus taking place immediately after, but by no means limited to, hippocampal SPW-Rs.

Probabilistic evaluation of n traces with no putative source: A likelihood ratio based approach in an investigative framework.

PubMed

De March, I; Sironi, E; Taroni, F

2016-09-01

Analysis of marks recovered from different crime scenes can be useful to detect a linkage between criminal cases, even though a putative source for the recovered traces is not available. This particular circumstance is often encountered in the early stage of investigations and thus, the evaluation of evidence association may provide useful information for the investigators. This association is evaluated here from a probabilistic point of view: a likelihood ratio based approach is suggested in order to quantify the strength of the evidence of trace association in the light of two mutually exclusive propositions, namely that the n traces come from a common source or from an unspecified number of sources. To deal with this kind of problem, probabilistic graphical models are used, in form of Bayesian networks and object-oriented Bayesian networks, allowing users to intuitively handle with uncertainty related to the inferential problem. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.

Trace element abundance determinations by Synchrotron X Ray Fluorescence (SXRF) on returned comet nucleus mineral grains

NASA Technical Reports Server (NTRS)

Flynn, G. J.; Sutton, S. R.

1989-01-01

Trace element analyses were performed on bulk cosmic dust particles by Proton Induced X Ray Emission (PIXE) and Synchrotron X Ray Fluorescence (SXRF). When present at or near chondritic abundances the trace elements K, Ti, Cr, Mn, Cu, Zn, Ga, Ge, Se, and Br are presently detectable by SXRF in particles of 20 micron diameter. Improvements to the SXRF analysis facility at the National Synchrotron Light Source presently underway should increase the range of detectable elements and permit the analysis of smaller samples. In addition the Advanced Photon Source will be commissioned at Argonne National Laboratory in 1995. This 7 to 8 GeV positron storage ring, specifically designed for high-energy undulator and wiggler insertion devices, will be an ideal source for an x ray microprobe with one micron spatial resolution and better than 100 ppb elemental sensitivity for most elements. Thus trace element analysis of individual micron-sized grains should be possible by the time of the comet nucleus sample return mission.

STRESS PROTEINS IN AQUATIC ORGANISMS: AN ENVIRONMENTAL PERSPECTIVE

EPA Science Inventory

The cellular stress response protects organisms from damage resulting from exposure to a wide variety of stressors, including elevated temperatures, ultraviolet (UV) light, trace metals, and xenobiotics. he stress response entails the rapid synthesis of a suite of proteins referr...

Quick Information Sheets.

ERIC Educational Resources Information Center

Wisconsin Univ., Madison. Trace Center.

This compilation of "Trace Quick Sheets" provides descriptions, prices, and ordering information for products and services that assist with communication, control, and computer access for disabled individuals. Product descriptions or product sources are included for: adaptive toys and toy modifications; head pointers, light pointers, and…

The Analysis of PPM Levels of Gases in Air by Photoionization Mass Spectrometry

ERIC Educational Resources Information Center

Driscoll, John N.; Warneck, Peter

1973-01-01

Discusses analysis of trace gases in air by photoionization mass spectrometer. It is shown that the necessary sensitivity can be obtained by eliminating the UV monochromator and using direct ionization with a hydrogen light source. (JP)

Eastern Denali Fault surface trace map, eastern Alaska and Yukon, Canada

USGS Publications Warehouse

Bender, Adrian M.; Haeussler, Peter J.

2017-05-04

We map the 385-kilometer (km) long surface trace of the right-lateral, strike-slip Denali Fault between the Totschunda-Denali Fault intersection in Alaska, United States and the village of Haines Junction, Yukon, Canada. In Alaska, digital elevation models based on light detection and ranging and interferometric synthetic aperture radar data enabled our fault mapping at scales of 1:2,000 and 1:10,000, respectively. Lacking such resources in Yukon, we developed new structure-from-motion digital photogrammetry products from legacy aerial photos to map the fault surface trace at a scale of 1:10,000 east of the international border. The section of the fault that we map, referred to as the Eastern Denali Fault, did not rupture during the 2002 Denali Fault earthquake (moment magnitude 7.9). Seismologic, geodetic, and geomorphic evidence, along with a paleoseismic record of past ground-rupturing earthquakes, demonstrate Holocene and contemporary activity on the fault, however. This map of the Eastern Denali Fault surface trace complements other data sets by providing an openly accessible digital interpretation of the location, length, and continuity of the fault’s surface trace based on the accompanying digital topography dataset. Additionally, the digitized fault trace may provide geometric constraints useful for modeling earthquake scenarios and related seismic hazard.

Hydrovolcanic and Hydrothermal Biomediated Mineral Growth in Basaltic Tuff, Surtsey Volcano, Iceland

NASA Astrophysics Data System (ADS)

Jackson, M. D.; Couper, S.; Ivarsson, M.; Stan, C. V.; Tamura, N.; Miyagi, L. M.; Moore, J. G.

2017-12-01

Fine-scale analyses of hydroclasts in 1979 Surtsey basaltic tuff drill core provide new methods for examining hydrovolcanic and hydrothermal magma-rock influences on biomediated alteration in palagonitized submarine tephra. Synchrotron source X-ray microdiffraction and microfluorescence studies from Advanced Light Source beamline 12.3.2, epifluorescent UVA illumination microscopy, S/TEM EDX compositional analyses, and Raman spectroscopy define diverse nanocrystalline clay mineral structures at 137.9 m depth (93.8 °C (1980)) and 102.6 m depth (141.3 °C (1980)). At 137.9 m, olivine contains endolithic microborings; vermicular microstructures in altered glass contain nontronite exhibiting crystallographic preferred orientation; and 75-150 µm sub-circular microstructures in altered glass contain Al-tobermorite, a calcium-silicate-hydrate with 11.3 Å interlayer spacing, zeolite, and epifluorescent, thread-like structures. At 102.6 m depth, concentrically-layered microstructures occur in altered glass and altered olivine. These have nontronite crystallographic preferred orientations that rotate around a longitudinal axis commonly occupied by a 10-80 µm long, epifluorescent thread-like structure. Pronounced carbon concentrations detected by S/TEM EDX trace layer boundaries. First-order Raman bands at 1370 cm-1 (disorder-related) and at 1580 cm-1 (order-related), and second-order bands at 2500-3300 cm-1 (overtone scattering) detect degraded organic carbonaceous matter, a strong indication of biological origin. Sub-circular nanostructures in altered glass at 137.9 m depth show similar spectra. Borehole fluid temperatures at 102.6 m, 141.3 °C in 1980, exceeded 130 °C, the assumed limit for growth of microorganisms, however. Previous analyses suggest an early low temperature episode in submarine deposits, prior to development of a hydrothermal system driven by 1964-1967 magmatic intrusions. The abundant traces of biomediated nanocrystalline clay mineral growth validate this hypothesis. Hydrovolcanic fragmentation apparently increased ingress of seawater from the marine biosphere. Both eruptive and hydrothermal water-rock interactions influenced palagonitic alteration at the submillimeter scale during diverse temperature chronologies in the very young volcano.

Hybrid Monte Carlo-Diffusion Method For Light Propagation in Tissue With a Low-Scattering Region

NASA Astrophysics Data System (ADS)

Hayashi, Toshiyuki; Kashio, Yoshihiko; Okada, Eiji

2003-06-01

The heterogeneity of the tissues in a head, especially the low-scattering cerebrospinal fluid (CSF) layer surrounding the brain has previously been shown to strongly affect light propagation in the brain. The radiosity-diffusion method, in which the light propagation in the CSF layer is assumed to obey the radiosity theory, has been employed to predict the light propagation in head models. Although the CSF layer is assumed to be a nonscattering region in the radiosity-diffusion method, fine arachnoid trabeculae cause faint scattering in the CSF layer in real heads. A novel approach, the hybrid Monte Carlo-diffusion method, is proposed to calculate the head models, including the low-scattering region in which the light propagation does not obey neither the diffusion approximation nor the radiosity theory. The light propagation in the high-scattering region is calculated by means of the diffusion approximation solved by the finite-element method and that in the low-scattering region is predicted by the Monte Carlo method. The intensity and mean time of flight of the detected light for the head model with a low-scattering CSF layer calculated by the hybrid method agreed well with those by the Monte Carlo method, whereas the results calculated by means of the diffusion approximation included considerable error caused by the effect of the CSF layer. In the hybrid method, the time-consuming Monte Carlo calculation is employed only for the thin CSF layer, and hence, the computation time of the hybrid method is dramatically shorter than that of the Monte Carlo method.

Hybrid Monte Carlo-diffusion method for light propagation in tissue with a low-scattering region.

PubMed

Hayashi, Toshiyuki; Kashio, Yoshihiko; Okada, Eiji

2003-06-01

The heterogeneity of the tissues in a head, especially the low-scattering cerebrospinal fluid (CSF) layer surrounding the brain has previously been shown to strongly affect light propagation in the brain. The radiosity-diffusion method, in which the light propagation in the CSF layer is assumed to obey the radiosity theory, has been employed to predict the light propagation in head models. Although the CSF layer is assumed to be a nonscattering region in the radiosity-diffusion method, fine arachnoid trabeculae cause faint scattering in the CSF layer in real heads. A novel approach, the hybrid Monte Carlo-diffusion method, is proposed to calculate the head models, including the low-scattering region in which the light propagation does not obey neither the diffusion approximation nor the radiosity theory. The light propagation in the high-scattering region is calculated by means of the diffusion approximation solved by the finite-element method and that in the low-scattering region is predicted by the Monte Carlo method. The intensity and mean time of flight of the detected light for the head model with a low-scattering CSF layer calculated by the hybrid method agreed well with those by the Monte Carlo method, whereas the results calculated by means of the diffusion approximation included considerable error caused by the effect of the CSF layer. In the hybrid method, the time-consuming Monte Carlo calculation is employed only for the thin CSF layer, and hence, the computation time of the hybrid method is dramatically shorter than that of the Monte Carlo method.

A study of phycophysiology in controlled environments

NASA Technical Reports Server (NTRS)

Krauss, R. W.

1973-01-01

In an attempt to understand the responses of CHLORELLA to various quantities and qualities of light in space flight life support system, studies were designed to give the maximum rates of growth as well as maximum yields at different densities of algae under different light intensities, and under light of different wave lengths. The results of studies on the effects of light on algal growth revealed that the effect was not only positive, as had been assumed in the case of photosynthesis, but that light had a negative action also. Light at the blue end of the spectrum was clearly inhibitory to cell division and vegetative reproduction. Carbon dioxide also limited growth by inhibition of cell divisions in CHLORELLA as well as in the colorless yeast SACCHAROMYCES.

Using Light Curves to Characterize Size and Shape of Pseudo-Debris

NASA Technical Reports Server (NTRS)

Rodriquez, Heather M.; Abercromby, Kira J.; Jarvis, Kandy S.; Barker, Edwin

2006-01-01

Photometric measurements were collected for a new study aimed at estimating orbital debris sizes based on object brightness. To obtain a size from optical measurements the current practice is to assume an albedo and use a normalized magnitude to calculate optical size. However, assuming a single albedo value may not be valid for all objects or orbit types; material type and orientation can mask an object s true optical cross section. This experiment used a CCD camera to record data, a 300 W Xenon, Ozone Free collimated light source to simulate solar illumination, and a robotic arm with five degrees of freedom to move the piece of simulated debris through various orientations. The pseudo-debris pieces used in this experiment originate from the European Space Operations Centre s ESOC2 ground test explosion of a mock satellite. A uniformly illuminated white ping-pong ball was used as a zero-magnitude reference. Each debris piece was then moved through specific orientations and rotations to generate a light curve. This paper discusses the results of five different object-based light curves as measured through an x-rotation. Intensity measurements, from which each light curve was generated, were recorded in five degree increments from zero to 180 degrees. Comparing light curves of different shaped and sized pieces against their characteristic length establishes the start of a database from which an optical size estimation model will be derived in the future.

Glass light pipes for solar concentration

NASA Astrophysics Data System (ADS)

Madsen, C. K.; Dogan, Y.; Morrison, M.; Hu, C.; Atkins, R.

2018-02-01

Glass waveguides are fabricated using laser processing techniques that have low optical loss with >90% optical throughput. Advanced light pipes are demonstrated, including angled facets for turning mirrors used for lens-to-light pipe coupling, tapers that increase the concentration, and couplers for combining the outputs from multiple lens array elements. Because they are fabricated from glass, these light pipes can support large optical concentrations and propagate broadband solar over long distances with minimal loss and degradation compared to polymer waveguides. Applications include waveguiding solar concentrators using multi-junction PV cells, solar thermal applications and remoting solar energy, such as for daylighting. Ray trace simulations are used to estimate the surface smoothness required to achieve low loss. Optical measurements for fabricated light pipes are reported for use in waveguiding solar concentrator architectures.

The vascular effects of trace amines and amphetamines.

PubMed

Broadley, Kenneth J

2010-03-01

Trace amines, including tyramine, beta-phenylethylamine (beta-PEA), tryptamine and octopamine, are biologically active amines mostly based on phenylethylamine, occurring in the body in trace amounts. They are a diverse group of naturally occurring and synthetic amines, which are also found in the diet and in herbal plants, such as ephedrine and cathinone. They include amphetamine and its analogues, such as MDMA ('ecstasy'), and synthetic proprietary sympathomimetic agents such as phenylpropanolamine and pseudoephedrine. On the vascular system they cause vasoconstriction and a rise in blood pressure. This effect is the basis of their use as nasal decongestants. For over 50 years, they have been assumed to be indirectly acting sympathomimetic amines, their responses being due to the release of noradrenaline from sympathetic neurones. There are, however, results that suggest that this is not their only mechanism of action and that they may also exert direct vascular effects independent of a noradrenergic mechanism. Recently, a group of novel trace amine-associated receptors (TAARs) have been cloned and identified in the brain and peripheral tissues including blood vessels. Trace amines bind to these cloned receptors and it is suggested that their vasoconstrictor effects can in part be attributed to this mechanism. This review describes the cardiovascular pharmacology of this diverse group of amines, their structures and uses and their endogenous synthesis and metabolism. The review also considers their clinical relevance as constituents of the diet, as therapeutic agents (ritodrine, phenylpropanolamine, and pseudoephedrine) and as drugs of abuse (amphetamine, 'ecstasy') and their mechanisms of action. 2009 Elsevier Inc. All rights reserved.

Loess as an environmental archive of atmospheric trace element deposition

NASA Astrophysics Data System (ADS)

Blazina, T.; Winkel, L. H.

2013-12-01

Environmental archives such as ice cores, lake sediment cores, and peat cores have been used extensively to reconstruct past atmospheric deposition of trace elements. These records have provided information about how anthropogenic activities such as mining and fossil fuel combustion have disturbed the natural cycles of various atmospherically transported trace elements (e.g. Pb, Hg and Se). While these records are invaluable for tracing human impacts on such trace elements, they often provide limited information about the long term natural cycles of these elements. An assumption of these records is that the observed variations in trace element input, prior to any assumed anthropogenic perturbations, represent the full range of natural variations. However, records such as those mentioned above which extend back to a maximum of ~400kyr may not capture the potentially large variations of trace element input occurring over millions of years. Windblown loess sediments, often representing atmospheric deposition over time scales >1Ma, are the most widely distributed terrestrial sediments on Earth. These deposits have been used extensively to reconstruct continental climate variability throughout the Quaternary and late Neogene periods. In addition to being a valuable record of continental climate change, loess deposits may represent a long term environmental archive of atmospheric trace element deposition and may be combined with paleoclimate records to elucidate how fluctuations in climate have impacted the natural cycle of such elements. Our research uses the loess-paleosol deposits on the Chinese Loess Plateau (CLP) to quantify how atmospheric deposition of trace elements has fluctuated in central China over the past 6.8Ma. The CLP has been used extensively to reconstruct past changes of East Asian monsoon system (EAM). We present a suite of trace element concentration records (e.g. Pb, Hg, and Se) from the CLP which exemplifies how loess deposits can be used as an environmental archive to reconstruct long term natural variations in atmospheric trace element input. By comparing paleomonsoon proxy data with geochemical data we can directly correlate variations in atmospheric trace element input to fluctuations in the EAM. For example we are able to link Se input into the CLP to EAM derived precipitation. In interglacial climatic periods from 2.3-1.56Ma and 1.50-1.29Ma, we find very strong positive correlations between Se concentration and the summer monsoon index, a proxy for effective precipitation. In later interglacial periods from 1.26-0.83Ma and 0.78-0.16Ma, we find dust input plays a greater role. Our findings demonstrate that the CLP is a valuable environmental archive of atmospheric trace element deposition and suggest that other loess deposits worldwide may serve as useful records for investigating long term natural variations in atmospheric trace element cycling.

Relative effect of temperature and pH on diel cycling of dissolved trace elements in prickly pear creek, Montana

USGS Publications Warehouse

Jones, Clain A.; Nimick, D.A.; McCleskey, R. Blaine

2004-01-01

Diel (24 hr) cycles in dissolved metal and As concentrations have been documented in many northern Rocky Mountain streams in the U.S.A. The cause(s) of the cycles are unknown, although temperature- and pH-dependent sorption reactions have been cited as likely causes. A light/dark experiment was conducted to isolate temperature and pH as variables affecting diel metal cycles in Prickly Pear Creek, Montana. Light and dark chambers containing sediment and a strand of macrophyte were placed in the stream to simulate instream temperature oscillations. Photosynthesis-induced pH changes were allowed to proceed in the light chambers while photosynthesis was prevented in the dark chambers. Water samples were collected periodically for 22 hr in late July 2001 from all chambers and the stream. In the stream, dissolved Zn concentrations increased by 300% from late afternoon to early morning, while dissolved As concentrations exhibited the opposite pattern, increasing 33% between early morning and late afternoon. Zn and As concentrations in the light chambers showed similar, though less pronounced, diel variations. Conversely, Zn and As concentrations in the dark chambers had no obvious diel variation, indicating that light, or light-induced reactions, caused the variation. Temperature oscillations were nearly identical between light and dark chambers, strongly suggesting that temperature was not controlling the diel variations. As expected, pH was negatively correlated (P < 0.01) with dissolved Zn concentrations and positively correlated with dissolved As concentrations in both the light and dark chambers. From these experiments, photosynthesis-induced pH changes were determined to be the major cause of the diel dissolved Zn and As cycles in Prickly Pear Creek. Further research is necessary in other streams to verify that this finding is consistent among streams having large differences in trace-element concentrations and mineralogy of channel substrate. ?? 2004 Kluwer Academic Publishers.

Geometrical evidence for dark matter: X-ray constraints on the mass of the elliptical galaxy NGC 720

NASA Astrophysics Data System (ADS)

Buote, David A.; Canizares, Claude R.

1994-05-01

We describe (1) a new test for dark matter and alternate theories of gravitation based on the relative geometries of the X-ray and optical surface brightness distributions and an assumed form for the potential, of the optical light, (2) a technique to measure the shapes of the total gravitating matter and dark matter of an ellipsoidal system which is insensitive to the precise value of the temperature of the gas and to modest temperature gradients, and (3) a new method to determine the ratio of dark mass to stellar mass that is dependent on the functional forms for the visible star, gas and dark matter distributions, but independent of the distance to the galaxy or the gas temperature. We apply these techniques to X-ray data from the ROSAT Position Sensitive Proportional Counter (PSPC) of the optically flattened elliptical galaxy NGC 720; the optical isophotes have ellipticity epsilon approximately 0.40 extending out to approximately 120 sec. The X-ray isophotes are significantly elongated, epsilon = 0.20-0.30 for semimajor axis a approximately 100 sec. The major axes of the optical and X-ray isophotes are misaligned by approximately 30 deg +/- 15 deg. Spectral analysis of the X-ray data reveals no evidence of temperature gradients or anisotropies and demonstrates that a single-temperature plasma (T approximately 0.6 keV) having subsolar heavy element abundances and a two-temperature model having solar abundances describe the spectrum equally well. Considering only the relative geometries of the X-ray and optical surface brightness distributions and an assumed functional form for the potential of the optical light, we conclude that matter distributed like the optical light cannot produce the observed ellipticities of the X-ray isophotes, independent of the gas pressure, the gas temperature, and the value of the stellar mass; this comparison assumes a state of quasi-hydrostatic equilibrium so that the three-dimensional surfaces of the gas emissivity trace the three-dimensional isopotential surfaces -- we discuss the viability of this assumption for NGC 720. Milgrom's Modification of Newtonian Dynamics (MOND) cannot dispel this manifestation of dark matter. Hence, geometrical considerations require, without mention of pressure or temperature, the presence of an extended, massive dark matter halo in NGC 720. Employing essentially the technique of Buote & Canizares (1992; Buote 1992) we use the shape of the X-ray surface brightness to constrain the shape of the total gravitating matter. The total matter is modeled as either an oblate or prolate spheriod of constant shape and orientation having either a Ferrers (rho approximately r-n) or Hernquist density. Assuming the X-ray gas is in hydrostatic equilibrium, we construct a model X-ray gas distribution for various temperature profiles. We determine the ellipticity of the total gravitating matter to be epsilon approximately 0.50-0.70. Using the single-temperature model we estimate a total mass approximately (0.41-1.4) x 1012 h80 solar mass interior to the ellipsoid of semimajor axis 43.6 h80 kpc. Ferrers densities as steep as r-3 do not fit the data, but the r-2 and Hernquist models yield excellent fits. We estimate the mass distributions of the stars and the gas and fit the dark matter directly. For a given gas equation of state and functional forms for the visible stars, gas, and dark matter, these models yield a distance-independent and temperature-independent measurement of the ratio of dark mass to stellar mass MDM/Mstars. We estimate a minimum MDM/Mstars greater than or equal to 4 which corresponds to a total mass slightly greater than that derived from the single-temperature models for distance D = 20h80 Mpc.

Geometrical evidence for dark matter: X-ray constraints on the mass of the elliptical galaxy NGC 720

NASA Technical Reports Server (NTRS)

Buote, David A.; Canizares, Claude R.

1994-01-01

We describe (1) a new test for dark matter and alternate theories of gravitation based on the relative geometries of the X-ray and optical surface brightness distributions and an assumed form for the potential, of the optical light, (2) a technique to measure the shapes of the total gravitating matter and dark matter of an ellipsoidal system which is insensitive to the precise value of the temperature of the gas and to modest temperature gradients, and (3) a new method to determine the ratio of dark mass to stellar mass that is dependent on the functional forms for the visible star, gas and dark matter distributions, but independent of the distance to the galaxy or the gas temperature. We apply these techniques to X-ray data from the ROSAT Position Sensitive Proportional Counter (PSPC) of the optically flattened elliptical galaxy NGC 720; the optical isophotes have ellipticity epsilon approximately 0.40 extending out to approximately 120 sec. The X-ray isophotes are significantly elongated, epsilon = 0.20-0.30 for semimajor axis a approximately 100 sec. The major axes of the optical and X-ray isophotes are misaligned by approximately 30 deg +/- 15 deg. Spectral analysis of the X-ray data reveals no evidence of temperature gradients or anisotropies and demonstrates that a single-temperature plasma (T approximately 0.6 keV) having subsolar heavy element abundances and a two-temperature model having solar abundances describe the spectrum equally well. Considering only the relative geometries of the X-ray and optical surface brightness distributions and an assumed functional form for the potential of the optical light, we conclude that matter distributed like the optical light cannot produce the observed ellipticities of the X-ray isophotes, independent of the gas pressure, the gas temperature, and the value of the stellar mass; this comparison assumes a state of quasi-hydrostatic equilibrium so that the three-dimensional surfaces of the gas emissivity trace the three-dimensional isopotential surfaces -- we discuss the viability of this assumption for NGC 720. Milgrom's Modification of Newtonian Dynamics (MOND) cannot dispel this manifestation of dark matter. Hence, geometrical considerations require, without mention of pressure or temperature, the presence of an extended, massive dark matter halo in NGC 720. Employing essentially the technique of Buote & Canizares (1992; Buote 1992) we use the shape of the X-ray surface brightness to constrain the shape of the total gravitating matter. The total matter is modeled as either an oblate or prolate spheriod of constant shape and orientation having either a Ferrers (rho approximately r(exp -n)) or Hernquist density. Assuming the X-ray gas is in hydrostatic equilibrium, we construct a model X-ray gas distribution for various temperature profiles. We determine the ellipticity of the total gravitating matter to be epsilon approximately 0.50-0.70. Using the single-temperature model we estimate a total mass approximately (0.41-1.4) x 10(exp 12) h(sub 80) solar mass interior to the ellipsoid of semimajor axis 43.6 h(sub 80) kpc. Ferrers densities as steep as r(exp -3) do not fit the data, but the r(exp -2) and Hernquist models yield excellent fits. We estimate the mass distributions of the stars and the gas and fit the dark matter directly. For a given gas equation of state and functional forms for the visible stars, gas, and dark matter, these models yield a distance-independent and temperature-independent measurement of the ratio of dark mass to stellar mass M(sub DM)/M(sub stars). We estimate a minimum M(sub DM)/M(sub stars) greater than or equal to 4 which corresponds to a total mass slightly greater than that derived from the single-temperature models for distance D = 20h(sub 80) Mpc.

Endoscopic hyperspectral imaging: light guide optimization for spectral light source

NASA Astrophysics Data System (ADS)

Browning, Craig M.; Mayes, Samuel; Rich, Thomas C.; Leavesley, Silas J.

2018-02-01

Hyperspectral imaging (HSI) is a technology used in remote sensing, food processing and documentation recovery. Recently, this approach has been applied in the medical field to spectrally interrogate regions of interest within respective substrates. In spectral imaging, a two (spatial) dimensional image is collected, at many different (spectral) wavelengths, to sample spectral signatures from different regions and/or components within a sample. Here, we report on the use of hyperspectral imaging for endoscopic applications. Colorectal cancer is the 3rd leading cancer for incidences and deaths in the US. One factor of severity is the miss rate of precancerous/flat lesions ( 65% accuracy). Integrating HSI into colonoscopy procedures could minimize misdiagnosis and unnecessary resections. We have previously reported a working prototype light source with 16 high-powered light emitting diodes (LEDs) capable of high speed cycling and imaging. In recent testing, we have found our current prototype is limited by transmission loss ( 99%) through the multi-furcated solid light guide (lightpipe) and the desired framerate (20-30 fps) could not be achieved. Here, we report on a series of experimental and modeling studies to better optimize the lightpipe and the spectral endoscopy system as a whole. The lightpipe was experimentally evaluated using an integrating sphere and spectrometer (Ocean Optics). Modeling the lightpipe was performed using Monte Carlo optical ray tracing in TracePro (Lambda Research Corp.). Results of these optimization studies will aid in manufacturing a revised prototype with the newly designed light guide and increased sensitivity. Once the desired optical output (5-10 mW) is achieved then the HIS endoscope system will be able to be implemented without adding onto the procedure time.

Introduction to Concurrent Engineering: Electronic Circuit Design and Production Applications

DTIC Science & Technology

1992-09-01

STD-1629. Failure mode distribution data for many different types of parts may be found in RAC publication FMD -91. FMEA utilizes inductive logic in a...contrasts with a Fault Tree Analysis ( FTA ) which utilizes deductive logic in a "top down" approach. In FTA , a system failure is assumed and traced down...Analysis ( FTA ) is a graphical method of risk analysis used to identify critical failure modes within a system or equipment. Utilizing a pictorial approach

Techniques for development of safety-related software for surgical robots.

PubMed

Varley, P

1999-12-01

Regulatory bodies require evidence that software controlling potentially hazardous devices is developed to good manufacturing practices. Effective techniques used in other industries assume long timescales and high staffing levels and can be unsuitable for use without adaptation in developing electronic healthcare devices. This paper discusses a set of techniques used in practice to develop software for a particular innovative medical product, an endoscopic camera manipulator. These techniques include identification of potential hazards and tracing their mitigating factors through the project lifecycle.

The detection of carbon dioxide leaks using quasi-tomographic laser absorption spectroscopy measurements in variable wind

DOE PAGES

Levine, Zachary H.; Pintar, Adam L.; Dobler, Jeremy T.; ...

2016-04-13

Laser absorption spectroscopy (LAS) has been used over the last several decades for the measurement of trace gasses in the atmosphere. For over a decade, LAS measurements from multiple sources and tens of retroreflectors have been combined with sparse-sample tomography methods to estimate the 2-D distribution of trace gas concentrations and underlying fluxes from point-like sources. In this work, we consider the ability of such a system to detect and estimate the position and rate of a single point leak which may arise as a failure mode for carbon dioxide storage. The leak is assumed to be at a constant ratemore » giving rise to a plume with a concentration and distribution that depend on the wind velocity. Lastly, we demonstrate the ability of our approach to detect a leak using numerical simulation and also present a preliminary measurement.« less

Refraction effects on the Galileo probe telemetry carrier frequency

NASA Technical Reports Server (NTRS)

Atkinson, D. H.; Spilker, T. R.

1991-01-01

As the Galileo probe relay radio link (RRL) signal propagates outward through the Jovian atmosphere, the atmosphere will manifest itself in two ways. First, the geometric path length of the signal is increased, resulting in a small change of the RRL signal departure angle from the proble (transmitter). Secondly, the velocity of the signal is decreased. For a spherical, static atmosphere with a known profile of refractivity versus altitude the effects of refraction on the RRL frequency can be found using a variation of standard ray-tracing techniques, whereby the ray departure angle is found by an iterative process. From the dispersive characteristics of a mixture of hydrogen and helium with trace amounts of methane and ammonia a simple model of the Jovian atmosphere is constructed assuming spherical symmetry and uniform mixing. The contribution to the RRL Doppler frequency arising from refraction is calculated, and its effect on the Doppler wind measurements is discussed.

Refreshing memory traces: thinking of an item improves retrieval from visual working memory.

PubMed

Souza, Alessandra S; Rerko, Laura; Oberauer, Klaus

2015-03-01

This article provides evidence that refreshing, a hypothetical attention-based process operating in working memory (WM), improves the accessibility of visual representations for recall. "Thinking of", one of several concurrently active representations, is assumed to refresh its trace in WM, protecting the representation from being forgotten. The link between refreshing and WM performance, however, has only been tenuously supported by empirical evidence. Here, we controlled which and how often individual items were refreshed in a color reconstruction task by presenting cues prompting participants to think of specific WM items during the retention interval. We show that the frequency with which an item is refreshed improves recall of this item from visual WM. Our study establishes a role of refreshing in recall from visual WM and provides a new method for studying the impact of refreshing on the amount of information we can keep accessible for ongoing cognition. © 2014 New York Academy of Sciences.

The trace metal composition of marine phytoplankton.

PubMed

Twining, Benjamin S; Baines, Stephen B

2013-01-01

Trace metals are required for numerous processes in phytoplankton and can influence the growth and structure of natural phytoplankton communities. The metal contents of phytoplankton reflect biochemical demands as well as environmental availability and influence the distribution of metals in the ocean. Metal quotas of natural populations can be assessed from analyses of individual cells or bulk particle assemblages or inferred from ratios of dissolved metals and macronutrients in the water column. Here, we review the available data from these approaches for temperate, equatorial, and Antarctic waters in the Pacific and Atlantic Oceans. The data show a generalized metal abundance ranking of Fe≈Zn>Mn≈Ni≈Cu≫Co≈Cd; however, there are notable differences between taxa and regions that inform our understanding of ocean metal biogeochemistry. Differences in the quotas estimated by the various techniques also provide information on metal behavior. Therefore, valuable information is lost when a single metal stoichiometry is assumed for all phytoplankton.

Potentials for transverse trace-free tensors

NASA Astrophysics Data System (ADS)

Conboye, Rory; Murchadha, Niall Ó.

2014-04-01

In constructing and understanding initial conditions in the 3 + 1 formalism for numerical relativity, the transverse and trace-free (TT) part of the extrinsic curvature plays a key role. We know that TT tensors possess two degrees of freedom per space point. However, finding an expression for a TT tensor depending on only two scalar functions is a non-trivial task. Assuming either axial or translational symmetry, expressions depending on two scalar potentials alone are derived here for all TT tensors in flat 3-space. In a more general spatial slice, only one of these potentials is found, the same potential given in (Baker and Puzio 1999 Phys. Rev. D 59 044030) and (Dain 2001 Phys. Rev. D 64 124002), with the remaining equations reduced to a partial differential equation, depending on boundary conditions for a solution. As an exercise, we also derive the potentials which give the Bowen-York curvature tensor in flat space.

Leftward lighting in advertisements increases advertisement ratings and purchase intention.

PubMed

Hutchison, Jennifer; Thomas, Nicole A; Elias, Lorin

2011-07-01

It has been reliably shown that light is assumed to come from above. There is also some suggestion that light from the left might be preferred. Leftward lighting biases have been observed across various mediums such as paintings, portraits, photographs, and advertisements. As advertisements are used to persuade the public to purchase products, it was of interest to better understand whether leftward lighting would influence future intention to purchase. Participants gave preference ratings for pairs of advertisements with opposing lighting directions. Attitude towards the advertisement and the brand as well as future purchase intention was then rated. Overall, participants indicated that they preferred advertisements with leftward lighting and were more likely to purchase these products in the future than when the same products were lit from the right. Findings are consistent with previously observed leftward lighting biases and suggest that advertisements with a leftward lighting bias might be more effective.

Some potential hazardous trace elements contamination and their ecological risk in sediments of western Chaohu Lake, China.

PubMed

Zheng, Liu-Gen; Liu, Gui-Jian; Kang, Yu; Yang, Ren-Kang

2010-07-01

The Chaohu is one of the largest five freshwater lakes in China. It provides freshwater for agriculture, life, and part of industry. The quality of water becomes worst and worst due to the toxic matter. In this study, we collected the samples from the sedimentary mud in the lake. The distribution of some potential hazardous trace elements (Cu, Ni, Cr, As, Pb, Cd, and Hg) in the sediments of western Chaohu Lake, has been determined and studied, and the enrichment factors, the index of geoaccumulation, and potential ecological risk were analyzed and calculated. The results show that: the levels of selected potential hazardous trace element vary from different sampling sites and significant anthropogenic impact of Pb and Cd occur in sediments. The contamination rank of Pb and Cd are moderate, and Pb has a light potential ecological risk, but Cd is heavy. The total potential ecological risk of the selected hazardous trace elements in this study in Chaohu Lake is moderate. Cluster and correlation analysis indicate that the selected potential hazardous trace element pollutant has different source and co-contamination also occur in sediments.

Do Leached Authigenic Fractions Reflect the Neodymium Seawater Composition?

NASA Astrophysics Data System (ADS)

Pimbert, A.; Gourlan, A. T.; Chauvel, C.

2016-12-01

Leaching of marine sediment is often used to recover past Nd seawater composition and reconstruct past ocean circulation. It is assumed to reliably extract REE from the authigenic fraction of sediment [1]. However, while most studies assume that the recovered signal is that of past seawater, very few report complete isotopic and trace element data that clearly demonstrate it is the case. We present new ɛNd values and REE contents measured on leachates of sediments from two Cretaceous marine sections deposited at shallow water depth (Taghazoute in Morocco) and at greater depth in the Atlantic (DSDP Site 367). REE patterns of leachates vary according to lithology: bell-shaped patterns or positive Ce anomalies for organic-poor samples and seawater-like patterns (negative Ce anomaly, low Nd/Yb ratio) for black shales. ɛNd values also vary: between -5.6 and -9.6 at Taghazoute and between -10 and -8.1 at Site 367. Interestingly, ɛNd values correlate with Ce anomalies for Taghazoute black shales. Samples with the largest Ce negative anomalies have the highest ɛNd while samples with no Ce anomalies have much lower ɛNd. This suggests the presence in the leached material of detritus mixed up with the authigenic fraction for sediments deposited in shallow environment. This confirms the findings made by Huck et al. [2] for fish teeth in a similar environment. In such environment, recovering the pristine seawater signal requires (a) the acquisition of both Nd isotopes and trace element contents, and (b) selection of the only Nd isotopic compositions associated to clear seawater trace element characteristics. For sediments deposited in open-ocean setting (Site 367), no detrital contamination affects leached fractions. The REE patterns vary depending on the nature of authigenic fraction but ɛNd remains constant. Here, ɛNd values can be used to discuss oceanic reconstructions. [1] Martin et al. (2010), Chem. Geol, 269, 414-431. [2] Huck et al. (2016), G3, 17, 679-698.

Trace element profiles in modern horse molar enamel as tracers of seasonality: Evidence from micro-XRF, LA-ICP-MS and stable isotope analysis

NASA Astrophysics Data System (ADS)

de Winter, Niels; Goderis, Steven; van Malderen, Stijn; Vanhaecke, Frank; Claeys, Philippe

2016-04-01

A combination of laboratory micro-X-ray Fluorescence (μXRF) and stable carbon and oxygen isotope analysis shows that trace element profiles from modern horse molars reveal a seasonal pattern that co-varies with seasonality in the oxygen isotope records of enamel carbonate from the same teeth. A combination of six cheek teeth (premolars and molars) from the same individual yields a seasonal isotope and trace element record of approximately three years recorded during the growth of the molars. This record shows that reproducible measurements of various trace element ratios (e.g., Sr/Ca, Zn/Ca, Fe/Ca, K/Ca and S/Ca) lag the seasonal pattern in oxygen isotope records by 2-3 months. Laser Ablation-ICP-Mass Spectrometry (LA-ICP-MS) analysis on a cross-section of the first molar of the same individual is compared to the bench-top tube-excitation μXRF results to test the robustness of the measurements and to compare both methods. Furthermore, trace element (e.g. Sr, Zn, Mg & Ba) profiles perpendicular to the growth direction of the same tooth, as well as profiles parallel to the growth direction are measured with LA-ICP-MS and μXRF to study the internal distribution of trace element ratios in two dimensions. Results of this extensive complementary line-scanning procedure shows the robustness of state of the art laboratory micro-XRF scanning for the measurement of trace elements in bioapatite. The comparison highlights the advantages and disadvantages of both methods for trace element analysis and illustrates their complementarity. Results of internal variation within the teeth shed light on the origins of trace elements in mammal teeth and their potential use for paleo-environmental reconstruction.

Heterogeneous photocatalytic oxidation of atmospheric trace contaminants

NASA Technical Reports Server (NTRS)

Ollis, David F.; Peral, Jose

1991-01-01

The following subject areas are covered: (1) design and construction of continuous flow photoreactor for study of oxidation of trace atmospheric contaminants; (2) establishment of kinetics of acetone oxidation including adsorption equilibration, variation of oxidation rate with acetone concentration and water (inhibitor), and variation of rate and apparent quantum yield with light intensity; (3) exploration of kinetics of butanol oxidation, including rate variation with concentration of butanol, and lack of inhibition by water; and (4) exploration of kinetics of catalyst deactivation during oxidation of butanol, including deactivation rate, influence of dark conditions, and establishment of photocatalytic regeneration of activity in alcohol-free air.

Modular Advanced Oxidation Process Enabled by Cathodic Hydrogen Peroxide Production

PubMed Central

2015-01-01

Hydrogen peroxide (H2O2) is frequently used in combination with ultraviolet (UV) light to treat trace organic contaminants in advanced oxidation processes (AOPs). In small-scale applications, such as wellhead and point-of-entry water treatment systems, the need to maintain a stock solution of concentrated H2O2 increases the operational cost and complicates the operation of AOPs. To avoid the need for replenishing a stock solution of H2O2, a gas diffusion electrode was used to generate low concentrations of H2O2 directly in the water prior to its exposure to UV light. Following the AOP, the solution was passed through an anodic chamber to lower the solution pH and remove the residual H2O2. The effectiveness of the technology was evaluated using a suite of trace contaminants that spanned a range of reactivity with UV light and hydroxyl radical (HO•) in three different types of source waters (i.e., simulated groundwater, simulated surface water, and municipal wastewater effluent) as well as a sodium chloride solution. Irrespective of the source water, the system produced enough H2O2 to treat up to 120 L water d–1. The extent of transformation of trace organic contaminants was affected by the current density and the concentrations of HO• scavengers in the source water. The electrical energy per order (EEO) ranged from 1 to 3 kWh m–3, with the UV lamp accounting for most of the energy consumption. The gas diffusion electrode exhibited high efficiency for H2O2 production over extended periods and did not show a diminution in performance in any of the matrices. PMID:26039560

Optical simulations of organic light-emitting diodes through a combination of rigorous electromagnetic solvers and Monte Carlo ray-tracing methods

NASA Astrophysics Data System (ADS)

Bahl, Mayank; Zhou, Gui-Rong; Heller, Evan; Cassarly, William; Jiang, Mingming; Scarmozzino, Rob; Gregory, G. Groot

2014-09-01

Over the last two decades there has been extensive research done to improve the design of Organic Light Emitting Diodes (OLEDs) so as to enhance light extraction efficiency, improve beam shaping, and allow color tuning through techniques such as the use of patterned substrates, photonic crystal (PCs) gratings, back reflectors, surface texture, and phosphor down-conversion. Computational simulation has been an important tool for examining these increasingly complex designs. It has provided insights for improving OLED performance as a result of its ability to explore limitations, predict solutions, and demonstrate theoretical results. Depending upon the focus of the design and scale of the problem, simulations are carried out using rigorous electromagnetic (EM) wave optics based techniques, such as finite-difference time-domain (FDTD) and rigorous coupled wave analysis (RCWA), or through ray optics based technique such as Monte Carlo ray-tracing. The former are typically used for modeling nanostructures on the OLED die, and the latter for modeling encapsulating structures, die placement, back-reflection, and phosphor down-conversion. This paper presents the use of a mixed-level simulation approach which unifies the use of EM wave-level and ray-level tools. This approach uses rigorous EM wave based tools to characterize the nanostructured die and generate both a Bidirectional Scattering Distribution function (BSDF) and a far-field angular intensity distribution. These characteristics are then incorporated into the ray-tracing simulator to obtain the overall performance. Such mixed-level approach allows for comprehensive modeling of the optical characteristic of OLEDs and can potentially lead to more accurate performance than that from individual modeling tools alone.

An animal model of fetal alcohol spectrum disorder: Trace conditioning as a window to inform memory deficits and intervention tactics.

PubMed

Hunt, Pamela S; Barnet, Robert C

2015-09-01

Animal models of Fetal Alcohol Spectrum Disorders (FASD) afford the unique capacity to precisely control timing of alcohol exposure and alcohol exposure amounts in the developing animal. These models have powerfully informed neurophysiological alterations associated with fetal and perinatal alcohol. In two experiments presented here we expand use of the Pavlovian Trace Conditioning procedure to examine cognitive deficits and intervention strategies in a rat model of FASD. Rat pups were exposed to 5g/kg/day ethanol on postnatal days (PD) 4-9, simulating alcohol exposure in the third trimester in humans. During early adolescence, approximately PD 30, the rats were trained in the trace conditioning task in which a light conditioned stimulus (CS) and shock unconditioned stimulus (US) were paired but separated by a 10-s stimulus free trace interval. Learning was assessed in freezing behavior during shock-free tests. Experiment 1 revealed that neonatal ethanol exposure significantly impaired hippocampus-dependent trace conditioning relative to controls. In Experiment 2 a serial compound conditioning procedure known as 'gap filling' completely reversed the ethanol-induced deficit in trace conditioning. We also discuss prior data regarding the beneficial effects of supplemental choline and novel preliminary data regarding the pharmacological cognitive enhancer physostigmine, both of which mitigate the alcohol-induced cognitive deficit otherwise seen in trace conditioning controls. We suggest trace conditioning as a useful tool for characterizing some of the core cognitive deficits seen in FASD, and as a model for developing effective environmental as well as nutritional and pharmacological interventions. Copyright © 2014 Elsevier Inc. All rights reserved.

An Animal Model of Fetal Alcohol Spectrum Disorder: Trace Conditioning as a Window to Inform Memory Deficits and Intervention Tactics

PubMed Central

Hunt, Pamela S.; Barnet, Robert C.

2014-01-01

Animal models of Fetal Alcohol Spectrum Disorders (FASD) afford the unique capacity to precisely control timing of alcohol exposure and alcohol exposure amounts in the developing animal. These models have powerfully informed neurophysiological alterations associated with fetal and perinatal alcohol. In two experiments presented here we expand use of the Pavlovian Trace Conditioning procedure to examine cognitive deficits and intervention strategies in a rat model of FASD. Rat pups were exposed to 5 g/kg/day ethanol on postnatal days (PD) 4–9, simulating alcohol exposure in the third trimester in humans. During early adolescence, approximately PD 30, the rats were trained in the trace conditioning task in which a light conditioned stimulus (CS) and shock unconditioned stimulus (US) were paired but separated by a 10-s stimulus free trace interval. Learning was assessed in freezing behavior during shock-free tests. Experiment 1 revealed that neonatal ethanol exposure significantly impaired hippocampus-dependent trace conditioning relative to controls. In Experiment 2 a serial compound conditioning procedure known as ‘gap filling’ completely reversed the ethanol-induced deficit in trace conditioning. We also discuss prior data regarding the beneficial effects of supplemental choline and novel preliminary data regarding the pharmacological cognitive enhancer physostigmine, both of which mitigate the alcohol-induced cognitive deficit otherwise seen in trace conditioning controls. We suggest trace conditioning as a useful tool for characterizing some of the core cognitive deficits seen in FASD, and as a model for developing effective environmental as well as nutritional and pharmacological interventions. PMID:25477227

Fabrication of thin-film thermoelectric generators with ball lenses for conversion of near-infrared solar light

NASA Astrophysics Data System (ADS)

Ito, Yoshitaka; Mizoshiri, Mizue; Mikami, Masashi; Kondo, Tasuku; Sakurai, Junpei; Hata, Seiichi

2017-06-01

We designed and fabricated thin-film thermoelectric generators (TEGs) with ball lenses, which separated visible light and near-infrared (NIR) solar light using a chromatic aberration. The transmitted visible light was used as daylight and the NIR light was used for thermoelectric generation. Solar light was estimated to be separated into the visible light and NIR light by a ray tracing method. 92.7% of the visible light was used as daylight and 9.9% of the NIR light was used for thermoelectric generation. Then, the temperature difference of the pn junctions of the TEG surface was 0.71 K, determined by heat conduction analysis using a finite element method. The thin-film TEGs were fabricated using lithography and deposition processes. When the solar light (A.M. 1.5) was irradiated to the TEGs, the open-circuit voltage and maximum power were 4.5 V/m2 and 51 µW/m2, respectively. These TEGs are expected to be used as an energy supply for Internet of Things sensors.

Design and stray light analysis of ultra-thin geometrical waveguide

NASA Astrophysics Data System (ADS)

Wang, Qiwei; Cheng, Dewen; Hou, Qichao; Hu, Yuan; Wang, Yongtian

2015-08-01

Nowadays, the waveguide has the advantages of small thickness and light weight so that it attracts more and more attention in the field of near-eye display. However, as a major problem, stray lights generated in the waveguide seriously degrade the display quality. In this paper, a geometrical waveguide with a beam-splitting mirror array (BSMA) is designed by using the non-sequential ray-tracing software LightTools, and great efforts are paid to study the causes and solutions of the stray light. With mass calculation and optimization based on the criterion of stray light/useful light ratio, an optimum design with the least amount of stray lights is found. To further eliminate the stray light, a novel structure that couples the rays into the waveguide is designed. The optimized waveguide has a FOV of 36° in the pupil-expanding direction of the waveguide, with stray light energy reduced to 1% over the useful light, the exit pupil diameter is 11.6mm at an eye relief of 20mm and the thickness is 2.4mm.

A novel calibration method of focused light field camera for 3-D reconstruction of flame temperature

NASA Astrophysics Data System (ADS)

Sun, Jun; Hossain, Md. Moinul; Xu, Chuan-Long; Zhang, Biao; Wang, Shi-Min

2017-05-01

This paper presents a novel geometric calibration method for focused light field camera to trace the rays of flame radiance and to reconstruct the three-dimensional (3-D) temperature distribution of a flame. A calibration model is developed to calculate the corner points and their projections of the focused light field camera. The characteristics of matching main lens and microlens f-numbers are used as an additional constrains for the calibration. Geometric parameters of the focused light field camera are then achieved using Levenberg-Marquardt algorithm. Total focused images in which all the points are in focus, are utilized to validate the proposed calibration method. Calibration results are presented and discussed in details. The maximum mean relative error of the calibration is found less than 0.13%, indicating that the proposed method is capable of calibrating the focused light field camera successfully. The parameters obtained by the calibration are then utilized to trace the rays of flame radiance. A least square QR-factorization algorithm with Plank's radiation law is used to reconstruct the 3-D temperature distribution of a flame. Experiments were carried out on an ethylene air fired combustion test rig to reconstruct the temperature distribution of flames. The flame temperature obtained by the proposed method is then compared with that obtained by using high-precision thermocouple. The difference between the two measurements was found no greater than 6.7%. Experimental results demonstrated that the proposed calibration method and the applied measurement technique perform well in the reconstruction of the flame temperature.

Representations and uses of light distribution functions

NASA Astrophysics Data System (ADS)

Lalonde, Paul Albert

1998-11-01

At their lowest level, all rendering algorithms depend on models of local illumination to define the interplay of light with the surfaces being rendered. These models depend both on the representations of light scattering at a surface due to reflection and to an equal extent on the representation of light sources and light fields. Both emission and reflection have in common that they describe how light leaves a surface as a function of direction. Reflection also depends on an incident light direction. Emission can depend on the position on the light source We call the functions representing emission and reflection light distribution functions (LDF's). There are some difficulties to using measured light distribution functions. The data sets are very large-the size of the data grows with the fourth power of the sampling resolution. For example, a bidirectional reflectance distribution function (BRDF) sampled at five degrees angular resolution, which is arguably insufficient to capture highlights and other high frequency effects in the reflection, can easily require one and a half million samples. Once acquired this data requires some form of interpolation to use them. Any compression method used must be efficient, both in space and in the time required to evaluate the function at a point or over a range of points. This dissertation examines a wavelet representation of light distribution functions that addresses these issues. A data structure is presented that allows efficient reconstruction of LDFs for a given set of parameters, making the wavelet representation feasible for rendering tasks. Texture mapping methods that take advantage of our LDF representations are examined, as well as techniques for filtering LDFs, and methods for using wavelet compressed bidirection reflectance distribution functions (BRDFs) and light sources with Monte Carlo path tracing algorithms. The wavelet representation effectively compresses BRDF and emission data while inducing only a small error in the reconstructed signal. The representation can be used to evaluate efficiently some integrals that appear in shading computation which allows fast, accurate computation of local shading. The representation can be used to represent light fields and is used to reconstruct views of environments interactively from a precomputed set of views. The representation of the BRDF also allows the efficient generation of reflected directions for Monte Carlo array tracing applications. The method can be integrated into many different global illumination algorithms, including ray tracers and wavelet radiosity systems.

Light-modulating pressure sensor with integrated flexible organic light-emitting diode.

PubMed

Cheneler, D; Vervaeke, M; Thienpont, H

2014-05-01

Organic light-emitting diodes (OLEDs) are used almost exclusively for display purposes. Even when implemented as a sensing component, it is rarely in a manner that exploits the possible compliance of the OLED. Here it is shown that OLEDs can be integrated into compliant mechanical micro-devices making a new range of applications possible. A light-modulating pressure sensor is considered, whereby the OLED is integrated with a silicon membrane. It is shown that such devices have potential and advantages over current measurement techniques. An analytical model has been developed that calculates the response of the device. Ray tracing numerical simulations verify the theory and show that the design can be optimized to maximize the resolution of the sensor.

Pollution prevention as a market-enhancing strategy: a storehouse of economical and environmental opportunities.

PubMed Central

Hoffman, J S

1992-01-01

EPA's (Environmental Protection Agency) Green Lights Program for energy-efficient lighting illustrates the economic benefits and the market-transforming value of a pollution prevention philosophy. Using technologies available today, and assuming current prices, this program is expected to reduce air pollution 5%, while saving the nation's businesses up to 20 billion in electric bills every year. However, these pollution prevention and savings estimates may be low. As Green Lights transforms the market for lighting services by creating a higher demand for better technologies at lower costs, the program will likely achieve even larger pollution reductions and electricity savings. PMID:11607262

Influence of thermal light correlations on photosynthetic structures

NASA Astrophysics Data System (ADS)

de Mendoza, Adriana; Manrique, Pedro; Caycedo-Soler, Felipe; Johnson, Neil F.; Rodríguez, Ferney J.; Quiroga, Luis

2014-03-01

The thermal light from the sun is characterized by both classical and quantum mechanical correlations. These correlations have left a fingerprint on the natural harvesting structures developed through five billion years of evolutionary pressure, specially in photosynthetic organisms. In this work, based upon previous extensive studies of spatio-temporal correlations of light fields, we hypothesize that structures involving photosensitive pigments like those present in purple bacteria vesicles emerge as an evolutionary response to the different properties of incident light. By using burstiness and memory as measures that quantify higher moments of the photon arrival statistics, we generate photon-time traces. They are used to simulate absorption on detectors spatially extended over regions comparable to these light fields coherence length. Finally, we provide some insights into the connection between these photo-statistical features with the photosynthetic membrane architecture and the lights' spatial correlation. Facultad de Ciencias Uniandes.

The Direct Lighting Computation in Global Illumination Methods

NASA Astrophysics Data System (ADS)

Wang, Changyaw Allen

1994-01-01

Creating realistic images is a computationally expensive process, but it is very important for applications such as interior design, product design, education, virtual reality, and movie special effects. To generate realistic images, state-of-art rendering techniques are employed to simulate global illumination, which accounts for the interreflection of light among objects. In this document, we formalize the global illumination problem into a eight -dimensional integral and discuss various methods that can accelerate the process of approximating this integral. We focus on the direct lighting computation, which accounts for the light reaching the viewer from the emitting sources after exactly one reflection, Monte Carlo sampling methods, and light source simplification. Results include a new sample generation method, a framework for the prediction of the total number of samples used in a solution, and a generalized Monte Carlo approach for computing the direct lighting from an environment which for the first time makes ray tracing feasible for highly complex environments.

Evolution of Trace Gases and Particles Emitted by a Chaparral Fire in California

DTIC Science & Technology

2012-02-07

length of 78 m and was then focused onto an MCT detector . The cell exchange time was about ten seconds when the flow con- trol valves were open and IR...through a 1064 nm Nd:YAG laser cavity where light scattered by the particles was measured by two avalanche photodiode detectors . Sufficiently light...collected with higher signal-to- noise . Smoke samples collected more than 1.8 km from the source showed signs of aging (O3 for- mation) and were not

Interactions between prefrontal cortex and cerebellum revealed by trace eyelid conditioning.

PubMed

Kalmbach, Brian E; Ohyama, Tatsuya; Kreider, Joy C; Riusech, Frank; Mauk, Michael D

2009-01-01

Eyelid conditioning has proven useful for analysis of learning and computation in the cerebellum. Two variants, delay and trace conditioning, differ only by the relative timing of the training stimuli. Despite the subtlety of this difference, trace eyelid conditioning is prevented by lesions of the cerebellum, hippocampus, or medial prefrontal cortex (mPFC), whereas delay eyelid conditioning is prevented by cerebellar lesions and is largely unaffected by forebrain lesions. Here we test whether these lesion results can be explained by two assertions: (1) Cerebellar learning requires temporal overlap between the mossy fiber inputs activated by the tone conditioned stimulus (CS) and the climbing fiber inputs activated by the reinforcing unconditioned stimulus (US), and therefore (2) trace conditioning requires activity that outlasts the presentation of the CS in a subset of mossy fibers separate from those activated directly by the CS. By use of electrical stimulation of mossy fibers as a CS, we show that cerebellar learning during trace eyelid conditioning requires an input that persists during the stimulus-free trace interval. By use of reversible inactivation experiments, we provide evidence that this input arises from the mPFC and arrives at the cerebellum via a previously unidentified site in the pontine nuclei. In light of previous PFC recordings in various species, we suggest that trace eyelid conditioning involves an interaction between the persistent activity of delay cells in mPFC-a putative mechanism of working memory-and motor learning in the cerebellum.

Evolution of Instrumentation for UV-Visible Spectrophotometry. Part I.

ERIC Educational Resources Information Center

Altemose, Ines R.

1986-01-01

Traces the development of instruments used in spectrophotometry. Discusses how spectrophotometric measurements are made. Describes the color comparator, the filter photometer, and the spectrophotometer. Outlines the evolution of optical systems, including light sources, the monochromator, the photodetector, double-beam optics, and split-beam…

Optical techniques: using coarse and detailed scans for the preventive acquisition of fingerprints with chromatic white-light sensors

NASA Astrophysics Data System (ADS)

Hildebrandt, Mario; Dittmann, Jana; Vielhauer, Claus; Leich, Marcus

2011-11-01

The preventive application of automated latent fingerprint acquisition devices can enhance the Homeland Defence, e.g. by improving the border security. Here, contact-less optical acquisition techniques for the capture of traces are subject to research; chromatic white light sensors allow for multi-mode operation using coarse or detailed scans. The presence of potential fingerprints could be detected using fast coarse scans. Those Regions-of- Interest can be acquired afterwards with high-resolution detailed scans to allow for a verification or identification of individuals. An acquisition and analysis of fingerprint traces on different objects that are imported or pass borders might be a great enhancement for security. Additionally, if suspicious objects require a further investigation, an initial securing of potential fingerprints could be very useful. In this paper we show current research results for the coarse detection of fingerprints to prepare the detailed acquisition from various surface materials that are relevant for preventive applications.

Cooling Timescale of Dust Tori in Dying Active Galactic Nuclei

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

Ichikawa, Kohei; Tazaki, Ryo, E-mail: k.ichikawa@astro.columbia.edu

We estimate the dust torus cooling timescale once the active galactic nucleus (AGN) is quenched. In a clumpy torus system, once the incoming photons are suppressed, the cooling timescale of one clump from T {sub dust} = 1000 K to several 10 K is less than 10 years, indicating that the dust torus cooling time is mainly governed by the light crossing time of the torus from the central engine. After considering the light crossing time of the torus, the AGN torus emission at 12 μ m becomes over two orders of magnitude fainter within 100 years after the quenching.more » We also propose that those “dying” AGNs could be found using the AGN indicators with a different physical scale R such as 12 μ m band luminosity tracing AGN torus ( R ∼ 10 pc) and the optical [O iii] λ 5007 emission line tracing narrow line regions ( R = 10{sup 2–4} pc).« less

BRDF invariant stereo using light transport constancy.

PubMed

Wang, Liang; Yang, Ruigang; Davis, James E

2007-09-01

Nearly all existing methods for stereo reconstruction assume that scene reflectance is Lambertian and make use of brightness constancy as a matching invariant. We introduce a new invariant for stereo reconstruction called light transport constancy (LTC), which allows completely arbitrary scene reflectance (bidirectional reflectance distribution functions (BRDFs)). This invariant can be used to formulate a rank constraint on multiview stereo matching when the scene is observed by several lighting configurations in which only the lighting intensity varies. In addition, we show that this multiview constraint can be used with as few as two cameras and two lighting configurations. Unlike previous methods for BRDF invariant stereo, LTC does not require precisely configured or calibrated light sources or calibration objects in the scene. Importantly, the new constraint can be used to provide BRDF invariance to any existing stereo method whenever appropriate lighting variation is available.

Design of LED projector based on gradient-index lens

NASA Astrophysics Data System (ADS)

Qian, Liyong; Zhu, Xiangbing; Cui, Haitian; Wang, Yuanhang

2018-01-01

In this study, a new type of projector light path is designed to eliminate the deficits of existing projection systems, such as complex structure and low collection efficiency. Using a three-color LED array as the lighting source, by means of the special optical properties of a gradient-index lens, the complex structure of the traditional projector is simplified. Traditional components, such as the color wheel, relay lens, and mirror, become unnecessary. In this way, traditional problems, such as low utilization of light energy and loss of light energy, are solved. With the help of Zemax software, the projection lens is optimized. The optimized projection lens, LED, gradient-index lens, and digital micromirror device are imported into Tracepro. The ray tracing results show that both the utilization of light energy and the uniformity are improved significantly.

Adaptive lighting controllers using smart sensors

NASA Astrophysics Data System (ADS)

Papantoniou, Sotiris; Kolokotsa, Denia; Kalaitzakis, Kostas; Cesarini, Davide Nardi; Cubi, Eduard; Cristalli, Cristina

2016-07-01

The aim of this paper is to present an advanced controller for artificial lights evaluated in several rooms in two European Hospitals located in Chania, Greece and Ancona, Italy. Fuzzy techniques have been used for the architecture of the controller. The energy efficiency of the controllers has been calculated by running the controller coupled with validated models of the RADIANCE back-wards ray tracing software. The input of the controller is the difference between the current illuminance value and the desired one, while the output is the change of the light level that should be applied in the artificial lights. Simulation results indicate significant energy saving potentials. Energy saving potential is calculated from the comparison of the current use of the artificial lights by the users and the proposed one. All simulation work has been conducted using Matlab and RADIANCE environment.

Optimization studies of the ITER low field side reflectometer.

PubMed

Diem, S J; Wilgen, J B; Bigelow, T S; Hanson, G R; Harvey, R W; Smirnov, A P

2010-10-01

Microwave reflectometry will be used on ITER to measure the electron density profile, density fluctuations due to MHD/turbulence, edge localized mode (ELM) density transients, and as an L-H transition monitor. The ITER low field side reflectometer system will measure both core and edge quantities using multiple antenna arrays spanning frequency ranges of 15-155 GHz for the O-mode system and 55-220 GHz for the X-mode system. Optimization studies using the GENRAY ray-tracing code have been done for edge and core measurements. The reflectometer launchers will utilize the HE11 mode launched from circular corrugated waveguide. The launched beams are assumed to be Gaussian with a beam waist diameter of 0.643 times the waveguide diameter. Optimum launcher size and placement are investigated by computing the antenna coupling between launchers, assuming the launched and received beams have a Gaussian beam pattern.

On the multi-scale description of micro-structured fluids composed of aggregating rods

NASA Astrophysics Data System (ADS)

Perez, Marta; Scheuer, Adrien; Abisset-Chavanne, Emmanuelle; Ammar, Amine; Chinesta, Francisco; Keunings, Roland

2018-05-01

When addressing the flow of concentrated suspensions composed of rods, dense clusters are observed. Thus, the adequate modelling and simulation of such a flow requires addressing the kinematics of these dense clusters and their impact on the flow in which they are immersed. In a former work, we addressed a first modelling framework of these clusters, assumed so dense that they were considered rigid and their kinematics (flow-induced rotation) were totally defined by a symmetric tensor c with unit trace representing the cluster conformation. Then, the rigid nature of the clusters was relaxed, assuming them deformable, and a model giving the evolution of both the cluster shape and its microstructural orientation descriptor (the so-called shape and orientation tensors) was proposed. This paper compares the predictions coming from those models with finer-scale discrete simulations inspired from molecular dynamics modelling.

Unmasking the masked Universe: the 2M++ catalogue through Bayesian eyes

NASA Astrophysics Data System (ADS)

Lavaux, Guilhem; Jasche, Jens

2016-01-01

This work describes a full Bayesian analysis of the Nearby Universe as traced by galaxies of the 2M++ survey. The analysis is run in two sequential steps. The first step self-consistently derives the luminosity-dependent galaxy biases, the power spectrum of matter fluctuations and matter density fields within a Gaussian statistic approximation. The second step makes a detailed analysis of the three-dimensional large-scale structures, assuming a fixed bias model and a fixed cosmology. This second step allows for the reconstruction of both the final density field and the initial conditions at z = 1000 assuming a fixed bias model. From these, we derive fields that self-consistently extrapolate the observed large-scale structures. We give two examples of these extrapolation and their utility for the detection of structures: the visibility of the Sloan Great Wall, and the detection and characterization of the Local Void using DIVA, a Lagrangian based technique to classify structures.

Energy, entropy and mass scaling relations for elliptical galaxies. Towards a physical understanding of their photometric properties

NASA Astrophysics Data System (ADS)

Márquez, I.; Lima Neto, G. B.; Capelato, H.; Durret, F.; Lanzoni, B.; Gerbal, D.

2001-12-01

In the present paper, we show that elliptical galaxies (Es) obey a scaling relation between potential energy and mass. Since they are relaxed systems in a post violent-relaxation stage, they are quasi-equilibrium gravitational systems and therefore they also have a quasi-constant specific entropy. Assuming that light traces mass, these two laws imply that in the space defined by the three Sérsic law parameters (intensity Sigma0 , scale a and shape nu ), elliptical galaxies are distributed on two intersecting 2-manifolds: the Entropic Surface and the Energy-Mass Surface. Using a sample of 132 galaxies belonging to three nearby clusters, we have verified that ellipticals indeed follow these laws. This also implies that they are distributed along the intersection line (the Energy-Entropy line), thus they constitute a one-parameter family. These two physical laws (separately or combined), allow to find the theoretical origin of several observed photometrical relations, such as the correlation between absolute magnitude and effective surface brightness, and the fact that ellipticals are located on a surface in the [log Reff, -2.5 log Sigma0, log nu ] space. The fact that elliptical galaxies are a one-parameter family has important implications for cosmology and galaxy formation and evolution models. Moreover, the Energy-Entropy line could be used as a distance indicator.

The role of public law-based litigation in tobacco companies’ strategies in high-income, FCTC ratifying countries, 2004–14

PubMed Central

Steele, Sarah L.; Gilmore, Anna B.; McKee, Martin; Stuckler, David

2016-01-01

Background Tobacco companies use a host of strategies to undermine public health efforts directed to reduce and eliminate smoking. The success, failure and trends in domestic litigation used by tobacco companies to undermine tobacco control are not well understood, with commentators often assuming disputes are trade related or international in nature. We analyse domestic legal disputes involving tobacco companies and public health actors in high-income countries across the last decade to ascertain the types of action and the success or failure of cases, develop effective responses. Methods WorldLii, a publicly available online law repository, was used to identify domestic court cases involving tobacco companies from 2004 to 2014, while outcome data from LexisNexis and Westlaw databases were used to identify appeals and trace case history. Results We identified six domestic cases in the UK, Australia and Canada, noting that the tobacco industry won only one of six cases; a win later usurped by legislative reform and a further court case. Nevertheless, we found cases involve significant resource costs for governments, often progressing across multiple jurisdictional levels. Discussion We suggest that, in light of our results, while litigation takes up significant time and incurs legal costs for health ministries, policymakers must robustly fend off suggestions that litigation wastes taxpayers' money, pointing to the good prospects of winning such legal battles. PMID:26036703

Measuring the CO/H Ratio Using a Symmetric Outflow with an Ionized Component in W51

NASA Astrophysics Data System (ADS)

Melo, Theresa; Ginsburg, Adam

2018-01-01

CO is a trusted tracer of H2 mass due to its abundance in the ISM and easy excitement in cold molecular clouds. Although H2 is the most abundant molecule in the Universe and essential to star formation, it is not directly observable. This project provides estimates for the mass of H2 in W51, which contains the closest pair of high-mass protoclusters in the Galaxy. In the W51 IRS2 area, there is a symmetric outflow, known as the "Lacy Jet", which is molecular on one side and ionized on the other. The outflow's blueshifted component intersects with an HII region, where it has a continuous structure in position-velocity space but becomes externally ionized. We observed the molecular gas with ALMA in the CO 2-1 line and the ionized gas with the VLA in the H77a recombination line. We measured the CO-to-H2 ratio by comparing the observed CO emission to the H77a and assuming that they trace the same material in different states. We present the initial measurements of the CO abundance, or the CO-to-H2 factor, and the CO “X-factor”, or the mass-to-light ratio, at different positions along the jet. We have demonstrated that this jet provides a unique laboratory for measuring the ratios between molecular and ionized species.

A VUV detection system for the direct photonic identification of the first excited isomeric state of 229Th

NASA Astrophysics Data System (ADS)

Seiferle, Benedict; von der Wense, Lars; Laatiaoui, Mustapha; Thirolf, Peter G.

2016-03-01

With an expected energy of 7.6(5) eV, 229Th possesses the lowest excited nuclear state in the landscape of all presently known nuclei. The energy corresponds to a wavelength of about 160 nm and would conceptually allow for an optical laser excitation of a nuclear transition. We report on a VUV optical detection system that was designed for the direct detection of the isomeric ground-state transition of 229Th. 229(m)Th ions originating from a 233U α-recoil source are collected on a micro electrode that is placed in the focus of an annular parabolic mirror. The latter is used to parallelize the UV fluorescence that may emerge from the isomeric ground-state transition of 229Th. The parallelized light is then focused by a second annular parabolic mirror onto a CsI-coated position-sensitive MCP detector behind the mirror exit. To achieve a high signal-to-background ratio, a small spot size on the MCP detector needs to be achieved. Besides extensive ray-tracing simulations of the optical setup, we present a procedure for its alignment, as well as test measurements using a D2 lamp, where a focal-spot size of ≈100 μm has been achieved. Assuming a purely photonic decay, a signal-to-background ratio of ≈7000:1 could be achieved.

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

Wuebbles, D.J.; Kinnison, D.E.; Lean, J.L.

Over the past decade, knowledge of the magnitude and temporal structure of the variations in the sun's ultraviolet irradiance has increased steadily. A number of theoretical modeling studies have shown that changes in the solar ultraviolet flux during the 11-year solar cycle can have a significant effect on stratospheric ozone concentrations. With the exception of Brasseur et al., who examined a very broad range of solar flux variations, all of these studies assumed much larger changes in the ultraviolet flux than measurements now indicate. These studies either calculated the steady-state effect at solar maximum and solar minimum or assumed sinusoidalmore » variations in the solar flux changes with time. It is now possible to narrow the uncertainty range of the expected effects on upper stratospheric ozone and temperature resulting from the 11-year solar cycle. A more accurate representation of the solar flux changes with time is used in this analysis, as compared to previous published studies. This study also evaluates the relative roles of solar flux variations and increasing concentrations of long-lived trace gases in determining the observed trends in upper stratospheric ozone and temperature. The LLNL two-dimensional chemical-radiative-transport model of the global atmosphere is used to evaluate the combined effects on the stratosphere from changes in solar ultraviolet irradiances and trace gas concentrations over the last several decades. Derived trends in upper stratospheric ozone concentrations and temperature are then compared with available analyses of ground-based and satellite measurements over this time period.« less

Determining Concentration of Nanoparticles from Ellipsometry

NASA Technical Reports Server (NTRS)

Venkatasubbarao, Srivatsa; Kempen, Lothar U.; Chipman, Russell

2008-01-01

A method of using ellipsometry or polarization analysis of light in total internal reflection of a surface to determine the number density of gold nanoparticles on a smooth substrate has been developed. The method can be modified to enable determination of densities of sparse distributions of nanoparticles in general, and is expected to be especially useful for measuring gold-nanoparticle-labeled biomolecules on microarrays. The method is based on theoretical calculations of the ellipsometric responses of gold nanoparticles. Elements of the calculations include the following: For simplicity, the gold nanoparticles are assumed to be spherical and to have the same radius. The distribution of gold nanoparticles is assumed to be a sub-monolayer (that is, sparser than a monolayer). The optical response of the sub-monolayer is modeled by use of a thin-island-film theory, according to which the polarizabilities parallel and perpendicular to the substrate are functions of the wavelength of light, the dielectric functions (permittivities expressed as complex functions of frequency or wavelength) of the gold and the suspending medium (in this case, the suspending medium is air), the fraction of the substrate area covered by the nanoparticles, and the radius of the nanoparticles. For the purpose of the thin-island-film theory, the dielectric function of the gold nanoparticles is modeled as the known dielectric function of bulk gold plus a correction term that is necessitated by the fact that the mean free path length for electrons in gold decreases with decreasing radius, in such a manner as to cause the imaginary part of the dielectric function to increase with decreasing radius (see figure). The correction term is a function of the nanoparticle radius, the wavelength of light, the mean free path and the Fermi speed of electrons in bulk gold, the plasma frequency of gold, and the speed of light in a vacuum. These models are used to calculate ellipsometric responses for various concentrations of gold nanoparticles having an assumed radius. The modeled data indicates distinct spectral features for both the real and the imaginary part of the dielectric function. An ellipsometric measurement would determine this distinct feature and thus can be used to measure nanoparticle concentration. By "ellipsometric responses" is meant the intensities of light measured in various polarization states as functions of the angle of incidence and the polarization states of the incident light. These calculated ellipsometric responses are used as calibration curves: Data from subsequent ellipsometric measurements on real specimens are compared with the calibration curves. The concentration of the nanoparticles on a specimen is assumed to be that of the calibration curve that most closely matches the data pertaining to that specimen.

Computing the total atmospheric refraction for real-time optical imaging sensor simulation

NASA Astrophysics Data System (ADS)

Olson, Richard F.

2015-05-01

Fast and accurate computation of light path deviation due to atmospheric refraction is an important requirement for real-time simulation of optical imaging sensor systems. A large body of existing literature covers various methods for application of Snell's Law to the light path ray tracing problem. This paper provides a discussion of the adaptation to real time simulation of atmospheric refraction ray tracing techniques used in mid-1980's LOWTRAN releases. The refraction ray trace algorithm published in a LOWTRAN-6 technical report by Kneizys (et. al.) has been coded in MATLAB for development, and in C-language for simulation use. To this published algorithm we have added tuning parameters for variable path segment lengths, and extensions for Earth grazing and exoatmospheric "near Earth" ray paths. Model atmosphere properties used to exercise the refraction algorithm were obtained from tables published in another LOWTRAN-6 related report. The LOWTRAN-6 based refraction model is applicable to atmospheric propagation at wavelengths in the IR and visible bands of the electromagnetic spectrum. It has been used during the past two years by engineers at the U.S. Army Aviation and Missile Research, Development and Engineering Center (AMRDEC) in support of several advanced imaging sensor simulations. Recently, a faster (but sufficiently accurate) method using Gauss-Chebyshev Quadrature integration for evaluating the refraction integral was adopted.

Optical coefficient measurements using bulk living tissue by an optical fiber puncture with FOV change

NASA Astrophysics Data System (ADS)

Nakazawa, Haruna; Doi, Marika; Ogawa, Emiyu; Arai, Tsunenori

2018-02-01

To avoid an instability of the optical coefficient measurement using sliced tissue preparation, we proposed the combination of light intensity measurement through an optical fiber puncturing into a bulk tissue varying field of view (FOV) and ray tracing calculation using Monte-Carlo method. The optical coefficients of myocardium such as absorption coefficient μa, scattering coefficient μs, and anisotropic parameter g are used in the myocardium optical propagation. Since optical coefficients obtained using thin sliced tissue could be instable because they are affected by dehydration and intracellular fluid effusion on the sample surface, variety of coefficients have been reported over individual optical differences of living samples. The proposed method which combined the experiment using the bulk tissue with ray tracing calculation were performed. In this method, a 200 μmΦ high-NA silica fiber installed in a 21G needle was punctured up to the bottom of the myocardial bulk tissue over 3 cm in thickness to measure light intensity changing the fiber-tip depth and FOV. We found that the measured attenuation coefficients decreased as the FOV increased. The ray trace calculation represented the same FOV dependence in above mentioned experimental result. We think our particular fiber punctured measurement using bulk tissue varying FOV with Inverse Monte-Carlo method might be useful to obtain the optical coefficients to avoid sample preparation instabilities.

A simple computational algorithm of model-based choice preference.

PubMed

Toyama, Asako; Katahira, Kentaro; Ohira, Hideki

2017-08-01

A broadly used computational framework posits that two learning systems operate in parallel during the learning of choice preferences-namely, the model-free and model-based reinforcement-learning systems. In this study, we examined another possibility, through which model-free learning is the basic system and model-based information is its modulator. Accordingly, we proposed several modified versions of a temporal-difference learning model to explain the choice-learning process. Using the two-stage decision task developed by Daw, Gershman, Seymour, Dayan, and Dolan (2011), we compared their original computational model, which assumes a parallel learning process, and our proposed models, which assume a sequential learning process. Choice data from 23 participants showed a better fit with the proposed models. More specifically, the proposed eligibility adjustment model, which assumes that the environmental model can weight the degree of the eligibility trace, can explain choices better under both model-free and model-based controls and has a simpler computational algorithm than the original model. In addition, the forgetting learning model and its variation, which assume changes in the values of unchosen actions, substantially improved the fits to the data. Overall, we show that a hybrid computational model best fits the data. The parameters used in this model succeed in capturing individual tendencies with respect to both model use in learning and exploration behavior. This computational model provides novel insights into learning with interacting model-free and model-based components.

Holography.

ERIC Educational Resources Information Center

Klein, H. Arthur

Holography is a process which numbers among its many applications the creation of holograms--unique three dimensional photographs that show spatial relations and shifts just as they exist in reality. This book recounts the history of holography, tracing its development from Euclid's theory of light rays through Huygens' theory of wave motion to…

PHOTOCHEMICAL EFFECTS ON NOX AND CO EMISSIONS IN A BRAZILIAN SAVANNA

EPA Science Inventory

Land clearing and burning in the tropics often results in increased solar irradiation of soil and surface organic matter. This increased light exposure may impact the emissions of nitrogen oxides (NOx) and carbon monoxide (CO), trace gases that play an important role in troposph...

Photocatalytic Coats in Glass Drinking-Water Bottles

NASA Technical Reports Server (NTRS)

Andren, Anders W.; Armstrong, David E.; Anderson, Marc A.

2005-01-01

According to a proposal, the insides of glass bottles used to store drinking water would be coated with films consisting of or containing TiO2. In the presence of ultraviolet light, these films would help to remove bacteria, viruses, and trace organic contaminants from the water.

Design and development of an injection-molded demultiplexer for optical communication systems in the visible range.

PubMed

Höll, S; Haupt, M; Fischer, U H P

2013-06-20

Optical simulation software based on the ray-tracing method offers easy and fast results in imaging optics. This method can also be applied in other fields of light propagation. For short distance communications, polymer optical fibers (POFs) are gradually gaining importance. This kind of fiber offers a larger core diameter, e.g., the step index POF features a core diameter of 980 μm. Consequently, POFs have a large number of modes (>3 million modes) in the visible range, and ray tracing could be used to simulate the propagation of light. This simulation method is applicable not only for the fiber itself but also for the key components of a complete POF network, e.g., couplers or other key elements of the transmission line. In this paper a demultiplexer designed and developed by means of ray tracing is presented. Compared to the classical optical design, requirements for optimal design differ particularly with regard to minimizing the insertion loss (IL). The basis of the presented key element is a WDM device using a Rowland spectrometer setup. In this approach the input fiber carries multiple wavelengths, which will be divided into multiple output fibers that transmit only one wavelength. To adapt the basic setup to POF, the guidance of light in this element has to be changed fundamentally. Here, a monolithic approach is presented with a blazed grating using an aspheric mirror to minimize most of the aberrations. In the simulations the POF is represented by an area light source, while the grating is analyzed for different orders and the highest possible efficiency. In general, the element should be designed in a way that it can be produced with a mass production technology like injection molding in order to offer a reasonable price. However, designing the elements with regard to injection molding leads to some inherent challenges. The microstructure of an optical grating and the thick-walled 3D molded parts both result in high demands on the injection molding process. This also requires complex machining of the molding tool. Therefore, different experiments are done to optimize the process parameter, find the best molding material, and find a suitable machining method for the molding tool. The paper will describe the development of the demultiplexer by means of ray-tracing simulations step by step. Also, the process steps and the realized solutions for the injection molding are described.

The influence of water vapor on atmospheric exchange measurements with an ICOS* based Laser absorption analyzer

NASA Astrophysics Data System (ADS)

Bunk, Rüdiger; Quan, Zhi; Wandel, Matthias; Yi, Zhigang; Bozem, Heiko; Kesselmeier, Jürgen

2014-05-01

Carbonyl sulfide and carbon monoxide are both atmospheric trace gases of high interest. Recent advances in the field of spectroscopy have enabled instruments that measure the concentration of the above and other trace gases very fast and with good precision. Increasing the effective path length by reflecting the light between two mirrors in a cavity, these instruments reach impressive sensitivities. Often it is possible to measure the concentration of more than one trace gas at the same time. The OCS/CO2 Analyzer by LGR (Los Gatos Research, Inc.) measures the concentration of water vapor [H2O], carbonyl sulfide [COS], carbon dioxide [CO2] and carbon monoxide [CO] simultaneously. For that the cavity is saturated with light, than the attenuation of light is measured as in standard absorption spectroscopy. The instrument proved to be very fast with good precision and to be able to detect even very low concentrations, especially for COS (as low as 30ppt in the case of COS). However, we observed a rather strong cross sensitivity to water vapor. Altering the water vapor content of the sampled air with two different methods led to a change in the perceived concentration of COS, CO and CO2. This proved especially problematic for enclosure (cuvette) measurements, where the concentrations of one of the above species in an empty cuvette are compared to the concentration of another cuvette containing a plant whose exchange of trace gases with the atmosphere is of interest. There, the plants transpiration leads to a large difference in water vapor content between the cuvettes and that in turn produces artifacts in the concentration differences between the cuvettes for the other above mentioned trace gases. For CO, simultaneous measurement with a UV-Emission Analyzer (AL 5002, Aerolaser) and the COS/CO Analyzer showed good agreement of perceived concentrations as long as the sample gas was dry and an increasing difference in perceived concentration when the sample gas was humidified. The difference in perceived CO concentration showed a clear correlation to the water vapor content in the sample air. For COS we could show that changes in water vapor also impacted on the perceived COS concentrations; the raise of the water vapor concentration would lead to an increasing underestimation of the COS concentration. Drying the air using a Nafion Dryer before entering the COS/CO Analyzer eliminated any water vapor induced artifacts and showed no adverse effects on the quality of the conducted measurements. *Integrated cavity output spectroscopy

High convergence efficiency design of flat Fresnel lens with large aperture

NASA Astrophysics Data System (ADS)

Ke, Jieyao; Zhao, Changming; Guan, Zhe

2018-01-01

This paper designed a circle-shaped Fresnel lens with large aperture as part of the solar pumped laser design project. The Fresnel lens designed in this paper simulate in size 1000mm×1000mm, focus length 1200mm and polymethyl methacrylate (PMMA) material in order to conduct high convergence efficiency. In the light of design requirement of concentric ring with same width of 0.3mm, this paper proposed an optimized Fresnel lens design based on previous sphere design and conduct light tracing simulation in Matlab. This paper also analyzed the effect of light spot size, light intensity distribution, optical efficiency under four conditions, monochromatic parallel light, parallel spectrum light, divergent monochromatic light and sunlight. Design by 550nm wavelength and under the condition of Fresnel reflection, the results indicated that the designed lens could convergent sunlight in diffraction limit of 11.8mm with a 78.7% optical efficiency, better than the sphere cutting design results of 30.4%.

Strontium and Trace Metals in the Mississippi River Mixing Zone

NASA Astrophysics Data System (ADS)

Xu, Y.; Marcantonio, F.

2001-12-01

Strontium is generally believed to be a conservative element, i.e., it is assumed that dissolved Sr moves directly from rivers through estuaries to the ocean. More recently, however, detailed sampling of rivers suggests a weak non-conservative behavior for Sr. Here, we present dissolved and suspended load Sr and trace metal data for samples retrieved along salinity transects in the estuarine mixing zone of the Mississippi River. Our cruises took place during times representing high, falling, and low Mississippi River discharge. Sr concentration and isotopic composition were analyzed for both dissolved particulate loads. Selected particle-reactive or redox-sensitive trace metals (Mn, Fe, U, V, Mo, Ti, and Pb) were analyzed simultaneously. In the dissolved load, Sr showed conservative behavior in both high- and low- discharge periods. Non-conservative behavior of Sr predominated during falling discharge in the summer. Significant positive correlations were found between Sr, Mo and Ti. U and V distributions were found to be essentially controlled by mixing of river water and seawater, but with significantly lower riverine concentrations during high-flow stage. Particulate element concentrations can be quite variable and heterogeneous. In this study, strong correlations were found between particulate Mn (and Fe) concentrations and particulate concentrations of Ti, U, V, and Pb. No such correlations with Mn (or Fe) were found for particulate Sr and Mo. There is a vast hypoxic zone along the coast of Louisiana in the Gulf of Mexico that exists during the summer months. Based on the Sr isotope systematics and the relationships between Sr and trace metals, we believe that this eutrophication may contribute to the non-conservative behaviors of Sr and other trace metals. We discuss the potential implications of this hypothesis on the Sr mass balance of present-day and past seawater.

Effects of cleaning methods upon preservation of stable isotopes and trace elements in shells of Cyprideis torosa (Crustacea, Ostracoda): Implications for palaeoenvironmental reconstruction

NASA Astrophysics Data System (ADS)

Roberts, L. R.; Holmes, J. A.; Leng, M. J.; Sloane, H. J.; Horne, D. J.

2018-06-01

The trace element (Sr/Ca and Mg/Ca) and stable isotope (δ18O and δ13C) geochemistry of fossil ostracod valves provide valuable information, particularly in lacustrine settings, on palaeo-water composition and palaeotemperature. The removal of sedimentary and organic contamination prior to geochemical analysis is essential to avoid bias of the results. Previous stable isotope and trace element work on ostracod shells has, however, employed different treatments for the removal of contamination beyond simple 'manual' cleaning using a paint brush and methanol under a low-power binocular microscope. For isotopic work pre-treatments include chemical oxidation, vacuum roasting and plasma ashing, and for trace element work sonication, chemical oxidation and reductive cleaning. The impact of different treatments on the geochemical composition of the valve calcite has not been evaluated in full, and a universal protocol has not been established. Here, a systematic investigation of the cleaning methods is undertaken using specimens of the ubiquitous euryhaline species, Cyprideis torosa. Cleaning methods are evaluated by undertaking paired analyses on a single carapace (comprising two valves); in modern ostracods, whose valves are assumed to be unaltered, the two valves should have identical geochemical and isotopic composition. Hence, when one valve is subjected to the chosen treatment and the other to simple manual cleaning any difference in composition can confidently be assigned to the treatment method. We show that certain cleaning methods have the potential to cause alteration to the geochemical signal, particularly Mg/Ca and δ18O, and hence have implications for palaeoenvironmental reconstructions. For trace-element determinations we recommend cleaning by sonication and for stable isotope analysis, oxidation by hydrogen peroxide. These methods remove contamination, yet do not significantly alter the geochemical signal.

Real-world emission factors for antimony and other brake wear related trace elements: size-segregated values for light and heavy duty vehicles.

PubMed

Bukowiecki, Nicolas; Lienemann, Peter; Hill, Matthias; Figi, Renato; Richard, Agnes; Furger, Markus; Rickers, Karen; Falkenberg, Gerald; Zhao, Yongjing; Cliff, Steven S; Prevot, Andre S H; Baltensperger, Urs; Buchmann, Brigitte; Gehrig, Robert

2009-11-01

Hourly trace element measurements were performed in an urban street canyon and next to an interurban freeway in Switzerland during more than one month each, deploying a rotating drum impactor (RDI) and subsequent sample analysis by synchrotron radiation X-ray fluorescence spectrometry (SR-XRF). Antimony and other brake wear associated elements were detected in three particle size ranges (2.5-10, 1-2.5, and 0.1-1 microm). The hourly measurements revealed that the effect of resuspended road dust has to be taken into account for the calculation of vehicle emission factors. Individual values for light and heavy duty vehicles were obtained for stop-and-go traffic in the urban street canyon. Mass based brake wear emissions were predominantly found in the coarse particle fraction. For antimony, determined emission factors were 11 +/- 7 and 86 +/- 42 microg km(-1) vehicle(-1) for light and heavy duty vehicles, respectively. Antimony emissions along the interurban freeway with free-flowing traffic were significantly lower. Relative patterns for brake wear related elements were very similar for both considered locations. Beside vehicle type specific brake wear emissions, road dust resuspension was found to be a dominant contributor of antimony in the street canyon.

Analyzing luminescent solar concentrators with front-facing photovoltaic cells using weighted Monte Carlo ray tracing

NASA Astrophysics Data System (ADS)

Woei Leow, Shin; Corrado, Carley; Osborn, Melissa; Isaacson, Michael; Alers, Glenn; Carter, Sue A.

2013-06-01

Luminescent solar concentrators (LSC) collect ambient light from a broad range of angles and concentrate the captured light onto photovoltaic (PV) cells. LSCs with front-facing cells collect direct and indirect sunlight ensuring a gain factor greater than one. The flexible placement and percentage coverage of PV cells on the LSC panel allow for layout adjustments to be made in order to balance re-absorption losses and the level of light concentration desired. A weighted Monte Carlo ray tracing program was developed to study the transport of photons and loss mechanisms in the LSC to aid in design optimization. The program imports measured absorption/emission spectra of an organic luminescent dye (LR305), the transmission coefficient, and refractive index of acrylic as parameters that describe the system. Simulations suggest that for LR305, 8-10 cm of luminescent material surrounding the PV cell yields the highest increase in power gain per unit area of LSC added, thereby determining the ideal spacing between PV cells in the panel. For rectangular PV cells, results indicate that for each centimeter of PV cell width, an additional increase of 0.15 mm to the waveguide thickness is required to efficiently transport photon collected by the LSC to the PV cell with minimal loss.

Development of multifunctional nanoparticles towards applications in non-invasive magnetic resonance imaging and axonal tracing.

PubMed

Du, Yan; Qin, Yubo; Li, Zizhen; Yang, Xiuying; Zhang, Jingchang; Westwick, Harrison; Tsai, Eve; Cao, Xudong

2017-12-01

A multifunctional nanobiomaterial has been developed by deliberately combining functions of superparamagnetism, fluorescence, and axonal tracing into one material. Superparamagnetic iron oxide nanoparticles were first synthesized and coated with a silica layer to prevent emission quenching through core-dye interactions; a fluorescent molecule, fluorescein isothiocyanate, was doped inside second layer of silica shell to improve photo-stability and to enable further thiol functionalization. Subsequently, biotinylated dextran amine, a sensitive axonal tracing reagent, was immobilized on the thiol-functionalized nanoparticle surfaces. The resulting nanoparticles were characterized by transmission electron microscopy, dynamic light scattering, X-ray diffraction, X-ray photoelectron spectroscopy, UV-Vis spectroscopy, magnetic resonance imaging and fluorescence confocal microscopy. In vitro cell experiments using both undifferentiated and differentiated Neuro-2a cells showed that the cells were able to take up the nanoparticles intracellularly and that the nanoparticles showed good biocompatibilities. In summary, this new material demonstrated promising performances for both optical and magnetic resonance imaging modalities, suggesting its promising potentials in applications such as in non-invasive imaging, particularly in neuronal tracing.

Assessment of the TRACE Reactor Analysis Code Against Selected PANDA Transient Data

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

Zavisca, M.; Ghaderi, M.; Khatib-Rahbar, M.

2006-07-01

The TRACE (TRAC/RELAP Advanced Computational Engine) code is an advanced, best-estimate thermal-hydraulic program intended to simulate the transient behavior of light-water reactor systems, using a two-fluid (steam and water, with non-condensable gas), seven-equation representation of the conservation equations and flow-regime dependent constitutive relations in a component-based model with one-, two-, or three-dimensional elements, as well as solid heat structures and logical elements for the control system. The U.S. Nuclear Regulatory Commission is currently supporting the development of the TRACE code and its assessment against a variety of experimental data pertinent to existing and evolutionary reactor designs. This paper presents themore » results of TRACE post-test prediction of P-series of experiments (i.e., tests comprising the ISP-42 blind and open phases) conducted at the PANDA large-scale test facility in 1990's. These results show reasonable agreement with the reported test results, indicating good performance of the code and relevant underlying thermal-hydraulic and heat transfer models. (authors)« less

Metamaterial devices for molding the flow of diffuse light (Conference Presentation)

NASA Astrophysics Data System (ADS)

Wegener, Martin

2016-09-01

Much of optics in the ballistic regime is about designing devices to mold the flow of light. This task is accomplished via specific spatial distributions of the refractive index or the refractive-index tensor. For light propagating in turbid media, a corresponding design approach has not been applied previously. Here, we review our corresponding recent work in which we design spatial distributions of the light diffusivity or the light-diffusivity tensor to accomplish specific tasks. As an application, we realize cloaking of metal contacts on large-area OLEDs, eliminating the contacts' shadows, thereby homogenizing the diffuse light emission. In more detail, metal contacts on large-area organic light-emitting diodes (OLEDs) are mandatory electrically, but they cast optical shadows, leading to unwanted spatially inhomogeneous diffuse light emission. We show that the contacts can be made invisible either by (i) laminate metamaterials designed by coordinate transformations of the diffusion equation or by (ii) triangular-shaped regions with piecewise constant diffusivity, hence constant concentration of scattering centers. These structures are post-optimized in regard to light throughput by Monte-Carlo ray-tracing simulations and successfully validated by model experiments.

Partially coherent isodiffracting pulsed beams

NASA Astrophysics Data System (ADS)

Koivurova, Matias; Ding, Chaoliang; Turunen, Jari; Pan, Liuzhan

2018-02-01

We investigate a class of isodiffracting pulsed beams, which are superpositions of transverse modes supported by spherical-mirror laser resonators. By employing modal weights that, for stationary light, produce a Gaussian Schell-model beam, we extend this standard model to pulsed beams. We first construct the two-frequency cross-spectral density function that characterizes the spatial coherence in the space-frequency domain. By assuming a power-exponential spectral profile, we then employ the generalized Wiener-Khintchine theorem for nonstationary light to derive the two-time mutual coherence function that describes the space-time coherence of the ensuing beams. The isodiffracting nature of the laser resonator modes permits all (paraxial-domain) calculations at any propagation distance to be performed analytically. Significant spatiotemporal coupling is revealed in subcycle, single-cycle, and few-cycle domains, where the partial spatial coherence also leads to reduced temporal coherence even though full spectral coherence is assumed.

Trace metal fluxes to ferromanganese nodules from the western Baltic Sea as a record for long-term environmental changes

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

Hlawatsch, S.; Garbe-Schonberg, C.D.; Lechtenberg, F.

Trace element profiles in ferromanganese nodules from the western Baltic Sea were analyzed with laser ablation inductively coupled plasma mass spectroscopy (LA-ICP-MS) and synchrotron-based micro-X-ray radiation techniques (fluorescence: mSXRF, and diffraction: mXRD) at high spatial resolution in growth direction. Of the trace elements studied (Zn, Cu, Cd, Ni, Co, Mo, Ba), Zn showed the most significant enrichment, with values in the outermost surface layers of up to six-fold higher than those found in older core parts. The high-resolution Zn profiles provide the necessary temporal resolution for a dating method analogous to dendrochronology. Profiles in various samples collected during two decadesmore » were matched and the overlapping sections used for estimation of the accretion rates. Assuming a continuous accretion of these relatively fast growing nodules (on average 20 mm a-1) over the last century, the Zn enrichment was thus assessed to have commenced around 1860/70 in nodules from the Kiel Bight and in 1880/90 from Mecklenburg Bight, reflecting the enhanced heavy metal emissions with rising industrialization in Europe. Apart from the obvious success with Zn, only As and Co show significant but only 1.5-fold enrichments in the most recent growth layers of the nodules. Other anthropogenic trace metals like Cu and Cd are not at all enriched, which, together with the distinct early-diagenetic Fe/Mn banding, weakens the potential of the nodules for retrospective monitoring.« less

Dry deposition fluxes and deposition velocities of trace metals in the Tokyo metropolitan area measured with a water surface sampler.

PubMed

Sakata, Masahiro; Marumoto, Kohji

2004-04-01

Dry deposition fluxes and deposition velocities (=deposition flux/atmospheric concentration) for trace metals including Hg, Cd, Cu, Mn, Pb, and Zn in the Tokyo metropolitan area were measured using an improved water surface sampler. Mercury is deposited on the water surface in both gaseous (reactive gaseous mercury, RGM) and particulate (particulate mercury, Hg(p)) forms. The results based on 1 yr observations found that dry deposition plays a significant if not dominant role in trace metal deposition in this urban area, contributing fluxes ranging from 0.46 (Cd) to 3.0 (Zn) times those of concurrent wet deposition fluxes. The deposition velocities were found to be dependent on the deposition of coarse particles larger than approximately 5 microm in diameter on the basis of model calculations. Our analysis suggests that the 84.13% diameter is a more appropriate index for each deposited metal than the 50% diameter in the assumed undersize log-normal distribution, because larger particles are responsible for the flux. The deposition velocities for trace metals other than mercury increased exponentially with an increase in their 84.13% diameters. Using this regression equation, the deposition velocities for Hg(p) were estimated from its 84.13% diameter. The deposition fluxes for Hg(p) calculated from the estimated velocities tended to be close to the mercury fluxes measured with the water surface sampler during the study periods except during summer.

Automated Urban Travel Interpretation: A Bottom-up Approach for Trajectory Segmentation.

PubMed

Das, Rahul Deb; Winter, Stephan

2016-11-23

Understanding travel behavior is critical for an effective urban planning as well as for enabling various context-aware service provisions to support mobility as a service (MaaS). Both applications rely on the sensor traces generated by travellers' smartphones. These traces can be used to interpret travel modes, both for generating automated travel diaries as well as for real-time travel mode detection. Current approaches segment a trajectory by certain criteria, e.g., drop in speed. However, these criteria are heuristic, and, thus, existing approaches are subjective and involve significant vagueness and uncertainty in activity transitions in space and time. Also, segmentation approaches are not suited for real time interpretation of open-ended segments, and cannot cope with the frequent gaps in the location traces. In order to address all these challenges a novel, state based bottom-up approach is proposed. This approach assumes a fixed atomic segment of a homogeneous state, instead of an event-based segment, and a progressive iteration until a new state is found. The research investigates how an atomic state-based approach can be developed in such a way that can work in real time, near-real time and offline mode and in different environmental conditions with their varying quality of sensor traces. The results show the proposed bottom-up model outperforms the existing event-based segmentation models in terms of adaptivity, flexibility, accuracy and richness in information delivery pertinent to automated travel behavior interpretation.

Automated Urban Travel Interpretation: A Bottom-up Approach for Trajectory Segmentation

PubMed Central

Das, Rahul Deb; Winter, Stephan

2016-01-01

Understanding travel behavior is critical for an effective urban planning as well as for enabling various context-aware service provisions to support mobility as a service (MaaS). Both applications rely on the sensor traces generated by travellers’ smartphones. These traces can be used to interpret travel modes, both for generating automated travel diaries as well as for real-time travel mode detection. Current approaches segment a trajectory by certain criteria, e.g., drop in speed. However, these criteria are heuristic, and, thus, existing approaches are subjective and involve significant vagueness and uncertainty in activity transitions in space and time. Also, segmentation approaches are not suited for real time interpretation of open-ended segments, and cannot cope with the frequent gaps in the location traces. In order to address all these challenges a novel, state based bottom-up approach is proposed. This approach assumes a fixed atomic segment of a homogeneous state, instead of an event-based segment, and a progressive iteration until a new state is found. The research investigates how an atomic state-based approach can be developed in such a way that can work in real time, near-real time and offline mode and in different environmental conditions with their varying quality of sensor traces. The results show the proposed bottom-up model outperforms the existing event-based segmentation models in terms of adaptivity, flexibility, accuracy and richness in information delivery pertinent to automated travel behavior interpretation. PMID:27886053

Illumination-compensated non-contact imaging photoplethysmography via dual-mode temporally coded illumination

NASA Astrophysics Data System (ADS)

Amelard, Robert; Scharfenberger, Christian; Wong, Alexander; Clausi, David A.

2015-03-01

Non-contact camera-based imaging photoplethysmography (iPPG) is useful for measuring heart rate in conditions where contact devices are problematic due to issues such as mobility, comfort, and sanitation. Existing iPPG methods analyse the light-tissue interaction of either active or passive (ambient) illumination. Many active iPPG methods assume the incident ambient light is negligible to the active illumination, resulting in high power requirements, while many passive iPPG methods assume near-constant ambient conditions. These assumptions can only be achieved in environments with controlled illumination and thus constrain the use of such devices. To increase the number of possible applications of iPPG devices, we propose a dual-mode active iPPG system that is robust to changes in ambient illumination variations. Our system uses a temporally-coded illumination sequence that is synchronized with the camera to measure both active and ambient illumination interaction for determining heart rate. By subtracting the ambient contribution, the remaining illumination data can be attributed to the controlled illuminant. Our device comprises a camera and an LED illuminant controlled by a microcontroller. The microcontroller drives the temporal code via synchronizing the frame captures and illumination time at the hardware level. By simulating changes in ambient light conditions, experimental results show our device is able to assess heart rate accurately in challenging lighting conditions. By varying the temporal code, we demonstrate the trade-off between camera frame rate and ambient light compensation for optimal blood pulse detection.

Optimizing detector geometry for trace element mapping by X-ray fluorescence.

PubMed

Sun, Yue; Gleber, Sophie-Charlotte; Jacobsen, Chris; Kirz, Janos; Vogt, Stefan

2015-05-01

Trace metals play critical roles in a variety of systems, ranging from cells to photovoltaics. X-Ray Fluorescence (XRF) microscopy using X-ray excitation provides one of the highest sensitivities available for imaging the distribution of trace metals at sub-100 nm resolution. With the growing availability and increasing performance of synchrotron light source based instruments and X-ray nanofocusing optics, and with improvements in energy-dispersive XRF detectors, what are the factors that limit trace element detectability? To address this question, we describe an analytical model for the total signal incident on XRF detectors with various geometries, including the spectral response of energy dispersive detectors. This model agrees well with experimentally recorded X-ray fluorescence spectra, and involves much shorter calculation times than with Monte Carlo simulations. With such a model, one can estimate the signal when a trace element is illuminated with an X-ray beam, and when just the surrounding non-fluorescent material is illuminated. From this signal difference, a contrast parameter can be calculated and this can in turn be used to calculate the signal-to-noise ratio (S/N) for detecting a certain elemental concentration. We apply this model to the detection of trace amounts of zinc in biological materials, and to the detection of small quantities of arsenic in semiconductors. We conclude that increased detector collection solid angle is (nearly) always advantageous even when considering the scattered signal. However, given the choice between a smaller detector at 90° to the beam versus a larger detector at 180° (in a backscatter-like geometry), the 90° detector is better for trace element detection in thick samples, while the larger detector in 180° geometry is better suited to trace element detection in thin samples. Copyright © 2015. Published by Elsevier B.V.

Optimizing detector geometry for trace element mapping by X-ray fluorescence

PubMed Central

Sun, Yue; Gleber, Sophie-Charlotte; Jacobsen, Chris; Kirz, Janos; Vogt, Stefan

2016-01-01

Trace metals play critical roles in a variety of systems, ranging from cells to photovoltaics. X-Ray Fluorescence (XRF) microscopy using X-ray excitation provides one of the highest sensitivities available for imaging the distribution of trace metals at sub-100 nm resolution. With the growing availability and increasing performance of synchrotron light source based instruments and X-ray nanofocusing optics, and with improvements in energy-dispersive XRF detectors, what are the factors that limit trace element detectability? To address this question, we describe an analytical model for the total signal incident on XRF detectors with various geometries, including the spectral response of energy dispersive detectors. This model agrees well with experimentally recorded X-ray fluorescence spectra, and involves much shorter calculation times than with Monte Carlo simulations. With such a model, one can estimate the signal when a trace element is illuminated with an X-ray beam, and when just the surrounding non-fluorescent material is illuminated. From this signal difference, a contrast parameter can be calculated and this can in turn be used to calculate the signal-to-noise ratio (S/N) for detecting a certain elemental concentration. We apply this model to the detection of trace amounts of zinc in biological materials, and to the detection of small quantities of arsenic in semiconductors. We conclude that increased detector collection solid angle is (nearly) always advantageous even when considering the scattered signal. However, given the choice between a smaller detector at 90° to the beam versus a larger detector at 180° (in a backscatter-like geometry), the 90° detector is better for trace element detection in thick samples, while the larger detector in 180° geometry is better suited to trace element detection in thin samples. PMID:25600825

Optimizing detector geometry for trace element mapping by X-ray fluorescence

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

Sun, Yue; Gleber, Sophie-Charlotte; Jacobsen, Chris

Trace metals play critical roles in a variety of systems, ranging from cells to photovoltaics. X-Ray Fluorescence (XRF) microscopy using X-ray excitation provides one of the highest sensitivities available for imaging the distribution of trace metals at sub-100 nm resolution. With the growing availability and increasing performance of synchrotron light source based instruments and X-ray nanofocusing optics, and with improvements in energy-dispersive XRF detectors, what are the factors that limit trace element detectability? To address this question, we describe an analytical model for the total signal incident on XRF detectors with various geometries, including the spectral response of energy dispersivemore » detectors. This model agrees well with experimentally recorded X-ray fluorescence spectra, and involves much shorter calculation times than with Monte Carlo simulations. With such a model, one can estimate the signal when a trace element is illuminated with an X-ray beam, and when just the surrounding non-fluorescent material is illuminated. From this signal difference, a contrast parameter can be calculated and this can in turn be used to calculate the signal-to-noise ratio (S/N) for detecting a certain elemental concentration. We apply this model to the detection of trace amounts of zinc in biological materials, and to the detection of small quantities of arsenic in semiconductors. We conclude that increased detector collection solid angle is (nearly) always advantageous even when considering the scattered signal. However, given the choice between a smaller detector at 90° to the beam versus a larger detector at 180° (in a backscatter-like geometry), the 90° detector is better for trace element detection in thick samples, while the larger detector in 180° geometry is better suited to trace element detection in thin samples.« less

The NGST and the Zodiacal Light in the Solar System

NASA Technical Reports Server (NTRS)

Gorkavyi, Nick; Ozernoy, Leonid; Mather, John; Taidakova, Tanya

1999-01-01

We develop a physical model of the zodiacal cloud incorporating the real dust sources of asteroidal, cometary, and kuiperoidal origin. Using the inferred distribution of the zodiacal dust, we compute its thermal emission and scattering at several wavelengths (1.25, 5, and 20 micron) as a function of NGST location assumed to be at 1 AU or 3 AU. Areas on the sky with a minimum of zodiacal light are determined.

Interpreting ambiguous ‘trace’ results in Schistosoma mansoni CCA Tests: Estimating sensitivity and specificity of ambiguous results with no gold standard

PubMed Central

Donnelly, Christl A.; Fenwick, Alan; Kabatereine, Narcis B.; Knowles, Sarah C. L.; Meité, Aboulaye; N'Goran, Eliézer K.; Nalule, Yolisa; Nogaro, Sarah; Phillips, Anna E.; Tukahebwa, Edridah Muheki; Fleming, Fiona M.

2017-01-01

Background The development of new diagnostics is an important tool in the fight against disease. Latent Class Analysis (LCA) is used to estimate the sensitivity and specificity of tests in the absence of a gold standard. The main field diagnostic for Schistosoma mansoni infection, Kato-Katz (KK), is not very sensitive at low infection intensities. A point-of-care circulating cathodic antigen (CCA) test has been shown to be more sensitive than KK. However, CCA can return an ambiguous ‘trace’ result between ‘positive’ and ‘negative’, and much debate has focused on interpretation of traces results. Methodology/Principle findings We show how LCA can be extended to include ambiguous trace results and analyse S. mansoni studies from both Côte d’Ivoire (CdI) and Uganda. We compare the diagnostic performance of KK and CCA and the observed results by each test to the estimated infection prevalence in the population. Prevalence by KK was higher in CdI (13.4%) than in Uganda (6.1%), but prevalence by CCA was similar between countries, both when trace was assumed to be negative (CCAtn: 11.7% in CdI and 9.7% in Uganda) and positive (CCAtp: 20.1% in CdI and 22.5% in Uganda). The estimated sensitivity of CCA was more consistent between countries than the estimated sensitivity of KK, and estimated infection prevalence did not significantly differ between CdI (20.5%) and Uganda (19.1%). The prevalence by CCA with trace as positive did not differ significantly from estimates of infection prevalence in either country, whereas both KK and CCA with trace as negative significantly underestimated infection prevalence in both countries. Conclusions Incorporation of ambiguous results into an LCA enables the effect of different treatment thresholds to be directly assessed and is applicable in many fields. Our results showed that CCA with trace as positive most accurately estimated infection prevalence. PMID:29220354

Pencil drawn strain gauges and chemiresistors on paper.

PubMed

Lin, Cheng-Wei; Zhao, Zhibo; Kim, Jaemyung; Huang, Jiaxing

2014-01-22

Pencil traces drawn on print papers are shown to function as strain gauges and chemiresistors. Regular graphite/clay pencils can leave traces composed of percolated networks of fine graphite powders, which exhibit reversible resistance changes upon compressive or tensile deflections. Flexible toy pencils can leave traces that are essentially thin films of graphite/polymer composites, which show reversible changes in resistance upon exposure to volatile organic compounds due to absorption/desorption induced swelling/recovery of the polymer binders. Pencil-on-paper devices are low-cost, extremely simple and rapid to fabricate. They are light, flexible, portable, disposable, and do not generate potentially negative environmental impact during processing and device fabrication. One can envision many other types of pencil drawn paper electronic devices that can take on a great variety of form factors. Hand drawn devices could be useful in resource-limited or emergency situations. They could also lead to new applications integrating art and electronics.

Access to the Arts through Assistive Technology.

ERIC Educational Resources Information Center

Frame, Charles

Personnel in the rehabilitation field have come to recognize the possibilities and implications of computers as assistive technology for disabled persons. This manual provides information on how to adapt the Unicorn Board, Touch Talker/Light Talker overlays, the Adaptive Firmware Card setup disk, and Trace-Transparent Access Module (T-TAM) to…

Engineering Light: Quantum Cascade Lasers

ScienceCinema

Claire Gmachl

2017-12-09

Quantum cascade lasers are ideal for environmental sensing and medical diagnostic applications. Gmachl discusses how these lasers work, and their applications, including their use as chemical trace gas sensors. As examples of these applications, she briefly presents results from her field campaign at the Beijing Olympics, and ongoing campaigns in Texas, Maryland, and Ghana.

X-ray ptychography, fluorescence microscopy combo sheds new light on trace

Science.gov Websites

Research Divisions Computing, Environment and Life Sciences BIOBiosciences CPSComputational Science DSLData CEESCenter for Electrochemical Energy Science CTRCenter for Transportation Research CRIChain Reaction Navigation Toggle Search Energy Environment National Security User Facilities Science Work with Us About

The Mind's Staircase: Exploring the Conceptual Underpinnings of Children's Thought and Knowledge.

ERIC Educational Resources Information Center

Case, Robbie; And Others

This book, which contains 19 chapters, examines children's learning processes in light of reconceptualizations of Piagetian theory. Part one traces the theoretical question underpinning this examination and includes three chapters: "General and Specific Views of the Mind, its Structure, and its Development"; "A Neo-Piagetian…

Policy as Performance: Tracing the Rituals of Racism

ERIC Educational Resources Information Center

Schick, Carol

2011-01-01

This article examines the relations between two contrasting education phenomena that occur generally and that have come to light in the geographic location where the author teaches and works. This first phenomenon is the proliferation of interest in issues of diversity and equity through education policies, theories, practices, and initiatives.…

NOX AND CO EMISSIONS FROM SOIL AND SURFACE LITTER IN A BRAZILIAN SAVANNA

EPA Science Inventory

Land clearing and burning in the tropics often results in increased solar irradiation of soil and surface organic matter. This increased light exposure and surface heating may impact the emissions of nitrogen oxides (NOx) and carbon monoxide (CO), trace gases that play an importa...

Journalism Education's Roots in Latin America Are Traced.

ERIC Educational Resources Information Center

Knudson, Jerry W.

1987-01-01

Discusses a document recently discovered in Bolivia that has cast new light on the background of journalism education in Latin America. Indicates that the movement toward the licensing of journalists was present from the beginning. Describes early journalism education in Argentina, Mexico, Ecuador, Peru, and Central America. (JD)

From Weber to Parsons and Shutz: The Eclipse of History in Modern Social Theory.

ERIC Educational Resources Information Center

Zaret, David

1980-01-01

Compares the relationship between theoretical synthesis and historical research in light of research by Max Weber, Talcott Parsons, and Alfred Schutz. Traces theoretical developments within one subfield of sociology (action theory) and relates these developments to research problems confronting contemporary theoretical work in sociology. (DB)

Using the orbiting companion to trace WR wind structures in the 29d WC8d + O8-9IV binary CV Ser

NASA Astrophysics Data System (ADS)

David-Uraz, Alexandre; Moffat, Anthony F. J.

2011-07-01

We have used continuous, high-precision, broadband visible photometry from the MOST satellite to trace wind structures in the WR component of CV Ser over more than a full orbit. Most of the small-scale light-curve variations are likely due to extinction by clumps along the line of sight to the O companion as it orbits and shines through varying columns of the WR wind. Parallel optical spectroscopy from the Mont Megantic Observatory is used to refine the orbital and wind-collision parameters, as well as to reveal line emission from clumps.

On-site Determination of Trace Arsenic by Reflection-Absorption Colorimetry of Molybdenum Blue Collected on a Membrane Filter.

PubMed

Hasegawa, Yuya; Suzuki, Yasutada; Kawakubo, Susumu

2017-01-01

An on-site determination method for trace arsenic has been developed by collecting it as molybdenum blue (MB) in the presence of tetradecyldimethylbenzylammonium chloride on a mixed cellulose ester membrane filter and by measuring reflection absorbance (RA) of MB on the filter using a laboratory-made palm-top size reflection-absorbance colorimeter with a red light-emitting diode. The value of RA was proportional to the amount of arsenic up to 0.5 μg with a detection limit of 0.01 μg. The proposed method was successfully applied to soil extract and hot-spring water samples.

Distribution of trace elements in certain ecological components and animal products in a dairy farm at Tirupati, Chittoor District, Andhra Pradesh, India.

PubMed

Raghu, V

2013-12-01

Biogeochemical characteristics of the cattle are dealt based on the observations made in Ayurveda in the light of modern scientific developments in applied environmental geochemistry. The biogeochemical characteristics of certain important ecological components and animal products of the stall-fed animals were studied. For this purpose, a dairy farm of Tirumala-Tirupati Devasthanams, a religious organization in Tirupati, Chittoor District, Andhra Pradesh was selected. This study is intended to trace out the trace element interactions in the ecological components (soil, water, fodder, feed) of the stall-fed animals and their output components viz. dung, urine and milk. Physical, physico-chemical properties and certain trace elements were determined for composite samples of ecological components and dung, urine, and milk of stall-fed animals. The variations in the distribution of pH and EC of urine and milk reflect the variations in their physico-chemical or hydro-chemical properties. As mentioned in Ayurveda, not only the properties of milk but also the properties of dung and urine reflect their diet and conditions of their habitat. Even though the diet is the same, the cows of different breeds yield milk of variable physical, physico-chemical properties and trace element composition which can be attributed to their body colour, substantiating Ayurveda.

Trace elements in hazardous mineral fibres.

PubMed

Bloise, Andrea; Barca, Donatella; Gualtieri, Alessandro Francesco; Pollastri, Simone; Belluso, Elena

2016-09-01

Both occupational and environmental exposure to asbestos-mineral fibres can be associated with lung diseases. The pathogenic effects are related to the dimension, biopersistence and chemical composition of the fibres. In addition to the major mineral elements, mineral fibres contain trace elements and their content may play a role in fibre toxicity. To shed light on the role of trace elements in asbestos carcinogenesis, knowledge on their concentration in asbestos-mineral fibres is mandatory. It is possible that trace elements play a synergetic factor in the pathogenesis of diseases caused by the inhalation of mineral fibres. In this paper, the concentration levels of trace elements from three chrysotile samples, four amphibole asbestos samples (UICC amosite, UICC anthophyllite, UICC crocidolite and tremolite) and fibrous erionite from Jersey, Nevada (USA) were determined using inductively coupled plasma mass spectrometry (ICP-MS). For all samples, the following trace elements were measured: Li, Be, Sc, V, Cr, Mn, Co, Ni, Cu, Zn, As, Rb, Sr, Y, Sb, Cs, Ba, La, Pb, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Th, U. Their distribution in the various mineral species is thoroughly discussed. The obtained results indicate that the amount of trace metals such as Mn, Cr, Co, Ni, Cu and Zn is higher in anthophyllite and chrysotile samples, whereas the amount of rare earth elements (REE) is higher in erionite and tremolite samples. The results of this work can be useful to the pathologists and biochemists who use asbestos minerals and fibrous erionite in-vitro studies as positive cyto- and geno-toxic standard references. Copyright © 2016 Elsevier Ltd. All rights reserved.

Effects of horizontal refractivity gradients on the accuracy of laser ranging to satellites

NASA Technical Reports Server (NTRS)

Gardner, C. S.

1976-01-01

Numerous formulas have been developed to partially correct laser ranging data for the effects of atmospheric refraction. All the formulas assume the atmospheric refractivity profile is spherically symmetric. The effects of horizontal refractivity gradients are investigated by ray tracing through spherically symmetric and three-dimensional refractivity profiles. The profiles are constructed from radiosonde data. The results indicate that the horizontal gradients introduce an rms error of approximately 3 cm when the satellite is near 10 deg elevation. The error decreases to a few millimeters near zenith.

Pick_sw: a program for interactive picking of S-wave data, version 2.00

USGS Publications Warehouse

Ellefsen, Karl J.

2002-01-01

Program pick_sw is used to interactively pick travel times from S-wave data. It is assumed that the data are collected using 2 shots of opposite polarity at each shot location. The traces must be in either the SEG-2 format or the SU format. The program is written in the IDL and C programming languages, and the program is executed under the Windows operating system. (The program may also execute under other operating systems like UNIX if the C language functions are re-compiled).

Physical Limitations of Phosphor layer thickness and concentration for White LEDs.

PubMed

Tan, Cher Ming; Singh, Preetpal; Zhao, Wenyu; Kuo, Hao-Chung

2018-02-05

Increasing phosphor layer thickness and concentration can enhance the lumen flux of white LED (W-LED). In this work, we found that increasing the phosphor layer thickness and concentration can increase its temperature, and there is also a maximum thickness and concentration beyond which their increase will not lead to lumen increase, but only temperature increase. Higher thickness and higher concentration also results in warm light instead of White light. The maximum thickness and concentration are found to be limited by the scattering of light rays with higher % decrease of blue light rays than the yellow light rays. The results obtained in this work can also be used to compute the temperature and thermo-mechanical stress distribution of an encapsulated LED, demonstrating its usefulness to the design of encapsulated LED packages. Simulation software like ANSYS and TracePro are used extensively to verify the root cause mechanisms.

Biconcave micro-optofluidic lens with low-refractive-index liquids.

PubMed

Song, Chaolong; Nguyen, Nam-Trung; Asundi, Anand Krishna; Low, Cassandra Lee-Ngo

2009-12-01

One of the current problems of micro-optofluidics is the choice of a suitable liquid with a high refractive index (RI). We report the use of a low-RI liquid in a biconcave liquid-core liquid-cladding lens for focusing light. For the characterization of the lens, a telescope system was constructed from polydimethylsiloxane lenses to collimate and expand a light beam emitted from an optical fiber. The tunable optofluidic biconcave lens focuses the parallel beam. Fluorescent dye diluted in an index-matching liquid was used for the visualization of the light rays in a beam-tracing chamber. The focused beam is tuned by adjusting the flow rate ratio between core and cladding streams.

Forensic Excavation of Rock Masses: A Technique to Investigate Discontinuity Persistence

NASA Astrophysics Data System (ADS)

Shang, J.; Hencher, S. R.; West, L. J.; Handley, K.

2017-11-01

True persistence of rock discontinuities (areas with insignificant tensile strength) is an important factor controlling the engineering behaviour of fractured rock masses, but is extremely difficult to quantify using current geological survey methodologies, even where there is good rock exposure. Trace length as measured in the field or using remote measurement devices is actually only broadly indicative of persistence for rock engineering practice and numerical modelling. Visible traces of discontinuities are treated as if they were open fractures within rock mass classifications, despite many such traces being non-persistent and actually retaining considerable strength. The common assumption of 100% persistence, based on trace length, is generally extremely conservative in terms of strength and stiffness, but not always so and may lead to a wrong prediction of failure mechanism or of excavatability. Assuming full persistence would give hopelessly incorrect predictions of hydraulic conductivity. A new technique termed forensic excavation of rock masses is introduced, as a procedure for directly investigating discontinuity persistence. This technique involves non-explosive excavation of rock masses by injecting an expansive chemical splitter along incipient discontinuities. On expansion, the splitter causes the incipient traces to open as true joints. Experiments are described in which near-planar rock discontinuities, through siltstone and sandstone, were opened up by injecting the splitter into holes drilled along the lines of visible traces of the discontinuities in the laboratory and in the field. Once exposed the surfaces were examined to investigate the pre-existing persistence characteristics of the incipient discontinuities. One conclusion from this study is that visible trace length of a discontinuity can be a poor indicator of true persistence (defined for a fracture area with negligible tensile strength). An observation from this series of experiments was that freshly failed surfaces through pre-existing rock bridges were relatively rough compared to sections of pre-existing weaker areas of geologically developed (though still incipient) discontinuities. Fractographic features such as hackle and rib marks were typical of the freshly broken rock bridges, whereas opened-up areas of incipient discontinuity were smoother. Schmidt hammer rebound values were generally higher for the rock bridge areas, probably reflecting their lower degree of chemical and physical weathering.

Stability of a Light Sail Riding on a Laser Beam

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

Manchester, Zachary; Loeb, Abraham, E-mail: zmanchester@seas.harvard.edu

2017-03-10

The stability of a light sail riding on a laser beam is analyzed both analytically and numerically. Conical sails on Gaussian beams, which have been studied in the past, are shown to be unstable without active control or additional mechanical modifications. A new architecture for a passively stable sail-and-beam configuration is proposed. The novel spherical shell design for the sail is capable of “beam riding” without the need for active feedback control. Full three-dimensional ray-tracing simulations are performed to verify our analytical results.

SDO Pick of the Week

NASA Image and Video Library

2017-12-08

Magnetic arcs of solar material spewing from our favorite sphere of hot plasma, the sun. Magnetic arcs of solar material held their shapes fairly well as they spiraled above two solar active regions over 18 hours on Jan. 11-12, 2017. The charged solar material, called plasma, traces out the magnetic field lines above the active regions when viewed in wavelengths of extreme ultraviolet light, captured here by NASA’s Solar Dynamics Observatory. Extreme ultraviolet light is typically invisible to our eyes, but is colorized here in gold for easy viewing. Credit: NASA/SDO

Search for pair-produced resonances decaying to jet pairs in proton–proton collisions at $$\\sqrt{s}$$=8 TeV

DOE PAGES

Khachatryan, Vardan

2015-04-24

Results are reported of a general search for pair production of heavy resonances decaying to pairs of hadronic jets in events with at least four jets. The study is based on up to 19.4 fb –1 of integrated luminosity from proton–proton collisions at a center-of-mass energy of 8 TeV, recorded with the CMS detector at the LHC. Limits are determined on the production of scalar top quarks (top squarks) in the framework of R-parity violating supersymmetry and on the production of color-octet vector bosons (colorons). First limits at the LHC are placed on top squark production for two scenarios. Themore » first assumes decay to a bottom quark and a light-flavor quark and is excluded for masses between 200 and 385 GeV, and the second assumes decay to a pair of light-flavor quarks and is excluded for masses between 200 and 350 GeV at 95% confidence level. Furthermore, previous limits on colorons decaying to light-flavor quarks are extended to exclude masses from 200 to 835 GeV.« less

Trace element abundances of high-MgO glasses from Kilauea, Mauna Loa and Haleakala volcanoes, Hawaii

USGS Publications Warehouse

Wagner, T.P.; Clague, D.A.; Hauri, E.H.; Grove, T.L.

1998-01-01

We performed an ion-microprobe study of eleven high-MgO (6.7-14.8 wt%) tholeiite glasses from the Hawaiian volcanoes Kilauea, Mauna Loa and Haleakala. We determined the rare earth (RE), high field strength, and other selected trace element abundances of these glasses, and used the data to establish their relationship to typical Hawaiian shield tholeiite and to infer characteristics of their source. The glasses have trace element abundance characteristics generally similar to those of typical shield tholeiites, e.g. L(light)REE/H(heavy)REE(C1) > 1. The Kilauea and Mauna Loa glasses, however, display trace and major element characteristics that cross geochemical discriminants observed between Kilauea and Mauna Loa shield lavas. The glasses contain a blend of these discriminating chemical characteristics, and are not exactly like the typical shield lavas from either volcano. The production of these hybrid magmas likely requires a complexly zoned source, rather than two unique sources. When corrected for olivine fractionation, the glass data show correlations between CaO concentration and incompatible trace element abundances, indicating that CaO may behave incompatibly during melting of the tholeiite source. Furthermore, the tholeiite source must contain residual garnet and clinopyroxene to account for the variation in trace element abundances of the Kilauea glasses. Inversion modeling indicates that the Kilauea source is flat relative to C1 chondrites, and has a higher bulk distribution coefficient for the HREE than the LREE.

Co-occurrence profiles of trace elements in potable water systems: a case study.

PubMed

Andra, Syam S; Makris, Konstantinos C; Charisiadis, Pantelis; Costa, Costas N

2014-11-01

Potable water samples (N = 74) from 19 zip code locations in a region of Greece were profiled for 13 trace elements composition using inductively coupled plasma mass spectrometry. The primary objective was to monitor the drinking water quality, while the primary focus was to find novel associations in trace elements occurrence that may further shed light on common links in their occurrence and fate in the pipe scales and corrosion products observed in urban drinking water distribution systems. Except for arsenic at two locations and in six samples, rest of the analyzed elements was below maximum contaminant levels, for which regulatory values are available. Further, we attempted to hierarchically cluster trace elements based on their covariances resulting in two groups; one with arsenic, antimony, zinc, cadmium, and copper and the second with the rest of the elements. The grouping trends were partially explained by elements' similar chemical activities in water, underscoring their potential for co-accumulation and co-mobilization phenomena from pipe scales into finished water. Profiling patterns of trace elements in finished water could be indicative of their load on pipe scales and corrosion products, with a corresponding risk of episodic contaminant release. Speculation was made on the role of disinfectants and disinfection byproducts in mobilizing chemically similar trace elements of human health interest from pipe scales to tap water. It is warranted that further studies may eventually prove useful to water regulators from incorporating the acquired knowledge in the drinking water safety plans.

Utility of the clue - From assessing the investigative contribution of forensic science to supporting the decision to use traces.

PubMed

Bitzer, Sonja; Albertini, Nicola; Lock, Eric; Ribaux, Olivier; Delémont, Olivier

2015-12-01

In an attempt to grasp the effectiveness of forensic science in the criminal justice process, a number of studies introduced some form of performance indicator. However, most of these indicators suffer from different weaknesses, from the definition of forensic science itself to problems of reliability and validity. We suggest the introduction of the concept of utility of the clue as an internal evaluation indicator of forensic science in the investigation. Utility of the clue is defined as added value of information, gained by the use of traces. This concept could be used to assess the contribution of the trace in the context of the case. By extension, a second application of this concept is suggested. By formalising and considering, a priori, the perceived utility of using traces, we introduce the notion of expected utility that could be used as decision factor when choosing which traces to use, once they have been collected at the crime scene or from an object in the laboratory. In a case-based approach, utility can be assessed in the light of the available information to evaluate the investigative contribution of forensic science. In the decision-making process, the projection or estimation of the utility of the clue is proposed to be a factor to take into account when triaging the set of traces. Copyright © 2015 The Chartered Society of Forensic Sciences. Published by Elsevier Ireland Ltd. All rights reserved.

Design of fiber optic probes for laser light scattering

NASA Technical Reports Server (NTRS)

Dhadwal, Harbans S.; Chu, Benjamin

1989-01-01

A quantitative analysis is presented of the role of optical fibers in laser light scattering. Design of a general fiber optic/microlens probe by means of ray tracing is described. Several different geometries employing an optical fiber of the type used in lightwave communications and a graded index microlens are considered. Experimental results using a nonimaging fiber optic detector probe show that due to geometrical limitations of single mode fibers, a probe using a multimode optical fiber has better performance, for both static and dynamic measurements of the scattered light intensity, compared with a probe using a single mode fiber. Fiber optic detector probes are shown to be more efficient at data collection when compared with conventional approaches to measurements of the scattered laser light. Integration of fiber optic detector probes into a fiber optic spectrometer offers considerable miniaturization of conventional light scattering spectrometers, which can be made arbitrarily small. In addition static and dynamic measurements of scattered light can be made within the scattering cell and consequently very close to the scattering center.

Fast imaging of live organisms with sculpted light sheets

NASA Astrophysics Data System (ADS)

Chmielewski, Aleksander K.; Kyrsting, Anders; Mahou, Pierre; Wayland, Matthew T.; Muresan, Leila; Evers, Jan Felix; Kaminski, Clemens F.

2015-04-01

Light-sheet microscopy is an increasingly popular technique in the life sciences due to its fast 3D imaging capability of fluorescent samples with low photo toxicity compared to confocal methods. In this work we present a new, fast, flexible and simple to implement method to optimize the illumination light-sheet to the requirement at hand. A telescope composed of two electrically tuneable lenses enables us to define thickness and position of the light-sheet independently but accurately within milliseconds, and therefore optimize image quality of the features of interest interactively. We demonstrated the practical benefit of this technique by 1) assembling large field of views from tiled single exposure each with individually optimized illumination settings; 2) sculpting the light-sheet to trace complex sample shapes within single exposures. This technique proved compatible with confocal line scanning detection, further improving image contrast and resolution. Finally, we determined the effect of light-sheet optimization in the context of scattering tissue, devising procedures for balancing image quality, field of view and acquisition speed.

High-output LED-based light engine for profile lighting fixtures with high color uniformity using freeform reflectors.

PubMed

Gadegaard, Jesper; Jensen, Thøger Kari; Jørgensen, Dennis Thykjær; Kristensen, Peter Kjær; Søndergaard, Thomas; Pedersen, Thomas Garm; Pedersen, Kjeld

2016-02-20

In the stage lighting and entertainment market, light engines (LEs) for lighting fixtures are often based on high-intensity discharge (HID) bulbs. Switching to LED-based light engines gives possibilities for fast switching, additive color mixing, a longer lifetime, and potentially, more energy-efficient systems. The lumen output of a single LED is still not sufficient to replace an HID source in high-output profile fixtures, but combining multiple LEDs can create an LE with a similar output, but with added complexity. This paper presents the results of modeling and testing such a light engine. Custom ray-tracing software was used to design a high-output red, green and blue LED-based light engine with twelve CBT-90 LEDs using a dual-reflector principle. The simulated optical system efficiency was 0.626 with a perfect (R=1) reflector coating for light delivered on a target surface through the entire optical system. A profile lighting fixture prototype was created, and provided an output of 6744 lumen and an efficiency of 0.412. The lower efficiency was mainly due to a non-optimal reflector coating, and the optimized design is expected to reach a significantly higher efficiency.

The effect of lunarlike satellites on the orbital infrared light curves of Earth-analog planets.

PubMed

Moskovitz, Nicholas A; Gaidos, Eric; Williams, Darren M

2009-04-01

We have investigated the influence of lunarlike satellites on the infrared orbital light curves of Earth-analog extrasolar planets. Such light curves will be obtained by NASA's Terrestrial Planet Finder (TPF) and ESA's Darwin missions as a consequence of repeat observations to confirm the companion status of a putative planet and determine its orbit. We used an energy balance model to calculate disk-averaged infrared (bolometric) fluxes from planet-satellite systems over a full orbital period (one year). The satellites are assumed to lack an atmosphere, have a low thermal inertia like that of the Moon, and span a range of plausible radii. The planets are assumed to have thermal and orbital properties that mimic those of Earth, while their obliquities and orbital longitudes of inferior conjunction remain free parameters. Even if the gross thermal properties of the planet can be independently constrained (e.g., via spectroscopy or visible-wavelength detection of specular glint from a surface ocean), only the largest (approximately Mars-sized) lunarlike satellites can be detected by light curve data from a TPF-like instrument (i.e., one that achieves a photometric signal-to-noise ratio of 10 to 20 at infrared wavelengths). Nondetection of a lunarlike satellite can obfuscate the interpretation of a given system's infrared light curve so that it may resemble a single planet with high obliquity, different orbital longitude of vernal equinox relative to inferior conjunction, and in some cases drastically different thermal characteristics. If the thermal properties of the planet are not independently established, then the presence of a lunarlike satellite cannot be inferred from infrared data, which would thus demonstrate that photometric light curves alone can only be used for preliminary study, and the addition of spectroscopic data will be necessary.

Intelligent structural health monitoring and damage detection for light-rail bridges

DOT National Transportation Integrated Search

1998-05-01

A global damage detection algorithm for bridge-like Structures is proposed. This method provides the capability of determining the reduction in both stiffness and damping parameters of the structural elements. It is assumed the mass of the structural...

Quantification and parametrization of non-linearity effects by higher-order sensitivity terms in scattered light differential optical absorption spectroscopy

NASA Astrophysics Data System (ADS)

Puķīte, Jānis; Wagner, Thomas

2016-05-01

We address the application of differential optical absorption spectroscopy (DOAS) of scattered light observations in the presence of strong absorbers (in particular ozone), for which the absorption optical depth is a non-linear function of the trace gas concentration. This is the case because Beer-Lambert law generally does not hold for scattered light measurements due to many light paths contributing to the measurement. While in many cases linear approximation can be made, for scenarios with strong absorptions non-linear effects cannot always be neglected. This is especially the case for observation geometries, for which the light contributing to the measurement is crossing the atmosphere under spatially well-separated paths differing strongly in length and location, like in limb geometry. In these cases, often full retrieval algorithms are applied to address the non-linearities, requiring iterative forward modelling of absorption spectra involving time-consuming wavelength-by-wavelength radiative transfer modelling. In this study, we propose to describe the non-linear effects by additional sensitivity parameters that can be used e.g. to build up a lookup table. Together with widely used box air mass factors (effective light paths) describing the linear response to the increase in the trace gas amount, the higher-order sensitivity parameters eliminate the need for repeating the radiative transfer modelling when modifying the absorption scenario even in the presence of a strong absorption background. While the higher-order absorption structures can be described as separate fit parameters in the spectral analysis (so-called DOAS fit), in practice their quantitative evaluation requires good measurement quality (typically better than that available from current measurements). Therefore, we introduce an iterative retrieval algorithm correcting for the higher-order absorption structures not yet considered in the DOAS fit as well as the absorption dependence on temperature and scattering processes.

Discriminating Majorana neutrino textures in light of the baryon asymmetry

NASA Astrophysics Data System (ADS)

Borah, Manikanta; Borah, Debasish; Das, Mrinal Kumar

2015-06-01

We study all possible texture zeros in the Majorana neutrino mass matrix which are allowed from neutrino oscillation as well as cosmology data when the charged lepton mass matrix is assumed to take the diagonal form. In the case of one-zero texture, we write down the Majorana phases which are assumed to be equal and the lightest neutrino mass as a function of the Dirac C P phase. In the case of two-zero texture, we numerically evaluate all the three C P phases and lightest neutrino mass by solving four real constraint equations. We then constrain texture zero mass matrices from the requirement of producing correct baryon asymmetry through the mechanism of leptogenesis by assuming the Dirac neutrino mass matrix to be diagonal. Adopting a type I seesaw framework, we consider the C P -violating out of equilibrium decay of the lightest right-handed neutrino as the source of lepton asymmetry. Apart from discriminating between the texture zero mass matrices and light neutrino mass hierarchy, we also constrain the Dirac and Majorana C P phases so that the observed baryon asymmetry can be produced. In two-zero texture, we further constrain the diagonal form of the Dirac neutrino mass matrix from the requirement of producing correct baryon asymmetry.

Automated recognition of the pericardium contour on processed CT images using genetic algorithms.

PubMed

Rodrigues, É O; Rodrigues, L O; Oliveira, L S N; Conci, A; Liatsis, P

2017-08-01

This work proposes the use of Genetic Algorithms (GA) in tracing and recognizing the pericardium contour of the human heart using Computed Tomography (CT) images. We assume that each slice of the pericardium can be modelled by an ellipse, the parameters of which need to be optimally determined. An optimal ellipse would be one that closely follows the pericardium contour and, consequently, separates appropriately the epicardial and mediastinal fats of the human heart. Tracing and automatically identifying the pericardium contour aids in medical diagnosis. Usually, this process is done manually or not done at all due to the effort required. Besides, detecting the pericardium may improve previously proposed automated methodologies that separate the two types of fat associated to the human heart. Quantification of these fats provides important health risk marker information, as they are associated with the development of certain cardiovascular pathologies. Finally, we conclude that GA offers satisfiable solutions in a feasible amount of processing time. Copyright © 2017 Elsevier Ltd. All rights reserved.

Guided wave tomography in anisotropic media using recursive extrapolation operators

NASA Astrophysics Data System (ADS)

Volker, Arno

2018-04-01

Guided wave tomography is an advanced technology for quantitative wall thickness mapping to image wall loss due to corrosion or erosion. An inversion approach is used to match the measured phase (time) at a specific frequency to a model. The accuracy of the model determines the sizing accuracy. Particularly for seam welded pipes there is a measurable amount of anisotropy. Moreover, for small defects a ray-tracing based modelling approach is no longer accurate. Both issues are solved by applying a recursive wave field extrapolation operator assuming vertical transverse anisotropy. The inversion scheme is extended by not only estimating the wall loss profile but also the anisotropy, local material changes and transducer ring alignment errors. This makes the approach more robust. The approach will be demonstrated experimentally on different defect sizes, and a comparison will be made between this new approach and an isotropic ray-tracing approach. An example is given in Fig. 1 for a 75 mm wide, 5 mm deep defect. The wave field extrapolation based tomography clearly provides superior results.

Ray-tracing studies and path-integrated gains of ELF unducted whistler mode waves in the earth's magnetosphere

NASA Technical Reports Server (NTRS)

Huang, C. Y.; Goertz, C. K.

1983-01-01

Gyroresonance and Landau resonance interactions between unducted low-frequency whistler waves and trapped electrons in the earth's plasmasphere have been studied. Ray paths for waves launched near the plasmapause have been traced. In agreement with recent findings by Thorne et al. (1979), waves have been found which return through the equatorial zone with field-aligned wave normal angles. However, when the growth along the ray path is calculated for such waves, assuming an electron distribution function of the form E exp -n sin exp m alpha, it is found that for all the waves considered, the local growth rate becomes negative before plasmapause reflection, limiting the total gain to small values. Most waves reach zero gain before reflection. This is the result of Landau damping at oblique propagation angles, which necessarily occurs before reflection can take place. It is concluded that the concept of cyclic ray paths does not provide an explanation for the generation of unguided plasmaspheric hiss.

The detection of conformational disorder by thermal analysis

NASA Astrophysics Data System (ADS)

Wunderlich, B.

Conformational disorder in crystals is found in many molecules that possess a plurality of conformational isomers. Typical examples are linear macromolecules such as polyethylene, polytetrafluoroethylene and trans-1,4-polybutadiene; and small molecules such as paraffins, cycloparaffins, soaps, lipids and many liquid-crystal forming molecules. Conformational motion is often coupled with the cooperative creation of disorder. In this case a heat and entropy of transition is observed by thermal analysis. Levels of transition entropies can be estimated, assuming most of the disorder can be traced to conformational isomerism. In case there is conformational disorder frozen-in at low temperature, thermal analysis can be used to find the glass transition of a condis crystal. An Advanced Thermal Analysis System has been developed, and will be described that permits a detailed interpretation of the thermal analysis traces. It rests with the establishment of high quality heat capacity for the rigid solid state (vibration only) and the mobile liquid state (vibrations and large amplitude cooperative motion).

The detection of conformational disorder by thermal analysis

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

Wunderlich, B.

1988-01-01

Conformational disorder in crystals is found in many molecules that possess a plurality of conformational isomers. Typical examples are linear macromolecules such as polyethylene, polytetrafluoroethylene and trans-1,4-polybutadiene; and small molecules such as paraffins, cycloparaffins, soaps, lipids and many liquid-crystal forming molecules. Conformational motion is often coupled with the cooperative creation of disorder. In this case a heat and entropy of transition is observed by thermal analysis. Levels of transition entropies can be estimated, assuming most of the disorder can be traced to conformational isomerism. In case there is conformational disorder frozen-in at low temperature, thermal analysis can be used tomore » find the glass transition of a condis crystal. An Advanced Thermal Analysis System has been developed, and will be described that permits a detailed interpretation of the thermal analysis traces. It rests with the establishment of high quality heat capacity for the rigid solid state (vibration only) and the mobile liquid state (vibrations and large amplitude cooperative motion). 36 refs., 3 figs.« less

Computer prediction of large reflector antenna radiation properties

NASA Technical Reports Server (NTRS)

Botula, A.

1980-01-01

A FORTRAN program for calculating reflector antenna radiation patterns was rewritten and extended to include reflectors composed of a number of panels. These individual panels must be analytic surfaces. The theoretical foundation for the program is as follows: Geometrical optics techniques are used to trace rays from a feed antenna to the reflector surface and back to a mathematical plane just in front of the reflector. The resulting tangential electric field distribution, assumed to be the only source of forward radiation, is integrated numerically to calculate the radiation pattern for a desired set of angles. When the reflector is composed of more than one panel, each panel is treated as a separated antenna, the ray-tracing procedure and integration being repeated for each panel. The results of the individual aperture plane integrations are stored and summed to yield the relative electric field strength over the angles of interest. An example and several test cases are included to demonstrate the use of the program and verify the new method of computation.

The constitution of the atmospheric layers and the extreme ultraviolet spectrum of hot hydrogen-rich white dwarfs

NASA Technical Reports Server (NTRS)

Vennes, Stephane

1992-01-01

An analysis is presented of the atmospheric properties of hot, H-rich, DA white dwarfs that is based on optical, UV, and X-ray observations aimed at predicting detailed spectral properties of these stars in the range 80-800 A. The divergences between observations from a sample of 15 hot DA white dwarfs emitting in the EUV/soft X-ray range and pure H synthetic spectra calculated from a grid of model atmospheres characterized by Teff and g are examined. Seven out of 15 DA stars are found to consistently exhibit pure hydrogen atmospheres, the remaining seven stars showing inconsistency between FUV and EUV/soft X-ray data that can be explained by the presence of trace EUV/soft X-ray absorbers. Synthetic data are computed assuming two other possible chemical structures: photospheric traces of radiatively levitated heavy elements and a stratified hydrogen/helium distribution. Predictions about forthcoming medium-resolution observations of the EUV spectrum of selected hot H-rich white dwarfs are made.

Multiframe super resolution reconstruction method based on light field angular images

NASA Astrophysics Data System (ADS)

Zhou, Shubo; Yuan, Yan; Su, Lijuan; Ding, Xiaomin; Wang, Jichao

2017-12-01

The plenoptic camera can directly obtain 4-dimensional light field information from a 2-dimensional sensor. However, based on the sampling theorem, the spatial resolution is greatly limited by the microlenses. In this paper, we present a method of reconstructing high-resolution images from the angular images. First, the ray tracing method is used to model the telecentric-based light field imaging process. Then, we analyze the subpixel shifts between the angular images extracted from the defocused light field data and the blur in the angular images. According to the analysis above, we construct the observation model from the ideal high-resolution image to the angular images. Applying the regularized super resolution method, we can obtain the super resolution result with a magnification ratio of 8. The results demonstrate the effectiveness of the proposed observation model.

A method to generate soft shadows using a layered depth image and warping.

PubMed

Im, Yeon-Ho; Han, Chang-Young; Kim, Lee-Sup

2005-01-01

We present an image-based method for propagating area light illumination through a Layered Depth Image (LDI) to generate soft shadows from opaque and nonrefractive transparent objects. In our approach, using the depth peeling technique, we render an LDI from a reference light sample on a planar light source. Light illumination of all pixels in an LDI is then determined for all the other sample points via warping, an image-based rendering technique, which approximates ray tracing in our method. We use an image-warping equation and McMillan's warp ordering algorithm to find the intersections between rays and polygons and to find the order of intersections. Experiments for opaque and nonrefractive transparent objects are presented. Results indicate our approach generates soft shadows fast and effectively. Advantages and disadvantages of the proposed method are also discussed.

Genius or Dynamic Learner? Benjamin Franklin's Path to Greatness

ERIC Educational Resources Information Center

Marcum, James W.

2008-01-01

While the remarkable accomplishments of Benjamin Franklin are unparalleled, the means of their attainment can be considered more accessible to ordinary people and not necessarily attributable to a special genius. The steady development of Franklin's knowledge and skills is traced in light of a new model of "dynamic learning," which is a method…

William Kessen and James Mark Baldwin: Lessons from the History of Developmental Psychology.

ERIC Educational Resources Information Center

Ferrari, Michel; Runions, Kevin; Fueser, Josephine J.

2003-01-01

Considers the work of developmental scholar William Kessen (1925-1999) in light of James Mark Baldwin, one of the founders and principal architects of developmental psychology. Traces Kessen's interest in Baldwin's thought and examines Baldwin's legacy for developmental psychologists. Asserts that Baldwin's theory sought to integrate the role of…

Disability Theatre in Australia: A Survey and a Sector Ecology

ERIC Educational Resources Information Center

Hadley, Bree

2017-01-01

In this paper, I use an ecologies approach to present reflections on the history of disability and deaf theatre in Australia, in light of the distinctive local policy, industry, and production frameworks that have supported or failed to support its development in particular directions. After tracing and categorising developments in the field to…

A Simple Hypnotic Approach to Treat Test Anxiety in Medical Students and Residents.

ERIC Educational Resources Information Center

Hebert, Stephen W.

1984-01-01

A simple hypnotic procedure to treat test anxiety is described that was used successfully with medical students and residents at the Wake Forest University Medical Center. A light trace is obtained and then the student is told to take such a hypnotic "journey" the evening prior to the test. (MLW)

Mirages in a Bottle

ERIC Educational Resources Information Center

Lopez-Arias, T.; Calza, G.; Gratton, L. M.; Oss, S.

2009-01-01

A simple experiment is presented to visualize inferior and superior mirages in the laboratory. A quantitative analysis is done using ray tracing with both photographic and computational techniques. The mirage's image, as seen by the eye or the camera lens, can be used to analyse the deflection and inversion of light rays. (Contains 6 footnotes, 1…

Optical design and fabrication of palm/fingerprint uniform illumination system with a high-power near-infrared light-emitting diode.

PubMed

Jing, Lei; Wang, Yao; Zhao, Huifu; Ke, Hongliang; Wang, Xiaoxun; Gao, Qun

2017-06-10

In order to meet the requirements of uniform illumination for optical palm/fingerprint instruments and overcome the shortcomings of the poor uniform illumination on the working plane of the optical palm/fingerprint prism, a novel secondary optical lens with a free-form surface, compact structure, and high uniformity is presented in this paper. The design of the secondary optical lens is based on emission properties of the near-infrared light-emitting diode (LED) and basic principles of non-imaging optics, especially considering the impact of the thickness of the prism in the design. Through the numerical solution of Snell's law in geometric optics, we obtain the profile of the free-form surface of the lens. Using the optical software TracePro, we trace and simulate the illumination system. The results show that the uniformity is 89.8% on the working plane of the prism, and the test results show that the actual uniformity reaches 85.7% in the experiment, which provides an effective way for realizing a highly uniform illumination system with high-power near-infrared LED.

Highly sensitive and selective dynamic light-scattering assay for TNT detection using p-ATP attached gold nanoparticle.

PubMed

Dasary, Samuel S R; Senapati, Dulal; Singh, Anant Kumar; Anjaneyulu, Yerramilli; Yu, Hongtao; Ray, Paresh Chandra

2010-12-01

TNT is one of the most commonly used nitro aromatic explosives for landmines of military and terrorist activities. As a result, there is an urgent need for rapid and reliable methods for the detection of trace amount of TNT for screenings in airport, analysis of forensic samples, and environmental analysis. Driven by the need to detect trace amounts of TNT from environmental samples, this article demonstrates a label-free, highly selective, and ultrasensitive para-aminothiophenol (p-ATP) modified gold nanoparticle based dynamic light scattering (DLS) probe for TNT recognition in 100 pico molar (pM) level from ethanol:acetonitile mixture solution. Because of the formation of strong π-donor-acceptor interaction between TNT and p-ATP, para-aminothiophenol attached gold nanoparticles undergo aggregation in the presence of TNT, which changes the DLS intensity tremendously. A detailed mechanism for significant DLS intensity change has been discussed. Our experimental results show that TNT can be detected quickly and accurately without any dye tagging in 100 pM level with excellent discrimination against other nitro compounds.

Melt fracturing and healing: A mechanism for degassing and origin of silicic obsidian

USGS Publications Warehouse

Cabrera, A.; Weinberg, R.F.; Wright, H.M.N.; Zlotnik, S.; Cas, Ray A.F.

2011-01-01

We present water content transects across a healed fault in pyroclastic obsidian from Lami pumice cone, Lipari, Italy, using synchrotron Fourier transform infrared spectroscopy. Results indicate that rhyolite melt degassed through the fault surface. Transects define a trough of low water content coincident with the fault trace, surrounded on either side by high-water-content plateaus. Plateaus indicate that obsidian on either side of the fault equilibrated at different pressure-temperature (P-T) conditions before being juxtaposed. The curves into the troughs indicate disequilibrium and water loss through diffusion. If we assume constant T, melt equilibrated at pressures differing by 0.74 MPa before juxtaposition, and the fault acted as a low-P permeable path for H2O that diffused from the glass within time scales of 10 and 30 min. Assuming constant P instead, melt on either side could have equilibrated at temperatures differing by as much as 100 ??C, before being brought together. Water content on the fault trace is particularly sensitive to post-healing diffusion. Its preserved value indicates either higher temperature or lower pressure than the surroundings, indicative of shear heating and dynamic decompression. Our results reveal that water contents of obsidian on either side of the faults equilibrated under different P-T conditions and were out of equilibrium with each other when they were juxtaposed due to faulting immediately before the system was quenched. Degassing due to faulting could be linked to cyclical seismic activity and general degassing during silicic volcanic activity, and could be an efficient mechanism of producing low-water-content obsidian. ?? 2011 Geological Society of America.

Retrieval of Vertical Aerosol and Trace Gas Distributions from Polarization Sensitive Multi-Axis Differential Optical Absorption Spectroscopy (MAX-DOAS)

NASA Astrophysics Data System (ADS)

Tirpitz, Jan-Lukas; Friess, Udo; Platt, Ulrich

2017-04-01

An accurate knowledge of the vertical distribution of trace gases and aerosols is crucial for our understanding of the chemical and dynamical processes in the lower troposphere. Their accurate determination is typically only possible by means of laborious and expensive airborne in-situ measurements but in the recent decades, numerous promising ground-based remote sensing approaches have been developed. One of them is to infer vertical distributions from "Differential Optical Absorption Spectroscopy" (DOAS) measurements. DOAS is a technique to analyze UV- and visible radiation spectra of direct or scattered sunlight, which delivers information on different atmospheric parameters, integrated over the light path from space to the instrument. An appropriate set of DOAS measurements, recorded under different viewing directions (Multi-Axis DOAS) and thus different light path geometries, provides information on the atmospheric state. The vertical profiles of aerosol properties and trace gas concentrations can be retrieved from such a set by numerical inversion techniques, incorporating radiative transfer models. The information content of measured data is rarely sufficient for a well-constrained retrieval, particularly for atmospheric layers above 1 km. We showed in first simulations that, apart from spectral properties, the polarization state of skylight is likely to provide a significant amount of additional information on the atmospheric state and thus to enhance retrieval quality. We present first simulations, expectations and ideas on how to implement and characterize a polarization sensitive Multi-Axis DOAS instrument and a corresponding profile retrieval algorithm.

A comprehensive ray tracing study on the impact of solar reflections from glass curtain walls.

PubMed

Wong, Justin S J

2016-01-01

To facilitate the investigation of the impact of solar reflection from the façades of skyscrapers to surrounding environment, a comprehensive ray tracing model has been developed using the International Commerce Centre (ICC) in Hong Kong as an example. Taking into account the actual physical dimensions of buildings and meteorological data, the model simulates and traces the paths of solar reflections from ICC to the surrounding buildings, assessing the impact in terms of hit locations, light intensity and the hit time on each day throughout the year. Our analyses show that various design and architectural features of ICC have amplified the intensity of reflected solar rays and increased the hit rates of surrounding buildings. These factors include the high reflectivity of glass panels, their upward tilting angles, the concave profile of the 'Dragon Tail' (glass panels near the base), the particular location and orientation of ICC, as well as the immense height of ICC with its large reflective surfaces. The simulation results allow us to accurately map the date and time when the ray projections occur on each of the target buildings, rendering important information such as the number of converging (overlapping) projections, and the actual light intensity hitting each of the buildings at any given time. Comparisons with other skyscrapers such as Taipei 101 in Taiwan and 2-IFC (International Finance Centre) Hong Kong are made. Remedial actions for ICC and preventive measures are also discussed.

Negative Leadership

DTIC Science & Technology

2013-03-01

others and their self-image as a leader (yellow light type of leader). “Toxic” leaders were described as being maladjusted , malcontent, and often...negative or toxic leadership (assuming they are using the correct definition), or do they, based on the social environment they grew up in, feel

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

Sun, Yue; Gleber, Sophie-Charlotte; Jacobsen, Chris

Trace metals play critical roles in a variety of systems, ranging from cells to photovoltaics. X-Ray Fluorescence (XRF) microscopy using X-ray excitation provides one of the highest sensitivities available for imaging the distribution of trace metals at sub-100 nm resolution. With the growing availability and increasing performance of synchrotron light source based instruments and X-ray nanofocusing optics, and with improvements in energy-dispersive XRF detectors, what are the factors that limit trace element detectability? To address this question, we describe an analytical model for the total signal incident on XRF detectors with various geometries, including the spectral response of energy dispersivemore » detectors. This model agrees well with experimentally recorded X-ray fluorescence spectra, and involves much shorter calculation times than with Monte Carlo simulations. With such a model, one can estimate the signal when a trace element is illuminated with an X-ray beam, and when just the surrounding non-fluorescent material is illuminated. From this signal difference, a contrast parameter can be calculated and this can in turn be used to calculate the signal-to-noise ratio (S/N) for detecting a certain elemental concentration. We apply this model to the detection of trace amounts of zinc in biological materials, and to the detection of small quantities of arsenic in semiconductors. We conclude that increased detector collection solid angle is (nearly) always advantageous even when considering the scattered signal. However, given the choice between a smaller detector at 90° to the beam versus a larger detector at 180° (in a backscatter-like geometry), the 90° detector is better for trace element detection in thick samples, while the larger detector in 180° geometry is better suited to trace element detection in thin samples.« less

Design and simulation of a lighting system for a shadowless space

NASA Astrophysics Data System (ADS)

Wang, Ye; Fang, Li

2017-10-01

This paper described implementing the shadowless space by two kinds of methods. The first method will implement the shadowless space utilizing the semblable principles used in the integrating sphere. The rays from a built in light source will eventually evolve into a uniform lighting through diffuse reflections for numerous times, consider that the spherical cavity structure and the inner surface with high reflectivity. There is possibility to create a shadowless space through diffuse reflections. At a 27.4m2 area, illuminance uniformity achieved 88.2% in this model. The other method is analogous with the method used in medical shadowless lamps. Lights will fall on the object in different angles and each light will generate a shadow. By changing the position distribution of multiple lights, increasing the number of light sources, the possibility of obtaining shadowless area will gradually increase. Based on these two approaches, two simple models are proposed showing the optical system designed for the shadowless space. By taking simulation software TracePro as design platform, this paper simulated the two systems.

Gamma ray spectroscopy employing divalent europium-doped alkaline earth halides and digital readout for accurate histogramming

DOEpatents

Cherepy, Nerine Jane; Payne, Stephen Anthony; Drury, Owen B.; Sturm, Benjamin W.

2016-02-09

According to one embodiment, a scintillator radiation detector system includes a scintillator, and a processing device for processing pulse traces corresponding to light pulses from the scintillator, where the processing device is configured to: process each pulse trace over at least two temporal windows and to use pulse digitization to improve energy resolution of the system. According to another embodiment, a scintillator radiation detector system includes a processing device configured to: fit digitized scintillation waveforms to an algorithm, perform a direct integration of fit parameters, process multiple integration windows for each digitized scintillation waveform to determine a correction factor, and apply the correction factor to each digitized scintillation waveform.

Applications of broadband cavity enhanced spectroscopy for measurements of trace gases and aerosols

NASA Astrophysics Data System (ADS)

Washenfelder, R. A.; Attwood, A. R.; Brock, C. A.; Brown, S. S.; Dube, W. P.; Flores, J. M.; Langford, A. O.; Min, K. E.; Rudich, Y.; Stutz, J.; Wagner, N.; Young, C.; Zarzana, K. J.

2015-12-01

Broadband cavity enhanced spectroscopy (BBCES) uses a broadband light source, optical cavity, and multichannel detector to measure light extinction with high sensitivity. This method differs from cavity ringdown spectroscopy, because it uses an inexpensive, incoherent light source and allows optical extinction to be determined simultaneously across a broad wavelength region.Spectral fitting methods can be used to retrieve multiple absorbers across the observed wavelength region. We have successfully used this method to measure glyoxal (CHOCHO), nitrous acid (HONO), and nitrogen dioxide (NO2) from ground-based and aircraft-based sampling platforms. The detection limit (2-sigma) in 5 s for retrievals of CHOCHO, HONO and NO2 is 32, 250 and 80 parts per trillion (pptv).Alternatively, gas-phase absorbers can be chemically removed to allow the accurate determination of aerosol extinction. In the laboratory, we have used the aerosol extinction measurements to determine scattering and absorption as a function of wavelength. We have deployed a ground-based field instrument to measure aerosol extinction, with a detection limit of approximately 0.2 Mm-1 in 1 min.BBCES methods are most widely used in the near-ultraviolet and visible spectral region. Recently, we have demonstrated measurements at 315-350 nm for formaldehyde (CH2O) and NO2. Extending the technique further into the ultraviolet spectral region will allow important additional measurements of trace gas species and aerosol extinction.

13C-MFA delineates the photomixotrophic metabolism of Synechocystis sp. PCC 6803 under light- and carbon-sufficient conditions.

PubMed

You, Le; Berla, Bert; He, Lian; Pakrasi, Himadri B; Tang, Yinjie J

2014-05-01

The central carbon metabolism of cyanobacteria is under debate. For over 50 years, the lack of α-ketoglutarate dehydrogenase has led to the belief that cyanobacteria have an incomplete TCA cycle. Recent in vitro enzymatic experiments suggest that this cycle may in fact be closed. The current study employed (13) C isotopomers to delineate pathways in the cyanobacterium Synechocystis sp. PCC 6803. By tracing the incorporation of supplemented glutamate into the downstream metabolites in the TCA cycle, we observed a direct in vivo transformation of α-ketoglutarate to succinate. Additionally, isotopic tracing of glyoxylate did not show a functional glyoxylate shunt and glyoxylate was used for glycine synthesis. The photomixotrophic carbon metabolism was then profiled with (13) C-MFA under light and carbon-sufficient conditions. We observed that: (i) the in vivo flux through the TCA cycle reactions (α-ketoglutarate → succinate) was minimal (<2%); (ii) the flux ratio of CO2 fixation was six times higher than that of glucose utilization; (iii) the relative flux through the oxidative pentose phosphate pathway was low (<2%); (iv) high flux through malic enzyme served as a main route for pyruvate synthesis. Our results improve the understanding of the versatile metabolism in cyanobacteria and shed light on their application for photo-biorefineries. Copyright © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Disorder-induced losses in photonic crystal waveguides with line defects.

PubMed

Gerace, Dario; Andreani, Lucio Claudio

2004-08-15

A numerical analysis of extrinsic diffraction losses in two-dimensional photonic crystal slabs with line defects is reported. To model disorder, a Gaussian distribution of hole radii in the triangular lattice of airholes is assumed. The extrinsic losses below the light line increase quadratically with the disorder parameter, decrease slightly with increasing core thickness, and depend weakly on the hole radius. For typical values of the disorder parameter the calculated loss values of guided modes below the light line compare favorably with available experimental results.

Estimating bioaccessibility of trace elements in particles suspended in the Athabasca River using sequential extraction.

PubMed

Javed, Muhammad Babar; Shotyk, William

2018-05-10

Employing protocols developed for polar snow and ice, water samples were collected upstream, midstream and downstream of open pit bitumen mines and upgraders along the Lower Athabasca River (AR). The purpose was to: i) estimate the bioaccessibility of trace elements associated with particulate matter in the AR using sequential extraction, and ii) determine whether their forms have been measurably impacted by industrial activities. Of the trace metals known to be enriched in bitumen (V, Ni, Mo and Re), a substantial proportion of V (78-93%) and Ni (35-81%) was found in the residual fraction representing stable minerals. In contrast, Mo and Re were partitioned mainly into more reactive forms (water soluble, acid extractable, reducible and oxidisable). Comparing the non-residual fractions in upstream versus downstream sites, only water soluble Re was significantly (P = 0.005) greater downstream of industry. In respect to the potentially toxic chalcophile elements (Cu, Pb and Tl), no measurable change was observed in Cu and Pb distribution in upstream versus downstream sites. Only residual Tl was found at upstream and midstream sites, whereas a significant proportion of Tl was also present in the reducible fraction in downstream sites. Overall, a greater proportion of trace metals in the residual fraction at midstream sites appears to be due to inputs of atmospheric dust, clearly evident in microscopic images: energy dispersive spectroscopy and x-ray diffraction analyses showed that these particles were predominantly silicates, which are assumed to have limited bioaccessibility. Copyright © 2018 Elsevier Ltd. All rights reserved.

Laser-based trace gas detection of ethane as a result of photo-oxidative damage in chilled cucumber leaves (invited)

NASA Astrophysics Data System (ADS)

Santosa, I. E.; Laarhoven, L. J. J.; Harbinson, J.; Driscoll, S.; Harren, F. J. M.

2003-01-01

At low temperatures, high light intensity induces strong photooxidative lipid peroxidation in chilling sensitive cucumber leaves. A sensitive laser-based photoacoustic detector was employed to monitor on-line the evolution of ethane, one of the end products of lipid peroxidation. The Δv=2 CO laser operated in the 2.62-4.06 μm infrared wavelength region with a maximum intracavity power of 11 W. In combination with an intracavity placed photoacoustic cell the laser was able to detect ethane down to 0.5 part per billion. Cucumber leaf disks chilled in the light produce ethane; the rate of ethane production depends on the applied temperature, light intensity, and period of chilling.

Quantifying the stability of trace explosives under different environmental conditions using electrospray ionization mass spectrometry.

PubMed

Sisco, Edward; Najarro, Marcela; Samarov, Daniel; Lawrence, Jeffrey

2017-04-01

This work investigates the stability of trace (tens of nanograms) deposits of six explosives: erythritol tetranitrate (ETN), pentaerythritol tetranitrate (PETN), cyclotrimethylenetrinitramine (RDX), cyclotetramethylenetetranitramine (HMX), 2,4,6-trinitrotoluene (TNT), and 2,4,6-trinitrophenylmethylnitramine (tetryl) to determine environmental stabilities and lifetimes of trace level materials. Explosives were inkjet printed directly onto substrates and exposed to one of seven environmental conditions (Laboratory, -4°C, 30°C, 47°C, 90% relative humidity, UV light, and ozone) up to 42 days. Throughout the study, samples were extracted and quantified using electrospray ionization mass spectrometry (ESI-MS) to determine the stability of the explosive as a function of time and environmental exposure. Statistical models were then fit to the data and used for pairwise comparisons of the environments. Stability was found to be exposure and compound dependent with minimal sample losses observed for HMX, RDX, and PETN while substantial and rapid losses were observed in all conditions except -4°C for ETN and TNT and in all conditions for tetryl. The results of this work highlight the potential fate of explosive traces when exposed to various environments. Published by Elsevier B.V.

Airborne mapping of Seoul's atmosphere: Trace gas measurements from GeoTASO during KORUS-AQ

NASA Astrophysics Data System (ADS)

Nowlan, C. R.; Al-Saadi, J. A.; Castellanos, P.; Chance, K.; Gonzalez Abad, G.; Janz, S. J.; Judd, L.; Kowalewski, M. G.; Liu, X.

2017-12-01

The Geostationary Trace gas and Aerosol Sensor Optimization (GeoTASO) instrument is a pushbroom airborne remote sensing instrument capable of making measurements of air quality and ocean color using backscattered UV and visible light. GeoTASO is an airborne test-bed for the upcoming Tropospheric Emissions: Monitoring of Pollution (TEMPO) and Geostationary Environment Monitoring Spectrometer (GEMS) geostationary satellite missions, which will measure air quality over North America and Asia, respectively. GeoTASO also acts as a satellite analogue during field campaigns. GeoTASO flew on the NASA Langley Research Center UC-12 aircraft during the Korea-United States Air Quality Study in May-June 2016, collecting spectra over South Korea during 30 flights over 19 flight days. These observations can be used to derive 2-D maps of tropospheric trace gases including ozone, nitrogen dioxide, sulfur dioxide, formaldehyde, nitrous acid and glyoxal below the aircraft at spatial resolutions between 250 m x 250 m and 1 km x 1 km, depending on the gas. We present spatially resolved trace gas retrievals over Seoul and its surrounding industrial regions, and comparisons with correlative satellite and campaign data.

An artificial intelligence approach to classify and analyse EEG traces.

PubMed

Castellaro, C; Favaro, G; Castellaro, A; Casagrande, A; Castellaro, S; Puthenparampil, D V; Salimbeni, C Fattorello

2002-06-01

We present a fully automatic system for the classification and analysis of adult electroencephalograms (EEGs). The system is based on an artificial neural network which classifies the single epochs of trace, and on an Expert System (ES) which studies the time and space correlation among the outputs of the neural network; compiling a final report. On the last 2000 EEGs representing different kinds of alterations according to clinical occurrences, the system was able to produce 80% good or very good final comments and 18% sufficient comments, which represent the documents delivered to the patient. In the remaining 2% the automatic comment needed some modifications prior to be presented to the patient. No clinical false-negative classifications did arise, i.e. no altered traces were classified as 'normal' by the neural network. The analysis method we describe is based on the interpretation of objective measures performed on the trace. It can improve the quality and reliability of the EEG exam and appears useful for the EEG medical reports although it cannot totally substitute the medical doctor who should now read the automatic EEG analysis in light of the patient's history and age.

Quantifying the Stability of Trace Explosives under Different Environmental Conditions using Electrospray Ionization Mass Spectrometry

PubMed Central

Sisco, Edward; Najarro, Marcela; Samarov, Daniel; Lawrence, Jeffrey

2017-01-01

This work investigates the stability of trace (tens of nanograms) deposits of six explosives: erythritol tetranitrate (ETN), pentaerythritol tetranitrate (PETN), cyclotrimethylenetrinitramine (RDX), cyclotetramethylenetetranitramine (HMX), 2,4,6-trinitrotoluene (TNT), and 2,4,6-trinitrophenylmethylnitramine (tetryl) to determine environmental stabilities and lifetimes of trace level materials. Explosives were inkjet printed directly onto substrates and exposed to one of seven environmental conditions (Laboratory, −4 °C, 30 °C, 47 °C, 90 % relative humidity, UV light, and ozone) up to 42 days. Throughout the study, samples were extracted and quantified using electrospray ionization mass spectrometry (ESI-MS) to determine the stability of the explosive as a function of time and environmental exposure. Statistical models were then fit to the data and used for pairwise comparisons of the environments. Stability was found to be exposure and compound dependent with minimal sample losses observed for HMX, RDX, and PETN while substantial and rapid losses were observed in all conditions except −4 °C for ETN and TNT and in all conditions for tetryl. The results of this work highlight the potential fate of explosive traces when exposed to various environments. PMID:28153227

Trace Elements in Basalts From the Siqueiros Fracture Zone: Implications for Melt Migration Models

NASA Astrophysics Data System (ADS)

Pickle, R. C.; Forsyth, D. W.; Saal, A. E.; Nagle, A. N.; Perfit, M. R.

2008-12-01

Incompatible trace element (ITE) ratios in MORB from a variety of locations may provide insights into the melt migration process by constraining aggregated melt compositions predicted by mantle melting and flow models. By using actual plate geometries to create a 3-D thermodynamic mantle model, melt volumes and compositions at all depths and locations may be calculated and binned into cubes using the pHMELTS algorithm [Asimow et al., 2004]. These melts can be traced from each cube to the surface assuming several migration models, including a simplified pressure gradient model and one in which melt is guided upwards by a low permeability compacted layer. The ITE ratios of all melts arriving at the surface are summed, averaged, and compared to those of the actual sample compositions from the various MOR locales. The Siqueiros fracture zone at 8° 20' N on the East Pacific Rise (EPR) comprises 4 intra-transform spreading centers (ITSCs) across 140 km of offset between two longer spreading ridges, and is an excellent study region for several reasons. First, an abundance of MORB data is readily available, and the samples retrieved from ITSCs are unlikely to be aggregated in a long-lived magma chamber or affected by along-axis transport, so they represent melts extracted locally from the mantle. Additionally, samples at Siqueiros span a compositional range from depleted to normal MORB within the fracture zone yet have similar isotopic compositions to samples collected from the 9-10° EPR. This minimizes the effect of assuming a uniform source composition in our melting model despite a heterogeneous mantle, allowing us to consistently compare the actual lava composition with that predicted by our model. Finally, it has been demonstrated with preliminary migration models that incipient melts generated directly below an ITSC may not necessarily erupt at that ITSC but migrate laterally towards a nearby ridge due to enhanced pressure gradients. The close proximity of the ITSCs at Siqueiros to the large ridges bounding the fracture zone provide a good opportunity to model this phenomenon and may help explain the variable ITE ratios found between samples collected within the transform and those near the ridges.

SPHEREx: Understanding the Origin and Evolution of Galaxies Through the Extragalactic Background Light

NASA Astrophysics Data System (ADS)

Zemcov, Michael; SPHEREx Science Team

2018-01-01

The near IR extragalactic background light (EBL) encodes the integrated light production over cosmic history, so traces the total emission from all galaxies along the line of sight up to the ancient first-light objects responsible for the epoch of reionization (EOR). The EBL can be constrained through measurements of anisotropies, taking advantage of the fact that extragalactic populations produce fluctuations with distinct spatial and spectral characteristics from local foregrounds. In particular, EBL anisotropies trace the underlying clustering of faint emission sources, such as stars, galaxies and accreting black holes present during the EOR, dwarf galaxies, and intra-halo light (IHL), all of which are components not readily detected in point source surveys. The fluctuation amplitude observed independently by a number of recent measurements exceeds that expected from the large-scale clustering of known galaxy populations, indicating the presence of a large integrated brightness from these faint and diffuse components. Improved large-area measurements covering the entire near-IR are required to constrain the possible models for the history of emission from stars back to the EOR.SPHEREx brings new capabilities to EBL fluctuation measurements, employing 96 spectral channels covering 0.75 to 5 microns with spectral resolving power R = 41 to 135 that enable SPHEREx to carry out a multi-frequency separation of the integrated light from galaxies, IHL, and EOR components using the rich auto- and cross-correlation information available from two 45 square degree surveys of the ecliptic poles. SPHEREx is an ideal intensity mapping machine, and has the sensitivity to disentangle the history of light production associated with EBL fluctuations. SPHEREx will search for an EOR component its to minimum required level through component separation and spectral fitting techniques optimized for the near-IR. In addition to broad-band intensity mapping that enhances and extends the Euclid survey, uniquely SPHEREx will enable tomography of cosmic large scale structure using line tracers such as Lya, Ha, Hb, O[II] and O[III], as highlighted in community workshops and AAS special sessions over the past several years.

Distinguishing the albedo of exoplanets from stellar activity

NASA Astrophysics Data System (ADS)

Serrano, L. M.; Barros, S. C. C.; Oshagh, M.; Santos, N. C.; Faria, J. P.; Demangeon, O.; Sousa, S. G.; Lendl, M.

2018-03-01

Context. Light curves show the flux variation from the target star and its orbiting planets as a function of time. In addition to the transit features created by the planets, the flux also includes the reflected light component of each planet, which depends on the planetary albedo. This signal is typically referred to as phase curve and could be easily identified if there were no additional noise. As well as instrumental noise, stellar activity, such as spots, can create a modulation in the data, which may be very difficult to distinguish from the planetary signal. Aims: We analyze the limitations imposed by the stellar activity on the detection of the planetary albedo, considering the limitations imposed by the predicted level of instrumental noise and the short duration of the obervations planned in the context of the CHEOPS mission. Methods: As initial condition, we have assumed that each star is characterized by just one orbiting planet. We built mock light curves that included a realistic stellar activity pattern, the reflected light component of the planet and an instrumental noise level, which we have chosen to be at the same level as predicted for CHEOPS. We then fit these light curves to try to recover the reflected light component, assuming the activity patterns can be modeled with a Gaussian process. Results: We estimate that at least one full stellar rotation is necessary to obtain a reliable detection of the planetary albedo. This result is independent of the level of noise, but it depends on the limitation of the Gaussian process to describe the stellar activity when the light curve time-span is shorter than the stellar rotation. As an additional result, we found that with a 6.5 magnitude star and the noise level of CHEOPS, it is possible to detect the planetary albedo up to a lower limit of Rp = 0.03 R*. Finally, in presence of typical CHEOPS gaps in the simulations, we confirm that it is still possible to obtain a reliable albedo.

Proper temperature of the Schwarzschild AdS black hole revisited

NASA Astrophysics Data System (ADS)

Eune, Myungseok; Kim, Wontae

2017-10-01

The Unruh temperature calculated by using the global embedding of the Schwarzschild AdS spacetime into the Minkowski spacetime was identified with the local proper temperature; however, it became imaginary in a certain region outside the event horizon. So, the temperature was assumed to be zero of non-thermal radiation for that region. In this work, we revisit this issue in an exactly soluble two-dimensional Schwarzschild AdS black hole and present an alternative resolution to this problem in terms of the Tolman's procedure. However, the process appears to be non-trivial in the sense that the original procedure assuming the traceless energy-momentum tensor should be extended in such a way that it should cover the non-vanishing case of the energy-momentum tensor in the presence of the trace anomaly. Consequently, we show that the proper temperature turns out to be real everywhere outside the event horizon without any imaginary value, in particular, it vanishes at both the horizon and the asymptotic infinity.

New photoionization models of intergalactic clouds

NASA Technical Reports Server (NTRS)

Donahue, Megan; Shull, J. M.

1991-01-01

New photoionization models of optically thin low-density intergalactic gas at constant pressure, photoionized by QSOs, are presented. All ion stages of H, He, C, N, O, Si, and Fe, plus H2 are modeled, and the column density ratios of clouds at specified values of the ionization parameter of n sub gamma/n sub H and cloud metallicity are predicted. If Ly-alpha clouds are much cooler than the previously assumed value, 30,000 K, the ionization parameter must be very low, even with the cooling contribution of a trace component of molecules. If the clouds cool below 6000 K, their final equilibrium must be below 3000 K, owing to the lack of a stable phase between 6000 and 3000 K. If it is assumed that the clouds are being irradiated by an EUV power-law continuum typical of WSOs, with J0 = 10 exp -21 ergs/s sq cm Hz, typical cloud thicknesses along the line of sight that are much smaller than would be expected from shocks, thermal instabilities, or gravitational collapse are derived.

Uncertainties associated with parameter estimation in atmospheric infrasound arrays.

PubMed

Szuberla, Curt A L; Olson, John V

2004-01-01

This study describes a method for determining the statistical confidence in estimates of direction-of-arrival and trace velocity stemming from signals present in atmospheric infrasound data. It is assumed that the signal source is far enough removed from the infrasound sensor array that a plane-wave approximation holds, and that multipath and multiple source effects are not present. Propagation path and medium inhomogeneities are assumed not to be known at the time of signal detection, but the ensemble of time delays of signal arrivals between array sensor pairs is estimable and corrupted by uncorrelated Gaussian noise. The method results in a set of practical uncertainties that lend themselves to a geometric interpretation. Although quite general, this method is intended for use by analysts interpreting data from atmospheric acoustic arrays, or those interested in designing and deploying them. The method is applied to infrasound arrays typical of those deployed as a part of the International Monitoring System of the Comprehensive Nuclear-Test-Ban Treaty Organization.

Better reproductive healthcare for women with disabilities: a role for nursing leadership.

PubMed

Phillips, Lorraine J; Phillips, Win

2006-01-01

This paper examines the reproductive healthcare experiences of women with disabilities in the light of commonly accepted principles of biomedical ethics. Recommendations are made for nursing to assume a leadership role in reducing gender and disability inequity in health care.

The research of the style of angel lobster eye x-ray optical system

NASA Astrophysics Data System (ADS)

Cheng, HuaQi; Liu, YuJiao; Zhang, ShaoWei; Hou, LinBao; Li, XingLong

2018-01-01

This paper has developed the theory research of wide field Angel lobster eye X-ray optical system based on the principle of entirely incidence. Combine the configuration characteristic of lobster eye, recommend the conclusion of beam of light focus on the half of radius whether point or parallel light. Designed the microchannel through the principle of real ray trace and got the relationship among different parameters about it using numerical value emulation. Got pixels and illumination pictures validated the wide field focus characteristic of Angel lobster eye by simulating the optical system.

Contribution to the theory of photopic vision: Retinal phenomena

NASA Technical Reports Server (NTRS)

Calvet, H.

1979-01-01

Principles of thermodynamics are applied to the study of the ultramicroscopic anatomy of the inner eye. Concepts introduced and discussed include: the retina as a three-dimensional sensor, light signals as coherent beams in relation to the dimensions of retinal pigments, pigment effects topographed by the conjugated antennas effect, visualizing lights, the autotropic function of hemoglobin and some cytochromes, and reversible structural arrangements during photopic adaptation. A paleoecological diagram is presented which traces the evolution of scotopic vision (primitive system) to photopic vision (secondary system) through the emergence of structures sensitive to the intensity, temperature, and wavelengths of the visible range.

Regge calculus and observations. II. Further applications.

NASA Astrophysics Data System (ADS)

Williams, Ruth M.; Ellis, G. F. R.

1984-11-01

The method, developed in an earlier paper, for tracing geodesies of particles and light rays through Regge calculus space-times, is applied to a number of problems in the Schwarzschild geometry. It is possible to obtain accurate predictions of light bending by taking sufficiently small Regge blocks. Calculations of perihelion precession, Thomas precession, and the distortion of a ball of fluid moving on a geodesic can also show good agreement with the analytic solution. However difficulties arise in obtaining accurate predictions for general orbits in these space-times. Applications to other problems in general relativity are discussed briefly.

Hierarchical majorana neutrinos from democratic mass matrices

NASA Astrophysics Data System (ADS)

Yang, Masaki J. S.

2016-09-01

In this paper, we obtain the light neutrino masses and mixings consistent with the experiments, in the democratic texture approach. The essential ansatz is that νRi are assumed to transform as ;right-handed fields; 2R +1R under the S3L ×S3R symmetry. The symmetry breaking terms are assumed to be diagonal and hierarchical. This setup only allows the normal hierarchy of the neutrino mass, and excludes both of inverted hierarchical and degenerated neutrinos. Although the neutrino sector has nine free parameters, several predictions are obtained at the leading order. When we neglect the smallest parameters ζν and ζR, all components of the mixing matrix UPMNS are expressed by the masses of light neutrinos and charged leptons. From the consistency between predicted and observed UPMNS, we obtain the lightest neutrino masses m1 = (1.1 → 1.4) meV, and the effective mass for the double beta decay 〈mee 〉 ≃ 4.5 meV.

The Burrell Schmidt Deep Virgo Survey: Tidal Debris, Galaxy Halos, and Diffuse Intracluster Light in the Virgo Cluster

NASA Astrophysics Data System (ADS)

Mihos, J. Christopher; Harding, Paul; Feldmeier, John J.; Rudick, Craig; Janowiecki, Steven; Morrison, Heather; Slater, Colin; Watkins, Aaron

2017-01-01

We present the results of a deep imaging survey of the Virgo cluster of galaxies, concentrated around the cores of Virgo subclusters A and B. The goal of this survey was to detect and study very low surface brightness features present in Virgo, including discrete tidal features, the faint halos of luminous galaxies, and the diffuse intracluster light (ICL). Our observations span roughly 16 degrees2 in two filters, reaching a 3σ limiting depth of {μ }B = 29.5 and {μ }V = 28.5 mag arcsec-2. At these depths, our limiting systematic uncertainties are astrophysical: variations in faint background sources as well as scattered light from galactic dust. We show that this dust-scattered light is well traced by deep far-infrared imaging, making it possible to separate it from true diffuse light in Virgo. We use our imaging to trace and measure the color of the diffuse tidal streams and ICL in the Virgo core near M87, in fields adjacent to the core including the M86/M84 region, and to the south of the core around M49 and subcluster B, along with the more distant W{}\\prime cloud around NGC 4365. Overall, the bulk of the projected ICL is found in the Virgo core and within the W{}\\prime cloud; we find little evidence for an extensive ICL component in the field around M49. The bulk of the ICL we detect is fairly red in color (B - V = 0.7-0.9), indicative of old, evolved stellar populations. Based on the luminosity of the observed ICL features in the cluster, we estimate a total Virgo ICL fraction of 7%-15%. This value is somewhat smaller than that expected for massive, evolved clusters, suggesting that Virgo is still in the process of growing its extended ICL component. We also trace the shape of M87's extremely boxy outer halo out to ˜150 kpc, and show that the current tidal stripping rate from low luminosity galaxies is insufficient to have built M87's outer halo over a Hubble time. We identify a number of previously unknown low surface brightness structures around galaxies projected close to M86 and M84. The extensive diffuse light seen in the infalling W{}\\prime cloud around NGC 4365 is likely to be subsumed in the general Virgo ICL component once the group enters the cluster, illustrating the importance of group infall in generating ICL. Finally, we also identify another large and extremely low surface brightness ultradiffuse galaxy, likely in the process of being shredded by the cluster tidal field. With the survey complete, the full imaging data set is now available for public release.

Quantitative Examination of a Large Sample of Supra-Arcade Downflows in Eruptive Solar Flares

NASA Technical Reports Server (NTRS)

Savage, Sabrina L.; McKenzie, David E.

2011-01-01

Sunward-flowing voids above post-coronal mass ejection flare arcades were first discovered using the soft X-ray telescope aboard Yohkoh and have since been observed with TRACE (extreme ultraviolet (EUV)), SOHO/LASCO (white light), SOHO/SUMER (EUV spectra), and Hinode/XRT (soft X-rays). Supra-arcade downflow (SAD) observations suggest that they are the cross-sections of thin flux tubes retracting from a reconnection site high in the corona. Supra-arcade downflowing loops (SADLs) have also been observed under similar circumstances and are theorized to be SADs viewed from a perpendicular angle. Although previous studies have focused on dark flows because they are easier to detect and complementary spectral data analysis reveals their magnetic nature, the signal intensity of the flows actually ranges from dark to bright. This implies that newly reconnected coronal loops can contain a range of hot plasma density. Previous studies have presented detailed SAD observations for a small number of flares. In this paper, we present a substantial SADs and SADLs flare catalog. We have applied semiautomatic detection software to several of these events to detect and track individual downflows thereby providing statistically significant samples of parameters such as velocity, acceleration, area, magnetic flux, shrinkage energy, and reconnection rate. We discuss these measurements (particularly the unexpected result of the speeds being an order of magnitude slower than the assumed Alfven speed), how they were obtained, and potential impact on reconnection models.

The role of public law-based litigation in tobacco companies' strategies in high-income, FCTC ratifying countries, 2004-14.

PubMed

Steele, Sarah L; Gilmore, Anna B; McKee, Martin; Stuckler, David

2016-09-01

Tobacco companies use a host of strategies to undermine public health efforts directed to reduce and eliminate smoking. The success, failure and trends in domestic litigation used by tobacco companies to undermine tobacco control are not well understood, with commentators often assuming disputes are trade related or international in nature. We analyse domestic legal disputes involving tobacco companies and public health actors in high-income countries across the last decade to ascertain the types of action and the success or failure of cases, develop effective responses. WorldLii, a publicly available online law repository, was used to identify domestic court cases involving tobacco companies from 2004 to 2014, while outcome data from LexisNexis and Westlaw databases were used to identify appeals and trace case history. We identified six domestic cases in the UK, Australia and Canada, noting that the tobacco industry won only one of six cases; a win later usurped by legislative reform and a further court case. Nevertheless, we found cases involve significant resource costs for governments, often progressing across multiple jurisdictional levels. We suggest that, in light of our results, while litigation takes up significant time and incurs legal costs for health ministries, policymakers must robustly fend off suggestions that litigation wastes taxpayers' money, pointing to the good prospects of winning such legal battles. © The Author 2015. Published by Oxford University Press on behalf of Faculty of Public Health.

No Martian soil component in shergottite meteorites

NASA Astrophysics Data System (ADS)

Barrat, J. A.; Jambon, A.; Ferrière, L.; Bollinger, C.; Langlade, J. A.; Liorzou, C.; Boudouma, O.; Fialin, M.

2014-01-01

We report on the major and trace element geochemistry of the impact melts contained in some shergottite meteorites. It has been previously proposed that some of these impact melts formed from a mixture of the host rock and a Martian soil component (e.g., Rao et al., 1999) or from partially weathered portions of the host rock (Chennaoui Aoudjehane et al., 2012). Our results contradict both of these theories. Trace element abundances of a glass pod from the EETA 79001A meteorite are identical to those of the host lithology, and indicate that no additional component is required in this case. The impact melts in Tissint share the same trace element features as the host rock, and no secondary phases produced by Martian secondary processes are involved. The light rare earth enrichments displayed by two small samples of Tissint (Chennaoui Aoudjehane et al., 2012) are possibly the result of some contamination of small stones on desert soil before the recovery of the meteorites.

Solar Proton Transport Within an ICRU Sphere Surrounded by a Complex Shield: Ray-trace Geometry

NASA Technical Reports Server (NTRS)

Slaba, Tony C.; Wilson, John W.; Badavi, Francis F.; Reddell, Brandon D.; Bahadori, Amir A.

2015-01-01

A computationally efficient 3DHZETRN code with enhanced neutron and light ion (Z is less than or equal to 2) propagation was recently developed for complex, inhomogeneous shield geometry described by combinatorial objects. Comparisons were made between 3DHZETRN results and Monte Carlo (MC) simulations at locations within the combinatorial geometry, and it was shown that 3DHZETRN agrees with the MC codes to the extent they agree with each other. In the present report, the 3DHZETRN code is extended to enable analysis in ray-trace geometry. This latest extension enables the code to be used within current engineering design practices utilizing fully detailed vehicle and habitat geometries. Through convergence testing, it is shown that fidelity in an actual shield geometry can be maintained in the discrete ray-trace description by systematically increasing the number of discrete rays used. It is also shown that this fidelity is carried into transport procedures and resulting exposure quantities without sacrificing computational efficiency.

Solar proton exposure of an ICRU sphere within a complex structure part II: Ray-trace geometry.

PubMed

Slaba, Tony C; Wilson, John W; Badavi, Francis F; Reddell, Brandon D; Bahadori, Amir A

2016-06-01

A computationally efficient 3DHZETRN code with enhanced neutron and light ion (Z ≤ 2) propagation was recently developed for complex, inhomogeneous shield geometry described by combinatorial objects. Comparisons were made between 3DHZETRN results and Monte Carlo (MC) simulations at locations within the combinatorial geometry, and it was shown that 3DHZETRN agrees with the MC codes to the extent they agree with each other. In the present report, the 3DHZETRN code is extended to enable analysis in ray-trace geometry. This latest extension enables the code to be used within current engineering design practices utilizing fully detailed vehicle and habitat geometries. Through convergence testing, it is shown that fidelity in an actual shield geometry can be maintained in the discrete ray-trace description by systematically increasing the number of discrete rays used. It is also shown that this fidelity is carried into transport procedures and resulting exposure quantities without sacrificing computational efficiency. Published by Elsevier Ltd.

Analysis of stray radiation for infrared optical system

NASA Astrophysics Data System (ADS)

Li, Yang; Zhang, Tingcheng; Liao, Zhibo; Mu, Shengbo; Du, Jianxiang; Wang, Xiangdong

2016-10-01

Based on the theory of radiation energy transfer in the infrared optical system, two methods for stray radiation analysis caused by interior thermal radiation in infrared optical system are proposed, one of which is important sampling method technique using forward ray trace, another of which is integral computation method using reverse ray trace. The two methods are discussed in detail. A concrete infrared optical system is provided. Light-tools is used to simulate the passage of radiation from the mirrors and mounts. Absolute values of internal irradiance on the detector are received. The results shows that the main part of the energy on the detector is due to the critical objects which were consistent with critical objects obtained by reverse ray trace, where mirror self-emission contribution is about 87.5% of the total energy. Corresponding to the results, the irradiance on the detector calculated by the two methods are in good agreement. So the validity and rationality of the two methods are proved.

Visual detection of trace nitroaromatic explosive residue using photoluminescent metallole-containing polymers.

PubMed

Toal, Sarah J; Sanchez, Jason C; Dugan, Regina E; Trogler, William C

2007-01-01

The detection of trace explosives is important for forensic, military, and homeland security applications. Detection of widely used nitroaromatic explosives (trinitrotoluene [TNT], 2,4-dinitrotoluene [DNT], picric acid [PA]) was carried out using photoluminescent metallole-containing polymers. The method of detection is through the quenching of fluorescence of thin films of the polymer, prepared by spray coating organic solutions of the polymer, by the explosive analyte. Visual quenching of luminescence (lambda(em) approximately 400-510 nm) in the presence of the explosive is seen immediately upon illumination with near-UV light (lambda(ex)=360 nm). Detection limits were observed to be as low as 5 ng for TNT, 20 ng for DNT, and 5 ng for PA. In addition, experiments with normal production line explosives and their components show that this technology is also able to detect composition B, Pyrodex, and nitromethane. This method offers a convenient and sensitive method of detection of trace nitroaromatic explosive residue.

Coronal Rain, Solar Storm

NASA Image and Video Library

2010-03-19

Explanation: In this picture, the Sun's surface is quite dark. A frame from a movie recorded on November 9th by the orbiting TRACE telescope, it shows coronal loops lofted over a solar active region. Glowing brightly in extreme ultraviolet light, the hot plasma entrained above the Sun along arching magnetic fields is cooling and raining back down on the solar surface. Hours earlier, on November 8th, astronomers had watched this particular active region produce a not so spectacular solar flare. Still, the M-class flare spewed forth an intense storm of particles, suddenly showering satellites near the Earth with high energy protons. The flare event was also associated with a large coronal mass ejection, a massive cloud of material which impacted our fair planet's magnetic field about 31 hours later. The result ... a strong geomagnetic storm. Credit: NASA/GSFC/TRACE To learn more go to: nasascience.nasa.gov/missions/trace To learn more about NASA's Sun Earth Day go here: sunearthday.nasa.gov/2010/index.php

A Photoluminescence-Based Field Method for Detection of Traces of Explosives

PubMed Central

Menzel, E. Roland; Menzel, Laird W.; Schwierking, Jake R.

2004-01-01

We report a photoluminescence-based field method for detecting traces of explosives. In its standard version, the method utilizes a commercially available color spot test kit for treating explosive traces on filter paper after swabbing. The colored products are fluorescent under illumination with a laser that operates on three C-size flashlight batteries and delivers light at 532 nm. In the fluorescence detection mode, by visual inspection, the typical sensitivity gain is a factor of 100. The method is applicable to a wide variety of explosives. In its time-resolved version, intended for in situ work, explosives are tagged with europium complexes. Instrumentation-wise, the time-resolved detection, again visual, can be accomplished in facile fashion. The europium luminescence excitation utilizes a laser operating at 355 nm. We demonstrate the feasibility of CdSe quantum dot sensitization of europium luminescence for time-resolved purposes. This would allow the use of the above 532 nm laser. PMID:15349512

Research on fiber-optic cantilever-enhanced photoacoustic spectroscopy for trace gas detection

NASA Astrophysics Data System (ADS)

Chen, Ke; Zhou, Xinlei; Gong, Zhenfeng; Yu, Shaochen; Qu, Chao; Guo, Min; Yu, Qingxu

2018-01-01

We demonstrate a new scheme of cantilever-enhanced photoacoustic spectroscopy, combining a sensitivity-improved fiber-optic cantilever acoustic sensor with a tunable high-power fiber laser, for trace gas detection. The Fabry-Perot interferometer based cantilever acoustic sensor has advantages such as high sensitivity, small size, easy to install and immune to electromagnetic. Tunable erbium-doped fiber ring laser with an erbium-doped fiber amplifier is used as the light source for acoustic excitation. In order to improve the sensitivity for photoacoustic signal detection, a first-order longitudinal resonant photoacoustic cell with the resonant frequency of 1624 Hz and a large size cantilever with the first resonant frequency of 1687 Hz are designed. The size of the cantilever is 2.1 mm×1 mm, and the thickness is 10 μm. With the wavelength modulation spectrum and second-harmonic detection methods, trace ammonia (NH3) has been measured. The gas detection limits (signal-to-noise ratio = 1) near the wavelength of 1522.5 nm is achieved to be 3 ppb.

Novel third-order Lovelock wormhole solutions

NASA Astrophysics Data System (ADS)

Mehdizadeh, Mohammad Reza; Lobo, Francisco S. N.

2016-06-01

In this work, we consider wormhole geometries in third-order Lovelock gravity and investigate the possibility that these solutions satisfy the energy conditions. In this framework, by applying a specific equation of state, we obtain exact wormhole solutions, and by imposing suitable values for the parameters of the theory, we find that these geometries satisfy the weak energy condition in the vicinity of the throat, due to the presence of higher-order curvature terms. Finally, we trace out a numerical analysis, by assuming a specific redshift function, and find asymptotically flat solutions that satisfy the weak energy condition throughout the spacetime.

Physics and the car business

NASA Astrophysics Data System (ADS)

Compton, W. Dale; Reitz, John R.

1981-01-01

Physicists have made important contributions to many areas of Ford Motor Company activity, particularly in areas of basic and applied research and product development. A number have assumed positions with management responsibility. Many of the technical problems facing the automotive industry today require a fundamental understanding, and the ability of physicists to contribute to the solution of these problems is greater now than it has been in the past. The present paper discusses some of these problems, and also traces a few case histories of physicists at Ford Motor Company; these illustrate the wide diversity of career paths for persons entering industry with a physics background.

Optimizing detector geometry for trace element mapping by X-ray fluorescence

DOE PAGES

Sun, Yue; Gleber, Sophie -Charlotte; Jacobsen, Chris; ...

2015-01-01

We report that trace metals play critical roles in a variety of systems, ranging from cells to photovoltaics. X-Ray Fluorescence (XRF) microscopy using X-ray excitation provides one of the highest sensitivities available for imaging the distribution of trace metals at sub-100 nm resolution. With the growing availability and increasing performance of synchrotron light source based instruments and X-ray nanofocusing optics, and with improvements in energy-dispersive XRF detectors, what are the factors that limit trace element detectability? To address this question, we describe an analytical model for the total signal incident on XRF detectors with various geometries, including the spectral responsemore » of energy dispersive detectors. This model agrees well with experimentally recorded X-ray fluorescence spectra, and involves much shorter calculation times than with Monte Carlo simulations. With such a model, one can estimate the signal when a trace element is illuminated with an X-ray beam, and when just the surrounding non-fluorescent material is illuminated. From this signal difference, a contrast parameter can be calculated and this can in turn be used to calculate the signal-to-noise ratio (S/N) for detecting a certain elemental concentration. We apply this model to the detection of trace amounts of zinc in biological materials, and to the detection of small quantities of arsenic in semiconductors. In conclusion, we conclude that increased detector collection solid angle is (nearly) always advantageous even when considering the scattered signal. However, given the choice between a smaller detector at 90° to the beam versus a larger detector at 180° (in a backscatter-like geometry), the 90° detector is better for trace element detection in thick samples, while the larger detector in 180° geometry is better suited to trace element detection in thin samples.« less

Optimizing detector geometry for trace element mapping by X-ray fluorescence

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

Sun, Yue; Gleber, Sophie -Charlotte; Jacobsen, Chris

We report that trace metals play critical roles in a variety of systems, ranging from cells to photovoltaics. X-Ray Fluorescence (XRF) microscopy using X-ray excitation provides one of the highest sensitivities available for imaging the distribution of trace metals at sub-100 nm resolution. With the growing availability and increasing performance of synchrotron light source based instruments and X-ray nanofocusing optics, and with improvements in energy-dispersive XRF detectors, what are the factors that limit trace element detectability? To address this question, we describe an analytical model for the total signal incident on XRF detectors with various geometries, including the spectral responsemore » of energy dispersive detectors. This model agrees well with experimentally recorded X-ray fluorescence spectra, and involves much shorter calculation times than with Monte Carlo simulations. With such a model, one can estimate the signal when a trace element is illuminated with an X-ray beam, and when just the surrounding non-fluorescent material is illuminated. From this signal difference, a contrast parameter can be calculated and this can in turn be used to calculate the signal-to-noise ratio (S/N) for detecting a certain elemental concentration. We apply this model to the detection of trace amounts of zinc in biological materials, and to the detection of small quantities of arsenic in semiconductors. In conclusion, we conclude that increased detector collection solid angle is (nearly) always advantageous even when considering the scattered signal. However, given the choice between a smaller detector at 90° to the beam versus a larger detector at 180° (in a backscatter-like geometry), the 90° detector is better for trace element detection in thick samples, while the larger detector in 180° geometry is better suited to trace element detection in thin samples.« less

Mohammed Al-Bussairi: A Towering Linguistic Figure from Sudan

ERIC Educational Resources Information Center

Siddiek, Ahmed Gumaa

2017-01-01

This paper sheds light on the late Mohammed Al-Busairi's affluent academic journey. I will trace his education and his work experience in teaching, supervision, translation, literature, with special focus on his writings on lexicography and dictionary making. We will read some of his works with critical clues. The man had a massive contribution to…

The Importance of Artificial Light in the Development of Night Photography.

ERIC Educational Resources Information Center

Wood, Deloris

This study traces the development of night photography, from February 7, 1839, when the effect of the moon on a Daguerreotype was first recorded by Alexander Von Humboldt, to the present. The contributions of the following photographers who advanced the field of night photography are discussed: Margaret Bourke-White, Paul Martin, Brassai, Bill…

SOURCE APPORTIONMENT OF INDOOR, OUTDOOR, AND PERSONAL PM2.5 IN SEATTLE, WASHINGTON, USING POSITIVE MATRIX FACTORIZATION

EPA Science Inventory

As part of a large exposure assessment and health effects panel study, 33 trace elements and light-absorbing carbon were measured on 24-hr particulate matter with an aero-dynamic diameter <2.5 um (PM2.5) fixed-site filter samples collected between September 26, 2000, and May 25, ...

Light atom quantum oscillations in UC and US

DOE PAGES

Yiu, Yuen; Aczel, Adam A.; Granroth, Garrett E.; ...

2016-01-19

High energy vibrational scattering in the binary systems UC and US is measured using time-of-flight inelastic neutron scattering. A clear set of well-defined peaks equally separated in energy is observed in UC, corresponding to harmonic oscillations of the light C atoms in a cage of heavy U atoms. The scattering is much weaker in US and only a few oscillator peaks are visible. We show how the difference between the materials can be understood by considering the neutron scattering lengths and masses of the lighter atoms. Monte Carlo ray tracing is used to simulate the scattering, with near quantitative agreementmore » with the data in UC, and some differences with US. The possibility of observing anharmonicity and anisotropy in the potentials of the light atoms is investigated in UC. Lastly, the observed data is well accounted for by considering each light atom as a single atom isotropic quantum harmonic oscillator.« less

A novel screen design for anti-ambient light front projection display with angle-selective absorber

NASA Astrophysics Data System (ADS)

Liao, Tianju; Chen, Weigang; He, Kebo; Zhang, Zhaoyu

2016-03-01

Ambient light is destructive to the reflective type projection system's contrast ratio which has great influence on the image quality. In contrast to the conventional front projection, short-throw projection has its advantage to reject the ambient light. Fresnel lens-shaped reflection layer is adapted to direct light from a large angle due to the low lens throw ratio to the viewing area. The structure separates the path of the ambient light and projection light, creating the chance to solve the problem that ambient light is mixed with projection light. However, with solely the lens-shaped reflection layer is not good enough to improve the contrast ratio due to the scattering layer, which contributes a necessarily wide viewing angle, could interfere with both light paths before hitting the layer. So we propose a new design that sets the draft angle surface with absorption layer and adds an angle-selective absorber to separate these two kinds of light. The absorber is designed to fit the direction of the projection light, leading to a small absorption cross section for the projection light and respectfully big absorption cross section for the ambient light. We have calculated the design with Tracepro, a ray tracing program and find a nearly 8 times contrast ratio improvement against the current design in theory. This design can hopefully provide efficient display in bright lit situation with better viewer satisfaction.

Measurement of the attenuation length of argon scintillation light in the ArDM LAr TPC

NASA Astrophysics Data System (ADS)

Calvo, J.; Cantini, C.; Crivelli, P.; Daniel, M.; Di Luise, S.; Gendotti, A.; Horikawa, S.; Molina-Bueno, L.; Montes, B.; Mu, W.; Murphy, S.; Natterer, G.; Nguyen, K.; Periale, L.; Quan, Y.; Radics, B.; Regenfus, C.; Romero, L.; Rubbia, A.; Santorelli, R.; Sergiampietri, F.; Viant, T.; Wu, S.

2018-01-01

We report on a measurement of the attenuation length for the scintillation light in the tonne size liquid argon target of the ArDM dark matter experiment. The data was recorded in the first underground operation of the experiment in single-phase operational mode. The results were achieved by comparing the light yield spectra from 39Ar and 83mKr to a description of the ArDM setup with a model of full light ray tracing. A relatively low value close to 0.5 m was found for the attenuation length of the liquid argon bulk to its own scintillation light. We interpret this result as a presence of optically active impurities in the liquid argon which are not filtered by the installed purification systems. We also present analyses of the argon gas employed for the filling and discuss cross sections in the vacuum ultraviolet of various molecules in respect to purity requirements in the context of large liquid argon installations.

Analysis of condition for uniform lighting generated by array of light emitting diodes with large view angle.

PubMed

Qin, Zong; Wang, Kai; Chen, Fei; Luo, Xiaobing; Liu, Sheng

2010-08-02

In this research, the condition for uniform lighting generated by array of LEDs with large view angle was studied. The luminous intensity distribution of LED is not monotone decreasing with view angle. A LED with freeform lens was designed as an example for analysis. In a system based on LEDs designed in house with a thickness of 20mm and rectangular arrangement, the condition for uniform lighting was derived and the analytical results demonstrated that the uniformity was not decreasing monotonously with the increasing of LED-to-LED spacing. The illuminance uniformities were calculated with Monte Carlo ray tracing simulations and the uniformity was found to increase with the increasing of certain LED-to-LED spacings anomalously. Another type of large view angle LED and different arrangements were discussed in addition. Both analysis and simulation results showed that the method is available for LED array lighting system design on the basis of large view angle LED..

Latent class analysis to evaluate performance of point-of-care CCA for low-intensity Schistosoma mansoni infections in Burundi.

PubMed

Clements, Michelle N; Corstjens, Paul L A M; Binder, Sue; Campbell, Carl H; de Dood, Claudia J; Fenwick, Alan; Harrison, Wendy; Kayugi, Donatien; King, Charles H; Kornelis, Dieuwke; Ndayishimiye, Onesime; Ortu, Giuseppina; Lamine, Mariama Sani; Zivieri, Antonio; Colley, Daniel G; van Dam, Govert J

2018-02-23

Kato-Katz examination of stool smears is the field-standard method for detecting Schistosoma mansoni infection. However, Kato-Katz misses many active infections, especially of light intensity. Point-of-care circulating cathodic antigen (CCA) is an alternative field diagnostic that is more sensitive than Kato-Katz when intensity is low, but interpretation of CCA-trace results is unclear. To evaluate trace results, we tested urine and stool specimens from 398 pupils from eight schools in Burundi using four approaches: two in Burundi and two in a laboratory in Leiden, the Netherlands. In Burundi, we used Kato-Katz and point-of-care CCA (CCAB). In Leiden, we repeated the CCA (CCAL) and also used Up-Converting Phosphor Circulating Anodic Antigen (CAA). We applied Bayesian latent class analyses (LCA), first considering CCA traces as negative and then as positive. We used the LCA output to estimate validity of the prevalence estimates of each test in comparison to the population-level infection prevalence and estimated the proportion of trace results that were likely true positives. Kato-Katz yielded the lowest prevalence (6.8%), and CCAB with trace considered positive yielded the highest (53.5%). There were many more trace results recorded by CCA in Burundi (32.4%) than in Leiden (2.3%). Estimated prevalence with CAA was 46.5%. LCA indicated that Kato-Katz had the lowest sensitivity: 15.9% [Bayesian Credible Interval (BCI): 9.2-23.5%] with CCA-trace considered negative and 15.0% with trace as positive (BCI: 9.6-21.4%), implying that Kato-Katz missed approximately 85% of infections. CCAB underestimated disease prevalence when trace was considered negative and overestimated disease prevalence when trace was considered positive, by approximately 12 percentage points each way, and CAA overestimated prevalence in both models. Our results suggest that approximately 52.2% (BCI: 37.8-5.8%) of the CCAB trace readings were true infections. Whether measured in the laboratory or the field, CCA outperformed Kato-Katz at the low infection intensities in Burundi. CCA with trace as negative likely missed many infections, whereas CCA with trace as positive overestimated prevalence. In the absence of a field-friendly gold standard diagnostic, the use of a variety of diagnostics with differing properties will become increasingly important as programs move towards elimination of schistosomiasis. It is clear that CCA is a valuable tool for the detection and mapping of S. mansoni infection in the field and CAA may be a valuable field tool in the future.

A comparison of gantry-mounted x-ray-based real-time target tracking methods.

PubMed

Montanaro, Tim; Nguyen, Doan Trang; Keall, Paul J; Booth, Jeremy; Caillet, Vincent; Eade, Thomas; Haddad, Carol; Shieh, Chun-Chien

2018-03-01

Most modern radiotherapy machines are built with a 2D kV imaging system. Combining this imaging system with a 2D-3D inference method would allow for a ready-made option for real-time 3D tumor tracking. This work investigates and compares the accuracy of four existing 2D-3D inference methods using both motion traces inferred from external surrogates and measured internally from implanted beacons. Tumor motion data from 160 fractions (46 thoracic/abdominal patients) of Synchrony traces (inferred traces), and 28 fractions (7 lung patients) of Calypso traces (internal traces) from the LIGHT SABR trial (NCT02514512) were used in this study. The motion traces were used as the ground truth. The ground truth trajectories were used in silico to generate 2D positions projected on the kV detector. These 2D traces were then passed to the 2D-3D inference methods: interdimensional correlation, Gaussian probability density function (PDF), arbitrary-shape PDF, and the Kalman filter. The inferred 3D positions were compared with the ground truth to determine tracking errors. The relationships between tracking error and motion magnitude, interdimensional correlation, and breathing periodicity index (BPI) were also investigated. Larger tracking errors were observed from the Calypso traces, with RMS and 95th percentile 3D errors of 0.84-1.25 mm and 1.72-2.64 mm, compared to 0.45-0.68 mm and 0.74-1.13 mm from the Synchrony traces. The Gaussian PDF method was found to be the most accurate, followed by the Kalman filter, the interdimensional correlation method, and the arbitrary-shape PDF method. Tracking error was found to strongly and positively correlate with motion magnitude for both the Synchrony and Calypso traces and for all four methods. Interdimensional correlation and BPI were found to negatively correlate with tracking error only for the Synchrony traces. The Synchrony traces exhibited higher interdimensional correlation than the Calypso traces especially in the anterior-posterior direction. Inferred traces often exhibit higher interdimensional correlation, which are not true representation of thoracic/abdominal motion and may underestimate kV-based tracking errors. The use of internal traces acquired from systems such as Calypso is advised for future kV-based tracking studies. The Gaussian PDF method is the most accurate 2D-3D inference method for tracking thoracic/abdominal targets. Motion magnitude has significant impact on 2D-3D inference error, and should be considered when estimating kV-based tracking error. © 2018 American Association of Physicists in Medicine.

A New Stochastic Approach to Predict Peak and Residual Shear Strength of Natural Rock Discontinuities

NASA Astrophysics Data System (ADS)

Casagrande, D.; Buzzi, O.; Giacomini, A.; Lambert, C.; Fenton, G.

2018-01-01

Natural discontinuities are known to play a key role in the stability of rock masses. However, it is a non-trivial task to estimate the shear strength of large discontinuities. Because of the inherent complexity to access to the full surface of the large in situ discontinuities, researchers or engineers tend to work on small-scale specimens. As a consequence, the results are often plagued by the well-known scale effect. A new approach is here proposed to predict shear strength of discontinuities. This approach has the potential to avoid the scale effect. The rationale of the approach is as follows: a major parameter that governs the shear strength of a discontinuity within a rock mass is roughness, which can be accounted for by surveying the discontinuity surface. However, this is typically not possible for discontinuities contained within the rock mass where only traces are visible. For natural surfaces, it can be assumed that traces are, to some extent, representative of the surface. It is here proposed to use the available 2D information (from a visible trace, referred to as a seed trace) and a random field model to create a large number of synthetic surfaces (3D data sets). The shear strength of each synthetic surface can then be estimated using a semi-analytical model. By using a large number of synthetic surfaces and a Monte Carlo strategy, a meaningful shear strength distribution can be obtained. This paper presents the validation of the semi-analytical mechanistic model required to support the new approach for prediction of discontinuity shear strength. The model can predict both peak and residual shear strength. The second part of the paper lays the foundation of a random field model to support the creation of synthetic surfaces having statistical properties in line with those of the data of the seed trace. The paper concludes that it is possible to obtain a reasonable estimate of peak and residual shear strength of the discontinuities tested from the information from a single trace, without having access to the whole surface.

The Use of Pro/Engineer CAD Software and Fishbowl Tool Kit in Ray-tracing Analysis

NASA Technical Reports Server (NTRS)

Nounu, Hatem N.; Kim, Myung-Hee Y.; Ponomarev, Artem L.; Cucinotta, Francis A.

2009-01-01

This document is designed as a manual for a user who wants to operate the Pro/ENGINEER (ProE) Wildfire 3.0 with the NASA Space Radiation Program's (SRP) custom-designed Toolkit, called 'Fishbowl', for the ray tracing of complex spacecraft geometries given by a ProE CAD model. The analysis of spacecraft geometry through ray tracing is a vital part in the calculation of health risks from space radiation. Space radiation poses severe risks of cancer, degenerative diseases and acute radiation sickness during long-term exploration missions, and shielding optimization is an important component in the application of radiation risk models. Ray tracing is a technique in which 3-dimensional (3D) vehicle geometry can be represented as the input for the space radiation transport code and subsequent risk calculations. In ray tracing a certain number of rays (on the order of 1000) are used to calculate the equivalent thickness, say of aluminum, of the spacecraft geometry seen at a point of interest called the dose point. The rays originate at the dose point and terminate at a homogenously distributed set of points lying on a sphere that circumscribes the spacecraft and that has its center at the dose point. The distance a ray traverses in each material is converted to aluminum or other user-selected equivalent thickness. Then all equivalent thicknesses are summed up for each ray. Since each ray points to a direction, the aluminum equivalent of each ray represents the shielding that the geometry provides to the dose point from that particular direction. This manual will first list for the user the contact information for help in installing ProE and Fishbowl in addition to notes on the platform support and system requirements information. Second, the document will show the user how to use the software to ray trace a Pro/E-designed 3-D assembly and will serve later as a reference for troubleshooting. The user is assumed to have previous knowledge of ProE and CAD modeling.

Quantitative Analysis of Trace Element Impurity Levels in Some Gem-Quality Diamonds

NASA Astrophysics Data System (ADS)

McNeill, J. C.; Klein-Bendavid, O.; Pearson, D. G.; Nowell, G. M.; Ottley, C. J.; Chinn, I.; Malarkey, J.

2009-05-01

Perhaps the most important information required to understand the origin of diamonds is the nature of the fluid that they crystallise from. Constraining the identity of the diamond-forming fluid for high purity gem diamonds is hampered by analytical challenges because of the very low analyte levels involved. Here we use a new ultra- low blank 'off-line' laser ablation method coupled to sector-field ICPMS for the quantitative analysis of fluid-poor gem diamonds. Ten diamonds comprised of both E- and P-type parageneses, from the Premier Mine, South Africa, were analysed for trace element abundances. We assume that the elemental signatures arise from low densities of sub-microscopic fluid inclusions that are analogous to the much higher densities of fluid inclusions commonly found within fluid-rich diamonds exhibiting fibrous growth. Repeatability of multiple (>20) blanks yielded consistently low values so that using the current procedure our limits of quantitation (10-ã blank) are <1pg for most trace elements, except for Sr, Zr, Ba, from 2-9pg and Pb ~30pg. Trace element patterns of the Premier diamond suite show enrichment of LREE over HREE. Abundances broadly decrease with increasing elemental compatibility. As a suite the chondrite normalised diamond patterns show negative Sr, Zr, Ti and Y anomalies and positive U, and Pb anomalies. All sample abundances are very depleted relative to chondrites (0.1 to 0.001X ch). HREE range from 0.1 to 1ppb as do Y, Nb, Cs. Other lighter elements vary from 2-30ppb. Pb reaches several ppb and Ti ranges from ppb values up to 2ppm. No significant difference were observed between the trace element systematics of the eclogitic and peridotitic diamonds. Overall, these initial data have inter-element fractionation patterns similar to those evident from fluid-rich fibrous diamonds and can be sued to infer that both types of diamond-forming fluids share a common origin.

The Red Light Receptor Phytochrome B Directly Enhances Substrate-E3 Ligase Interactions to Attenuate Ethylene Responses.

PubMed

Shi, Hui; Shen, Xing; Liu, Renlu; Xue, Chang; Wei, Ning; Deng, Xing Wang; Zhong, Shangwei

2016-12-05

Plants germinating under subterranean darkness assume skotomorphogenesis, a developmental program strengthened by ethylene in response to mechanical pressure of soil. Upon reaching the surface, light triggers a dramatic developmental transition termed de-etiolation that requires immediate termination of ethylene responses. Here, we report that light activation of photoreceptor phyB results in rapid degradation of EIN3, the master transcription factor in the ethylene signaling pathway. As a result, light rapidly and efficiently represses ethylene actions. Specifically, phyB directly interacts with EIN3 in a light-dependent manner and also physically associates with F box protein EBFs. The light-activated association of phyB, EIN3, and EBF1/EBF2 proteins stimulates robust EIN3 degradation by SCF EBF1/EBF2 E3 ligases. We reveal that phyB manipulates substrate-E3 ligase interactions in a light-dependent manner, thus directly controlling the stability of EIN3. Our findings illustrate a mechanistic model of how plants transduce light information to immediately turn off ethylene signaling for de-etiolation initiation. Copyright © 2016 Elsevier Inc. All rights reserved.

Golden gravitational lensing systems from the Sloan Lens ACS Survey - II. SDSS J1430+4105: a precise inner total mass profile from lensing alone

NASA Astrophysics Data System (ADS)

Eichner, Thomas; Seitz, Stella; Bauer, Anne

2012-12-01

We study the Sloan Lens ACS (SLACS) survey strong-lensing system SDSS J1430+4105 at zl = 0.285. The lensed source (zs = 0.575) of this system has a complex morphology with several subcomponents. Its subcomponents span a radial range from 4 to 10 kpc in the plane of the lens. Therefore, we can constrain the slope of the total projected mass profile around the Einstein radius from lensing alone. We measure a density profile that is slightly but not significantly shallower than isothermal at the Einstein radius. We decompose the mass of the lensing galaxy into a de Vaucouleurs component to trace the stars and an additional dark component. The spread of multiple-image components over a large radial range also allows us to determine the amplitude of the de Vaucouleurs and dark matter components separately. We get a mass-to-light ratio of M de Vauc LB ≈ (5.5±1.5) M⊙L⊙,B and a dark matter fraction within the Einstein radius of ≈20 to 40 per cent. Modelling the star formation history assuming composite stellar populations at solar metallicity to the galaxy's photometry yields a mass-to-light ratio of M, salp LB ≈ 4.0-1.3+0.6 M⊙L⊙,B and M, chab LB ≈ 2.3-0.8+0.3 M⊙L⊙,B for Salpeter and Chabrier initial mass functions, respectively. Hence, the mass-to-light ratio derived from lensing is more Salpeter like, in agreement with results for massive Coma galaxies and other nearby massive early-type galaxies. We examine the consequences of the galaxy group in which the lensing galaxy is embedded, showing that it has little influence on the mass-to-light ratio obtained for the de Vaucouleurs component of the lensing galaxy. Finally, we decompose the projected, azimuthally averaged 2D density distribution of the de Vaucouleurs and dark matter components of the lensing signal into spherically averaged 3D density profiles. We can show that the 3D dark and luminous matter density within the Einstein radius (REin ≈ 0.6 Reff) of this SLACS galaxy is similar to the values of Coma galaxies with the same velocity dispersions.

Ocular aberrations with ray tracing and Shack-Hartmann wave-front sensors: Does polarization play a role?

NASA Astrophysics Data System (ADS)

Marcos, Susana; Diaz-Santana, Luis; Llorente, Lourdes; Dainty, Chris

2002-06-01

Ocular aberrations were measured in 71 eyes by using two reflectometric aberrometers, employing laser ray tracing (LRT) (60 eyes) and a Shack-Hartmann wave-front sensor (S-H) (11 eyes). In both techniques a point source is imaged on the retina (through different pupil positions in the LRT or a single position in the S-H). The aberrations are estimated by measuring the deviations of the retinal spot from the reference as the pupil is sampled (in LRT) or the deviations of a wave front as it emerges from the eye by means of a lenslet array (in the S-H). In this paper we studied the effect of different polarization configurations in the aberration measurements, including linearly polarized light and circularly polarized light in the illuminating channel and sampling light in the crossed or parallel orientations. In addition, completely depolarized light in the imaging channel was obtained from retinal lipofuscin autofluorescence. The intensity distribution of the retinal spots as a function of entry (for LRT) or exit pupil (for S-H) depends on the polarization configuration. These intensity patterns show bright corners and a dark area at the pupil center for crossed polarization, an approximately Gaussian distribution for parallel polarization and a homogeneous distribution for the autofluorescence case. However, the measured aberrations are independent of the polarization states. These results indicate that the differences in retardation across the pupil imposed by corneal birefringence do not produce significant phase delays compared with those produced by aberrations, at least within the accuracy of these techniques. In addition, differences in the recorded aerial images due to changes in polarization do not affect the aberration measurements in these reflectometric aberrometers.

CALCLENS: weak lensing simulations for large-area sky surveys and second-order effects in cosmic shear power spectra

NASA Astrophysics Data System (ADS)

Becker, Matthew R.

2013-10-01

I present a new algorithm, Curved-sky grAvitational Lensing for Cosmological Light conE simulatioNS (CALCLENS), for efficiently computing weak gravitational lensing shear signals from large N-body light cone simulations over a curved sky. This new algorithm properly accounts for the sky curvature and boundary conditions, is able to produce redshift-dependent shear signals including corrections to the Born approximation by using multiple-plane ray tracing and properly computes the lensed images of source galaxies in the light cone. The key feature of this algorithm is a new, computationally efficient Poisson solver for the sphere that combines spherical harmonic transform and multigrid methods. As a result, large areas of sky (˜10 000 square degrees) can be ray traced efficiently at high resolution using only a few hundred cores. Using this new algorithm and curved-sky calculations that only use a slower but more accurate spherical harmonic transform Poisson solver, I study the convergence, shear E-mode, shear B-mode and rotation mode power spectra. Employing full-sky E/B-mode decompositions, I confirm that the numerically computed shear B-mode and rotation mode power spectra are equal at high accuracy (≲1 per cent) as expected from perturbation theory up to second order. Coupled with realistic galaxy populations placed in large N-body light cone simulations, this new algorithm is ideally suited for the construction of synthetic weak lensing shear catalogues to be used to test for systematic effects in data analysis procedures for upcoming large-area sky surveys. The implementation presented in this work, written in C and employing widely available software libraries to maintain portability, is publicly available at http://code.google.com/p/calclens.

Ponderomotive and weakly relativistic self-focusing of Gaussian laser beam in plasma: Effect of light absorption

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

Patil, S. D., E-mail: sdpatilphy@gmail.com; Takale, M. V.

2016-05-06

This paper presents an influence of light absorption on self-focusing of laser beam propagation in plasma. The differential equation for beam-width parameter is obtained using the Wentzel-Kramers-Brillouin and paraxial approximations through parabolic equation approach. The nonlinearity in dielectric function is assumed to be aroused due to the combined effect of weakly relativistic and ponderomotive regime. To highlight the nature of propagation, behavior of beam-width parameter with dimensionless distance of propagation is presented graphically and discussed. The present work is helpful to understand issues related to the beam propagation in laser plasma interaction experiments where light absorption plays a vital role.

The structure, mixing angle, mass and couplings of the light scalar f0(500) and f0(980) mesons

NASA Astrophysics Data System (ADS)

Agaev, S. S.; Azizi, K.; Sundu, H.

2018-06-01

The mixing angle, mass and couplings of the light scalar mesons f0 (500) and f0 (980) are calculated in the framework of QCD two-point sum rule approach by assuming that they are tetraquarks with diquark-antidiquark structures. The mesons are treated as mixtures of the heavy | H > = ([ su ] [ s bar u bar ] + [ sd ] [ s bar d bar ]) /√{ 2 } and light | L > = [ ud ] [ u bar d bar ] scalar diquark-antidiquark components. We extract from corresponding sum rules the mixing angles φH and φL of these states and evaluate the masses and couplings of the particles f0 (500) and f0 (980).

Infrared analysis of LMC superbubbles

NASA Technical Reports Server (NTRS)

Verter, Fran; Dwek, Eli

1990-01-01

Researchers are analyzing three superbubbles in the Large Magellanic Cloud (LMC), cataloged by Meaburn (1980) as LMC-1, LMC-4 (a.k.a. Shapley Constellation III), and LMC-5. Superbubbles are the largest infrared sources in the disks of external galaxies. Their expansion requires multiple supernovae from successive generations of star formation. In LMC superbubbles, the grains swept up by shocks and winds represent an interstellar medium (ISM) whose abundances are quite different from the Galaxy. By applying the Dwek (1986) grain model, we can derive the composition and size spectrum of the grains. The inputs to this model are the dust emission in the four Infrared Astronomy Satellite (IRAS) bands and the interstellar radiation field (ISRF) that provides the heating. The first step in the project is to derive the ISRF for star-forming regions on the periphery of superbubbles. Researchers are doing this by combining observations at several wavelengths to determine the energy budget of the region. They will use a UV image to trace the ionizing stellar radiation that escapes, an H alpha image to trace the ionizing stellar radiation that is absorbed by gas, and the four IRAS images to trace the stellar radiation, both ionizing and non-ionizing, that is absorbed by dust. This multi-wavelength approach has the advantages that we do not have to assume the shape of the IMF or the extinction of the source.

Probing the local environment of the supernova remnant HESS J1731-347 with CO and CS observations

NASA Astrophysics Data System (ADS)

Maxted, N.; Burton, M.; Braiding, C.; Rowell, G.; Sano, H.; Voisin, F.; Capasso, M.; Pühlhofer, G.; Fukui, Y.

2018-02-01

The shell-type supernova remnant HESS J1731 - 347 emits TeV gamma-rays, and is a key object for the study of the cosmic ray acceleration potential of supernova remnants. We use 0.5-1 arcmin Mopra CO/CS(1-0) data in conjunction with H I data to calculate column densities towards the HESS J1731 - 347 region. We trace gas within at least four Galactic arms, typically tracing total (atomic+molecular) line-of-sight H column densities of 2-3× 1022 cm-2. Assuming standard X-factor values and that most of the H I/CO emission seen towards HESS J1731 - 347 is on the near-side of the Galaxy, X-ray absorption column densities are consistent with H I+CO-derived column densities foreground to, but not beyond, the Scutum-Crux Galactic arm, suggesting a kinematic distance of ˜3.2 kpc for HESS J1731 - 347. At this kinematic distance, we also find dense, infrared-dark gas traced by CS(1-0) emission coincident with the north of HESS J1731 - 347, the nearby H II region G353.43-0.37 and the nearby unidentified gamma-ray source HESS J1729 - 345. This dense gas lends weight to the idea that HESS J1729 - 345 and HESS J1731 - 347 are connected, perhaps via escaping cosmic-rays.

Global Estimates of Trace Gas Fluxes Affected by Land Use Change and Irrigation of Major Crops

NASA Astrophysics Data System (ADS)

Ojima, D. S.; del Grosso, S.; Parton, W. J.; Keough, C.

2005-12-01

Cropland conversions have altered many fertile regions of the earth and have modified the biogeochemical and hydrological cycling in these regions. These croplands are significant sources of N trace gas emissions however, the extent of changing trace gas emission due to land management changes and irrigation need further analysis. We use the DAYCENT biogeochemical model which is a daily time step version of the CENTURY model. DAYCENT simulates fluxes of N2O between croplands and the atmosphere for major crop types, and allows for a dynamic representation of GHG fluxes that accounts for environmental conditions, soil characteristics, climate, specific crop qualities, and fertilizer and irrigation management practices. DAYCENT is applied to all world cropland regions. Global datasets of weather, soils, native vegetation and cropping fractions were mapped to an approximate 2° x 2° resolution. Non-spatial data (such as planting date and fertilizer application rates) were assigned as point values for each region (i.e. country), and were assumed to be similar within crop types across the region. Three major crops were simulated (corn, wheat and soybeans) under both irrigated and non-irrigated conditions. Results indicate that N2O emission for maize and soy bean increase between 3 to 10%, where as wheat emission decline by about 1% when irrigated systems are compared to non-irrigated systems.

Surface Ocean Radiocarbon Reservoir Ages From Land-Sea Tephra Correlation Constrains Deglacial Chronology and Ocean Circulation in the Southeast Bering Sea

NASA Astrophysics Data System (ADS)

Cook, M. S.; Miller, R.; White-Nockleby, C.; Chapman, A.; Mix, A. C.

2017-12-01

Radiocarbon estimates of the past ocean are valuable because unlike passive tracers, radiocarbon has the potential to trace both the distribution and rate of transport of water masses. Most studies using paired radiocarbon measurements on planktonic and benthic foraminifera assume that the surface reservoir age was constant at the preindustrial value, which if incorrect, can strongly bias radiocarbon reconstructions. The subarctic Pacific is ringed by volcanic arcs, and there is great potential to use tephrochronology as a stratigraphic tool in sediments from the last glacial and deglaciation, and assign calendar ages to the marine sediment without relying on calibrated planktonic radiocarbon ages. In this study, we use major and trace element analysis of volcanic glass to match tephras between radiocarbon-dated lake cores from Sanak Island in the eastern Aleutians to marine cores from Umnak Plateau in the southeast Bering Sea. There are numerous thin tephras preserved in laminated sediments from the Bolling-Allerod and early Holocene in marine cores from depths (1000-1500 m) within the modern oxygen minimum zone. We find that trace elements are crucial in distinguishing tephras from individual eruptions. Our preliminary radiocarbon measurements suggest that the benthic-atmosphere radiocarbon differences and marine surface reservoir ages in the Bolling-Allerod are similar to pre-industrial values, supporting previously published radiocarbon reconstructions from the region.

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

Spitz, A.H.; Boynton, W.V.

Six ureilites (ALHA77257, ALHA81101, ALH82130, PCA82506, Kanna, and Novo Urei) were analyzed using neutron activation analysis for Ca, Sc, Cr, Mn, Fe, Co, Ni, Zn, Ga, REE, W, Re, Os, Ir, and Au. The authors examined bulk samples as well as acid-treated samples. In bulk samples the refractory siderophiles' concentrations range from approximately 0.1 to 1.0 times CI chondrites while the volatile siderophiles' concentrations range from approximately 0.1 to 1.0 times CI chondrites while the volatile siderophiles range from about 0.07 to 0.3 times CI chondrites. Rare earth elements (REEs) in ureilites are quite depleted and display light and heavymore » rare earth enrichments. The Antarctic meteorites display either much less pronounced v-shaped patterns or no enrichment in the light rare earths at all. In terms of the new trace-element results, ureilites do not fall into the coherent groups that other workers have defined by chemical or petrographic characteristics. Trace elements do provide additional constraints on the models for the petrogenesis of ureilites. In particular, the siderophile element abundances call for simplified models of chemical processing rather than the complex, multistage processing called for in silicate fractionation models. REE concentrations, on the other hand, imply multistage processing to produce the ureilites. None of the ureilite petrogenesis models extant account for the trace element data. These new data and the considerations of them with respect to the proposed ureilite petrogenesis models indicate that the direction of modeling should be toward contemplation of mixtures and how the components the authors observe in ureilites behave under such conditions.« less

Laser vaporization of trace explosives for enhanced non-contact detection

NASA Astrophysics Data System (ADS)

Furstenberg, Robert; Papantonakis, Michael; Kendziora, Christopher A.; Bubb, Daniel M.; Corgan, Jeffrey; McGill, R. Andrew

2010-04-01

Trace explosives contamination is found primarily in the form of solid particulates on surfaces, due to the low vapor pressure of most explosives materials. Today, the standard sampling procedure involves physical removal of particulate matter from surfaces of interest. A variety of collection methods have been used including air-jetting or swabbing surfaces of interest. The sampled particles are typically heated to generate vapor for analysis in hand held, bench top, or portal detection systems. These sampling methods are time-consuming (and hence costly), require a skilled technician for optimal performance, and are inherently non-selective, allowing non-explosives particles to be co-sampled and analyzed. This can adversely affect the sensitivity and selectivity of detectors, especially those with a limited dynamic range. We present a new approach to sampling solid particles on a solid surface that is targeted, non-contact, and which selectively enhances trace explosive signatures thus improving the selectivity and sensitivity of existing detectors. Our method involves the illumination of a surface of interest with infrared laser light with a wavelength that matches a distinctive vibrational mode of an explosive. The resonant coupling of laser energy results in rapid heating of explosive particles and rapid release of a vapor plume. Neighboring particles unrelated to explosives are generally not directly heated as their vibrational modes are not resonant with the laser. As a result, the generated vapor plume includes a higher concentration of explosives than if the particles were heated with a non-selective light source (e.g. heat lamp). We present results with both benchtop infrared lasers as well as miniature quantum cascade lasers.

Coupled optical-thermal-fluid and structural analyses of novel light-trapping tubular panels for concentrating solar power receivers

NASA Astrophysics Data System (ADS)

Ortega, Jesus D.; Christian, Joshua M.; Yellowhair, Julius E.; Ho, Clifford K.

2015-09-01

Traditional tubular receivers used in concentrating solar power are formed using tubes connected to manifolds to form panels; which in turn are arranged in cylindrical or rectangular shapes. Previous and current tubular receivers, such as the ones used in Solar One, Solar Two, and most recently the Ivanpah solar plants, have used a black paint coating to increase the solar absorptance of the receiver. However, these coatings degrade over time and must be reapplied, increasing the receiver maintenance cost. This paper presents the thermal efficiency evaluation of novel receiver tubular panels that have a higher effective solar absorptance due to a light-trapping effect created by arranging the tubes in each panel into unique geometric configurations. Similarly, the impact of the incidence angle on the effective solar absorptance and thermal efficiency is evaluated. The overarching goal of this work is to achieve effective solar absorptances of ~90% and thermal efficiencies above 85% without using an absorptance coating. Several panel geometries were initially proposed and were down-selected based on structural analyses considering the thermal and pressure loading requirements of molten salt and supercritical carbon-dioxide receivers. The effective solar absorptance of the chosen tube geometries and panel configurations were evaluated using the ray-tracing modeling capabilities of SolTrace. The thermal efficiency was then evaluated by coupling computational fluid dynamics with the ray-tracing results using ANSYS Fluent. Compared to the base case analysis (flat tubular panel), the novel tubular panels have shown an increase in effective solar absorptance and thermal efficiency by several percentage points.

Evaluation of methods for trace-element determination with emphasis on their usability in the clinical routine laboratory.

PubMed

Bolann, B J; Rahil-Khazen, R; Henriksen, H; Isrenn, R; Ulvik, R J

2007-01-01

Commonly used techniques for trace-element analysis in human biological material are flame atomic absorption spectrometry (FAAS), graphite furnace atomic absorption spectrometry (GFAAS), inductively coupled plasma atomic emission spectrometry (ICP-AES) and inductively coupled plasma mass spectrometry (ICP-MS). Elements that form volatile hydrides, first of all mercury, are analysed by hydride generation techniques. In the absorption techniques the samples are vaporized into free, neutral atoms and illuminated by a light source that emits the atomic spectrum of the element under analysis. The absorbance gives a quantitative measure of the concentration of the element. ICP-AES and ICP-MS are multi-element techniques. In ICP-AES the atoms of the sample are excited by, for example, argon plasma at very high temperatures. The emitted light is directed to a detector, and the optical signals are processed to values for the concentrations of the elements. In ICP-MS a mass spectrometer separates and detects ions produced by the ICP, according to their mass-to-charge ratio. Dilution of biological fluids is commonly needed to reduce the effect of the matrix. Digestion using acids and microwave energy in closed vessels at elevated pressure is often used. Matrix and spectral interferences may cause problems. Precautions should be taken against trace-element contamination during collection, storage and processing of samples. For clinical problems requiring the analysis of only one or a few elements, the use of FAAS may be sufficient, unless the higher sensitivity of GFAAS is required. For screening of multiple elements, however, the ICP techniques are preferable.

Rectangular illumination using a secondary optics with cylindrical lens for LED street light.

PubMed

Chen, Hsi-Chao; Lin, Jun-Yu; Chiu, Hsuan-Yi

2013-02-11

The illumination pattern of an LED street light is required to have a rectangular distribution at a divergence-angle ratio of 7:3 for economical illumination. Hence, research supplying a secondary optics with two cylindrical lenses was different from free-form curvature for rectangular illumination. The analytical solution for curvatures with different ratio rectangles solved this detail by light tracing and boundary conditions. Similarities between the experiments and the simulation for a single LED and a 9-LED module were analyzed by Normalized Cross Correlation (NCC), and the error rate was studied by the Root Mean Square (RMS). The tolerance of position must be kept under ± 0.2 mm in the x, y and z directions to ensure that the relative illumination is over 99%.

Hydrologic data collected in Maumelle and Winona reservoir systems, central Arkansas, May 1989 through October 1992

USGS Publications Warehouse

Green, W. Reed; Louthian, Bobbie L.

1993-01-01

Physical, chemical, and biological water-quality data were collected and compiled for sites located in the Lakes Maumelle and Winona reservoir systems May 5, 1989, to October 30, 1992. Data were collected in order to establish a comprehensive water-quality data base for the two systems and will be used in water-quality interpretive chemical variables (temperature, pH, specific conductance, dissolved oxygen, light transparency, and penetration); solids, and major cations and anions); trace metals; organics (pesticides and industrial organic chemicals); and biological components (bacteria and chlorophyll-a); and nutrients, trace metals, and organic contaminants in bed material. Reservoir sedimentation was measured by comparing fathometry measurements taken during the study to pre-impoundment tophographic maps.

Why the Brain Knows More than We Do: Non-Conscious Representations and Their Role in the Construction of Conscious Experience

PubMed Central

Dresp-Langley, Birgitta

2011-01-01

Scientific studies have shown that non-conscious stimuli and representations influence information processing during conscious experience. In the light of such evidence, questions about potential functional links between non-conscious brain representations and conscious experience arise. This article discusses neural model capable of explaining how statistical learning mechanisms in dedicated resonant circuits could generate specific temporal activity traces of non-conscious representations in the brain. How reentrant signaling, top-down matching, and statistical coincidence of such activity traces may lead to the progressive consolidation of temporal patterns that constitute the neural signatures of conscious experience in networks extending across large distances beyond functionally specialized brain regions is then explained. PMID:24962683

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

Anand, Sampurn; Mohanty, Subhendra; Dey, Ujjal Kumar, E-mail: sampurn@prl.res.in, E-mail: ujjal@cts.iitkgp.ernet.in, E-mail: mohanty@prl.res.in

Cosmological phase transitions can be a source of Stochastic Gravitational Wave (SGW) background. Apart from the dynamics of the phase transition, the characteristic frequency and the fractional energy density Ω{sub gw} of the SGW depends upon the temperature of the transition. In this article, we compute the SGW spectrum in the light of QCD equation of state provided by the lattice results. We find that the inclusion of trace anomaly from lattice QCD, enhances the SGW signal generated during QCD phase transition by ∼ 50% and the peak frequency of the QCD era SGW are shifted higher by ∼ 25%more » as compared to the earlier estimates without trace anomaly. This result is extremely significant for testing the phase transition dynamics near QCD epoch.« less

Chemical characteristics and origin of H chondrite regolith breccias

NASA Technical Reports Server (NTRS)

Lipschutz, M. E.; Biswas, S.; Mcsween, H. Y., Jr.

1983-01-01

Petrologic data and contents of Ag, Bi, Cd, Co, Cs, Ga, In, Rb, Se, Te, Tl and Zn-trace elements spanning the volatility/mobility range-in light and dark portions of H chondrite regolith breccias and L chondrite fragmental breccias are reported. The chemical/petrologic characteristics of H chondrite regolith breccias differ from those of nonbrecciated chondrites or fragmental breccias. Petrologic characteristics and at least some trace element contents of H chondrite regolith breccias reflect primary processes; contents of the most volatile/mobile elements may reflect either primary or secondary processing, possibly within layered H chondrite parent object(s). Chemical/petrologic differences existed in different regions of the parent(s). Regoligh formation and gardening and meteoroid compaction were not so severe as to alter compositions markedly.

Hollow Waveguide Gas Sensor for Mid-Infrared Trace Gas Analysis

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

Kim, S; Young, C; Chan, J

2007-07-12

A hollow waveguide mid-infrared gas sensor operating from 1000 cm{sup -1} to 4000 cm{sup -1} has been developed, optimized, and its performance characterized by combining a FT-IR spectrometer with Ag/Ag-halide hollow core optical fibers. The hollow core waveguide simultaneously serves as a light guide and miniature gas cell. CH{sub 4} was used as test analyte during exponential dilution experiments for accurate determination of the achievable limit of detection (LOD). It is shown that the optimized integration of an optical gas sensor module with FT-IR spectroscopy provides trace sensitivity at the few hundreds of parts-per-billion concentration range (ppb, v/v) for CH{submore » 4}.« less

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

Miller, L. B.; Donohoe, S. P.; Jones, M. H.

This article reports on the testing and comparison of a prototype hydrogen fuel cell light tower (H2LT) and a conventional diesel-powered metal halide light trailer for use in road maintenance and construction activities. The prototype was originally outfitted with plasma lights and then with light-emitting diode (LED) luminaires. Light output and distribution, lighting energy efficiency (i.e., efficacy), power source thermal efficiency, and fuel costs are compared. The metal halide luminaires have 2.2 and 3.1 times more light output than the plasma and LED luminaires, respectively, but they require more power/lumen to provide that output. The LED luminaires have 1.6 timesmore » better light efficacy than either the metal halide or plasma luminaires. The light uniformity ratios produced by the plasma and LED towers are acceptable. The fuel cell thermal efficiency at the power required to operate the plasma lights is 48%, significantly higher than the diesel generator efficiency of 23% when operating the metal halide lights. Due to the increased efficiency of the fuel cell and the LED lighting, the fuel cost per lumen-hour of the H2LT is 62% of the metal halide diesel light tower assuming a kilogram of hydrogen is twice the cost of a gallon of diesel fuel.« less

Trace Contaminant Control: An In-Depth Study of a Silica-Titania Composite for Photocatalytic Remediation of Closed-Environment Habitat Air

NASA Technical Reports Server (NTRS)

Coutts, Janelle L.

2013-01-01

This collection of studies focuses on a PCO system for the oxidation of a model compound, ethanol, using an adsorption-enhanced silica-TiO2 composite (STC) as the photocatalyst; studies are aimed at addressing the optimization of various parameters including light source, humidity, temperature, and possible poisoning events for use as part of a system for gaseous trace-contaminant control system in closed-environment habitats. The first goal focused on distinguishing the effect of photon flux (i.e., photons per unit time reaching a surface) from that of photon energy (i.e., wavelength) of a photon source on the PCO of ethanol. Experiments were conducted in a bench-scale annular reactor packed with STC pellets and irradiated with either a UV-A fluorescent black light blue lamp O max=365 nm) at its maximum light intensity or a UV-C germicidal lamp O. max=254 nm) at three levels of light intensity. The STC-catalyzed oxidation of ethanol was found to follow zero-order kinetics with respect to CO2 production, regardless of the photon source. Increased photon flux led to increased EtOH removal, mineralization, and oxidation rate accompanied by lower intermediate concentration in the effluent. The oxidation rate was higher in the reactor irradiated by UV-C than by UV-A (38.4 vs. 31.9 nM s-1 ) at the same photon flux, with similar trends for mineralization (53.9 vs. 43.4%) and reaction quantum efficiency (i.e., photonic efficiency, 63.3 vs. 50.1 nmol C02 mol photons-1 ). UV-C irradiation also led to decreased intermediate concentration in the effluent compared to UV -A irradiation. These results demonstrated that STC-catalyzed oxidation is enhanced by both increased photon flux and photon energy. The effect of temperature and relative humidity on the STC-catalyzed degradation of ethanol was also determined using the UV-A light source at its maximum intensity.

Can Biomass Burning Explain Isotopically Light Fe in Marine Aerosols?

NASA Astrophysics Data System (ADS)

Sherry, A. M.; Anbar, A. D.; Herckes, P.; Romaniello, S. J.

2016-02-01

Iron (Fe) is an important micronutrient that limits primary productivity in large parts of the ocean. In these regions, atmospheric aerosol deposition is an important source of Fe to the surface ocean and thus has a critical impact on ocean biogeochemistry. Fe-bearing aerosols originate from many sources with potentially distinct Fe isotopic compositions. Consequently, Fe isotopes may provide a new tool to trace the sources of aerosol Fe to the oceans. Mead et al. (2013) first discovered that Fe in the fine fraction of Bermuda aerosols is often isotopically lighter than Fe from known anthropogenic and crustal sources. 1 These authors suggested that this light isotopic signature was likely the result of biomass burning, since Fe in plants is the only known source of isotopically light Fe. More recently, Conway et al. found that Fe in the soluble fraction of aerosols collected during 2010-2011 North Atlantic GEOTRACES cruises also showed light isotope values, which they likewise attributed to biomass burning.2 These studies are further supported by new modeling work which suggests that biomass burning aerosols should contribute significant amounts of soluble Fe to tropical and southern oceans.3To test if biomass burning releases aerosols with a light Fe isotope composition, we are conducting lab-scale biomass burning experiments using natural samples of vegetation and leaf litter. Burn aerosols were collected on cellulose filters, then digested and analyzed for trace metal concentrations using inductively-coupled mass spectrometry (ICP-MS). Fe isotopes were determined by using multiple collector ICP-MS following separation and purification of Fe using anion exchange chromatography. We will discuss metal concentration and isotope data from these experiments with implications for the interpretation of Fe isotope signals in aerosol samples. 1Mead, C et al. GRL, 2013, 40, 5722-5727. 2 Conway, T et al. Goldschmidt Abs 2015 593. 3Ito, A. ES&T Lett, 2015, 2, 70-75.

Demystifying Organizational Transformation: A Poetical Look at "Tomorrow's Schools".

ERIC Educational Resources Information Center

Mitchell, Brad; Varner, Donna

It is widely assumed that empowerment represents the organizational transformation strategy to help schools fulfill a broad array of announced goals, such as academic excellence, economic prosperity, military security, and social equity. This paper directs a demystifying light on the rhetoric and rationality of organizational transformation theory…

MOCVD-Grown InGaAsP Double Heterostructure Diode Lasers

DTIC Science & Technology

1993-08-01

assuming refractive index and its dispersion for InGaAsP and InGaP corresponding to the known values for AIGaAs compounds with the same bandgap [13...in the refractive index between the waveguide and cladding layers provides light confinement within the optical cavity. Separate optical and

Super-Parent: An Analysis of State Educational Controls.

ERIC Educational Resources Information Center

Erickson, Donald A.

This study represents an attempt to discern what responsibility the State should assume for regulating the education of the young, and what is the most defensible approach to fulfilling that responsibility. Analyses of this type could be timely, especially in the light of the spreading "alternative schools" movement; growing recognition among…

Enhanced Nonlinear Optical Devices Using Artificial Slow-Light Structures

DTIC Science & Technology

2010-08-19

through a slit of about 2 mm width. Lock -in detection is performed by modulating the 86 MHz pulse train at 2 kHz, and average incident power is 75 mW...condition [8]: knωt = nk ω t +mK, (5) where n is the harmonic order, K is a reciprocal lattice vector with |K| = 2π/Λ, Λ is the aperture spacing, m is the...diffraction order, and kt represents a transverse light wave- vector . For a square lattice, and assuming that the optical wavevectors have only the x̂

Spatial distribution of fluorescent light emitted from neon and nitrogen excited by low energy electron beams

NASA Astrophysics Data System (ADS)

Morozov, A.; Krücken, R.; Ulrich, A.; Wieser, J.

2006-11-01

Side-view intensity profiles of fluorescent light were measured for neon and nitrogen excited with 12keV electron beams at gas pressures from 250to1400hPa. The intensity profiles were compared with theoretical profiles calculated using the CASINO program which performs Monte Carlo simulations of electron scattering. It was assumed that the spatial distribution of fluorescent intensity is directly proportional to the spatial distribution of energy loss by primary electrons. The comparison shows good correlation of experimental data and the results of numeric simulations.

A study on a portable fluorescence imaging system

NASA Astrophysics Data System (ADS)

Chang, Han-Chao; Wu, Wen-Hong; Chang, Chun-Li; Huang, Kuo-Cheng; Chang, Chung-Hsing; Chiu, Shang-Chen

2011-09-01

The fluorescent reaction is that an organism or dye, excited by UV light (200-405 nm), emits a specific frequency of light; the light is usually a visible or near infrared light (405-900 nm). During the UV light irradiation, the photosensitive agent will be induced to start the photochemical reaction. In addition, the fluorescence image can be used for fluorescence diagnosis and then photodynamic therapy can be given to dental diseases and skin cancer, which has become a useful tool to provide scientific evidence in many biomedical researches. However, most of the methods on acquiring fluorescence biology traces are still stay in primitive stage, catching by naked eyes and researcher's subjective judgment. This article presents a portable camera to obtain the fluorescence image and to make up a deficit from observer competence and subjective judgment. Furthermore, the portable camera offers the 375nm UV-LED exciting light source for user to record fluorescence image and makes the recorded image become persuasive scientific evidence. In addition, when the raising the rate between signal and noise, the signal processing module will not only amplify the fluorescence signal up to 70 %, but also decrease the noise significantly from environmental light on bill and nude mouse testing.

Violence Viewing and Adolescent Aggression: A Longitudinal Study.

ERIC Educational Resources Information Center

Viemero, Vappu

A longitudinal field study conducted in Turku, Finland, traced the development of aggression as a function of the viewing of violence by children from the ages of 7 and 9 to the ages of 15 and 17 to explore the connection between violence viewing and viewers' aggression, and to shed light on the question of causality. The 220 subjects, both male…

Lighting up micromotors with quantum dots for smart chemical sensing.

PubMed

Jurado-Sánchez, B; Escarpa, A; Wang, J

2015-09-25

A new "on-the-fly" chemical optical detection strategy based on the incorporation of fluorescence CdTe quantum dots (QDs) on the surface of self-propelled tubular micromotors is presented. The motion-accelerated binding of trace Hg to the QDs selectively quenches the fluorescence emission and leads to an effective discrimination between different mercury species and other co-existing ions.

Gender Segregation within Different Educational Levels: Austrian and Finnish Trends in the Light of Educational Reform, 1981-2005

ERIC Educational Resources Information Center

Prix, Irene

2012-01-01

Within most educational systems, men and women tend to specialize in different fields of study. Comparing Austria and Finland, this article traces the extent and patterns of gender segregation within different educational levels between 1981 and 2005. Relying on official enrollment figures, a logarithmic index is used to measure overall and…

Global-local duality in eternal inflation

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

Bousso, Raphael; Yang, I-S.

2009-12-15

We prove that the light-cone time cutoff on the multiverse defines the same probabilities as a causal patch with initial conditions in the longest-lived metastable vacuum. This establishes the equivalence of two measures of eternal inflation which naively appear very different (though both are motivated by holography). The duality can be traced to an underlying geometric relation which we identify.

ROLE OF THE PHOTO-FENTON REACTION IN THE PRODUCTION OF HYDROXYL RADICALS AND PHOTOBLEACHING OF COLORED DISSOLVED ORGANIC MATTER IN A COASTAL RIVER OF THE SOUTHEASTERN UNITED STATES

EPA Science Inventory

Photochemical reactions involving colored dissolved organic matter (CDOM) in natural waters are important determinants of nutrient cycling, trace gas production and control of light penetration into the water column. In this study the role of the hydroxyl radical ((OH)-O-.) in CD...

Multipass optical device and process for gas and analyte determination

DOEpatents

Bernacki, Bruce E [Kennewick, WA

2011-01-25

A torus multipass optical device and method are described that provide for trace level determination of gases and gas-phase analytes. The torus device includes an optical cavity defined by at least one ring mirror. The mirror delivers optical power in at least a radial and axial direction and propagates light in a multipass optical path of a predefined path length.

Searching for a Crack to Let Environment Light In: Ecological Biopolitics and Education for Sustainable Development Discourses

ERIC Educational Resources Information Center

Gough, Annette

2017-01-01

This article traces the shifts in environmental education discourses from the 1972 UN Conference on the Human Environment, to the 2012 UN Rio+20 Conference on Sustainable Development, and beyond through a biopolitical lens. Each of the earlier shifts is reflected in environmental, sustainability and science education policies and curricula--but…

Thomas Jefferson's Road to the White House. Teaching with Historic Places.

ERIC Educational Resources Information Center

Hunter, Kathleen

This unit focuses on Thomas Jefferson's route from his home at Monticello in Virginia to the White House when he traveled to Washington in November of 1800 for the upcoming presidential election. The document traces his journey by phaeton, a four wheeled light carriage, from Monticello to: (1) James Madison's home at Montpelier, a distance of 28…